Patent GB-191008961-A (GB)
Title: Improvements in Photographic Shutters used in proximity to the Lens.
Inventor: WHITEHEAD FRANK PHILIP
IPC: G03B9/20
Filed: 1910-04-13
Granted: 1911-04-06
Abstract: 8961. Whitehead, F. P. April 13. Shutters with pivoting blades. - In a pivoting-blade shutter, each blade carries a pinion in gear with an internally toothed ring encircling the exposure aperture. The toothed ring is provided with projections which are operated by a moving part. For ordinary instantaeous exposures the projections are successively engaged by a spring- driven moving part, and the blades are moved in a continuous direction during an exposure. The pawls or levers actuating the toothed ring are designed with a view to making the time of opening and closing the aperture small in comparison with the time the aperture is open. The shutter is adaptable for reflex cameras. The toothed ring C, Figs. 4 and 8, rotates in a circular bearing between a plate B and a clamping-plate D. The plate B is fastened to the main supporting-plate F on the shutter case A<1> and is spaced from this plate F by the peripheral edge B<2>. The shutter blades H are mounted between the plates B, F and are pierced with holes H', Fig. 5, which slip on pinions E. The pinions extend between the plates F, D through holes cut in the plate B and gear with the gear-wheel C. The pinions rotate on pins which are screwed from the underside into the plate D. The toothed ring C has pins C<3> on its periphery, which are spaced so that the number of teeth between consecutive pins is equal to the number of teeth on the pinion, and an exposure is effected by rotating the ring through the spaced distance of the teeth. For instantaneous exposures, the ring is actuated by a spring-driven moving part. For time and bulb exposures a lever W<2>, Fig. 9, is notched to engage normally one of the pins C<3>. The lever W<2> is pivoted to the lever W<1>, which itself is pivoted on the shaft W<9> of the operating-lever W, Fig. 1. The lever W<2> is held in engagement with the ring by the spring W<4>. On actuating the lever W for a bulb or time exposure, the levers W<1>, W<2> are turned until the lever W<2> engages a shaped shoulder T' of the lever T, which corresponds to the open position of the blades. The blades can be held open for a time exposure by throwing over the arm X to hold the lever W. The arm X is held by friction. In the open position a pin W<8> on the lever W engages between the lever T and a stop Y on the plate B, which thus prevents the instantaneous-release pawl R from being actuated when the shutter is open for focusing or for a time exposure. On releasing the lever W, the parts are returned by springs W<4>, W<6>. For instantaneous exposures, the spring-driven moving part in one modification comprises a pawl P<1> pivoted to the disk O on the spring shaft I<2>, Fig. 8. The spring Q connected between the pawl P<1> and the drum O enables the pawl to ride over any pin C<3> in setting the shutter by pulling over the projecting handle O<1> in a clockwise direction. The shutter is held in set position by the lever R engaging the notch O<3>. The release levers actuates the arm T, which in turn actuates the lever R. Also simultaneously the lever W is retracted from the ring by the end of the lever T. In revolving over. the pawl P' carries the pin C<2> with it, thus actuating the shutter blades. Near the end of its motion a notch O<4> throws a spring-controlled lever into engagement with the adjacent pin C<3> to arrest the gear-wheel C. A second spring- controlled lever V prevents the gear-wheel from turning backwards in setting the shutter. The exposure is determined by the tension of the spring I, which is adjusted by turning the shaft J, to which one end of the spring I is attached. The spring is tensioned by winding the key L in an anti-clockwise direction and the tension or exposure is indicated on a disk N' geared to the shaft. The spring is held tensioned by the projection M<2> of the spring-controlled lever M. The key L has two faces L<1> which push aside the projection M<2> tensioning the spring but, when the projection M<2> is retracted for letting down the spring, a second projection M<3> acts as a Geneva stop and arrests the key at every half turn. Thespringisthus prevented from unwinding suddenly. In a modified construction, the toothed ring is moved by a spring-actuated slide A, Fig. 11. The slide carries a spring-controlled lever C, cut with shaped notches C<2>, C<3>, which engage with the adjacent projection of the toothed ring when the slide is released by the release lever E. At the end of the stroke the slide A moves the lever F to arrest the toothed ring. Further alternative modifications are to have an externally toothed ring, or to actuate the shutter by toothed gearing meshing with one of the blade pinions. The shutter is adaptable for a reflex camera by continuing the shafts of the levers W, S into the camera and connecting them with the mirror arrangements so that the lever W is first released after focusing and then the lever S to complete the exposure.