GB737853A - Method of producing electrical condensers - Google Patents

Abstract

737,853. Capacitors. STANDARD TELEPHONES & CABLES, Ltd. Dec. 11, 1953 [Jan. 21, 1953], No. 34514/53. Class 37. In a tubular capacitor comprising alternate metallic and dielectric layers, the dielectric layers produced by winding a layer of glass fibres on to the partly-formed capacitor and then subsequently melting the fibres to form a uniform thin layer of glass. As shown in Fig. 1, a layer of metal 5, e.g. silver or copper, is formed on a central insulating or insulated-metallic core 4 and a layer of glass fibre is wound upon this from a reel 1. - A short length of the metallic layer is left uncovered at one end. The fibres are then fused together and a further metallic coating deposited on the glass layer thus formed, with however the projecting portion at the other end of the capacitor. A further layer of fibres is then wound on to the metallic layer and the process repeated to form a number of metallic layers 5 which alternately project at one end or the other of the capacitor, as shown in Fig. 2. The alternately projecting layers are bound together by means of metallic tapes 6 to which the connecting wires 7 are attached. Finally the whole capacitor is covered with glass fibres which are then melted together to form a glass envelope for the capacitor. As an alternative to the above method of construction, the complete set of alternate glass-fibre and metallic layers may be deposited on to the central core before the heat treatment is carried out, the fusion of all the glass fibres being carried out in a single operation. The core of the capacitor may comprise either a solid rod or hollow tube of a ceramic material, or a high melting-point glass (e.g. quartz glass) or it may be of metal coated with glass. The metallic layers may be deposited as foil or by spraying, dusting, vaporization or cathodic sputtering or by chemical deposition such as by reduction of solutions of inorganic salts or by the decomposition of metallic compounds in the gas-phase (e.g. metal carbonyl compounds). The glass dielectric may have a proportion of other substances added to it to increase its dielectric constant, e.g. the oxides of lead, barium, zirconium and titanium may be added either alone or mixed. The heat treatment may be carried out in vacuo or in a neutral or reducing atmosphere (e.g. hydrogen).