Belichtungssteuervorrichtung fuer photographische Apparate

1,213,747. Photographic shutters. INTERNATIONAL POLAROID CORP. Oct. 9, 1968 [Oct. 9, 1967], No.47888/68. Heading G2A. A photographic shutter has an opening blade 22 mounted for movement between aperture 110 blocking and unblocking positions, a closing blade 24 mounted for movement between aperture unblocking and blocking positions, a control member 38 movable between a first and second positions, first and second drive springs 50, 48 acting upon the control member and the opening and closing blades respectively, the opening and closing blades being held in their respective aperture blocking and unblocking positions by retaining means during movement of the control member from its first to its second position, which movement tensions the first and second drive springs, the movement of the control member to its second position releasing the retaining member and thus releasing in time sequence the opening and closing blades. The exposure time is controlled by a timing circuit Fig. 2 (not shown) which includes a photo-resistor (82) charging a capacitor (106), the circuit being energized by the closure of a switch S1 operated by the depression of shutter release 20 and the timing operation commenced upon the opening of switch 52 upon commencement of the exposure by movement opening blade 22. The closing blade 24 is held in its unblocking position by an edge 32 abutting an edge 34 of opening blade 22 which is held by retaining member 65 after energization of the timing circuit an electromagnet 46 is energized to attract a keeper 88 mounted upon closing blade 24 and thus hold closing blade in its unblocking position irrespective of the movement of the opening blade, the electromagnet being de-energized by the timing circuit to terminate the exposure. The control member, opening and closing blades are all mounted for rotation on a hub 26. After exposure and upon release of shutter release 20, spring 44 returns the control member to its first position, and an abutment 42 on the control member brings the opening shutter and thus also the closing shutter to their initial positions, and projection 74 of retaining member 65 engages portion 76 of the opening blade.