GB308776A - Improvements in or relating to acoustic devices - Google Patents

Abstract

308,776. Electrical Research Products, Inc., (Assignees of Giles, L. W.). March 31, 1928, [Convention date]. Loud-speakers; magnetic instruments; diaphragms.-A moving coil acoustic device, such as a loudspeaker, has the coil centred by spring members, preferably elliptically shaped, arranged tangentially with respect to the coil. The Figures show a construction of moving coil loud-speaker employing a diaphragm 1 comprising a frustoconical section 2 and a conical section 3 having its base secured to the frusto-conical section at a point intermediate the inner and outer ends thereof. The conical section stiffens the diaphragm so that it is capable of vibrating as a whole through the entire audible frequency range and prevents interference between the air pressures at the top and bottom of the inside surface of the frusto-conical section. The stiffening member instead of being conical may assume other shapes, e.g. flat. The outer edge of the diaphragm is supported on flexible material 4, such as silk, rubber, thin leather, &c., clamped between rings 5, 6 and has its inner edge secured to a cylindrical member 16 carrying a coil 8 and formed with a plurality of lugs 15. The coil 8 is disposed, in the annular air gap formed by concentric pole-pieces 11, 13, the pole-piece 13 being integral with the core 10 whilst the pole-piece 11 is detachably secured thereto by screws 58 to permit assembly of the winding 12. A ring 36 is secured by screws 34 to the pole-piece 11 and carries arms 30 for supporting the ring 5. Ring 36, arms 30 and ring 5 are preferably formed as an integral structure. The coil 8 is centred in the air gap by a number of elliptically shaped springs 14 spaced equally and tangentially around the coil. One end of each spring 14 is mounted on a lug 15 by means of a screw 21, insulating bushing 22, insulating washer 23 and nut 24 whilst the bottom of each spring is mounted on a terminal 54 'by a screw 42. The terminal 54 is mounted on the pole-piece 11 by screw 39, insulating bushing 43 and insulating member 41. The two ends of the coil 8 are secured to the screws 21 of two of the springs and wires 50 are run from the corresponding terminals 54 to contacts mounted on an. angle iron carried by the ring 36.