Fuel ignition system having interlock protection and electronic valve leak detection

Claim 2

In a fuel ignition system including a pilot valve operable when energized to supply fuel to a pilot outlet for ignition to establish a pilot flame, and a main valve operable when energized to supply fuel to a burner apparatus for ignition by the pilot flame to provide a flame at said burner apparatus, a control circuit comprising interlock means including first switching means operable when enabled to energize said pilot valve, and to prepare an energizing path for said main valve, activate means operable in response to a request for heat to enable said first switching means, second switching means, flame sensing means for maintaining said second switching means disabled in the absence of a flame at said pilot outlet to permit said first switching means to be enabled by said activate means and for enabling said second switching means to operate when a pilot flame is established at said pilot outlet to prevent said first switching means from being enabled by said activate means, and delay means enabled by said second switching means when a pilot flame is sensed to effect the energization of said main valve at the end of a time interval initiated by the operation of said second switching means, said flame sensing means preventing the energization of said main valve in the event that a flame is provided at said burner apparatus during said time interval.

Claim 3

A system as set forth in claim 1 wherein said interlock means further includes timeout means energized in response to said activate means to define a trial for ignition interval and to cause interruption of the supply of fuel to at least said pilot outlet if a pilot flame fails to be established during said trial for ignition interval.

Claim 4

A system as set forth in claim 2 wherein said pilot valve and said main valve comprise a redundant valve structure wherein fuel is supplied to said main valve over said pilot valve only when said pilot valve is operated, said timeout means deenergizing said pilot valve at the end of said trial for ignition interval in the absence of a pilot flame to prevent fuel from being supplied to said pilot outlet and said burner apparatus.

Claim 5

A system as set forth in claim 2 wherein said delay means includes third switching means operable when enabled to energize said main valve, and enabling means responsive to said second switching means to enable said third switching means, said enabling means including timing means for delaying the enabling of said third switching means for said time interval after said second switching means operates.

Claim 6

A system as set forth in claim 4 wherein said flame sensing means includes means for causing said second switching means to disable said delay means and to cause said timeout means to deenergize said pilot valve if a flame is provided at said burner apparatus before said third switching means is enabled.

Claim 7

A system as set forth in claim 4 wherein said third switching means is operable when enabled to deenergize said timeout means.

Claim 8

A system as set forth in claim 4 wherein said second and third switching means include means for providing an energizing path for said interlock means to permit enabling of said first switching means, the enabling of said first switching means being prevented whenever said energizing path for said interlock means is interrupted when said activate means operates.

Claim 9

In a fuel ignition system including a pilot valve operable when energized to supply fuel to a pilot outlet for ignition to establish a pilot flame, and a main valve operable when energized to supply fuel to a burner apparatus for ignition by the pilot flame to provide a flame at said burner apparatus, a control circuit comprising interlock means including first switching means operable when enabled to energize said pilot valve, activate means for enabling said first switching means, second switching means, flame sensing means energized continuously and independently of said activate means for causing said second switching means to be disabled in the absence of a flame at said pilot outlet to permit said first switching means to be enabled by said activate means and for causing said second switching means to be enabled whenever a pilot flame is provided at said pilot outlet to prevent said first switching means from being enabled by said activate means, and delay means responsive to said second switching means to effect the energization of said main valve at the end of a time interval initiated by the enabling of said second switching means, said flame sensing means preventing the energization of said main valve in the event that a flame is provided at said burner apparatus during said time interval.

Claim 10

In a fuel ignition system including a pilot valve operable when energized to supply fuel to a pilot outlet for ignition to establish a pilot flame, and a main valve operable when energized to supply fuel to a burner apparatus for ignition by the pilot flame to provide a flame at said burner apparatus, a control circuit comprising interlock means including first switching means operable when enabled to energize said pilot valve, activate means for enabling said first switching means, second switching means, flame sensing means energized continuously and independently of said activate means for causing said second switching means to be disabled in the absence of a flame at said pilot outlet to permit said first switching means to be enabled by said activate means and for causing said second switching means to be enabled whenever a pilot flame is provided at said pilot outlet to prevent said first switching means from being enabled by said activate means, and delay means responsive to said second switching means to effect the energization of said main valve at the end of a time interval initiated by the enabling of said second switching means, said flame sensing means preventing the energization of said main valve in the event that a flame is provided at said burner apparatus during said time interval.

Claim 11

A system as set forth in claim 8 wherein said flame sensing means includes a controlled switching device and timing means for controlling said controlled switching device to effect enabling of said second switching means when a pilot flame is established and to prevent enabling of said second switching means in the absence of a pilot flame.

Claim 12

A system as set forth in claim 9 wherein said flame sensing means includes limiting means operable when enabled to permit said controlled switching device to maintain said second switching means enabled when a flame is provided at said burner apparatus, said limiting means being disabled during said time interval preventing said controlled switching device from maintaining said second switching means enabled when a flame is provided at said burner apparatus during said time interval.

Claim 13

In a fuel ignition system including a pilot valve operable when energized to supply fuel to a pilot outlet for ignition to establish a pilot flame at said pilot outlet, and a main valve operable when energized to supply fuel to a burner apparatus for ignition by the pilot flame to provide a flame at said burner apparatus, a control circuit comprising interlock means including first switching means, activate means for enabling said first switching means over a first circuit path to complete a second circuit path to energize said pilot valve, second switching means, flame sensing means for causing said second switching means to complete said first circuit path in the absence of a flame at said pilot to permit said first switching means to be enabled and for causing said second switching means to interrupt said first circuit path whenever a pilot flame is provided at said pilot outlet thereby preventing enabling of said first switching means, and delay means including third switching means and enabling means operable when connected to said second circuit path to enable said third switching means to connect said main valve to said second circuit path for energization thereover, said second switching means connecting said enabling means to said second circuit path after a pilot flame is provided, said enabling means including timing means to delay the enabling of said third switching means for a time interval after said enabling means is connected to said second circuit path, said flame sensing means including limiting means for preventing the energization of said main valve in the event that a flame is provided at said burner apparatus during said time interval.

Claim 14

In a fuel ignition system including a pilot valve operable when energized to supply fuel to a pilot outlet for ignition to establish a pilot flame at said pilot outlet, and a main valve operable when energized to supply fuel to a burner apparatus for ignition by the pilot flame to provide a flame at said burner apparatus, a control circuit comprising interlock means including first switching means, activate means for enabling said first switching means over a first circuit path to complete a second circuit path to energize said pilot valve, second switching means, flame sensing means for causing said second switching means to complete said first circuit path in the absence of a flame at said pilot to permit said first switching means to be enabled and for causing said second switching means to interrupt said first circuit path whenever a pilot flame is provided at said pilot outlet thereby preventing enabling of said first switching means, and delay means including third switching means and enabling means operable when connected to said second circuit path to enable said third switching means to connect said main valve to said second circuit path for energization thereover, said second switching means connecting said enabling means to said second circuit path after a pilot flame is provided, said enabling means including timing means to delay the enabling of said third switching means for a time interval after said enabling means is connected to said second circuit path, said flame sensing means including limiting means for preventing the energization of said main valve in the event that a flame is provided at said burner apparatus during said time interval.

Claim 15

A system as set forth in claim 11 wherein said interlock means includes timeout means connected in said first circuit path, said timeout means being energized over said first circuit path in response to operation of said activate means to define a trial for ignition interval during which said pilot valve is energized, and to deenergize said pilot valve at the end of said trial for ignition interval in the absence of a pilot flame.

Claim 16

A system as set forth in claim 12 wherein said third switching means comprises a switch device having first normally closed contacts connected in said first circuit path and operable to override said timeout means when a pilot flame is provided during said trial for ignition interval, and second normally open contacts for connecting said main valve to said second circuit path, said first and second contacts employing a common armature of said switch device whereby should said second contacts become welded together, said first contacts cannot reclose, thereby preventing the enabling of said interlock means.

Claim 17

A system as set forth in claim 13 wherein said switch device has third normally open contacts connected to said limiting means to override said limiting means during said time interval and to enable said limiting means after said time interval.

Claim 18

A system as set forth in claim 11 wherein said second switching means comprises a switch device having first normally closed contacts connected in said first circuit path and second normally open contacts for connecting said delay means to said second circuit path, said first and second contacts employing a common armature of said switch device whereby should said second contacts become welded together, and first contacts are prevented from reclosing thereby preventing the energizing of said interlock means.