Patent GB-984434-A (GB)
Title: Photographic camera
IPC: G03B7/12
Filed: 1961-12-08
Abstract: 984,434. Photographic cameras; diaphragms. AGFA A.G. Dec. 8, 1961 [Dec. 15, 1960], No. 44083/61. Headings G2A and G2J. In a camera having a diaphragm comprising two coaxial resiliently coupled rotatable diaphragm leaf bearing rings rotatable relatively against the loading of the resilient coupling, the rings are further coupled by a mechanism for effecting such relative rotation, the arrangement being such that, by rotation of one of the rings, the two rings can be rotated together from a region in which the said mechanism is idle to a region in which is is responsive to the position of a control means to cause a relative rotation of the rings to adjust the diaphragm. As shown, each diaphragm blade 8 is supported between rings 6,7 which are connected by a spring 17 and a linkage 19, 20. The ring 6 may be manually set by a fingerpiece 25 to bring a reference mark 26 to a chosen position on a scale 27 having three distinct portions,viz for flash exposures (27a), for automatic exposure control operation (27b), and for bulb exposures (27c),and the ring is held in the selected position by a spring 29 engaging in fixed notches 28 (extent incomplete as shown). When set to automatic operation as shown, on release of a spring-driven plunger 5 by depressing the slide 50, the plunger descends until arrested by the stepped cam 4 thereon engaging the needle 3 of the exposure meter galvanometer 2 and in its descent rotates the ring 7, by engaging the projection 39, to close down the diaphragm. The slide 50 may either by locked in the depressed position so as to enable a separate shutter release to be operated or the last part of the depression of the slide may itself release the shutter. The exposure meter galvanometer may be rotatable by a knob 51 to take account of film sensitivity. When the ring 6 is set for bulb or flash exposures, automatic control must be rendered ineffective, as by causing as shown the spring 17 to rotate the ring 7 to move the projection 39 out of the path of the plunger 5. When the bulb exposure range 27c is used, the diaphragm is set by hand, the ring 7 being held stationary by its edge 22 engaging a fixed pin 23 so that the ring 6 moves to provide the chosen aperture. When set to the flash exposure range 27a, the ring 6 has been rotated so that the free pivot 40 of the linkage 19, 20 lies radially inwards of a lever 34, the position of which is controlled by a cam surface 32 on a rotatable ring 30 bearing a distance scale and is connected to the camera focusing mechanism. The diaphragm aperture is thus adjusted, after setting the flash factor on scale range 27a by movement of the ring 6,by movement of the distance scale ring 30 causing the linkage 19, 20 to move the ring 7. In a modification the ring 30 and lever 34 may be coupled by a pin-and-slot connection. Reference is also made to applying the invention to cameras with semi-automatic exposure value setting, the shutter speed being preselectable and ring 7 coupled to a follow-up pointer for the needle 3, and to cameras without exposure value setting, the galvanometer 2 and associated mechanism being omitted.