GB586979A - Dynamic phonograph pick-up - Google Patents

Abstract

586,979. Gramophone pick - ups. PHILCO RADIO & TELEVISION CORPORATION. Sept. 11, 1944, No. 17341. Convention date, Sept. 11, 1943. [Class 40 (iv)] [Also in Group XXXVI] A gramophone pick'-up of the moving-coil type comprises a coil-supporting member encircling and spaced from a supporting element carrying resilient means which engages the coil-supporting member at opposite points to provide resilient pivots for the coil-supporting member provided with a stylus whereby the coil is oscillated in a flux-traversed gap produced by a magnetic field structure. The pickup can be used alternatively for lateral-cut or hill-and-dale records by adjustment of the magnet system. The coil 22 carried by the cylindrical portion 19a of a member 19, of thin sheet material such as aluminium or parchment paper, having a conical portion 19b carrying a stylus 3, is oscillated in a gap formed between an enlarged portion of a centre polepiece 6<1> and polepieces 7, 8 associated with permanentlymagnetized blocks 10, 11, the latter block being adjustably secured by a bolt 16 to a non- magnetic spacer block 9, e.g. of brass. The coil supporting member 19 frictionally engages two blocks 25, 26 of soft rubber which are cemented into slots cut in the member 6<1>, and leave bevelled ends conforming to the conical portion 19b and extending below the member 61. The pick-up can be changed from lateralcut operation to hill-and-dale operation by rotating the magnetized block 11 through 180 degrees. In a modification, Figs. 8, 9, 10 (not shown), the blocks 25, 26 are replaced by a single U-shaped block located in a diametral plane of the member 6<1>. In a further modification, Figs. 12, 13 a single block 29 is secured in a slot 30 with enlarged ends merging into longitudinal slots 31, 32. This arrangement increases the vertical resilience of the mounting and enables a less resilient rubber to be employed. In a further modification, Figs. 14, 15, 18, limited to operation with lateral-cut recording the coil-supporting member 5, including the stylus 3 and the coil 22 is supported on resilient blocks 33, 34 located in recesses in the pole member 35 which is formed with an extension 35a located in a spacer block 36 of non-magnetic material. A permanentlymagnetized block 37 is secured to pole-pieces 40, 41 having extensions 40<1>, 41<1> which, together with the pole-piece 35 form the gap for the coil 22. Portions of the length of the leads 47, 48 from the coil 22 to terminal tags 45, 46 are encased between thick parchment paper laminae 49, 50 cemented together and forming a stiffened ribbon conductor 44, having its upper part 51 attached by adhesive to the block 36 and having its lower part curved and terminating in a straight portion 52, the ribbon being effective to damp movement of the member 5 greater than that occasioned by the grooves of the record.