GB340219A - Improvements in electromagnetic devices for reproducing or recording sound - Google Patents

Abstract

340,219. Phonographic recorders and reproducers. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.-(Assignees of Jones, W. C. ; 262, State Street, Flushing, New York, U.S.A.) Sept. 20, 1929, No. 28605. Convention date, Dec. 19, 1928. [Class 40 (iv).] An electromagnetic vibration translating device, such as a sound reproducer or recorder, of the kind in which the casing is filled with a viscous damping material, comprises a four-gap magnetic structure and a diaphragm which forms a closure for the casing and serves as a pivot for the armature. As shown, a T-shaped armature 7 has its reed portion 1 protruding through the diaphragm 3 into the gap between pole pieces 6 of a magnet 11. The ends of the armature 7 are arranged to form gaps 8, 9 between further pole pieces 10 secured to the pieces 6. Coils 4 surround the pole pieces 10. The diaphragm does not form an essential part of the magnetic circuit, Fig. 5 showing the flux path when the device is at rest, and Fig. 6 the flux path when the device is used as a phonograph reproducer. A diameter of the diaphragm serves as the pivotal axis of the reed, this diameter being stiffened by a strip 5. The pole pieces 6, 10 are connected by a bridge piece 14, which is formed with apertures for engagement by a suitable tool for adjusting the position of the pole pieces. In a modification, a single coil surrounds the armature, and the pole pieces 10 are bent at right angles. Specifications 231,216 and 290,264, [both in Class 40 (iv), Telephones &c.], are referred to.