GB325354A - Electromagnetic sound reproducer - Google Patents

Abstract

325,354. Brandes, Ltd., (Brandes Laboratories, Inc.). Jan. 14, 1929. Magnetic instruments-Relates to a sound-reproducer in which pole pieces 4, 5, Fig. 1, of a magnet have two coils 28, 29 disposed with their axes at right-angles to the pole pieces and surrounding an armature 8. The invention consists in providing combined means for centering the armature and spacing the coils comprising a plurality of plates 32 - - 35, Fig. 3, and an intermediate plate 36 which carries the armature so that it is controlled by the torsion of the portion 36<c>. These plates are secured by bolts to bridge members 38, 39 secured to the pole pieces by bolts 40. The permanent or electromagnet 1 is secured to the pole pieces by bolts 20, 21. The plates may alternatively be secured in grooves 43, 44, Fig. 4, in the pole pieces 4, 5 which may bridge two magnets 40, 41. In a modification (Fig. 3, not shown) using two magnets the pole pieces carry bridges to which are bolted the spacing and centering plates. Various devices for transmitting vibrations to the diaphragm are shown. In Fig. 1, a strip 9, 11, rigidly attached to a pole piece 4 and the armature 8, carries a rod 12, with a sleeve 14 located by a nut 15, to which the diaphragm is attached. In a modification (Fig. 2, not shown) the upper portion 9 of the flexible strip is replaced by a rigid rod, and in Figs. 7 and 8 the resilient member 51 is connected to bridge 50 mounted on the pole pieces and connected to the armature 8 by a rod 17.