Direct ignition system for gas appliance with DC power source

In an ignition control system for use with an appliance having a source of gas, a main valve for supplying gas from said source to said appliance, and a thermostat for generating a call-for-heat signal, the combination comprising:

• flame detection circuit means normally coupled to a source of dc electrical power;
• said flame detection circuit means including flame sensing relay means;
• checking relay means actuated by said call-for-heat signal;
• said flame sensing relay means and said checking relay means having contacts interlocking with each other and with said main valve such that said checking relay means and said flame sensing relay means must be energized in sequence before said main valve can be energized;
• said flame detection circuit means further including drive circuit means for energizing said flame sensing relay means when enabled;
• timing circuit means operative to supply stored energy to said flame detection circuit means and to enable said drive circuit means for a limited trial-for-ignition period;
• probe means having a first conductance in the presence of a flame and a second conductance in the absence of a flame;
• said checking relay means being responsive to a call-for-heat signal for isolating said timing circuit means and said flame detection circuit means from said dc power source, whereupon said flame detection circuit means is energized by stored energy provided by said timing circuit means, and for connecting said timing circuit means in circuit with an enabling input of said drive circuit means and said probe means for permitting said timing circuit means to enable said drive circuit means for said trial-for-ignition period, said probe means preventing said timing circuit means for disenabling said drive circuit means if said probe means is in said first conductance state when said checking relay means connects said timing circuit means to said enabling input of said drive means, said flame sensing relay means being operated for energizing said valve for said trial for ignition period, said probe means changing to said first state of conductance in the presence of a flame to inhibit time out of said timing circuit means and thereby preventing de-energization of said flame sensing relay means, said probe means permitting said timing circuit means to time out and deenergize said flame sensing relay means to shut off said valve if a flame is not sensed by said probe means within said limited time, and said flame detection circuit means being deactivated, preventing the operation of said valve if said flame sensing relay means fails to operate before the energy stored by said timing circuit means is depleted.

In a direct ignition control system for use with an appliance having a source of gas, a main valve for supplying gas from said source to said appliance, and a thermostat for generating a call-for-heat signal, the combination comprising:

• flame detection circuitry including first switching means, trial-for-ignition timing circuit means for generating a timing signal for a predetermined time when enabled, and first flame responsive sensor means having first and second conductance states responsive to the absence and presence of a flame respectively;
• spark generator means including a source of high voltage energy and a spark gap located in the path of fuel from said source and having first and second conductance states in response to the absence and presence of a flame respectively;
• second switching means responsive to a call-for-heat signal for coupling said trial-for-ignition timing circuit means to said first switching means, enabling said timing circuit means to generate its timing signal and permitting said first switching means to be enabled by said timing signal for said predetermined time, said first switching means, when enabled by said timing signal, actuating said valve and energizing said spark generator means to generate a spark in said spark gap to ignite said fuel, said first flame responsive sensor means preventing time out of said trial-for-ignition timing circuit means when said first flame responsive sensor means switches to said second conductance state, but permitting said trial-for-ignition timing circuit means to time out and thereby de-energize said first switching means if said first flame responsive sensor means does not switch to said second conductance state during said trial-for-ignition period, and second flame responsive sensor means including an enable circuit connected in circuit with said spark gap for enabling said spark generator means when said spark gap is in said first conductance state and for disabling said spark generator means when said spark gap switches to said second conductance state.

In an ignition control system for use with an appliance having a source of gas, a main valve for supplying gas from said source to said appliance, and a thermostat for generating a call-for-heat signal, the combination comprising:

• flame detection circuitry including first switching means, a trial-for-ignition timing circuit including a capacitor which is charged and then permitted to discharge for generating a timing signal for a predetermined time when actuated, and first flame responsive sensor means having first and second conductance states responsive to the absence and presence of a flame respectively;
• spark generator means including a source of high voltage energy and a spark gap located in the path of fuel from said source and having first and second conductance states in response to the absence and presence of a flame respectively;
• second switching means responsive to a call-for-heat signal for actuating said trial-for-ignition timing circuit to enable said first switching means for said predetermined time, said first switching means, when enabled by said timing circuit, actuating said valve and energizing said spark generator means to generate a spark in said spark gap to ignite said fuel;
• and second flame responsive sensor means associated with said spark gap for disabling said spark generator when said spark gap switches to said second conductance state, said first flame responsive sensor means inhibiting further time out of said trial-for-ignition timing circuit when said first flame responsive sensor means switches to said second conductance state, but permitting said trial-for-ignition timing circuit to time out and thereby de-energize said first switching means if said first flame responsive sensor means does not switch to said second conductance state during said trial-for-ignition period, and re-cycle time circuit means, said second switching means connecting said re-cycle time circuit means in circuit with said capacitor of said trial-for-ignition timing circuit and a source of power to permit said capacitor to charge to a sufficient voltage to enable said first switching means for said predetermined time only when said second switching circuit means is de-energized, whereby said system may be re-cycled by opening said thermostat and thereby de-energizing said second switching circuit means.

In an ignition control system for use with an appliance provided with a source of gas, a valve for supplying gas from said source to said appliance, and a thermostat for generating a call-for-heat signal, the combination comprising:

• relay circuit means for coupling a source of electrical power to said valve when energized;
• timing circuit means for generating a timing signal defining a limited trial-for-ignition period of a first duration in response to a call-for-heat signal;
• probe means having a first conductance state in the presence of a flame in said appliance and a second conductance state in the absence of a flame;
• switching circuit means responsive to said call-for-heat signal for connecting said timing circuit means in circuit with said relay circuit means and with said probe means, said timing circuit means including a capacitor which charges to a first valve and then discharges from said first valve, generating said timing signal to permit said relay circuit means to be enabled during said trial-for-ignition period, said probe means normally being in said second conductance state at the commencement of said trial-for-ignition period and operative to permit said timing circuit means to time out and thereupon disable said relay circuit means if said probe means does not switch to said first conductance state prior to the end of said trial-for-ignition period, but to prevent said timing circuit means from timing out and cause said capacitor to charge through said probe means to a second, lesser valve and thereby maintain said relay circuit means enabled when said probe means switches to said first conductance state in response to a flame being established during said trial-for-ignition period, and said probe means being responsive to a flame-out to switch to said second conductance state to cause said capacitor to discharge from said second valve, enabling said timing circuit means to commence a re-ignition time period of a second duration which is shorter than said first duration whenever a flame-out is sensed during a heating cycle, and said timing circuit means disabling said relay means if said probe means does not switch to said first conductance state prior to the end of said re-ignition time period.