Patent GB-905765-A (GB)
Title: Shutter and diaphragm mechanism
IPC: G03B7/00
Filed: 1960-09-29
Abstract: 905,765. Photo-electric exposure control. INTERNATIONAL POLAROID CORPORATION. Sept. 29, 1960 [Oct. 22, 1959], No. 33487/60. Class 40 (3). [Also in Group XX] A shutter and diaphragm mechanism is arranged so that on operation of an actuator, an aperture defined by the diaphragm means of the mechanism, is first uncovered by the shutter means of the mechanism and then closed by the diaphragm means. As shown (Figs. 4 and 5) the diaphragm comprises two blades 50, 52 pivoted about shafts 38, 36 and coupled for movement together in opposite directions by intermeshing gear-wheels 54, 56, respectively. Blade 52 is coupled by way of shaft 36 to an arm 66 (Fig. 9-rear elevation) which is acted on by a spring 67. One end of this spring 67 is anchored on a lever 176 pivoted about a pin 178 and urged-in the rest position shown-by spring 182 into engagement with a fixed lug 184. In this rest position, spring 67 is fully relieved of tension and is acted on by spring 182 to push the arm 66 into a position in which the blades 50, 52 fully cover the aperture 22 in the shutter base-plate 20. The shutter (Fig. 6) comprises two blades 28, 30 pivoted freely about shafts 36, 38 and coupled for movement together in opposite directions by intermeshing gear-wheels 32, 34, respectively. An extension of blade 28 is acted on by a spring 40 and is held in the tensioned position shown by the engagement of a pin 140 on this extension with a surface 130 of a member 88 of a timing device. The mechanism operates as follows: On rotation of a bell-crank lever 156 about its pivot 158, by means of a projection 168 on a spring-urged link 162 coupled to said lever 156, the lever 176 is pivoted in a clockwise direction, spring 67 is tensioned and the diaphragm blades are opened by means of the arm 66. This opening movement is arrested when an aperture corresponding to the prevailing light conditions is reached, as determined by the engagement between a pin 74 on an extension 72 of the blade 50 and a clamped control cam 80 (cf. Figs. 4 and 8) which is carried by the needle 110 of an exposure meter galvanometer 106. The cam 80 is clamped by means of a lever 122 which is coupled to the bell-crank lever 156 by way of an over-running clutch, the shaft 120 and the links 160 and 154. Further rotation of lever 156 brings lever 176 into engagement with a pin 194 on a spring- urged lever 186 coupled by way of a shaft 136 with a release pawl 134 for the member 88. On actuation of this pawl 134, the member 88 rotates about its shaft 124 under loading by a spring 128 and releases pin 140 from surface 130 for opening of the shutter blades under loading of their spring 40. Further rotation of the member 88 is delayed by means of a bellows 82, one end of which is connected to the member 88 and the other fixed end of which is coupled to a valve block 94 having a valve opening 98. The effective opening of the valve is varied for controlling the exposure time by means of a slit opening 102 in a plate 100 carried by said needle 110 of the exposure meter. This plate 100 has also been clamped during operation of the mechanism by means of a clamp-plate 112 having a cam projection 114 thereon for cooperation with an arm 118 carried by said shaft 120. After a variable delay as determined by the light conditions, a pin 150 on an impulse member 142-freely pivoted about shaft 38-is released by the surface 130. This member 142 then pivots under loading of its spring 144, engages an extension 70 of the blade 50 with its pin 152, and moves the diaphragm blades into their fully covering position-as determined by fixed pin 68 and as shown in Fig. 5-to end the exposure. Members 156, 154, 160, 176 and 186 return to their original position under their respective spring loadings. The shutter blades, and members 142 and 88 are returned to their original positions by means of elements 216, 218 and 224, respectively-cf.Figs. 11 and 12- which elements are connected to shafts 206 and 210 having intermeshing gear segments thereon and are operated by handle 202. The galvanometer casing 106 may be rotatable to make allowance for film sensitivities and/or filter factors.