Abstract A control circuit is provided to control the operation of a gasheated automatic clothes dryer having a positive temperature coefficient thermistor positioned to sense burning of gas within the burner and to correspondingly control the supply of gas to the burner. An electrically operated valve for supplying gas to the burner is controlled by a time delay bimetal switch having a bimetal heater in electrical series with the thermistor whereby the output of the bimetal heater depends upon the resistance of the thermistor. The increased resistance of the thermistor in the presence of flame is effective to disable the bimetal heater from opening the bimetal switch thereby maintaining gas flow to the burner, the heater, unless disabled by the thermistor, being effective to open the bimetal switch and deenergize the valve after a predetermined interval, thereby to terminate gas flow to the burner in the absence of flame.
-. A gas-heated automatic clothes dryer comprising: a gas burner adapted to heat a stream of air blowing past said burner; an electrically operated valve for supplying gas to said burner; a time delay bimetal switch having contacts connected to control said valve; means including a positive temperature coefficient thermistor and a bimetAl heater for controlling the operation of said bimetal switch; and said means including a control circuit connecting said thermistor and said bimetal heater in electrical series, whereby the output of said bimetal heater depends upon the resistance of said thermistor, the increased resistance of said thermistor in the presence of flame being effective to disable said bimetal heater form opening said bimetal switch thereby maintaining gas flow to said burner, said heater, unless disabled by said thermistor, being effective to open said bimetal switch and deenergize said valve after a predetermined interval, thereby to terminate gas flow to said burner in the absence of flame.
Claim 2
Dependent Claim
96 words
The invention of claim 1 additionally including: an electrically operated igniter for initiating flame at said burner; an igniter circuit connected in electrical series with said thermistor and with said time delay bimetal switch for supplying current to said igniter when said bimetal switch is closed and when the resistance of said thermistor is low, whereby said igniter will provide a means of igniting the gas flow at said burner during the period of the time delay of said bimetal switch and will be disabled by said thermistor when said thermistor senses flame within said burner.