Temperature controller

Claim 1

A TEMPERATURE CONTROLLER FOR MAINTAINING THE TEMPERATURE IN A ZONE AT A PREDETERMINED LEVEL, SAID CONTROLLER COMPRISING: MEANS IN HEAT EXCHANGE RELATIONSHIP WITH SAID ZONE FOR VARYING THE TEMPERATURE THEREOF WHEN ENERGIZED; A TRIGGERABLE SEMICONDUCTOR SWITCHING DEVICE FOR SWITCHING THE FLOW OR POWER TO SAID MEANS; MEANS FOR SUPPLYING A.C. ELECTRIC POWER TO SAID MEANS AND SAID SEMICONDUCTOR SWITCHING DEVICE; A THERMISTOR ADAPTED TO SENSE THE TEMPERATURE IN SAID ZONE; RESISTANCE MEANS FORMING WITH SAID THERMISTOR A RESISTANCE BRIDGE, THE UNBALANCE OF THE BRIDGE BEING A FUNCTION OF THE TEMPERATURE OF SAID THERMISTOR; A SATURABLE MAGNETIC CORE; FIRST CIRCUIT MEANS INTERCONNECTED WITH SAID BRIDGE AND INCLUDING A FIRST WINDING ON SAID CORE FOR MAGNETIZING SAID CORE IN ONE DIRECTION TO AN EXTENT WHICH IS A FUNCTION OF THE UNBALANCE OF SAID BRIDGE DURING A.C. HALF CYCLES OF ONE POLARITY; AND SECOND CIRCUIT MEANS INCLUDING A SECOND WINDING FOR MAGNETIZING SAID CORE IN THE OPPOSITE DIRECTION TO AN EXTENT WHICH INCREASES WITH TIME DURING A.C. HALF CYCLES OF OPPOSITE POLARITY, SAID SECOND WINDING BEING INTERCONNECTED WITH SAID SEMICONDUCTOR SWITCHING DEVICE FOR TRIGGERING SAID DEVICE INTO CONDUCTION AFTER SAID CORE SATURATES, THE PHASE ANGLE AT WHICH SAID DEVICE IS TRIGGERED BEING A FUNCTION OF THE PREVIOUS MAGNETIZATION OF SAID CORE BY SAID FIRST CIRCUIT MEANS WHEREBY THE PROPORTION OF TIME DURING WHICH SAID DEVICE CONDUCTS VARIES AS A FUNCTION OF THE TEMPERATURE OF SAID ZONE TO MAINTAIN THE ZONE TEMPERATURE AT SAID PREDETERMINED LEVEL.