Patent GB-774958-A (GB)
Title: Improvements in or relating to photographic shutters
IPC: G03B9/20
Filed: 1955-07-26
Abstract: 774,958. Photographic shutters. KODAK, Ltd. July 26, 1955 [July 28, 1953], No. 21563/55. Class 98(1) A photographic shutter comprises a rotatable ring operatively connected to the shutter blades for driving them in an exposure-making direction, a ring gear on the blade drive ring, and a number of power drive units that are selectively movable into and out of driving engagement with the ring gear, each drive unit including a spring-operated pinion which in the operative position of the drive unit meshes with the ring gear. A further drive unit may be permanently engaged with the blade ring. As shown in Fig. 1, the shutter is provided with a blade-driving ring 16 which has an inner ring gear 15 meshing with the five pinions 14 on the shafts 13 carrying the shutter blades 12 and an outer ring gear 17 with which meshes the driving pinion 22 of the fixed drive unit 20 and with which may also mesh one or more of the driving pinions 22 of the movable drive units 21. Each movable drive unit 21 has a pawl 91 which engages the pinion 22 before it disengages from the ring gear 17, and the power of the spring drive of each unit, fixed or movable, may be adjusted initially by pawl-and-ratchet means. The speedsetting ring 35, Fig. 6, has a finger-piece 6 and is carried for limited rotation on pins engaging the slots 112 therein. The ring 35 carries a number of stop members 36. Fig. 1, lying in the path of the arm 37 of the latch 35<SP>1</SP>, which latch is urged counter clockwise by a spring 39 against a stop pin 41. The ring 16 is moved counterclockwise in shutter-setting by means of the lever 5 (not' shown) which rotates a pinion 71 normally out of engagement with the ring gear 17 but engaged therewith for setting by the movement of a re-setting slide which rocks a lever 74 carrying the pinion 71. In the set position, the lug 33 on the ring 16 is engaged by the latch 34 having a lug engaged by the shutter trigger 4, the other side of the lug 33 being engaged by the latch 35<SP>1</SP>, which is thus restrained from counterclockwise movement towards the stop 41, the arm 37 lying between two of the stop members 36 accordingly preventing movement of the ring 35 sufficient to change the shutter speed while it is in this set position. When the trigger 4 is actuated to trip the shutter, two cover blades provided to prevent exposure during setting are opened and the lug 33 moves out of the path of the latch 35<SP>1</SP> to permit it to turn to remove the arm 37 from the path of the stops 36, so that the ring 35 may be turned to change the shutter speed before the next setting operation. Near the end of the bladeopening movement of the ring 16, the lug 33 strikes the nose 55 of a latch 48 and is caught between this and a second latch 52, a pin 56 carried by the ring 16 striking a spring 57 to slow down the ring and to cause sufficient rebound to effect the latching. To effect further retardation, a lug 63, Fig. 8, on the pinion 22 of the fixed drive unit strikes, during the anticlockwise shutter-opening rotation of the pinion 22, a projection 70 on the loose ratchet segment 64 to which is attached the end of the spring 67, the resulting tensioning of which retards the pinion 22. The pawl 65, which engages the ratchet 64 under the action of the spring 65<SP>1</SP>, has a lug 87 engaged by the lug 88 on the lever 84 under the action of the spring 89, and in the exposure movement of the ratchet 64, a lug (not shown) carried by the pinion 22, en- .gages and slips past the lever 84 which turns clockwise relative to the pawl 65. In the re-setting movement, the pinion 22 turns clockwise and the lug strikes the lever 84 to release the pawl 65 from the ratchet 64 and permit the ratchet to swing clockwise until it strikes the resilient stop 85, the impact on which may, if desired, be reduced by the provision of a simple gear retard. The lever 74, Fig. 1, rocked by the re-setting slide to bring the pinion 71 into contact with the ring gear 17 also moves a lever to release the latches 48, 52 via the pin-and-slot connection 80, 81. Each pawl 91 is urged by a spring 93 towards its associated pinion 22 and has a flange 94 riding on the periphery of the speed setting ring '35, Figs. 1 and 6, which has notches 96. Adjustable pins 98 of the movable drive units 21 engage with cam surfaces 97 on the inner periphery of the ring 35. When a drive unit is disengaged, the flange 94 bears on the circular outer part of the ring '35 and the pawl 91 engages with the pinion 22, while the pin 98 engages the lower inner part 97<SP>1</SP> of the ring 35. On turning the ring 35 counterclockwise, the higher part of 97 of the ring moves the pinion 22 into engagement with the ring gear 17 and the pawl 91 follows and still restrains the pinion 22 from movement, since the flange 94 enters the notch 96. As the pinion 22 meshes with the ring gear 17, the flange 94 rides out of the notch 96 and the pawl 91 disengages. The reverse action takes place as the ring 35 is moved to bring a pinion 22 out of mesh with the ring gear 17. The cam 'surfaces 97 and the notches 96 are so located on the ring 35 to bring the appropriate driving units into operation according to the speed desired. A retarding mechanism for slower speeds comprises a pinion 103, Fig. 1, mounted with a weight 105 on the shaft 104 and engaged by the pivoted gear segment 102 on the shaft 101. The segment 102 has a tail 102<SP>1</SP> carrying a pin 110 spring-urged into contact with the cam surface 111, Fig. 6, of the ring 35. When the ring 35 is appropriately positioned, a lug 106, Fig. 1, on the blade ring 16 engages, in the clockwise opening movement of the ring 16, a pawl 100 also on the shaft 101, and the lever portion 107 of the pawl 100 engages a lug 108 on the segment 102, and the movement of the ring 16 is thereby retarded. In setting, the lug 106 again engages the pawl 100, but the lever 107 moves idly relative to the segment 102. In an 'aircraft camera; the setting lever 5 may be operated by a motor through a onerevolution clutch.