Patent GB-909796-A (GB)
Title: Improvements in or relating to mechanism for focussing photographic cameras
IPC: G03B7/00
Filed: 1959-04-03
Abstract: 909,796. Photographic cameras. DECKEL, H., and DECKEL, F. W. April 3, 1959 [April 30, 1958], No. 11364/59. Classes 97 (1) and 98 (1).  A photographic camera incorporating a focusing arrangement in which at least part of the objective is displaceable in the direction of the optic axis, is characterized by the provision of at least two alternative focusing mechanisms for displacing the objective, any one of which can be brought into operative position at will. As shown (Fig. 2), a housing 14 of an objective and shutter mechanism (not shown) is secured to a holder 12 on the face 10 of a camera. A scale 20d on the shutter speed setting ring 20b controlling operation of shutter blades 18, cooperates with a fixed mask 21, as also does a scale 22d on the diaphragm setting ring 22b which adjusts diaphragm blades 22 by way of arm 22c<SP>1</SP> on ring 22c, pin 22a<SP>1</SP>, and diaphragm control ring 22a. A releasable coupling operated by push-button 20e carried by a grip 20c on the speed-setting ring, may be provided between rings 20b and 22b for setting the camera in terms of exposure values. Fixed lenses 26a and 26b are carried by base-plate 24 and mount 28b screwed into housing 14, and a lens 26c is carried by an axially displaceable mount 28c adjusted for focusing by either of two mechanisms. In the first mechanism, arm 22c<SP>1</SP> on the diaphragm intermediate ring 22c engages a slot in a rotatable focusing control ring 36 having two projecting cams 36a followed by axially spring-pressed pins 36b on mount 28c. The cams are arranged so that the upper limit of the range of focus is always at #, while the lower variable limit is read off against mark 22e on focusing scale 30c. To change to the second focusing mechanism, a focusing control ring 30 is rotated, disengaging spring-loaded ball 34 from notch 30b (Fig. 3) and engaging instead an elongated recess 30b. Cam elements 36a are then inoperative and cam elements 24a on baseplate 24 are engaged by follower pins 24b on the movable mount 28c, which has a pin 28c<SP>11</SP> engaging an axial slot 30a in ring 30. The mount thus moves axially as it rotates with control ring 30, and the actual distance of focus is read off on scale 30c against mark 21. In a modification (Fig. 5, not shown) in which provision is made for taking flash photographs, an index mark F on ring 30 is adjustable to correspond with a flash factor scale on ring 32, in which position ball 34 engages one of a number of additional notches diametrically opposite notch 30b, and pins 36b again engage cam surfaces 36a. Rotation of diaphragm setting ring 22b then automatically adjusts the diaphragm and focusing mechanisms in accordance with the pre-set flash factor; the actual distance of focus being read off on scale 30c against a mark on ring 22d, almost diametrically opposite mark 22e. In further modifications, three cam elements for each mechanism may be provided, the mechanism may be used in interchangeable objectives, the diaphragm mechanism may be controlled by an exposure meter, as for instance in Specification 909,795, and a close distance focusing mechanism similar to the first type described may also be provided in which the nearest point of focus is kept at say 8 metres.