US1538870A - Spark plug - Google Patents

Description

May 19, 1925- A. CHAMPION SPARK PLUG Filed March 8, 1920 T 'bwve'm rm U 4, @r DP Q 1 Mo 1 440 L Patented May 19, 1925.

UNITED STATES 1,538,870 PATENT OFFICE.

ALBERT CHAMPION, 0F FLINT, MICHIGAN, ASSIGNOR TO A C SPARK PLUG COMPANY,

OF FLINT, MICHIGAN, A CORPORATION OF MICHIGAN. v

SPARK PLUG.

Application filed March 8, 1920. Serial No. 364,015.

specification.

My invention relates to spark plugs of the general class or type wherein a series of sparks are caused to pass between an outer electrode which is supported by the hollow metallic shell or casing of the plug,

and an inner electrode which extends through an insulating member secured in place within said outer shell or casing; and particularly to certain features associated with the outer of the said electrodes, that is the one which is carried by and projects from the inner end of the external hollow metallic shell or casing of the plug.

The principal object of my invention is.

to rovide an improved form, construction, and arrangement of the outer electrode of a spark plug of the general class or type above referred to and by the use of which improvements a more rlgid and a stronger outer electrode is secured; and at the same time to provide a plug in which the life thereof is prolonged, because of a distribution of the sparks which are produced when the plug is in use throughout a greater ortion of the extremities of the inner an of the fixed outer electrodes than has heretofore commonly been the case.

With the above and other objects of invention in view, my invention consists in the improved fixed or outer electrode construction and arrangement illustrated in the accompanying drawing and hereinafter deform of spark plug equipped with one form of my improved electrode, the view being partly in section and partly in side elevation.

Figure 2 is a sectional view showing the inner end of the spark plug shown in F ig ure 1 upon a larger scale, the outer electrode being somewhat modified as to certain of its features.

Figure 3 is a view similar to Figures 1 and 2, but showing a slightly different form of my invention.

F igure l is a view showing the inner end of a plug having an electrode made in accordance with my invention, and in which the same differs somewhat from the form shown in the other figures.

Figure 5 is a fragmentary view illustrat ing the form of electrode shown in Figure 2 upon a larger scale, and in perspective, to show the arrangement of the base thereof relative to the portion of the outer casing from which it projects.

Figures 6 to 10, inclusive, are fragmentary views illustrating various modifications of my improved outer electrode, particularly as regards the form or shape of the free end thereof.

Referring now to the drawing, the reference numeral 10 designates the external'hollow metallic shell or casing of a spark plug of common and well known form, and within which an insulating member 11 is secured in any of the ways at present employed in securing insulating members in place within .such shells or casings; while the reference numeral 12 designates the inner electrode of the plug, the same being supported in a central position within a passage formed in and extending longitudinally of the said insulating member.

Carried by and extending from the inner end of the metallic shell or casing 10 is an outer electrode designated by the reference numeral 13, one end of which is welded or otherwise secured to the end of the said shell or casing. This outer electrode is ob long, or substantially rectangular, in cross section, and the inner end or base thereof is secured to the inner end of the shell or casing in any way, as by welding the same to said inner end as above stated and in accordance with the patent to A. Schmidt, No. 1,319,423, October 21, 1919. The arrangement of the said outer electrode is shown as lot) such that its base portion where it is welded to the free end of the shell or casing has its longer dimension extending circumferentially of the said inner end; so that the greatest dimension of the joint between said electrode and the surface of the shell from which it projects extends at right angles to the diameter of said shell;

The free end of the outer electrode 13, to which the reference numeral 14 is applied, is bent over toward the central electrode at substantially a right angle to the body portion of said outer electrode, and the length of said bent over portion is such that its extremity lies adjacent the central electrode 12 of the finished plug, so that sparks may pass betewen the electrodes when the plug is in use.

Various of the advantages of my invention will be secured by the use of an outer electrode extending from the inner end of the shell or casing of the plug and the end of which is bent over so as to lie adjacent the inner electrode and the cross section of which outer electrode is substantially .rectangular, as above'pointed out. I prefer, however, to twist the bent over portion 14 of the said outer electrode throughout an angle of substantially ninety degrees, so as to cause the extremity thereof to extend substantially parallel with the end portion of the central electrode adjacent which it lies. Such a construction and arrangement of the outer electrode results in a distribution of the sparks which pass between the extremities of the electrodes throughout a much greater area than would be the case if the outer electrode was circular in cross section; thus distributing the wear due to the passage of the sparksbetween the two electrodes throughout a much greater area than would otherwise be the case and prolonging the life of the plug.

The extremity of the outer electrode may if desired be provided with a pluralit of sparking points or teeth, as indicate by the reference numerals 15, which construction provides a plurality of points between which the spark pass and a plug in which the sparks passing between the central electrode and the outer electrode will pass between various points ofsaid electrodes; each spark occurring between the central electrode and some one point of the outer electrode, the particular points between which the spark passes being determined in the case of each discharge by the resistanceof the path along whichthe current flows. It therefore follows that as soon as the resistance of the path along which sparks are assumedto be passing becomes greater than the resistance of another path the sparks will cease to pass between the first assumed points, and will pass between another point of the outer electrode and the central electrode; thus distributing the wear due to the passage of the sparks between all the points upon the outer electrode, or along the entire length thereof if the extremity of said electrode is not provided with distinct teeth and providing an electrode structure in which the life of the outer electorde is very much increased.

It will furthermore be appreciated that my invention provides an electrode of uniform cross section throughout, and one which may be formed from w1re of oblong or rectangular cross section as hereinbefore explained; and which electrode when twisted so as to provide a sparking edge extending parallel with the inner electrode results in a plug in which the sparks are distributed throughout a much greater area than would otherwise ordinarily be the case; such end being attained, as will be appreciated, with- I out imparting any special shape to the extremity' of the outer electrode as the distribution of the sparks" throughout the entire area thereof will occur even if the toothed construction at the end be not employed. At the same time the outer electrode is of greater strength because of the form of the wire employed in the formation thereof and the arrangement of the welded joint between its fixed end and the end of the external shell or casing; and the twisting of the same intermediate its length provides an extremely rigid form of electrode and one in which the change in angular position between the two parts thereof at the right angle at which the twist occurs imparts increased strength and rigidity to the electrode at the bend thereof, which has heretofore been a weak point in spark plug electrodes of the right angular type, that is of the type wherein the free end of the electrode is bent over at a right angle to the body portion thereof to cause its extremity to lie close to the central electrode of the plug.

The use of wire oblong in cross section in the formation of the outer electrode in addition to providing strength and rigidity therein provides an electrode of increased mass through which a free flow of heat may occur from the spark gap where heat is pro-. duced by the passage of the sparks along and through said electrode and to the external casing of the plug, and from there to the engine, thus providing for the conduction of the heat produced at the spark gap away therefrom more effectively than would be the case if an electrode of less cross sectional area was employed and maintaining a comparatively low temperature at the spark gap, while at the same time retaining the advantages of an outer electrode separate from the shell or casing of the plug and projecting from the innerend thereof.

The advantages of enhanced strength and stiffness and of increased mass for providing a more free flow of heat from the sparking points inherent in an outer electrode which is oblong in cross section as disclosed herein are secured irrespective of the form of the extremity thereof at which the sparks pass from said electrode to the inner electrode; from which it follows that the extremit-y of the said outer electrode ma be variously shaped without departing rom my invention regarded in its broader aspect, and as comprehending an outer electrode which is oblong in cross section. Thus in the form of my invention illustrated in Figure 1 the extremity of the stationary electrode is straight, while in Figures 2,.3, 4 and 5 it is serrated,a distribution of the sparks throughout the area of the extremity being however secured in both cases; while in the form illustrated in'Figure 6 there are two surfaces 16 arranged at about a right angle to one another and in between which surfaces the inner electrode 17 is 10- cated, thus securing a distribution of the sparks between the central electrode and the two surfaces in question.

In the form of electrode illustrated in Figures 7 and 8 the end of the electrode is tapered, as indicatedat 18 and '19, thus'reducing the area at the extremity thereof as is permissible in the case of an electrode made from analloy which wears away slowly at the sparking points without, however,

7. reducing the strength or stiffness of the electrode as a whole which is imparted to it by its oblong cross sectional area and without reducing the efiiciency thereof as regards the conduction of heat away from the sparking point and to the shell of the plug; While Flgure 9 sho s a form of electrode in which the end2 thereof is widened, thus providing an edge of greater length than the width of the electrode and a more extended surface along or over which the. sparks may be distributed as hereinbeforeexplained; such edge being either serrated as shown, or smooth ifsuch form is deemed desirable.

Figure 10 shows a form of my invention in which the outer electrode 21 while still oblong in cross section is secured in place to the outer shell 22 of the plug with its longer dimension radial, relative to the cen- Letters Patent tral electrode; the base of the said outer electrode being either welded to the flat end 'tral electrode.

tion thereof, and t sparking points or teeth.

carried by said shell and projectingfrom the inner end thereof, and the arrangement of which electrode is such that its longer dimension extends circumferentially of the end of said shell or casing; .and a central electrode supported by an insulating member secured in place within said shell; the free end of said outer electrode being bent substantially at right angles to the fixed portion thereof, and twisted through an angle of substantially ninety degrees, and

the/extremity of which outer-electrode extends substantially parallel with and lies adjacent the said central electrode and is provided witha plurality of sparking points or teeth. I

2. In a spark-plug of the class described, an external hollow metallic shell or casing; an outer electrode oblong in cross section 1 carried by said shell and projecting from the. inner endthereof, and the arrangement of whlch electrode is such that its longer dimension extends circumferentially of said shell or casing; and a central electrode sup- -ported by an insulating member secured in place within said shell; the free end of said,- outer electrode being bent substantially at right angles to'the fixed portion thereof, and twisted through an angle of substa-ntially ninety degrees, and the extremity of which outerelectrode extends substantially parallel with and lies 3. In a spark plug of theclass described, an external hollow metallic shell or casing; an outer electrode oblong in cross section carried by said shell and projecting fromthe inner end thereof, and the arrangement of which electrode is such that its longer dimension. extends circumferentially of the end of said shell or casing; and a central electrode supported by an insulating ber secured in place within said shell; the

free end of said outer electrode being bent j substantially at right angles to the fixed pore extremity'of said outer electrode lying adjacent said .central elecadjacent the said cenj trode and being providedwith aplurality of I 4. In a spark plu of the class-described,

an external hollow s ell or casing; an outer electrode oblong in cross section carried by said shell and projecting from the innerend thereof; and a central electrode supported by an insulating'member secured in place AL ERT CHAMPION,

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