GB872160A - - Google Patents

Abstract

872,160. Gramophone pick-ups. CLEVITE CORPORATION. Feb. 9, 1959 [Feb. 10, 1958 (2)], No. 4411/59. Class 40 (4). [Also in Group XL (b)] An electromechanical transducer element capable of simultaneous two-channel operation and particularly applicable to stereophonic recording and/or reproduction of sound on record discs is characterized by an elongated hollow body of radially polarized ferroelectric ceramic material having a longitudinal axis of symmetry and a plurality of electrodes forming three terminals, and in that the direction of polarization and arrangement of said electrodes are such that the maximum electrical potentials at two of said terminals with reference to the third terminal are associated with perpendicular planes of flexural deformation of said body. In the pick-up shown in Fig. 1, a tubular ceramic body, e.g. of barium titanate or lead zirconate titanate, is mounted on a flexible shaft 12 secured to a support 16 and provided with a stylus point 14. The body 20 is provided with external electrodes 22, 24, 26 and 28 and an internal electrode 30 and is polarized as indicated by the arrows P in Fig. 4. The electrodes are connected as shown to three terminals A, B and G. The external electrodes may be connected together by conductive strips applied to the body 20 and the connection to the internal electrode 30 may be made through the conductive surface of the shaft 12. Flexure of the body 20 in the vertical X-X<SP>1</SP> plane produces a maximum potential at terminal B with respect to terminal G and a minimum potential, effectively zero, at terminal A, while flexure in the horizontal Y-Y<SP>1</SP> plane produces a maximum potential at terminal A. Flexure in other planes produces respective potentials at terminals A and B which are proportional to the respective vector components of the displacement in the planes X-X<SP>1</SP> and Y-Y<SP>1</SP>. Two stereophonically related tracks, one " hill and dale " and the other " lateral " may thus be recorded or reproduced simultaneously. In an alternative embodiment, Fig. 9, the polarity of the polarization P is uniform around the body 20 and the connections to the terminals A, B and G are modified accordingly. Further alternatives comprise arranging the planes X-X<SP>1</SP> and Y-Y<SP>1</SP> at 45 degrees to the plane of the record disc and making the body 20 of square or other polygonal cross-section.