Patent GB-909795-A (GB)
Title: Improvements in or relating to photographic cameras
IPC: G03B7/12
Filed: 1959-03-26
Abstract: 909,795. Photo-electric exposure control. DECKEL, H., and DECKEL, F. W. March 26, 1959 [April 3, 1958], No. 10726/59. Class 40 (3). [Also in Group XX] In a photographic camera equipped with a photo-electric exposure meter, a shutter speedsetting member and a diaphragm aperturesetting member, in which for the purpose of adjusting the camera in terms of exposure values one setting member is freely movable and the other displaceable against a restoring force into an end position and adapted during its return motion to be intercepted by a stop member in the position required to set up the camera according to the given exposure value, the stop member is a differential rocker of which one operative point is positioned by a cam element associated with the freely movable member, whereas the position of a second operative point is controlled by means responsive to the indication of the exposure meter, and a third operative point acts as an abutment for the interception of a stepped cam element mounted on or coupled with the returning setting member. As shown (Figs. 1 and 2), a photographic camera is provided with shutter blades 18 operated by a shutter mechanism contained in an annular space 16 in known manner and also with diaphragm blades 28a which are adjusted by a control ring 26 coupled to a blade-actuating ring 28, through a pin 28b. The mechanism for adjusting the camera in terms of exposure values is operated as follows: The position of a film-sensitivity setting ring 22 relative to a shutter speed ring 20b is adjusted according to the particular film being used (scale 22a and index 20e are provided for this purpose) after their spring- locking means (Figs. 4 and 5, not shown) has been released, and the ring 20b is then adjusted to the desired shutter speed, as indicated on a scale 20d by a fixed index mark (not shown). When the film is next wound on, the shutter is cocked in known manner and since an abutment 26a of ring 26 is engaged by an arm 48b from a cocking ring 48, the diaphragm mechanism is moved to its fully open position (as in Fig. 2). On subsequent depression of a release button 44b, a spring 44c depresses a sleeve 44a and exposure meter pointer 38 becomes clamped between a stationary quadrant 40 and a stirrup 42 which is deflected about an axis 42a by a linkage system comprising members 42b and 42c. On further depression of button 44b, a locking pawl 50 is disengaged by a pawl 44e through a linkage 44f, thus permitting ring 48, and as a result ring 26 also, to return to their respective uncocked positions. As an abutment 26c moves out of engagement with a pin 34a, a disc 34, and a feeler 36 rotate under loading of a spring 34c until the feeler comes into contact with the clamped pointer 38. As a result, the position of the fulcrum 32a, of the differential rocker 32, which is carried by an arm 30 rotatable about a fixed pin 30a, is adjusted by engagement of pin 32a, and cam surface 34a to a position depending on the prevailing light conditions as measured by the exposure meter. The position of a pin 32c on rocker 32 is determined by a cam surface 24b of a ring 24, which is connected by an arm 24a for rotation with the setting ring 22. The position of abutment 32d on the rocker is thus dependent on the prevailing light conditions and on the preselected shutter and film speeds, and it engages with a stepped cam section 26b on the ring 26 so as to give the appropriate diaphragm setting. Near the end of the return movement of the cocking ring, the shutter is released. To ensure that the diaphragm is set in all cases before this release, there is inserted a retarding mechanism comprising an escapement wheel 46a and a pallet 46b. Ring 54, which is visible in a viewing window (Fig. 1) is graduated in f-numbers, is connected for rotation with the ring 24 by a linkage 52 and indicates by co-operation with the pointer 38 the diaphragm aperture which will be set for any given shutter speed and film sensitivity. Leading lines on a stationary member 56 are provided for bridging the gap between the visible part of the pointer 38 and the f-number scale. In a modification (Fig. 6, not shown), abutment 26c is omitted and disc 34 is moved into the illustrated starting position, locked there and later released by a control arrangement driven from cocking shaft 46. Also in the modified embodiment the stirrup 42 is arranged to be released on depression of the button 44b, from a detent latching device and to engage the pointer 38 under its own spring loading even after the button 44b has been released until the latch is re-engaged at the end of an exposure by another control arrangement connected to the clcoking shaft 46. In a further modification (Figs. 7 and 8-Fig. 7 not shown), a rotatable control disc 58 is movable by means of handle 58a from an inoperative position in which the camera fimctions as above into an operative position shown in Fig. 8 in which the diaphragm is set manually. In this operative position, the disc covers pointer 38 and leading lines 56 and moves the feeler 36 into an inactive end position. Further, the diaphragm is set by means of the control ring 22 which has to be uncoupled from the ring 20 for the purpose. The selected aperture may be read off on scale 54a against mark 58e. Fig. 1 also shows an arrangement by which the lens is adjusted to shorten focused distances as the diaphragm aperture is reduced. An arm 26c from ring 26 engages a forked arm 70b of a ring 70 on which are provided projecting cams 70a co-operating with pins 64b carried by the front lens mount 64, rotation of ring 26 thus causing axial movement of mount 64 under loading of springs 66. Specification 778,933 is referred to.