Patent GB-171342-A (GB)
Title: A photographic projection copying or contact printing apparatus for making photo-mechanical printing plates
IPC: G03F7/22
Filed: 1920-05-04
Abstract: 171,342. Boedicker, H. C. May 4, 1920. Printing-apparatus.-Relates to contact printing or projection copying apparatus more especially such as described in Specification 155,340, designed for making photomechanical printing plates and adaptable for registered repeat printing, either by contact printing or projection. The apparatus comprises a base 1, Fig. 1, mounted on springs 2 and supporting a frame 44 for the printing plates and a movable carriage 3. The carriage 3 carries a transversely movable bed plate 33 having a slide 91 on which the lamp, negative holder, lens and bellows are detachably and adjustably mounted. The printing plate can be stepped vertically in the frame 44. Fig. 1 shows the apparatus adapted for projection copying, while Fig. 2 shows it adapted for contact printing with the lens and condenser supports removed and the negative holder 169 reversed, the negative 70 being mounted in a carrier 147 on the holder 169. Mounting and adjustment of carriage.-The carriage 3 has flanges 6, Fig. 5, carrying screwed adjustable bushes 7 for the bearings of the rollers 4 which run on V-shaped tracks 5. The carriage may be freely movable manually or mechanically moved by a wheel 10, Figs. 1 and 2, which rotates a central screw shaft 16. The screw shaft passes through a split nut 17, 18, Fig. 9, mounted in a fixed casing 19 on the base 1, and the two parts can be released or clamped on the screw by means of eccentric shafts 20, 21 and jointed connections operated by a lever 31. Mounting and adjustment of bed-plate.-The bed-plate 33 is mounted to slide transversely on the carriage 3 by means of dovetailed slides 42, 42<a>, Fig. 2, (the latter section being adjustable), at the forward end of the carriage and flat ways at the centre and the other end 43, Fig. 1, of the carriage, thereby allowing for relative expansion or contraction. The transverse movement is effected by screw shafts 35, 39 threaded through nuts 41 on the bed-plate and operated from the hand-wheel 34. To provide accurate stepping adjustment of the bed-plate and negative for repeat printing or the registration of colour negatives, the hand-wheel 34 is provided with a micrometer scale, Fig. 2, passing a zero mark 74 on the carriage for fine registration and for rough registration a tape 73 passes round the carriage 3 over friction rollers and is attached to a bracket 77, Fig. 16, on the bed-plate 33. The tape 73 extends through apertures at 80 in the sides of the carriage 3 and carries a pointer 72 moving over a graduated scale 73'. The ends of the tape are connected by a spring 88, Fig. 16, to keep the tape taut. A counter 75, Fig. 2, is provided which is stepped on each complete rotation of the wheel 34. Means for reciprocating the slide.-The slide 91 carries the supports 159, 161, Fig. 1, for the lens holder and condenser holder on the inner pair of ways 165, 166, Fig. 13, and the supports 160, 153 for the negative holder and the lamp holder on the outer pair of ways 163, 164 thereby enabling the holders to be closely positioned. When the negative holder is adjusted and the apparatus used for contact printing as shown in Fig. 2, and to enable the negative to be moved out of contact with the printing-plate and repositioned with the same pressure as before, the slide 91 can be reciprocated a limited distance in the bed-plate 33 by means of eccentrics 97, 98, Figs. 13 and 14, which engage lugs 100, 101 on the slide 91, the eccentrics being feather keyed to a transverse shaft 96 mounted on the carriage 3, and operated by the hand-lever 99. Locking means for carriage and frame.-For use in contact printing the carriage 3 is registered and locked in engagement with the printing-plate frame 44 as a unitary structure by bolts 140 which engage slots 141 in the frame 44 and are clamped therein by an eccentric shaft 143. Lamp support.-The lamp support 150, Fig. 1, is vertically adjustable by racks 151 and pinions turned by the head 156, a clamping nut 157, Fig. 22, being provided to fix it in position by clamping the pinion shaft 155. Negative holder.-To strengthen the rigidity of the negative holder 169, Fig. 2, for contact printing, removable braces 158 may be secured to the holder and to the slide 91. Light-excluding curtains.-To enable the apparatus to be used in a lighted room, two pairs of light-screening curtains 216, 217 and 218, 219, Fig. 29, are mounted on spring rollers 216<1>, 217<1> and 218<1>, 219<1> respectively situated round the printing-plate holder 48. When the apparatus is used for projection the forward ends of the upper and lower curtains 216, 217 are connected, as by clips 220<a>, Fig. 30, to the bellows frame. The side curtains 218, 219 lie snugly against the edges of the top and bottom curtains and their free ends have rigid bindings 220, 221, Fig. 26, and are attached to the front corners of the top and bottom curtains. To close further the open end of the box-like structure formed by the curtains, additional curtains 222, 223 are mounted on spring rollers 223<1> on the bellows frame, the free ends being attached to the bindings 220, 221 of the side curtains. When the apparatus is used for contact printing the curtains 222, 223 are moved and the rigid bindings of side curtains to which the forward ends of the top and bottom curtain are attached are slidablv attached to the sides of the front of the negative box carrier 147, Fig. 2. Specifications 171,121 and 171,343 also are referred to.