US2622578A - Spark plug - Google Patents

Description

23, 1952 H. H. 'VOGEL ET AL 2,622,578

SPARK PLUG Filed July 18, 1950 INVENTOR. Ho ward H. l/age/ Roy 14 Pafon .5 Que @w A TToR/VEYS Patented Dec. 23, 1952 2,622,578: I SPARK PLUG Howard H. Vogeland Roy W. Paton, Toledo, Ohio, assignors to Champion Spark Plug Company,

Toledo, Ohio, a corporation of'Delaware Application July 18, 1950, Serial Nip 174,424

This invention relates to spark plugs, and particularly to those having an internal auxiliary spark gap associated with the center electrode.

The primary object of the invention is the provision in a spark plug of an auxiliary gap in the center electrode structure that is adjustable during the assembly of the parts to accurately establish, within a very close permissible tolerance, a predetermined gap dimension suitable for the particular plug, so that such dimension is maintained for the usable life of the plug.

Another object of the invention is to provide a gap-forming structure that cannot be tampered with or changed from the exterior of the spark plug once it has been adjusted.

Still another object of the invention is to provide a gap-forming structure for the center electrode assembly of a spark plug that contains a minimum of parts and requires a minimum assembly and adjustment time.

Further objects and advantages of the invention will be apparent from the following detailed description, and from the accompanying drawings illustrating one embodiment thereof, in which Fig. l is a central longitudinal section of a spark plug embodying the invention, and Fig. 2 is a cross-section on the line 2-2 in Fig. 1.

Referring to the drawings, I designates the customary metal shell of a spark plug having at its lower or firing end the ground electrode 2, which, so far as the present invention is concerned, may be of any suitable form and construction. The customary insulator 3 is mounted in the shell in any suitable manner and has an axial bore 4 therethrough in which the center electrode 5 is mounted with its firing end exposed and suitably spaced with respect to the ground electrode 2 to provide the proper spark gap therebetween, as well understood in the art. The bore 4 at the lower or firing end of the insulator is of reduced diameter and this forms a shoulder 6 internally of the core against which a shoulder or enlargement 'I on the center electrode seats.

The center electrode 5, which is of the wire type, projects up into the large portion of the bore 4 in spaced relation to its wall and, for the purpose of the present invention, terminates some distance short of the upper end of the bore, as shown. The space around the electrode for a distance outward from the shoulder 6, but short of its end, is packed with a suitable sealing and holding body 8 to firmly and hermetically seal the electrode in the core. This provides a free 2 7 space between the outer end portion of the center electrode and the wall of the bore 4.

After the sealing of the electrode 5 within the bore 4 has been effected, an adjustable gapforming thimble or sleeve 9 of electrical conductive material and of an outside diameter to fit easily in the bore 4, and having a socket [0 in its lower or inner end of a size to fit closely the upper free end of the electrode, is forced into the bore and down over the upper electrode end so as to form a portion of the electrode. This thimble makes close electrical contact with the electrode and has sufficient frictional engagement with the electrode to firmly hold the thimble in an adjusted position in the assembly. This is important, as the top or exposed end of the thimble forms the inner or lower surface of an auxiliary spark gap [0 in the bore 4 of the core, and the thimble should, therefore, not only be capable of accurate positioning Within the core but of maintaining the adjusted relationship of the center electrode and thimble.

In practice, a depth gauge is used to properly position the thimble in the core with a permissible tolerance in the order of .004 of an inch and the pressed fit of the thimble on the electrode enables this to be easily accomplished The thimble 9 havin been positioned, the terminal stud II is suitably secured at its inner end in the upper open end of the insulator bore 4, with such end of the stud in predetermined spaced relation to the thimble end to form the desired auxiliary spark gap l2 therebetween. In the present instance, the stud is shown as threaded into the bore end with a suitable cement l3 therebetween and the depth of projection of the stud into the bore is limited and accurately determined by a flange hi on the stud shouldering against the core end. If desired, the stud may have an axial relief passage [5 therethrough from the gap space H! so that the gap may be relieved of ionized and dissociated air. Since the dimensioning and positioning of the parts forming the gap is made with respect to a common plane, the top of the insulator, variations in the length of the insulator, the absolute length of the center electrode Wire, the relative disposition of the shoulder parts 6 and 1 may all be disregarded in determining the width of the auxiliary spark gap. It will further be seen that once the stud H has been seated, the gap cannot be tampered with or changed.

We wish it understood that our invention is not limited to any specific construction, arrangement or form of the parts, as it is capable of 3 numerous modifications and changes without de-'- parting from the spirit of the claim.

What we claim is:

In a spark plug having an insulating core with an axial bore therethrough, and a center electrode fixedly mounted in said bore with its terminal connecting end spaced inwardly a predetermined distance from the terminal end oi the bore, the improvement which consists in providing a free space in the bore around said terminal end portion of said electrode, an electrical conductor element having a tight sliding fit on the electrode in said space with its outer end in predetermined spaced relation to the adjacent core end to permit said element to be pressed into predetermined spaced relation to the terminal end of the core, and a terminal stud mounted in the terminal end of said bore with its inner end in predetermined gap-forming spaced relation to the outer end of said element, said terminal stud having a bore therethrough extending from said space to atmosphere at the top of said stud whereby ionized air within said space may be vented.

HOWARD H. VOGEL. ROY W. PATON.

REFERENCES CITED The following references are of record in the file of this patent:

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