United States Patent" - 1191 Seider

1111 3,861,855 1451 Jan. 21, 1975

[54] AUTOMATIC COMBUSTION CONTROL 75 Inventor: Se mour Seider, H lett H b , Primary Examiner-‘Edward G- Favors

[ 1 N‘yY_ ew at or Attorney, Agent, or Firm-Alan K. Roberts

[73] Assignee: B.S.C. Industries Corp., Hewlett [57] ABSTRACT ’ Harbor’ .N‘Y' The control of efficiency of combustion is effected by [22] Filed; Dec, 19, 1973 the use of a smoke detector and mechanical ampli?er,

I and by solid state devices for the detection and ampli [211 Appl' No" 426’323 fication of electrical signals produced thereby, with

the ultimate purpose of positioning a modulating-type [52] us. 01. ............................... .. 431/76, 236/15 E clcctric motor which in turn adjusts a fuel 0" valve [51] 1111. C1. ............................................ .. F23n 5/08 and Primary and secondary air valves or dampers by [58] Field 6: Search .............. .. 431/76, 79; 236/15 E means of mechanical linkagcs- Either a Single motor

or three separate modulating-type electric motors can [56] References Cited be used for the three combustion control functions,

UNITED STATES PATENTS i.e., fuel valve positioning, primary air valve or 3,549,089 12/1970 116161611 ........................... .. 236/15 E dzrsrilgggigosmomng and secm'dary 3" valve or damper 3,701,622 10/1972 Ducasse ..... .. p g‘

3,723,047 3/1973 De Livois ............................ .. 431/76 33 Claims, 19 Drawing Figures

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AUTOMATIC COMBUSTION CONTROL

FIELD OF INVENTION

This invention relates to the automatic maintenance of a pre-set level of efficiency of combustion and is par ticularly useful for the control of the combustion of light to medium weight fuel oils, commonly referred to as No. 2 fuel oil and No. 4 fuel oil, in furnaces used for heating air, water, or for the production of steam. This invention is applicable to any fluid fuel, gas fuel or solid fuel such as powdered coal.

BACKGROUND

It has long been known that the efficiency of combus tion can be determined by the measurement of the quality of ?ue gases resulting from such combustion. Good combustion of ?uid fuels results in effluents which are high in CO2 and low in CO, and which con tain very little solid matter or smoke. As a practical matter, the highest efficiency readily obtainable in day to-day automatic operation of unattended fluid fuel burners is usually accompanied by a slight haze of pale blue smoke, or obscuration, at the chimney or vent. ‘Completely clear ?ue gas venting usually signi?es ex cess air and lower efficiency of combustion. Heavier ‘smoke of darker color and density usually signifies in sufficient air and lower efficiency of combustion. While there exist, at this time, many devices to mea

sure smoke level in ?ue gases and to act, upon reaching a predetermined level, to sound an alarm, or to shut down the burner, or to provide combinations of these responses there does not exist, a simple, practical de vice that will, on attaining the pre-determined smoke level, automatically modulate the air-oil ratio to main tain that pre-determined level and thus maintain the combustion efficiency desired, without relying on man ual resetting on the part of service personnel. The rea son for this appears to reside in the insufficient sensitiv ity of existing devices which therefore do not permit discrimination between very low levels of smoke den sity as is necessary to maintain a close level of light smoke density in the ?ue gases. Among the patents disclosing devices relating to the

invention are the following:

3,238,992 2,562,507 1,947,303 3,224,838 2,545,732 1,906,244 3,216,661 2,533,430 1,849,638 3,193,199 2,511,177 1,779,513 3,162,846 2,441,025 1,766,980 3,074,644 2,393,897 1,764,715 3,049,300 2,371,590 1,710,772 2,966,209 2,366,170 1,688,126 2,874,763 2,361,294 1,645,350 2,816,863 2,352,143 1,644,123 2,784,912 2,324,821 1,599,410 2,780,414 2,285,564 1,562,087 2,762,568 2,285,287 1,550,410 2,760,922 2,018,925 1,482,125 2,737,347 2,008,562 1,417,374 2,622,967 1,997,797 935,763 2,592,847 1,987,433 RE 19,592

From the above listed patents, it is believed pertinent to mention in detail only the Decker U.S. Pat. No. 1,987,433, the Brooke Jr. et a1. U.S. Pat. No. 2,285,564, the Logan U.S. Pat. No. 2,441,025 and the Dijt et al. U.S. Pat. No. 3,243,116. With respect to the Decker Patent, this discloses im

provements in the automatic control of combustion in

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2 furnaces. However, aside from the fact that this patent fails to disclose a smoke ampli?er, the basic premises in this patent differ substantially from the apparatus to be disclosed hereinunder. Specifically, the Decker de vice is essentially a semi-manual device matching steam rate to a predetermined fuel rate. The draft in this de vice is adjusted to match the steamrate to the fuel rate. As a part of the control system, an automatic CO2 ana lyzer overrides the steam rate control. Also, an opacity device in the smoke stack furtheroverrides the steam rate control. There is no control of fuel rate but rather only a control of draft rate. Accordingly, as will be seen, this device is not comparable to the device pro vided in accordance with the invention. The Brooke Patent also relates to combustion con

trols and is observed to be especially advantageous for furnaces using ?uid fuel or the like including gas, oil or powdered coal. It is stated that the Brooke invention permits controlling combustion ?uid according to the quality or character of the furnace gases in a reliable, accurate and satisfactory manner. As will be seen, this invention fails to disclose a smoke ampli?er and thus cannot achieve the advantageous quality of control that is achieved in accordance with the invention. More over, this patent fails further to disclose any of the fea tures which will become evident hereinafter. As to the Logan U.S. Pat. No. 2,441,025, this patent

also discloses improvement in automatic oil burner controls. Brie?y, this patent discloses a system which will not work as efficiently as the system of the present invention, since it depends upon mechanical relays and unampli?ed smoke detection. The present invention, it willbe seen, is a de?nite improvement over what is dis closed by Logan. With respect to the Dijt U.S. Pat. No. 3,243,l 16, the

control methods are dissimilar from that which will be described below and there is no provision of smoke am pli?cation. The principal objection to the devices discussed

above and the devices of the above listed patents is that they all fail to take into account that the ideal level of smoke is a relatively low level which cannot effectively be picked up by ‘a smoke detecting means such as a photocell or photoelectric cell. This results in a rela tively poor quality of control which is con?rmed by the fact that none of the aforementioned devices have found substantial use in industry or in residential heat mg.

SUMMARY OF INVENTION

In accordance with the invention, it is proposed to measure the smoke density in the smoke pipe or ?ue of a furnace by means of radiation from a uniformly radi ating source such as an incandescent light bulb. The ra diation falls on a photosensitive cell, preferably a cad

' mium-sulphide type cell, whose resistance to electrical

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?ow varies with the intensity of the light impinging upon it. As the smoke interferes with the passage of light through the smoke pipe, and therefore regulates the quantity of light impinging upon the photocell, the resistance of the cell will vary in direct proportion to the quantity of smoke passing through the smoke pipe. However, as the level of smoke to be measured and maintained is very low in the pertinent range, a smoke gathering device or ampli?er is used to concentrate the smoke level in the area of the light beam. This is a

3 unique feature of the invention to be explained in detail hereinafter. By applying a ?xed voltage across the resistance of a

divider network including the photocell, a varying volt age is created. This voltage is amplified and fed to a solid state analog-to-digital converter. This solid state converter creates, for example, a four-bit word which represents the level of smoke detected by the photo cell. These four-bit words trigger an appropriate triac switching circuit for controlling the resistance coupled to a modulating electric motor and, in turn, controlling its position, thereby controlling the air-oil ratio and, fi nally, the smoke level in the smoke pipe. From the above, it will be noted that it is an object

of the invention to provide an improved'combustion control apparatus. It is a further object of the invention to provide improvements which avoid the defects re sulting from prior efforts to run control systems by the detection of a relatively low level of smoke density. Yet another object of the invention is to provide an

improved system which is relatively unsusceptible to deposits of soot or the like from the smoke being exam ined. Still another object of the invention is to provide a system which is relatively independent of the heat contained in the smoke being run through the detector system. Yet another object of the invention is to pro vide improvements which are readily adapted to cur rently existing equipment. To achieve the above and other objects of the inven

tion, there is more generally provided a combustion control apparatus comprising a fuel input means, con trol means for regulating said fuel input means, smoke density detecting means for detecting and measuring the density of smoke generated by combustion of said fuel and for adjusting said control means in accordance with said density, and smoke accumulating means for amplifying the density of said smoke to facilitate the detecting and measuring of the same by said detecting means.

According to a feature of the invention, the fuel input means may include further means for the introduction of an oxygen containing gas such as air into the input means, said control means and detecting means regu lating the introduction of said gas by said further means.

According to another aspect of the invention, the combustion takes place in a combustion chamber and there is provided an admission means for the admission of an oxygen containing gas into said chamber, said control means and detecting means regulating the ad mission of said gas into the chamber by said admission means.

According to yet another feature of the invention, the aforesaid detecting means includes a source of light and a photoelectric cell arranged transversely of said ?ue and defining a sighting axis, said amplifying means including a concave shield facing against the direction of travel of the smoke in said ?ue and overlapping said axis to accumulate smoke between the source and cell. More particularly, the aforesaid shield may have a

cross~section which is a segment of a circle. In addition, the cross-section may be a triangular or polyhedral seg mentor any other such concave form, or partially con cave sections protruding from each side of the flue, and being discontinuous, thus affording an opening to pas sage of a portion of the smoke through the concave form, the form being capable of accumulating smoke in

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4 such a manner as to constitute a smoke ampli?er thereby facilitating the operation of the source of light and photoelectric cell combination.

In accordance with one aspect of the invention, the aforesaid control means may include a single motor for controlling all of the various controls. According to an other aspect of the invention, separate motors may be employed for operating the various controls. Advantageously, the aforesaid light source and

photo-electric cell are supported by tubular supports on opposite sides of the ?ue through which passes the gas being examined. These supports may, in accor dance with the invention, include sections of thermally insulating material to isolate the source and the cell thermally from the ?ue. According to another advantageous aspect of the in

vention, the apparatus thereof includes blowers con nected to the aforesaid tubular supports to pressurize the same and cool the source and cell and thereby to minimize contamination of the source and cell by solids from the smoke. Yet another advantageous feature of the invention

consists of an adjustable smoke de?ector in the ?ue up stream of the smoke accumulating means to direct the smoke towards the accumulating means. The de?ector can be mounted on hinges in the ?ue and means can be provided for adjusting the angle of the de?ector in the ?ue. ,

According to still another aspect of the invention, the aforesaid control means has a regulating limit. In addi tion, there can be provided alarm means for indicating the reaching of said limit and delay means to prevent the actuating of said alarm means until the limit has been reached for a predetermined period of time. According to another aspect of the invention, the

fuel input means includes a fuel storage means, a pump connected to said storage means, a burner, a first valve coupling said pump to said burner, a plurality of return by-pass valves returning said fuel to said storage means to reduce the supply of fuel to said storage means and solenoid means to control said valves. The aforesaid by-pass valves are advantageously ar

ranged in cascade manner and the aforesaid solenoid means includes solenoids associated with the by-pass valves to control the same. In this arrangement, the ?rst valve is a normally closed valve and the by-pass valves are normally open valves. According to yet another aspect of the invention, the

aforesaid control means includes a modulating motor coupled to the detecting means and mechanical linkage means coupling said motor to said fuel input means. According to yet another aspect of the invention, the

aforesaid control means includes a modulating motor, analog-to-digital conversion means being coupled to said detecting means, said detecting means generating an electrical signal which is converted into a digital sig nal by said conversion means and triac switch means controlled by said conversion means to operate said modulating motor.

Further, there may be provided an ampli?er means coupled between the aforesaid detecting means and conversion means and offset control means coupled to said ampli?er means. Still further there may be pro vided a voltage divider coupled to and controlled by said detecting means. Moreover, there may be pro vided a resistor network coupled between said motor and triac switch means.

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The above and further objects and features of the in vention will befound in the detailed description which follows hereinafter.

BRIEF DESCRIPTION OF DRAWING

The invention will be explained hereinafter in con nection with the associated drawing in which: FIG. 1 is a diagrammatic illustration of an apparatus

provided in accordance with one embodiment of the invention: FIG. 2 is an enlarged view of a section of FIG. 1; FIG. 3 is a sectional view taken along line IlI-—III of

FIG. 1; FIG. 4 is a longitudinal section through a correspond

ing portion of the apparatus; FIG. 5 is a chart illustrating the operation of the

smoke accumulator means of the invention; FIG. 6 is a block diagram of the electrical solid state

circuitry by means of which the operation of the photo electric cell is converted into control signals and me chanical control action; FIGS. 7(a) and 7(b) constitute, together, a schematic

circuit diagram corresponding to the circuit shown in block diagram form in FIG. 6; FIG. 8 illustrates a modi?cation of the apparatus il

lustrated in FIG. 1; FIG. 9 is a block diagram illustrating an alarm system

for use with any of the aforegoing embodiments; FIG. 10 illustrates an alarm system for use in connec

, tion with the embodiment of FIG. 8; FIG. 11 is a diagrammatic illustration of a means for

controlling the amount of fuel fed to the system of the invention; FIG. 12 is ‘a schematic view of the electrical portion

of the apparatus illustrated in FIG. 11; FIG. 13 is a perspective view of a part of the appara

tus of FIG. 1; v

FIGS. l4(a)—(d) arecross-sectional views through modi?ed embodiments of the invention with respect to the smoke accumulator means; and FIG. 15 is a top plan view of still a further form of

smoke accumulator.

DETAILED DESCRIPTION

As has been indicated above, FIGS. 1 and 2 diagram matically show apparatus provided in accordance with one embodiment of the invention. This apparatus com prises a combustion chamber 20, a burner or injection nozzle 22, a ?ue 24 for the venting of gases from the combustion chamber 20, a smoke detector and ampli fier section 26, a chimney 28 for the escape of ?ue gases and an electronic control section 30 which re sponds to the smoke detector and ampli?er section 26 as indicated by the control line 32. A photoelectric cell 34 employed in accordance with the invention is indi cated at 34 adjacent the section 20. A modulating motor 36 is indicated atop the burner

22. It includes a displaceable control arm 38. By means of a link 40, the control arm 38 is connected to the oil valve 42 which controls the amount of oil admitted from the oil pipe 44 via extension 46 into the burner 22. .

By means of a link 48, the arm 38 is connected to a primary air damper 50 which controls the admission of air or other such oxygen containing gas into the burner 22 via input pipe 52. The link 48 is furthermore con nected via a link 54 to the secondary air damper 56 by

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6 measn of which control is effected on the amount of air which is admitted directly into the chamber 20. The controller 30 is connected electrically to the

motor 36 as indicated by connection 60. The controller 30 is itself controlled by the smoke amplifier and detec tor section 26 which will be more clearly understood by reference to FIGS. 3 and 4.

In FIGS. 3 and 4, it is seen that the section 26 consists of a casing 70 which may be, for example, of rectangu lar cross-section and which is provided with ?anges 72 which enable connection of the section into the ?ue of the furnace. On opposite sides of the casing 70 are provided tubu

lar sections 74 and 76. To these tubular sections 74 and 76 are respectively connected blowers 78 and 80. Ex tending from the tubular sections 74 and 76 are asbes tos tubes 82 and 84, respectively, at the extremities of which are mounted casings 86 and 88. The casing 88 is indicated diagrammatically as in

cluding alight source 90. The casing 86 is diagrammat ically indicated as including a photocell or photoelec tric cell 92. De?ned between .the source 90 and the photoelectric cell is a sighting axis 94.

It will be observed that a concave shield 96 constitut ing a smoke ampli?er is mounted adjacent the sighting axis 94 and in partially overlapping relationship with the same. It will be, moreover, observed that the shield 96 opens in the downstream direction relative to the direction of smoke travel indicated by arrow 98 or, in other words, the shield 94 opens in a direction opposite to the direction of travel of the smoke. The provision of the shield 96 functions to amplify

the smoke density. This is further aided by the provi sion of a de?ector 100 which is mounted on a hinge 102 within the casing 70. The angular disposition of the de?ector 100 is controlled by a threaded rod 104 which engages the hinged de?ector by means of a rounded tip 106. The adjustment of the threaded rod 104 is con trolled by a knob 108 and the rod 104 is locked in posi tion by means of a lock not 110. The de?ector 100 serves to con?ne the passage for

the flow of smoke into a throat section indicated at T. The smoke is therefore de?ected in the illustrated ex ample upwardly towards the shield 96 whereat an accu mulation of smoke takes place and the density of smoke is ampli?ed.

Surprisingly it has been found that the accumulation of smoke and thereby the ampli?cation of density thereof takes place in a predictable manner which can be utilized to enable the photocell 92 to perform its function with greater efficiency and accuracy. The re sults of the ampli?cation are more particularly indi cated by the chart which appears in FIG. 5. The chart appearing in FIG. 5 compares the relative

smoke density in Ringelman Nos. as against resistance in ohms of the photoelectric cell. The abscissa of the chart shows relative smoke density and the ordinate shows resistance in ohms of the photoelectric cell. Curve 120 shows the results with the smoke amplifier. Curve 122 shows the comparative results without the smoke ampli?er. As appears in the box accompanying the chart of FIG. 5, the percentage difference at Rin gelman No. l is 13 percent. At Ringelman No. 2, the difference is 27.2 percent. At Ringelman No. 3, the percentage difference is 39.6 percent. At Ringelman No. 4, the percentage difference is 85.5 percent. At Ringelman No. 5, the percentage difference is 233.3

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percent. These differences have been found suf?cient to convert a relatively ineffective structure into a highly efficient and accurate control and therefore the smoke shield of the invention constitutes an ampli?er which is a very important feature of the invention.

In addition to the above, the provision of blowers 78 and 80 is a further feature of the invention inasmuch as these pressurize tubular extensions 74 and 76 and thereby impede the flow of soot and other such solids from the section 26 into the light source casing 88 and into the casing 86 for the photoelectric cell 92 thereby protecting these elements from the accumulation of dirt and thus in turn decreasing the need for mainte nance and replacement. Furthermore, they particularly maintain the accuracy of response to the smoke levels in the ?ue gas by greatly reducing the spurious re sponses created by soot deposits on the light source and the photocell. -

At the same time, the blowers 78 and 80 provide an other signi?cant advantage in that they reduce the tem peratures of the operative elements by which smoke detection is effected whereby the longevity of these ele ments is much improved. As a result, they particularly maintain the accuracy of response to the smoke levels in the flue gas by greatly reducing the spurious re sponses by the photocell due to excessive changes in ambient temperature.

Still further, the provision of asbestos tubes 82 and 84 prevents the conduction of heat from tubular sec tions 74 and 76 to casings 86 and 88 whereby an addi tional protection against heat is afforded.

In FIG. 6 is indicated in block diagram form the elec trical circuitry provided in accordance with the inven tion in association with the photoelectric cell 92 and the light source 90, the smoke amplifier and detector section 26 also being generally indicated along with the sighting axis 94.

In FIG. 6, it is particularly seen that there is provided a voltage divider indicated generally at 130, said volt age divider including a variable resistance 132 and a brush 134. The voltage divider also includes the photo electric cell'92. A voltage is applied across the voltage divider by means of terminals 136 and 138. Variable resistor 132 is preferably set to equal the photocell re sistance at a no-smoke or preferred smoke level. As a result, any voltage variation at junction 140 will be a direct indication of the resistance variation of the pho tocell 92 and therefore a direct indication of the obscu ration caused by the smoke passing through the light beam generated by the light source 90. The'voltage appearing at junction 140 is fed into an

ampli?er 142 to raise its level. An additional feature of the invention is provided at this point in the form of an offset control 144. The offset control, through the bias ing of the solid state ampli?er 142, provides for a man ual adjustment to place the initial “no-smoke" voltage reading into anyone of four quantization regions. In af fect, this allows a very simple method of setting the zero point of the associated modulating motor which is the point about which the modulating motor will oper ate. This feature obviates the necessity of changing the aforedescribed linkages whenever a small adjustment is necessary in order to change the range of movement of the associated oil valves and the associated air damp ers.

The voltage output for the ampli?er 142 is fed to the analog-to-digital converter 146. The purpose of this

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8 converter is to change the analog input from the pre ceding state into a digital word outputof, for example, 4 bits. This output is fed into a digital ampli?er and triac switching section 148 which ?rst ampli?es the dig ital word input to the necessary levels and then reads the input word in such a manner as to switch or gate one of a series of triac switches. This gating or switch ing action of the triac switches connects the common lead output of the resistor network 150 to a different point in the network. As the network is connected in a potentiometer con?guration, its three wire output is suitable for direct connection to a three-wire-input modulating type motor such as is employed to consti tute the motor 36 (see also FIGS. 1 and 2).

In this example, the total resistance across the poten tiometer connected resistance network 150 is 135 ohms to match the input requirement of a Honeywell M 900 series modulating type motor. It can as well be very simply changed to the 270 ohms required by the same motor when used with other primary controls or to any desired value of resistance to match any input characteristic desired for any model of suitable modu lating motor.

It is to be noted that each triac gating switch in the ampli?er and triac gate switch section 148 is singly op erated as the input signal strength reaches the particu lar quantization setting of that particular triac, which input signal is fed to it by the analog-to-digital con verter 146.

It has been found from trial and experience that six gates and therefore six steps of resistance variation in the output of the resistor network 150 give a very satis factory level of sensitivity of control for the modulating motor. Therefore, although discussion hereinunder may describe a different number of gating devices, it is to be understood that any number of gating devices may be employed but that six or more are preferable.

In the above-noted arrangement, the smoke detector and ampli?er have been shown as being mounted hori zontally. It can as well be mounted vertically. In the lat ter event, the position of the shield, with respect to the de?ector is less signi?cant. When the shield is mounted horizontally, it must be mounted so that the variable de?ector is at a lower level than is the shield or collec tor baf?e. A schematic diagram of a circuit constituting the

block diagram of FIG. 6 appears in FIGS. 7(a) and (b) wherein can be seen the photoelectric cell 92, the vari able resistor 132, brush 134, junction 140 and voltage

' input terminals 136 and 138. Junction 140 is connected via a resistor 170 to the

negative input of an operational ampli?er 172. The positive input terminal of this operational ampli?er is connected via a tap 174 on a resistor 176 which is con nected across the photoelectric cell 92 and the variable resistor 132. The operational ampli?er 172 has a vari able feedback resistor 178 and the output of the opera tional ampli?er 172 is connected via resistor 180 to line 182 which is connected to the positive input terminals of operational ampli?er 184, 186 and 190 and to the negative input terminals of operational ampli?ers 188, 192 and 194. A line 196 is provided which is connected between

resistors 198 and 200. Resistor 198 is connected to ground at a terminal 202. Line 196 is connected to the negative input terminal of operational ampli?er 184

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and to the positive input terminal of operational ampli- - fier 188.

In addition ‘to the above, there are further provided resistors 210 and 212 connected to a junction 214. Re sistor 212 is connected to voltage source terminal 138 whereas resistor 210 is connected to ground at terminal 202. Junction 214 is connected to the negative input of operational ampli?er 190 and to the positive input of operational ampli?er 194. ' The output of operational amplifier 184 is connected

to NAND gate 220. The outputs of operational ampli fier I86 and 188 are connected to NAND gate 222. The outputs of operational ampli?er 190 and 192 are connected to both inputs of NAND gate 224 and the output of operational ampli?er 194 is connted to both inputs of NAND gate 226. Also included in the circuit illustrated in FIG. 7 are

operational amplifiers 228, 230, 232 and 234. The pos itive input terminal of operational amplifier 228 is con nected to NAND gate 220 whereas the negative input of operational ampli?er 228 is connected via line 236 to ground as are the negative input terminals of opera tional ampli?ers 230, 232 and 234. The positive input terminal of operational amplifier

230 is connected to the output of NAND gate 222 whereas the positive input terminals of operational am plifier 232 and 234 are connected to the outputs of NAND gates 224 and 226 respectively. The output ter minals of operational ampli?er 228, 230, 232 and 234 are respectively connected to transistors 238, 240, 242 and 244. The collectors of these transistors are respec tively connected to triac switches 246, 248, 250 and 252. The emitters of he transistors are connected to -6 volts at terminal 136 via resistors 247, 249, 251 and 252. A resistor 254 is connected to triac 250 and resistors

256 and 258 are connected to triac 246 and to output terminal 260. Output terminal 262 is connected via re sistor 264 to triac 252 which is connected to triac 250 by resistor 266. Output terminal 268 is connected to ground terminal 202.

In FIG. 7(b), it is seen that motor M includes two bal ancing relay coils Cl and C2 with terminals T1 and T2 connected respectively to terminal 268 and to variable resistor R. The shaft S‘of the motor M also appears and is directly connected to brush B. Shaft S operates to control brush B to maintain balanced current in coils Cl and C2.

In the above, the operational ampli?ers may be Fair child operational Amplifiers p. A747 or equivalents thereof. The aforesaid NAND gates may be I.C. RCA 40ll NAND gates or equivalents thereof. The above noted transistors may be Motorola transistors 2N2905A or equivalents thereof. The triacs may be RCA triacs 40528 or equivalents. The circuitry shown in schematic form operates generally as indicated here inabove with respect to the block diagram appearing in FIG. 6. Whereas a single modulating type motor has been in

dicated as operative with respect to all controls in con nection with the above described embodiment of the invention, FIG. 8 indicates the use of a plurality of modulating type motors for effecting each of the con trols. More particularly, the burner 22 discharging into combustion chamber 20 can be seen in FIG. 8 along with oil valve 42 and dampers 50 and 56. Contrary to the preceding embodiment of the invention, there are

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10 here seen modulating motors 280, 282 and 284 all op erating independently in the manner indicated above with respect to motor 36. In this embodiment of the in vention, however, motor 280 controls the oil valve 42 separately from the control of dampers 50 and 56 and motors 282 and 284 respectively and separately control dampers 56 and 50. ' The three motor modi?cation provides a much sim

pler installation as only electrical connections need be made. This avoids the installation of the rod linkages mentioned hereinabove as well as their individual ad justments and the maintenance of such adjustments. In addition, the use of separate motors provides a much more flexible control of three functions because, by electrical. switching only, the three motors can be driven in unison as to direction or any one or more of the three motors can be reversed with respect to the others. This is easily accomplished by means of switch ing methods well known in the art and derivable from what has been described hereinabove. A further feature of the invention is shown in FIGS.

9 and 10. In FIG. 9, the single modulating motor em bodiment is shown with a single-pole double-throw switch 290 being mounted at the end of the shaft of the modulating motor 36 with which it is associated. If the situation should arise that the motor 36 is driven be yond its normal operating range to an extreme position, this would be indicated by the end switch 290. This would operate in turn to energize the time delay relay 292 which in turn would operate the associated and connected alarm 294. Therefore, after a predetermined and preset delay of, for example, 30 seconds, a system would operate to shut off the associated burner and would also operate a suitable alarm or set of alarms dia grammatically indicated at 294. The purpose of this alarm and shut-down capability

is that if the modulating motor is at an extreme period for more than a predetermined period of time, then the situation being examined by the automatic control sys tem is of such severity as to be beyond the ability of the system to correct it. This extreme condition might be caused by grossly excess smoke, a mechanical or elec trical failure or fault or by other such circumstances as might cause the modulating motor to assume a position which is antithetic to good operation and to maintain it beyond a prescribed limit. In this embodiment, the invention adds the capability of a smoke shut-down de vice.

FIG. 10 illustrates the same capability with respect to separate motors 280, 282 and 284 which, in such em bodiments, are provided with end switches 296, 298 and 300 respectively. Herein, all of the end switches are connected to delay device 302 which, in turn, is connected to an alarm system 304 which represents both an alarm and a capability of shutting down the as sociated burner. FIG. ll shows an accessory device to further expand

the usefulness of the invention. This ?gure shows a four-step modulating control system which when used in conjunction with the ef?ciency and control system described above will permit limiting the ?ring rate from a predetermined low point to full capacity in four steps.

Practical experience has shown that a minimum ?r ing rate of about 50 percent is the lowest that can be expected from an automatically controlled burner without service outages created by the fuel supply re duction although, as will be seen, any desired minimum

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fuel rate can easily be set into the control devices as can the size of the increments of the other three fuel rate steps. '

In FIG. 11 is shown a fuel storage tank 320 con nected to an outlet line 322 and a return line 324. An oil transfer pump 326 is provided, the output line of which is indicated at 328. Line 328 feeds into a nor mally closed solenoid-operated oil valve 330.

Referring, for example, to the embodiment illus trated in FIGS. 1 and 2, the accessory being described is attached to the oil valve 42 which feeds the burner 22 and which is controlled by the motor 36 for control ling combustion in the chamber 20.

In order to further control the oil flow to meet vary ing demand, three additional normally open solenoid operated oil valves 332, 334 and 336 are provided and are connected to the line 328. These solenoid-operated oil valves respectively have metering orifices diagram matically indicated at 338, 340 and 342 which in turn open into line 344 connected to return line 324 as is a by-pass line 346. FIG. 12 shows the electrical connection for the

above-described device. When the main temperature control device which may be, for example, a thermostat calls for heat, it closes a switch indicated at 360. Volt age is thereby applied to a primary oil burner combus tion control such as a Honeywell No. 4147 or the like. When this control in the course of its cycle calls for the opening of the oil valve, a switch shown at 362 closes thereby applying voltage to the first stage of a four stage modulating controller 364. This controller may be either pressure actuated, a pressuretrol, an air tem perature actuator mechanism, a thermostat, a water temperature actuator mechanism, an aquastat or any similar control device. Assuming that there is a cold start and all for internal

switchs 366, 368, 370 and 380 of controller 364 are calling for heat and hence are closed, voltage will be applied to the switch 366 and to relay coil 382 which will close, transferring voltage through contacts 384 to solenoid-controlled oil valve 330 causing it to open and allowing oil to enter the oil burner 22. As solenoid oil valves 332, 334 and 336 are normally open, much of the oil being pumped by pump 326 is by-passed back to the oil storage tank 320 via oil return line 324. By selection of the size of the solenoid-operated oil

valves and metering ori?ces, the amount of oil fed back to the burner at this stage of operation is limited to pro vide a suitable low-?re operation of the oil burner.

It should be noted at this point that, just prior to igni tion of the fuel in the furnace 20, the smoke detector and amplifier section described hereinabove and the electronic controller see a clear smoke pipe and hence the primary air damper such as that indicated at 50 in FIG. 1 and the secondary damper 56 also seen in FIG. 1 will be in the minimum air position. This is the de sired position for a low-?re start. The variable oil valves 42 (see FIGS. 1 and 11) will be in open position and will not at this point control the oil ?ow. Instead the solenoid-operated oil valve 330 will effect this control. Voltage is also applied to the controller 364 and, par

ticularly, the switch 368 through relay contacts 386. As it has been assumed that switch 370 is closed calling for heat, then voltage is applied to the primed delay relay 388 which will close after a predetermined time delay of, for example, 30 seconds. The purpose of this delay is to allow the fire to stabilize after having first been

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12 started by the opening of solenoid-operated oil valve 330 in the low-fire mode and also to allow the smoke efficiency regulating mechanism described above time to adjust the variable oil valve 42 and the associated dampers if necessary to adjust the fuel-air ratio for good combustion.

After the predetermined time delay, relay 388 will close applying voltage to its contacts closing the associ ated solenoid-operated oil valve 332 reducing the amount of oil being by-passed back to the oil storage tank 320. Voltage is sequentially applied to the next two relays 390 and 392 which operate in the manner described above so that eventually all of the valves 332, 334 and 336 will be closed whereby a maximum amount of oil will be fed to the burner 22 giving the high-?re operation desired. As the controller 364 approaches its setting, its

switches will start to open in reverse order. Switch 380 will open followed by the opening of switch 370 fol lowed by the opening of switch 368. As each switch opens, its corresponding relay will open and the corre sponding valve will open, reducing pressure at the oil burner thereby reducing ?re size. Finally, the valve 330 will close shutting off oil flow to the burner in entirety. As will be seen from the above description, the sec

tions are connected in cascading arrangement. During the course of the cascading of the oil valve control both in upward and downward direction, the ?ame is moni tored and controlled by the smoke detector and ampli fier section and the electronic controller described above. A maximum efficiency is maintained along with a predetermined smoke level as has been described.

It can be seen that the cascading is managed by the controller 364 and that this may be held steady at any stage or may move in either direction from any stage to satisfy the input signals to the controller. It will also be seen that each stage requires a time delay and that no stage is skipped in the process of cascading upwards. Hence, it is not possible to get a high-tire start which is an important safety feature and frequently a legal re quirement under the various safety codes.

It should be noted that the number of stages in the cascade arrangement is not critical. Four stages are used for the purposes of illustration. However, a very large burner might use more than four stages whereas a smaller burner might find two stages satisfactory.

It should be also noted that the controls shown with respect to FIGS. 11 and 12 incorporate electromechan ical relays. These electromechanical relays can readily be replaced by solid state electronic devices. FIG. 13 shows some mechanical details relating to

FIG. 1 which also illustrates chamber 20, burner 22, motor 26, arm 38, valve 42, link 54 and damper 56. Also appearing in FIG. 13 are links 400 and 402 for ro tating pivots, 404 and 406 which respectively control oil valve 42 and damper 50 (see FIG. 1). Other forms of mechanical arrangements are also possible. From what has been stated hereinabove, it will now

be appreciated that there is provided in accordance with the invention a combustion control apparatus comprising a fuel input means, control means for regu lating the fuel input means, smoke density detecting means for detecting and measuring the density of the smoke generated by combustion of the fuel and for ad justing the control means in accordance with said den sity, and smoke accumulating means for amplifying the density of the smoke to facilitate the detecting and

3,861,855 13

measuring of the same by said detecting means. Further refinements, arrangements and accessories have also been indicated. While a smoke accumulator has been described

above which has generally the form of a segment of a circle, other forms of such shields are possible, as has been indicated hereinabove. Thus, for example, a tri angular shield is indicated at 450 in FIG. 14(a), a sec tion of a polygon is indicated at,452 in FIG. 14(b), a further form of a section of a polygon is indicated at 454 in FIG. 14(c) and a further possible section involv ing the use of multiple sides is indicated at 456 in FIG. 14(d). > ' v

In the above description, the shields employed as smoke accumulators extended continuously from one side of the flue to the other. This is not necessarily re quired. Each such shield may be broken up into two or more parts extending transversely of the ?ue, such as indicated at 460 and 462 in FIG. 15. Moreover, the shields may be provided with vents or slots, such as are generally indicated at 464 and 466 in FIG. 15. The aforegoing variations are illustrative only and are

not intended to be limiting of the invention inasmuch as many oter modi?cations are possible within the scope of the invention. Thus, for example, the slots or vents appearing in FIG. 15 may as well be applied to the variations illustrated in FIGS. l4(a)-(d) or to the type of shield indicated earlier in this description. There will now be obvious to those skilled in the art

many modi?cations andvariations of the constructions and circuits set forth hereinabove. These modifications and variations will not depart from the scope of the in vention if defined by the following claims. What is claimed is: l. Combustion control apparatus comprising a fuel

input means, control means for regulating said fuel input means, smoke density detecting means for detect ing and measuring the density of smoke generated by combustion of said fuel and for adjusting said control means in accordance with said density, and smoke ac cumulating means for amplifying the density of said smoke to facilitate the detecting and measuring of the same by said detecting means.

2. Apparatus as claimed in claim 1 wherein said fuel input means includes further means for the introduc tion of an oxygen containing gas into said input means, said control means and detecting means regulating the introduction of said gas by said further means.

3. Apparatus as claimed in claim 1 comprising a com bustion chamber, and admission means for the admis sion of an oxygen containing gas into said chamber, said control means and detecting means regulating the admission of said gas into the chamber by said admis sion means.

4. Apparatus as claimed in claim 3 wherein said fuel input means includes further means for the introduc tion of an oxygen containing gas into said input means, said control means and detecting means regulating the introduction of said gas by said further means.

5. Apparatus as claimed in claim 1 comprising a ?ue for venting said smoke and wherein said detecting means includes a source of light and a photoelectric cell arranged transversely of said ?ue and de?ning a sighting axis, said amplifying means including a con cave shield facing against the direction of travel of the smoke in said ?ue and at least overlapping said axis to accumulate smoke between the source and cell.

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I4 6. Apparatus as claimed in claim 2 comprising a ?ue

for venting said smoke and wherein said detecting means includes a source of light and a photoelectric cell arranged transversely of said ?ue and de?ning a sighting axis, said amplifying means including a con cave shield facing against the direction of travel of the smoke in said flue and at least overlapping said axis to accumulate smoke between the source and cell.

7. Apparatus as claimed in claim 3 comprising a ?ue for venting said smoke and» wherein said detecting means includes a source of light and a photoelectric cell arranged transversely of said ?ue and defining a sighting axis, said amplifying means including a con cave shield facing against the direction of travel of the smoke in said ?ue and at least overlapping said axis to accumulate smoke between the source and cell.

8. Apparatus as claimed in claim 4 comprising a ?ue for venting said smoke and wherein said detecting means includes a source of light and a photoelectric cell arranged transversely of said ?ue and de?ning a sighting axis, said amplifying means including a con cave shield facing against the direction of travel of the smoke in said ?ue and at least overlapping said axis to to accumulate smoke between the source and cell.

9. Apparatus as claimed in claim 5 wherein said shield has a cross-section which is a segment of a circle.

10. Apparatus as claimed in claim 5 wherein said shield has a cross-section which is triangular.

11. Apparatus as claimed in claim 5 wherein said shield has a cross-section which is a segment of a poly gon.

12. Apparatus as claimed in claim 2 wherein said control means includes a single motor for controlling both said fuel input means and said further means.

13. Apparatus as claimed in claim 3 wherein said control means includes a single motor for controlling both said fuel input means and said admission means.

14. Apparatus as claimed in claim 4 wherein said control means includes a single motor for controlling said fuel input means, said further means and said ad mission means.

15. Apparatus as claimed in claim 2 wherein said control means includes separate motors for controlling said fuel input means and said further means.

16. Apparatus as claimed in claim 3 wherein said control means includes separate motors for controlling said fuel input means and said admission means.

17. Apparatus as claimed in claim 4 wherein said control means includes separate motors for controlling said fuel input means, said further means and said ad mission means.

18. Apparatus as claimed in claim 5 comprising tubu lar supports respectively supporting said source and cell in opposite sides of said ?ue.

19. Apparatus as claimed in claim 18 wherein said supports include sections of thermally insulating mate rial to isolate the source and cell thermally from said ?ue. '

20. Apparatus- as claimed in claim 18 comprising blowers connected to said tubular supports to pressur ize the same and cool the said source and cell and to minimize contamination of the source and cell by solids from the smoke.

21. Apparatus as claimed in claim 1 comprising an adjustable smoke de?ector in the ?ue upstream of said smoke accumulating means to direct said smoke to wrads the accumulating means.

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22. Apparatus as claimed in claim 21 comprising means hingeably supporting said de?ector in the ?ue and means for adjusting the angle of the de?ector in said ?ue.

23. Apparatus as claimed in claim 1, wherein said control means has a regulating limit, comprising alarm means for indicating the reaching of said limit and delay means to prevent the actuation of said alarm means until the limit has been reached for a predeter mined period of time.

24. Apparatus as claimed in claim 1 wherein said fuel input means includes a fuel storage means, a pump con nected to said storage means, a burner, a ?rst valve coupling said pump to said burner, a plurality of return by-pass valves returning said fuel to said storage means to reduce the supply of fuel to said storage means, and solenoid means to control said valves.

25. Apparatus as claimed in claim 24 wherein said by-pass valves and in cascade arrangement and said so lenoid means includes solenoids associated with the by pass valves to control the latter.

26. Apparatus as claimed in claim 25 wherein said first valve is a normally closed valve and the by-pass valves are normally open valves.

27. Apparatus as claimed in claim 1 wherein said control means includes a modulating motor coupled to

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16 said detecting means and mechanical linkage means coupling said motor to said fuel input means.

28. Apparatus as claimed in claim 1 wherein said control means includes a modulating motor, analog to digital conversion means coupled to said detecting means, said detecting means generating an electrical signal which is converted into a digital signal by said conversion means, and triac switch means controlled by said conversion means to operate said modulating motor.

29. Apparatus as claimed in claim 28 comprising an amplifier means coupled between said detecting means and conversion means, and offset control means cou pled to said amplifier means.

30. Apparatus as claimed in claim 29 comprising a voltage divider coupled to and controlled by said de tecting means.

31. Apparatus as claimed in claim 30 comprising a resistor network coupled between said motor and triac switch means.

32. Apparatus as claimed in claim 5 wherein said shield includes a plurality of spaced parts arranged transversely of said ?ue.

33. Apparatus as claimed in claim 5 wherein said shield is provided with at least one vent.

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