US2604087A - Spark plug - Google Patents

Description

July 22, 1952 D. W. GREGORY ETALA SPARK PLUG Filed Sept. 22, 1948 INVENTORS yles M Greyafy l (d i?. aldaffare i Y wh/wm Y ATTORNEYS Patented July 22', 1952 `ADouglas'fW. Gregory, Vergennes, Vt., aand; Egidiol R. Balda'ss'are, New VYork, N. Y.,-'-.assignors to `*Simmonds Aerocessories, Inc., Tarrytown, NSY., a corporation of New York 'Application SeptemberfZZ,

(Cl. 12s-169) 5 Claims.

Thislf'invention?relates to" imp'r'ovementsr in a' method-Lof:makingr spark plugs and` in. the" spark plugsfinad'e l thereby; f. -In a' more particular sense the invention `relates .aymethod of bonding metals with ceramics; for 'example 1a metal elec- 5 trodetoan insulatorto form l1a Vgastight yseal -be` tween'fthetwo. y

Various methods have beenemployed for the sealing lof electrodes Y in spark plugror igniter vin` sulatorsf" One successful' method comprisesa'seal formedfbymeltingifg-lass c'ontainingvrgraphite or metal powder inside'the ceramic insulator and the' ceramic/and?` th'el metallic electrodev contained.v thereinin accordancelwith- U. Se Patent 2,106,578. In contradistinction;processes-have:been devel- 15 opedffor'thel formingmi spark'plug center'v electrodes :bymeans of feasting: metal in the 'insulator borel toii'make permanent" and -xing engagement l withfa'fsparkingltip located' in theinsulator bore at itsrspar'kingend-in accordance WithSU. S. Pat` ent 2;*162,'062, the advantage'thusgainedbeing the formation of." iin/electrical: conductor having form, f position)4r and'iproperties which' make for the` increasedponductionzof heat fromy said sparking-tip and, lessicertainly,lircmfthe insulatorY nose,` while mechanically ."'flxing and'at thel same 4time ntegrally unitingthefparts ini the insulator.'

Sparkfplugsfmadeiusing ithis latter4 process 'aswell lastl'ioseiproduoed according Ito thefdesigns'- and proce'ssesisetforth iii-British`v Patents 533,759,A 547,119; 559,805?andl56.?,064 fhave been found t0 ShowfgaS-leakageasin' the usual method of presl` sure .testing spark plugs.: vrFoi-.such reason it hasA beenrnecessaryfto use additional sealing frneans' y suchirasy represented byth'e above citedU. S.' Pat-` ent 2;l06,578' invaddition to the subject vcasting process :1in l.order to insure Vgas-tightness consid'- ered .essentialtov consistent performance in`r spark plug operation.

Plugs :made/by castingor h'ot formingsilver in the insulator Jhavebeen `examined-in detail by breaking:thefzinsulatorfand exposing the cast metal core conductor. It was 'found' that vthe cast metalficore Was-smooth and `that; itvdid not adheretothe-Wall of the insulator. The insulator had apparently/served merely as a'mold for casting oriormingthefsilver.' f n Accordinglrto the' present invention a method 'has beenfdiscovered vbywhich ya cast metal is against thepassageof gas through threfinsulafA tor bore and toA enhance the .interchange of heat between the-*metalr and ceramicy insulator components.

The primaryf'object of the "invention is-,-there- .l l fore, tok provide fanA improved'. method ffor :bonding c a metal tconductor' tof the inside wall ofv a; spark i pluginsulator;

prevent c gasA leakage; n

Another object of theinventionis tos-.provide an improved 'method *off building-r af metal v`toa ceramic material.

Another object of 5 they inventionfis;l to. provide f an improved t spark-1 plug f in which i the electrode i conductor' is bondedto the inside Wall ofthe spark plug insulator.

Accordingto` apreferred'form of y the invention i t the improved spark plug is manufactured bythe steps of mounting-a mjetal sealing--conejorfspike 1 in the lowerportion oinafsparkplug insulatongthe cone being electrically connected toa-sparking'` 'tip extending from the tip of the insualtor pro- Y viding abody of moltenymetal*havingfafmelting point of approximatelythat ofsilVer-around Vthe cone and to a' considerable vdepth in theinsulator,V inserting a. second ,metal'fsealing';y cone 1or spikeV pointed downwardlyA inthe insulator; abQveithe body of molten metal," and `applying pressure'to' the secondy cone to Ydrive it into andvtoapply pres.;y

sure to the moltenm'etalinltheiinsulator, whereby: o the moltenf metal is driven-suddenly into intimate" contact with the, hot inside-Wall iolthe -`insulator f and bonded thereto.`

In afspe'cicform-'of theinventionxtheisealing coneused'in theybottom of :the-insulatorflist'pref y eraloly of*nickeLp-whilethesecond coneis prefer ably` of steel' 'and nickel;` and silver :plated:'with1` the silversubsequently brazed'asiin hydrogen.l

In the drawings: l

Fig. 1 is avertical' or'longitudinalfview of a'24 f spark' plug'f 'insulator ofA Iconvention'alf construe-i tion showin-g` the relationship of the 'parts'z inf the 1 l initial stageiof the procesa?4 Fig. 215s view'simuar'tolthat fFigf. V1j show# ing the' relationshipk ofthe parts' after fthe silver? orl othe'rfmtar has been -fmeited iii-th insulation Fig. 3 is a longitudinal sectional view showing the relationship of the parts at the conclusion of the process.

Figs. 4, 5, 6 and 7 show modified forms of upper sealing cones or spikes which may be used in carrying out the improved process;

Figs. 8 and 9 show modified forms of lower sealing cones or spikes. Referring to Figs. 1 to 3 inclusive, of the drawings, the improved spark plug of the present invention is made by providing a spark plug insulator ID of conventional design and made, for example, by sintering aluminum oxide or other suitable ceramic. This insulator, preferably of an aluminum oxide type, has an upper relatively long bore I2 of large diameter, a lower relatively long bore I4 of substantially smaller diameter, and a tip bore I6 substantially smaller than the bore I4 and preferably of the correct size to t a sparking tip such as themetal tip I8, or an extension of a cone 20, to which a relatively shorter sparking tip may be appended. The rst step in the process is to provide a lower sealing cone or spike such as the spike 2U which is preferably of nickel, and which is also large enough or may be mechanically up-set or otherwise processed to preclude its complete passageoutwardly through bore I6. The lower sealing cone or spike 20 may be provided with an extension of suitably small diameter to project through bore I`6 whereafter it may attach to the sparking tip I8 of relatively short length. In the form shown in Fig. 1, lower cone 20 is welded to the sparking tip I8, the welding joint being shown at 22, and as providing a rim resting in the lower portion of the bore I4. It is not necessary that the cone or spike 20 be of larger diameter than that of the sparking tip IB, but it preferably extends substantially into the bore I4. After the cone 20 is in place a section of a silver wire 24 is set in the insulator on the cone so that when it melts it will somewhat more than fill the bore I4. Instead of using silver wire powdered silver or other form of silver or a silver alloy may be used. Copper may also be used.

The insulator I6 with the elements shown in Fig. 1 is set in upright position in a suitable furnace in which the insulator is heated to a temperature above 1760 F., which is sufcient to melt the silver and cause it to run down in the bore I4 and surround the cone 20 in the manner shown in Fig. 2 of the drawings. If the cone 20 is welded or otherwise attached to the sparking tip I8 prior to starting the process, the arrangement is preferably such that none of the silver comes in contact with the tip I8 which is preferably of platinum or a platinum alloy of tungsten. The insulator containing the molten silver is removed from the furnace to a specially arranged press, after which an upper sealing cone or spike member 26 is quickly inserted into the insulator and plunged or driven into the molten metal by applying a tool under pressure to the upper part of the cone. The cone 26, as shown in Fig. 2, includes a pointed spike section 28 and an upper open top shell section 3U into which the tool for applying the pressure may be inserted. The entire cone 26 may be of Bessemer steel such, for example, as screw stock and silver plated.

The pressure applied to the cone 26 should be somewhat of the order of 4,000 pounds per square inch and applied quickly but over a period of a few seconds rather than instantly. W'hen the cone quickly chills the silver and at the sam time forces the melted silver against the hot wall of the insulator I0. The shape of the cone 26 furthermore causes the chilling of the silver from the inside out. When the silver 32 has frozen it forms an intimate contact with the lower cone 20, with the upper cone 26 and with the contiguous insulator Wall, especially in the areas adjacent to members 20 and 26.

Fig. 3 shows a vertical section through the insulator after the foregoing operations have been completed and it will be noted that the silver I2 is thoroughly bonded to the inside wall of the insulator I0 and that the lower cone 20 extends into the body of silver while the sparking tip I6 has not been contacted by the molten silver in the casting operation. The upper part of the body of silver 32 completely surrounds the lower portion of the cone 26, the tip of which is somewhat deformed to provide a sort of lock or enlarged portion around and over which the cast The upper cup-shaped or hollow section lll-ot l the cone 26 is one convenient form of cone from i.

the standpoint of applying pressure in the operation and also from the standpoint of using the cup to receive a resistor or a terminal connector such as might be required in spark plug design.

The invention is not restricted to the useof a particular form of upper sealing cone shown in Fig. 2 of the drawings, but one of the forms shown in Figs. 4 to '7 inclusive, may be used. In Fig. 4 the cone 34 includes the upper hollow section similar to lthat of cone 26 and an anchor section 36 which is adapted to be driven into the molten metal in the insulator so that the metal will solidify above the section 36 and anchorl the cone therein. The form shown in Fig. .5 is somewhat similar to that shown in Fig. 4. but is provided with a button type anchor member 38 Whiehjs adapted to be embedded into the molten silver under pressure, and which transmits a greater portion of the driving force downwardly through the silver column beneath it.

The cone structure shown in Fig. 6 includes a body 40 provided with the upper cup-shaped section and with a low melting point anchor member 42 keyed to the body 4u but provided with an end section adapted to be embedded in the molten silver and to be melted thereby. The melting of the end section of the member 42 provides an intimate fused bond for anchoring thev cone in the silver body.

The sealing cone shown in Fig. 7 includes a pointed spike section 43 similar to the spike 26 of the cone 25, an intermediate enlarged section 44 of slightly larger diameter than the bore I2 of the insulator. This sealing cone also includes an upper pointed section 45 of about the same diameter as the spike section 43.

molten silver in a manner similar to that of the sealing cone 26, the driving member extending around the upper section 45 and vbearing on the shoulder of the section 44. The entire sealing cone is of solid metal and functions in much the same manner as the sealing cone or spike member 26. After the sealing cone is drivenV into the l molten silver and the spark plug assembled. the

The sealingl cone shown in Fig. 7 is driven into the body of asomo?? iipperJsection-il- 'serves to. .engage .the conductor or damping material in the:bore .I 2 in accordance-.z

with the usual practice.y v`The conesf. shownvin Figs.l 4zto -.7r are i advantageously made of Bessemer..

steelscrew.` stock` and silver plated.

Fig. 8 of the drawings illustrates a modified'V tormbr'lowerfsealing cone construction comprising apointed upper portion lli-.of somewhat larger; diameter than the .bore I6; the section. being; beveled@ down ter a, smaller` cylindrical section 48Sy adapted;v to.. t .the bore I6. and extendf therethrough.; f The. lower. .end fof the cylindrical .section -48 is iwelded. or: brazed .to al sparking .tip550 f which.is..preferably of platinum or ansalloy; as referred to.; This tip maybe convenientlyiwelded'- to theectioni.afterthe-upper coneis installed..

'I'heA insulator Inf shown; in. Fig.. 8l may have: a

countersunk portion .52 at; the lower.. end;` of the-1 bore- 'l 6 :so that -theweld v'between the tipfand the section. 4B; is upfj within this countersunk portion,pas.;indicated. The section .48..will therefore begsomewhatshielded from high temperaturesgandspark conditions existing inthepcyl-4 index' of fthe internal combustion engine in which...

the spark` plug -is used.

Fig.L v9; showsa modified form `of lower sealing coneior spike made of the same materials as' that-Shownin Fig. 1, and comprising a sparking tip 54 Vwelded to aqspike orcone 55 by` an extending rim-,likawelding jointv 58 having thev same function :as the vwelding joint 22 inFig. 1. The spike-.56 isof somewhat larger diameter than the tip Bland is provided with aplurality of super- '1 or moresuch'actions, but-that has not beende-` posed, annular grooves 69 `of the shape shown..

One. ormore grooves llmay be used, which areadapted .tor receive molten silver when the pressureisapplied, as-described above.y The sealing coneshown in Fig. Qtherefore provides a structure, Iaftercasting of the silver, in which vone or moreannular flanges of, silver in the groove or groovesy (iIJposi-tively` retain ythespike or cone in the silvercastingand aid `in forming a .tight immovable connection adapted to facilitate heat y sultisjshown in Fig. 3. Furthermore, spark pluggunlts made in accordanceV withthe process K of thefpresent invention havefalso been broken up aroundthe.silver-casting to investigate they bondbetween the body of silver and the wall of the insulator l0.

In breaking up the lower portion of the insulator it was foundvthat -it had to bebroken into relatively small pieces in order to. remove most of it fromfithe body of silver 32; kEventhen,` iny a: larga-majority of cases, the bodyof silver .was

substantiallyy completely -coveredY `with the material of the insulator in chips and layers, showing that the bond between the silver and the insulator was stronger than the internal bond of the insulator. In many cases where attempts were made to break the insulator away from the body of cast silver it was found that a considerable number of pieces of the insulator would adhere tenaciously to the body of silver and that further breaking of these pieces would still leave an irregular coating of the insulator material on the silver all along the casting.

Not all, but a large majority of the insulators,

brokenfupto determine the adherencenoi!the.VA f silvertothe-insulator.: show a uniform bond bes; f tween-the silver and theceramic insulator. 'However; iny all cases there was' denite bonding fbcf tweenthe silver `and the insulator, and4 all vunits@v f werefleak-.prooh asdistinguished from spark plug.` units made by previously known-processes, such. as those yrefer-red to above. Spark plugs made by. f previously known silver casting methods were lll'A side-of lthewsilver castwas smoothand vnot bonded broken-and examinedto -lnd only that the :out-

to the insulator.

The-phenomenon involved in the bonding of f the silver-y to4 the ceramic insulator without the use oany bonding agent`y is not fully understood; but, irriportant-asarel the pressure vrelationships-v of the' process, investigation has shownv thatnickel, such as the nickel cone.-20 or 56, facilitates l bonding. There may be some complicated physical, chemical or catalyticaction involved, or two termined; It does appear from investigation, however, that thecarrying out of-the process in an atmosphere of hydrogen adversely afectsf the bonding.

It also appea-rsnot'agltogether desirable to make cone v2ll1ofa material which -will readily form" a fusionI bond `withthe silver-'or of heat conducting This ispossiblyone of4 thek'eys to theA success Lof-fthe process-for reasons whichmay be explainedaasvfollows: In an insulator-whichisA cooling after processing' as Yldescribed'f* the-bond betweenv the ceramic and" the silver' isy greater metal.

thanl that ybetween the silver and the nickel-of cone,y 20.

may occur without opening -up any leakage paths.

In order fto oit-set `possible maladjustment of thev heatowffpattern asaectingfheat picked up Vby the sparking tip, coney 20-v may/.be made Ato `con-y taingrooves v asf shown in Fig. 9,- such that will insure.;intimate-@mechanical pressure exerted vbe tweerrsueh. grooves duringT the contraction phase of thegprocessl Heat flow` at the cone to 'silver interfacermayalso beinsured by the .employment of plated or brazedgcoatings whichcoveronly-a portion of. the sealing.` cone or welded extensions.

of a -metal yor metals. which. enterv into. fusion bondinggwith .the .molten silver.

The .1 unusual: results obtained. with'i sparkzplug.. i

units,mayin. some respectsbe due to .the posi;- tions and manner of using the spaced upper and lower cones,A or to these factors in combination. withtheuseof nickel and presence orair. When the upper '.cone is plungedinto the molten silver under..pressure,the:fupper,and lower cone `tips appear.v to'. act as. plungers Yand-force .the molten f silver`r toward ,the-hot lwall. ofV theinsulator l0.; At the-.same time the .coolingis most rapidiat, thetopgand bottomfandy vfrom the insideyofthe I body.. inview of the.cold upperconeand the. conduction of yheat from the "cone .20 .to .the tip..

Stresses set up in this region as a result of the differences between `the-contractionrates Aof the silverand ceramic-are thus relieved v at the silver-nickel linterface-where break-'downy a sealing or' bonding material has been found*l to give certain advantages over othermetals because it can be heated and processed in the open atmosphere without a special type of furnace to prevent oxidation. Other metals or alloys melting in the neighborhood of the melting point of silver may be used, for example, copper or a metal powder mixture consisting of 80% silver, 9% iron, 9% nickel, 1% carbon and 1% flux such as borax. Other silver alloys may be used, as for example, sterling silver or an alloy containing from 1% to 5% of nickel.

According to the preferred form oi the invention, the lower sealing cone is made of pure nickel or steel plated with nickel, while the upper sealing cone is of steel plated successively with nickel and then with silver, the latter of which is subsequently hydrogen brazed` to the nickel undercoating. In some cases a copper undercoating may be used in place of nickel.

The process may be employed for the bonding of metals to ceramic materials and to glass for various purposes. Many insulatingrnaterials are glass or contain glass.

What is claimed as new is:

1. A spark plug including a central insulator having a sparking tip of corrosion-resisting metal projecting from its lower end, a metal sealing member comprised of nickel connected to said tip and extending into said insulator, a body of cast metal containing silver surrounding said member and intimately bonded to the inside wall of the insulator by direct contact of the cast metal with the insulator wall, and an upper sealing member anchored in said cast metal body by means of a projection extending into the body and partially enclosed thereby, the upper portion of the upper sealing member substantially fitting the bore of the insulator.

2. A spark plug insulator construction ccmprising a ceramic body having a longitudinal bore and a tip portion from which a metal sparking tip of corrosion-resisting metal extends, a cast metal body in the insulator bore in the portion adjacent said sparking tip, a nickel spike electrically connected to said tip and embedded in said metal body, and a second metal member having an elongated pressure-exerting and pointed anchoring portion extending into the opposite end of said metal body and anchored therein, the cast metal body and the wall of the insulator being bonded together by a bond adapted to join and seal the metal body with respect to the insulator.

3. A spark plug insulator construction comprising an elongated ceramic insulator having a longitudinal bore, a nickel connector and sealin-g member located at its operating end and extending into the insulator bore as well as extending outwardly from the operating end of the insulator, a metal sparking tip of corrosion and erosion resisting metal secured to the outwardly-extending end of said member, and a cast metal body in the bore in contact with and sur-- body being bonded directly to the inside wallof f the insulator bore with a. strong intimate bond adapted to provide an effective seal against the leakage of gas between the metal body and the i insulator.

4. A spark plug including a central ceramic insulator having an axial bore, a sparking tip of corrosion resisting metal projecting from the lower end of the insulator, a metal sealing member connected to said tip and extending into thev bore of said insulator, a body of cast metal con-y taining silver surrounding said member and in' 1 timately bonded to the inside wall of the insulator by direct contact of the cast metal with the nsulator wall, andan upper metal sealing mem- 'ber plated successively with nickel and silverl said upper. sealing member being anchored in said cast metal body by means of a projection extending into the body and partially enclosed thereby,

the upper portion of said upper sealing member substantially fitting the bore of the insulator.

5. A spark plug insulator construction comprising an elongated ceramic insulator having a longitudinal bore, a metal sealing-member extending from the bore at the operating end of the insulator and also extending into the bore and terminating therein with a pointed end as a sealing means, a cast metal body in the insulatorV bore surrounding and bonded to the portion of the metal sealing member in the bore, said cast metal body extending in the bore beyond said f pointed end, and a metal member having an elongated pressure-exerting pointed anchoring portion extending into the cast metal body at its end remote from the operating end of the insulator and anchored in and bonded to the cast metal body in spaced relation to said pointed end,

said cast metal body being bonded directly tov the inside wall of the insulator bore with a strong intimate bond adapted to provide an effective seal against the leakage of gases between the cast metal body and the insulator.

DOUGLAS W. GREGORY. EGDIO R. BALDASSARE.

REFERENCES CITED The following references are of record in the le or this patent:

UNITED STATES PATENTS

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