Spark plug with integral retainer nut

A spark plug located in a generally cylindrical spark plug receiving bore in an internal combustion engine, the bore communicating with a combustion chamber of the internal combustion engine and including a threaded portion and a generally frustoconical seat portion, the spark plug comprising;

• a center electrode having a cylindrical body with a tip at one end and a terminal near the other end;
• an insulator radially surrounding the center electrode and having a substantially cylindrical body with at least first and second diameter sections separated by a shoulder, the diameter of the second diameter section being greater than the diameter of the first diameter section;
• a ground shield surrounding said insulator first diameter section and including near one end a frustoconical section juxtaposed with the insulator shoulder and a ground electrode near the other end having a portion including a tip receiving centrally located aperture radially aligned with the center electrode tip and defining therewith a spark gap;
• and
• an annular retainer surrounding said insulator second diameter section and including a portion having threads that are matched with the bore threads, the annular retainer providing a seal between the ground shield frustoconical section and the frustoconical seat portion of the bore to establish an electrical ground between the shield and head while at the same time sealing the combustion chamber from the surrounding environment.

The method of fabricating a spark plug of the type having a center electrode with a tip at one end and a terminal near the other end and an insulator radially surrounding the center electrode, the insulator having a substantially cylindrical body with at least first and second diameter sections separated by a first shoulder, and second and third diameter sections separated by a second shoulder where the diameter of the second section is greater than the diameters of the first and third sections comprising:

• axially passing a cylindrical shell ground shield of the type having a ground electrode near one end and a flared frustoconical flange near the other over the first diameter section to engage the flared frustoconical flange with the first shoulder;
• axially passing a cylindrical shell retainer of the type having an interior frustoconical ledge and exterior threads over both the third and second diameter sections to engage the frustoconical ledge with the second shoulder;
• and
• radially collapsing a portion of the retainer about the flared frustoconical flange to secure the ground shield and retainer together with the insulator captured therebetween.

A spark plug comprising:

• an elongated center electrode;
• an insulator disposed radially around said elongated center electrode having a first diameter section separated by a first shoulder from a second diameter section and a third diameter section separated by a second shoulder from the second diameter section with the second diameter section located intermediate the first and third diameter sections and the diameter of the second section being greater than the diameters of the first and third diameter sections;
• a cylindrical ground shield, having a ground electrode on one end and a flange on the other end, disposed around the first diameter section with the flange engaging the first shoulder;
• and,
• a cylindrical retainer disposed around the third diameter section and the second diameter section including an internal portion which engages the second shoulder and an end portion which engages said cylindrical ground shield near the first shoulder to capture said insulator therebetween.