GB1099425A - Improvements in moving coil loudspeakers - Google Patents

Abstract

1,099,425. Loudspeakers. RADIO RENTASET PRODUCTS Ltd., [trading as GOODMANS INDUSTRIES]. July 25, 1966 [Aug. 16, 1965]. No. 34934/65. Heading H4J. A moving coil loudspeaker is made by pressing an annular spacer 4 of deformable material between a centre pole piece 3 and the inner side wall of a magnet pot 1 by a front plate 5 so as to retain the centre polepiece 3 in alignment with the front plate 5 and magnet pot 1. The polepiece 3 has a skirt 10 which on assembly slightly oveilaps a magnet 2. The magnet pot 1 is formed with an inner annular recess 7 to receive the front plate 5 and an outer annular recess (8), Fig. 1 (not shown) to receive the inner flange 9 of a chassis 6. The spacer 4 is of low density polyethylene or other plastics material which will flow outwardly under axial compression. Its axial bore has a frusto-conical portion 11 corresponding to the skirt 10. In manufacture, a centre gauge occupies the air gap and the components are assembled in inverted position over the lower die plate of a press which is then closed. Spacer 4 prevents the front plate 5 from fully seating in the recess 7. The pressure deforms the spacer 4 outwardly to cause it to make contact with the inner walls of the magnet pot 1 all round its circumference. The lower die plate has short radially extending ridges and under pressure these ridges " stake " or " swage " the front plate 5 to the magnet pot 1. The chassis 6 can be similarly attached to the magnet pot 1 in the same operation.