Patent GB-839332-A (GB)
Title: Improvements in or relating to photographic cameras
IPC: G03B7/00
Filed: 1957-06-21
Abstract: 839,332. Photographic cameras. ZEISS IKON A. G. June 21, 1957 [July 23, 1956; (2); July 28, 1956], No. 19658/57. Class 98 (1) In a photographic camera, the iris diaphragm is controlled by two independently rotatable rings, one of which is connected to the exposure time setting member and the other of which is connected with a diaphragm aperture setting member, so that changes in the setting of the exposure time result in compensating changes of the diaphragm aperture for a given light value, to which the diaphragm aperture setting member is adjusted. As shown in Fig. 1, the iris diaphragm, which is housed together with a shutter mechanism in the objective mounting, consists of five leaves, each having two pins pointing in opposite directions. One set of pins engage apertures 4 in a control ring 5 (Fig. 2), while the other pins are guided in slots 6 formed in a control ring 7. Control rings 5, 7 are respectively connected by arms 8, 9 to setting rings 10, 11. The setting rings bear respectively a diaphragm aperture scale 15 and an index 16 by which the scale is read (see also Fig. 3). An exposure time setting ring 12 bears an exposed time scale 13, to be read against an index 14 on the camera housing, while a further setting ring 17 bears a scale 18 of light values, to be read against an index 19 on the camera housing. The setting rings 11 and 12 are connected for rotation together by means of strap 21 so that when the exposure time is varied by rotating ring 12 the diaphram aperture changes to keep the exposure value constant. Rings 17 and 10 are connected by bar 20 to adjust the diaphragm aperture in acordance with the light value indicated. As shown in Fig. 7, the shutter housing of a camera carries a setting ring 26 bearing an index 27 co-operating with a fixed exposure time scale 40 and a diaphragm setting ring 28 combined with a ring 29 which may carry a light-value scale. An exposure meter within the camera housing has a pointer 32 and a follow-up member 34 visible through a window 33. In use, the index 27 is set to a desired exposure time. Since the setting ring 26 is coupled to one of the diaphragm control rings, the diaphragm is set at the same time. The camera is pointed at the subject and by means of a setting member 35 coaxial with the film-rewinding knob 36, the follow-up member 34 is brought into register with the pointer 32, and at the same time the second diaphragm control ring, which is geared to the member 35, is operated to adjust the diaphragm aperture. A known kind of film speed indicating member 39, acting on the gear train between the member 35 and the diaphragm control ring, allows for the emulsion speed of the film in use. As shown in Fig. 8d, an arrangement for a roll-film reflex camera includes an exposure time setting ring 41, having a pointer 42 movable over a scale 43 of exposure times is connected by an arm 411 to a control ring 412 for the iris diaphragm. The second control ring 413 has a pin-and-slot connection 414, 415 with the first control ring 412. The ring 413 is coupled unidirectionally to a setting ring 44 by an arm 416. An index 47 on ring 44 moves over a light value scale 417. Ring 44 carries a diaphragm aperture scale 45. A lost-motion coupling 418, 419, 420 is provided between setting rings 41, 44 allowing relative rotation to the extent of the diaphragm scale 45. The control ring 413 can be rotated clockwise with respect to the control ring 412 to the extent that arm 416 moves from its full-line position to its dotted line position. A spring 421 tends to return ring 413 to the position shown. A member 422, mounted on a shutter operating member, bears in one direction only against the end 424 of a spiral spring 423, the other end 425 of which engages unidirectionally the arm 416. Member 422 is movable at least to its dotted line position, sweeping over the light value scale 417. The operation of winding the film re-sets the mirror, and causes the shutter blades to open; the shutter-operating member bearing member 422 being moved clockwise, so that through action of spring 423 (which is stronger than spring 421) control ring 413 is rotated until its arm 416 reaches the dotted line position. Ring 44, which is held in position by a click-stop device, and which is coupled to ring 413 in one direction only, remains stationary so that the diaphragm is opened to its fullest extent for viewing and focusing. Ring 413 is stopped with arm 416 in its dotted line position by its lost-motion connection with ring 412, which is also held in position by a clickstop device. Member 422, however, can move further, owing to the resilience of spring 423. When an exposure is to be made, the shutter-operating member is allowed to return, closing the shutter blades. Member 422 returns, allowing arm 416 of ring 413 to return until engaged by ring 44, so that the diaphragm closes down to the pre-set stop. The mirror moves up, and the shutter is operated to make the exposure. In modifications of the arrangement shown in Fig. 8: (1) one end of spring 423 is fixed, and the other end, which is engaged by member 422, has a notch engaged by a lug on control ring 413. During movement of member 422, the lug rides out of the notch at the end of movement of ring 413, and re-enters during the return movement. (2) Member 422 bears directly on arm 416 of control ring 413, and control ring 412 is connected to its setting ring 41 in one direction only. (3) Member 422 bears directly on arm 416 of control ring 413, and cam slots in control ring 412, which cause the diaphragm leaves to open, have arcuate or spiral extensions which allow ring 412 to rotate beyond the position in which the diaphragm is fully open.