Patent GB-968940-A (GB)
Title: A device for regulating the exposure time in photographic cameras
IPC: G03B9/58
Filed: 1962-07-20
Abstract: 968, 940. Camera exposure regulators. ALFRED GAUTHIER G.m.b.H. July 20, 1962 [July 31, 1961], No. 27968/62. Heading G2A. An apparatus for giving a range of controlled exposure times larger than those provided by the mechanism of the camera itself has a device connecting it to the cable release connection of the camera in which, when a release is actuated, a ram is displaced to operate the shutter, which is main- - tained open by a " B" -exposure device, a flash which is operated as the shutter becomes fully open, and a retarding mechanism actuated by an electromagnet whose circuit is energized as the flash contacts close, the retarding mechanism being adjustable as to run-down time, at the end of which the ram returns to its original position and the "B"-exposure device allows the shutter to close. Fig. 2 shows a camera shutter in which the shutter blade ring 6 is driven by a spring-loaded disc 12. When cocked, the disc 12 is retained in that position by a lever 14, which is tripped to release the shutter drive by another lever 15, actuated in turn by a rod 21 operated by the plunger of a cable release 32. A device for carrying out "B"-exposures comprises a stop lever 27, which is made operative when the time-setting ring 29 is set to the mark "B" on scale 30, in which case a lug 27b on lever 27 is located in a widened part of a groove 29a in ring 29; this allows lever 27 to move  with lever 15, and engage with disc 12 to prevent it from turning. Otherwise the lug 27b is located in a narrow part of the same groove, which holds lever 27 inoperative. The apparatus for controlling the additional exposure times is contained in a separate housing 31, Fig. 1, joined by a connector 32 to the cable release of Fig. 2. The cable release is operated by a plunger 63, spring-loaded upwards with its top end bearing against a cam 61. This is mounted on a carrier plate 33 which is urged upwards by springs 34, 35. To tension the mechanism, the plate is forced downwards against the springs by a slider 52 until it abuts against stops 38, 39. Mounted on plate 33 is a spring-driven train of gear-wheels 43, 44, 45, 46, and this spring is tensioned by a rack-and-pinion arrangement as slider 52 moves downwards. The gear train is retained in the tensioned position by a projection 55b at the end of a lever 55. The cam 61 is rigidly fixed to the gear-wheel 46. Fig.1 shows the.mechanism in the tensioned position, ready for the release of the shutter, plate 33 being retained by a stop lever 40 engaging in a recess 33b on the plate. On pressing the release knob 58, lever 55 is. pivoted out of engagement with gear-wheel 43, so that the tensioned gear train runs down. Cam 61 rotates about the spindle it shares with gear-wheel 46, and consequently pushes plunger 63 downwards to operate the cable release of Fig. 2 and so open the shutter, which is retained open by the "B"- exposure arrangement. The retarding mechanism comprises a gear train 64, 65.... ending in a stop anchor 69, and driven by a spring 70. An extension 33d, 33e of plate 33 engages with a driver pawl 73 mounted with gear-wheel 64, so that the latter, with its driving spring 20, is also tensioned as plate 33 is pushed downwards. The retarding gear train is retained in the tensioned position by a lever 77, which has a tooth 77b at one end locking against a pin 78 on gear-wheel 65. As soon as the shutter is fully open, a flash device is fired by a contact arrangement 22, 23, 24, which at the same time closes a circuit to energize an electromagnet 80. This attracts core 81 which is formed as a lever engaging against lever 77. The latter is thus pivoted out of engagement with gear-wheel 65, so that the retarding mechanism is released to run down. The run down period is adjustable, and is varied by turning a disc which rotates a cam disc 98 lockable in any selected position on the spindle 66 of gear-wheel 64. When cam 61 runs down from the tensioned position of Fig. 1, it pushes a slidable pin 97, which in turn pushes a lever 93 out of locking engagement with another lever 88. This is spring-biased clockwise, and a slight movement, on being released, brings a bent-over lug 88a, at one end into abutment against cam disc 98. The latter is rotating anticlockwise as the retarding mechanism runs down, and when the projecting cam portion moves clear of lug 88a, the lever 88 swivels fully, so engaging stop lever 40, and pivoting it out of engagement with recess 33b in plate 33. Plate 33 is thus released to move upwards under the action of springs 34, 35, which also releases plunger 63 to move upwards under the action of its own loading spring 62. This in turn releases the spring- loaded pin 21 to move upwards, so finally allowing the camera shutter to close, and terminate the "B"- exposure.