Patent GB-754283-A (GB)
Title: Improvements in or relating to photographic shutters
IPC: G03B9/14
Filed: 1954-07-12
Abstract: 754,283. Photographic shutters. KODAK, Ltd. July 12, 1954 [July 15, 1953], No. 20274/54. Class 98 (1). In a photographic shutter wherein the shutter casing comprises two interengaging parts providing peripherally disposed slots for the passage and movement of external shutter operating members, one of the parts constitutes a cover member and has an internal annular flange adjacent to the slots to reduce admission of light through the slots to central exposure apertures in the two casing parts which partly for light trapping purposes are provided with extensions around the apertures, the extensions being directed towards each other and defining therebetween a narrow space for accommodating shutter blades. As shown in Fig. 6, the shutter casing comprises a front casing part 1 and a rear casing part 8 secured together by screws the latter having a peripheral flange 10 and a central inner flange 11 continued inwards to form an annular plate 12 surrounding the central exposure aperture 13. The front part 1 has a peripheral groove 91 engaging with a circular edge 10e of the flange 10 of the rear part. Slots 41 90 and 56 Fig. 3 are provided in the flange 10 for the passage of the shutter trigger 40, the pointer 5 co-operating with a diaphragm scale, and a pointer 3 adjustable to instantaneous and time exposure indications. The casing part 1 has a central inwardly-tapered part having steps 15 of circular form leading to the front exposure aperture 14. A glass closure plate 16 may be provided. The casing part 1 has annularly arranged extensions 19 directed towards the extension 11 on the part 8, the extensions 19 and 11 being separated by a narrow space 20 for accommodating shutter blades. The slots 41, 90, and 56 are shielded internally by the annular flange 92. The extension 11 supports a rotatable shutter blade operating ring 35 held in place by the spring arms 50 and normally biased by the spring 37 to the position of Fig. 3 in which it is located by the engagement of the arm 49 with the bladeoperating lever 29. In this position, the lug 48 having a ramp 52 is adjacent to the arm 43 of the trigger 40 biased to the position shown by the spring 46. Operation of the trigger, or of a cable release screwed in the opening 72 and operating the trigger via lever 70 and trigger arm 44, turns the ring 35 clockwise to snap the lug 34 having the ramp 36 under the shoulder 33 on the blade-operating lever 29, the spring arms 50 allowing axial movement of the ring 35. When arm 43 leaves the lug 48, the ring 35 rotates anticlockwise to rock the blade-operating lever 29 to operate the pair of shutter blades pivoted on studs 24, 25, the lever 29 returning under the action of the spring 30 to close the blades when lug 34 passes away from the shoulder 33. A lug 22 on lever 29 engages the contact 9<SP>1</SP> connected to the flash-synchronizing contact plug 9. In the clockwise movement of the ring 35, the movement of the lug 80 away from the shoulder 81 of the weight 82 permits this to rotate anticlockwise under the action of the arm 85 of the spring 30 until it engages the pin 821, and the return anticlockwise movement of the ring 35 is retarded as it rocks the weight 82 clockwise against the action of the spring 30. The shutter blades are thus open a relatively long time in relation to the time taken for their opening and closing movements. When the pointer 3 is moved anticlockwise from the position shown in Fig. 3 to the " Bulb"  exposure position, the lug 55 on the lever 581 moves into a position to intercept the lug 54 on the ring 35 in its return movement and thus hold the shutter blades open until the trigger is again depressed. The front casing part 1 supports an iris diaphragm assembly 100, Fig. 5, by means of a flange 104 provided with bayonet slot openings 106 into which lugs 107 on the diaphragm-operating ring 119 are inserted and the ring turned. The ring 119 is controlled by points 5 on the arm 191.