Thermal coupler for a dryness control circuit

Claim 1

In combination with a rotatable drum dryer dryer control for controlling drying operations of a dryer having a treatment zone for treating fabrics, comprising: a programmer including a timer motor for connection to an electrical supply, and timer contacts operated by said timer motor through a programmed sequence for controlling drying operations; heating means for supplying a flow of heated air to the treatment zone including a heating circuit for connection to the electrical supply and comprising a heater and a thermOstat connected in series with said heater and thermally coupled to the treatment zone for opening and closing said series circuit in response to predetermined temperatures in the treatment zone; and timer control means disposed remotely from said heating means connecting and electrically isolating said timer motor and said heating means, said timer control means comprising a single device having a two terminal input connected to said series circuit, resistance means connected to said two terminal input, a two terminal heat responsive variable impedance output connected to said timer motor and responsive to current flow through said resistance means due to operations of said thermostat to change the impedance of said output between values which are respectively sufficient and insufficient to prevent operation of said timer motor, a casing surrounding said resistance means and said variable impedance means for partially isolating said variable impedance means from the environment and heat sink means connected with said casing for partially coupling said variable impedance means to the environment for controlling the rate of change in impedance of said variable impedance means when said series circuit is open.