US2910118A

US2910118A - Electrically operable safety control apparatus

Info

Publication number: US2910118A
Application number: US633793A
Authority: US
Inventors: Carl J Bishofberger
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1957-01-11
Filing date: 1957-01-11
Publication date: 1959-10-27
Anticipated expiration: 1976-10-27

Description

Oct. 27, 1959 c. J. BISHOFBERGER 2,910,113

I ELECTRICALLY OPERABLE SAFETY CONTROL APPARATUS Filed Jan. 11, 1957 2 Sheets-Sheet 1 2e 21 LINE I' w w 'l 2| I8 I I LZ? M 20 60 |6I1\ I r 68- 22 \TRANSFOMR I I Q 62 I I 72 9e 31; as I I 39 9o 33 40 H I I as I I I I "GI I I I I I E I I I I I I I INVENTOR.

CARL J. BISHOFBERGER 1959 A c. J. BISHOFBERGER 2,910,118

ELECTRICALLY OPERABLE SAFETY CONTROL APPARATUS Filed Jan. 11, 1957 2 Sheets-Sheet 2 INVEN TOR. CARL J. BISHOFBERGER ATTORNEY United States Patent ELECTRICALLY OPERABLE SAFETY CONTROL APPARATUS Carl J. Bishofberger, Minneapolis, Minn., assiguor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application January 11, 1957, Serial No. 633,793

3 Claims. (Cl. 158-28) The present invention is concerned with an improved control apparatus and more particularly with an improved control apparatus for use with a fuel burner unit to monitor the proper operation of the fuel burner unit.

In many burner installations it is desirable to initially energize an ignition means which in turn ignites the fuel being supplied to the burner. When flame is established at the burner, the energization of the ignition means is no longer necessary, and in some cases it is even undesirable. Therefore, it becomes advisable to provide means for de-energizing the ignition means after energization thereof is no longer necessary. This ignition timing period may begin upon the initial supplying of fuel to the fuel burner unit, the duration of the ignition timing period being longer than that time normally necessary to establish flame at the burner unit.

In the event that flame is not established at the fuel burner unit, or in the event that once established the flame becomes extinguished, it is necessary to provide in a control apparatus of this type a means for de-energizing the burner in response to the absence of flame. This means likewise takes the form of a timer and is usually termed a safety switch timer. The function of this safety switch timer is such that after a predetermined time period of energization thereof certain switch means are actuated to de-energize the fuel burner unit such that unburned fuel is no longer fed to the fire box.

It is an object of the present invention to provide an improved control apparatus utilizing the principles above described wherein a timer, which functions both as an ignition timer and a safety switch timer, is associated with a flame responsive means to provide both timing functions. I

It is a further object of the present invention to provide an improved burner control apparatus which when combined with a remotely located flame sensing means causes a flame relay to be actuated in response to the presence of flame, which relay is so constructed and arranged as to cooperate with a timer to cause the timer to function as an ignition timer upon flame being established and for the same timer to function as a safety switch timer upon no flame being established.

It is a further object of the present invention to provide an improved burner control apparatus having a main control relay which is constructed and arranged to control the supplying of fuel to a fuel burner unit, having a flame relay which is responsive to the presence of flame at the fuel burner unit, and having a timer so constructed and arranged that the timer and its associated switch means function as an ignition timer when flame is in fact established at the fuel burner unit and alternately functions as a safety switch timer when flame is not established at the fuel burner unit.

It is still a further object of the present invention to provide a mechanically interlocked bimetal timer and electromagnetic relay such that movement of the relay rice armature determines the extent of movement of the bimetal timer, the movement of the bimetal timer normally being to a first position from which it is capable of returning in the event that the relay is energized, and the movement of the bimetal timer being to a second extreme position upon the relay being de-energized, with means being provided to manually move the relay armature and reset the bimetal timer from the extreme position.

These and other objects of the present invention will be apparent to those skilled in the art upon reference to the following specification, claims and the drawings, of which Figure 1 is a combined schematic and diagrammatic representation of the improved control apparatus of the present invention,

Figure 2 is a showing of the mechanically interlocked relay and timer of the apparatus of Figure 1 with both the relay and timer in the run position,

Figure 3 is a showing of the inter-locked relay and timer of the apparatus of Figure 1 with the timer in the lockout or extreme position, and

Figure 4 is a showing of the physical arrangement of a portion of the apparatus disclosed in Figure 1, showing an embodiment of the mechanical placement of the timer and the relay along with the manually operable means which is effective to reset the timer from the lockout position in which it is shown in Figure 3 to the position shown in Figure 1.

Referring specifically to Figure 1, the reference numeral 10 designates generally a fuel burner unit. This fuel burner unit is shown as a gun-type oil burner including a motor 11 which upon being energized supplies oil to an oil nozzle 12 and likewise supplies combustion air to the area surrounding the nozzle 12. The oil at the nozzle 12 is ignited by means of spark electrodes 13 and 14, which in turn are connected to an ignition transformer 15. The reference numeral 16 designates a flame responsive switch which is located within the blast tube 17 of the gun-type oil burner.

This flame responsive switch 16 is shown diagrammatically in Figure 1 and may take a variety of forms. Functionally, flame responsive switch 16 is a normally open switch which is closed upon flame being established at the nozzle 12 of the burner unit 10.

Operation of the burner unit 10 is controlled by means of a thermostat is which is responsive to the need for operation of the burner unit to close its associated switch. The thermostat 18 is normally remotely located from the burner unit 10 in the area to be heated by the flame at the burner unit. The thermostat 18 is connected to the burner control apparatus included within the broken linesdesignated by the reference numeral 19. This burner control apparatus is normally remotely located from the fuel burner unit 19 and likewise remotely located from the flame sensor, or flame responsive switch 16.

Burner control apparatus 19 includes a main control relay in the form of a transformer relay designated generally by the reference numeral 2t This transformer relay includes a primary winding 21 and a secondary winding 22 along with an armature construction designated generally by the broken line 23, which is connected to control switches 24 and 25, The primary winding 21 of transformer relay 20 is connected to a source of alternating voltage by conductors 26 and 27. As is well known, upon a circuit being completed such that current flows in the secondary winding 22 of this transformer relay, the relay is energized and the armature structure 23 is effective to cause the switches 24 and 25 to move to their closed circuit condition.

The burner control apparatus 19 likewise includes a flame relay 28 having an energizing winding 29 and a movable switch blade 31'). The movable switch blade 30 is biased, by means not shown, to engage contact 31 when the winding 29 of relay 28 is tie-energized. Upon energization of winding 23, movable switch blade 39 engages contact 32 and disengages contactSl; The fiame'relay 28 likewise includes a further movable member in the form of a latch 33 which is arranged to cooperate with a timer and snap means designated generally by means of the reference numeral 34'. The timing means of the structure 3 includcs'a first ambient temperature compensating bimetal 35 and a second active bimetal 36 which is-associated with an actuating heater 37. The compensating bimetal 35 is resiliently biased by means of a bolt 9S and spring 99 at the left hand end of the bimetal. The right hand end of the bimetal is rigidly attached to a yoke member 38 which is pivoted at pivot 39. The right hand end of the active bimetal 36 is likewise rigidly attached to the yoke member 38 while the left hand'member thereof floats free and includes a further rigid member 40 which attaches the timer to a first movable member 41 of a snap or over center means.

As indicated by means of the arrows labeled H in Figure 1, the ambient temperature compensating bimetal 35 is affected by the ambient temperature and the center portions thereof bows in a downward direction upon a rise in temperature. This bowing of the bimetal 35 controls the position of the yoke 38 and therefore compensates the action of the active bimetal 36 for the ambient temperature. Upon energization of the actuating heater 37, the left hand end of the active bimetal 36 moves in an upward direction, causing movement of member 41 in an upward direction through the coupling 40.

The snap action, or over center means includes a second movable member 42, which with member 41, is pivoted at a common pivot as provided by post 43, the over center or snap action being effected by means of a spring 44 which is attached to each of the

members

41 and 42 and biases each of the memberstoward the com mon pivot provided by means of post 43. As is well known; as the member 41. moves in an upward direction, the line of force formed by the spring of 4.4 travels'above the pivot in post 43 and thereupon causes the right hand end of member 42 to quickly move in an upward direction, thereby giving a snap acting effect.

The right hand end of the member 42 controls a switch means including

switches

45 and 46, theseswitches being normally in their closed conditions.

Referring to Figure 4, an actual mechanical layout of the portion of the apparatus of Figure 1 showing the mechanical relationship of the timer and snap acting means 34 and the flame relay 28 can be seen. In this figure, the compensating bimetal 35, the yoke 38, the active bimetal 36, and the heater 37 can clearly be seen. Furthermore, the

movable members

41 and 42, the spring 44, and the post 43 of the snap acting means can be seen. The actual contact structure of the snap acting means is shown and the switch 45 is identified. The switch .6 lies directly behind the switch 45 and each switch includes its separate spring blade 43 which is attached at the left hand thereof to an insulating board 49 and is attached to a further insulating board i) coupled to the right hand end of the spring blade. The insulating board St) is coupled to a further member 51, which in turn couples the switch means to the right hand end of the movable member 42 such that the switch means is operated by movement of the movable member 42.

Furthermore, the construction of the flame relay 28 is shown. This construction includes a: U-shaped core member 52 which is provided with a pole face 53 against which an armature 54 is moved, against the bias of spring 55 upon energization of the Winding of relay 28. The armature 54 of relay 28 carries a member 47 of insulating material which member cooperates with the common blade 30 of the relay switch means and likewise co operates with the further movable member 33.

Relating the actual structure of Figure 4 to the diagrammatic showing of Figure 1, upon energization of the relay winding 28, the movable armature 54 is attracted to the pole face 53 and the insulating member 47 swings in a clockwise direction about the pivot point 56. This movement of member 47 causes movable switch blade 30 to disengage stationary contact 31 and to move into engagement with stationary contact 32. Furthermore, after a given distance of movement of element 47, element 47 engages movable member 33 and moves this member 33 to the right, such as shown in Figure 2.

Referring once again to Figure 4, the control apparatus is shown encased in a container designated by the reference numeral 19, this being diagrammatically indicated by the broken line 19 of Figure 1. The reference numeral 57 designates a metal cover which is fastened in position by means of a bolt 53. The reference numeral 59designates a manually operable means in the form of a button whichcan be manually moved in a downward direction to engage armature 54 and manually move this armature into engagement with the pole face 53. As will bedescribed, this manual means 59 is a reset means to reset the control apparatus from its lockout position as shown in Figure 3 to its standby position as shown in Figure 1.

Referring once again to Figure 1, the control apparatus is shown in its standby condition. That is, there is no flame at the burner unit 10 since the thermostat 18isiri a position indicating that there is no need for operation of the burner unit. The transformer relay 20 is def-energized, thereby maintaining switches 24 and 25 in their open condition, the timer of the means 34 is in the cold or de-energized position such that switch means 45' and 46 are in their closed circuit position. Flame relay 28 is de-energized, the flame responsive switch 16' being in the open circuit condition due to the absence of flame at the burner unit 10.

If it is now assumed that there isa subsequent call for operation of the burner unit 10 as evidenced" by the thermostat is closing its switch, the transformer relay 20, and particularly the secondary winding 22 thereof, is energized through a circuit which can be traced from the right hand terminal of the winding 22 through can: ductors 6t) and 61, thermostat 18, conductor 62, heater 37, conductors 63 and -64, starting switch 45, conduc tor 65, Switchblade 3t and contact 31 of relay 28, and conductors 6e, 67, and 68 to the left hand terminal of the secondary winding 22. From this above'trace'd circuit it can be seen that in order for the transformer relay 20 to be energized it is necessary for the timer and the snap action means of the structure 34 to be in its cold or de-energized position such that the starting switch 45 is closed. Furthermore, the flame r'elay 28" must'b e in a position sensing the absence of flame at the burner unit 10, thereby causing switch blade 30 to engage con: tact 31'.

Energization of the transformer relay 20 causes the switch means 24 and 25 to move to'the circuit closing conditions. The switch means 25 of transformerrelay 20 completes a circuit which can'be called an intermediate energizing circuit for the secondary winding of transformer relay 20. This intermediate energizing circuit can be traced from the right hand terminal of transformer secondary winding 22 through

conductors

60 and 61", thermostat 18, conductors 62, heater 37', conductors 63 and 64, start switch 45, conductor 69, switch 25, and coriductors 70 and 63 to the left hand terminal of the secondary winding 22 of the transformer relay. From this above traced circuit is can be seen that energization of the secondary winding 22 is no longer dependent upon the flame relay 28'being in its rte-energizedcondition;

The switchmeans 24of the transformer relay 20; upon being closed,completes an energizing circuit for both the ignition transformer 15 and the motor 11 of thefuel burner unit. The energizing circuit for the motor 1 can be traced from the power line conductor 26 through conductor 71, switch means 24, conductors 72 and 73, motor 11 and conductor 74 to the power line conductor 27. The energizing circuit for the ignition transformer 15 can be traced from the power line conductor 26 through conductor 71, switch means 24, conductors 72 and 75, ignition transformer 15, conductor 76, ignition switch 46 and conductor 78 to power line conductor 27. From this last traced circuit it can be seen that energizationof the ignition transformer 15 is dependent upon the ignition switch 46 being closed and on its associated timer and snap action means being in the cold or de-energized position.

The apparatus of Figure 1 is now in the starting position wherein the transformer relay is energized to thereby energize both the burner 11 and the ignition transformer 15 and wherein the heater 37 of the bimetal timer is energized such that the timing function of the control apparatus is progressing.

A flame is normally established at the fuel nozzle '12 and as a result thereof the flame responsive switch 16 moves to its closed circuit condition. This causes energization of the winding 29 of the flame relay 28 through a circuit which can be traced from the right hand terminal of the secondary winding 22 of transformer relay 20 through

conductors

60 and 79, flame responsive switch 16, conductor 80, winding 29, and

conductors

81, 67, and 68 to the left hand terminal of the secondary winding 22 of the transformer relay. Energization of the flame relay 28 causes movable switch blade 30 to disengage stationary contact 31 and to move into engagement with stationary contact 32. 'This completes a holding energization circuit for the secondary winding 22 of transformer relay 20. This holding energizing circuit can be traced from the right hand terminal of the secondary winding 22 through

conductors

60 and 61, thermostat 18, conductor 62, heater 37, conductors 63 and 82, contact 32 and switch blade 30 of relay 28,

conductors

65 and 69, switch means 25, and conductors 7t) and 68 to the left hand terminal of the secondary winding 22 of the transformer relay. From this above traced circuit it can be seen that the continued energization of the transformer relay 20 is dependent only upon a continued call for operation of the burner unit 10 as indicated by thermostat 18 maintaining its switch in a circuit closing condition. Furthermore, it can be seen that the heater 37 of the bimetal timer remains energized.

Furthermore, energization of the flame relay 28 causes the movable member 3-3 to be moved to the left as shown in Figure 2. It will be remembered that the heater 37 of the bimetal timer is energized immediately upon there being a call for operation of the burner unit 10. The timing function of this bimetal timer is of a nominal length during which a flame is normally established at the burner unit. In other words, under normal operation, the flame relay 28 is energized before the timer and snap means of the structure 34 is actuated.

Therefore, a short time after flame is sensed by the flame responsive means 16 to energize relay 28, the active bimetal 36 of the bimetal timer is heated sufiiciently to cause the left hand end thereof to move in an upward direction. As the left hand end of this bimetal moves upward, the movable member 41 of the snap acting means is likewise moved and rotated in a clockwise direction about the pivot provided by post 43. This movement continues until the spring 44 goes over center, whereupon the member 42 snaps upward, rotating in a counterclockwise direction about the pivot provided by post 43, to thereby open the starting switch 45 and the ignition switch 46.

This position is shown in Figure 2 and is the run position of the timer. From Figure 2 it can be seen that the active bimetal 36, now in the hot condition, maintains the movable member 41' of the snap acting means in a 6 position to cause movable member 42 to snap in the upward direction. The opening of the starting contact 45 opens the initial energizing circuit for the transformer relay 20, above traced. The opening of the ignition contact 46 de-energizes the ignition transformer 15.

As can be seen in Figure 2, since the flame relay 28 was in the energized condition to thereby position member 33 to the right, the movable member 42 when it snaps in the upward direction engages this member 33 and the toothlike projection 86 provided on member 33 engages the opening provided in the end of the member 42. The cooperation of the member 33 of flame relay 1 28 and the member 42 of the snap acting means is such that upon a subsequent cooling of the active bimetal 36, which causes the element 41 of the snap acting means to rotate in a counterclockwise direction about its pivot, the member 42 follows as spring 44 once again moves over center to thereby reclose the starting switch 45 and the ignition switch 46.

The apparatus of Figure 1 is now in the run condition wherein the burner motor 11 is energized through the energization of' the transformer relay 20, the flame relay 28 'is energized due to flame responsive switch 16 sensing the presence of flame at the burner unit 10, and the heater 37 of the bimetal timer is energized, having caused the bimetal timer and the snap acting means to move to the position shown in Figure 2. At the end of the call for heat, the thermostat 18 opens its switch and the transformer relay 20 is de-energized, thereby deenergizing the burner motor 11. A flame no longer exists at the burner unit and the flame responsive switch 16 responds to this absence of flame to open its contact thereby tie-energizing the relay 28.

The de-energization of the transformer relay 20 causes the heater 37 of the bimetal timer to be de-energized and the de-energization of the flame relay 28 causes the movable switch blade 30 to disengage contact 32 and move into engagement with contact 31. However, the member 33 operated by the flame relay, the snap acting means and the bimetal timer remain in the position shown in Figure 2. While the heater 37 is de-energized the active bimetal 36 has not cooled as yet and remains in the hot position shown in Figure 2. The member 33, controlled by relay 28, is hinged at 106 on a flexible metal strip which is fastened to a stationary member 87. With the projecting tooth 86 of member 33 engaged in the opening 85 of the member 42, member 33 remains in the position shown in Figure 2 and is biased by the flexible metal strip on which it is mounted so that member 33 will return to the position shown in Figures 1 and 4 when released. The active bimetal 36 of the bimetal timer now cools and the left hand thereof moves in a downward direction, carrying movable member 41 in a downward direction also. After a given amount of movement, the spring member 44 moves over center of the pivots provided in post 43 and the member 42 of the snap acting means snaps in a downward direction, thereby releasing member 33 allowing it to again assume the position shown in Figures 1 and 4, and also closing the initial starting contacts 45 and the ignition switch 46.

The apparatus is once again in the standby condition shown in Figure 1. Considering now the mode of operation of the apparatus in Figure 1 wherein a flame is not established at the burnerunit 10, once again assume that the call for operation of the burner unit 10 is indicated by the thermostat 18. As above described, the transformer relay 20 is energized to thereby energize the burner motor 11 and the ignition means 15. As pointed out above, the initial energization of the transformer relay 20 is dependent upon the starting contact 45 being in a closed condition. In this manner the contact 45, along with the snap acting means in the timer 34, functions as an ignition interlock arrangement since it is impossible to energize the burner motor 11 unless the ignition contact 46 is closed to thereby cause energization of the ignition transformer at the same time that the burner motor 11 is energized. V V H In the event that flame is not established the trans: former relay is maintained energized through a circuit of Figure 1 which can be traced from the right hand terminal of the secondary winding 22 through

conductors

60 and 61, thermostat 18, conductor 62, heater 37, con doctors 63 and 64, starting contact 45, conductor 6 9, relay switch means 25, and conductor 68 to the left hand terminal of the secondary winding 22. Therefore, the burner motor 11 and the ignition transformer 15 remain energized in an attempt to establish flame at the burner unit 10 only so long as the starting contact 45 is in the closed condition. However, after a predetermined time period of energization of the heater 37, the active bimetal 36 is heated to the condition to cause the movable member 41 of the snap acting means to move over center, thereby carrying member 42 in an upward direction, as above described. h v

I In this instance, the flame relay 28 is not in a condition sensing the presence of flame at the time that the snap acting means is operated and therefore the member 33 remains in the position shown in Figures 1', 3', and 4. In this event, the movable member 42 moves upward to an extreme or lockout position wherein the right hand end of this member engages a further toothlike projection 99 provided on the member 33. This can be seen more clearly in Figure 3 which has been labeled lockout position of timer. The operation of the timer and snap acting means to the position shown in Figure 3 opens the starting contact 45 to thereby de-energize the transformer relay and prevent further fuel being sup plied to the burner unit 10. Likewise, the heater 37 of the bimetal timer is de-energized and the active bimetal 36 starts to cool. The apparatus of Figure 3 is shown in the position wherein the snap acting means has just been operated and the active bimetal 36 is shown in the hot condition. However, this bimetal subsequently cools and the left hand end thereof moves in a downward direction to thereby cause movable member 41 to rotate in a counterclockwise direction about its pivot provided in post 43. However, in this event, the movement of bimetal 36 to its cold position does not cause suflicient, movement of member 41 to allow spring 44 to move over center of the pivots provided in post 43. Therefore, the member 42 remains in its position shown in Figure 3 and the device has been locked out. In this above mentioned mode of operation, the starting contact 45 functions as a safety switch contact since the failure to establish combustion has been detected and the starting contact 45 has been opened and remains open such that the thermostat 18 no longer has control over the burner unit 10.

It is necessary now for the manual operator 59 shown in Figure 4 to be manually operated, thereby calling attention to the fact that there may be a defect in the burner unit 10. The apparatus is once again restored to the standby condition by depressing the manual operator 59 in a downward direction until it engages the armature 54 of flame relay 23 thereby causing the insulating member 47 to engage the member 33 and move it to the left, from the position shown in Figures 1, 3 and 4 to the position shown in Figure 2. This causes the movable member 42 of the snap acting means to be moved in a downward direction as it is forced down along the inclined surface 95 provided in the member 33, see Figure 3. As soon as the member 42 has been moved a short distance in the downward direction, the spring 44 moves over center and the member 42 snaps into

position closing contacts

45 and 46, thereby placing the apparatus once again in the standby condition shown in Figure l.

The above explanation has covered the mode of operation wherein a flame is normally established at the burner unit -10 and also the mode of operation where a flame is not initially established at the burner nnit. Consider now the mode of operation wherein a flame is initially established but due to a fault of one type or another the flame is subsequently extinguished even though the thermostat 18 continues to call for operation of the burner unit. It will be remembered that so' long as flame is present at the burner unit 10 the apparatus operates as shown in Figure 2. However, upon the abserice of flame being sensed by the flame responsive means 16, the flame relay 28 is de-energizcd and movable switch blade 39 disengages contact 32 and moves into' engagement with contact 31. As can be seen from Figure 2, thestarting switch 45 is now open and upon switch blade 30 disen: gaging contact 32 the transformer relay 20 i'sde-energized to thereby deenergize the burner motor 11 and theignition transformer 15. Furthermore, the heater 37 of the bimetal timer is de-energized and the'active bimetal 35 begins to cool. The cooling of this bimetal timerre sets the snap acting means to the position shown in Figure 1 after a given time period during which the unburned fuel in the fire box is withdrawn from the fire box by means of natural draft conditions. h y b As soon as the starting switch 45 and theignition switch 46 again assume their closed condition the apparatus recycles since the thermostat 18 remains in a condition calling for operation of the burner unit 10. The apparatus now functions as above described to either establish a flame at the burner unit 10 or to assume the lockout condition shown in Figure 3 in the event that some defect exists in the burner unit 10 making it impossible to establish a flame at the burner unit.

From the above explanation it can be seen that I have provided a novel control apparatus particularly adapted for use with a fuel burner unit and incorporating an inter lock timer and relay structure to function as an ignition timer in one mode of operation of the apparatus and as a safety switch timer in another further mode of operation of the apparatus. I M

Other modifications of the present invention will be apparent to those skilled in the art and it is intended thatthe scope of the present application be limited solely by the scope of the appended claims.

I claim as my invention:

1. Control apparatus for use with a fuel burner having ignition means, means responsive to the need for operation of the fuel burner, and combustion responsive switch means responsive to the presence of flame at the fuel burner, comprising; a bimetal timer having an actuating heater; over center means including a first and a second movable member having a common pivot point, spring means interconnecting said first and second movable members in such a manner that movement of one of said movable members from a first to a second position causes the second movable member to move from a first toa second position; means operativel'y connecting said bimetal timer to said one movable member of said over center means to thereby cause said one movable member to move from said first to said second position upon said bimetal timer heater being energized for a predetermined length of time; a first and a second switch controlled by movement of the second movable member of said over center means, said first and second switches being closed in the first position of said second movable member and being open in the second position of said second movable member; a flame rela'y having an armature, an actuating winding anda first and second switch controlled thereby, said first flame relay switch being closed when said flame relay winding isde-energiz'ed and said second flame relay switch being closed when said flame relay winding is energized; interlock means controlled by said flame relay armature and cooperating with said second movable member of said over center means to limit the movement of said second movable member as said second movable member moves toward its second position after the predetermined time period of energization of said bimetal timer heater, the extent of movement of the second movable member of said over center means being such that when said flame relay winding is energized said second movable member returns to the first position upon cooling of said bimetal timer after the heater of said bimetal timer has been de-energized and when said flame relay winding is not energized said second movable member moves to an extreme lockout position from which it does not return; manually operable means cooperable with the armature of said flame relay to manually reset said second movable member to its first position in the event that it moves to said extreme position; energizing circuit means for, said flame relay winding including terminals adapted to be connected to the com bustion responsive switch means; a control relay having an actuating winding and first and second switches controlled thereby; energizing circuit means for said control relay winding including terminals adapted to be connected to the means responsive to the need for opera tion of the fuel burner, said bimetal timer heater, said first switch controlled by said second movable member, and said first switch of said flame relay; an intermediate energizing circuit for said control relay winding including the second switch of said control relay connected in parallel with the first switch of said flame relay; a holding energizing circuit for said main relay winding including the second switch of said flame relay connected in parallel with the first switch controlled by said second movable member; and burner energizing circuit means including terminals adapted to be connected to the fuel burner and the ignition means whereby the fuel burner is energized through a circuit including the first switch of said control relay and the ignition means is energized through a circuit including the first switch of said control relay and the second switch controlled by said second movable member.

2. Control apparatus for use with a fuel burner having ignition means, means responsive to the need for operation of the fuel burner, and combustion responsive switch means responsive to the presence of flame at the fuel burner, comprising; a bimetal timer having an actuating heater; over center means including a first and a second movable member having a common pivot point, spring means interconnecting said first and second movable members in such a manner that movement of one of said movable members from a first to a second position causes the second movable member to move from a first to a second position; means operatively connecting said himetal timer to said one movable member of said over center means to thereby cause said one movable member to move from said first to said second position upon said bimetal timer heater being energized for a predetermined length of time; a first and a second switch controlled by movement of the second movable member of said over center means, said first and second switches being closed in the first position of said second movable member and being open in the second position of said second movable member; a flame relay having an armature, an actuating winding and a switch controlled thereby, said flame relay switch'being closed when said flame relay winding is energized; interlock means controlled by said flame relay armature and cooperating with said second movable member of said over center means to limit the movement of said second movable member as said second movable member moves toward its second position after the predetermined time period of energization of said bimetal timer heater, the extent of movement of the second movable member of said over center means when said flame relay winding is energized being such that said second movable member returns to the first position upon cooling of said bimetal timer after the heater of said bimetal timer has been tie-energized, and upon failure of said flame relay winding to be energized said second movable member moves to an extreme IOQkQUt position from which it does not return; manually operable means cooperable with the armature of said flame relay to manually reset said second movable member to its first position in the event that it moves to said extreme position; energizing circuit means for said flame relay winding including terminals adapted to be connected to the combustion responsive switch means; a control relay having an actuating winding and a switch controlled thereby, energizing circuit means for said control relay winding including terminals adapted to be connected to the means responsive to the need for operation of the fuel burner, said bimetal timer heater and said first switch controlled by said second movable member; a holding energizing circuit for said control relay winding including said flame relay switch connected in parallel with the first switch controlled by said second movable member; and burner energizing circuit means including terminals adapted to be connected to the fuel burner and the ignition means whereby the fuel burner is energized through a circuit including said control relay switch and the ignition means is energized through a circuit including said control relay switch and the second switch controlled by said second movable member.

3. The combination comprising; a bimetal timer having a bimetal actuator and a heater associated therewith, said heater being arranged to heat said bimetal and to cause movement of said bimetal from a first to a second position upon being heated; a first and a second movable member having a common pivot point, spring means interconnecting said first and second member coupled to said first and second member on opposite sides of said pivot point respectively such that movement of one of said movable members suflicient to cause said spring means to move from one side of said pivot point to the other also causes the other movable member to follow said one movable member; means operatively connecting said bimetal to said first movable member to cause said first movable member to move from a first position to a second position upon said bimetal moving from its first to its second position to thereby cause said spring means to move from one side of said pivot point to the other, said bimetal normally returning said first movable member to its said first position upon cooling of said bimetal; control means, means operatively connecting said control means to be controlled by movement of said second movable member, a relay having a winding and a movable armature, and interlock means controlled by said movable armature when said relay Winding is energized and arranged to limit the movement of said second movable member as said bimetal moves to said second position, the limited movement of said second movable member being such that upon said bimetal cooling said spring means moves from said other side of said pivot point back to said one side and said second movable member thereby follows the movement of said first movable member, said second movable member moving to an extreme position as said bimetal moves to said second position in the event said relay winding is de-energized, the position of said second movable member in said extreme position being such that upon said bimetal cooling said spring means does not move back to said one side of said pivot point.

References Cited in the file of this patent UNITED STATES PATENTS