Patent GB-848812-A (GB)
Title: mprovements in and relating to photo-electric exposure meters and photographic cameras incorporating such exposure meters
IPC: G03B7/06
Filed: 1957-01-09
Abstract: 848,812. Photographic exposure meters. HEIDECKE, R., and FRANKE, H., [trading as FRANKE & HEIDECKE FABRIK. PHOTOGR. PRAZISIONS-APPARATE]. Jan. 9, 1957 [June 29, 1956; Sept. 28, 1956], No. 839/57. Class 98(1) In a photo-electric exposure meter having a follow up pointer adjustable mechanically by means of an exposure time scale, and which must be brought into coincidence with the pointer of the electric measuring instrument for determining the exposure value, a single control cam is provided for adjusting the follow up pointer and a number of reading off windows associated with the measurement sensitivity ranges are provided for the exposure value scale. The electrical indicating instrument is mounted within the focusing knob on the body of a twin lens photographic camera, as described in Specification 826,162. As shown in exploded views of Figs. 3 and 4, the meter 20 is mounted in a cylindrical housing 21, on a base plate 29 which has lugs by which it is attached in a bayonet socket 12 mounted within the hollow knob 5, and contacts 27, 28 co-operating with contacts 17, 18 in the socket 12 connected to a photo-electric cell mounted above the lenses. A web 33 on the base plate 29 carries the follow up pointer 36, which has a needle eye point 42 whereby it may more easily be brought into coincidence with the meter pointer 31. A slide member 44 is guided to move longitudinally by a slot 43 therein embracing a screw 34 which forms the pivot for the pointer 36, and by a pin 45 slidable in a slot 46 in a sleeve 47. which, when the exposure meter is assembled, is bolted to base-plate 29 and encloses the meter 20. The slide member has a pin-and-slot connection with the follow up pointer 36. A spring 39 surrounding spring 34 acts on pointer 36, and so urges the pin 45 on slide 44 into contact the cam ring 56 which is rotatable on the sleeve 47, and is surrounded by an adjusting ring 53 carrying a build setting ring 24 and a scale 25. The knob 5 surrounds sleeve 53, and is connected by a crank arm 10 engaging a recess 26 in the knob to the focusing shaft 9. The scale 25 is read through windows 251, 25<11> in a sleeve 51, corresponding to the two measurement ranges afforded by varying the sensitivity of the sound, e.g. by masking part of the cell surface. As shown in Fig. 2, a slide member 82 is guided in a frame 81 which holds a honey combe lens 18 and is fixed in front of the photo-electric cell by means of hollow rivets 84. The frame 81 and a spring plate 85 behind it are secured to a housing 86 by screws 87 which pass through holes 88 in an escutcheon plate 19, rivets 84 and holes 89 in plate 85 and are threaded into holes 90 in housing 86, which is secured to the camera housing. A lever 78 pivoted to housing 86 carries a spring 92 with a turned over end 93 engaging a slot 94 in slide member 82. A debent 95 fixed to lever 78 retains it in alternative positions. A diffuser 98 can be fixed onto the grooved heads 96 of screws 87 by hooked projections 99. One of the windows 251, 2511 may be masked automatically in accordance with the cell masking operation. In this arrangement cam ring 52 is fitted with an internal disc cam 67 (Figs. 3, 4), which actuates a lever 69 pivoted at 68 and having a forked end 70 engaging a pin 71 projecting from a shaft 73. A bent part 74 of shaft 73 lies between pins 75 on a member 76 slidably mounted on the camera body and connected to a slide 66 which operates the change over handle of the photo-electric cells. Film sensitivity is allowed for by varying the relation between cam ring 52 and scale ring 25. When the cam ring has been rotated to an end position, the ring may be moved further, overcoking the resistance between a spring 52 of the cam and teeth 55 formed on the inside of the scale ring, until the appropriate number on a film sensitivity scale marked on the cam ring 52 is visible through a window 61 on the front flange of the setting ring 24. Specification 843,391 also is referred to.