Electric dryer control circuit

Claim 1

IN A FABRIC DRYING MACHINE HAVING A DRYING CHAMBER AND A MAIN ELECTRIC HEATER FOR SUPPLYING DRYING HEAT TO FABRICS IN SAID CHAMBER: A CONTROL CIRCUIT ADAPTED TO BE CONNECTED ACROSS A THREE-WIRE SOURCE OF POWER INCLUDING FIRST, SECOND AND THIRD TERMINALS, SAID FIRST AND SECOND TERMINALS BEING POWER TERMINALS AND SAID THIRD TERMINAL BEING A NEUTRAL TERMINAL, SAID MAIN HEATER HAVING ONE END THEREOF CONNECTED TO SAID FIRST TERMINAL; MEANS FOR AUTOMATICALLY TERMINATING ENERGIZATION OF SAID MAIN HEATER IN RESPONSE TO A DRY CONDITION OF THE FABRICS INCLUDING A CONTROL THERMOSTAT POSITIONED TO SENSE TEMPERATURE RISES OF FABRICS AND TO TRIP AT A PREDETERMINED HIGH TEMPERATURE, SAID MAIN HEATER BEING DE-ENERGIZED IN RESPONSE TO TRIPPING OF SAID THERMOSTAT; MEANS FOR VARYING THE TRIP TEMPERATURE OF SAID THERMOSTAT INCLUDING A BIASING ELECTRIC HEATER CONNECTED BETWEEN SAID SECOND AND THIRD TERMINALS, SAID THERMOSTAT TRIPPING AT A FIRST FABRIC TEMPERATURE WHEN SAID BIASING HEATER IS ENERGIZED AND AT A SECOND FABRIC TEMPERATURE WHEN SAID BIASING HEATER IS NOT ENERGIZED; AND TWO-POSITION MANUALLY OPERABLE SWITCH MEANS CONNECTED TO THE OTHER END OF SAID MAIN HEATER AND TO ONE END OF SAID BIASING HEATER, SAID SWITCH MEANS IN ITS FIRST POSITION BEING CONNECTED TO ONE OF SAID SECOND AND THIRD TERMINALS AND TO THE OTHER END OF SAID BIASING HEATER, SAID SWITCH MEANS IN ITS SECOND POSITION BEING CONNECTED TO THE OTHER OF SAID SECOND AND THIRD TERMINALS.