Patent GB-756693-A (GB)
Title: Improvements in or relating to photographic cameras
IPC: G03B7/00
Filed: 1954-01-04
Abstract: 756,693. Photographic twin lens cameras with interconnected diaphragm and shutter speed settings. HEIDECKE, R., and FRANKE, H., [trading as FRANKE & HEIDECKE FABRIK PHOTOGR PRAZISIONS-APPARATE]. Jan. 4, 1954 [Jan. 19, 1953; Oct. 16, 1953], No. 145/54. Class 98 (1). In a twin lens camera having diaphragm, shutter speed and light value scales arranged concentrically of the view-finder objective and coupled to the diaphragm and shutter speed setting means which are each manually adjust. able by a knob, the shutter speed knob is coupled additionally to the diaphragm setting means and the diaphragm knob is coupled additionally to the light value scale setting means and one or each of the couplings between the knobs and the additional setting means includes a disengageable drive. As shown, shutter speed and diaphragm aperture adjusting rings 6, 7 surrounding the taking objective and geared to toothed drums 8, 9 bearing speed and stop scales 10, 11 arranged coaxially with the finding and focusing objective are rotated through gears 16, 17 on shafts 4, 5 by knobs 2, 3. Shaft 5 also carries a gear 26 meshing with a gear 29 on a shaft 28 which is borne in an arm 27 pivoted on the shaft 5 and which engages in a slide 34, while shaft 4 carries a gear 19 meshing with a gear 22 freely rotatable on a fixed shaft 21 which carries a pawl 36 and is carried by an arm 20 urged anticlockwise by a spring 23 about its supporting shaft 4 and engaging in the slide 34. By pushing the cross slide 34 to the right as shown by means of the thumb piece 35, gear 29 is meshed with a toothed drum 31 bearing a light value scale 32 and disposed coaxially with the drums 8, 9 so that by rotating the knob 3 the light value and stop scales are rotated simultaneously while the shutter speed ring and scale are held stationary by a pin (not shown) on a slide 37 which is urged to the right by the spring 23 engaging a ratchet-wheel 38 on the shaft 4. On releasing the slide 34 which is returned by the spring 23, the gear 29 is disengaged and the gear 22 is meshed with the stop drum 9, but the exposure value drum 31 is still latched by the pin engaging the ratchet-wheel 38. On pressing the slide 37 to the left, rotation of either the speed or stop knobs 2, 3 adjusts the speed and stop settings in complementary senses so as to maintain a fixed light value. Alternatively (Fig. 2, not shown), the shaft of the speed knob may be carried, by a pivoted arm connected to the cross-slide which is connected to a similar arm on a shaft bearing a pinion constantly in mesh with the light value drum and with a pinion on the shaft of the stop knob which is borne in the pivoted arm. On pressing the cross-slide to the right, pinions on the speed shaft are unmeshed from the speed and stop adjusting rings while a pinion on the stop shaft is meshed with the stop ring and a pawl on the stop shaft locks the speed scale drum. After adjustment of the light value and stop setting and release of the slide, the pinion and pawl on the stop shaft are disengaged and the shaft is locked by the pinion engaging a fixed pawl, while the speed shaft is moved to mesh its pinions with the speed and stop rings. In a modification (Fig. 3, not shown), both setting shafts carry a single long pinion and a pawl, the pinion on the speed shaft engaging the speed and stop scale drums and the pawl on it locking the light value drum, while the pinion on the stop shaft engages the light value and stop drums and the pawl on this shaft locks the speed drum. In another embodiment (Fig. 4, not shown), in which the pinions on the shafts of the setting knobs are permanently in mesh, the stop knob shaft has only one pinion connecting the stop adjusting ring and scale drum, and the shaft of the speed knob carries a pinion meshing with the speed scale drum and a clutch spring engaging a pinion fixed on a freely rotatable coaxial shaft and meshing with the stop scale drum, the freely rotatable shaft carrying at its outer end a mark co-operating with a light value scale on the speed knob. Since the resistance to adjusting the shutter speed is greater than that to adjusting the diaphragm, and may be increased by a ball catch engaging in holes in the speed adjusting ring, rotation of the stop knob adjusts the diaphragm and moves the mark on the freely rotatable shaft relatively to the light value scale on the speed knob due to slipping of the clutch connection, while rotation of the speed knob adjusts simultaneously both shutter speed and diaphragm.