US1985986A - Oil burner control - Google Patents

Description

Jan. 1, 1935. c, HALL 1,985,986

OIL BURNER CONTROL- Filed Feb. 24. 1930 Inventor" Chester 1'. Hal l b5 His Attorney Patented I, 1935 UNITED. STATES OIL BURNER CONTROL Chester 1. Hall, Philadelphia, Pa asaignol' to General Electric Company, a corporation of New York Application February 24, 1930, Serial No. 430,497

38 Claims.

My invention relates to control devices and has for its principal object a fully automatic control device for aburner for fluids such as oil and gases, although it may be adapted to other burners which depend for ignition upon an electric spark or hot filament, gas or oil flame and the like.-

In oil burners making use of such ignition the spray of oil is not always at first ignited. If the motor operating the oil pump continues to function, after a failure to establish a flame, since no means are provided to dissipate the oil enough oil may collect in the fire box to cause an explosion when ignition does take place.

Difliculty has also been experienced during operation due to slugs of water in the oil temporarily shutting off the oil supply and thus extinguishing the flame. Due to only a slight cooling of the refractories when the oil spray is againresumed, enough oil is permitted to accumulatev before ignition takes place to cause an explosion.

It is an object of the present'invention to automatically start the fuel supply motor and the ignition system of the burner whenever there is a call for heat and to automatically shut down the apparatus when no further heat is needed.

Another object of my invention is to cut out the ignition system when a flame has been established and to lock in the fuel supply motor.

Another object of my invention is to provide means whereby several opportunities are given the ignition device to ignite the oil, and if the flame still fails the apparatus will be made inoperative. To make it operative it will be neces-- sary to reset the apparatus by hand, thus calling for an inspection.

A further object of my invention is to prevent the accumulation of oil in a hot fire box and causing an explosion whenever the flame has been extinguished.

Another object of my invention is to provide a safety device operative to disconnect the whole apparatus whenever dangerous heat or pressure conditions arise.

A further object of my invention is the provision of an automatic means for changing the operating temperatures of the apparatus for day and night operation. Other objects will hereinafter appear.

The preferred embodiment of my invention consists of a synchronous motor for continuously driving a time controlled mechanism, which automatically switches in the nightor day thermostats which in turn initiate operation of the apparatus.

This motor also drives what is termed a recycling mechanism for opening and closing an ignition circuit at short intervals, thus presenting several opportunities for igniting the oil. When the flame is established a flame responsive device placed in the fire box of the furnace and operated by the flame cuts out the ignition system and locks in the fuel supply motor.

The fuel supply motor is also controlled by the recycling device, the motor being operated at intervals simultaneously with the ignition system. The intervals of operation are so spaced that any gases in the fire box are permitted to be drawn off by natural draft while the motor and ignition system are deenergized. Of course the ignition system could be continuously energized during recycling until a flame is established.

Should the flame fail during operation the flame responsive device energizes the recycling mechanism to reignite the oil by reenergizing the ignition system. A definite time period is provided after flame failure before the ignition and fuel supply motor circuits are reestablished by the recycling device. This permits accumulated gases opportunity to be drawn off.

The recycling operation is accomplished by means of cam actuated contacts which are rendered operative whenever a starting coil is energized by the closing of a thermostat calling for heat. The starting coil operates a pivoted member upon which a cam is mounted. This brings the cam shaft into contact with a driving pulley of the synchronous motor. The rotation of the cam actuates the contacts to open and close the ignition system and fuel supply motor circuits. In the event that the recycling device fails to cause ignition of the 011 after a predetermined number of intermittent operations of the fuel supply motor and ignition system, limiting or counting means are provided for rendering the recycling device inoperative, thus inviting inspection to determine the cause of the failure less of the position of the time switch 12.

power supplied through lines L1 and In. This synchronous motor drives a time controlled switch 12 which makes contact with contact elements 13 and 14. This motor also drives a pinion 15 which engages under certain conditions with the gear 16 mounted on the movable shaft 16 to drive the recycling cam 17. As shown one end of the shaft 16 is provided with a pivot bearing and the other end is rotatably supported on the pivoted armature 19 of the electromagnet 19. Thus when the electromagnet 19 is energized to attract its armature 19', the shaft 16 is tilted so as to bring the gear 16 into driving relation with the pinion 15 and thereby rotate the recycling cam 17. Gear 16 is so designed that pinion 15 is prevented since the pinion- 15 will merely slip with respect to the gear 16. This action takes place when the member supporting the lower contact of the pair of contacts 20 is in the last depression in the cm 1'7. Thus the contacts will remain in the open position until the apparatus is inspected. The coiled spring 18, after electromagnet 19 has been deenergized and the shaft 16' moved to disengage the gear 16 from pinion 15, rotates the shaft 16' in a clockwise direction so that upon reenergization of the electromagnet 19 to effect tilting movement of the shaft 16' in the manner just described, the gear 16 will again engage-the pinion 15 to be driven thereby. 21 designates the ignition transformer which supplies the 11 energy to produce a spark at the electrodes 22 for igniting the spray of oil. 23 is the fuel supply motor. 24 and 24 designate mercury switches actuated by means of a stack thermostat 30.

31 designates a starting transformer and 32 a locking transformer which is actuated by means of the electromagneticalLv operated member 33. 35 and 36 designate the night and day thermostats and 3'7 designates a switch for arbitrarily determining the controlling thermostat rege'lrlle operation of this embodiment is as follows:

When the switch 50 is closed the primary of transformer 31 is energized. If the time control switch 12 is in contact with the element 13 and the thermostat 36 moves to the left hand contact in calling for heat, a circuit is completed through the secondary of the transformer 31, conductor 40, thermostat 36, switch 37, conductor 43, through the time switch, the electromagnetic device 33 and conductor 41 to the other side of the transformer. This actuates device 33 closing its contacts and placing the primary of transformer 32 across the line. A circuit is completed through the secondary of this transformer by means of its winding. This looks transformer 32 into the circuit and prevents the movement of the thermostat 36 to a neutral position from disturbing the operation of the device.

A safety switch 51 normally closed establishes a circuit from one side of the line L: to one side of the ignition transformer 21 and one side of the fuel supply motor 23. A circuit is established through the electromagnetically operated device 19, contacts 28 and 29 of the mercury switch 24' and the contacts of the electromagnetically operated device 33 to the opposite side of the line L1. 19 actuates its armature to establish a driving connection between pinion 15 and gear 16 and upon rotation of the cam 17 in a counterclockwise direction the contacts 20 are intermittently closed and opened. This closing of the contacts places the primary of transformer 21 across lines L1 and L2. This circuit may be traced from line L: through switch 51 to one side of the primary of the transformer 21, through the contact 20, contacts 28 and 29 of mercury switch 24, through the contacts of the electromagnetically operated device 33 to the other side of the line L1. The circuit through the motor is also established from the line L2 through the switch 51, motor 23, contacts 25 and 26 of mercury switch 24, contacts 20, contacts 29, 28 of mercury switch 24' and contacts of the device 33 to the other side of the line L1.

Upon the establishment of a flame the stack thermostat 30 operates to tilt the mercury switches 24 and 24', breaking the contacts at 26 and 29 and establishing contact at 27 and 28 of switch 24'. The circuit through device 19 is opened permitting the pinion and gears 15 and 16 to demesh. The cam is returned to its inoperative position. This action results in taking out of the circuit the primary of the ignition transformer 21 and in placing the motor 23 directly across lines L1 and L2 through contacts 27, 28 of mercury switch 24' which circuit is maintained until the thermostat 36 is actuated to call for less heat.

When the thermostat 36 is caused by the room temperature to move to the right hand contact, the electromagnetically operated device 33 is shorted, thus deenergizing its coil and permitting the contacts to be opened. This opens the circuit through the motor and extinguishes the oil flame. Upon cooling of the gases in the stack the thermostat 30 returns the mercury switches to their starting position to again render the recycling device operative to reestablish a flame when more heat is called for by the thermostat. As has been pointed out above, if no flame is established the recycling device will operate to lock contacts 20 in the open position after a predetermined number of intermittent operations of the recycling device. Under these conditions the electromagnet 19 remains energized to hold the gear 16 in engagement with the pinion 15 although there is no further rotation of the gear 16 by the pinion 15 since the pinion merely slips with respect to the gear 16 when it encounters the segmental. cutaway portion of the gear 16 referred to above. When upon inspection the difliculty responsible for the non-establishment of flame is corrected, it is then necessary to reset the control apparatus by hand to render it again operative to establish flame. This manual resetting operation is accomplished by momentarily opening the switch 51 and then reclosing this switch. Upon the opening of switch 51, the electromagnet 19 is deenergized thereby permitting the coil spring 18 to return the gear 16 and the recycling cam 17 to their initial position in the manner described above.

Thermostat 35 is rendered operative when the time switch 12 is in contact with segment 14 through conductor 42 and switch 37. A switch 37 is provided which places either thermostat 35 or 36 in the controlling circuit regardless of the position of the time switch, as will be readily menses seen'by tracing out the circuits. Thus assuming contact 12 of the time switch in engagement with the segment 13 and the switch 37 in the position shown, thermostat 36 is included in the controlling circuit.

switch 37 is rotated slightly in a counterclockwise direction. Assuming contact 12 in engagement with the segment 14, thermostat 35 is in the controlling circuit with switch 37 in the position shown. However, a slight rotation of switch 37 in the clockwise direction will serve to cut out thermostat 35 and cut in thermostat 36. In other words, with the switch 37 rotated from the position in which it is shown, slightly in the counterclockwise direction, the thermostat 35 is effective to control the heating apparatus with the contact 12 of the time switch engaging either of the segments 13 or 14. Conversely-with the switch 37 rotated slightly in the clockwise direction, thermostat 36 controls the heating apparatus at all times.

The embodiment of the invention illustrated and described herein has been selected for the purpose of clearly setting forth the purpose in volved. It will be apparent however, that the invention is susceptible of being modified to meet the different conditions encountered in its use and I therefore aim to cover by the appended claims all modifications within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is- 1. In a heat control device, a normally continuously energized operating electric motor, a circuit maker and breaker adapted to be operated by said electric motor, a day and a night thermostat individually operative for controlling operation of saidcircuit maker and breaker by said electric motor in accordance-with temperature conditions, and a timer continuously operated by said electric motor for rendering the day and the night thermostat operative at predetermined time intervals.

2. In a heat control means, a fuel supply motor, an ignition system therefor, a plurality of thermostats, a recycling device including an electric driving means, an adjustable time control switch for determining day and night operation of said thermostats and driven by said driving means, a circuit making and breaking means driven by said driving means for intermittently energizing the fuel supply motor and ignition system under the control of said thermostats.

3. In a control device, an electric time control means, a circuit making and breaking device, anelectro-responsive device to operate said circuit making and breaking device, a plurality of heat responsive devices adapted to separate 1y control said electro-responsive device and connections between said time controlled means and heat responsive devices to determine selective operation of said heat responsive devices at different' periods.

4. In a control device, an adjustable time control switch, an electric driving motor therefor, a circuit making and breaking means adapted to be interconnected with the motor for operation thereby, electro-responsive means for controlling the interconnection of the circuit making and breaking means with the motor, a plu rality of heat responsive devices for separately controlling the operation of said electro-responsive means, and connections between said time switch and heat-responsive devices'for selective- Then in case it is desired toplace the thermostat 35in the controlling circuit,

ly determining the separate operation of said heat responsive devices.

5. In a heat control system, a plurality of heat responsive means, a time control means for periodically determining individual operation of said heat responsive means, and a member for determining operation of said heat responsive means at any time and rendering said time controlled means ineffective.

6. In a heat control system, a night thermostat and a day thermostat, an adjustable time control switch for periodically determining the operative thermostat, and a switching means for rendering said time controlled means inefiective and determining the operative thermostat at any time.

7. In an oil burner control system, a continuously operating electric motor, an adjustable time control switch operated thereby, a fuel supply motor and an electrical system for igniting the fuel, a cam operated intermittent circuit mak ing and breaking device adapted'to be driven by said continuously operating motor and interconnected with said time switch for intermittently energizing said supply motor and ignition system, a day thermostat and a night thermostat selectively rendered operative by said time switch and electroresponsive means operating under the control of said thermostat to control the cam operated device to be driven by the motor and means operative upon establishing a flame for deenergizing the ignition system and maintaining said fuel supply motor energized.

8-. In an oil burner control system, a continuously operating electric motor, a fuel supply motor and an ignition system for igniting the fuel,

for causing operation of said cam operated de-' vice by said continuously operated motor, and means for deenergizing the ignition system and maintaining said motor in operation uponestablishing a flame, and means rendering the said cam operated device inoperative upon failure to establish a flame after a predetermined number of intermittent operations.

9. In an oil burner control system, a fuel supply motor and an electrical ignition system for igniting the fuel, a cam operated circuit making and breaking device for intermittently energizing said fuel supply motor and ignition system to establish combustion, a continuouslyoperating electric motor for'driving said cam operated circuit making and breaking device and normally disconnected therefrom, electroresponsive means for establishing operative connectionsbetween the continuously operating motor and the cam operated circuit making and breaking device, a day and a night thermostatic switch for controlling said electroresponsive means, an adjustable time switch driven by said continuously operated motor for selectively rendering the day and night thermostatic switch operative to control said electroresponsive means, combustion responsive means for controlling said electroresponsive means to disconnect said cam operated device from the continuously operating. motor, means controlled by said combustion responsive means for maintaining said fuel supply motor energized upon establishment of combustion and means rendering the cam operated device inactive upon failure to establish combustion after a predetermined number of intermittent operations.

10. In a heat control device, electrically operated heat control means, a normally continuously energized electric motor, switch mechanism for controlling the operation of said heat control means, a cam for intermittently operating said switch mechanism and adapted to be driven by said motor, a member supporting said cam and movable from one position to another position to establish driving connections between said motor and said cam, and thermostatic means for controlling the driving connections between the motor and cam responsively to predetermined temperature conditions.

11. A mechanical relay in a heat control device, comprising a normally continuously energized electric motor, a cam shaft, a cam on said cam shaft, means for supporting said cam shaft and movable from one position to another position to establish driving connections between said motor and said cam shaft, a circuit maker and breaker adapted to be intermittently operated by said cam when said driving connections are established, and a heat responsive means for controlling movement of said cam shaft supporting means to establish said driving connections in accordance with temperature conditions.

12. A mechanical relay in a heat control device, comprising a normally continuously energized electric motor, heat control means including a circuit maker and breaker, a cam adapted to be driven by said motor for intermittently operating said circuit maker and breaker, a cam shaft for supporting said cam and means for supporting said cam shaft and movable from one position to another position to establish driving connections between said motor and said cam shaft, and a thermostatic means for controlling movement of said cam shaft supporting means to establish the driving connections between said motor and said cam shaft responsive to predetermined temperature conditions.

13. In a, heat control means, means for feeding fuel, means for igniting said fuel, means for controlling said fuel-feeding means and said igniting means for initiating combustion, means including a timing motor for operating said controlling means intermittently until combustion occurs, and means operated by said timing motor for limiting the number of said intermittent operations to a predetermined number and for disabling said controlling means when combustion fails to take place after said, predetermined number of intermittent operations.

14. A heating device including electrically operated means for feeding fuel, an electrically operated igniter therefor, circuits for energizing said fuel-feeding means and said igniter, control means for said circuits having a rotatable timing cam for causing intermittent energization of said fuel-feeding means and said igniter to initiate combustion, a second circuit for said fuelfeeding means, means responsive to combustion conditions for operating said timing cam to open said first circuits, wherebyzsaid igniter is maintained deenergized, and for closing said second circuit to maintain said fuel-supply motor energized when combustion is established, and a temperature-responsive device movable between two positions and movable to one position under predetermined temperature conditions for control-= ling operation of said intermittent control means to initiate combustion and movable to another position under other predetermined temperature conditions for controlling said second circuit to deenergize said fuel-supply motor.

15. A heating device including electrically operated means for feeding fuel, an electrically operated igniter therefor, controlling means for intermittently energizing said fuel-feeding means and said igniter to initiate combustion, electromagnetic means for controlling operation of said intermittent controlling means, a second electromagnetic means forcontrolling energization of said first electro-magnetic means, temperature-responsive means responsive to predetermined temperature conditions for energizing said second electro-magnetic means, a combustion-responive device for deenergizing said first electro-magnetic means to cause deenergization of said igniter and for maintaining said fuel-supply motor energized, said temperature-responsive means deenergizing said second electro-magnetic means under other predetermined temperature conditions for deenergizing said fuel-supply means.

16. In a heating apparatus, means for feeding fuel, means for igniting the fuel, means for controlling said fuel-feeding means and said igniting means for initiating combustion, means for operating said controlling means intermittently, a counting mechanism associated with said intermittent operating means to be advanced from an initial position to a final position for limiting said intermittent operations to a predetermined number, and means responsive to combustion conditions for rendering said intermittent means ineffective, for maintaining said fuel feeding meansin operation and for resetting said counting mechanism to initial position when combustion is established 'before said counting mechanism reaches the final position.

17. In a heating apparatus, means for feeding fuel, means for igniting said fuel, means for controlling said fuel-feeding means and said igniting means for initiating combustion, timing means for operating said controlling means intermittently until combustion occurs, a counting meansoperated by said timingmeans andmovable from an initial position to a final position for limiting said intermittent operations to a predetermined numher, and combustion-responsive means for rendering said counting means ineffective, for maintaining said fuel feeding means in operation. and having electro-magnetic means associated therewith for causing resetting of said counting means to initial position when combustion is established.

18. In a heating apparatus, means for feeding fuel, means for igniting said fuel, means for controlling said fuel-feeding means and said igniting means for initiating combustion, timing means for operating said controlling means intermittently, means operated by said timing means and movable from an initial position to a final position fox-,limiting said intermittent operations to a predetermined number, electro-magnetic means operatively associated with said timing means and limiting means to control the same, and combustion-responsive means for controlling said electro-magnetlc means to render said timing means ineffective to operate said controlling means, for maintaining said fuel feeding means in operation, and for causing resetting of said limiting means to initial position when combustion is established.

19. In a heating apparatus, means for feeding fuel, ignition means therefor, a starting circuit for said fuel-feeding means, means for intermittently energizing said starting circuit. electromagnetic means associated with said intermittent means for controlling operation of said intermittent means, a second electro-magnetlc means associated with said first electro-magnetic means to control energization of said starting circuit by said intermittent means, means associated with said intermittent controlling means to be advanced from initial position to a final position for limiting said intermittent operations to a predetermined number, a running circuit for said fuel-feeding means, means responsive to combustion for causing said first electro-magnetic means to render said intermittent means ineffective, said combustion-responsive means cooperating with said second electro-magnetic means to close said running circuit upon establishing combustion, said first electro-magnetic means causing resetting of said limiting means upon operation of said combustion-responsive means when combustion is established.

20. In a control for a combustion heating device, the combination of thermostatic control means, atiming motor having cooperating electromagnetic. means controlled by said thermostatic means for intermittently establishing combustion conditions for the heating device and means jointly controlled by said timing motor and said electromagnetic means for limiting the intermittent establishment of combustion conditions to a predetermined number.

21. In a combustion heating device, the com bination, of electrically operated fuel supply means, an electric igniter for the fuel, a timing motor having electromagnetic circuit controlling means cooperating therewith for intermittently energizing said fuel supply means and said igniter to establish combustion conditions, thermostatic means for controlling said electromagnetic means, and counting means jointly controlled by said timing motor and said electromagnetic means for limiting the intermittent energizations of said fuel supply means and said igniter to a predetermined number.

22. In a fuel burner, the combination of a fuel supply motor, an electric igniter, switchmechanism for controlling said fuel supply inotor and igniter to initiate combustion, means including a constant speed motor driven timing device for intermittently operating said switch mechanism, and counting means operated by said timing device for rendering said switch mechanism ineffective after a predetermined number of intermittent operations.

. 23. In a combustion heating device, the combination of motor operated fuel supply means, electric ignition means therefor, switch mechanism for energizing said motor operated fuel supply means and said ignition means to initiate combustion, a motor driven rotary cam timing device having electromagnetic controlling means cooperating therewith for intermittently effecting operation of said switch mechanism, counting means operated by said timing device for rendering said switch mechanism ineffective after a predetermined number of intermittent operations, means responsive to combustion cooperating with said electromagnetic means for maintaining the motor operated fuel supply means continuously energized upon establishment of combustion, and temperature responsive means for controlling said electromagnetic means to initiate and terminate operation of said fuel supply means.

' 24. In a combustion heating device, the combination of a fuel supply motor, an electric igniter,

circuit controlling means including an electric motor driven rotary cam timing device having electromagnetic controlling means for intermittently energizing the fuel supply motor and igniter to establish combustion, thermostatic means for controlling said circuit controlling means, counting means operated by said timing device from an initial position to a final position for limiting the intermittent energizations of said fuel supply motor and igniter to a predetermined number when combustion is not established, and combustion responsive means for deenergizing the igniter upon establishing combustion and for maintaining the fuel supply trolling said electromagnetic means to terminate operation of said cam when combustion is established, and for maintaining said fuel feeding means continuously energized thereafter, and a thermostatic switch for controlling said electromagnetic switch to efiect operation of said intermittent means to establish combustion and to stop operation of said fuel feeding means after combustion is established in accordance with predetermined temperature conditions.

26. In a combustion heating device, electrically operated means for feeding fuel, and an electric igniter therefor, switch mechanism having an electric motor driven rotatable cam. for intermittently energizing said fuel feeding means and igniter to initiate combustion and having electromagnetic means for controlling the operation of said cam, an electromagnetic switch for energizing said electromagnetic means to initiate the operation of said cam, means responsive to combustion cooperating with said electromagnetic switch for controlling the energization f said electromagnetic means to terminate the op ration of said cam upon establishing combustion and for maintaining said fuel feeding means continuously energized independently of the rotatable cam when combustion is established, and thermostatic means for controlling the energization of said electromagnetic switch to initiate operationof said intermittent means under predetermined temperature conditions and to deenergize said fuel feeding means after combustion is established under other predetermined tempera- .magnetic means to effect deenergization of said ignition means and for maintaining said fuel feeding means continuously energized upon establishment of combustion, and a temperature responsive means for energizing said second electromagnetic means under predetermined temperature conditions to initiate combustion and for deenergizing said second electromagnetic means to stop operation of said fuel feeding means after combustion is established under other-temperature conditions.

28. A control device for an electrically driven burner, including electrically operated means for intermittently energizing said burner to initiate combustion, means for controlling energization of said intermittent energizing means, a thermostat movable between two positions, an electromagnetic device for operating said control means for said intermittent device, said electro-magnetic device being energized when said thermostat moves to one position, means operated by the electro-magnetic device when said electro-magnetic device is energized for shunting said thermostat, whereby said electro-ma gnetic device will remain energized when-said thermostat moves to an intermediate position, and means responsive to combustion conditions for causing deenergization of said intermittent energizing device and for maintaining said burner energized when combustion is established, said thermostat moving to the other position to deenergize said electrically driven burner.

29. A heating system including an electrically operated oil burner, means for intermittently energizing said oil burner to start the same, means for controlling operation of said intermittent means, a thermostat movable between two positions, an electro-magnetic device controlled thereby for operating said controlling means for said intermittent energizing means when said thermostat moves to one of said positions to energize said electro-magnetic device, means operated by said electro-magnetic device for shunting said thermostat after said thermostat has moved to said one position, whereby said electro-magnetic device will remain energized when said thermostat moves to an intermediate position, means responsive to combustion for rendering saidintermittent means ineffective with said burner energized when combustion is established, said thermostat moving'to said other position to stop the oil burner.

30. A heating system including an electrically operated oil burner, electrically operated means for intermittently energizing said oil burner to start operation of the same, means for controlling energization of said intermittent means, a thermostat movable between two positions, an electro-magnetic device controlled thereby for operating said controlling means for said intermittent means to intermittently energize said oil burner when said thermostat moves to one of said positions to energize said electro-magnetic device, means operated by said electro-magnetic device for shunting said thermostat after said thermostat has moved to said one position, whereby said electro-magnetic device will remain energized when said thermostat moves to an intermediate position, means responsive to combustion for causing deenergization of said intermittent means when combustion is established while said burner is energized whereby said burner will remain energized, said thermostat moving to said other position to deenergize said electro-magnetic means to stop the oil burner.

.31. A heating device including means for feeding fuel and an igniter therefor, a controlling means for controlling said fuel-feeding means and igniter to attempt to initiate combustion at predetermined temperature conditions, said controlling means including a constant-speed motoroperated timing cam mechanism for repeating the ignition attempts for periods of predetermined short duration at definite predetermined selected intervals, and means operated by said controlling means for limiting the number of ignition attempts and for rendering said control system ineffective when combustion fails to take place during the last attempt.

32. A heating device including means for feeding fuel, an igniter therefor, controlling means for controlling said fuel-feeding means and said igniter to attempt to initiate combustion, electroresponsive means including a constant-speed motor-operated timing cam mechanism for rendering said controlling means effective intermittently at definite predetermined selected intervals for periods of predetermined short duration, and means operated by said controlling means for limiting the number of intermittent operations and for rendering said control system in eifective when combustion fails to take place during the last time that said control means is rendered effective.

33. A heating device including electrical means for feeding fuel, an igniter for said fuel-feeding means,-an electrical control for energizing said fuel-feeding means and said igniter to initiate combustion, an electromagnetic means and a timing cam mechanism cooperating therewith for causing repeated operation of said control at deflnite predetermined selected intervals, means responsive to combustionfor cooperating with said electromagnetic means for maintaining said fuelfeeding means energized when combustion is established independently of the operation of said timing cam mechanism, temperatureresponsive means for rendering said electro-mag netic means effective under predetermined temperature conditions to causeenergization of said fuel-feeding means and igniter and for short-circuiting said electro-magnetic means under other predetermined temperature conditions to cause deenergization of said fuel-feeding means.

34. In combination a burner having an igniter, means'for feeding fuel thereto, electrical means for controlling said fuel-feeding means comprising a primary thermal control means operable at a plurality of different temperature ranges, a synchronous motor connected to a power source to be constantly energized, means operable by said motor toshift said primary control means to operate at selected temperature ranges at selected times, a timing device operated by said motor and means controlled by said timing device upon operation of the primary control means to control said fuel-feeding means.

35. A heating system including means for feeding fuel, means for igniting said fuel, means for controlling said fuel-feeding means and said igniter for attempting to initiate combustion in said heater, means including electro-magnetic means for operating said controlling means intermittently at predetermined intervals for a predetermined period of time, and means mechanically operated by said controlling means for limiting the number of said intermittent operations and for disabling said controlling means when combustion fails to take place.

36. A heating device including means for feeding fuel, an igniter therefor, of a control system comprising means for controlling said fuel-feeding means and said igniter to initiate combustion at predetermined temperatures, means including electro-magnetic. means for rendering said controlling means eifective for a predetermined period of time intermittently, and

means mechanically operated by said controlling means for limiting the intermittent operation of said electromagnetic means and for disabling said control system when combustion fails to take place.

37. The combination with a. heating system including means for feeding fuel, ignition means therefor, of a control system therefor comprising means for controlling said fuel feeding means and ignition means for attempting to initiate combustion, said means including a rotating timing motor for operating said controlling means to attempt to initiate combustion at recurring definite predetermined selected intervals, and counting mechanism associated with said controlling means and operable to disable said control system when combustion fails to take place after a predetermined number of attempts, said mechanism thereafter requiring a manual resetting to again render said control system effective.

38. The combination with a heating system including means for feeding fuel, an igniter therefor, of a control system therefor comprising means for controlling said fuel feeding means and igniter to attempt to initiate combustion, said means including a rotating timing motor for repeating said combustion attempts for periods of predetermined short duration at definite predetermined intervals, and counting mecha- 1

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