Patent GB-742599-A (GB)
Title: Improvements in photographic cameras
IPC: G03B13/20
Filed: 1953-03-03
Abstract: 742,599. Photographic cameras with interchangeable objectives coupled automatically with range- and view-finders. BERTRAM, E., and BERTRAM, W., [trading as BERTRAM, FABRIK PHOTOTECHNISCHER MESSGERAETE, E. & W.]. March 3, 1953 [March 4, 1952], No. 5846/53. Class 98 (1). In a camera adapted to receive in a bayonet type fastening interchangeable mounts having objectives of different focal lengths and adapted to impart to transmission members in the camera to an extent related to said focal lengths the rotary bayonet locking movement of mount, the said transmission members are arranged to adjust appropriately for each objective the position of a first slide and also a second slide or a series of fixedly-connected slides, the first slide being shaped to pre-set a movable optical part of a coupled rangefinder, the second slide or series of slides being shaped to pre-set a distance scale co-operating with the range-finder, means adjusting the field of view of a view-finder, and means for indicating the depth of focus. As shown, each interchangeable objective has a recess in the rear end of its mount which engages a lug 13 on a ring 11 rotatable on the camera body and spring-urged to a standard position, and on rotating the objective to permit bayonet lugs thereon to latch with bayonet catches on the camera body, the ring is rotated to move through toothed sector 12, pinion 14, telescopic shafts 15, 16 and pinion 18, a rack 19 fixed to a block 22 slidable on a fixed cross guide rod 21 by an amount determined for that objective, three objectives being catered for as described. A pin 37 on the block 20 engages in a slot 38 in an extension 39 of a fore-and-aft slide 40 mounted in fixed guides 23 and having a cross groove 41 in which engages a pin 42 on a bellcrank lever 43 which is pivoted on a plate 57 (Figs. 3 and 5, not shown), adjustable during manufacture on a fixed plate 23 in a direction perpendicularly across the camera axis. The forked end of the bell-crank lever 43 engages a pin on a cross slide 46 mounted in a guide 47 and having three steps against which a pivoted arm 48 is spring-pressed, said arm being engaged by a pivoted arm 50 carrying a link 36 which moves vertically a parallax-compensating diaphragm for a view-finder and also carrying the adjustable mirror 54 of a short home base range-finder, the other end of the base of which is defined by a fixed semireflector substantially parallel to the mirror 54. A bracket 22 secured to the block 20 has a cam slot 58 embracing a pin 60 on a verticallymovable panel 62 bearing three focusing scales and carries an arm 69 (Fig. 9), bearing a pin 68 which moves vertically a wedge-shaped slide 70 to which is pin-and-slot connected a pair of spring-connected shears 64 pivoted at 66 on a fixed upright 61 and serving to indicate the depth of focus, an indicator carried by the plate 57 indicating the object distance. The free end of the bracket 22 engages in a further cross slide 24 having a slot engaging a pin 28 projecting through a slot 29 in a guide 25 from a carrier 27 keyed for fore-and-aft movement and supporting the plano-concave front lens 26 of a reversed Galilean view-finder to alter its field of view.