US2884996A - Combustion control system - Google Patents

Description

May 5, 1959' H. R. HULETT ETAL 2,384,996

COMBUSTION CONTROL SYSTEM Filed March 6, 1957 Sheet-Sheet i INVENTOR5 ,wwer H0457? MAM/[7v swam? m-ramwvs Mia May 5, 1959 H. R. HULETT ETAL v 2,884,996

COMBUSTION CONTROL SYSTEM Filed March 6, 1957 2 Sheets-Sheet 2 1NVENTOR5 HENFY 9. H04 577' am/5m a, HELLE? United States ?atent COMBUSTIGN CONTROL SYSTEM Henry R. Hulett, Portola Valley, and Kenneth G. Heller,

Redwood City, Calif., assignors, by mesne assignments, to American Radiator & Standard Sanitary Corporation, New York, N.Y., a corporation of Delaware Application March 6, 1957, Serial No. 644,295

2 Claims. (Cl. 158-28) This invention relates to and in general has for its object the provision of a control system for the fuel burners of the combustion chambers of oil furnaces, boilers and the like.

During the last decade or two, the fuel burners of this type generally have been under the control of a stack switch operable in response to variations in the stack temperature. Since this type of control must be mounted on, and partially in the stack, and since it can operate properly only within a limited temperature range the choice of its location is correspondingly limited. Furthermore, stack control is inherently slow in response and less accurate than controls directly sensing the burner flame.

More specifically, the object of this invention is the provision of a fuel burner control system wherein: the burner is under the control of a flame sensing thermocouple; the room thermostat signal is relayed to the fuel control motor (pump motor in the case of oil); the burner is automatically recycled after a suflicient time delay to allow vapors to be scavenged from the combustion chamber; provision is made for inactivating and looking out the fuel control motor in the event of flame failure during operation or ignition failure during startup to thereby require manual resetting in order to recycle under these conditions; and wherein provision is made for inactivating the fuel control motor in the event that the reset button is held depressed or tampered with.

Still another object of this invention is the provision of a new reset button actuated relay switch under the control of a relay coil, bimetal element and flame sensing thermocouple.

The invention possesses other advantageous features, some of which, with the foregoing, will be set forth at length in the following description where that form of the invention which has been selected for illustration in the drawings accompanying and forming a part of the present specification is outlined in full. In said drawings, one form of the invention is shown, but it is to be understood that it is not limited to such form, since the invention as set forth in the claims may be embodied in a plurality of forms.

Referring to the drawings:

' Fig. 1 is a schematic illustration of a control system embodying the objects of our invention.

Fig. 2 is a simplified wiring diagram of the system illustrated in Fig. l.

As best shown in Fig. 1, the objects of our invention have been embodied in a system including the combustion chamber 1 of a furnace or boiler 2 and which as usual includes a stack 3. 7

Associated with the combustion chamber is a motor 4 for controlling the delivery of fuel to an oil burner 5 connected to the combustion chamber.

Disposed within the combustion chamber 1 adjacent the burneroutlet 6 is a flame sensing thermocouple 7, and

' optionally a limit control thermostat 8- can be mounted within the furnace adjacent the stack intake 9. Operatively associated with the burner 5 is an ignition control transformer 11 including a primary winding 11a and a secondary winding 11b.

Mounted in the room the temperature of which is to be controlled by the system under consideration is a thermostat 12.

Mounted in any suitable and accessible location but preferably adjacent the furnace 2 is a control panel or cabinet here generally indicated by the reference number 13 and which is provided with a supporting base or frame member 14 for the various control elements presently to be described.

Supported from the cabinet 13 is a control transformer generally designated by the reference numeral 15 and including a core 16, a primary winding 17, and a secondary winding 18, the primary winding 17 being connected through leads 19 and 21 respectively to cabinet terminals 22 and 23. The terminal 22 communicates through a lead 24 with one side of the limit control thermostat 8 (if this be used) and the other side communicates through a lead 25 with one leg of a line voltage supply switch 26. The cabinet terminal 23 communicates through a lead 27 and a lead 28 with the other leg of the line switch 26. As a result of this circuit it will be seen that when the line switch 26 is closed the transformer 15 is energized.

Gang switch assembly Fixed within the control cabinet is an insulating mounting block 31 and embedded therein intermediate their ends are two pairs of spaced parallel spring fingers 32 and 33, and 34 and 35, the fingers 32 and 34 being somewhat longer than the fingers 33 and 35. Secured to the opposed inner faces of the fingers 32 and 33 at the lower free ends thereof are line voltage contacts 36 and 37 together constituting a line voltage switch 38. Similarly secured to the lower free ends of the fingers 34 and 35 are opposed low voltage holding contacts 39 and 41 together constituting a low voltage holding switch 42. The fingers 32, 33, 34 and 35 merely serve as movable means for permitting the contacts 36 and 37, and 39 and 41, to move in either direction along a predetermined path out of contact with each other or to enable the contacts of each pair of contacts to be brought into engagement with each other. Normally with the spring fingers 32, 33, 34 and 35 in their positions of rest, they serve to hold or bias the switches 38 and 42 in or to their open positions.

Secured to the outer free ends of the elongated spring fingers 32 and 34 transversely thereof is a tie bar 43 of insulating material. Fixed to the left end of the insulating mounting block 31 is a depending biasing leaf spring 44 and secured to the lower end thereof is a transversely extending gang operator 45 here illustrated as a rod arranged to pass through transversely aligned apertures formed in the spring fingers 32, 33, 34 and 35 with positive clearance. Affixed to the operator 45 between the spring fingers are discs or shoulders 46, 47 and 48 of a thickness substantially less than the distance between the spring fingers. The discs or shoulders 46, 47 and 48 should be so located axially of the gang operator 45 that with the spring fingers and biasing leaf spring 44 in their normal at rest positions, the disc 46 lies immediately adjacent the spring finger 33, the disc 47 lies immediately adjacent the spring finger 34 and the disc 48 lies immediately adjacent the spring finger 35. Formed on the left end of the gang operator 45 adjacent the spring finger 32 is a cylinder 49 slidable in a counterbored bearing 51 formed in the control panel 13. Also slidable in the counterbored bearing 51 in axial alignment with the gang operator cylinder 45 is a reset button 52 biased away from the left end of the cylinder by a coil spring 53, the spring 53 being held in its proper positions by a retaining washer 54. 1

As a result of this construction it will be seen that if the reset button is depressed against the biasing action of its associated spring 53 so as to move the gang operator to the right, the cylinder 49 and discs 46, 47 and 48 will operate to move the switch contacts 36, 37, 39 and 41 of the switches 38 and 42 to the right in unison or as a gang without closing the switches 38 and 42. This movement is, of course, effected against the biasing action of the leaf spring 44 and the spring fingers 32, 33, 34 and 35. Since the tie bar 43 is aflixed to the ends of the elongated spring fingers 32 and 34, the tie bar 43 will also have been moved to the right. Now if the tie bar 43 is held in its new position, and the reset button 52 is released, the gang operator 45 will return to its normal position under the influence of its associated biasing leaf spring 44 thus permitting the free lower ends of spring fingers 33 and 35 to return to their normal positions and to bring the contact 37 into engagement with v the contact 36 and the contact 41 into engagement with the contact 39. This, therefore, results in closing the line voltage switch 38 and the low voltage switch 42. This structure, therefore, constitutes a spring biased lost motion gang switch enabling both contacts of both the switches 38 and 42 to be moved from a first open position along a given path to a second open position and then to permit one contact of each switch to retract so as to thereby close each switch. Furthermore, by then releasing the other contact of each switch, both switches will return to their original open positions.

Relay coil assembly Mounted in the cabinet 13 adjacent the gang switch assembly and operatively associated therewith is a relay I coil assembly generally designated by the reference numeral 61. This assembly includes a relay coil 62 provided with a core 63. Secured to the base of the relay coil 62 is an angle shaped bracket 64 including a leg 65 overlying the relay coil and formed with an upwardly extending lug 66 adjacent its base. Pivoted to the angle bracket 64 is a relay coil armature 67 extending between the core 63 and bracket leg 65. Connected to and between the lug 66 and the upper free end of the armature 67 is a coil tension spring 68 serving to bias the armature nated by the reference numeral 94 responsive to the movement of the armature rod 86. As shown in Fig. 1 the armature 85 is locked in its open position when the latch hook 72 is disposed beneath the latch shoulder 89 under the influence of the biasing spring 68. The upper free end of the rod 86 is arranged to be properly guided by a portion of frame number 14 associated with the cabinet 13.

As a result of this construction it will be seen that if the latch hook 72 is in its retracted position and the holding magnet 81 is energized, the magnet will serve to bias the armature 85 downwardly and to bias the lock-out switch 94 to its closed position.

Actuating bimetal assembly Mounted to a portion of the cabinet frame member 14 is a bifurcated fitting 101 and pivoted thereto by a pin 102 is a mounting block 103. Fixed to the upper face of the mounting block 103 cantileverwise is a bimetal element 104 arranged to warp or curl downwardly in re sponse to a decrease in temperature. Merging with or forming a continuation of the outer free end of the bimetal element 104 is a bifurcated member or fork 105 arranged to straddle the pin 86 and provided with fulcrum teats 106 arranged to seat or bear on the upper face of the disc 87. Mounted on the lower face of the outer end of the fork 105, and insulated therefrom, are a pair of contact members 107 and 108. Supported by a portion of the cabinet frame member 14 is a bracket 109 and mounted thereon, and insulated therefrom, is s. contact member 111 aligned with the contact member 107 and forming therewith an ignition switch 112. Similarly mounted on a portion of the frame member 14 is a bracket 113 and carried thereby is a contact member 114 aligned with the contact member 108 and forming therewith a recycling switch 115. Here it should be noted that the lock-out switch 94, the ignition switch 112 and the recycling switch 115 are so correlated as to close in that order. Mounted on a portion of the supporting outwardly to its open position against the lower free and inwardly turned end of the bracket leg 65. Secured to an extension 69 of the armature 67 is an angle 71 which in turn is connected to the right end of tie bar 43. Formed on the lower free end of the armature extension 69 is an outwardly turned latch hook 72, the function of which will be later described.

As a result of this construction, it will be seen that if the relay coil 62 be energized its armature will be drawn and/or held in its closed position and that since the tie bar 43 is secured to it, the tie bar will be under the control of the relay coil and the line and low voltage switches 38 and 42 will be closed.

Holding magnet assembly Mounted in the control cabinet 13 beneath the gang switch assembly is a holding magnet assembly generally indicated by the reference numeral 81. Included in this assembly is an electromagnet 82 including a winding 83 mounted in a fixed casing 84. Operatively associated with the magnet 82 is an armature 85. Secured to and extending upwardly from the armature 85 is a pin 86 and fastened thereto intermediate its ends is a disc or shoulder 87. Surrounding the pin 86 between the disc 87 and the top of the magnet casing 84 is a compression spring 88 sewing to bias the armature to its upper open position. Secured to the pin 86 above the disc 87 is latch shoulder 89 merging with an offset switch arm 91. Mounted on the lower free end of the switch arm 91 is a contact element 92 arranged to engage an opposed but fixed contact element 93 adjustably carried by frame member 14. The contact elements ,92 and 93 together form a normally closed lock-out switch generally desigmember 14 is an actuating magnet 116 serving to bias the fork 105 downwardly when the fork has been moved downwardly within the effective field of the magnet and to lock the fork in its lowermost position.

Secured to the lower face of the mounting block 103 is an ambient temperature compensating bimetal element 117 paralleling the bimetal 104. Secured to the cabinet frame member 14 is a bracket 118 and threaded thereto in alignment with the outer end of the bimetal element 117 is an adjusting screw 119. The upper free end of the screw 119 is provided with a shouldered portion 121 of reduced diameter for receiving the outer end of the bimetal element 117. The screw 119, therefore, serves as a means for adjusting the position of the overlying bimetal element 104 and the normal pressure thereof of its fulcrum teats 106 on the disc 87. The lower bimetal element 117 is arranged to compensate for variations in the ambient temperature so that the upper bimetal element 104 can operate independent of such variations. Operatively associated with the bimetal element 104 is a resistance element or heater 122 serving as means for actuating this element. If due to a decrease in temperature the bimetal element 104 warps downwardly and the latch hook 72 is in its retracted position so as to permit the pin 86 to move downwardly, the bimetal element 104 serves to depress the magnet armature towards its closed position and against the biasing action of the compression spring 88. When the fork comes-within the influence of the field of the actuating magnet '116 this magnet then takes over and serves to hold the fork and its associated elements in its depressed position.

's'ociated spring finger 32, a lead 131, lead 19, lead 24, limit control thermostat 8, and lead 25 with one side of the switch 26. The other contact 37 communicates through its associated spring finger 33, a lead 132, a control cabinet terminal 133, a lead 134, with one of the motor terminals 135, through the opposed motor terminal 136, a lead 137, a lead 138 and through lead 28 to the other leg of the switch 26.

The low voltage switch 42, which is gang operated with line voltage switch 38, is in series circuit with the relay coil 62, the secondary winding 18 of the transformer 15, the look-out switch 94, the house thermostat 12 and the bimetal heater 122 and serves to close this circuit provided that the lock-out switch 94 is closed. To this end the contact 39 to the low voltage switch 42 communicates through its associated spring finger 34, through a lead 141, a terminal 142, a lead 143, heater 122, a lead 144, a cabinet terminal 145, the house thermostat 12, a lead 146, a cabinet terminal 147, a lead 148, the look-out switch 94, a lead 149, the secondary winding 18 of the transformer 15, a lead 151, a terminal 152 of the relay coil 62, through the coil to its other terminal 163, a lead 164, a lead 165, the spring finger 35 to the other contact 41 of the low voltage switch 42.

The recycling switch 115 which is gang operated with the ignition switch 112, is shunted around the low voltage switch 42 and like the switch 42 serves to close the relay coil circuit above described. To this end the contact 108 of the switch 115 communicates through a lead 165 with the terminal 142 and its other contact 114 communicates through a lead 166 and a terminal 167 with the lead 164.

The ignition switch 112 puts the primary winding of the ignition transformer 11 across the main supply line through the switch 26 and through the line voltage switch 38, the switches 112 and 38 being in series with each other. To this end the contact 111 of the ignition switch 112 communicates through a lead 171 with a cabinet terminal 172, through a lead 173, the primary winding 11a of the ignition transformer 11 and through a lead 174 connected to the line 138 through a terminal 175. The lead 138 in turn communicates through a terminal with the main line lead 28 and hence to one leg of the main switch 26. The other contact 107 of the ignition switch 112 communicates through a lead 175 with a terminal 176 and through a line voltage switch 38 with the lead 131. The lead 131 communicates with a terminal 177 with the lead 19 which as previously described communicates through the cabinet terminal 22, lead 24, thermostat 8 and lead 25 with the other leg of the main line switch 26.

The winding 83 of the holding magnet 82 is in closed circuit with the flame sensing thermocouple 7 and to this end one side of the coil 83 communicates through a lead 178 with a cabinet terminal 179, this terminal being connected through a lead 181 with one side of the thermocouple 7. The other side of the thermocouple communicates through a lead 182 with the remaining cabinet terminal 183 which in turn communicates through a lead 184 with the other end of the winding 83 of the holding magnet 81.

The entire hook up above described has been illustrated in simplified form in Fig. 2 so that the two major circuits (high voltage and low voltage) can be more easily traced. Here although the operating elements of the system have been indicated by reference numerals and legends, no attempt has been made to apply reference numerals to the connecting lines or leads.

Starting up after safety lockout In both figures the system has been shown in its lockout inoperative position, that is with all of its various switches shown in their open position.

Now assuming that the main switch 26 is closed, and that the bimetal element 104 is cold and that, therefore,

6 its outer free end is downwardly biased withits teats 106 exerting a downward pressure on the disc 87. So far nothing can happen for since the latch hook 72 is disposed beneath the latch shoulder 89 the holding magnet armature pin 86 is locked against any downward movement. If now the reset button 52 be momentarily depressed the line voltage and low voltage gang switches 38 and 42 will move bodily to the right but without closing. Simultaneously, the latch 72 will be disengaged from its associated latching shoulder 89 thus leaving the armature and its associated pin 86 free to move downwardly under the biasing action (if any) of the bimetal element 104. If at this point and as above assumed, the outer end of the bimetal element is biased downwardly it will flex downwardly thereby depressing the pin 86. The downward movement of the bimetal ele' ment 104 brings it within the influence of the actuating magnet 116 which then takes over to complete the down Ward movement of the bimetal element 104 and to hold it in its depressed position. During this movement'the lock-out switch 94, the ignition switch 112 and the recycling switch 115 sequentially close in that order. The latter two switches are so adjusted that they will close only when the bimetal element is within the pull-in region of the actuating magnet 116. The downward stroke of the pin 86 terminates when the holding magnet armature 85 contacts the core of the holding magnet 82. Under these conditions the secondary or low voltage circuit is closed and the system can go into normal operation; That is, relay coil 63 is energized, pulling in armature 67 and closing line voltage switch 38 and low voltage switch 42. 4 Motor and ignition thus start. Here it should be noted that since the ignition switch 112 closes before the recycling switch 115 and the line voltage switch 38, the motor and ignition transformer 11 are energized simultaneously and no danger exists that fuel will be delivered to the furnace before ignition.

With current flowing in the secondary or low voltage circuit the temperature of the heater 122 and the bimetal element 104 will rise. When the upward flexing force of the bimetal element overcomes the pull of the actuating magnet 116, the bimetal element 104 will snap upward thereby opening in rapid succession first the recycling switch 115 and then the ignition switch 112. Ignition thus ceases although the low voltage circuit still remains closed through the low voltage switch 42 which as above described is shunted around the recycling switch 115.

In normal operation, the flame is established imme diately, causing the flame sensing thermocouple 7 to heat up rapidly enough to energize the holding magnet 82 before the bimetal 104 snaps away from the actuating magnet 116. The pin 86 thus stays down and the lock-out switch 94 remains closed. The burner, therefore, continues to operate.

Abnormal starting operation (ignition failure) Should the flame fail to be established, the starting operation is identical with that above described with respect to normal starting except that the holding magnet 82 remains deenergized. The holding magnet pin 86 then follows the actuating bimetal element 104 upward until the lock-out switch 94 opens. Since this opens the secondary or low voltage circuit, the relay coil 62 is deenergized allowing its armature 67 and associated latch hook 72 to snap open under the influence of the biasing spring 68. The lock-out switch 94 is so adjusted that this action occurs when the latching shoulder 89 of the pin 86 is slightly above the latch hook 72 thereby permitting the latch hook to return to its locking position beneath the shoulder 89, all as indicated in Fig. 1. Since, due to the switch differential, the lock-out contact 94 will not remake until latching shoulder 89 has fallen below the latch position, manual resetting is necessary to unlatch, and return to automatic operation.

Normal shutdown with thermostat satisfied If the house thermostat 12 opens, the secondary circuit and its relay coil 62 are de-energized immediately. Here it is important to note that under these conditions the holding magnet 82 is also de-energized but only after a time delay sulficient to permit the thermocouple 7 to cool. The latch hook will, therefore, move to the left as viewed in Fig. 1, over the latch shoulder 89 instead of under it. Consequently, no lock here occurs. The heater 122 and bimetal element 104- then cool, thus allowing the latter to flex and then snap down under the influence of the actuating magnet 116. The ignition and recycling switches 112 and 115 close in response to the latter movement. The time lag in the operation of the bimetal element 104 (cooling time) is desirable to allow any vapors in the combustion chamber to be scavenged therefrom. Here it should be noted that the lock-out switch 94 remains closed throughout the normal running and shutdown cycles. With all three switches (112, 115 and 94) closed, the control is ready to recycle if the house thermostat 12 again calls for heat.

Power failure In the event of a power failure the system returns to the starting position just as in the case above described with respect to normal shutdown. If the power failure occurs when the house thermostat 12 is open, no action occurs in the control.

Flame failure during operation With the thermostat calling for heat (closed) current flows in the secondary or low voltage circuit. Here the situation is the same as in the case of normal starting and running operation; the relay coil 62 is energized and pulling on its armature, the fuel control motor 4 is running, the heater 122 is energized, and the actuating bimetal element 104 is hot and upwardly flexed. The ignition and recycling switches 112 and 115 are open, the holding magnet 82 is energized and holding its armature 85 and associated elements down and the lock-out switch 94 is closed.

Flame failure is first sensed by the holding magnet 82 which becomes de-energized, and after a short period its holding force has dropped sufiiciently to permit the biasing spring 88 to snap the pin 86 upward. As in the case of ignition failure, the lock-out switch 94 opens and this in turn opens the secondary or low voltage circuit and de-encrgizes the relay coil 62. The latch hook 72 then locks under the latch shoulder 89 and consequently manual resetting is required to again initiate automatic operation.

We claim:

1. A combustion control system comprising: a combustion chamber; a fuel burner operatively associated with said combustion chamber; a fuel control motor operatively associated with said burner for controlling the delivery of fuel thereto; an ignition transformer operatively associated with said burner for controlling the ignition of fuel delivered to said burner; a control transformer; said motor, the primary winding ofsaid control transformer and the primary winding of said ignition transformer being connected in parallel across a voltage supply line; a relay coil; an armature operatively associated with said relay coil; means operatively associated with said armature for biasing it towards its unattracted position; an electromagnet; flame sensing means within said combustion chamber for energizing said electromagnet; an armature operatively associated with said electromagnet; means operatively associated with said electromagnet armature for biasing it towards its unattracted position; a lock-out switch operatively associated with said electromagnet armature and including a contact member movable in response to the movement of said electromagnet armature; an actuating bimetal element operatively associated with said electromagnet armature including means for biasing said armature towards its attracted position in response to the movement of said bimetal element; a heater operatively associated with said bimetal element; normally open ignition transformer and recycling switches operatively associated with said bimetal element and responsive to the movement thereof; a lock-out latch member operatively associated with said contact member, with said electromagnet armature and with said relay coil armature and movable in response to the movement of said relay coil armature for selectively holding said lockout switch open or for permitting said lock-out switch to close in response to the movement of said electromagnet armature; a line voltage switch and a low voltage switch each including first and second switch contact members arranged for movement in a predetermined path in either direction; first means for biasing said contact members to a first open position; second spring biased means for moving said contact members unidirectionally along said path to a second open position; means operatively associated with the trailing contact members of each said line voltage and low voltage switches and with said relay coil armature for moving said trailing contact members to said second position in response to the movement of said relay coil armature; and a control thermostat; said low voltage and recycling switches being connected in parallel with each other and in series with said bimetal element heater, with said control thermostat, with said lock-out switch, the secondary winding of said control transformer and with said relay coil.

2. A combustion control system comprising: first and second circuits inductively coupled by a first transformer, said first circuit being arranged to be placed across a power line; an ignition control transformer shunted across said first circuit respectively through normally open first and second switches; a burner actuating motor shunted across said first circuit through said second switch, said motor being in parallel circuit with said transformer and with said first switch; said second circuit including in series the coil of a first electromagnet normally open third and fourth switches in parallel circuit with each other; a heater; a room thermostat and a normally closed lock-out switch; a third closed circuit including in series a flame sensing means and the coil of a second electromagnet; an armature operatively associated with said second electromagnet coil and with said lock-out switch; a bimetal element operatively associated with said heater; a gang operator for actuating said first and fourth switches in response to the movement of said bimetal element; an armature operatively associated with the coil of said first electromagnet; a manually controlled lost motion first gang operator for actuating said second and third switches; and a second gang operator associated with said last named armature and with said second and third switches for operating the second and third switches to closed positions upon the energization of said first coil.

References Cited in the file of this patent UNITED STATES PATENTS 2,180,675 Gille Nov. 21, 1939 2,408,047 Cunningham Sept. 24, 1946 2,558,658 Markham June 26, 1951 2.593.518 Aubert Apr. 22, 1952

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