Patent GB-679972-A (GB)
Title: Improvements in or relating to photographic cameras
IPC: A01D51/00
Filed: 1949-11-15
Abstract: 679,972. Photograhic copying cameras. LINZELL, L., and PICTORIAL MACHINERY, Ltd. Nov. 15, 1950 [Nov. 15, 1949], No. 29267/4.9. Class 98 (i). A photo-reproduction camera has a magazine at one side thereof for storing several photomechanical screens in spaced vertical planes perpendicular to the camera axis, a carrier for supporting each screen in the magazine incorporating a horizontal track which is parallel with the plane of the screen and on which the screen may be moved between an inoperative position, in the magazine and an operative position at the back of the camera, a screen carrier at the back of the camera for supporting a screen in a vertical operative position perpendicular to the camera axis, the latter carrier incorporating a horizontal track on which the screen may be guided for lateral movement towards and away from the magazine, and means for shifting the magazine carriers relatively to the, camara back carrier, in a horizontal direction normal to the plane of each screen whereby the tracks of the magazine carriers are selectively aligned with the track at the camera back to, permit movement of the selected screen, along, the aligned tracks for transfer to and from the operative and inoperative positions. In the form shown, a photo-reproduction camera 10, Fig. 1, has fitted, to one side and adjacent the back thereof a magazine 11 in which three screen carriers are stored. Each carrier comprises a, bracket 40, Fig. 11, fixed at each end of the upper edge of a screen holder frame 12 on which a screen is removably, held by adjustable stops and supporting, a pair of flanged rollers 41 which rest on a, rail 42 extending transversely of the magazine. The carriers are interconnected by end cross bars 45 and a central cross-bars 46, Fig. 1. The latter carries  a block 47 slidable along a rod 48 deposed: normally to the rails 42 and each bar 45 carries blocks 49, Fig. 11, through which passes a rod 50, journalled in bearings 51, 52 and having at one end a threaded part screwed into one block 49 and near the other end a sprocket 251. Each. carrier also includes channel guides 32, Fig. 11, in which the lower edge of a screen holder 12 fits, carried by register bars 53 interconnected by a plate 54 on a pair of blocks 55, one of which engages the threaded part of a rod 58 having a sprocket 59. An endless chain 60 is entrained around the sprockets 251, 59, Fig. 1, and a handle 62 is provided on one rod 58 so that by rotation thereof the carriers are moved as a unit to position any one of the screen holders 12 opposite a slot in the side of the camera 10. In order that rotation of the handle 62 may be arrested when the required screen holder 12 is opposite the slot in the camera's side, the base of the magazine 11 is provided with a plate 71, Fig. 5, carrying three walls 72, 73, 74, the walls 72, 73 being interconnected by a cross-bar 83. Journalled in the walls 72, 73 is a rod 76, rotatable by a handle 77 having a pointer 78 movable over a scale marked 1-2-3 and carrying three cams 79, each corresponding to a particular screen and offset by 120 degrees relative to the others. Each cam comprises three recesses 80, 81, Fig. 6, offset by 120 degrees for co-operation with a roller 82 on a spring-urged plunger 94 slidable in the cross-bar 83. The opposite end of each plunger has a pin 84 engaged between the limbs of the forked arm 85 of a bell-crank lever 86, each of which is journalled on a rod 87 and is spring urged anticlockwise about this rod at 89. The other arm 90 of each lever 86 passes through a guide slot 91 in the wall 74 so as to lie beneath a locking plate 92 carried by the pair of blocks 55 on one of the screwed shafts 58 and having on its underside a slot 93, Fig. 6. In use, handle 77 is rotated until the pointer 78 aligns with one of the marks on the scale 1-2-3, such rotation causing the recess 80 in the appropriate cam 79 to co-operate with the roller 82 on the plunger associated with said cam so that the corresponding bell-crank lever arm 90 abuts the lower edge of the plate 92. Thus, when handle 62 is rotated to move the screen carriers, the plate 92 moves therewith and movement is arrested when said arm 90 enters the slot 93 in said plate. In this position the required screen holder is aligned with a slot in the camera side wall and the rail 42 carrying said holder is in alignment with a rail 104, Fig. 1, across the upper part of a frame mounted in the back of the camera. Each screen holder 12 has a lug 105, Fig. 10, which moves into a recess 109 in a block 106 when said holder is moved into position for transfer to the camera. This block is slidable along a rail 108 by means of a chain 115 entrained around sprockets 116, 117, Fig. 1, and driven by a handle 120 coupled to a sprocket 118 and to the sprocket 116 by a chain 119. A spring-urged slide within the block 106 has secured to each side thereof plates 110, 111 which abut a stop plate 122, Fig. 10, when the block is moved to the pick-up position and so free the recess 109 for reception of the lug 105. On reverse rotation of handle 120, the screen holder is moved on to rail 104 and thus into the camera and at the same time the plates 110, 111 move so as to keep the lug 105 in the recess 109. Immediately before the screen holder reaches its correct position in the camera, a lug on the holder abuts a block on a bar which is parallel to the rail 108 on which block 106 slides and has a pin and oblique slot connection with a fixed rail. Thus, this lug moves the bar towards the screen holder and, when the latter reaches its correct position, the bar clamps the screen holder against lugs on the frame at the back of the camera. A holder for a circular screen is also described.