Patent GB-391139-A (GB)
Title: Improvements in or relating to electrical phonograph reproducers
IPC: H04R1/16
Filed: 1931-10-16
Abstract: 391,139. Gramophone pick-ups. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.- (Assignees of King, J. H. ; 28, Green Avenue, Amityville, New York, U.S.A.) Oct. 16, 1931, No. 28827. Convention date, Dec. 12,-1930. [Class 40 (iv).] A moving coil phonograph reproducer in which the coil is rigidly connected to a coaxial stylus and moves axially in a radial magnetic field has the coil and stylus supported by resilient supports spaced apart from one another in an axial direction and having low stiffness in the direction of the axis of the coil and relatively great stiffness in all directions perpendicular to the axis, the supports comprising perforated discs or washers whose inner and outer peripheral surfaces engage the coil and stylus assembly and the body of the reproducer respectively over the whole or a major portion of their circumferences. The gramophone pick-up shown in Fig. 1 comprises a magnet 1 contacting at its ends with magnetic members 2, 3 and beld in position by a setscrew 4 in the U-shaped bracket 5, the bent over ends of which engage a hole 6 in each side of a U-shaped nonmagnetic member 7 which is rigidly connected to the member 2 and the block 8 of insulating material. A polepiece 9 secured in the member 3 by screw 10 projects downwardly into a hole 11 in the member 2 to form an annular air gap 12. In this gap is located a coil 13 wound on a cup member 14 which is connected to a metal tube 15 in the lower end of which is cemented the stylus 16. The tube 15 is supported by very resilient rubber discs 17, 18 which engage recesses 19, 20 in members 21, 22 which are held together by screws 23 to form a housing. This housing is attached to the body of the pick-up before the polepiece 9 is put in place, the screws 24 fitting loosely in holes in the members 21, 22 so that the coil 13 can be accurately centred in the gap 12 by a mandrel inserted in the member 3 and fitting tightly into the member 14, after which the screws 24 are tightened up. The housing is closed by a dust cover 25. Plug terminals 27 embedded in the insulating material 8 serve both as an electrical connection between the coil 13 and the external circuit and as a mechanical connection for attaching the pickup to its supporting arm. If desired, more than two discs may be employed for supporting the tube 15 and the discs may increase in thickness from the stylus upwards, Fig. 3 (not shown), or, as shown in Fig. 4, the resilent mounting 33 may be all in one piece and adapted to support the tube 15 at two, three or more positions, the relative thicknesses of the projecting portions being varied, if desired. The lateral stiffness of the supports may be increased by making the recesses 19, 20, Fig. 1, of slightly smaller diameter than the discs 17, 18 so that when the housing is assembled, the tightening of the screws 23 compresses the discs towards the tube 15. According to a further modification, the members 17, 18 may be perforated so as to form segments of a circle contacting with the tube over the major portion of its circumference. Specification 363,449 is referred to.