GB725397A - Improvements in optically true suction support for photographic film, copy or other material - Google Patents

Abstract

725,397. Pneumatic supports for photographic film or copy material. HALPERN, B. R. June 15, 1953, No. 16454/53. Classes 98(1) and 98 (2). A porous suction wall composed of fine granular material having minute channels extending therethrough has a continuously smooth optically true supporting surface for the photographic material and is provided with a suctionapplying chamber arranged to create uniformly distributed suction at such surface. The surface may be flat, curvilinear, part spherical, or may comprise the inside or outside of a cylinder ; or may have a functional curvature such as logarithmic as shown in Fig. 11, in which the photographic material 33 is placed on suction wall 44 behind which is chamber 30 with suction pipe 31. To deal with photographic materials of different sizes, Fig. 2, the copy board of a process camera, and Fig. 3, show suction surface 11 and vacuum back frame 18 defining suction chambers 20 of successively increasing size separated by continuous walls or flanges 19 as of rubber, which chambers can be cut into and out of service by valve 21 on suction chest 17 controlling bores or passages 22 leading to the several chambers 20. The suction wall may be made up of metal, silicon carbide, sand or stone particles which pass through 36 to 100 mesh sieves combined with a resinous binder and formed under heat and pressure in a mould having the desired plane or curved surface.