US2391457A - Spark plug electrode construction - Google Patents

Description

Dec. 25, 1945. c, F. cA'RLsoN SPARKPLUG ELECTRQDE CONSTRUCTION Filed Feb. l, 1944 Zvw,

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UNITE-o sTATEsJ PATENT OFFICE sraax PLU'G ma coNs'rnUc'noN Chester F. Carlson, New York, N. Y., assilnor to P. R. Mallory & Co., Inc., Indianapolis, Ind., a corporation oi' Delaware Application February i, 1944, serial No. 520,883

` s claims. (ci. 12s-169) This invention relates to sparkplugs and elecwith another metal. 'I'his results in a desirable f j construction but is expensive to produce and can v An object oi' the invention is to improve spark only vbe used where the core is of lower melting plug electrodes and the plugs in which' they are point and can be cast in the shell, or the two incorporated. metals can be readily brazed together.' It is also Other objects of the invention will be appardiilicult to insure that a perfect metal-to-metal ent from the description and claims. bond is obtained inside the closed end of the In the drawing: i l shell.

Figure 1 shows a spark plus. partly in section, Coatings produced by electric plating generhavinga center electrode embodying features of ally have insuilicient density and erosion resistthe invention; ance to withstand the erosive effects of sparking Figure 2 is an, enlarged section of the end of over long periods of operation. the center electrode of Figure 1; According to the present invention a spark Figure 3 is a-section on the line 3-3 of Figplug electrode is formed of 'awire or rod having ure 2: 15 a core of one metal clad with abonded sheath Figure Y4 shows a modied electrode; l of al second metal and doubled upon itself to Figure 5 is a section on the line 5-5 of Figprovide a bend or loop at the sparking tip. This ure 4; provides a composite construction of improved Figure 6 shows a further modification; I performance and lower cost which can be read- Figure 7 is 'a section on the line 'I-l of Flg- 20 ily produced with conventional manufacturing ure 6: equipment.

Figure 8 shows a still further modification; 'I'he clad wire or rod may be made by several and methods. One method is to pass a wire of the Figure!) is a section through a modified `eleccore material through an electro-plating bath trode. 25 where the sheath of desired thickness and com- It is ditllcuit to ilnd a single metal or alloy position is applied. After plating, the wire is which combines all the properties desired inf, a passed through a series of hot `or cold drawing spark plug electrode and which'can stand up unsteps to reduce it to the diameter desired and to der heavy service for long periods. The sparking apply Suicient hot or cold working of the sheath surface must be formed. of a material which is metal t'o change its metallurgical structureandv resistant to the erosive effects-of the sparks or` increase its density and erosion resistance. arcs formed during ignition and also the explod- Another method is to braze a rod of ,one metal ins gases, which contain lead and other reactive into a tube of another 'metal followed by drawcompounds. -The electrode must also have adeins t0 the desired diameterquate strength at the high temperatures encoun- 86 A further method/is to Ishrink a tube of one tered, such as redheat. and must have sumcient metal onto a rod of another metal and furnace thermal conductivity tocarry-heat awayfrom the the assembly in a reducing atmosphere to prohot tip at a rate which will cool it below ignition duce pressure welding or bonding of the twol laytemperature `of the .explosive mixture between ers without fusion;

explosions. to avoid pre-ignition. Where pre- 40 A still further method is to illl a tube with a cious metals are used, economy is also an immolten metal of lower melting point.

portant condertlon- One desirable composite wire or rod comprises. Heretofore it has been proposed to form a a core of a high thermal conductivity metal such composite electrode tip having a sparking tip of' as silver, copper and their various alloys and a one metal on a rod of another metal. This has sheath of good resistance to spark erosion such the disadvantage of exposing a welded or brazed as nickel.

joint near the sparking area. It has been found Another combination comprises acore of ductile that erosion is increased at or near such Joints, molybdenum wire having a sheath of platinum .probably due to the presence of minute impurior of a nickel alloyhaving low coemcient of ex ties at-the Joint or to a discontinuity in the crys- 5 pansion, such nickel-chromium, nickelmantal structure. There is also the danger of failganese, nickel-molybdenum, nickelfiron-molybre of the weld and 1 of the splfking tip dlll'-` denum, nlckel-iron-chromium-molybdenum aling operation. lo.

Another construction has been proposed in Figures 1. 2 and 3 illustrate an aviation which a metaltube having a closed end is illled u plug Il and a center electrode l I'therefor. The

cover a doubled portion whether sharply electrode II is of a composite construction comprising a round nickel rod I2 having a sparking tip I3 weldedthereto, formed of a folded and swaged wire or rod having a core I4 oi' one metal and a sheath I5 of another metal.

The electrode can be made in the following manner. A length of clad wire, such as nickelclad copper, which has been drawn to improve the bond and the properties of the nickel coating, is bent double and hot or cold swaged to deform the original shape of the wire and bring the doubled section or loop into substantially cylindrlcal cross-section with flat ends. Squaring of the ends may be completed by grinding or swaging, but the coating layer is not cut through at the folded end. The end at which the core material is exposed is then butt welded to the end of nickel rod I2, by resistance or flash-arc weld'- inB. for example, by the method described in Holt Patent 2,323,660 issued Ju1y e, 1943.

I3. It will be noted that the only .place where the core material I4 can be exposed is at the welded joint 1, which is remote from the sparking zone and is protected within the bore of the in' sulator.

It is contemplated that the entire center electrode member II may be formed frgm thefolded and swaged wire in some cases.

Figures 4 and 5 show a modified electrode in which the coated wire or rod is bent `into a loop I6, preserving the round form of the wire. The two ends of the wire section are brought 'into parallel relation side-by-side and welded onto the face of a flange Il on the end of a rod I8 which passes through the ceramic insulator Il of the plug.

Figures 6 and 7 illustrate a form in which a core 20 of fiat strip stock is coated with a layer 2| of erosion resistant metal. The coated strip is doubled upon itself and welded in a recessed flange 22 on the end oi center rod 23.

Figure 8 `illustrates a form in which the coated wire 24 is sealed in the center of ceramic insulator 25 and the end section is bent into loop 26. The i end of the wire is inserted in a recess 21 in the ceramic alongside the opposite side of the loop.

In some cases the end may-be welded to the opposite side of the loop where they are in contact.

Figure 9 shows a tri-metallic wire which can be used in any of the preceding structures. Some materials, such as platinum and other precious metal alloys, are good sparking point materials, but if illled with a high conductivity metal such as copper or silver which has a high expansion coemcient, the platinum sheath will burst when the electrode becomes heated. In the wire of Figure 9 the core 2l of copper, silver or other high conductivity metal is enclosed in an intermediate sheath 29 of a strong metal or alloy, such as nickel and nickel alloys, which will n ot burst under the expansion pressure of the cori.l metal. An outer sheath 30 of spark resistant metal such as platinum, platinum alloys or other precious metals is applied Yover the intermediate sheath 29.

In the following claims the words loops and fold" are to be construed broadly en'o h to ned as shown in Figures 1 and 6 or bent into loop as shown in Figures' 4 and 8.

While speciiic embodiments` of the invention have been described, it is intended to coverthe invention broadly within the spirit and scope of the appended claims.

What is claimed is: Y

1. A spark plug electrode comprising a wire having a core of a high thermal conductivity arranged to effectively disperse sparking heat from said electrode and a sheath integrally bonded 'thereto formed of a material of good'resistance to spark erosion, said electrode wire being doubled upon itself to provide a sparking tip in the form of a loop, the-ends oi said wire being remote from the sparking area of said electrode.

2. A spark plug comprising an insulating body, an electrode member passing through .said body and sealed therein, said electrode projecting from said body to form a sparking tip, at least the projecting portion of said electrode comprising a wire having a core of metal of high thermal conductivity arranged to effectively disperse sparking heat from said electrode and a sheath of metal of good spark erosion resistance, said wire being doubled upon'itself to provide a loop at the sparking lgip, and a second electrode member .projecting toward said loop to form a sparking gap therewith,

3. A spark plug insulator and center electrode assembly comprising an insulating body having a passage therethrough, andan electrode member extending through said passage, said electrode member having at least a section thereof formed of a clad wire comprising a core of high conduca rounded tivity metal arranged to eiectively dispersesparking heat from said electrode and a sheath of metal of good spark erosion resistance, said wire being folded upon itselfto provide a sparking tip in the form of a loop projecting from said insulating body, theends of said loop being in lateral adjacency and both entering the passage i in said insulator, whereby only the sheath of said wire is exposed.

4. A spark plugcenter electrode having a sub stantially circular cross-section, at least the sparking tip thereof being formed of a clad wire folded upon itself to form a fold or loop, said wire having a core of high conductivity metal arranged to eiectively disperse sparking heat from said electrode and a sheath of metal of good spark erosion resistance, said folded wire having substantially. semi-circular cross-section so that the two sides of the fold together form a rod of substantially circular cross section.

5. A spark plug electrode comprising a sparking tip' formed of'a section of clad wire having a core of high conductivity metal arranged to eifectively disperse sparking heat from said elecf trode and a sheath of metal of good spark erosion resistance, said wire being doubled upon itself, and a body for said electrode comprising a metal rod, the two lends of said section of clad wire being welded to the end of said metal rod.

6. A spark plug electrode comprising a body formed of a metal rod, and a sparking tip welded to the endthereof formed of a section of clad wire having a core of high conductivity metal arranged to effectively disperse sparking heat vfrom said electrode and a sheath of metal of good spark erosion resistance, said section of wire being doubled upon itself and having its ends welded t'o the end of said metal rod.

7. A spark plug electrode comprising a wire having a core of high conductivity metal, an incontinuance of thecontour and cross section sonst? y 3 termediate sheath of high strength metal and sparls'exosion, and said wire being doubled on afa outer sheath of meta! resistant to spark itself to form a sparking ntip at its doubled non n erosion. tion, with the ends of said wire closely adjacent 8. A spark plug electrode .comprising a solid each other and secured to the end of said elecelectrode rod and an end section on said rod in 6 trode rod, the sleeve legs formed by said doubling y' in contact with each other throughout their exdimension of said rod, said end section compristent, the core legs formed by saiddoublingeps ing a wire having a core of high thermal conducyrated thronghouttheir extent by portions -oi said tivity and an open ended sleeve bonded to said sleeve legs, said core ends being covered by said core and completely surrounding and covering lo electrode rod end, and the doubled wire being said core between said sleeve ends, said sleeve .effectively in the form of asolid rod. v being formed of material of good resistance to CHESTER F. CARLSON;

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