GB912017A - Improvements in iris diaphragms - Google Patents

Abstract

912,017. Iris diaphragms. WRAY (OPTICAL WORKS) Ltd. June 24, 1960 [Sept. 25, 1959], No. 32736/59. Class 97 (1). An iris diaphragm in which the two plates on which are mounted the leaves forms the adjustable substantially circular aperture of the diaphragm are moved relatively to one another, to adjust the aperture, by means of an operating member, the rotation of which to enlarge the aperture causes movement first in one direction and then in the opposite direction of a gear member which is coupled to one of the plates and so first decreases and then increases the rate at which the aperture opens. Preferably, the angular movements of the operating member between all consecutive standard apertures are substantially equal. As shown in Fig. 1, the diaphragm leaves 5 are each pivoted to a plate 2 and a plate 7. The plate 2 is rotated by a sleeve 1 which surrounds the lens mount 4 and is connected to the plate 2 by a pin 3 extending through a circumferential slot in the lens mount 4. The plate 7 is also rotated relative to the lens mount 4, this plate having rigidly mounted thereon a hollow cylinder 12 with teeth 14 which mesh with a gear 16 on a shaft 17 terminating in a pinion 18 that engages with a rack 19 carrying a pin 20 which extends through a slot 21 in the sleeve 1. This slot 21 is such that as sleeve 1 is rotated to adjust the diaphragm aperture, the rack 19 will be moved axially first in one direction and then the other so as to produce a corresponding movement in plate 7. In a second form, one of the plates is fixed and the other plate is rotated by a gear segment which is pivoted to the rotatable sleeve 1 and carries a pin engaging a fixed cam on the lens mount 4, this cam being designed to alter the rate of movement of the movable plate with respect to the sleeve 1.