Corona charging device

Claim 1

Xerographic reproducing apparatus, said apparatus comprising: means for forming a powder image on a charge retentive surface and transferring the image to a substrate; means for assisting in the removal of said substrate from said surface, said means comprising a corona device including an electrode and a conductive shield which is self-biased by means of a resistor through which the shield is connected to ground; a preclean corona device comprising an electrode having an insulative coating and a conductive shield; means for applying a.c. power to said preclean electrode, said insulative coating being thick enough to substantially preclude net d.c. current flow from said preclean electrode; and a self-biasing electrical circuit connecting said conductive shield of said preclean corona to ground, said circuit including means to cause sufficient current to flow in said circuit for effecting substantial neutralization of charged residual toner electrostatically adhered to said charge retentive surface when said surface with said charged residual toner is moved past said preclean electrode and a.c. power is applied to said preclean electrode; corona devices for uniformly electrostatically charging said charge retentive surface and electrostatically transferring toner images to said substrate, each of said corona devices for charging and transferring comprising a conductive shield and an electrode; said means for applying a.c. power comprising a single secondary winding and all of said electrodes being operatively connected thereto; and said shields of said corona devices for charging said charge retentive surface and transferring toner images being partially self-biased and partially biased via said secondary winding.