Patent GB-546195-A (GB)
Title: Improvements in or relating to sound recording and reproducing apparatus
IPC: G11B7/00
Filed: 1941-03-27
Abstract: 546,195. Optical sound recording and reproducing apparatus. ELECTRICAL RESEARCH PRODUCTS, Inc. March 27, 1941, No. 4142. Convention date, April 3, 1940. [Class 40 (ii)] [Also in Group XX] An apparatus for recording and reproducing sound on and from multiple tracks on films comprises interchangeable sets of recording and reproducing devices. As shown, the supply reel 1, a take up reel 16, and a sound gate 7 with associated devices. are mounted in a casing on a base with uprights such as 17. The film is extracted through a light seal 2 from the supply reel 1 by a driven sprocket 3, and is drawn into the driven take-up reel 15 through another light seal from another driven sprocket 6. A spring-tensioned band-brake 40 provides uniform drag on the supply reel 1 during running and serves to stop the rotation of this reel when the driving motor is switched off. The sprockets 3, 6 are driven by worm gears 35, 34 from the shaft 31 of a motor 28, and the take-up reel 15 is driven by coiled spring belts from a pulley on the shaft of a wheel 39, driven by a pinion 38 on the shaft of the sprocket 6. A film footage counter is also driven by the motor shaft through a worni gear The sound-gate 7 is a drum driven by the film. The film is guided in relation to the sprockets 3, 6 and the soundgate 7 by rollers 5, 4, 8, 9, 101, 10, 11, 13, 14. In addition the film is pressed against the soundgate 7 by a roller 12 on one arm 54 of a lever pivoted at 55 and having its other arm 52 urged clockwise by a spring 56. This arm 52 is connected by a link 51 to an arm of a bellcrank lever 47 pivoted at 48 and carrying the roller 11 at the end of its other arm. A spring 57 urges the lever 47, counter clockwise. When the motor is started the comparatively strong pull on the film by the driven sprocket 6 causes the spring 57 to yield and the roller 12 to be applied firmly against the sound-gate 7 by the spring 56. This serves to ensure the drive of the sound-gate by the film. When the parts have speeded up, the tension in the film is substantially relaxed and the roller 12 presses only lightly on the sound-gate. To ensure a uniform speed of rotation, the shaft of the sound-gate 7 carries a fly-wheel device which may be as described in Specification 543,844. Reproducing units 69 .. 72 are detachably mounted at the top of pillars 17 and may be replaced by recording units which may be as described in Specification 544,600, [Group XL]. Corresponding optical units are detachably secured by bolts 27 just over the sound-gate drum 7, the recording units have terminal cylindrical lenses and the reproducing units have terminal spherical lenses. These lenses are spaced and staggered to co-operate with four tracks on the film lying over four grooves in the sound-gate drum 7. Glass rods 61 .. 64 extend from inside these grooves to photoelectric cells 65 .. 68 in a compartment closed by a cover 30. The cells are detachably mounted in sockets on a vertical panel resiliently secured by brackets to standards, amplifiers (not shown) are mounted on a chassis attached to the panel. The cells are connected to loud speakers and these may be used for monitoring during recording.