Automatic dryer control

Claim 1

IN DRYING APPARATUS, THE COMBINATION OF MEANS DEFINING A DRYING CHAMBER FOR THE MATERIAL TO BE DRIED, MEANS DEFINING INLET AND EXHAUST DUCTS COMMUNICATING WITH SAID DRYING CHAMBER, MEANS FOR CIRCULATING AIR THROUGH SAID DRYING CHAMBER AND SAID INLET AND EXHAUST DUCTS, HEATER MEANS FOR HEATING THE AIR, FIRST RESISTIVE MEANS FOR SENSING THE AIR TEMPERATURE IN SAID INLET DUCT, SECOND RESISTIVE MEANS FOR SENSING THE AIR TEMPERATURE IN SAID EXHAUST DUCT, THERMOMATIVE SWITCH MEANS RESPONSIVE TO THE COMBINED RESISTANCE OF SAID RESISTIVE MEANS AND EFFECTIVE WHEN THE TEMPERATURE JOINTLY SENSED BY SAID FIRST AND SECOND RESISTIVE MEANS REACHES A SUMMED CRITICAL VALUE TO CONTROL THE DRYING ACTION, SELECTOR MEANS FOR SELECTING ANY OF A PLURALITY OF DRYING CYCLES, MOTOR MEANS RESPONSIVE TO SAID SWITCH MEANS FOR CAUSING SAID SELECTOR MEANS TO ALTERNATELY ENERGIZE AND DE-ENERGIZE SAID HEATER MEANS DURING THE SELECTED DRYING CYCLE AND TO TERMINATE THE DRYING ACTION, AND VOLTAGE COMPENSATING HEATING MEANS COOPERATING WITH SAID SWITCH MEANS TO RENDER ACTUATION OF SAID MOTOR MEANS DIRECTLY DEPENDENT UPON SAID CRITICAL VALUE AND INSENSITIVE TO VOLTAGE CHANGES.