Patent GB-607752-A (GB)
Title: Improvements relating to photographic camera shutters
IPC: G03B9/20
Filed: 1946-02-11
Abstract: 607,752. Photographic shutters. KODAK, Ltd. Feb. 11, 1946, Nos. 4235 and 4236. Convention dates, Oct. 23, 1944, and Aug. 8, 1945. [Class 98 (i)] This invention relates to a shutter of the kind having two concentric blade rings which rotate simultaneously in opposite directions and double-ended blades connected to these rings so that rotation of the rings causes a unidirectional movement of the blades which effects an exposure by first removing one end of the blade from the exposure aperture and then bringing the other end into it, a second exposure being made by reversing the directions of travel of the rings and blades. According to the invention there is provided a spring- driven master member capable of being coupled alternately to each of the rings, so that successive movements of the member in the same direction reverse the directions of movement of blade and rings, and also means for arresting, and then releasing again, the rings and blades near the middle of their movement to produce prolonged exposures. As shown, blade rings 7, 8 and a master member ring 19 are slidably seated in concentric slots in a plate 4 supporting the shutter mechanism, the blade rings being interconnected by pins 17, 18 engaging the forked ends 15, 16 of a member 13 pivoted at 14 on the plate 4. Doubleended shutter blades 9 are pivoted at 10 on their axes of symmetry upon the ring 8 and are connected by pins 12 to forks 11 carried by the ring 7. The shutter is set by moving the master member handle 20 to the right extending the spring 23. This setting movement causes a leaf spring 34 mounted on the rim 2 to drive a ratchet-wheel 33 which is mounted at 37 on the handle, round one tooth, i.e. through 60 degrees and so rotates a triangular selector cam 32 carried thereby. Thus, alternate setting movements cause the cam projections 60 to engage a roller on the end of a member 54, constrained to move radially by a pin 49 on it engaging in a fork in the handle 20 and urged to follow the cam by spring 55, whereby the pin 49 engages alternately lug 47 on ring 7 and lug 48 on ring 8. The shuttersetting movement of the handle also sets the retard mechanism by engaging a pin 66 projecting through a slot 65 in the plate 4 and mounted on one end of a link 67 having at its other end a pin 68 engaging a slot 69 in a toothed sector plate 70 pivoted at 71 and urged against a stop 57 by a spring 72, said sector plate meshing with a gear 73 of a retard train including a pallet escapement and a ratchet or slip clutch to disconnect the retarding drag during setting. The angle through which the sector plate is rotated is determined by a cam ring 75 which is followed by the pin 68 and which is adjusted by selecting the desired shutter speed indicated by index 77. When this index is set to " bulb " or to <1>/50 sec. or higher speeds the corresponding projections 81, 82 engage a pin 80 on an arm 79 carried by the sector plate to hold the retard mechanism inoperative. On depressing the shutter release lever 27, the hook 26 moves away to allow the master member to rotate and drive, through pin 49, one or other of the blade rings, say 8, to open the shutter. When making a prolonged " instantaneous " exposure the shutter once opened is prevented from closing by a detent 84 on a lever 85 engaging the left side of the lug 48 on the ring 8, and the shutter remains open until sector plate 70 strikes a pin 88 to trip the lever 85 to release the blade ring 8 and allow the shutter to close. For bulb exposures, a hump 95 on the cam 75 holds the detent end of the lever 85 clear of the lug 48 by depressing the projection 96 on the opposite end of the lever, while simultaneously a projection 93 rides off the surface 98 on the cam ring, by which it is normally held inoperative, into contact with a projection 126 on the shutter release 27. On depressing the release the blade rings rotate and the detent 94 is swung into the path of lug 47 on ring 7, thus holding the shutter open as long as the release is held depressed. Specification 588,776 is referred to.