GB518491A - Improvements in or relating to vibration translating devices such as loudspeakers orphonographic pick-ups - Google Patents

Abstract

518,491. Loud-speakers ; gramophone pick-ups. EICHHORN, C. E. Aug. 18, 1938, No. 24343. [Class 40 (iv)] In a vibration translating device, such as a loudspeaker unit or a phonographic pick-up comprising a vibrating armature having a driving surface adjacent a magnetic air-gap, the driving faces of the armature and the magnetic air-gap are so constructed in relation to one another that the armature forms zones. which overlap the air-gap to different extents, for instance zones which are narrower than, of the same width as and of greater width than the air-gap, and which are distributed symmetrically over the entire extent of the driving face of the armature. As shown in Figs. 1, 3, an armature 1 of rectangular cross-section and of slightly greater width than the air-gap between the pole-pieces 7, 8 is formed at its driving face with oblique surfaces 2 formed by planes passing through the middle points of the sides and inclined at approximately 45 degrees to the plane of the air-gap. In modifications, Figs. 4 and 7, the gap-forming surfaces of the pole-pieces are of zig-zag or sinuous form, and in a further modification, Figs. 5, 11, the driving face of the armature is formed with circular recesses 12. The armature may be formed by a number of adjacent bars of which the ends are staggered on both sides of the central axis of the armature so that the driving face extends in a sinuous or zig-zag line. In one construction, Fig. 8, used. as a loud-speaker movement a sheet iron ring 13 is secured around the bars adjacent the driving face of the armature. Specification 383,879 is referred to.