US2543962A

US2543962A - Spark plug construction

Info

Publication number: US2543962A
Application number: US78619A
Authority: US
Inventors: Harold R Feichter
Original assignee: US QUARRY TILE Co
Current assignee: UNITED STATES QUARRY TILE Co; US QUARRY TILE Co
Priority date: 1947-10-01
Filing date: 1949-02-26
Publication date: 1951-03-06
Anticipated expiration: 1968-03-06

Description

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sms rwc consuwcnon originar-rim on. .1i-1947 Harald R. Reich ver @M 1f/eff March 6, 1951 Patented Mar. 6, 1951 UNITED STATES PATENT OFFICE SPARK PLUG CONSTRUCTION Harold It. Felchter, Canton, Ohio, assignor to United States Quarry Tile Company, Canton, Ohio, a corporation of Delaware (Cl. 12S-169) 4 claims. 1

The invention relates to spark plug construction and to spark plugs for use in internal combustion engines for automobiles, aircraft, or wherever it is desired to ignite a combustible mixture, and this application is a division of my application, Serial No. 777,350, filed October l, 1947, now U. S. Patent 2,478,259, granted August 9, 1949.

In a usual spark plug there are included a multiplicity of parts some of which are metal and which require a relatively large number of manufacturing operations for the production of the separate parts and their assembly.

In a usual spark plug there is included a metal ground shell in which a tubular insulator is inserted, and the tubular insulator has a bore extending entirely through the insulator, and a rod electrode is located in and extends through the bore of the insulator.

At the lower end oi' the metal ground shell there is welded or otherwise secured a ground electrode, and the lower end of the central rod electrode is spaced from the ground electrode. It is necessary to provide a gas sealing cement between the rod electrode and the bore of the insulator and it is also necessary to provide a gas tight seal between the insulator and the shell.

In other words a usual spark plug includes a multiplicity of parts which make the cost of production relatively expensive, the assembly of the parts being complicated and ditllcult to control to provide for a uniform nished Product which does not deteriorate in use.

The objects of the .present invention include the provision of an improved spark plug construction which is inherently adapted for a long period of use and which requires less metal than a usual spark plug construction, metal having become scarce as compared with ceramic material, and in which there is a reduction in the number of parts required to produce the lmproved spark plug on the one hand, and which provides the spark plug with substantially improved properties as compared with present spark plugs on the other hand. One of the more important of these improved properties is the minimizing of the necessity of replacing the spark plug at intervals as frequently as has been necessary lprior to the present improvements.

The properties oi the improved spark plugs of the present invention include freedom from gas leakage, freedom from rapid deterioration of the electrodes of the spark plug, convenient replaceability of the ground electrode, an arrangement of the reduced number of parts permitting broad scope in the design as to the size and shape of the parts of the spark plug, a relative arrangement of the size and shape of the parts of the spark plug whereby there may be a greatly increased length of the electrical leakage path between the central electrode of the plug and ground, without increasing the overall length of the plug as compared with conventional practice. A further property of one form of the improved spark plug of the present invention in addition to the foregoing is the maintaining of a constant position of the lower end of the central electrode. and the transfer of heat by convection through circulation of a conducting liquid as well as by its own conduction, from the tip of the insulator or electrode to other portions and surfaces of the insulator.

The foregoing and other objects are attained by the spark plug construction, parts, combinations, and sub-combinations, which comprise the present invention, the nature of which is set forth in the following general statement, and preferred embodiments of which together with their mode of use are set forth by way of example in the following description, and which are particularly and distinctly Ipointed out and set forth in the appended claims forming part hereof.

The nature of one preferred embodiment of the improved spark plug of the 'present invention may be stated in general terms as including an insulator body preferably of vfired ceramic material, the insulator body having formed therein a well with an open upper end and the insulator body including a bottom wall extending across the lower end of the well. Electrode material is located in the well, and the insulator body includes a lower end having formed thereon external threads adapted for being screwed into an internally threaded opening in the wall of a combustion chamber such as the combustion chamber of an internal combustion engine. A replaceable metal ground electrode is provided on the lower end of the insulator body adjacent the bottom wall of the well.

By way of example, a number of embodiments of the improved spark plug construction of the present invention are illustrated in the accompanying drawings forming part hereof, in which Figure 1 is a'longitudinal axial sectional View of a first preferred embodiment of improved spark plug hereof Fig. la is a similar view of the insulator body shown in Fig. l, before assembly in the complete spark plug;

Fig. 2 is a similar view of a second embodiment of the improved spark plug construction hereof;

Fig. 3 is a similar view of a third embodiment of the improved spark plug construction hereof Fig. 4 is a similar view of a fourth embodiment of the improved spark plug construction hereof;

Fig. 5 is a similar view of a fifth embodiment of the improved spark plug construction hereof;

Figs. 6, 7, and 8 are views similar to Fig. la, showing modified forms of 'insulator bodies for the improved spark plugs hereof;

showing a modified form of ground electrode;

Fig. l is a view similar to Fig. 1 of a sixth em bodiment of the improved spark plug construction hereof;

Fig. 11 is a view similar to Fig. 1 of a seventh embodiment of the improved spark plug construction hereof.

Fig. 12 is a bottom plan view of the spark plug construction of Fig. looking in the direction of the arrows I2-I2, Fig. 10;

Fig. 13 is a transverse cross section of the spark plug construction of Fig. 10 as on the line I3-II, Fig. 10;

Fig. 14 is a view similar to Fig. 1 of an eighth 'embodiment of the improved spark plug construction hereof;

Fig, 15 is a similar view of a ninth embodiment of the improved spark plug construction hereof; and

Fig. 16 is a similar view of a tenth embodiment of the improved spark plug construction hereof.

Similar numerals refer to similar parts throughout the several views.

The rst preferred embodiment of the improved spark plug hereof is illustrated in Fig. 1 and is indicated generally by I0 and includes an insulator body II preferably made of fired ceramic material preferably having a high alumina content of upwards of 92 per cent, and also other ingredients, such as set forth in any of my U. S. Letters Patents No. 2,413,441, No. 2,414,367, No. 2,414,368, and No. 2,414,369.

The insulator body II is shown in Fig. 1a before assembly in the complete spark plug I0, and the insulator body II has formed therein a well I2 with an open upper end I3, and the insulator body II furthermore includes a bottom wall Il extending across the lower end of the well I2. The insulator body II is elongated, and the well I2 extends longitudinally coaxially with the longitudinal axis I5 of the insulator body II. Metal electrode material is located in the well I2 which may be as shown in Fig. 1 a rod I6 of metal such as steel. The upper end I1 of the well I2 may be enlarged and provided with internal threads, and the metal electrode rod I6 may have an enlarged head IB which is externally threaded and screwed in the internally threaded enlarged upper end I1 of the well I2. The bottom wall Il is preferably thinner than the surrounding walls of the insulator body, and in itself seals the lower end of the well I2, and covers the lower end of the electrode rod I6 therein. The bottom wall Il preferably has a thickness between the limits of 5 thousandths and 125 thousandths of an inch. In addition, when desirable, the electrode rod I6 may be sealed in the well I2 in a usual manner as by ceramic cement.

The insulator body I'I has a reduced lower end indicated generally by I! which includes an intermediate externally threaded portion 20 and a still smaller externally threaded extremity 2|.

The spark plug I0 furthermore includes a replaceable ground electrode indicated generally by 22 which is made of metal such as steel or other hard metallic substance, and which includes an internally and externally threaded ferrule portion 23 whose internal threads are screwed on the externally threaded extremity 2l of the insulator body II, and the external threads of the ferrule 23 match the externally threaded portion 20 of the insulator body Il. The replaceable ground electrode 22 furthermore includes one or more electrode tips or points 24 made of nickel or like material and extending in- 4 wardly from the ferrule portion 22. The insulator body II furthermore includes a larger upper portion 2l and an annular shoulder 2l between the inner end of the threaded portion 2l and the larger upper portions 2l, which has a larger transverse cross section than the transverse cross section at any place of the reduced lower end II.

A metal combustion chamber wall 21 which may be a wall of a combustion chamber o! an internal combustion engine has formed therein an internally threaded opening 2l in which are screwed the externally threaded lower end portion 20 of the insulator body II and the externally threaded ferrule portion 23 of the replaceable ground electrode 22.

In using the spark plug Il the central rod electrode I6 and the grounding metal combustion chamber wall 21 are connected in a usual ignition circuit which applies a potential to the central electrode rod It, and from the lower end thereof contacting the well bottom wall Il potential is applied to the bottom wall Il until its charge is sufficient to cause a spark between the bottom wall I4 and the electrode tips 24.

In the improved spark plug Il the upper portion 25 of the insulator body II may have any desired form and dimensions which are not subject to the form and dimensional limitations of a usual spark plug where the ground shell must be crimped over or otherwise fastened to an enlargement on the usual insulator body.

In the improved spark plug III there is freedom from gas leakage by reason of the location of the central electrode IB in the well I2, the solid bottom wall Il of insulating material extending across the lower end of the well I2. Thus protecting the central electrode It prevents rapid deterioration of the lower end of the electrode IB. When the electrode tips of the ground electrode 22 become burnt oi! too much, a replacement ground electrode 22 may be conveniently and easily applied to the insulator body I I. It is also to be noted that the length of the upper portion 25 of the insulator body II is substantial whereby there is a greatly increased length of the electrical leakage path between the upper head I8 of the central electrode Il and the grounding combustion chamber wall 21, thisincreased length of the electrical leakage path being eifected without increasing the overall length of the plug as compared with conventional practice in spark plug construction where ground shells are used which extend a considerable distance above the combustion chamber wall in which the spark plug is mounted.

In Fig. 2 there is shown a second embodiment of the improved spark plug hereof indicated generally by IIII and which is generally similar to the spark plug Il, but in the spark plug IIB the insulator body III has a bore II2 extending entirely through the body, and a center electrode IIS located in the bore II2 has its lower end protruding below the lower end of the insulator body IIL In the spark plug IIB there is also a replaceable ground electrode |22. The spark plug Ill has all the advantages of the spark plug III with the exception of lacking a central electrode in a well.

In Fig. 3 there is shown a generally conventional spark plug indicated generally by 2Il including a ground shell 23| at the lower end of which there is screw connected a replaceable ground electrode 222 which constitutes one of the improvements of the present invention. The

v ground shell 230 has mounted therein in a usual manner an insulator 2II in the central bore 2I2 of which there is sealed a central electrode 2li in the usual manner.

In Fig. 4 there is shown aspark plug indicated generally by IIII which is of generally conventional construction including a ground shell 330 mounting an insulator body SII which is modified from conventional construction by including awell SI2 having a bottom wall 3I4 extending across the lower end of the well SI2, this being one of the improvements of the present invention. There is located .in the well H2 a central elec. trode IIC.

In Fig. 5 there is shown a spark plug indicated generally by 4I4 which is of modified conventional construction and includes a ground shell 430'. One of the improved removable ground electrodes of the present l invention indicated generally by 4221s screw connected to the lower end of Vthe ground shell, and the ground shell mounts an insulator body 4II which is formed to include another of ythe improvements of the present invention; namely a central well 4I2 havingr a bottom wall 4I4 extending across its lower end. A -central electrode 4I6 yis located in the well 4VI2.` f l l' In Fig. 6 there is shown a modified insulator body indicated generally Vby 5II whichv isygen` erally similar to the insulator body II`, the insulator body EII having formed thereina central well SI2 having an open upper end 5|.3 andaA bottom wall 514 extending lacrossthe lower end of the well SI2. Differing from the solid bottom Wall I4 ofthe insulator'body II, the bottom wall 5I4 has a microscopic hole 5I4jrl formed therethrough by being puncturedy by a high tension electrical discharge passed therethrough by plac-` ing'th'e wall 5I4 between electrodes ofv an electric circuit-in which there is a, sufcient potential dierence between the electrodes'to eiect the puncturing. In Fig. 6, -the 'microscopic hole 5I4-I'is necessarily magnified. i l

For properly locating the hole 5I4-I, the top face of the bottom wall 5I4 slopes to a central point-` 5I4-2 which insures that thespuncturingV high tension electrical discharge will pass through the wall lI5I4 at the central point 5I4-'2, the wall 5 I 4 being thinnest at that point.

In Fig. 'l there is shown another modified in-V sulator body indicated generally by GII which is also generally similar to the insulator body'I I, theinsulator body SII having formed therein a central well SI2 havingan open `upper end SIS and a bottom wall H4 extending across the lower end of the well SI2. Thev bottom wall I4 ofthe insulator body II is formed entirely of insulation material, preferably fired ceramic material. The bottom wall 6I4 differs from this in that the bottom wall BI4 has one or more ne metallic wires such as platinum extending therethrough, these wires being inserted in the bottom wall before the ilring is eiIected, the ilring serving toseal the wires in the bottom wall.

In Fig. 8 there is shown a modiiied insulator body indicated generally by III which is again generally similar to the-insulator body I I, the insulator body 'II I having formed therein a central well I I 2 having an open upper end 1 I 3 and a bottomwall 1I'4 extending across the lower end of the well 1 I2. Instead of being of insulation material as is the solici bottom wall I4 of the insulator II, the bottomwall H4 includes a portion or is entirely made, as shown in the drawing, of conducting material, such as a combination of ceramic material and a metallic powder such as iron, nickel, chromium, or tungsten, sintered together.

The insulator bodies SII, SII, and 1II each includes a different means whereby a reduced potential difference is required to effect the passage of an electrical discharge or current through their respective bottom walls M4, U4, and '|I4, as compared with the potential difference required to eiect the passage of a discharge through the solid bottom wall I4 oi.' insulation material of the insulator body II, where all of the bottom walls have the same thickness.

In Fig. 9 there is shown a spark plug indicated generally by 8I0 which is generally similar to the spark plug I0. but in the spark plug IIB the ground electrode 822 is formed by sprayed metal on thevreduced` lower end IIS of the insulator body BI I.

It should also be noted that the'replaceable ground electrode 22 on the insulator body II as shown preferably is screw connected with the insulator body II. In addition to being mere- 1yy screwed on the insulator body II, the replaceable ground electrode' 22 may be thermally sweated thereon.

- In Figs. l0, 12, and 1,3 there is shown a spark plug indicated generally by SID which is generally similar to the spark plug II) with lthe exception of thel construction and arrangement of the well and central electrode. The spark plug 9I0 includes an insulatorb'ody 9i I having formed therein'a central well SI2 having an open upper end 9I3 and a bottom wall 91,4 extending across the ,lower end of the Well SI2. The well 9I2 has an increasedudiameter as compared with the diameter ofuthe well I2 of the insulator body II of the spark plug III. l

the lower end of the vwell SI2 there is located a'body of conducting'liquid preferably liquid metal SIS-I which may b e mercury or a lower melting alloy of bismuth, tin`, lead, and antimony, or similar'material'. There is also locatedvin the well 4SI2 a metalelectrode rod SIS, the lower end of which extends into the body of liquid metal SIS-I, and the metal electrode rod SIE has an enlarged head SIB which is externally threaded and screwed in the internally threaded enlarged upper end SI1 of the well SI2. A body of cement 93| seals the upper portions of the electrode rod SIB between the' body of liquid metal 9I6--I and the head sla. l l

' In the spark plug 9I0 the lower body of liquid metal SIS-I andthe electrode rod SIS whose lower end is immersed in the body of liquid metal QII-I constitute a composite central electrode in which the lower' end oi the body of liquid metal SIG-I always rests upon the upper face of the well bottom wall 9 I 4. In other words the position oi' the lower end oi the composite central -electrode of the spark plug 9I0 always remains con-` stant,v where as disintegration of the lower tip of the central electrode rod 9 I 6 may take place if the lower Jtip of the central electrode rod SIG ex tends to the top surface of the well bottom wall SI4, and no body of liquid metal SIS-I is used. The'body of liquid metal SIG-I flows into any void produced in it on top oi' the well bottom wall 9I4.

Moreover, in the operation of an internal combustion engine, for example, in which the spark plug SIU is in use, the hot gases in the combustion chamber served by the spark plug SIU heats the lower :end of the spark plug 9I0 and the body of liquid metal` SIS-I therein causing circulation ananas of the liquid metal SIB-I, whereby there is a transfer of heat from the lower end I3 of the insulator body SII to upper portions and surfaces of the insulator body SI I, this transfer of heat being effected by convection of the body of circulating-liquid metal SIS-I, as well as by its own conduction.

In Fig. ll there is shown a spark plug indicated generally by llt-I9 which is generally similar to the spark plug I and includes an insulator body IOII having formed therein a central well I9I2 having an open upper end IIII3, and the insulator body IIII has a lower end I9I9 which has formed therein a bore I9l2-I which has a diameter reduced from that of the well I9I2. An intermediate electrode shank IIN-2 is located and sealed in the bore I9I2-I and has on its upper end an enlarged head IIN-3 which fits and seals the lower end of the bore I9I2. A body of conducting liquid IIlIB-I is located in the lower end of the well I9 I2 and rests upon `the top of the enlarged head IMI-3 on the intermediate electrode shank INS-2. A metal electrode rod IIIS is located in the well I9I2 and has its lower end immersed in the body of conducting liquid IMS-I, and a body of cement IIII seals the upper portions of the electrode rod VI 9I9.

In Fig. 14 there is shown a spark plug indicated generally by I IIB which is generally similar to the spark plug 9 I l. The spark plug I I I9 includes an insulator body IIII having formed therein a central well III2 having an open upper end III3 and a bottom wall I I I4 extending across the lower end of the well III2. The insulator body IIII has a reduced lower end III! having a bottom face IIII-I, and the well bottom wall IIIl is spaced above the bottom face I I II-I In the lower end III! of the insulator body IIII there is formed an internally threaded socket III9-3 in which is screwed an externally threaded intermediate electrode III32. The wall IIIl may be provided. if desired, with one or more microscopic holes formed by puncture by an electrical discharge.

In the lower end of the well III2 there is located a body of conducting liquid IIIl-I on top of which is a layer of powdered carbon IIN- 4. There is also located in the well III2 a metal electrode rod IIIB. the lower end of which extends into the layer of powdered carbon I IIS-4.

In Fig. l there is shown a spark plug indicated generally by I2I0 which includes the improvements of the spark plug IIIO embodied in a construction which is otherwise conventional.

In Fig. 16 there is shown a spark plug indicated generally by I3I9 which is generally similar to the spark plug I2III, with certain exceptions. The spark plug I3I0 includes an insulator body IIII with a bottom face NIS-I and the insulator body I3I I has formed therein a well I3I2 having a bottom wall I3II extending across the lower end of the well I3I2. The bottom wall I3II is spaced above the bottom face I3I3-I of the insulator body IIII, and in the lower end I3I9 of the insulator body I3II there is formed a downwardly opening socket I3 I 9 3.

The spark plug I3I9 furthermore includes a metal ground shell |330 on the lower end of which is a metal electrode tip |324 whose outer end extends into the socket HIS-3.

The embodiments of the present invention illustrated and described herein are by way of example and the scope of the present invention is not limited to the same or to the particular details thereof but is commensurate with any and all novel subject matter contained herein which may at any time properly under the patent laws be set forth in the claims hereof or originating herein, and the elements of any such claims are intended to include their functional or structural equivalents.

Iclaim:

1. In spark plug construction, an Insulator body having a bottom face and the insulator body having formed therein a well with an open upper end and the insulator body including a well Vbottom wall extending entirely across and closing the lower end of the well, the well bottom wall being spaced above the insulator body bottom face. a metal ground electrode adjacent the lower end of the insulator'body. electrode material in the well, and the insulator body having formed therein a downwardly opening socket below the well bottom wall. and an intermediate electrode in the socket.

2. In spark plug construction, an insulator body having a bottom face and the insulator body having formed therein a well with an open upper end and the insulator body including a well bottom wall extending entirely across and closing the lower end ol.' the well. the well bottom wall being spaced above the insulator body bottom tace. a ground electrode adjacent the lower end of the insulator body, electrode material in the well, and the insulator body having formed therein a downwardly opening socket below the well bottom wall. and an intermediate electrode Ain the socket.

3. In spark plug construction. an insulator body having a bottom face and the insulator body having formed therein a well with an open upper end and the insulator body including a well bottom wall extending entirely across and closing the lower end of the well, the well bottom wall being spaced above the insulator body bottom face, a ground electrode adjacent the lower end of the insulator body, electrode material in the well, and the insulator body having formed therein a downwardly opening socket below the well bottom wall, and wnducting material in thesocket.

4. In spark plug construction, an insulator body having a bottom face and the insulator body having formed therein a well with an open upper end and the insulator body including a well bottom wall extending entirely across and closing the lower end of the well, the well bottom wall being spaced above the insulator body bottom face, a ground electrode adjacent the lower end of the insulator body, electrode material in the well, and the insulator body having formed therein an internally threaded downwardly opening socket below the well bottom wall, and an externally threaded intermediate electrode screwed inthe socket.

HAROLD R. FEICHTER.

REFERENCES CITED The following references are of record in the file of this paient:

UNITED STATES PATENTS Number Name Date 1,491,752 Richey Apr. 22, 1924 2,072,732 Devers Mar. 2, 1937 2,093,848 Randolph et al. Sept. 2l, 1937 2,318,440 Wall May 4, 1943