Patent GB-929908-A (GB)
Title: Improvements in or relating to photographic shutters
IPC: G03B9/10
Filed: 1961-04-21
Abstract: 929,908. Photographic shutters. KODAK Ltd. April 21, 1961 [April 21, 1960], No. 14435/61. Class 98 (1). A shutter comprises a shutter exposure blade mounted on a support having an exposure aperture to rotate between a closed position covering the exposure aperture and an open position, a return spring urging the blade from open to closed position, an inertia member mounted on the support to move to and from a rest position, means for imparting a sharp impact to the blade to move it from its closed position, means for simultaneously moving the inertia member from its rest position, a stop for limiting the opening movement of the blade, and means connecting the inertia member and blade to allow relative movement after the blade has engaged the stop so as to hold the blade in the open position against the action of the return spring until the energy in the inertia member has been dissipated when the inertia member returns to its rest position and the blade is returned to its closed position by the return spring. As shown, the shutter comprises a blade 13 pivoted at 12 on an insulating support 10 and closing an exposure aperture 11 and adapted to be driven by an impact lever 26 having a driving spring 28 tensioned on cocking the shutter by an arm 40 operated manually or by the film winding mechanism, the lever being latched in the cocked position by the trigger 42. On depressing the trigger the blade 13 is driven clockwise and an inertia member consisting of a spring arm 22 attached to the blade 13 and bearing a weight 24 moves with it. For speeds of <SP>1</SP>/ 100  second or slower, the blade is arrested by a blade extension 14 engaging segments 51 or 60 of an adjustable stop cam rotatable on a pin 18 or a fixed stop pin 65 in accordance with the exposure time selected by the arm 52 secured to the cam, but the inertia member moves a distance S beyond the blade to its most clockwise dotted position shown, thus holding the blade in the open position. When the energy of the inertia member has been dissipated, the member and the shutter blade are returned to the full line rest position by a return spring 19, rebound of the shutter blade being prevented by the snubbing action of a stop wall 80. For a speed of <SP>1</SP>/ 200  second, the inertia member is arrested before the shutter blade by engaging a pin 70 which has been displaced to the lower end of the slot 71, while for a speed of <SP>1</SP>/ 250  second the pin 70 is displaced along a portion (not shown) of the slot extending towards the stop 65 so as to arrest the inertia member and shutter blade as soon as the aperture 11 is fully opened. Flash contacts are provided by a resilient arm 85 having a turned-down end with a ramp profile passing through a hole 86 in the blade 13 and resting on the insulating support 10, the circuit being completed through the blade on its opening movement when the arm 85 rides up and on to the blade. In specified modifications, (a) the shutter blade may be an apertured plate; (b) the shutter may be selfcocking the trigger causing tensioning of the spring 28 before releasing the lever 26 and a further lever-spring combination being provided to return the lever 26 after exposure; and (c) the inertia member may be pivoted separately from the shutter blade and provided with its own return spring and may be driven by a separate impact means while a spring connection between the inertia member and shutter blade is provided.