US2474941A

US2474941A - Spark responsive burner control

Info

Publication number: US2474941A
Application number: US674578A
Authority: US
Inventors: Walter C Hasselhorn; Eugene H Zlebold
Original assignee: Cook Electric Co
Current assignee: Cook Electric Co
Priority date: 1946-06-05
Filing date: 1946-06-05
Publication date: 1949-07-05
Anticipated expiration: 1966-07-05

Description

July 5, 1949. w. c. HASSELHORN EFAL 9 49 SPARK RESPONSIVE BURNER CONTROL Filed June 5, 1946 Patented July 5, 1949 SPARK RESPONSIVE BURNERCONTROL,

-Walter C. Hasselhorn and Eugene H. Zlebold,

Chicago, 111., assignors to Cook Electric Company, Chicago, 111., a corporation of Illinois Application June 5, 1946, Serial-No. 814,578

The present invention relates to furnaces and has special reference to control apparatus for gas fired furnaces.

More particularly, this invention relates to safety control means for preventing the accumulation of gas in the furnace which, if ignited,

might result in an explosion. The control means may comprise ignition apparatus such as a spark plug which is constantly energized at regular short intervals to ignite the gas entering the furnace from any cause whatsoever before there is sufficient accumulation thereof to result in an explosion. As a further safety measure a safety valve may be placed in the gas supply line which will be closed automatically if there is failure of the ignition apparatus. Thus, accumulation of gas in the furnace is prevented either by igniting the gas as it enters the furnace or if there is any failure in the ignition circuit, completely shutting off the supply of gas to the furnace by a safety valve additional to the regular supply valve.

Gas firedfurnaces have heretofore been subject to explosions caused by the ignition of accumulated gas therein either as the result of the main gas control valve failing to seat tightly and allowing gas to leak therebeyond into the furnace, by failure of the ignition system or pilot, or as the result of the flames being extinguished while the main gas control valve is open to permit the flow of gas to the furnace. If the furnace, with an accumulation of gas therein. is ignited as the result of the actuation of the igniting device or by any other means, serious damage may ensue.

The supply of gas to the furnace is usually con- 9 Claims. (c1. 158- 28) z i The type'of electric ignition apparatus previously employed is usually arranged to be energized when the thermostat calls for heat and the trolled by a temperature responsive device such as a room thermostat which operates to open the main gas control valve when heat is called for and to close the valve shutting off the supply of gas therethrough when no heat is called for. The gas control valve may be actuated by a solenoid controlled by the room thermostat, which opens or closes the current supply line to the solenoid.

For igniting the gas when the main gas control valve is opened the furnace is provided with ignition means which may comprise a gas pilot or electrically energized spark producing means such as a spark plug. Should the gas pilot be extinguished or the electric ignition system be defective and thecontrol valve thereafter opened gas control valve is opened to permit gas to flow to the furnace, and after the gas is ignited, is deenergized and remains thus until the gas control valve is again opened. Consequently, if there is any leakage of gas by the gas control valve when the latter is in closed position an explosive mixture will collect in the furnace where it will be ignited when the thermostat calls for heat and the spark producing means is again energized. Likewise, if the flame is extinguished by a down draft or other cause, gas will continue to flow into the furnace forming an explosive mixture therein.

The present invention is designed to overcome the disadvantages of the prior art furnaces by preventing at all times the accumulation of gas in the furnace from any cause whatsoever.

Accordingly, it is an object of the invention to provide improved control apparatus for gas fired furnaces adapted periodically to energize the ignition device whereby to provide a constant but regulated sparking thereat and effect what may be called a scanning operation by the ignition device in order to assure continued burning of the gas and eliminate accumulations between firings that may cause explosions of a serious character.

It is a further object of the invention to provide an improved safety control of the character indicated in which gas is supplied only if the ignition apparatus isfunctioning.

In carrying out the invention in one form. control apparatus for a furnace having a valve controlling the supply of gas to the burner thereof is provided comprising means responsive to a condition for controlling the valve, spark producing means for igniting gas supplied to the burner, ignition means independent of the responsive means for providing continuous cyclic energization of the spark producing means and a safety valve operable to shut off the supply of fuel to the furnace upon failure of said ignition means. The cyclic energization of the spark producing means serves continuously to provide timed ignition sparks to the furnace and assure burning without explosion of the gases flowing past the supply valve.

For a more complete understanding of the invention, reference should now be had to the accompanying drawing in which the single figure is a schematic representation of a furnace and a control system embodying the invention.

Referring more particularly to the drawing,

the invention is shown embodied in safety control apparatus for a gas fired furnace wherein the gas is supplied to a burner in through a conduit II. It is to be understood that the invention, while described with reference to a gas fired furnace, is not limited thereto, but may extend to oil fired furnaces where explosive mixtures of air and liquid fuel may be formed. Two gas control valves l2 and I3 are advantageously provided in the fuel supply conduit ii, the valve l3 being adapted to open and close to control the supply of fuel to burner i8 and the valve i2 being a safety valve which is normally open, but is automatically closed to shut off the flow of gas during faulty conditions of furnace operation. The supply valve I! may, for example, be of a well known type having a damper or shutter i 4 arranged inside of a valve casing, the shutter l4 being externally actuated by an arm l5 through a spring l6, and a solenoid IT. The solenoid i1 includes a plunger I 8 and a winding i9 to be energized for attracting plunger is to move the arm i5 through a pin connection as shown, thereby opening the shutter l4. The spring is is stretched out when plunger I8 is attracted to bias shutter M to its closed position, and, when coil i9 is deenergized, the spring is returns to its normal position effecting closing of the shutter l4 to shut off the flow of fuel. Any other suitable type of valve may be employed if desired.

The safety valve l2, shown diagrammatically, may also be of a well known type having an internal valve seat 28 arranged within the valve body and a plug or piston 2i which is received upon the valve seat 28 to shut off the flow of gas. The plug 2| is connected to a stem 22 having a sleeve 22a fixed thereon and provided with a notch 23 into which a plunger 24 is adapted to be received in any well known manner. A casing 25 may be arranged over valve l2, the top of which is provided with a guide 29 having an opening therein for the valve stem 22. Attached to the outer end of valve stem 22 is a handle 21. A spring under compression is placed about stem 22 between the guide 28 and the outer end of the sleeve 22a so as to urge plug 2i upon the valve seat 20. The valve I2 is arranged to havevalve plug 2i tightly and firmly fit upon valve seat through the spring 28 to assure that no fuel may leak therethrough when the valve is closed.

In the position shown, the valve i2 is open with the plug 2i off of valve seat 28 and the end of the plunger 24 received within the notch 23 thereby preventing closing of the valve. A compression spring 29 urges the plunger away from sleeve 22a and out of notch 23. The plunger 24 forms the movable element of a solenoid including the coil 3|, which when energized urges the plunger 24 toward sleeve 22a and maintains it in the notch 23 against the biasing force of spring 29. Thus. the coil 3i must be energized in order to hold plunger 24 in the notch 23, and when 'energization is removed from coil 3i the spring 29 removes plunger 24 from the notch 23 allowing the spring 28 to close valve l2. After this valve has once been closed by the removal of energy from coil 3|, it can be opened only by manually moving the valve stem 29 outwardly against the force of spring 28 until the plunger 24 moves into the notch 23, this occurring only while energy is applied to coil 3|.

Fuel supplied to the burner i8 is ignited by a spark plug 32 which has energy supplied to it from a transformer 33 energized in turn from an alternating current source 34 such, for example, as an ordinary house circuit of one hundred and ten volts. The transformer 33 includes a primary winding 35 and a secondary winding 38, the primary winding being excited through an interrupter 31 driven by a motor 38. The interrupter produces energy impulses which are supplied to the primary 35 of the transformer which in turn induces a voltage in the secondary winding 38, the secondary winding having a high number of turns relative to the primary winding, and consequently supplying a high voltage impulse to the spark plug 32 as is well understood by those skilled in this art. The motor 38 operates continuously to cause interrupter 31 to make and break the circuit at a predetermined rate. This rate is such that the intervals between successive sparkings of the spark plug 32 are of insufiicient duration to permit the accumulation of an explosive mixture of fuel in the furnace and may be of the order of a few seconds.

The valve i3 is caused to open and close for controlling the supply of fuel to the burner i0 under the influence of condition responsive means, which, for example, may be the contacts 39 of a thermostatic device which opens its contacts at one temperature and closes its contacts at another temperature, both of which may be predetermined. If the furnace is used in a. house heating system the contacts 39 may be in a room thermostat set to maintain the room temperature between any desired limits. Energy is supplied by means of a transformer 48 through contacts 39 of the thermostatic device to the coil i9 of solenoid i1, whereby when contacts 39 are closed coil I9 is energized to open shutter i4 to supply fuel to the burner l8, and, when the contacts 39 are opened, coil i9 is deenergized, thereby permitting spring 5 to close shutter i4.

The primary circuit of transformer 33 includes one side of source 34, switch 5!, conductor 4|, conductor 42, conductor 43, interrupter 31, conductor 44, conductor 45, primary winding 35 of transformer 33, conductor 48, and conductor 41 back to the other side of the source of supply 34. The secondary circuit includes the inductive coupling between primary and secondary windings 35 and 36, conductor 48, winding 49, and spark plug 32, including the gap 30. 'The circuit for supplying energy to spark plug 32 is of course a closed cirruit, the ground connections at the spark plug and the secondary winding 38 indicating the points which are connected together as will be understood.

The motor 38 driving interrupter 31 is connected to the source of supply 34 through the following circuit: From one side of source 34, through switch 5i, conductors 4|, 42, and 52, motor 38, conductor 53, conductor 54, conductors 48 and 41 back to the other side of source 34. It will thus be seen that whenever the switch Ii is closed the motor 38 will be energized and hence will drive the interrupter 31. The interrupter 31 in turn will make and break the circuit to the primary 35 of the transformer 33, thereby supplying impulses of voltage to spark plug 32 causing sparks to jump at the gap 38. A condenser 55 is connected across the interrupter I! by means of conductors 58 and 51 to prevent sparking across interrupter contacts during its operation.

The circuits for operating control valve i3 include a circuit from the source 34 to primary 58 of transformer 40 and a circuit from the secondar of transformer 40 to solenoid I! as follows: From one side of source 84 through switch 8|, conductor 4|, conductor 88, conductor 8|, primary winding 88, conductor 82. and conductors 84, 48, and 41 to the other side of source 36. From secondary winding 83 through conductor 64. contacts 39 of the thermostatic device. conductor 38, winding IQ of solenoid I1, and through conductor 86 to the secondary windin: 83.

With the circuits and apparatus as thus far described, and assuming that the switch 8| is closed and that the safety valve I2 is open, the operation of the system will be substantially as follows: With the switch 8| closed, the motor 38 is energized to drive the interrupter 3! thereby providing sparks at the spark gap 38 through the transformer 33. These sparks are supplied continuously irrespective of whether or not fuel is being supplied to the burner l8 since the motor 38 and the interrupter 31 are connected to the source 34 entirely independently of contacts 39 of the thermostatic device. An indicating device 81, which for example may be a neon glow lamp, may be connected from the conductor 58 to ground (adjacent spark plug 32) to indicate whenever energy is being supplied to the spark plug, the neon lamp glowing under the influence of the sparks being supplied and not glowing when sparks are not being supplied as is well understood. When the thermostat calls for heat and its contacts 89 are closed, the coil i9 is supplied with energy through the circuit described causing the shutter It to open. The gas being supplied to the burner III as a result thereof is ignited by the sparks at gap 30. When no heat is being called for the thermostat contacts are open and the circuit to winding I9 is interrupted, thereby allowing spring it to close the shutter ll. Consequently no fuel is supplied to the burner l8. However, sparks continue to jump across the gap 38 since the motor 38 and the interrupter 31 are continuously operating. Hence, if the burner flame should be extinguished or any fuel should leak through the valve I3. this fuel would be ignited by the spa'rk plug 32 and an explosive mixture would not accumulate within the furnace chamber.

Means are provided for closin the safety valve in the event that the spark plug 32 should become faulty, or any part of the circuit for supplying energy to the spark plug 32 should fall so that the spark plug 32 did not receive any impulses.

Without. such means, fuel could accumulat within th furnace chamber since, if the thermostat is calling for heat, the valve I 3 may be completely open. To prevent this situation from occurring, a relay 60 has its coil 49 in series with the spark plug 32, thereby forming part of a safety circuit to effect closing of the safety valve I2 whenever the spark plug 32 is not receiving energy.

The safety circuit for this apparatus includes a. relay I2, controlled by relay 80. for interrupting the circuit to coil 3| upon failure of the ignition circuit. The relay 60 is provided with a coil 49, a core 88, and an armature (not shown) adapted to be attracted by the core 68 for open ng the normally closed contacts H. The relay i2 is of a time delay type including a. pair of normally closed contacts 13 adapted to be opened when the relay coil 14 is energized. The coil 14 is provided with an iron core l5, one end of which may be provided with a short circuited winding or conducting slug IS, the core 15 being adapted to attract its armature (not shown) to open contacts II. The short circuited winding or con- 6 ducting slug It provides a short time delay in the opening of the contacts 13 after current begins flowing through the circuit of winding ll, as is well understood.

The coil 14 of relay I2 is energized from the source 34 through a transformer 18 and contacts H of relay 88. The circuits for energizing transformer 18 include a circuit from source 34 to the transformer and from the transformer to winding 14. The transformer 18 has a primary winding I9 and a secondary winding 8|. The winding I9 may be connected, as shown, in parallel with primary winding 38 of transformer 33 and thereby be supplied with current impulses through the interrupter 31. The winding 14 of relay I2 is energized from the secondary winding 8| of transformer I8 through the following circuit: From winding 8| through conductor 82, conductor 83, closed contacts 1|, conductor 84, conductor 85, coil H, and conductor 86 to the winding 8|. The contacts II are closed when current is not flowing through coil 49. Whenever transformer 18 is energized through the closing of interrupter 31, a current impulse will be sent through the secondary coil 8| and its circuit including coil 14 of relay l2 and contacts if the latter are at the time allowed to remain closed. This energization of coil ll of relay I2 will open its contacts I3 to break the circuit of coil 3| at auxiliary valve 2| to close the latter. This is undesirable in normal operation as each impulse is sent through the circuit of sparking means 32. Consequently, coil l9 in this circuit of sparking means 32 will be energized by each current impulse to break the circuit of coil 14 of relay [2 by opening contacts 1|. This can be accomplished by the armature (not shown) of relay 60 lifting post 59 to lift the upper of the two contacts 1 I, or by any other arrangement of the relay parts that will accomplish the same result. During normal operation of the system with switch 5| closed, current will constantly flow through coil 3| to keep coil 3| energized and auxiliary valve |2 held open. Contacts I3 in th circuit of coil 3| will remain closed because coil 74 of relay 12 will not be energized. Relay 60 will actuate to open contacts ll before relay 12 will be actuated to open contacts 13, upon each current impulse, due to the slow acting character of relay 12, and consequently, this slow action of relay 12 will prevent any current impulse through the circuit of secondary 8| of transformer 18, although only momentary, from energizing coil 14 to the extent of actuating relay 12 and operating contacts 13. However, upon failure of sparking means 32 properly to function for any one of a number of reasons, as for example, a break in the wiring, relay to will leave contacts ll closed. Current will then flow through the circuit of relay 12 long enough to actuate relay 72 to cause the opening of contacts l3 and the deenerglzation of coil 3| to close safety valve i2. Relay 12 will hold contacts 13 open until the breakdown is repaired and the system is restored to its normal operating condition.

In order to prolong or enlarge the spark at gap 30 upon a current impulse through the circuit,

of secondary 36 of transformer 33, a condenser 9| may be suitably disposed as in the wire 48,- so that it can be charged as the current impulse exists in the line and then can discharge itself at the gap as the flow of the current impulse ceases whereby to enlarge the spark and hence be more positive in effecting ignition.

The control apparatus thus provides safety during all aspects of furnace operation, two fuel valves being provided to assure that the fuel will be shut off when necessary. During ordinary furnace operation ignition impulses are continuously supplied so that fuel in the furnace due to any cause will be ignited instead of accumulating to form a possibly dangerous mixture and during instances where ignition impulses are not supplied the fuel supply is shut off entirely by deenergizing coil 3| and cannot be turned on until ignition impulses are again supplied.

Without further elaboration, the foregoing will so fully explain the gist of our invention that others may, by applying current knowledge, readily adapt the same for use under varying conditions of service, without eliminating certain features, which may properly be said to constitute the essential items of novelty involved, which items are intended to be defined and secured to us by the following claims.

We claim:

1. Control apparatus for a furnace having a valve in a fuel supply line for controlling the supply of fuel to the burner of said furnace and means responsive to a condition for controlling said valve, comprising spark producing means for igniting fuel supplied to said burner, energization means independent of said responsive means for continually supplying energy impulses to said spark producing means. a second fuel supply valve in said supply line, and means directly responsive to failure of said energization means for effecting the closing of said second valve.

2. Control apparatus for a furnace having a valve in a fuel supply line for controlling the supply of fuel to the burner of a furnace and means responsive to a condition for controlling said valve, comprising spark producing means for igniting fuel supplied to said burner, energization means independent of said responsive means for continually supplying energy impulses to said spark producing means, a manually reset fuel supply safety valve in said supply line, and means directly responsive to failure of said energization means for effectin the closing of said safety valve.

3. Control apparatus for a furnace having a valve in a fuel supply line for controlling the supply of fuel to the burner of a furnace comprising spark producing means for igniting the fuel at said burner, temperature responsive means for controlling said valve, a source of energy for said temperature responsive means and said spark producing means, a circuit including an interrupter for continually supplying energy impulses from said source to said spark producing means, a motor connected to said source and independent of said temperature responsive means for continuously operating said interrupter, a fuel supply safety valve in said supply line, and means directly responsive to failure of said spark producing means for closing said safety valve.

4. Control apparatus for a furnace having a valve in a fuel supply line for controlling the supply of fuel to the burner of said furnace, comprising spark producin means for igniting the fuel at said burner, temperature responsive means for controlling said valve, a source of energy for said responsive means and said spark plug means, a circuit including an interrupter for continually supplying energy impulses from said source to said spark producing means, a motor connected to said source and independent of said temperature responsive means for continuously operating said interrupter, a fuel supply safety valve in said supply line, means including a circuit connected to said source and adapted when energized to hold said valve open, and means responsive to lack of energy at said spark producing means for interrupting said safety valve circuit to effect closing of said safety valve.

5. Control apparatus for a furnace having a valve in a fuel supply line for controlling the supply of fuel to the burner of said furnace, comprising spark producin means for igniting the fuel at said burner, temperature responsive means for controlling said valve, a source of energy for said temperature responsive means and said spark producing means, a circuit including an interrupter for continually supplying energy impulses from said source to said spark producing means, a motor connected to said source and independent of said temperature responsive means for continuously operating said interrupter, a fuel supply safety valve in said supply line, means including a circuit connected to said source and adapted when energized to hold said valve open, means responsive to lack of energy at said spark producing means for interrupting said safety valve circuit to effect closing of said safety valve, and time delay means associated with said spark producing circuit for delaying closing of said safety valve onin'omentary failure of said last mentioned circu 6. Control apparatus for a furnace having a valve in a fuel supply line for controlling the supply of fuel to the burner of said furnace, comprising spark producing means for igniting said fuel, a transformer for supplying energy from a source to said spark producing means, an interrupter for exciting said transformer, temperature responsive means for controlling said valve, a transformer for supplying energy from said source to said temperature responsive means, a motor connected to said source and independent of said temperature responsive means for continuously operating said interrupter, a fuel supply safety valve in said supply line, means including a circuit connected to said source and adapted when energized to hold said safety valve open, a relay energized from said source for controlling said safety valve circuit, and contacts responsive to lack of energy at said spark producing means for deenergizing said relay thereby interrupting said safety valve circuit to effect closing of said safety valve.

7. Control apparatus for a furnace having a valve in a fuel supply line for controlling the supply of fuel to the burner of said furnace and thermostatic means for controlling said valve, 55 comprising spark producing means for igniting fuel at said burner, energization means independent of said thermostatic means for continually supplying energy impulses to said spark producing means, a safety valve in said supply 60 line biased to closed position, means including an electric circuit adapted to hold said safety valve in open position while said circuit is energized, and means responsive to lack of energy in said spark producing circuit for breaking said 65 safety valve circuit.

8. Control apparatus for a furnace having a valve in a fuel supply line for controlling the supply of fuel to the burner of said furnace and thermostatic means for controlling said valve,

70 comprising spark producing means for igniting fuel at said burner, energization means independent of said thermostatic means for continually supplying energy impulses to said spark producing means, a safety valve in said supply line 7 biased to closed position, means including an elec- 9 tric circuit adapted to hold said safety valve in open position while saidcircuit is energized, and relay means responsive to lack of energy in said spark producing circuit for breaking said safety valve circuit.

9. Control apparatus for a furnace having a valve in a fuel, supply line for controlling the supply of fuel to the burner of said furnace and thermostatic means for controlling said valve, comprising spark producing means for igniting fuel at said burner, energization means independent of said thermostatic means for continually supplying energy impulses to said spark producing means, a safety valve in said supply line biased to closed position, means including an electric circuit adapted to hold said safety valve in open position while said circuit is energized, and a control circuit having a relay for breaking said safety valve circuit upon energize.- tion of said control circuit. a source of energy 10 for said control circuit, and means responsive to lack of energy in said spark producing circuit for effecting energization of said control circuit.

WALTER C. HASSELHORN. EUGENE H. ZIEBOLD.

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

UNITED STATES PATENTS