US 2470033 A
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May 10, 1949c F. R. HENsEL SPARK PLUG Filed Nov. 27, 1 945 ATTO RNEY man May 10,1949 2,470,033
2,470,033 SPARK PLUG Franz R. Hensel, Indianapolis, Ind., asslgnor to I P. R. Mallory & Co., Inc., Indianapolis, Ind., a corporation of Delaware Application November 27, 1345, Serial No. 631,205
2 Claims. l This invention relates to spark plugs. An object of the invention is to improve spark plug electrodes.
Other objects of the invention will be apparent from the description and claims.' 5 rapidly from the sparking tip.
111th@ draWngI l Palladium is a highly satisfactory electrode Figure 1 shows a portion of a Spark plug, partly material and approaches platinum in its perin section, illustrating the spark plug electrodes; formance. As disclosed in U. S. Patent 2,335,821
Figure 2 is an "enlarged longitudinal section of to E. M. Wise et al., a fairly heavy plate of palamOdiCaiOn f the electrodes; and l0 ladium can be produced in accordance with the Figure 3 is another electrode combination ,of following bath composition and conditions: the present invention.
The invention contemplates a spark plug with auadnlm as PdC}2"' 50 grams per mer mmonium chloride-- to 50 grams per liter nickel electrodesl having a roughened surface Temperature 50., C and all B lectrodeposfed coating of platinum or 15 Current density-:llt: l0 amperes per square foot palladium base materials. A .tation Air lift Before deposition of the precious metal coatg1 y ing, the surface of the nickel electrode is rst BY using Prepared palladium allOdBS the 00m roughened by such means as etching, sand blastposition of the bath is maintained and there is ing, knurling, or any other suitable method. gg) no necessity for replenishing. Smooth ductile The purpose of this roughening is to create sharp deDOSiS Carl be made at a rapid rate. DBDOSS protrusions which will promote corona discharge 0f .025 have been made in 16% hOlllS- When or lower the sparking voltage when the plug plating upon Such metals aS'niCkel, C0DD1',10I1 is fired. and silver a preliminary strike from a low metal Nickel is destroyed rather rapidly by spark 2j ion concentration bath of palladium, gold, platierosion. According tothe present invention the 1111111, rhodium 01 Other noble mel/91S iS Preferadvantages of a roughened surface is obtained ably depostedrsttogether with good resistance to spark erosion The use of a palladium plate maybe 921111011- by use 0f a deci-,Tomate of platinum or pallarly desirable for side electrodes, with the palladium base material over the roughened nickel. ladium thickness being -010 Inch- The gap The resulting electrode structure and composigrowth in Spark plug eleCtIOdeS OCCUI'S p01? Only tion has a, long nie and 10W and Consistent Sparkon the center electrode but also on the side elecing voltage. trode. A combination of a palladium plated In Figure 1, the center electrode may comprise nickel Side electrode Versus a tungstn 01' tun?- a cylindrical section ll of nickel or nicke1 base 35 Sten alloy Center electrode results 1n supenol metal tip `welded to the end of a nickel, nickel performance and decreased sap growth. alloy, iron ahoy or copper alloy rod l2 which is Figure 3 shows a combination of a center elecembedded in the ceramic insulator I3 of the trod@ tip 45 0f tungsten 01 tungsen allOy Weldil spark plug. The roughened Working surface of to an electrode `rod 40 with a side electrode tip the electrode is coated With an electrodepOsit i0 0f r0ughened-mcke1 2| eletroplated Wlth mail# lt of palladium or platinum. The side electrode mlm 01 Dalladlum 24- may b'e produced in a like manner with a, rough- The palladium may also be used for platingy ened nickel tip 2l, electroplated with a palladium the Center electrode. The base of the electrodes or platinum base metal 24 and welded into a may be either nickel ora nickel a1l0y,ora copper nickel, iron or copper alloy rod 22 which is Welded 45 O1 Silver COIed nickel. The electrode can be to the metal shell i5 of the plug. If either one masked in such a manner that only the areas or both of the electrodes are wholly composed of at which actual sparking occurs are electroplatednickel, the electrode rod may be formed of one Platinum may be electrodeposited from compiece of nickel, which obviates the necessity of plex sodium platinate baths or from phosphate, welding the electrode tip. sulfate or nitrite ammine baths.
The electrode may be made of a nickel-iron Instead of platinum and palladium it is also alloy, containing 42% nickel, for example, whose possible to electroplate `alloys of such metals. coefficient of expansion is lower than that of pure This may be accomplished by codeposition of the nickel or of high nickel alloys, and approximates alloying elements or by plating the elements onto the coeflicient of expansion of platinum. each other and forming the alloys by a diffusion (Cl. 12s-169) 2 Figure 2 shows a modiflcation of the spark plug electrode which, .besides the roughened nickel 3l and the palladium plate 34, contains a copper or silver core 33 to conduct heat away process such as heating the plated assembly in a non-oxidizing atmosphere.
These alloying methods may be employed to form platinum-palladium, platinum-rhodium or palladium-rhodium alloys. Suitable palladiumchromium and platinum-chromium alloys can be formed by electrodeposition. Other'alloying elements for platinum or palladium are nickel, manganese, copper, silver and gold, all of which lend themselves to electrodeposition. i
The palladium or platinum plated roughened nickel electrodes of the present invention when used in automotive or aircraft spark plugs have the advantage of withstanding the erosive action of the spark resulting in gap growth. YHence, frequent adjustment of electrodes is obviated. Also the sharp protrusions of the roughened nickel promote a corona discharge which lowers the sparking voltage. Thus, a spark plug containing one or both electrodes as described in the present invention effectively increases the efllciency of automotive, aircraft or stationary engines.
While specic embodiments of the invention have been described, it is intended to cover the invention broadly within the spirit and scope of the appended claims.
What is claimed is:
1. A spark plug comprising a pair of spaced electrodes, one of said electrodes 'being formed 4 predominantly of tungsten and at least the sparking area of the other electrode being formed predominantly of nickel the surface of which has been roughened, and an electrodeposited coating of palladium over said nickel surface.
2. A spark plug comprising a pair of spaced electrodes, at least the sparking areas of said electrodes being formed ofnickel the surface of which has been roughened, and an electrodeposited coating of palladium over said nickel surface, the surface of said electroplated coating conforming to the configuration of the said nickel surface.
FRANZ R. HENSEL.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date y 1,445,712 'Reiinhout Feb. 20, 1923 2,028,749 John et al Jan. 28, 1936 2,296,033 Heller Sept. 15, 1942 2,391,455 Hensel Dec. 25, 1945 FOREIGN PATENTS Number Country Date 163,786 Great Britain May 24, 1921 206,532 Great Britain Nov. 5, 1923