Fail-safe gas feed and ignition sequence control apparatus and method for a gas-fired appliance

Claim 1

A fail-safe combustion control apparatus for controlling the gas feed and ignition sequence in a gas-fired appliance, comprising circuitry including: power leads selectively connected to an external source of electrical power; an incandescent igniter for kindling gas to provide a flame; a gas feed time delay switch means having an operator and a normally open contact; a flame sensing means having a cold contact and a hot contact for detecting said flame; a time delay lockout switch means having an operator and a normally closed contact; said incandescent igniter, said gas feed time delay switch means operator, said normally closed contact of said time delay lockout switch means and said cold contact being connected in series across said power leads; a solenoid means for controlling a gas valve; said solenoid means, said normally closed contact of said time delay lockout switch means and said normally open contact of said gas feed time delay switch means being connected in series across said power leads; said time delay lockout switch means operator and said cold contact being connected in series across said power leads; and a holding resistor; said holding resistor, said hot contact, said solenoid means and said normally closed contact of said time delay lockout switch means being connected in series across said power leads.

Claim 6

A method for controlling the gas feed and ignition sequence in a gas-fired appliance having a combustion control apparatus comprising circuitry including an electrical igniter, a gas feed time delay switch means, a solenoid means for controlling a gas valve, a holding resistor, a flame sensing means and a time delay lockout switch means connected in circuit with power leads of an electrical power source selectively connected to the power leads, including the steps of: selectively connecting the electrical power source to the power leads; energizing the igniter, the gas feed time delay switch means and the time delay lockout switch means when the flame sensing means detects that no flame is present; energizing the solenoid means under control of the gas feed time delay switch means when the igniter heats to a temperature required to kindle the gas, thereby opening the gas valve so that gas feeds over the igniter; inhibiting further operation of the igniter and the solenoid means under control of the time delay lockout switch means if the flame sensing means fails to detect kindling of a flame, thereby providing fail-safe operation if the gas is not kindled; energizing the solenoid means only through the resistor under control of the flame sensing means when a flame is detected so that the gas valve is held open; de-energizing the time delay lockout switch means under control of the flame sensing means when a flame is detected; de-energizing the solenoid means so as to close the gas valve under control of the holding resistor when the electrical power source fails, thereby providing fail-safe operation if a temporary electrical power outage occurs; and de-energizing the solenoid means so as to close the gas valve under control of the flame sensing means when the gas supply is interrupted, thereby providing fail-safe operation if the gas supply is temporarily interrupted.

Claim 7

A method for controlling the gas feed and ignition sequence in a gas-fired appliance having a combustion control apparatus comprising circuitry including an electrical igniter, a gas feed time delay switch means, a solenoid means for controlling a gas valve, a holding resistor, a flame sensing means and a time delay lockout switch means connected in circuit with power leads of an electrical power source selectively connected to the power leads, including the steps of: selectively connecting the electrical power source to the power leads; energizing the igniter, the gas feed time delay switch means and the time delay lockout switch means when the flame sensing means detects that no flame is present; energizing the solenoid means under control of the gas feed time delay switch means when the igniter heats to a temperature required to kindle the gas, thereby opening the gas valve so that gas feeds over the igniter; inhibiting further operation of the igniter and the solenoid means under control of the time delay lockout switch means if the flame sensing means fails to detect kindling of a flame, thereby providing fail-safe operation if the gas is not kindled; energizing the solenoid means only through the resistor under control of the flame sensing means when a flame is detected so that the gas valve is held open; de-energizing the time delay lockout switch means under control of the flame sensing means when a flame is detected; de-energizing the solenoid means so as to close the gas valve under control of the holding resistor when the electrical power source fails, thereby providing fail-safe operation if a temporary electrical power outage occurs; and de-energizing the solenoid means so as to close the gas valve under control of the flame sensing means when the gas supply is interrupted, thereby providing fail-safe operation if the gas supply is temporarily interrupted.