| 摘要 |
943,341. Photographic shutters. AGFA A. G. May 2,1960 [May 2, 1959], No. 15413/60. Heading G2A. A photographic shutter assembly includes, in combination, support means, rotary drive means carried by said support means for driving a shutter, said rotary drive means having a projection, and timing means carried by said support means for retarding the operation of said rotary drive means, said timing means including a double crank linkage, the coupling member of which, coupling the cranks of the linkage, has a free end portion located in the path of turning movement of said projection and acting as a pawl in co-operation with said projection so that the latter engages said coupling member to cause the timing means to co-operate with the drive means to retard the operation thereof, the cranks of the linkage being in the form of discs or disc sectors. As shown, a retard mechanism comprises a pawl 16 pivotally connected at 17,18 to two rotatable discs 10,11 and having an extension 19 projecting into the path of movement of a projection 9 of a shutter master member 5. To vary the delay provided by the mechanism, the initial position of the pawl 16 may be adjusted by means of a timing cam disc having a cam 23 which is engaged under loading of a spring 21 by a pin 22 on disc 11. The discs 10 and 11 may be constructed as escapement wheels, in which case escapement pallets 12,13 may be rendered operative (as pallet 12) or inoperative (as pallet 13) by adjustment of cams 29, 35 respectively of the said timing cam disc. The master member drives the shutter blade ring 2a by way of a triangular cam member 5a and is held in the tensioned position and later released by means of a latch 3. In modifications, the coupling between pawl 16 and disc 11 may comprise a lost motion coupling so that the instant at which this disc becomes effective for providing delay may be varied, discs 10 and 11 may be constructed as disc sectors and intermediate gear-wheel transmissions may be provided between either or both of the pallets 12, 13 and the discs 10 and 11. The link discs or sectors may be made of a polyamide. Alternatively, the link discs or sectors may be made of a metal such as brass or steel and the escapement pallets of a material such as polyamide or polystyrene. The polyamide may incorporate a solid lubricant such as molybdenum sulphide or graphite.
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