US2408047A - Burner control apparatus - Google Patents

Description

Patented Sept. 24, 1946 UNITED STATES PATENT OFFICE BURNER CONTROL APPARATUS Lewis L. Cunningham, Glendale, Calif., assignor to Perfex Corporation, Milwaukee, Wis., a corporation of Wisconsin l Application June 20, 1941, Serial No. 398,923

23 Claims. l

This invention relates in general to control apparatus, and more particularly to automatic controls for burners.

The primary object of this invention is the provision of a safety control device for a burner which functions to place the burner out of operation in the event of flame failure or extinguishment of the lire, and which is simple and inexpensive in construction and reliable in operation.

Other objects of the invention will become apparent from the following description and the appended claims.

For a full disclosure of the present invention reference is made to the following detailed description and to the accompanying drawing, in which Fig. 1 illustrates schematically one form which the invention may take;

Fig. 2 shows a portion of the apparatus of Fig. 1 in the position it assumes while the burner is operating properly; and

Fig. 3 is a View similar to Fig. 2 but showing the parts in the positions they assume when the burner is stopped due to flame failure.

Referring primarily to Fig. 1, reference character I indicates an electric motor for operating a burner which may :be van oil burner o-r a Stoker. The burner might also be a gas burner, and in such case the motor I would operate the gas valve therefor. Reference character 2 indicates an electrical igniter for the burner which may be of any satisfactory form. The motor I and the igniter 2 are controlled by means of a relay generally indicated as 3. This relay is illustrated diagrammatically as comprising a coil 4 which operates switch arms 5, 6 and I through a suitable armature, not shown. When the relay coil 4 is energized the switch arms 5, 6 and 1 engage contacts 8, 9 and I0 respectively. When coil 4 is deenergized the switch arms are disengaged from their respective contacts as shown.

The ignter 2 and the relay 3 are controlled by means of a timing device or switching mechanism generally indicated as I I. This device is diagrammatically illustrated as comprising a bimetal element I2 which is xedly secured to a lblock I3 at one end and which carries an armature I 4l and I'I maybe of any desired construction and.

are diagrammatically shown as attached to a spring member 20 which is riveted at its midpoint to the bimetal element I2, the contacts I6 and Il extending through suitable apertures in element I2. Contacts I'I and I9 cooperate to form an igniter switch for controlling the igniter 2. Contacts I6 and I8 cooperate to form a starting switch for the relay 3. The bimetal element I2 is provided with a pair of electric heating elements 2I and 22. When the bimetal element I2 is relatively cold it assumes the position shown in which the movable contacts I6 and I'I engage the fixed contacts I8 and I9, the armature I4 being attracted by the permanent magnet I5 but :being spaced therefrom by engagement of the movable contacts with the xed contacts. However, when the bimetal element I2 is heated under the action of heaters 2| or 22, this element tends to bow upwardly, being initially restrained from such movement by the attraction of armature I4 to magnet I5. When element I2 is heated sufficiently to overcome the magnetic attraction it snaps upwardly, causing the movable contacts to disengage the fixed contacts. When the element I2 cools down due to the heaters 2| and 22 being deenergized, this element -bows downwardly and the movable contacts engage the xed contacts with snap action.

The relay 3, in addition to the switch arms 5, 6 and I, also includes a pivoted movable mem- |ber 24, having an armature portion 25 which is adapted to cooperate with the open end of the U-shaped permanent magnet I5 when the relay is deenergized. This provides a magnetic shunt and thus decreases the eiect o-f the permanent magnet I5 on the armature I4. The armature 25, movable with the relay, also serves to increase the voltage across relay 4 necessary to cause the relay to pull in. The relay also includes a mechanical stop member 26, which for illustrative purposes is shown as attached t0 the pivoted member 213. This stop member 26 includes an end portion 21 which is located in the path of movementl of the movable member or bimetal element I2 whenever the relay 3 is deenergized. When the relay 3 is energized, the stop means 2l is withdrawn from the path of movement of the free end of bimetal element I2, as shown in Fig. 2.

The control system also includes a combustion responsive device generally indicated as 30. This device may include an expansible element 3I which is xed at one end and which extends into the stack or combustion chamber of the furnace, the free end of this member being attached to a non-expanding rod 32 which operates through a slip friction mechanism 33 to rock an operating beam 34 about a fixed pivot 35 and between adjustable stops 36 and 31. This operating beam positions a combustion stop means 38 which is shown in the form of a movable abutment. When no combustion is present, the thermal element 3l is cool, which causes the operating beam 34 to be urged against the cold stop 36. This causes the abutment 38 to be clear of the path of movement of the free end of bimetal element I2 as shown. When combustion takes place the ther-A mal element 3| becomes heated, expanding and acting through the slip friction device 33 to rock the operating beam 34 counter clockwise, thus bringing the abutment 38 into the path of movement of bimetal element I2 as shown in Fig. 2. The combustion responsive means 3|) also serves to position the movable relay contact B lwhich cooperates with the relay switch arm 5. This is illustrated diagrammatically as accomplished by an insulating member 39 secured to the operating beam 3,4, this insulating member carrying a stiff Contact arm 4() and an adjusting screw 4 I. The movable oontaot t may loe carried by a resilient arm 4,2 attached to arm 4i). The operating mechanism for the movable relay contact 8 is proportioned so that this Contact. will remain olisengaged from the switch arm whenever the Operating beam 34 1.5 irl its @01d POSSOIJ, 21S SlQWll- A150 the lange @f lllOVQlllQll 0f 'the IllOV- able .Contact 8 preferably .should not substantially overlap. with that of the switch arm 5. so that when the switeh. ann 5 is in the position shown dee to the relay beine deenereized it will not be encased .by the movable Contact 8, regardless of whether combustion is presentv or not. The combustion responsive devise 3G. also may operate a second switch for controlling the heater 22 of the timing device II. This switch is diagrammatically shown as comprising a switch arm 43 which is carried by an insulating member 44 attackled to operating beam 34, this switch arm cooperating with a stationary contact 45. The movable Contact 43 should engage the stationary contact 45 only when vcombustion is present.

In addition to the control instrumentalities above described, the system also includes a con-. dition responsive device 43 which may be a room thermostat or other device for starting the burner upon demand for heat and for stopping the same when the demand for heat is satisfied. The control system also includes a transformer 49 having a primary coil 50 and a secondary coil 5I. Preferably the system also includesV a limit or safety control 52 which may be a thermostat or pressure responsive device on the furnace for placing the burner out of operation in case of excessive furnace temperatures or pressures.

Operation With the parts in the positions shown, the roomU thermostat `48, is satisfied, which causes the relay coii 4v to be deenergized. The motor and AVer for the burner at this time are deener'- n d,4 Also the bimetal element I2 is cold, causing the movable contacts I6I andl I1 to engage the fixed contacts I8 and I9. As the burner is not in operation the operating beam 34 of the combustion responsive dev-ice is in its cold position, in which the abutment 38 is clear of the path of movement of the bimetal element I2. The movable contact 43 at this time is disengaged from the Xed contact 45 and the movable contact 8 is positioned so that it cannot be engaged by the switch arm 5 of the relay, even if the relay were energized. At this time a potential starting circuit for the relay 3 is vprovided as follows: from line wire 53, limit control 52, line wire 54, wire 55, wire 55, bimetal element I2, movable contact I5, stationary contact I8, wire 51, relay coil 4, wire 58 and transformer primary coil 5.0 to line wire 59. As the room thermostat 48 is satisfied it opens the circuit through secondary coil 5I and the transformer primary coil .50 therefore acts as a choke, which prevents substantial flow .of current through the relay coil 4. The relay 3 is thus deenergized even though the potential starting circuitl through contacts I8 and L8 is completed.

When the room thermostat calls for heat it closes a circuit between the transformer secondary 5| and electric heater 2| as follows: from secondary 5I, wire 60, thermostat 48, wire 6|, heater 2| and wire 62 to secondary 5I. This causes current to flow through the electric heater `2| Afor heating bimetal element I2 and simultaneously reduces the choke action of the transformer 49 suiciently to permit the relay 3 to pull in to running position. Thus switch arms 6 and 1 are brought into engagement with, contacts 9 and I0. However, the switch arm 5 does not at this time engage the contacts B due to the combustion responsive device still being in its cold position. Engagement of switch arm 1 with contact I0 energizes the burner motor I. Engagement of switch arm 6 with contact 9 establishes an energizing circuit for the ignitcr 2 as follows; line wire ,54,V wire 55, wire 56, bimetal element I2, movable contact I1, stationary contact I9, wire 64, contact 9, switch arm 5, wire 65 and igniter 2 to line wire 59. Thus when the thermostat calls for heat the relay 3 is energized, the burner motor being placed into operation directly and, the igniter being energized through the igniter contacts I1 and I9 of the timing device Il. Also the electric heater 2| of the timing devie is energized simultaneously with starting of the burner, At this time the relay stop mem- 45 ber 21 is withdrawn from the path of movement ofthe bimetal element I2 as shown in Fig. 2.

CTI

Occurrence of proper combustion If combustion occurs properly the operating 5.0 beam 34 will be moved againsty its hot stop 31 wherein the abutment 38 is in the path of movement of the free end of bimetal element I2. This same movement of `the operating beam 34 will also shift the movable relay contact 8 into engagement ywith the switch arm 5. Engagement of contact 8 with switch arm 5 will establish a new energizing circuit for the relay coil which is independent of the starting switch I 6-I8. This holding Ql.'A running circuit is as follows: from line 60 Wire 54, wire 56, flexible arm 42, movable contact 8, switch arm 5, wire 61, wire 51, relay coil 4 wire. 58. and transformer primary `Sil to line wire 59.4 In lresponse to combustion the combustion responsive device in addition to moving the abutment 3,8 in to active position and establishing a holding or running circuit for the relay, also causes switch arm 43 to engage contact 4 5 which energizes the heater 2,2; of the timing device ll. This `circuit may be traced as follows: from line wire 54, wire 55, wire 56, bimetal element I2, movable contact I1, stationary contact I9, -wire B4, wire 68, heater 22, wire 69, movable contact 43, iixedcontact 4 5, wire 1I), ballast resistor 1I, and wireV 1-2V to line wire 59,. The heater 2| when en- 7'5 ergized alone would cause the movable contacts to snap away from the xed contacts in a predetermined period of time, such as 90 seconds after starting of the burner. The purpose oi the heater 22 and the combustion contacts 43-45 is to shorten this period when the burner operates properly. When combustion occurs the operation of the igniter is unnecessary and it is desirable to place it out of operation a short time thereafter. Due to the heater 22 supplementing the action of heater 2I, the bimetal element I2 is heated in a short time sufficiently to overcome the attraction of armature I4 to magnet I5. The bimetal element then snaps upwardly against the abutment 38 as shown in Fig. 2, in which position the movable contacts I6 and I' are disengaged from contacts I8 and I9. Disengagement of contact I'I from contact I9 breaks the energizing circuit for the igniter 2 and also breaks the energizing circuit for the heater 22. The igniter is therefore placed out of operation and the heater 22 is deenergized, the bimetal element I2 being retained in its hot position solely by the influence of heater 2I. Disengagement of contact IB from contact I8 breaks the starting circuit for the relay. The relay, however, is maintained energized through the holding or running circuit extending through combustion contact 8 and switch arm 5 of the relay. When the room thermostat becomes satisfied it opens its circuit, thus deenergizing heater 2l and once more causing the transformer i9 to function as a choke for deenergizing the relay coil 4. The relay switch arms 5, and therefore disengage their respective contacts and the burner stops. Due to the switch arm 5 now being disengaged from the contact 8 the relay cannot be energized oncer more until the bimetal element I2 cools down lfor reengaging contacts I6 and II with contacts I8 and I9. As a result the burner can never be started unless the ignition controlling contacts I'I and I9 of the timing device I2 are in engagement.

Failure of flame on starting If combustion does not take place after starting of the burner, the operatingr beam 3l! of the combustion responsive device will remain in the position shown in which the abutment 38 is out of the path of bimetal element I2, the combustion contact 8 is out of reach of switch arm 5, and in which the switch 43-45 for the accelerating heater 22 is open. Under these conditions the burner will operate with the ignition on until the heater 2l heats the bimetal element I2 sufliciently to cause this element to overcome the attraction of magnet I5. This period is preferably approximately 90 seconds. At the end of this period the bimetal element I2 snaps upwardly. As the abutment 33 is not in its path, this element will snap upwardly to a position beyond the relay abutment member 2`I. At the same time the contact I6 is disengaged from contact IS ,which breaks the starting circuit for relay coil 4. Due to the holding or running circuit for the relay coil never having been closed, the relay becomes deenergized at this time and moves to its out position for stopping the burner. The relay abutment 2'I now becomes interposed between the free end of bimetal element I2 and the cold position thereof, as shown in Fig. 3, which prevents reengagement of the starting contacts Iii-I 8 and 'also prevents engagement of the ignition contacts I1 and I9. Due to the maintaining of the starting contacts I6 and I8 open in this manner, the relay cannot `be energized until the abutment 21 is withdrawn from the path of movement of bimetal I2. This may be done manually by any suitable manual reset means. Such means is indicated diagrammatically in Fig. 1 as comprising a plunger 'I5 which is urged inwardly by a spring 16, this plunger extending through the abutment member 26 and having an enlarged head TI. By pulling on a handle portion 'I8 the abutment 21 may be withdrawn from the path of movement of bimetal I2, thus resetting the instrument for further operation of the burner. It will be noted that as the transformer primary 5i) is in series with the relay coil, the secondary 5I of the transformer becomes deenergized when the control assumes its lockout position of Fig. 3. Consequently the heater 2I is deenergized at this time and the bimetal element I2 becomes cold. v4Thus when the resetting member I8 is operated, the bimetal I2 snaps to its cold position forv permitting immediate restarting of the burner.

Failure of flame while running When the burner has been operating properly but then loses its flame, the operating beam 34 of the combustion responsive device 3l! will berocked clockwise from its hot stop 37 to its cold stop 33, thus moving the abutment 38 out of the path of bimetal element I2 and also shifting the combustion contact 3 out of reach of the switch arm 5.

The particular sequence of operation which occurs upon flame failure during operation of the burner depends upon the setting of the adjusting screw 4I which positions the Contact 8 with respect to the abutment member 38. lf non-recycling operation is desired, the adjusting screw 4I is adjusted so that the Contact 8 remains in engagement with the switch arm 5 until the abutment member 3S is shifted clear of the bimetal element I2. The relay coil 4 will thus remain energized and the relay abutment will thus remainl out of the path of bimetal I2 at the time that the combustion abutment 38 releases this element. The element I2 will therefore snap from the position of Fig. 2 to the position of Fig. 3. Upon further movement of the operating beam 34 the contact 8 will disengage from switch arm 5 which breaks the running circuit for the relay. The relay will therefore become deenergized, moving to its out position for stopping the burner and causing its abutment 38 to prevent return of the bimetal I2 to its cold position. The burner will therefore remain out of operation until the control is manually reset.

If it is desired that the control recycle after a flame failure during operation of the burner, instead of locking out immediately as above described, the adjusting screw 4I may be adjusted so that the movable contact 8 disengages the switch arm 5 before the abutment 38 is shifted out of the path of bimetal element I2. With this adjustment of screw 4I, upon a flame failure the operating beam 34 will be rocked toward its cold stop 36. The first action of this movement will now be to disengage contact 8 from switch arm 5. This will break the running circuit for the relay coil 3 and consequently this coil will be deenergized and also the heater 2l will be deenergized. The relay will thus drop out and stop the burner and the bimetal element I2 will begin cooling. Due to the abutment 38 still being in engaging relationship with the bimetal element I2 when the relay drops out, the relay abutment 21 when it returns to the position sh-own in Fig. 1 will not prevent return movement of the bimetal I 2 to its cold position. When the 'bimetal element `t2 cools sufficiently to cause reengagement of the movable contacts .I6 and I1 With the iixed contacts I8 and I9, the burner will restart in the manner above described. If combustion now occurs before the bimetal-element moves to its hot position, the control will operate in the manner described for retaining the burner in operation until the thermostat 48 becomes satisfied. If llame does not occur within the timing period of the timing device I I the control will lock out in the manner described above and will retain the burner out of operation until the control is manually reset.

Power failure In the event that the :power should fail While the burner is running and after the ignition is cut off, the relay 3 will drop out and the heater 2l will become deenergized. W hen power is restored the burner Will not start until the bimetal element cools down and returns to its cold position in which the starting switch and the timer ignition switch are closed. In the event that a power failure occurs just after the burner is started and before the bimetal AI2 shifts to its hot position, the relay will drop out as above described. Due to the magnetic shunt 25 being shifted adjacent the permanent magnet I5 upon dropping out of the relay, the attraction of armature III to permanent magnet I5 Will be considerably reduced, Consequently ii bimetal element I2 is heated a substantial amount it will now snap to its hot position. The burner therefore cannot restart until the bimetal element .I2 cools and returns to its cold position. This arrangement insures a full trial starting `period When power is resumed.

From the foregoing description it Will be apparent that the present invention provides a sim- `ple burner control system which provides for a safety shut down oi the burner in the event of flame failure either upon starting of the burner or while the burner is running. It will also be apparent that the present invention controls the ignition for the burner` and provides an entirely safe sequence of operation. While I have shown and described a preferred form of the invention, it is obvious that many changes may be made without departing from the spirit and scope of the invention. Also various parts may be omitted from the complete system Without departing from the invention. For example, the ignition contacts I1 and i9 may be omitted Where it is desired that the igniter operate continuously with the burner. Also the relay switch arm 5 could be omitted in certain applications of the invention. It is desired to be limited only by the scope of the appended claims.

What is claimed is:

1. In a burner control system, the combination oi, control means responsive to the demand for heat for starting and stopping the burner, starting means movable from an inoperative position to a starting position, means normally preventing the burner from starting when the starting means is in said inoperative position and providing for starting of the burner when the starting means is in starting position, said starting means moving to inoperative position irrespective of combustion after starting of the burner, running means including combustion responsive means and a movable member' operated thereby, said movable member being moved `to running position only upon presence of combustion and serving to maintain the burner in operation ndependently of said starting means and under the control of said heat demand responsive means, and means responsive to failure of combustion for preventing return of the starting means to starting position irrespective of said heat .demand responsive means.

2. In a burner control system, the combination or, control means responsive to the demand for heat for starting and stopping the burner, starting means movable from an inoperative position to a starting position, means normally vpreventing the burner from starting when the starting means is in said inoperative position and providing for starting of the burner when the starting means is in starting position, said starting means moving to inoperative position after starting of the burner, running means including combustion responsive means and a movable member operated thereby, said movable member being moved to running position only upon presence of combustion and serving to maintain the burner in operation independently of said starting means and under the control oi said heat demand responsive means, means including mechanical holding means acting upon failure of combustion to prevent return movement of the starting means to starting position, and manual reset means for said holding means,

3. In a burner control system, the combination of, control means responsive to the demand for heat for starting and stopping the burner, starting means movable from an inoperative position to a starting position, means normally preventing the burner from starting when the starting means is in said inoperative position and providing for starting of the burner when the starting means is in starting position, said starting means moving to inoperative position irrespective of combustion after starting of the burner, running means including combustion responsive means and a movable member operated thereby, said movable member being moved to running Dosition only upon presence of combustion and serving to maintain the burner in operation independently of said starting means and under the control oi said heat demand responsive means, means including mechanical holding means acting upon failure or combustion to prevent return movement of the starting means to starting position, and manual reset means for said holding means.

fi. In a burner control system, the combination or, control means responsive to the demand for heat for starting and stopping the burner, starting means movable from an inoperative position to a starting position, means normally preventing the burner from starting when the starting means is in said inoperative position and providing for starting of he burner when the starting means is in starting position, said `starting means moving to inoperative position after starting of the burner, running means including combustion responsive means and a movable member operated thereby, said movable member being moved to ruiming position only upon presence of combustion and serving to maintain the burner in operation independently of said starting means and under the control of said heat demand responsive means, said running means being incapable of initiating operation of the burner irrespective oi said vcombustion responsive means, and means acting upon failure of combustion to prevent return of the starting means to starting position irrespective of said heat demand responsive means.

5. In a burner control system, the combination of, control means responsive to the demand for heat for starting and stopping the-burner, starting means movable from an inoperative position to a starting position, means normally preventing the burner from starting when the starting means is in said inoperative position and providing for starting of the burner when the starting means is in starting position, said starting means moving to inoperative position after starting of the burner, running means including combustion responsive means and a movable member operated thereby, said movable member being moved to running position only upon presence of combustion and serving to maintain the burner in operation independently of Vsaid starting means and under the control of said heat demand responsive means, said running means being incapable of initiating operation of the burner irrespective of said combustion responsive means, means including mechanical holding means and acting upon failure of combustion to prevent return movement of the starting means to starting position, and manual reset means for said holding means.

6. In a burner control system, the combination of, control means responsive to the demand for heat for starting and stopping the burner, starting means movable from an inoperative position to a starting position, means normally preventing the burner from starting when the starting means is in said inoperative position and providing Vfor starting of the burner when the starting means is in starting position, said starting means moving to inoperative position irrespective of combustion after starting of the burner, running means including combustion responsive means and a movable member operated thereby, said movable member being moved to running position only upon presence of combustion and serving to maintain the burner in operation independently of said starting means and under the control of said heat demand responsive means, said running means being incapable of initiating operation of the burner irrespective of said combustion responsive means, and means acting upon failure of combustion to prevent return of the starting means to starting position irrespective of said heat demand responsive means.

7. In a burner control system, the combination of, control means for starting and stopping the burner including-a, starting circuit for the burner, starting switch means for said starting circuit, a running circuit for maintaining the burner in operation under the control of said control means independently of said starting circuit and being incapable of initially placing the burner into operation, rst combustion responsive means for rendering the running circuit inoperative at all times when combustion is not present, and means including second combustion responsive means for controlling the starting switch means selectively to open the starting circuit and maintain the same open upon failure of combustion, or for opening the starting circuit and effecting reclosing of the same thereafter if combustion is proper.

8. In a burner control system, the combination of, control means for starting and stopping the burner, a starting switch arranged to prevent starting of the burner by said control means until the starting switch is in a starting position, running switch means arranged to maintain the burner in operation under the control of said control means independently of the starting switch means and being incapable of initiating operation of the burner, means including rst combustion responsive means for rendering the running switch means operative when combustion is present and inoperative at all times when combustion is not present, means actuated after starting of the burner for moving the starting switch from said starting position, and means including second combustion responsive means for controlling said starting switch selectively to eiect return movement thereof to starting position after proper combustion or to maintain it away from starting position upon combustion failure.

9. In a burner control system, the combination of, a relay for starting and stopping the burner, condition responsive means responsive to the demand for heat in` circuit with said relay, means including a starting switch for said relayA and arranged to prevent starting of the `burner until the starting switch is in starting position, holding switch means operated by said relay and adapted. to maintain the burner in operation independently of said starting switch, said holding switch means being incapable of initiating operation of the burner, means including combustion responsive means for rendering said holding switch means operative when combustion is present and inoperative at all times when combustion is not present, means actuated after starting of the burner for moving said starting switch from said starting position, and means operative upon failure of combustion for preventing return movelment of said starting switch` to starting position irrespective of said condition responsive means. 10. In a burner control system, the combination-of, a relay for starting and stopping the burner, control means for controlling said relay, starting switch means for controlling the relay and arranged to prevent starting of the burner until the starting switch means is in startingposition, means including a running Switch for controlling said relay and arranged to maintain the burner in operation under the control of said control means independently of said starting switch means, rst means including combustion responsive means for actuating said running switch to maintain the burner in operation independently of said starting switch means only while proper combustion takes place, means actuated after starting of the burner for moving said starting switch means from starting position irrespective of combustion, and second means including combustion responsive means for selectively preventing return or effecting return of the starting switch means to starting position.

11.A In a burner control system, the combination of, a relay controlling the burner and having a iirst position in which the burner operates and a second position in which the burner is normally out of operation, heat demand responsive means for controlling said relay and normally causing said relay to assume its first position upon demand for heat and to assume its second position when the demand for heat is satisiied, means including a starting switch for preventing movement of the relay from its second position to its first position unless the starting switch is in starting position, actuating means for the starting switch including a timing device for moving said starting switch from starting position a period of time after starting of the burner, means including combustion responsive means for maintaining the relay in its iirst position independently .of said starting switch when. combustion is present while causing movement thereof to its secing movement of the starting switch to starting position upon failure of combustion with the relay in its first position, while permitting return of the starting switch to starting position upon movement of the relay to its second position prior totermination of combustion.

l2. In a burner control system, the combination of, a relay controlling the burner and having a firstr position in which the burner operates and a second' position in which the burner is normally out of operation, heat demand responsive means for controlling said relay and normally causing said relay to assume its rst position upon demand for heat and to assume its second position when the demand for heat is satisfied, means including a starting switch for preventing movement of the relay from its second position to its first position unless the starting' switch is in starting position, actuating means for the starting switch' including a timingdevice for moving said stanting switch from starting position a period of time after starting of the burner, means including .combustion responsive means' for maintaining the' relay in its first position independently of said starting switch when combustion is present While causing movement ithereolf to its second position upon failure of combustion, stop means actuated by movement of the relay to its second position for preventing movement of the starting switch to starting position, and combustion responsive means for preventing said stop means from being effective when the relay moves to its second position while combustion is present.

13; In a burner control system, the combinationA of, a relay controlling the'burner and having a first position in which the burner operates and a second position in which the burner is normally out of operation, heat demand responsive means for controlling said' relay and normally causing said relay to assume its first position upon demand for heat and to assume its second position when the demand for heatv is satisfied, means including a staiitlng switch for preventing movement of the relay from its second position to its rst position unless the starting switch is in starting position, actuating means for the s'tarting switch including a, timing device for moving said starting switch from starting position a period of time after starting of the burner, a movableV stop member adapted when in operative position to'limit movement of theactuating means after movement of the starting switch from starting position, said movable stop member when inY inoperative position permitting continued movement of the actuatingl means, means for moving said stop member' to operative position when combustion is present and for moving said stop` member to inoperative position when combustion is absent, means including combustion responsive means for maintaining the relay in its rst position independently of said starting switch. when combustion is present while'causing movement thereof to its second position upon failure of combustion, and a second stop member operated by said relay upon movement to its second position and adapted to prevent return of the starting switch to starting position unless the movementof said actuating means is'` limited by said first stop member.

14. In a burner control system, the combination of, a relay 'controlling' the burner and having a iirst position in which the burner operates and a second position in which the burner is nor'- mally out of operation, heat demand responsive means for controlling said relay and normally causing said relay to assume its first position upon demand for heat andto assume its second position when the demand-for heat is satisfied, means including a movable member and arranged to prevent the relay from moving from its second to its first position unless said movable member is in starting position, means for causing said movable member to move away lfrom starting position. a, period of time after starting of the burner, means including combustion responsive means for maintaining the relay in its first position if combustion is present, and stop means controlled conjointly by the relay and combustion responsive means for preventing' movement of said movable member to starting position upon failure of combustion With the relay in its first position, while permitting return of the movable member to starting posiltion upon movement of the relay to its second position prior to termination of combustion.

l5. In a burner control system, the combination of, a relay controlling the burner and having a first position in which the burner operates and av second position in which the burner is normally out of operation, heat demand responsive means for controlling said relay andV normally causing said relay to assume its first position upon demand for heat and to assume its second position when the demand for heat is satisfied, means including a movable member arranged to prevent the burner from starting unless said movable member is in starting position, means for causing said movable member to move away from starting position a period of time a'fter starting of .the burner while permitting said burner to continue to operate, and means controlled by the relay and combustion responsive means for causing the movable member to remain away from starting position upon failure of combustion with the relay in its first position, while effecting return of the movable member to starting position after movement of the relay to its second position prior to termination of combustion.

16. In a burner control system, the combination of, a relay controlling the burner and having a rst position in which the burner operates and a second position in which the burner is normally out of operation, heat demand responsive means for controlling said relay and normally causing said relay to assume its first position upon demand for heat and to assume its second position when the demand for heat is satisfied, means including a movable member arranged to prevent the burner from starting unless said movable member is in starting position, means for causing said movable memberA to move away from starting position a period of time after starting of the burner while permitting said burner to continue to operate, stop means actuated by movement of the relay to its second position lfor preventing movement of the movable member to starting position, and combustion responsive means for preventing said stop means from being effective when the relay moves to its second position While Icombustion is present.

17. In a burner control system, the combination of, a relay controlling the burner and having a first position in which the burner operates and a second position in which the burner is normally out of operation, heat demand responsive means for controlling said relay and normally causing said relay to assume its rst position upon demand for heat and to assume its second position when lthe demand for heat is satisfied, means including relay actuated' means actuated by 13 movement of the relay to its second position for preventing movement of the relay to its rst position, and combustion responsive means for preventing said relay actuated means from being effective when the relay moves to its second position while combustion is present.

18. In a burner control system, a source of high voltage, a high voltage switch for selectively connecting or disconnecting the source of high voltage and the burner, means comprising a low voltage circuit and a room thermostatic switch connected therein for operating said high voltage switch, a movable member, means for normally causing said movable member to move from starting position to running position after the burner starts and to return to starting position after the burner stops, means comprising a second high voltage switch operated by said movable member for preventing the iirst high voltage switch from initially closing unless the movable member is in starting position, and means responsive to lack of combustion for opening said rst high voltage switch and for preventing return of the movable member to starting position.

19. In a burner control system, means responsive to the demand for heat for stopping and starting the burner, means including first combustion responsive means for stopping the burner in case of ilame failure during operation, said iirst combustion responsive means being incapable of preventing restarting of the burner, means including second combustion responsive means arranged to maintain the burner out of operation until manually reset, and means for relatively adjusting the combustion responsive means to selectively provide a recycling or non-recycling sequence of operation.

20. In a burner control system, the combination of, combustion responsive means for shutting down the burner in case of flame failure, automatic means for restarting the burner following a purging period after such flame failure shutdown, and adjustable means for selectively preventing or permitting restarting of the burner by said automatic means.

2l. In a burner control system, the combination of, means including timing means and combustion responsive means ior providing a trial operating period of the burner when first started, said means being constructed and arranged to permit continued operation if combustion is obtained'but to stop the burner and prevent further operation until manually reset if combustion is not obtained, means for shutting down the burner on llame failure while the burner is in operation, automatic means for restarting the burner following a purging period after such name failure shutdown, and selective means for selectively preventing or permitting restarting of the burner by said automatic means.

22. In a burner control system, the combination of, a relay for controlling the burner, means including a movable member arranged to prevent initial energization of the relay unless the movable member is in starting position, means for causing said movable member to move from starting position toward a second position after energization of the relay, a rst movable abutment operated by the relay and moved into the path of movement of the movable member when the relay is deenergized and out of the path of movement of said movable member when the relay is energized, said iirst abutment being adapted to prevent return of the movable member from its second position back -to starting position, combustion responsive means, a second movable abutment operated by the combustion responsive means, said second abutment being moved out of the path of movement of the movable member when' combustion is not present and being moved into the path of movement of the movable member when combustion is present, said second abutment in such position preventing the movable member from moving to said second position.

23. In a burner control system for a burner having a motor and igniter, the combination of, a relay for controlling the motor and igniter, a safety switch for controlling the relay, an ignition switch, timing means, means including a movable member operated by the timing means and having a starting position in which both of said switches are closed and a second position in which said switches are open, combustion responsive means acting upon presence of combustion to maintain the relay energized after said movable member moves from starting position, a rst movable abutment operated by the relay and moved into the path of movement of the movable member when the relay is deenergized and moved out of said path when the relay is energized, a second movable abutment operated by the combustion responsive means, said second abutment being moved out of the path of movement of the movable member when combustion is not present and being moved into said path when combustion is present, said second abutment in the latter position preventing the movable member from moving to said second position.

LEWIS L. CUNNINGHAM.

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