GB1086268A - Temperature control circuit for synthetic fibre processing machine - Google Patents

Abstract

1,086,268. Automatic temperature control of synthetic fibre. GENERAL ELECTRIC CO. Dec.22, 1964 [Jan.16, 1964], No.52095/64. Heading G3R. A system for controlling the temperature of a drawn fibre comprises a heating element 31 for heating a plate over which the fibre is drawn and a thermistor 47 which senses the temperature of the plate, the thermistor 47 forming part of a bridge circuit the other arms of which include a fixed 3 volt potential, a variable 0-17 volt potential, varied by a potentiometer 53, and a potentiometer 51, the potentiometers 51, 53 being used to set the desired temperature of the fibre and the bridge out-of-balance rendering a transistor 45 conductive to charge a capacitor 41 over the base T of a unijunction transistor 29 when the voltage applied to terminal 23 is positive such that when the capacitor is fully charged unijunction transistor 29 fires generating a pulse across a resistor 39 which is applied to the gate electrode of a silicon controlled rectifier 35 so energizing the heating element 31. The system includes a change-over switch 59 operated by the breaking of the fibre to substitute a variable 0-3 volts for the fixed 3 volt potential in the bridge circuit so that if a breakage of the fibre occurs the temperature of the heated plate is controlled at a low value. The sensing device 47 may be a thermocouple and may sense the temperature of the fibre itself. The supply 21, 22 may be A.C. or unsmoothed rectified A.C. If more than one fibre is being drawn each may be provided with a heating device all of which may be commonly controlled by the potentiometer 53 as illustrated by blocks 67, 69.