Patent GB-573910-A (GB)
Title: Improvements in or relating to roll-film photographic cameras and the like
IPC: G03B19/04
Filed: 1944-06-05
Abstract: 573,910. Photographic roll-film cameras. OLIVER, G. F. N. June 5, 1944, No. 8940/43. [Class 98 (i)] A photographic roll-film camera comprises a case, an objective in the case, film-feeding means for feeding film from a roll through the focal plane of the objective, a shutter having a constant width slit and mounted adjacent and parallel to the focal plane to move normal to the length of its slit substantially in its own plane, means biassing the shutter to move in one direction, a latch for retaining the shutter against such movement and operable to release the shutter for such movement, and a one-way operative connection between the film-feeding means and the shutter which actuation of the former to feed the film moves the latter against , the bias on it at substantially the same speed as the film is moved. As shown, the shutter comprises a slotted metal plate 15 pivoted at its upper and lower edges to pairs of levers 16, 17. Levers 17 are mounted on a spindle 32 carrying a toothed sector 33 meshing with a pinion 35 rigidly connected to a metal disc 37 (e.g. of aluminium or copper) rotatable between the polepieces 38, of the permanent magnet 40, the sector 33 and the plate 15 being urged upwardly by spring 41. Upward movement of plate 15 is restrained by a pivoted catch 42 engaging latch member 43 on the lever 17, a release trigger 46 bearing on the tail 45 of catch 42. Operation of trigger 46 releases shutter plate 15 to expose the film, the shutter speed being controlled by rotation of the disc 37 between the polepieces 38. The magnet 40 may be rotated by an external knob to adjust the shutter speed. The disc 37 may be of a metal having a substantially constant coefficient of resistivity to avoid temperature variations. The film is wound from spool 20 over rollers 22 and 23 and then downwardly in front of a presser plate 24 past the exposure position 14 to a take-up spool 25 rotatable by an external winding knob. The presser plate 24 is mounted by springs 26 on a cross-bar 27 mounted on a lever 28 extending downwardly into engagement with a cam 29 on the spindle of the takeup spool 25. The cam 29 has three notches and when the lever 28 drops into a notch the presser plate 24 engages the film. As soon as the winding knob is operated, the lever 28 is moved to relieve pressure on the film. The lever 28 is urged forwardly by a spring 30. The take-up spool 25 has three pins 47 each in turn engaging a lever 50 making a pin-and-slot connection with the lever 52 on the spindle 32. Since the spool 25 makes one-third of a turn to wind on a fresh section of film, operation of the winding- knob moves plate 15 down at approximately the same speed as the film to reset the shutter and at the same time to expose a portion of the film equal in width to the slit. These sections of the film are wasted. The shutter plate 15 may be arranged to move in a straight line, the relative sizes of pinion 35 and sector 33 may be varied to alter the speed range of the shutter, and the magnet may rotate and the conductor remain at rest. In a modification, the sector is not mounted directly on the spindle 32 and the ratio of the lever connection therebetween is adjustable.