Patent GB-784083-A (GB)
Title: Improvements in or relating to camera shutters
Inventor: HILL-VENNING JOHN
IPC: G03B9/08
Filed: 1954-09-16
Abstract: 784,083. Photographic shutters. PETO SCOTT ELECTRICAL INSTRUMENTS, Ltd. Sept. 15, 1955 [Sept. 16, 1954], No. 26924/54. Class 98(1) In a photographic shutter of the kind in which a number of pivoted blades are driven by a spring wound up prior to the operation of the shutter, the spring drives the blades through rotating member provided with a brake-operating projection caused, towards the end of the opening movement of the blades, to engage a brakecam which it moves against the resistance of a brake to bring the blades gently to rest at the termination of their opening movement. The spring may be wound by an electric motor. The shutter may be normally closed and opened and closed to make an exposure, or may be one which is normally open and which is closed for a predetermined time immediately after making a night exposure with a flashbomb to cut off the afterglow of the bomb and is then again opened. As shown, the shutter comprises an annular plate 11, Fig. 1, having outer and inner flanges 12 and 14, Fig. 2. In the lugs 16 of the inner flange 14 are holes 17 for the pivots of the shutter blades 18, which are connected together by links 20 and are stiffened at their hubs by plates 21 of which one has a lug to which is pivoted a main operating link 23 connected to a crank pin 24 on a disc 25 carried on the spring-driven shaft 26. The top end of the shaft 26 is carried in a bush 126, Fig. 1, on which rotates a gear 30 to which is anchored one end of the main spring 32 which surrounds the shaft 26 and is anchored at the lower end to a disc 33. The bracket 27 carries, an electric motor 34 having a shaft carrying the pinion 35 engaging the gear 36, the shaft of which operates a worm reduction gear driving the spindle 39 through the spring clutch 139. The spindle 39 carries a pinion 40 driving the gear 43 through reduction gears 41, 42, and the gear 43 engages the gear 30. A hand winding spindle 45 is also geared to the spindle 39. The cam disc 55 has a slot 56 into which a cam follower 54 drops to open contacts 51, 52 in the motor circuit when the spring 32 is fully wound. The crank disc 25, Fig. 2, is surrounded by a ring 58 separated from the disc 25 by a rubber ring 159 bonded to both parts. The ring 58 carries a projection 59 engaged by the pawl 60. The snail cam 64, Fig. 1, is engaged by a lever on the spindle 161, Fig. 2, which carries a lever 162 pivoted to the lever 110 carrying a pin 163 engageable by the latch 111. A release pawl 65 engages in a notch 165 in the ring 58. Just as the spring 32 is fully wound, the cam 64 allows the lever on the spindle 161 to move to free the pawl 60 from the projection 59, whereupon the disc 25 moves slightly to become held only by the pawl 65, which is controlled by an electromagnet 68, Fig. 1. Interruption of the current to the electromagnet 68 releases the pawl 65 to allow the shutter to operate. The C- shaped portion 69 of the pawl 60 is engaged by the nose 59 to reset the pawl 60, and then the nose contacts the tail 70 of the lever 71 to rotate the flywheel 73 and brake the shutter as the blades 18 approach the fully open position. A centrifugal brake pad 76 brakes the flywheel 73. which is returned to its original position by the spring 74. The shutter-opening time is controlled by the engagement of the nose 59 with the abutment 80 on the lever 81 of which the other end engages in the slot 82 in the rocker 83 which has a nose 85 engaging a notch in the lever 86. An escapement mechanism comprises a toothed quadrant 87 meshing with the pinion 88 fast on the gear 89 driving the escape wheel 91 which co-operates with the anchor 92. A pin on the wheel 91 rocks the lever 86 to release the rocker 83 and allow the lever 81 to move to permit the shutter to close. A speed-control arm 93 concentric with the gear 89 determines the extent of rotation of the wheel 91 when the shutter is re-set and hence the time before the rocker 83 is released after shutteropening. A cam below the disc 33 moves a lever 99, Fig. 1, on the spindle 95 as the blades are opening to move the arm 94, also on the spindle 95, to tension the spring 98, which urges the arm 94 to drive, through the pin 96, the lever 97 fast to the quadrant 87 and thus set the escapement in motion. The arm 93 is adjusted by a spindle 101, Fig. 1, having a notched cam disc 102 having a cam slot operating a lever on the shaft 100 carrying the arm 93. In the extreme position of the spindle 101 the quadrant 87 and the rocker 83 are not released and the shutter stays open after release. As the shutter closes, a lever 105, Fig. 1, pivoted at 106 and carrying a pawl engaging a 'notch in the cam 55 is moved by the cam previously referred to as operating the lever 99 to move the cam 55 sufficiently to raise the follower 54 to close the contacts 51, 52 and restart the motor 34.