Patent GB-655511-A (GB)
Title: Improvements in or relating to photographic shutters having built-in flash-lamp synchronising means
IPC: G03B9/70
Filed: 1948-10-11
Abstract: 655,511. Photographic shutters; shutters combined with flash-lamps. CLIFFORD, T. W., WRIGHT, L., TILLEY, B., TILLEY, G. C., [Representatives of TILLEY, N. S.], and TAYLOR, TAYLOR & HOBSON, Ltd. Oct. 11, 1948, No. 26432. [Class 98 (i)] In a photographic shutter having a master member controlling the opening and closing of the shutter which is set prior to each exposure and also having a built-in flashlamp synchronizing means, said means comprises intermediate mechanism through which the master member actuates the flash-lamp circuit contacts, a setting member manually operable from outside the shutter casing, and means whereby the setting member brings the intermediate mechanism into or retracts it from the effective path of the master member and also determines the speed of the master member during its operative engagement with the intermediate mechanism. Preferably the timing of the start of the period during which the contacts are held closed, relatively to the shutter reaching its open position, is advanced or retarded by advancing or retarding the time of engagement between the master member and the intermediate mechanism, while the termination of said period succeeds the shutter reaching its fully open position for all positions of adjustment of the setting member for the intermediate mechanism. The synchronizing means may also comprise retardation means movable into or retractable from the effective path of the master member by said setting member which, when in an off position retracts both the intermediate mechanism and the retardation means from out of the effective path of the master member, while when in an "on" position, brings the intermediate mechanism into said path, with or without the retardation-means according to duration of the lamp energization period required, movement of the setting member within the " on " range progressively increasing or decreasing the effective retardation applied to the master member by the retardation means. As shown, shutter blades 20 are pivoted on a mechanism base-plate 1 and pin- and-slot connected at 22, 23 to a blade ring 19, which carries a pin 18 engaging a slot 17 in a bell-crank lever 14 pivoted on the base 1 at 10. A master member ring 5 having a cam 7 which engages the bell-crank lever 14 is set by rotating it clockwise against the action of its driving spring 6 and is held set by the nose of a pivoted latch 25 engaging a hook 24 on the ring. On depressing the release trigger 28, whose movement is limited by a lever 32 pivoted at 33, the master ring latch is released and the nose 8 of a lever 9, also pivoted at 10 and spring-urged anticlockwise against a lug 13 on the lever 14, is engaged by the cam 7 so that it turns the lever 14 anticlockwise against its spring 15, so that the blade ring opens the shutter, which remains open while the nose 8 moves along the periphery 7<SP>1</SP> of the cam 7 and is then closed by the nose moving down the cam slope 32 and allowing the spring 15 to return the lever 14 to its initial position. An extension 40 of the master ring 5 is arranged so that, when the blades are fully opened, it engages a sector gear 41 forming part of a pallet and star-wheel type of retard train 43, the duration of the shutter opening being determined by the initial position of the sector gear whereby different exposures are obtained. During setting, the cam 7 rotates the lever 9 clockwise against its spring so that the cam passes between the nose 8 and the outer shutter wall 2, the shutter thus remaining closed during setting. A flashlamp synchronizing mechanism, comprising contact closing means engaged by the master ring 5 and also retarding means for said ring, is mounted between two plates 93, 94 secured as a unit in the shutter at 95, 96. The retarding means comprises a lug 74 on a pawl 73 pivoted at 72 on an inertia wheel 61 which is spring-urged anticlockwise and geared to a star-wheel 68 and pallet 70. The pawl 73 is spring-urged clockwise so that its tail engages the pivot of the wheel 61, thereby limiting its clockwise movement, but can be moved against its spring so as to ride on the ring 5 during setting of the shutter. The disposition of the pawl, and hence the retardation applied to the master ring by engagement of the pawl with the hook 24, is determined by the cam 76 on an eccentric pivoted at 66 and manually movable by a knob (not shown), engaging in a forked extension 77 of said eccentric which also carries cams 79, 80. Bell-crank levers 53, 54 freely mounted on a pivot 55 are provided with lugs 58, 59 for engagement with the outer faces of cam extensions 40, 60 on the master ring, and the tails 81, 82 of said levers, controlled by the cams 79, 80 determine the closing of contacts 46, 47 by the arms 52, 51 which are urged clockwise by springs 56, 57 but held clear of the contacts by a return leaf-spring 48. When the flashlamp lag setting member 77 is moved to its extreme anticlockwise position, the cams 79, 80 rotate both bell-crank levers anticlockwise so that their lugs 58, 59 are out of the path of the cams 40, 60 and the cam 76 holds the retardation lug 74 out of the path of the hook 24 so that on operating the release trigger an ordinary daylight exposure is made. On moving the member 77 a short distance clockwise to the position for synchronizing lamps of zero lag shown in Fig. 7, the cam 76 still holds the lug 74 clear of the hook 24 and cam 79 still holds the lug 58 clear of the cam 40, but cam 80 allows the lug 59 to move into the path of the cam 60. Thus on operating the trigger 28, the cam 60 rotates the lever 54 to close the contacts 46, 47, this being arranged to occur as the cam 40 meets the retard sector gear 41, the blades then being fully opened. For lamps of finite lag, the member 77 is moved still further clockwise, so that the lug 74 moves into the path of the hook 24 and the lug 58 moves into the path of the cam 40. On releasing the master ring 5, the arm 52 of the lever 53 is caused to close the contacts 46, 47 and then the hook 24 meets the retardation lug 74 slowing the master ring by an amount which accounts for the lag of the lamp. Soon after the closing of the contacts, the lug 58 slides off the cam 40 but the contacts are held closed by the cam 60 engaging the lug 59 prior to the lug 58 leaving the cam 60, the contacts remaining closed whilst the shutter is fully open as determined by the sector gear 41. Due to the return spring 48, the lugs 58, 59 are caused to ride up the ramp-like rear faces 44, 49 of the cams 40, 60, thereby preventing closing of the contacts during setting. In a modification (Fig. 9, not shown), only a single bell-crank lever is employed for closing the contacts, two master ring hooks being provided, so that by suitable setting of the master ring a single lever can perform the function of both levers 53, 54, the construction being otherwise largely identical with that of the first embodiment. The Provisional Specification describes a modification in which the shutter master ring is provided with two hooks so that the ring may be latched set in either of two positions as in the embodiment of Fig. 9, while the contacts are closed by a bell-crank lever for lamps of finite lag and by two spring-connected pivoted levers which move together when the synchronizer is set for instantaneous flashlamps.