Patent GB-1062960-A (GB)
Title: Improvements in or relating to slide projectors
IPC: G03B23/08
Filed: 1965-06-23
Abstract: 1,062,960. Optical-projection apparatus. BELL & HOWELL CO. June 23, 1965 [June 23, 1964], No. 26554/65. Heading G2J. In a slide projector in which a slide magazine is cycled through the projector by motor driven slide changing means, each slide is routed out of and into the magazine twice. The slide first emerges, for previewing, at a subordinate projection gate, from which it can be removed for re-orientation. After being returned to the magazine, the latter is stepped through one slide space to present the slide to a main projector gate, while the next slide is being previewed. A previewing station Fig. 16 (not shown) includes illuminating means, a projection lens (48), a reflector (49), a ground-glass viewing screen (43) built into the top of the projector casing and manually operable slide removing means (227) Figs. 2 and 3 (not shown). The magazine 31 may be of special construction having slide receiving slots open at the top and bottom Figs. 18-25 (not shown). Alternatively, a conventional magazine, having a solid bottom, may be inverted over an adapter frame Figs. 26-29 (not shown) so that it seats in the magazine guide channel (37) Fig. 2 (not shown). The slides are retained in the magazine by spring clips (53) which, when moved aside, allow them to drop into two frames 187 and 139 under the control of lifter arm 180. Frame 187 is vertically movable in guides by means of cam 194. Frame 139 is horizontally slidable on rod 104 between the previewing position (Fig. 8) and a position overlapping frame 187. A slide changing motor rotates shaft 120 to move cam plate 118 through one revolution for each complete viewing cycle. As teeth 119 engage pinion 113, shaft 104 is rotated to raise the frame 187 and step the magazine 31 through rotation of pinion 82. The upward movement of frame 187 releases the spring slide retaining clips, thus allowing a pair of slides to be supported on the raised lifter arm 180. The lifter arm is thereafter cam operated Fig. 12 (not shown) to lower the slides into frames 187 (which is at its projection position) and 139. When the slides have been received in their respective frames, cam 149 becomes operative to move frame 139 into the previewing position, through the co-operation of lever 153 and racks 155, 160 and pinions 161, 158. This results in the withdrawal of shutter (163) Figs. 3 and 5 (not shown) from the main projector beam and the clamping of a slide against frame 187. The drive to shaft 120 may be interrupted at this point, to prolong viewing, by an electromagnetically operated clutch Fig. 4 (not shown). The slide changing motor continues to run and drives a cooling fan. A reversible lens focusing motor is provided. On re-instating the drive to shaft 120, cam 149 is again operative to return frame 139 into alignment with frame 187 and to replace the shutter in the main projection beam. Lifter arm 180 is raised to return the slides to magazine 31. The resumed rotation of shaft 104 initially lowers frame 187, to allow the spring clips to return to their slide engaging positions and then begins to step the magazine. The forward stepping motion of the magazine may be replaced by a backward step on actuating gear reversing means, driving pinion 82, by means of a solenoid (97) Fig. 9 (not shown). In order to free the magazine for manual positioning or withdrawal, shaft 120 may be manually de-clutched at an appropriate point in the operating cycle by a knob (231) Figs. 6 and 7 (not shown).