Patent GB-907584-A (GB)
Title: Improvements in or relating to photographic cameras
IPC: G03B7/06
Filed: 1959-01-29
Abstract: 907,584. Photographic cameras. HEIDECKE, R., and FRANKE, H., [trading as FRANKE & HEIDECKE FABRIK PHOTOGR. PRAZISIONS-APPARATO.]. Jan. 29, 1959 [Feb. 8, 1958; March 6, 1958], No. 3162/59. Class 98 (1). In a photographic camera of the kind provided with a photoelectric exposure meter having two measuring ranges, said camera having a single followup pointer movable over the scale of the exposure meter measuring instrument and coupled to the diaphragm and shutter-speed setting members by a differential mechanism including first and second levers respectively actuable by said setting members, said levers are coupled together by a slide member movable in a stationary guide extending transversely of the levers and pivotally connected to both levers, the said first lever co-operates with means to rotate the followup pointer and the said second lever is connected to means actuable to change over the range of the photo-electric exposure meter. As shown (Fig. 1) the invention is embodied in a twin lens camera having a camera objective axis O-O and a viewfinder objective axis S-S. An aperture setting knob 10 is coupled to the diaphragm (not shown) through a gear 8, a ring gear 4 bearing an aperture scale 6 and a diaphragm actuating ring gear 2. An exposure time setting knob 11 is coupled to the shutter (not shown) through a gear 13 and a shutter driving ring gear 1, this latter gear also meshing with a ring gear 3 bearing an exposure time scale 5. Movements of rings 1 and 2 are respectively conveyed to vertically movable racks 17 and 18 by gears 13 and 15 on a shaft 12 and by gears 7 and 16 on a hollow shaft 14. Engaging in forks 23, 24 of the racks 17, 18 are end pins 37, 36 of two levers 35, 34 of a differential lever system, the two levers being coupled medially by a coupling member 29 slidable in a groove 28 in a fixed plate 25 and having slots 31, 30 engaged by pins 33, 32 on the respective levers. Movement in a recess 50 of a stud 38 on the lever 35 is normally prevented by a spring-urged member 51 having a projection 51a thereon and thereby defining two alternative rest positions for the stud 38. A similar stud 39 on the other lever 34 is movable in a slot 40 on the plate 25 and is engaged under spring loading by a pivoted member 41 coupled to the follow-up pointer 45 of the exposure meter. The positions of studs 38 and 39 are not affected by adjustments of knobs 10 and 11 at constant light value, in which adjustments racks 17 and 18 move equal amounts. However, the arrangement is such that, when during adjustment of the light value setting by means of knobs 10 and/or 11 an end of one of the exposure meter ranges is reached, in which end position stud 39 bears against one end of slot 40, further adjustment of the light values is arranged to urge stud 38 into the other of its rest positions against the resistance of the spring-urged member 51, whereby, by means of a link 49 and a lever 48, a mask member (for example) behind lenticular photo-cell windows 47 is moved to change over the range of the exposure meter. The pin and fork connections 37, 23 and 36, 24 allow for movement of the objective support during focusing. The racks may however be mounted on a stationary part of the camera if the portions of shafts 12 and 14 between gear-wheels 7 and 16 are constructed in a telescopic manner. To provide adjustment for film sensitivity, knob 11 is coupled to shaft 12 through a clutch (Figs. 2 and 3, not shown) but is at all times connected for rotation with gear-wheel 13 by two pins visible in Fig. 1. When knob 55 is depressed against spring loading, a series of projections and recesses forming the clutch are disengaged and knob 55 and shaft 12 may be given an additional rotation independent of knob 11 to bring the mark 61 to an appropriate point on the film sensitivity scale 62. In a modified embodiment (Fig. 5), the two levers 81, 82 of the differential gear system have end studs 71, 72 engaging forks 73, 74 as in the previous embodiment but the end studs 68 and 69 in this case engage in a slot 70 of a slidably mounted member 67. A stud 79 on the lever 81 is coupled to a link 77 for adjusting the position of a follow-up pointer (not shown) and limits movement of this link as a result of its engagement with fixed abutment plates 75, 76, which abutments form guides for the link 77. A further link 78 is guided in the abutment plates 75, 76 and is coupled to the lever 82 by way of a stud 80. This link 78 is connected-for example -to mask means for effecting change-over of the range on the exposure meter and is constrained to adopt either one of its two end positions due to the action of an over-centre snap-action mechanism comprising a compression spring 94, a bridge piece 92 having pins 87 and 88 guided in slots 90, 91 and by levers 85, 86 respectively pivoted at fixed points 83, 84. Movement of the snap-action mechanism to change over the range of the exposure meter is effected by means of the engagement between studs 79 and either one of abutments 96, 97 on the levers 85, 86. Specification 756,693 is referred to.