US2681101A - Motor and ignition safety control system for liquid fuel burners - Google Patents

Description

June 1954 N; .1. MOSELY MOTOR AND IGNITION SAFETY CONTROL SYSTEM FOR LIQUID FUEL BURNERS Filed Nov. 27, 1951 INVENTOR. 3km M M M ATTORNEY Patented June 15, 1954 MOTOR AND IGNITION SAFETY CONTROL SYSTEM FOR LIQUID FUEL BURNEBS Neal J. Mosely,

gheny County, Corporation,

Mount Lebanon Township, Alle- Pa., assignor to Detroit Controls a corporation of Michigan Application November 2'7, 1951, Serial No. 258,339

8 Claims.

This invention relates to new and useful improvements in control systems for liquid fuel burners and more particularly to a primary control system which is constructed of a minimum number of control parts.

In the past, many types or control systems, devices and circuits have been proposed for controlling the operation of liquid fuel burners, but substantially all of those have involved the use of very complicated circuits involving many switches, relays, and complicated timing mechanisms. In this invention there is provided a control system having a minimum number of operating control parts to provide for maximum simplicity and eirlciency in operation.

Accordingly, it is one object of this invention to provide a new and improved control circuit for liquid fuel burners.

Another object is to provide a control circuit for liquid fuel burners having as few control switches and as simple a timing mechanism as possible.

Another object is to provide a liquid fuel burner control system which will turn on a burner motor and ignition, after a predetermined time turn oil the ignition, and if no flame occurs in the burner by the time the ignition is turned off, will, after a predetermined further period of time, turn off the burner motor, all with a minimum number of control switches and circuits.

Another object is to provide a liquid fuel burner control circuit and control devices therefor which are simply and inexpensively constructed and assembled.

Other objects will become apparent from time to time throughout the specification and claims as hereinafter related.

This invention comprises the new and improved construction and combination of parts and their operating relationship each to each, which will be described more fully hereinafter and the novelty of which will be particularly pointed out and distinctly claimed.

In the accompanying drawing, to be taken as part of this specification, there is clearly and fully illustrated a preferred embodiment of this invention, in which drawing the figure shows in more or less diagrammatical form a control system for liquid fuel burners which is the subject of this invention.

Referring to the drawing by characters of reference there is shown a liquid fuel burner IIlI having a burner motor I02 and an electric spark ignition 503. There is provided a transformer IM having a primary I015 supplied from a high r spring I38 and 6 2. voltage power source Hit and having a secondary coil Illl. From the high voltage power source I136 the wire H13 connects to the contact arm H8 of a switch H9. The switch H9 comprises contact arms H8 and I26 carrying normally closed contacts HI and I22, respectively, biased into initial engagement with each other. From the wire I08, the wire H6 connects to one side of the burner motor IE2. From the contact arm I26 of the switch us a wire !23 connects to one end portion of the primary coil I24 of the ignition transformer I25. The ignition transformer I25 has a secondary coil mi and wires i2? and I28 leading therefrom to the spark ignition W3. The other end portion of the ignition primary coil its is connected as at E29 to a return wire I30 from the burner motor I62 which is connected to the contact arm i3i of a switch H2. The switch I32 comprises contact arms l3l and I33 carrying contacts H4 and I35, respectively. The contact arm I33 is biased toward engagement of the contacts E34 and I35 but is restrained by engagement with a stop I66. The contact arm I3! is biased away from the contact arm I33 and is engaged by a thrust transmitting member MI. The contact arm N3 is connected by a wire I36 back to the other side of the high voltag power source I05. There is provided a snap mechanism I31 which is co-operable with the contact arm I33 and is operable upon predetermined movement in one direction to snap the arm E33 away from the arm I3 I. The snap mechanism I31 may be any suitable snap mechanism, but for the purposes of this disclosure is shown as an overcenter a suitable adjustment mechanism therefor such as an adjustable screw I39, The adjustment screw I39 is operable to vary the relation of the spring I38 to the contact arm I33. The compressive force of spring l38 biases the contact arm I33 toward the contact arm I3I and into engagement with the stop its. A reset member Hit is provided in overlying relation to the contact arm I33 to reset the same from an overcenter snapped open position. The contact arm H8 is biased for movement along with the contact arm I20 of the switch I It which is moved by a suitable thrust transmitting member I42 and which transmits movement through member MI to the contact arm I3I of the switch I32. There is provided a timing means Hi l, which comprises a bi-metal member I45 which is operated in accordance with the heat output of a resistance heater I46 and the force against which the member I45 must work. Since the bimetal member I45 warps at a rate which is determined by the 3 rate of heat input and the force against which it works, and since the heating of the bimetal by the resistance heater I46 is a function of the time that the heater was energized, it is apparent that the timing operation of the bimetal may be adjusted by varying either the distance which it must move or the force against which it must work. The screw I39 is operable to adjust the compressive force exerted by the spring I38 and thus varies the timing operation by varying the force against which the bimetal must work. If the compression of spring I38 is increased the bimetal must warp with a greater force, which requires a longer heating period. Similarly the spring I38 could be adjusted to vary the snap point of the arm I33 by varying the distance which that arm must move before snapping over center. The resistance heater I46 is connected to one side of the transformer secondary II]? by a wire I48 and is connected by wires I49, I50 and II to the fixed contacts I52 and I53 of a singlepole, double-throw switch I54. A resistor I55 is provided in circuit between the wires I49 and I5I to modify the operation of the resistance heater I45 for the timing means I44. The movable pole I56 of the switch I54 carries contacts I57 and I58 cooperable with fixed contacts I52 and I53, respectively, and is connected by wire I59 to a fixed contact I60 of a room thermostat IfiI. The switch operating pole I56 of the switch I54 is operated by a suitable flame responsive means I52 such as a bi-metal helix positioned for response to flame temperature in the burner stack I53. The room thermostat It! has a suitable temperature responsive member such as a bimetal I64 connected by a wire I65 to the other side of the transformer secondary I01 and carries a movable contact I56 cooperable with the fixed contact I60.

Operation In operation this system functions generally as follows:

The resistance heater I46 and bi-metal member I45 co-operate to form an electro-thermal timer for operating the switches H9 and I32.

fected appreciably by burner temperature. When the room thermostat contacts I60 and I 65 are closed calling for heat, a circuit is completed from the transformer secondary I01 through wire I45, resistance heater I46, wire I49, wire I50, contacts I52 and I5? of switch I54, wire I59, contacts I60 and I65 of the thermostat IIiI, thermostat blade I54, and wire I65, completing the connection to the transformer secondary I07. With this circuit completed, the heat output of the heater I45 will cause the bi-metal I45 to move at a rate dependent upon the heat output of the heater I45, the type of bi-metal used in the member I45, and the resistance against which the bi-metal member I45 must operate. As the bi-metal member I 45 is moved upwards, it moves the thrust member I42 against the contact arm I and thus moves the contact arm I 3| to move the switch contact I34 into engagement with contact I35. When the contacts I34 and I35 are brought into engagement, a high voltage circuit is completed from the power source I06 by way of wire I58, contact blade I I8, contacts I2I and I22, and contact blade I20 to "wire I23 connected to the ignition I24. From wire I08 adjacent the switch III the circuit divides and part is connected through the ignition and part through the burner motor. The circuit through the burner motor extends from wire I58 by way of wire H6. The circuit through the ignition was previously described. The burner and ignition circuits join again at point I 29 on wire I35 which connects to contact arm IBI of the switch I 32. The circuit is completed back to the other side of the high voltage power source through contact arm I 3!, contacts I34 and I 35 when closed, contact arm I33 and wire I35. At this stage of the operation, with both switches closed, both the burner motor and ignition are energized and in the normal course of operation flame should occur in the burner. After the predetermined time (determined by the physical constants of the heater I46 and bi-metal I), the contact arms IIS and I2I) of the switch IIQ will be moved until the contact arm I I8 engages the stop I4 3, and upon further movement the contacts I?! and I22. are separated, thus breaking the circuit to the ignition transformer I24. If at this point no flame has occurred in the burner, the bi-metal member I45 of the timer I54 will continue to move, and after predetermined further movement the contact arms I3I and I33 of the switch I32 will be moved to an overcenter position relative to the snap mechanism I37 and the contact arm I33 and switch contact I35 will move away from the contact I34 with a snap movement, thus breaking the circuit to both the burner motor I 5.32 and ignition transformer I24. If flame occurs in the burner It! after the closing of the switch contacts I I and I35 of switch I32, and prior to the re-opening of those contacts, the fiame responsive bi-metal I52 will move the contact pole I of the doublethrow switch I54 and open the contacts I52 and I5'I and close the contacts I53 and I58 to place the resistor I55 in series circuit with the resistance heater I45 for the bi-metal member I45. When the resistor I55 is placed in series with the resistance heater I45, the voltage drop through the resistor I45 is reduced to a point such that the heat output thereof to the bi-metal member I45 is sufiicient to maintain the same in an actuated position between the point at which the contacts I2I and I22 of switch I I 9 are opened and the point at which the switch I 32 is snapped open. It will be seen then that in normal operation when the system is required to produce heat, the timing means first causes the switches to be placed in a position to energize both the ignition and burner motor. After a predetermined time the ignition switch is opened and the burner motor circuit remains on. If flame has occurred in the burner by this time, the timer mechanism will hold the switches in this position. Upon deenergizaticn, the ignition switch will first close and then the switch I 32 controlling both the burner and ignition will reopen (by engagement of contact arm I33 with stop member I66). The closing of the ignition switch just prior to deenergization of the system will cause a momentary ignition at this time and will consume any residual combustible gases left in the burner. On the other hand, if flame does not occur in the burner by the time the ignition switch is opened, the timer mechanism moves the switch I32 until the same is snapped open, as previously described, and the burner and ignition are both shut down by that operation. After the switch I32 has been snapped open, it is necessary that the contact arm I33 and contact I35 be reset manually from this safety position and the reset button I40 is provided for that purpose. It should also be noted that the snap mechanism it! includes an adjustment means such as the screw I39 for the overcenter spring its to vary its relation to the contact arm 133 and thus vary the time required to move to a safety snapped open position.

From the foregoing descriptions or" the system disclosed herein, it is seen that there is here provided a very simple control system for a liquid fuel burner having a very simple timing mechanism and having considerably less than the usual number of control switches and other control parts therefor.

While there has been described herein only a form of this invention, it will be obvious to those skilled in the art that other modifications of this system are possible without departing from the scope and intent of this invention as defined in the appended claims.

Having thus described the invention, what is claimed and is desired to be secured by Letters Patent of the United States is:

1. In a burner control system, a liquid fuel burner, a burner motor and electric circuit therefor, an electric ignition means and circuit therefor, a first switch havinginitially closed contacts in said ignition circuit, a second switch connected in series with said first switch and having contacts in both said motor and said ignition circuits, said second switch having a contact arm and a snap mechanism cooperable therewith operable to cause the same to be snapped to an open position after actuating movement in one direction through a predetermined range, means cooperable with said first switch to cause the same to be opened after movement less than said predetermined range, electric timing means for actuating said switches, a circuit for said timing means, said timing means being arranged to actuate said switches sequentially so that said second switch is closed first, after a predetermined time said first switch is opened, and upon actuation through said predetermined range said second switch is reopened with a snap movement, means controlling energization of said timing means circuit, and means operable to stop said timing means at a point of actuation subsequent to opening said first switch and prior to reopening said second switch.

2. In a burner control system, a liquid fuel burner, a burner motor and electric circuit there for, an electric ignition means and circuit therefor, a first switch having initially closed contacts in said ignition circuit, a second switch connected in series with said first switch and having contacts in both said motor and said ignition circuits, said second switch having a contact arm and a snap mechanism cooperable therewith operable to cause the same to be snapped to an open position after actuating movement in one direction through a predetermined range, means cooperable with said first switch to cause the same to be opened after movement less than said predetermined range, electric timing means for actuating said switches, a circuit for said timing means, said timing means being arranged to actuate said switches sequentially so that said second switch is closed first, after a predetermined time said first switch is opened, and u on actuation through said predetermined range said second switch is reopened with a snap movement, means controlling energization of said timing means circuit, and means responsive to the occurrence of fiame in said burner to stop said timing means at a point of actuation subsequent '5 to opening said first switch and prior to reopen ing said second switch.

3. In a burner control system, a liquid fuel burner, a burner motor and electric circuit therefor, an electric ignition means and circuit therefor, a first switch having initially closed contacts in said ignition circuit, a second switch connected in series with said first switch and having initially open contacts in both said motor and said ignition circuits, said second switch having a contact arm and a snap mechanism cooperable therewith operable to cause the same to be snapped to an open position after actuating movement in one direction through a predetermined range, means cooperable with said first switch to cause the same to be opened after movement less than said predetermined range, electric timing means reversibly actuated for actuating said switches, a circuit for said timing means, said timing means actuating said switches in said one direction upon energization and in the other direction upon de-energization, said timing means being arranged to actuate said switches sequentially so that said second switch is closed first, after a predetermined time said first switch is opened, and upon actuation through said predetermined range said second switch is reopened with a snap movement, a thermostatic switch responsive to the temperature of the space heated by said burner to control energization of said timing means circuit, and means responsive to the occurrence of flame in said burner to stop said timing means at a point of actuation subsequent to opening said first switch and prior to reopening said second switch.

4. In a burner control system, a liquid fuel burner, a burner motor and electric circuit therefor, an electric ignition means and circuit therefor, a first switch having initially closed contacts in said ignition circuit, a second switch connected in series with said first switch and having initially open contacts in both said motor and said ignition circuits, said second switch having a contact arm and a snap mechanism cooperable therewith operable to cause the same to be snapped to an open position after actuating movement in one direction through a predetermined range, means cooperable with said first switch to cause the same to be opened after movement less than said predetermined range, electric timing means comprising a bimetallic heat motor and resistance heater therefor, reversibly actuated upon heating and cooling for actuating said switches, a circuit for said resistance heater, said timing means actuating said switches in said one direction upon energization and in the other direction upon de-energization, said timing means being arranged to actuate said switches sequentially so that said second switch is closed first, after a predetermined time said first switch is opened, and upon actuation through said predetermined range said second switch is reopened with a snap movement, a thermostatic switch responsive to the temperature of the space heated by said burner to control energization of said resistance heater circuit, and means responsive to the occurrence of fiame in said burner to reduce the heat output of said resistance heater to said bimetallic heat motor to a point operable to maintain the same in an actuated position less than the predetermined range of movement required for reopening said second switch.

5. In a burner control system, a liquid fuel burner, a burner motor and electric circuit there- 7 for, an electric ignition means and circuit therefor, a first switch having initially closed contacts in said ignition circuit, a second switch connected in series with said first switch and having initially open contacts in both said motor and said ignition circuits, said second switch having a contact arm and a snap mechanism cooperable therewith operable to cause the same to be snapped to an open position after actuating movement in one direction through a predetermined range, means cooperable with said first switch to cause the same to be opened after movement less than said predetermined range, electric timing means comprising a bimetallic heat motor and resistance heater therefor, reversibly actuated upon heating and cooling for actuating said switches, a circuit for said resistance heater, said timing means actuating said switches in said one direction upon energization and in the other direction upon de-energization, said timing means being arranged to actuate said switches sequentially so that said second switch is closed first, after a predetermined time said first switch is opened, and upon actuation through said predetermined range said second switch is reopened with a snap movement, a thermostatic switch responsive to the temperature of the space heated by said burner to control energization of said resistance heater circuit, parallel circuits connected in series with said resistance heater, a resistor in one of said parallel circuits for reducing the heat output of resistance heater to a point such that said timing means heat motor cannot move through said predetermined distance to reopen said second switch, a double throw switch connected to said parallel circuits for switching between them, and means responsive to the occurrence of flame in said burner to actuate said double throw switch to connect the circuit including said re sistor in series connection with said resistance heater.

6. A burner control system as defined in claim 5 including a movable reset member cooperable with said second switch contact arm for resetting the same from said snapped open position.

7. A burner control system as defined in claim 5 including means to adjust said snap mechanism to vary the time of energization of said timing means required to snap open said second switch.

8. A burner control system as defined in claim 6 including means to adjust said snap mechanism to vary the time of energization of said timing means required to snap open said second switch.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,674,051 McCabe June 19, 1928 1,876,281 Eiseman 1 Sept. 6, 1932 2,012,322 Satchwell Aug. 27, 1935 2,135,829 McGoldrick Nov. 8, 1938 2,170,426 Haney Aug. 22, 1939 2,261,586 McGrath Nov. 4, 1941 2,593,518 Aubert Apr. 22, 1952

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