Patent GB-539136-A (GB)
Title: Improvements in or relating to focal plane shutters for photographic cameras
IPC: G03B9/34
Filed: 1940-08-27
Abstract: 539,136. Photographic focal-plane shutters. KODAK, Ltd. Aug. 27, 1940. No. 13526. Convention date, Oct. 17, 1939. [Class 98 (i)] In a focal-plane shutter comprising a pair of curtains defining a variable-width slot, a pair of co-axial spools for receiving tapes on the leading curtain, a co-axial drum between the spools for receiving the following curtain, and spring rollers to which the other ends of the curtains are attached, the end spools are wound from the drum or drum shaft, through a clutch which permits, without manual adjustment the continued winding of the drum to form the slit after the spools are latched and also rotation of the drum in either direction relatively to the spools to decrease or increase the slot. In the form shown, the following curtain F.C. is wound on a drum 19 secured to a shaft 18, and tapes 15 from the leading curtain are wound on spools 16, 17 loosely mounted on the same shaft. The upper spool 16 is rotated from the shaft 18 during winding by a one-way drive friction clutch formed by a coil spring 46 which surrounds both the shaft 18 and a sleeve 45 having a flange 44 on which is a pawl 41 which drives a ratchet 42 on the spool. The winding movement of the spool 16 is limited by a lost-motion washer 53, a lug on which is engaged by a pin 51 on the spool and which rotates until a lug 52 on it engages a fixed pin 54. At this time a pivoted latch 56 engages a notch in the flange 44, so preventing reverse movement of the spool 16, which is thus locked against rotation in either direction. Continued rotation of the shaft 78 winds the following curtain further on to the drum 19 to form the slit, the spring clutch 18 slipping during such movement. The lower tape spool 17 is urged by a spring 47 connecting it to the drum 19 to turn so that it always maintains the lower tape 15 taut. Rotation of the drum 19 is limited by lost-motion means comprising loose washers 61, 65 and the spool 17, which are provided with co-operating lugs and pins so that a lost-motion drive is imparted from the drum to the washer 65, which is finally arrested by engaging a fixed pin. The speed-adjusting knob 3 is carried by a shaft 70 rotatably mounted on a pivoted arm 71 which rocks when the edge of the knob is pressed so that a gear 75 on the shaft 70 meshes with a gear 76 on a shaft 35, Figs. 7, 9. The gear 76, a speed-indicating dial plate 5, and a gear 36 are normally clutched to the shaft 35 by a plate 78 urged radially outwards by a spring to cause an arm 79 carried by it and engaging a radial slot in a washer 100 secured to the shaft to engage selectively one of a number of notches so formed in the gear 36 and corresponding to the speed graduations on the plate 5. When the gear 75 engages the gear 76 an extension 82 of the arm 71 moves the plate 78 to unclutch the gear 36, which is then rotated to the desired setting by rotation of the speed-adjusting knob 3, the shaft 18 being simultaneously rotated through gears 37, 39, 40 to adjust the slit, while the spring clutch 46 slips. On release of the speed-adjusting knob the arm 71 moves under spring action to disengage the gear 75 and allows the latch arm 79 to lock the gear 36 to the shaft 35. The shutter is wound by oscillating an arm which, as described in Specification 513,738, rotates a gear 26 on a stub shaft 30 concentric with the shaft 35, from which gear the film-winding spindle (not shown) is driven. A single-toothed ratchet 31 secured to the shaft 30 engages a pawl 32 pivoted on a disc-form extension 34 of the shaft 35, which is thus rotated, the gear 36 on the shaft rotating the shaft 18 through the gears 37, 39, 40. Depression of the release knob rocks a bell-crank 84 which through a link 86 swings a release lever 87. A pin 90 on this lever engages a cam finger 91 on a shaft 92 carrying the latch 56 which is thus disengaged from the notch in the disc 44, and immediately after an arm 69 of the lever 87 disengages the pawl 32 from the ratchet 31. Both curtains are thus freed to make the exposure, during which the spool 16 is latched to the drum 19 by the pawl and ratchet 41, 42. After the exposure, the following curtain moves further to close the slit the pawl 41 moving over the ratchet. As shown, the spools 16, 17 may be of a different diameter from that of the drum 19, so that the width of the slit varies during the exposure to compensate for change in the speed of the curtains, as described in Specification 532,852. Specification 537,068 also is referred to.