GB375538A - Loud speaker - Google Patents

Abstract

375,538. Loud-speakers. MAGNAVOX CO., 155, East Ohio Street, Chicago, U.S.A. June 17, 1931, No. 17562. Convention date, Feb. 20. [Class 40 (iv).] Relates to loud-speakers of the kind having a conical diaphragm, with an attached actuating coil which is located in an annular air gap formed between a central magnet pole and a surrounding pole. According to the invention, the rim of the diaphragm 16 is clamped between a plate 21 and a support 19 engaging and extending outwardly from the magnet structure, and the plate 21 is engaged by a member such as 26, Fig. 1, which extends through the apex of the diaphragm and cooperates with the inner magnet pole 11 to hold the parts together. In the construction shown in Fig. 1, the member 26 is an extension of the magnet pole itself, and is engaged by a nut 25 and a non-magnetic washer 27 on the outer side of the plate 21. A modification is described, Fig. 4 (not shown), in which instead of the extension 26 of the magnet pole, a brass &c. bolt passes through the plate 21 and through the apex of the diaphragm, and screws into a hole in the pole 11. A further modification of this feature is shown in Fig. 5, wherein a shorter extension 26 of the pole 11 is provided, and is engaged by an internally threaded bolt 36, preferably of brass, passing through the plate 21. The annular polepiece 13 carries a non-magnetic spacing ring 14, which serves to centre the air gap correctly. A flexible coilcentring device 18, Fig. 1, is mounted on a member 17, secured to the polepiece 13. Figs. 5 and 6 show a modified form of coil-centring device 38 consisting of a ring 42 engaging the diaphragm and coil 15, and flexible arms 43 which are attached to a support 37. This is adjustably secured to the annular polepiece 13 by screws 39. Ears 44 on the ring 42 carry terminals to which leads for the coil are connected. The pot member 10 of the magnet, in the construction shown in Fig. 5, is formed by pressing, and has flanges 31 between which the pot is cut away to provide for circulation of air to cool the coil 12. In a further modification, the coil-centring device is mounted directly upon the diaphragm housing 19. The rim of the housing 19 has a flange 28, Fig. 1, which receives a vibration damping packing 29, adapted to engage with a baffle or cabinet wall. Alternatively, the flange 28 may be turned outwardly to overlap and frame the baffle hole. In this case, the member 21 may be ornamented and if desired provided with a silk backing.