GB351255A - Improvements relating to sound reproducing instruments - Google Patents

Abstract

351,255. Loud-speakers. WILLSON, H. C., Walton, Beckminster Road, Wolverhampton. June 27, 1930, No. 19658. [Class 40 (iv).] A magnet system for a telephone receiving - instrument comprises polepieces which are rigidly cast or moulded in position in a non-magnetic support, the polar faces being formed by a cutting operation through the polepieces after the latter are fixed in position. The polepieces consist of two steel stampings, Fig. 3, bent in opposite manner and secured in a die-cast base a of non-magnetic material by means of dovetailed feet b, b<1>, h, h<1> and countersunk recesses. The bent stampings comprise portions c, c<1> .. g, g<1>, the central vertical portions e, e<1> being cut through to leave air gaps l, l<1>, thus producing four poles between which the speech coil k, Fig. 2, is mounted. Two permanent magnets are clamped against the parts c, c<1>, f, f<1> by means of screws in tapped lugs projecting upwards from the base a. The reed o consists of a stamping which is reduced in thickness at a slotted part r to produce the required natural frequency. Near its fixed end the reed o is clamped by means of a nut x and screw w on a plate u, which rests on the upper convex end of a pillar v, so that the position of the reed may be adjusted, under the control of a compression spring z, by means of a screw y.