GB613163A - Improvements in or relating to electric printing apparatus - Google Patents

Abstract

613,163. Printing-machines. GOSS PRINTING PRESS CO., Ltd. June 13, 1946, No. 17769. Convention date, July 12, 1945. [Class 100(ii)] In the electrical method of printing in which the ink passes from an inked design cylinder under the action of an applied electromotive force across a narrow gap between the inked cylinder and a coacting cylinder around which the web or sheet to be printed passes, the electrical circuit is arranged to develop a periodically varying electrical force differential. As shown in Fig. 1 the web 14 is passed around a cylinder 16 and is spaced by a few thousandths of an inch from the inked design cylinder 10 which is connected to earth. The cylinder 16 is connected to a source 18 of a high positive electrical potential by means of a circuit comprising a variable high resistance 19 and a shunt circuit including a condenser 20 and a high resistance 21. The alternate charging and discharging of the condenser 20 causes a periodically varying difference of potential across the gap between the cylinder 10 and the web 14, and is adapted to prevent damage to the paper by arcing. In Fig. 3 the current from a source of high positive potential 68 passes through a stepup transformer one winding 80a of which is connected to a cylinder 66 around which the web passes, and the other winding 80b is connected to the output of a square wave generator 81 operating at a relatively low frequency. In a further modification the circuit is somewhat similar to that shown in Fig. 1, but the condenser 20 is replaced by means for periodically applying an additional high voltage D.C. potential across the resistance 21. In this form the width of gap between the cylinders 10. 16 is limited by wedge-shaped glass members arranged with a small gap only between their apices, and the cylinder 16 may be replaced by a small stationary metal bar. U.S.A. Specifications 1,820,194 and 2,224,391 are referred to.