Patent GB-923761-A (GB)
Title: Improvements in or relating to shutters for cameras
IPC: G03B9/18
Filed: 1960-04-01
Abstract: 923,761. Photographic cameras. KABUSHIKI KAISHA KOPARU. April 1, 1960 [April 6, 1959], No. 11621/60. Class 98 (1). A focal plane shutter comprises a first and a second curtain group respectively connected with a first and a second actuating lever, which are pivotally connected with a shutter baseplate having an exposure aperture, and also comprises a shutter actuating device which comprises a first and a second main spring connected with their respective actuating levers for driving their respective curtain group from a cocked position to a released position in the shutter releasing period, a first cylindrical cam mounted fixedly around a second device having a flange gear portion engaging with a shutteroperating device, a second cylindrical cam rotatably mounted around the second device axially displaced from and positioned selectively in predetermined angular positions with respect to the first cylindrical cam, a first and a second latch member for holding the respective actuating levers in a shutter cocked positions, a first and a second latch-operating member operatively engaging with the first and second cylindrical cams respectively, the second device being rotatable by the shutter-operating device, whereby the cams are rotated by a return spring of the shutter-operating device during the shutter releasing period, to actuate the first and the second latch members in succession as determined by the angular displacement between the first and the second cams. As shown (Fig. 2), opening curtain plates 26, 26a and closing curtain plates 26c, 26ac are respectively movable in front of an exposure aperture O by means of parallelogram linkages 27, 28 and 27c, 28c. Shutter operation is controlled by a drum D which carries two grooved control cylinders 17, 18 and runs down in the anticlockwise direction at shutter release under loading by a spring 12b on a shaft 12 and coupled to the drum D by means of gears 16a and 12a. Operation of the control mechanism for the opening blades will be described with respect to Fig. 8 which shows this mechanism in the tensioned and ready-forexposure condition. On rotation of cylinder 17 at shutter release, a lever 29 pivoted at 27a is pivoted downwards by the engagement of a pin 29a in a groove 17a and eventually by means of a pin 29b thereon pivots a spring-urged cranklever 30 slightly in the anticlockwise direction, thereby releasing a hook portion 28a of lever 28 (pivoted at 28b) from a lug 30a. Lever 28 thereupon rotates in the clockwise direction under loading by a powerful spring 32 for opening of the blades 26, 26a. The closing blades are controlled in a similar manner by grooved cylinder 18, and the exposure time is varied by adjusting the relative angular position of these cylinders. When main driving spring 12b is retensioned and drum D rotated back to its original position (cf. Fig. 2), lever 28 is also returned to its tensioned position (Fig. 8) by means of a spring-urged lever 31 pivoted thereon and having a hook portion 31a for engaging with pin 29b on the lever 29. The spring 12b on shaft 12 is retensioned by operation of a lever 7 having a one-way coupling with a film wind shaft 7c, this shaft being coupled to the shaft 12 by way of gears 11a and 11b and a gear 13 which is coupled to the gear 12a by a releasable coupling comprising a projection 12c (Fig. 10) on gear 12a and a spring-urged pawl 13a on gear 13. Shutter release is effected by a release knob 8, depression of which releases pawl 13a from projection 12c by means of a pivoted lever 14, and the drum D is then free to run down to control an exposure as described above. Drum D comprises a number of concentric cylinders-Fig. 4 (not shown)-which are so arranged that the relative angular positions of rotatable cylinders 17, 18 may be adjusted prior to exposure by means of an exposure time adjusting knob 10, which does not partake in the running down of drum D. Cylinder 18 is also so rotatably mounted in drum D that during recocking it corresponds in angular position to cylinder 17 and therefore also with a zero exposure time-a cover-plate is therefore not required.