Patent GB-549103-A (GB)
Title: Improvements in or relating to shutter operating mechanism of projection apparatus for transparencies
IPC: G03B21/16
Filed: 1942-03-17
Abstract: 549,103. Optical-projection apparatus. KODAK, Ltd. March 17, 1942, No. 3554. Convention date, July 19, 1941. [Class 97 (i)] A shutter cutting off the light beam during slide changing is moved from its operative position, at the end of a slide-changing operation, by a piston which is actuated by air from a supply for cooling the slides &c. and is released by operation of the slide carrier ; movement of the shutter to cut off the beam may be controlled by hand or may be effected automatically if the cooling air supply fails. Fig. 1 shows a projector mounted on a casing 11 containing, in a chamber 36, a motor 13 and fan 12 drawing air through an opening 21 and discharging it through a conduit 26 around a slide carrier in a chamber 18 and across the front of a condenser lens 17. The air passes into a chamber 19 and is guided by vanes 31 around a lamp 15 and reflector 16, and between the condenser lenses, to a discharge chamber 37 separated from the chamber 36 by a partition 35. The vanes 31 are carried by a cover 38 mounted on a pivoted arm 40 and provided with a securing screw 41. An aluminium shutter 50 is vertically slidable between the condenser lenses and is mounted on a rod 51 extending from a piston 55, Fig. 2, within a chamber 54 extending on both sides of the partition 35. The top 53 of the chamber 54 has a hole 61, Fig. 8, by which air passes from the chamber 36 into a flexible cylinder 56 connected within the chamber 54 to the piston 55, thus normally holding the shutter 50 in a lowered inoperative position. A valve-controlled hole 75 communicates with the chamber 37 ; when this hole is opened, the pressure within the cylinder 56 falls and permits the raising of the shutter to cut off position by a spring 68, through a lever 65 pivoted at 67. Both the holes 61, 75 may be controlled by valves, the valves 76, 77 being mounted on a plate 78 carried by pivots 79 so that only one valve is closed at any time, the valve 77 controlling the hole 61 being open during normal projection. The shutter 50 moves into cut-off position if hand pressure is applied to a push button 81 ; this results in the lowering of a lever 86 against the action of a spring 98 so that a spring 87 connecting the lever 86 and the valve 76 may open the valve 76 and close the valve 77. A spring controlled lever 90 may engage a groove 88 in a rod 83, connecting the button 81 and the lever 86, to hold the button in the lowered position and the valve 77 closed. Failure of the pressure due to the fan also permits the spring 68 to raise the shutter 50 to cut off position. The slide carrier 29 may carry a plate 113 at each end to engage alternatively, and to push, one of two extensions 111 on the ends of a horizontally reciprocable member 105 when slide-changing has been completed. Movement of the member 105 rocks a lever 99 about its pivot 100 to move the lever 90 and free the button 81. The spring 98 then raises the button, and moves the valve 77 from the hole 61 so that the air pressure restored within the cylinder 56 operates the piston 62 to remove the shutter 50 from the cut off position.