GB710344A - Improvements in or relating to electric spark discharge devices - Google Patents

Abstract

710,344. Sparking plug. K.L.G. SPARKING PLUGS, Ltd. April 3, 1952 [Jan. 3, 1951], No. 291/51. Class 7(4) In an electrical spark discharge device comprising in combination a discharge portion having an inner electrode 10, Fig. 1, and an outer metallic sheath 18, the inner electrode 10 and the sheath being separated by and attached to an insulator 14 which projects uncovered from that end of the sheath 18 which is opposite to the discharge end thereof, a terminal portion having an inner metallic member 20 and an outer metallic cover sheath 23 that are separated by an insulator 22, the member 20 and sheath 23 being arranged so that one end of member 20 is engageable with an electric lead, there is provided a metallic connector 30 joining the ends of the member 20 and electrode 10. The electrode 10 is joined at the end opposite the sparking tip 11 to a member 12 that is threaded to the insulator 14 which is sealed at three places to the electrode 10 by vitreous cementing material 15, 16, 17, the electrode being grooved to accommodate the centre seal; the sheath 18 is shaped to provide the earthed electrode 19. The member 12 has one end of the rod 30 welded thereto the outer end of which is welded to a part 21 of the terminal portion, the part 21 being attached to member 20, the outer end 26 of which is connected to a screened H.T. cable, not shown. The insulator 22 is threaded to the part 21 the latter having attached thereto the sheath 23 with a spherical seating 24 and a bore 25 for the cable. In a modification, the rod which is joined to the igniting device by a universal joint is surrounded by and in electrical contact with a tube, the two constituting a telescopic means which allows the distance between the igniting and terminal devices to be varied; a locking device consisting of a split collet and a nut is provided between the rod and tube. The seating 24 and socket 81, Fig. 3, enables the entire apparatus to be housed at any angle in the wall of a gas turbine jet pipe 80, in the centre of which is an after burner jet 83 having a baffle 84; the igniting device is mounted in a pocket 85 of the baffle 84 and where it is connected by a ball to the rod 30 it may be disposed at any angle in relation to the terminal device. The igniting device may be of the surface discharge type, the separating member being made semi-conductive in the manner described in Specification 700,860, [Group V]. According to the Provisional Specification the interior of the sleeve is lined with mica where it is spaced from the insulator.