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3.1 Control circuit of pumpIn each delivery pump (P1,P2), the amount of delivery can be changed depending upon the loads

applied. The flow-rate is controlled by means of detecting the pressure between the pumps, to restrain amaximum load in the system. The functions for front drum, rear drum hoist and travel operations can beperformed at the same time. A maximum load is totally controlled in this system by means of detectingthe pressure of pumps (P1,P2) though the pilot line.

Pump P3 is used for swing motion (including retracting motion) only. The horsepower of the pump istotally controlled, thus the engine can be run without stopping when an overload is applied, as the flow-rate at P1 and P2 is cotrolled by swing load pressure.Pump control When the pump control switch located on the rear drum control lever is turned on, the discharge amountof the P1 and P2 pumps are controlled to a minimum.

It can be used to fine-control the hoisting and lowering of the hook. This switch also allows slowing thefront, rear, third, fourth drum, boom hoist, and travel operations.

Pump Type Pump No. Driven Actuator

Variable DeliveryPump (Tilting Plate)

Fixed Delivery GearPump

Pilot Line, Clutch Line, Brake Lline, Pump Control,Counterweight Removal Line, Travel High Speed Line

P4

P1 R.H. Travel, Boom Hoist, Rear Low 1-Speed, Front High 2-Speed

P2 L.H. Travel, 3rd/4th Drum, Rear High 2-Speed, Front Low 1-Speed

P3 Swing, Retract, Pump Regulator Control

2 Types And Driven Actuator Of Pumps

3 Explanation Of Control Circuit

Pump Control

Sump Tank

EngineP1 P3

P4

4-Series Control Valve

From Pilot Line (R.H. Travel, Boom Hoist,Rear Low 1-Speed,Front High 2-Speed)

To Control Device(Pilot, Clutch, Brake Line)

Accumulator

P2

R.H. TravelBoom Hoist

Rear Low 1-SpeedFront High 2-Speed

L.H. Travel3rd/4th Drum

Rear High 2-SpeedFront Low 1-Speed

Hydraulically OperatedElectrically Operated

From Pilot Line (L.H. Travel, 3rd/4th Drum,Rear High 2-Speed,Front Low 1-Speed)

Counterweight Cylinder Line

Oil Cooler

Swing And Retract

Gate Lock

CB04-001

XX

0504 2/14



R.H. Travel Control Lever

L.H. Travel Control Lever

To P1 PumpRegulatorTo P2 PumpRegulator

Control Valve

Control Valve

To Tank

Rear Drum Control Lever

Motor

Motor

Rear DrumFront Drum

4th Drum

3rd Drum (LBCE Supply)

Front Drum Control Lever

3rd/4th Drum Control Lever

Boom Hoist Control Lever

To P1 PumpRegulator

To P1 PumpRegulator

Boom Hoist Drum

To P2 PumpRegulator

To P2 PumpRegulator

To P1 PumpRegulator

To P2 PumpRegulator

1 Speed

2 Speed

Swing Control Lever

Relief Valve

P3P1 P4P2

Accumulator

7.84MPa(1137psi)

Line Filter

Hydraulic PowerSource

Counterweight Removal Device

Engine

Lever

L.H.Swing

R.H.Swing

Swing Device

Motor

2 Speed

1 Speed

CB04-002

X

Motor

Motor

X

"Stop" Side

Poilot PressureCut

"Operation" Side

3.2 Pilot circuit

3/14

The power source in the pilot circuit is pump P4. The pressure of pump P4 is also used for the brakes and clutches of the front, rear, 4th and boom hoist, the brakes in the swing mechanism, counterweight cylinders.The circuit pressure is controlled at 7.84MPa (1137psi) by the relief valve.

[Hydraulic power source]The hydraulic power source consists of an accumulator, relief valve and line filter. When the pressure reaches 7.84MPa (1137psi), a relief valve opens to return this hydraulic pressure to a tank.Even if the engine is stopped, the pressure will not drop suddenly since the reverse of pressurized hydraulic oil is prevented with a check valve. Still, the pressure drop may not be perfectly prevented due to some internal leakage in remote

control (pilot) valves and solenoid valves. In fact, the accumulator is necessary to maintain the circuit pressure constant for a while, by supplying the pressure into the circuit since the circuit pressure will drop to zero instantaneously whenleaking occurs in any part of the circuit as the hydraulic oil is incompressible.The pressure, however, will gradually drop and finally fall to zero. The accumulator is filled with nitrogen gas (N2) under 4.5MPa (653psi) and the circuit pressure from 7.84MPa (1137psi) to 4.5MPa (653psi) drops gradually but once the

pressure becomes lower than 4.5MPa (653psi), it will drop sharply.[Pilot pressure cut]When the lever located at an entrance of the operators cab is pushed forward, pressurized oil is returned to the tank and all the functions are stopped.It prevents the accident due to forgetting returning the control levers or wrong operations.


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Front Drum

P1

Front Drum Control Lever

LSOL: Lowering Stop Solenoid ValveBSOL: Brake Solenoid ValveCSOL: Clutch Solenoid ValveESOL: Emergency Solenoid Valve


Lowering

Brake Cylinder

CSOL BSOL

LSOL


2-Speed

HoistingRear Drum Control Lever

1-Speed

Clutch

Motor

P2

P4

2

Control Valve

CB04-003

0.39 to 2.74MPa(56.6 to 397psi)

Front Drum Lock Toggle Switch

Front Drum

S/C

HSOL: Hoisting Stop Solenoid Valve

11

6

ESOL4

3

5

HSOL7

S/CSafety Controller

Buzzer

Lock Pawl

Motor

Switch(Front)Switch(Rear)

Limit Switch

Overhoist Limit Switch(Normally Switched ONWhen The Weight IsApplied.)

Control Panel

R.H. Control PanelFree Mode

Lock ModeAuto-Brake Mode

28.4MPa(4119psi)

.7MPa(102psi)

.7MPa(102psi)

Rear Drum

Lowering

Brake Cylinder

CSOL BSOL

LSOL


2-Speed

Hoisting

1-Speed

Clutch

Motor

To Tank

2

Control Valve

0.39 to 2.74MPa(56.6 to 397psi)

S/C

11

6

ESOL4

3

5

HSOL7

28.4MPa(4119psi)

3.3 Front and rear drum circuitBasically the front drum and rear drum circuits are independent of each other. As mentioned before,

pumps P1 and P2 are of the variable delivery type. The P1 and P2 are designed to ensure efficientfunctions by restraining a maximum load. In addition, the line speed can be changed from low to highspeed and vice versa with a control valve. In the 2-speed circuit in the high-speed (2-speed) mode, thefront and rear drum are driven with the pressurized hydraulic oil delivered from both P1 and P2 pumps.

The pilot pressure functions the control valve. As this line is explained in 3.2, description will be madeonly of the pressure line here. Since the front and rear drums have the same circuits, the front drum isexplained herein.When the front drum control lever is set to the hoisting position (pulled toward), the pressurized

hydraulic oil of the P2 pump will flow in the direction of the arrow ( ) from the control valve. The oil isdirected to a winch motor through the check valve to rotate the motor and then its pressure will decrease.The oil will return to the sump tank again through the control valve.


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When the lever is returned to the neutral position, the hoist side of the control valve is a blocked circuit,thus the motor will not reverse. Of course, the reverse current of oil can be prevented with a check valvewithin the counterbalancing valve. Eventually, a double reverse current preventing system is availableas the control valve with neutral block position also function as a check valve preventing the reversecurrent. The control valve alone does not give an effective sealing so, the counterbalancing valve mainlyfunctions to block the oil flow.A relief valve set to 28.4MPa (4119psi) is provided in the counterbalancing valve. In normal operation,

this relief valve does not function. If any overloads or problems are produced in the circuit, the main reliefvalve 29.4MPa (4264psi) will function prior to this relief valve to protect the circuit. If the pressure isreleased instantaneously, the relief valve in the counterbalancing valve may function in some cases. Butthe counterbalancing valves will never function to release the pressure unless the main relief valve is outof order as the latter is set to the lower pressure limit.When the control lever is set to the lowering position (pushed forward), the pressurized hydraulic oil will

flow in the direction of the arrow ( ) from the control valve.But as the circuit is closed while the pressure is low, the oil does not flow in the circuit. The pilot

pressure exceeds the spring force only when the pressure reaches .7MPa (102psi), and the bypasscircuit is then opened to reverse the motor.In the case of front drum operation, pump P1 and P2 will run and the motor speed is doubled for the

high speed operation with the control lever shifted at high speed stage. The combined operation of thefront drum high speed and rear drum low speed cannot be got in this circuit, the rear drum operation isstopped.

[Anti-two block]When the hook is raised too high (to the head sheave anti-two block switch), the limit switch activates

to send a signal to the solenoid valve HSOL7, so that the pilot line for hoisting is changed over to the tankport.This will make the control valve return to the neutral position. The motor stops and an audio/visualalarm Two-block Limit.

[Front and rear drum pawl lock]The drum pawl lock is provided as a device to prevent the hook or the suspended load from falling.When the toggle switch is turned to the lock side, the electric motor of the pawl lock is activated and the

pawl is engaged with the drum at the same time a signal is sent to the solenoid valve LSOL 5. The valvewill connect the load lowering pilot line to the tank port. This will return the control valve to the neutralposition. When the toggle switch is on the lock side, pressurized oil from P5 flows to the tank port withoutoperation even if the control lever is turned to the lowering side. This produces a safety circuit, whichdoes not damage the machine at all.

[Lever lock] The function of control lever stops when lever lock switch on the control panel is turned to the lock side.When lever lock switch is turned to the lock side, a signal is sent to the solenoid valve LSOL5 and

HSOL7. Even if the control lever is set to hoisting/lowering position, the pilot pressure is connected totank port, the drum dose not rotate.


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[Explanation of brake function]No foot braking is required since the brake is automatically applied when the control lever is placed in

neutral position. But the automatic brake can not be applied when the brake mode is placed at the freemode (bucket mode) side.The brake has two systems. One is the automatic brake system and the other is the foot brake (free fall)

system. These two systems can be changed over by the manual select switch on the control panel andthe safety switch on the brake pedal for prevention of accidental changing.

[Automatic brake system]The automatic brake is activated by a spring force and is released hydraulically. No pilot pressure will

be charged with the front and rear drum control levers placed in neutral position. The BSOL2 and ESOL4in the automatic brake line activates by the signal sent from the pressure switch 1 which detects the pilotpressure, to flow out the oil from the release cylinder, to apply brake by a spring force. On the other hand,on the clutch side, the signal from the pressure switch 1 operates the CSOL6 to continuously guide thepressurized oil in order to activate the clutch. When the front and rear drum control levers are positionedto Hoisting (or Lowering), pilot pressure is charged and the BSOL 2 is activated. Pressure oil goesthrough BSOL 2 and is blocked briefly by ESOL 4 until 4 is activated, so the brake is not released yet. Onthe other hand, when the clutch line reaches 6.5MPa (943psi) the pressure switch 3 is activated andactivates the emergency brake ESOL 4. The brake pressurized oil flows through BSOL 2 and ESOL4,flowing into the brake release cylinder, releasing the brake.

[Foot brake system]The free fall (bucket mode) operation is made by selecting the switch of the front and rear drum control

lever at the same time, pushing the brake pedal lightly. With the free fall conditions, the pressurized oil isdirected to the release cylinder of the automatic brake device, and the automatic brake is released. Thebraking operation can be made by the foot brake. The brake will be applied through the link mechanismby pressing the foot pedal.For safety reasons, if the engine stops for reason or clutch pressure goes below 5.9MPa (856psi), the

ESOL4 is activated by the pressure switch 3 to apply the brake automatically. At the same time, thelowering stop LSOL5 is also activated to prevent suspended load from falling.


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3rd/4th Drum Control Lever

LSOL: Lowering Stop Solenoid ValveBSOL: Brake Solenoid ValveCSOL: Clutch Solenoid ValveESOL: Emergency Solenoid Valve


Lowering

CSOL BSOL

LSOL

To P2 PumpRegulator

Hoisting

P2

P4

2

CB04-004

.39 to 1.47MPa(56.6 to 213psi)

3RD/4TH Drum Lock Toggle Switch

Fourth Drum

S/C

HSOL: Hoisting Stop Solenoid Valve

Third Drum : Illustrated By LBCE

11

6

ESOL4

3

5

HSOL7


Buzzer

Lock Pawl

Motor

Switch

Switch (3RD/4TH SELECT)

Limit Switch

Overhoist Limit Switch(Normally Switched ONWhen The Weight IsApplied.)

Control Panel

R.H. Control PanelFree Mode

Lock ModeAuto-Brake Mode

.7MPa(102psi)

34.3 MPa(4975psi)

( )3RD4TH

Fourth Drum

Brake Cylinder

Clutch

3.4 Fourth drum circuitThe fourth drum is driven with the variable capacity pump P2 .The control lever is common to the third and fourth drum and change the switch on the control panel for the purposeof use.The hydraulic circuit for the fourth drum is the same as the front and the rear drum.However this circuit has not "High speed (2nd speed)".


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CB04-005


Buzzer

Boom Hoist Lever

Lowering Hoisting

Check Block

To P1 PumpRegulatorControl Valve

Brake/Drum Lock Solenoid Valve

Pressure Switch

P4

Drum

Drum Lock

Brake

P1

12

4

3


Boom

Overhoist Limit Switch

22.5MPa (3263psi)

1.76MPa (255 psi)

XX

.39 to 1.47MPa(56.6 to 213psi)

3.5 Boom hoist circuitThis circuit is basically the same as those of front and rear drum winches with the exception that the 2-

speed control system is not provided.The pressure for the boom hoist is produced by pump P1. When the control lever is moved to the

hoisting position, (pulled toward the operator), the pressurized hydraulic oil will flow in the arrow ( )direction as the pilot pressure moves the spool of the control valve.


9/140504

The oil passes through a check valve in the counterbalancing valve to rotate the motor, and then returnsto the control valve under low pressure from the motor, and to the sump tank. On the other hand, thesame pilot pressure is detected with a pressure switch and the solenoid valve in the brake line and drumlock circuit are energized. Thus, the pressure in the pilot line (P4) is directed to the brake cylinder anddrum lock cylinder to release the brake and drum lock before the motor rotates.When the control lever is returned to the neutral position, the pilot pressure will become low and the

pressure switch will cut off the electric current to the solenoid. Then the spool is changed over and thepressure in the brake line and drum lock is cut off returning the oil to the tank port. The disk will be appliedagain by means of a force produced by a spring of the brake cylinder to lock the drum with secure stop ofthe motor. In addition, boom lowering is prevented by the drum lock.Although a counterbalancing valve is incorporated into this circuit like the front and rear drum circuits,

the disk brake is also used to secure sufficient motor locking. The select switch of free mode is notprovided is the difference from the front and rear drum brake mechanism.When the control lever is moved to the lowering position (pushed forward), the oil flow direction will be

reversed, flowing in the direction of the arrow ( ).The motor can not be reversed since a check valve inthe counterbalancing valve is provided in the return circuit.The oil is returned to the control valve by opening the bypass circuit with pilot pressure produced from

the self-pressure. With this function, the motor will rotate and the boom can be lowered by rotating thedrum. The pilot pressure can be applied smoothly with a throttle valve provided in the pilot line, thus theboom can be lowered smoothly. The pilot pressure is 1.76MPa (255 psi). and changes over the functionsof valve as the bypass circuit.

[Boom over hoist limiting device]When the boom reaches raising limit, the limit switch activates to send signal to the solenoid valve 1, so

that the pilot line for hoisting is changed over to the tank port. This will make the control valve return to theneutral position. The motor stops, and the buzzer sounds.


10/140504


Swing Brake Solenoid

Swing Device

SwingMotor

BrakeReleaseCylinder

20.6 MPa (2988 psi)

Retract Cylinder

Rotating Joint

Swing/Retract Control Valve

P4P2 P1

R.H. L.H.

Sump TankCB04-006

XX

Swing Control Lever

Swing Brake Release Switch

R.H.L.H.

.39 to 1.47Mpa(56.6 to 213psi)

Line Filter

EngineRelief Valve

Accumlator

P3

3.6 Swing circuit The swings are independent from each other. The circuit is same as the R.H. swing and L.H. swing.

3.6.1 Swing circuitWhen the swing lever is pushed forward, (L.H. swing) the oil pressurized by pump P3 will flow in the

direction of the arrow ( ) from the control valve. The pressurized hydraulic oil actuates the swing motorand returns to the control valve under low pressure and then to the sump tank ( ). If the rotation of themotor is stopped by any external pressure applied, the oil will be bypassed through a relief circuit(20.6MPa(2988psi)) of the control valve to protect the circuit since the highly pressurized oil is dead-locked in the circuit.The swing brake release switch on the swing lever is used for parking temporarily after the swing is

stopped, and should not be put into function during swinging. If actuated in swinging, accidents mayoccur. There is a method to stop the swing at the required position, in which the swing is stopped byshifting the control lever slightly in the reverse direction.Normally, the swing speed is controlled by means of the control lever stroke.

3.6.2 Swing brake circuitBy placing the switch on the swing lever in ON, the pressurized oil is directed in the brake release

cylinder to release a wet-type multi-plate brake.By placing the switch in OFF, the solenoid valve should be in OFF. The pressurized oil in the brake

release cylinder is drained and the wet-type multi-plate function to brake the swing by spring pressure.


11/140504

Right Travel Device

To Tank

P1

P4

P2

R.H. Travel Control Lever.39 to 1.47Mpa (56.6 to 213psi) L.H. Travel Control Lever.39 to 1.47Mpa(56.6 to 213psi)

To P1 Pump RegulatorTo P2 Pump Regulator


CB04-007

Forward Backward Forward Backward

Control Valve Control Valve

Rotating JointD H G A BC

.02MPa(2.9psi)

20.6MPa(2988psi)

.02MPa(2.9psi)

20.6MPa(2988psi)

Ps Pm2PsPm2

Pm1Pm1

Travel Motor(L.H)

TTP2

P2P1

P1R/C R/C

Backward Backward

Control PanelTravel High SpeedSelect Solenoid Valve

Shoe Extension Cylinder

Travel High Speed Switch

Forward Forward

3.7 Travel circuitThe travel motor receives the pressurized hydraulic oil from two pumps, which do not flow together.The pumps P1 and P2 supply the pressurized oil to the R.H. motor and L.H. motor respectively. Dis-

crepancy in discharge of P1 and P2 pumps may cause uneven travelling or unbalanced travelling whichmay be increased by circuit resistance. To avoid this trouble, the pressure of both pumps must bechecked and then corrected to be equal in the regulator circuit in this system.


12/140504

3.7.1 Travel circuitWhen the travel control lever is pushed forward or backward, the oil pressurized by pump P1 will flow in

the direction of the arrow ( ) as the pilot pressure .39 to 1.47MPa (56.6 to 213psi) changes over thecontrol valve spool, and reaches the brake valve through a rotating joint. The brake valve opens thepipeline,directing the pressurized oil to the motor. As the motor has a brake with it, the oil alone can notrotate it. Therefore, a part of the pressurized oil must be directed to the brake cylinder to release the diskbrake to free the motor. Oil pressure from the motor will become low and the oil will return to the sumptank under low pressure throuth the control valve along the return circuit.With the control lever set to the neutral position, the brake valve blocks the oil circuit to stop the motor

and at the same time, the spring releases the oil in the brake release cylinder and the multi-plate brakeapplies and the motor drive shaft is secured. This prevents the machine from traveling on a slope.If any load greater than the rotating torque is applied on to the travel motor, the motor will stop and the

oil pipeline circuit will close resulting in breakage on instruments or piping as the pressure will rise too far.A safety valve therefore, is necessary to prevent any breakage or damage in the circuit. The pressure isreleased to the tank port by opening the bypass circuit with the main relief valve 29.4MPa (4264psi) inthe control valve.A relief valve (set pressure: 32.4MPa (4699psi)) to release the overpressure is provided in the motor

unit.

3.7.2 High speed circuitWhen the travel high speed switch on the control panel is placed in "ON" side, the travel high speed

select solenoid valve is changed over and the control hydraulic oil generated from pump P4 changesover the speed select valve built in the travel motor through the solenoid valve and the rotating joint.The regulator in the motor is activated by the pressurized oil and a tilting angle of the tilting plate be-comes smaller.Therefore, the travel operation can be made at high speed with motor speed increased. (The motordisplacement is decreased.)

3.7.3 Shoe extension cylinder circuitWhen the travel control lever is placed forward or backward, the oil, as the above mentioned, will flow to

the shoe extension cylinder at the same time the travel motor is started, to give appropriate tension(adjustment value) shoe extension cylinder automatically. The condition is maintained even if the lever isplaced in neutral.The pressurized oil is maintained by the check valve, and unless the external pressure is applied, the

shoe does not contract. If the external pressure exceeds 20.6MPa (2988psi), the check valve will beopened. The check valve releases the pressurized oil to prevent applying excessive force to the shoeand the drive equiment.

Note: Refer to the operator's manual for tension adjustment value.3.7.4 Travel brake circuitWhen the travel motor is driven, the pressurized oil is directed in the brake release cylinder to release.

With the lever in neutral, the control valve is in neutral and the pressurized oil in the brake releasecylinder is directed to the tank. The brake is actuated by the spring force.


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CB04-008

Retract Cylinder

Swing/Retract Control Valve

Rotating Joint

To Swing

Sump Tank

20.6Mpa(2988 psi)

P3 Engine

Extend Retract

3.8 Retract cylinder circuitThe retract cylinder, installed on side frames.When the retract lever is placed in the Extend side, the pressurized oil with pump P3 will flow in the

direction of the arrow ( ).When the retract lever is placed in the Retract side, the pressurized oil from pump P3 will flow in the

direction of the dotted arrow ( ). If any external pressure is applied, the oil will be bypassed through arelief circuit (20.6 Mpa (2988 psi)) of the control valve to protect the circuit since the highly pressurized oilis deadlocked in the circuit.


14/140504

Sump Tank

Relief Valve

Accumulator

To Control Device

CB04-009

P3 P4

T P

20.6MPa(2988psi)

Counterweight Removal Clyinder

Line Filter

P2P1

Engine

3.9 Counterweight cylinder circuitThe counterweight removal/installation cylinder line is controlled by pump P4. The oil discharged fromthe pump P4 usually flows to control devices such as the pilot line, clutch, brake line. The control valve isused for counterweight removal/installation. When the lever is set to the Extend (lowering) side, thepressurized oil from P4 pump flows in the direction of arrow ( ), passing through the line filter, controlvalve and the cylinder. The oil on the Retract side in the cylinder flows in the direction of dotted line ( ),passing through the flow control valve, control valve and the sump tank. On the other hand, when thelever is set to the Retract (lifting) side, the oil flows reversely.When the oil is fed continuously by the P4 pump, its temperature rises causing damages of devices andpiping. A safety circuit for prevention of such damages is provided, where the main relief valve of thecontrol valve is activated at 20.6Mpa (2988psi) to lead the oil to the sump tank.Other control devices cannot be used during operation of the counterweight removal/installation cylinder.

link-belt ls-108 hylab 5 hydraulic diagram.pdf

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