Patent GB-565664-A (GB)
Title: Improvements in or relating to focal plane shutters for photographic cameras
IPC: G03B9/34
Filed: 1943-07-06
Abstract: 565,664. Photographic roller blind shutters. KODAK, Ltd. July 6, 1943, No. 10951. Convention date, July 17, 1942. [Class 98 (i)] Relates to shutters of the kind comprising a pair of blinds which move together over the exposure aperture with an exposure slot of pre-set width therebetween during instantaneous exposures, the said blinds being drawn across the exposure aperture from unwinding rollers by the pull of spring winding rollers when an exposure is made, the unwinding rollers comprising a pair of spaced co-axial rollers for receiving tapes on the leading blind, and a drum between said spools for receiving the following blind ; and relates more particularly to such shutters wherein means is provided for varying the width of the slot after the blinds have been wound. The invention consists mainly in improved means for varying the width of the exposure slot for instantaneous exposures, comprising a rotatable shutter speed setting member carrying a stop which limits the rotation of a member movable with one only of the blinds during the blind-winding operation in order to produce an exposure slot whose width depends on the set position of this stop, said setting and blind members carrying also coupling elements capable of being engaged with each other by an axial displacement of the setting member after the blind-winding operation, whereby both members may be rotated to adjust the position of one blind relatively to the other in order to produce any desired alteration of the setting effected during said winding operation. The invention includes also a gear train for winding the blinds, with a slip clutch between the gears operating the respective blinds, and provision for making " bulb " exposures. As shown, the leading and following blinds 1, 2 are connected on one side of the exposure aperture A respectively to spring rollers 3, 4, while on the other side of the aperture the tapes of blind 1 are connected to spaced rollers 7 pinned to a shaft 9, and the blind 2 is connected to a drum 8 turning loosely on shaft 9 between the rollers 7. The blind-winding mechanism comprises gears 15, 25, 28 mounted on a fixed stub shaft 26 ; gear .15 is coupled to the upper roller 7 through gears 13, 12 ; gear 25 is coupled to drum 8 through gears 24, 23, 21 ; and gear 28 is the prime mover, hand or power driven. Rotation of gear 28 is imparted to gear 25 through a single-tooth ratchet 29 fast with gear 28 and engaging a pawl 30 pivoted to gear 25; while rotation of gear 25 is imparted to gear 15 through a pawl 62 pivoted to gear 25 and engaging a ratchet wheel 61 turning freely on shaft 26 and carrying a slip clutch in the form of spring members 60 bearing frictionally against gear 15. The shutter setting device comprises a disc 41 secured to a shaft 43 whch is rotatable by a knob 44 and also displaceable axially against the action of a spring 45; the disc carries speed graduations visible through a window 42, and a pin 46 adapted to enter one of a series of holes 47 in the body B to lock the disc in adjusted position after it has been axially displaced by the knob 44, turned to the desired setting, and released. The setting movement causes a pin 48 depending from the disc to take up a position in which it will be encountered by a co-operating pin 49 on gear 15 at an earlier or later stage in the blind winding operation ; the encounter arrests the gear 15 and, therefore, also the blind 1, but owing to the provision of the slip clutch 60, the blind 2 continues to be wound, opening up between the blinds an exposure slot of the desired width. Should it now be desired to alter this width before making the exposure, this may be done by operating the knob 44 in precisely the same manner to set the disc to the new speed reading. To render this possible, advantage is taken of the fact that after the blind-winding operation the stops 48, 49 are in contact (Fig. 1) to provide coupling elements in the form of a pin 50, adjacent to pin 48 on the disc 41, adapted to enter a bore 51 in the pin-49 on gear 15 when the disc is axially displaced ; thus, disc 41 and gear 15 are coupled together, and rotation of the knob 44 to the new setting displaces blind 1 to adjust the exposure slot width, blind 2 meanwhile remaining stationary owing to the slip of clutch 60 if the slot is being widened, or owing to the slip of ratchet mechanism 61, 62 if the slot is being narrowed. The shutter release comprises a pivoted, spring-biassed trigger 34, an arm 33 on which trips the ratchet pawl 30 when the trigger is actuated, thus releasing the gears 25, 15, so that the spring rollers 3, 4 may operate to move the blinds, separated by the pre-set exposure slot, across the exposure aperture A. To provide for a " bulb " exposure, the disc 41 has a notch 65, Fig. 8, into which, when the disc is set to " bulb," a pin 163 on a spring- biassed lever 160 pivoted to the body B is adapted to drop ; this action causes a stop 66 carried by an arm 67 of the lever 160 to take up a position in the path of a stop 68 so placed on the gear 25 that, as the shutter runs down on release, blind 2 is prevented from following blind 1 across the exposure aperture A, the slip arrangement between the gears 15, 25 rendering this movement of blind 1 possible. The aperture A thus remains uncovered until pressure on the trigger 34 is released, when its spring 36 restores it to inoperative position, causing the arm 33 on the trigger to lift the arm 67 of the lever 160 so that the pin 163 rises out of the notch 65 in the disc 41 and the stop 66 moves out of the path of the stop 68, thereby setting free the gear 25 so that the spring roller 4 may operate to draw the blind 2 over the aperture A. Specification 565,666 is referred to.