Igniter plug with vibration damping means

Abstract

An igniter plug having a center conductor, an insulator and a conductive outer shell. The insulator surrounds and supports the center conductor axially within the shell along a substantial portion of the length of the center conductor. The insulator is of reduced diameter toward the discharge end of the igniter and terminates short of the full length of the center conductor. The center conductor extending beyond the insulator terminates short of the discharge end of the igniter and has a discharge electrode of greater diameter than the center conductor affixed to the center conductor end. The electrode terminates at the discharge end of the igniter. A helical compression spring is fitted over the center conductor between the end of the insulator and the electrode to absorb vibrations of the center conductor and electrode.

The invention claimed is: 
     
       1. In an igniter plug having a tubular metal shell, one end of which is adapted to mate with a connector on an ignition cable for supplying electrical energy to said plug and the other end of which is formed with a circumferential shoulder serving as a first electrode for spark discharge of electrical energy supplied to said plug; a core insulator extending axially through said shell, said core insulator being formed in first and second parts,   said first core part having an axial bore therein extending the length thereof and aligned with the axis of said shell; said first core part extending substantially from said one end of said shell and terminating at the forward end short of and spaced from said other end of said shell, the diameter thereof along a length adjacent the terminating portion thereof being reduced,   said second core part having a central bore adapted to receive and telescope over said reduced diameter portion of said first core part,   said second core part extending forwardly beyond the forward end of said first core part and abutting against said shoulder at said other end of said shell;   a central conductor extending through said bore of said first core part with the forward portion of said conductor projecting beyond the forward end of said first core part and terminating within said bore of said second core part, said center conductor being rigidly sealed within said bore of said first core part at a single point located in the vicinity of said one end of aid shell; and   a second discharge electrode fixed to the end of said forward portion of said central conductor and extending through said bore of said second core part and terminating substantially coplanarly with said other end of said shell:   improved means for damping vibrations of said central conductor and said second discharge electrode, wherein the improvement comprises:   helical spring fitted coaxially over said forward portion of said central conductor with one end of said spring bearing against the forward end of said first core part and the other end of said spring bearing against said second discharge electrode so as to apply axially directed forces to said first core part and to said second discharge electrode.   
     
     
       2. The improvement as claimed in claim 1, with additionally, a washer positioned coaxially over said forward portion of said central conductor with one face of said washer abutting against the forward end of said first core part, said one end of said spring bearing against the face of said washer opposite said one face. .Iadd.   
     
     
       3.  An igniter plug having a tubular metal shell, a tubular insulator extending axially within said shell said insulator having a main portion with a forward end and a separate end portion which is telescoped over the forward end of said main portion and a conductor extending loosely through a bore of the main portion of said insulator and coaxially to said shell, aid conductor having a forward end and a discharge electrode affixed to its forward end, which electrode in turn passes through a bore in the separate end portion of said insulator, and said conductor and said electrode extending beyond the forward end of the main portion of said insulator, means interposed between said electrode and the forward end of the main portion of said insulator, for applying axially-directed forces to the main portion of said insulator and said electrode and damping radial vibration of said conductor and said electrode induced by the loose fit of the conductor and said electrode within the bores of the main and end portions of said insulator. .Iaddend. .Iadd.4. The igniter plug as claimed in claim 3, wherein said means comprises a helical spring. .Iaddend. .Iadd.5. The igniter plug as claimed in claim 4, wherein said helical spring is fitted coaxially over the forward end of said conductor between said electrode and the forward end of the main portion of said insulator. .Iaddend. .Iadd.6. The igniter plug as claimed in claim 4, wherein said means further comprises a collar slidably, coaxially positioned over the forward end of said conductor and interposed in contacting relationship between said forward end of the main portion of said insulator and said helical spring, said collar device being in a 
     
     
        close diametral fit with said conductor. .Iaddend. .Iadd.7.  The igniter plug as claimed in claim 6 wherein said collar is a washer. .Iaddend.