Patent GB-884452-A (GB)
Title: Improvements in or relating to optical projectors
IPC: G03B23/04
Filed: 1960-03-28
Abstract: 884,452. Slide projectors. LEITZ G.m.b.H., ERNST. March 28, 1960 [March 28, 1959], No. 10884/60. Class 97(1). An optical projector for automatically projecting a series of transparencies in a magazine and for displacing the magazine by one slide between successive projection operations has means provided for returning the magazine to an initial position after the last slide of a series has been shown, the returning means being operated by a control means. In the embodiment shown slides 4 are placed in compartments in a magazine and glass plates are placed at either end of the series; each plate has a projection which enters a slot in the magazine and can be abutted by an arm 17a of a control member 17, which is mounted on the same shaft as ratchet wheels 19, 42. A motor 24 is mounted on the same shaft as a cam disc 28, a clutch (not shown), a toothed ring 32 and a disc 30 rotatable in the direction A only and having a groove 36 for a tooth on wheel 19 and a cam 35 for rotating wheel 19 by one tooth in the arrowed direction. When the slides have been put in the magazine switch 25b is manually closed and the magazine is driven by a rack 20 which is engaged by wheel 19 until 17a abuts a projection on plate 5, 6 and is rotated to close switch 23 or 22 to operate the motor 24 and hence to rotate shaft 27. During the initial rotation of shaft 27 (half a rotation has been performed in Fig. 4) a rack 34 is operated via gearing 32, 33 to lower a slide from a projection gate (if it is there) into the magazine. After half a rotation wheel 19 is rotated by one tooth by cam 35 and moves the magazine on by one slide compartment. During this movement operation of the slide changing parts is prevented by a part of the ring 32 which has no teeth. During the final approximate half revolution of the disc the slide is raised to the projecting position. During projection of the slide the motor is stopped for a length of time determined by a mechanism 26. This cycle is repeated until all slides in the series have been projected and the abutment of the other one of plates 5, 6 abuts 17a and rotates it to close the other of switches 22, 23 and to close switch 51 of an electromagnet 50 which results in lever 46 being rotated to move arm 41 along shaft 37 to engage wheel 42. Cam 29 then causes levers 38 and 41 to oscillate and rotate wheel 42 and hence 19 to move the magazine in the reverse direction until it is in its initial position when the whole process starts again. In other embodiments described (a) the switch 17 is designed so that on abutting a projection on a plate to effect reverse it moves the arm 41 into the correct position mechanically (b) the return movement is effected by a spring which is tensioned by the initial movement of the magazine (c) two separated motors are used for the forward and return movements of the magazine a switch operating switches in the two motor circuits and a clutch between one motor and the magazine (d) the switch 17 comprises two switch members slidable along a guide to vary the distance between them which are operated by abutments fixed on the magazine.