GB551977A - Improvements in and relating to spark plugs and other electrical devices - Google Patents

Abstract

551,977. Sparking plugs; electric insulators. BENDIX AVIATION CORPORATION May 23, 1941, No. 6663. Convention date, July 9, 1940. [Class 7 (iv)] [Also in Groups V and XXXVI] A sparking plug comprises an electrode 16 extending completely through a rigid tubular insulator 20 consisting of ceramic material, or aluminium oxide, with finely divided metal particles dispersed in at least a part thereof to increase the heat conductivity. The insulator, which is applicable to other electrical apparatus, is formed by baking a dampened mixture of about three volumes of powdered ceramic material or aluminium oxide of about 300 mesh or finer and one volume of metallic powder such as nickel or tungsten of about 200 mesh or finer. The outer layer or the lower end of the insulator may be of pure ceramic material or aluminium oxide. As shown, the electrode 16 extends through the flange 15 of a nut 13, which carries a shielding barrel 14, and the insulation includes a mica wrapping 18 and yielding stacks 19, 23 of mica washers. The stack 23 is held by peening over the upper end of the electrode to engage a washer 22. The spaces between the insulating and metallic parts around the upper end of the electrode may be filled with a heatresistant insulating material made from cashewnut shell oil, as described in Specification 549,580. In modifications, (a) the upper part of the mica stack 23 is replaced by a ceramic sleeve ; (b) the insulator 20 extends through the flange 15 and within the mica stack 23, the part within and just below the flange 15 being impregnated with metallic powder. The Specification as open to inspection under Sect. 91 comprises also a modification in which the nut 13 is integral with the body 10, and the construction of sparking-plug described in Specification 549,631. This subject-matter does not appear in the Specification as accepted.