International Business Machines Corporation

Philip Theodore Gianos

Joseph E Cunningham, Jr

Claude Herbert Feistel

A copier fuser roll's temperature is accurately maintained by supplying selected half-cycles of current from a power supply to a heater in accordance with signals from a temperature sensor. Each sequential half-cycle is assigned a unique digital input number which accesses a table of digital output numbers having values chosen to correspond to one or more half-cycles. Sensor signals are sampled and digital temperature error numbers, determined by the fuser roll temperature and a desired roll temperature, are derived. The temperature error and output numbers are compared and, whenever a comparison occurs, the corresponding half-cycle of current operates the heater. Thus, depending upon the difference between a desired and the actual roll temperature, variable numbers of evenly spaced complete half-cycles, having a total positive-to-negative ratio approaching unity, are selected.

Automatic temperature controller for an electrophotographic apparatus

An amplitude limiting amplifier followed by a filter network is interposed between the voltage amplification stage and the impedance matching stage in a Butler oscillator. This allows both the voltage amplification stage and the impedance matching stage to be operated in a linear mode at all times which assures that a piezoelectric crystal connected between the stages is connected in a relatively low, constant impedance path and is driven by a sinusoidal waveform, free of distortion, to assure maximum frequency stability.

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Boulder, CO, United States of America

Philip Theodore Gianos