GB447958A - Improvements in photo-electric sound pick-ups - Google Patents

Abstract

447,958. Gramophone pick-ups. JOHNSON, R. G., 21, South Oswald Road, Edinburgh.-(Johnson, E. N.; 24, Westminster Court, Highlands Road, Yeoville, Johannesburg, South Africa) Oct. 23, 1934, No. 29023/35. Divided out of 443,981. [Class 40 (iv)] Relates to photoelectric sound pickups of the kind in which the oscillating stylus carrier supports a mirror 14 whereby a beam of light 20 is influenced in accordance with the movement of the stylus and in turn varies the current in a circuit including a photoelectric cell 22. In order to provide a carrier of small moment of inertia, the stylus 17 is mounted in a socket 15 formed directly on a spindle 5 and is clamped by a screw 13 passing through a bore in the spindle, while the spindle is resiliently mounted by means of surrounding rubber sleeves in bearings 7 and has the mirror 14 directly secured to one end. The bearings 7 are arranged on plates 3 pivotally mounted on the end 2 of the tone arm, and the plates 3, after being adjusted to grip the sleeves 6, are secured by bolts passing through the plates, the tone-arm and a clamping-member 4. A rubber sleeve 19 surrounding the socket 15 is located in a socket 18 in the tone-arm 2. In this way the stylus 17 follows the sound-track by executing pivotal movements about the spindle 5 against the damping and centralizing action of the rubber sleeves 6, 19. The variation in the intensity of the reflected beam of light falling upon the photo-electric cell 22 is produced by means of a fixed cut-off 21. According to the Provisional Specification, the bearings 7 may be formed in plates arranged in superposed instead of collateral relationship.