GB725365A - Improvements in spark plugs - Google Patents

Abstract

725,365. Sparking plugs. GENERAL MOTORS CORPORATION. April 15, 1953 [May 2, 1952], No. 10267/53. Class 7 (4). In a sparking plug of which the insulator 6 is enclosed and protected against damage by a shield 14 formed by two separate cylindrical sleeves 64, 68, the latter are jointed together, end-to-end, during assembly in order to accommodate any warping of the insulator 6 by setting themselves at a slight angle to one another. Within the stepped insulator bore is a centre-electrode assembly comprising a firing tip, having a soft-metal core 31 and a heat-resistant sheath 33, a conducting seal 32, a screw member 34, a resistance 36, a spring 38 and a contact cap 40 retained in a groove in the insulator by a shoulder 42. The insulator 7 has shoulders 20, 22 which co-operate, respectively, with a ledge 44 in the shell, and the lower edge 50 of the shield 14 by means of which the insulator is retained in the shell 10. The upper shield-sleeve 68 embodies an upper inturned flange 70 which is of the same diameter as the interior of the upper end 24 of the insulators, a metal gasket 76 filling the space between the top of the insulator and the flange. The lower shield-sleeve 64 is welded or brazed to the shell, the two shield sleeves being similarly secured together after a gauge has been positioned in the top of the plug to ensure that the insulator is concentric with the shield ; this may result in the sleeves 64, 68 being out of alignment with each other. The earth electrode 12 comprises a number of inwardly extending arms which are welded to the shell after a tubular gauge has been inserted in the spark gap ; this provides a spark gap of uniform length and may necessitate the electrode 12 being set at a slight angle within the shell recess 56.