Patent GB-918975-A (GB)
Title: Improvements in or relating to optical projectors
IPC: G03B23/04
Filed: 1960-12-20
Abstract: 918,975. Slide projectors. LEITZ G.m.b.H., ERNST. Dec. 20, 1960 [Dec. 28, 1959; Nov. 30, 1960], No. 43731/60. Class 97 (1). An optical projector comprises means for moving a slide-magazine along a guide channel and a locking member which, in its operative position extends into the guide channel for limiting movement of the magazine when the latter is introduced into the guide channel, the locking member being retractable from its operative position to allow subsequent movement of the magazine along the guide channel. As shown in Figs. 1, 2 and 3, a bracket-like portion 5 covers the guide channel 2 in the region of the entry aperture for slides 3, contained in magazine 4, to be conveyed to and from the projection position by a reciprocable slide-changing member 7 movement of which causes roller 23 to rotate and feed the magazine step-by-step. A two-armed locking lever 15 is pivotable about the spindle 14 and also about an axis at right-angles to the spindle axis in the sense of the arrow B. A projection 19 of lever 15 protrudes into the guide channel, under tension in spring 17, to form a locking member for the magazine 4. When the latter is inserted in the guide channel and bears against projection 19 to pivot lever 15 on the spindle 14 until it engages an abutment 21a, the first slide is in line with the slide-changing arm 7. During the first phase of movement of the latter, the part 8 engaging the upper portion 22 of locking-lever 15 pivots the latter in the sense B to retract projection 19 from engagement with the front wall of the magazine. Under the tension of spring 17 (arranged diagonally with respect to each of the pivoting axes of lever 15) projection 19 moves along the side-wall of the magazine as lever 15 pivots on spindle 14 until it is arrested by the engagement of its upper portion 22 with an abutment 216. The slide-changing movement of arm 7 may be controlled manually by knob 12 (Fig. 1) via a rack-and-pinion, or by means of an electric motor 25, which in the embodiment of Fig. 8 is reversible and can drive a cam disc 34, via a free-wheel clutch 27, in clockwise rotation whereby the arm 7 is reciprocated by means of pin-and-slot connections of rod 37 with the cam disc 34 and arm 7. The extreme positions of arm 7 correspond to alignment with the magazine and the projection position respectively. When a slide reaches the projection position, cam 34a operates switch 36 to reverse motor 25 and cam disc 34 stops rotating. Depression of key 33 restores the former state of rotation of motor 25 and cam disc 34 is driven clockwise to return the slide to magazine 4 and, as the latter advances, to feed the next slide. At the end of its rim, magazine 4 operates switch 26 to include switch 35 in the circuit and cause cam disc 34 to stop when cam 34a operates switch 35 to reverse, and hence uncouple, the motor drive when the arm 7 is in the position shown. This allows withdrawal of the magazine and insertion of a new one. In a further embodiment, a non-reversible motor is used and is adapted by a similar cam- and-switch mechanism to stop the motor at the appropriate positions.