Patent GB-766426-A (GB)
Title: Electrophotographic printing machine
IPC: G03G15/30
Filed: 1955-03-25
Abstract: 766,426. Printing machines. INTERNATIONAL BUSINESS MACHINES CORPORATION. March 25, 1955 [March 29, 1954], No. 8738/55. Class 100(2). [Also in Group XX] A machine for printing on a web, images corresponding to record cards 20 Fig. 1 comprises a projector 25 for throwing a light image of the card on an electrically charged photosensitive plate 36 mounted on a rotating cylinder 29, a developing chamber 39 for applying powder to the surface of plate 36 the powder being attracted to the charged image areas of the plate, an impression cylinder 40 for pressing the web against the cylinder 29 to transfer the powder image to the web and pressing rollers 58 for pressing into the paper of the web and thereby fixing the transferred image. The record cards are fed from a stack 21, through pairs of forwarding rollers 23, 24, through the projector 25 and are received in a stacker 22. In the projector the card passes between an aperture member 27 and a mirror 28. A lamp 26 throws a beam of light on the narrow band of the record card exposed through the slit in the member 27, the illuminated strip of the card being projected on to the photosensitive plate 36. In the form of Fig. 1 the plate is electrostatically charged by movement past an ion-producer 32. Those parts of the surface upon which light falls are discharged but the dark image areas remain charged and are coated with power in the device 39. When no card is present the mirror reflects the light and discharges the whole surface of the plate. The roller 40 has a metal core and a soft semi-insulating sleeve 42 e.g. of "conducting rubber." The metal core is connected to a high voltage source through a switch 71 and the cylinder 29 is earthed. The roller 40 is mounted on three-armed levers which are spring 'loaded in a clockwise direction. The arms 46 carry a follower roller 48 for co-operation with a cam 62 which is adapted to turn the levers against the action of the spring. The third arms 49 carry a roller 50 adapted to co-operate with a feea roller 59 to advance the web. Displacement of the levers by cam 62 causes the feed rollers to separate and the cylinder 40 to leave cylinder 29 and clamp the web 38 against a brake shoe 65. Cam 62 is driven in synchronism with a cam controlling contacts C1 in parallel with switch 71 so that the cylinder 40 may be connected to the high voltage source only when it is in contact with the printing cylinder and the web is being moved between them. The web is fed from spool 56 between drag rollers 57 over idle roller 55, over cylinder 40, between pressing rollers 58, feed rollers 50, 59 and rollers 60 to spool 61. The upper presser roller is cleaned of powder by an oil pad 68 and the printing plate 36 is cleaned before again coming under the ionproducer by a rotating brush 66 of pile fabric. In a modification (Fig. 2, not shown) the ion producer is replaced by a roller connected to a high potential source This roller consists of a metallic core and a sleeve e.g. of conducting rubber." In this modification the impression cylinder 175, Fig. 5, is immovably mounted and consists of a central cylinder 178, and end discs 176, 177 of larger diameter which roll on the surface of the plate 136 and so space the cylinder 178 therefrom that the web 138 passes between the cylinder 178 and plate 136 without bearing on the latter. The feed roller 159 is driven by a gear sector in gear-box 181 so as to advance the web when printing is in operation to keep it stationary when no printing is in progress. The powder is caused to migrate from the plate 136 by a high potential change on roller 178 which is interrupted when no printing is in progress by switch C2 operated by a cam driven through gear box 181. The main cylinder 129 is driven through a gear-box 180 by a motor 134 the speed of the cylinder being the same as the speed of the web when this is being fed. By this means, in both embodiments, spaced images (130a) from the record cards, which are developed on the plate 36 or 136 are reproduced on the web with a reduced spacing. The web may be displaceable axially of the cylinder so as to receive only nart of the image thereon.