GB1304273A - - Google Patents

Abstract

1304273 Automatic control of temperature WINDMÍLLER & HÍLSCHER 9 March 1970 [21 March 1969] 11158/70 Heading G3R In a cascade regulator arrangement for controlling the temperature of an extruder 1, the respective datum temperature levels of a plurality of sequence controllers R(--) each controlling a respective coil for heating a respective portion of the extruder wall, are modified by the output of a guide controller including a bridge 3. The guide controller has a potentiometer 5 on which a desired temperature value XK(F) for a plastics mass being extruded, is pre-set. A thermo-couple 2 senses the actual temperature X(F) of the plastics mass. The thermo-couple voltage is added across an output resistor R4 of an amplifier TrV(F) to a feedback voltage derived from the output voltage Y(F+NG) of the guide controller amplifier 6 fed into the amplifier TrV(F). The value Y(F+NG) is significant of the difference between the desired and actual temperatures of the plastics mass, the zero level of this value being determined by a bias source NG. A further feedback loop via R7 C8 provides an integration component. Thermo-couples such as 11 sense the wall temperature at intervals along the extruder duct and their respective outputs X(1--) are algerbraically added to the guide control value voltage Y(F+NG) at a respective amplifier TrV(1---). The guide voltage polarity opposes the polarity of the thermo-couples 11 voltages. Thereby the outputs of amplifiers 14 of the sequence controllers are made to follow the output from the guide controller irrespective of their pre-set wall temperature values XK(1---). The amplifiers 14 outputs energize respective heating coils 9 to raise the wall temperature until the difference output from the guide controller becomes zero when the temperature of the plastics mass reaches the desired value. The amplification factors of the amplifiers 14 are individually selectable and determine the proportional characteristics of the sequence controllers R(1---). The cascade regulator may have PI or PID characteristics. A meter connected to the guide controller output gives an indication V(F+NG) which is a measure of the quality of the control, the less the indication departs from zero the better the control.