Patent GB-906320-A (GB)
Title: Improvements relating to shutter mechanisms
IPC: G03B9/08
Filed: 1960-12-20
Abstract: 906,320. Photo-electric exposure control. INTERNATIONAL POLAROID CORPORATION. Dec. 20, 1960 [Dec. 21, 1959], No. 43759/60. Class 40 (3). [Also in Group XX] A shutter mechanism comprises two shutter blades for opening and closing an aperture, the first blade being movable from a position in which the blade fully covers the aperture to a position to one side of the aperture so that the aperture is then fully uncovered by the blade, and the second blade being movable from a position at the said side of the aperture to a position in which the second blade fully covers the aperture, the mechanism also comprising an actuator for bringing about the movements of the first and second blades in sequence. As shown, the shutter mechanism comprises two blades 26, 28 pivoted about a single post 30. In the rest position (Fig. 1) in which aperture 22 is covered by blade 26, the blades are under tension by springs 46, 50, respectively, but are prevented from moving by the engagement of pins 144, 146 with cam portions 134, 132 of an actuator element 88. This element 88 is pivoted at 124, and, on release by movement of a lever 140, is urged by a spring 128 in an anti-clockwise direction (Fig. 1) at a speed determined by a photo-electrically-controlled pneumatic timing device 82, whereby blades 26, 28 are released sequentially for effecting exposure through the aperture 22. A diaphragm is also provided (Figs. 1 and 8) comprising two blades 56, 58, pivoted respectively at 64 and 66 and interconnected for movement together by a link 60. The diaphragm is moved-prior to each exposure-from a fully covering position to a position corresponding to the prevailing light conditions as determined by the photo-electric control device comprising a photo-cell 104 and a galvanometer 106 with pointer 110. The sequence of events leading to exposure is as follows. On pivoting a lever 156 about its pivot 158 in an anti-clockwise direction (Fig. 3), by means of a spring-urged link 162 and a lever 160, a rod 120 is also rotated. This rod bears an element 118 for co-operation with a cam projection 114 on a clamping-plate 112 whereby an apertured plate 100 is clamped in a position corresponding to the prevailing light conditions against the valve block 94, with openings 116, 102 and 98 in registry. Also coupled to rod 120 by way of an over-running clutch is an arcuate element 122 for clamping a flange portion of a diaphragm controlling cam 80 against the outer periphery of galvanometer housing 106. At the same time, by means of a projecting arm 196 which engages with a pin 198 on a spring-urged lever 186 pivoted at 188 and by means of a torsion spring 192, one end of which is engaged by a pin 190 on lever 186 and the other end of which is coupled to a lever 76 fixed to a shaft 64 carrying diaphragm blade 56, this shaft is rotated for effecting closure of the diaphragm blades to positions determined by the engagement of a pin 78 on blade 58 with the cam 80. By means of a nose 236 on the lever 156 which co-operates with a spring-urged latch member 230, spring-urged re-setting means 200 are released for return to their rest positions. Finally, by way of an extension 166 of the lever 160 which co-operates with a pin 184 of a spring- urged bell-crank lever 176, the shaft 142 is rotated for effecting release of the shutter by movement of the lever 140. As mentioned above, immediately prior to exposure the resetting means 200 is released to return under loading of spring 218 to a rest position in which lever 202 engages a flange portion 216 of mechanism mounting-plate 20. After exposure, resetting of the shutter and diaphragm mechanism may be effected by a return movement of lever 202 into the position shown in Fig. 3, whereupon pin 210 on link 208 re-engages with spring-urged latch 230. At the same time, by means of a crank 212, shaft 30 is rotated together with blade 28, said blade being coupled to said shaft by an over-running clutch. Blade 26 is returned to its original position by an element 226 mounted on a shaft 222 coupled to a toothed sector 220 engaging with a pinion 214 on the shaft 30. Timing element 88 is returned to its original position by a toothed sector 224 which is in engagement with sector 220 and is coupled to element 88 by way of a shaft 124 and an overrunning clutch. In modifications, the galvanometer may be rotatably mounted to make allowance for film sensitivities and filter factors, and other fluids, for example a liquid, may be used in the bellows 84.