GB875187A - Electrical temperature control system - Google Patents

Abstract

875,187. Electric control systems. TELCON METALS Ltd. Oct. 14, 1957 [Oct. 12, 1956], No. 31200/56. Class 40 (1). In a system for subjecting a chamber to a desired temperature treatment comprising a predetermined rate of heating, period at the maximum or soak temperature and rate of cooling, a thermocouple in the chamber is connected in series with a voltage which varies in a predetermined manner to control the heating and cooling and a timing device controls the period for which the soak temperature is maintained. As shown, closure of main switch S1- drives motor M adjusting slider S which supplies a voltage sufficient to cause operation of controller D to begin heating the chamber. As the slider moves it closes micro-switch S2 preparing the timing circuit and then progressively reduces the voltage from potentiometer P. Meanwhile the output of thermocouple C increases. Provided the total output is below a predetermined level the controller heats the chamber. If it rises above it the controller cuts out the heating source. Thus the rate of heating is controlled by the speed of the motor. When the slider reaches the end of its travel the thermocouple voltage alone is adequate to cut out the controller and the soak temperature is maintained. If the temperature falls below the soak temperature, thermocouple C again operates the controller to switch on the heat. Operation of microswitch S3 energizes relay Ry which. latches and de-energizes motor M and sets motor-driven timer T in operation to time the soak period. At the end of the period the timer sets motor M running in reverse and rate of cooling is controlled in the same manner as the rate of heating.