Patent GB-1014642-A (GB)
Title: Copying machines, such as photographic enlargers
IPC: G03B21/10
Filed: 1962-04-27
Abstract: 1, 014, 642. Photographic copying apparatus. MINNESOTA MINING & MANUFACTURING CO. April 27, 1962 [April 27, 1961], No. 16196/62. Headings G2A and G2H. A copying apparatus comprises a projection lens with a light source behind it so as to project an image on to a reflecting device, the reflecting device, light source, and lens all being positionally adjustable and interconnected so that adjustment of one automatically effects appropriate focusing adjustment of the others, and a mirror movable from one position where it receives the image from the reflecting device to reflect it to photosensitive copy paper to another position where it allows the said image to fall directly on a viewing screen. The machine comprises a main housing 2, to the base of which is fixed a pair of rails 5 forming a guide track. The light source is in a separate enclosure 19 outside the main housing, and moving on guides 20. It comprises a lamp and reflector, and a projection lens (Fig. 6, not shown). The lamp and reflector can be moved towards the lens by a manually operated mechanical linkage. Movably mounted on rails 5 is a sled 8 carrying a turret 30; the turret carries two projection lenses 28, 29, of differing magnificantion, and can pivot on a pin 31 to bring either lens into the operating position. In Fig. 2, lens 28 is shown in this position. When the other lens is required, a pin extending downwards from the light source 19 engages the forked end of an arm 32 and pivots it about its axis 33; its other end is also forked, and engages a pin 34 on turret 30, so swinging the turret round to bring the other lens 29 into the operative position. Also sliding on guide rails 5 is another sled 7, carrying two mirrors 47, 48 at 45 degrees to the vertical, which reflect the projected image on to a viewing screen 3. A rotatable shaft 37 carries two cams 39, 40. A fine-focus block 42 on lens sled 8 has a cam follower 43, and is connected to the lens turret 30 by a connecting rod 44. The face of the cam follower is positioned against either cam 39 or cam 40, according to which lens is in the operating position. Fine focus adjustment is achieved by movement of a shaft 49, which slides the fine-focus block 42 and cam follower backwards and forwards in a guide 50 permanently fixed to the lens sled. Also mounted on a shaft 37 is a gear 38, which drives a rack 46 fixed to the mirror sled 7. Thus when shaft 37 is rotated, the shape of the cams 39, 40 maintains the projection lens in the proper focal position relative to the mirrors 47, 48 as the sled 7 also moves. The viewing area 11 is shown in detail by Fig. 4. A swinging mirror 52 is attached to a slotted arm 53 pivoted on a pin 54. A motor-driven arm 56 has a roller 57 engaging in the slot 58, and can drive the mirror from the position shown in full lines, in which it is operational and reflecting, to the position shown in broken lines,where it is non-operational. When it is in the operational position, the image received from the mirrors 47, 48 is reflected again to a photosensitive sheet 64, thus making an exposure. If the mirror 52 is folded down into its non-operational position, a blind 61 is at the same time drawn by a cable 62 across the photosensitive sheet to shield it against exposure. In this position, the,image is thrown directly on to a viewing screen 3. The transparency which is to be projected and enlarged is supported in a film holder 6, adjustable horizontally and vertically (Fig. 5, not shown). An adjustable mask is provided for cropping or masking the projected image. A paper-measuring device, to minimise wastage of photosensitive paper, is incorporated (Fig. 10, not shown), and may be integrally connected with the mask. In the form described, the photosensitive paper is developed by an electrolytic method, and consists of a photoconductive layer on a conductive backing. The developing section may be integral with the apparatus. As shown in Fig. 9, the exposed sheet passes round a roller 70, and developer solution is applied to it by a soft porous roller 71, itself wetted by a roller 66 dipping into bath 65. A wringer roller 76 removes excess liquid. The conductive backing of the paper sheet is made the anode, and a suitable electrode immersed in the developer solution to act as a cathode.