GB585217A - Spark plug manufacture - Google Patents

Abstract

585,217. Sparking - plugs. TRIGGS, W. W. (United States Quarry Tile Co.). April 5, 1944, No. 6375. [Class 7 (iv)] The insulator of a sparking plug comprises a fired ceramic body having a highly polished surface produced by mechanical polishing after firing; carbon deposit on the exposed surface is thus reduced. Polishing may be restricted to surfaces 16, 17 subject to the high temperature gases and to shoulders 18, 20 on collars 21, which take a bearing in the sparking plug casing. The remaining surfaces especially the neck 19, may be glazed to increase their strength. The insulator is made homogeneous and dense from substances not subject to attack by lead compounds &c. in the combustion gases, e.g., -the inert oxides of alumina, magnesia, zirconia, and titania. The polishing is effected in a revolving or moving lap, the abrasives being in powder, paste or liquid-suspension form and the insulator being revolved or rapidly moved therein. Abrasives which may be used are alundum powder, fused aluminium oxide grain, carborundum powder or silicon carbide. Powdered quartz or flint, finely powdered zirconium silicate, chromium oxide, rouge or iron oxide may also be used after first polishing has already been performed. In a modification the collars 21 are replaced by a tapered nose and neck. Reference has been directed by the Comptroller to Specifications 302,893, 308,708, [both in Class 7 (iv)], 340,865 and 344,256.