GB498218A - Improvements in loud speakers - Google Patents

Abstract

498,218. Loud-speakers. CINAUDAGRAPH CORPORATION. Nov. 15, 1937, No. 31313. Convention date, Nov. 14, 1936. [Class 40 (iv)] A loud-speaker comprises a chassis unit connected with the periphery of a vibratory diaphragm carrying a voice-coil, centring means which connect the inner portion of the chassis with the diaphragm and hold the voicecoil accurately centred with respect to a magnet-engaging device or devices on the chassis, and a magnet unit having an air-gap for the voice-coil and a chassis-engaging device or devices at or near its periphery accurately centred with respect to the air gap and cooperating with the engaging device or devices of the chassis-unit to connect the chassis unit and magnet unit in such a manner that when the loud-speaker is assembled, the voice-coil is accurately centred in the air gap. The chassis 1 is formed with a flange 30 forming a seating for the peripheral flange 7 of the diaphragm 2 and a shoulder 10 to which the outer part of a centring member 4, constituted by a corrugated stiffened gauze-like fabric is cemented. In addition, the chassis 1 has a flange 17 accurately fitting the outer surface of a former or mandrel 20, Fig. 2, corresponding to the outer surface of the outer pole-plate 14, Fig. 1. When the chassis unit is mounted on the mandrel so that the voice-coil cylinder 8 fits on the core member 21 and any relative movement between the diaphragm 2, the chassis 1 and the centring device has taken place, the diaphragm is cemented to the flange 30 and to the centring device 4. The diaphragm is held firmly against its seating and against the centring device during the setting period of the cement by a ring 23, and the centring device is supported by an annular ring 22 on the mandrel 20. The chassis unit is clamped to the magnet unit 5 by a flanged ring 19 clamped by a fastening passing through flanges 6. In a modified construction and mode of assembly, the chassis unit is placed on an anvil member provided with locating pins which engage holes in the chassis and with a central shouldered member on which the voicecoil fits accurately, the chassis unit being lowered relative to the anvil so that the peripheral portion of the diaphragm takes up a free and unstrained portion relative to the chassis, Fig. 3 (not shown). After the diaphragm has been cemented to the chassis, the centring member is cemented to the diaphragm and chassis when the latter is placed on a former having a central projection forming a close fit for the voice-coil cylinder and provided with locating pins corresponding accurately to those on the anvil member, Fig. 4 (not shown). The chassis unit 35, including the diaphragm C<1> and centring member 48, is then mounted on the outer poleplate by means of the dowel pins 54, and the assembly of the loud-speaker is completed by bolts 55 which pass through slightly oversize holes in the chassis 35. A felt ring 46 is interposed between the peripheral flange of the diaphragm C<1> and the chassis 35 and a felt mounting ring 60 is cemented to the upper surface of the flange 37.