Patent GB-862678-A (GB)
Title: Improvements in or relating to a transparency changing apparatus for optical projectors
IPC: G03B23/04
Filed: 1958-08-18
Abstract: 862,678. Optical-projection apparatus. LEITZ G.m.b.H., E. Aug. 18, 1958 (Aug. 19, 1957], No. 26468/58. Class 97(1) A remotely controlled electrically driven magazine type slide changing mechanism has means for moving the slides to and fro between the projection position and the magazine with or without moving the magazine forward. The main parts of one embodiment are shown in Figs. 4 (part) and 11 (part). Various contacts shown in those Figures form part of an electric motor control circuit as shown in Fig. 3. The motor 21 can be caused to run in either direction by closing the contact 25, in a push button switch remote from the projector, on to contacts 24 or 26 respectively. The direction of rotation corresponding to either pair may be reversed by a reversing switch comprising moving contacts 68, 69 and fixed contacts 70, 71, 72. Whichever movement of the contact 25 is used to start the motor, the movement can be maintained by closing contacts 57, 58, provided the contact 99 is closed on to the appropriate one of the contacts 100, 101. These contacts are operated in the required sequence to achieve the desired functions by the mechanism shown in part in Figs. 4 and 11. The motor 21 drives, through a reduction gearing, a shaft 32, on which are mounted a disc 33, carrying a roller 38 on an eccentrically mounted pin 37, a disc 34, with a notch 45 in which is pivoted a cam 44, a cam 35. the profile of which consists of two interconnected circular portions of different radii, and an eccentric 36 located in a notch 96 in a lever 79 pivoted at 80. The roller 38 engages a slot 40 in a plate 39 pivoted at 41 and carrying a roller 42 engaged in a fork 16 forming part of a vertically movable member 14 coupled to the vertically movable operating member of a slide changing mechanism as described, for example, in Specification 807,779. By producing appropriate rotations of the shaft 32 vertical movements are transmitted to the member 14 to produce the necessary functions of the slide changer. The cam 35 actuates a lever 97 which operates the contact 99. Rotation of the shaft 32 can cause either of the cams 43, 44 to engage a pivoted lever 48, urged anti-clockwise by a spring 59 and having a flange 51 for operating the contact 58. Another flange 50 engages a flange 52 on a pivoted lever 53 urged anti-clockwise by a spring 55. The end 60 of the lever 48 bears against the flange 64 on a pivoted lever 61, also spring urged anticlockwise, and having an end 63 which can, when required, be engaged with notches 64, 65 on a lever 66. The latter is movable between stops 74, 75 on a pivot 73 and is coupled to the lever 79 by a spring 77. The contact system shown in Fig. 11 is operated by the nose 81 attached to the lever 79. The position of the parts shown in Fig. 4 corresponds to that of the changing mechanism where there is no slide in the projection position. To move a slide into the projection position, the push button switch is operated to close contacts 24 and 25 and cause the motor to run to drive the shaft 32 and the cam assembly anticlockwise. The cam 44 pivots into the notch 45 allowing the lever 47 to pivot anti-clockwise, allowing the contacts 57, 58 to close and engaging the nose 63 in the notch 65 and lock the lever 66 against the stop 74. The contacts 57, 58 cause the motor to run on, even if the contacts 24 and 25 are released, until the lever 47 is lifted again by the cam 43, opening the contacts 57, 58 again, as shown in Fig. 7. The roller 38, engaging the slot 40, has by now rotated the plate about the pivot 41 to lift the member 14 by the amount required to feed a slide into position for projection. The eccentric 36 has meanwhile rotated to turn the lever 79 about its pivot 80 so that the nose 81 engages and closes the contacts 87, 88 to complete the circuit of the projection lamp 90, as shown in Fig. 7. At the same time the clockwise rotation of the lever 47 turns the lever 61 so that its end 63 moves out of the notch 65 of the lever 66. The lever 79 has by now tensioned the spring 77 to move the lever 66 against the stop 75. To replace the slide, in the projection position, by another, the push button switch is operated to close the contacts 25 and 26. Because of the movement of the lever 66 and the reversal of the switch formed by the contacts 68-72, the motor runs in the same direction as before, the cam 35 moving the contact 99 on to the contact 100 so that the motor circuit is again held on by the contacts 57, 58. The movement continues for a complete revolution of the shaft 32 and ceases when the cam 43 lifts the lever 47 again to open the contacts 57, 58. During this movement the member 14 is first moved downwards, the slide changing mechanism being such that this movement first withdraws the slide in the projection position and then moves the magazine forward. The member 14 is then moved upwards to move the next slide into position. During this cycle the lamp circuit is maintained by the contacts 87, 88 held closed by the latch 85, although the lever 79 moves away from the position shown in Fig. 7 and back again. To switch off the projector, the push button is operated to close the contacts 24, 25 again. In the position of the contacts 68-72, shown in Fig. 7, this causes the motor to run to turn the shaft 32 clockwise. The cam 44 now becomes effective and lifts the lever 47 to stop the motor when the parts have returned to the position shown in Fig. 4. The return movement of the lever 79 causes the nose 81 to act on the lever 83 as shown in Fig. 11, to close the contacts 93, 94 and energise, from the lamp supply, a coil which heats a bimetallic strip 95 causing it to bend to the position shown dotted and lift the lever 86 to disengage the latch 85 from the contacts 84, 87 switching off the lamp. The time delay in the heating of the bimetallic strip is sufficient to prevent the lamp being switched off during the cycle of operations for exchanging slides described above. To project again the same slide as before, switching off requires the same movements as moving a slide to the projection position initially, and is effected by closing contacts 24, 25. To project the next slide, the contacts 25, 26 are closed to cause the motor to drive the shaft 32 clockwise until stopped by the contacts 57, 58 opening in the position shown in Fig. 7. During this movement the member 14 is first driven downwards to move the magazine forward and then upwards to move a slide into the projection position.