US3032098A - Oil burner control - Google Patents

Description

May 1, 1962 J. E. WILDER OIL BURNER CONTROL Filed Dec. 12, 1958 semi l I 7396791405747 I (04/605 770/1/ FfSRQ/VS/ l f 7715911057217 6%, m ilzzm ,lifarrzggs.

United States Patent Office 3,032,098 Patented May 1, 1962 3,032,098 OIL BURNER CONTROL Justin E. Wilder, Goshen, ImL, assignor to Penn Controls, Inc, Goshen, Ind., a corporation of Indiana Filed Dec. 12, 1958, Ser. No. 780,051 3 Claims. (Cl. 158-28) This invention relates generally to oil burner controls, and particularly to constant ignition oil burner controls adapted for controlling portable space heaters or the like.

In the curing of concrete in building structures it is conventional to utilize portable oil burning space heaters referred to as salamanders. These burners are required to operate for extended periods without attention, and in dust laden atmospheres. Control circuits utilized in controlling the operation of these salamander heaters must meet several requirements among them provision for a purge or scavenger operation of the burner fan at the end of a burner on-period until the combustion chamber is cooled and purged of products of combustion. Further, the switches in the circuit and the controlling thermostat should preferably be of the line voltage type so that their contacts will be less sensitive to accumulation of dust.

It is an object of the present invention to provide a control circuit for oil fired salamander type heaters in oil valve 12, by means of a wire 23. A wire 24 connects the'wire 22 and the wire 16, this connection being at a point intermediate of the switch R1, and the burner and ignition means. A wire 26 connects the wire 17, intermediate the switch SS and the switch P3 to one side of the primary coil 27 of a step-down transformer 28, the other side of the primary coil being connected to the lead wire 14.

The secondary coil 29 of the transformer is connected by means of a wire 31 to one side of an electrical resistance heater P, which when heated operates the switches P1, P2 and P3, and thereby functions as a purge or warp switch heater. The other side of the heater P is connected by means of a wire 32 to one side of a closed hot combustion responsive switch CH. The other side of the switch CH is connected to one side of a closed cold combustion responsive switch CC. The switches CC and CH may be operated by means of a suitable linkage from a combustion temperature responsive element, such as helical bimetal 30. The wire 32 further connects the other side of a the switch CC to one side of an electrical safety switch heater SSH, the safety switch heater being connected by which the majority of the switch contacts in the circuit,

including the thermostat contacts, are line voltage.

A further object of the present invention is to provide a control circuit of the type referred to above, providing a timed purge period in which the burner motor fan is maintained in operation subsequent to opening of the means of a wire 33 to the other side of the transformer secondary coil 29. A wire 34 connects an electromagnetic coil R to the wire 31, the other side of the relay coil being connected by means of a wire 36 to an intermediate tap 37 on the transformer secondary coil 29 through the normally open relay switch R2. A wire 38 connects the juncture of the relay coil R and the switch R2 to the commonsides of the switches CH and CC;

It will be understood that the warp switch assembly provided by the heater P, and the switches P1, P2 and P3 operated thereby, is of a conventional type, wherein the heater raises the temperature of a bimetal member controlling the position of one of the contacts of each of the switches; The switches P2 and P3 are preferably operated with a-snap-action, but need not-be of the overlapping Referring to the drawing, the circuit shown controls a conventional oil burner indicated schematically at 10, the burner being provided with a fan which drives air through the combustion chamber. The burner construction per se forms no part of the present invention, and its structure is therefore not shown in detail.

Co-operating with the burner is a conventional ignition means 11, which also is of conventional type and may include an ignition transformer and spark electrodes. An oil supply valve is indicated at 12, and this valve may take the form of a normally closed, solenoid-operated valve controlling the supply of oil to the burner 10, the solenoid valve being of a conventional type.

The circuit for controlling these elements includes power supply Wires 13 and 14, which may be connected to a suitable line voltage source of electrical power. A wire 16 connects the burner and ignition means to the power lead 13, and has interposed therein a relay switch R1. A wire 17 connects the space temperature responsive thermostat 18 to the wire 13, and further connects the normally closed contacts of a safety switch SS in series with the thermostat. The wire 17 further connects in series therewith the normally open contacts of a purge or warp switch P3, and the solenoid actuator for the oil valve 12. The oil valve, ignition means and burner are connected to the lead wire 14 by means of a wire 19. A wire 21 connects one side of a normally open warp switch P1 to the wire 13. A wire 22 electrically connects the other side of the switch P1 to one side of a normally closed warp switch P2. The other side of the switch P2 is connected to the wire 17 intermediate the switch P3, and the type. The relay coil R operates switches Rland R2 and moves them to closed position when energized. The safety switch assembly comprising the heaterSSH and the switch SS is of a conventional type wherein, uponthe heater being energized for a pre-determined time the switch SS is latched open by a latch L and is not reclosed upon deenergization of the heater, but must be manually reclosed on reset. The switches CH and C0 are of a conventional type operated by a stack temperature responsive element, usually in the form of a bimetal helix, which responds upon a rise in stack temperature at the burner to operate the switch.

In operation, with the circuit components in their position shown in the drawing, the circuit to the transformer 28 is broken at the thermostat 18, and the relay coil R is consequently in a de-energized state. Switch R1 is open and the burner, ignition means and oil valve are consequently de-energized. Upon a call for heat evidenced by closure of the thermostat 18, a circuit will be completed to the primary coil 27 of the transformer 28, which may be traced from the wire 13, through thermostat 18, switch SS and wire 26. Completion of the circuit to the transformer provides power to the relay coil R by a circuit which may be traced from one side of a secondary coil 29, through wire 33, heater SSH, switch CC, wire 32, wire 38, wire 36, relay coil R, wire 34, and via. wire 31 back to the secondary coil 29.

Energization of relay coil R closes the holding switch R2 and also closes the burner controlling switch R1. This energizes the burner and ignition means, and, through wires 24, 22, switch P2 and wire 23, also opens the oil valve 12. Ignition of the oil thereupon occurs, raising the temperature of the heater stock. It will be noted that upon closure of thermostat 18 and energization of transformer secondary coil 29, the heater SSH is also energized and the purge heater P remains de-energized since the circuit thereto is broken at switch CH. Normally the safety switch assembly is adjusted so that the heater SSH will open the switch SS approximately one and one-half minutes after it is energized.

In a normal operating cycle, prior to the termination of this one and one-half minute period, the switch CC will be moved to open position. Response to an increase in stack temperature will subsequently move the switch CH to closed position, energizing the purge heater P. A timed period after energization of this heater, the switches P1 and P3 will be closed and simultaneously the switch P2 will be opened. Closure of switch P3 maintains the valve 12 open even though switch P2 is opened. Switches P2 and P3 are operated simultaneously, with a snapaction, but need not overlap since a momentary de-energization of the actuator for valve 12 has no detrimental effect on the burner operation.

When the thermostat 18 is satisfied, its contacts will open, closing the oil valve 12 and de-energizing the transformer 28 and consequently relay coil R. This opens switch R1, however, even though switch R1 is opened, the burner motor fan will be maintained in operation through a circuit which may be traced from wire 13, through wire 21, switch P1 and wire 24. This purging operation of the burner motor will be maintained for a period timed by the cooling of the heater P sufiiciently to open switch P1. Cooling of heater P also resets the switches P2 and P3 to their original positions. With this cooling of heater P an operating cycle of the burner is completed. When the temperature of the enclosure being heated again falls below the control point of the thermostat, another burner cycle will be initiated.

In the event of ignition failure, that is, failure of the coil to ignite at the start of a burner on-period, the switch CC will remain closed and the heater SSH will open the safety switch SS, shutting the oil valve 12 and de-energizing transformer 28 and relay coil R to shut down the burner motor and the ignition means. In the event of flame failure mid-way in the burner on-period, the switch CC will reclose energizing safety switch heater SSH to subsequently open the safety switch SS to close oil valve 12.

It should be noted that the arrangement whereby the actuator for the oil valve 12 is energized at the start of a burner on-period through switch R1 and is de-energized immediately upon opening of the thermostat provides a means whereby the energization and de-energization of the oil valve actuator is simultaneous with the closing and opening of the thermostat if, and only if, the relay coil R is energized. This provides a safety factor in that relay R cannot be energized upon closing of the room thermostat unless the stack temperature responsive switch CC has moved to its closed position after the termination of the preceding burner on-period, thus giving an indication that the stack temperature responsive switch is in proper operating condition for the next burner on-period. The arrangement is thus such that valve 12 cannot be opened unless the burner motor is also energized.

The circuit arrangement is such that the majority of the controlling switches, including the thermostat, are in the line voltage portion of the circuit and are thus less susceptible to fouling by dust. The relay coil and heaters P and SSH are low voltage components and thus are of less costly construction.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as other modifications may readily suggest themselves to persons skilled in this art and within the broad scope of the invention, reference being had to the appended claims.

The invention claimed is:

, l. A control circuit for an electric motor operated fluid fuel burner of the constant ignition type adapted for line voltage network including a main burner switch con-' trolling the application of line voltage to the burner motor, a second line voltage network including a space temperature responsive thermostatic switch, a normally closed safety switch and primary coil of a stepdown transformer all serially connected, a combustion responsive element, a first switch actuated by said element which is closed in the absence of combustion at said burner, a second switch actuated by said element which is closed in the presence of combustion at said burner, an electromagnetic operator for said main burner switch, a thermalelectric operator for said safety switch, a warp switch heater, a low voltage circuit network including a starting circuit comprising said safety switch operator, said first switch actuated by said element and said electromagnetic operator all serially connected across the secondary coil of said transformer, a holding circuit for said electromagnetic operator comprising a holding switch operated by said electromagnetic operator connected in series with said electromagnetic operator and a portion of said transformer secondary coil, an energizing circuit for said warp switch heater compris ing said heater, said second switch actuated by said ele-' ment and said holding switch all serially connected across said portion of said transformer secondary coil,- an electrically operated fluid fuel valve adapted when energized to permit the flow of fuel to said burner motor and to stop the flow of fuel thereto when de-energized, a first circuit for energizing said oil valve including a normally closed warp switch adapted to be opened by said warp switch heater and connecting said valve to said main burner switch, a second energizing circuit for said oil valve including a normally open switch adapted to be closed by said warp switch heater and connecting said valve operator in a circuit lead joining the switch and said transformer primary coil, whereby upon closure of said space temperature responsive thermostatic switch said oil valve is energized through said normally closed warp switch and upon opening of said normally closed warp switch and closing of said normally open warp switch by said warp switch heater said valve is energized through said normally open warp switch, and means for retaining said burner motor in operation for a purge period subsequent to opening of said space temperature responsive thermostatic switch, said last mentioned means comprising a second normally open warp switch operated by said warp switch heater and connected in shunt around said main burner switch.

2. A control circuit for an electric motor operated fluid fuel burner adapted for heating an enclosure, said control circuit comprising a first line voltage network including a main burner switch controlling the application of line voltage to the burner motor, a second line voltage network including a space temperature responsive thermostatic switch, a normally closed safety switch and primary coil of a step-down transformer all serially connected, a combustion responsive element, a first switch actuated by said element which is closed in the absence of combustion at said burner, a second switch actuated by said element which is closed in the presence of combustion at said burner, an electrical operator for said main burner switch, an electrical operator for said safety switch, a warp switch heater, a low voltage circuit network including a starting circuit comprising said safety switch operator, said first switch actuated by said element and said main burner switch operator all serially connected across the secondary coil of said transformer, a holding circuit for said main burner switch operator comprising a holding switch operated by said main burner switch operator connected in series with said main burner switch operator and a portion of said transformer secondary coil, an energizing circuit for said warp switch heater comprising said heater, said second switch actuated by said element and said holding switch all serially connected across said portion of said transformer secondary coil, an electrically operated fluid fuel valve adapted when energized to perrnit the flow of fuel to said burner motor and to stop the flow of fuel thereto when de-energized, a first circuit for energizing said oil valve including a normally closed Warp switch adapted to be opened by said warp switch heater and connecting said valve to said main burner switch, a second energizing circuit for said oil valve including a normally open switch adapted to be closed by said warp switch heater and connecting said valve operator in a circuit lead joining the switch and said transformer primary coil, whereby upon closure of said space temperature responsive thermostatic switch said oil valve is energized through said normally closed warp switch and upon opening of said normally closed warp switch and closing of said normally open Warp switch by said warp switch heater said valve is energized through said normally open warp switch, and means for retaining said burner motor in operation for a purge period subsequent to opening of said space temperature responsive thermostatic switch, said last mentioned means comprising a second normally open warp switch operated by said warp switch heater and connected in shunt around said main burner switch.

3. A control circuit for an electric motor operated fluid fuel burner of the constant ignition type adapted for heating an enclosure, said control circuit comprising a first line voltage circuit network including a main burner switch controlling the application of line voltage to the burner motor, a second line voltage network including a space temperature responsive thermostat, a normally closed safety switch and primary coil of a step-down transformer all serially connected, a combustion responsive element, a first switch actuated by said element which is closed in the absence of combustion at said burner, 21 second switch actuated by said element which is closed in the presence of combustion at said burner, an electromagnetic operator for said main burner switch, a thermalelectric operator for said safety switch, a warp switch heater,

a low voltage circuit network including a starting circuit comprising said safety switch operator, said first switch actuated by said element and said electromagnetic operator all serially connected across the secondary coil of said transformer, a holding circuit for said electromagnetic operator comprising a holding switch operated by said electromagnetic operator connected in series with said electromagnetic operator and a portion of said transformer secondary coil, an energizing circuit for said warp switch heater comprising said heater, said second switch actuated by said element and said holding switch all serially connected across said portion of said transformer secondary coil, an electrically operated fluid fuel valve adapted when energized to permit the flow of fuel to said burner motor and to stop the flow of fuel thereto when tie-energized, a first circuit for energizing said oil valve including a normally closed warp switch adapted to be opened by said warp switch heater and connecting said valve to said main burner switch, a second energizing circuit for said oil valve including a normally open switch adapted to be closed by said warp switch heater and connecting said valve operator in a circuit lead joining the switch and said transformer primary coil, whereby upon closure of said space temperature responsive thermostat said oil valve is energized through said normally closed warp switch and upon opening of said normally closed warp switch and closing of said normally open warp switch by said warp switch heater said valve is energized through said normally open warp switch, and switch means shunting said main burner switch for retaining said burner motor in operation for a purge period subsequent to opening of said space temperature responsive thermostat.

References Cited in the file of this patent UNITED STATES PATENTS

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