GB549631A - Improvements in or relating to spark plugs and a method of making the same - Google Patents

Abstract

549,631. Sparking plugs. BENDIX AVIATION CORPORATION. May 23, 1941, No. 8951/42. Convention date, July 9, 1940. Divided out of 551,977. [Class 7 (iv)] The electrode 16 and insulating means such as a mica wrapping 18 are surrounded by a soft metal tube 31 and a rigid sleeve 30 of ceramic material or aluminium oxide, a conical enlargement at the end, of the bore of the tube 31 being intimately engaged by the coned upper end of the insulating sleeve 30. The tube 31 and sleeve 30 are held between a shoulder 28 on the member 13 and the head 17 of the electrode. The coned upper end of the sleeve 30 may be coated with metal stich as copper applied by flame-spraying as described in U.S.A. Specifications Re-issue 20,425 and 2,108,990, or may be impregnated with powdered metal such as nickel or tungsten. In assembling the plug, the sleeve 30 is rotated to grind itself an accurate seat in the 'soft metal of the tube 31. The sleeve 30 is made by mixing dry metallic and ceramic or oxide powders for the upper end 32, moistening to form a paste, adding to a plain ceramic or oxide paste forming the 'main part of the sleeve; moulding, drying at low temperature, and baking or firing at' about 2,200‹ F. The insulation comprises also a cushioning stack of mica washers 23 held in place by peening the countersunk end of the. electrode 16 over a washer 22, and the spaces in the parts around the upper end of the electrode may be filled with an insulating filling material derived from cashew-nut oil as described in Specification 549,580.