Patent GB-441158-A (GB)
Title: Improvements in or relating to loudspeakers with oscillatory coil
IPC: H04R9/04
Filed: 1934-11-22
Abstract: 441,158. Loud-speakers. LISSAUER, W., 2, Gasvej, Horsens, Denmark. Nov. 22, 1934, Nos. 33544 and 33545. Convention dates, Dec. 15, 1933 and Sept. 10, 1934. [Class 40 (iv)] An internal or external centring device for the moving coil of a loud-speaker is provided with evenly distributed radial projections which are secured directly upon an annular part or supporting ring of the pole plate by means of a separate continuous ring or by adhesive, whereby stresses in the centring device and consequent tilting of the coil are avoided. As shown in Figs. 1 and 2, an external centring device for the coil B consists of a cut-away disc A with a number of radial arms H which are clamped against a ring E on the pole plate by a ring F secured by screws, and the disc has an equal number of radial arms A1 which are displaced relatively to the arms H. The disc A may be formed with two or more concentric sets of arcuate perforations, or it may be covered or constructed to form of itself a diaphragm. The ring F may have recesses corresponding to the arms H so that it may be passed bayonet-wise over the disc A after the latter has been assembled with the coil and diaphragm, or the ring F may be made in parts. The diaphragm may be supported solely by the centring device. The disc A may be very thin and made of fibrous material impregnated with artificial resin, or of aluminium or of its alloys. The disc A may be of elongated form, Fig. 5, for use with a diaphragm and coil of similar form in cross section suitable for fitting in the lower part of a radio receiver cabinet. The joint between the diaphragm C and the coil B, Fig. 7, may be reinforced by a double-flanged ring K of aluminium or of its alloys, and in a modification, Fig. 8 (not shown), the upper flange of this ring is conical and fits the diaphragm and the conical flange may be corrugated. The supporting ring E, Fig. 1 may be replaced by a flange on the pole plate or by the edge of a recess therein. For internal centring, the device may be made as a ring which is as narrow as possible in order to provide the greatest possible circumference for securing the internal projections M, or it may be secured to the conical diaphragm at a distance from the neck, Fig. 4 (not shown). The Specification as open to inspection under Sect. 91 comprises also the application of the centring device to a diaphragm (not shown), the surface of which is produced from one or two groups of inclined straight lines as a variant of a hyperboloid of revolution ; or the elongated cross section of the diaphragm may comprise two parallel lines with their ends connected by semicircles, the surface comprising two half-perboloids of revolution each generated by the rotation of an inclined line about the axis, and these lines may be embodied as actual rods. In modifications the half-hyperboloid may be replaced by a sector, the semicircles may be replaced by a series of arcs of different radii, or the cross section may be elliptical or oval consisting of a series of arcs of different radii. As shown in Fig. 7 (Cancelled) the pole plate D is cut away at D and provides two long narrow air gaps for the straight portions only of an elongated coil B ; this arrangement facilitates centring. This subject-matter does not appear in the Specification as accepted.