GB696515A - Apparatus for charging an insulating layer - Google Patents

Abstract

696,515. Apparatus for charging electrophotographic plates. BATTELLE DEVELOPMENT CORPORATION. April 3, 1951 [April 6, 1950], No. 7689/51. Class 98 (ii). The apparatus comprises an electrode source of gas ions, a conductive electrode having a surface spaced from the ion source, relatively movable supports for an insulating layer and the ion source for moving the insulating layer between the ion source and the conductive electrode, a control electrode between the insulating layer and the ion source, a potential source for applying a high voltage between the ion source and the control electrode, and a second potential source for applying a lower potential between the control electrode and the conductive electrode, whereby the control electrode determines the potential which is applied to the insulating layer by the ion source and maintains said potential uniform and of the same polarity as the ion source. As shown, an electrophotographic plate comprising a photoconductive insulating layer 2 on a conducting layer 8 is carried to and fro over a conductive guide plate 3 by conductive conveyer belts 10, 11 moved by pulleys 19 driven by an electric motor 12 beneath parallel wires 5 which are supported by insulating blocks 6 and from which a corona discharge passes to the plate 3. A control grid 7 of trough shape is formed by parallel wires also secured to the blocks 6 and serves to ensure that the apparatus raises electrophotographic plates of a given kind always to approximately the same potential. A half-wave rectifier supplies the steady potentials required by the discharge electrode 5 and the control grid 7, the remainder of the conducting elements of the apparatus including a plate 22 over the electrode 5 being earthed. If desired, stepped-up A.C. may be fed to the discharge electrode 5 which may be biased by a steady potential while the control grid is supplied with a steady potential or a potential of a single sign pulsating in synchronism with the discharge electrode voltage. By suitable choice of the potentials applied, the layer 2 may be given a positive or negative charge of any chosen potential. The parallel wires of the control grid along the inclined sides of the trough may be replaced by metal plates, or alternatively the grid may be formed of metal mesh disposed with its strands transverse of the direction of movement of the layer 2. The wires of the discharge electrode 5 may be replaced by a row of needles and may be covered by a grounded conducting shield carried by spaced insulating blocks across the bottom of which the parallel wires of the control grid extend.