US2612151A - Spark plug and method of making the same - Google Patents

Description

Sept. 30, 1952 H. A. BRINSON ET AL v SPARK PLUG AND METHOD OF MAKING THE SAME INVENTORS.

via/2%? 1 2% m l mui l/mg Filed Ndv. r 27, 1946 ATTORNEY Patented Sept. 30, 1952 SPARK PLUG AND METHOD OF MAKING THE SAME Harry A. Brinson and Embry D. Faatz, Sidney, N. Y., assignors to Bendix Aviation Corporation, New York, N. Y., a corporation of Delaware Application November 27, 1946, Serial No. 712,636

This invention relates generally to spark plugs for internal combustion engines, and more particularly to a center electrode assembly that is adapted to be assembled as a unit in said spark plugs.

One of the objects of the present invention is to provide a novelly constructed center electrode assembly for a spark plug.

Another object of the invention is to provide "a novel center electrode assembly so constructed that the transfer of heat from the center electrode to the surrounding insulator is facilitated.

Another object is to provide a novel center electrode assembly which is so constructed that the leakage of gases through the bore of the insulation surrounding the center electrode is substantially eliminated.

A further object is to provide a novel method of constructing the center electrode assembly of a spark plug.

A still further object is to provide a novel method of mounting a center electrode in the bore of an insulator whereby said bore is sub,- stantially filled by said electrode, thus providing a good contact of high heat conductivity between said electrode and insulator.

Theabove and further objects and novel features of the invention will more fully appear from the following detailed description when the same I is read in connection with the accompanying drawing. It is to be expressly understood, however, that the drawing is for the purpose of illustration only and is not intended to define the 9 Claims. (01. 123-469) limits of the invention, reference for this latter purpose being had primarily to the appended claims.

In the drawing, the single figure is an elevation view, partly in section and with parts broken away, showing a center electrode assembly constructed in accordance with the principles of this invention.

Referring to the drawing, the novel center electrode assembly indicated generally at 5 is adapted for embodiment in spark plugs of the general. type disclosed in United States Patent No. 2,356,104, granted August 15, 1944, to Tullio log nola. As shown, the center electrodev assemblyli comprises anfinsulator B molded or otherwise suitably' constructed of suitable ceramicor other'heatresisting material, and provided centrally thereof with a bore having three portions of diiferent lengths and increasing in diameter from one end of said insulator to the opposite end thereof. The shortest and smallest diameter bore portion 1 opens outwardly through the lower end of insulator 6 and inwardly into the lower conical end of the longest intermediate bore portion 8 which is somewhat larger in diameter than bore portion 1 and opens outwardly into the lower square end of the largest diameter bore portion 9 that is somewhat shorter than the bore portion 8 and opens outwardly through the upper end of insulator 6. The conical end of bore portion 8 and the square end of bore portion 9 form rests against the conical shoulder Ill to hold said tip against endwise outward displacement from said insulator. Tip [2 is made of a corrosion resisting metal-which has a high melting point, such as platinum, for example. the intermediate bore portion 8 and extending for a substantial distance above the head 13 of tip I2 is a center electrode bar 14 of metal that softens at a temperature which will not appreciably affect the insulator 6 and the tip l2. Silver, which has a melting point of approximately 1760 F., has been found suitable for this purpose when a platinum tip l2 which has a melting point of approximately 3200 F., and an insulator 5 of ceramic or like material are used, Center electrode bar It is electrically connected to tip 12, and in order to insure good electrical contact between said bar and said tip a thin disc 15 of electrically conductive metal that is fusible at a temperature which will not melt the bar l l is preferably disposed between the latter and tip 12.

A disc I5 of silver solder which has a melting point of approximately 1240 F., and a remelting point of approximately 1340" F. which is above normal engine. operating temperature, has been found suitable for this purpose when a silver bar [4 is used. U

Extending over the upper end of insulator 6 Disposed within and projecting into the bore portion 9 is a terminal [G which is formed with a conical shank IT, a straight shank l8, and a socketed end I9 that is smaller in diameter than the diameter of said portion, the socket in said end being provided with a conical upper wall. The bar l4 and terminal I8 are electrically connected by means of a conductor 20 which is in the form of a wire made of any suitable resilient electrically conductive material, such as, for example, molybdenum, and may be round, fiat, or half-round in transverse crossssection. Conductor 20 is provided with a hooked upper end adapted to receive thereover the socket 19 of terminal [5, a curved or bent intermediate portion, and a straight lower end which projects into a suitable opening 2| formed in the upper end of bar l4. Conductor 20 is mechanically and electrically secured to bar- I4 in any suitable manner, as by swedging the upper end of said bar, .this operation being effected before the latter is placed in insulator 6.

In making the center electrode assembly 5, the tip l2, the disc I5, and the bar [4 with the conductor 20 secured thereto, are placed in the order named in position through the upper end of insulator 6 with the head l3 of said tip abutting the shoulder It, the disc resting on said head, .and the bar resting on said disc.

The annular space with the bore portions 8 and 9 around the conductor 29 is then filled with a sealing material 22 which has a high melting point and in its final form is a unitary rigid mass which has interlocking relation with terminal [6 at the straight .-shank 18, as will appear hereafter, to thereby lead oxide and boro silicate lass is preferably usedbecause of its insulating characteristics and its-coeefiicient of expansion. A satisfactory composition for the lead boro-silicate glass contains 20 to 60% lead oxide and 80 to 40% of glass, the

of silicon dioxide, 12.3 parts of sodium tetraborate, 7.8 partsof boric acid, 2.2 parts of aluminum oxide, and .6 part of potassium carbonate. The described mixture of powdered glass and lead oxide will soften at approximately 1400 R, a temperature below the melting points of the bar M andtip l2, and above normal engine operating temperature. It will be understoodthat other types of sealing material may b employed which will be plastic-like or pasty only when heated to a temperature above the maximum operating temperature of the spark-plug, but below any temperature which might be detrimental to the parts of the assembly 5, i. e. to the insulator Band the parts installed in the bore thereof.

When the bore portion 5 is filled with a predetermined quantity of the sealing material 22 in finely divided powder form and said material is settled, such as by vibration of the assembly, tamping, or the like, the terminal I6 is then placed in the bore portion 9 with the socket I9 thereof engaging the hooked end of conductor 20. vThe insulator 6 is then heated in a suitable manner, as in a furnace or by directing one or more flames from gas jets against the outer surface of said insulator, to a temperature between the melting point of disc l5 and the melting point of .bar- [4, whereupon said disc is melted, said bar is softened but not melted, and the sealing. material 22'is rendered pasty or plastic. While insulator 6 is being heated, longitudinal compression pressure. is applied by a suitable press or the like to the terminal l6, and when the disc i5 is melted, the bar i4 is softened, and the sealing material 22 is rendered plastic, as described, the socket I9 of said terminal is forced over the hooked end of the conductor 28 until said end is properly seated within said socket and the head of the terminal is engaged with the upper end of insulator 6, whereupon longitudinal compression pressure is applied by the terminal 16 to the plastic sealing material 22 causing it to hydraulically compress the softened bar M in the longitudinal direction and thereby expand said bar radiallywithin the bore portion 8 into contact with the surrounding wall of insulator 6. A total pressure of approximately 30 pounds upon terminal 13 has been found to be sufficient for this purpose when a silver bar I4 is used. When the plastic sealing material 22 is compressed, as described, said material is alsov forced into the space within and about the socket Iii and about the shank $8 of terminal Hi.

When the parts are assembled with contact established as illustrated and described, the assembly is allowed to cool while maintaining sufficient pressure upon the terminal l6 until the sealing material 22 has solidified. 1

With the hereinbefore described method of assembly, the insulator bore portion 8 is substantially filled by the bar 14 for at least a portion of the length thereof, thus providing good contact between said bar and the wall of insulator 6 for good and rapid conduction of the heat from the bar to the insulator. All danger of the bar l4 melting and flowing down the walls of the tip l2 to contaminate the latter is eliminated. The tip 12 and bar I4 are soldered together, therebyaiding in establishing good electrical and heat conconducting contact between the same. The escape of gases through the bore portion 9 isprevented by the sealing material 22 which also serves to hold the conductor 28 in contact with the terminal l6 and the parts in assembled relation.

The dimensions of the hooked end of conductor 20 are such that a firm contact is established by the compression of said hook as the socket I9 is forced thereover. The curved mid-section of the conductor 20 permits the latter to be compressed sufiiciently to insure proper seatingof the hooked end thereof insocket l9, and to be expanded or lengthened when bar M is compressed. The conical wall in socket l9 provides four places of contact for conductor 20, i. e. two upon the sides of said socket and two upon the sides of said wall. In order to insure good electrical contact, between the conductor 20 and the terminal [6, the socket [9 may, if desired. have solder therein which will melt when the assembly is heated in the construction thereof.

There is thus provided a novel center electrode assembly wherein a longitudinally extending portion of the bore in the insulator is sub stantially filled by a solid portion of thecenter electrode, thus providing a good contact between the center electrode and the insulator for rapid conduction of the heat from said center electrode to said insulator. There is also provided a novel method of assembling the center electrode in the insulator whereby filling of the bore-in said i sulator by said center electrode is effected Without danger of contaminating the exposed tip thereof.

Although only a. single embodiment of the invention is illustrated in the accompanying drawins and described in the foregoing specification,

' andscope of the invention, as will now bejapparent to those skilled in'the'art. For example, thejdisc "15 may be eliminated and properelectrical contact-between the up-12 m thebarll may be established when theljlatter is compressed during the assembling'operation. Fora definition of the limits "of the invention, reference is had primarily to the appended claims. .\What is claimed is;

1; A center electrode assembly for a spark plug comprising an insulator having a bore therethrough, a metallic electrode tip projecting from said bore, a metallic electrode bar which has been compressed within said bore in a direction towards said tip and thereby expanded radially into contact with the insulator wall surrounding said bore, and means fused in said bore between said tip and said bar and forming an electrically conductive connection therebetween.

2. A center electrode assembly comprising an insulator having a bore therethrough, portions of said bore being of different diameters providing a shoulder therebetween, a metallic electrode tip projecting through the smaller portion of said bore and having a laterally projecting portion disposed within the larger portion of said bore and enga ed with said shoulder, a metallic electrode bar disposed within the larger portion of sa d bore and which has been compressed therein in a direction towards said tip and thereby expanding radiallv into contact with the insulator wall surrounding said larger bore portion, 7

said bore being of different diameters providing 1 a shoulder therebetween, a platinum electrode tip proiectin through the smaller portion of said bore and having a laterally proiecting portion dis osed within the lar er portion of said bore and en a ed with said shoulder, a silver electrode bar disposed within the larger portion of said a direction towards said tip and thereby expanded radially into contact with the insulator wall surro nding said larger bore portion, and a silver alloy disc fused in the larger bore portion and bore and which has been compressed therein in cally and electrically secured-together as a single 5. The method of making-a center electrode assembly having an insulator with a central bore,

which comprises placing a metallic'electrode tip,

'ametallic disc and a metallic electrodebar in said bore'in the order named and in abutting relation with the tip projecting in part from-one end of the bore and the free end of the bar spaced inwardly from the opposite end-of 'saidbore, said bar having a melting point below the melting point of said tip and said disc having a melting point below the melting point of said bar, filling a portion of the space within the bore above the bar with a mixture of finely divided fusible materials of which one component has a melting point below the melting point of said bar, heating said insulator, tip, disc, bar, and mixture to a temperature below the melting temperature of said bar at which said bar becomes soft, said disc becomes molten andsaid mixture becomes plastic, applying pressure to said mixture whilst in the plastic state in a direction towards said bar whereby the latter whilst in the softened state is compressed by said mixture in a longitudinal direction and expanded radially into contact with the surrounding wall of said insulator,

and then cooling the entire assembly.

6. A spark plug center electrode including an insulator tube having a smaller internal shoulder toward one end and a larger internal shoulder between the first shoulder and the other end, a spark electrode abutting the smaller shoulder and projecting from the end, a bar soldered to said spark electrode and compressed within the tube between the shoulders, a hooked wire set in the bar and projecting past the second shoulder toward the other end of the tube, in-

sulation under pressure against the bar and about the wire, and a cap electrode sealing the other end of the tube having a socket receiving the hooked end of the wire in compressed insulation.

7. A spark plug center electrode including an insulator tube having a smaller internal shoulder toward one end and a larger internal shoulder between the first shoulder and the other end,

a spark electrode abutting the smaller shoulder and projecting from the end, a bar connected to said spark electrode and compressedwithin the tube between the shoulders, a flexible connector set in the bar and projecting past the second shoulder toward the other end of the b tween the bar and the tin and forming an electricallv conductive connection between said bar and said tip.

4. The method of making a center electrode assembly having an insulator with a central bore,

which includes the steps of placing a metallic electrode tip, a metallic disc, and a metallicelectrode bar in said bore in the order named and in abutting relation and with the tip projecting in part from said bore, said tip, disc and bar having different melting points, heating said insulator, tip, disc and bar to a temperature at which said bar becomes soft without melting and said disc becomes molten, applying pressure upon the exposed end of said bar whilefit is in softened state to cause the latter to expand radially into contact with the surrounding wallof said insulator, and then cooling the assembly whereby the compressed bar and the tip are mechanitube, insulation under pressure against the bar and about the flexible connector, and a cap electrode at the other end of the tube having a socket receiving the hooked end of the wire in compressed insulation.

8. A center electrode assembly for a spark plug comprising an insulator having a bore therein with an internal cone-like seat adjacent one end thereof, an electrode tip having a portion projecting from said bore and a head portion engaging said seat and substantially filling the adjacent portion of said bore, and a solid section -of metal expanded into engagement with the walls of said bore and having the end thereof bonded to said head portion, such as by soldering.

9. A center electrode assembly for a spark plug comprising an insulator having a bore therein with an internal cone-like seat adjacent one end thereof, an electrode tip having a portion adjacent portion of said bore, a solid section of 7 metal; expanded into: engagement with the walls 7 BEIFEBJ'JN(3E8 CITED of said bore and having the end thereof bonded r n references are of record the to"saidi.-head portion, such as by soldering, a me of this. patent; wire connector having a. bend at one end and the" other end thereof embedded in said metal 5 v UNITED STATES PATENTS 7 section, :a terminal. having. a recess for receiving Number Name Datethe bend at the end of said wire and an en- ,293,381 Carington Aug. 18,1941? larged portion in said bore, and a solid mass of 2,3 0,287 Smith Oct. 10,1944 electrically non-conductive sealing material en- 2,4 0,917 Corbin May 28, 1946 eompassing said enlarged portion and filling the 10 2, 06,966 Pfeil p 3, 1 bore around said wire. v 2,416,107 Litton. Feb. 18, 1947 v HARRY A. BRINSON. I FOREIGN PATENTS D. Number Country Date 7 t a 15 559 805 Grea Britain Mar: 1944

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