GB428455A - Improvements in or relating to shutters for photographic cameras - Google Patents

Abstract

428,455. Photographic shutters. BILLING, N. P., 6, Lower Regent Street, London. Nov. 3, 1933, No. 30637. [Class 98 (i)] The shutter comprises a pair of movably mounted components, the first having an exposure aperture and the second forming a closure member for this aperture, in combination with a shutter setting element operatively connected to both components with lost motion between the setting element and the first component after an initial movement of the latter so that the components are movable through different distances. The shutter components may be discs, revolving round an axis parallel to the lens axis, and provided with gear elements engaging a common gear wheel. In the form shown, the shutter comprises leaves 5, 6, Fig. 7, the leaf 6 comprising a toothed ring having a large aperture 29 and a small solid sector 30, and the leaf 5 comprises a disc having gear teeth only on part of the periphery and a sector-shaped aperture 31. The teeth of both gears engage a pinion 7 on the same shaft 37 as a second pinion engaging teeth on the inside of a ring for setting the shutter. A ratchet wheel 14, Fig. 8, is also mounted on this shaft which is provided with a coil spring. A pawl 16 engages the ratchet 14 and a second pawl 15 engages a pin 43 on the pawl 16. The shutter is set by rotating the setting ring which moves the aperture 31 out of register with the lens aperture, the leaf 5 then stopping owing to the absence of gear teeth on part of the periphery, and simultaneously the leaf 6 is rotated and the spring on the shaft 37 wound up. For instantaneous exposure the pawl 16 is pressed, the length of exposure depending on the angular separation of the leaves 5, 6. For time exposures, the pawl 15 is pressed lifting the pawl 16 clear of the ratchet 14, but leaving a projection 41 on the pawl 16 in the path of a stud 40 on the ratchet wheel. The exposure is terminated by pressing the pawl 16. In a modified form, a crown wheel is used to replace the ratchet wheel 14. The return speed of the shutter may be checked by means of a brake. Specifications 423,035 and 423,226 are referred to.