GB1467972A - Method and apparatus for charging by corona discharge - Google Patents

Abstract

1467972 Corona charging apparatus K I P KK 12 March 1974 [30 March 1973] 10920/74 Heading H1X In a method of charging at least a portion of the surface of a body using a corona discharge device with a plurality of electrodes extending over all the portion and spaced evenly at all times therefrom and in which there is relative movement at least laterally between said body and a corona discharge device, the displacement current flowing across the body is varied smoothly, increasing at the commencement of the charging until a maximum is reached and then decreasing gradually so that the deposited charge has an even distribution across the portion. The corona device may comprise a plurality of parallel wire electrodes and the body to be charged may be a photo-sensitive element utilized in electrophotography and comprising insulating, photo-conductive and grounded electrode layers bonded together (Fig. 1, not shown). The method of the invention is stated to prevent the formation of a striped charge pattern owing to the large charging current which normally flows at the commencement or on interruption of charging. The control circuit shown comprises a driving circuit 10 for moving the corona discharge device 4 at a constant speed in response to an input signal. During movement the device 4 operates a first switch (not shown) included in a synchronizing circuit 11 for energizing a current regulator 12 connected to a time controller 13 including a plurality of variable resistors R1, R2, R3. R1 is used to control the build-up rate of the current to a predetermined value which is maintained constant under control of R2 until run down under control of R3. The output from the regulator 12 is applied to a voltage source 14 supplying the discharge device 4. At termination of the charging a signal is fed back from regulator 12 to circuit 11 to de-energize regulator 12, source 14 and device 4. The latter at the same time actuates a second switch (not shown) to de-energize the driving circuit 10. The displacement current waveform of Fig. 6 (not shown) may also be obtained by varying the distance between the corona discharge device and the surface of the body to be charged while maintaining constant the current flowing through the grounded support using apparatus described w.r.t., Fig. 9 (not shown). The method may also be applied to a rotary drum type copying machine.