Patent GB-702493-A (GB)
Title: Improvements in or relating to photographic roller-blind shutters having continuously adjustable time-setting devices
IPC: G03B9/34
Filed: 1951-09-12
Abstract: 702,493. Photographic roller-blind shutters. LEITZ GES., E. Sept. 12, 1951 [Sept. 26, 1950], No. 21465/51. Class 98(1) In a photographic roller-blind shutter having a continuously adjustable time setting device, the two exposure effecting blinds being driven by independent springs, the first blind is releasable by operation of a shutter trigger device and the second blind is subsequently releasable during the release movement of the first blind by a latch disengaging an abutment on a blocking disc for holding the second blind set, the instant of disengagement of the latch from the abutment and thereby the time interval between the release of the two blinds being controlled by a release member displaceable by a setting cam operatively connected to and settable by a time-setting means of the camera which remains at rest during the release movement of the shutter, the release member being displaceable by the said setting cam in a substantially tangential direction relative to an abutment on a further disc rotatable in synchronism with the release movement of the first blind, the said release member being turned when abutting the abutment on the said further disc to cause the disengagement of the said latch and thereby the release of the second blind in dependence on the setting of the timesetting means. As shown, a double blind self-capping setting-type shutter of the kind described in Specification 481,520, in which during setting the tape rollers 4 of the first or opening blind secured on a shaft 3 are connected to the winding drum 5 of the second or closing blind freely mounted on said shaft by engagement of a slot 4c on one tape roller with a pin 10 on the drum 5 and the two separately spring-driven blinds of the shutter are held set due to this engagement by a one-way spring brake on the film winding shaft said brake acting also as a slipping clutch for the gear which is geared to the shaft. 3, is provided with a time setting means continuously adjustable by a knob 7 and comprising a set of cams 12a, 12b, 12c. On depressing the shutter trigger, the trigger rod disengages a gear in the train holding the shutter set thereby releasing the shaft 3 and tape rollers 4 while a spring on the base of the shutter frame is also depressed by the trigger and is followed by a shaft 14 to which is secured a lever 13. Thus the opening blind is released while the closing blind is held by the lever 13, which is spring urged clockwise against a fixed block 17, being in latching engagement with an abutment 11a which is freely mounted on the shaft 3 in a fork in which engages the pin 10 on the drum 5. As the rollers 4 rotate, a cam 9a on a disc 9 secured to the shaft 3 rotates with them and engages a release lever 20 moving it clockwise to bear against and move anti-clockwise a stud 16 on the lever 13 to release the closing blind. Fig. 2 shows the exposure controlling means set for a fast exposure. As the knob 7 and cams 12a-c are rotated anti-clockwise to adjust the shutter for longer exposures, the nose 19a on the lever 19 pivoted at 18 and spring-urged against the cam 12a moves steadily inwards so that the surface 20a of the lever 20 pivoted at 20d to the lever arm 19b and spring-urged against the stud 16 is withdrawn substantially tangentially to the left from the path of the cam 9a thereby increasing the exposure slot width by delaying the release of the closing blind. For still longer exposures, when the surface 20a has moved to its extreme left position, a finger 24 on a plate 22, pivoted at 23 and carrying a retard mechanism, is moved inwardly by a spring 22a in following the cam 12b so that a projection 31a on a gear sector 31 of a gear train 32 is brought into the path of an abutment 11b on the disc 11 to delay further the release of the closing blind. For the longest instantaneous exposures, a nose 25a on a lever 25 pivoted at 26 and bearing against the cam 12c moves inwardly so that an arm 25b allows a pallet 28 carried on an anti-clockwise-urged pivoted link 34 to engage with a star wheel 33 of the gear train, whereby still longer delays of the release of the second blind are produced. When the pallet is engaged with the star wheel, a cam 29 rotated by the shutter setting means causes lever 25 to disengage the pallet during setting. For bulb exposures, the cam 12a causes the lever 20 to be wholly withdrawn from the path of the cam 9a and the cam 12b moves the retard mechanism anti-clockwise to withdraw the projection 31a from the path of the abutment 11a. On depressing the trigger, the opening blind is released as usual, while the closing blind remains held by the latching lever 13 until the trigger is released when this rises to free the abutment 11a so that the closing blind is released to end the exposure.