GB437783A - Improvements in or relating to vibration translating devices such as electric reproducers for use with sound records - Google Patents

Abstract

437,783. Phonographic reproducers. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.- (Assignees of Wiebusch, C. F. ; 417, West 114th Street, New York, U.S.A.) Feb. 26, 1935, No. 6128. Convention date, March 3, 1934. [Class 40 (iv)] In a vibrationtranslating device such as a pick-up for sound records in which the low frequencies are attenuated, a damped resilient connection is provided between the magnetic system and the vibrating armature or coil such that at low frequencies, e.g. at 50-100 cycles per second, the magnetic structure vibrates out of phase with the vibrating armature or coil, increasing the relative velocity of the generating element with respect to the field and so increasing the output. In addition, the magnetic structure may be mounted on a damped resilient support. As shown in Figs. 1 and 3, a coil 18 moving in the annular gap between poles 22, 23 of a magnet 15 is carried on one end of the L-shaped stylus arm 19. The pivot 20 of the stylus arm is mounted in a rubber bearing between brass plates 27, 28, the plate 28 having a forked arm 281 which extends on each side of the stylus arm to form a guard. Additional damping for the stylus arm is provided by a rubber pad 30 pressed against a rod or wire 32 on the stylus arm by a cover-plate 31. The frame 16 which carries the magnet 15 may be mounted on a thin flexible plate 33 and its movements damped by a rubber pad 34 secured to the frame 16 and the support 161. Formulae are given connecting the relative velocity of the generating elements with the velocity of the stylus tip and the mechanical constants of the reproducer, and the selection of suitable mechanical constants is discussed.