US2484008A - Fuel pressure responsive burner controlling apparatus - Google Patents

Description

Get. 11, 1949., F. B. AUBERT FUEL PRESSURE RESPONSIVE BURNER CONTROLLING APPARATUS Filed Nov 1, 1945 IN V EN TOR.

v ATTORNEY Patented Oct. 11, l949 FUEL PRESSURE RESPONSIVE BURNER CONTROLLING APPARATUS Fred B. Aubert, Detroit, Mich. Application November 1, 1945, Serial No. 626,034

This invention relates to newand useful improvements in apparatus for controlling the operation of fluid fuel burners.

An object of the invention is to provide means for stopping the supply of fuel to the burner upon extinguishment of the burner fiame.

Another object is to provide an apparatus in which burner operation is dependent upon predetermined fuel pressure.

Another object is to provide means by which the burner Operating motor is deenergized upon initial occurrence of flame and is reenergized by predetermined fuel spraying pressure.

Another object is to provide electron tube safety means for controlling burner operation.

Another object is to provide means to delay the start of burner operation until the safety means is conditioned for operation.

The invention consists in the cooperative relation and sequential operation of the parts of the apparatus, to be more fully described hereinafter, and the novelty of which will be particularly pointed out and distinctly claimed. 7

In the accompanying drawing, to be taken as a part of this specification, there is fully and clearly shown a preferred embodiment of the invention, in which drawing, the figure is a diagrammatic view of the fuel burner controlling apparatus. I

Referring to the drawing by characters of reference, l designates generally a heating apparatus such as a boiler or furnace having a burner 2 with a combustion air delivery tube 3 supplied with air by a fan 4 driven by an electric motor 5. A liquid fuel pump 6 is driven bythe motor 5 through suitable gearing and has its inlet connected to a fuel pipe '1 leading from a source of fuel such as a tank. The pump 6 discharges through a pipe 8 to a fuel nozzle 9 for spraying fuel into the air supplied by the tube 3. Ignition electrodes W are provided to ignite the discharging fuel and are supplied with current from the secondary coil of their ignition transformer II. The heating apparatus I is provided with the usual safety limit switch 12 responsive to temperature or pressure of the heat exchange medium in the boiler or furnace and operable to stopthe motor 5 at the desired maximum safe limit or temperature.

Connected into the fuel pipe 8 there is a pressure conveying pipe l3 connected to the pressure chamber 14 of a pressure responsive switch device l5. The chamber I l which 7 air is closed and sealed by a diaphragm [6 which is held against movement by pressure in the preferably contains 25 Claims. (Cl. 158-28) chamber M by a spring I! which exerts a pressure of say sixty pounds per square inch in opposition to movement of the diaphragm l6 by the chamber pressure. The pipe I3 is preferably a so called capillary tube and is of sufficiently small bore so as to delay the transmission of pressure from the pipe 8 to the diaphragm l 6. Further delay of pressure transmission to the diaphragm I6 is accomplished by the air cushion in the chamber I4. The diaphragm l6 actuates a switch operating rod 18 which may be of electric insulating material and which is operatively connected to snap acting switch arms l9 and 20 such that the arms are moved in unison. The arm l9 operates a normally closed switch 2| which controls the ignition transformer H and the circuit of a resistance heater 22 of a timer or warp switch 23. The arm l9 also controls the normally closed contacts of a tube relay controlling switch 24. Cooperable with the arm l9 there is a holding magnet 25 which is energized upon closure of a normally open switch 26 controlled by the arm IS. The arm 2!! controls a normally closed motor starting switch '21 and a normally open motor running circuit switch 28.

The motor 5 is energized from main line wires 29 and 30 of which the wire 30 is the ground wire. In the line wire 29 there is a switch 3| which is closed during the heating season and which is opened solely when it is desired to deenergize the entire control apparatus and burner. Connected across the main line Wires is the primary coil 32 of a. step down transformer 33 having a tube filament heating secondary coil 34 supplying say 6 volts and a control circuit secondary coil 35 supplying about 24 volts. Leading from one terminal of the coil 35 there is a lead wire 36 connected to one terminal of the relay operating coil 37 of a main relay control switch 38 which is normally open and controls the operation of the motor 5 and the ignition transformer I i. From the other terminal of the relay coil 3'! a lead wire 39 connects to the temperature responsive bimetal arm 40 of an automatic control switch 4| such as a room thermostat; The arm 40 cooperates with a fixed switch contact 4| connected by a lead wire 42 to one terminal of an electron tube 43 functioning as a time delay switch which has its other terminal connected by a lead wire 44 to a lead wire 45 which connects to the other terminal of the secondary coil 35. The tube 43 is preferably, as shown, an electron tube having its anode 46 connected to the wire 42 and having its cathode 41 which is heated by the filament 48, connected to the wire 44. The grids 49 are connected together and to the wire 42 by a Wire 59 so that the tube becomes conducting when the cathode 41 is heated to operating temperature by the filament 48. The filament 48 is connected by lead wires I and 52 to the lead wires 53 and 54 respectively, which are connected respectively to the end terminals of the transformer secondary coil 34. Connected between the wires 36 and 53 there is a fixed condenser 55. The tube 43 is of the same type or has the same energizing or cathode heating time as the electron control tube 56 which is preferably of the gas charged trigger type such as an R. C. A. No. 2051. The filament 51 is connected by lead wires 58, 59 to the transformer secondary coil 34 by the lead wires 53, 54 respectively. The tube 56 controls the circuit of the relay coil 69 of a double throw relay switch having a normally closed motor starting switch 6| and a normally open motor running and relay coil holding switch 62. The coil 69 has one terminal connected to the switch 62 by lead wires 63, 64 and to the fixed contact of the pressure operated switch 24 by lead wires 64, 65, 66. The other terminal of coil 69 is connected by a lead wire 61 to one terminal of a resistance 68 which has its other terminal connected by a lead 'wire 69 to the anode 19. The cathode TI is connected by a wire 12 to the filament wire 58 and thence through wire 53 and a wire 13 to the ground wire 39. The screen grid 14 is connected to one terminal of a resistor which has its other terminal connected by a lead wire 16 to the cathode lead wire 12. The other resistor terminal is also connected by a lead wire 11 to one terminal of a resistor 18 having its other terminal connected to ground, as at 19. A third lead wire 89 connects the other terminal of resistor 15 to one side of a fixed condenser 8| having itsother side connected by a lead Wire 82 to the relay coil wire 61. The control grid 83 is connected by a lead wire 84 to a lead wire 85 which is connected to the cathode 86 of a photo-electric cell 81 having its anode 86 connected to ground as at 89 by a lead wire 99. The cell 81 is housed and is provided with a sight tube 9I aimed at the area of the burner flame of the burner 2 so as to respond to the occurrence and failure of flame. The cell housing shields the cell 81 from response to any other light than that of the burner fiame. The control grid lead wire 84 is connected by a lead wire 92 to one side of a variable condenser 93 which has its other side connected by a lead wire 94 to the lead wire 45 which connects to the secondary coil 35 so that the control grid 83 is negatively biased. The shield grid 14 which has its negative bias determined by the resistor 15, determines the extent to which the control grid 83 must become more positive or less negative in order for the tube 56 to be conductive. The variable condenser 93 determines the extent of negative drain necessary upon conductivity of the photo-cell 81 in order to overcome the bias of the grid 83.

The timer or warp switch 23 is of the conventional type having normally closed contacts 95 movable to open position by a bimetal operating arm 96 heated by the resistance coil 22. lhe arm 96 is locked in open position by a spring pressed manually released latch member 91 which operates in the usual manner to hold the contacts 95 in position when they have been separated by the operation of the blade 96.

The operation of the control apparatus and '4 burner is as follows: The switch 3I is closed to place the control apparatus in operation. However the operating circuit for the main control switch 38 will only be completed after sufiicient time delay necessary to heat the filament 51 of the control tube 56 because the switch tube 43 requires the same heating time for its filament 48 as does the filament 51 before the circuit can be completed through the relay coil 31. Although this operation occurs at the beginning of a heating season upon closure of switch 3|, the primary purpose of the tube 43 is to assure sufficient warming up of the control tube 56 folllowing a main line current failure so that the burner motor cannot be started until the control tube '56 is properly responsive to occurrence of flame at the burner. Assuming that the tube 43 has heated up sufiiciently to be current conductive then upon a call for heat by the room thermostat which closes switch M, the relay coil 31 will be energized to close the main switch 38 by the following circuit; from the secondary coil 35 through wire 36 to coil 31 thence through wire 39, closed switch 4| and wire 42 to the anode 46 and thence through the tube 43 to the cathode 41 and by lead wires '44, 45 back to the transformer coil 35. Closure of the main switch 38 will start operation of the burner motor 5 through the closed limit switch I2, timer switch and starting switches 6| and 21 by the following motor starting circuit: from line wire 29 through closed switch 3I and wire 98 to the closed limit switch l2, thence by lead wire 99 to the closed timer switch 95, from timer switch blade 96 via lead wire I99 to the fixed contact of main switch 38 thence through wires I91 and I92 to the switch arm of the tube relay closed starting switch 6|, through wire I93 to the fixed contact of starting switch 21, from the switch blade 29 via lead wire I94 to one terminal of the motor 5 and from the other motor terminal via wire I95 to the wire 39 which is at ground potential. Closure of the main switch 39 also closes the ignition transformer circuit simultaneously with the closure of the motor starting circuit, the ignition circuit being as follows: From switch 38 and lead wire I9I through lead wire I96 to switch arm I9, through closed switch 2| to lead wire I91 and thence through lead wire I98 to one terminal of the ignition transformer primary coil I99 having its other terminal connected by wire III) to the wire 39. Main switch 38 also simultaneously closed the circuit for the timer switch resistance heater 22 via the following circuit: from switch 38 via lead wires I9I, I96, switch 2I, lead wire I91 and lead wire III to one terminal of the heater coil 22 and from the other coil terminal via wire NZ to the wire 30. Switch 36 also prepared the tube relay circuit for current flow upon the tube 56 becoming conductive in response to occurrence of flame at the burner. Operation of the motor 5, due to closure of switch 38, drives the pump 6 to build up pressure in the nozzle supplying pipe 8 and as soon as the pressure is suflicient, at say forty pounds per square inch, to discharge an ignitable spray of fuel, the spark ignition occurring between the electrodes I9 will ignite the fuel. Instantly that flame occurs at the burner, the photo-cell 81 will become conductive thereby driving the control grid 83 sufficiently toward positive so that the tube 56 becomes conductive. Instantaneously with the occurrence of flame, the relay coil 69 will therefore be energized through the following circult: from main switch 38 through Wires I9I, I96,

switch arm I 9, closed'switch 24, wires 66, 65-and 64 to the coil 60 and thence via wire 61, resistor 68,.wire 69 to anodelll, through the tube 56' to cathode II and via wires 12,58, 53 and 13 to the wire 30. Energization of coil 60 breaks the motor starting circuit at switch 6| and closes switch 62 preparatory to closure of switch 28 to complete the running circuit of the motor. Closure of switch 62 has closed the holding circuit for the coil 60 through the tube 56, this circuit being from main switch 38 through wires lfll and H32 to the now closed switch 62 and thence via wires 63 and 64 to the coil 68 from which; the circuit continues through the tube 56 to the wire 36, as above described. Assuming that the pump, 6 is operating normally, the build up of pressure in the pipe 8 from the forty pounds per square inch at which flame occurred to the minimum safe operating fuel pressure of say sixty pounds per square inch will occur in about one second or less and this occurrence of operating pressure will, even though delayed by the resistance of the tube l3 and the air cushion in chamber l4, actuate the snap acting switch arms I9 and 20 preferably within one second from the time of opening of the motor starting switch 6|. Although the motor is deenergized during this interval after opening of switch 6|, the motor inertia is sufiicient to maintain and build up pressure so that the flame will not become extinguished in normal operation. Operation of the switch device I 5 closes the motor running switch 28 so that the motor 5 is reenergized through the following'circuit: from main switch 38 via wires -||l|, I02 to closed switch 62, wires 63, 65 and H3 to the now closed running switch 28, then via switch blade 20 and wire N14 to one terminal of the motor 5 which has its other terminal connected by wire I05 to the wire 30. Operation of the switch device |5 also opens the switch 2| to break the circuit to the ignition transformer primary coil I69 and to the timer resistance heater 22. In addition, the operation of the switch arm I 9 opens the switch 24 to break the first circuit through lead wires 66, 65 and 64 to the tube relay coil 60 which however is maintained energized as above described through the now closed switch 62. The switch arms l9 and 28 are held in their pressure operated position by the holding magnet 25 which is cooperable with the switch arm [9, the magnet 25 being energized by closure of switch 26 through the following circuit: from switch 38 via wires ll, I05, switch arm I9, closed switch 26, wire H4 to the magnet coil 25 andthence via wire H5 to the wire 38. The burner motor 5 will now continue in operation to heat the apparatus I until the main switch 38 is opened by opening of the control switch 4|. Should there be a failure of flame during normal burner operation after the pressure switch device |5 has functioned to close the circuit of the magnet holding coil 25, the electron control tube 56 will be instantly blocked against current flow between the anode and cathode by the control grid 83 thereby deenergizing the relay coil 60 so that the switch 62 will be opened and the switch 6| will be closed. Opening of switch t2 breaks the circuit through which the coil 66 was maintained energized and since the. first circuit at switch 24 through which the coil so was originally energized is held broken by the magnet coil 25, the motor circuit cannot be re-established even though there might be a reoccurrence of flame at the burner. If, during burner starting operation, flame does not occur before pressure builds up in the pipe 8 to the minimum desired sixty pounds spraying pressure, then the switch device l5 will open the motor starting circuit at the switch 21 and also break the energizing circuit for the tube relay coil 60 at the switch 24 and since the magnet 25 i simultaneously energized by closure of switch 26, the motor circuit will be held open until the main switch 38 is opened to deenergize the magnet-coil 25. If, when there is a call for heat, pressure does not build up to the minimum desired operating pressure within the time limit of say sixty seconds required for operation of the safety warp or timer switch 23, then the contacts will be opened and locked open by the latch 91 thereby breaking the motor circuit and preventing starting of the burner motor until the reset button H6 has been actuated to release the bimetal arm 26 for reclosure of the contacts 95. When the switch 4| is opened as will occur when the room thermostat is satisfied by the ambient temperature reaching the desired degree, the coil 31 will be deenergized thereby opening the main switch 38 to deenergize the burner. The opening of switch 38 will deenergize the holding coil 25 so that the switches of the pressure device l5 return to the position shown in the drawing and will also deenergize the relay coil 66 so that the switches 6| and 62 return to their shown position, thus placing the system in condition for a new cycle of burner operation when the switch 4| is again closed.

What is claimed and is desired to be secured by Letters Patent of the United States is:

1. A liquid fuel burning apparatus, comprising a burner, a pump for supplying liquid fuel under pressure to the burner, a motor for driving said pump, a starting circuit for said motor, meansto close said circuit, means to ignite the fuel discharged at said burner, means instantly acting upon occurrence of flame at said burner to break said starting circuit, a running circuit for said motor, two open switches in said running circuit, said instantly acting means acting also to close one of said two switches, and means responsive to predetermined fuel pressure and operable to close the other of said running circuit switches to establish current flow through said motor. a

2. A liquid fuel burning apparatus, comprising a burner, a pump for supplying liquid fuel under pressure to the burner, a motor for driving said pump, a starting circuit for said motor, a pair of normally closed switches in said circuit, a running circuit for said motor, a pair of normally open switches in said running circuit, a switch controlling current flow to said circuits, means to ignite the fuel discharged at said burner, means instantly acting upon occurrence of flame at said burner to open one of said normally closed switches and to close one of said normally open switches, and means responsive to predetermined fuel pressure and operable to open the other of said normally closed switches and to close the other of said normally open switches.

3. A liquid fuel burning apparatus, comprising a burner, a pump for supplying liquid fuel under pressure to the burner, a motor for driving said pump, a starting circuit for said motor, means to close said circuit, means to ignite the fuel discharged at said burner, a relay switch having normally closed contacts in said starting circuit, electron tube control means instantly acting upon occurrence of flame at said burner .76 to actuate said relay switch to break said start mg circuit-a running circuit for said motor, an open switch in said running circuit, means responsive to predetermined fuel pressure and operable to close said running circuit switch; and means operable, upon actuation of said pressure responsive means, to hold said running circuit switch closed independently of said pressure responsive'means. l

4. A liquid fuel burning apparatus, comprising a burner, a pump for supplying liquid fuel under pressure to said burner, a motor for driving said pump, means to ignite the fuel discharged at said burner, a starting circuit for said motor, means to close said circuit, a running circuit for said motor, a pair of normally open switches in said running circuit, means instantly acting upon occurrence of flame at said burner to break said starting circuit and to close one of said running circuit switches, fuel pressure operated means to close the other of said running circuit switches; and means operable, upon actuation of said pressure responsive means, to hold said other running circuit switch closed independently of said pressure operated means.

'5. A liquid fuel burning apparatus, comprising a burner, a purnp for supplying liquid fuel under pressure to said burner, a motor for driving said pump, means to ignite the fuel discharged at said burner, a starting circuit for said motor, means to close said circuit, a running circuit for said motor, a pair of normally open switches in said running circuit, means instantly acting upon occurrence of flame at said burner to break said starting circuit and to close one of said running circuit switches, fuel pressure operated means to close the other of said runningcircuit switches, a switch in said starting circuit and opened by said fuel pressure operated means, and means to hold said last-named switch open so that flame failure will not restart said motor.

6. A liquid fuel burning apparatus, comprising a burner, a pump for supplying liquid fuel under pressure to said burner, a motor for driving said pump, means to ignite the fuel discharged at said burner, a starting circuit for said motor, a running circuit for said motor, relay switch means having a closed switch in said starting circuit and an open switch in said running circuit, first and second circuits for energizing said switch means, said open switch controlling said second switch means energizing circuit, an electron tube responsive to burner flame and blocki-ng current flow through said first and said second switch means energizing circuits, a switch controlling current flow through said circuits, a closed switch in said first switch means energizing circuit, means cooperable with said tube and instantly acting upon occurrence of a burner flame to render said tube conductive thereby to energize said switch means to .open said closed starting circuit switch and to close said open running circuit switch, a second closed switch in said starting circuit, means responsive to predetermined fuel pressure and operable to open said second-named closed switch and said lastnamed switch; and means operable, upon actuation of said pressure responsive means, to hold open said second-named closed switch and said last-named switch.

7. A liquid fuel burning apparatus, comprising a burner, a pump for supplying liquid fuel under pressure to the burner, a motor for driving said pump, a'starting circuit for said motor, an ignition means circuit in parallel with said starting circuit, electric ignition means in said ignition means circuit and operable to ignite the fuel discharged at said burner, a closed controlling switch in said parallel ignition means circuit, a. main switch operable to close said starting circuit and said ignition means circuit, a switch in said parallel starting circuit, means instantly acting upon occurrence of a burner flame to open .said last-named switch to break said starting circuit, a running circuit for :said motor, an .open switch in said running circuit, and means responsive to predetermined fuel pressure and operable to close said running circuit switch and to open said ignition means controlling switch.

:8. A liquid fuel burning apparatus, comprising a burner, a pump for supplying liquid fuel under pressure to the burner, a motor for driving said pump, a starting circuit for said motor, means to ignite the fuel discharged at said burner, electric timing means having a switch controlling current flow to said motor and having a controlling circuit, a closed switch in said controlling circuit, a main switch to close said starting circuit and said controlling circuit, means instantly acting upon occurrence of a burner flame to open said starting circuit, .a running circuit for said motor, two open switches in said running circuit, said instantly acting means acting upon occurrence of flame to close one .of said two switches, and means responsive to predetermined fuel pressure and operable to close the other of said running circuit switches and to open said closed controlling circuit switch.

9. A liquid fuel burning apparatus, comprising a burner, a pump for supplying liquid fuel under pressure to the burner, a motor for driving said pump, a starting circuit for said motor, electric ignition means for the fuel discharged at said burner and having an energizing circuit, elec-- tric timing means having a switch controlling current flow to said motor and having a controlling circuit, a closed switch in said energizing circuit and in said controlling circuit, a main switch to close said starting circuit, to close said energizing circuit for said ignition means and said controlling circuit, means instantly acting upon occurrence of a burner flame to open said starting circuit, a running circuit for said motor, an open switch in said running circuit and closed by said instantly acting means, a second open running circuit switch, and means responsive to predetermined fuel pressure and operable to close said second-named running circuit switch and to open said closed controlling and energizing circuit switch.

'10. A liquid fuel burning apparatus, comprising a burner, a pump for supplying fuel under pressure to said burner, an electric motor for driving said pump, a starting circuit for said motor, a running circuit for said motor, an ignition circuit having burner igniting electrodes, a relay switch coil energizing circuit, a relay switch coil holding circuit, a warp switch heater circuit, a holding magnet circuit, a main relay switch controlling all of said circuits, a relay switch having closed contacts in said starting circuit and open contacts in said coil holding and running circuits and having its coil in said coil energizing and holding circuits, an electron tube responsive to burner flame and in said coil energizing and holding circuits and having a control grid blocking current flow therethrough, means instantly acting upon occurrence of flame at said burner to render said grid sufiiciently positive for current flow through said tube, a pressure switch responsive to fuel pressure and having closed contacts in said starting circuit and open contacts in said running circuit, said pressure switch having closed contacts in said coil energizing circuit and in said ignition and heater circuits and having open contacts in said magnet circuit, a holding magnet in said holding magnet circuit and operable to hold said pressure switch in pressure actuated position, a warp switch controlling current flow to the switch contacts of said main relay switch and having a resistance heater in said heater circuit, and a control switch in circuit with the coil of said main relay switch.

11. A liquid fuel burning apparatus, comprising a burner, a pump for supplying fuel under pressure to said burner, an electric motor for driving said pump, a starting circuit for said motor, a running circuit for said motor, an ignition circuit having burner igniting electrodes, a relay switch coil energizing circuit, a relay switch coil holding circuit, a warp switch heater circuit, a holding magnet circuit, a main relay switch controlling all of said circuits, a relay switch having closed contacts in said starting circuit and open contacts in said coil holding and running circuits and having its coil in said coil energizing and holding circuits, an electron tube responsive to burner flame and in said coil energizing and holding circuits and having. a control grid blocking current flow therethrough, means instantly acting upon occurrence of flame at said burner to render said grid sufiiciently positive for current flow through said tube, a pressure switch responsive to fuel pressure and having closed contacts in said starting circuit and open contacts in said running circuit, said pressure switch having closed contacts in said coil energizing circuit and in said ignition and heater circuits and having open contacts in said magnet circuit, a holding magnet in said holding magnet circuit and operable to hold said pressure switch in pressure actuated position, a warp switch controlling current flow to the switch contacts of said main relay switch and having a resistance heater in said heater circuit, a control switch in circuit with the coil of said main relay switch, and means maintaining said last-named circuit open until said electron tube is at operating temperature.

12. A fuel burning apparatus, comprising a burner, a conduit for supplying fuel to said burner, means responsive to fuel pressure in said conduit, electrically energized means controlling the supply of fuel through said conduit, a circuit for initially energizing said electrically energized means to supply fuel, means to ignite the fuel discharged at said burner, means instantly acting to break said circuit upon occurrence of flame at said burner, an operating circuit for said energized means, and two open switches in said operating circuit, said instantly acting means acting also to close one of said two switches, said responsive means acting to close theother of said two switches to establish current flow through said operating circuit to said energized means; and means operable, upon actuation of said pressure responsive means, to hold said other switch closed independently of said responsive means. v

13. In a liquid fuel burning apparatus, a

burner, a pump for supplying fuel under pressure to said burner, a motor for driving said pump,

means to ignite the fuel discharged at said burner, a motor startingcircuit, amotor running circuit, relay switch means having a normally closed switch in said starting circuit and a normally open switch in said running circuit and operable when energized to open said closed switch and to close said open switch, first and second energizing circuits for energizing the coil of said relay switch means, said second coil energizing circuit being closedupon energization of said relay coil and maintaining said relay coil energized upon breaking of said first coil energizing circuit, electron tube control means blocking current flow through said first and said second coil energizing circuits and instantly acting upon occurrence of flame to permit current flow through said first coil energizing circuit, and means operable by predetermined fuel pressure to open said first coil energizing circuit and to close said running circuit.

14. A liquid fuel burning apparatus, comprising a burner, a pump for supplying liquid fuel under pressure to the burner, a motor for driving said pump, a starting circuit for said motor, means to close said circuit, means to ignite the fuel discharged at said burner, means instantly acting upon occurrence .of flame at said burner to break said starting circuit, a running circuit for said motor, two open switches in said running circuit, said instantly acting means acting also to close one of said two switches, means responsive to predetermined fuel pressure and operable to close the other of said running circuit switches to establish current flow through said motor, and means operable, upon actuation of said pressure responsive means, to hold said other running circuit switch closed independently of said pressure responsive means.

15. A liquid fuel burning apparatus, comprising a burner, a pump for supplying liquid fuel under pressure to the burner, a motor for driving said pump, a starting circuit for said motor, a pair of normally closed switches in said circuit, a running circuit for said motor, a pair of normally open switches in said running circuit, a

switch controlling current flow to said circuits, means to ignite the fuel discharged at said burner, means instantly acting upon occurrence of flame at said burner to open one of said normally closed switches and to close one of said normally open switches, means responsive to predetermined fuel pressure and operable to open the other of said normally closed switches and to close the other of said normally open switches, and means operable, upon actuation of said pressure responsive means, to hold said other running circuit switch closed independently of said pressure responsive means.

16. A liquid fuel burning'apparatus comprising a burner, means for supplying liquid fuel under pressure to said burner, electrical circuit means for controlling said fuel supply means and comprising an initial circuit and an operating circuit, a closed switch in said initial circuit, an open switch in said operating circuit, means responsive to the pressure of fuel flowing from said fuel supply means to said burner and operable to open said initial circuit switch and to close said operating circuit switch, releasable means operable, upon actuation of said pressure responsive means, to hold said operating circuit switch closed independently of said pressure responsive means, and means to return said switches to their initial positions upon release of said holding means.

17. A liquid fuel burning apparatus comprising a burner, means for supplying liquid fuel under ,pressure to said burner, electrical circuit means i9! controlling said fuel supply means and comprising an initial circuit and an operating circuit, means to control said initial circuit, an open switch in said operating circuit, means responsive to the pressureof fuel flowing from said fuel supply means to said burner and operable to close said operating circu't switch, means to hold said operating circuit switch closed inde-- pendently of said pressure responsive means, and said holding means including a circuit subject to the control of said initial circuit controlling means.

18. Means for controlling" the operation of a fuel supply pump for a liquid fuel burner comprising starting circuit means having a normally closed switch, running circuit means having a normally open switch, means responsive to fuel pressure, means operable by said responsive means at a predetermined pressure to open said starting switch and to close said running switch; releasable means operable, uplon actuation of said pressure responsive means, to hold said switches in responsive means actuated position irrespective of decrease of pressure below said predetermined pressure, and means to return said switches to their initial positions upon release of said holding means.

19. Means for controlling the operation of a fuel supply pump for a liquid. fuel burner comprising starting circuit means having a normally closed switch, running. circuit means having a normally open switch, aswitch controlling said starting and said circuit means, means responsive to fuel' pressure, means operable by said responsive means at a predetermined pressure to open said starting switch and to close said running switch,,means operable to hold said switches in responsive means actuated position irrespective of decrease of pressure below said predetermined pressure, and said holding means including a. circuit responsive to the. control of said control switch.v

20. Means for controlling the operation of a fuel supply pump for a liquid fuel burner comprising starting circuit means having a normally closed switch, running circuit means having a normally open switch, holding circuit means having a normally open switch and a. relay coil, means responsive to fuel. pressure and. operable at a predetermined pressure to open said starting switch and to close said running switch and said holding switch, and said relay coil. being operable upon: closing of said holding switch to hold said holding switch and saidrunning switch inpressure actuated position irrespective of decrease of fuel pressure below said predetermined pressure.

21-. Means for controlling the operation of a fuel supply pump tor a liquid fuel burner comprising startingcircuit means having a normally closed switch, running circuit means having a normally openswitch, holding circuit means having a normally open switch and a relay coil, a control switch controiling said circuit means, means responsive to fuel pressure and operable at apredetermine'd pressure: to-open said starting switch and to close said running switch and said holding switch, saidrelay coil being operable upon closing ofsaid holding switch to hold said holding switch and said run-ning switch in pressure actuated position irrespective of decrease of fuel pressure below said predetermined pressure, and said control switch controlling said holding circuit means so that upon opening said control switch said relay coil may be deenergized 12 to release said switches to thecontrol of saidpressure responsive means.

22. Means for controlling. the operation of a fuel pump and an electric ignition for a liquid fuel burner comprising a pumpstarting circuit, an ignition circuit, a pump running. circuit, closed switches in said starting and ignition circuits, on open switch insaid running circuit, means responsive to fuel pressure and operable at a predetermined pressure: to open said starting and ignition circuit switches and to close said running circuit switch;' releasable means operable, upon actuation of said pressure responsive means, to: hold said running circuit switch closed irrespective of drop. in fuel pressure below said predetermined pressure, and spring means for opening: said running circuit switch upon release of said holding means;

23. Means for controlling the operation of a fuel pump and an electric ignition for a liquid fuel burner comprising a starting circuit having a normally closed switch, an ignition circuit-havinga normally closed switch, a running circuit having a normally open switch, a holding circuit having a normally open switch and a relay coil, means responsive to: fuel pressure and operable atapredetermined pressure to open said starting and ignition circuit switches and to close said running and holding circuit switches, and said relay coil being operable upon closing of said holding circuit switch to hold said holding circuit switch and said running circuit switch closed irrespective of drop in fuel pressure. below said predetermined pressure.

24. Means for controlling the operation of a fuel pump and an electric ignition for a liquid fuel burner comprising a starting circuit, a running circuit, an ignition circuit, a holding circuit, a control switch for controlling energization of all of said circuits, a relay switch having a pair of closed contacts in said starting circuit and a pair of open contacts in said running circuit, a circuit for the coil of said relay switch including an electron tube adapted for control by a flame-responsive photo-electric cell so that said relayswitch maybe responsive to the occurrence of flame at the burner, a second closed switch in said starting circuit, a second open switch in said running circuit, a closed switch in said ignition circuit, an open switch in said holding circuit, a fuel pressure responsive means operable at a predetermined pressure to open said second starting switch and said ignition switch and to close said second running switch and said holding switch, a relay coil in said holding circuit operable to be energized by closing of said holding switch and operable to hold said holding switch and said second running switch closed irrespective of drop in fuel pressure below said predetermined pressure, and said firstnamed control switch controlling said holding circuit so that upon opening of said control switch said relay coil may be deenergized and thereby releasing said last-named switches to the control of said pressure responsive means.

25. A liquid fuel burning apparatus comprising a burner, means for supplying liquid fuel under pressure to said burner, electrical circuit means for controlling said fuel supply means and comprising an initial circuit and an operating circuit, means responsive to the occurrence of flame at said burner and operable to control said operating circuit, a switch spring biased to open position in said operating circuit, means responsive to the pressure of fuel flowing from said fuel 13 supply means to said burner and operable to close said operating circuit switch, and means, operable upon actuation of said pressure responsive means, to hold said operating circuit switch closed against its opening bias independently of said pressure responsive means and in cooperation with said flame responsive means to establish said operating circuit.

FRED B. AUBERT.

REFERENCES CITED The following references are of record in the file of this patent:

Number McIlvaine Mar. 6, 1945

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