GB315230A - Telephonic loud speaker - Google Patents

Abstract

315,230. Farrand Inductor Corporation, (Assignees of Farrand, C. L.). July 9, 1928, [Convention date]. Loud-speakers; magnetic instruments. - The armature of a loud-speaker is mounted between, and moves parallel to, a plurality of pole-pieces under the influence of a varying flux which increases in two non-contraposed pole-pieces. The armature 1, Fig. 1, in its normal position overlaps portions of the faces of the pole-pieces, the broken arrows indicating the direction of the magnetic flux, When the coil 2 is energized in one direction, the superposed flux, indicated by the full arrows, Fig. 2, increases the flux between poles N2, S1, and decreases the flux between poles N1, S2, so that the armature moves as shown in Fig. 2. If the coil 2 is energized in the opposite direction, the armature moves in the reverse direction. The armature 1, Fig. 4, is mounted on leaf springs 3, 4, which provide the restoring force, the magnet 9 supplying the initial flux. The coil 2 may be replaced by four coils surrounding the pole-pieces. The armature may be cylindrical, Fig. 10, and may assume varying forms, Figs. 7, 9, not shown. In a modification, Fig. 12, only two pole-pieces are used, and the increase of flux may take place in two pole-pieces on the same side of the armature, the overlap of the pole-pieces by the armature varying with the degree of energization of the coil 37. The maximum amplitude of vibration of the armature is approximately half the width of the pole-pieces and the armature overlaps one half of the pole-pieces in its position of rest.