Process for cleaning spark plugs on internal combustion engines

Claim 2

A spark plug comprising: (a) an elongated insulator body having a center electrode passing therethrough and a metal sleeve surrounding the insulator body over a major portion of its length and in good heat conducting relationship therewith, said metal sleeve contacting the outside of the insulated body; (b) an outside annular electrode spaced from the end of the center electrode to define a spark gap therebetween; and (c) a depression in said insulator body between the electrodes, said depression having a concave shape in a cross-section parallel to the longitudinal axis of the center electrode, said depression located solely within the limits of said insulator body and said metal sleeve having a shape other than one forming a contiguous line with said depression, the surface of said depression being below the line directly connecting the center electrode and the outside annular electrode.

Claim 3

The spark plug of claim 1 in which the outside electrode is annular and has projections uniformly about its periphery.

Claim 4

The spark plug of claim 1 in which the outside electrode is annular and has recesses uniformly about its periphery.

Claim 5

The spark plug of claim 1 in which the metal sleeve has threads on its outer periphery for securing the spark plug in place.

Claim 6

The spark plug of claim 1 in which the metal sleeve is spaced from the outside of the insulator body over a major portion of its length by a small air gap.

Claim 7

The spark plug of claim 1 in which the curved shape of the depression is parabolic.

Claim 8

The spark plug of claim 1 in which the plane of the outside electrode is perpendicular to the longitudinal axis of the center electrode.

Claim 9

The spark plug of claim 1 in which the insulator body is retained in the metal sleeve at the end adjacent the spark gap by a conical edge on the insulator body which contacts the inside of corresponding surface of the metal sleeve.

Claim 10

The spark plug of claim 1 in which the end of the center electrode protrudes beyond the surface of said depression.

Claim 11

A process for removing deposits of combustion residues from the ceramic insulator body of a spark plug located in an engine cylinder during operation of the engine comprising: (a) producing a spark across a gap of at least one mm with a current of at least 70 mA and a voltage of 20 kV; (b) deflecting said spark by means of a flow of gas in the engine cylinder combustion space against the end of said insulator body; and (c) maintaining said insulator body at approximately the engine coolant temperature by a sleeve which surrounds it, said sleeve having threads on the outer periphery thereof for securing said spark plug in place, said spark plug further comprising: (1) an elongated insulator body having a center electrode passing therethrough and a metal sleeve surrounding the insulator body over a major portion of its length and in good heat conducting relationship therewith, said metal sleeve contacting the outside of the insulated body; (2) an outside annular electrode spaced from the end of the center electrode to define a spark gap therebetween; and (3) a depression in said insulator body between the electrodes, said depression having a concave shape in a cross-section parallel to the longitudinal axis of the center electrode, said depression located solely within the limits of said insulator body and said metal sleeve having a shape other than one forming a contiguous line with said depression, the surface of said depression being below the line directly connecting the center electrode and the outside annular electrode.

Claim 12

A process for removing deposits of combustion residues from the ceramic insulator body of a spark plug located in an engine cylinder during operation of the engine comprising: (a) producing a spark across a gap of at least one mm with a current of at least 70 mA and a voltage of 20 kV; (b) deflecting said spark by means of a flow of gas in the engine cylinder combustion space against the end of said insulator body; and (c) maintaining said insulator body at approximately the engine coolant temperature by a sleeve which surrounds it, said sleeve having threads on the outer periphery thereof for securing said spark plug in place, said spark plug further comprising: (1) an elongated insulator body having a center electrode passing therethrough and a metal sleeve surrounding the insulator body over a major portion of its length and in good heat conducting relationship therewith, said metal sleeve contacting the outside of the insulated body; (2) an outside annular electrode spaced from the end of the center electrode to define a spark gap therebetween; and (3) a depression in said insulator body between the electrodes, said depression having a concave shape in a cross-section parallel to the longitudinal axis of the center electrode, said depression located solely within the limits of said insulator body and said metal sleeve having a shape other than one forming a contiguous line with said depression, the surface of said depression being below the line directly connecting the center electrode and the outside annular electrode.