GB1167881A - Improvements in or relating to Electro-Photographic Enlargers. - Google Patents

Abstract

1,167,881. Photographic enlargers. NATIONAL RESEARCH DEVELOPMENT CORP. May 17, 1967 [May 17, 1966], No.21965/66. Headings G2A and G2H. Photographic apparatus for producing an enlarged print of a photographic transparency particularly an enlarged electro-photographic print, comprises a support 24 for the transparency 7, a viewing table 5, an optical system including a mercury lamp 15 emitting ultraviolet and visible light the former activating a sheet of copy paper which is insensitive to visible light and a projection system 9 for projecting an enlarged image of the transparency 7 on to a sheet of said copy paper mounted on the table 5, together with developing and fixing means 11, and drive means for moving an exposed sheet of copy paper from the table 5 through the developing and fixing means. Then, the copy paper on the table 5 may be observed in visible light during the exposure to the ultraviolet radiation. As shown in the electro-photographic apparatus of the Figure, two stacks of copy paper 37 are carried on trays 35 which are pivotally mounted in shelves 33 and urged upwards by springs 39. The shelves 33 slide on runners 47 so that the trays 35 may be withdrawn from the apparatus for reloading with copy paper. For each stack 37, a roller 41 is releasably coupled through a click mechanism with a drive mechanism, so that a sheet of copy paper is selectively dispensed from one tray 35 and passed between a drive roller 49 and an idler roller 51 to a charger 3. The charger 3 comprises a metal box 65 containing two pairs of parallel corona wires 67 between which the copy paper passes. High potentials of opposite polarity are applied to the pairs of wires to charge the copy paper. The paper then contacts a conveyer band 79 and is brought to lie in the exposure position on the table 5. After exposure the band 79 is driven to carry the paper to a tray 89 of developing liquid containing charged toner particles. The liquid is also pumped from a storage tank 91 to a spray bar 95. Squeegee rollers 97, 99 remove excess developer-liquid and direct the copy paper towards a heater bar 101. Warm air is directed by a fan 103 on to the copy. Finally the copy is selectively directed on to a conveyer 119 and then on to a band 115 or directly on to the band 115. The band 115 extends transversely of the apparatus and dispenses the finished copy. The drive mechanism comprises a motor 127 which indirectly drives a chain 131 which is in turn connected to drive rollers along the path of the copy paper. The projection system is arranged at the front of the apparatus and includes a mirror 23 pivotally positioned above the table 5 to reflect an enlarged image on to the copy paper. The size of the copy produced is varied by adjusting the position of the mirror 23 and refocusing the projection system 9.