Patent GB-695450-A (GB)
Title: Apparatus for making copies by electrophotographic reproduction
Inventor: WALKUP LEWIS E
IPC: G03G15/26
Filed: 1950-03-07
Abstract: 695,450. Producing photographic copies electrically. BATTELLE DEVELOPMENT CORPORATION. March 7,1950, No. 5702/50. Class 98 (ii). [Also in Group XVI] Apparatus for producing photographic copies electrically comprises a cabinet having lighting means for exposing, through a transparent panel on which the matter to be copied is placed, a charged electrophotographic plate, which consists of an electrically conductive backing carrying a photoconductive insulating layer, i.e. a layer which is an insulator in the dark but is rendered conducting by light, to produce an electrostatic image on the plate, and an electrostatic charging unit movable within the cabinet and adapted to charge the plate and also to transfer from the plate after development a powder image to a receptive sheet such as paper. The electrophotographic plate is preferably carried in a dark slide which fits into the cabinet and which is adapted to be removed and clamped to a powder-dusting tray so that by rocking the tray developing powder is moved across the exposed electrostatic image-bearing plate to produce a powder image. As shown, a dark slide 2, Fig. 7, containing a metal plate coated with a photo-conducting insulating layer is inserted coated face down in grooves 21 in a box 7, the cover of the slide is withdrawn, and the insulating layer is then uniformly charged by means of high potential wires 13 supported on insulating blocks 14 on a plate 12 which is slidable by means of a handle 22 lengthwise of the box, at one end of which is disposed a switch which closes the charging circuit as soon as the plate 12 is moved away, the plate 12 having a tongue 17 engaged in a groove 17<SP>1</SP> and an insulating block having a conducting bush sliding on a metal bar 19 connected to rectified high potential source. The cover of the dark slide is then replaced, the slide is Withdrawn, the matter to be copied is placed on a glass cover-plate 9 and covered with the dark slide which is located face downwards by a frame 8<SP>1</SP> and rests on springs 11. The lamps 39 are then lit and remain alight for a period determined by a time switch, the cover of the slide is withdrawn, and the slide is pressed down by hand on to the copy to expose the charged photoconducting layer and discharge it imagewise. The dark slide is again closed and is then placed face downwards over a tray 32 containing an electroscopic developing powder, the slide is clamped to the tray by catches 38 thereon engaging. a hinged platen 36, the slide cover is removed, and the electrostatic image is then developed by rocking the tray about its trunnions 31 which rest in bearings 28. The powder mage-bearing plate in the slide is then covered with a paper sheet and placed face upwards in grooves 26. The plate 12 is then moved to and fro over the slide so that the powder image is transferred to the paper by electrostatic attraction due to high potential wires 15, similar to the wires 13, carried by insulating blocks 16. The slide is then removed from the box 7 and the powder image on the paper sheet is affixed thereto by passage between two heated plates to fuse the powder or by means of a suitable volatile solvent. The photoconducting layer is cleaned of any remaining developing powder prior to further use by means of a tray, similar to 32, and containing a cleaning powder, mounted on bearings 29. The upper set of high potential wires 13 may be dispensed with and the lower set 15 used for charging the photo. conducting plate providing the glass plate 9 is covered meanwhile.