US2720255A

US2720255A - Safety burner control apparatus

Info

Publication number: US2720255A
Application number: US330523A
Authority: US
Inventors: Carl J Bishofberger
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1953-01-09
Filing date: 1953-01-09
Publication date: 1955-10-11
Anticipated expiration: 1972-10-11

Description

Oct. 11, 1955 c. J. BISHOFBERGER 2,720,255

SAFETY BURNER CONTROL APPARATUS Fild Jan. 9, 1955 ;64 9 203 44- {202 I m M I 56 H 73 691,. ,n l v? I 7 ION HEATING=42-CLOSES,43OPENS,44 OPENS 52 -53 |Q-WHEEQEQEQ1E i P 1 I i l as . 3 I22 I04 INVENTOR. I WAN 557 CARL BISHOFBERGER Y ION HEATING= 42 CLOSES, 43 OPENS, 44 OPENS a i, g e

| ON COOLIN 42 OPENS, 44 CLOSES, 43 CLOS'ES h ATTORNEY United States Patent SAFETY BURNER CONTROL APPARATUS Carl J. Bishofberger, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application January 9, 1953, Serial No. 330,523

7 Claims. (Cl. 15828) This invention relates to a burner control apparatus making use of a burner control relay, a safety cutout device, and a combustion responsive means, the control apparatus providing an initial energizing circuit and a nonpickup holding circuit for the relay, with the non-pickup holding circuit being controlled both by the combustion responsive means and by in contacts of the relay.

Specifically, this invention is an improvement over the burner control apparatus disclosed in the co-pending application of Carl D. Ward, Serial No. 280,103, filed April 2, 1952.

The burner control apparatus disclosed in the above mentioned co-pending application incorporates a burner control relay in a circuit including a safety cutout device, an ignition timer, and flame responsive means, with the above mentioned components connected to provide an initial energizing circuit and a holding circuit for the relay, these circuits being controlled only by the flame responsive means. In this control apparatus the momentary opening and re-closing of the room thermostat during a particular time in the operating cycle of this control deenergizes the burner, however, the relay remains partially energized through the non-pickup holding circuit which includes the actuator for the ignition timer.

It has been found that in this condition of operation, while the burner control apparatus operates in a safe manner, there is a tendency for the relay to buzz or chatter due to the energization through the non-pickup holding circuit. This noise tends to travel up the heating ducts of the furnace and creates an unpleasant sensation in the area being heated. Also, the actuator of the ignition timer is not completely deenergized and, when a bi-metal type timer is used, the recycling of the control is with a shortened ignition period.

It is therefore an object of the present invention to provide an improved burner control apparatus having ignition timing means wherein immediate recycling of the burner will not result in a shortened ignition period.

It is a further object of the present invention to provide an improved burner control apparatus having a relay with an initial energizing circuit including a safety switch actuator and having a non-pickup holding circuit including current limiting impedance means, with the non-pickup holding circuit being completed by in contacts of the relay and with flame responsive means arranged to provide for recycle on flame failure.

It is a further object of the invention to provide an improved burner control apparatus having a burner control relay with an initial energizing circuit including closed cold contacts of a flame responsive means and a safety cut-out means, and having a non pick-up holding circuit including a closed cold switch and closed hot switch of the flame responsive means, ignition timing means, and in contacts of the relay, the closed hot and closed cold switches being arranged to give recycle upon flame failure and the in contacts of the relay preventing partial energization of the ignition timer or relay during recycle.

It is a further object of the present invention to provide an improved burner control apparatus having burner control means, safety cutout means, ignition timing means, and flame responsive means with the above named means connected to allow recycle on flame failure, to prevent even limited energization of the ignition timing means or burner control means during recycle, and to provide an interlock between the energizing circuit for the apparatus and the ignition timing means.

These and other objects will readily become apparent as the following specification is read in the light of the accompanying drawing in which Figure 1 is a showing of the improved burner control apparatus, and

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

Referring specifically to Figure 1, a fuel burner unit 10 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 the thermostat shown within broken lines 14, which thermostat, upon the need for operation of the burner unit 10, closes

contacts

15 and 16.

Referring specifically to the improved burner control apparatus 13, a burner control relay 17 is provided having a relay winding or actuator 18 and an armature 19. The armature 19 of relay 17 is shown in its inoperative or deenergized position and is provided with

bridging bars

20, 21, and 22. Upon energization of relay Winding 18, the armature moves bridging bar 20 into engagement with in contact 23, bridging bar 21 into engagement with the in

contacts

24 and 25, and bridging bar 22 into engagement with in

contacts

26 and 27. A switch which is closed when relay 17 is deenergized is provided for the relay 17 and includes stationary contact 28 and contact blade 29 connected to and movable with the in contact 27 Upon energization of the relay winding 18, armature 19 moves

bridging bars

20, 21, and 22 into engagement with the in contacts and due to the press back of the relay the in contacts 23 through 27 are moved to the left to broken line position 30. The movement of the in contacts to this broken line position 30 moves the contact blade 29 to the left and causes the contact blade 29 to disengage the stationary out contact 28.

Also included within the burner control apparatus 13 is a safety cutout device 31 having normally closed

contacts

32 and 33, a bi-metal member 34, a reset acactuator 35, and an electrically energizable actuating heater 36. Upon a predetermined time period of energization of the heater 36, the bi-metal 34 warps to the right out from under the normally closed

contacts

32 and 33 to allow the contacts to disengage. Upon subsequent cooling of the bi-metal member 34, the reset actuator 35 can be depressed to reset the

contacts

32 and 33 to their normal position as shown in Figure l.

A timer 37 is provided having a closed cold switch including contact 38, a bi-metal member 39, and an electrically energizable actuating heater 40. After a predetermined time period of energization of heater 40 above a given minimum energization level, the bi-metal element 39 warps to the left to disengage the contact 33. Upon the bi-metal element 39 cooling, the element 39 again engages contact 38 as shown in Figure l.

A combustion responsive means 41 is shown having a closed hot switch 42, a first closed cold switch 43, and a second closed cold switch 44. A bimetal actuator is shown at 45 and is normally located to be responsive to the presence or absence of combustion at the burner unit 10. The bimetal actuator 45 is effective upon heating to move to the left as shown by the arrow in Figure 1. Movement of bimetal actuator 4-5 is transmitted by 3 means of a rod, shown by dotted line 46, and by members 288 and 201 to the

switches

42, 43 and 44.

The

members

200 and 201 are mounted in slip friction engagement with the rod, shown by dotted line 46, and moved with the rod until sufiicient force is applied to stop such movement, at which time the members 280 and 201 will remain stationary and slide upon the rod.

The blades upon which the

switches

43 and 44 are mounted are biased so that as member 200 moves to the left the

switches

43 and 44 also move to the left until stops 202 and 283 are engaged to cause

switches

43 and 44 respectively to open. The blade upon which righthand member of switch 42 is mounted is biased to the right to engage member 201.

The combustion responsive means 41 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 45 begins to move to the left. This movement causes

members

200 and 201 to also move to the left. When member 2111 has moved a predetermined distance, closed hot switch 42 closes. Subsequently, when member 200 has moved a predetermined distance, the right-hand member of closed cold switch 43 engages stop 202 to stop this member. Further movement of member 200 causes closed cold switch 43 to open.

Again after a short time of movement, stop 203 engages the common member of closed

cold switches

43 and 44 and further movement of member 200 to the left causes closed cold switch 44 to open.

When combustion ceases at the burner unit 10, the bimetal actuator 45 cools and moves to the right to the position shown in Figure 1. First initial movement to the right causes member 261 to also move to the right and open thereby closed hot switch 42. Further movement to the right causes member 200 to close closed cold switch 44. Still further movement to the right causes closed cold switch 43 to be closed.

A transformer 47 having a primary 48 and a secondary 49 is shown associated within the burner control apparatus 13 to supply power to circuits which include the burner control relay 17, the timer 37, the safety cutout device 31, and the closed hot and closed cold switches of the combustion responsive means 41. A plurality of ter minals are also associated with the burner control apparatus 13. The

terminals

50 and 51 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 52 and 53 are adapted to be connected to the fuel burner 11 and ignition means 12 respectively to supply power to the burner unit under the control of the burner control apparatus 13.

In Figure 1 the apparatus is shown in its stand-by condition. That is, the timer 37 has its closed cold switch in closed position, the safety cutout device 31 has its

contacts

32 and 33 in engaging position, the relay 1"] is in its deenergized position, and the combustion responsive means 41 is in a condition indicating the absence of combustion at the burner unit 10.

Assuming that power is applied to the

power input terminals

50 and 51, an initial energizing circuit can be traced for the primary 48 of the transformer 47 from the power input terminal 50 though the primary 48, conductor 54, bi-metal element 39 and closed contact 38 of timer 37, conductor 55, contact blade 29 and stationary out contact 28 of relay 17, conductor 56, and conductor 57 to the power input terminal 51. From this last traced circuit it can be seen that in the stand-by condition in order for power to be applied to the primary 48 it is necessary first for the timer 37 to be in its cold position, and second for the relay armature 19 to be in its deenergized position such that contact blade 29 engages out contact 28.

Assume now that there is a need for operation of the burner unit 10 which the thermostat 14. senses by closing

contacts

15 and 16. An initial energizing circuit can now be traced for the relay 17 from the upper terminal of the secondary 49 through conductor 58,

contacts

33 and 32 of safety cutout device 31, relay winding 18, conductor 59,

contacts

15 and 16 of thermostat 14, conductor 6t), conductor 61, actuator 36 of the safety cutout device 31, conductor 62, first closed cold switch 43 of combustion responsive means 41, and conductor 64 to the lower terminal of secondary 49.

At this time, the actuator 36 of the safety cutout device 31 is operatively energized, that is, if the combustion responsive means 41 does not operate to indicate the establishment of combustion at the burner unit 10, the safety cutout device 31 will be actuated to the position where the

contacts

32 and 33 are disengaged.

Energization of relay 17 causes the relay armature 19 to move bridging bars 20, 21, and 22 into engagement with the in contacts 23 through 27. Consider at this time the instant the bridging bars 20, 21 and 22 have just engaged the in contacts 23 through 27 of the relay 17. The initial energizing circuit for the primary 48, above traced, is still completed through contact blade 29 and out contact 28, however, a holding circuit is now also established for the primary 48. This holding circuit can be traced from the power input terminal 50 through primary 48, conductor 54, conductor 65, bridging bar 21 and in contact 24 of relay 17, conductor 66, and conductor 57 to power input terminal 51. The relay armature 19 completes its movement to take up the press back of the relay and moves the in contacts 23 through 27 to the left to the position shown by the broken line 30 and therefore it causes contact blade 29 to disengage out contact 28 of the relay 17. This breaks the initial energizing circuit for the primary 48 for the transformer 47, however, the above traced holding circuit is effective to supply power to the primary 48 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 terminals 52 and 53. The energizing circuit for the burner motor 11 can be traced from power line 67 through conductor 68, burner motor 11, terminal 52, conductor 69, in contact 25 bridging bar 21 and in contact 24 of relay 17, conductor 66, conductor 57, and input terminal 51 to power line conductor 70. The energizing circuit for the ignition means 12 can be traced from the power line conductor 67 through conductor 68, ignition means 12, terminal 53, conductor 71, in contact 26 bridging bar 22 and contact 27 of relay 17, conductor 55, contact 38 and bi-metal element 39 of timer 37, conductor 65, bridging bar 21 and in contact 24 of relay 17, conductor 66, conductor 57, and terminal 51 to power line conductor 70.

It will be noted that a circuit, placing actuator 40 in parallel with actuator 36, can be traced from the upper terminal of secondary 49 through conductor 58,

contacts

33 and 32 of safety cutout device 31, relay 17, conductor 59,

contacts

15 and 16 of thermostat 14, conductor 60, conductor 76, bridging bar 20 and in contact 23 of relay 17, conductor 75, actuator 40 of timer 37, conductor 74, second closed cold switch 44 of combustion responsive means 41, and conductor 64 to the lower terminal of secondary 49. It would appear that the actuator 40 is now operatively energized. However, the relative impedance of actuator 40 and actuator 36 is such that so long as the first closed cold switch 43 remains closed the actuator 40 is effectively shorted through actuator 36. By way of illustration, it has been found desirable to select the following impedance values for the actuators 36 and 40: Ohm

Actuator 36 Actuator 40 The burner control apparatus 13 is now in its starting phase wherein the burner motor 11 is energized, the ignition means 12 is energized, the timer 37 is operatively deenergized, and the safety cutout device 31 is energized.

Assume now that a flame is established at the burner unit 10, the bi-metal actuator 45 of the combustion responsive means 41 will respond to the presence of combustion at the burner unit and will actuate its associated closed hot and closed cold switches in the sequence above described. The bi-metal actuator 45 will first cause the closed hot switch 42 to close. The closing of the closed hot switch 42 has no effect at this time since closed hot switch 42 is in parallel with closed cold switch 44, which switch is already closed.

A short time after the closing of closed hot switch 42, the closed cold switch 43 opens. This has the effect of deenergizing the actuator 36 of the cutout device 31, and at the same time removes the relatively low impedance shunt from the actuator 40 of the timer 37. The actuator 40 is now operatively energized and begins to heat the bi-metal element 39. In this condition the relay 17 is maintained energized through the closed hot switch 42 of the combustion responsive means 41, the actuator 40 of the timer 37, contact 23 and bridging bar 20 of relay 17, and thermostat 14. A short time after the opening of closed cold switch 43, the closed cold switch 44 opens. The function of the closed cold switch 44 is to provide recycle and will be more completely explained later.

After a predetermined time period of energization of the actuator 40 of timer 37, the contact 38 disengages bi-metal element 39. This breaks the above traced initial energizing circuit for the primary 48 of transformer 47, however it will be remembered that a holding energization circuit for the primary 48 has been established upon relay 17 being energized. The opening of the closed cold switch of the timer 37 also breaks the above traced energizing circuit for the ignition means 12 to thereby turn off the ignition at the burner unit 10.

The burner control apparatus 13 is now in its runing phase with the burner motor 11 energized, the ignition means 12 deenergized, the actuator 36 to safety cutout device 31 deenergized, the bi-metal actuator 45 of the combustion responsive means 41 responding to the presence of combustion at the burner unit 10, and the actuator 40 of the timer 37 operatively energized to maintain the timer contact 38 disengaged from bi-metal 39.

Assume now that the thermostat 14 has been satisfied by a sufficient period of operation of burner unit 10 and has accordingly opened the

contacts

15 and 16. The energizing circuit for relay 17 is therefore broken and the relay armature 19 returns to its inoperative position such as is shown in Figure 1. This immediately deenergizes the burner unit 10 and also breaks the holding circuit for the primary 48 of transformer 47. As shown in Figure 1, the deenergization of relay 17 causes contact blade 29 to engage out contact 28 of relay 17.

If as soon as relay 17 is deenergized there is a second call for heat, the relay 17 cannot again be energized since the primary 48 of transformer 47 is deenergized due to contact 38 disengaging bi-metal 39 of timer 37. After a short period of cooling, bi-metal 39 again engages contact 38. This energizes transformer 47. However, during the time required for the bi-metal member 39 to cool, the bi-metal actuator 45 of the combustion responsive means 41 has been cooling and first actuates the closed hot switch 42 to open position. At this time the closed

cold switches

43 and 44 and the closed hot switch 42 are all open.

A short time after the opening of closed hot switch 42, closed cold switch 44 closes. At this time the above traced non pick-up holding circuit is still open at switch blade 23 and bridging bar of relay 17 and therefore relay 17 cannot be energized. If it were not for the nonpickup holding circuit being open at this time, limited energization of the relay 17 and actuator 40 of timer 37 would occur. This, as above mentioned, would cause an objectionable buzz or chatter of relay 17 and would also tend to shorten the ignition period. A short time after closing of closed cold switch 44, the closed cold switch 43 closes. It has been found that the combustion responsive means 41 at this point in the operation of the apparatus 13 tends to produce an intermittent condition of engaging and disengaging of closed cold switch 43 for a short period of time. It will be remembered that the initial energizing circuit for the relay 17 includes the closed cold switch 43 and if it were not for the closed cold switch 44 which is closed at this point, it would be possible for the relay armature 19 to move between its operative and inoperative position a number of times before the combustion responsive means 41 positively closes closed cold switch 43.

To explain more fully the utility of providing the closed cold switch 44, consider that the closed cold switch 43 has been closed for a very short period of time and then opened due to the inherent characteristics of bi-metal actuator 45 of the combustion responsive means 41. The initial closing of closed cold switch 43 completes the initial energizing circuit for relay 17 and the relay armature 19 moves to its operative position. The closed cold switch 43 now opens, however the relay is maintained energized through the non-pickup holding circuit, above traced, which includes in series with the relay winding 18, the closed cold switch 44, the actuator 40 of timer 37, and in contact 23 and bridging bar 20 of relay 17. It is immediately recognized that with relay 17 energized the burner unit 10 is energized and bi-metal actuator 45 is again subjected to the heat of combustion. In this case the closed cold switch 43, which has been momentarily closed as pointed out above, may not re-close but bimetal actuator 45 will be effective to close closed hot switch 42 and then open closed cold switch 44.

However, if combustion is not again established at the burner unit 10, the closed cold switch 43 will again close and be positively closed by bi-metal actuator 45 of cornbustion responsive means 41 to complete the initial energizing circuit for the relay winding 18 which includes the actuator 36 of safety cutout device 31. Burner unit 10 then remains energized until the normally closed

contacts

32 and 33 of the safety cutout device 31 are opened in response to a predetermined time period of energization of the actuator 36. The opening of the

contacts

32 and 33 deenergizes the relay 17, thereby deenergizing the burner unit 10. The actuator 36 of a safety cutout device 31 is now deenergized and the bi-metal member 34 subsequently cools. The depressing of the actuator 35 now resets the

contacts

32 and 33 to their engaging position and if there is still a call for heat by thermostat 14 the burner control apparatus 13 begins its cycle to attempt to establish combustion at the burner unit 10.

Species of Figure 2 Referring now specifically to Figure 2, a modification of the apparatus of Figure 1 is shown with the common elements between the two figures retaining the same reference numerals. In Figure 2 the burner unit 10 has been omitted, however, the

conductors

68, 69, and 71 connect to the burner unit 10 in the manner shown in Figure 1.

The apparatus of Figure 2 is shown in the stand-by condition, the initial energizing circuit and holding circuit for the primary 48 of transformer 47 being identical to that of Figure 1.

Assume now that there is a call for heat by the thermostat 14. An energizing circuit can be traced for relay 17 from the upper terminal of the secondary 49 through the conductor 100,

contacts

15 and 16 of thermostat 14, conductor 101, normally closed

contacts

32 and 33 of safety cutout device 31, conductor 102, actuator 36 of safety cutout device 31, conductor 103, closed cold switch 43 of combustion responsive means 41, conductor 104, conductor 105, winding 18 of relay 17, conductor 106, and conductor 107 to the lower terminal of secondary 49. Upon energization of relay 17, armature 19 moves to the energized position and in the manner above described, the holding circuit of primary 48 is established and the initial energizing circuit for the primary is broken. Also, in the manner above described, the fuel burner 11 and ignition means 12 are energized.

Upon the armature 19 moving to the energized position, the bridging bar 20 engages in contact 23 of relay 17. The engagement of 20 and 23 completes two circuits. The first of these circuits includes the actuator 40 of the timer 37 and can be traced from the upper terminal of secondary 49 through conductor 100,

contacts

15 and 16 of thermostat 14, conductor 101,

contacts

32 and 33 of safety cutout device 31, conductor 110, bridging bar 20 and in contact 23 of relay 17, conductor 111, actuator of timer 37, conductor 112 and conductor 107 to the lower terminal secondary 49. It can be seen that the actuator 40 of the timer 37 is now operatively energized and the ignition timing period has begun. A predetermined time hereafter the contact 38 will disengage the bi-metal member 39.

The second circuit completed by engagement of bridging bar 20 within contact 23 is a circuit which includes the blocking resistor 120 and the closed cold switch 44 of combustion responsive means 41 connected in parallel with the actuator 36 of safety cutout device 31. This shunt circuit can be seen by tracing the circuit from the lower terminal of actuator 36 through a conductor 102, conductor 110, bridging bar 20 and in contact 23 of relay 17, conductor 111, conductor 121, blocking resistor 120, conductor 122, closed cold switch 44, closed cold switch 43, and conductor 103 to the upper terminal of actuator 36 of safety cutout device 31. At this time the shunt circuit including blocking resistor 120 has very litle effect due to the relative impedances of blocking resistor 120 and actuator 36. By way of illustration, it has been found desirable to select the following impedance values for the actuator 36 and the blocking resistor 120:

Ohms Blocking resistor 120 50.0 Actuator 36 12.6

From the above values, it can be seen that the above traced shunt circuit has a high enough impedance so that the current flow through the actuator 36 remains substantially unchanged as the armature 19 of the relay 17 moves to the energized position.

Assume that combustion is now established at the burner unit 10. The bi-metal actuator of the combustion responsive means 41 will sense this combustion and actuate the closed hot and closed cold switches in the manner above described. The closed hot switch 42 is the first switch to be actuated by the combustion responsive means 41 and will be closed a short time period after the establishment of combustion at the burner unit 10. The closing of the closed hot switch 42 has no effect at this time since it is connected in parallel with the already closed cold switch 44. A short time thereafter the closed cold switch 43 opens. This has two effects. First the actuator 36 of safety cutout device 31 is deenergized, and secondly a non-pickup holding circuit is established for the relay 17. This non-pickup holding circuit can be traced from the upper terminal of the secondary 49 through the conductor 100, contacts 15 and 16- of thermostat 14, conductor 101,

contacts

32 and 33 of safety cutout device 31, conductor 110, bridging bar 20 and in contact 23 of relay 17, conductor 1'11, conductor 121, blocking resistor 120, conductor 122, closed cold switch 44 in parallel with closed hot switch 42 to conductor 105, relay winding 18, conductor 106, and con- '8 ductor 107 to the lower terminal of secondary 49. Here again it can be seen that this non-pickup holding circuit is completed only when relay 17 is energized.

A short time thereafter the ignition timer 37 is actuated due to energization of the actuator 40 and causes contact 38 to disengage bimetal 39 to deenergize the ignition means 12 in the manner above described.

The burner control apparatus 13 is now in the running condition with the burner motor 11 energized, the ignition means 12 deenergized, the actuator 40 of timer 37 energized, the actuator 36 of safety cutout device 31 deenergized, and the relay 17 energized through the nonpickup holding circuit. A short time thereafter the closed cold switch 44 opens, however, the opening of this switch at this time has no effect upon the circuit to relay 17 which remains completed through closed hot switch 42.

Upon satisfaction of the thermostat 14 the

contacts

15 and 16 of the thermostat 14 open. This breaks the energizing circuit for the relay 17 and the armature 19 moves to the deenergized position to deenergize the burner 10 and to also deenergize the actuator 40 of the timer 37.

Assume now that there is an immediate call for recycle as evidenced by the

contacts

15 and 16 of thermostat 14 again closing. At this time a closing of the thermostat contacts has no effect since the primary 48 of the transformer 47 is deenergized due to the contact 38 being disengaged from bi-metal member 39 of timer 37.

A short time thereafter contact 38 engages bi-metal member 39 and thev primary 48 of transformer 47 is en ergized. During the time required for the bi-metal member 39 to cool, the bi-metal actuator 45 of the combustion responsive means 41 has been cooling and first actuates the closed hot switch 42 to open position. The closed cold switch 44 is next actuated to closed position however, this has no effect at the present time since the non-pickup holding circuit is open at the relay contact 23. The fact that the non-pickup holding circuit is open at this time prevents limited energization of the relay which would tend to cause the relay to hum or chatter.

A short time thereafter the closed cold switch 43 closes to complete the initial energizing circuit for the relay 17. As above mentioned, it is a characteristic of the bi-metal actuator 45 of combustion responsive means 41 to cause intermittent engagement of the closed cold switch 43 when they are first closed due to the actuator 45 cooling. However, once the relay armature 19 is moved to the energized position the above mentioned non-pickup holding circuit which includes the closed cold switch 44, the blocking resistor 120, and the in contact 23 and bridging bar 20 of relay 17, has been completed and the subsequent momentary opening of the closed cold switch 43 will not cause the relay 17 to be deenergized.

The energization of the relay 17 in the manner above described again causes the burner unit 10 to be cycled to establish flame at the unit. If for some reason flame is not established at the burner unit 10 the safety cutout device 31 is actuated to open the normally closed

contacts

32 and 33 in the manner above described with reference to Figure 1.

From the above description of the operation of the present invention as applied to Figures 1 and 2 it can be seen that the burner control apparatus 13 provides an initial energizing circuit for the burner control relay 17 and provides a non-pickup holding circuit for the relay to maintain the relay energized after the flame responsive means 41 has responded to the presence of combustion at the burner unit 10. It can also be seen that this nonpickup holding circuit, because it is controlled by in contacts of the relay, is ineffective to supply even limited energization to the relay 17 when the relay armature 19 is in the deenergized position and thereby insures that no objectionable noise will. be generated due to limited energization of the relay 17. It can also be seen that since the energizing circuit for the actuator 40 of timer 37 is completed. through in contacts of the relay 17, a

possibility of a shortened ignition period due to premature energization of the actuator 40 is prevented and actuator 40 can be energized only when the burner control apparatus 13 is going through its cycle of operation in the normal manner.

While the present invention has been shown with reference to a first and second modification it is understood that the invention is limited solely by the scope in the appended claims.

I claim as my invention:

1. A burner control apparatus for use with a fuel burner and means responsive to the need for operation of the fuel burner, comprising: a safety switch having an electrically energizable actuator and a normally closed switch, said switch opening after a predetermined time period of energization of said actuator; a fuel burner control relay having a winding and switching means having at least one switch; flame responsive means having first and second switches closed in the absence of combustion and a third switch open in the absence of combustion, said third switch being connected in parallel with said second switch; a source of power; energizing circuit means for said relay including said winding, the normally closed switch and actuator of said safety switch, said first switch of said flame responsive means, and leads adapted to be connected to means responsive to the need for operation of the fuel burner; current limiting impedance means; and non-pickup holding circuit means for said relay including said winding, the switch of said safety switch, said one switch of the switching means of said relay, and said second and third switches of said flame responsive means.

2. Burner control apparatus comprising, burner control means having an electrically energizable actuator and having switching means having a first switch adapted to be connected to energize a fuel burner when said actuator is energized; a safety cutout device having an electrically energizable actuator and a normally closed switch which opens after a predetermined time period of energization of said actuator; bimetallic flame responsive means having first and second overlapping switches which are closed in the absence of combustion and having a third switch which is open in the absence of combustion, said second and third switches being connected in parallel; said flame responsive means operating upon the establishment of flame to close said third switch, then open said first switch, and then open said second switch; said flame responsive means operating upon the subsequent failure of combustion to first open said third switch, then close said second switch, and then close said first switch; energizing circuit means for said burner control means including said burner control means actuator, the normally closed switch and actuator of said safety cutout device, said first switch of said flame responsive means, and means responsive to the need for operation of the fuel burner; current limiting impedance means; and a nonpickup holding circuit for said burner control means including said burner control means actuator, the normally closed switch of said safety cutout device, said second and third switches of said flame responsive means, said current limiting impedance means, a second switch of said switching means of said burner control means which is closed when said burner control means is energized, and said means responsive to the need for operation of the fuel burner.

3. A burner control apparatus comprising: a burner control relay having a winding and switching means having a first switch adapted to be connected to energize a fuel burner when said relay is energized; a safety switch having a relatively low impedance actuator and a normally closed switch which opens after a predetermined time period of energization of said actuator; flame responsive means of the type having a bi-metal actuator responsive to the heat produced by the establishment of combustion at the fuel burner, said flame responsive means having first and second pairs of closed cold coritacts and a third pair of closed hot contacts, said second and third pair of contacts being connected in parallel; said flame responsive means operating upon the establishment of flame to first close said closed hot contact pair, then open said first closed cold contact pair, and then open said second closed cold contact pair; said flame responsive means operating upon the failure of combustion to first open said closed hot contact pair, then close said second closed cold contact pair and then open said first closed cold contact pair; energizing circuit means for said relay including said relay winding, the normally closed switch and the relatively low impedance actuator of said safety switch, said first closed cold contact pair, and means responsive to the need for operation of the fuel burner; relatively high impedance current limiting means; non-pickup holding circuit means for said relay including said relay winding, the normally closed switch of said safety switch, said first and third pairs of contacts of said flame responsive means, said relatively high impedance current limiting means, and a second switch of said switching means of said relay which is closed when said relay is energized; said non-pickup holding circuit means being substantially short circuited by said energizing circuit means because of the relative impedances of said safety switch actuator and said current limiting means until said first closed cold contact pair of said flame responsive means is opened and being ineffective because of said second switch of said relay switching means to supply even reduced power to said relay winding upon recycle until said first closed cold contact pair closes as the bimetal actuator of said flame responsive means cools.

4. A burner control apparatus for use with a fuel burner having ignition means, comprising; a burner control relay having switching means having a first and a second switch; safety cutout means having a 10W impedance actuator and a normally closed switch; flame responsive means having first and second closed cold contact pairs and a third closed hot contact pair, said second and third contact pairs being connected in parallel; energizing circuit means for said relay including said actuator and normally closed switch of said safety cutout means, said first closed cold contact pair of said flame responsive means, and means responsive to the need for operation of the fuel burner; ignition timing means having a high impedance actuator and a normally closed switch; nonpickup holding circuit means for said relay including said normally closed switch of said safety cutout means, said second and third contact pairs of said flame responsive means, said first switch of said switching means of said relay which are closed when said relay is energized, and said actuator of said ignition timing means; said nonpickup holding circuit means being substantially shunted by said energizing circuit means so long as said first contact pair of said flame responsive means is closed, said actuator of said ignition timing means being effectively energized upon said first contact pair of said flame responsive means opening to thereby subsequently deenergize the ignition means for the fuel burner; a power energizing circuit for said apparatus including said normally closed switch of said ignition timing means, and a power holding circuit for said apparatus including said second switch of said switching means of said relay which is closed when said relay is energized.

5. A burner control apparatus for use with a fuel burner having ignition means, comprising; a burner control relay having first and second in contacts; a safety switch having an electrically energizable actuator and a normally closed switch; flame responsive means having first and second pairs of closed cold contacts and a pair of closed hot contacts, said closed hot contacts being connected in parallel with said second pair of closed cold contacts; energizing circuit means for said relay including the actuator and normally closed switch of said safety switch, the first pair of closed cold contacts of said flame responsive means, and means responsive to the need for operation of the fuel burner; current limiting impedance means; non-pickup holding circuit means for said relay including said second closed cold contacts of said cornbustion responsive means, said current limiting impedance means, and said first in contacts of said relay; ignition timing means having an actuator and a normally closed switch, an energizing circuit for said ignition timing means actuator including said first in contacts of said relay, said actuator opening said normally closed switch of said ignition timing means after a predetermined time period of energization of said actuator; an initial power energizing circuit for said apparatus including said normally closed switch of said ignition timing means; and a power holding circuit for said apparatus including said second in contacts of said relay.

6. A burner control apparatus for use with a fuel burner having ignition means, comprising; a burner control relay having in contacts; a safety switch having an electrically energizable actuator and a normally closed switch; flame responsive means having first and second pairs of closed cold contacts and a pair of closed hot contacts, said closed hot contacts being connected in parallel with said second pair of closed cold contacts; energizing circuit means for said relay including the actuator and normally closed switch of said safety switch, the first pair of closed cold contacts of said flame responsive means, and means responsive to the need for operation of the fuel burner; current limiting impedance means; nonpickup holding circuit means for said relay including said second closed cold contacts of said combustion responsive means, said current limiting impedance means, and said in contacts of said relay; ignition timing means having an actuator and a normally closed switch, and an energizing circuit for said ignition timing means actuator including said in contacts of said relay, said actuator opening said normally closed switch of said ignition timing means after a predetermined time period of energization of said actuator.

7. A burner control apparatus for use with a fuel burner and means responsive to the need for operation of the fuel burner, comprising; an electromagnetic actuator, switching means controlled by said actuator and having a first switch adapted to be connected to energize a fuel burner when said electromagnetic actuator is energized, an electrically energizable safety cutout actuator and cutout switching means controlled thereby, flame responsive means having first and second switches closed in the absence of flame and a third switch open in the absence of flame, said third switch being connected in parallel with said second switch, a source of power, energizing circuit means connecting said electromagnetic actuator to said source of power including said safety cutout actuator, said cutout switching means, leads adapted to be connected to the means responsive to the need for operation of the fuel burner, and said first switch of said flame responsive means; current limiting impedance means; and a non-pickup holding circuit for said electromagnetic actuator connecting said electromagnetic actuator to said source of power including said second and third switches of said flame responsive means, said impedance means, and a second switch of the switching means of said electromagnetic actuator.

References Cited in the file of this patent UNITED STATES PATENTS 2,075,289 Judson Mar. 30, 1937 2,086,823 Shaw July 13, 1937 2,370,847 Dempster Mar. 6, 1945 2,604,148 Witherspoon July 22, 1952