US2139793A - Spark plug - Google Patents

Description

Dec. 13, 1938. c. R. BENTON j 2,139,793

SPARK PLUG Filed June 15, 1936 Ju /Z727 Patented Dec. 13, 1938 UNITED STATES PATIENT OFFICE SPARK PLUG Cecil B. Benton, Vergennes, Vt. Application an. 15, 1936, Serial No. 85,201

3 Claims.

The inventionrelates to spark plugs. The primary object of the invention is to pro vide an electrode on the shell of the plug, usually the ground electrode which can be readily and accurately deformed or varied to provide the optimum gap for sparking and also shields the sparking face on the center electrode from direct contact with the flame in the cylinder.

Another object of the invention is to achieve this primary object with a diversity of forms of electrodes, and with spark plugs for engines having different output characteristics.

Other objects of the invention will appear from the detailed description.

)5 The invention consists in the several novel features which are hereinafter set forth and are more particularly defined by claims at the conclusion hereof. r P

In the drawing: a to Fig. 1 is a longitudinal section of a spark plug embodying one form of the invention;

Fig. 2 is a section, on an enlarged scale,

through the electrodes and shell, illustrating the manner of resetting the electrode on the shell to 1'3 vary, and provide the optimum gap between the a spark plug comprising a shell II), which is provided with the usual screw-thread for engaging a corresponding internal thread in the engine cas- 4 ing and with a polygonal flange ll whereby the assembled plug may be screwed into the casing;

a center electrode l2 having a cylindrical termi-' nal l3 at its inner end on which the flat circular sparking face I4 is formed; and a stem 9 extending longitudinally through the plug; a sleeve l5 of suitable insulation surrounding the stem 9 and engaged by a shoulder IE on electrode l2; a coupling ring l1 provided with a screw-thread I8 50 for engaging a corresponding internal thread in the shell l0 and having a shouldered inner end for engaging a gasket 20 and forcing it against a conoidal surface in the shell; a collar 2| fixed to the outer end of the stem 9 of electrode 12 and 55 for electrical connection with a conductor wire;

and a sleeve 22 of insulation between collar 2| and ring [1.

The-ground contact 24 consists of a strip of metal extending across the cylindrical opening in the inner end of shell ID, with its ends 25 seated 5 in recesses cut in the end of the shell and secured therein by brazing or welding, as indicated at 26. The central portion 21 of the strip 24 is offset longitudinally of the axis of the inner electrode 12, being bent as at 28 between the portions'25 l0 and 21. The inner face of ofiset portion 21 forms the sparking face of the ground electrode. The electrode 24 is shaped from a strip of fiat stock and its central portion 21 is of sufificient width or area to overlie the sparkingface l4 on the central electrode l2 so it will shield the sparking face I 4 of the central electrode from the'flame in the cylinder and prevent scouring of the sparking face I4 by such flame. The central electrode 12 is usually made of a spark-resisting alloy of steel, because it is insulated from the shell and is thus not as well cooled by intimate contact with the cylinder head. The electrode 24 is formed of a metal, steel or alloy which is suificiently ductile or malleable so as to avoid any spring-action i when it is deformed and so that when it is impacted by a tool, such as a suitable hammer, the central portionj1 will remain set in its deformed shape with practically :no tendency to spring back to its normal shape. This degree of ductility 30 or malleability may be attained by subjecting the 7 metal to suitable heat treatment.v The heat applied to the ends 25 of the strip, for welding or brazing them to the shell, may be utilized to some extent for this purpose. The ground electrode may be made-of spark-resisting alloy; since it can be separately formed from the shell or integrally formed therewith. In either event, the material should be sufficiently ductile ormalleable to eliminate any spring-action when it is deformed, com- 40 pressed or bent, and to cause it to remain set in its adjusted position or shape.

When the gap between thesparking surfaces on the electrodes becomes excessive from use or wear, an ordinary hammer of suitable size may be 5 usedto pound down the portion 21 of the strip forming the electrode 24. A templet or strip a, indicated by dotted lines in Fig. 2, of a correct thickness to correspond to the optimum gap between the electrodesfi may be inserted between them while the portion 21 of the strip forming electrode 24 is hammered down to provide the proper gap; On account of the softness or lack of spring in the metal forming the electrode 24,v the central portion 21 will be set, as indicated face on its inner side will be brought down to the correct distance from the sparking face of the center electrode, without resulting in any substantial recession of the sparking face on portion 21 from the strip a or the sparking face Id of the inner center electrode. By hammering down the entire central portion 21 and the use of 'a templet, the normal parallelism of the sparking-faces, which are perpendicular to the axis of the electrode I 2, will be retained. By forming the ground electrode of metal which will remain set in the position in which it is hammered, it makes it possible to provide a spark plug in which the sparking faceof the center electrode is shielded by the ground electrode to prevent direct contact of the flame with the sparking face of the inner electrode and to easily vary or adjust the sparking faces-for the correct or most efllcient spark gap.

In the event that the gapbetweenthe sparking faces of the electrodes is too small, after the electrode 24 has been applied, the gap may be increased by screwing out the assembly consisting of the electrode I2, sleeves I5, 22 and ring ll slightly, inserting a templet a and then screwing 'down the said assembly. Usually, use of the plug increases the gap and the adjustment required is a decrease of the gap, which is done by hammering the portion 21 of electrode 24, as before described.

In low output engines, the diameter of the cylindrical end l3 of the inner electrode is smaller than the diameter used in high output engines.

In the modification illustrated in Figs l and 5, the electrode 24 on the shell is made of metal having the ductile and springless properties hereinbefore described and comprises a central portion 21* of sufficient area to extend over the sparking face on the large cylindrical .end I3 of the central electrode il of a spark plug fora high output engine. The ends Mi of the strip 24 are brazed or welded in recesses in the end of the shell se In this modification the electrode 24* is normally fiat and its entire flat central portion is adapted to be deflected or hammered tdwardthe sparking face M of the inner electrode, as indicated by dotted lines in Fig. 4, so asto maintain parallelism between the sparking" surfaces. In 'high output engines, it is desired to terminate the central electrode inwardly of the end of the shell as shown. In this case, the central portion 22 is deflected downwardly by a suitable hammer to keep its inner face in parallelism with the sparking face it and the metal between the central portion and the end portions 25 is deflected downwardly and stretched, as indicated at 28 While this isdone a templet may be inserted between the sparking faces of the electrodes to arrest and set the central portion of the strip the correct distance'from the sparking face I4 and provide the correct spark gap.

Fig. 6 illustrates a modified form of ground electrode of ductile or malleable metal having the same properties as those hereinbefore described and which comprises a circumferential rim 30 which is brazed or welded, as indicated at 3!, to the shell ill"; a central portion 32 adapted to extend over and shield the sparking face on the end of the inner electrode 82', and a series of connecting arms 33 between the annular portion 30 and the central portion 3!. The central portion 32 may be deflected by a hammer, as hereinbeioredescribed, when the sparking faces are to be brought together to compensate for wear. In t his form of the invention the arms 33 are offset 75 adjacent the annular portion 30 to permit the deformation of the metal while the central portion is being hammered to form the desired sparkgap.

The invention exemplifies a spark plug with an electrode on the shell which shields the sparking face of the central electrode from direct contact with the cylinder flame and isreadily and accurately variable to provide the optimum spark-gap.

The invention also provides for variation of the spark-gap by hammering, which results in resetting or adjusting the metal'without spring-action. The invention also provides for embodying these features in ground electrodes'of different forms. The invention also provides a ground electrode having these characteristics which provide for recession of the spark-plug gap into the shell for high output engines.

The invention also provides a ground electrode having, these characteristics which may be separately formed'from the shell, sothat they may be made of spark-resisting metal, although it is to be understood that in some instances the invention may be applied to ground electrodes which, for cheapness in manufacture, are integrally formed with the shell.

stricted to the details set forth, since these may be modified within the scope of the appended claims, without departing from the-spirit and scope of the invention.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent is:

1. A spark. plug comprising a shell-provided with means whereby it may be secured to an engine-casing, an inner electrode in the shell having a flat sparking-face at its inner end, and a flat strip forming a coacting electrode, bridging the inner end of the shell, formed separately from and having both of its ends permanently bonded to the shell and comprising an integral central portion having a substantially flat sparking-face parallel with the sparking-face on the inner electrode, said strip being formed of malleable or duetile metal which can be pounded or deflected to- Ward the sparking-face on the innerelectrode to vary the gap between the sparking-faces by deformation between its central portion and both of its bonded ends, so that the central portion will remain set and maintain the parallelism between the sparking-faces.

the shell and comprising an integral central por-,

tion having a substantially flat sparking-face parallel with the sparking-face on the inner electrode and longitudinally extending portions between the central portion and the bonded portion,

said. strip being formed of malleable or ductile metal which can be pounded or deflected toward the'sparking face on the inner electrode to vary the gap between the sparkingafaces by deformations in the longitudinally extending portions, so that the central portion will remain set and maintain the parallelismbetween the sparking-faces.

3. A spark plug comprising a shell providedwith means whereby it may be secured to an engine-casing, an inner electrode in, and terminating inwardly of, the shell having a flat sparking-face at its inner-end, and a transversely straight flat strip forming a coacting electrode,

bridging the inner end of the shell, formed separately from and having both of its ends permanently bonded to the shell and comprising an integral central portion having a. substantially fiat sparking-face narallel with the sparking-face on the inner electrode, said strip being formed of malleable or ductile metal which can be pounded or deflected toward the sparking-face on the inner electrodeto vary the gap between thesparkingfaces by deformations between its central portion and both of its bonded ends, so that the central portion will remain set and maintain the paral- B lelism between the sparking-faces.

CECIL R. BENTON.

Images