Printing machine high voltage power system and circuit

Abstract

The high D.C. voltage power supply device for the electrodes of an electrostatic ink mist prevention system in rotary printing machines has a conventional full-wave voltage doubling circuit consisting basically of a transformer, plug-in rectifiers, plug-in capacitors and plug-in bleeder resisters. Additional circuitry mounted on an interchangeable printed circuit board comprising exclusively standard solid state switching elements such as an integrated circuit for producing an output pulse when the line voltage goes through zero voltage, which is utilized for turning the high voltage on and off via an SCR firing circuit in addition to illuminating a pilot light via a triac firing circuit. The D.C. high voltage load current is sensed across a resistor, and a resistor potentiometer is provided for setting the high voltage current turn-off trip point. A timing device is provided for re-energizing the solid state circuitry after a preset time interval. The pilot light starts flashing when the triac is fired from the flashing circuit; but as long as a fault is still present, the system turns off again. This is repeated until the fault is cleared away, whereupon the solid state circuitry re-energizes the system automatically.