Abstract:
In an electrostatographic copier in which an imaging surface is corona charged by high voltage biased electrodes, particularly those in which corona wires overly a reusable photoreceptor, protection of the imaging surface from arcing from the corona electrodes, particularly in the case of corona wire breakage, is provided by automatic rapid interruption of the high voltage to the electrodes, by electrically detecting a sudden change in the current to the electrode. This detection is accomplished at low voltage levels, yet with appropriate circuitry the high voltage can be rapidly switched off or shorted to ground. Simple, low cost exemplary circuits using high speed relays or gas discharge tubes controlled by current change detectors are disclosed. Detection of sudden changes in the true electrode-to-imaging surface current, independent of changes in electrode-to-shield currents is provided.