Patent GB-621871-A (GB)
Title: Photographic cameras
IPC: G03B33/00
Filed: 1946-06-26
Abstract: 621,871. Photographic cameras. POWERS PHOTO ENGRAVING CO. June 26, 1946, No. 19131. Convention date, Sept.. 14. 1945. [Classes 98 (i) and 98 (ii)] A camera particularly suitable for taking colour separation negatives has means for supporting a focusing screen or a sensitive plate, means for slidably supporting a second sensitive plate or a processed negative plate serving as a mask either to overlie the first plate in register therewith or to be positioned completely to one side thereof, and means cooperating with the second supporting means to position the second plate correctly. Preferably a transparent sheet of the same refraction as this second plate is provided to be movable into register with the first plate to act as a compensating plate if the second plate is removed. As shown, a cabinet containing spare plates or other material supports a horizontal copying camera mounted on rails along which the lens board and the copy board are moved separately by hand wheels feeding threaded rods through sleeves carried by the two boards, the rear plateholding portion 35 of the camera remaining fixed. Slidably mounted therein on upper 64 (not shown) and lower rails 60, respectively, is the second or masking plate 87, which is held firmly in the exposure position by leaf-springs 89 attached to plates 90 at top and bottom of the exposure frame, and is loosely retained in the non-exposure position by a backing plate 92 and a strap 95 extending between the rails 60, 64, the upper rail 64 being interrupted at the non-exposure position to allow removal of the plate 87. The ground glass screen or plate 67 is held in the exposure position by a metal strip 66 secured to the bottom rail 60 and a vertically slidable spring plate, pin-and-slot connected to the upper rail. A transparent compensating plate 107 is mounted in a frame 130 carried by upper (not shown) and lower chains 116 passing round sprockets 113 rotatable by handle 115, the frame engaging guides as 139. Also attached to the chains is a bar 120 slidable along guides (Fig. 6, not shown) and having a lip 121 which can engage the left-hand end of the plate 87. The sequence of operation is as follows. A sensitized plate 87 is inserted into the right-hand end of the guideway formed by rails 60, 64 and is pushed to the left by hand until it engages a stop 98 which is urged counterclockwise by a leaf-spring 104 and whose operative surfaces extend above and below the lip 121. The camera is then focused using the ground glass screen, and the plate 87 exposed, developed, fixed, washed and dried and then replaced in its guideway to act as a mask plate. The focusing screen is then replaced by a sensitive plate for the exposure. To withdraw the mask the handle 115 is rotated whereupon lip 121 returns the mask towards the right-hand end of the guideway, leaving it supported by the strap 95, and simultaneously the compensating plate 107 is moved into register with the exposure aperture. Thus the plate 67 may be exposed through the mask for a portion only of the whole exposure time without disturbing the focusing adjustment. The Specification as open to inspection under Sect. 91 refers to Specification 19130/46, as open to inspection under Sect. 91. This reference does not appear in the Specification as accepted.