Patent GB-650737-A (GB)
Title: Photographic shutter
IPC: G03B9/22
Filed: 1947-09-19
Abstract: 650,737. Photographic shutters. GENERAL ANILINE & FILM CORPORATION. Sept. 19, 1947, No. 25597. Convention date, Oct. 17, 1946. [Class 98 (i)] A shutter comprises several pivoted shutter blades which are interconnected by a mechanical linkage, a master member, which is movable in a straight line path and includes a cam-slot and a coupling between the cam slot and the blades, the cam slot being so shaped that, during the movement of the master member to open and close the shutter, the shutter blades are constantly accelerated and then constantly retarded. Provision is made for instantaneous, time and bulb exposures. The shutter shown is housed in a casing 10 and comprises four blades 12, Figs. 1 and 7, each of which is pivoted at 15 and is strengthened in the region of its pivot by a riveted plate 16, having projecting ears 18 to each of which one end of one of four interconnecting links 19 is pivotally secured by pins. One of these pins 49, engages a notch 62, Fig. 6a, in a lever 48 which is pivotally attached at 47 to a plate 44 and is spring-urged anti-clockwise. Plate 44 is pivoted at 45 and has a pin 46 which rides in a cam-slot 37 provided in the master member 24, Fig. 1, which is movable along a spindle 23 under the action of a power spring 25. The shutter is set by clockwise rotation of a ring 26 which comprises a manually-operable lever 29, a cam surface 28 and a projection 27. On such rotation of this ring the cam surface 28 first contacts a spring-urged lever 51 which is turned to press down a lever 55 having a limited sliding movement determined by pins which ride in slots therein; lever 55 moves the lever 48 so that the pin 49 is disengaged from the notch 62. Thus, movement of the pin 49 and consequent opening of the shutter blades is obviated, even though the master member 24 moves against the spring 25 due to the contact of the projection 27 therewith. Such movement of the master member continues until a latching lever 65, Fig. 2, which is pivoted at 63 and has a projection 67, falls into place and prevents movement of the master member 24 from its set position. The shutter speed setting ring 103, Fig. 8, is rotatable in the shutter casing and has a circumferential flange bearing graduations, which are observable on the outside of the shutter casing on which is a co-operating index mark; an outer knurled part of this ring facilitates rotation thereof. This ring includes a cam slot on one surface of which rides a pin 92, Fig. 8, fast on a spring-urged lever arm carrying the pallet of an escapement mechanism; a cam slot in which rides a pin 98, which projects from a rotatable spring-tensioned sector gear of the escapement mechanism, which gear has a nose for engagement with the master member in its travel to effect a shutter opening; and a cam slot in which ride projections 75, 80 from two levers 73, 76, respectively, Fig. 2, which are pivoted at 63 together with latching lever 65. Lever 76 is operative for bulb exposures, while both lever 73 and lever 76 are operative for time exposures. Movement is imparted to these levers and to unlatch lever 65 by a trigger 68, Figs. 1 and 2, which projects from the casing and is pivoted therein at 69, Fig. 1. Instantaneous exposures.-The speed setting ring is rotated until the correct graduation thereon coincides with the index mark on the casing, the projections 75, 80 of levers 73, 76 lie in the cam pathway 112 of the ring 103 so that levers 73, 76 are rendered inoperative, the projection 92 of the pallet of the retard mechanism lies in the pathway 106 or 107 of the speed ring according to whether the shutter speed is to be slow or very fast, and the projection 98 from the sector gear lies in the pathway 109 or 110, the latter in the case of fast speeds. Release of the master member 24 by pressing downwardly on the trigger 68 so that a shoulder 70 thereon, Fig. 2, contacts the projection 67 on the latching lever and turns it, causes the master member to move to the right in Fig. 1, and open the shutter blades prior to contact with the nose of the sector gear in the escapement mechanism; the blades then remain open for a time depending on the action of the escapement mechanism, the master member thereafter continuing its movement to close the blades. Bulb and time exposures.-The speed ring is rotated to render the pallet inoperative and the lever 73 is rendered inoperative, when a bulb exposure is desired. Thus, for a bulb exposure, the master member 24 opens the shutter blades and first contacts the nose of the sector gear of the retard mechanism whereby the master member is slowed up prior to its engagement with the bulb lever latch; when trigger 68 is released, it rotates clockwise under spring action so that the shoulder 71 therein contacts the projection 78 on the lever 76 and turns this lever to release the master member which continues in its path to close the blades. For a time exposure, the master member after contact with the nose of the sector gear of the retard mechanism engages a latch on lever 76, which is thereafter released by movement of the trigger; the master member continues in its path until arrested by the lever latch 73, which is only released when the trigger is pressed downwardly so that its shoulder 70 contacts the projection 75 on the lever and turns it. The Specification as open to inspection under Sect. 91 describes a modification wherein an additional spring may be brought into use for the higher shutter speeds. This subject-matter does not appear in the Specification as accepted.