Patent GB-462716-A (GB)
Title: Improved photographic shutter
IPC: G03B9/08
Filed: 1935-08-07
Abstract: 462,716. Photographic shutters. I. G. FARBENINDUSTRIE AKT.-GES. Aug. 7, 1935, Nos. 22312 and 22313. Convention dates, Aug. 9, 1934 and Feb. 16, 1935. [Class 98 (i)] In a focal plane shutter, a pair of rigid blind slides are released in succession by the driving mechanism of a pivoted blade shutter which acts on levers holding the blind slides through a sector ring. On the wall of the casing 1 are mounted a rotary ring 2 and guides 3, 4, the latter holding the leader slide 5 and the follower slide 6 of the shutter. The slides are held by springs 5a, 6a and have transverse rails 7, 10 respectively, each carrying a projecting tooth 8, 11 which can engage pawls 9, 12 respectively. The pawls 9, 12 are pivoted on a screw 13, and a spring 14 holds the pawl 9 against a pin 15 which is on the rotary ring 26 and which also passes through a slot 12a in the pawl 12. The shutter is set by a button 22 on a rail 20 which in its downward movement abuts against a lever 25 to swing an arm 27 in a clockwise direction. The arm 27 engages a pin 29 on the slide 5 and moves both slides 5, 6 to the set position held by the pawls 9, 12'in engagement with the teeth 8, 11. A wedge piece 28 then directs the arm 27 away from engagement with the pin 29. For exposures of 1 to 1/200 seconds, a cam surface 19 on the exposure scale pinion 18 is in engagement with the release lever 17 which is retained in the release position. The sector ring operating mechanism is set by the lever 16. When the button 22 is depressed, a small bell-crank lever 21 engages the lever 16 and sets the shutter, the slides also being brought to the set position. At the end of the movement, the lever 21 strikes its horizontal arm against a pin and is turned to release the lever 16 and make the exposure. The pin 15 is moved by the sector ring 2 and presses aside the pawl 9 to release the slide 5. In the further movement of the pin 15 determined by the adjusting mechanism of the sector shutter mechanism, the pawl 12 is moved aside and liberates the slide 6. The bell-crank 21 in its return slides over the pin 16a. If exposures of less than 1/200 second are to be made, the slides are secured to move together. On the transverse rail 7 of the slide (Fig. 5) a hooked lever 32 is pivoted at 31 and is pressed inward by a spring 32a into the stepped end 10b of the rail 10 which it engages by a hook 32b. A surface 32c of the hook 32b is engaged by an eccentric 33, the position of which determines which step is engaged by the hook and consequently the width of the exposure slot. When the following slide 6 is released, the two move together to effect the exposure and at the end of the movement the nose 32d of the hooked lever engages a pin 36 and lifts the hook out of engagement with the slide 10. When the eccentric is at the zero mark the hook is lifted out of engagement with the stepped end of the slide. When the pinion 18 is moved to the position for " bulb " and " time " exposures, the cam 19 releases the arm 17 and the sector shutter mechanism is simultaneously moved to the " B " and " T " positions. After setting the slide by depression of the button 22, the shutter is operated by movement of the lever 17 to the release position. In a modification, Fig. 7, variation of the slot width for very short exposures is obtained by a pin 37 on the adjusting ring 2b engaging a pivoted spring-urged lever 38 so that upon setting of the shutter slides 5, 6, the inclined face of the lever 38 engages a pin 39b on a latch 39, to move the latter to a position for engaging a notch 10b, 10c, or 10d on the follower slide. The latch 39 is pivoted on the leader slide, and is frictionally held in any position to which it is set. The notches 10b, 10c and 10d are inclined to yield a positive engagement with the latch, but after completion of exposure, the latch engages the inclined surface 41a and is rocked out of engagement with the notches.