Patent GB-626452-A (GB)
Title: Improvements in and relating to photographic cameras
IPC: G03B7/00
Filed: 1945-12-10
Abstract: 626,452. Photographic cameras. BILLON, M. M. M. Dec. 10, 1945, No. 33388. Convention date, June 15, 1939. [Classes 97 (i) and 98 (i)] The rotatable rings controlling adjustments of shutter speed and diaphragm aperture in a photographic camera are coupled together so that rotation of one ring causes a rotation of the other ring in a direction which compensates for the variation in the quantity of light admitted during an exposure consequent on the rotation of the first ring, and a setting member is connected .to the rings to rotate both to alter the quantity of light admitted. The coupling member is a differential gear, of which the cage is connected to or forms the setting member, which may be coupled to an extinction photometer. As shown, Figs. 3, 4, shutter speeds and diaphragm apertures are controlled by rotatable rings 1, 3 respectively. The rings are in part toothed to mesh with the sun wheels 4, 4<SP>1</SP> of a differential gear coupled by a number of planet wheels 6, 6<SP>1</SP> &c. on axles 7, 71 &c. Rotation of one ring thus causes an equal and opposite rotation of the other ; and the rings are so coupled to the shutter and diaphragm mechanisms that the quantity of light admitted during exposure is kept constant when either control is varied. This quantity of light is varied by adjusting the differential cage in accordance with the speed of the emulsion in use and the light value. The light value may be estimated independently, or, preferably, determined by means of an extinction photometer incorporated in the cage and including a fixed tube 10 carrying at one end a translucent disc 16 of peripherally stepped opacity. A tube 8 supporting the differential cage is mounted to rotate on the tube 10, and is slightly elliptical in cross-section to provide sufficient friction to prevent rotation of tube 8 except by manual adjustment of a knob 13, which has an eccentric aperture 15 just in front of the screen 16. A mirror 17 at the other end of tube 10 reflects light entering through the aperture 15 and passing through the screen 16 upwards to a tube 18. In operation, the knob 13 is rotated until half of the edge of aperture 15 becomes indistinct, viewed through the tube 18, and either the shutter speed or the diaphragm opening is set by means of the rings 1 or 3. Adjustment for emulsion speed is made, when necessary, by means of a scale of Scheiner degrees on a fixed flange 19 ; the number of an arbitrary scale on the tube 8 opposite the speed at which the instrument is calibrated is moved, after adjustment for extinction, opposite the speed number on the flange 19 corresponding to the speed of the emulsion in use. When the photometer is omitted, the tube 8 is set in accordance with an independant light intensity determination by means of the scales on the tube 8 and the flange 19. The Specification as open to inspection under Sect. 91 comprises also mechanism in which the control rings have locking means enabling them to be rotated together, and are so arranged that a rotation altering shutter speed is accompanied by an alteration in diaphragm aperture sufficient to keep the quantity of light admitted a constant determined by the relative positions of the rings when locked. A ring 1, Fig. 5 (Cancelled), coupled to the shutter speed control is locked to a ring coupled to the diaphragm control by a spring-urged locking member releasable by a knob 20 carrying an index. A part ring 24 slidable in grooves 23 on the ring 1 has an aperture which registers with marks H, PA or E on the ring 1, according to the season. A similar member 27, slidable in grooves 28 on the member 24, has an aperture 30 which registers with the appropriate film speed inscribed on the member 24. Knob 20 is depressed to release the rings which are rotated relatively to bring the index on the knob opposite the appropriate indication of a scale 31 on the member 27 according to weather conditions. This subject-matter does not appear in the Specification as accepted.