Patent GB-747612-A (GB)
Title: Improvements in or relating to photographic apparatus
IPC: G03B27/32
Filed: 1953-02-16
Abstract: 747,612. Photographic projection printing apparatus. GUPPY, R. E. May 6, 1954 [Feb. 16, 1953], No. 4291/53. Class 98 (1). A camera and a copyholder are carried at opposite ends of a pivotally mounted unit constituted by relatively displaceable parts, each of which can be moved towards and away from the pivotal axis of the unit to vary the distance between the camera and copyholder, and means is provided for simultaneously effecting adjustment of said parts towards or away from a pivoted supporting part, which carries the said unit and is pivoted about the pivotal axis thereof, by equal amounts so that the unit is maintained substantially in balance about its axis, the arrangement being such as to permit the camera and copyholder to be brought as required into a position for loading and unloading. As shown, the front and rear walls of a cabinet 1 having an aperture 3 in its top has bearings for horizontal trunnions 6 on cross members 8 which support as a unit by means of threaded apertures engaged by threaded rods 12 a copying camera which comprises a pair of telescoping rectangular tubes 4, 9 supporting respectively a lens board and a bellows-connected dark slide holder and a copyholder-supporting enclosure 5 making with the tube 4 a light-tight housing. The rods 12 which are connected by a chain 15 and have their unthreaded ends rotatably supported in bearings 13 on the tube 4 each have one thread 14 engaging in the cross members 8 of half the pitch of a second thread 14<SP>1</SP> which engages a threaded collar 11 on the dark slide holder tube 9 so that on operating manually or by an electric motor 18 a chain drive 17 to one of the rods, the housing 4, 5 is moved downwardly and the tube 9 is moved upwardly an equal amount to maintain balance about the trunnions 6. Secured to one trunnion is a pulley 31 belt-driven from an electric motor 33 against a spring brake being arranged to act on the trunnion, while the housing 4, 5 carries a pair of spring-pressed plungers which as the dark slide or copy board approach the aperture 3 engage horizontal bowed springs near the top and bottom of the cabinet in recesses in which the plungers engage to arrest the apparatus in either the position shown or the inverted position. The lens board is movable for focusing purposes along tracks 21a on the tube 4 by a manually-rotatable screw 23. The copyholder comprises a transparent receiving plate 25 and a hinged clamping cover 25a having a removable centre 25b and held closed by a catch against an opening spring. To facilitate location of copy this may be covered with a transparent sheet with framing lines. If the copy is opaque it may be lit either by lamps 29 on hinged doors 30 in the enclosure 5 or by lamps in the cabinet shining through apertures in the enclosure, while with transparent copy the centre 25b of the holder cover is removed for illumination by either a discharge lamp 39, movable against the cover by a hand-driven screw or a similar lamp secured to the cover. A stock of negative holders 42 and a focusing screen 43 may be stored on ledges Z surrounding the aperture 3. To avoid use of a focusing screen, spring measuring drums may be carried on the tube 9 and connected to the copyholder board and lens board. The camera may be provided with half tone screens and colour filters behind the lens. The lenses and filters may be mounted on motor-driven turrets or like carriers. By using either the lamp 39 or by lighting a sheet of white paper on the copyholder with the lamp 29, low contrast positives may be produced by contact printing for use as colour correction masks, while with the apparatus in the inverted position by locating a negative in the camera and illuminating it with the lamp 39 enlargements may be made on light-sensitive material placed in the copyholder. In a modification, the trunnions are journalled in blocks slidable in vertical guides and secured to rods pin-andslot connected to counterweighted pivoted levers so that the camera and copyholder unit is raised to bring the negative holder or copyholder always exactly to the level of the top of the cabinet. To effect centring of the apparatus both the housing 4, 5 and the negative holder frame carry at each a pair of rollers arranged to engage a downwardly-facing rail on opposite walls of the cabinet. A vertically movable half-tone screen magazine may be attached to the cabinet so that the selected screen may be brought level with the cabinet top and slid out of the magazine for ready attachment to the camera. When using lamps which cannot be rapidly switched on and off, so that shielding is necessary prior to exposure, opening spring roller blinds of red, green, or amber plastic may be automatically brought into shielding position when the copyholder swings into its loading position and to facilitate loading of the copy the blinds may be ruled diagonally to indicate frame sizes. A magazine for the lightsensitive material may also be used. The Provisional Specification refers to a lever extending laterally of the lens mount for manual adjustment of the diaphragm or by a guide rod between the ends of the housing 4, 5 to effect automatic adjustment while focusing.