US2720254A

US2720254A - Safety burner control apparatus

Info

Publication number: US2720254A
Application number: US280103A
Authority: US
Inventors: Carl D Ward
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1952-04-02
Filing date: 1952-04-02
Publication date: 1955-10-11
Anticipated expiration: 1972-10-11

Description

Oct. 11, 1955 Q 13, WARD 2,720,254

SAFETY BURNER CONTROL APPARATUS Filed April 2, 1952 ON HEATING 5l-OPE -s,s2-cl.osEs. so-o eus ON COOLING 52-OPENS, 50-6LOSES, SI-GLOSES IN V EN TOR. CARL D. WARD Mx M ATTORNEY United States Patent SAFETY BURNER cor-srnor APPARATUS Carl D. Ward, Minneapolis, Minn, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application April 2, 1952, Serial No. 280,103

11 Claims. (Cl. 15828) This invention relates to a burner control apparatus having a safety cutout device, an ignition timer, and a safety interlock circuit such that the burner control apparatus offers a maximum protection against unsafe conditions which may arise at the burner unit being controlled.

The prior art devices have incorporated one or more of the above mentioned features into burner controls, however, these burner controls for the most part have been complex circuits having a great number of components which from the cost standpoint rendered these prior art devices unsuccessful in the competitive market.

It is therefore an object of the present invention to provide an improved burner control apparatus having a minimum number of components and incorporating a novel circuit whereby the ignition timer actuator and the safety cutout actuator are electrically interconnected to provide for energization for the safety cutout actuator until flame is established at the controlled fuel burner and then to provide for deenergization of the safety cutout actuator and energization of the ignition timer actuator.

It is the further object of the present invention to provide an improved burner control apparatus wherein an ignition timer controls, in circuit closing position, the supply of power to an ignition means of a burner unit and also controls a safety interlock circuit to insure that power cannot be applied to the burner control apparatus until the ignition timer is in its circuit closing position.

It is a further object of the present invention to provide an improved burner control apparatus wherein a burner control relay is operatively energized upon a need for operation of the burner control unit to initiate a starting period for a fuel burner during which a safety cutout device is energized, and upon the establishment of combustion atthe fuel burner a holding circuit is established for the burner control relay and a running period is initiated for the fuel burner wherein a post ignition timer is energized to subsequently deenergize an ignition transformer, with the initial energizing circuit of the burner control itself being initially dependent upon the post ignition timer being in its circuit closing position and on the burner control relay being in its deenergized position and with a holding energization circuit formed for the burner control when the burner control relay assumes its energized position.

Figure 1 is a showing of the improved burner control apparatus, and;

Figure 2 is a showing of a modification of a portion of the burner control apparatus of Figure 1.

Referring specifically to Figure l, a fuel burner unit is shown having a fuel burner 11 and an ignition means 12. The burner unit 10 is controlled by the improved burner control apparatus shown within broken lines 13, and the apparatus 13 is under the control of a thermostat shown within the broken lines 14, which thermostat is responsive to a need for operation of the burner unit 10 to close contacts 15 and 16.

Referring specifically to the improved burner control apparatus 13, a burner control relay 17 is provided hav- 2,720,254 Patented Oct. 11, 1955 ing a relay winding 18, and an armature 19. The armature 19 of the relay 17 is shown in its inoperative or deenergized position and is provided with bridging bars 20 and 21. Upon energization of the relay winding 18, the armature 19 moves the bridging bar 20 into engagement with in

contacts

22 and 23 and the bridging bar 21 into engagement with in contacts 24 and 25. A relay out contact 26 is provided for the relay 17. Contact blade 27 engages out contact 26 and is connected to and movable with the in contact 25. Upon energization of the relay winding 18 the armature 19 moves the bridging bars 20 and 21 into engagement with the in contacts and due to the press back of the relay the in contacts 2255' are moved to the left to broken line position 28. The movement of the in contacts to this broken line position 28 moves in contact 25 and contact blade 27 to the left and causes the blade 27 to disengage the out contact 26.

Also included within the burner control apparatus 13 is a safety cutout device 30 having normally closed

contacts

31 and 32, a bimetal member 33, a reset actuator 34, and an electrically energizable actuating heater 35. Upon a predetermined time period of energization of the heater 35, the bimetal 33 warps to the right out from under the normally closed

contacts

31 and 32 to allow the contacts to disengage. Upon a subsequent cooling of the bimetal element 33, the reset actuator 34 can be depressed to reset the

contacts

31 and 32 to their normal position as shown in the figure.

A timer 36 is provided having an electrically energizable actuating heater 39, and a normally closed cold switch comprising a contact 37, and a bimetal member 38. After a predetermined time period of energization of the heater 39 above a given minimum energization level, the bimetal element 38 warps to the left to disengage contact 37. Upon the bimetal element 38 cooling the element 38 again engages contact 37 as shown in the figure.

A combustion responsive means 40 is shown having a hot closed switch 52, a first cold closed switch 51, and a second cold closed switch 50. A bimetal actuator is shown at 46 and is normally located to be responsive to the presence or absence of combustion at the burner unit 10. The bimetal actuator 46 is effective upon heating to move to the left as shown by the arrow in Figure 1. Movement of bimetal actuator 46 is transmitted by means of a rod, shown by dotted line 47, and by members 200 and 201 to the

switches

50, 51 and 52.

The members 200 and 201 are mounted in slip friction engagement with the rod, shown by dotted line 47, and move with the rod until sufiicient force is applied to stop such movement, at which time the members 200 and 201 will remain stationary and slide upon the rod.

The blades upon which

switches

50 and 51 are mounted are biased so that as member 200 moves to the left the

switches

50 and 51 also move to the left until

stops

202 and 203 are engaged to cause

switches

51 and 50 respectively to open. The blade upon which the right hand member of switch 52 is mounted is biased to the right to engage member 201.

The combustion responsive means 40 is shown in the cold position in Figure 1, that is, with no flame present at the burner unit 10. Upon combustion being established at the burner unit 10, the bimetal actuator 46 begins to move to the left. This movement causes members 200 and 201 to also move to the left. When member 200 has moved a predetermined distance, the right hand member of cold closed switch 51 engages stop 202 to stop this member. Further movement of member 200 causes cold closed switch 51 to open.

During this movement of member 200, member 201 has also moved to the left and a short time of movement after cold closed switch 51 opens, hot closed switch 52 closes. Again after a short time of movement, stop 203 engages the common member of cold closed

switches

50 and 51 and further movement of member 200 to the left causes cold closed switch 50 to open.

When combustion ceases at the burner unit 10, the bimetal actuator 46 cools and moves to the right to the position shown in Figure 1. First initial movement to the right causes member 201 to also move to the right and open thereby hot closed switch 52. Further movement to the right causes member 200 to close cold closed switch 50. Still further movement to the right causes cold closed switch 51 to be closed.

A transformer 53 having a primary 54 and a secondary 55 is shown associated within the burner control apparatus 13 to supply power to circuits which include the burner control relay 17, the timer 36, the safety cutout device 30, and the hot closed and cold closed switches of the combustion responsive means 40. A plurality of terminals are also associated with the burner control apparatus 13. The

terminals

56 and 57 are the power input terminals to the burner control apparatus 13 and are adapted to be connected to a source of electrical power, which power is supplied to the burner unit under the control of the burner control apparatus 13 and the thermostat 14. The

terminals

58 and 59 are adapted to be connected to the thermostat 14 and are efiectively connected together upon a need for operation of the burner unit 10 which the thermostat 14 senses by closing the contacts and 16. Terminal 60 is adapted to be connected to the ignition means 12 of the burner unit 10 while terminal 61 is adapted to be connected to the burner 11 of the burner unit 10.

Operation Referring to the Figure 1, the apparatus is shown in its standby condition. That is, the timer 36 has its normally closed cold switch in the closed position, the safety cutout device has its

contacts

31 and 32 in engaging position, the relay 17 is in its deenergized position, and the combustion responsive means 40 is in a condition indicating the absence of combustion at the burner unit 10.

Assuming that power is applied to the

power input terminals

56 and 57, an initial energizing circuit can be traced for the primary 54 of the transformer 53 from the power input terminal 56 through the primary 54, conductor 62, bimetal element 38 and contact 37 of the timer 36, conductor63, contact blade 27 and out contact 26 of the relay 17, conductor 64, and conductor 65 to the power input terminal 57. From this last traced circuit it can be seen that in the standby condition in order for power to be applied to the primary 54 it is necessary first, for the closed cold switch of timer 36 to be in its cold position, and second, for the relay armature 19 to be in its deener gized position such that the switch blade 27 engages the out contact 26. This important feature will be discussed more fully later.

Assume now that there is a need for operation of the burner unit 10 which the thermostat 14 senses by closing the contacts 15 and 16. An initial energizing circuit can now be traced for the relay 17 from the upper terminal of the secondary 55 through conductor 66,

contacts

32 and 31 of the safety cutout device 30, relay winding 18, terminal 59, thermostat 14, terminal 58, conductor 67, conductor 68, heater of the safety cutout device 30, conductor 69, cold closed switch 51, conductor 70, and conductor 71 to the lower terminal of the secondary 55., At this point it should be noted that a shunt circuit can be traced around the heater 35 of the safety cutout device 30 from conductor 67 through conductor 100, resistor 73, conductor 74, and cold closed switch 50 of the combustion responsive means to conductor 70, which circuit therefore places the heater 35 in parallel with resistor 73. This last traced circuit is a first nonpickup holding circuit for relay 17. This is appropriately called a non-pickup holding circuit since the impedance of the resistor 73 is such that the level of energization furnished by this circuit to relay winding 18 of the relay 17 is below that value necessary for the relay armature 19 to move from its inoperative to its operative position but of a sufficient level to maintain the armature 19 at its operative position. in other words, if it is assumed for the sake of explanation that the relay 17 is energized initially through this non-pickup holding circuit, the relay armature 19 will not be moved into engagement with the in contacts of the relay 17 since the level of energization furnished to winding 18 is insufiicient to cause the armature 19 to be moved.

In this phase of operation of the burner control apparatus 13 the actuator 35 of the safety cutout device 30 is operatively energized, that is, if the combustion responsive means 40 does not operate to indicate the establishment of combustion the safety cutout device 30 will be actuated to the position where the

contacts

31 and 32 are disengaged. By way of illustration, it has been found desirable to select the following impedance values for the actuating

heaters

35 and 39 and the resistor 73:

Ohms Actuating heater 35 8 Actuating heater 39 28 Resistor 73 30 From the above values, it can be seen that the above traced shunt circuit has an impedance value of 30 ohms while the impedance of safety cutout heater 35 is only 8 ohms and therefore for all practical purposes the shunt circuit has a negligible amount of the electric current flowing through it. It is intended that the above stated impedance values in no way limit the present invention but these impedance values are given to more clearly point out the manner in which the actuator 35 is operatively energized in this initial phase of operation of burner control apparatus 13.

Energization of the relay 17 causes the relay armature 19 to move the bridging bars 20 and 21 into engagement with the in contacts 22 through 25 of the relay 17 Consider at this time the instant when the bridging bars 20 and 21 have just engaged the in contacts 22 through 25 of the relay 17. The initial energizing circuit for the primary 54, above traced, is still completed through contact blade 27 and out contact 26 of the relay 17, however, aholding circuit is now also established for the primary 54. This holding circuit can be traced from the power input terminal 56 through primary 54, conductor 62, conductor 80, bridging bar 20, in contact 22 of relay 17, conductor 81, and conductor to the power input terminal 57. The relay armature 19 now completes its movement to take up the press back of the relay and moves the in contacts 22 through 25 to the left to the position shown by the broken line 28 and therefore causes contact blade 27 to disengage out contact 26 of the relay 17. This breaks the initial energizing circuit for primary 54 of the transformer 53, however, the above traced holding circuit is effective to supply power to the primary 54 so long as the relay 17 remains in its energized position.

The movement of the relay armature 19 to its energized position causes power to be supplied to the burner unit 10 through the

terminals

60 and 61. The energizing circuit for the burner motor 11 can be traced from power line 82 through conductor 83, conductor 84, burner motor 11, conductor 35, terminal 61, conductor 86, in contact 23, bridging bar 20 and in contact 22 of the relay 17, conductor 81, conductor 65, and power input terminal 57 to power line conductor 87. The energizing circuit for the ignition means 12 can be traced from the power line conductor 82 through conductor 83, ignition means 12, conductor 88, terminal 68, conductor 89, in contact 24, bridging bar 21 and in contact 25 of relay 17, conductor 63, contact 37 and bimetal 38 of the timer 36, conductor 80, bridging bar 20 and in contact 22 of relay 17, conductor 81, conductor 65, and power input terminal 57 to power line conductor 87.

This is the starting phase of the burner control unit 13 wherein the burner motor 11 is energized, the ignition means 12 is energized, the timer 36 is operatively deenergized, and the safety cutout device 30 is operatively energized.

Assume now that a flame is established at the burner unit 10, the bimetal actuator 46 of the combustion responsive means 40 will respond to the presence of combustion at the burner unit and will actuate its associated hot closed and cold closed switch in the sequence above described. The bimetal actuator 46 will first cause the cold closed switch 51 to open. The opening of the cold closed switch 51 opens the initial energizing circuit for the relay 17 and renders the above traced first nonpickup holding circuit effective to maintain the relay energized. The opening of the cold closed switch 51 therefore deenergizes the heater 35 of the safety cutout device 30. The timing period of the safety cutout device is so selected that for a normal start up of the burner unit 10 a flame is established and bimetal actuator 46 of the combustion responsive means 40 responds to the establishment of combustion to deenergize the heater of the safety cutout device 30 before the

safety cutout contacts

31 and 32 disengage.

A short time after the opening of the cold closed switch 51, the hot closed switch 52 of the combustion responsive means closes. The closing of the hot closed switch 52 initiates the establishment of a second non-pickup holding circuit for the relay 17. This second non-pickup holding circuit can be traced from the upper terminal of secondary 55 of the transformer 53 through conductor 66,

contacts

32 and 31 of the safety cutout device 30, relay winding 18, terminal 59, thermostat 14, terminal 58, conductor 67, conductor 72, heater 39 of the timer 36, conductor 101, hot closed switch 52 of the combustion responsive means 40, conductor 91, and conductor 71 to the lower terminal of the secondary 55.

At this time both the above mentioned first non-pickup holding circuit and the second non-pickup holding circuit are energized. It will be noted that the resistor 73 is now in parallel with heater 39 of the timer 36. However the heater 39 remains operatively deenergized, that is, the level of energization supplied to the heater 39 at this time is not sufficient to cause the bimetal 38 to disengage contact 37 of the timer 36. This can readily be seen by referring to the above table of impedance values given for purposes of illustration. From this table it can be seen that the 28 ohm actuating heater 39 of the timer 36 has in parallel therewith the 30 ohm resistor 73 and for this condition the heater 39 remains operatively deenergized.

A short period of time after the closing of the hot closed switch 52, the cold closed switch of the combustion responsive means 40 opens to open the above mentioned first non-pickup holding circuit. The function of the cold closed switch 50 will be explained in greater detail later.

With the opening of the above traced first non-pickup holding circuit for the relay 17 heater 39 of the timer 36 is operatively energized since the heater 39 is no longer in parallel with resistor 73 and the entire relay current flows through the heater 39 to operatively energize the heater 39.

A predetermined time after the establishment of this second non-pickup holding circuit, the bimetal 38 of the timer 36 is heated to a condition where the engagement of the bimetal 38 to the contact 37 is broken. It will be remembered that the energizing circuit for the ignition means 12 dependent upon the cold closed switch of timer 36 being closed and upon the relay armature 19 being in its energized position. Therefore, the opening of the cold closed switch of the timer 36 deenergizes the ignition means 12 of the burner unit 10.

The burner control apparatus 13 is now in its running condition with the burner motor 11 energized, the ignition means 12 deenergized, the heater 35 of the safety cutout.

device 30 deenergized, the bimetal actuator 46 of the combustion responsive means 40 responding to the presence of combustion at the burner unit 10, and the heater 39 of the timer 36 operatively energized to maintain the timer cold closed switch open.

Assume now that the thermostat 14 has been satisfied by a sufiicient period of operation of burner unit 10 and has accordingly opened the contacts 15 and 16. The energizing circuit for the relay 17 is therefore broken and the relay armature 19 returns to its inoperative position such as shown in the Figure 1. This immediately deenergizes the burner unit 11 and also breaks the holding circuit for primary 54 of the transformer 53. As shown in the Figure l, the deenergization of relay 17 causes switch blade 27 to engage out contact 26 of the relay 17.

The bimetal actuator 46 of the combustion responsive means 40 now responds with an inherent time delay to the absence of combustion at the burner unit 10 to operate its associated hot closed and cold closed switches in the above mentioned sequence. The hot closed switch 52 first opens. At this time the cold

closed switches

50 and 51 and the hot closed switch 52 are open. If at this time there is a second call for heat, as evidenced by the thermostat 14 closing the contacts 15 and 16, the relay 17 cannot be energized since the initial energizing circuit for the relay and the non-pickup holding circuits for the relay are open at the associated hot closed and cold closed switches of the combustion responsive means 40. Likewise, before another cycle of operation of the burner unit 10 can be initiated it is necessary for the bimetal 38 of the timer 36 to return to the cold position to close the normally closed cold switch and thereby close the initial energizing circuit of the primary 54.

A short time after the opening of hot closed switch 52, cold closed switch 50 of the combustion responsive means 40 closes. Assume for the moment that the cold closed switch of the timer 36 is now in the closed position, to close the initial energizing circuit of primary 54, and that there is a call for heat. The first non-pickup holding circuit for the relay 17 can now be traced from the upper terminal of the secondary 56 of the transformer 53 through conductor 66,

contacts

32 and 31 of the safety cutout device 30, winding 18, terminal 59, thermostat 14, terminal 58, conductor 67, conductor 100,

resistor 73, conductor 74, cold closed switch 50 of the combustion responsive means 40, conductor 70, and con-' ductor 71 to the lower terminal of the secondary 55. The resistor 73 limits the level of energization of the relay winding 18 below that which is necessary to cause the relay armature 19 to be moved to operative position so that at this time the relay is not energized. A short time after the closing of cold closed switch 50. the cold closed switch 51 closes.

It has been found that the combustion responsive means 40 at this point in the operation of the apparatus 13 tends to produce an intermittent condition of closing and opening of cold closed switch 51 for a short period of time. It will be remembered that the initial energizing circuit for the relay 17 includes the cold closed switch 51 and if it were not for the cold closed switch 50 which is closed at this point to close the first non-pickup holding circuit it would be possible for the relay armature 19 to move between its operative and inoperative positions a number of times before the combustion responsive means 46 positively closed cold closed switch 51.

To explain more fully the utility ofproviding the cold closed switch 50, consider that the cold closed switch 51 has been closed for a very short period of time and then opened due to the inherent characteristics of bimetal actuator 46 of the combustion responsive means 40. The initial closing of the cold closed switch 51 completes the initial energizing circuit for the relay 17 and the relay armature 19 moves from its inoperative to its operative position. The cold closed switch 51 now opens, however the relay is maintained energized through the first nonpickup holding circuit, above traced, which includes in series with the relay winding 18, the resistor 73, and the cold closed switch 50. It is of course immediately recog nized that the cold closed switch 51 will again immediately close and be positively closed by bimetal actuator 46 of the combustion responsive means 40 to complete the initial energizing circuit for the relay winding 18 which includes the heater 35 of the safety cutout device 30.

Since it has been assumed that there is a call for heat as evidenced by the closing of the contacts and 16 of the thermostat 14, the above cycle of operation will be repeated and a flame will again be established at the burner unit 10.

Opemtion on flame failure Assume now that a flame is not established at the burner unit 10 after control apparatus 13 has been energized upon a call for heat by the thermostat 14. The bimetal actuator 46 of the combustion responsive means 40 will not therefore actuate the associated hot closed and cold closed switches from the positions shown in the Figure 1 and the relay winding 18 will remain energized through the initial energizing circuit which includes the heater 35 of the safety cutout device 30. After a predetermined time of energization of the heater 35 the safety cutout device will be actuated to cause the

contacts

31 and 32 to disengage. The relay 17 is therefore de'energized arid the relay armature 19 assumes its inoperative position to deenergize the burner unit 10. However, the primary 54 of the transformer 53 remains energized through the initial energizing circuit which includes the normally closed cold switch of the timer 36 and the out contact 26 of the relay 17. The opening of

contacts

31 and 32 also causes the heater of the safety cutout device 30 to be deenergized and after a predeter'mined length of time the bimetal 33 associated with the safety cutout device 30 cools so that depressing the reset actuator 34 resets the

contacts

31 and 32 to their engaging position so that the relay 17 is again energized to make a second attempt to establish flame at the burner unit 10.

Assume now that the burner control apparatus 13, upon a call for heat by the thermostat 14, has established the running condition at the burner unit 10 and that there is a subsequent flame failure. The bimetal actuator 46 for the combustion responsive device will first open the hot closed switch 52 to deenergize the relay 17 and thereby deenergize the burner motor 11. The cold closed switch will then close to energize the above mentioned first non-pickup holding circuit for the relay 17. A short time thereafter the cold closed switch 51 will close and the relay 17, the heater 35 of the safety cutout device 30 and the burner unit 10 will again be energized to attempt to reestablish a flame at the burner unit 10. If, due to some fault in the burner unit 10, a flame is not established the safety cutout device 30 will operate to break the energizing circuit for the relay 17 at the

safety cutout contacts

31 and 32 and will also deenergize the heater 35 of the safety cutout device 30. After a predetermined length of time bimetal 33 of the safety cutout device 30 cools and the reset actuator 34 can be depressed to reset the

contacts

31 and 32 to their engaging position. If there is still a call for heat by the thermostat 14 the burner unit 10 will again be energized to attempt to establish flame at the burner unit.

Modification of Figure 2 Referring now specifically to Figure 2, a modification of the apparatus of Figure l is shown with the common elements between the two figures retaining the same reference numerals. The modification of Figure 2 can be completely visualized by replacing the circuitry of Figure 1, which includes the

heaters

35 and 39, the resistor 73,

" tor 73.

and the hot closed and cold closed switches of the combustion responsive means 40, by the circuitry shown in Figure 2. In the modification of Figure 2, the above described first non-pickup holding circuit for relay 17 has been changed.

The initial energizing circuit for relay 17 in the apparatus of Figure l is identical with that in the modification of Figure 2 in that in both instances the circuit includes conductor 67 conductor 68, heater 35 of safety cutout device 30, conductor 69, cold closed switch 51 and conductor 70.

The first non-pickup holding circuit of Figure 2 diflfers from the first non-pickup holding circuit of Figure l in that this circuit of Figure 2 includes the resistor 73 andheater 39. This first non-pickup holding circuit of Figure 2 can be traced from conductor 67 through conductor 72, heater 39 of timer 36, resistor 73, conductor 74, and cold closed switch 50 to conductor 7 0.

The second non-pickup holding circuit for relay 17 is substantially identical in both Figures 1 and 2 in that in both instances the second non-pickup holding circuit includes the heater 39 of the timer 36 and the hot closed switch 52 of the combustion responsive means 40.

Referring again to Figure 2, assume that thermostat 14 calls for heat by closing contacts 15 and 16. The relay 17 will now be energized through the initial energizing circuit which includes conductor 67, conductor 68, heater 35 of safety cutout device 30, conductor 69, cold closed switch 51 of combustion responsive means 40, conductor 70, and conductor 71. It will be noted that in parallel with the above traced initial energizing circuit is the first non-pickup holding circuit which can be traced from conductor 67 through conductor 72, heater 39 of timer 36, resistor 73, conductor 74, cold closed switch 50 of combustion responsive means 40, conductor 70, and conductor 71. At this time the heater 35 of the safety cutout device 30 is operatively energized while the heater 39 of the timer 36 is operatively deenergized. This can be more clearly seen by referring to the table of impedance values for

heaters

35 and 39 and resistor 73. The above traced initial energizing circuit contains only the 8 ohm heater 35 for the safety cutout device 30 while the first non-pickup holding circuit includes in series the 28 ohm heater 39 for the timer 36 and the 30 ohm resis- It can therefore be seen that negligible current flows through the first non-pickup holding circuit at this time so that heater 39 is operatively deenergized.

A flame is now normally established at the burner unit 10 and the bimetal actuator 46 of the combustion responsive means 46 senses the flame and first opens the cold closed switch 51. This opens the initial energizing circuit for relay 14 thereby deenergizing the heater 35 of the safety cutout device 30, however, the relay 17 remains energized through the above traced first non-pickup holding circuit. At this time the heater 35 of the safety cutout device 30 is operatively deenergized and the heater 39 of the timer 36 remains operatively deenergized. It is recognized that the level of energization of the heater 39 has increased at this time due to the opening of the initial energizing circuit, however, the resistor 73 acts as a current limiting resistor and prevents the heater 39 from being operatively energized.

A short time after the opening of the cold closed switch 51 the hot closed switch 52 closes. The closing of hot closed switch 52 completes the second non-pickup holding circuit which can be traced from conductor 67 through conductor 72, heater 39 of timer 36, conductor 90, hot closed switch 52, and conductor 91 to conductor 71. It can be seen that the function of the hot closed switch 52 is to short out that portion of the first non-pickup holding circuit which includes resistor 73 thereby increasing the level of energization in the heater 39 of the timer 36 to a point where the heater is now operatively energized.

A short time after closing of the hot closed switch 52 the cold closed switch 50 opens to break the above mentioned first non-pickup holding circuit. After a predetermined time of energization of the heater 39, the timer 36 operates to disenage contact 37 from bimetal 38 to thereby deenergize the ignition means 12. The apparatus is now in its running condition.

Assume now that the thermostat 14 has been satisfied and that it therefore opens contacts 15 and 16. The relay 17 will become deenergized and therefore the burner unit will be deenergizedv The bimetallic actuator 46 of the combustion responsive means 40 senses the absence of flame at the burner unit 10 and first opens the hot closed switch 52. A short time thereafter the cold closed switch 50 closes to complete the above mentioned first non-pickup holding circuit. It will be remembered from the discussion above that if the thermostat 14 is again calling for heat at this time the relay 17 will not move armature 19 due to the fact that this first non-pickup holding circuit limits the level of energization of the relay 17 below that which is necessary to cause the relay 17 to move its armature 19 to the operative position.

A short time after the closing of cold closed switch 50 the cold closed switch 51 closes. This completes the initial energizing circuit for the relay 17 and if at this time the thermostat 14 is calling for heat the relay 17 will be energized and the cycle of operation of the burner apparatus 13 will be repeated to establish flame at the burner unit 10.

From the above description of the operation of the present invention it can be seen that the burner control apparatus 13 maintains the heater 35 of the safety cutout device 30 energized until the combustion responsive means 40 indicates that a flame is present at the burner unit 10 and in the absence of the establishment of combustion at the burner unit 10 the safety cutout device 30 deenergizes the relay 17 and thereby deenergizes the burner unit 10 to prevent the unlimited supply of fuel in the absence of combustion.

It can therefore be seen that I have provided an improved burner control apparatus wherein an ignition timer functions with a single set of contacts to provide both ignition timing and interlocking means such that power cannot be applied to the burner control apparatus until the energizing circuit for the ignition means is in a condition to be completed upon energization of the burner control relay.

I claim as my invention:

1. A burner control apparatus for use with a fuel burner and a burner ignition means under the control of means responsive to the need for operation of the burner, comprising; a relay arranged to be energized upon a need for operation of the burner, first relay controlled swtching means closed upon energization of said relay, second relay controlled switching means opened upon energization of said relay, flame responsive switching means including means responsive to combustion at the fuel burner to actuate the switches of said flame responsive switching means to a first condition upon the presence of combustion or to a second condition upon the absence of combustion at the fuel burner, timing means having timing switching means and an electrically operable actuator connected to be energized to open said timing switching means after a time delay upon the switches of said flame responsive switching means assuming said first condition and to be operatively deenergized to thereby close said switching means after a time delay upon the switches of said flame responsive switching means assuming said second condition, a transformer having a primary and a secondary winding, means connecting said secondary winding to energize said relay upon a need for operation of the burner and upon the switches of said flame responsive switching means being in said second condition, energizing circuit means connecting said primary to terminals adapted to be connected to a source of power and depending upon said timing switching means being closed and said second relay controlled switching means being closed, circuit means connecting terminal means adapted to be connected through the fuel burner to a source of power and depending upon said first relay controlled switching means being closed, circuit means connecting terminal means adapted to be connected through the ignition means to a source of power depending upon said first relay controlled switching means being closed and said timing switch means being closed, and holding circuit means for the primary of said transformer maintaining said primary energized after the opening of said timing switching means and said second relay controlled switching means, said holding circuit means including said first relay controlled switching means in closed condition.

2. Burner control apparatus for use with a fuel burner and burner igniting means under the control of means responsive to the need for operation of the fuel burner, comprising; a relay having a winding and switching means which assume a first or a second condition depending upon Whether said winding is deenergized or energized; a safety cutout device having normally closed switch contacts and an electrically energizable actuator; a timer having a normally closed switch and an electrically energizable actuator; combustion responsive means having first and second sets of cold closed switches and a hot closed switch, said combustion responsive means arranged to open said first cold closed switch, close said hot closed switch and then open said second cold closed switch upon combustion being established; impedance means; an initial energizing circuit for said relay arranged when completed to operatively energize said relay winding and including terminals adapted to be connected to means responsive to the need for operation of the fuel burner, the normally closed switch contacts and actuator of said safety cutout device, and said first cold closed switch of said combustion responsive means; a first holding circuit for said relay in parallel with the actuator of said safety cutout device including the actuator of said timer, said impedance means and said second cold closed switch of said combustion responsive means, the relative impedance of said initial energizing circuit and said first holding circuit being such that the actuator of said safety cutout device is operatively energized and the actuator of said timer is operatively deenergized; a second holding circuit for said relay in parallel with the actuator of said safety cutout device including the actuator of said timer and said hot closed switch of said combustion responsive means; said combustion responsive means upon combustion being established opening said initial energizing circuit for said relay to deenergize the actuator of said cutout device and closing said second holding circuit for said relay to energize the actuator of said timer; and circuit means arranged to supply power to terminals adapted to be connected to a fuel burner and burner igniter, said last named circuit means depending upon said relay switching means being in said second condition to supply power to the fuel burner and upon said timer switch being closed to supply power to the burner igniter.

3. Burner control apparatus for use with a fuel burner and burner igniting means under the control of means responsive to the need for operation of the fuel burner, comprising; a relay having a winding and switching means which assume a first or a second condition depending upon whether said winding is operatively deenergized or energized; a safety cutout device having normally closed switch contacts and an electrically energizable actuator; a timer having a normally closed switch and an electrically energizable actuator; combustion responsive means having first and second cold closed switches and a hot closed switch, said combustion responsive means arranged to open said first cold closed switch, close said hot closed switch and then open said second cold closed switch upon combustion being established; impedance means; an initial energizing circuit for said relay arranged when completed to operatively energize said relay winding and including terminals adapted to be connected to means responsive to the need for operation of the fuel burner, the normally closed switch contacts and actuator of said safety cutout device, and said first cold closed switch of said combustion responsive means; a first holding circuit for said relay in parallel with the actuator of said safety cutout device including the actuator of said timer, said impedance means and said second cold closed switch of said combustion responsive means, the relative impedance of said initial energizing circuit and said first holding circuit being such that the actuator of said safety cutout device is operatively energized and the actuator of said timer is operatively deenergized; a second holding circuit for said relay in parallel with the actuator of said safety cutout device including the actuator of said timer and said hot closed switch of said combustion responsive means; said combustion responsive means upon combustion being established opening said initial energizing cir cuit for said relay to deenergize the actuator of said cutout device and closing said second holding circuit for said relay to energize the actuator of said timer; circuit means arranged to supply power to terminals adapted to be connected to a fuel burner and burner igniter, said last named circuit means depending upon said relay switching means being in said second condition to supply power to the fuel burner and upon said timer switch being closed to supply power to the burner igniter; power input terminals arranged to be connected to a source of power for supplying power to the above mentioned circuits; an initial power energizing circuit for the above mentioned circuits including said power input terminals, said relay switching means in said first position, and said timer switch in closed condition; and a power holding circuit for the above mentioned circuits including said power input terminals and said relay switching means in said second position.

4. Burner control apparatus for use with a fuel burner and burner igniting means under the control of means responsive to the need for operation of the fuel burner, comprising: a relay having a winding and switching means which assume a first or a second condition depending upon whether said winding is deenergized or energized; a safety cutout device having normally closed switch contacts and an electrically energizable actuator; a timer having a normally closed switch and an electrically energizable actuator; combustion responsive means having first and second cold closed switches and a hot closed switch, said combustion responsive means arranged to open said first cold closed switch, close said hot closed switch and then open said second cold closed switch upon combustion being established; impedance means; an initial energizing circuit for said relay arranged when completed to operatively energize said relay winding and in cluding terminals adapted to be connected to means responsive to the need for operation of the fuel burner, the normally closed switch contacts and actuator of said safety cutout device, and said first cold closed switch of said combustion responsive means; a first holding circuit for said relay in parallel with the actuator of said safety cutout device including said impedance means and said second cold closed switch of said combustion responsive means, the relative impedance of said initial energizing circuit and said first holding circuit being such that the actuator of said safety cutout device is operatively energized; a second holding circuit for said relay in parallel with the actuator of said safety cutout device including the actuator of said timer and said hot closed switch of said combustion responsive means; said combustion responsive means upon combustion being established opening said initial energizing circuit for said relay to deenergize the actuator of said cutout device and closing said second holding circuit for said relay to energize the actuator of said timer; and circuit means arranged to supply power to terminals adapted to be connected to a fuel burner and burner igniter, said last named circuit means 12 depending upon said relay switching means being in said second condition to supply power to the fuel burner and upon said timer switch being closed to supply power to the burner igniter.

5. Burner control apparatus for use with a fuel burner and burner igniting means under the control of means responsive to the need for operation of the fuel burner, comprising: a relay having a winding and switching means which assume a first or a second condition depending upon whether said winding is operatively deenergized or energized; a safety cutout device having normally closed switch contacts and an electrically energizable actuator; a timer having a normally closed switch and an electrically energizable actuator; combustion responsive means having first and second cold closed switches and a hot closed switch, said combustion responsive means arranged to open said first cold closed switch, close said hot closed switch and then open said second cold closed switch upon combustion being established; impedance means; an initial energizing circuit for said relay arranged when completed to operatively energize said relay winding and including terminals adapted to be connected to means responsive to the need for operation of the fuel burner, the normally closed switch contacts and actuator of said safety cutout device, and said first cold closed switch of said combustion responsive means; a first holding circuit for said relay in parallel with the actuator of said safety cutout device including said impedance means and said second cold closed switch of said combustion responsive means, the relative impedance of said initial energizing circuit and said first holding circuit being such that the actuator of said safety cutout device is operatively energized; a second holding circuit for said relay in parallel with the actuator of said safety cutout device including the actuator of said timer and said hot closed switch of said combustion responsive means; said combustion responsive means upon combustion being established opening said initial energizing circuit for said relay to deenergize the actuator of said cutout device and closing said second holding circuit for said relay to energize the actuator of said timer; circuit means arranged to supply power to terminals adapted to be connected to a fuel burner and burner igniter, said last named circuit means depending upon said relay switching means being in said second condition to supply power to the fuel burner and upon said timer switch being closed to supply power to the burner igniter; power input terminals arranged to be connected to a source of power for supplying power to the burner control apparatus; an initial energizing circuit for the burner control apparatus including said power input terminals, said relay switching means in said first position, and said timer switch in closed condition; and a holding circuit for the burner control apparatus including said power input terminals and said relay switching means in said second position.

6. A burner control apparatus for use with a fuel burner having burner igniting means and means responsive to the need for operation of the fuel burner, comprising; a transformer, a burner control relay having switch contacts, a safety cutout device including switch contacts and an electrically energizable actuator, a timer including a switch and an electrically energizable actuator, combustion responsive switch means having a first and a second condition of operation depending upon the absence or presence of flame; an initial energizing circuit for the primary of said transformer including said timer switch, a holding energizing circuit for the primary of said transformer including said relay switch contacts; an initial energizing circuit for said relay including the secondary of said transformer, the actuator of said safety cutout device, said combustion responsive switch means in said first condition of operation, and terminals adapted to be connected to means responsive to the need for operation of the fuel burner; a holding energizing circuit for said relay including the actuator of said timer and said combustion responsive switch means in said second condition of operation; said combustion responsive switch means being effective upon the establishment of combustion at the fuel burner to switch from said initial energizing circuit for said relay to said holding energizing circuit for said relay to thereby deenergize the actuator of said safety cutout device and to energize the actuator of said timer; circuit means including said relay switch contacts to supply power to terminals adapted to be connected to a fuel burner, and circuit means including said relay switch and said timer switch contacts to supply power to terminals adapted to be connected to a burner igniting means.

7. A burner control for use with a fuel burner and burner igniting means under the control of means responsive to the need for operation of the fuel burner, comprising: a transformer having a primary and a secondary; an ignition timer having an electrically energizable actuator and arranged after a time delay to actuate first switching means from a circuit closing to a circuit opening condition, second switching means including an actuator and a plurality of switches, said actuator upon energization thereof being arranged to actuate the switches of said second switching means from a first to a second condition with negligible time delay, one of said plurality of switches being closed when in said first condition and open when in said second condition, the other of said plurality of switches being open when in said first condition and closed when in said second condition, circuit means including a switch of said second switching means which is closed in said second condition adapted to supply power to terminal means arranged to be connected to a fuel burner, circuit means including said first switching means in said circuit closing condition and a switch of said second switching means which is closed in said second condition adapted to supply power to terminal means arranged to be connected to burner igniting means; circuit means connecting said timer actuator and said second switch means actuator to the secondary of said transformer to be energized thereby including terminals arranged to be connected to means responsive to the need for operation of the fuel burner; power input terminals adapted to be connected to a source of power, an initial energizing circuit for the primary of said transformer including said last named terminals, said first switch means in said circuit closing condition and said one switch of said second switch means which is closed in said first condition, and a holding circuit for the primary of said transformer to be effective after said first switching means is actuated to circuit opening condition to thereby open said initial energizing circuit, said holding circuit including said power input terminals and a switch of said second switch means which is closed in said second condition.

8. A burner control for use with a fuel burner and an ignition means, comprising: a transformer having a primary and a secondary, a.relay having switch means arranged when said relay is energized to complete a circuit supplying power to terminals adapted to be connected to a fuel burner and ignition means, a timer having an electrically energizable relatively high impedance actuator and a normally closed switch arranged when opened by a predetermined time period of energization of said high impedance actuator to discontinue the supplying of power to the ignition means terminal, a safety cutout device having an electrically energizable low impedance actuator and a normally closed switch connected in controlling relation to said relay and arranged to be opened after predetermined time period of energization of said low impedance actuator, combustion responsive means responsive to combustion at the fuel burner and having a cold closed switch and a hot closed switch, an initial energizing circuit connecting said relay to the secondary of said transformer and including said low impedance safety cutout actuator and the cold closed switch of said combustion responsive means, a holding circuit for said relay shunting said safety cutout actuator and said cold closed switch including said high impedance timer actuator and arranged to be completed by the hot closed switch of said combustion responsive means, said combustion responsive means thereby being effective upon response to combustion at the fuel burner to deenergize said safety cutout actuator and energize said timer actuator, an initial energizing circuit for the primary of said transformer including said normally closed switch of said timer, and a holding energizing circuit for the primary of said transformer including further switch means arranged when said relay is energized to complete said holding circuit.

9. A burner control apparatus for use with a fuel burner under the control of means responsive of the need for operation of the fuel burner, comprising: a transformer having a primary and a secondary, a relay having in and out contacts; a safety cutout device having normally closed contacts and an electrically energizable actuator; a timer having a normally closed switch and an electrically energizable actuator; means responsive to combustion at the fuel burner, combustion responsive switch means controlled by said last named means and having a first and second operative condition depending upon the absence or presence of combustion; an initial energizing circuit connecting said relay to the secondary of said transformer including said normally closed safety cutout contacts, said safety cutout actuator, said combustion responsive switch means in said first condition, and terminals adapted to be connected to means responsive to the need for operation of the fuelburner; a holding energizing circuit maintaining said relay connected to the secondary of said transformer including the electrically energizable actuator of said timer and controlled by said combustion responsive switch means in said second condition, said combustion responsive switch means arranged to switch from said relay initial energizing circuit to said holding circuit upon response to combustion to thereby operatively deenergize said safety cutout actuator and operatively energize said timer actuator; power input terminals; an initial power energizing circuit connected to supply power to the primary of said transformer including said power terminals, said out contacts of said relay, and said normally closed timer switch; and a power holding circuit to continue the supply of power to the primary of said transformer including the in contacts of said relay.

10. A burner control for use with a fuel burner unit having a fuel supply component and an ignition component, both of which are energized during starting and only the fuel supply component of which is energized during running, the fuel burner unit being under the control of means responsive to the need for operation of the fuel burner, comprising: a burner control relay having an actuating winding and in and out relay switch contact means, a bimetal timer having an electrically energizable heater therefor and a closed cold timer switch, an energizing circuit for said relay including said relay winding and terminals adapted to be connected to means responsive to the need for operation of the fuel burner, first circuit means arranged for completion by said in relay switch contact means to supply power to terminal means adapted to be connected to a fuel burner unit to energize the fuel supply component, second circuit means arranged for completion by said in relay switch contact means and including said closed cold timer switch to supply power to terminal means adapted to be connected to the ignition component, said timer switch being connected in said second circuit means to open said second circuit means to deenergize the ignition component of the fuel burner unit a predetermined time after energization of said timer heater, combustion responsive means normally responsive to combustion at the burner unit, an energizing circuit for said timer heater operatively energizing said heater upon said combustion responsive means responding to combustion, an initial power energizing circuit controlling the supply of power to the. above mentioned circuits including power input terminals adapted to be connected to a source of power, said out relay switch contact means and said closed cold switch of said timer, and a holding power energizing circuit for supplying power to the above mentioned circuits including said in relay switch contact means.

11. A burner control apparatus for a fuel burner and burner ignition means under the control of means responsive to the need for operation of the fuel burner, comprising: a relay having an electrically energizable actuator and switch means having an energized and deenergized condition; timer means having an electrically energizable actuator and switch means, said timer switch means being actuated from a first to a second condition with time delay upon energization of said timer actuator; safety cutout means having an electrically energizable actuator and switch means controlled thereby; combustion responsive means having means responsive to combustion at the fuel burner and having switch means controlled thereby, said combustion responsive switch means assuring a first or a second condition depending upon the absence or presence of combustion; a transformer having a primary and a secondary winding; an initial energizing circuit for said primary winding controlled by said relay switch means in said deenergized condition and said timer switch means in said first condition; a holding energizing circuit for said primary Winding controlled by said relay switch means in said energized condition; an energizing circuit for said relay actuator controlled by said safety cutout switch means, said combustion responsive switch means in said first condition, and by terminals adapted to be connected to means responsive to the need for operation of the fuel burner; a holding energizing circuit for said relay actuator including said timer actuator and controlled by said combustion responsive switch means in said second condition, said combustion responsive switch means thereby operatively deenergizing said safety cutout actuator and operatively energizing said timer actuator upon the presence of combustion; first circuit means controlled by said relay switch means in said energized condition to supply power to terminal means adapted to be connected to the fuel burner, and second circuit means controlled by said relay switch means in said energized condition to supply power under the control of said timer switch means to terminal means adapted to be connected to the burner ignition means.

References Cited in the file of this patent UNITED STATES PATENTS 2,086,823 Shaw July 13, 1937 2,188,565 Bower Jan. 30, 1940 2,217,886 Baak Oct. 15, 1940 2,308,295 Miller Jan. 12, 1943 2,385,426 Taylor et al. Sept. 25, 1945 2,440,700 Rosche May 4, 1948 2,486,612 Pratt Nov. 1, 1949 2,552,973 Judson May 15, 1951 2,604,148 Witherspoon July 22, 1952