Patent GB-281111-A (GB)
Title: Improvements in or relating to photographic film-packs
IPC: G03B17/34
Filed: 1926-12-30
Abstract: 281,111. Storr, B. V., and Ilford, Ltd. Dec. 30, 1926. Change-boxes, self-contained. - Relates to a daylight-loading refill for photographic film packs, of the kind comprising an envelope of opaque paper or like material which is formed of U-shape so as to constitute two separate overlying chambers, the front chamber having an exposure opening and containing the unexposed films, and the rear chamber being adapted to receive exposed films which are pulled from the front chamber by flexible draw-tabs attached singly to the films and extending round the bend of the U and through a slit at the free end of the rear chamber. According to the invention the walls of the receptacle at the bend are spaced apart from each other to permit free movement of the films around the bend. In the form shown in Figs. 1 and 2, the receptacle comprises a front chamber closed at the end 17 and having an exposure opening 15, and a rear chamber provided at the end 25 with a light-trapped slot 27 for the passage of the freeends of the draw-tabs. The inner walls 18 of the two chambers are integral with each other, but the outer walls 16 terminate at the bend and the folds 20 near the bend are slit for a short distance so that when a cap 21 of opaque paper is slipped over the bend, the film passage at the bend is wide enough to permit free movement of the films during change. A flap 24 provided on the wall 16 of the front chamber is tucked into the rear chamber round the films after loading to ensure further security against ingress of light. To facilitate loading, the draw-tab of the usual safety cover is made longer than the other tabs and is folded over their ends; and a detachable paper apron 32 is attached at the inside of the upper edge 31 of the exposure opening 15, and is secured to the sides of this opening by a. paper patch 33, so that the films may be guided in light-tight manner past the edges of the exposure opening. In modifications, (1) the outer walls 16 are continuous and the inner walls 18 are discontinuous at the bend: (2) the two chambers are initially separate and are joined only by the. cap; (3) the cap is formed from the same blank as the wall 16 of the front chamber; (4) the flap 24 is replaced by a modified safety-cover, the full-width part of which is long enough to extend round the bend both before and after it is drawn from the front to the rear chamber; and (5) the light trap at the draw-slot 27 is formed, not on the end of the front chamber as shown in Fig. 2, but on the draw-tab of the safety cover, and further protection mav be afforded by an additional safety cover having at its end near the light-trap a slotted fold through which the draw-tabs pass. In use, a U-shaped spring-pressure plate, Fig 4, is inserted between the limbs of the loaded receptacle, which is then inserted in a sheet-metal casing, Fig. 5, provided with exposure opening 40, draw-slot 41, and closure cap 42. The whole is finally loaded into the usual adapter on the camera. The casing and pressure plate are used repeatedly, but the paper film receptacle is discarded after being used once. Individual films may be removed for development after withdrawing the paper receptacle from the casing and removing the cap 21.