Patent GB-836483-A (GB)
Title: Automatic slide changing mechanism for optical projectors
IPC: G03B23/04
Filed: 1958-02-10
Abstract: 836,483. Optical-projection apparatus. AIREQUIPT MANUFACTURING CO. Inc. Feb. 10, 1958 [April 12, 1957], No. 4332/58. Class 97(1) A slide changing mechanism for an optical projector comprises a motor driven member for moving slides successively back and forth between the magazine and the projection position, means to move the magazine forward after each slide is projected and an adjustable mechanical timing device for controlling the time for which each is projected. As shown in Fig. 1, a slide magazine 2 is carried on a baseplate 8 and a slide holder 7 is engaged by a lever 12 and pushed into the projection position 11. The lever 12 has a cam groove, not shown, formed in one face and engaging a pin carried by a member 17, the shape of the cam groove being such that inward movement of the lever 12 moves it downwardly to engage its hooked end on a notch 22 on the slide holder 7 so that reverse movement of the lever 12 withdraws the slide to the magazine. The lever 12 is carried by a slider 15 which is actuated, through a link 42 driven by the motor 30 through the mechanism shown in exploded view in Fig. 16. The motor 30 drives through reduction gearing, a crank which reciprocates a link 38 coupled to a disc 32 carried with various other parts indicated on a fixed shaft with its axis at 35, the various parts being separated by stationary washers 39a anchored on a pin 269. A pawl 156 on the disc 32 engages ratchet teeth on a member 150 and rotates this member until disengaged when a projection 159 on the pawl strikes the surface 158 of a cam 157. The point in the stroke of the pawl at which this occurs is adjusted by rotating a pinion 161, engaging teeth on the cam, by means of a knob 163. This determines the number of strokes of the pawl required to rotate the member 150 until a pin 151 thereon strikes a cam surface 134 on a latch member 131 which retains the projection 113 on a member 98. This member is then rotated by a spring 112. A pin 105 on the member 98 is engaged in a slot 106 in a member 96 carried on the supporting spindle with a slotted hole and rotation of the member 98 moves the member 96 radially inwards allowing a follower member 94 engaged with the surface 95 to move inwards under the action of a spring 99. The member 94 is pivoted at 93 on a member 41 and pushes a hook 90 into a notch 91 in the member 32 so that the member 41 moves with the member 32 to reciprocate the link 42 and the slide engaging lever 12. After one cycle the member 94 strikes the member 98 and moves it back to be latched by the member 131. The parts are thus returned to their initial stationary position which is that where a slide is in the projection position. A fresh cycle is started to bring the next slide into position when the timing device actuates the latch 131 again or when it is released manually by depressing a button 122. Prolonged projection of any slide may be effected by depressing a button 161 concentric with the knob 163. This releases a member 164, pivoted at 165, which is then moved by a spring 194 so that a cam surface 166 holds the pawl 156 free of engagement with the ratchet 150, until the button 122 is depressed to restart the slide changing cycle during which a projection 195 on the member 96 moves the member 164 back to its inoperative position. The link 38 is formed of parts 140, 145 capable of relative sliding movement in the event of jamming or if the lever 12 strikes the side of the magazine as it is inserted. Relative movement of the parts is normally prevented by spring urged rollers 148 carried by the part 145 engaging notches in the part 140. The projection 79 formed on, and the spring- loaded pawl 78 carried by the member 41, effect the operation of the device for moving the slide magazine forward as each slide is projected. After the lever 12 has removed the slide from the magazine and has been detached therefrom continued movement of the member 41 brings the projection 79 into contact with a projection on a pivoted claw which then engages and rotates a gear wheel meshing with a rack carried by the film magazine: On the return movement of the member 41 the pawl 78 returns the gear-driving pawl without movement of the gear or the magazine. The Specification also describes pnuematic and solenoid-operated remote actuation devices which are alternatives to the manual button 122. Also described is a device for supporting the weight of the mechanism, including a telescopic leg the extension of which may be adjusted by a ratchet device.