Digitally controlled tube build-up compensator for a glass fiber forming

Abstract

A digitally controlled apparatus for varying the temperature of a glass fiber forming bushing over a period of time is disclosed. A clock generates timing pulses at a predetermined frequency to a BCD counter. The output signals from the BCD counter are fed to a comparator means. BCD output signals generated by a plurality of manually operable switch assemblies are also fed to the comparator means. The switch assemblies are set by an operator to generate a predetermined number related to the amount of time required to wind a strand of glass fibers upon a tube. The comparator means generates an output pulse when the count of the BCD counter equals the number set by the switch assemblies, then resets the BCD counter to zero. The output pulses from the comparator means are fed to a binary counter. The output lines from the binary counter are connected to a digital to analog converter. The converter generates an analog output signal which is proportional to the magnitude of the number from the binary counter. The maximum value of the output signal is determined by a referance voltage. The output signal from the converter is combined with an actual bushing temperature signal from a thermocouple attached to the bushing into a composite feedback signal. The composite signal is fed to a temperature controller for the bushing. The converter output signal modifies the thermocouple output signal so as to cause the temperature controller linearly increase the temperature of the bushing as the tube is being wound with a strand of glass fibers. As a result, the diameter of the strand is maintained relatively constant.