Patent GB-555136-A (GB)
Title: Improvements in or relating to photographic camera shutters
IPC: G03B9/08
Filed: 1942-02-03
Abstract: 555,136. Photographic shutters. KODAK, Ltd. Feb. 3, 1942, No. 1441. Convention date, March 28, 1941. [Class 98 (i)] In a shutter of the type which is set before the exposure and comprises a pair of shutter members which are moved one after the other on release, the leading member is held before release by a latch and the following member by a selected one of two latches associated respectively with mechanisms for determining exposures in a high and a low speed range. The shutter shown. is similar to that described in Specification 537,914, and comprises first and second shutter plates 18, 19 slidably mounted by means of rollers 20 carried by them and engaging rails 16, 17, the plates having portions 21, 22 which extend rearwardly towards the focal plane and forming between them an exposure slit which passes across the exposure opening 23. The plates 18, 19 are moved independently by a spring 24 the ends of which are secured to them, and are moved to set the shutter by the operation of the filmwinding knob which, as described in the Specification above referred to, causes a lever 28 to swing clockwise about its pivot 29 and engage a roller 31 on the plate 18, which is thereby moved to the left and carries the plate 19 before it. The plate 18 is retained in the set position by a pivoted latch 33 which engages a bracket 32 on it, and the plate 19 is held either by a latch 40 engaging a pin 41, or by a latch 42 engaging a rack element 43, according to whether a high or low speed automatic exposure is to be given. In the first case, i.e. for exposures of from <SP>1</SP>/ 25  to <SP>1</SP>/ 1000  of a second, the operation of a dial member adjusts the slidable member 46 of a two-part lever pivoted at 45 and carrying the latch element 40, thereby altering the lateral position of a cam 48 formed on the member 46, as described in Specification 537,914. Depression of the shutter release disengages the latch 33, releasing the first plate 18. When this has moved sufficiently to form a slit corresponding to the speed setting the bracket 32 engages the cam 48 and rocks the lever 46 to disengage the latch 40, 41, thereby releasing the second plate 19. To maintain the slit constant during the exposure the plates 18, 19 are locked together by a toothed spring-urged pawl 56, Fig. 12, pivoted at 55 to the plate 18 and engaging a bracket 60 on the plate 19. When the plate 18 is released the pawl slides over the bracket until the plate 19 is also released, when the flange 60 is maintained in engagement with the same tooth of the pawl owing to the spring tension on the plate 19 being adjusted to a higher value than that on the plate 18. On completion of the exposure, a flange 58 on the pawl runs up a fixed cam 59, so releasing the pawl and allowing the plate 19 to move to close the slit. When slow speeds of over <SP>1</SP>/ 25  of a second are to be used the high speed dial is adjusted to a neutral position, in which it slides the lever member 46 so that a cam 49 on it rides on to a pin 50, thus tilting the lever and disengaging the latch 40, 41. At the same time, interlocking means between the high and low speed setting dials; as described in Specification 555,137, is set so that the latter may be adjusted. The slow speeds are controlled by a gear retard mechanism driven by a hairpin spring 91 engaging an oscillatable arm 86 on the shaft of one of the gears. During setting of the shutter the lever 28 rocks an arm 95 having a pin and slot connection with it anticlockwise, so moving an arm 98 pivoted to the arm 95 to the left. The end 99 of the arm 98, which is guided in a horizontal path by a slotted flange 114 engaging a stud 107, moves a slide 100 having a cam face 101 which engages a pin 102 on the arm 86 and moves it to tension the driving spring 91 of the retard gear. When the shutter is set, the return movement of the lever 28 withdraws the arm 98 from the setting position, but the slide 100 is held by a lug 112 which is engaged by a pin 26 on the shutter plate 18. When the first plate 18 is released a spring 108 pulls back the slide 100, leaving arm 86 free to move under the action of spring 91 and of the retard gearing until a pin (not shown) on it strikes the tail 105 of the latch 42 and disengages it from the rack 43 on the second plate 19, which then moves. The retard gear and latch are mounted on a carriage 83 which is adjusted horizontally to vary the angular setting movement given to the arm 86 by the slide 100, and hence the time of the exposure. For this purpose, a pin 82, Fig. 6, on the carriage is engaged by a slot 81 in an arm 80 pivoted at 70 which is angularly adjusted by a heart-shaped cam 77 on the shaft of the slow-speed dial, the cam engaging lugs 79 on the sides of an opening in the arm. When the slow-speed dial is at neutral the carriage 83 is in the extreme left-hand position, in which the latch 42 lies to the lefthand side of the rack 43, and is therefore inoperative.