Patent GB-571030-A (GB)
Title: Improvements in or relating to photographic shutters having built-in flash lamp synchronizing devices
IPC: G03B9/70
Filed: 1943-08-06
Abstract: 571,030. Photographic shutters. KODAK, Ltd. Aug. 6, 1943, No. 12719. Convention date, Aug. 7, 1942. [Class 98 (i)] In a shutter of the setting type having a built-in synchronizing device for synchronizing the flash of a flashbulb and the opening of the shutter when making instantaneous exposures, a master member connected to the setting member by a lost motion connection which permits movement of the setting member relatively to the master member after the latter has been set, the setting member and master member being-temporarily held in the set condition by shutter releasing means, and a synchronizing device including a normally open switch adapted to be closed by movement of the setting member from its set position and while the latter is moving idly with respect to the master member, means actuated by the setting member are provided for retarding the movement thereof after the setting member has closed the switch and before it releases the master member, whereby the desired delay occurs between the closing of the lamp circuit and opening of the shutter in accordance with the lag of a given flashbulb. As shown, the shutter comprises a casing 10 having a mechanism plate 11 and a flange 12 provided with slots 13, 15 through which extend the release trigger 14 and the setting member 16. A spring 20 is attached at one end to a pivoted master member 17 and at the other to a pin 22. The wall 24 of a slot in the master member ends in a shoulder 25. The setting member 16 has an arcuate portion 26 mounted in an arcuate slot so that the member can move between a set and unset position. On moving to the set position, a pin 27 engages the wall 24 and rotates member 17 clockwise to tension the spring 20 and then moves over shoulder 25 to hold the shutter set. The member 16 is urged counter-clockwise by the spring 29, and is releasably held in set position by a nose 31 on the trigger 14 engaging an upturned lug 32 on the end of the portion 26. The trigger 14 is biassed clockwise by a spring 33. On depressing the trigger, the member 16 is released, but the member 17 is not released until the pin 27 has left shoulder 25 and entered the slot. The member 17 carries a pivoted latch 35 having a hook 37 engaging a pin 38 carried by the blade ring 39. The trigger 14 may have an arm 41 co-operating with a cable release. The lug 45 on the setting member extension 26 closes a normally open switch in the flashbulb circuit on movement of member 16 but prior to movement of member 17 and engages means retarding the movement of member 16 between the closing of the switch and the release of member 17. The switch includes a pivoted contact 47 comprising an insulating arm 48 fixed to a rotatable sleeve 49 carrying a metal arm 53 having two lugs 54 embracing the edges of arm 48 and a tail 55 engaged by spring 56. The arm 48 carries a metal pin 51 electrically connected to the jack 57 insulated from flange 12 by an insulated wire 58. A pivoted lever 60 has a nose portion 62 adapted to engage the pin 51 to close the circuit. A jack 63 electrically connected to the lever 60 through the casing receives a plug connected to a circuit including a flashbulb L and a battery B. On movement of member 16 from the set position the lug 45 pivots the lever 60 to close the switch. A gear segment 70 forming one end of lever 60 meshes with a pinion 71 fixed to a fly-wheel 72 and retards the movement of the setting member towards its unset position. Other gears may be included. A finger 75 on the arm 53 engages a rotatable cam surrounding the lens barrel and having a pointer co-operating with a scale marked in millisecond lags, operation of the pointer varying the spacing of the switch contacts. To compensate for shutter lag with instantaneously flashing lamps, an insulated third contact 83 is engaged by a lug on the blade ring 39 when the shutter blades are fully open, and is connected to jack 57 or to a third jack. When using such lamps, contacts 51 and 62 are prevented from contacting by a high part on the rotatable cam corresponding with the zero point on the lag scale. Specifications 523,136 and 537,208 are referred to.