Patent GB-634679-A (GB)
Title: Improvements in or relating to photographic shutters
IPC: G03B9/10
Filed: 1947-07-21
Abstract: 634,679. Photographic shutters; cameras combined with flashlamps. KODAK, Ltd. July 21, 1947, Nos. 19535 and 19536. Convention dates, Aug. 7, 1946. [Class 98 (i)] A shutter having a support on which is pivoted a trigger, a cover-plate which normally covers an exposure aperture in the support, and a shutter blade provided with a slot aperture, has separate springs connecting the coverplate to the trigger and to the shutter blade, a latch for holding the cover-plate stationary, means carried by the trigger for tensioning the spring between the trigger and the cover-plate and subsequently releasing the cover-plate, which moves away from the exposure aperture and tensions the spring between it and the shutter blade until this spring snaps past deadcentre to rotate the shutter blade to make the exposure. A switch may be arranged in the path of the cover-plate so that as it moves clear of the exposure aperture a flash-lamp circuit is completed, return movement of the coverplate breaking said, circuit. As shown, a supporting plate 1 having flanges 2 for attaching the shutter to a camera has an exposure aperture 3 and pivotally supports a shutter blade 4 at 5 and a cover-plate 7 and trigger 17 at 8. The cover-plate is latched in the rest position shown against accidental movement by a recess in an arm 22 of a bell-crank lever 23 which is spring-urged clockwise, engaging a lug 21 on the cover-plate arm 9. On depressing the trigger, a spring 14 between it and the cover-plate is tensioned until a projection 27 on the trigger engages an arm 26 of the lever 23 releasing the cover-plate latch when the tensioned spring 14 rotates the cover-plate clockwise clear of the exposure aperture 3. As the end 10 of this plate moves across the shutter blade it compresses the hairpin spring 11 until this snaps past its dead-centre position and rotates the shutter blade anticlockwise so that its arcuate slot 6 passes across the exposure aperture. As shown, the slot 6 normally lies over the exposure aperture and the exposure is started by movement of the cover-plate and continued and finished by the shutter blade, giving an exposure of about <SP>1</SP>/ 30  sec. For shorter exposures the slot does not normally cover the exposure aperture and the exposure is made by the movement of the shutter blade alone. On releasing the depressed trigger the coverplate is first returned to cover the exposure aperture by a spring 20 compressed by the clockwise movement of this plate, and in so doing the spring 11 is again compressed and finally returns the shutter blade to the starting position. The travel-of the shutter blade is limited by shoulders 31, 30 successively engaging opposite sides of a stop 32, rebound being unimportant, since after the exposure the slot 6 moves well past the aperture 3 and on the return of the shutter blade to rest the aperture is closed by the cover-plate. An adjustablydisposed insulated contact 50 connected to one side of a flashlamp circuit is engaged by the cover plate 7 to complete it through the earthed side of the lamp socket 55 in synchronism with the opening of the aperture 3, the flashlamp circuit being opened by the return of the coverplate to cover the aperture. Specification 537,209 is referred to.