Improvements in the shutter operating mechanism of photographic cameras

Abstract

603,960. Actuating means for photographic camera shutters. SPECTO, Ltd., and HOBBS, H. W. Nov. 19, 1945, No. 31008. [Class 98 (i)] In a photographic camera in which a strip film is carried for exposure around a continuously rotating drum and is fed between supply and take-up spools mounted within the drum, the shutter operating mechanism comprises a shaft which rotates with the camera drum and carries a screw-threaded member, a sliding carriage having means for engaging the screw thread, shutter operating means on the carriage, and cams on the shaft which actuate the shutter operating means as the carriage is moved axially of the shaft. As shown, the mechanism comprises a carriage 1 slidable on guides 2, supported by a frame 3 and extending parallel to the shaft 4 of the camera drum. Upon the carriage are mounted two pairs of electromagnets 5, 6 and an armature 7 of inverted U-form, pivoted thereon at the extremities of the U. A flat cylinder 12 mounted on the shaft 4 carries on each edge of its curved surface a cam 27. As the camera drum rotates the cams close pairs of contacts 26 supported on the carriage 1 which open and close the shutter. To start a sequence of operations a switch 25 is closed energizing one pair of series connected electromagnets, say 5. These in turn attract the armature 7 so that a cam 8 carried by the armature depresses a plunger 10 against the action of a spring 11 causing the bottom of the plunger to engage in a turn of the screw thread on the cylinder 12 and thus traverse the carriage along the guides until one end of the armature engages one limb of a T- shaped bar 15 which rocks about a vertical axis and which carries roller 16 on a parallel axis on the rearwardly projecting stem, said roller engaging a roller mounted with arms vertical on a laterally disposed leaf-spring. When the bar is engaged by the armature it actuates a movable switch contact 21 opening circuit through contact 22 and closing circuit through contact 23 with a snap-over action due to the lost motion between the roller 16 and the forked end of the vertical switch arm 19. This switching de-energizes the magnets 5 so that the plunger 10 rises out of the screwthread groove and the carriage is returned by a spring against a stop on the guides 2. The cams 27 and the contacts 26 are so designed that they engage only once during the movement of the carriage in the forward direction and the electrical circuit contains means (not shown) to isolate the contacts during the return movement of the carriage. The electrical shutter operating means may be replaced by mechanical means comprising star or Geneva type wheels mounted upon a shutter operating shaft carried by the carriage and adapted to be engaged and rotated by pins carried by the threaded cylinder on shaft 4.

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