GB465425A - Improvements in and relating to spark plugs - Google Patents

Abstract

465,425. Sparking - plugs ; electric couplings. BREEZE CORPORATIONS, Inc. April 20, 1936, No. 11275. Convention date, June 12, 1935. [Class 7 (iv)] [Also in Group XXXVI] A bushing 19 of copper or other good heat-conducting metal and a metal hoop 22 of low conductivity are compressed by swaging about the electrode 14 and mica insulating wrappings 17. Both members are flanged, the surface of flange 20 being shaped to lie against an internal shoulder in the casing. The members 19, 22 are internally expanded before assembly on the insulation. A sealing agent is applied to the overlapping edges of the mica wrapping. The central electrode 14 is of low or negligible conductivity, and heat transmission to the outer end of the plug is reduced by boring out the electrode. The sparking terminal 15 may be integral with or attached to the stem 14 which may be coated with a material of greater heat emissivity. Before lateral compression of the members 22, the whole assemblage of the electrode, bushings, insulations and cap 25 is axially compressed and the end 28 turned over. The inwardly curved end 8 of the casing is radially slotted leaving a partly annular spark-gap. A shielded coupling for preventing highfrequency emission consists of a metal tube 33 and insulation 37, 38 beaded at one end for engagement with a metal union 35 screwed on to the plug gland-nut. The insulation encloses a threaded bush 40 through which passes a pointed screw 41. Spiral springs 42, 46 make electrical connection with the nut 25 and exposed end 44 of the cable. Overheating of the insulation 45 is avoided by forming ribs 39 in the insulation 38 for allowing air to circulate. Conical packing 47 covered in metal 48, a ferrule 50 and a coupling.nut 52 complete the connection to the braided cable 49. Specification 397,661, [Group XXXVI], is referred to.