Patent GB-1186320-A (GB)
Title: A Photographic Shutter having an Electronic Timing Device
IPC: G03B9/58
Filed: 1968-06-27
Abstract: 1,186,320. Shutter control mechanism. PRONTOR-WERK ALFRED GAUTHIER G.m.b.H. June 27, 1968 [July 26, 1967] , No.30622/68. Heading G2A. A camera shutter having an electronic timing device including electromagnet for holding the shutter blades open, and an electronic device for delaying the opening of the shutter blades after the release has been actuated, is characterized in that the electromagnet is not connected to the energizing source until the end of the delay period. Fig.1 shows the shutter mechanism in the tensioned position, the shutter driving disc being latched against the action of spring 7 by a lever 8. When released by lever 8, disc 4 runs down clockwise, a pawl 5 linked thereto driving a ring 6 in known fashion in a reciprocating movement to open and then close the shutter blades. When the blades are open, a catch 12 falls behind a lug 6a of ring 6, so preventing its return, and thus locking the shutter open until the catch is disengaged. The delaying action is controlled by a three-armed lever 22, which is shown in Fig. 1 in the delaying position. When an exposure without any delayed action is required, lever 22 is pivoted anticlockwise from this position, which renders the delay mechanism inoperative. In this case, when the release lever 10 is pressed, lever 8 is disengaged from disc 4, allowing it to execute the shutter-opening movement, after which ring 6 is latched against return by catch 12. A switch S 1  is closed, which energizes the circuit for controlling the exposure time Fig.2 (not shown). During this period the electromagnet 18 is energized, so holding the armature 16 and hence lever 14 in the position shown. After an exposure time determined by a photo-electric resistor or a fixed resistor in the switching circuit, the tripping part of the circuit changes over, and the electromagnet 18 is de-energized. Lever 14 is then pulled clockwise by a spring 17, and its upper arm 14a pushes catch 12 out of engagement with lug 6a. Ring 6 is thus allowed to rotate anti-clockwise to close the shutter blades. If the delayed action is required, lever 22 is pivoted into the position of Fig. 1. The end 22b is now in the path of a lug 6b on ring 6, so that after traversing the short distance S, movement of ring 6 is arrested, with the shutter still closed. A further pair of levers 24, 26, on the same pivot and also linked together mechanically, are drawn by a spring 28, in the "no delay" position, so that the armature 27 attached to lever 26 is out of contact with an electromagnet 29. When lever 22 is moved into the "delay"position Fig. 1, levers 24 and 26 assume the position shown, with armature 27 abutting electromagnet 29. A lug 24a of lever 24 locks in front of lug 22e of lever 22, preventing return movement thereof. Movement of lever 22 also closes a switch S 4 , so that when shutter release 10 is pressed, electromagnet 29 also becomes energized, so holding armature 27. When the delay period has elapsed, as determined by the "delay" part of the circuit, electromagnet 29 is de-energized, and levers 24 and 26 are rotated clockwise by spring 28. Thus lever 22 is no longer locked by lever 24, and can return to its original position under the action of springs 23. The normal shutter-opening, timing, and shutterclosing operations can now take place as described above.