GB333280A - Improvements in and relating to sound reproducing devices - Google Patents

Abstract

333,280. Poupard, C. H., and Welch, A. P. May 8, 1929. Diaphragms; magnetic instruments.-A moving coil sound-reproducing device comprises a metal diaphragm and coil-supporting extension made in one integral piece without seams, joints or overlaps. The diaphragm and extension are preferably formed from aluminium or aluminium alloy by pressing between dies, spinning or by electrodeposition or coating. Fig. 1 shows a construction employing a conical diaphragm 1 integrally provided with a coil-supporting extension 2, the coil 7 being wound on a portion 4 between shoulders 5, 6. In the modified construction, Fig. 2, the reduced portion 4 extends to the free end of extension 2, the coil being held against shoulder 5 by a sleeve 8 having an inturned flange 9. If desired, the coil may be fixed to the internal surface of the sleeve or may be wound on the exterior of a sleeve adapted to fit within an extension of the diaphragm. The extension and sleeve function as a short-circuited turn of the coil. The diaphragm may be formed with circumferential, radial or other corrugations and the extension 2 may also be stiffened by the provision of corrugations, ribs or recesses. The diaphragm, extension 2 or sleeve 8 may be formed, as by pressing, with integral lugs or clips for securing the coil leads. Various means are described for attaching the marginal portion 3 of the diaphragm to a flexible suspension. Thus the portion 3 may be pierced with holes for use with a thread or like suspension or its surface may be roughened, as by perforating, for attachment of a flexible ring thereto by adhesive. Fig. 6 shows a modification in which the portion 3 is formed with radial slots 13 terminating in holes 14, the alternate portions 15, 16 thus formed being bent in opposite directions and a flexible suspension ring applied therebetween and attached to the diaphragm by pressing the portions 15, 16 flat. Alternatively, the flexible ring 17 may be gripped by a flanged over portion 18 of the diaphragm as shown for example in Fig. 8. According to further modifications, the diaphragm may be formed adjacent its periphery with circumferential corrugations or may be made of less thickness so as to be itself sufficiently flexible or it may be integrally formed with radial or other extending suspension strips or ligaments. A thread suspension may be employed for both the diaphragm and extension 2.