Electronic pilot ignition and flame detection circuit

Claim 2

In an automatic fuel ignition system including a pilot source for establishing a pilot flame and valve means operable when energized to supply a gaseous fuel to burner apparatus, an electronic control circuit for monitoring the pilot flame and controlling the energization of said valve means, said control circuit comprising pilot flame sensing means including sensing electrode means located in the proximity of the pilot source for sensing said pilot flame, and pulse generating means controlled by said pilot flame sensing means to provide pulse outputs of a first amplitude whenever the pilot flame is established and to provide pulse outputs of a second amplitude whenever the pilot flame is extinguished, and switching means responsive to pulses at said first amplitude to effect energization of said valve means, said switching means being disabled whenever pulses at said second amplitude are provided by said pulse generating means to cause deenergization of said valve means to prevent the flow of said gaseous fuel to the burner apparatus whenever the pilot flame is extinguished.

Claim 3

An electronic control circuit as set forth in claim 1 wherein said pulse generating means includes a normally non-conducting controlled switching device, first circuit means including capacitor means connected to an input electrode of said controlled switching device and means connected to a source of potential to provide a charging path for said capacitor means, discharge circuit means including said controlled switching device for discharging said capacitor means whenever said controlled switching device is rendered conductive, said pilot flame sensing means including second circuit means connected to a control electrode of said controlled switching device and operable to periodically render said controlled switching device conductive permitting said capacitor means to discharge over said discharge path to provide said pulse outputs.

Claim 4

An electronic control circuit as set forth in claim 2 wherein said second circuit means includes further capacitor means chargeable at a first rate whenever the pilot flame is established to provide a potential at said control electrode to render said controlled switching device conductive at a time when said capacitor means of said pulse generating means has charged to a first voltage and chargeable at a second rate whenever the pilot flame is extinguished to provide a potential at said control electrode to render said controlled switching device conductive at a time when said capacitor means of said pulse generating means has charged to a second voltage.

Claim 5

An electronic control circuit as set forth in claim 2, wherein said pilot source includes a pilot valve means operable when energized to supply pilot gas to an outlet, and pilot ignition means operable when energized to generate ignition sparks for igniting pilot gas emanating from said outlet to establish a pilot flame, said normally non-conducting controlled switching device being responsive to pulses at said first amplitude to effect the deenergization of said pilot ignition means.

Claim 6

An electronic control circuit as set forth in claim 4, wherein said switching means includes a further controlled switching device which is normally disabled and enabled by pulses at said first amplitude to effect energization of said valve means.

Claim 7

An electronic control circuit as set forth in claim 11, wherein said valve means includes a solenoid operated valve having a main gas valve coil and a secondary coil, said secondary coil being energized to cause the pilot ignition means to be disabled whenever said main gas valve coil is energized.

Claim 8

An electronic control circuit as set forth in claim 5, wherein said switching means further includes normally deenergized relay means, said relay means being energized by said further controlled switching device to control the energization of said gas valve means whenever pulses of said first amplitude are provided by said pulse generating means.

Claim 9

An electronic control circuit as set forth in claim 7, wherein said relay means is operable when energized to effect deenergization of said pilot ignition means.

Claim 10

An electronic control circuit as set forth in claim 1, further including power means adapted to be coupled to a direct current source of power for supplying a DC power signal to said control circuit, and inverter means responsive to said DC power signal to provide alternating current signals for said control circuit.

Claim 11

In an automatic fuel ignition system, pilot ignition means operable when energized to generate ignition sparks for igniting pilot gas emanating from a pilot source to establish a pilot flame, pilot flame monitoring means including flame sensing means having sensing electrode means located adjacent said pilot source for sensing said pilot flame and pulse generating means including a controlled switching device having first and second control electrodes, first capacitor means connected to said first control electrode, second capacitor means connected to said second control electrode, means for permitting said first capacitor means to charge to a predetermined value to provide a first potential at said first control electrode, means permitting said second capacitor means to charge to a predetermined value at a first rate whenever said pilot flame is extinguished and at a second rate whenever said pilot flame is established to provide a second potential at said second control electrode, said controlled switching device being enabled whenever the potential difference between said first and second control electrodes exceeds a predetermined value to permit said first capacitor means to discharge over said controlled switching device to effect the generation of pulse outputs of a first amplitude whenever the pilot flame is established and pulse outputs of a second amplitude whenever the pilot flame is extinguished, switching means responsive to pulses of said first amplitude to de-energize said pilot ignition means and to prepare an energizing path for gas valve means which supplies gas to gas burner apparatus, said switching means being disabled whenever pulses of said second amplitude are provided by said pulse generating means to interrupt said energizing path for said gas valve means and effect energization of said pilot ignition means whenever said pilot flame is extinguished.

Claim 12

In an automatic fuel ignition system, pilot ignition means operable when energized to generate ignition sparks for igniting pilot gas emanating from a pilot source to establish a pilot flame, pilot flame monitoring means including flame sensing means having sensing electrode means located adjacent said pilot source for sensing said pilot flame and pulse generating means including a controlled switching device having first and second control electrodes, first capacitor means connected to said first control electrode, second capacitor means connected to said second control electrode, means for permitting said first capacitor means to charge to a predetermined value to provide a first potential at said first control electrode, means permitting said second capacitor means to charge to a predetermined value at a first rate whenever said pilot flame is extinguished and at a second rate whenever said pilot flame is established to provide a second potential at said second control electrode, said controlled switching device being enabled whenever the potential difference between said first and second control electrodes exceeds a predetermined value to permit said first capacitor means to discharge over said controlled switching device to effect the generation of pulse outputs of a first amplitude whenever the pilot flame is established and pulse outputs of a second amplitude whenever the pilot flame is extinguished, switching means responsive to pulses of said first amplitude to de-energize said pilot ignition means and to prepare an energizing path for gas valve means which supplies gas to gas burner apparatus, said switching means being disabled whenever pulses of said second amplitude are provided by said pulse generating means to interrupt said energizing path for said gas valve means and effect energization of said pilot ignition means whenever said pilot flame is extinguished.

Claim 13

An electronic control circuit as set forth in claim 10 wherein said switching means includes normally de-energized relay means having contact means connected in an enErgizing path for said valve means and a normally disabled controlled switching device connected in series with a coil of said relay means across a source of potential, said controlled switching device of said switching means being enabled responsive to pulses at said first amplitude to effect energization of said relay means to operate said contact means to permit energization of said gas valve means.

Claim 14

An electronic circuit as set forth in claim 11 wherein said relay means includes further contact means connected in an energizing circuit for said pilot ignition means and operated whenever said relay means is de-energized to permit energization of said pilot ignition means.

Claim 15

In an automatic fuel ignition system including pilot source means for establishing a pilot flame and valve means operable when energized to supply a gaseous fuel to burner apparatus, an electronic control circuit for monitoring the pilot flame and controlling the energization of said valve means said control circuit comprising pilot flame monitoring means having a controlled switching device, first circuit means including capacitor means connected to a source of cyclical AC voltage and to a first control electrode of said controlled switching device to permit said capacitor means to charge during each first half cycle of the AC voltage thereby providing a potential at said first control electrode, second circuit means connected to said AC voltage source and to a second control electrode of said controlled switching device including sensing electrode means located in the proximity of the pilot source means for sensing the pilot flame such that said second circuit means provides a potential at said second control electrode effective to render said controlled switching device conductive at a first time during each first half cycle of the AC voltage whenever the pilot flame is extinguished and to render said controlled switching device conductive at a later time during each first half cycle of the AC voltage whenever the pilot flame is established, output means for providing a discharge path over said controlled switching device for said capacitor means whenever said controlled switching device is rendered conductive to provide a pulse output, and switching means responsive to the pulse output provided by said flame monitoring means whenever the pilot flame is established to prepare an energizing path for said valve means, said switching means being disabled to interrupt said energizing path for said valve means whenever the pilot flame is extinguished, and said controlled switching device being maintained non-conductive in the event of a component failure in said pilot flame monitoring circuit means.

Claim 16

In an automatic fuel ignition system including pilot source means for establishing a pilot flame and valve means operable when energized to supply a gaseous fuel to burner apparatus, an electronic control circuit for monitoring the pilot flame and controlling the energization of said valve means said control circuit comprising pilot flame monitoring means having a controlled switching device, first circuit means including capacitor means connected to a source of cyclical AC voltage and to a first control electrode of said controlled switching device to permit said capacitor means to charge during each first half cycle of the AC voltage thereby providing a potential at said first control electrode, second circuit means connected to said AC voltage source and to a second control electrode of said controlled switching device including sensing electrode means located in the proximity of the pilot source means for sensing the pilot flame such that said second circuit means provides a potential at said second control electrode effective to render said controlled switching device conductive at a first time during each first half cycle of the AC voltage whenever the pilot flame is extinguished and to render said controlled switching device conductive at a later time during each first half cycle of the AC voltage whenever the pilot flame is established, output means for providing a discharge path over said controlled switching device for said capacitor means whenever said controlled switching device is rendered conductive to provide a pulse output, and switching means responsive to the pulse output provided by said flame monitoring means whenever the pilot flame is established to prepare an energizing path for said valve means, said switching means being disabled to interrupt said energizing path for said valve means whenever the pilot flame is extinguished, and said controlled switching device being maintained non-conductive in the event of a component failure in said pilot flame monitoring circuit means.

Claim 17

An electronic control circuit in a fuel ignition system as set forth in claim 13 wherein said pilot source means includes a pilot source and pilot ignition means operable when energized to generate ignition sparks for igniting pilot gas emanating from said pilot source to establish a pilot flame, said switching means including normally de-energized relay means having contact means for normally connecting said pilot ignition means to said AC voltage source to energize said pilot ignition means whenever the pilot flame is extinguished, said relay means being energized to operate said contact means to thereby disconnect said pilot ignition means from said AC voltage source whenever the pilot flame is established.

Claim 18

An electronic control circuit in a fuel ignition system as set forth in claim 14 wherein said switching means further includes a further controlled switching device connected in series with a coil of said relay means to said AC voltage source, said further controlled switching device being normally non-conducting and being rendered conductive responsive to the pulse output of said flame monitoring means to effect energization of said relay means during each first half cycle of said AC voltage whenever the pilot flame is established, said relay means having further contAct means connected in an energizing circuit for said valve means and operated whenever said relay means is energized to permit energization of said valve means.

Claim 19

An electronic control circuit is a fuel ignition system as set forth in claim 15 wherein said switching means includes means for maintaining said relay means energized during each second half cycle of the AC voltage.

Claim 20

An electronic control circuit in a fuel ignition system as set forth in claim 16 wherein said output means of said pilot flame monitoring means includes a pair of resistors connected in parallel between an output electrode of said controlled switching device and a point of reference potential for said AC voltage source.

Claim 21

In an automatic fuel ignition system including a pilot source for establishing a pilot flame and valve means operable when energized to supply a gaseous fuel to burner apparatus, an electronic control circuit for monitoring the pilot flame and controlling the energization of said valve means comprising input means, said control circuit including first and second conductor means for supplying a cyclical AC voltage to said control circuit, a normally non-conducting controlled switching device, first circuit means connected between said first and second conductor means, said first circuit means including first capacitor means connected to a first control electrode of said controlled switching device and chargeable during each first half cycle of said AC voltage to provide a potential at said first control electrode, second circuit means including second capacitor means connected between a point of reference potential and said second conductor means, means for connecting a second control electrode of said controlled switching device to said point of reference potential, sensing electrode means, and means for connecting said sensing electrode means to said first conductor means, said sensing electrode means being located in the proximity of the pilot source and positioned in a spaced relationship with said point of reference potential to provide a gap therebetween which is bridged by the pilot flame whenever the pilot flame is established such that a charging path for said second capacitor means is provided between said first and second conductor means over said gap to permit said second capacitor means to charge at a first rate whenever the pilot flame is extinguished to thereby provide a potential at said second control electrode and to permit said second capacitor means to charge at a faster rate whenever the pilot flame is established and bridges said gap to thereby provide a potential at said second control electrode, said controlled switching device being rendered conductive whenever the potential difference between said first and second control electrodes exceeds a predetermined amount such that said controlled switching device is rendered conductive at a first time during each first half cycle of the AC voltage whenever the pilot flame is extinguished and at a later time during each first half cycle of the AC voltage whenever the pilot flame is established, output means for permitting said first capacitor means to discharge over said controlled switching device whenever said controlled switching device is rendered conductive to effect the generation of a pulse output, and switching means responsive to the pulse output provided over said output means whenever the pilot flame is established to prepare an energizing path for said valve means, said switching means being disabled to interrupt said energizing path for said valve means whenever the pilot flame is extinguished.

Claim 22

In an automatic fuel ignition system including a pilot source for establishing a pilot flame and valve means operable when energized to supply a gaseous fuel to burner apparatus, an electronic control circuit for monitoring the pilot flame and controlling the energization of said valve means comprising input means, said control circuit including first and second conductor means for supplying a cyclical AC voltage to said control circuit, a normally non-conducting controlled switching device, first circuit means connected between said first and second conductor means, said first circuit means including first capacitor means connected to a first control electrode of said controlled switching device and chargeable during each first half cycle of said AC voltage to provide a potential at said first control electrode, second circuit means including second capacitor means connected between a point of reference potential and said second conductor means, means for connecting a second control electrode of said controlled switching device to said point of reference potential, sensing electrode means, and means for connecting said sensing electrode means to said first conductor means, said sensing electrode means being located in the proximity of the pilot source and positioned in a spaced relationship with said point of reference potential to provide a gap therebetween which is bridged by the pilot flame whenever the pilot flame is established such that a charging path for said second capacitor means is provided between said first and second conductor means over said gap to permit said second capacitor means to charge at a first rate whenever the pilot flame is extinguished to thereby provide a potential at said second control electrode and to permit said second capacitor means to charge at a faster rate whenever the pilot flame is established and bridges said gap to thereby provide a potential at said second control electrode, said controlled switching device being rendered conductive whenever the potential difference between said first and second control electrodes exceeds a predetermined amount such that said controlled switching device is rendered conductive at a first time during each first half cycle of the AC voltage whenever the pilot flame is extinguished and at a later time during each first half cycle of the AC voltage whenever the pilot flame is established, output means for permitting said first capacitor means to discharge over said controlled switching device whenever said controlled switching device is rendered conductive to effect the generation of a pulse output, and switching means responsive to the pulse output provided over said output means whenever the pilot flame is established to prepare an energizing path for said valve means, said switching means being disabled to interrupt said energizing path for said valve means whenever the pilot flame is extinguished.

Claim 23

An electronic control circuit as set forth in claim 18 wherein said first circuit means includes means for limiting the potential at said first control electrode of said controlled switching device to a predetermined value.

Claim 24

An electronic control circuit as set forth in claim 18 wherein said second circuit means includes means connected between said second controlled switching devIce and said second conductor means for limiting the potential at said second control electrode.

Claim 25

An electronic control circuit as set forth in claim 18 wherein said switching means comprises normally de-energized relay means having an energizing coil and contact means connected in the energizing path for said valve means and a further normally non-conductive controlled switching device connected in series with said coil between said first and second conductor means, said further controlled switching device being rendered conductive by the pulse output provided over said output means during each first half cycle of the AC voltage whenever the pilot flame is established to effect energization of said relay means to operate said contact means.

Claim 26

An electronic control circuit as set forth in claim 19 wherein said further controlled switching device is rendered non-conductive during each second half cycle of the AC voltage and said switching means further includes means for maintaining said relay means energized during the second half cycle of the AC voltage.

Claim 27

An electronic control circuit as set forth in claim 3 wherein said controlled switching device is maintained non-conductive in the event of a component failure in said pilot flame monitoring means.