GB855440A - Improvements in or relating to surface discharge sparking plugs or other ignition devices - Google Patents

Abstract

855,440. Surface discharge sparking plugs or other ignition devices. LODGE PLUGS Ltd. Dec. 30, 1957 [Dec. 29, 1956; Jan. 26, 1957], Nos. 39578/56 and 2888/57. Class 7(4). At least one neutral electrode separates semi-conducting sparking surfaces between the centre or main electrode and the earthed electrode. In Fig. 1 the neutral electrode is indicated at 14. As shown in Fig. 2 the right hand half 18 of the surface at the end of the insulator 12 is made semi-conducting in known manner while a substantially segmental portion 19 of the end surface of the insulator 15 is made semi-conducting. The whole of the outer annular end surfaces of the insulators 12, 15 may have semiconducting properties. The neutral electrode 14 may consist of a number of interconnected concentric annuli. In Fig. 3 the neutral electrode comprises a metallic washer 20. The semiconducting inner surfaces of the insulators 21, 22 may be on one cylindrical surface. A number of metal washers 20 each separating a pair of coaxial annular insulators 21, 22 may be provided. In Fig. 4 insulators 25, 26 are separated by the metallic washer 20. If desired only a part of the inner peripheries of the insulators 21, 22 and the outer peripheries of the insulators 25, 26 may be semi-conducting. The tubular insulator 28 may be of mica but preferably it is of ceramic material such as that sold under the Registered Trade Mark "Sintox" similar to that of the insulator 11 and to that of the annular insulators 12, 15 of Figs. 1 and 2, 21, 22 of Fig. 3 and 25, 26 of Fig. 4 on which the semi-conducting surfaces are formed. The plug is for jet engines or other gas turbines or for oil fired furnaces and combustion chambers.