GB645403A - Improvements in or relating to sparking plugs - Google Patents

Abstract

645,403. Sparking plugs. SMITS, W. B. April 3, 1947, No. 9091. Convention date, Feb. 14, 1939. [Class 7(iv)] In a surface discharge sparking plug comprising two spaced electrodes 1, 2 and a body 3, of such material as porcelain, mechanically connecting but electrically insulating the electrodes so as to provide an end face across which the sparks sweep, the body 3 has an exposed surface layer 4 of material having an electrical resistance less than that of the remainder of the body, the layer being formed by the incorporation therein of electrically conducting particles, such as platinum produced, for example, by burning a solution of chloride of platinum in oil into the porcelain; the layer may be produced by heating such substances as oxides of alkaline earth metals or any high melting point organic substance which readily carbonizes, for example, asbestos may be used as the insulator whilst a solution of copal resin in petrol is applied to the end face of the asbestos ; the layer may also be produced by coating the end face of the insulator with a silicate, such as enamel, which on becoming heated in the engine cylinder absorbs carbon particles from the combustion process. Specification 483,383 is referred to.