GB631387A - Improvements in or relating to low tension sparking plugs - Google Patents

Abstract

631,387. Sparking-plugs. SMITS, W. B. Dec. 4, 1946, No. 35962. Convention date, Dec. 14, 1945. [Class 7 (iv)] In a low-tension sparking-plug, the electrodes 1, 3, Fig. 1, of which are separated from one another by an electrically-insulating member 2 on the surface of which the igniting spark comes into existence, the electrodes having active surfaces 10, 11 which diverge in the direction from the separating member to the outside so as to form a groove or recess the bottom of which is constituted by the insulating member 2, it is arranged that the divergency of the active surfaces of the electrodes from the bottom of the groove is such and the active surfaces are so disposed that the igniting spark produced on the bottom is forced spontaneously out of the groove. The outer electrode 1, which has a tapered bore is mounted upon the correspondingly tapered insulating member 2 whilst upon the inside of the member 2 is the central-electrode 3. The electrodes 1 and 3 and member 2 are pressed together by an insulator 4, a washer 5 and nuts 6, 7 mounted and screwed respectively, on the central electrode 3. The spaces between the insulator 4, outer electrode 1 and member 2 are filled with synthtic rubber or other similar electrically insulating elastic organic substance thereby ensuring gas-tight joints. The sparking surfaces 10 and 11 of the central and outer electrodes respectively enclose an angle of about 30 deg. thereby forming the groove or recess in the bottom of which the sparks are produced. The head of the outer electrode is slotted at 12 in order to obtain a degree of resiliency and a washer 15 of electrically conductive and heat resistant material is placed under the head of the central electrode 3. The above assembly is housed within a holder 13, Fig. 2, which is provided with a leading-in insulator 14 for the electrical connection of the sparking plug In a modification, the angle between the sparking surfacees 10 and 11 is greater than 30 deg. and the electrodes may be made of such material as copper, silver or an alloy of these metals, with arsenic and beryllium ; further the sparking surfaces of the electrodes may be galvanized or otherwise treated in order that they may acquire a better resistance to heat. Specification 631,386 is referred to. The Specification as open to inspection under Sect. 91 comprises also a modification in which the electrodes and separating member are united by melting or sintering. This subject-matter does not appear in the Specificaton as accepted.