Patent GB-776582-A (GB)
Title: Improvements in or relating photographic shutters
IPC: G03B17/02
Filed: 1955-05-17
Abstract: 776,582. Photographic shutters. DECKEL, H., and DECKEL, F. W. May 17,1955 [May 25, 1954], No. 14194/55. Class 98(1) A photographic shutter comprises a shutter speed setting member and a diaphragm setting member capable of being adjusted to different relative positions, the shutter speed setting member being provided, in addition to a scale indicating the exposures capable of being automatically timed by the shutter mechanism, with a scale indicating a number of exposures of longer duration. As shown in Figs. 1 and 2, a base plate 14 carrying a forwardly extending lens tube 16 is mounted within a shutter casing 10 carrying a rearwardly extending lens tube 12. The diaphragm and shutter blades (not shown) are arranged in known manner in the space 18 between the base plate 14 and the rear wall of the shutter casing 10. The annular space 20 within the shutter casing 10 accommodates shutter drive means of known construction. A shutter speed setting ring 22, mounted for rotation about the front lens tube 16 in the front part of the annular space 20, has a driving connection with an externally mounted actuating ring 28, which, together with the shutter speed setting ring 22, is retained in position on the shutter casing by an annular cover plate 30 and a ring member 32 screwed on to the front lens tube 16. A release lever (not shown) and a shutter setting lever 34 extend through the rear of the shutter casing. A cap-shaped graduated ring 36 is mounted between the shutter speed setting ring 22 and the actuating ring 28 and is connected to the ring 22. The ring 36 bears a shutter speed setting scale 42 and a scale 44 indicating integrated exposure values. A cap-shaped diaphragm setting member 46 is mounted for rotation on the rear surface of the shutter casing 10. A coupling ring 48 surrounds the shutter casing and is slidably mounted on the cylindrical portion of the graduated ring 36. Coupling ring 48 has formed therein a radially inwardly projecting coupling tooth 50 which is engageable with any one of a number of coupling slots formed in the rear end face of the graduated ring 36. A key 54 formed on the inside of the coupling ring 48 engages a complementary groove 56 in the diaphragm setting member 46 so that the coupling ring 48 may slide axially with respect to member 46, but is rotatable therewith. This enables the coupling tooth 50 to be withdrawn from engagement with one slot 52 against action of a wavy annular spring 66, and to be engaged with another slot 52. Coupling ring 48 bears a single index mark 60 co-operating with the scale 44 of integrated exposure values on the ring 36, and also a scale 58 of diaphragm stops which is arranged opposite the shutter speed setting scale 42. Thus the coupling ring 48 may be moved back, turned until the index mark 60 is brought opposite the required integrated exposure value on the scale 44 on ring 36, when the diaphragm values on ring 48 will be brought opposite the appropriate shutter speeds on the scale 42. Either the actuating ring 28 or the coupling ring 48 may then be rotated to bring the required combination of shutter speed and diaphragm aperture opposite a mark 62 on a fixed part of the camera body. Due to the action of the coupling ring 48, the shutter speed adjusting member 22 and the diaphragm setting member 46 will be adjusted in compensating directions. If for a desired diaphragm aperture the required exposure time is longer than the longest exposure time for which the shutter can be set, the required exposure time is indicated on a supplementary scale 70. If, after setting the ring 48 to bring the required stop on the scale 58 opposite the mark 62, the exposure indicated is found on the supplementary scale 70, then ring 48 is disengaged from ring 36, and the actuating ring 28 is turned until the mark B (for bulb exposures) on ring 36 is brought opposite the mark 62. A bulb exposure is then made of the duration previously indicated on the supplementary scale 70. If desired, the supplementary scale 70, instead of overlapping the light value scale 44, might form a continuation of the shutter speed scale 42, the integrated exposure value scale 44 and the corresponding index 60 being shifted around the shutter body. Alternatively, scale 70 may be formed on the front face of ring 28. The couplinig between the ring 36 and the diaphragm setting member 46 may be effected by a resilient arm instead of by the ring 48. The scale 44 of integrated exposure values may be omitted, the ring 48 being then adjusted so as to bring a required stop value opposite a required shutter speed. The scale of longer exposures is also useful where the setting members are not inter-connected.