GB384684A - Improvements in and relating to sound reproducing apparatus - Google Patents

Abstract

384,684. Optical sound reproducing apparatus. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Taylor, J. B. ; 1279, Lowell Road, Schenectady, New York, U.S.A.) June 19,1931, No. 17816. Convention date, June 20, 1930. [Class 40 (ii).] Comprises a sound-reproducing apparatus adapted for use in playing, examining, and analysing any desired portion of a film sound record. The sound film 4, Fig. 1, is fed through a casing 1 by a sprocket 31. Journalled in bearings in the casing 1 and in a plate 7, Fig. 2, rigid therewith, is a shaft 8 to which is secured an optical system 9. On the shaft 8 is mounted freely a drum 12 which supports the sound film 4, one edge of.the film overhanging the end of the drum. The optical system 9 is provided with a bracket 15 to which is secured a photo-electric cell 16. After passage through the sound record, the reproducing light beam is reflected on to the cell 16 by a mirror 18 carried by a bracket 19 which is mounted pivotally at 20 to the casing of the optical system 9. Electric current for the light source of the optical-system and the photoelectric cell 16 is supplied by leads which are run through the shaft 18 and 'are connected with clip rings 25 which contact with brushes 26. A worm 29 on the shaft of the driving motor 28 meshes with a worm wheel 30 which transmits rotary movement to the optical system 9 and to the sprocket 31 by means of a differential device 34 so that the optical system and the film are given a relative speed suitable for sound reproduction. Mounted on the shaft 39 of the sprocket 31 and on the shaft 8 are brake discs 40, 41, respectively, against one or the other of which a brake 42 is adapted to be passed. The brake 42 is mounted on an arm 43 pivoted to the casing 1 and biased to engage either of the brake discs by a spring 45. By means of a finger-piece 46 the brake may be thrown from one brake-disc to the other. For ordinary sound reproduction, the apparatus is operated with the brake 42 engaging the disc 41 so that the optical system 9 is held stationary while the film is fed through the machine. If repetition of the reproduction from a particular part of the record is desired, the brake 42 is made to engage the disc 40 to stop the movement of the film and allow rotation of the optical system 9 so that reproduction of that part of the record supported by the drum is repeated. For more closely locating a particular word or tone, two shields 48, 49 rotatably .mounted on the bearing of the shaft 8 are adjusted so that only the required portion of the record is available between the adjacent edges of the shields for passage of the light beam therethrough.