US3918881A

US3918881A - Fuel ignition control arrangement

Info

Publication number: US3918881A
Application number: US447167A
Authority: US
Inventors: Russell Byron Matthews
Original assignee: Johnson Service Co
Current assignee: Johnson Service Co
Priority date: 1974-03-01
Filing date: 1974-03-01
Publication date: 1975-11-11
Anticipated expiration: 1992-11-11

Abstract

A control arrangement for a fuel ignition system having gas burner apparatus for burning gaseous fuel flowing thereto under the control of a valve in response to a thermostaticallycontrolled switch requesting ignition and having a gaseous fuel igniting device includes a switching device for controlling the energization of a spark producing circuit for causing the fuel igniting device to produce a flame, a bi-stable device responsive to the switching device causing the energization of the spark producing circuit for de-activating the valve and thus for terminating the gas flow to the burner apparatus, and a flame sensing circuit responsive to the presence of the flame produced by the fuel igniting device for causing the switching device to de-energize the spark producing circuit, the bi-stable device being responsive to the switching device de-energizing the spark producing circuit for activating the burner valve to permit gas flow therethrough.

Description

nited States Patent Matthews Nov. 11, 1975 i 1 FUEL IGNITION CONTROL Primary Emmi)wrCarroll B. Dority. Jr.

ARRANGEMENT Attorney. Agent. or Firm.lohnson. Dicnner. Emrich [75] Inventor: Russell Byron Matthews, Goshen, & Wagner Ind. [73 A J h S C [57] ABSTRACT sslgncu enlc-e ompany A control arrangement for a fuel ignition system hav- Milwaukee. Wis. mg gas burner apparatus for burning gaseous fuel [22] Filed: Mar. 1, 1974 flowing thereto under the control of a valve in re- [2 1] Appl No: 447,167 sponseto a thermostatiCally-controlled switch requesting ignition and having a gaseous fuel igniting dC\'1CC includes a switching device for controlling the energi- [52] US. Cl. 431/46 zation of a spark producing circuit for causing the fuel [51] Int. Cl. F23Q 9/08 igniting device to produce a flame. a bi-stable device [58] Field of Search 431/25. 46. 43. 45. 47 responsive to the switching device causing the energization of the spark producing circuit for de-activating [56] References Cited the valve and thus for terminating the gas flow to the UNITED STATES PATENTS burner apparatus. and a flame sensing circuit respon- 2'626657 1/1953 Wilson 431/25 to the presence of the flame produced the fuel 2.800.176 7/1957 Morrison 431/4 gniting dC\lCC for causing the switching device to de- 3347380 6/1969 p ct m u 431/46 energize the spark producing circuit, the bi-stable de- 3.449.055 6/1969 Blackett t 431/46 vice being responsive to the switching device de- 3.519.376 7/1971) Dietz 431/46 energizing the spark producing circuit for activating 3.705.783 12/1972 Warren.... 431/ the burner valve to permit gas flow therethrough. 3.718.423 2/1973 Matthews 431/264 16 Claims. 5 Drawing Figures 30 A F- 2/ THS c4 RM 36 re E MAIN PR5 GAS VALVE o MGV 0 !,R2 32 US. Patent Nov.l1, 1975 Sheet2of5 3,918,881

MeV-A AC MAIN GAS VALVE I C5-A Sheet 5 of5 3,918,881

U.S. Patent 'Nbv. 11, 1975 FUEL IGNITION CONTROL ARRANGEMENT BACKGROUND OF THE INVENTION 1. Field of the Invention.

The present invention relates to fuel ignition systems, and it more particularly relates to a fuel ignition control arrangement for a fuel ignition system for the proper igniting of fuel supplied to burner apparatus of the system.

2. Description of the Prior Art.

Many known fuel ignition systems employ standing pilot flames for igniting gaseous fuel supplied to burner apparatus of a fuel ignition system. Automatic fuel ignition control circuits have been employed for the purpose of establishing automatically a flame in the burner apparatus of the system, and for maintaining the flame established by re-lighting it automatically should it become inadvertantly extinguished due to windy conditions or the like. Such a circuit is described in U.S. Pat. No. 3,718,423. While such control circuits are highly reliable and efficient in operation, it'would be highly desirable to have an automatic fuel ignition system in which unburned gas is prevented from flowing from the burner apparatus, when the pilot is extinguished and ignition spark production is initiated. When the spark ignitor is enabled, ignition spark production may be delayed in time. Delayed sparks may be caused by many different conditions, such as insulation breakdown of high voltage cable lines, conductive scale across the electrodes of the spark producing circuit and the scale becoming displaced after a period of time, and other such conditions. The duration of the delay may vary, with the maximum delay being the time delay of a Baso valve controlling the supply of gaseous fuel to the system before the Baso valve opens due to the extinction of the flame. Accordingly, during the delay in the production of the spark, unburned gas pouring from the main burner apparatus could easily accumulate gas for 45 to 60 seconds.

SUMMARY OF THE INVENTION The principal object of the present invention is to provide a new and improved fuel ignition system ,control arrangement which automatically re-lights gaseous fuel in an ignition system, and in which gaseous fuel is prevented from flowing from a main gas burner apparatus whenever a pilot igniter is enabled.

Briefly, the above and further objects are realized in accordance with the present invention by providing in an automatic fuel ignition system an arrangement in: cluding a switching device for controlling the energization of a spark producing circuit for causing the ignition of gaseous fuel to produce a pilot flame, a bi-stable device responsive to the switching device causing the energization of a spark producing circuit for de-activating the valve and thus for terminating gas flow to the main burner apparatus, and a flame sensing circuit responsive to the presence of the pilot flame for causing the switching device to de-energize the spark producing circuit for activating the valve to permit gas flow therethrough. Thus, the gas flow to the main gas burner is automatically terminated during the time when the pilot flame is being re-established, following an inadvertant extinction of the flame. Other features relate to a pilot valve and main gas valve interlock arrangement provided to insure against wasted fuel and for safety purposes.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic circuit diagram of a fuel ignition system control arrangement, which is constructed in accordance with the principles of the present invention;

FIG. 2 is another fuel ignition system control arrangement, which is constructed in accordance with the present invention, and which is adapted to be used with an input transformer;

FIG. 3 is yet another schematic circuit diagram of a control arrangement, which is constructed in accordance with the present invention;

FIG. 4 is a schematic circuit diagram of a fuel ignition arrangement having a pilot and main gas valve interlock arrangement in accordance with the present invention; and

FIG. 5 is a schematic circuit diagram of another fuel ignition arrangement having a pilot and main gas valve interlock arrangement in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and more particularly FIG. 1, there is shown the ignition system control arrangement including an ignition circuit 20 having an ignition transformer T1 for applying voltages between a pair of

ignition electrodes

21 and 22 to ignite a gaseous fuel emanating from a pilot conduit 23 of a gas burner apparatus (not shown). One of the electrodes 21 is connected to the secondary winding 36 of the ignition transformer and the second electrode 22 is connected to ground, or to the conduit 23. Alternatively, the conduit 23, which is grounded, may serve as the grounded electrode 22.

The ignition circuit 20 has a pair of input leads 30 and 31 connectable to an AC. voltage source, which may be a standard 60 Hertz, volt A.C. line voltage source. A relay R1, a diode DI, the primary winding 32 of the ignition transformer T1, a capacitor C1 and a second diode D2 are connected in a series circuit between the

line conductors

30 and 31 providing a unidirectional circuit path for charging capacitor C1 to a predetermined voltage whenever the voltage on line 30 is positive with respect to line 31. A controlled switch ing device, embodied in the exemplary example as a silicon controlled rectifier SCRl, has an anode-cathode circuit connected between

junction points

33 and 34 in shunt with the primary winding 32 of the ignition transformer and the capacitor C1. The silicon controlled rectifier which is normally non-conducting, provides a normally open shunt circuit permitting capacitor C1 to charge whenever line 30 is positive with respect to line 31.

Whenever the silicon controlled rectifier is rendered conductive, the relay R1 operates in series with the cathode-anode circuit of the silicon controlled rectifier SCRI. Therefore, in accordance with the present invention normally-closed contacts Rl-A are of the realy R1 connected in series with the main gas valve MGV for the burner apparatus and a thermostatically-controlled normally-closed switching device THS between the

leads

30 and 31 open the circuit to the main gas valve MGV to prevent the flowing of gaseous fuel to the main burner apparatus. As a result, should both the flame to the main burner apparatus and the flame produced at the pilot conduit 23 be extinguished inadvert- 3 antly, the silicon controlled rectifier SCRl is rendered conductive to cause the relay R1 to operate, whereby the contacts R1-A open to de-energize the main gas valve solenoid MGV to prevent any unburned gas from flowing out of the main burner apparatusv A capacitor C2 is connected between the cathode of the silicon controlled rectifier SCRl and line conductor 31. The gate of the silicon controlled rectifier SCR1 is connected over a resistor R2 to line conductor 31.

A pair of resistors R3 and R4 are connected in series across

conductors

30 and 31. The junction of the resistors R3 and R4 is connected to the cathode of the silicon controlled rectifier at junction 34. Whenever the voltage on line 31 is positive with respect to line 30 current flow over the unidirectional current path is blocked by diodes D1 and D2, and thus current flows over resistors R3 and R4 from line 31 to line 30.

The resultant voltage drop across resistor R4 provides a potential at the cathode of the silicon controlled rectifier SCRl relative to the gate of the silicon controlled rectifier sufficient to trigger the silicon controlled rectifier SCRl into conduction. Consequently, a shunt circuit path is provided across the series connected primary winding 32 of ignition transformer T1 permitting the capacitor C1 to discharge through the primary winding 32 and the anode-cathode circuit of the silicon controlled rectifier SCRl.

The secondary winding 36 of the ignition transformer T1 has one end 37 connected to the ungrounded ignition electrode 21, and a second end 38 connected over isolation capacitor C4 to line 30 and to a control circuit 40 which includes a transistor Q1. The base of transisto: O1 is connected over a resistor R5 and a diode D3 to end 38 of the secondary winding and over capacitor C3 to conductor 31. The collector of the transistor O1 is connected to the cathode of the silicon controlled rectifier SCRl at junction 34. The emitter of transistor O1 is connected directly to line conductor 31.

During the operation of the circuit 20, when the flame at the conduit 23 is extinguished, the silicon controlled rectifier SCRl is rendered conductive and nonconductive alternatingly in an oscillating manner to cause a series of current pulses in the primary winding 32 and thus a series of voltage pulses are induced in the secondary winding 36 for the purpose of generating a series of sparks across the

electrodes

21 and 22 until the gaseous fuel emanating from the conduit 23 is ignited. In order to maintain the relay R1 operated to insure that the main gas valve MGV is open during the ignition process, a capacitor C5 and a suitably poled diode D4 are each connected in parallel with the relay coil R1 to cause it to have a slow-to-release operation for a predetermined time delay interval which is greater than the period of oscillation of the silicon controlled rectifier SCRl, the ignition transformer T1 and the capacitor Cl.

OPERATION OF THE IGNITION CIRCUIT For purposes of illustration of the operation of the automatic fuel ignition circuit provided by the present invention, it is assumed that the ignition circuit is energized with the silicon controlled rectifier SCRl nonconducting and transistor Q1 being cut off, and that the flame is provided between the

ignition electrodes

21 and 22 and at the main burner apparatus.

When line conductor 30 becomes positive with respect to line conductor 31 during a first half cycle of the applied AC voltage, current from the AC source 4 flows through relay R1, diode D1 and the primary winding 32 of ignition transformer T1 to charge capacitor C1 and through diode D2 to the line conductor 31.

During the next half cycle of the applied A.C. voltage, line conductor 31 becomes positive with respect to line conductor 30 and current flows from line conductor 31 through resistors R4 and R3 to line conductor 30. The voltage drop across resistor R4 is sufficient to trigger the silicon controlled rectifier SCRl to conduction. When the silicon controlled rectifier SCRl is rendered conducting, capacitor C1 discharges through the primary winding 32 of ignition transformer T1 and the anode-cathode circuit of the silicon controlled rectifier SCRl which is connected in parallel with the primary winding 32 and capacitor C1. The discharge of capacitor C1 through the primary winding 32 provides a current pulse in the primary winding 32. This current pulse in turn produces a voltage pulse in the secondary winding 36 of the ignition transformer T1, which is applied to the

ignition electrodes

21 and 22, generating a spark across

electrodes

21 and 22. The spark gap provided by the electrodes is placed in the region adjacent the outlet 26 of the conduit 22. Accordingly, when the gas flow control valve 25 is open and gas is emanating from the conduit 23, the sparks generated will ignite the gas.

The ignition sequence with capacitor C1 being charged and discharged during alternate half cycles of the power signal will continue, providing sparks between the

electrodes

21 and 22 at the rate of 60 sparks per second until the gas is ignited. The capacitor C5 and diode D4 maintain the relay R1 operated during the oscillations.

When a flame is present between the

electrodes

21 and 22, the resistance between the electrodes decreases. Accordingly, when the gas has been ignited, and as line conductor 31 again becomes positive with respect to line conductor 30, current from A.C. source flows from the conductor 31 through capacitor C3, resistor R5, diode D3, the secondary winding 36 of the ignition transformer T1 to electrode 21, and through the flame to electrode 22 which is connected to ground. This current flow produces a voltage across capacitor C3 causing the base of transistor 01 to become positive with respect to emitter of transistor Q1, driving transistor Q1 into saturation. Consequently, transistor Q1 through its emitter-collector circuit, effectively short-circuits the gate to cathode circuit of the SCRl, causing SCRl to be turned off.

Transistor Q1 remains conducting as long as the flame remains lit such'that the silicon controlled rectifier SCRl is not triggered into conduction and capacitor C1 does not discharge. Therefore, the current flow through relay R1 is reduced to zero and the relay restores to arm the main gas valve circuit. Thus, when the flame is lit, the control circuit 40 inhibits the generation of sparks between

electrodes

21 and 22.

If the pilot flame and the main burner flame suddenly become extinguished, such as by flame-out or sudden interruption in the gas supply, the impedance of the charging path for capacitor C3 increases to a value where capacitor C3 discharges and transistor O1 is cut off. Under such condition, silicon controlled rectifier SCRl again conducts during alternate half cycles of the applied voltage to permit relay R1 to operate and to permit capacitor C1 to discharge thereby effecting the generation of sparking between

electrodes

21 and 22 to reestablish the flame. Relay R1 operates and opens the circuit to the valve MGV to turn off the gas flowing to the main burner apparatus until a flame is established at the

electrodes

21 and 22. When a flame is established, the relay R1 is de-energized to cause the valve MGV to open, causing gas to flow to the burner apparatus for ignition by the thus established pilot flame.

In one exemplary embodiment, the circuit components may have the followingvalues:

Relay Rl Resistor R2 100 ohms Resistor R3 680K ohms Resistor R4 6800 ohms Resistor RS megohms Capacitor Cl l microfarad Capacitor C2 0.47 microfarads Capacitor C3 0.01 microfarads Capacitor C4 680 micromicrofarads Diodes Di, D2, D3 7 Silicon Control Rectifier SCRl CIOGB Transistor Ql 2N5355 Transformer T1 The foregoing values are provided to illustrate one embodiment for the fuel ignition circuit provided by the present invention and are not intended as a limitation of true scope of the invention.

Referring now to FIG. 2 of the drawings, there is shown a circuit A which is similar in design and operation to the circuit 20 of FIG. 1, except that the circuit 20A is adapted to operate from a 24 volt A.C. source (not shown) over an input transformer T2. Portions of the circuit 20A which are similar to the corresponding portions of the circuit 20 are designated in FIG. 2 with the same reference character as used in FIG. 1 with the addition of the letter A. For example, the relay R1 of FIG. 1 is designated Rl-A of the circuit 20A of FIG. 2.

The transformer T2 includes a primarywinding 43 adapted to be coupled to a 24 volt A.C. source with the thermostatic switch TI-IS-A, relay contacts RlA-A, and valve MGV-A being connected in a series circuit in shunt with the primary winding 43. A secondary winding 45 supplies power to the remaining portions of the circuit 20-A.

Referring now to FIG. 3, there is shown a circuit 208 which is constructed in accordance with the present invention and which is similar to the circuit 20 of FIG. 1. The portions of the circuit 203 which correspond to similar portions of the circuit 20 are designated by similar reference characters, except that the reference characters of FIG. 3 have an additional letter B at the end thereof. Forexample, the relay R1 of FIG. I has a corresponding relay Rl-B of the circuit 20B of FIG. 3. The circuit 208 is similar to the circuit 20 except that the circuit 20B is designed to operate from a 24 volt A.C. source (not shown) except that the relay Rl-B operates in response to the conduction of the silicon controlled rectifier 'SCRI-B without being directly coupled to the anode thereof.

A coupling capacitor 51 connects the line-B to the shunt-connected primary winding 32-B of an ignition transformer Tl-B, a capacitor Cl-B and a diode 53. A series circuit including the relay contacts RlA-B, the thermostatic contacts TI-IS-B and the main gasvalve MGV-B is connected directly between the input leads 30-B and 3l-B. The silicon controlled rectifier SCRl-B has its cathode-anode circuit connected between the opposite end of the primary winding 32,-B of the transformer Tl-B and a diode D2-B. The relay Rl-B'is connected to the lead 31-B between the diode D2-B and the opposite end of the diode 53, and thus the relay Rl-B is connected in series with the lead 3l-B between 6 the shunt-connected circuit including the valve MGV-B and the shunt-connected circuit including the silicon controlled rectifier SCRl-B. The gate of the silicon controlled rectifier SCRl-B is connected to a point 54 between a pair of series-connected biasing resistors 55 and R2-B which are connected between the capacitor Cl-B and through a suitably poled diode 57 to the relay Rl-B. In place of the transistor 01 of the circuit 20, a programmed unijunction transistor 59 has its cathode-anode circuit connected between the resistor 55 and the relay Rl-B with its-gate electrode connected to a point 61 between a pair of biasing resistors 62 and 64, which in turn are connected between the relay Rl-B and a suitably-poled diode D3-B, and which have a capacitor 66 connected thereacross. A secondary winding 36-8 of the transformer Tl-B is connected at its lower end to the diode D3-B and has a capacitor C4-B connected between the electrode 22-B and the winding 36-8, the capacitor C4-B: serving the same function as the corresponding capacitor in the circuit 20 of FIG. 1.

I Referring now to FIG. 4, there is shown a circuit 20A, whichis similar to the circuit 20A of FIG. 2, and which includes a pilot valve andmain valve interlocking arrangement to provide additional protection against an unsafe failure condition caused by component failures. Components of the circuit 20A which are similar in design and operation to corresponding components of the circuit 20A have the same reference character as the corresponding reference characters for the circuit 20A. with the addition of a prime notation. For example, the diode D3-A of FIG. 2 corresponds to the diode D3-A of FIG. 4.

The circuit 20-A has the main gas valve MGV-A' connected in parallel with a pilot valve PV, the valve MGV-A' being connected between the line 31-A and a point 51 through normally-closed contacts RlA-A of the relay Rl-A', the valve PV being connected between the line 3l-A' and the point 51 through normally-open contacts RlA-B of the relay Rl-A' and a holding resistor 53 connected in parallel with the contacts RlA-B. The point 51 is connected through a normally-open pressure switch PS to a point 55, which in turn is connected through normally-open thermostatic contacts THS-A' to the line 30A and to the upper end of the input winding 43.

When the thermostat contacts close, the circuit 20A is energized to close contacts RlA-B and opencontacts RlA-A'. With gas available, the pressure switch contacts are closed to complete the circuit to the pilot valve. The pilot valve and main valve are connected in series communication with gas under pressure and the pilot gas is taken off at a tapping between the two valves. v I Y Therefore, as previously described with circuits 20 and 20A, with circuit 20-A' energized, sparks appear at the electrodes and with the pilot valve energized, gas is present and therefore an ignited pilot results.

As soon as the pilot flame is ignited, the circuit 20-A' reacts to turn off the spark generator and de-energize the relay Rl-A' to allow the normally-closed contacts RlA-A' to make and turn on the main gas valve. The holding resistor 53 maintains the pilot valve on, but it limitsthe current supplied to the valve so that it cannot open through resistor 53,. e

For safety purposes, an effective open circuit in the relay Rl-A or other circuit components or leads prevents the normally-open contacts RlA-B from closing and the pilot valve remains closed. The pilot valve being connected in series communication with the main gas also prevents gas from flowing to the main burner. Also, an effective short circuit in the relay Rl-A' of the circuit -A' maintains the pilot valve energized and the main gas valve de-energized. Under flameout conditions, the circuit 20-A reacts to open the RlA-A' contacts in less than 0.8 second and an attempt is made to re-ignite the pilot.

The pressure switch is utilized to protect against multiple failures, such, for example, as one occurring during a call for heat followed by a successful ignition and an open circuit occurs in the circuit 20-A followed by a gas interruption, the system would continue to supply unburned gas if it were not for the pressure switch PS,

which reacts to open its contacts and de-energize the pilot valve which cuts off the gas supply to both the pilot and the main burner.

Referring now to FIG. 5, there is shown a circuit 20A, which is identical to the circuit 20A with the addition of a bi-metallic warp switch WS operated by its heater WSH connected in series with the pilot valve PV" between it and the normally-open contacts RlA- B". Components of the circuit 20A" which are similar in design and operation to corresponding components of the circuit 20A have the same reference character' but instead of a prime notation, a double prime is employed. The fluid communications between the pilot valve and the main gas valve are omitted for sake of clarity in FIG. 5, although it is to be understood that a similar such arrangement is provided as shown in FIG. 4.

The warp switch WS shuts off the pilot gas in the event the pilot gas did not ignite. [f pilot ignition did not take place, RlA-B" contacts in series with the warp switch heater and the pilot valve remain closed to cause thewarp-switch heater to actuate the warp switch contacts to the open position to shut down the system. Manual resetting is required to try the operation again.

I claim:

1. In a fuel ignition system having gas burner apparatus for burning gaseous fuel flowing thereto under the control of valve means in response to thermostaticallycontrolled switching means requesting ignition, and having means for igniting gaseous fuel, a control arrangement comprising spark producing means including an ignition transformer having a primary winding and a secondary winding, capacitor means, means including a bi-stable switching device connecting said primary winding and said capacitor means in a series unidirectional current path across a source of cyclical A.C. voltage for charging said capacitor means to a predetermined voltage during each first half cycle of the AC. voltage, switching means including a controlled switching device having a pair of electrodes connected in a shunt circuit path across said capacitor means and said primary winding and a control electrode connected to a point of reference voltage, said controlled switching device being enabled responsive to each second half cycle of the AC. voltage for causing discharge of said capacitor means through said primary winding for producing a pulse of current through said primary winding, a pair of ignition electrodes spaced apart to provide a gap therebetween and connected in a series circuit with said secondary winding whereby an ignition spark is generated between said electrodes whenever a pulse of current is provided in said primary winding, said electrodes being positioned so that ignition sparks between said electrodes will ignite gas from said gas burner apparatus to provide a flame which bridges the gap between said electrodes, said bi-stable switching device being energized in response to enabling of said controlled switching device to deactivate said valve means, and thus terminate gas flow to the burner apparatus, and control means enabled whenever a flame bridges the gap between said electrodes to inhibit said controlled switching device thereby preventing the generation of further ignition sparks and disabling said bi-stable switching device whereby said valve means is activated to permit gas flow therethrough.

2. A control arrangement according to claim 1, wherein said bi-stable switching device is a relay having normally-closed contact means for controlling said valve means.

3. A control arrangement according to claim 2, wherein said controlled switching device includes a silicon controlled rectifier coupled in series with an operate coil of said relay to cause it to operate whenever said rectifier is rendered conductive, first and second input means adapted to be coupled to a source of AC. power, said valve means being coupled in a first shunt circuit across said first and second input means, said silicon controlled rectifier being coupled in a second shunt circuit across said first and second input means with said relay being coupled in series with said second input means between said first and said second shunt circuits.

4. A control arrangement according to claim 2, further including an input transformer having a primary winding and a secondary winding, said valve means being connected in series with said normally-closed contact means and with the thermostatically-controlled switching means, the series circuit including said valve means, said normally-closed contact means and the thermostatically-controlled switching means being in parallel with said primary winding, said primary winding being adapted to be connected to a source of alternating power;

S. A control arrangement according to claim 1 wherein said control means includes a transistor having an output circuit connected to an electrode of said controlled switching device and a control electrode, and circuit means connected in series with said secondary winding and said ignition electrodes for providing a control voltage over said control electrode whenever a flame bridges said ignition electrodes for enabling said transistor to extend a disabling potential to one electrode of said controlled switching device to maintain said device non-conductive.

6. in an automatic fuel ignition system for providing electronic ignition of gas eman'ating from gas burner apparatus, a bi-stable switching device, an ignition circuit including an ignition transformer having a primary winding and a secondary winding, charging path means including said bi-stable switching device, capacitor means, and said primary winding connected across an AC. voltage source for charging said capacitor means to a predetermined voltage, a normally turned off silicon controlled rectifier having an anode-cathode circuit connected in shunt with said primary winding and said capacitor means, means for effecting the turnon of said silicon controlled rectifier after said capacitor means is charged to said predetermined voltage, enabling said capacitor means to discharge through said primary winding and the anode-cathode circuit of said silicon controlled rectifier thereby providing a pulse of current through said primary winding, a pair of ignition electrodes spaced apart to provide a gap therebetween and connected in a series circuit with said secondary winding so than an ignition spark is generated between said ignition electrodes whenever a pulse of current is provided in said primary winding, said ignition electrodes being positioned so that ignition sparks between said electrodes will ignite gas from said gas burner apparatus to provide a flame which bridges the gap between said electrodes, control means enabled whenever a flame bridges the gap between said electrodes to inhibit turnon of said silicon controlled rectifier thereby preventing the discharge of said capacitor means and the generation ofignition sparks, said bi-stable switching device being deenergized when said silicon controlled rectifier is inhibited for energizing said gas valve means, to supply gas to the gas burner apparatus, said bi-stable switching device being energized when said silicon controlled rectifier is rendered conductive to deenergize said valve means.

7. In an automatic fuel ignition system adapted to be connected to a source of gaseous fuel under pressure and adapted to ignite the fuel supplied to a burner apparatus in response to a thermostatically-controlled switching means, a fuel ignition arrangement comprising spark producing means operable when enabled for producing ignition sparks for igniting a gaseous fuel, pilot valve means operable when energized to supply gaseous fuel under pressure to said spark producing means to produce a pilot flame, sensing means for detecting the presence of said pilot flame, main valve means operable when energized to supply fuel from said pilot valve means to the burner apparatus, and control means including a bi-stable device responsive to enabling of said spark producing means for energizing said pilot valve means when fuel ignition is requested by said thermostatically-controlled means, said bi-stable device preventing operation of said main valve means when energized, and said bi-stable device being de-energized in response to said sensing means detecting a pilot flame for causing said main valve means to be energized to supply fuel to the burner apparatus for ignition by said pilot flame.

8. A fuel ignition arrangement according to claim 7, further including means coupling the inlet of said main valve means and the outlet of said pilot valve means in fluid communication.

9. A fuel ignition arrangement according to claim 8, further including means conveying fuel from the outlet of said pilot valve means to said spark producing means.

10. A fuel ignition arrangement according to claim 7, wherein said bi-stable device comprises a relay having normally closed contacts for controlling said main valve means and having normally open contacts for controlling said pilot valve means.

10 11. A fuel ignition arrangement according to claim 7, further including holding path means for maintaining said pilot valve means energized after said main valve means is energized to supply fuel from said pilot valve means to the burner apparatus.

12. A fuel ignition arrangement according to claim 11, further including time delay means for de-energizing said pilot valve means after a predetermined time interval when fuel ignition fails to occur.

13. A fuel ignition arrangement according to claim 12, wherein said time delay means comprises a bi-metallic switching means having switching contacts in series with said thermostatically-controlled means.

14. In an automatic fuel ignition system including a pilot valve means operable when energized to supply gaseous fuel to a burner apparatus for ignition to establish a pilot flame and main valve means operable when energized to supply gaseous fuel from said pilot means to said burner apparatus for ignition by said pilot flame, a fuel ignition arrangement comprising a bi-stable switching device for controlling the energization of said main valve means and said pilot valve means, ignition means including an ignition transformer having a primary winding and a secondary winding, charging path means including said bi-stable switching device, capacitor means, and said primary winding connected in series across an A.C. voltage source for charging said capacitor means to a predetermined voltage, a normally non-conductive controlled switching device connected in shunt with said primary winding and said capacitor means, means for effecting the turnon of said controlled switching device after said capacitor means is charged to said predetermined voltage, enabling said capacitor means to discharge through said primary winding thereby providing a pulse of current through said primary winding, means including said secondary winding for permitting an ignition spark to be generated whenever a pulse of current is provided in said primary winding for igniting gas from said gas burner apparatus providing a pilot flame, said bi-stable switching device being energized in response to enabling of said controlled switching means to effect energization of said pilot valve means, flame sensing means enabled whenever a pilot flame is established to inhibit said controlled switching device to thereby prevent the generation of ignition sparks and to effect deenergization of said bi-stable switching device for deenergizing said pilot valve means and energizing said main valve means.

15. A fuel ignition arrangement according to claim 14 further including means for providing a holding path for said pilot valve means for maintaining said pilot valve means energized whenever said bi-stable switching device is deenergized.

16. A fuel ignition arrangement according to claim 14 wherein said bi-stable switching device is a relay.

Claims

1. In a fuel ignition system having gas burner apparatus for burning gaseous fuel flowing thereto under the control of valve means in response to thermostatically-controlled switching means requesting ignition, and having means for igniting gaseous fuel, a control arrangement comprising spark producing means including an ignition transformer having a primary winding and a secondary winding, capacitor means, means including a bi-stable switching device connecting said primary winding and said capacitor means in a series unidirectional current path across a source of cyclical A.C. voltage for charging said capacitor means to a predetermined voltage during each first half cycle of the A.C. voltage, switching means including a controlled switching device having a pair of electrodes connected in a shunt circuit path across said capacitor means and said primary winding and a control electrode connected to a point of reference voltage, said controlled switching device being enabled responsive to each second half cycle of the A.C. voltage for causing discharge of said capacitor means through said primary winding for producing a pulse of current through said primary winding, a pair of ignition electrodes spaced apart to provide a gap therebetween and connected in a series circuit with said secondary winding whereby an ignition spark is generated between said electrodes whenever a pulse of current is provided in said primary winding, said electrodes being positioned so that ignition sparks between said electrodes will ignite gas from said gas burner apparatus to provide a flame which bridges the gap between said electrodes, said bi-stable switching device being energized in response to enabling of said controlled switching device to deactivate said valve means, and thus terminate gas flow to the burner apparatus, and control means enabled whenever a flame bridges the gap between said electrodes to inhibit said controlled switching device thereby preventing the generation of further ignition sparks and disabling said bi-stable switching device whereby said valve means is activated to permit gas flow therethrough.

3. A control arrangement according to claim 2, wherein said controlled switching device includes a silicon controlled rectifier coupled in series with an operate coil of said relay to cause it to operate whenever said rectifier is rendered conductive, first and second input means adapted to be coupled to a source of A.C. power, said valve means being coupled in a first shunt circuit across said first and second input means, said silicon controlled rectifier being coupled in a second shunt circuit across said first and second input means with said relay being coupled in series with said second input means between said first and said second shunt circuits.

4. A control arrangement according to claim 2, further including an input transformer having a primary winding and a secondary winding, said valve means being connected in series with said normally-closed contact means and with the thermostatically-controlled switching means, the series cirCuit including said valve means, said normally-closed contact means and the thermostatically-controlled switching means being in parallel with said primary winding, said primary winding being adapted to be connected to a source of alternating power.

5. A control arrangement according to claim 1 wherein said control means includes a transistor having an output circuit connected to an electrode of said controlled switching device and a control electrode, and circuit means connected in series with said secondary winding and said ignition electrodes for providing a control voltage over said control electrode whenever a flame bridges said ignition electrodes for enabling said transistor to extend a disabling potential to one electrode of said controlled switching device to maintain said device non-conductive.

6. In an automatic fuel ignition system for providing electronic ignition of gas emanating from gas burner apparatus, a bi-stable switching device, an ignition circuit including an ignition transformer having a primary winding and a secondary winding, charging path means including said bi-stable switching device, capacitor means, and said primary winding connected across an A.C. voltage source for charging said capacitor means to a predetermined voltage, a normally turned off silicon controlled rectifier having an anode-cathode circuit connected in shunt with said primary winding and said capacitor means, means for effecting the turnon of said silicon controlled rectifier after said capacitor means is charged to said predetermined voltage, enabling said capacitor means to discharge through said primary winding and the anode-cathode circuit of said silicon controlled rectifier thereby providing a pulse of current through said primary winding, a pair of ignition electrodes spaced apart to provide a gap therebetween and connected in a series circuit with said secondary winding so than an ignition spark is generated between said ignition electrodes whenever a pulse of current is provided in said primary winding, said ignition electrodes being positioned so that ignition sparks between said electrodes will ignite gas from said gas burner apparatus to provide a flame which bridges the gap between said electrodes, control means enabled whenever a flame bridges the gap between said electrodes to inhibit turnon of said silicon controlled rectifier thereby preventing the discharge of said capacitor means and the generation of ignition sparks, said bi-stable switching device being deenergized when said silicon controlled rectifier is inhibited for energizing said gas valve means, to supply gas to the gas burner apparatus, said bi-stable switching device being energized when said silicon controlled rectifier is rendered conductive to deenergize said valve means.

11. A fuel ignition arrangement according to claim 7, further including holding path means for maintaining said pilot valve means energized after said main valve means is energized to supply fuel from said pilot valve means to the burner apparatus.