GB607848A - Improvements relating to gramophone pick-up and recording devices - Google Patents

Abstract

607,848. Gramophone pick-ups. BAKER, D. J. March 14, 1946, No. 7991. Convention date, March 12, 1945. [Class 40 (iv)] A recording or reproducing head comprises a horizontal magnetic reed clamped at one end and with its other end free to oscillate in a horizontal plane between the poles of a magnet and carrying the stylus substantially at right angles to its axis. The reed has a natural frequency in the upper audio-frequency range. The reed 8, Figs. 1, 2, is a flat strip of magnetic material, rigidly secured at one end to a metal block 6, set in a vertical plane and surrounded by a coil 12 which may be wound directly on it or spaced by means of a former. The free end has the stylus 9 permanently secured to it and vibrates in the vertical air-gap between the poles of a magnet 5, Fig. 3. The moulded plastic body of the pick-up provides emplacements for the block 6 and magnet 5 and also has two pillars 14 between the reed and which there is damping material 13. The reed may be laminated or may be constructed so as to be relatively rigid over the greater part of its length, but flexible at the extreme end. This assists in obtaining a high resonance frequency which is preferably of the order of 10,000 c.p.s. A rubber washer 10 may surround the stylus to exclude dust. In another construction, the reed is made short in length and the block 6 is set correspondingly close to the magnet, Fig. 6 (not shown). The Specification also describes a modification in which a second coil, of similar magnetic characteristics to that on the reed, is mounted adjacent to the latter and connected in opposition to it, so as to overcome the effects of external magnetic fields.