Wellman Thermal Systems Corporation

Frank T Walton

A method of making a glow plug includes the steps of swaging a sheath of a heater having an internal heating coil therein and a compressible washer at the open end of the sheath to reduce the sheath's diameter and to force some of the washer out of the sheath to leave a washer portion of a diameter larger than the swaged sheath diameter. The heater is force fitted into a housing with the external washer being press fitted against an internal bore wall of the housing to form an air-tight seal with the bore wall. This eliminates the usual brazing step of brazing the sheath to the housing to seal against flow of combustion gases therebetween.

Glow plug

A glow plug has an outer metal housing have a wall defining an internal axially extending bore and a tubular heater that has an external tubular sheath of metal with a heated end of the sheath extending outwardly of the housing and an opposite internal end within the housing bore. The sheath is structurally secured to and electrically connected to the metal housing and the sheath has a closed outer end. An electrical heating element is positioned within the heater sheath and is electrically connected to the tubular sheath. The heating element has a conductor extending outwardly from the other end of the sheath. Electrical insulating material fills the space between the heating element and the sheath. An insulative compressible washer member is compressed between the sheath and the conductor to provide a first interference fit seal to prevent the flow of gas between the sheath and conductor and into the interior of the tubular heater. The wall defining the axially extending bore includes an upper tapered section that is of reduced diameter in the upward direction to compress the insulative compressible washer member as the tubular heater is forced further into the housing bore and includes an upper cylindrical section thereabove of a diameter smaller than the inlet side of the tapered section to engage and compress the compressible washer member to form a tight second interference fit seal between the housing and the tubular sheath to further upward flow of gas. An upper end of the sheath is compressed by the tapered section and then by the upper cylindrical section of the wall to make metal-to-metal contact therewith. The compressible washer member abuts and extends radially outwardly across the upper end of the sheath.

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Shelbyville, IN, United States of America

Frank T Walton