Patent GB-986233-A (GB)
Title: Improvements in or relating to optical projectors and transparency stack containers therefor
IPC: G03B23/04
Filed: 1962-07-10
Abstract: 986,233. Optical projection apparatus. ERNST LEITZ G.m.b.H. July 10, 1962 [Sept. 2, 1961], No. 26447/62. Heading G2J. A slide projector having a slide changing frame and a guide channel to guide a slide magazine of known compartmented form may alternatively be used with a slide stack container in which the slides are initially arranged in face-toface contact in one stack and after projection are returned to form a second similar stack. As shown (Figs. 4 and 5), a slide stack container 4 comprises a base plate 31 with two projections 19 for engagement in recesses 18 provided in the base 17 of the magazine guide channel (Fig. 1-not shown). Slides are initially arranged in face to face contact in a stack 24 between a wall 22 slidably mounted on a rod 28 between stops 33 under loading of a spring 32 and a pressure plate 26 also slidably mounted on the rod 28 and loaded by a spring 29 which at the other end is secured to a similar slidable pressure plate 27. A flat spring 35 is secured to the wall 22 on one side and a bent spring 34 (Figs. 5 and 6a) on the other, the two springs forming between them a guide path 37. The slidable projector slide changing frame 9, which lies opposite the wall 22 when the container is mounted in the projector is provided with a projecting runner 36 knife edge 39. Slide changing operation: Starting from the position of Figs. 5 and 6a in which a slide has just been returned to the container 4, on movement of the frame 9 towards the projection position (not shown) that slide which then lies adjacent the wall 22 in the stack 24 will be separated from the rest of the stack by the knife edge 39 and removed from the container 4 through the gap between a front wall member 42 and the wall 22 by the part 10 of the frame 9. The runner 36, during this phase of operation, slides along the guide path 37 and deflects the bent end 40 of the spring 34 as it leaves the container 4. On returning the frame 9, after projection, toward the container 4, the runner 36 engages the bent end 40 of the spring 34 and deflects this and the wall 22 against the spring 32 so that the transparency slide being returned follows a path between the wall 22 and the plate 27 (or last returned slide in the stack 25). The wall 22 has a specially shaped portion 38 to facilitate this return movement. As soon as the runner 36 projects beyond the spring 34 (as in Figs. 5 and 6a) the wall 22 springs back to its original position whereby a fresh transparency slide is brought into position for engagement by the knife edge 39. The wall member 42 may be adjustable to vary the gap between itself and the wall 22 to allow for different thicknesses of slides. In a modification (Figs. 2 and 3 - not shown) the wall 22 is fixed relative to the base plate 31 and the whole container is arranged to move sideways against spring loading each time a transparency is returned after projection. In further modifications in which both wall 22 and base plate 31 are stationary in the projector the end 10 of the slide 9 is provided with a member 45 (as in Fig. 7) which is pivotable under spring loading. In the modification of Fig. 9 (not shown), the end 10 is provided with two alternatively usable members, one pivotable transversely to the slide 9 (as in Fig. 7) and one not (for use with ordinary slide magazines).