GB1084874A - Improvements in and relating to methods of fastening a moving coil, a diaphragm and a centering member of an electro-acoustic transducer to each other - Google Patents

Abstract

1,084,874. Moving coil transducers. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. April 15, 1965 [April 17, 1964], No. 16245/65. Heading H4J. In making a moving-coil transducer a diaphragm 2 and flexible centring member 3 are secured by a connecting sleeve containing deformable and hardenable material to the moving coil 1 by applying axial pressure to the various integers while resisting the radial forces arising as a result of the axial pressure. In manufacture, a lower template 16 is slipped on to a cylindrical jig 12 and the coil 1 is disposed on the jig 12. Output wires 6, 7 are taken upwards. A double-layered paper ring 19 impregnated with phenol-formaldehyde resin is placed in the lower template 16. The flexible centring member 3 is arranged on the frustoconical end 22 of the lower template 16, this member 3 being centred by an integral cylindrical collar 21. The diaphragm 2 is placed on the member 3 and is centred by a similar integral collar 20. Collars 20, 21 are impregnated with resin. A core 13 is next slid into the lower template 16 and jig 12, the lower end 15 serving as a guide. An upper template 17 is slid on to the core 13 and has an end 23 which mates with end 22. Pressure is applied to the upper template whilst the core 13, the lower part of template 17 and the upper part of template 16 are subjected to induction heating. The resin-impregnated ring 19 is softened and collapses and templates 16, 17 move downwards against compression of a spring 18. The distance between end 23 and the upper face of the coil 1 is reduced and the interior space is filled by the collars 20, 21, the ring 19 and the resin, whereupon thermohardening occurs. Heating is then stopped and the transducer assembly is cooled and removed. The ring 19 may be omitted if the collars 20, 21 are sufficiently long. Alternatively the annular space including the ring 19 may be filled with powder, which is subsequently heated and compressed. As a further alternative the sleeve may be made by injection moulding. The output leads 6, 7 are adhered to the diaphragm 2. A central dust protecting cap 8 (Fig. 1, not shown) is subsequently adhered to the inner periphery of the diaphragm 2. The method of manufacture is applicable to microphones and loud-speakers.