Spark plug construction

{
  "publication_number": "US3940649A",
  "country": "US",
  "kind": "A",
  "title": "Spark plug construction",
  "abstract": "The spark plug has been designed so as to, be capable of being disassembled for cleaning, have a substantially full shield for the spark gap end of the center electrode portion, enable the center electrode to be readily replaced, if desired, enable partial cleaning of the spark plug gap area without removal of the spark plug from an associated engine, and have a substantially full gas seal defined between the base of the spark plug and the spark plug insulative sleeve.",
  "claims": [
    "1. A spark plug including a tubular base having large and small diameter end portions and defining a small diameter central bore extending through the small diameter end portion, a coaxial large diameter bore extending through the large diameter end portion communicating with said small diameter bore and an annular shoulder at the inner end of the large diameter bore facing toward the outer end thereof, a one-piece tubular insulative body including a diametrically enlarged mid-portion and opposite smaller diameter end portions, said body being telescoped into the tubular base with said mid-portion loosely received in said large diameter bore and seated against said shoulder and one of said smaller diameter end portions projecting into and loosely received in said small diameter bore, at least the free end of said one smaller diameter end portion having a central bore formed therethrough terminating inwardly in an enlarged counterbore opening outwardly through the other small diameter end portion, an electrode rod loosely telescoped into said counterbore and seated in the inner end thereof, a combined closure and electrical terminal removably secured in the outer end of said counterbore and electrically engaged with the adjacent end of said rod, said small diameter end of said base including a ground electrode including a portion thereof registered with but spaced from the outer end of said central bore, and a thrust nut telescoped over the other smaller diameter end portion of said insulating body, abutted against the adjacent axial end of said mid-portion and threadedly engaged in said large diameter bore, said shoulder including a peripherally continuous groove formed therein and the adjacent axial end of said enlarged mid-portion of said body includes a peripherally continuous rib tightly seated in said groove, the engagement of said rib in said groove comprising the sole area of direct contact of said insulative body with said base.",
    "2. The combination of claim 1 wherein said ground electrode includes a generally U-shaped support including generally parallel legs interconnected at one pair of corresponding ends by means of a bight portion extending therebetween, the central portion of said bight portion comprising the portion of said ground electrode registered with said central bore, the free ends of the legs of said support being anchored to diametrically opposite portions of the free end of the small diameter end portion of said base.",
    "3. The combination of claim 2 wherein said central portion of said bight portion comprises a spherical enlargement.",
    "4. The combination of claim 1 wherein said ground electrode is constructed of Stellite and said electrode rod is constructed primarily of carbon."
  ],
  "cpc": [
    "H01T 13/04",
    "H01T 13/20",
    "H01T 13/40",
    "H01T 13/56"
  ],
  "assignees": [
    "BERSTLER FRANCIS E"
  ],
  "filing_date": "1974-07-09",
  "publication_date": "1976-02-24",
  "grant_date": "1976-02-24",
  "priority_date": "1974-07-09",
  "application_number": "US-48685474-A",
  "family_id": "23933475",
  "citations": [
    "US1098637A",
    "US1442423A",
    "US2685872A",
    "US3300672A",
    "US3581141A"
  ]
}