Patent GB-138635-A (GB)
Title: Improvements in photographic shutters
IPC: G03B9/22
Filed: 1920-02-04
Abstract: 138,635. Ponton, H. R. Nov. 26, 1918, [Convention date]. Shutters with pivoting blades.-The shutter can be used for bulb or time exposures whilst the spring for producing instantaneous exposures at various speeds is cocked and without releasing the spring. The lever E, Figs. 1 and 8, which engages a notch d of the spring barrel D when the spring is cocked, is only operated by the operating lever I when the setting disk L, Fig. 9, is set for instantaneous exposures and is not affected when the disk is set for bulb or time exposures even though the spring for instantaneous exposures is cocked. The disk L rotates four cams K<1>, K<2>, K<3>, K<4> one of which controls the position of a lever M, M<1> used for bulb exposures, another controls the position of levers P, Q' for time exposures, a third cam controls the position of a lever G, G<1> pivoted on the lever E to bring the end G<1> of the lever into contact with the lever I so that the combined lever G<1>, E will be actuated by the lever 1 to release the spring barrel D, and the fourth cam controls through a lever Z, Fig. 1, the dash-pot orifice Y or other device for varying the instantaneous exposure speeds. For bulb and time exposures, the shutter blades are operated by a pin b, and for instantaneous exposures by another pin b<1> on the disk B carrying the shutter blades. In setting the disk L for bulb exposures, the cam K<1> moves the lever M into a position in which, on depressing the lever I, the other end m<1> of the lever moves the pin b in the slot o, and on releasing the lever I the spring N returns it, and the spring C acting on the pin b' closes the shutter blades. In setting the disk L for time exposures, the lever M is kept in position by the cam K<1>, and the end of a lever P drops into a depression in the cam K<2> and releases the lever Q' from the retaining catch p'. On operating the lever I, the end m<1> of the lever M moves the pin b which engages behind the end g' of the lever Q<1> and the shutter is held open. On a second depression of the lever I a spring-controlled pivoting plate S on the lever M, which in the first movement was held inoperative by the pin b now swings over under the influence of the spring T as shown in Fig. 6 and engages the pin Q' on the lever Q<1> to disengage the lever Q' from the pin b<1>. The shutter is then again closed by the spring C acting on the pin b<1>. The pin Q<2> on the lever Q<1> normally serves as a limiting stop for the plate S. In setting the disk L for instantaneous exposures. the cam K<3> acting on a pin G<2> tilts the lever G, G<1> which is pivoted on the lever E into a position in which, on operating the lever I, the combined lever G<1>, E will be actuated to release the spring barrel D. The cam K<1> is shaped so as to allow the spring N to keep the lever M, M<1> inoperative and the cam K<2> tilts the lever P so that its end p<1> holds the time lever Q<1> inoperative. On operating the lever I for an instantaneous exposure, the shutter is opened by the rotating barrel D through link-work V, W, W<1> and the spring C closes the shutter at a speed determined by the disk L and cam K<4>, and a dash-pot, the piston of which is connected to the barrel D as shown in Fig. 1.