Patent GB-838683-A (GB)
Title: Improvements in or relating to optical projectors
IPC: G03B23/04
Filed: 1958-08-14
Abstract: 838,683. Optical-projection apparatus. LEITZ G.m.b.H., E. Aug. 14, 1958 [Aug. 19, 1957], No. 26148/58. Class 97(1) The same reversible electric motor drives both a cooling fan and, through a free-wheel device, the slide-changing mechanism. The form shown comprises a disc 10 in continuous driving connection with a motor 3 which is also in continuous driving connection with the fan. When the disc 10 is driven clockwise the disc 12 is also rotated by the freewheel mechanism. The direction of motor rotation is determined by whether the current is supplied to the terminal 33 or 34, the other connection being to the terminal 48. The switches 43, 44, 45 are contained in a remote control box 42. Closure of the main switch 46 completes the circuit to terminal 34 through contacts a of switches 44, 45 and 27 of switch 25. The rotation of the disc 10 is anticlockwise and the disc 12 is undriven. A single slide-changing cycle is initiated by closing the arm of switch 44 on to contact c, thus completing the circuit to terminal 33 instead. The reverse motor rotation, once started, drives the disc 12 clockwise and the finger 24 is disengaged from the switch 25 to permit it to close on to the contact 26 and maintain the motor circuit until one revolution of the disc 12 has been completed and the finger 24 returns the switch 25 to its previous position. During this rotation a crank pin (not shown), carried by the disc 12 and coupled to the slide changer, effects one complete cycle of the slide changer starting from a position in which a slide is in position for projection. After this slide is retracted, a pinion, not shown, on a shaft 64 is rotated to move the magazine forward to bring the next slide to the projection position. This rotation is effected by the engagement of a toothed wheel 63 with the curved slots 66 or 67 in one of two members 55, 56 pivoted at 57, 60 to the disc 12 and biased in opposite directions by springs 58, 61 against stops 59, 62. The spring bias is relatively weak and insufficient to overcome the resistance to rotation of the wheel 63. Thus the member 56 is ineffective to rotate the wheel during clockwise rotation of the disc 12 and is deflected on its pivot against the action of the spring 61 but the wheel is rotated by the member 55. Similarly the member 55 is ineffective and the member 56 effective during anti-clockwise rotation. To remove a transparency from the projection position, without replacement, the switch 45 is depressed on to contact c to energize the motor terminal 33, through the contact 51 of a switch 49, until the finger 24 strikes the rod 50 to move the switch 49 on to a contact 52 and re-energize the terminal 34. To move the magazine forward, without projecting a slide, the switch 43 is moved on to the contact 40, thus completing a circuit to the motor terminal 33 through a contact 31 of a switch 30. The disc 12 then rotates until the finger 24 strikes the end 28a of a rocker 28 to move the switch on to the contact 32. This reverses the motor, but in this region of rotation of the disc 12 the freewheel is rendered ineffective by a latch 13, actuated by a stationary ramp 53, to connect the disc 12 to the disc 10 by engaging one of the notches 14 therein. The reverse motor rotation rotates the disc 12 until the finger 24 strikes the end 28b of the rocker 28 to produce further reversal. A continuous oscillation is produced, during each cycle of which the member 55 acts on the wheel 63 to move the magazine one step. Lost motion is provided in the connection to the slide changer to prevent any movement being transmitted during this oscillation. Similarly, by moving the switch 43 to the contact 41 an oscillation is produced by the co-operation of the finger 24 and the rocker 29 during which the member 56 acts on the wheel 63 to step the magazine backwards. Any necessary subsequent re-setting of the rockers 28, 29 is effected by the action of the arm 24a, projecting from the disc 12 and acting on pins projecting upwards from the rocker arms 28b, 29b.