systems and components in commercial vehicles (english) · 2020-07-08 · 4 operation of air...

SYSTEMS AND COMPONENTS FOR COMMERCIAL VEHICLES

PRODUCT CATALOGUE

Systems and Components in Commercial Vehicles

Edition 2

This publication is not subject to any update service.You will find the current version on the internet athttp://www.wabco.info/8150100033

2011/2015 WABCO Europe BVBA – All rights reserved.

The right of amendment is reservedVersion 3/12.2011(en)

8150100033 815 010 003 3

31

Page

Operation of Air Braking Systems ..................................................... 4

1. Motor VehiclesBraking System ............................................................................. 6Components of the Motor Vehicle’s Braking System........................... 7

2. TrailersBraking System ........................................................................... 64Equipment For Trailer Braking Systems ............................................ 66

3. Anti-Lock Braking System (ABS) .................................................... 83

4. Sustained-Action Braking Systems On Motor Vehicles ................ 95

5. EBS - Elektronisch geregeltes Bremssystem ............................... 101

6. Air Suspension Systems and ECAS (Electronically Controlled Air Suspension)................................... 111

7. Clutch Servo..................................................................................... 123

8. Air Braking Systems In Agricultural Vehicles ....................................................................... 127

9. ETS and MTS - Elektronic Door Control Systems For Motor Coaches .......................................................................... 137

10. Installation Of Pipes And Screw Unions ....................................... 151

11. Index ................................................................................................. 163

Table of Contents

4

Operation of Air Braking Systems

1. Compressed Air Supply

The compressed air supplied by the com-pressor (1) flows to the air dryer (3) viathe unloader (2) which automatically con-trols the pressure within the system with-in a range of between 7.2 and 8.1 bar, forinstance. In the air dryer, the water va-pour in the air is extracted and expelledthrough the air dryer’s vent. The dried airthen flows to the quadruple-circuit pro-tection valve (4) which, if one or severalcircuits are defective, secures the intactcircuits against any loss in pressure.Within the service braking circuits I andII, the air supply from the reservoirs (6and 7) flows to the brake valve (15). InCircuit III the air supply from the reservoir(5) flows through the 2/2-way valve whichis integrated in the trailer control valve(17) to the automatic hose coupling (11)and on to the check valve (13), the handbrake valve (16) and the relay valve (20)into the spring-loaded portion of the Tris-top spring brake actuators (19). Circuit IVsupplies air to any ancillary consumers,in this case an exhaust brake.

The trailer’s braking system receivescompressed air through the hose cou-pling (11) with its supply hose connected.This air then passes the line filter (25)

and the relay emergency valve (27) be-fore reaching the reservoir (28) and alsoflows to the supply ports of the ABS relayvalves (38).

2. Operation:

2.1 Service Braking SystemWhen the brake valve (15) is actuated,compressed air flows via the ABS sole-noid control valve (39) into the brakechambers (14) of the front axle and to theload-sensing valve (18). This valve re-verses and the air flows via the ABS so-lenoid control valve (40) into the servicebrake portion (brake chambers) of theTristop spring brake actuators (19). Thepressure in the brake cylinders generat-ing the force required for the wheel brakedepends on the amount of force appliedto the brake valve, and on the load car-ried on the vehicle. This brake pressureis controlled by the load-sensing valve(18) which is connected to the rear axleby means of a linkage. Any change in thedistance between the vehicle’s chassisand its axle caused by loading or unload-ing the vehicle causes the brake pres-sure to be continuously adjusted. At thesame time, via a pilot line, the load-emptyvalve integrated in the brake valve is af-fected by the load-sensing valve. Thus

the brake pressure on the front axle isalso adjusted to the load carried on thevehicle (mostly on lorries).

The trailer control valve (17) actuated bythe two service braking circuits pressuriz-es the pilot connection of the relay emer-gency valve (27) after passing the hosecoupling (12) and the connecting “con-trol“ hose. The air supply from the air res-ervoir (28) is thus allowed to passthrough the relay-emergency valve, thetrailer release valve (32), the adaptervalve (33) and on to the load-sensingvalve (34) and the ABS relay valve (37).The relay valve (37) is actuated by theload-sensing valve (34) and the com-pressed air flows to the brake chambers(29) on the front axle. The ABS relayvalves (38) are actuated by the load-sensing valve (35), and the compressedair is allowed to pass to the brake cham-bers (30 and 31). The service pressureon the trailer, which is similar to the out-put pressure from the towing vehicle, isautomatically adjusted by the load-sens-ing valves (34 and 35) for the load carriedon the trailer. In order to prevent overb-raking of the wheel brake on the frontaxle in the partial-braking range, theservice pressure is reduced by the adapt-er valve (33). The ABS relay valves (on

5

the trailer) and the ABS solenoid controlvalves (on the towing vehicle) are used tocontrol (pressure increase, pressurehold, pressure release) the brake cylin-ders. If these valves are activated by theABS ECU (36 or 41), this control processis achieved regardless of the pressure al-lowed to pass by the brake valve or therelay emergency valve.

When they are not needed (solenoids aredead), the valves operate as relay valvesand achieve a faster increase or de-crease of the pressure for the brake cyl-inders.

2.2 Parking Braking SystemWhen the hand brake valve (16) is actu-ated and locked, the spring-loaded por-tions of the Tristop spring brakeactuators (19) are exhausted fully. Theforce needed for the wheel brake is nowprovided by the heavily preloadedsprings of the Tristop spring brake actua-tors. At the same time, the pressure inthe line leading from the hand brakevalve (16) to the trailer control valve (17)is reduced. Braking of the trailer com-mences by the pressure increasing in theconnecting ‘supply’ hose. Since theguideline of the Council of the EuropeanCommunities (RREG) that a tractor-trail-

er combination must be held by the motorvehicle alone, the pressure in the trailer’sbraking system can be released by mov-ing the hand brake lever into its ‘control’position. This permits the parking brakingsystem to be examined as to whether itfulfills the provisions of the RREG.

2.3 Auxiliary Braking SystemDue to sensitive graduation of the handbrake valve (16) the lorry can be brakedby means of the spring-loaded portionseven if the service braking systems I andII have failed. The brake force for thewheel brake is produced by the force ofthe preloaded springs of the Tristopspring brake actuators (19) as describedunder ‘Parking Braking System’ althoughthe spring-loaded portions are not ex-hausted fully but only to the extent re-quired for the braking performance.

3. Automatic Braking of the Trailer

In the event of the connecting ‘supply’line breaking, the pressure will drop rap-idly and the relay emergency valve (27)will cause full application of the trailer’sbrakes. In the event of the connecting‘control’ line breaking, the 2/2-way valveintegrated in the trailer control valve (17)

will, when the service braking system isactuated, throttle the passage of the sup-ply line leading to the hose coupling (11)to such an extent that the rupture of thesupply line causes a rapid drop in pres-sure in the supply line and the relayemergency valve (27) causes the trailerto be braked automatically within the le-gally stipulated time of no more than 2seconds. The check valve (13) securesthe parking braking system against anyinadvertent actuation if the pressuredrops in the supply line leading to thetrailer.

4. ABS ComponentsThe motor vehicle usually has three tell-tale lamps (ASR having one additionallamp) fitted for indicating functions andfor continuously monitoring the system. Italso has a relay, an information moduleand an ABS socket (24).

After actuating the driving switch, the yel-low telltale lamp will come on if the trailerhas no ABS or if the connection has notbeen established. The red lamp will go offwhen the vehicle exceeds a speed of ap-prox. 7 k.p.h. and the safety circuit of theABS electronics has not detected an er-ror.

Operation of Air Braking Systems

6

Air braking system with ABS/ASR (4S/4M)

Legend:

Pos.1 Compressor2 Air dryer with combined

unloader3 Four circuit protection valve4 Air reservoir5 Clamps6 Test coupling7 Drain valve8 Check valve9 Brake valve with integral

auto load proportioning valve10 Hand control valve with

trailer control11 Relay valve12 Piston cylinder13 Brake chamber14 ASR-Control cylinder

15 3/2 Solenoid valve16 Tristop-Brake actuator17 Quick release valve18 Load sensing valve19 Knuckle joint20 Trailer control valve21 Hose coupling, supply22 Hose coupling, control23 Two-Way valve24 ABS Warning lamp25 ABS Info lamp26 ABS-socket27 Sensor extension cable28 Solenoid cable29 Socket 30 Sensor braket

31 Sensor with cable32 Pole wheel33 ABS-Solenoid valve34 Electronic control unit35 Info module36 Pressure switch37 Proportional valve38 3/2 Directional control valve

1238

1

2 3

4,5

7

14

37

917

13

33

28

2729,3031,32

24

25

34 35

18

19 15

6

26

11

23

16

21

2220

10

8

36

7

1.

Components Of TheMotor Vehicle’s Braking System

8

Air Intake Filters1.

Moist Air Filter

Purpose:To prevent impurities from the air gettinginto the compressor (by using suction fil-ters) or into the vents of compressed airequipment (by using vent filters); theyalso serve to muffle the noise caused bythe intake of air or by blowing it off.

Operation:Moist air filters (for normal operating con-ditions). The air is taken in through anopening in the cap, flows through the fil-ter medium where it is cleaned and thenflows on to the air intake of the compres-sor.

Oil Bath Air Cleaner

Operation:Oil bath air cleaner (for air containing alarge mount of dust)

The air is taken in through the sieve platebelow the cap and the central pipe, andthen passed across the surface of the oilwhere any dust particles can settle. Fromthe surface of the oil, the air is pushedupward, flows through a filter packagewhich retains any impurities which maystill be contained in the air and any oilparticles carried over before reachingthe air intake of the compressor.

Moist Air Filter432 600 . . . 0 to 432 607 . . . 0

Oil Bath Air Cleaner432 693 . . . 0 to 432 699 . . . 0

9

Purpose:Production of compressed air for roadvehicles and static systems.

Operation:The pulley on the end of the crankshaft isrotated by a vee-belt driven off the vehi-cle’s engine. This rotation causes theconnecting rods to to move the pistons.As the piston travels downwards clean

air from either the engine air cleaner orthe moist air filter (or alternatively an oilbath air cleaner) is drawn in trough theinlet valve. As the piston moves up-wards, the inlet valve closes, and air ispumped through the delivery valve intothe the reservoir.

The type of lubrication depends on theconstruction of the compressor, and canbe splash or pressure fed.

Compressor 1.Single CylinderAir Compressor 411 1 . . . . . 0 and 911 . . . . . . 0

Twin CylinderAir Compressor411 5 . . . . . 0 and 911 5 . . . . . 0

10

Air Cleaner1.

Purpose:To clean the air delivered by the com-pressor and to precipitate the humidity itcontains.

Operation:The air entering at port 1 flows throughannular gap A into Chamber B. As itpasses through the gap A, the air coolsand some of the water vapour it containswill condensate. The air then flowsthrough the filter (a) to Port 2.

At the same time, the pressure in Cham-ber B opens the inlet (3) of the valvebody (d) and the condensate runsthrough the filter (f) into Chamber C. As

the pressure in Chamber B falls, the inlet(3) closes and the outlet (b) opens. Thecondensate is now blown outside by thepressure in Chamber C. When the pres-sures in Chambers B and C are bal-anced, outlet (b) closes.

Pin (C) can be used to check whether theautomatic drain valve is working proper-ly.

Air Cleaner432 511 . . . 0

11

Air Dryer432 410 . . . 0 and 432 420 . . . 0

Purpose: Drying of the compressed air supplied bythe compressor by extracting the mois-ture present in the air. This is effected bya progress of cold regenerated adsorp-tion drying where the air compressed bythe compressor is led through granulates(adsorbens) capable of adsorbing themoisture contained in the air.

Operation:Variant 1 (Control Via Separate Un-loader Valve 432 420 ... 0)

In the feed phase, the compressed airsupplied by the compressor flows viaPort 1 into Chamber A. Here the conden-sate caused by the reduction in tempera-ture will collect, reaching Outlet (e) viaDuct C.

Via Fine Filter (g) integrated in the car-tridge, and via Annulus (h), the air willreach the upper side of Desiccant Car-trige (b), being cooled in the process,and further condensate will precipitate.Moisture is extracted from the air as itpasses through Granulate (a) this mois-ture is absorbed by the surface and the

fine ducts [diameter: 4 x 106 m = 4Å(Angström)] of the extremely porousgranulate.Since the oil molecules are more than 4Åin size they cannot enter the fine ducts ofthe granulates. This makes the granulaterobust. The steam portion of the oil is notadsorbed. The dried air reaches the airreservoirs via Check Valve (c) and Port21. At the same time, the dried air alsoreaches the re-generation reservoir viathrottling port and Port 22.

When cut-out pressure in the system isreached, Chamber B is pressurized fromthe unloader valve via Port 4. Piston (d)moves downwards, opening Outlet (e).The air, the condensate plus any impuri-ties and oil carbon from Chamber A willbe emitted via Duct C and Outlet (e).

When cut-in pressure at the unloadervalve is reached, Chamber B is ventedonce again. Outlet (e) closes and the dry-ing process will commence as describedabove.

Any malfunction due to icing in extremeconditions in the area of Piston (d) canbe prevented by fitting a Heating Car-tridge (g) which will switch on at temper-atures below 6°C and switch off againwhen the temperature reaches approx.30°C.

Variant 2 (Control Via Integral Unload-er Valve 432 410 ... 0)

The process of drying the air is as de-scribed under Variant 1 In this version,however, the cut-out pressure will reachChamber D via Bore (l), acting on Dia-phragm (m). After overcoming the springresistance, Inlet (n) will open, and Piston(d), now pressurized, will open Outlet (e).

The air supplied by the compressor willnow be emitted via Chamber A, Duct Cand Vent 3. Piston (d) also acts as apressure relief valve. In the event of anyexcess pressure, Piston (d) will auto-matically open Outlet (e). If, due to airconsumption, the supply pressure in thesystem falls to a value below cut-in pres-sure, Inlet (n) will close and the pressurefrom Chamber B will be reduced via theunloader valve's vent. Outlet (e) willclose and the drying process will com-mence once again.

Air Dryer 1.

432 420 432 410

12

Air Dryer1.

Air Dryer With Return-FlowLimiting Valve432 413 . . . 0 and 432 415 . . . 0

The single-chamber air dryers from thisseries have an integrated return-flow lim-iting valve which permits the requiredamount of air to be taken from the mainreservoir provided the multiple-circuitprotection valve permits a return flow.Thus no separate regenerating reservoiris required.

Operation:Variant 1 (Control Via Separate Un-loader Valve 432 413 ... 0)

In the delivery phase the compressed airsupplied by the compressor flowsthrough Port 1, opens the check valve (i)and flows into Chamber A. Due to thedrop in temperature, condensation watercollects there which reaches the outlet(e) through Duct C.

The air is dried as described under 432420. At the same time, dried air alsoflows into Chamber E, pressurizing dia-phragm (o). This arches towards theright, releasing the passage betweenChambers E and G via Throttling Port (s).The air supply also reaches Chamber Hvia Filter (l), pressurizing Valve (q). Once

the force of the pressure spring, presetby means of Screw (r), has been over-come, Valve (q) is lifted. The air supplywill now reach Chamber F, acting on theother side of the diaphragm (o) with aslightly lower pressure in keeping withthe retention of Valve (q).

When the cut-off pressure within the sys-tem has been reached, Chamber B ispressurized by the unloader via Port 4.The piston (d) moves downwards andopens the outlet (e). The check valve (i)closes the passage to Port 1 and the airfrom Chamber A flows through Duct Cand is emitted to atmosphere at the outlet(e).

Due to the drop in pressure in ChamberG, the check valve (c) closes. The air tobe regenerated is now taken from the airreservoirs, which is why a multiple-circuitprotection valve must permit its returnflow. The air supply at Port 21 flowsthrough Chamber E, the throttling port (s)where it expands, on into Chamber Gand thus to the underside of the granu-late cartridge (b).

As it passes through the granulate car-tridge (b) in an upward direction, the hu-midity on the surface of the granulate (a)is taken up by the air and emitted to at-mosphere at Vent 3 after passing Duct Cand the opened outlet (e). The return flowis completed when the pressure on the

left of the diaphragm (q) has been re-duced to a point where it reaches its clos-ing position.

When the cut-in pressure at the unloaderis reached, the pressure in Chamber B isreduced once again. The outlet (e) clos-es and the drying process starts again asdescribed above. Outlet 31 also has asafety valve for the pressure side.

Variant 2 (Control Via Integral Unload-er Valve 432 415 ... 0)

In this variant, the cut-off pressure reach-es Chamber J via the connecting holeinto Chamber J and acts on the dia-phragm (m). After the spring force hasbeen overcome, the inlet (n) opens andthe piston (d) which is now pressurizedopens the outlet (e).

The air delivered by the compressor nowflows through Chamber A, Duct C and isemitted to atmosphere at Vent 3. The pis-ton (d) at the same time acts as a popvalve. When the pressure is excessive,the piston (d) automatically opens theoutlet (e).

If air consumption causes the supplypressure within the system to fall belowthe cut-in pressure, the inlet (n) closesand the pressure from Chamber B is re-duced through the vent of the unloadervalve. The outlet (e) closes and the dry-ing process begins again.

432 413 432 415

13

Twin Chamber Air Dryer432 431 . . . 0 and 432 432 . . . 0

Operation:a) Control without Integral Un-

loader ValveThe compressed air supplied by thecompressor flows to Bore E via Port 1.Due to a reduction in temperature, con-densate may form at Bore E, reachingIdling Control Valve (m) via Bore L. FromBore E, the compressed air will passValve (k), enter Chamber B, and reachthe upper side of Desiccant Cartridge (c)via Fine Filter (e) integrated into the car-tridge, and via Annulus A.

Through Sieve Plate (a), the pre-cleanedcompressed air will pass upwardsthrough Granulate (b) sewn into a filterbag in Cartridge (c), reaching Bore G viaSieve Plate (d) and Check Valve (f).

As the air passes through Granulate (b),the inherent moisture is retained by theextremely porous granulate. From BoreG, the compressed air reaches the airreservoirs through Check Valve (g) andvia Port 2.

Through the throttling port of Valves (fand p) designed according to the sweptvolume of the compressor used, part ofthe dried compressed air from Bore Gwill reach the underside of Cartridge (s),passing Granulate (r) in an upward direc-tion (backflush). In this process, themoisture adhering to the fine ducts of theextremely porous Granulate (r) is takenup by the dried air and reaches Vent 3via Annulus K, Chamber H and past theopen rear side of Valve (o).

The additional Charging Valve (h) en-sures that Control Valves (k and o) donot switch over when the system is filledinitially. Valve (h) will not open until asupply pressure of > 5 bar has beenreached at Port 2, permitting com-pressed air to reach Chamber C. If thetimeswitch element integrated in the so-lenoid valve then opens the current sup-ply to Trip Coil (j), Armature (i) will beattracted. Compressed air from Cham-ber C will now flow into Chamber D and,via Bore F, into Chamber M, moving thecontrol valves against the spring forceinto their end positions on the left.

The passage from Bore E to Chamber Bis closed. The compressed air present inChamber B will now be emitted at Port 3

after passing by the open rear side ofControl Valve (k) and going through BoreN. Check Valve (g) will close and thepressure in the system continues to beensured. As a consequence of the pres-sure reduction in Chamber B, CheckValve (f) will also close.

The compressed air supplied by thecompressor will now flow from Bore Ethrough Chamber H, Annulus K andthrough Granulate (r) of Cartridge (s).The drying process of the compressedair is as described before. After Valve (p)and Check Valve (g) have opened, thedried air reaches the reservoirs via Port2. Through the throttling port of Valve (f),dried air reaches the underside of Gran-ulate (b), causing a back-flushing proc-ess to take place here, too.

After approx. 1 minute, the time-switchelement will break the current supply tothe trip coil. Armature (i) will close thepassage from Chanber C, opening thevent, thus reducing the pressure inChambers D and M. Through the springforce and the pressure in Bore G, thecontrol valves are returned to their endpositions on the right. Control Valve (o)will close the passage to Chamber H,and Control Valve (k) will open the pas-

Air Dryer 1.

432 431

14

Air Dryer1.

sage to Chamber B. The compressed airsupplied by the compressor is now againfed into Granulate (b), and the dryingprocess will commence as described be-fore, with alternating cartridges continu-ing to be used at one-minute intervals.

When the unloader valve switches toidling once the input cut-out pressure hasbeen reached, pressure is being fed in atPort 4, pressurizing, and moving down-wards, Piston (m), opening the idlingcontrol valve. Any condensate and impu-rities will be emitted together with the airsupplied in the idling phase via Vent 3.When the unloader valve switches toload, Port 4 is vented and the idling con-trol valve closes the passage to Vent 3.

Any malfunction due to icing in extremeconditions in the area of Piston (e) canbe prevented by fitting a Heating Car-tridge (g) which will switch on at temper-atures below 6°C and switch off againwhen the temperature reaches approx.30°C.

b) Control Via Integral UnloaderValve

The air is dried as described under a).The pressure building up at Port 2 whenthe system is being filled is also present

in Chamber P, pressurizing the under-side of Diaphragm (t). As soon as theforce resulting therefrom is larger thanthe force of Pressure Spring (n), Dia-phragm (t) will arch, taking with it Piston(q). This opens Inlet (u), and Piston (m),now pressurized, is moved downward,opening the idling control valve. Any con-densate and impurities will be emitted to-gether with the air supplied in the idlingphase via Vent 3. The compressor willcontinue to run idle until the pressurewithin the system has fallen to a valuebelow the unloader valve's cut-in pres-sure. The pressure in Chamber P belowDiaphragm (t) will fall simultaneously.Pressure Spring (n) will move Piston (q)and Diaphragm (t) back to their originalpositions. Outlet (u) will close, and thepressure from Chamber O will be re-duced via the vent of the unloader valve.The idling control valve with Piston (m)will close once again. The compressedair will now again flow into Bore E andreach the air reservoirs via Port 2 afterbeing dried in Desiccant Containers (b orr). The system is subsequently filledonce again up to the cut-out pressure ofthe unloader valve.

Application:Depending on the respective application,WABCO provides Single and TwinChamber Air Dryers.

The decision of whether to use a Singleor a Twin Chamber Air Dryer will dependon the compressor's swept volume andon its duty cycle.

Single Chamber Air Dryerscan normally be used for applications upto a swept volume of � 500 litres/minuteand a duty cycle of up to � 50%. Any de-viations of these standard values shouldbe tested in road-test runs.

Twin Chamber Air Drierscover the area > 500 litres/minute and >50% up to 100% duty cycle. Swept vol-umes in excess of 1000 litres/ minuteshould be tested in road-test runs

432 432

15

Purpose:To automatically control the operatingpressure in an air braking system and toprotect its pipes and valves from contam-ination. Depending on the variant used, italso serves to control a downstream anti-freeze pump or single chamber air dryer.

Operation:a) UnloaderThe compressed air supplied by thecompressor flows via Port 1 and Filter (g)to Chamber B. When Check Valve (e)has opened, it flows through the lineleading from Port 21 to the air reservoirsand to Chamber E. Port 22 is intendedfor controlling a downstream anti-freezepump.

Pressure builds up in Chamber E, actingthe underside of Diaphragm (c). As soonas that pressure is greater than the forceof Compression Spring (b), preset bymeans of Screw (a), diaphragm (c) willarch upward, taking with it Piston (m).Outlet (l) closes and Inlet (d) opens, per-mitting the compressed air to pass fromChamber E to Chamber C, forcing Piston(k) downwards against the force of Com-pression Spring (h). Outlet (i) opens andthe compressed air supplied by the com-pressor is released to atmosphere viaExhaust 3. The fall in pressure in Cham-

ber B closes Check Valve (e), thus se-curing the pressure in the system.

The compressor will now continue to idleuntil the pressure within the system fallsbelow the Unloader's cut-in pressure.The pressure in Chamber E below Dia-phragm (c) continues to fall. This causesthe force of Compression Spring (b) topush the diaphragm, together with Piston(m), downwards. Inlet (d) closes, Outlet(l) opens and the air from Chamber C isreleased to atmosphere at Exhaust 3 af-ter passing Chamber F and a connectinghole. Compression Spring (h) forces upPiston (k) and outlet (i) is closed. The airsupplied by the compressor now flowsinto Chamber B, passing Filter (g), andopens Check Valve (e). The system isonce again being filled until the Unload-er's cut-off pressure has been reached.

b) Unloader with Pilot Connec-tion 4 and Port 23

This type of Unloader differs from thetype described under a) merely in theway the cut-off pressure is controlled.The cut-off pressure is not taken from in-side the unloader but from the supply linedownstream from the air dryer. The pas-sage from Chamber B to Chamber E isclosed, and there is no Check Valve (e).Via Port 4 and Chamber A, the air from

the reservoir flows to Chamber E, actingon Diaphragm (c). After that it continuesto operate as described under a). Thepassage between Chambers C and D isopen, permitting pilot pressure fromChamber C to be taken at Port 23 to ac-tuate the single chamber air dryer.

c) Tyre inflation connectionAfter removing the protective cap, thetyre inflation hose is fastened by meansof a union nut moving Pin (f). The pas-sage between Chamber B and Port 21 isclosed. The air supplied by the compres-sor now flows from Chamber B to the tyreinflation hose, passing Pin (f). In theevent of the pressure in the system ex-ceeding 12+2 bar or 20 bar respective-ly during this process, Piston (k) which isdesigned to act as a safety valve willopen Outlet (i) and the pressure is re-leased to atmosphere via Exhaust 3.

Before using the tyre inflation facility, thereservoir pressure must be reduced to avalue below the Unloader's cut-in pres-sure since no air can be extracted whilstthe compressor is running idle

12–

Unloader 1.Combined Unloader975 303 . . . 0

16

Safety Valves1.

Purpose:To limit the pressure within a pneumaticsystem to the permissible maximum.

Operation:The compressed air flows through Port 1and beneath the disk valve (c). When theforce resulting from pressure x surfaceexceeds the preset force of the pressurespring (a), the disk valve (c) is forced up-wards with the piston (b). The excesspressure escapes to atmosphere

through Vent 3 until the force of thespring is greater once again and the diskvalve (c) closes.

The function of the safety valve can bechecked by raising the piston (b).

Safety Valves434 6 . . . . . 0 and934 6 . . . . . 0

434 608 ... 0 934 601 ... 0

434 612 ... 0

17

Purpose:To automatically inject anti-freeze fluidinto the braking system to prevent anymoisture present in pipes and its down-stream components to freeze.

Operation:Depending on the type of anti-freezepump used, it can be fitted downstreamor upstream of the unloader.

Whilst in the anti-freeze pump which isfitted upstream of the unloader the pilotpulse is taken directly from the feed linevia an internal hole as the unloaderchanges from the idle to the load cycle,this pilot pulse has to be taken from aseparate line if the anti-freeze pump is fit-ted downstream of the unloader.

In either case, however, anti-freeze fluidis only injected into the system once theunloader has switched the compressorover to its load cycle, i.e. to supplyingcompressed air into the system.

1. Without a separate pilot con-nection (Fig. 1)

The compressed air supplied by thecompressor flows through the anti-freezepump from Port 1 to Port 2 (Hole J). Thepressure thus building up via Hole (H) inChamber (F) forces Piston (E) to the left.No anti-freeze fluid can reach Chambers(C) or (R) as Hole (K) is closed. The fluidpresent in Chamber (R) is displaced bythe further movement of Piston (E). Itpasses Valve Seat (N), reaching Hole (J)and is dispersed in the braking system bythe passing stream of air.

Once the operating pressure has beenreached in the reservoir, the unloaderswitches the compressor to idle. Thepressure drops in Hole (J) and thus Hole(H) and Chamber (F). CompressionSpring (G) returns Piston (E) to its origi-nal position. Through the re-opened Hole(K), more anti-freeze fluid flows from itsreservoir to Chamber (R).

These processes are repeated everytime the unloader actuates the compres-sor.

2. With a separate pilot connec-tion (Fig. 2)

This operates similarly to the processesdescribed under 1. above. With this vari-ant, the actuating pressure is suppliedvia Port 4 from a separate component,e.g. from the unloader.

Operation and Maintenance:At temperatures below +5°C, the pumpneeds to be activated by turning Lever(B) to Position I. The level of anti-freezefluid must be checked daily.

As temperatures rise above +5°C, thepump can be deactivated by turning Le-ver (B) to Position 0.

During the warm season, the fluid reser-voir does not need to be filled. The posi-tion of Lever (B) is immaterial.

The anti-freeze pump does not requireany special maintenance.

Anti-Freeze Pump 1.Anti-Freeze Pump 932 002 . . . 0

Fig. 1

Fig. 2

18

Purpose:To retain a safe working pressure in theintact circuits of a triple circuit brake sys-tem when one circuit has failed.

Design:Type I With all brake circuits intact valves (c andj) are always kept closed, except duringthe charging operation, by compressionspring acting in the closing direction.

Type II By means of the springs acting under thevalves (c and j) these valves remain openabove a preset opening pressure. In theevent of a slight pressure drop in circuits1 or 2 crossflow from the circuit with thehighest pressure, into the other circuitstakes place. This reduces the frequencyof operation of the unloader.

Operation:Compressed air, passing from the un-loader valve through port 1 into the tripleprotection valve, opens the valves (c and

j) after the preset opening pressure (pro-tection pressure) has been reached, rais-ing the diaphragms (b and k) against theaction of the pressure springs (a and l).The compressed air then flows throughports 21 and 22 into the air reservoirs ofcircuits 1 and 2. It also passes into cham-ber (A) after the non-return valves (d andh) have opened, opens valve (e) andflows through port 23 into circuit 3. Fromcircuit 3 the auxiliary and parking brakeequipment of both the motor vehicle andthe trailer are supplied with air.

If for example circuit 1 fails because of aleak, the compressed air still being sup-plied from the unloader, first passes intothe leaking circuit. But as soon as a pres-sure drop occurs in circuits 2 or 3 afterapplication of the brakes, valve (j) closesbecause of the pressure spring (l) andthe intact circuit under load, is refilled un-til the opening pressure of the valve (j) isreached. This refilling can occur becausethe pressure remaining in the intact cir-cuits after any application of the brakes

exerts a counter-force on pressure spring(a or g) through diaphragm (b or f). Thusvalve (c or e as the case may be) can stillopen even though the opening pressurefor valve (j) has not yet been reached.Pressure protection for circuits I and IIIworks in exactly the same way in theevent of failure of circuit II.

In the event of failure of the auxiliarybrake circuit, a crossflow of air from thereservoirs of circuits 1 and 2 into circuit 3occurs until valve (e) can no longer bekept open by the falling crossflow pres-sure, and it closes when the preset open-ing pressure is reached. The pressuresin the two main brake circuits remainsafeguarded to the level of the openingpressure for the defective circuit 3.

In the event of failure of circuit 1 or 2 be-low the opening pressure of the valves (cor j respectively), the non-return valves(d and h) protect the intact circuit from thefaiIed circuit.

Multi-Circuit Protection Valves1.

Type I

Type II

Three-Circuit Protection Valve934 701 . . . 0

19

Four-Circuit Protection Valves934 702 . . . 0 934 713 . . . 0 / 934 714 . . . 0

Purpose:Retention of pressure in the intact brak-ing circuits in case of failure of one ormore circuits in a four-circuit air-brakingsystem.

Operation: Depending on the variant used, the fourcircuits are connected in parallel and allfour circuits are filled equally, or Circuits3 and 4 are secondary to Circuits 1 and2. The quadruple-circuit protection valvemay, depending on the variant, have by-pass holes in all circuits which ensurethat the braking system is filled from 0bar should one circuit fail.

Compressed air flows from the unloadervalve through port 1 into the protectionvalve and through by-pass bores (a, b, c,and d). It continues through check valves(h, j, q and r) into the four circuits of the

system. Simultaneously, pressure buildsup below valves (g, k, p and s), openingthe valves after reaching the set openingpressure (protection pressure). Also, dia-phragms (f, l, o and t) are raised againstthe force of compression springs (e, m, nand u). Compressed air then flowsthrough ports 21 and 22, to circuit 1 and2 air reservoirs of the service brake sys-tem, and through ports 23 and 24 into cir-cuits 3 and 4. Circuit 3 suppliescompressed air to the emergency andparking brake system of the truck and tothe trailer supply line; circuit 4 suppliesthe auxiliary systems.

If one of the service brake circuits (e.g.circuit 1) fails, air flows from the otherthree circuits into the failed circuit untilthe dynamic valve closing pressure isreached. The force of compressionsprings (e, m, n and u) causes valves (g,k, p and s) to close. If air is consumed incircuits 2, 3, or 4, refilling will occur to thelevel of the set opening pressure of thefailed circuit. Pressure protection of theintact circuits takes place in the sameway if another circuit fails.

If one circuit (e.g. circuit 1) fails, and inaddition, for any reason the pressuredrops to zero bar within the intact cir-cuits, then, when the brake system refills,compressed air flows initially through by-pass bores (a, b, c and d) into all four cir-cuits. The resulting pressure build-up be-low the diaphragms ( f, l and o) of theintact circuits decreases the openingpressure of valves (g, k and p). Furtherpressure increase in port 1 causesvalves (g, k and p) to open. Intact circuits2, 3 and 4 are refilled to the level of theset opening pressure of failed circuit 1and are protected at that level.

Multi-Circuit Protection Valves 1.

934 702

934 713

20

APU - Air Processing Unit1.

APU - Air Processing Unit 932 500 . . . 0

Description:The APU (Air Processing Unit) is multi-functional, i. e. it is a combination of sev-eral types of equipment. It includes an airdryer with an unloader valve, with or with-out heating, depending on the variant, asafety valve and a tyre inflation connec-tor. A multiple-circuit protection valvewith one or two integrated pressure limit-ed valves and two integrated checkvalves is flanged to the air dryer.

Some versions also have a double pres-sure sensor mounted on the multiple-cir-cuit protection valve for measuring thesupply pressures in the service brakingcircuits.

Purpose:The air dryer is used to dry and cleansethe compressed air delivered by the com-pressor, and to control the supply pres-sure. The flanged multiple-circuitprotection valve is used to limit and guardthe pressure in multiple-circuit brakingsystems.

Operation:The compressed air delivered by thecompressor enters at Port 11 and passes

a filter before reaching the granulate car-tridge. As it flows through the granulate,the air is filtered and dried (please refer toAir Dryer 432 410 ... 0 on Page 11). Thedried air then flows through Port 21 toSupply Port 1 of the flanged multiple-cir-cuit protection valve. When the level ofsupply pressure has been reached, theintegrated unloader valve actuates theidle valve and the compressor now deliv-ers to atmosphere. In the idle phase, thegranulate is regenerated in the returnflow via Port 22 with dried and non-com-pressed air.

The air dryer includes a safety valvewhich opens if the pressure becomes ex-cessive. To prevent functional defects ofthe idle valve in winter, a heating systemhas been integrated. The tyre inflationconnector or Port 12 can be used to fillthe system externally (workshop). The airreservoirs for air suspension are con-nected to Port 24.

In a first step, the pressure at Supply Port1 (10 ± 0.2 bar) of the multiple-circuit pro-tection valve is reduced to the level re-quired for the service braking systems,and in a second step (8.5 bar) to thelevel required for the trailer’s braking sys-tem.

In the event of one circuit failing, the

pressure in the other circuits will initiallyfall to the dynamic closing pressure (dueto the trailer) but will then rise again untilit reaches the opening pressure (9.0bar Circuits 1 + 2 and 7.5 bar Cir-cuits 3 + 4) of the defective circuit (= se-cured pressure). This requires thecompressor to be running and to delivermore compressed air. If this pressure isexceeded, the air delivered will escapeinto the defective circuit and thus beevacuated to atmosphere.

An electronic pressure sensor unit per-mits the continuous display of the pres-sures in the service braking circuits. Inaddition, Circuits 3 and 4 have outputs(25 and 26) secured by one check valveeach.

When pressurizing the braking systemstarting at 0 bar, the service braking cir-cuits (1 and 2) are filled first in keepingwith EC guideline 71/320/EEC.

00 4,–

00 3,–0

0 3,–

21

Air Reservoir 1.

Purpose:Storage of the compressed air deliveredfrom the compressor.

Construction:The reservoir consists of the cylindricalportion in the centre with welded-inarched bases and screw necks for con-necting pipes. The use of high-tensilesteels of even material thickness for allair reservoir sizes permits operatingpressures in excess of 10 bar in air res-ervoirs of volumes below 60 litres.

The reference plate is glued on andmust, in keeping with EN 286: 2, containthe following data: number and date ofthe standard, manufacturer's name, seri-al number, modifications, the manufac-turing date, the licence number, thevolume in litres, permissible operating

pressure, minimum and maximum oper-ating temperatures, the CE symbol if inaccordance with 87/404/EC. The nameplate is covered with a sticker showingthe WABCO part number. In the event ofthe air reservoir having been painted bythe vehicle manufacturer, that stickermust be removed to make the actual ref-erence plate become visible.

The air reservoir should be drained reg-ularly to remove any condensate. It is ad-visable to use drain valves which areavailable for both manual and automaticactuation. Regularly check the mountingon the frame and the clamp clips.

Air Reservoir950 . . . . . . 0

Draining the reservoir with a drain valve

22

Drain Valves1.

Purpose:It prevents the accumulation of water inpipe lines and brake chambers throughautomatically draining the reservoirs.

Operation:Air from the auxiliary port on the unload-er enters the control port 4 and pushesthe piston (a) to its lowest position. Waterfrom the reservoir enters port 1 andpasses into chamber (A) via the undercutdiameter on piston (a).

Water in the control line passes intochamber (A) via the small hole in the pis-ton (a).

As the unloader cuts-out, the pressure inthe control line falls to zero, and the pres-sure in the reservoir pushes the piston(a) to its uppermost position, and the wa-ter is ejected via the undercut diameter(b).

The O-ring check valve covering thesmall hole in piston (a) prevents waterand reservoir air in chamber (A) from en-tering the control line - (which might oc-cur during that last few revolutions of thecompressor when the vehicle engine isswitched off, if it were not for the O-ring).

Automatic Drain Valve434 300 . . . 0

Purpose:To drain condensation water from the airreservoir and, if necessary, to exhaustthe compressed air lines and reservoirs.

Operation:Valve (b) is held closed by spring (a) and

by pressure in the reservoir. Pulling orpushing actuating pin (c) in a lateral di-rection opens tilting valve (b). This per-mits both compressed air andcondensation water to escape from thereservoir. On releasing actuating pin (c),valve (b) closes

Drain Valve934 300 . . . 0

23

Drain Valve And Air Pressure Gauges 1.

Purpose:Protection of the compressed-air equip-ment from ingress of condensate bymeans of automatic draining of the airreservoir.

Operation:When the air reservoir is filled, com-pressed air passes through filter (a ) inchamber (B) on to the valve diaphragm(c). This lifts off the inlet (b) on its outerperiphery. Compressed air flows togeth-er with accumulated condensate, if any,out of the air reservoir into chamber (A),where the condensate accumulatesabove the outlet (d). After pressure equi-librium is established between the twochambers the valve diaphragm (c) clos-es the inlet (b).

If, because of a braking action, for exam-ple, the pressure in the air reservoir falls,the pressure in the chamber (B) is re-duced, while in chamber (A) the full pres-sure is at first maintained. The higherpressure in chamber (A) acts from belowon the insert (c) and lifts it off the outlet(d). The condensate is forced out by theair cushion in chamber (A). When thepressure in chamber (A) has fallen farenough to establish a pressure equilibri-um between chamber (B) and (A) again,the insert (c) closes the outlet (d).

To check the function of the drain valvethe outlet can be opened manually bypressing inwards the pin (e) seated in theoutlet.

Automatic Drain Valve934 301 . . . 0

Purpose:Air pressure gauges are used to monitorthe pressure in air reservoirs and brakelines.

Operation:In the single air pressure gauge 453 002,the pressure from the reservoir stretchesthe tube spring which, via a lever andrack, moves the pointer which is mount-ed on a pivot shaft.In the case of a drop in pressure thepointer is returned to the reading of re-

maining pressure by means of a torsionspring.

In the double air pressure gauge 453197, a further red pointer indicates thepressure of air entering the brake cham-bers when brakes are applied. Whenbrakes are released, a torsion spring re-turns this red pointer to the zero position.Reservoir and service pressure readingsare divided into 0 to 10 and 0 to 25 barsrespectively.

Air Pressure Gauges 453 . . . . . . 0

453 002 453 197

24

Check Valves1.

Purpose:To protect the pressurized lines againstunintentional venting.

Operation:Air can only pass in the direction indicat-ed by the arrow. Return flow of the air isprevented by the check valve closing the

inlet in the event of a drop in pressure inthe supply line.

When the pressure rises in the supplyline, the springloaded check valve againopens the passage which results in anequalization of pressure.

Check Valve 434 01. . . . 0

Check-Choke Valve434 015 . . . 0

Purpose:To make sure that the pressure in airreservoirs is not unintentionally de-creased.

Operation:The compressed air from the feed pipeopens Valve (a) and reaches the air res-ervoir provided its pressure is higherthan that within the reservoir. Valve (a)will remain open until the pressures in

the feed pipe and the reservoir areequal.Valve (a) prevents the air from returningfrom the reservoir as, when the pressurein the feed pipe is reduced, the valve it isclosed by Compression Spring (b) andthe higher reservoir pressure.

Air can pass through the check valveonly in the direction from the feed pipetowards the reservoir.

Purpose:To restrict the air flow, optionally whenthe connected line is pressurized or de-pressurized.

Operation:As the air enters in the direction indicat-ed by the arrow, the check valve (a) fit-ted in the housing is raised off its seatand the connected pipe is pressurizedwith no restriction. When the feed pipe ispressurized, the check valve closes and

Port 2 is vented through the throttlingport (b). The cross-section of the throttlecan be adjusted using the adjusterscrew (c). Turning it clockwise will re-duce the cross-section, thus retardingthe venting process, and turning it anti-clockwise will increase the cross-sec-tion.By connecting the air-supply against thedirection indicated by the arrow, pressu-rizing can be throttled, and venting canbe unrestricted.

Check Valve 434 021 . . . 0

unrestricted in direction of air flow

434 019

434 014

direction of air flow

25

Charging Valve 1.

Purpose:Charging Valve with return flow The passing of compressed air to secondair brake reservoir only when the ratedpressure for the system in the first reser-voir has been reached. If the pressure inthe first reservoir falls below that of thesecond reservoir there is a feedbacksupply of air from the second reservoir.

Charging Valve without return flowThe passing of compressed air to auxilia-ry equipment (e. g. door actuation, auxil-iary and parking braking systems, servoclutch, etc.) only when the rated pressurefor the braking system has been reachedin every air reservoir.

Charging Valve with limited returnflow The passing of compressed air to otherconsumers (e. g. auxiliary and parkingbraking systems) only when the ratedpressure for the braking system hasbeen reached in all reservoirs. Also theprotection of pressure for the motor vehi-

cle in the event of the trailer's supply linefailing.

If the pressure in the air reservoirs of theservice braking system drops, part of thecompressed air will return until the clos-ing pressure (which is dependent on theopening pressure) is reached

Operation:With all charging valves, the compressedair passes in the direction of the arrowinto the housing and through port (g) un-der diaphragm (d) which is pressed intoits seat by adjusting spring (b) and piston(c). When the charging pressure hasbeen reached, the force of the adjustingspring (b) is overcome so that the dia-phragm (d) is lifted from its seat, openingport (e). The air flows directly or afteropening of non-return valve (h) to thereservoirs or consumers in the directionof the arrow.

Charging valves with return flow allowthe compressed air to flow back from the

second reservoir after the opening ofcheck valve (f) if the pressure in the firstreservoir has dropped by more than 0.1bar.

In the case of charging valves without re-turn flow, return flow is not possible sincenon-return valve (h) is kept closed by thehigher pressure in the second reservoir.

Charging valves with limited return flowallow the air to flow back until the closingpressure of diaphragm (d) is reached.When this is reached, adjusting spring(b) presses diaphragm (d) into its seatvia piston (c), thus preventing any furtherpressure compensation in the directionopposite to the direction of the arrow.

The charging pressure can be adjustedon all types by turning adjusting screw(a). Turning clockwise increases charg-ing pressure, turning anti-clockwise hasthe opposite effect.

Charging Valve 434 100 . . . 0

with return flow

without return flow with limited return flow

26

Pressure Limiting Valves 1.

Purpose:To limit the output pressure to a presetvalue.

Operation:The Pressure Limiting Valve is set insuch a way that its output pressure onthe low-pressure side (Port 2) is limited.Spring (a) constantly acts on Pistons (cand d), holding Piston (c) in its upper endposition where it is in contact with Hous-ing (h). Inlet (b) is open. The supply airflows from Port 1 to Chamber C and onto Chamber D, reaching the downstreamcomponents via Port 2.

When the pressure building up in Cham-

ber D exceeds the force of CompressionSpring (a), Pistons (c and d) are forceddownwards. Valve (g) closes Inlet (b)and an end position has been reached.

As air is consumed at the low-pressureside, the pressures at Piston (c) are nolonger balanced. Spring (a) will force Pis-tons (c and d) upwards once again. Inlet(b) opens and more air is supplied untilthe pressure has reached the preset val-ue and the pressures are once again bal-anced.

In the event of the pressure on the low-pressure side exceeding the present val-ue, Piston (c) which is designed as a

safety valve will open Outlet (e). The ex-cess pressure will be released to atmos-phere via Exhaust 3.

If the pressure in Chamber C falls belowthat in Chamber D, Valve (f) will beopened. The compressed air fromChamber D will now return through HoleB to Port 1 until the force of Spring (a) isgreater once more, opening Inlet (b). Thepressures between Ports 2 and 1 are bal-anced.

Please note:The 475 010 ... 0 range of pressure limit-ing valves (see Page 71) is also used onthe motor vehicle.

Pressure Limiting Valve 475 009 . . . 0

Purpose:To limit the output pressure.

Operation:The compressed air from the high-pres-sure side, Port 1, flows through the inlet(e) and Chamber B to the low-pressurePort 2. This also causes the diaphragmpiston (c) to be pressurized through HoleA although this is initially being held in itslower position by the pressure spring (b).

When the pressure in Chamber B reach-es the level set for the low-pressure side,the diaphragm piston (c) overcomes the

force of the pressure spring (b) andmoves upwards, together with thespring-loaded valve (d), closing the inlet(e).When the pressure in Chamber B hasrisen above the preset value, the dia-phragm piston (c) continues to move up-wards and is raised off the valve (d). Theexcess pressure escapes to atmospherethrough the drill hole in the piston rod ofthe diaphragm piston (c) and the ventvalve (a).In the event of any leakage in the low-pressure line, Port 2, causing a loss inpressure, the force acting on the dia-

phragm piston (c) falls and causes it tomove downwards, opening the valve (d).An amount of compressed air equallingthe amount of pressure lost is now fed inthrough the inlet (e). When the pressurein the high-pressure line is reduced, thepressure in Chamber B which is nowhigher will initially open the inlet (e) of thevalve (d). Due to the drop in pressure be-neath the diaphragm piston (c), this pis-ton will move downwards, keeping thevalve (d) open. The pressure in the low-pressure line is reduced by the valveconnected with the high-pressure side.

Pressure Limiting Valve 475 015 . . . 0

27

Brake Valves 1.

Purpose:Sensitive increase and decrease in thepressure of the single-circuit servicebraking system of a motor vehicle.

Operation:When the plunger in the spring plate (a)is actuated, the piston (c) moves down-ward, closing the outlet (d) and openingthe inlet (e). The air supply at Port 11flows through Chamber A and Port 21 tothe downstream braking equipment ofthe service braking circuit.

The pressure building up in Chamber Aacts on the underside of the piston (c).This is forced upwards against the forceof the rubber spring (b) until the force act-ing on both sides of the piston is bal-anced. In this position, both the inlet (e)

and the outlet (d) are closed, and a neu-tral position has been reached.

At full brake application, the piston (c) ismoved to its lower neutral position, andthe inlet (e) remains open.

When the pressure in the service brakingcircuit is to be decreased, this process isreversed and can also be achieved grad-ually. The pressure in Chamber A forcesthe piston (c) upwards. The pressure inthe service braking system is now re-duced partially or fully, depending on theposition of the plunger, through openingthe outlet (f) and Vent 3.

Brake ValveFor Single-Circuit BrakingSystems461 111 ... 0With Treadle461 113 ... 0

461 111

461 113

28

Brake Valves1.

Brake Valve With Treadle461 307... 0

Purpose:Sensitive increase and decrease in thepressure of the twin-circuit service brak-ing system of a motor vehicle.

Operation:When the treadle (r) is pushed down, thegraduating piston (a) moves downwards,closing outlet (p) and opening inlet (o).This causes total or partial increase inthe pressure for the brake cylinders ofthe first circuit and the trailer controlvalve from supply port 11 via port 21, de-pending on the amount of force applied.

In this process, the pressure in ChamberA will initially build up beneath the gradu-ating piston (a) and also, through thehole (n), in Chamber B, acting on the re-lay piston (b) of the second circuit. Therelay piston (b) is forced downwardsagainst the force of the spring (l), takingwith it piston (c). This also causes outlet(j) to be closed and inlet (k) to be opened.Compressed air flows from 12 via Port 22into the brake cylinders of the second cir-cuit which are pressurized according tothe controlling pressure in Chamber B.

Because of the force of the spring (l), thepressure in Chamber C is always slightly

lower than that in Chambers A and B.

The pressure building up in Chamber Aalso acts on the underside of the gradu-ating piston (a) which is thus forced up-wards against the force of the rubberspring (q) until the forces on both sides ofthe piston (a) are balanced. In this posi-tion, inlet (o) and outlet (p) are closed(neutral position).

Similarly, as the pressure is increased inChamber C, acting on the underside ofthe pistons (b) and (c), together with thespring (l), these pistons are forced up-wards until they have also reached theirneutral position, i. e. until inlet (k) andoutlet (j) are closed.

When the brakes are fully actuated, thepiston (a) is moved into its lower neutralposition and inlet (o) remains open. Thefull pressure now present in Chamber Bforces the relay piston (b) into its lowerneutral position, and piston (c) keeps in-let (k) open. The full amount of air supplyflows into both service braking circuits.

When the brakes are released, i. e. thepressure in both circuits is decreased,this process is reversed and can also beachieved gradually. The pressure in bothcircuits is reduced through the releasevalve (h).

In the event of Circuit II failing, Circuit Icontinues to operate as described.Should Circuit I fail, the relay piston (b) isno longer actuated; Circuit II then worksmechanically as follows: When thebrakes are actuated, piston (a) is forceddownward. As soon as it makes contactwith the insert (m) which is firmly con-nected to piston (c), this piston (c) is alsopushed downward in the course of itsdownward stroke; outlet (j) closes and in-let (k) opens. Thus Circuit II continues tobe fully operational even if Circuit I hasfailed since piston (c) now operates as agraduating piston.

Different variants of the brake valve havean additional feature allowing the infinite-ly variable adjustment, within a certainrange, of the predominance of Circuit Iover Circuit II by means of pressure re-tention in Circuit II. For this purpose, theinitial tension of the spring (f) is alteredby means of turning the cap (g). As pis-ton (c) moves downwards, the insert (m)connected to it will first make contact withthe spring-loaded plunger (e) beforeclosing outlet (j) and opening inlet (k).The preset initial spring tension now de-termines which pressure in Chamber Cwill move the piston (c) upward off theplunger (e) to reach its neutral position.

with lever 461 491 . . . 0

29

Brake Valves 1.

461 315 ... 0

461 317 ... 0

Variant 461 315 180 0- integrated noise muffler -

Brake Valve461 315 . . . 0With Treadle461 317 . . . 0

Purpose:Sensitive increase and decrease in thepressure of the twin-circuit service brak-ing system of a motor vehicle. Some variants from the 461 315 ... 0 se-ries have an integrated noise muffler toreduce the space required for installingthe valve.

Operation:When the plunger in the spring plate (a)is actuated, piston (c) moves downward,closing outlet (d) and opening inlet (j).The air supply at Port 11 flows throughChamber A and Port 21 to the down-stream braking equipment of servicebraking circuit I. At the same time, com-pressed air flows via Hole D into Cham-ber B, acting on the upper side of piston(f) which is forced downward, closingoutlet (h) and opening inlet (g). The air

from Port 12 flows through Chamber Cand Port 22 to the downstream brakingequipment of Service Braking Circuit II.

The pressure building up in Chamber Aacts on the underside of piston (c). Thisis forced upwards against the force of therubber spring (b) - in variants 180 againstthe force of the pressure springs - untilthe force acting on both sides of piston(c) is balanced. In this position, inlet (j)and outlet (d) are closed, and a neutralposition has been reached.

Similarly, as the pressure is increased inChamber C, acting on the underside ofpiston (f), forcing it upwards again untilits neutral position has been reached. In-let (g) and outlet (h) are closed.

When the brakes are fully actuated, pis-ton (c) is moved into its lower neutral po-sition and inlet (j) remains open. Thepressure in Chamber B also forces pis-ton (f) into its lower neutral position,keeping inlet (g) open. The full amount ofair supply flows into both service brakingcircuits.

When the pressure in the service brakingcircuit is to be decreased, this process isreversed and can also be achieved grad-ually. The pressure in Chambers A and Cforces the pistons (c and f) upwards. Thepressure in both circuits of the servicebraking system is now reduced partiallyor fully, depending on the position of theplunger, through opening the outlets (dand h) and Vent 3.

In the event of one circuit failing, e. g. Cir-cuit II, Circuit I continues to operate asdescribed. If, however, Circuit I fails, pis-ton (f) is moved downwards by the valvebody (e) when the brakes are actuated.Outlet (h) closes and inlet (g) opens. Aneutral position has been reached, asdescribed above.

30

Brake Valves1.

Purpose:Sensitive increase or decrease in thepressure in the dual-circuit service brak-ing system of the motor vehicle andelectrical actuation of the retarder.

Operation:When the treadle (a) is pushed down,Switch I and subsequently, when themechanical pressure point has beenovercome, Switch II are actuated. Thiscauses the first or second braking stageof the retarder to be activated withoutany compressed air flowing into theservice braking system.

As the treadle (a) is pushed down fur-ther, Switch III is actuated, activating thethird braking stage of the retarder. At thesame time the piston (c) moves down-ward.

The operation of this brake valve is sim-ilar to that of 461 315 (description onPage 29).

When the pressure in the two circuits ofthe service braking system is being de-creased, the switching stages of the re-tarder are deactivated as the treadle (a)moves upwards.

Fig. 2 shows a treadle with a built-inproximity switch which is activated whenthe treadle has moved through approx. 2degrees.

Brake Valve With Electrical Switch Or Sensor461 318 . . . 0

Fig. 2

31

Brake Valves 1.

Purpose:Sensitive actuation of the dual circuittruck during brake application and re-lease service brake system. Automaticcontrol of the front brakes through the in-tegrated auto load proportioning valve.

Operation:Operation of pushrod located in springseat (a) forces piston (c) downward, clos-ing outlet (d) and opening inlet (j). Supplypressure at port 11 flows via chamber Aand port 21 to brake boosters installeddownstream as part of service brake cir-cuit I. At the same time compressed airflows through port E into chamber B, ex-erting pressure against surface x1 of pis-ton (f). This is forced downward, openingoutlet (h) and closing inlet (g). Supplypressure air at port 12 flows via chamberC and port 22 to brake boosters fitteddownstream as part of service brake cir-cuit II.

Actual pressure reaching circuit II (seepressurized air circuit) is dependent onpressure modulated by the automaticload proportioning valve. This reacheschamber D via port 4, exerts pressureagainst surface x2 of piston (f), thus aug-menting the force exerted against the topof piston (f).

The pressure built up in chamber A ex-erts a force against the bottom of piston(c). This is forced upward against thepressure exerted by rubber spring (b) un-til pressure is equalized at both ends ofpiston (c). Both inlet (j) and outlet (d) areclosed in this position. An end position isreached.

Correspondingly, pressure built up inchamber C forces piston (f) to move up-ward again, until here too an end positionis reached. Both inlet (g) and outlet (h)are closed.

When brake is applied fully, piston (c) isforced to its lower end position, while theoutlet (j) remains open at all times. Thesupply pressure air acting on surface x1via port E in chamber B, augmented bythe full brake pressure of the rear axlecircuit, forces piston (f) into its lower endposition. Inlet (g) is opened and the sup-ply pressure air flows unimpeded intoboth service brake circuits.

The two service brake circuits are ex-hausted in reverse sequence. This toocan be carried out in steps. The brakepressure built up in chambers A and Cforces the pistons (c) and (f) upwards.Both service brake circuits are fully or

partially exhausted - depending on push-rod position - via the outlets (d) and (h)as these open, as well as through vent 3.The pressure in chamber D is reducedvia the automatic load proportioningvalve fitted upstream.

If pressure is lost in one circuit, e. g. cir-cuit II, circuit I continues to function in themanner described. If, however, there is aloss of pressure in circuit I, piston (f) isforced downward by valve body (e) whenbrakes are applied. Outlet (h) closes andinlet (g) opens. An end position isreached as described above.

Brake Valve461 319 . . . 0

32

Brake Valves1.

Purpose:Sensitive increase or decrease in thepressure in the dual-circuit service brak-ing system of the motor vehicle andpneumatic control of the retarder via thebuilt-in pressure control valve.

Operation:When the treadle (a) is pushed down, thelever (b) initially moves the valve (g)downwards. Outlet (d) closes and inlet (f)opens. The air supply present at Port 13flows through Chamber A and Port 23 tothe downstream retarder. The pressurebuilding up in Chamber A acts on the pis-ton (e). As soon as the force resultingtherefrom is greater than that of the pres-sure spring (c), the piston (e) is forceddownwards. Inlet (f) closes and a neutralposition has been reached. As the trea-dle (a) is pushed down further, the pres-

sure at Port 12 is increased as a ratio oftreadle travel. At the end of the idle trav-el, the pressure in Chamber A is greaterand the pressure is no longer increasedat Port 23 when the service braking sys-tem of the motor vehicle becomes oper-ative.

The operation of the brake valve is simi-lar to that of 461 315 (description onPage 29).

When the pressure in the two circuits ofthe service braking system has been de-creased, the valve (g) is again pushedupwards during the idle travel of the trea-dle (a). Outlet (d) opens and the com-pressed air from Port 23 is reduced viaVent 3 of the pressure control valve.

Brake Valve461 324 . . . 0

Brake Valve With Lever461 482 . . . 0

33

Single Chamber Brake Actuator 1.

Purpose:Producing the brake force at the wheelbrakes using compressed air. Units areavailable with mechanical or hydraulicoutputs.

Operation:As soon as air enters the actuator, the

force on the piston is transmitted throughthe push rod onto the brake lever (or thehydraulic master cylinder). When thepressure is released, the spring pushesthe piston (or the diaphragm) back to itsrunning condition.

Piston Cylinder421 0. . . . . 0 and 921 00 . . . . 0

Brake Chamber423 00 . . . . 0 and 423 10 . . . . 0

Brake Chamber For Expanding Wedge Brake423 0. . . . . 0 and 423 14 . . . . 0

for Disc Brake

34

Air/Hydraulic Actuators1.

Purpose:Pneumatic actuation of the attached hy-draulic master cylinder in air/hydraulicbraking systems.

Operation:When the service braking system is actu-ated, the compressed air from the brake

valve flows through Port A and intoChamber B. The pressure building upthere forces the piston (a) to the rightagainst the force of the pressure spring(c). Force F, this being pressure timessurface, is being transferred via the pres-sure bar (b) onto the piston of the flangedmaster brake cylinder.

When the braking process is ended, thepressure in Chamber B is reduced by theupstream brake valve. At the same time,the pressure spring (c) returns the piston(a) to its original position.

Piston Type Air/HydraulicActuator421 30 . . . . 0

Air/Hydraulic DiaphragmActuator423 0 . . . . . 0

Purpose:Pneumatic actuation of the attached hy-draulic master cylinder in air/hydraulicbraking systems.

Operation:When the service braking system is actu-ated, the compressed air from the brakevalve flows through Port A and intoChamber B. The pressure building upthere acts on the diaphragm (a) andpushes it, together with the piston (b), tothe right against the force of the pressurespring (d). Force F, this being pressure

times surface, is being transferred via thepressure bar (c) onto the piston of theflanged master brake cylinder.

When the braking process is ended, thepressure in Chamber B is reduced by theupstream brake valve. At the same time,the pressure spring (d) returns both thepiston (b) and the diaphragm (a) to theiroriginal positions.

A filter (e) fitted in front of the air outletholes of the cylinder cover prevents dirtor dust penetrating into the inside of the

cylinder when the piston (b) returns to itsoriginal position.

These diaphragm actuators can have awear and/or stroke indicator fitted for thedriver to see which condition the wheelbrakes are in.

Mechanical wear indicators are designedas drag indicators, i. e. it does not returnautomatically. It is actuated after 50% ofthe total stroke and has markings show-ing the driver the amount of wear on thebrake linings.

35

Tristop ® - Spring Brake Actuator425 3 . . . . . 0 for ExpandingWedge Brakes and925 . . . . . . 0 for Cam Brakes

Purpose:Combined spring brake - diaphragmbrake chambers (Tristop ® Spring BrakeActuators) are used to generate thebrake force for the wheel brakes. Theyconsist of the diaphragm portion for theservice braking system and the spring-loaded portion for the auxiliary and park-ing braking systems.

Operation:a) Service Braking System:When the service braking system is actu-ated, compressed air flows into ChamberA via Port 11, acting on diaphragm (d)and forcing piston (a) to the right againstcompression spring (c). Via piston rod(b), the force generated acts on the slackadjuster and thus on the wheel brake.

When the pressure in Chamber A is re-duced, compression spring (c) movespiston (a) and diaphragm (d) back intotheir original positions. The brake cham-ber of the Tristop ® Spring Brake Actua-tor operates independently from itsspring-loaded portion.

b) Parking Brake:When the parking brake is actuated, thepressure in Chamber B is fully or partiallyreleased via Port 12. In this process, theforce of the relaxing compression spring(f) acts on the wheel brake via piston (e)and pressure rod (b).

The maximum braking force of thespring-loaded portion is achieved whenChamber B is pressureless. Since thisbraking force is achieved exclusively bymechanical means, i. e. by compressionspring (f), the spring-loaded portion maybe used for the parking brake. When thebrake is released, the pressure is onceagain increased in Chamber B via Port12.

c) Mechanical Release Mechanism:For emergencies, the Tristop ® SpringBrake Actuator has a mechanical re-lease mechanism for its spring-loadedportion. Should the pressure at Port 12fall to zero, the hexagon head screw (g)wrench size 24 can be screwed out to re-lease the parking brake.

d) Quick-Release Facility(only 425 ... ... 0)To actuate the quick-release function,the bolt head (h) is hit with a hammer.This causes the balls (i) to be releasedfrom the locking mechanism and thepressure bar (f) is returned by the returnforces of the wheel brake.

After remedying the loss in pressure,Port 12 is pressurized once again. Thereturning piston (e) again prestressesthe compression spring (f). At the sametime, the balls (i) lock back into place.

Tristop ® - Spring Brake Actuator 1.

425 ... ... 0

925 ... ... 0

36

Slack Adjuster1.

Automatic Slack Adjuster433 54 . . . . 0 and 433 57 . . . . 0

Slack Adjuster433 50 . . . . 0

Purpose:Transmission of the brake forces to thewheel brake. Automatic readjustment ofthe brake shaft to compensate for liningwear, making the brake cylinder operateroughly within the same stroke range.

Operation:When the brakes are not actuated, thelower edge of the adjuster plate’s jaw isin contact with the pin (e) acting as afixed point. When the brakes are actuat-ed, the adjuster plate (b) covers the dis-tance between the pin (e) and the upperedge of the jaw.

If lining wear has caused the stroke ofthe brake cylinder to increase, the upper

edge of the adjuster plate’s jaw (b)makes contact with the pin (e) and is heldthere. This causes the coupling (g) con-nected to the adjuster plate (b) to beturned in the winding direction of theclutch spring (c) on the worm shaft (f).When the brakes are released, the SlackAdjuster returns to its original position,with the lower edge of the adjusterplate’s jaw again resting against the pin(e), turning the coupling (g) on the wormshaft (f) against the winding direction ofthe clutch spring (c). This turning motioncauses the clutch spring (c) to be un-wound and to sit firmly against the hole inthe coupling (g) of the adjuster ring (d).The resulting high coefficient of frictiondrives the adjuster ring (d) which inter-

locks with the worm shaft (f). The wormshaft (f) and the worm wheel (h) now turnthe brake shaft in the operating direction,thus achieving the best possible adjust-ment for the wheel brake.

To prevent vibrations from turning thecoupling (g) on the worm shaft (f), it ispushed against the adjuster ring (d) bythe spring (a) and thus held in place.

In addition to the version described here,there is one variant which is actuated inthe opposite direction. In that case, thepin (e) is in contact with the upper edgeof the adjuster plate’s jaw (b). Adjust-ment is effected in the same way.

Purpose:Easy, quick and continuous readjust-ment of the brake shaft to compensatefor lining wear, making the brake cylinderoperate roughly within the same strokerange.

(Particularly important for hard linings orpower brakes, and if brake chambers areused, because of the shorter pistonstroke.)

Operation:For readjustment, a ring spanner isplaced on the hexagon (b) of the SlackAdjuster’s mechanism and moved byturning the worm (a). The brake shaftand thus the brake cam are readjustedvia the worm wheel (d). The ball catch (c)for the hexagon (b) prevents unintention-al adjustment of the Slack Adjuster.

371

Hand Brake Valves 1.

Purpose:Sensitive actuation of the trailer controlvalve in order to prevent jack-knifing ofarticulated vehicles and other tractor-trailer combinations (underrun brake).

Operation:In the driving position, the supply pres-sure at Port 1, supported by the pressurespring (i), keeps the valve (g) closed.When the hand lever (a) is in its neutralposition, the cam (c) transfers no forceonto piston (l). The pressure springs holdthe pistons (k and l) in its upper neutralposition, and Port 2 is connected withExhaust 3.

When the hand lever (a) is actuated, thecam (c) forces piston (l) downwards. Thesprings (d and e) are compressed, alsocausing piston (k) to be displaced. Thevalve seat (h) closes the passage be-tween Chamber A and Exhaust 3, andthe valve (g) is raised of the valve seat(j).

The air supply flows into Chamber A andthrough Port 2 to the downstream trailercontrol valve until a pressure level isreached which is similar to the preten-sion of the springs (d and e). The valve(g) closes the inlet valve seat (j) withoutopening the outlet valve seat (h). A finalposition has been reached.

Any additional change in the position ofthe lever also causes the tension of thesprings to alter and output of a corre-sponding control pressure as a ratio ofthe force applied by the cam (c). Similar-ly it is possible to grade evacuation, ei-ther within the partial braking range or forcomplete evacuation of the pilot lineleading to the trailer control valve.

The Hand Brake Valve can be suppliedwith a feature permitting the hand leverto be locked into various positions. Lock-ing or unlocking of this feature isachieved by pushing a button (b).

Hand Brake Valve961 721 . . . 0

38 1

Hand Brake Valves1.

Hand Brake Valve961 722 2. . 0

Purpose:Sensitive actuation of the auxiliary brak-ing system and the parking brake in com-bination with the spring brake actuator.Control position to check the motor vehi-cle’s parking brake.

Design:The Hand Brake Valve consists of a ba-sic valve for the auxiliary and parkingbraking systems which may, dependingon the variant used, also have a safetycircuit valve (emergency release valve)and/or a test valve.

Hand Brake Valve961 722 1. . 0

Purpose:Sensitive actuation of the auxiliary brak-ing system and the parking brake in com-bination with the spring brake actuator.

21

11

3

b

eA

dB

g

FeststellbremsstellungFahrtstellung

a

driving position parking brake position

Version I

22

21

11

3

b

H

cGe

F

A

dB

g

Druckpunkt

Feststellbremsstellung

Prüfstellung

Fahrtstellung

a


test positionworking point

39

Hand Brake Valves 1.

Version I (Variant 252)The test valve combined with the basicvalve can be used to determine whetherthe mechanical forces of the towing vehi-cle’s parking brake are great enough tohold the tractor-trailer combination on acertain uphill or downhill gradient whenthe trailer’s braking system is released.

In the driving position, Chambers A, B, F,G and H are connected and the supplypressure flows to the spring compressionchambers through Port 21 and to thetrailer control valve through Port 22.When the hand lever (a) is actuated, thepressure in Chambers B, F and H is re-duced until it is fully evacuated when theworking point has been reached. Whenthe working point is exceeded, the actu-ating lever reaches an intermediate posi-tion: that of the locked parking brake. Bymoving the lever further to its test posi-tion, the compressed air in Chamber Aflows through Chamber G and openedvalve (c) into Chamber H. By pressuriz-ing Port 22, the relay-emergency valve isactuated which in turn neutralizes the

pneumatic actuation of the brakes in thetrailer which occurred when the auxiliaryor parking brake was actuated. The trac-tor-trailer combination is now held by themechanical forces of the towing vehicle’sspring brake actuators alone. As soon asthe actuating lever (a) is released, it re-turns to its parking brake position inwhich the trailer’s braking system sup-ports the parking brake.

Version II (Variant 262)for power-driven vehicles withpneumatic release deviceAnnex V of the Guideline of the Councilof the European Community defines thatspring braking systems have to have ei-ther a mechanical or a pneumatic auxilia-ry release device. In Version II, the basicvalve has been combined with a safetycircuit valve (emergency release valve)which is intended as a pneumatic auxilia-ry release device.

From separate supply circuits, both Ports11 and 12 are pressurized with com-pressed air. The output pressures 21 and23 reach the spring brake actuatorthrough a 2-way valve. In the event of a

burst pipe causing the pressure to fail an-ywhere in the spring compression circuit,this does not cause uncontrolled emer-gency braking. The emergency releasevalve acts as a pipe rupture safeguardand protects the pressure in the springbrake actuator through the intact 2nd cir-cuit. The driver is alerted to the defect bythe release control lamp but the springbrake actuator remains in its releasedposition.

When the hand lever (a) is turnedthrough approx. 10°, the valve (f) willclose the passage between Chambers Eand D. The compressed air at Port 23 isevacuated to atmosphere throughChamber C and Port 1. Subsequently thenormal, graduated function of the basicvalve begins for braking or parking thevehicle.

Operation:In the driving position, the passage lead-ing from Chamber A to Chamber B isopen and the air at Port 11 flows throughPort 21 into the spring compressionchambers of the Tristop ® Spring BrakeActuators. When the auxiliary brakingsystem is actuated via the hand lever (a),valve (e) closes the passage betweenChambers A and B. The compressed airfrom the spring compression chambersescapes to atmosphere through theopen outlet (d) at Port 3. This causes thepressure in Chamber B to fall and thepiston (b) is forced downwards by thepressure spring (g). As the outlet closes,a final position is reached in all partialbraking positions so that there is alwaysthe right amount of pressure dependingon the desired retardation.

When the hand lever (a) is moved furtherbeyond the working point, a parkingbrake position is reached. Outlet (d) re-mains open and the compressed air isevacuated from the spring compressionchambers.

Within the auxiliary braking range be-tween the driving position to the workingpoint, the hand lever (a) will automatical-ly return to the driving position when re-leased.

23

21

11

3

b

12

Druckpunkt

FeststellbremsstellungFahrtstellung

e

Ad

B

g

Cf

DE

a

Version II


working point

40

Hand Brake Valves1.

Hand Brake Valve961 723 ... 0

Purpose:Actuation of the linkage-free auxiliarybraking system and the parking brake incombination with spring brake actuatorsfor power-driven vehicles which have notrailer attached.

Hand Brake Valve 961 723 1.. 0 is usedtogether with spring brake actuators forlinkage-free auxiliary and parking brak-ing systems. The additional port for actu-ation of the trailer control valve permitsthe transmission of the brake forces tothe trailer. A control position to check themotor vehicle’s parking brake has beenintegrated.

Operation:1. Auxiliary BrakeIn the driving position, valve (c) keepsthe passage between Chambers A and Bopen and the air supply at Port 1 flowsthrough Port 21 and on into the springcompression chambers of the Tristop®Spring Brake Actuators. At the sametime, compressed air flows through thetest valve (b) into Chamber C and on toPort 22, acting on Port 43 of the trailercontrol valve.

When the auxiliary braking system is ac-tuated by means of the hand lever (a),valve (c) closes the passage betweenChambers A and B. The compressed airfrom the spring compression chambersescapes to atmosphere through theopened outlet (d) at Port 3. This alsocauses the pressure in Chamber B todrop, and the piston (e) is forced down-ward by the force of the pressure spring(f). As the outlet closes, a neutral positionis reached in all partial braking positions,thereby ensuring that the spring com-pression chambers always contain theappropriate pressure for the desired re-tardation.

2. Parking PositionWhen the hand lever (a) is moved furtherbeyond the working point, the parkingposition is reached. The outlet (d) re-mains open and the compressed air fromthe spring compression chambers isevacuated completely.

Within the auxiliary braking range, fromthe driving position to the working point,the hand lever (a) will automatically re-turn to its driving position when released.

The test valve combined with the basicvalve can be used to ascertain whetherthe mechanical forces of the towing vehi-cle’s parking braking system are capable

of holding the tractor-trailer combinationon a certain uphill or downhill gradientwhen the trailer’s braking system is notactuated.

3. Test PositionIn the driving position, Chambers A, Band C are connected and the supplypressure flows through Port 21 to thespring compression chambers andthrough Port 22 to the trailer controlvalve. When the hand lever (a) is actuat-ed, the pressure in Chambers B and C isreduced until it is fully evacuated whenthe working point is reached. Whenmoved beyond the working point, thehand lever (a) reaches an intermediateposition: the locked parking position.

When the hand lever (a) is then movedfurther into the test position, the com-pressed air from Chamber A flowsthrough the open valve (b) into ChamberC. By acting on Port 22, the relay-emer-gency valve is actuated which in turnneutralizes the pneumatic actuation ofthe brakes on the trailer caused by theuse of the auxiliary or parking brake. Thetractor-trailer combination is now beingheld by the mechanical forces of the tow-ing vehicle’s spring-brake actuators. Assoon as the hand lever (a) is released, itwill return to its parking brake positionwhich assists the trailer’s parking brake.

961 723 1 . . 0961 723 0 . . 0

41

Solenoid Valves 1.

Purpose:To pressurize an air line when current issupplied to the solenoid.

Operation:The supply line from the air reservoir isconnected to port 1. The armature (b)which forms the valve core keeps inlet(c) closed by the load in pressure spring(d).

When a current reaches solenoid coil (e),armature (b) is lifted, outlet (a) is closed

and inlet (c) is opened. The compressedair from the supply line will now flow fromport 1 to port 2, pressurizing the workingline.

When the current to solenoid coil (e) isinterrupted, pressure spring (d) will re-turn armature (b) to its original position.Inlet (c) is closed, outlet (a) is openedand the working line is exhausted viachamber (A) and exhaust 3.

3/2-Way Solenoid Valvenormally open472 17. . . . 0

Purpose:To vent an air line when current is supp-lied to the solenoid.

Operation:The supply line from the air reservoir isconnected to port 1 and thus air is allo-wed to flow through chamber (A) andport 2 into the working line connected toport 2. The armature (b) which forms thecore of the valve is forced down byspring (d), closing outlet (c).

When a current reaches solenoid coil (e),the armature (b) is lifted, inlet (a) is clo-

sed and outlet (c) is opened. The com-pressed air from the working line will nowescape to atmosphere via port 3 and thedownstream operating cylinder is exhau-sted.

When the current to solenoid coil (e) isinterrupted, pressure spring (d) will re-turn armature (b) to its original position.Outlet (c) is closed and inlet (a) is ope-ned, again allowing air to pass to theworking line via chamber (A) and port 2.

3/2-Way Solenoid Valvenormally closed472 07. . . . 0 and472 17. . . . 0

42 1

Relay Valves1.

Overload Protection Valve473 017 . . . 0 and973 011 20 . 0

Purpose:Prevention of compounding of forces incombined spring brake cylinders andbrake chambers (Tristop brake actua-tors) during simultaneous operation ofthe service and spring brake systems.and thereby protection of the mechanicalactuation equipment against overload.Also rapid supply and evacuation of com-pressed air from spring brake cylinders.

In the 973 011 20. 0 series, the usualconnection (brake valve connected toPort 41 and hand brake valve connectedto Port 42) will cause a reduced pressure(p42 = 8 bar, p2 = 6.5 bar) to reach thespring-loaded portions of the Tristop ®Spring Brake Actuators while the handbrake valve is in the driving position (sa-ving energy in normal driving operation).

Operation:a) Driving position.In the driving position, chamber (A) iscontinuously supplied with compressedair through port 42 from the handbrakevalve. The pressurized piston (a), togeth-er with piston (b), keeps outlet (e) closedand through the depressed valve stem(c) keeps inlet (d) open. Port 2 receivesthe full pressure from the reservoirthrough port 1. The spring brake cylin-ders connected to port 2 are suppliedwith compressed air (reduced if variant973 011 20. 0 is used), and the springbrakes are released.

b) Actuation of the service brake system alone.On actuation of the vehicle brake valve,compressed air flows through port 41 intochamber (B) above piston (b). Becauseof the counter-forces in chambers (A)and (C), the pressure reaching chamber(B) has no effect on the operation of therelay valve. The spring brake section ofthe Tristop actuators continues to be

supplied with compressed air and theyare thus released, while the diaphragmsection supplied with compressed air di-rectly from the tractor brake valve reacts.

c) Actuation of the spring brake system alone.Actuation of the handbrake valve effectspartial or complete evacuation of cham-ber (A). Piston (a), relieved of pressure,is pushed upwards by piston (b), which isexposed to the reservoir pressure inchamber (C). Outlet (e) thereby opens,while inlet (d) is closed by the rising valve(c). This results in evacuation, accordingto the position of the handbrake lever, ofthe spring brake cylinders through port 2,valve stem (c) and exhaust port 3, so thatthe spring brakes are actuated.With partial brake application, outlet (e)closes after the process of evacuationand the pressure equilibrium whichthereby arises in chambers (A) and (C).The relay valve is thus in the neutral po-sition. However, with full brake applica-tion inlet (e) remains open.

473 017 ... 0 973 011 20. 0

431

Relay Valves 1.d) Simultaneous actuation of the service and spring brake systems.1. Service braking with evacuated, i. e.,actuated spring brake cylinders.The spring brake reservoirs are evacuat-ed. If the service brake is also actuated,compressed air flows through port 41into chamber (B) and acts on piston (b),which since chamber (C) is evacuated,moves downwards to close outlet (e) andopens inlet (d) through valve (c). Com-pressed air now flows from 1 throughchamber (C) to 2 and into the springbrake reservoirs. The spring brake isthereby released but only to the extendthat the service brake pressure rises.There is therefore no compounding ofthe two braking forces.

The pressure building up in chamber (C)raises piston (b) as soon as the pressuredelivered at 2 has become greater thanthe pressure present in chamber (B). In-let (d) closes and the relay valve is in theneutral position.

2. Spring braking while service brake isbeing actuated.The service braking system is being ac-tuated within the partial braking range, i.e. Chamber B is pressurized. If now theparking brake is actuated in addition,causing the pressure in Chamber A to bereduced, the supply pressure in Cham-ber C forces the pistons (a and b) up-wards. The valve body following themcloses the inlet (d) and opens the outlet(e). Depending on the level of the servicebraking pressure, compressed air fromthe spring compression chambers will beevacuated to atmosphere through theoutlet (e) and Vent 3 until the pressure inChamber B is greater once again and thepiston (b) closes the outlet (e). A neutralposition has been reached.

When the hand brake valve is actuatedfully, Port 42 is evacuated completely.Since it is impossible for the pressure inChamber C to be lower than that inChamber B, the spring brake is only op-

erated to the extent permitted by the re-spective braking pressure. Compound-ing of the brake forces does not takeplace when the brakes are actuated fully.

On vehicles with an emergency releasefacility, this type of connection may notbe used for Variant 973 011 2.. 0 (differ-ent diameters of pistons a and b). To pre-vent a difference in pressures at thedownstream two-way valve, actuation ofthe hand brake valve must be throughPort 41, and that of the brake valve atPort 42.

When the service brake is released (withparking brake still being actuated),Chamber B is evacuated once again.The pressure in Chamber C is greater,forcing piston (b) upwards. Outlet (e)opens and the spring compressionchambers are connected with Vent 3.

Relay Valve(Plastic Type)973 006 . . . 0

Purpose:Control of the spring-loaded portion onlyin the Tristop ® Spring Brake Actuatorand more rapid increase or decrease inpressure when the hand brake valve isactuated.

Operation:The output pressure from the hand brakevalve flows into Chamber A through Port4, forcing piston (a) into its lower end po-sition, closing the outlet (b) and openingthe inlet (c). The air supply at Port 1 now

flows into Chamber B and through Port 2into the spring-loaded portion of the Tris-top® Spring Brake Actuator.

When the hand brake valve is operated,the pressure in the pilot line is partly orfully evacuated at Port 4. Piston (a) ispushed upward once again by the pres-sure in Chamber B, and the excess pres-sure at Port 2 is evacuated toatmosphere through the outlet (b) andVent 3.

44 1

Relay Valves1.Relay Valve With AdjustablePredominance973 003 000 0

Purpose:To rapidly increase or decrease thepressure of compressed air equipmentand to shorten the response and pres-sure build-up times in air braking sys-tems.

Operation:When the braking system is actuated,compressed air flows through Port 41into Chamber A, forcing the pistons (aand b) downwards. This causes the out-let (c) to be closed and the inlet (e) to beopened. The air supply preset at Port 1flows through Chamber B and on toPort2 to, providing pressure for thedownstream brake cylinders, accordingto the actuating pressure, with a pre-dominance depending on the preset ini-tial tension of the pressure spring (g).

The pressure building up in Chamber Bacts on the undersides of the pistons (aand b). Because of the difference in theeffective areas of piston (a), only piston

(b) is forced upwards against the actuat-ing pressure in Chamber A and the forceof the pressure spring (g). The valve (d)following piston (b) closes the inlet (e)and a neutral position has beenreached.

By turning the adjuster screw (f), the ini-tial tension of the pressure spring (g) canbe changed to achieve a pressure pre-dominance of Ports 2 over Port 41 of upto 1 bar.

When the pressure in the pilot line is par-tially reduced, piston (a) is forced up-wards once again, opening outlet (c),and the excess pressure at Ports 2 isevacuated through Vent 3. If the actuat-ing pressure at Port 41 is fully evacuat-ed, the pressure in Chamber B pushespistons (a and b) to their upper neutralposition and the outlet (c) opens. Thedownstream brake cylinders are evacu-ated fully through Vent 3.

451

Automatic Load Sensing Valves 1.

Purpose:Automatic regulation of the braking forceat the hydraulic wheel cylinders in rela-tion to the load on the vehicle.

Operation:The load sensing valve is fastened to thechassis frame and controlled by a ten-sion spring (c), which is connected to theback axle either directly or by means of alink lever and rod. With increasing load-ing the distance between the axle andthe frame changes. As a result the ten-sion spring (c) is more heavily loadedand the resulting force is carried throughthe lever (b), the bolt (a) as well as thepiston (l) to the load sensing valve.

On applying the service brake systemand with it the hydraulic brake mastercylinder, the hydraulic brake pressurebuilding up in the rear axle circuit passesthrough port 11 into space (A). The pres-sure travels further through the opened

passage (d), into space (D) and port 21to the rear axle wheel cylinders. At thesame time the brake pressure in the frontaxle circuit passes through the port 12into space (B) and moves the piston (h)to the right and end of its stroke againstthe force acting on its rear side in space(A). Should the hydraulic brake pressureinside the rear axle circuit and thereforein space (D) rise above the valve, whichcorresponds with the spring force ap-plied at the lever (b), the pressure inspace (D) moves the piston (l) to theright. The valve (e) closes the passage(d) and a shut-off position is reached.

With a further increase in pressure atport 11, the valve (e) remains closed,and no increase in the output pressuretakes place (cut-off characteristic).

With a reduction in the hydraulic pres-sure at port 11 the higher pressure inspace (D), which acts through the drilling

(C) on the non-return valve (f), movesthis to the left against the force of thespring (g). The brake pressure in the rearaxle circuit now falls through the drilling(C), the by-pass (k) and the port 11. Theforce of the tension spring (c) pressesthe piston (l) back to the left, the valve (e)opens the passage (d) and the brakepressure now passes through the pas-sage (d) to port 11.

Should the front brake circuit fail the hy-draulic brake pressure will only build upon applying the service brake system inspaces (A and D). With it the piston (h) ispressed to the left and end of its stroke.The valve tappet (j) pulls the valve (e) upand the passage (d) remains constantlyopen. The hydraulic brake pressure nowpasses unhindered to the rear axle wheelcylinders.

Automatic Load SensingValve468 402 . . . 0

46 1

Automatic Load Sensing Valves1.

Purpose:Automatic regulation of the braking forceat the hydraulic wheel cylinders in rela-tion to the load on the vehicle.

Operation:The load sensing valve is fastened to thechassis frame and controlled by a ten-sion spring (c) which is connected to theaxle either directly or by means of a linklever and rod. With increasing loadingthe distance between the axle and theframe changes. As a result the tensionspring (c) is more heavily loaded and theresulting force is transmitted through thelever (b). the bolt (a) and the piston (f) tothe brake apportioning valve.

On applying the service brake systemand with it the hydraulic brake mastercylinder the hydraulic brake pressurebuilding up in the rear axle circuit passesthrough port 1 into space (A), the pres-sure passes through the opened valve(d) into space (B) and further throughport 2 to the rear axle wheel cylinders.Should the hydraulic brake pressure in-side the rear axle circuit and therefore inspace (B) rise above the valve, whichcorresponds with the spring force ap-plied at the lever (b), the pressure in

space (B) moves the piston (f) to theright. The valve (d) closes and a shut-offposition is reached.

With a further increase in pressure atport 1, and therefore in space (A) thepiston (f) is again moved to the left. Thevalve (d) open and fluid passes throughport 2 to the wheel cylinders, increasingthe pressure. When the force to the righton piston (f), resulting from the pres-sures in spaces (A and B) again reactsthe valve corresponding to the springforce applied at the lever (b), the valve(d) closes again.

With a reduction in the hydraulic brakepressure at port 1 and with it also inspace (A), the valve (d) is openedthrough the pressure present in space(B). The brake pressure in the rear axlecircuit is now reduced through port 1 andthe previously operated master cylinder.The force of the draw spring (c) transmit-ted by the bolt (a) presses the piston (f)back to the leftward end of its stroke dur-ing a pressure decrease in space (B).The valve (d) rests on the housing (e)and remains open.

Automatic Load SensingValve 468 404 . . . 0

471

Automatic Load Sensing Valves 1.Automatic Relay Load Sensing Valve 475 710 . . . 0

Purpose:To automatically control the brakingforce as a function of the spring deflec-tion and thus of the vehicle load. The in-tegral relay valve ensures rapid supplyand exhaust of the brake actuators.

Operation:The valve is mounted on the vehiclechassis and connected to a fixed point onthe axle by a flexible arm or a linkage.When the vehicle is empty, the distancebetween the axle and the valve is great-est and lever (j) is in its lowest position.As the vehicle is loaded, this distance isreduced and lever (j) moves from its”empty“ position towards its ”fully laden“position. The movement of lever (j) caus-es cam (i) to rotate and to lift valve tappet(h) to a position corresponding to the ve-hicle load.

On application of the brakes, air from thetruck foot-brake valve or relay emergen-cy valve enters chamber (A) via port 4,forcing down piston (b). Outlet (d) isclosed and inlet (m) opened. Com-pressed air at port 4 reaches chamber(C) below diaphragm (e), acting on theeffective surface area of relay piston (f).

At the same time, air flows into chamber(D) via opened valve (a) and passage(E), acting on the upper side of dia-phragm (e). This initial by-pass pressureeliminates any reduction in pilot pressure(up to 1.0 bar max.) in the ”partially lad-en“ condition. As the pilot pressure con-tinues to rise, piston (n) is forced upagainst the load of spring (o), closingvalve (a).

The pressure building up in chamber (C)forces down relay piston (f). Outlet (g)closes and inlet (k) opens. The supplypressure at port 1 now flows into cham-ber (B) via inlet (k) and to the brake actu-ators via ports 2. At the same time,pressure builds up in chamber (B) actingon the underside of relay piston (f). Assoon as this pressure exceeds the pres-sure in chamber (C), relay piston (f)slides down, closing inlet (k).

As piston (b) moves down, diaphragm (e)is forced against vane (I). As soon as theforce in chamber (C) acting on the under-side of the diaphragm is equal to theforce acting in piston (b), the pistonmoves upward. Inlet (m) is closed. A bal-anced position is reached.

The position of valve tappet (h) which iscontrolled by the position of lever (j) de-termines the output pressure. Piston (b)with vane (I) need to cover a certainstroke depending on the position of valvetappet (h) before valve (c) begins to op-erate. This stroke also changes the ef-fective surface area of diaphragm (e). Inthe ”fully laden“ position, the input pres-sure at port 4 is the same as that reach-ing chamber (C). As full pressure isapplied to relay piston (f), it keeps inletvalve (k) open and the brake pressure isnot regulated.

When the pilot pressure at port 4 is re-duced, relay piston (f) is forced up by thepressure in ports 2. Piston (b) is forcedup by the pressure in chamber (C). Out-lets (d and g) open and the compressedair escapes to atmosphere via exhaust 3.

In the event of the linkage breaking, thevalve will automatically move to theemergency control curve of the cam (i)whose output pressure is approximatelyhalf the service braking pressure whenthe vehicle is fully laden.

48 1



Purpose:Automatic control of the brake force de-pending on the bellows pressure andthus on the load of the vehicle. The inte-grated relay valve assures quick pressu-rizing and venting of the brake cylinders.

Operation:The load-sensing valve is actuated bythe pressure of both circuits of the air bel-lows from Ports 41 and 42. The pistonvalve (i) pushes the working piston (j)with the radial cam (m) to the left againstthe force of the spring (l). This causes theradial cam (m) to take the valve tappet(h) to the appropriate position for the ve-hicle’s load.

The compressed air output by the brakevalve flows through Port 4 and on intoChamber A, acting on the piston (b). Thisis forced downward, closing the outlet (d)and opening the inlet (q). The com-pressed air from Port 4 flows into Cham-ber C beneath the diaphragm (e), actingon the effective area of the relay piston(f).

At the same time, compressed air flowsthrough the open valve (a) and Duct Einto Chamber D, acting on the upper sideof the diaphragm (e). This pressure pre-dominance causes the reduction in thepartially-laden range to be neutralized at

low actuating pressures (up to 0.8 bar).As the actuating pressure continues torise, the piston (r) is forced upwardsagainst the force of the spring (s) and thevalve (a) closes.

The pressure building up in Chamber Cforces the relay piston (f) downwards.The outlet (g) closes and the inlet (o)opens. The air supply at Port 1 now flowsthrough the inlet (o) into Chamber B andthrough Ports 2 to the downstream com-pressed-air brake cylinders. At the sametime, pressure builds up in Chamber Bwhich acts on the underside of the relaypiston (f). As soon as this pressure ex-ceeds that in Chamber C, the relay pis-ton (f) moves upwards, closing the inlet(o).

As the piston (b) moves downwards, thediaphragm (e) makes contact with thefan-type disk (p), thereby continuouslyincreasing the effective diaphragm area.As soon as the force in Chamber C whichacts on the underside of the diaphragm(e) is equal to the force acting on the pis-ton (b), that piston moves upwards. Inlet(q) is closed and a neutral position hasbeen reached.

The position of the valve tappet (h) whichdepends on the position of the radial cam(m) determines the output control pres-sure. The piston (b) with the fan-type disk(p) must have covered a stroke depend-ing on the position of the valve tappet (h)before the valve (c) begins to act. This

stroke also causes the effective area ofthe diaphragm (e) to be changed. In thefully-laden position, the output pressurefrom Port 4 is passed on into Chamber Cat a ratio of 1:1. The full pressure actingon the relay piston (f) causes the inlet (o)to be kept open and the input controlpressure is not adjusted.

When the actuating pressure at Port 4 isreduced, the pressure in Ports 2 forcesthe relay piston (f) upwards and the pis-ton (b) is forced upwards by the pressurein Chamber C. The outlets (d and g)open and the compressed air is evacuat-ed to atmosphere through Vent 3.

If the pressure in one air bellows fails, theload-sensing valve automatically movesto a position which approximately corre-sponds to half the pressure in the intactactuating circuit. If the pressure drops inboth air bellows, the small pressurespring (k) in the ram cylinder moves theworking piston to the right to the pointwhere the tappet is automatically takenthrough the dip onto the radial cam. Theoutput pressure then roughly corre-sponds to half the service braking pres-sure of the fully laden vehicle.

Test connection 43 allows the load-sens-ing valve to be checked on the vehicle.For this purpose, the piston valve is pres-surized with the preset test pressurewhile the pressure of the air bellows areautomatically separated from the load-sensing valve.

49

Automatic Load Sensing Valves 1.

1


Purpose:Automatic control of the brake force de-pending on the spring deflection and thuson the load of the vehicle. By the integra-ted relay valve the brake cylinders arequickly pressurized and vented.

Function:The load sensing valve is fixed on the ve-hicle frame and connected via a linkagewith a fixed point on the axle resp. on theknuckle joint. The distance between theaxle and the load sensing valve is thelongest in unladen condition, the lever (j)is in its lowest position. When the vehicleis laden, the distance becomes smallerand the lever (j) is moved from its unlad-en position into full-load direction. Thepin (i) which is turned in the same sensewith lever (j) moves the rod (q) via camsin the bearing cover (p) and thus thevalve tappet (g) into the postion corre-sponding to the load.

The compressed air (control pressure)which is delivered by the brake valveflows via the port 4 into the room A andpressurizes the piston (b). The piston (b)is moved to the left, closes the outlet (d)and opens the inlet (m). The compressedair which is delivered at the port 4 flowsinto the room C left of the diaphragm (e)

and through the channel F into the roomG and pressurizes the active surface ofthe relay piston (f).

At the same time, compressed air flowsvia the open valve (a) and the channel Einto the room D and pressurizes the rightside of the diaphragm (e). This anticipa-tory control of the pressure eliminatesthe reduction ratio in partial laden rangeat small input pressures (up to max. 1,4bar). When the input pressure increasesagain, the piston (n) is moved against theforce of the spring (o), and the valve clos-es.

The pressure which builds-up in room Gmoves the relay piston (f) downwards.The outlet (h) closes and the inlet (k)opens. The supply air at port 1 flows nowvia inlet (k) into room B and reaches viathe ports 2 the subsequent air brake cyl-inders. At the same time, pressure buildsup in room B which acts on the bottomside of the relay piston (f). As soon asthis pressure becomes a bit higher thanthe pressure in room G, the relay piston(f) moves upwards, and the inlet (k) clos-es.

While the piston (b) is moving to the left,the diaphragm (e) touches the washer (l),and thus increases constantly the activesurface of the diaphragm. As soon as theforce which acts in room C on the left

side of the diaphragm is identic to theforce which acts on the piston (b), piston(b) moves to the right. The inlet (m) clos-es and a final position is reached.

The position of the valve tappet (g),which depends on the position of the le-ver (j), is decisive for the active surface ofthe diaphragm and so for the deliveredbrake pressure. The piston (b) with thewasher (l) must make a stroke corre-sponding to the position of valve tappet(g), before the valve (c) starts working.This stroke changes the active surface ofthe diaphragm (e). In full-load positionthe active surfaces of the diaphragm (e)and the piston (b) have identic size. Thusthe pressure delivered at port 4 is deliv-ered in a 1:1 ratio into room C and soalso into room G. As the relay piston (f) ispressurized with full pressure, the relaypart delivers the pressure 1:1. Thatmeans, there is no reduction of the inputbrake pressure.

After the input pressure at port 4 is ex-hausted, the pressure in room C movesthe piston (b) to the right and the pres-sure in the ports 2 moves the relay piston(f) upwards. The outlets (d and h) open,and the compressed air escapes to at-mosphere via exhaust 3.

50


1


Purpose:Automatic control of the brake force de-pending on the bellows pressure andthus on the load of the vehicle. The inte-grated relay valve assures quick pressu-rizing and venting of the brake cylinders.

Function:The load sensing valve is controlled bythe pressure of the two circuits of the bel-lows via ports 41 and 42. The control pis-ton (i) which is pressurized by thebellows pressure moves the valve tappet(g) against the force of the spring (j) intothe position corresponding to the load.Thus the average value of the bellowspressures 41 and 42 is effective.

The compressed air delivered from thebrake valve (control pressure) flows viaport 4 into room A and pressurizes piston(b). Piston (b) is moved to the left, closesoutlet (d) and opens inlet (m). The com-pressed air delivered at port 4 flows intoroom C left of the diaphragm (e), as wellas through channel F into room G andpressurizes the active surface of the re-lay piston (f).

At the same time, compressed air flowsvia the open valve (a) and channel E intoroom D and pressurizes the right side ofthe diaphragm (e). This anticipatory con-trol of the pressure eliminates the reduc-

tion in the partial laden range at smallinput pressures (up to max. 1,4 bar).When the input pressure increasesagain, the piston (n) is moved against theforce of the spring (a) and the valve clos-es.

The pressure which builds-up in room Gmoves the relay piston (f) downwards.The outlet (h) closes and the inlet (k)opens. The supply air at port 1 flows nowvia inlet (k) into room B and reaches thesubsequent air brake cylinders via theports 2. At the same time, pressurebuilds up in room B which acts on thebottom side of the relay piston (f). Assoon as this pressure becomes a bithigher than the pressure in room G, therelay piston (f) moves upwards and theinlet (k) closes.

While the piston (b) is moving to the left,the diaphragm (e) touches the washer(l), and thus increases constantly the ac-tive surface of the diaphragm. As soonas the force which acts in room C on theleft side of the diaphragm, is identic tothe force which acts on the piston (b),piston (b) moves to the right. The inlet(m) closes and a final position isreached.

The position of the valve tappet (g),which depends on the position of thecontrol piston (i), is decisive for the activesurface of the diaphragm and thus for thedelivered brake pressure. The piston (b)

with the washer (l) must make a strokewhich corresponds to the position of thevalve tappet (g), before the valve (c)starts working. This stroke changes alsothe active surface of the diaphragm (e).In full-load position the active surfaces ofdiaphragm (e) and piston (b) have thesame size. Thus the pressure deliveredat port 4 is delivered in 1:1 ratio into roomC and so also into room G. As the relaypiston (f) is pressurized with full pres-sure, the relay part delivers the pressure1:1. The delivered brake pressure is notreduced.

After the control pressure at port 4 is ex-hausted, the pressure in room C movesthe piston (b) to the right and the pres-sure in the ports 2 move the relay piston(f) upwards. The outlets (d and h) openand the compressed air escapes to at-mosphere via exhaust 3.

If one bellows pressure fails, the valvemoves automatically into a positionwhich corresponds to approx. half thepressure of the intact control circuit. Ifboth bellows pressures fail, the valvemoves automatically into unladen posi-tion.

The test valve with port 43 makes it pos-sible to check the load-sensing valve inthe vehicle. For this the control circuits41 and 42 are pressurized via the testhose while the bellows pressures areseparated from the valve by connectingthe test hose.

511

Knuckle Joint433 302 . . . 0 and 433 306 . . . 0

Purpose:To prevent damage to the automaticload sensing valve.

Operation:In the event of large axle movements inexcess of the range of movement of theautomatic load sensing valve, arm (e),which is horizontal while at rest, is de-flected about a fixed point in housing (c).Pressure springs (a) and (b) exert pres-sure on ball (d) providing constant ten-sional contact with housing (c) until arm

(e) again returns to its normal horizontalposition where it is again in full contactwith the front face of the housing.

Deformation of the connecting linkage tothe automatic load sensing valve is pre-vented by a ball joint (f) or the rubberthrust member attached to arm (e).

Knuckle Joint 1.

433 306

433 302

52 1

Purpose:To control the braking force at the frontaxle of trucks or truck-tractors in re-sponse to the load-sensing valve on therear axle, as well as to provide for thequick release of air from the brake cham-bers.

Operation:During braking, output pressure from thedual-brake valve passes through port 1to the upper side of the step piston (d),pushing it downward against its stop. As

a result, double valve (a) closes outlet (b)and opens inlet (c), thus permitting inputpressure to flow through ports 2 to thebrake chambers.

Simultaneously, changes in output pres-sure (effected by the load condition of thevehicle) are directed by the load-sensingvalve on the rear axle, thru port 4, ontothe ring surface of step piston (d). Inlet(c) closes whenever the ratio betweenthe input pressures (ports 1 and 4) andoutput pressures (ports 2) is equivalent

to the aspect ratio of step piston (d).

Whenever the control pressures at ports1 and 4 drop, the higher brake chamberpressure raises piston (d) and doublevalve (a). Outlet (b) then opens to a de-gree determined by the control pressure,and a partial or complete the quick re-lease of air from the brake chamber oc-curs via exhaust 3.

Emty / Load Valve and Pressure Reducing Valve1.

Empty / Load Valve 473 300 . . . 0

d

1

2 2

3

c

ba

4

d

1

2 2

3

c

ba

Pressure Reducing Valve473 301 . . . 0

Purpose:To reduce the input pressure at a definedratio and to rapidly reduce the pressureof the downstream components of thebraking system.

Operation:Via Port 1, compressed air flows intoChamber A, forcing differential piston (d)downward against compression spring(a). Outlet valve (b) is closed and inletvalve (c) opened. Via Port 2, the com-

pressed air flows to the downstreamcomponents of the braking system.

At the same time, the pressure buildingup in Chamber B will act on the under-side of piston (d). As soon as the forceson the underside and the smaller uppersurface of differential piston (d) is bal-anced, the piston is raised and inlet valve(c) closed. The ratio of the pressures willthen be equal to the ratio of the two sur-faces of the differential piston.

When the pressure at Port 1 falls, thehigher pressure in Chamber B forces dif-ferential piston (d) upwards. Outlet valve(b) opens, and the pressure for thedownstream components of the brakingsystem will be reduced partially or in full.Compression spring (a) holds the differ-ential piston in its upper final positioneven if there is no pressure acting on it.

53

Empty / Load Valve 1.

Purpose:To control the braking force at the frontaxle by the rear axle load-sensing valve,as weIl as to provide for the quick releaseof air from the brake chambers.

Operation:a) Brakes actuated - partially loadedvehicle:When the service brake system is actuat-ed, the air pressure controlled by the rearaxle ALV is supplied to the brake cham-bers of the rear axle, and is delivered ascontrol pressure to port 4 of the empty/load valve. This control pressure is trans-mitted via bore (E) into chamber (C)where it acts upon the upper surface ofpiston (d) against the force of compres-sion spring (e). At a pressure of 0.5 bar,the piston is lowered to the stopped posi-tion. Spring loaded valve (b), moving inconjunction with piston (d), closes inlet(c) and outlet (f) opens. The control pres-sure also acts in chamber (B) upon thering-shaped area of piston (a).

Simultaneously, the output pressure ofcircuit (II) of the tractor brake valve istransmitted via port 1 to chamber (A) andacts upon the top of piston (a). Piston (a)

is moved down, outlet (f) closes, and inlet(c) opens. The compressed air flows viachamber (D) and port 2 into the front axlebrake chambers.

The built-up pressure in chamber (D)then moves piston (a) upwards. Inlet (c)closes and a neutral position is reached.

b) Brakes actuated - fully loaded vehi-cle:The operation of the empty/load valvewith a fully loaded vehicle is the same aspreviously described. When the tractorbrake valve is actuated, the control pres-sure acts now with full service brakepressure in chambers (A and B) and thepressure reduction is interrupted. The in-put to output pressure ratio through theentire range of brake pressures is in thiscase 1 :1.

When exhausting the brake system,pressure at ports 1 and 4 decreases viathe dual-circuit brake valve. Simultane-ously, the brake pressure in chamber (D)moves piston (a) upwards. Inlet (c) clos-es and outlet (f) opens, and the brakechambers connected to port 2 are ex-hausted via exhaust port 3.

Piston (d) remains in its lower stop posi-tion until pressure at port 4 drops to 0.5bar. With further pressure decrease inchamber (C), compression spring (e)then moves piston (d) upwards. Outlet (f)closes and inlet (c) opens, and the re-maining pressure in port 2 is exhaustedvia port 1.

c) Operation when the rear axle brakecircuit fails:If the rear axle brake circuit fails, port 4and chamber (C), above piston (d), re-main without pressure when the servicebrake system is actuated. The force ofcompression spring (e) keeps piston (d)in its upper stop position. Inlet (c) re-mains constantly open. Compressed airfrom the service brake circuit (II) of thedual-circuit tractor brake valve, flowswithout limitation through the empty/loadvalve to the front axle brake chambers.

Empty / Load Valve473 302 . . . 0

54

Purpose:To control the dual-line trailer brake sys-tem, in conjunction with the dual-circuittractor brake valve and the hand controlvalve for spring brake actuators.

Operation:a) Control from the dual-circuit tractorbrake valveUpon actuation of the tractor brake valve,compressed air flows from service brakecircuit (I), through port 41, into chamber(A) and pushes down pistons (a and i).When piston (i) comes to rest on valve(d), outlet (c) closes and inlet (h) opens,filling chamber (C). Compressed airpasses from chamber (C), throughchamber (B), to port 2 and supplies thetrailer control line in proportion to servicebrake circuit (l) pressure with a gain de-pending upon the pre-set tension ofspring (b).

The built-up pressure in chamber (B)acts upon the underside of pistons (a andi). Due to the different operating surfaceof piston (a), only piston (i) is raisedagainst the control pressure in chamber(A), forcing compression spring (b) up-wards. The sequential action of valve (d)closes inlet (h), and a neutral position isreached. With full brake application,

however, the pressure on the upper sideof piston (i) is predominant and inlet (h)remains open.

The pre-set tension of compressionspring (b) can be changed by turning theadjusting screw (j) until the pre-set pres-sure gain of port 41, in relation to port 2,reaches 1 bar maximum.

Simultaneous to the operations takingplace in port 41, service brake circuit (II)supplies chamber (E), beneath dia-phragm (e), with compressed air throughport 42. However, due to the filling ofchamber (B and D), the pressure abovepiston (g) and diaphragm (e) predomi-nates and the position of piston (g) doesnot change. If service brake circuit (I)fails, port 42 is supplied with compressedair through circuit (II). The pressure inchamber (E), beneath diaphragm (e),moves piston (g) and valve (d) upwards.Piston (i), now in its upper end position,closes outlet (c) and opens inlet (h) sothat the trailer control line receives com-pressed air proportional to the tractorbrake application.

With partial brake application, piston (g),after pressure build-up in chamber (B),moves downwards, inlet (h) closes and a

neutral position is reached. With fullbrake application, the pressure in cham-ber (E) predominates and inlet (h) re-mains open.

When controlled through circuit (II) of theservice brake system, the trailer brakevalve operates without predominance.

b) Control from the hand control valveThe progressive evacuation of the springbrake actuators through the hand controlvalve brings about a correspondingevacuation of chamber (D) through port43. The supply pressure, now predomi-nant in chamber (C), moves piston (g)upwards. The supply of air to port 2 thentakes place in the same way as for thecontrol of chamber (E) in the event of fail-ure of service brake circuit (I).

After completion of the braking action,ports 41 and 42 are exhausted, and port43 is re-pressurized. The pressure inchamber (B) causes pistons (a and i) andpiston (g) to return to their original posi-tions. Outlet (c) opens and the com-pressed air in port 2 is exhaustedthrough the hollow piston body (f) andexhaust port 3 to the outside.

Trailer Control Valves1.Trailer Control Valve with predominance 973 002 . . . 0

55

1.

Purpose:To control the dual line trailer brake sys-tem, in conjunction with the dual circuittractor brake valve and the hand controlvalve for spring brake actuators.

If the trailer control line breaks or is dis-connected, and the tractor brake valve isapplied, the supply of air from the tractorto the trailer is restricted by the 2/2 wayvalve; simultaneously, pressure in thetrailer supply line is exhausted.

Operation:While the air brake system is filling, sup-ply air passes through port 11 into the 2/2 way valve and acts upon piston (l).Piston (l) is moved against the force ofthe spring (n) into its upper position. Sup-ply air passes through chamber (C) andport 12 to the automatic hose coupling.

a) Control from the dual circuit trac-tor brake valve

Trailer Control Valves

Upon actuation of the tractor brake valve,compressed air flows from the servicebrake circuit 1, through port 41, intochambers (A) and (G) and pushes downpistons (c and l). Pistons (c) are pusheddown at the same time. When piston (c)comes to rest on valve (g), outlet (e) clos-es and inlet (f) opens. Compressed airpasses from chamber (C), throughchamber (B), to port 22 and supplies thetrailer control line in proportion to theservice brake circuit 1 pressure.

At the same time as the aforementionedoperations are proceeding, compressedair flows through channel (k) into cham-ber (F) and acts upon the underside ofpiston (l). At a control pressure of ap-proximately 4 bar, the compressed airabove piston (l) predominates, movingthe piston downwards until it stops at thehousing edge (m). This movement is de-signed to keep piston (l) from seizing.

The pressure building up in chamber (B)acts upon the undersides of pistons (c)and moves this upwards against the con-trol pressure acting in chamber (A). Thesequential action of valve (g) closes inlet(f) and a neutral position is reached. Withfull brake application. however, the pres-sure above piston (c) is predominant andinlet (f) remains open.

Simultaneous to the operations takingplace at port 41, service brake circuit 2supplies chamber (E), beneath the dia-phragm (i), with compressed air throughport 42. However, due to the filling ofchambers (B and D), the pressure abovepiston (h) and diaphragm (i) predomi-nates, and the position of piston (h) doesnot change. If service brake circuit 1 fails,port 42 is supplied with compressed airthrough circuit 2. The pressure in cham-ber (E), beneath diaphragm (i), movespiston (h) and valve (g) upwards. Piston(c), now in its upper end position, closesoutlet (e) and opens inlet (f) so that thetrailer control line receives compressedair proportional to the tractor brake appli-cation.

With partial brake application, piston (h),after pressure build up in chamber (B),moves downwards, inlet (f) closes, and aneutral position is reached. With fullbrake application, the pressure in cham-ber (E) predominates and inlet (f) re-mains open.

When controlled through circuit 2 of theservice brake system, the trailer brakevalve operates without gain.

If the trailer control line (connected toport 22) breaks while the service brake

system is actuated, no pressure build upoccurs in chambers (B and F). The con-trol pressure in chamber (G) moves pis-ton (l) downwards, and the flow from port11 to port 12 is partially restricted. At thesame time, pressure in the trailer supplyline (port 12) exhausts through open inlet(f) and through the trailer control line rup-ture, and causes automatic trailer brak-ing.

b) Control from the hand controlvalve

The progressive evacuation of the springbrake actuators through the hand controlvalve brings about a correspondingevacuation of chamber (D) through port43. The supply pressure, now predomi-nant in chamber (C), moves piston (h)upwards. The supply of air to port 22then takes place in the same way as forthe control of chamber (E) in the event offailure of service brake circuit 1.

After completion of the braking action,ports 41 and 42 are exhausted, and port43 is repressurized. The pressure inchamber (B) causes pistons (c and h) toreturn to their original positions. Outlet(e) opens and the compressed air in port22 is exhausted through the hollow pis-ton body (j) and exhaust port 3 to the out-side.

Trailer Control Valve with 2/2 Way Valve and without predominance 973 002 5 . . 0

56

Trailer Control Valves1.

Trailer Control Valve with predominance 973 008 . . . 0

Purpose:To control the trailer’s twin-line brakingsystem together with the dual-circuitbrake valve and the hand brake valve forspring-brake actuators.

If a line ruptures, or the trailer’s controlline has not been connected, actuation ofthe brake valve on the motor vehicle willcause a reduction of the air supply fromthe towing vehicle to the trailer and a si-multaneous pressure reduction in thetrailer’s supply line.

Operation:a) Actuation from the dual-circuit

brake valveWhen the brake valve on the motor vehi-cle is actuated, compressed air flowsfrom service braking Circuit 1 throughPort 41 into Chamber B, acting on piston(e). This moves downwards, closing theoutlet (g) and opening the inlet (k) as itsits on the valve (j). The air supply fromPort 11 flows through Chamber G to Port2 and pressurizes the trailer’s controlline, the pressure being similar to that in

service brake Circuit 1, with a predomi-nance (1 bar max.) set by means of theadjuster screw (f).

The pressure building up in Chamber Dacts on the underside of piston (e). Dueto the difference in the effective areas ofpiston (e), the actuating pressure inChamber C and the force of the pressurespring (l) causes that piston to move up-wards. The valve (j) following piston (e)closes the inlet (k) and a neutral positionhas been reached. At full brake applica-tion, the pressure acting on the upperside of piston (e) is greater and the inlet(k) remains open.

When the pressure in Chamber B is in-creased, piston (b) is forced downwardsagainst the pressure of the control spring(d). The valve (c) is opened by the ad-juster screw (f) and the actuating pres-sure then building up in Chamber Csupports the downward control of piston(e). This can cause the output pressureat Port 2 to be lower than the actuatingpressure at Port 41. When the adjuster

57

Trailer Control Valves 1.screw (f) is turned anti-clockwise, for in-stance, the pressure in Chamber C is re-duced, and to maintain the balance, theoutput pressure is increased.

Simultaneously with the processes atPort 41, Chamber A is pressurized fromthe service braking circuit through Port42. Since, however, the force generatedby pressurizing Chambers B and Cwhich acts on the upper side of piston (e)is greater, the position of piston (a) is ir-relevant. If a defect causes the servicebraking Circuit 1 to fail, only Port 42 ispressurized from Circuit 2. The pressurethus building up in Chamber A forcespiston (a) downwards and pushes piston(e) ahead, and the trailer’s control linereceives its pressure as describedabove, albeit without any predominance.

b) Actuation from the hand brakevalve

The graded evacuation of the spring-brake actuators through the hand brakevalve causes the pressure in Chamber Fto be reduced accordingly through Port43. The supply pressure at Port 11 nowbeing higher forces piston (h) upwards.Port 2 is then pressurized as for Cham-ber A if service braking Circuit 1 fails.

When the braking process is ended,Ports 41 and 42 are evacuated again, orPort 43 pressurized. This causes pistons(a and e), and piston (h) (by the pressurein Chamber D) to return to their originalpositions. Outlet (g) opens and the com-

pressed air in Port 2 is evacuated to at-mosphere through the tubular piston (h)and Vent 3.

c) Safeguard Against Rupture OfThe Pilot Line

When the braking system is being filledwith compressed air, the air supply flowsthrough Port 11 and Chamber G to Port12 and from there to the automatic ‘Sup-ply’ hose coupling.

When the brakes are actuated, an actu-ating pressure is built up through Port 2in the line leading to the ‘Control’ hosecoupling, the required air being fed infrom Port 11. This causes the pressureabove the piston (3) to fall slightly. At thesame time, compressed air from Port 41is fed beneath piston (i) through Duct E.The pressure in Chamber G rises again,causing the piston to be forced down-wards (play motion to prevent piston (i)from getting stuck).

If a rupture of the trailer’s control line pre-vents pressure building up at Port 2, pis-ton (i) remains in its upper position andblocks the passage leading to ChamberG. The air supply from Port 11 to Port 12is throttled and the pressure in the trail-er’s supply line (Port 12) is reducedthrough the open inlet (k) at the point ofrupture in the trailer’s control line, thuscausing automatic braking of the trailer.

58

Trailer Control Valves1.

Trailer Control Valve with predominance and 2/2 Way Valve 973 009 . . . 0

Purpose:To control the trailer’s twin-line brakingsystem together with the dual-circuitbrake valve and the hand brake valve forspring-brake actuators.

If a line ruptures, or the trailer’s controlline has not been connected, actuation ofthe brake valve on the motor vehicle willcause a reduction of the air supply fromthe towing vehicle to the trailer and a si-multaneous pressure reduction in thetrailer’s supply line. This process causesimmediate automatic braking of the trail-er.

Operation:When the braking system is being filledwith compressed air, the air supply flowsthrough Port 11 into the 2/2-way valveand acts on piston (k). This is forced up-wards into its upper neutral end positionagainst the force of pressure spring (l)and supported by the pressure spring (j).Through duct (i), the air supply flows intoChamber D to Port 12 and from there

through Port 12 to the automatic ‘Supply’hose coupling.

a) Actuation from the dual-circuitbrake valve

When the brake valve on the motor vehi-cle is actuated, compressed air flowsfrom service braking Circuit 1 throughPort 41 into Chambers A and F, actingon pistons (a and k). Piston (a) movesdownwards, forcing piston (b) down. Aspiston (b) sits on the valve (g), the outlet(e) is closed and the inlet (f) is opened.The air supply flows through Chamber Bto Port 22 and pressurizes the trailer’scontrol line, the pressure being similar tothat in service brake Circuit 1, with a pre-dominance of 0.2 ± 0.1 bar, this beingadjustable by means of the adjusterscrew (d).

At the same time, compressed air flowsinto Chamber G through the hole (c),moving piston (m) against the force ofthe spring. The valve (n) sits on the ad-juster screw (d), opening the passage to

59

Trailer Control Valves 1.Chamber E. The air flows into ChamberE and supports the forces acting on theunderside of piston (b).

The pressure building up in Chambers Band E acts on the different effective are-as of piston (b), pushing it upwards, to-gether with piston (a), against theactuating pressure in Chamber A. Thevalve (g) following pistons (b and a) clos-es the inlet (f) and a neutral position hasbeen reached. At full brake application,the pressure acting on the upper side ofpiston (a) is greater and the inlet (f) re-mains open.

Simultaneously with the processes atPort 41, Chamber H above piston (b) ispressurized from the service braking cir-cuit through Port 42. Since, however, theforce generated by pressurizing Cham-ber A which acts on the upper side of pis-ton (a) is greater, the position of pistons(a and b) does not change.

If a defect causes the service brakingCircuit 1 to fail, only Port 42 is pressu-rized from Circuit 2. The pressure thusbuilding up in Chamber H beneath piston(a) forces piston (b) downwards. Thiscloses the outlet (e) and opens the inlet(f), and the trailer’s control line is pressu-rized accordingly, albeit without any pre-dominance.

Within the range of partial brake applica-tion, the pressure building up in Cham-bers B and E pushes piston (b) upwardsonce again. The inlet (f) closes and aneutral position has been reached. At fullbrake application, the pressure in Cham-ber H is greater and the inlet (f) remainsopen.

In the event of a rupture of the trailer’scontrol line (Port 22), no pressure buildsup in Chambers B and E when the serv-ice braking system is actuated. The air isevacuated to atmosphere at the point ofrupture through the open inlet (f) andPort 22. This causes piston (k) to bepushed down further by the actuatingpressure acting in Chamber F, throttlingthe supply pressure flowing from Port 11to Port 22. At the same time, the pres-sure in the trailer’s supply line (Port 12)is reduced through the open inlet (f) atthe point of rupture in the trailer’s controlline, causing automatic braking of thetrailer.

b) Actuation from the hand brakevalve

The graded evacuation of the spring-brake actuators through the hand brakevalve causes the pressure in Chamber Cto be reduced accordingly through Port43. The supply pressure in Chamber Dnow being higher forces piston (h) up-wards. Port 22 is then pressurized as forChamber H if service braking Circuit 1fails.

When the braking process is ended,Ports 41 and 42 are evacuated again, orPort 43 pressurized. This causes pistons(a and be), and piston (h) (by the pres-sure in Chamber C) to return to their orig-inal positions. Outlet (b) opens and thecompressed air in Port 22 is evacuatedto atmosphere through the tubular pistonand Vent 3.

60

Wendelflex ® - Hose Connection1.Wendelfelx ® -Hose Connection452 711 . . . 0

Purpose:1) Connection of the air brake system of

the tractive unit with that of the semitrailer.

2) Connection of sections of the airbrake system, which have variablelength between themselves.

Construction:Wendelflex is a coiled hose, which ex-pands with length alterations and re-tracts to its original length whenreleased.

From the hose connection to the first coilthe hose is stiffened through an in builtrelical spring which prevents kinking inthis susceptible region.

Wendelflex hose connections need noadditional gantries or supports. TheWendelflex hose connection is made outof black Polyamid 11. For a visual differ-entiation of the hose connections thehose couplings are supplied with col-oured covers.

Polyamid 11 resists all substances oc-curing on vehicles such as e.g. petrole-um products, oils and greases. Thepipes will also withstand alkalis, unchlo-rinated solvents, organic and inorganicacids and diluted oxydizing agents. (Useof chlorinated cleansing agents is there-fore to be avoided). Resistance againstspecial substances can be given on re-quest.

611

Coupling Heads 1.

A1

A2

B1

C1

Purpose:To connect the air brake system of a tow-ing vehicle to a trailer in accordance withEEC regulations. The coupling headsconform to ISO Std. 1728.

Description:Coupling head versions A1, B1 and C1for the supply line have red covers and acentrally cast protrusion to prevent mealcoupling, versions A2 and B2 for theservice line have a yellow cover and acast protrusion on one side to preventmeal coupling. Versions B and C are fit-ted with automatic shut off valves.

Connecting:The coupling heads are connected by lo-cating the guides of both couplings androtating the flexible connected couplingto lock. After locking, a good seal is es-tablished between the coupling heads.

The cast protrusions ensure that con-nections between incorrect couplingsare not made (Refer to chart showingvarious types).

– Coupling C1 with A1, B1 with A1 andB2 with A2.During coupling the sealing ring ofcoupling head type A, opens the au-tomatic shut off valve fitted to types Bor C. A sealed, through connection isthen established. The shutoff valvesclose automatically when the cou-plings are disconnected.

– Coupling A2 with A2.When connecting identical couplingheads without shut off valves. a pres-sure is established between the seal-ing rings.

Coupling Heads for dual line braking system952 200 . . . 0

62

Duo-Matic Quick Coupling1.Duo-Matic Quick CouplingFor Trailers452 80. . . . 0

Purpose:To connect the compressed air brakingsystem of the motor vehicle to that of thetrailer.

Operation:When attaching the trailer, handle (b) ispushed downwards; this causes protec-tive caps (a) and (d) to open. The Duo-Matic trailer portion is placed below theprotective caps and handle (b) is re-leased. Torsion spring (e) acts upon pro-tective caps (a) and (d), pushing thetrailer portion against the automatic clos-ing valves (c), causing them to open:Compressed air now reaches the trailer.

Tractor portion

Trailer portion 452 804 012 0

452 802 009 0

Duo-Matic Quick CouplingFor Semi-trailers452 80. . . . 0

Purpose:To connect the compressed air brakingsystem of the semi-trailer tractor to that ofthe semi-trailer.

Operation:When attaching the semi-trailer, handle(b) is pushed downwards; this causesprotective caps (a) and (d) to open. TheDuo-Matic tractor portion is placed belowthe protective caps and handle (b) is re-leased. Torsion spring (e) acts upon pro-tective caps (a) and (d), pushing thetractor portion against the contact sur-face. The automatic shut-off valves (c)open and compressed air reaches thesemi-trailer.

Tractor portion

Semi-trailer portion 452 803 005 0

452 805 004 0

63

Equipment ForTrailer Braking Systems

2.

64

Trailer complying with the ECE Directive

Trailer with twin-line air braking system2.

Council Directive 71/320/EEC of the ”Eu-ropean Communities“ and ECE Regula-tion 13 are contained in the manualentitled ”Legal Requirements“.

This manual is available from our Depart-ment AM-M4, Tel. (511) 922 1688 quot-ing Part Number 815 000 051 3.

651

Legend:1. Hose coupling2. Line filter3. Double release valve with check valve4. Relay emergency valve5. Two-way valve6. Brake Chamber7. Air reservoir8. Drain valve9. Quick release valve10. ABS electronics

11. ABS relay valve12. ABS parking socket13. Dummy coupling with fastening14. Load sensing valve with integral knuckle joint15. Load sensing valve with integral test valve16. Plate, ALV setting17. ABS-Elektrowendel18. Tristop Spring Brake Actuator19. Pressure limiting valve20. Adjusting valve

Semi-trailer with twin-line airbraking system 2.

Semi-trailer complying with the ECE Directive

66 1

Purpose:To protect the air braking system againstdirt.

Operation:The compressed air reaching the line fil-ter via port 1 passes through the filtercartridge in which any particles of dirt areretained; the compressed air is cleanedbefore it reaches any downstream appli-ances from port 2.

If the line filter is blocked, the filter car-tridge is pushed upwards against theforce of the pressure spring and the com-pressed air will pass through the line fil-ter without being cleaned.

If port 1 is exhausted while the filter car-tridge is blocked, the pressure in port 2can push the cartridge downwardsagainst the force of the compressionspring. This permits return flow from port2 to port 1.

Trailer Release Valve963 00. . . . 0

Purpose:To release the braking system for thepurpose of moving a trailer that is discon-nected from the tractor unit. The doublerelease valve has been designed for usein braking systems using Tristop® springbrake actuators.

Operation:When a semitrailer is connected to theprime mover, air from the supply lineflows through port 11 into chamber (B). Ifpiston (a) is still in the release position itis pushed out into the driving position bythe supply pressure. The air from thesupply line then flows through port 2 to

the relay emergency valve and on to thereservoir on the trailer.

When the trailer is uncoupled, port 11and therefore chamber (B) are exhaust-ed causing the relay emergency valve toapply the trailer brakes. To release thebrakes, piston (a) is pushed home man-ually using knob (b). This closes the pas-sage from port 11 to port 2 and aconnection between chamber (A) andport 2 is established.

The reservoir pressure of the semi-trailerat port 12 flows to the relay emergencyvalve via port 2, causing it to reverse.The brake actuators are exhausted andthe trailer brakes released.

Air Line Filter and Trailer Release Valve2.Line Filter432 500 . . . 0

671

Trailer Release Valve 2.

Purpose:Releasing the braking system (for sys-tems with Tristop® cylinders) to moveunhitched trailers.

Operation:While coupling the trailer onto the vehi-cle, make sure that the piston (a) is still inparking position; if yes, push it to thedriving position. When the coupling headis connected, compressed air flowsthrough port 1-1 into chamber A. If thepiston (c) is still in release position, it ispushed out into driving position by thesupply pressure. The air supply thenpasses through port 21 into the relayemergency valve and then into the trail-er's air reservoir.

Compressed air flows through port 1-2into chamber B, opens the check valve(b), passes through chamber C and port22 into the downstream two-way quickrelease valve and pressurises theTristop® cylinder's spring compressionchambers.

Pressure in Port 1-1 and, subsequently,chamber A is reduced in the unhitchedposition. To release the service brakingsystem, use the actuating knob to pushthe piston (c) until stop. This blocks thepassage from port 1-1 to port 21,and aconnection is created between chamberA and port 1-2.

The air supply at port 1-2 flows throughport 21 into the trailer emergency valveand switches it to driving position, there-by reducing the pressure in the brakecylinder.

The piston (a) is pulled out when theparking brake is activated. The com-pressed air in chamber C and at port 22is released into the atmosphere via ex-haust 3. The downstream quick releasevalve reverses and pressure is reducedin the Tristop® cylinder's spring com-pression chambers.

Trailer Release Valve963 001 05 . 0

68 1

Relay Emergency Valves2.

Relay Emergency Valve with adjustable predominance 971 002 150 0 and Trailer Release Valve 963 001 012 0

Purpose:To control the twin-line braking system ofa trailer.

Operation:a) Relay Emergency ValveCompressed air passes from the tractorthrough the supply line hose coupling toport 1, passes grooved ring (c) and con-tinues through port 1-2 to the trailer res-ervoir.

Upon actuation of the tractor brakes,compressed air flows via the hose cou-pling in the control line and port 4 to theupper side of piston (a). The piston isforced down and by seating on valve (f)closes outlet (b) and opens inlet (g). Airfrom the trailer reservoir port 1-2 nowflows via ports 2 to the downstreambrake valves and into chamber (C) viapassage (A). Pressure builds up againstvalve (k).

As soon as the pressure in chamber (C)predominates, valve (k) opens againstthe force of pressure spring (i). The airflows into chamber (D) via passage (B),

acting on the underside of piston (a). Asa result of the compounding of forces inchambers (D) and (E), the pilot pressureacting on the upper side of piston (a) isovercome and piston (a) is forced up.

In the case of partial brake application,valve (f) closes inlet (g) and a neutral po-sition is reached. In the case of full brakeapplication, inlet (g) is kept open by pis-ton (a) over the entire braking process.

A maximum predominancce of 1 bar canbe established between ports 2 and 4 bymeans of adjusting the tension of pres-sure spring (i) using set screw (h).

When the tractor brakes are released,port 4 is vented and the pressure in ports2 forces piston (a) upward to the top of itsstroke. Inlet (g) is closed and outlet (b) isopened. The compressed air at ports 2 isexhausted to atmosphere through valve(f) and exhaust 3. Due to the drop inpressure in chamber (C), the com-pressed air in chamber (D) flows viabores (j) of valve (k) into chamber (C)and on to exhaust 3.

When the trailer is uncoupled or in theevent of a rupture in the supply line, port1 is exhausted and the pressure actingon the upper side of piston (d) is re-duced. The load in pressure spring (e)and the supply pressure at port 1-2 forc-es up piston (d) and valve (f) closes out-

let (b). As piston (d) continues to moveup, it moves away from valve (f) and inlet(g) opens. The supply pressure at port 1-2 flows to the downstream brake valvesvia ports 2 at a 1:1 ratio.

b) Trailer Release ValveIf the relay emergency valve is used incombination with automatic load-sensingbraking or a manually adjustable load ap-portioning valve without a release posi-tion, Trailer Release Valve 963 001 . . . 0permits the trailer being moved when un-coupled. For this purpose, piston (l) ispushed home by hand via push (m). Thiscloses the passage from port 11 of thetrailer release valve to port 1 of the relayemergency valve and a connection be-tween port 1 of the relay emergencyvalve and port 12 of the trailer releasevalve is established. Pressure from thetrailer reservoir at port 12 flows throughport 1 of the relay emergency valve,causing it to reverse into the driving posi-tion. The brake actuators are exhausted.

If piston (l) is not pulled out manually allthe way when the trailer is re-coupled,the supply pressure from the motor vehi-cle will force it out. The release valve isonce more in its normal position in whichport 11 of the release valve and port 1 ofthe relay emergency valve are connect-ed.

69

Relay Emergency Valves 2.

1

Relay Emergency Valve with adjustable predominance 971 002 152 0

Purpose:To control the twin-line braking system ofa trailer when the braking system of theprime mover is actuated. Automaticbraking of the semi-trailer in the event ofpartial or total loss of pressure in the sup-ply line.

This relay emergency valve should beused particularly in long multi-axle semi-trailers.

Operation:a) Service Brake ApplicationCompressed air passes from the primemover through the supply line hose cou-pling to port 1, passes grooved ring (c)and continues through port 1-2 to thesemi-trailer reservoir. At the same time,compressed air from the supply line forc-es down piston (c) and valve (e) againstthe load in pressure spring (d). Outlet (a)opens and ports 2 are connected with ex-haust 3.

Upon actuation of the tractor brakes,compressed air flows via the hose cou-pling in the control line and port 4 to theupper side of piston (k). The piston isforced down and by seating on valve (e)closes outlet (a) and opens inlet (f). Airfrom the semi-trailer reservoir port 1-2now flows via ports 2 to the downstreambrake actuators and into chamber (D) viapassage (B). Pressure builds up againstvalve (i). As soon as the pressure inchamber (C) predominates, valve (i)opens against the force of pressurespring (h). The air flows into chamber (E)via passage (C), acting on the undersideof piston (k). As a result of the com-pounding of forces in chambers (A) and(E), the pilot pressure acting on the up-per side of piston (k) is overcome andpiston (k) is forced up.

In the case of partial brake application,valve (e) closes inlet (f) and a neutral po-sition is reached. In the case of full brakeapplication, inlet (f) is kept open by piston(k) during the entire braking process.

A maximum predominance of 1 bar canbe established between ports 2 and 4 bymeans of adjusting the tension of pres-sure spring (h) using set screw (g).

When the tractor brakes are released,port 4 is vented and the pressure in ports(2) forces piston (k) upward to the top ofits stroke. Inlet (f) remains closed andoutlet (a) is opened. The compressed airat ports 2 is exhausted to atmospherethrough valve (e) and exhaust 3. Due tothe drop in pressure in chamber (A), thecompressed air in chamber (E) flows viabores (j) of valve (i) into chamber (D) andon to exhaust 3.

b) Automatic BrakingWhen the trailer is uncoupled, or in theevent of a rupture in the supply line, port1 is exhausted and the pressure actingon the upper side of piston (c) is reduced.The load in pressure spring (d) and thepressure from the reservoirs at port 1-2force up piston (c), and valve (e) closesoutlet (a). As piston (c) continues tomove up, it moves away from valve (e)and inlet (f) opens. Via ports 2, the reser-voir pressure flows to the brake cham-bers at a 1:1 ratio.

In the case of the control line rupturing,automatic braking takes effect as de-scribed above since the pressure in thesupply line is reduced as soon as thetowing vehicle is braked.

70

Relay Emergency Valves2.

1

Relay Emergency Valve with adjustable predominance 971 002 300 0

Purpose:To control the twin-line braking system ofa trailer.

Operation: The relay emergency valve, passing thegrooved ring (c), to Port 1-2 and on to thetrailer’s air reservoir.

When the motor vehicle’s braking sys-tem is actuated, air flows through the‘control’ hose coupling and Port 4 until itreaches the upper side of piston (a). Thismoves downwards, and as it rests on thevalve (f) it closes the outlet (b) and opensthe inlet (g). The compressed air from thetrailer’s air reservoir (Port 1-2) now flowsthrough Ports 2 to the downstream brakevalves and Duct C into Chamber B,where the pressure begins to rise.

As soon as the force in Chamber B isgreater, the valve (k) is opened againstthe force of the pressure spring (i). Theair now flows through Duct A into Cham-ber D, acting on the underside of piston

(a). Through the compounding of theforces acting in Chambers D and E, thepilot pressure acting on the upper side ofpiston (a) is overcome and that pistonmoves upwards.

Within the range of partial brake applica-tion, the valve (f) following piston (a)closes the inlet (g) and a neutral positionhas been reached. At full brake applica-tion, piston (a) keeps the inlet (g) openfor the whole of the braking process.

By adjusting the initial tension of thepressure spring (i) by turning the setscrew, a pressure predominance of up to1 bar can be set for Ports 2 over Port 4.

When the braking process in the motorvehicle is ended, causing Port 4 to beevacuated, piston (a) is moved to its up-per end position by the air pressure inPorts 2. The compressed air in Ports 2 isevacuated to atmosphere through valve(f) and Vent 3. Due to the fall in pressurein Chamber B, the compressed air inChamber D flows back through the holes(j) in valve (k) into Chamber B and fromthere to Vent 3.

When the trailer is disconnected, or ifthere is a rupture in the supply line, the

pressure in Port 1 is evacuated and thepressure on the upper side of piston (d)is reduced. The force of the pressurespring (e) and the supply pressure atPort 1-2 pushes piston (d) upwards,moving valve (f) and closing the outlet(b). As piston (d) continues to move up-wards, it is raised off valve (f) and the in-let (g) opens. The trailer’s air supply atPort 1-2 flows through Ports 2 to thedownstream brake valves in full.

The relay emergency valve is also avail-able with a release valve 963 001 01. 0,its part number being 971 002 7.. 0. For‘Operation’, please refer to Page 68.

711

Purpose:To limit output pressure to a preset level.

Operation:The air fed into chamber (A) via port 1(high-pressure) flows through inlet (d)into chamber (B) and on to port 2 (low-pressure). At the same time, piston (e) ispressurized but is initially held at the topof its stroke by pressure spring (f).

As soon as the pressure in chamber (B)reaches the level set for the outlet pres-sure, piston (e) overcomes the load inpressure spring (f) and moves down.Valves (a) and (c) close inlets (b) and (d).If the pressure in chamber (B) has in-creased above the preset level, piston(e) will continue its downward motion,thus opening outlet (h). The excess airwill escape to atmosphere through pis-ton (e) and exhaust 3. As the presetpressure level is reached, outlet (h) isclosed once more.

In the event of a leakage in the low-pres-sure line causing a loss in pressure, pis-ton (e) will lift valve (a). Inlet (b) opensand the required quantity of air is fedthrough. In Variant 475 010 3.. 0, piston(e) will raise valve (c), thus closing inlet(d).

When port 1 is exhausted, the higherpressure in chamber (B) lifts valves (c)and (a). Inlet (d) opens and the low-pres-sure line is exhausted via chamber (A)and port 1. In the process, piston (e) isreturned to the end of its stroke by theload in pressure spring (f).

The set pressure limit can be alteredwithin a certain range by changing thecompression of spring (f) by means ofadjusting screw (g).

Pressure Limiting Valves 2.

475 010 0 . . 0

475 010 3 . . 0

Pressure Limiting Valve475 010 . . . 0

72 1

Relay Valves2.

Purpose:To rapidly supply and evacuate com-pressed air from pneumatic equipmentand to reduce response times in pneu-matic braking systems.

Operation:When the braking system is actuated,compressed air flows into chamber (A)via port 4, forcing down piston (a). Outlet(c) is closed and inlet (b) is opened. Thesupply pressure at port 1 now flows intochamber (B) and to the downstreambrake actuators via ports 2.

The pressure buidling up in chamber (B)acts on the underside of piston (a). Assoon as this pressure begins to exceed

the supply pressure in chamber (A), pis-ton (a) is forced up. Inlet (b) closes and aneutral position is reached.

When the pilot pressure is partially re-duced, piston (a) is moved up onceagain. Outlet (c) is opened and the ex-cess pressure at port 2 escapes via ex-haust 3. If the pilot pressure at port 4 failscompletely, the pressure in chamber (B)forces piston (a) to the top of its strokeand outlet (c) opens. The downstreambrake actuators are exhausted fully viaexhaust 3.

973 001 . . . 0 973 011 00 . 0

Relay Valve973 001 . . . 0 and973 011 00. 0

731

Height Limiting Valve andQuick Release Valve

Purpose:Height limitation on vehicles with an airlift device.

Operation:The height limiting valve is mounted onthe chassis of the vehicle using bolt (c).Tappet (b) is connected to the axle via asteel cable. If during a lifting operationusing the raise/lower valve, the distancebetween the chassis and the axle ex-

ceeds the specified limit, tappet (b) ispulled down, followed by valve (a) whichcloses the connection between ports 1and 2. When tappet (b) is pulled out, port2 is exhausted.

After lowering of the chassis, tappet (b)returns to its original position and valve(a) re-opens the connection betweenports 1 and 2.

2.Height Limiting Valve964 001 . . . 0

Quick Release Valve973 500 . . . 0

Purpose:Rapid evacuation of long control or pilotlines, and of brake actuators.

Operation:When there is no air on the valve, theouter edge of diaphragm (a) which isslightly prestressed seats against ex-haust 3, closing the passage from port 1to chamber (A). Compressed air fromport 1 pushes back the outer edge and

reaches the downstream brake actua-tors via ports 2.

When the pressure at port 1 is reduced,the higher pressure in chamber (A) forc-es diaphragm (a) to arch upwards. De-pending on the reduction in pressure, thedownstream brake actuators are nowpartially or completely exhausted via ex-haust 3.

74

Adapter Valve and 3/2 Directional Control Valve2.

Purpose:To reduce the braking force of the axle tobe adapted during partial brake applica-tions and rapid exhausting of brake actu-ators.Trailers being operated inmountainous regions and frequently cov-ering downhill journeys always show in-creased wear on the brake linings of thefront wheels because the arrangement ofthe larger front-wheel brake actuators re-quired for stopping will cause excessbraking on the front axle. By using thisAdapter Valve, the brake force on thefront axle is reduced on the front axle tothe extent that both axles are brakedevenly; this does not, however, in anyway impair the brake force in emergencybraking.

Operation:Piston (b) is held at the top of its strokeby the load in pressure spring (c). Dia-phragm (a) closes the passage from port1 to ports 2. When the brakes are ap-plied, the air flows via port 1 to the upperside of diaphragm (a) where pressurebegins to build up. As soon as this pres-sure exceeds that of pressure spring (c)set by means of screw (d), piston (b) isforced down. The air now flows past theouter edge of diaphragm (a) and viaports 2 to the downstream brake actua-tors.

The pressure building up at ports 2 alsoacts on the underside of diaphragm (a),thus supporting the force of pressure

spring (c). As soon as these forces ex-ceed the pressure acting on the upperside of diaphragm (a), piston (b) is re-turned to the top of its stroke. A neutralposition is reached.

If the pressure at port 1 is increased fur-ther, the load in pressure spring (c) isgradually overcome and the air finallyreaches the brake actuators at a 1:1 ra-tio. After a reduction in pressure at port 1,pressure spring (c) forces piston (b) up tothe top of its stroke. The pressure inchamber (B) forces diaphragm (a) toarch upward. Depending on the reduc-tion in pressure at port 1, the brake actu-ators are exhausted partially orcompletely.

Adapter Valvewith linear characteristic975 001 . . . 0

3/2 Directional Control Valve463 036 . . . 0

Purpose:Alternate connection of the service line(consumer) with the pressure line or theexhaust, the valve locking into either po-sition.

Operation:When turning knob (a) is actuated in arotary direction, piston (b) is moved

downwards via a cam. Outlet (d) closesand inlet (c) opens, and the compressedair at Port 1 flows into the service line viaPort 2. When turning knob (a) is turnedthe other way, piston (b) is returned to itsoriginal position by the force of the com-pression spring. Inlet (c) closes and theservice line is exhausted via outlet (b)and Port 3.

75


Operation:The supply line from the air reservoir isconnected to port 1. The armature (d)which forms the valve core keeps inlet(c) closed by the load in pressure spring(b).

When a current reaches solenoid coil (a),

armature (d) is lifted, outlet (e) is closedand inlet (c) is opened. The compressedair from the supply line will now flow fromport 1 to port 2, pressurizing the workingline.

When the current to solenoid coil (a) isinterrupted, pressure spring (b) will re-turn armature (d) to its original position.Inlet (c) is closed, outlet (e) is openedand the working line is exhausted viachamber (A) and exhaust 3.

Solenoid Valves 2.

1

3

2

4

e

A

d

a

b

c

3/2-Way Solenoid ValveNormally Closed472 1. . . . . 0

Purpose:To vent an air line when current is sup-plied to the solenoid.

Operation:The supply line from the air reservoir isconnected to port 1 and thus air is al-lowed to flow through chamber (A) andport 2 into the working line connected toport 2. The armature (d) which forms thecore of the valve is forced down byspring (b), closing outlet (c).

When a current reaches solenoid coil (a),

the armature (d) is lifted, inlet (e) isclosed and outlet (c) is opened. Thecompressed air from the working line willnow escape to atmosphere via port 3and the downstream operating cylinderis exhausted.

When the current to solenoid coil (a) isinterrupted, pressure spring (b) will re-turn armature (d) to its original position.Outlet (c) is closed and inlet (e) isopened, again allowing air to pass to theworking line via chamber (A) and port 2.

3/2-Way Solenoid ValveNormally Open472 1. . . . . 0

1

3

24

e

A

d

a

b

c

76

Load Sensing Relay Emergency Valve2.

Purpose:Control of the dual-line trailer brakingsystem when the motor vehicle's brakingsystem is operated. Automatic control ofthe braking force as a function of vehicleload by means of the integrated load-sensing valve.Automatically braking the trailer in theevent of partial or complete loss of pres-sure in the supply line.The Load-Sensing Relay EmergencyValve is specifically designed for semi-trailers with several axles.

Operation:The valve is mounted on the vehiclechassis and is attached to a spring armon the axle via a linkage. When the vehi-cle is empty, the distance between theaxle and the valve is greatest and lever(j) is in its lowest position. As the vehicleis loaded, this distance is reduced and le-ver (j) is moved towards its "fully laden"position. The movement of lever (j) caus-es the cam plate to move tappet (l) to aposition corresponding to the vehicleload.

Via the hose coupling of the supply lineand port 1, pressure from the motor vehi-cle passes groove ring (h), port 1-2 andthen reaches the semi-trailer's air reser-voir. At the sime time, piston (k) andvalve (g) are moved downwards by thesupply pressure. Outlet (n) opens andports 2 are connected with exhaust 3.

When the motor vehicle's braking systemis operated, air flows to chamber (A) viathe hose coupling in the control line andport 4, pushing down piston (b) whichcloses outlet (d) and opens inlet (p). Theair from port 4 reaches chamber (C) be-low diaphragm (e), acting on the effectivesurface area of relay piston (f).

At the same time, air flows to chamber(B) via open valve (a) and passage (E),acting on the upper side of diaphragm(e). This initial by-pass pressure elimi-nates any reduction in pilot pressure (upto 1.0 bar max.) in the "partially laden"condition. As the pilot pressure continuesto rise, piston (r) is forced up against theload of spring (s), closing valve (a).

Load Sensing Relay Emergency Valve475 712 . . . 0

77

Load Sensing Relay Emergency Valve 2.Through the pressure building up inchamber (C), relay piston (f) is forceddownwards. Outlet (n) closes and inlet(m) opens. The supply pressure at port1-2 now flows into chamber (D) via inlet(m) and then reaches the downstreambrake actuators via ports 2. At the sametime, pressure builds up in chamber (D),acting on the underside of relay piston(f). As soon as this pressure exceedsthat in chamber (C), relay piston (f)moves upwards, closing inlet (m).

As piston (b) moves downwards, dia-phragm (e) is pushed against vane (o),thus continuously increasing the effec-tive diaphragm surface area. As soon asthe force acting on the underside of thediaphragm in chamber (C) is equal tothat acting on piston (b), the pistonmoves upwards. Inlet (p) is closed, a bal-anced position is reached.

The position of tappet (l), which is de-pendent on the position of lever (j), deter-mines the output braking pressure.Piston (b) with vane (o) needs to cover astroke according to the position of tappet(l) before valve (c) begins to operate.This stroke also changes the effectivesurface area of diaphragm (e). In the "ful-ly laden" position, the input pressure atport 4 flows into chamber (C) at a ratio of1:1. Since relay piston (f) receives fullpressure, it keeps inlet (m) open and theinput braking pressure is not controlled.

When the motor vehicles braking systemis released, port 4 is exhausted and relaypiston (f) is pushed into its upper positionby the pressure in ports 2. Outlets (d)and (n) open and the air in ports 2 andchamber (C) is released to atmospherevia exhaust 3.

Automatic BrakingWhen the supply line is disconnected orbroken, port 1 will be exhausted and thepressure on the upper side of piston (k)is reduced. The pressure from the airreservoirs at port 1-2 pushes piston (k)upwards. Valve (g) closes outlet (n). Aspiston (k) continues to move upward, itwill leave valve (g) and inlet (m) opens.Full reservoir pressure now reaches thebrake actuators via ports 2. In the eventof the control line breaking, automaticbraking will take place as describedabove since the pressure in the supplyline is reduced in connection with thetrailer control valve via the defective lineas soon as the towing vehicle is braked.

78 1

Automatic Load Sensing Valve2.

Automatic Load Sensing Valve 475 713 . . . 0

Purpose:Automatic control of the braking force inpneumatic actuators as a function of thevehicle load.

Operation:The load sensing valve is mounted onthe vehicle chassis and is actuated via aconnecting cable attached to the axle bymeans of a tension spring. When the ve-hicle is empty, the distance between theaxle and the valve is greatest and lever(f) is in its lowest position. As the vehicleis loaded, this distance is reduced and le-ver (f) moves from its ”empty“ position to-wards its ”fully laden“ position. Themovement of lever (f) causes cam plate(g) to move valve tappet (i) to a positioncorresponding to the vehicle load.

Output pressure from the relay emergen-cy valve reaches chamber (A) via port 1,acting on piston (b) which is forced down,closing outlet (c) and opening inlet (k).The air now flows to chamber (E) belowdiaphragm (d) and via ports 2 to thedownstream brake actuators.

At the same time, air flows into chamber(d) via opened valve (a) and channel (B),and acts on the upper side of diaphragm(d). This pressure control provides un-modulated output at low pilot pressures.If the pilot pressure increases further,piston (l) is forced up against the load inpressure spring (m) and valve (a) closes.

The downward motion of piston (b) re-leases diaphragm (d) from its seat in theload sensing valve, pushing it against thefanned out portion of piston (b). The ef-fective surface area of the diaphragm isthus increased continuously until it ex-ceeds the area of the upper side of thepiston. Thus, piston (b) is raised againand inlet (k) closed. A neutral position isreached. (Inlet (k) will remain open onlyin fully laden condition ”1:1“). The pres-sure delivered to the actuators of the fullyladen vehicle corresponds to the pres-sure in the load sensing valve deliveredfrom the relay emergency valve. With apartially laden or unladen vehicle, how-ever, this pressure is reduced according-ly.

When the brake pressure has been re-duced, piston (b) is forced up by the

pressure in chamber (E). Outlet (c)opens, and the air is exhausted to atmos-phere via valve tappet (i) and exhaust 3.

With each brake application, air flowsinto chamber (F) via passage (C), actingon washer (e) which is pushed againstvalve tappet (i). At a brake pressure 0.8bar, a frictional connection is establishedbetween valve tappet (i) and the housing.The load sensing valve's reducing ratio isthus locked and remains so even whenthe distance between the axle and thechassis is changed further. Tensionspring (h) compensates these variationsin travel.

An integral pressure spring in the loadsensing valve moves valve tappet (i) intothe ”fully laden“ position in the event ofthe linkage fracturing.

791

Automatic Load Sensing Valve 2.

Automatic Load Sensing Valve 475 714 . . . 0

Purpose:Automatic regulation of the brake pres-sure in pneumatic brake actuators on air-sprung axles (axle assemblies) as afunction of the pilot pressure of the airbellows.

Operation:The load sensing valve is mounted onthe vehicle chassis with the exhaust 3pointing downwards. Ports 41 and 42 areconnected to the air suspension bellowson both sides of the vehicle by means ofpipes.

The pilot pressure from the bellows actson pistons (m) and (k). Depending on thispressure which varies with the vehicleload, guide sleeve (i) with its attachedcam (h) are moved against spring (z) andthe position is set depending on the vehi-cle load.

When the brakes are applied, com-pressed air from the relay emergencyvalve flows into chamber (A) via port 1,pressurizing piston (d) which is forceddown, closing outlet (e) and opening inlet(c). The air now flows into chamber (B)below diaphragm (f) and to the down-stream actuators via ports 2.

At the same time, air flows into chamber(C) via opened valve (b) and passage(F), acting on the upper side of dia-phragm (f). This pressure control pro-vides unmodulated output at low pilotpressures when the vehicle is partiallyladen. If the pilot pressure increases fur-ther, piston (a) is forced up against theload in pressure spring (s) and valve (b)closes.

The downward motion of piston (d) re-leases diaphragm (f) from its seat in theload sensing valve, pushing it against thefanned-out portion of piston (d). The ef-fective surface area of the underside ofdiaphragm is thus increased continuous-ly until the forces on either side of the pis-ton are the same as on the underside ofdiaphragm (f). Thus, piston (d) is raisedagain and inlet (c) closed. A neutral posi-tion is reached. (Inlet (c) will remain openonly in the fully laden condition). Thepressure in the actuators then corre-sponds to the vehicle load and the outputbrake pressure of the tractor brake valveor the relay emergency valve.

When the brake pressure is reduced (re-lease of the brakes), piston (d) is forcedup by the pressure in chamber (B). Outlet(e) opens and the air is exhausted to at-mosphere via valve tappet (r) and ex-haust 3.

Every brake application forces air intochamber (E) via passage (D), acting onmoulded rubber part (p) which is forcedagainst valve tappet (r). Any brake pres-sure > 0.8 bar establishes a frictionalconnection between valve tappet (r) andthe housing. The load sensing valve's re-duction ratio is blocked and is main-tained even when dynamic axle loadshifting occurs when the brakes are ap-plied. If the bellows load increases with apartially laden vehicle, roller (g) ispushed against spring (o). Tappet (r)does not move from the position it was inwhen the brakes were first applied.

For checking the load sensing valve, atest hose is connected to port 43. As it isscrewed into place, piston (n) is pushedinto the housing, breaking the connec-tion of ports 41 and 42 to pistons (m) and(k). At the same time, a connection is es-tablished from port 43 to pistons (m) and(k). The load sensing valve adjusts to aregulating position corresponding to thepressure in the test hose.

80 1

Load Sensing Relay Emergency Valve2.

Load Sensing Relay Emer-gency Valve 475 715 . . . 0

Purpose:Regulation of the dual-line trailer brakingsystem when the towing vehicle's brak-ing system is actuated.Automatic regulation of the brake forceby means of the integrated load-sensingvalve as a function of the vehicle loadand thus of the actuating pressure of theair bellows.Automatic braking of the trailer in theevent of partial or complete loss of pres-sure in the supply line.

The Load-Sensing Relay EmergencyValve is specifically designed for air-sprung semi-trailers with several axles.

Operation:The valve is mounted on the vehiclechassis with the exhaust 3 pointingdownwards. Ports 41 and 42 are con-nected to the air suspension bellows onboth sides of the vehicle.

The pilot pressure from the air suspen-sion bellows acts on pistons (p) and (o).Depending on this pressure which varieswith the vehicle load, guide sleeve (n)with its attached cam is moved againstspring (m) and the position is set de-pending on the vehicle load.

The air from the motor vehicle reachesthe semi-trailer's air reservoir via the”supply“ hose coupling, port 1, port 1-2and grooved ring (h). At the same time,the supply pressure forces down piston(r) and thus valve (g). Outlet (t) opensand ports 2 are connected with exhaust3.

When the brakes are applied, com-pressed air flows via the hose coupling inthe control line and port 4 to chamber(A), acting on piston (b) which is forceddownwards, closing outlet (d) and open-ing inlet (v). The compressed air fromport 4 reaches chamber (C) below dia-phragm (e), acting on the effective sur-face area of relay piston (f).

At the same time, air flows into chamber(B) via open valve (a) and passage (G),acting on the upper side of diaphragm(e). This pressure control provides un-modulated output at low pilot pressures(up to 1.0 bar) when the vehicle is partial-ly laden. As the pilot pressure increasesfurther, piston (w) is forced up againstthe load in pressure spring (x) and valve(a) closes.

The pressure building up in chamber (C)forces relay piston (f) downwards. Outlet(t) closes and inlet (s) opens. The supplypressure present at port 1-2 now flowsinto chamber (d) and to the downstreembrake actuators via ports 2.

This causes pressure to increase inchamber (D) which acts on the undersideof relay piston (f). As soon as this pres-sure exceeds that in chamber (C), relaypiston (f) moves upwards and inlet (s)closes.

As piston (b) moves downwards, dia-phragm (e) moves against vane (u), thus

811

Load Sensing Relay Emergency Valve 2.continuously increasing the effective sur-face area of the diaphragm. As soon asthe force acting on the underside of thediaphragm in chamber (C) is the sameas that acting on piston (b), the piston ismoved upwards. Inlet (v) is closed and aneutral position is reached.

The position of tappet (i) which dependson the position on guide sleeve (n), de-termines the output pressure. Piston (b)with vane (u) must cover a stroke corre-sponding to the position of tappet (i) be-fore valve (c) begins to operate. Thisstroke changes the effective surfacearea of diaphragm (e). In the ”fully laden“position, the input pressure at port 4flows into chamber (C) at a ratio of 1:1.Since relay piston (f) receives full pres-sure, it keeps inlet (s) open and the inputbraking pressure is not controlled.

When the motor vehicle's braking sys-tem is released, port 4 is exhausted andrelay piston (f) is pushed into its upperposition by the pressure in ports 2. Out-lets (d) and (t) open and the air in ports 2and chamber (C) is released to atmos-phere via exhaust 3.

Every brake application forces air intochamber (E) via passage (F), acting onmoulded rubber part (k) which is forcedagainst valve tappet (i). Any brake pres-sure > 0.8 bar establishes a frictionalconnection between valve tappet (i) andthe housing. The relay emergencyvalve's reduction ratio is blocked and ismaintained even when dynamic axleload shifting occurs when the brakes areapplied. If the bellows load increaseswith a partially laden vehicle, roller (l) ispushed against spring (j). Tappet (i) doesnot move from the position it was in whenthe brakes were first applied.

For checking the load-sensing valve, atest hose is connected to port 43. As it isscrewed into place, piston (q) is pushedinto the housing, breaking the connec-tion of ports 41 and 42 to pistons (p) and(o). At the same time, a connection is es-tablished from port 43 to the pistons. Theload-sensing valve adjusts to a regulat-ing position corresponding to the pres-sure in the test hose.

Automatic Braking:When the supply line is disconnected orbroken, port 1 will be exhausted and thepressure on the upper side of piston (r) isreduced. The pressure from the air res-ervoirs at port 1-2 pushes piston (r) up-wards. Valve (g) closes outlet (t). Aspiston (r) continues to move upward, itwill leave valve (g) and inlet (s) opens.Full reservoir pressure now reaches thebrake actuators via ports 2.

831

3.

Anti-Lock Braking System (ABS)

84 1

Anti-Lock Braking System (ABS)3.Introduction: Anti-Lock Braking Systems (ABS) are

used to prevent locking of a vehicle’swheels as a result of excessive actuationof the service braking system, especiallyon slippery roads. As a consequence,lateral control is maintained on brakedwheels even at full brake application toensure that both the stability and steera-bility of a vehicle are ensured as far asphysically possible. At the same time,the utilization of the available adhesionof the tyre on the road and thus vehicleretardation and stopping distance areoptimized.

Following their introduction by WABCOFahrzeugbremsen, a division of WABCOStandard GmbH, in the early Eighties,Anti-Lock Braking Systems (ABS) arenow being offered by nearly all Europeanmanufacturers of commercial vehicles.

In recent years, WABCO has continu-ously worked on further improving theexcellent quality and performance char-acteristics of ABS.

Key developments have been:

� The introduction of Drive-Slip Controlsystems (ASR) in 1986

� The introduction of the ABS ”VARIO-C“ for trailers in 1989The increasing demand of trailermanufacturer for simple installationand testing whilst maintaining theusual WABCO quality standard hasbeen the reason for WABCO devel-oping its new ABS generation, VarioCompact ABS - VCS. Both modularsystems are based on state-of-the-art electronics technology with high-performance micro computers andhigh-capacity data storage, takingmodern diagnostic principles into ac-count.

� With the ABS/ASR ‘C’ generation formotor vehicles and motor coaches,WABCO has presented a systemwhich offers the following essentialtechnical novelties:

ABS-Functions� Control Performance

By further optimizing the control algo-rithm, the utilization of adhesion andcontrol comfort were improved evenmore.

� Setting ECU ParametersModern memory modules can beused to set customer-specific vehicledata either when the ECU is beingmade or after production of a com-mercial vehicle.

ASR-Functions� Pneumatic Engine Control

IIn combination with a proportionalvalve designed for that purpose anda suitable control cylinder in the actu-ating linkage of the fuel-injectionpump, considerable improvements intraction and in control comfort areachieved.

� Electronic Engine ControlThe ECU has interfaces to commer-cial electrical or electronic enginecontrol systems, and correspondingSAE interfaces.

� Functional DisplayThe driver is informed of any auto-matic actuation of the ASR system,thus indicating to him that the roadmay be slippery.

Special Functions

� Top Speed Control

� ABS/ASR Function Switch

� Diagnostic Interface / Flash Code

WABCO has continuously improved theperformance of this safety system. Theconstantly rising competitive pressure inthe transport trade and falling vehicleprices have not stopped at ABS, either.

The highlights listed below which applyto the 4th generation of ABS/ASR are in-tended to specifically meet these re-quirements.

851

Anti-Lock Braking System (ABS)

ABS/ASR D VersionThe New Generation of ControlUnitsChanged vehicle concepts, the desire forfurther improving functions and continu-ous cost reductions for the system haveculminated in the development of the DVersion of ABS/ASR.

Special Features:� The single plug concept:

This design permits the allocation ofpartial cable harnesses on the vehi-cle to their respective plugs.

� The valve relays previously locatedoutside the control unit have nowbeen integrated.

� The D Version has a databus inter-face for communication with othersystems.

� ABS/ASR systems now only requireone ASR solenoid valve (differentialbrake valve).

3.

4-Channel ABS/ASR (C Version)4-wheel motor lorry with rear-wheel drive

ABS/ASR componentsABS components

1. pole wheel and sensor2. brake chamber (front axle)3. ABS solenoid control valve4. air reservoir5. Tristop spring-brake actuator

(rear axle)6. ABS solenoid control valve7. two-way valve8. differential brake valve9. electronic control unit10. proportional valve12. ASR actuating cylinder13. ASR functional switch14. ABS indicator lamp15. ASR indicator lamp

4- Channel ABS/ASR (D Version)

86

Anti-Lock Braking System (ABS)3.

WABCO’s top speed limiting system withits proportional valve (GBProp) complieswith the latest European legislation forthe equipment of heavy-duty commercialvehicles with cruise control systems andhas been granted EC type approval forthe parts.

Its components include the ABS/ASRECU, a proportional valve and actuatingcylinders which have been used suc-cessfully in recent years in WABCO-ABS/ASR systems for pneumatic enginecontrol. Other components include idle-stop cylinders (only required for single le-ver fuel-injection pumps), a speed set/ASR functional switch and an ASR indi-cator lamp plus a speedograph with C3/B7 output.

The speed limiter begins to operate evenbefore the vehicle has reached the max-imum speed stored in the ECU in a non-volatile EE-PROM memory. Via the pro-portional valve and the actuating cylin-der, the control lever of the fuel-injectionpump is moved so that the vehicle’s per-missible maximum speed cannot be ex-ceeded.

In addition, GBProp allows the driver toset a limiting speed freely selectable an-ywhere between 50 k.p.h. and the presetmaximum speed by actuating the speed-set/ASR functional switch and have thisspeed monitored by the system althoughhe has to continue to push down the ac-celerator pedal (this not being a fully au-tomatic cruise control system).

The top speed stored in the ElectronicControl Unit (ECU) can either be definedby the vehicle manufacturer (at the endof production) or by officially authorizedworkshop personnel at a service stationusing WABCO’s Diagnostic Controller.

The ECU stores any faults which mayoccur by type and frequency and, via theinterface designed to ISO 9141 and bymeans of the Diagnostic Controller, per-mits the error memory to be read out ordeleted, functional testing to be doneand the system’s parameters to be set.

Integrated Speed LimiterGBProp

ABS/ASRGBProp ECU

air reservoir

speed-set/ASR functional switch

speedograph

proportional valve

actuating cylinder

indicator lamps

87

VCS is a ready-to-install ABS system fortrailers meeting all legal requirements ofthe A category.The range of systems extends from a 2S/2M system for semitrailers to a 4S/3Msystem for towbar trailers or, for in-stance, a semitrailer with a steering axle.

In keeping with the specific needs of thetrailer manufacturers, VCS is availableeither as a compact unit or as a modularsystem, i. e. ECU and valves are in-stalled separately.Both ABS relay valves and ABS solenoidvalves can be used. The choice dependson the braking system used, and moreparticularly on time response. It is impor-tant that the appropriate ECU is used.

If the control valves are not electricallyactuated, the ordinary increase or de-crease of brake pressure the driverneeds is not affected. The special func-tion of ”maintaining brake pressure“serves to improve both the control per-formance of the ABS system, and airconsumption.

� one ECU (Electronic Control Unit)with one, two or three control chan-nels, subdivided into the followingfunctional groups:

� input circuit� main circuit� safety circuit� valve actuation

In the input circuit, the signals generatedby the respective inductive sensors arefiltered and converted into digital infor-mation for determining period lengths.

The main circuit consists of a microcom-puter. It contains a complex programmefor the computation and logical operationof the control signals and for outputtingthe actuating variables for the valve con-trol system.

The safety circuit monitors the ABS sys-tem, i. e. the sensors, solenoid controlvalves, ECU and wiring, before the vehi-cle moves off and whilst it is in motion, ir-respective of whether the brakes arebeing actuated or not. It alerts the driverto any errors or defects by means of anindicator lamp and shuts off the whole orpart of the system. Whilst the conven-tional brake remains operational, it isonly the anti-lock system which is deacti-vated wholly or in part.

The valve actuation contains (outputstages) which are actuated by the sig-nals from the main circuit and whichswitch the current for actuating the con-trol valves.

The electronic control unit of the VARIOCompact ABS is a further developmentfrom the established Vario-C ABS, build-ing on its proven principles.

Anti-Lock Braking System (ABS) 3.Vario Compact ABS (VCS)for Trailers

ABS Relay Valve **)

1 st and 2 nd rely valves

3 rd relay valves

Supply ISO 7638

Diagnosis 24N (24S) Supply *)

*) optional **) optionally flanged to compact unit

with retarder control *) integrated speed switch (ISS) *) Sensors (2 or 4)

88


Purpose:The purpose of the solenoid controlvalve on the trailer is to increase,reduce or hold the pressure in the brakecylinders during a braking processdepending on the control signals, inmilliseconds, received from the ECU.

Operation:a) Pressure IncreaseValve solenoids I and II are not ener-gized, the inlet of valve (i) and the outletof valve (h) are closed. The pilot cham-ber (a) of diaphragm (c) is pressureless.The compressed air at Port 1 flows fromChamber A through the open inlet (b)into Chamber B and from there throughPort 22 to the brake cylinders. At thesame time, the compressed air alsoflows through the hole (d) into the pilotchamber (g) of diaphragm (f), and outlet(e) remains closed.

b) Pressure ReduceWhen the ABS ECU transmits the signalto decrease the pressure, valve solenoidI is energized, valve (i) closes the pas-sage to Vent 3 and the passage to the pi-

lot chamber (a) is opened. Thecompressed air from Chamber A flowsinto the pilot chamber (a) and diaphragm(c) closes inlet (b) leading into ChamberB. At the same time, valve solenoid II re-verses, valve (h) closes the passage ofhole (d), permitting the compressed airfrom pilot chamber (g) to escape throughVent 3. Diaphragm (f) opens outlet (e)and the at Port 2 escapes to atmospherevia Vent 3.

c) Pressure HoldBy receiving a pulse, the passage toVent 3 is closed by valve (h) as valve so-lenoid II reverses. The compressed airfrom Chamber A flows through the hole(d) back into the pilot chamber (g) and di-aphragm (f) closes outlet (e). Thus thepressure in Chamber B and thus thebrake cylinders cannot increase or de-crease.

Solenoid Control Valve472 195 . . . 0

89

ABS Relay Valve472 195 02 . 0

Anti-Lock Braking System (ABS) 3.

Purpose:The purpose of the solenoid controlvalve on the trailer is to increase, re-duce or hold the pressure in the brakecylinders during a braking process de-pending on the control signals, in milli-seconds, received from the ECU.Thisconsists of two subassemblies:The actual relay valve and the electro-magnetic control valve.

Operation:a) Supply pressure present but no:The annular piston (c) is pushed againstthe seat (b) by the pressure spring (d),closing Port 1 against Chamber B (andthus Port 2).As (e. g. 1 bar) is applied at Port 4, thisflows via the solenoids (M1 and M2) intothe upper piston chamber A, forcing pis-ton (a) downwards. A small gap opens atthe seat (b) and air from Port 1 flows intoChamber B. At Outlet 2 and thus in thebrake cylinders, pressure begins to rise.Since the upper and lower sides of piston(a) have identical surfaces, that pistonwill return to its original position as soonas the pressure at 2 is equal to that at 4.The annular piston (c) is again in contactwith the seat (b) and the passage from 1to Chamber B is closed.

When the falls, piston (a) is raised andthe pressure in Port 2 escapes to Vent 3through Chamber B.

b) Operation in ABS control:Pressure Increase:The solenoids (M1 and M2) are deadand there is actuating pressure in Cham-ber A. Piston (a) is in its lower end posi-tion and the air supply flows from Port 1to 2.

Pressure hold:Solenoid M1 is energized and the arma-ture has attracted. This causes the airsupply from Port 4 to Chamber A to beinterrupted (in spite of the rise in actuat-ing pressure).

The pressures in Chamber A and B areequalized. The annular piston againrests on seats (b). The compressed aircannot flow from 1 to 2 or from 2 to 3(outside).

Pressure Reduce:Solenoid M2 is energized, the passageto Chamber A thus being closed. Theraised seal at the foot of M2 opens thepassage to Vent 3 and the pressure fromChamber A escapes to atmospherethrough the inside opening of the annularpiston (a). This causes piston (a) to beraised and the pressure from Port 2 andthe connected brake cylinder escapes toatmosphere through Chamber B andVent 3.

90


1

ABS Relay Valve472 195 04 . 0(Flat twin valve)

Purpose:ABS relay valve (flat twin valve) consistsof two relay valve parts with commonports for supply pressure and controlpressure. It is used in the air braking system in frontof the brake cylinders to modulate thebraking pressure in the brake cylinders.When the valve is activated by the ABSelectronic control unit, the pressure in thebrake cylinders is modulated (pressureincrease, pressure hold, pressure re-lease) regardless of the pressure al-lowed to pass by the brake valve or theemergency valve. The device has a two-relay-valve function in passive position(i.e. without solenoid activation), and isused to increase and decrease pressurein the brake cylinder through short re-sponse and pressure build-up and re-lease times.

Operation:Pressure build-up without ABS Con-trol:Both valve solenoids (M1 and M2) arede-energized, the annular piston (f) ispressed against the seat (e) by the pres-sure spring (b), and the passage fromport 1 to chamber B is closed.

If control pressure is supplied at port 4, it

flows through the solenoids (M1 and M 2)into the upper piston chamber A, pressesthe piston (c) against the annular piston(f) and opens the narrow gap in the seat(e). The supply pressure at port 1 flowsthrough the filter (a) into chamber B andinto port 23. There is pressure build-upalso in the brake cylinders. The sameprocess also takes place in the oppositerelay valve for ports 22. Since the upperand lower sides of the piston (c) haveequal surfaces, the piston returns to itsoriginal position as soon as the pressureat ports 22 and 23 is equal to the pres-sure at port 4. The annular piston (4) liesclose to the seat (e) again, and the pas-sage from port 1 to chamber B isblocked.

If the control pressure decreases, thepiston (c) is raised and the pressure inports 22 and 23 is released via chamberB to exhaust 3.

Operation with ABS-Control:

a) Pressure build-upThe solenoids (M1 and M2) are de-ener-gized and control pressure builds up inchamber A. The piston (c) is in its leftstop position and air supply flows fromport 1, through ports 22 and 23, into thebrake cylinders.

b) Pressure releaseSolenoid M2 is energized and closes thepassage from port 4 to chamber A. The

raised gasket at the bottom of M2 clearsthe way to exhaust 3 and the excesspressure from chamber A escapes throu-gh the inner opening of the piston (c) toexhaust 3. This raises the piston (c), andthe pressure on the brake cylinder is re-leased accordingly.

c) Pressure holdSolenoid M2 is de-energized again, sole-noid M1 is energized, and the armatureattracted. Thus, (despite the increasingcontrol pressure) air supply from port 4 tochamber 4 is interrupted.There is equal pressure in chambers Aand B, and the annular piston(f) is pres-sed against the seat (e) by the pressurespring (b). Compressed air can neitherflow from 1 to 22 and 23, nor from 22and 23 to 3 (into the atmosphere).

d) Pressure releasePower is supplied to solenoids M1 andM2. The passage from port 4 to chamberA is closed and compressed air fromchamber A escapes via the check valve(d) on port 4, whereas the pressure fromchamber B and from ports 22 and 23 nowescapes through the fully open outlet(the piston (c) is in its right stop position)on the seat (e) and exhaust 3 into the at-mosphere.

91


1

ABS Sensor Installation

Clamping Bush899 759 815 4

The clamping bush has 4 spring ele-ments held on one side only which, whenunder stress, generate a force betweensensor and hole causing defined friction-al engagement in the direction of thesensor.This causes the sensor to be hold by theclamping bush in such a way that when itis being fitted it can be pushed againstthe pole wheel and automatically adjuststo a minimum gap when the vehicle is in

motion. This eliminates the process ofhaving to adjust the gap and aligning thesensor (cable exit).

In open arrangements, the clampingbush and the sensor are fitted with atemperature and splash-resistant grease(Staburags or silicone grease - Part No.830 502 06. 4) to protect them from cor-rosion and dirt.

The rotary motion of the wheel is pickedup by means of a pole wheel (1) movingwith the hub and a pulse-generating sen-sor (3) held in the brake spider plate by aclamping bush (2).Pole wheels for medium and heavy-dutycommercial vehicles have 100 teeth.

Because of the diagonal referencespeed forming, the ratio of the number ofteeth and the wheel’s circumferencemust be identical on front and rearwheels, any deviation not exceeding afew percent.

ABS Sensor441 032 . . . 0

The inductive sensor comprise a perma-nent magnet, core and coil. The magnet-ic flux surrounding the coil is cut by the

rotating motion of the toothed wheel in-ducing an A.C. voltage whose frequencyis directly proportional to wheel speed.

92 1


Purpose:Via the pressure allowed to pass by theactuating cylinder, the proportional valvecontrols the control lever of the fuel-in-jection pump.

The output pressure is directly propor-tionate to the solenoid flux controlled bythe ECU (GBProp) by means of pulse-width modulation (PWM) with which theproportional valve is actuated. The lowhysteresis permits a wide range of cylin-der pressures to achieve both very rapidand virtually stationary adjusting move-ments for the control lever.

Operation:In the basic position (valve solenoid notenergized), the solenoid armature is incontact with the plunger (a) and keepsthe inlet (b) closed.

When current reaches the solenoid, thearmature forces the plunger (a) down-wards, opening the inlet (b). The air sup-ply at Port 1 now flows through Port 2and on to the actuating cylinder. De-pending on the pulse output by the ECU,the pressure in the actuating cylinder iseither held at a constant level (armatureattracts, closing the inlet) or reduced (ar-mature continues to attract, opening theoutlet (c) and the compressed air es-capes to atmosphere through Port 3).

Proportional Solenoid Valve472 250 . . . 0 (GBProp)

931


The actuating cylinder is fitted in the ad-justing linkage between the acceleratorand the fuel-injection pump. When actu-ated from the proportional valve, thecompressed air flows through Port andinto Chamber A, moving the piston to-wards the left. The piston rod which isnow being retracted causes the control

lever of the fuel-injection pump to bemoved towards its idling position. De-pending on the space available for instal-lation, either retracting (Fig. 1) orprotruding (Fig. 2) operating cylindersare used.

Operating Cylinder(Idle-Stop Cylinder)421 444 . . . 0 (GBProp)

For single-lever fuel-injection pumps, anidle-stop cylinder is required to preventthe engine being switched off by thespeed limiter if the pump lever can bebrought to the zero-delivery position bythe actuating cylinder.

Operating Cylinder(Actuating Cylinder)421 44. . . . 0 (GBProp)

Fig. 1

Fig. 2

951

4.

Sustained-Action Braking SystemsOn Motor Vehicles

96 1

Sustained-Action Braking Systems On Motor Vehicles4.

Legend:a quadruple system protection

valve

b air reservoir

d operating current relay

e 3/2-way solenoid valve

f operating cylinder for fuel injection pump

g operating cylinder for the exhaust butterfly valve

i towing vehicle foot brake valve with an electrical switch

Fig. 2:Circuit for the electro-pneumatic enginebrake in combination with the servicebraking system operated by compressedair.Upon application of the dual-circuit brakevalve (i), the electrical switch of the brakevalve activates the engine brake via the

operating contact relay (d) and the 3/2-way solenoid valve (e). This means thatit is activated every time the servicebraking system is being used, thus sup-porting the air brake and reducing thewear on the mechanical foundationbrake to the greatest possible extent.

Legend:a quadruple system protection

valve

b air reservoir

c towing vehicle foot brake valve

d operating current relay

f operating cylinder for fuel injection pump

g operating cylinder for the exhaust butterfly valve

h 3/2-way valve

According to Section 41 of the GermanMotor Vehicle Construction and UseRegulation, motor coaches with a per-missible total weight in excess of 5.5 tand other motor vehicles with a permissi-ble total weight in excess of 9 t have tohave an additional sustained-actionbraking system fitted. Sustained-actionbrakes are engine brakes or systemswhich achieve a similar braking perform-ance.The purpose of an engine brake is to

brake the towing vehicle independentlyfrom the service braking system, therebyreducing the wear on the mechanicalfoundation brake to the greatest possibleextent.

Fig. 1:The engine brake is switched on bymeans of a foot-operated three-wayvalve (h) which supplies air pressure forthe operating cylinders for the butterflyvalve and the fuel-injection pump.

Fig. 1

Fig. 2

971

Sustained-Action Braking SystemsOn Motor Vehicles 4.

Purpose:To pressurise and exhaust operating cyl-inder e. g. exhaust braking system.

Operation:The compressed air arriving from the airreservoir flows through Port 1 and reach-es the 3/2-way valve, until it reaches theunderside of the closed inlet valve (e).When the actuating button (a) is pusheddown, the plunger (b) is forced down-wards against the force of the pressurespring (c) until it makes contact with theinlet valve (e), closing the outlet (d) and,as it continues to move downwards,opening the inlet valve (e). The com-

pressed air now flows through Port 2 tothe downstream operating cylinders.

When the actuating button (a) is re-leased, the pressure spring (c) forces theplunger (b) back into its upper end posi-tion. Pushed by the supply pressure andthe pressure spring (f), the inlet valve (e)follows the upward motion of the plunger(b) and closes the passage to Port 1.Through the opening outlet (d) the com-pressed air from Port 2 now flows to Port3 and the operating cylinders are evacu-ated once again.

3/2-Way Valve463 013 . . . 0

98 1

Sustained-Action Braking Systems On Motor Vehicles4.

Air Cylinder421 410 . . . 0 and 421 411 . . . 0

Purpose:Shutting off the fuel injection pump andoperating the butterfly in the exhaustbrake system.

Operation:Air enters the cylinders from either the 3way valve or the 3 way magnet valvethrough port 1. As pressure builds up be-hind piston (a) the push rod (b) movesoutwards against the load of springs (c).

Cylinder 421 410 . . . 0 is connected tothe lever on the fuel injection pump, sothat when operated, the lever movesfrom the ”idle“ position to the ”stop“ posi-

tion. The cylinder is also connected intothe throttle linkage, so that as long as theexhaust brake is in operation, it is impos-sible to depress the accelerator pedal.

Cylinder 421 411 . . . 0 is connected tothe butterfly in the exhaust pipe, so thatwhen operated, the butterfly closes. Theback pressure created in the enginegives a braking effect to the vehicle.

When the cylinders are exhausted, thesprings (c) push the piston (a) back to itsoriginal position.

421 411

412 410

991

Sustained-Action Braking SystemsOn Motor Vehicles 4.

Purpose:To switch on or off electrical units andlamps according to the application.

Operation:Application ”E“ (normally open)On reaching the switch pressure the dia-phragm (d) together with the contactplate (e) is raised and a connection at thepoles (a and b) is made.

With a pressure fall this connection isagain interrupted.

Application ”A“ (normally closed)On reaching the switch pressure the dia-phragm (d) is raised together with thetappet. The tappet (c) lifts the contactplate (e) and the connection at the poles(a and b) is interrupted.

With a pressure fall this connection is re-made.


Operation:The supply line from the air reservoir isconnected to port 1. The armature (b)which forms the valve core keeps inlet(c) closed by the load in pressure spring(d).

When a current reaches solenoid coil (e),armature (b) is lifted, outlet (a) is closed

and inlet (c) is opened. The compressedair from the supply line will now flow fromport 1 to port 2, pressurizing the workingline.

When the current to solenoid coil (e) isinterrupted, pressure spring (d) will re-turn armature (b) to its original position.Inlet (c) is closed, outlet (a) is openedand the working line is exhausted viachamber (A) and exhaust 3.

Pressure Switch441 014 . . . 0

3/2-Way Solenoid ValveNormally Closed472 170 . . . 0

Fig. "E" Fig. "A"

1011

5.

EBS - Electronically ControlledBraking System

102 1

EBS - Electronically Controlled Braking System5.

Introduction: Increasing competition in the transporttrade has also caused the requirementsfor braking systems to be increasedsteadily. The introduction of the Elec-tronically controlled Braking SystemEBS is the logical step to meet this andother requirements. EBS permits perpet-ual optimized balancing of the brakingforces among the individual wheelbrakes, and of the towing vehicle and itstrailer.

The comprehensive diagnostic and mon-itoring functions of the Electronicallycontrolled Braking System are one of thebasic requirements for effective fleet lo-gistics. EBS enhances vehicle and roadsafety by means of reducing the stoppingdistance, achieving improved brakingstability and montitoring the braking sys-tem. In addition, EBS considerably im-proves both economic efficiency anddriving comfort.

Benefits of EBS EBS Effectively Reduces Maintenance Costs.

� EBS combines a large number offunctions. The objective is to reducemaintenance costs whilst maximizingbraking safety, e.g. by minimizinglining wear of the wheel brakes.

� Individual control according to thewear criteria on both front and rearaxles harmonizes lining wear. Byevenly spreading the load across allwheel brakes, total wear is minimi-zed. In addition, maintenance andlining change intervals coincide. Lai-dup costs are drastically reduced.

System Design For this reason, EBS will be included innew vehicle series, the pioneer beingACTROS from Daimler-Benz which hasan electronically controlled air brakingsystem fitted as standard equipment.This system by name of ”Telligent®Braking System“ from Daimler-Benz (for-merly EPB), is a joint development byDaimler-Benz and WABCO.

Please note:The term ”Telligent® Braking System“comprises the whole of the braking sys-tem, not only its controlling system whichwe call EPB.

The ACTROS ”Telligent® Braking Sys-tem“ contains some specific Daimler-Benz features for which WABCO, in ap-plications for vehicles from other manu-facturers, has substituted its ownsolutions. These include the followingfunctions described in the publication inmore detail:

– redundancy valve, rear axle redun-dancy

– special control functions in the areaof brake force distribution (differenti-al, drive-slip control DSR), liningwear control and trailer control

– testing and diagnostic methods typi-cal for ACTROS.

Modular Design of WABCO EBSThe configuration and the structure ofWABCO’s EBS permits a high degree offlexibility for the vehicle manufacturer

when designing the system. For this rea-son, the most varied of needs can bemet:

• partial or full system,• type of redundancy, • trailer control strategy, • elecrical interfaces, etc.

For meeting the essential requirementsof the vehicle owner, WABCO recom-mends an EBS which comprises indivi-dual pressure control on front and rearaxles and trailer control, and which provi-des for pneumatic redundancies in allbraking circuits.

This EBS consists of a dual circuit andan overriding single-circuit electro-pneu-matic circuit. This configuration is descri-bed as 2P/1E-EBS.The single circuit electro-pneumatic partof the system consists of one centralelectronic control unit (central module),the axle modulator with integrated elec-tronics for the rear axle, a brake signaltransmitter with parely pneumatical inte-grated stroke sensors and brake swit-ches, an electro-pneumatic control valveand two ABS valves for the front axle,plus an electro-pneumatic trailer controlvalve.An expansion of this configuration by anadditional axle modulator for the rear ax-les would then provide a 6-channel EBS.The structure of the subordinate dual-cir-cuit pneumatic part of the system is basi-cally identical with that of a conventionalbraking circuit. This part of the systemserves as a backup and becomes effec-tive only if the electro-pneumatic circuitfails.

1031

EBS - Electronically ControlledBraking System 5.

EBS Brake System for Track 4x2:

Legend: 1 Central Module 4 Solenoid Modulator Valve - ABS 7 Trailer Control Valve2 Brake Signal Transmitter 5 Rear Axle Modulator3 Proportional Relay Valve 6 Backup Valve

104


Legend:

1 Brake Signal Transmitter (BWG)2 Proportional-Relay Valve3 Solenoid Modulator Valve - ABS4 Speed Sensor5 Wear Sensor6 Backup Valve7 Rear Axle Modulator8 Trailer Control Valve

Function Scheme:

105


The brake signal transmitter is used togenerate electrical and pneumatic si-gnals to apply to, or release pressurefrom, the Electronically controlled Bra-king System (EBS). This unit is designedfor two pneumatic and electrical circuitsrespectively. Commencement of actuati-on is electrically recorded. The start ofactuation is electrically perceived by adouble switch (1). The travel of the actu-ating plunger (b) is picked up and resultsin the pulse-width modulated output as

an electrical signal. In addition, the pneu-matic redundancy pressures in Circuits 1(Port 21) and 2 (Port 22) are transmitted,that of Circuit 2 being retained slightly.Via an additional pilot connection 4 it ispossible (at a customer’s specific re-quest) to adjust the pneumatic charac-teristic of the 2nd circuit. In the event ofone circuit failing (electrical or pneumat-ic), the other circuits remain operational.

Brake Signal Transmitter480 001 . . . 0

The central module is used to controland monitor the Electronically controlledBraking System. From the signal re-ceived from the brake signal transmitterit determines the vehicle’s intended re-tardation. Together with the wheelspeeds measured by the wheel speedsensors, the intended retardation is theinput signal for EBS control which usesthese readings to establish the indexpressure values for the front and rear ax-les and the trailer control valve. The in-dex pressure for the front axle iscompared with the actual value taken,and any differences are balanced bymeans of the proportional relay valve.

Output of the trailer control pressure isachieved in a similar manner. In addition,the wheel speeds are evaluated to com-mence ABS control by modulating thebrake pressures in the brake cylinders inthe event of the wheels showing a ten-dency to lock. The central module ex-changes data, via the EBS system bus,with the axle modulator (or axle modula-tors in 6S/6M systems). Electrical braking systems for trailers areactuated via a data interface to ISO11992. The central module communi-cates with other systems of the towingvehicle (engine control, retarder, etc.) viaa vehicle data bus.

Central Module446 130 . . . 0

Zentralmodul Central Module

106


Proportional Relay Valve 480 202 ... 0

In the Electronically controlled BrakingSystem, the proportional relay valve isused as an actuator for the output ofbrake pressures at the front axle.

It consists of a proportional solenoidvalve (a), a relay valve (b) and a pres-sure sensor (c). Electrical actuation andmonitoring are effected by the centralmodule of the hybrid system.

The control current determined by theelectronics is converted by the propor-

tional relay valve (a) into control pressurefor the relay valve. The output pressure(port 2) of the proportional relay valve isproportional to that pressure. The pneu-matic actuation of the relay valve (port 4)is effected by the redundant pressure ofthe brake signal transmitter (port 22).

Backup Valve 480 205 ... 0

The backup valve is used to rapidly in-crease or decrease the pressure for thebrake cylinders on the rear axle in thecase of a backup; it consists of severalvalve units which have to perform the fol-lowing functions, among others:

� 3/2-way valve to prevent backup ope-ration if the electro-pneumatic bra-king circuit is not defective

� relay valve function for improving thetime response of the backup

� pressure retention in order to syn-chronize the commencement of pres-sure output on the front and rearaxles in the event of a backup

� pressure reduction to avoid overbra-king of the rear axle to the largestpossible extent in the case of a backup.

107


The axle modulator controls the brakecylinder pressures on both sides of oneor two rear axles. It contains two inde-pendent pneumatic pressure controlchannels (Channels A and B), each con-taining one inlet and one exhaust valve,plus one pressure sensor, sharing oneelectronic control unit. The index pres-sures and external monitoring functionsare provided by the central module.

In addition, two speed sensors monitorand evaluate the wheel speeds. In theevent of a tendency to lock or to spin be-ing detected, the index value provided isadjusted.

Two sensors can be connected for mon-itoring lining wear.

The axle modulator has one additionalport for connecting a backup pneumaticbraking circuit. One double check valveper side transmits the higher of the twopressures (electro-pneumatic or redun-dant) to the brake cylinder.

Axle Modulator480 103 . . . 0

108 1


Trailer Control Valve 480 204 . . . 0

In the Electronically controlled BrakingSystem, the trailer control valve is usedas a control element to output the hosecoupling pressures.

The trailer control valve consists of a pro-portional solenoid valve (a), a relay valve(c), a breakaway emergency valve (d)and a pressure sensor (b). Electrical ac-tuation and monitoring are effected bythe central module.

The control current determined by theelectronics is converted by the propor-

tional solenoid valve into control pres-sure for the relay valve. The outputpressure of the trailer control valve isproportional to that pressure.

The pneumatic actuation of the relayvalve is effected by means of the backuppressure from the brake signal transmit-ter (port 42) and the output pressurefrom the hand brake valve (port 43).

1091

EBS On The Trailer The scheme on page 64 and 65 eachshow EC air braking systems widelyused in Europe today. On a semitrailer,this braking system essentially consistsof a relay emergency valve, a load-sens-ing valve and the ABS.In the Vario-Compact System shownhere, the ABS relay valves and the elec-tronic control unit have been combined.Frequently, however, these componentsare fitted separately. On the drawbartrailer, another load-sensing valve, athird ABS relay valve, an adapter valveon the front axle and a pressure limitingvalve on the rear axle are added to thecomponents listed above. Although thisEC braking system is now highly sophis-ticated, especially through the use ofABS, there is still room for the improve-ments listed below:

� Reduction of the variety/number ofcomponents and thus installationscosts.

� Dispensing with the required air val-

ves and their adjustment by introdu-cing electronic control and the simplesetting of parameters this permits.

� By using pressure control circuitswhich operate with a high degree ofprecision, it is possible to almostcompletely eliminate the deviations incharacteristics encountered today.

� The ”electrical brake line“ and elec-tronic control can considerably impro-ve the time response and thuscontribute towards reducing the stop-ping distance and improving the sta-bility of the tractor-trailer combination.

� Extending the diagnostic features forthe whole of the braking system,including maintenance and repair in-structions.

It was these possible improvementswhich provided the basis for the develop-ment of an electronically controlled EBSon the trailer

EBS For Semitrailers 4S/2M1 EBS relay emergency valve2 EBS trailer modulator3 ABS sensor4 axle load sensor5 pressure sensor6 pressure switch7 redundancy valve

System DescriptionFi. 1 shows the standard EBS for a 3-axle semitrailer. It electronically controlslateral braking pressures. The systemconsists of a compact dual-circuit trailermodulator with a digital data interface toISO 1199-2 to the EBS towing vehicle,an EBS relay emergency valve, an axleload sensor and ABS sensor. When used

on drawbar trailers or semitrailers with asteering axle, a system is needed whichincludes an additional EBS relay valveon the steering axles, see Fig 2.

Trailers with the electronic braking sys-tem described must be compatible withboth conventional towing vehicles andtowing vehicles which use EBS, allowing


Abb. 1 Fig. 1

Reserve

Brake

110 1

EBS For Drawbar Trailers4S/2M1 EBS relay emergency valve2 EBS trailer modulator3 ABS sensor4 axle load sensor5 pressure sensor6 pressure switch7 redundancy valve8 EBS relay valve

pneumatic redundant braking in theevent of EBS failure. This results in three possible types of op-eration:

Operation with new towing vehicleswith EBS and extended ISO-7638plug-in connection with CAN inter-face.

All EBS functions can be utilized. Thetrailer receives the index values from thetowing vehicle via the data interface.

Oeration with conventional towing ve-hicles with ISO-7638 plug-in connec-tion for the trailer’s ABS supply butwith no CAN interface

All EBS functions can be utilized, with theexception of the transmission of the in-dex values via the CAN data interface.

The index values are provided by thepressure sensor in the relay emergencyvalve which picks up the actuating pres-sure for the trailer.

Redundancy Operation

In the event of a failure of the electricalvoltage supply, ordinary pneumatic brak-ing can always be achieved, althoughwith no load-sensing or ABS functions.In redundancy operation, the time re-sponse is similar to that of today’s con-ventional braking systems. If the EBStrailer is operated pneumatically, an im-proved time response is achieved sinceelectrical sensing of the actuating pres-sure saves time. When used with an EBStowing vehicle and actuation via CAN,the pressure in the EBS trailer builds upalmost simultaneously with that in thetowing vehicle.


Abb. 2

Reserve

Brake

Fig. 2

1111

6.

Air Suspension Systems And ECAS(Electronically Controlled Air Suspension)

112 1

Air Suspension Systems6.In commercial vehicles and motor coach-es, more and more air-suspensions arebeing used.

In commercial vehicles with interchange-able platforms they achieve a considera-ble reduction in loading and unloadingtimes. On coaches, ride comfort is im-proved by means of the spring force be-ing adjusted to the number ofpassengers travelling on the coach and aboarding level which remains the sameat all times.

Air Suspension SystemWhen planning and designing air sus-pension systems, the following systemtypes have been used to date:

� a)air suspensions with a closed aircircuit

� b)air suspensions with a semi-closedair circuit

� c)air suspensions with an open aircircuit.

The systems mentioned under a) and b)are mainly used in passenger cars, theirbenefit being that they consume a smallamount of air so that the compressor canbe smaller due to its lesser delivery re-quirements. In addition, there is little con-densate or dirt. Such systems are,however, technically complex and fairlyexpensive to buy.

For that reason, motor coaches andcommercial vehicles use air suspensionsystems with an open air circuit. Sincethis system evacuates air which is not re-quired back to atmosphere, the air com-pressor has to be larger. This type of airsuspension system is straightforward interms of its circuit and the valves it uses.

Of course neither types of suspension(mechanical spring suspension elementsor air suspension systems) can meet alltechnical requirements. Comparing bothsystem types, however, shows that airsuspensions offer significant advantagesover mechanical suspensions. This ap-plies especially where the wheel suspen-sion elements are to be separated fromother suspension members to achievebetter road holding qualities.

Benefits of Air Suspension Systems

1. By adjusting the bellows pressure asa ratio of the load carried, the dis-tance between the road surface andthe vehicle’s superstructure will al-ways be the same. This means thatnot only is the boarding or loadinglevel constant, but also the headlightsetting.

2. Due to the adjusting pressure in thebellows, spring comfort is not sub-ject to any major changes, regard-less of the load carried. Thepassenger on a motor coach will al-ways perceive the same pleasanttype of oscillation. Sensitive loadsare carried without any major dam-age. An empty or partially laden ve-hicle will no longer ‘jump’.

3. Both steering stability and the trans-mission of brake forces are im-proved since tyre-road adhesion isalways achieved for all wheels.

4. The pressure in the air suspensionbellows which is dependent on theload carried is also ideal for control-ling load-sensitive braking (‘ALB’).

5. In interchangeable platform opera-tion, air suspension systemsachieve efficient loading and unload-ing of container vehicles.

6. Protects the road surface.

In an air suspension system, the equip-ment for air compression, for the storageof compressed air and for pneumaticcontrol must form a unit with the wheelsuspension and other elements. The dia-gram on this page illustrates this for anair suspension system on semitrailers.

2, 3 41 42

21

ALB-Regler

Vorrat

von derBetriebsbremsanlage 6

4

1

5

Luftfederbalg

8

1 21

7

8

2221

2423

191 2

1 2

22

2312

Example for Semitrailers (raise and lower)

supply

from the servicebraking system

air suspension bellows

load-sensing valve

1131

Purpose:To control the pressure in the air suspen-sion bellows in proportion to the vehicleload.Levelling Valve 464 006 100 0 has anadditional 3/2 directional control valvewhich closes from a pre-defined, adjust-able lever angle and which takes on anexhaust function when the lever ismoved further. This "height limitation"prevents the vehicle being raised abovethe permissible level by means of theraise/lower valve.

Operation:The vehicle body with its levelling valvewill move down as the load on the bodyis increased. The linkage between thevehicle axle and the levelling valve rais-es both lever (f) and guide (d) via eccen-tric cam (e). As guide (d) moves up, italso lifts its pin, thus opening inlet valve(b), allowing air from the reservoir to flowthrough the valve via port 1 and checkvalve (a) into the air bellows which areconnected to ports 21 and 22. In order tominimize air consumption, the outside ofthe pin is machined in such a way thatthe passage of air through the valve isregulated at two levels depending on thedeflection of lever (f).

As the pressure in the air bellows in-creases, the chassis height is adjusted,and lever (f) causes inlet valve (b) toclose. In this position, ports 21 and 22are connected to each other via a trans-verse throttle.

When the vehicle load is decreased, thereverse process takes place. The vehiclechassis is now raised by the excesspressure in the air suspension bellowsand lever (f) with eccentric cam (e) andguide (d) are pulled down. This causesthe pin to be moved downwards from itsseat on inlet valve (b), permitting excesspressure from the air bellows to escapeto atmosphere via drilling (c) and ventholes 3. With this drop in pressure in theair bellows, the chassis height is loweredand lever (f) is returned to its normal hor-izontal position. As drilling (c) is blockedby the pin resting on inlet valve (b), thelevelling valve is again in a balanced po-sition.

Levelling Valve464 006 . . . 0

Air Suspension Systems 6.

114 1

Raise/Lower Valve463 032 . . . 0

Purpose:To raise and lower the chassis of air-sprung semi-trailers and vehicles with in-terchangeable platforms (lifting facility).

Operation:In the "travelling" position of the hand le-ver, the lifting mechanism is inoperative.The raise/lower valve allows the freepassage of air from the levelling valves(ports 21 and 23) to the air suspensionbellows (ports 22 and 24).

The valve also permits four more posi-tions of the hand lever for filling and emp-tying the air suspension bellows forraising and lowering purposes.

To raise the chassis, the hand lever isunlocked by axial pressure and moved tothe "raise" position in which ports 21 and23 are closed, blocking the action of thelevelling valves, while the suspensionbellows 22 and 24 are connected to thereservoir by port 1.

When the required lift height has beenattained, the hand lever is moved to the

"raise stop" position in which the levellingvalve ports 21 and 23 and the suspen-sion bellows ports 22 and 24 are closed.The platform supports can now beswung into position.

It is then necessary to lower the chassisbelow its normal level to deposit the con-tainer or platform on the supports and todrive out the chassis. This is done withthe hand lever in the "lower" position. Asin the "raise" position, ports 21 and 23are closed but air suspension bellows 22and 24 are now exhausted through ex-haust port 3.

This operation, too, is terminated bymoving the lever to the "lower stop" posi-tion. Ports 21, 23, 22 and 24 are closed.Before the vehicle is driven, the hand le-ver must be moved to the "travelling" po-sition to allow the levelling valves to bere-connected to the air bellows.

Air Suspension Systems6.

212223

24

13

STOP STOP

I II III IV V

1151

The letters ECAS stand for

ElectronicallyControlledAirSuspension

ECAS is an Electronically Controlled AirSuspension system for vehicles and in-cludes a large number of functions. Theconventional system has been signifi-cantly enhanced through the use of anElectronic Control Unit (ECU):

� Reduction of air consumed whilst thevehicle is moving

� It is possible to maintain different le-vels (e.g. ramp operation) by meansof automatic readjustment

� In the case of complex systems, in-stallation is easier

� Additional functions such as tractionhelp, programmable vehicle levels,tyre deflection compensator, over-load protection and automatic liftingaxle control can easily be integrated

� Due to large valve diameters, pres-surizing and venting processes areaccelerated

� Easy operation and maximum safetyfor those operating the system due toone single control unit

� Highly flexible system due to the factthat electronics can be programmedvia operating parameters (trailingend programming)

� Clear-cut safety concept and diagno-stic facility.

With conventional air suspension sys-tems, the valve which measures theheight also controls the air bellows,where as ECAS achieves control bymeans of an electronic control unit(ECU) actuating the air bellows via sole-noid valves, using information receivedfrom sensors.

The ECU not only controls the normalheight of the vehicle, it also, via the re-mote control unit, permits control of theother functions which, in conventional airsuspension systems, require additionalvalves such as height adjustment valvesand height limiting valves.

Over that, a large number of additionalsystem functions are available

ECAS is adjustable to suit the differenttypes of trailer.

ECAS only works when the ignition isON. Power supply for the trailer is nor-mally provided via the ABS system. Con-necting the ABS system is alsonecessary to ensure that ECAS receivesthe so-called C3 signal, i.e. informationon the current speed of the vehicle.

To permit adjustment of the level of atrailer not connected to a towing vehicle,an optional facility for a storage batterymay be provided for an additional powersupply on the trailer.

ECAS -Electronically Controlled Air Suspension 6.

Introduction:

Example for operation in a semi-trailer without lifting axle

Basic system:1 ECU (Electronic Control Unit) 2 RCU (Remote Control Unit)3 Height Sensor4 Solenoid Valve5 Air Bellows

leve

l

116 1

ECAS - Electronically Controlled Air Suspension6.

Description of operationA Height Sensor (3) will continuouslymonitor the vehicle's height and send itsreadings to the ECU (1). In the event ofthe ECU finding that the normal level isnot being maintained, a Solenoid Valve(4) is activated in such a way that, bypressurizing or venting, the level is ad-justed accordingly.

Below a pre-defined speed (and whenvehicle is stationary), the RCU (2) can beused to change the index level (useful forloading-ramp operation, for example).

An indicator lamp (situated on the front ofthe trailer, and visible from the truck's cabthrough the rear-view mirror) is used tonotify the driver that the trailer is outsideits normal ride height and to inform aboutany faults the ECU may have discovered.

Circuit diagram of basic system:1 ECU (Electronic Control Unit) 2 RCU (Remote Control Unit)3 Height Sensor4 Solenoid Valve5 Air Bellows

ECAS electronic

diagnostics

Power Supply module ECAS

ABS Vario C

24N ISO 7638 24S

stop

ligh

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spee

d si

gnal

grou

nd

Kl. 3

0 Kl

. 15

1171

ECAS-Electronic Control Unit (ECU)446 055 . . 0

The Electronic Control Unit (ECU)The Electronic Control Unit is the heart ofthe system and is connected with the in-dividual components on the motor vehi-cle by means of a 35-pole or 25-poleplug-in terminal. The ECU is located in-side the driver’s cab.

Together with a plug-in terminal for con-necting the ECAS ECU for trailer’s to theother components, the ECU is mountedon the trailer's chassis in a protectivehousing. This protective housing is simi-lar to that of the ABS VARIO-C system.The ECU can be used for implementinga large number of system configurations.The plug-in terminal has a connector forevery height sensor, pressure sensorand solenoid valve. Depending on thesystem used, parts of the terminal maynot be used.

As in the ABS system, the cables are fedthrough glands in the lower part of thehousing. To facilitate the allocation of theindividual cables to the plugs, bands aretaped around the cables.

OperationThe ECU contains a microprocessorwhich processes digital signals only. Amemory managing the data is connected

to this processor. The outlets to the sole-noid valves and to the indicator lamp areswitched via driver modules.

The ECU is responsible for– constantly monitoring the incoming

signals

– converting these signals into counts

– comparing these values (actual va-lues) to the values stored (index va-lues)

– computing the required controllingreaction in the event of any deviation

– actuating the solenoid valves

Furthermore, the ECU is responsi-ble for– managing and storing the various in-

dex values (normal levels, memory,etc.)

– data exchange with the RCU and theDiagnostic Controller

– regularly monitoring the function ofall system components

– monitoring the axle loads (in sy-stems with pressure sensors)

– plausibility testing of the signals re-ceived (for error detection)

– error recovery.

In order to ensure rapid control reactionto any changes in actual values, the mi-croprocessor processes a fixed programin cycles of some milli-seconds, with oneprogram cycle covering all of the abovetasks.

This program cannot be modified and isfixed in a program module (ROM). How-ever, it will use values stored in a freelyprogrammable memory. These values,the parameters, effect the computingprocesses and thus the ECU's control-ling reactions. They are used to commu-nicate to the computing program thecalibrating positions, the system configu-ration and the other preset values con-cerning the vehicle and functions.


ECU 35 pins

ECU 25 pinsECU for Trailer’s

ECU 35 pins

118 1

ECAS Solenoid Valve472 900 05 . 0

Valve for the axle with two height sensors

The solenoid valve shown in the illustra-tions below has three solenoids. One so-lenoid (6.1) controls a central breathervalve (also known as a central 3/2 direc-tional control valve), the others controlthe connection between the two air bel-lows (2/2 directional control valves) andthe central breather valve.

This valve can be used for establishingwhat is known as 2-point control in whichboth height sensors on both sides of theaxle separately control the level of bothsides of the vehicle so that the body iskept horizontal even when the load is notevenly distributed.

Design of the ValveSolenoid 6.1 actuates a pilot valve (1),and the actuating pressure from thisvalve flows through hole (2) and acts onpiston valve (3) of the breather valve.The pilot valve receives its pressure viaport 11 (supply) and connecting hole (4).

This drawing shows the breather valve inits venting position in which air fromchamber (5) can flow to port 3 via thehole of the piston valve.

As solenoid 6.1 is energized, pistonvalve (3) is pushed downwards, initiallycausing valve plate (6) to close the holeof the piston valve. The valve plate isthen pushed off its seat (hence the name'seat valve'), and supply pressure canflow into chamber (5).

The other two valves connect the air sus-pension bellows with chamber (5). De-pending on which solenoids (6.2 or 6.3)are energized, piston valves (9) or(10)are pressurized via holes (7) or (8),opening valve plates (11) and (12) toports 22 and 23.A solenoid valve for control of the otheraxle can be fitted to port 21.


Solenoid Valves Special solenoid valve blocks have beendeveloped for the ECAS system. Bycombining several solenoid valves inone compact block, both space and in-stallation time are kept to a minimum.

The solenoid valves are actuated by theECU as a control element; they convertthe voltage present into a pressurizing orventing process, i.e. they increase, re-duce or maintain the air volume in thebellows.

In order to achieve a large throughput ofair, pilot valves are used. The solenoidsinitially actuate those valves with a smallnominal width, and their control pressure

is then passed to the piston surfaces ofthe actual switching valves (NW 10 andNW 7 respectively).

Different types of solenoid valves areused, depending on the application: Forcontrolling a single axle, one seat valveis sufficient whilst a complex slidingvalve is required for controlling the liftingaxle.

Both types of solenoid valves are basedon a modular principle: Depending onthe application, the same housing isused to accommodate different parts ofvalves and solenoids.

119

This valve is similar to the valve de-scribed above but it contains fewer parts.

Since port 14 is connected to port 21 ofthe valve described above, no breathervalve is needed and only one pilot valve(1) is used. The piston valves (3) of bothair suspension bellows valves are pres-surized via two connecting holes (2) sothat each pressurizing or venting proc-ess is effected evenly for both bellowsvia chamber (5).

If the solenoid is not energized, thevalves are closed, as shown in the illus-tration. At this time, the only connectionbetween the bellows is the lateral choke(7), through which any difference in pres-sures can gradually be compensated.

The valve is connected to the air supplyvia port 12. This port is needed merely topermit the pilot valve to displace the pis-ton valve.


Valve for an axle with one height sensor

ECAS Solenoid Valve472 905 1 . . 0

Sliding valve with rear axle block and lifting axle block


Valve for the bus with a kneeling function


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By means of the RCU the driver can in-fluence the vehicle's level within the per-missible maximum limits. However, thiscan only be done whilst the vehicle iseither stationary or has not exceeded thedriving speed parameter.

The control keys for changing the vehi-cle's level are accommodated in a handyhousing which is connected, via a coiledcable and a socket on the vehicle, withthe ECU.

There are different RCUs depending onthe type of system used. The above illus-tration shows a unit with the largest pos-

sible number of functions. The functionsof this RCU are:

– raising and lowering of the chassis

– setting normal level

– stop

– storage and actuation of two prefe-rence levels

– raising and lowering of the lifting ax-le, or unloading or loading the trai-ling axle

– switching automatic lifting axle ope-ration on and off.

ECAS Height Sensor441 050 0 . . 0

From the outside, the height sensorlooks similar to WABCO's conventionallevelling valve which means that it canoften be fitted in the same location on thevehicle frame (the pattern of the two up-per mounting bores is similar to that ofthe levelling valve).

The sensor housing contains a coil inwhich an armature is moved up anddown. Via a connecting rod, the arma-ture is connected to a cam on the lever's

shaft. The lever is connected to the vehi-cle axle.

As the distance between the superstruc-ture and the axle changes, the lever isturned, causing the armature to moveinto or out of the coil. This changes thecoil's inductance.

This inductance is being measured bythe electronic control unit at short inter-vals and converted into a height signal.


ECAS Remote Control Unit446 056 0 . . 0

446 056 0.. 0 446 056 1.. 0

121

The pressure sensor produces a voltageoutput which is proportional to the pres-sure present. The measuring range liesbetween 0 and 10 bar; a pressure of 16bar must not be exceeded.

The signal voltage is sent to the ECU viaa connecting plug. Furthermore, the sen-sor must receive a supply voltage fromthe ECU via a third conductor. The cableharness must be encased in a hose orsimilar material in such a way that thehousing - which is otherwise waterproof -can ”breathe“.

Under no circumstances should thepressure sensor be connected to theconnecting line between air suspensionbellows and solenoid valve since thiscould result in wrong readings whenpressurizing or venting is in progress.

If air suspension bellows with two thread-ed ports, as offered by renowned manu-facturers of air suspension systems,cannot be used, a special connectormust be fitted.

This connector can consist of a T-shaped pipe union, with a small pipe be-ing welded into its pressure sensor con-nection protruding into the inside of thebellows, thereby sensing the ”settled“bellows pressure (these fittings areavailable from WABCO).

A normal tee-piece can be used but onlywhen a high raise/lowering-speed is notrequired. Two examples:

– One axle is sensed (drawbar-trailerwith one LA). The feed pipe frombellows to solenoid should be small(nominal size ø 6) but the connec-tion between bellows and sensor lar-ge.

– Two axles are sensed (3-axle semi-trailer with one LA). Use ø 12 pipebetween the sensed bellows. Fit thepressure sensor in a tee piece nextto one bellows. The line from the so-lenoid valve should be ø 9) enteringthe system at the other bellows.

Pressure Sensor441 040 00 . 0


1231

7.

Clutch Servos

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Clutch Servos7.Clutch Servo970 051 ... 0Modular Series

Purpose:To reduce the force required to pushdown the clutch pedal and to permit sen-sitive and accurate actuation of theclutch.

Design:The clutch servo consists of three parts:

– hydraulic slave cylinder

– control valve

– pneumatic servo cylinder.

Possible variants:

– trigger valve for transmission control

– optional feature for pressure sen-sors

– wear indicator.

Operation:The clutch servo is connected with the airreservoir for ancillary consumers via Port1, and with the pedal-operated hydraulicmaster cylinder via Port 1-4.

a) Clutch not engaged:During the declutching process, the airpressurized by the pedal-operated mas-ter cylinder is forced into Chambers Cand D through Port 1-4. This causes pis-

ton (a) to move to the left, closing the out-let (b) and opening the inlet (c). It thusallows the compressed air to pass fromPort 1 into Chamber A and from therethrough the duct (d) into Chamber B.Pneumatic and hydraulic pressures forcepiston (e) to the right, causing the clutchto disengage through the forcing lever (f).The air pressure in Chamber A balancesthe hydraulic pressure in Chamber D andthe control valve is in its neutral position.

b) Clutch engagedWhen the clutch is engaged once again,the oil from Chambers C and D returns tothe pedal-operated master cylinder. Pis-ton (a) returns to its original position onthe right, the inlet (c) closes and the pres-sure in Chambers B and A is evacuatedthrough the opening outlet (b) and Vent3.

The hydraulic and pneumatic pressuresat piston (e) fall, releasing the way backinto the engaged position. Through duct(g), the pressure in Chamber E can riseor fall.

The pressure in Chamber B remains pro-portional to the hydraulic pressure inChamber C at all times, thus giving thedriver full control when engaging theclutch.

If the air pressure is insufficient, it is pos-sible to declutch solely with the hydraulicpressure acting on piston (e). However,this requires greater force to be appliedto the clutch pedal.

The design of the modular series in-cludes automatic readjustment of theclutch, and some variants also have amechanical wear indicator.

For vehicles with Electronic Drive Con-trol (EAS), clutch servos from the 970051 4.. 0 series have a pressure sensorfitted.

EAS is a system which permits pulling ofand changing gear with standard aggre-gates without a clutch pedal having to beactuated. The driver can either changegear manually by actuating a master unitsimilar to EPS, or the process can be au-tomatic through the electronic controlunit.

1251

Clutch Servos

Purpose:To reduce the clutch pedal effort and toprovide a smooth and precise clutch op-eration.

Design:The clutch servo consists of two parts:

– a servo device: hydraulically control-led pneumatic control valve

– an actuating unit: differential cylinderunder hydraulic and pneumatic pres-sure which transmits force to theclutch mechanism.

Different modifications are possible:

– pneumatic valve with plunger (3 wayvalve),

– threaded port at the pneumatic ser-vo chamber,

– clutch wear warning device: electri-cal, mechanical or pneumatic,

– integral pneumatic pressure limitingdevice.

Operation:The clutch servo is connected to the aux-iliary reservoir via port 1, and via port 1-4to the pedal actuated hydraulic mastercylinder.

Clutch disengagement position:When disengaging the clutch, the oilforced by the pedal actuated clutch mas-ter cylinder enters through port 1-4 intochambers (C) and (D). Piston (a) movesto the right, closes outlet (b), opens inlet(c) allowing the compressed air from port1 to enter into chamber (A), and to flowthrough channel (g) into chamber (B).

Forced by the pneumatic pressure, pis-ton (f) moves to the right causing theclutch to disengage by means of a pushrod connected to the clutch actuating le-ver. The pneumatic pressure in chamber(A) balances the hydraulic force in cham-ber (D) closing inlet (c).

Clutch engagement position:When reengaging the clutch, the oil inchambers (C) and (D) is returned to the

pedal controlled clutch master cylinder.Piston (a) returns to the right, closes inlet(c), opens outlet (b) and allows the com-pressed air to be vented from chambers(A) and (B) to the atmosphere throughport 3. The hydraulic and pneumaticpressures on pistons (e and f) decrease,allowing them to return to the left, to theclutch engagement position. The airpressure partially returning throughchannel (d) compensates for the vacuumin chamber (E).

At all times, the pneumatic pressure inchamber (B) remains proportional to thehydraulic pressure in chamber (C) thusgiving the driver full control of the clutchengagement.

If there is insufficien't compressed air,clutch disengagement is still possiblewith the hydraulic pressure acting on pis-ton (e). However, this requires greaterpedal effort.

The spring behind piston (e) compen-sates for clutch friction wear.

7.Clutch Servo970 051 . . . 0Special Design

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8.

Air Braking Systems InAgricultural Vehicles

128

Air Braking Systems In Agricultural Vehicles8.

Brief Description Of The Dif-ferent Air Braking SystemsIn the single-line braking system, a singleair line between the tractor and its traileris used to fill the air reservoirs on thetrailer while the vehicle is in motion, andas the trailer is braked the pressure inthat line is reduced.

In the twin-line braking system, there isone line each between the tractor and itstrailer, one for filling the trailer’s air reser-voirs and one for controlling the brakingprocess (by reducing the pressure). Thebenefit of such a system is that the sup-ply of compressed air on the trailer isalso being topped up during the brakingprocess.

In a combined single and twin-line brak-ing system, this system can use eitherthe principle of the single-line or the twin-line system. Towing vehicles with a sin-gle-line and a twin-line connection for thetrailer thus permit both trailers with a sin-gle-line or with a twin-line braking systemto be connected.

It is important to remember that thebrakes of a trailer with a single-line sys-tem cannot be operated if it is used be-

hind a tractor with a twin-line brakingsystem; the same also applies vice-ver-sa.

Benefits Of A Twin-Line Air Braking System� The operating pressure and thus the

additional braking force can be sensi-tively graded. The same also appliesto long downhill gradients.

� Because of its adjustable predomi-nance on the relay emergency valve,the tractor-trailer combinationremains stretched-out and the trailerdoes not run up to its tractor.

� Less wear on the tractor’s brakes andthus longer life and lower mainte-nance cost.

� Any slight leakage does not effect theperformance. The compressor al-ways supplies sufficient compressedair for the braking system, also duringthe braking process.

� Unintentional disconnection of thetrailer from the tractor causes the trai-ler to be braked automatically (brea-kaway brake).

� High level of safety and enhancedride comfort. The jerking commonwith trailers which have had overrunbrakes fitted is prevented.

� It is not possible to mismatch hosecouplings due to the built-in mis-match-safeguard.

� Non-polluting because the medium,air, can be emitted directly to at-mosphere.

� Easy and simple to retrofit the air bra-king system.

Design of the Air Braking SystemThe air braking system shown in the illus-tration is a high pressure braking system(HPR) whose pressure level is controlledby an unloader valve (2). This supplypressure of 14 bar is limited to 7.3 bar bythe pressure limiting valve (4) locateddownstream from the air reservoir, thusin effect achieving a normal pressurebraking system (NPR). The trailer's brak-ing system (in this illustration it is a dualline braking system) is actuated by themaster cylinder (7) via an air/hydraulicdual line trailer control valve (8).

129

Air Braking Systems In AgriculturalVehicles 8.

Operation:Driving PositionThe compressed air from the compres-sor (1) flows via the unloader valve (2)which automatically controls the operat-ing pressure of the tractor's air compres-sion system, into the air reservoir (3).The supply pressure reading is shown onthe pressure gauge (5).

From the air reservoir (3), the air flowsvia the pressure limiting valve (4), set to7.3 bar, to the dual line trailer controlvalve (8), the 3/2 way valve (6), the sin-gle line trailer control valve (9) and on tothe supply hose coupling. In the trailercontrol valve (9), the pressure is limitedto 5.3 bar which reaches the hose cou-pling (11) (single line).

If a dual line trailer is attached, the supplypressure of 7.3 bar flows via the hosecouplings (10) to the trailer passing theline filter (15), the relay emergency valve(16) and finally the air reservoir (22).

To supply a second trailer with com-pressed air, two additional hose cou-plings (23 and 24) have been providedon the trailer. These are connected to thesupply and pilot lines downstream fromthe relay emergency valve (16).

Braking PositionWhen the brake pedals are actuated, the3/2 way valve (6) is opened and the trail-er control valve (8) receives the supplypressure of 7.3 bar.

This causes a small amount of pressureto reach the relay emergency valve (16)through the pilot line, actuating it. Thetrailer’s air supply now flows from the airreservoir (22) through the relay emer-gency valve, the adapter valve (17) andthe load-sensing valve (18) to the brakecylinders (20) on the front axle, andthrough the pressure limiting valve (19)and the load-sensing valve (18) to thebrake cylinders on the rear axle.

When the brake pedal is pushed downfurther, pressure is built up in the hydrau-lic master cylinder (7) which increasesthe actuating pressure at the trailer con-trol valve (8). Depending on the level ofhydraulic pressure, the trailer controlvalve (8) also builds up the pressure inthe pilot line leading to the relay emer-gency valve (16) and, through the load-sensing valves (18), transmitted to thebrake cylinders as a ratio of the load car-ried.

When the hydraulic braking pressure inthe tractor's braking system has been re-

duced, the air pressure in the pilot lineleading to the relay emergency valvealso falls, causing the pressure in thebrake chambers (20) to be reduced viathe adjusting valve and the load sensingvalves. The passage in the 3/2 way valveis closed once again, and the supplypressure of 5.3 bar (single line) begins tobuild up in the line between the trailercontrol valve (9) and the hose coupling(11).

130 1


Purpose:Limitation of output pressure.

Operation:Compressed air directed into chamber Athrough high-pressure port 1 flowsthrough inlet (j) and chamber B to low-pressure port 2. Pressure is thereby alsobrought to bear via hole (c) on diaphragmpiston (b), which is initially retained in itslower position by compression spring (a).

When pressure in chamber B reachesthe level to which the low-pressure sideis adjusted, diaphragm piston (b) over-comes the force of spring (a) and movesupwards with spring-loaded valve (i),thus closing inlet (j).

If pressure in chamber B rises above theset level, diaphragm piston (b) movesfurther upwards and is thereby lifted offvalve (i). Excess compressed air es-capes to atmosphere through hole (h) ofvalve (i) and exhaust 3.

If pressure starts to drop in the low-pres-sure line, this relieves diaphragm piston(b) of pressure so that it moves down-wards and pushes valve (i) open until asufficient quantity of compressed air hasbeen supplied through inlet (j).

Should the pressure in the high-pressureline rise above the maximum permittedlevel, safety valve (g) opens against theforce of compression spring (f) and al-

lows the excess compressed air to es-cape to atmosphere through hole (e) anddust cover (d). Pressure in the low-pres-sure line is not affected by this process.

The pressure existing in the low-pres-sure line is fully retained when the high-pressure line is evacuated.

The line at low-pressure port 2 can beevacuated only through equipment con-nected on that side.

Pressure Limiting Valve973 503 . . . 0

Compressed Air Generating System:

normal pressure - combined sin-gle line and dual line system hy-draulically actuated

Legend:1 Compressor2 Combined Unloader3 Air Reservoir 20 l4 Drain Valve5 Pressure Gauge7 Trailer Control Valve, single line8 Hose Coupling, supply line9 Hose Coupling, control line

10 Hose Coupling, single line11 Trailer Control Valve12 3/2-Directional Control Valve13 Master Cylinder

1311


3/2-Directional Control Valve563 020 . . . 0

Purpose:To alternately control the pilot line withthe supply line or the exhaust upon actu-ation of the brake.

Operation:When the tractor's brake pedals are ac-tuated, Piston (a) is forced to its upperposition by the spring force. The com-pressed air from the supply line at PortP2 now reaches Port A and from there

the downstream trailer control valve.This causes a brake pressure to be out-put for the trailer even before the hydrau-lic tractor brake becomes effective.

When the tractor's brake is released,Piston (a) is pushed downward onceagain by the brake pedal and the pas-sage is closed. The compressed air fromthe pilot line is now reduced via theopened passage to Port R2.

Shut-Off Cock452 002 . . . 0 and952 002 . . . 0

Purpose:To shut off an air line and vent the downstream line.

Operation:When the lever (a) is parallel to the lon-gitudinal axis of the stop cock the eccen-tric shaft (c) pushes valve (d) to the leftagainst the spring (e). Air passes unre-stricted from port 1 through the inlet (f) to

the line leading from port 2. If the lever(a) is turned through 90 degrees to itsstop, the spring (e) moves valve (d) tothe right and the inlet (f) is closed. Theline leading from port 2 is vented throughthe exhaust drilling (b).

132 1


Purpose:To control the dual line braking system ofthe trailer in connection with the trailer'shydraulic master brake cylinder or its hy-draulic transmitter.

Variant 252 provides for additional pneu-matic actuation, causing trailer brakepressure to be activated ven before thetractor's brake becomes effective.

Operation:In the release position, CompressionSpring (e) pushes Valve Sleeve (d) ontoInlet (c), keeping it closed. Port 2 is con-nected with Exhaust 3 via Outlet (b).

When the brake pedal is depressed, thehydraulic control pressure will act on Pis-ton (h) via Port 4, displacing that piston,together with Graduating Piston (a), tothe right. Outlet (b) is closed, Inlet (c)opens and the compressed air present atPort 1 flows to the relay emergency valvevia Port 2. The compressed air acting onGraduating Piston (a) moves it to the leftagainst the hydraulic control pressure,and Inlet (c) is closed. A final positionhas now been reached.

Some dual circuit Variants is also fittedwith an additional pneumatic controlport. This permits an upstream 3/2-way

valve to pressurize Port 42 and thusChamber A with an actuating pressure of7.3 bar when the brake pedal is de-pressed. Piston (a) closes Outlet (b),opening Inlet (c). Thus a small amount ofactuating pressure reaches the relayemergency valve via Port 2 before actu-ating pressure builds up at Port 4.

Any increase in the hydraulic actuatingpressure will also cause the pressure atPort 2 to be increased. As the brake ped-al is released, Ports 4 and 42 will be de-pressurized, causing the pressure inPort 2 to return Graduating Piston (a) toits original position. Outlet (b) opens, andPort 2 is vented via Exhaust 3.

The Trailer Control Valve also has aHand Brake Lever (f) which, as the handbrake is actuated, will push Piston (a)against Valve Sleeve (d), thus openingInlet (c), causing full braking of the trailer.

Trailer Control Valvefor dual line trailer braking systems470 015 . . . 0

1331

Purpose:To control the single or dual line brakingsystem of the trailer in connection withthe trailer's hydraulic master brake cylin-der or its hydraulic transmitter.

Operation:In the valve's release position, Compres-sion Spring (e) pushes Valve Sleeve (d)onto Inlet (c). The air supplied via Port 1flows via Hole A into Chamber B, raisingPiston (h) which takes with it Piston (k)and Valve (i). Inlet (l) is opened, permit-ting the air supplied to flow via Port Z intothe trailer's (single) control line. Whenthe forces of Pistons (h and k) are bal-anced, Inlet (l) is closed and the pressureat Port Z is limited to 5.2 bar. Port 2 isvented via Outlet (b) and Exhaust 31.

When the brake pedal is depressed, thehydraulic control pressure will act on Pis-ton (m) via Port 4, displacing that piston,together with Graduating Piston (a), tothe right. Outlet (b) is closed, Inlet (c)opens and the compressed air can nowflow via Port 2 to the control line trailer'sdual line braking system. The com-pressed air acting on Graduating Piston(a) moves it against the hydraulic controlpressure, and Inlet (c) is closed. A finalposition has now been reached. At thesame time, the pressurized Piston (h) ispushed downwards. Outlet (j) is opened,

and Port Z is partially vented via Exhaust32. A final braking position has beenreached when the force in Chamber Bacting on the underside of Piston (h) isgreater than the force acting on the top ofPistons (h and k). Piston (h) is raised toa point where Outlet (j) and Inlet (l) areclosed.

When the brake pedal is released, Port 4is depressurized, causing the pressurein Port 2 to return Graduating Piston (a)to its original position, opening Outlet (b).Port 2 is vented via Exhaust 31. At thesame time, the pressure acting on thetop of Piston (h) is reduced and the sup-ply pressure in Chamber B pushes it toits top end position. Via opened Inlet (l),Port Z is once again pressurized up to5.2 bar.

The Trailer Control Valve also has aHand Brake Lever (f) which, as the handbrake is actuated, will push Piston (a)against Valve Sleeve (d), thus openingInlet (c), causing full braking of the trailer.


Trailer Control Valvefor single or dual line trailer braking systems470 015 5 . . 0

134 1

Trailer Control Valvewith pressure control471 200 . . . 0

Purpose:To control the single line air braking sys-tem of the trailer in combination with thetrailer control valve attached to the footbrake lever for the tractor's dual line trail-er braking system and for limiting theoutput pressure to 5.2 bar.

Operation:In the release position, CompressionSpring (a) will hold Diaphragm Pistonwith Valve Sleeve (c) in its lower end po-sition. Outlet (d) is closed and Inlet (e)open. The compressed air from the trac-tor's air reseervoir flows via Port 1 to Port2 and reaches the relay emergencyvalve via the hose couplings. At thesame time, the compressed air flows, viaHole C, into Chamber D below Piston(h), and via Hole A into Chamber Eabove Piston (h). As soon as the pres-sure in Chamber B and in the line to thetrailer has reached 5.2 bar, Valve (g) isforced downwards against the force ofCompression Spring (f) until Inlet (e) isclosed.

When the tractor's foot brake is actuated,the output pressure from the trailer con-trol valve which is affixed to the footbrake lever for the dual line trailer brak-ing system will, via Port 4, reach Cham-ber F where a pressure will now build upbelow the Cup Collar which forces Dia-phragm Piston (b) with Valve Sleeve (c)upwards against the force of Compres-

sion Spring (a). Outlet (d) opens.Through Valve Speeve (c) and ExhaustHole 3, sufficient air will now be emittedto atmosphere to achieve the abruüt re-duction in pressure required for ad-vanced retardation of the trailer.

At the same time, the pressure in Cham-ber D will fall and Piston (h) is forceddownwards by the supply pressure inChamber E acting on its upper portion. Ittakes with it Valve Sleeve (c) which inturn closes Outlet (d) as it settles on thedouble cone valve.

As described above, the increased brak-ing effect of the tractor causes the pres-sure of the trailer's control line to befurther reduced whilst the advanced re-tardation of the trailer is maintained.When the tractor brake is released, thepressure in Chamber F is reduced onceagain, causing Diaphragm Piston (b) andValve Sleeve (c) being forced down-wards through the force of CompressionSpring (a). Inlet (e) opens and the supplyair present at Port 1 flows to the trailer'scontrol line via Port 2.


1351

Purpose:To control the braking forces of the trail-er’s brake cylinders as a ratio of the loadsetting.

Operation:When the brakes are applied, the pres-sure from the flanged relay emergencyvalve arriving at Port 1 flows into Cham-ber A and through the opened inlet (d)and Chamber B to Port 2 and thus to thetrailer’s brake cylinders. At the sametime, pressure is applied to the piston (e)which is initially being held in its upperend position by the spring (f). The forceof the spring (f) is dependent on the posi-tion of the lever (g) - together with thecam (j) - which is either ‘empty’, ‘halfload, or ‘full load (or even ‘1/4 load’ or ‘¾load’, on some vehicles). As soon as thecontrol pressure in the cylinders and onthe piston (e) corresponding to the loadsetting has been reached, the piston (e),together with valve (c) and spring-loadedvalve (a) will slide downwards, closing in-lets (b and d). This prevents the pressurein the cylinders from rising further.

In the event of any leakages in the trail-er’s braking system, the drop in pressurewill cause valve (a) to be raised by thepiston (e). Inlet (b) opens and more com-pressed air is supplied accordingly.

When the tractor’s brakes are released,Port 1 and Chamber A become pressure-

less. The higher pressure in Chamber Braises valve (c) and with valve(a). Inlet(d) opens and the brake cylinders areevacuated through Port 1 and the relayemergency valve. The reduction in thepressure acting on piston (e) causes thatpiston to be returned to its upper end po-sition by the spring (f).

The ‘release’ position which a number ofvariants of this load apportioning valvehave is used to release the brake whenno trailer is attached. To achieve this, theshape of the cam (j) relaxes the spring (f)to the point where piston (e) movesdownward, opening the outlet of thevalve (a). The compressed air from thebrake cylinders can escape to atmos-phere through the axial hole in piston (e)and Vent 3.

The adjuster screw (i) is used to adjustthe pressure reaching the cylinders fromthe load apportioning valve in the ‘empty’position. When the lever of the load ap-portioning valve is in its ‘full load’ posi-tion, that screw is accessible afterremoving the cap in Vent 3 and permitsthe initial tension of the spring (f) to beadjusted. Unscrewing the screw (i) caus-es the pressure in the cylinders to be in-creased, screwing it in causes thatpressure to be reduced. The pressurecan be similarly adjusted for the ‘halfload’ position. To do this, the ‘release’position is selected, and the adjustment

is achieved by turning screw (h). On loadapportioning valves which do not have a‘release’ position, screw (h) is reachedby selecting the ‘empty’ position and un-screwing the screw on the side of thebottom housing (this screw being foundonly on those variants).

When turning the screws (h or i), the loadapportioning valve must always be pres-sureless.


Load Apportioning Valve475 604 . . . 0

1371

9.

ETS and MTS - Electronic DoorControl System For Motor Coaches

138 1

System Design of ETS

ETS - Electronic Door Control System For Motor Coaches9.

Introduction Due to more stringent safety regulations,the motor buses of urban public transportand the motor coaches of private opera-tors in Germany have had to have safetycontrols fitted since the early eighties toprotect their passengers and to reducethe hazard of accidents in workshops.The two major criteria which have had tobe met since then are:

� features for opening and closingdoors to protect both persons andobjects

� features for the prevention of sud-den door movements after re-pres-surizing of cylinders.

Although these demands focusing on im-provements in technical safety were metby the introduction of the two WABCOsystems, following the pressureless andthe pressure-reduced principle, it verysoon turned out that - in terms of thenumber of appliances fitted and ease ofmaintenance - there was still room forfurther improvements.

This caused WABCO to develop an elec-tronically controlled system which fullytakes into account the following key re-quirements:

– safety for passengers

– reduction of the safety hazard in theworkshop

– easy to use by workshop staff

– reduction of system cost

– no service or maintenance required.

The development, focusing on these de-mands, resulted in the Electronic DoorControl System which has been pro-duced since late 1987 and is known bythe abbreviation

* E T S *The most important improvements whichhave been achieved are as follows:

– elimination of the limit and drum-type switches

– no more adjustment work to be doneby the vehicle manufacturer ortransport company

– development of a standard systemaccepted by all bus manufacturersin terms of their respective safetypolicies

– use of ETS in combination with sim-ple, time-tested pneumatic actuati-ons

– reduction of jamming forces.

Pneumatic ControlCompared with the pressureless and thepressure-reduced circuits, the use ofETS achieves a considerable reductionin the number of components fitted. Theyare replaced by a single door valvewhich has two key attributes:

� increasing and decreasing thepressure in the cylinder chambers(4/2 function = ordinary door ope-ration)

� reducing door slamming after re-pressurizing the cylinders followingthe actuation of the emergencycock. The door continues to be‘powerless’ after this process. Thedoor leaves can be moved by handto prevent any hazard to passen-gers.

139

ETS - Electronic Door Control SystemFor Motor Coaches 9.

Fig. 1

emergency cock

door valve

dynamic pressure switch displacement transducer

Fig. 1Example for an ETS system with rota-ry drive

The layout of an ETS door control systemshown above illustrates how the variousdoor components are connected. Thisexample shows a system with a rotarydrive, i. e. the door operating cylinder ismounted directly to the rotary pillar of thedoor leaf.

In this example, the door is monitored bya dynamic pressure switch in addition tothe displacement transducer. The dy-namic pressure switch is actuated by apressure pulse from the rubber seal ofthe main front edge. The ETS ECU has aseparate inlet for this function.

Fig. 2ETS system with linear door drive

.

This diagram shows the pneumatic con-nection with a linear cylinder drive. Theelectrical circuit is identical to that of therotary drive.

In both types of drive, the opening and

closing speeds of the door leaves can beadjusted by means of suitable throttlesor panels. For details on such adjust-ments, please refer to the vehicle docu-ments provided by the vehiclemanufacturer.

Fig. 2

140


Electronic ControlElectrical control is achieved by an elec-tronic control unit with a micro-controllerinside. It is available in two basic ver-sions:

– actuation control by the driver only

– automatic system for automatic dooractuation.

Both types of ECU contain identical com-puter programmes. Adjustment to the

various functions is made by means of aspecial programming process. The typeof ECU can be identified by the plug-inconnectors:

The ordinary control unit has a 25-poleterminal, as does the automatic controlunit which, however, also has a 15-polesocket for the automatic functions and atwo-way (manual-automatic) switch.

ETS - ECU446 020 . . . 0

4/2-Way Cock(Emergency Cock)952 003 . . . 0

Purpose:The emergency cock is needed to evac-uate the air in the door operating cylin-ders in a hazard situation, for thepurpose of repairs, or if the door operat-ing system has failed to permit the doorleaves to be moved by hand. At thesame time, it actuates the door valve insuch a way that when the door operatingsystem is pressurized once more, thedoor operating cylinders are rendered‘powerless’. Variant 952 003 031 0 of thisemergency cock has a switch for actuat-ing a warning facility.

Operation:In the normal position of the T-handle(a), compressed air from the supply lineflows through Port 1, through the 4/2-way cock and on through Ports 2 into theoperating lines.

By turning the handle (a) through 90° intothe emergency position, the supply lineis cut off and the operating lines areevacuated through Port 3.

normal position emergency position

1411


Purpose:In normal operation, the door valve actslike a 4/2-way valve and is used to alter-nately pressurize the chambers of thedoor operating cylinders. Unlike oldersystems, the door of the vehicle - if itmakes contact with an obstacle whileopening - becomes ‘powerless’ whichmeans that the door valve simultaneous-ly pressurizes all chambers of the cylin-der, causing the door to stop. Thisprevents people getting jammed, and thedoor leaves can be pushed by hand.

Operation:Opening And Closing of DoorsTo switch the door valve to ‘open’, a but-ton on the dashboard has to be pushed.This causes the ECU (outlet PIN 15) toclose the electric circuit to Solenoid A ofthe door valve, and the armature movesupward. The compressed air in hole (b)flows into chamber (c), acting on piston(a) which is forced to the right, also push-ing piston (f) into its end position on theright. In this position, Port 11 (energysupply) is connected with Port 21/22 andthe compressed air flows through thedoor valve into the opening chamber ofthe door operating cylinders. Since Port23/24 is connected with Vent 3, the doorsopen.

When the driver pushes the door buttonon the dashboard once more, the doorvalve is reversed into the ‘close’ positionby energizing Solenoid B (piston (f)moves piston (a) into its left end posi-tion). The closing chambers of the door

operating cylinders are pressurized, orthe opening chambers are evacuated.The doors close.

Jamming Protection: Reversal WhenClosing the DoorIf a person or an object gets jammed be-tween the main front edges of the doors,the motion of the door is impeded. Viathe electronic displacement transducer(potentiometer), this impediment is de-tected and processed in the electronics.The door’s electronics now reverse thedoor valve to its opening direction andthe doors are opened by the reversalprocess. After the driver has againpushed the button on the dashboard,thus providing another switching pulse,the door cylinders are pressurized intheir closing direction and the doors willclose.

Jamming Protection: Reversal WhenOpening the DoorIn order to comply with the guidelines forautomatic doors and for doors on motorcoaches actuated by the driver, the con-struction must be such to ensure thatpassengers who are located within thedoor area on the vehicle cannot getjammed as the doors open.

For this purpose, Solenoid C of the doorvalve is used, together with the electronicdisplacement transducers. If a person oran object is jammed by the back edge ofthe opening door, this impediment is per-ceived by the electronic displacementtransducer and processed by the elec-tronics. Solenoid C of the door valve is

energized. The valve reverses and pres-surizes chamber (g); both pistons (a andf) are in their end positions and bothsides of the door operating cylinders arepressurized through Ports 21/22 and 23/24. This causes the door operating cylin-ders to be virtually ‘powerless’. The doorleaves are brought to a stop and can bemoved by hand.

In this context it is important to know that- due to the difference in the surfaces ofthe pistons of the door operating cylinder- the door leaves slowly move to theiropen position when the obstacle hasbeen removed. However, the door cannow be closed at any time when the driv-er pushes the button on the dashboard.

Actuation of Emergency CockWhen the emergency cock is actuated,the door valve is actuated pneumaticallythrough Port 4. The door operating sys-tem is evacuated via the emergencycock. The door operating cylinders arepressureless, so that the door does notmove and can be opened manually. If thedoor is to be operated once again it issufficient to return the emergency cock toits normal position. Through the doorvalve (pneumatically operated via Port 4)all chambers of the door operating cylin-ders are pressurized - as described un-der ‘Jamming Protection: ReversalWhen Opening the Door’. The driver canthen close the door again by pushing thebutton on the dashboard.

4/3-Way Solenoid Valve(Door Valve)372 060 . . . 0

142 1


Door Operating Cylinderfor single-phase closing motions with damping on both sides422 802 . . . 0

Purpose:To open and close hinged and foldingdoors.

Operation:When the door valve is actuated, thecompressed air flows through Port 12into Chamber A. The pressure buildingup there forces the piston (c) and thepressure bar (d) to the right, opening thehinged door. At the same time, ChamberB is evacuated through Port 11 and theupstream door valve.

When the door valve is actuated onceagain, Chamber B is pressurizedthrough Port 11 and the pressure inChamber A is reduced through Port 12.The alternating increase in pressure onthe piston (c) forces it, together with thepressure bar (d), back to the left, and thehinged door closes.

The speed of the opening and closingprocess can be adjusted by means of thethrottle screws (a and f). To preventheavy and noisy impact of the door as itopens or closes, the door operating cyl-inder has two additional throttles (b ande) which achieve a buffering effect (slow-ing the motion towards the end).

The compressed air displaced by thefront end of the piston (c) in the door’sopening motion initially escapes evenlythrough throttle (f) and Port 11. However,approx. 40 mm before the end of thestroke has been reached it has to passthe buffer throttle (e) since the reinforcedpart of the pressure bar (d) protrudinginto the radial seal (g) prevents a furtherevacuation of Chamber B through throt-tle (f). The buffer effect for the closingdoor is achieved in a similar manner. Thecompressed air initially escaping evenlyfrom Chamber A through throttle (a) andPort 12 is forced past buffer throttle (b)approx. 40 mm before the end of thestroke.

The door operating cylinder has beendesigned in such a way that by switchingover the lines from the door valve endingat Ports 11 and 12, the motions are re-versed. The door will then open when thepiston rod is retracted, and close whenthe piston rod is extended.

1431


Door Cylinderfor single phase closing mo-tion with damping when pis-ton rod extends or retracts422 808 . . . 0

Purpose:To open and close slide glide and bifolddoors for buses. Application is specifical-ly for doors equipped with reverse con-trol system.

Operation:Upon activating the door valve, com-pressed air flows via port 12 into cham-ber (A). The pressure build up movespiston (a) as well as piston rod (b) to theright thereby opening the attached door.Simultaneously, chamber (B) is ventedvia port 11 and the subsequent solenoiddoor valve. At the same time, the twoports of the reverse switch, which areconnected to ports 41 and 42, are pres-surized or vented.

Reactivating the door valve, pressurizeschamber (B) via port 11, and chamber(A) pressure decreases via port 12. Dueto the pressure differences acting uponpiston (a), piston (a) and piston rod (b)move this time to the left and close theattached door. Also the reverse controlswitch is pressurized or vented as in thedoor opening process.

The door cylinder is equipped with an ad-justable throttle (d) which produces con-siderable damping as the piston rodnears the end of its motion preventingthe attached door from slamming.

Fig. A with damping as the piston rodapproaches full extension:During the initial phase of door opening,displaced air escapes unhindered viabore (C), however, at approximately 40mm before the end of the stroke, the wid-er diameter segment of the piston rodpenetrates the radial seal, preventingfurther venting of chamber (B) via bore(C), instead forcing air to vent throughthe damping throttle, which is adjustableby set screw (d).

Fig. B with damping as the piston rodapproaches full retraction:Approximately 40 mm before the end ofthe stroke, the inner bore of piston rod(b) surrounds and seals tube (e), nowforcing compressed air in chamber (A) tovent through throttle (d), which is adjust-able by set screw (d).

Fig. A

Fig. B

144 1


Pressure Switch441 014 . . . 0

The pressure switch is used to switchsolenoid valves or indicator lamps offand on. Correspondingly, there is an on-switch and an off-switch.

The switch position is dependent uponthe detail function of the facility to be

controlled. The pressure switch is not ad-justable within the respective series.

For purpose and operation, please referto Page 99.

Displacement Transducer446 020 4 . . 0

The displacement transducer (sensor)is a displacement-controlled potentiome-ter. In the opening process, the voltagerises from approx. 0.9 volts to approx.14 volts whilst in the closing process itfalls from approx. 14 volts to approx.0.9 volts. These voltage variations are

detected and processed by the door’selectronics. If the door hits an obstacleas it opens or closes, the electronics per-ceive this immediately and actuate thedoor valve 372 060 ... 0 accordingly.

145

MTS - Modular Door ControlFor Motor Coaches 9.

1

System MTS:

MTS was developed and first used in1997 based on the experience acquiredwith ETS. The special feature of this sys-tem is that it can be used with any doormodel. Inward swivelling doors, outwardswinging doors and swivel sliding doorswith pneumatic or electrical drive can becombined with one another without prob-lems!

Another innovation is also the connec-tion to the vehicle electric unit. Here, it ispossible to use a CAN data bus. There-fore, only two lines are required to controlup to 5 motor coach doors.

For vehicles without a central data bus,conventional cabling can be used as analternative. However, contrary to othersystems, the lines must only be connect-ed to the electronic control unit of the firstdoor.

Whether you are using a CAN or conven-tional cabling, the individual doors mustbe connected via the system CAN bus

and signal processing is centralised inthe control unit on the first door. Thisalso enables you to avoid the complicat-ed relay interconnections inherent in tra-ditional control.

Many parameters can be set in the soft-ware, in order to easily adapt control tospecific customer requirements. For allvehicle doors this data is stored on thecontrol unit of the first door. This way,the electronic control units on all the oth-er doors can be changed without takingthe parameters into account.

Naturally, the MTS system can perform adiagnosis: diagnosis takes place via thevehicle CAN bus or via a separate “K“line, regardless of the type of connectionused.

If Pneumatic doors are used, they aremonitored via pressure switches andnewly developed potentiometers whichare fitted directly on the heel post. Dueto mechanical coding, these sensors donot require any settings. Electrically driv-en doors can equally be monitored with

the help of these potentiometers; alter-natively, pulse generators installed in theengine can be used together with an in-dex switch.

A simple start-up program is used to bal-ance all the tolerances while using eachdoor for the first time. For this you onlyneed to move the doors once to the twostop positions by pressing the workshoppush buttons continuously.

The well-proven ETS principle was de-veloped for pneumatically driven doors.As a result, the damping mechanism in-tegrated into the cylinders is no longernecessary. This function is now per-formed by the door control valve. Sinceit is electronically controlled, damping ispossible at any moment. Apart from thecost-related advantages, this also resultsin much more flexible adaptability to themovement of the different doors. Thisalso prevents misadjustments, therebyincreasing operational safety.

MTS system principle:

Connection to a vehicle with CAN data bus

Connection to a vehicle with conventional cabling

Vehicle data bus

System data bus

Basic module

Extension module

Extension module

Door signals

Door drive

Door signals

Door drive

Door signals

Door driveSafety

devicesSafety devices

Safety devices

Door 1 Door 2 Door “n“

System data bus

Basic module

Extension module

Extension module

Door signals

Door drive

Door signals

Door drive

Door signals

Door driveSafety

devicesSafety devices

Safety devices

Door 1 Door 2 Door “n“

Conventional lines

Diagnosis K-Line

146

MTS - Modular Door Control For Motor Coaches9.

1

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MTS electronic control unit 446 190 . . . 0

MTS electronic control units have 60PINs, divided into 5 different 3-seriesplugs (6, 9, 12, 15 and 18 PINs), whichmakes confusion impossible. Specialcare was taken to combine functionalgroups as much as possible, and toavoid double pinning.

9-pin: CAN data bus interfaces ofthe vehicle and system bus,diagnosis interface, addressinputs

18-pin:* power supply, drive (valvesand/or engines), sensoranalysis

15-pin: door-specific functions, e.g.workshop push button, feel-ing wing edge, ramp, en-trance lighting, automaticfunctions, etc.

12-pin:* used only on door 1 for con-ventional connection, for in-stance, of driver's pushbut-tons, fault indication light,halt brake, red/green indica-tor, etc., if no CAN vehicledata bus is available.

6-pin:* used only on door 1 for con-ventional connection (most-ly) of automatic functions, forinstance door release, babycarriage function, stop re-quest output, etc. if no CAN

vehicle data bus is available.It is also possible here toconnect a driver's pushbut-ton for door 3 (not allowed byGermany lt. § 35e of StVZO!)

There are differences on the plug side,between pneumatic door controls andelectronic door controls, especially withregard to the composition of the 18-pinplug. For MTS-P, 1 or 2 door control valves, 1or 2 position sensors and 2 or 4 pressureswitches are connected, depending onthe number of door wings and/or the re-quired function. For MTS-E, 1 or 2 engines with 2-chan-nel incremental indicators and the corre-sponding limit switches or analogueposition sensors can be connected ac-cordingly. The power supply connectionand speed signal connection are identi-cal (only on door 1).

*): For pneumatic doors, an under-equipped MTS variant (“extensionmodule“) is available for use only ondoor 2. The 6-pin and 12-pin plughave no function here. The extension module can only con-trol one door control valve

MTS door sensor 446 190 15 . 0

148

MTS - Modular Door Control For Motor Coaches9.

1

4/3 solenoid valve (MTS door control valve) 472 600 . . . 0

A switch-selected exhaust air throttlewas added to the MTS valve in additionto the functions described on page 141(door control valve). Since the cylinders are controlled by theelectronic control unit, they are brakedbefore reaching the respective end posi-tions.

Door operating cylinder exhaustiontakes place without restriction if sole-noids A, B, and C are idle, since pres-sure is exerted on the diaphragm (g).

An additional solenoid C is actuated bythe electronic control unit to brake thedoor operating cylinder, depending onthe direction of movement (one of the ex-ternal solenoids A or B is activated). Airis supplied to the chamber (h), exertspressure on the diaphragm (g) and thelatter closes the passage to exhaust 3.Now, exhaust air from the door operatingcylinder can only escape into the atmos-phere via the adjustable throttle.

MTS - door operating cylinder 422 812 . . . 0

The compressed air expelled from thedoor control valve flows through port 12into the cylinder and moves the piston tothe right. Pressure is reduced at thesame time from chamber B via port 11and the connected door control valve.

If the door control valve is activatedagain, chamber B is pressurized via port

11 and the pressure in chamber A is re-duced via port 12. Due to the changingpiston pressurisation, the piston movesback to the left together with the push rodand the linked door closes.

149


1

MTS emergency cock with switch 952 003 . . . 0

In normal position, air supply flowsthrough port 1 via the cock and entersthe door control valve through port 2.Port 4 is connected to exhaust (port 3).

If the emergency cock is moved 90° tothe emergency position, air supply thenflows to port 4 and the downstream doorcontrol valve is pneumatically switchedto “powerless function“ (pressure is re-duced from both door operating cylindersides).

At the same time, the electronic controlunit receives an emergency cock activa-tion signal via the integrated switch.

To prevent the door wings from movingsuddenly after emergency cock reset,the door control valve always pressuris-es both cylinder sides simultaneously af-ter a “powerless function“.

1511

10.

Installation Of Pipes AndScrew Unions

152 1

Installation Of Pipes And Screw Unions10.The dimensions and versions of the butt-joint couplings are mainly based on DINstandards 74 313 to 74 319.Push-in couplings correspond mainly toDIN standard 2353. Butt-joint couplingsare approved for use up to a pressure of10 bar, push-in couplings up to a pres-sure of 100 bar.

Steel couplings are used for steel andnylon pipes. The surface of adaptors andnuts are bonderized and oiled or brightgalvanized and yellow passivated.

For copper pipes, brass couplings areavailable.

General Informations

Push in couplings are used for the follow-ing pipe diameters:

Consisting of the following parts:

1 Connector with internal taper2 Cutting ring3 Pipe nut

Butt joint couplings are used for the fol-lowing pipe diameters:


1 Connector2 Sealing washer (internal)3 Thrust ring4 Cutting ring5 Pipe nut

The function of the cutting ring is thesame in both kinds of couplings. Whenthe pipe nut is tightened, the cutting ringis compressed by the internal taper of theconnector and cuts into the outer wall ofthe pipe to create a collar and form asealed joint. The additional thrust ring inbutt-joint couplings is sealed with a seal-ing washer normally made of fiber, or ofzinc in couplings exposed to high tem-peratures.

Important:Before fitting the coupling, check thethread for damage. Any damagedthreads must be reworked. In order toprevent the thread seizing, it should begreased using graphite grease, Part No.830 503 004 4 (50 gramme tube).

Since all sealing washers settle underload, the fittings of new vehicles or instal-lations must be retightened after a shorttime. The same also applies after the re-placement of devices, since new sealingwashers must always be used. Beforeretightening unions, first loosen the pipenut to avoid damaging the pipe.

Any non-compliance could lead to loss ofpressure within the system and thus tobrake failure!

Road vehicles

6 x 1 Instrumentation lines and control lines

8 x 1Engine exhaust brake,door actuating devices,special equipment

10 x 1 Control lines

12 x 1 Brake lines and supply lines

Road vehicles

15 x 1.5 Brake lines and supply lines

18 x 2Connection from compressor to pressure regulator, supply lines

1 2 3

1 2 3 4 5

General Information for Steel Pipes

1531

Installation Of Pipes And Screw Unions

The pipe must be cut off at right angles.A pipe saw-jig should be used.

After sawing the pipe, the resulting burrsand swarf must be carefully removed. Inorder to avoid these parts getting into thepiping system after fitting, thus destroy-ing valve seats or blocking filters, either

of which would cause failure of the brak-ing system.

Important:Do not use a pipe cutter !This would mean that no right angle isachieved in cutting and would result inexcessire burrs, both inside and out.

As a consequence:the internal diameter would be reducedand the union not being tight.

10.Assembly Instructions for Steel Pipe

With pipes with an external diameter upto 10 mm, it is advisable to screw theconnector of the coupling into the deviceand to assemble the pipe directly at theplace of installation.

The prepared pipe end, with pipe nut andcutting ring, is pushed directly into theconnector and the pipe nut is screwed onby hand until contact with the cutting ringis felt.

The pipe must now be pushed againstthe stop in the connector and the pipe nutmust be tightened by about three- quar-ters of a turn, where by the pipe must notrotate with the nut. Since the cutting ringhas now gripped the pipe, further push-

ing of the pipe is unnecessary. Finaltightening is effected by turning the nutby about one turn. Then loosen the pipenut and check whether the cutting ringhas penetrated the outer skin of the pipeand the raised collar is visible in front ofthe edge. If necessary, the pipe nut mustbe tightened further.

It does not matter if the cutting ring canbe rotated on the pipe end.

After completion of the joint, or after loos-ening, the pipe nut is to be tightened witha normal spanner, without applying anyexcessive force.

Push in Couplings

Before tightening the pipe nut

After tightening the pipe nut

1 Butt end3 Cutting ring2 Internal taper4 Visible collar

1

2

3

4

Visible collar

A mark made on the pipe nut makes it easier to count the specified number of turns.

154

Installation Of Pipes And Screw Unions10.Pre-assembly must be carried out in avice. The screw spanner must have alength which is approximately 15 timesthe width across flats. If necessary, itshould be extended using a pipe.

Tighten the coupling in the vice first.Screw on pipe nut by hand up to stop atcutting ring. Press pipe with thrust ringagainst front side of connector. Thentighten pipe nut with a 3/4 turn (Caution:Pipe must not turn at the same time!).The cutting ring now grips the pipe endand further pressing is no longer neces-sary. Final tightening is carried out if thepipe nut is tightened again with a 3/4

turn. The ring now cuts into the pipe, vis-ibly bunching in front of its first cuttingedge.

Final tightening is faciliated if the pipe nutis lossened a number of times, so that oilcan find its way again between the fric-tion surfaces.

During final assembly, please see thateach pipe end the corresponding thrustring get back to the coupling where pre-assembly has been carried out.

Insert thrust ring and sealing washer.


1 Visible collar2 Sealing washer3 Thrust ring4 Cutting ring

These pre-assemblies in large numbersrequire an enormous amount of time ifthey are to be produced in the way de-scribed above. In such cases, a pre-as-sembly unit is advisable. With it thecutting rings can be fitted quickly. Thedevice is not tied to one work-place butcan be used where desired.

1

2 3 4

Butt joint Couplings

Instructions for Bending and Fitting of Pipes

Basically pipe for braking systems mustnever be hotworked since this will de-stroy the surface protection, and thescaling of the pipe can cause break-downs.

Bending of the pipe is best carried outwith a commercial pipe bender.

155

Installation Of Pipes And Screw Unions 10.Assembly Instructions: for Throttle Inserts

By the use of throttled inserts, the charg-ing and exhausting time can be adjustedto the particular requirements. The throt-tle can be inserted into the push-in cou-pling, if the pipe nut has first beenloosened and the pipe pulled out. Pleasemake sure that the pipe end is shortenedby the thickness of the insert's rim.

for Copper PipeThe assembly instructions above are in-tended for the use of steel pipe. If soft-annealed copper pipe (Cu soft) is to beused, sleeve inserts must be used in thepipe ends to prevent crushing the pipewhen tightening the pipe nut.

The insert is to be lightly driven into thepipe until it is flush with the pipe end. Theteeth on the insert are pressed into theinner wall of the pipe so that the insertprevented from moving or failing out dur-ing assembly of the pipe.

The bending radius must never be lessthan 2D. The pipe end behind the bendshould, as far as possible, have a totallenght of at least 2 H..

When fitting the pipes, care must be tak-en that they are without stresses afterthe pipe nuts have been tightened. Thismeans that before tightening, the pipesfit so well that the tightening processdoes not serve to position them properly.

Any non-compliance of this could re-sult in damage to the units, e. g. causefissures in the cylinder base.

Hose CouplingsWithin a compressed air installation thetransition from pipe to hose, or converse-ly from hose to pipe, will repeatedly oc-cur if moving parts have to be connected.If the pipe ends cannot be formed into asatisfactory standard hose nozzle, ahose coupling must be used for such ajoint. It is not permissible to push thehose onto a plain cut-off pipe end.

Any non-compliance can result in thehose slipping off the pipe when pressu-rized. This would result in a sudden fail-ure of the braking system.

Cut off hose at right-angles and pushonto the hose nozzle as far as the stop.The hose must be secured with a hoseclamp.

The tools illustrated in the comments onsteel pipes are available from ERMETO ARMATUREN GMBH, D-33652 Bielefeld, Germany.

Throttle Insert

Insert pushed in

Insert driven in

Push-in coupling with sleeve insert fully assembled

156 1

General Information on Nylon Pipes

Installation Of Pipes And Screw Unions10.Use and Installation in Automotive VehiclesThe physical and mechanical propertiesof nylon pipe are very different fromthose of steel pipe.

Extensive tests and sample installationsin motor vehicles using various grades ofnylon have shown that because of thespecial properties of the material, flexiblenylon pipe of black polyamide 11 arebest suited for pneumatic braking sys-tems and associated equipment.

PropertiesMaterialBlack polyamide 11, flexible, resistant toheat and light, even to intense ultra-violetradiation.

Physical Properties

Mechanical Properties

Permissible TemperaturesIn normal vehicle operation, tempera-tures of - 40 °C to + 60 °C are permissi-ble.

The indicated temperature of + 60 °Cduring continuous loading for the flexiblegrade was selected so that no changesin the properties of the material occur. Attemperatures over + 60 °C the softeningagent contained in this material canslowly disappear and the material as-sumes the properties of the semi-rigidgrade.(Constant temperature loading capacityof the semi-rigid grade + 100 °C).

The physical properties of the semi-rigidand flexible pipes are the same. The val-ues for mechanical properties such astensile strength, elastic elongation andworking pressures are higher in the caseof semi-rigid pipe. By reason of theirgreater mechanical resistance to defor-mation (bending), semi-rigid pipes aremore difficult to lay than flexible ones.

Becauses of the limited temperatureloading capacity of polyamide 11, it is ad-visable not to use nylon pipe in the vicin-ity of the engine or exhaust system.Particular care should be taken whenwelding to ensure that the pipes are notdamaged, and if necessary they shouldfirst be dismantled.

If a sprayed vehicle is dried in a brakingchamber or using radiant heaters, theunpressurised pipework must not besubjected to temperatures up to 130 °Cfor longer than 60 minutes.

In order to avoid damage to nylon pipeswhen welding, a plate should be fitted onthe vehicle:

Available in German only.Part Number 899 144 050 4

Density at +20°C 1.04 g/cm³

Moisture absorption at + 20° C(between 30 and 100%relative air humidity) 0.5 to 1.9%

Specific heat 2.44 J/gK

Thermal conductivity 1.05 kJ/m.h.K.

Linear coefficient of expansion between -20° C and +100° C 15 x 10-5 (1/°C)

Melting point +186°C

tensile strength 4800 N/cm²

Elongation at rupture at 20°C 250%

Elastic elongation 3.7%

PipeDimensions

min. Bursting Pressurein bar

max. WorkingPressure at 20°C in bar

6 x 1 81 278 x 1 57 1910 x 1 45 15

12 x 1,5 57 1915 x 1,5 45 1518 x 2 51 17

This vehicle is equipped with

�� Tecalan nylon pipes Caution during welding operations.

Permissible exposure to heat of unpressurised lines: Not more than 130°C for 60 minutes.

��

157

Chemical ResistancePolyamide 11 is resistant to all mediaused in the motor vehicle such as petro-leum products, oils and greases. Thetubes are also resistant to alkalis, un-chlorinated solvents, organic and inor-ganic acids and diluted oxidising agents.(The use of cleaning agents contain-ing chlorine should be avoided). Ad-vice on resistance to chemicals otherthan those indicated can be given on re-quest.

Change in LengthWhen installing nylon pipes particular at-tention should be paid to their change inlength at different temperatures. Thechange in length of the pipe is approxi-mately 13 times that for a steel pipe.

The coefficients of expansion are:

For steel pipes 1.15 x 10-5 per °C

For nylon pipes 15 x 10-5 per °C

This indicates a change of length per me-tre of 1.5 mm for every 10 °C differencein temperature. This change in lengthmust not be restricted by the fittings hold-ing the pipe.To fasten the pipes in position, plastic-lined pipe clamps or clamps or holdersmade entirely of plastic should, be used.It should be possible for the pipe to moveeasily in the fastenings, so that tempera-ture induced changes in length can bedistributed uniformly over the entirelength of the pipe. The pipe should beclamped at approximately 50 cm inter-vals.

CouplingsThe range of coupling from Wabco usedin vehicles can also be used for nylonpipes. Clamping rings represent similarlyeffective unions for pipes. To ensuregood seal and tight fit of the couplings,sleeve inserts should be used for all as-semblies with cutting rings and thrustrings. The sleeves should not be forcedor driven in, as otherwise the pipes ex-pand and the cutting rings can no longerbe pushed on.

The couplings are made push-in cou-plings and buttjoint couplings.

The function of the cutting ring is thesame in both kinds of union.

When the pipe nut is tightened, the cut-ting ring is compressed by the internal ta-per of the connector and cuts into theouter wall of the pipe - to create a collarand form a sealed joint. The pipe sealedby the firm fit of the cutting ring on the in-ternal taper. The additional thrust ring inbutt-joint couplings is sealed with a seal-ing washer, which normally consists offiber.

Before fitting male couplings, the threadsof the connecting pieces should bechecked for damage. Damaged threadsmust be rectified. In order to prevent thethread seizing it is advisable to smear itwith graphite grease before screwing in.The seal can be made with fiber or alu-minium sealing rings or with thrust ringsand O-rings. Do not use hemp or liquidjointing compounds.

Since all sealing washers settle underload, the couplings of new vehicles or in-stallations must be retightened after ashort time. The same also applies afterthe replacement of devices, since newsealing washers must always be used.Before retightening fittings first loosenthe pipe nut to avoid damaging the pipe.

When assembling the coupling it is im-portant that the end of the pipe istrimmed at right angles and inserted intothe coupling as far as the stop. To trimthe pipe property at right angles, use canbe made of cutting devices which can beobtained for pipes with an external diam-eter of up to 22 mm.

Installation Of Pipes And Screw Unions 10.

158

Assembly Instructions on Nylon Pipes

Installation Of Pipes And Screw Unions10.Push-in couplings used for the followingpipe diameters:


1 Connector with internal taper 2 Sleeve insert 3 Cutting ring 4 Pipe nut

Butt-joint couplings are used forthe following pipe diameters:


1 Connector 2 Sealing washer 3 Thrust ring 4 Sleeve insert 5 Cutting ring 6 Pipe nut

Push-in CouplingsFor pipes with an external diameter of upto 10 mm, it is advisable to screw thethread of the coupling into the device andto assemble the pipes directly at theplace of installation.

The prepared pipe end, with insert, pipenut and cutting ring, is pushed directlyinto the connector and the pipe nut isscrewed up by hand until contact with thecutting ring is felt. (Figure see page 153)

The pipe must now be pushed againstthe stop in the connector and the pipe nutmust be tightened according to thetorque table below. The pipe must not ro-tate with the nut.

Table of permissible tighteningtorques

If the indicated torques are not achieved,the force required for loosening is re-duced, and if they are exceeded thesleeve insert will be deformed.

Before tightening the pipe nut


1 Sleeve insert2 Butt end3 Internal taper4 Cutting ring5 Visible collar

6 x 1 As instrumentation lines

8 x 1 As auxiliary systems, e.g., air suspensions

10 x 1 As control lines with limitedvolumetric throughput

12 x 1.5As control lines with larger vol-umetric throughput, as general lines within a brake system or as lines to the brake actuator.

15 x 1.5Lines for general supply and to braking cylinders in braking systems.

18 x 2Supply line between air reser-voir and relay valve for high air flow.

1 2 3 4

1 2 3 4 5 6

Pipedimensions

Tightening torque

Loosening forces at

6 x 1 13 to 14 Nm 13 Nm = 460 N8 x 1 15 to 18 Nm 15 Nm = 580 N10 x 1 20 to 30 Nm 20 Nm = 870 N12 x 1.5 25 to 35 Nm 30 Nm = 1200 N

1 2

3

4

5

159

The following method can be used tokeep as close as possible to the correcttightening torques when they cannot beaccurately measured:

Tighten the pipe nut of the coupling fin-gertight and then 1½ to 1¾ turns with aspanner. It is necessary for the thread tobe in good condition. Then loosen the pipe nut and checkwhether the cutting ring has penetratedthe outer skin of the pipe and the raisedcollar is visible in front of the edge.

Butt-joint CouplingsButt-joint couplings are assembled asdescribed under push-in couplings. Anadditional thrust ring and sealing washer,however, must be used.


1 Visible collar2 Sealing washer3 Thrust ring4 Cutting ring5 Sleeve insert

Table of permissible tighteningtorques:

Bending of Nylon PipesThe pipe can be bent cold, keeping to thebending radi indicated below. Since,

however, it has a tendency to straighten,it should be fastened before and aftereach bend.

To avoid kinking, the minimum bendingradi shown in the following table must beadhered to. .

Technical Inspection of the Brak-ing System

Inspecting authorities have given theirapproval in principle to the use of nylonpipe for pneumatic lines in vehicles as analternative to the steel pipe and brakehose previously used. This approval issubject to the connection that suitablematerial is used for this purpose, and thatthe installation instructions applicable tonylon piping are complied with.

By marking their nylon pipe with the in-scription „WABCO-TECALAN“, WABCOprovide a guarantee that the material issuitable in accordance with terms of de-livery. Correct installation of the nylonpiping can be checked at the time of finalinspection of the vehicle using the instal-lation instructions mentioned above.

Pipedimen-sions

Tighteningtorques

Looseningforces at

15 x 1.5 30 to 45 Nm 30 Nm = 2100 N18 x 2 40 to 60 Nm 40 Nm = 2450 N

1

2 3 4

5

Dimensions of Pipe

min. Bending Radius r

6 x 1 30 mm8 x 1 40 mm10 x 1 60 mm12 x 1.5 60 mm15 x 1.5 90 mm18 x 2 110 mm


160

WABCO Quick Connecting Fitting System for Air Braking Systems

General Comments

Installation Of Pipes And Screw Unions10.

The connecting elements offer thefollowing benefits:

� A high degree of leakage protection:Cascade dynamic sealing

� No corrosion since the individualcomponents are made of brass orstainless steel.

� Quick assembly since no time-consuming fitting of sleeves,fastening of union nuts and reworkingin the case of leakages is needed.

� The seal against the pipe is effectedby means of a special seal located infront of the clamping element whichmeans that the clamping element

cannot damage the sealing area onthe plastic pipe. The seal preventsboth air getting out and dirt getting in.

� The threaded screw-in portions havean integrated seal suitable forthreaded connections to DIN 3852and for connections the type ofVOSS plug-in unions.

� The throughput resistance is similarto that of the cutting-ring coupling.

� Operating temperature range-45°C to +100°C (peak +125°C).

� Integral Air Passage (Sunnest innersupporting ring wall thickness) forbetter and quicker brake response.

Swivel Part

Connector

Connector Pivot

Applications The quick connection fitting system issuitable for all air lines in vehicles usingplastic pipes.

Any type of plastic pipe can be used:

WABCOPart number

External-Øx wallthickness

Operatingpressure at20°C in bar

828 251 908 6 6 x 1 27

828 251 907 6 8 x 1 19

828 251 906 6 10 x 1 15

828 251 905 6 12 x 1.5 19

828 251 904 6 15 x 1.5 15

828 251 903 6 18 x 2 17

161

Tube in a ConnectorAll Connectors are stamped with tube di-mension, and a batch number.

The pipes must be cut at right angle. Amaximum deviation of 5° is permissible..

The pipe must be pushed fully home intothe push-in connector. No tool is needed.Whilst pushing in the pipe, turn it slightly.

It is advisable to mark the length pushedin to be able to check it later..

The push-in lengths and the forces re-quired for pushing the pipe into the thepush-in connectors are shown in the ta-ble below.

Push-In lengths:

After inserting the pipe, check the clampby applying a pulling force of at least 20 to 50 N.

Tightening torques

General CommentsFor reasons of safety, the connectioncannot be severed once the pipe hasbeen pushed in.

If the unit is to be exchanged, the con-nection must be unscrewed from the unit.The connection will turn on the pipe inthe process. In the event of the sealingring between the unit and the connectionjoint being damaged, it must be re-placed.

For elbows and tees fixed to the unit bymeans of a counter-nut, the same O-rings and compression rings are used asfor the cutting-ring couplings.

L = Push-In length

e = Marking

External pipe-Ø x wall thickness

Push-In lengthin mm (± 0,5)

Push-Inforces in N

6 x 1 20 < 100

8 x 1 21 < 120

10 x 1 25 < 120

10 x 1.25 25 < 120

10 x 1.5 25 < 120

12 x 1.5 25 < 150

15 x 1.5 27 < 150

15 x 2 27 < 150

16 x 2 27 < 180

18 x 2 28 < 200

Thread Tightenningtorques

M 10 x 1 16 - 20 Nm

M 12 x 1.5 22 - 26 Nm

M 14 x 1.5 26 - 30 Nm

M 16 x 1.5 32 - 38 Nm

M 22 x 1.5 36 - 44 Nm

Assembly Instructions:


162

Installation Of Pipes And Screw Unions10.Assembly Instructions: For theRO ConnectionThe range includes two sizes of RO con-nectors: RO 13 and RO 15.

The RO connection: Plug-In Pivot (maleRO) and Plug-On Swivel part (femaleRO) = Building Block (Turnable).

The Plug-In Pivots are straight partswhere as the Plug-In Swivel parts arenumerous form parts:Elbows, Tees; Crosses . . .

The connection should be done manual-ly by pluging the two parts together to thebottom, with a combined rotation.

A twisting pull should then be applied forcontrol.

Because of the swivelling of the buildingblock (turnable), the RO connectionmust not be used:

– Between the truck and it's trailer, orthe axles and the trailer chassis.

– To connect a brake device preca-riously balanced.

When a RO connection is already usedin a kit (swivelling combination). A male/

female screwed connection with a coun-ternut for firm locking after orientation,being the alternative solution.

Replacement and interchangea-billty The interchangeability is possible proivd-ed that:

– The threads used are in accordanceto ISO 4039-1 or ISO 4039-2 (me-tric).

– The tubes used are in accordancewith DIN 74 324/ DIN 73 378 or NFR12-632 (metric) or ISO 7628.

Only the connection RO (between pivotsand swivel parts) is not interchangeablewith parts from other manufacturers be-cause of a exclusive design.

The WABCO quick connection fittingsystem can consequntly be used in re-pleacement of both:

– Tratitional 24° screwed compressionfittings range (with nuts and slee-ves).

– All types of other quick connectionfitting systems.

Plug and rotation

163

Index: Page

1. Components of the Motor Vehicle’s Braking System7Air Cleaner 432 511 ... 0 10Air Dryer 432 4.. ... 0 11Air/Hydraulic Actuators 421 30. ... 0 / 423 0.. ... 0 34Air Intake Filters 432 6.. ... 0 8Air Pressure Gauges 453 ... ... 0 23Air Reservoir 950 ... ... 0 21Anti-Freeze Pump 932 002 ... 0 17APU - Air Processing Unit 932 500 ... 0 20Automatic Load Sensing Valves 68 40. ... 0 / 475 7.. ... 0 45Brake Chamber 421 0.. ... 0 / 423 ... ... 0 33Brake Valves 461 11. ... 0 / 461 3.. ... 0 27Check Valves 434 0.. ... 0 24Charging Valve 434 100 ... 0 25Compressor 411 ... ... 0 / 911 ... ... 0 9Coupling Heads 952 200 ... 0 61Drain Valves 434 300 ... 0 / 934 30. ... 0 22Duo-Matic Quick Coupling 452 80. ... 0 62Emty / Load Valve 473 30. ... 0 52Four-Circuit Protection Valves 934 7.. ... 0 19Hand Brake Valves 961 72. ... 0 37Knuckle Joint 433 30. ... 0 51Pressure Limiting Valves 475 009 ... 0 / 475 015 ... 0 26Pressure Reducing Valve 473 301 ... 0 52Relay Valves 473 017 ... 0 / 973 0.. ... 0 42Safety Valves 434 6.. ... 0 / 934 6.. ... 0 16Slack Adjuster 433 5.. ... 0 36Solenoid Valves 472 ... ... 0 41Three-Circuit Protection Valve 934 701 ... 0 18Trailer Control Valves 973 00. ... 0 54Tristop®-Spring Brake Actuator 425 3.. ... 0 / 925 ... ... 0 35Unloader 975 303 ... 0 15Wendelflex ® -Hose Connection 452 711 ... 0 60

2. Equipment For Trailer Braking Systems 63Adapter Valve 975 001 ... 0 74Automatic Load Sensing Valve 475 713 ... 0 78

475 714 ... 0 79Directional Control Valve 463 036 ... 0 74Height Limiting Valve 964 001 ... 0 73Line Filter 432 500 ... 0 66Load Sensing Relay EmergencyValve 475 712 ... 0 76

475 715 ... 0 80Relay Emergency Valves 971 002 ... 0 68Relay Valves 973 0.. ... 0 72Solenoid Valves 472 1.. ... 0 75Trailer Release Valve 963 00. ... 0 66Pressure Limiting Valve 475 010 ... 0 71Quick Release Valve 973 500 ... 0 73

3. Anti-Lock Braking System (ABS) 83ABS Relay Valve 472 195 ... 0 89ABS Sensor 441 032 ... 0 91

Index 11.

164

Index11.Page

Clamping Bush 899 760 510 4 91Operating Cylinder 421 44. ... 0 93Proportional Solenoid Valve 472 250 ... 0 92Solenoid Control Valve 472 195 ... 0 88

4. Sustained-Action Braking Systems On Motor Vehicles 953/2-Way Valve 463 013 ... 0 97Air Cylinder 421 41. ... 0 98Pressure Switch 441 014 ... 0 99Solenoid Valve 472 170 ... 0 99

5. EBS-Electronically Controlled Braking System 101Axle Modulator 480 103 ... 0 107Backup Valve 480 205 ... 0 106Brake Signal Transmitter 480 001 ... 0 105Central Module 446 130 ... 0 105Proportional Relay Valve 480 202 ... 0 106Trailer Control Valve 480 204 ... 0 108

6. Air Suspension Systems and ECAS (Electronically Controlled Air Suspension) 111ECAS - ECU 446 055 ... 0 117ECAS Height Sensor 441 050 ... 0 120ECAS Remote Control Unit 446 056 ... 0 120Levelling Valve 464 006 ... 0 113Pressure Sensor 441 040 ... 0 121Raise/Lower Valve 463 032 ... 0 114Solenoid Valve 472 90. ... 0 118

7. Clutch Servos 123Clutch Servo 970 051 ... 0 124

8. Air Braking Systems In Agricultural Vehicles 1273/2-Directional Control Valve 563 020 ... 0 131Load Apportioning Valve 475 604 ... 0 135Pressure Limiting Valve 973 503 ... 0 130Shut-Off Cock 452 002 ... 0 / 952 002 ... 0 131Trailer Control Valve 470 015 ... 0 / 471 200 ... 0 132

9. ETS and MTS Elektronic Door Control System For Motor Coaches 1374/2-Way Cock 952 003 ... 0 1404/3-Way Solenoid Valve 372 060 ... 0 1414/3-Way Solenoid Valve 472 600 ... 0 148Dorr Operating Cylinder 422 80. ... 0 142Dorr Operating Cylinder 422 812 ... 0 148Displacement Transducer 446 020 ... 0 144ETS - ECU 446 020 ... 0 140MTS - ECU 446 190 ... 0 147

10. Installation Of Pipes And Screw Unions 151

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technologies onboard. In addition, WABCO provides the industry with advanced fleet management solutions and aftermarket services. WABCO reported sales of $2.9 billion in 2014. The company is headquartered in Brussels, Belgium, and has 11,000 employees worldwide. For more information, visit www.wabco-auto.com

WABCO (NYSE: WBC) is a leading innovator and global supplier of technologies that improve the safety and efficiency of commercial vehicles. Founded nearly 150 years ago, WABCO continues to pioneer breakthrough products and systems for braking, stability, suspension, transmission automation, and aerodynamics. Today, all of the world’s leading truck, bus and trailer

systems and components in commercial vehicles (english) · 2020-07-08 · 4 operation of air...

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