US2262769A - Spark plug - Google Patents

Description

H. K. KING Nov. 18, 1941.

SPARK PLUG Filed Feb. 19, 1941 2 Sheets-Sheet 1 INVENTOR HENRY KENDA LL KING Patented Nov. 18, 1941 SPARK PLUG Henry Kendall King, Cabin John. Md. Application February 19, 1941, serial Nb. 379,600

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 17 Claims.

My invention relates to spark plugs and provides a new and novel type of construction and arrangement of parts whereby certain difficulties inherent in present types of plugs are minimized or obviated and also certain new advantages are realized, as will presently appear.

One object of my invention is to provide a plug, the joints between the insulation of which will become tighter with increase of temperature during operation.

Another object is to reduce the possibility of leakage of current or electrical breakdown of the insulation.

A further object is to provide a plug of small overall diameter.

A still further object is to provide a plug which can be easily cleaned without disassembly.

A still further object is to provide a plug, the electrode of which will undergo minimized wear or erosion during long service.

An additional object is to provide a plug 4with self-cleaning gaps. A still further object is to provide a plug in which those parts that are most subject to wear or'damage can be readily replaced.

A still further object is to provide a plug having an improved thermal path for the conduction of heat away from the electrodes.

A still further object is to provide a plug with readily replaceable parts in which the possibility of escape of gas -through necessary gaskets with damage to insulation is reduced to a minimum.

These and other objects will appear more fully in the detailed description of the invention which follows. Although four embodiments of the present invention are illustrated in the accompanying drawings, it is to be expressly understood that these drawings are for the purpose of illusdiameter is desired.

Fig. 2 illustrates a modication of the design of Fig. 1, permitting the use of two-piece construction, and allow-ing greater heat ow away from the central electrode.

Fig. 3 illustrates a modification of the design of Fig. l, permitting greater heat ow away from the central electrode.

Fig. 4 illustrates a modification of the design of Fig. l, permitting the use of a three-piece construction with a readily removable core, and a vent to minimize possibility of entrance of gas into the upper barrel.

My first object, that of providing increased tightness-of the joints between insulating members, isattained bythe use of a conical inner electrode, and conical sleeves for intermediate electrodes, all placed in a conical recess in the outer electrode. These electrodes are separated by conical sleeves of insulating material. As heating occurs. with operation the greatest proportionate 1 expansion will occur at the base of the inner electrode because a higher temperature is found there than at the .upper portion of the inner electrode or at the bases of the remaining electrodes, and further because a larger volume of metal is located at the base of the inner electrode than at the other places mentioned. Thus, the inner electrode will be gripped by the innermost intermediate electrode more tightly at its base than elsewhere. The bases of the intermediate electrodes will also expand in asimilar way, each against the next outer one, but to a lesser degree than the one within it, so as a result all electrodes, and the insulating sleeves, which are stretched by them, are more tightly held at their bases than elsewhere.

The metal electrodes will expand longitudinally in a greater amount than the insulating sleeves, having a higher coefficient of expansion. As the electrode-insulating sleeve assembly is held more tightly at its base, this longitudinal expansion will cause the conical electrodes. to wedge tightly into the enveloping conical insulating sleeves instead of sliding through them as would occur if the electrodes were cylindrical, and tightening of the joints will occur with the heat of expansion. Control of tightening of seal at the base with heat of use may be obtained by choosing material for electrodes which will have a coefficient of expansion so related to coeflicients of expansion of insulating material that desired degree of tightening will occur. Electrodes may be of two metals, one forming a plated coating on the other or being a distinct sleeve appropriately joined.`

The second object, that of reducing the possibility of leakage of current or electrical breakdownpf insulation, is obtained by means of the use of sleeves or cigarettes of insulating material rather than stacks of washers.

With the mica washer type of design, nonhomogeneity of adjacent rings, formations of carbon, oil or other foreign material at joints or on abutting surfaces, or air between abutting poorly fitted or loosened surfaces may occur. Such loosening frequently occurs due to spindle shank elongation in service. These occurrences will cause displacementof the dielectric flux eld and may cause local concentrations of suilicient ux density to result in breakdown of the insulation at such points. sisting of homogenous cigarettes such excessive flux densities are much less likely to occur.

One modification shown in Fig. 1 is especially With the insulation conterial which separate these electrodes are in vatransverse plane nearly the same as the plane'of the electrode faces` Thus, the end of the plug being very nearly a plane, the insulator' surfaces are exposed and readily accessible for cleaning, as desired in the fourth object.

The use of electrodes consisting of 'annular rings provides a large surface over whiclrwear and erosion are distributed. For these reasons,- therefore, wear or erosion 'is minimized during long service, as desired in the fifth object.

The sixth object, to provide a self-cleaning the' cylinder side fails at any point gas will escape through the void space and vent. Thus, there is almost no possibility of gas causing failure of the outer gasket, entering the upper barrel and causing damage to the insulating material there,

Aduring the interval between failure of the inner gasket and an opportunity.to replace same.

Referring in detail to Fig. 1, the spark plug 'bami n, of conductive materiau, is adapted to besecured b'yfscrew threads I2 into the engine cylinder wallyI3., gasket I4 making a gas-tight jointp The base of barrel II projects into the cylinderand formsthe outer electrode I5. Barrel n 'I.Ii$ hollow, a truncated conical recess I6 being gap, is obtained by the use of multiple series gaps.

When one gap is fouled the remaining gaps will,

still permit a spark to be formed, and the heat of the resulting combustion will act to destroy the deposit and clean the fouled gap. Furthermore, when a spark occurs across the remaining gap of the circuit the vfirst momentary surge of current is extremely high. This current, passing through the high resistance ofthe fouled gap,

generates a high temperature, whichl also` will i tend to oxidize the fouling substance andclean the gap. As a thermal gradient will exist between the inner and outer electrodes, conditions to cause fouling of all gaps simultaneously are unlikely to occur. Proper design, in the embodiments shown in Figs. 2, 3 and 4, of the axial distance between the gaps, willpermit placing these gapstso that when at operating temperature one or more will be outside the temperature ranges within which lead fouling and carbon fouling occur;

The seventh object, to provide for replacement' i of the barrel, plug and other parts which are most subject to wear or damage, is attained in' embodiments shown in Figs. 2 and 4 by two-piece and three-piece construction, dividing the barrel of embodiment shown in Fig.. 1' into an upper barrel and a plug in embodiment'sh'own in Flg. 2, and into an upper barrel, plug and inner electrode in the form of a core in embodimentshown in Fig. 4.

The eighth object, to provide' an improved thermal path for removal of heat by conduction is attained in the embodiment shown in Fig. 2

by using electrode assemblies in which the electrode proper consists of metal chosen for its noncorrosive properties, while the electrode shank is of metal chosen for its high thermal conductivity. This object also is attained in the embodiment shown in Fig. 3 by using material of high thermal conductivity and placing. the inner electrode, the

hottestfpart. ofthe plug; within the interior of.

u ternal end ofbarrel I I.

formed' commencingA at outer electrode I5 and progressing with decreasing diameter a portion of 4thejlength until meeting at shoulder I'I a cylindrical recess I8 formed commencing at the ex- The face of shoulder I1 is normal to the longitudinal axis of barrel II, and 'its greatest diameter is less than that of cylindrical recess I8, so that cylindrical slot I3 is formed at the innermost portion of cylindrical recess I 8.

Within conical recess AI6 are inserted several intermediate electrodes 20, two of which are shown in the present embodiment. These electrodes 20 consist of sleeves of conductive material, of truncated-conical shape, and of successively greater length so that the innermost is the longest. truncated conical sleeves of insulating material 2|, each one of length somewhat less than the.

' the base 'of insulating sleeves 2I and 23 lie in a plane parallel to this plane but transposed from l it intothe conical recess I6 a slight amount so that the series spark gaps 24 are formed between electrodes I5, 20 and 22=.l

A cylindrical sleeveZI-of insulating material is inserted in cylindrical recess I8, resting in slot I3. A stack of discs 26 of insulating material, of

varying internal diameters, fills the space between cylindrical sleeve 25 and the conical insulating sleeves 2| and 23, the innermost disc resting on shoulder I'I andthe outermost disc held by washer21 which, along with suitable means for connecting ignition wiring, is suitably secured. to the small end of inner electrode 22 so that ,the assembly is tightly held.

the plug so that a relatively short path is pro-` vided to thev exterior radiating. surfaces of-'the plug.

The ninth object, toreduce, mp9.; piugwitn readily replaceable parts, the possibility of escape,

of gas throughgaskets'with damage to insulating material, is attained in the' embodiment shown in Fig. 4. In this three-piece design werhave the outer. electrode in the form of an. annular core containing the remaining electrodes. v core is placed within the-barrel-base plug assembly, making contact at thexedges of -the two flat surfaces through gas-tight Washers.. Between the outer cylindrical surface of the core and the plugz there is left a void space; a vent passage 'equipped with a check valve leads .to the. atmosphere from this annular void space. Thus, if thewasher on Nut 28 is made integral with barrel II or attached thereto by suitable means, and is adapted to t a wrench for convenience in installing the barrel I I in-the'cylinder wall I 3. Barrel II has lexternalthreads 29 at its outer end adapted to receive the shielding harness connection.

Referring in detail to Fig. 2, the spark plug barrel 3|, ofconductive material, is adapted to be secured by screw threads 32 into hollow baseplug 50, also of conductive material, gasket 34 making a gas tight joint. Plug 50 has its upper portion internally threaded to receive barrel 3I, and is adapted to be secured by screw threads 5I into the engine cylinder wall 33, gasket 52 making a gas` tight joint.

The. outer end of plug 50 is adapted to t a wrench for convenience ininstalling the plug 50 in the cylinder wall 33.

The electrodes 20 are placed within.

The outer end of plug 50 forms vthe outer electrode 35. Plug. 50 is hollow, a truncated conical recess 36 being formed commencing at the outer' end and progressing with increasing diameter a portion of the length and meeting at shoulder 31 a cylindrical recess '38 formed commencing at the inner end of plug' 50. Barrel 3| has a cylindrical bore 39 of diameter equal to the outer face of plug 50. l

Within conical recess 36 are inserted several intermediate electrode assemblies 40, two of which are shown in the present embodiment. These electrode assemblies 40 consist of sleeves of conductive material, of truncated conical shape, and of successivelygreater length so that the innermost is the longest. Each electrode assembly 40 consists of twosleeves of conductive material of truncated conical shape, permanently joined by suitable means,.one being an extension of the other. The portion having the largest diameter of base is made of material chosen for its non-corrosive properties and forms the electrode proper. The other portion is made of material chosen for its high thermal conductive properties. The plane of junction is slightly within the surrounding insulating sleeve. The electrode assemblies 40 are placed within truncated conical sleeves of insulating material 4|,

-trode within'it. Within the innermost of the intermediate electrode assemblies 40 is placed the inner electrode assembly 42, a solid truncated cone of conductive material longer than the innermost of the intermediate electrode assemblies 40, surrounded by an insulating sleeve 43` similar to sleeves 4|.

The inner electrode assembly 42 consists of two truncated cones of conductive material permanently joined by suitable means, one being an extension of the other. The portion having the largest diameter of' base is made of material chosen for its non-corrosive properties and forms the electrode proper. The other portion is made of material chosen for its high thermal conductive properties. The plane of junction is slightly within the surrounding insulating sleeve.

The bases of the insulating sleeves 4| and 43 by a slight amount fail to extend to the bases of the corresponding electrodes 35, 40 and 42, so

that the series spark gaps 44 are formed between electrodes 35, 40 and 42. 'Ihe inner electrode 42 and intermediate electrodes 40 are so placed with reference to the outer electrode 35 that each extends progressively further into the cylinder.

A cylindrical sleeve 45 of insulating material g is inserted in cylindrical bore 33 resting 0n the outer face of plug 50. A stack of discs 46 of insulating material, of varying internal diameters, iills the space between cylindrical sleeve 45 and the conical insulating sleeves 4| and 43 and electrodes 40, the innermost disc resting on the outer face of plug and the outermost disc held by washer 41 which, along with suitable means for connecting ignition wiring, is suitably secured to the small end of inner electrode 42 vso that the assembly is tightly held.

Nut 48 is made integral with barrel 3| or attached thereto by suitable means, and is adapted to t a wrench for convenience in installing the barrel 3| in the plug 50. Barrel 3| has external threads 49 at its outer end adapted to receive a shielding harness connection.

Referring in detail to Fig. 3, the ,spark plug barrel 6| of conductive material, which is also of high thermal conductivity, is adapted to be ybeing formed commencing at outer electrode and progressing with decreasing diameter a portion of the length `until meeting at shoulder 61 'a cylindrical recess 68 formed commencing at Sleeve 15, of

the external end of barrel 6|. insulating material, covers the inside of cylindrical recess 68 abutting' against the shoulder 61, which shoulder is of width slightly less than the thickness of sleeve 15. Within conical recess 66 are inserted several intermediate electrodes 10, two of which are shown in the present embodiment. These electrodes 10 consist of sleeves of conductive material, which is also of high thermal conductivity, of truncated conical shape.

The electrodes 10 are placed within conical sleeves of insulating material 1|. Within the innermost of the intermediate electrodes 10 is placed the inner electrode 12, a solid truncated cone of conductive material which is also of high thermal conductivity, surrounded by an l insulating sleeve 13 similar to sleeves 1|. 'I'he inner electrode 12 and intermediate electrodes 10 are so placed that the outer of the intermediate electrodes 10 has its base in the same plane as the base of outer electrode 65, and the remaining electrodes have their bases progressively furth'er away from the interior of the cylinder.

The bases of the sleeves 1| and 13 are in th'e same planes as the bases of the electrodes 10 and 12 which they surround. The series spark gaps 14 are around the ends of the sleeves 1I and 13.

An insulating piece 16 fills the space between' cylindrical'sleeve 15 and the conical insulating sleeves 1| and 13 and electrodes 10. The outer end of insulating piece 16 is held by Washer 11 which, along with suitable means for connecting ignition wiring, is suitablyA secured to the small end of inner electrode 12, so that the assembly is tightly held.

Nut 18 is made integral with barrel 6I or attached thereto by suitable means, and is adapted to t a wrench for convenience in installing the barrel 6| in the cylinder wall 63. Barrel 6| has external threads 19 at its outer end adapted to receive a shielding harness connection.

Referring in detailto Fig. 4, the spark plugv barrel 8|, of conductive material, is adapted to be secured by screw threads 82 into hollow base plug |00, also ofvconductive material, abutting against shoulder 81. Plug 00 has its upper portion internally threaded to receive barrel 8| and is adapted to be screwed by screw threads |0| into the engine cylinder 83, gasket 84 making a gas tight joint. The outer end of plug |00 is adapted to fit a wrench for convenience in installing the plug |00 in the cylinder wall 83. Plug |00 has a cylindrical recess |08 commencing at its inner end.

Core |03, an annular ring of conductive material, is of larger diameter than that of cylindrical recess |08. Core |03 has beveled edges. An annular recess |09 is formed in the interior of plug |00, between the end of cylindrical recess |08 and shoulder 81, to receive core |03 and leave a void space around its periphery. Gasket H0, of conductive material, separates the core |03 The baseof barrel 6| projects into the at its beveled edge. from plug Where the core |03 fits into annular recess |09, with a gastight seal. Vent passage will permit escape of gas from the void space of annular recess |09 incase of failure of gasket 0. Vent passage I is tted with check valve I2, of standard design. Barrel 8| has a cylindrical recess H3, the inner end of which is beveled to continue annular recess |09. Gasket ||4 separates core |03 at a beveled edge'from barrel 8| at. the

extension of annular recess |09, with a gas-tight.

seal.

The inner flat surface ofcore |03 forms the outer electrode 85. Core 03 is hollow, a truncated conical recess 85 being formed commencing at outer electrode 85 and progressing with decreasing diameter. Within conical recess 86 are inserted several intermediate electrodes v90, two of which are shown in the present embodiment. These electrodes 90 consistof sleeves of conductive material, of truncated conical shape, and of successively greater length so that the innermost is the longest. .The electrodes 90 are placed within truncated conical sleeves of insulating material 9|, each one of length somewhat less than the electrode within it. Within the innermost of the intermediate electrodes 90 is placed the inner electrode 92, a solid truncated cone of conductive material longer than the innermost of the intermediate electrodes 90, surrounded 'by an insulating sleeve 93 similar to sleeves 9|. them, have a thin coating of plated metal or a thin sheath ||5 placed about their exterior surfaces covering the area within cylinder 83, in

order to improve the heat ow and the tighten-f` ing of the seal on expansion, by choice of material for sheaths ||5 having suitable coeicient of heat conductivity and coeilicient of expansionl The bases of the insulating sleeves 9| and v93 lie in the same respective planes as the bases of the corresponding electrodes 85, 90 and 92.

The series gaps 94 occur around the bases of` insulating sleeves 9| and 93. The inner electrode 92 and intermediateelectrodes 90 are so placed with reference to the outer electrode 85 that each extends progressively further into the cylinder. A cylindrical sleeve 95 of insulating material is inserted in cylindrical recess 88 resting in slot 89 formed on the outer plane surface of core |03. A stack of discs 96 of insulating material, of varyingl internal diameter, fills the space between cylindrical sleeve 95 and the conical insulating sleeves 9| and 93, theinnermost disc resting on the outer planesurface of core |03 and the outermost disc held by washer 91 which, along with suitable means for connecting ignition Wiring, is suitably secured to the'sm'all end of inner electrode 92 so that the assembly is tightly held. Nut 98 is made integral With barrel 8| or attached thereto by suitable means, and is adapted to t a wrench for convenience in installing the barrel 8| in the plug |00. Barrel 8| has external threads 99 at its outer end adapted to receive a shielding harness connection.v

As will be readily apparent to one skilled in the art who has this disclosure at hand, various further modifications may be made of my invention with attainment of some or all of my objects.

Ihese modifications include omission of theradio interference shield; use of a single gap; use of cylindrical electrodes with appropriate rolling,

Electrodes 85, 90 and 92, or some o1'l sulating material, and similar variations which do not depart from the nature of the invention and are within the scope of what is hereinafter claimed.

'I'he invention described herein may be manu-v factured and/or used by or forthe Government of the United States'of America for governmental purposes Without the payment of any royalties thereon or therefor. k

I claim: n

1. In a spark plug having the `feature of increased tightness vof internal sealing during operation due to the heat generated, the combination including an integrally formed exterior body member, intermediate electrodes in the form of axially extended truncated conical sleeves, an

vinner electrode in the form ofr an axially extended truncated cone, the bases having the larger diameters of said conical sleeves and said cone being within and toward the base of said exterior body member and lying in diverse planes, the diversity of said planes and the axial extension of said sleeves. being suicient to cause the operating temperature'of the base of at least one of said electrodes to lie without the respective thermal range in which fouling of said plug by deposits of-each product of combustion will occur, and insulating ymeans in the form of homogeneous conical sleeves to separate said electrodes from said exteriorbody member and from each other, wherebythe degree of tightening of the seal between said electrodes and said body member is increased vduring operation.

2. In a spark plug having the feature of increased tightness of internal sealing during operation dueto the heat generated, the combination including an outer barrel, a hollow base plug. a gasket of electrically conductive material, an

annular core, intermediate electrodes in the form said planes and the axial extension of said sleeves 60. 3. In a spark plug having the, feature of in being suiiicient to cause the operating temperature of the base of at least one of said electrodes to lie without the respective thermal range in which fouling of said plug by deposits of each.

product of combustion will occur, and insulating means in the form of homogeneous conical sleeves to separate said electrodes from said annular core and from each other, whereby-the degree of tightening of the' seal between said electrodes and said core is increased during operation.

creased -tightness of internal sealing during operation due to heat generated, the combination including an outer barrel, a hollow base plug removably secured thereto, an annular core within said base plug, intermediate electrodes. in the form of truncated conical sleeves, an inner electrode in the form of a truncated cone, the bases having the larger diameters of said conical sleeves and said cone being within and toward the base of said hollow base plug and lying in diverse planes so that the operating temperature of each of said electrodes will lie within a different thermal range, insulating means in the form of homogeneous conical sleeves to separate said electrodes from said core and from each other, said electrodes having recesses formed on those portions adjacent to said insulating means, which portions are toward the base of said hollow base plug, and heterogeneous metallic coatings filling said recesses, whereby the degree of tightening of the seal between said electrodes and said core' is increased during operation and may be controlled through choice o thev materials of said electrodes and said heterogeneous coatings.

4. In a spark/plug having the feature of increased tightness of internal sealing during operation due to heat generated, the combination including an outer barrel, a hollow base plug, a gasket of electrically conductive material, an annular core, the surface of which is separatedA from said base plug by said gasket and by an annular void space, means to permit escape of gas direct to the atmosphere from said void space 4in case of failure of said gasket, intermediate electrodes in the form of truncated conical sleeves, an inner electrode in the formv of a truncated cone, the bases having the larger diameters of said conical sleeves and said cone being within and toward the base of said hollow base plug and lying in diverse planes so that the operating temperature of each of said electrodes will lie within a diierentthermal range, insulating means in the form ofhomogeneous conical sleeves to separate said electrodes from said core and from each other, said electrodes having recesses formed on those portions adjacent to said insulating means, which portions are toward the 'base of said hollow base plug, and heterogeneous metallic coatings filling said recesses, whereby the degrec-of tightening of the seal between -said electrodes and said core is increased during operation and may be controlledthrough choice' of the materials of said electrodes and said heterogeneous coatings.

5. In a spark plug having the feature of increased tightness of internal sealing during operation due to heat generated, the combination including an exterior body member, intermediate electrodes in the form of truncated conical sleeves, an inner electrode in the form of a truncated cone, the bases having the larger diameters of said conical sleeves and said cone being within and toward the base of said exterior body member and lying in diverse planes so that the operating temperature of each of s'aiclelectrodes will lie within a diierent'thermal range, insulating means in the form of homogeneous conical sleeves to separate said electrodes from said exterior body member and from eachother, said electrodes having recesses formed on those portions adjacent to said insulating means, which portions are toward the base of said exterior body member, and heterogeneous metallic coatings iilling said recesses, whereby the degree of tightening of the seal between said electrodes and said exterior body member is increased during operation and may be controlled through choice of the materials of said electrodes and said heterogeneous coatings.

including an exterior body member, intermediate electrodes in the form of truncated conical sleeves, an inner electrode in the form 'of a trunous conical sleeves to separate said electrodes from said exterior body member and from each other, said electrodes having recesses formed on those portions adjacent to said insulating means,

Y. which portions are toward the bases of said electrodes, and'heterogeneous metallic coatings filling said recesses, whereby the degree of tightening of the seal between said electrodes and said exterior body member is increased during operation and may be controlledl through choice of the materials of said electrodes and said heterogeneous coatings. y

'7. In a sparkplug having the feature of increased tightness of internal sealing during op- `'eration due to heat generated, the combination including an exterior body member, an electrode in theform of `a truncated cone Within said body member, thebase having the larger diameter of said cone lying within and toward the base of said exterior body member, insulating means in the form of a homogeneous conical sleeve between said electrode and said exterior body member, said electrode having a recess formed on that portion adjacent to said insulating means, which portion is toward the base of saidelectrode, and a heterogeneous metallic coating filling said recess, whereby the degree of tightening of the seal between said electrode and said exteriorbody member is increased, during operation and may be controlled through choiceI of the materials of said electrode and said heterogeneous coating.

8. In a spark plug having the feature of increased tightness of internal sealing during operation due to heat generated, the combination including an exterior body member, intermediate I electrodes, an inner electrode, insulating means cated cone, the bases havingA the larger diameters of said conical sleeves and said cone being within and toward the base of saidv exterior body member, insulating means in the form of homogeneto separate said electrodes from said exterior body member and from each other, said electrodes having recesses formed on those portions adjacent to said insulating means, Kwhich portions are toward the base of said exterior body member, and heterogeneous metallic coatings filling said recesses, wherebyl the degree of tightening of the -seal between said electrodes and said exterior body member is increased during operation andmay be controlled through choice of the materials of said electrodes! and said heterogeneous coatings.

9. In a spark plug having the feature of increased tightness of internal sealing during op,- eration due to heat generated, the combination including an exterior body member, an electrode within and near the base of said body member, insulating means between said electrode and said exterior body member, said electrode having a recess formed on that portion adjacent to said insulating means, Which portion is toward the base of'said exterior body mem-I ber, and a heterogeneous metallic coating lling said recess, whereby the degree of tightening of .the seal between said electrode and said exterior body member is increased during operation and may be controlled through choice of the materials of` said electrode and said heterogeneous coating.

10. In a spark plug having the feature of increased tightness of internal sealing during operation due to the heat generated, the combination including an outer barrel, a hollow base plug, intermediate electrodes in the form of truncated conical sleeves, an inner electrode in the form of a truncated cone, the bases having the larger diameters of said conical sleeves and said cone being within and toward the base of said hollow base plug and lying in diverse planes so that Yth'e'operating temperature of each 0f said electrodes will lie within a different thermal range, fsaid intermediate electrodes and inner electroderbeing of metal chosen for its non-corrosivelproperties, intermediate shanks in the formof truncated conical sleeves permanently ioined'to the -bases having the smaller diameters oisaid intermediate electrodes, an inner shank -in the-form of a truncated cone permanently joined to the base having the smaller diameter of said inner electrode, said intermediate shanks and linner shank being of metal chosen i'or its high thermal, conductive properties to promote transfer of heat from the bases of said elec-- trades,A and insulating means in the form oi ho-` rmogeneo'us conical sleeves to separate said elecbination including an exterior body member, in-

termediate electrodes in the form of truncated conical sleeves, an inner electrode in the form oi a truncated cone, thegbases having the larger' v diameters of said conical sleeves and said cone being within. and toward the base of said exterir 'body member and lying in diverse planes so that the operating temperatures of each of said electrodes will lie in a vdierent thermal frange, said intermediate electrodes and inner electrode being of metal chosen for its noncorrosive properties, intermediate shanks in the 'formi of truncated conical sleeves permanently joined to the bases having the smaller diameters of said intermediate electrodes, an inner shank in the form of a truncated cone permanently vjoined to the base having the smaller diameter of said inner electrode, said intermediate shanks and inner shank being of metal chosen for its lhigh thermal conductive properties to promote transfer of heatfrom the bases of said electrodes, andinsulating means in the form of homogeneous conical sleeves to v`separate said electrodes and shanks from said exterior body member and from each other, whereby the degree of tightening of the-seal between 'said electrodes and said body member is increased during Operation. L y

v 12. In a/sparkplug having the feature of increased tightnessof internal sealing during operation due to theheat generated, the combina- `tion includingan exterior body` member, intermediate el'ctrodes in' the 'form of truncatedooni- 'fcal sleeves, an inner electrode in the form of 'a truncated cone, the bases having the v,larger .diameters of said conical sleeves and said cone being toward the base of said exterior body member, said intermediate electrodes and inner elec- Y "trode being of metal chosen for its non-corrosive' proper-ties, intermediate shanks in the form of 'truncated conical sleeves permanently Joined to lthe 'bases having the smallerdiameters of said intermediate electrodes, an inner shank in the form of a truncated cone permanently joined to'the'base havingfthe smaller diameter of said inner electrode, said intermediate shanks and inner shank being of metal chosen for its high- "thermal conductive properties to promote transfer of heat from the bases of said electrodes, and

'abonne insulating means in the form o'f homogeneous conical sleeves to separate said electrodes land said shanks from said exterior body member and from each other, whereby the degree of tighten-v `non-corrosive properties, intermediate shanks, an

inner shank, said shanks being permanently Joined to said electrodes and being of metal chosen for its high thermal conductive properties to promote transfer of heat from the base of said electrodes, and insulating means to separate .said electrodes and said shanks from said exterior body member Aand from each other.

14. In a spark plug having the feature of long life, the combination including an exterior body member, an electrode in the form of a truncated cone within said body member, the base having the larger diameter of said cone being toward the base of said body' member, said electrode being of metal chosen for its non-corrosive properties, a shank in the form of a truncated cone permanently joined to the base having the smaller diameter of said electrode, said shank being of metal chosen for its high thermal properties to promote transfer of heat from `rthe base of Asaid electrode, and insulating means in the form of a homogeneous conical sleeve between said electrode and shank .and said exterior bodymember, whereby the degree of Ytightening of the-seal between said electrode andsaid body memberlis increased during operation.

. and said exterior body member, and covering tif) inally joined to said electrode to promote trans- 'fer-of heat from the base'of said electrode, in-

sulating meansvbetween said shank and electrode means to shield said shank from the heat of combustion on firing of said spark plug.

16. In a spark plug, the combination including an'outerlba'rrel, a hollow base plug, a gasket'o'f electrically conductive-material, an annular core,

thesurface of which is vseparated from said base -plug by said gasket and by an annular void -`space, means to permit escape of gas direct to Vthe atmosphere from said void space in case of failure of said gasket, intermediate electrodes, an inner electrode, and insulating means to separate said electrodes from. said annularzcore and from each other.

17. In a vspark p1ug, the cmbinauoxrincmding an outer barrel, a hollow base plug, a `gasket .of Aelectrically conductive material, an annular core,

the surface of which is separated from said. base plug bysaid gasket and by an annular void space, means to permit escape of gas direct to the atmosphere from said Void space in case of 4failure of said gasket, an inner electrode, and insulating means between said electrode and said an- `nular core.

HENRY -KENDALL KING.

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