US3569765A

US3569765A - Spark plug with cuplike center electrode

Info

Publication number: US3569765A
Application number: US790298A
Authority: US
Inventors: Forest J Moray
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-01-10
Filing date: 1969-01-10
Publication date: 1971-03-09
Anticipated expiration: 1988-03-09

Abstract

The central electrode of a spark plug has a receptacle cup buried in an open cavity of a ceramic body to receive a plug terminal of a connecting wire. The electrode and cup are made separately and are secured together by a welded joint between the cup and the edges of radial vanes on the inner end of the electrode or by the inner end of the electrode being butt-welded to the bottom of the cup or by the electrode inner end and a portion of the cup interfitting telescopically and being bonded together or by the inner end of the electrode and the cup being connected

Description

United States Patent [1113,569,765

[72] Inventor ForestJ.M0ray 2,954,495 9/1960 Zeller 313/136X.

1513 Brooks St., Seattle, Wash. 98055 3,076,113 1/1963 Candelise 3 13/1 36X [21 App]. No. 790,298 [22] Filed Jan. 10, 1969 [45] Patented Mar. 9, 1971 Primary Examiner-Roy Lake Assistant Examiner-C. R. Campbell Attorney-Robert W. Beach [54] SPARK PLUG WITH CUP LIKE CENTER g ?g Figs ABSTRACT: The central electrode of a spark plug has a receptacle cup buried in an open cavity of a ceramic body to [52] 11.8. CI 313/136, eceive a plug terminal of a connecting wire The electrode 135, 144 and cup are made separately and are secured together by a [51] Int. Cl H0lt 13/34 welded joint between the cup and the edges of radial vanes on [50] Field Of l 35, the inner end of the electrode or by the inner end of the elec- 136, 144 trlode being butt-welded to the bottom of the cup'or by the e ectrode inner end and a portion of the cu interfittin tele- [56] References cued scopically and being bonded together or by the inner 5nd of UNITED STATES PATENTS the electrode and the cup being connected through interposed 2.604.087 7/1952 Gregory et al. 3 13/ l 36X sealing material having good electricity-conducting properties.

PATENTE DMAR 91911 SHEET 1 [1F 2 5 v1 7/11. rm I alil/1 m ATTORNEY SPARK PLUG WITH CUP LEKE CENTER ELECTRODE The spark produced by a conventional spark plug installation in an internal combustion engine is not as strong as neces sary for the most efficient operation of the engine because either the resistance of the circuit to the central spark plugterminal is too high or electricity leaks from the spark plug or its connecting wire to ground, or both.

A principal object of the present invention is to provide a connection between a spark plug connecting wire and the central terminal of a spark plug which is of comparatively low impedance. Such object is accomplished particularly by providing a large area for transfer of electrical energy between the spark plug wire terminal and a receptacle connected effectively to the central electrode of the spark plug.

A further object is to eliminate or at least to reduce greatly leakage of electricity from the spark plug connecting wire or central electrode of the spark plug to ground passing the spark gap of the spark plug.

A further object is to provide a spark plug for effective connection to a spark plug wire which has a structure that can be assembled easily and quickly.

FIG. l is a top perspective of a spark plug showing parts in exploded relationship and having parts broken away;

FIG. 2 is a fragmentary longitudinal section of a portion of such spark plug;

FIG. 3 is a transverse section taken on line 3-3 of FIG. 2;

FIG. 4 is a longitudinal section through such spark plug;

FIG. 5 is a top perspective of portions of a spark plug showing an alternative type of construction, parts of the structure being broken away;

FIG. 6 is a fragmentary longitudinal section of a portion of such a spark plug;

FIG. 7 is a longitudinal section'through the completed spark P g;

FIG. 8 is a top perspective of parts of a different type of spark plug shown in exploded relationship and having parts broken away;

FlG. 9 is a longitudinal section through a spark plug incorporating such parts;

FIG. 10 is a top perspective of parts of a somewhat modified spark plug with portions broken away; FIG. 11 is a top perspective of parts of still a different spark plug having parts broken away;

FIG. 12 is a longitudinal section through a spark plug incorporating such parts; and

MG. 13 is a top perspective of parts of a further modified spark plug;

FlG. 14 is a longitudinal section through a spark plug incorporating such parts; and

FIG. 15 is a transverse section through this spark plug taken on line l5 -]l5 ofFIG. id.

The outer metal shell 1 of the spark plug is conventional, having a reduced end portion 2 which is threaded to be screwed into the conventional spark plug hole of an internal combustion engine. An external band 3 of this shell is of hexagon shape for engagement by a wrench to tighten the spark v plug. An insulating body of sinteredalumina or other ceramic material has an enlarged portion 4 fitting within the shell and a neck 5 projecting from such enlarged portion through the threaded neck 2 of the metal shell. The enlarged portion of the body is sealed relative to the shell by

gaskets

6 and 7 at opposite ends of the enlarged body portion. The flange 8 on the end of the metal shell I remote from its neck 2 overlaps the enlarged portion of the insulating body to hold it in place in the shell.

The central electrode includes a stem 9 extending through a central bore in the insulating body so that its outer end is disposed in proximity to the grounded, side electrode prong it) carried by the shell l. The end of the insulating body bore remote from the neck 5 opens into the hollow interior of the insulating body. Such hollow interior is formed within an an nuiar end portion ll of the insulating body remote from the neck 5 and an intermediate portion 12 of such body joining the annular end portion and the enlarged portion. An external shoulder 13 is formed at the junction between the body end portion 1 1 and the body central portion 12.

A sheath of flexible rubber or plastic is provided for the hollow end portion 11 of the insulatingbody and includes a neck 14 projecting generally in continuation of the insulating body hollow end portion, a liner l5 projecting oppositely from neck 14 into the hollow of the insulating body and a skirt 16 extending over the end of the insulatingbody and having an inner rib engaged with the insulating body shoulder 13 to hold the sheath in place on the body end.

In the cavity 17 pf the insulating body is received a buried electrode cup 1% which is inserted into the body cavity from the relationship shown in FIG. 1 to that of FIG. 2. Adjacent to the flared lip of cup 18 is a shoulder 19 preferably formed by an exterior annular rib 20. The inner groove formed by this rib receives a projection of a connecting wire plug to hold it in place. The inner end portion 21 of the cup is constricted to fit closely the radial outer edges of radial vanes 22 carried by the inner end of the central electrode stem 9. The shoulder between the main cup body and such constricted end portion 7 installed in the metal mounting shell 1 and secured in place by rolling the flange fiover the enlarged portion of the insulating body. The electrode component is then fabricated by forming the stem 9 and vanes 22 separately from the cup 18. These two parts are then assembled by bonding the radially outer edges of the vanes 22 to the inner wall of the constricted inner cup end 21. Such bonding can be effected by a spot welding or a brazing operation, for example. When these parts are secured together, passages are formed through the constricted cup portion 21 between adjacent vanes 22 and the wall of such constricted cup portion.

The electrode component and the body component shown in exploded relationship in FIG. 1 can now be assembled by inserting the electrode component stem first into the body cavity. As the electrode component moves lengthwise into the body cavity, the end of the electrode stem enters the body bore and such inserting movement continues until the components have reached their assembled relationship shown in FIGS. 2 and 3. A small amount of sealant in powdered or fluid condition, which need not be of electrically conductive character, can then be poured into the cup 18 so that it will flow through the passages between the vanes 22 into the annular portion of the cavity adjacent to the opening of the body bore into it and encircling the roughened or knurled portion 23 of the electrode stern. Such sealant will bond to the roughened portion of the stern so as to hold the electrode component in the insulating body. At the same time, the sealant closes any passage which might exist from the body cavity, through the body bore alongside the electrode stem h, to the tip of the body neck 5.

After the electrode component has been inserted into the insulating body cavity and secured in place, the spark plug assembly is ready to be installed in a spark plug port of an internal combustion engine and an ignition wire connected to it. Such a wire 25 is shown in phantom in FIG. 4 and is illustrated as having a central conducting wire 26. The bare end of such conducting wire beyond the end of the wire s insulating cover is embedded in a conducting plug terminal 27 which may be a clip or a solid knob to fit snugly in the outer main portion of the electrode cup 18. Such knob is of an extent lengthwise of the wire substantially equal to the depdi of the electrode cup so as to provide large surface areas on the periphery of the knob and on the inner wall of the cup between which surfaces electricity can transfer from the spark plug wire to the electrode when the plug terminal is fitted snugly into the outwardly opening cup 18 as shown in FIGS. and 7. An insulating

sheath

14, 15, 16 can be fitted over the wire before the plug 27 is inserted into the cup 18 and after the plug is in place can be slid down over the hollow end 1 l of the insulating body in the manner shown in FIG. 4. Such sheath deters leakage of electricity from the spark plug wire plug 27 along the surface of the spark plug wire and sheath to the metal shell 1 by protecting against accumulation of a film of oil, dirt and moisture on the insulating body of the spark plug which would be electrically conductive.

In the spark plug of FIGS. 5, 6 and 7, the metal shell 1 and insulating body of ceramic material secured in the shell are the same as described in connection with FIGS. 1 to 4. Also, the electrode component of this spark plug is similar to the corresponding component of the spark plug of FIGS. 1 to 4, except for the connection between the stem 9 and the cup K8. in this instance, the inner end of the electrode stem does not have vanes, but the inner end portion 28 is roughened, such as by being knurled over a substantial length. Moreover, the electrode has an annular rib 29 at the junction between the portion of the stern which is inserted into the bore of the insulating body and the roughened inner end portion 28 of the stem. Such rib will seat on the bottom of the body cavity 30 at the entrance to the bore as shown in FIG. 6 so as to limit lengthwise movement of the stem into the bore.

It is preferred that the inner portion 30 of the body cavity have a double-step conformation so that one of such steps will encircle the roughened inner end portion 28 of the electrode stem as shown in FIG. 6. Whether or not the inner end portion of the insulating body cavity has a double step, the inner end portion 31 of the electrode cup 18 is constricted to a size such that its inner end will fit reasonably snugly in the inner end portion of the cavity. Such constricted cup portion 31 should be long enough to extend into the smaller portion of the stepped body cavity, but should be short enough so that the inner end of such constricted portion will be spaced a substantial distance from the electrode stem rib 29 when the cup and the stem are both inserted into the insulatingbody cavity to their limiting positions as shown in FIG. 6.

It will be seen in FIG. 6 that, when the electrode cup and stem elements have been fully inserted into the cavity of the insulating body 4, the constricted inner end portion 31 of the cup 18 will be spaced radially outwardly from the roughened end portion 28 of the electrode stem in substantially concentric arrangement. Also, such constricted cup portion and roughened electrode stem portion are disposed in overlapping relationship over a substantial distance axially of the stem and cup. With the parts in this relationship, electrically conductive sealant 32 shown in FIG. 7 can be poured in fluid condition into the space between the roughened portion of the electrode stem and the constricted portion of the cup as shown in FIG. 7. This sealant may, for example, be a mixture of glass and conductive powder, preferably copper. Such conductive seals are disclosed in U.S. Pats. No. 2,106,578 of Schwartzwalder et al. and U.S. Pat. No. 2,248,415 of Schwartzwalder et al. Reliance on such conductive sealant to transmit the current to the electrode stem is, of course, not as desirable as providing a continuous solid metal path for the electricity. Such sealant, when hard, will secure the stem portion of the electrode in the insulating body bore and will seal any space between the electrode stem and the wall of such bore beneath the rib 7.9. Also, such sealant will bond the roughened inner end portion 28 of the stem to the constricted portion 31 of the cup and provide a good electrically conductive path from the cup to the stem. The plug 27 of the spark plug wire can be fitted into the electrode cup 18 as shown in F IG. 7 and as previously described in connection with FIG. d. Also, this spark plug will be provided with a sheath l4, l5, 16 like that described with reference to FIG. 4.

The construction of the spark plug shown in H08. 3 and 9 is the same as that of FlGS. l to d and that of FIGS. 5 to 7, except for the interfitting structures forming the inner end of the electrode stem 9 and of the electrode cup 18. In this instance, the inner end of the electrode stem 9 carries a cup 33 having one or more slots 34 extending lengthwise of it. Preferably, an annular rib 35 encircles the base of such cup at its junction with the inner end of the stem so as to form on the stem a shoulder of substantial radial width which will seat on the bottom of the insulating body cavity for limiting lengthwise movement of the stem 9 through the insulating body bore.

The inner end portion 36 of the electrode cup 18 is constricted to a size to fit snugly within the electrode stem cup 33 in telescoping relationship as shown in MG. 9. in this instance, the inner end of the cup is closed to conserve sealant, which is not needed in the center of the cup stem, but such stem could be open as in the types of cups shown in FlGS. l to 7. Preferably, the outer surface of the electrode stem cup 33 is roughened, such as by knurling 37, to improve the bond of electrically conductive sealant 38 to it.

In assembling the spark plug shown in FIGS. 8 and 9 the metal shell 1 and insulating body 4 are first assembled as described above and the stem 9 is inserted into the body cavity and through the bore of such body. A predetermined amount of sealant 38 is then placed in the cavity of the ceramic body after which the electrode cup 18 is inserted into the insulating body cavity. As the constricted cup portion 36 is pressed axially into the cup 33, the pressure which it exerts on the sealant will displace sealant to the exterior of the stem cup through slots 34 which will be forced to flow upward within the annular space between the wall of the insulating body cavity and the exterior of the electrode cup 33. A good electrically conductive path is thus formed from the constricted portion 36 of cup 18 to the stem cup 33, by direct contact or through a film of sealant, and from the closed end of the cup 18 through sealant to the bottom of the stem cup 33.

An alternative type of electrode component construction is shown in H6. 10. In this instance, instead of the extension of cup 18 being hollow, a solid cylinder 39 of metal is fitted into a tubular neck 40 projecting from the bottom of the cup. Such cylinder and neck are bonded together, such as by welding, soldering or brazing. The cylinder 39 is of a size to fit snugly into the cup 33 on the end of the electrode stem 9. In this instance, the lip of the cup is flared outward to facilitate entry of the cylinder into the cup. Alternatively, the outer end of the cylinder 39 could be chamfered.

The stem and cup parts of the electrode component shown in FIG. ll) can be installed in the spark plug body 4 in the same manner as described in connection with the spark plug of F KG. 9. The electrode stem is installed first, then the sealant 38 and finally the cup part of the electrode component. The sealant will act both to bond the cup 33 to the insulating body of the spark plug and the cup cylinder 39 to the electrode stem cup 33 as the sealant is formed by the cylinder through the slots 34.

In the spark plug of FIGS. 11 and 12 the shell and insulating body construction again is the same as described above. Also, the electrode stem is like that of the spark plugs shown in FIGS. 1 to 4 and FIGS. 5 to 7, except that the inner end por tion 42 having the roughened surface 23 is longer than that shown in FIGS. 1 to 4 and does not have radial vanes. It is preferred that this stem not have an annular rib such as the rib 29 of the stem shown in FIGS. 5 to 7. Moreover, in this instance, the electrode cup 18 does not have a constricted inner end portion, but, instead, has a closed bottom 63. The central portion of this bottom is secured to the inner end of the inner stem portion 42 by a button weld M or other bonding techniques so that the cup and the stem form an integral electrode component.

In order to assemble the electrode component of HG. ll with a spark plug body, a plug can be placed in the electrodereceiving bore in the insulating body 4, after which sealant 45 can be placed in the insulating body cavity. Such sealant need not be of electrically conducting character. The electrode assembly is then inserted into the insulating body cavity and the end of the electrode forces the plug down through the bore ahead of it. insertion of the end of the electrode into the cavity will raise the level of the sealant so that it can make a good bond between the electrode'and the insulating body cavity. The plug will simply be pushed out of the insulating body bore and inward movement of the electrode component will be terminated by engagement of the bottom of the electrode cup with a shoulder of the body cavity;

An alternate procedure for assembling theelectrode component and the body component of the spark plug shown in FIGS. 11 and 12 is to dip the electrode stem 9 in sealant so that some of the sealant adheres to the stem. As the stem is pushed into the body bore, the sealant will be stripped off the stem and accumulate in the cavity.

The stem 9 and cup 18 of the spark plug electrode shown in FIGS. 13 and 14 are the same as the corresponding electrode stem and cup of the spark plug shown in FIGS. 11 and 12, except that in this instance arcuate apertures 46 are provided in the bottom of the cup between the cup wall and the central portion of the bottom which is bonded tothe electrode stem.

By using an electrode component having this type of construction, it is not necessary to plug the bore of the insulating body and place sealant in the body cavity before the electrode component is installed or to place sealant on the electrode stem. Instead, the electrode component can be installed in the insulating body and thereafter sealant 47 can be supplied to the cavity around the roughened inner stern portion 43 through the apertures 46 in the cup bottom. Such apertures are shown clearly in FIG. 15.

lclaim:

1. In spark plug mechanism connected to a spark plug electric current supply wire, an insulating spark plug body having therein a deep cavity opening toward the outer end of the spark plug to receive such wire, an electrode stem extending through the inner end of said insulating spark plug body from the inner portion of its cavity, a metal cup element received within the inner portion of such insulating spark plug body cavity and opening outwardly, a plug element fitted snugly into the opening of said cup element and attached to the end of the spark plug wire, and electrically conducting means connecu'ng said cup element and said electrode stem.

2. In the spark plug mechanism defined in claim 1, the cup element having an open inner end and the electrically conducting means including a plurality of radially projecting vanes carried by the adjacent endof the electrode stem and having their outer edges received within and connected to the inner end of the cup element.

3. In the spark plug mechanism defined in claim 1, the electrically conducting means including a tubular member and an inner member fitting telescopically within said tubular member.

4. In the spark plug mechanism defined in claim 3, the telescoping members being spaced radially from each other, and conductive sealant lodged between and in electrically conducting engagement with both of the two telescoping members. I

5. In the spark plug mechanism defined in claim 3, the telescoping members interfitting snugly and the outer tubular member being slit axially.

6. In the spark plug mechanism defined in claim 5 the inner telescoping member being hollow.

7. In the spark plug mechanism defined in claim 1, the electrically conducting means including a bonded joint directly connecting the electrode stern and the element to which it is electrically connected.

8. In the spark plug mechanism defined in claim 1, the cup element having a closed bottom and the adjacent end of the electrode stem being bonded directly to said cup element bottom.

9. In the spark plug mechanism defined in claim 8, the portion of the cup element bottom between the sides of the cup element and the electrode stem being apertured.

mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 569,765 Dated March 9, 1971 Inventor(s) Forest J. Moray It is certified that error appears in the above-identified patem and that said Letters Patent are hereby corrected as shown below:

Abstract page, column 1 cancel "Seattle" in the address 1 and insert --Renton--.

Column 6, line 22 after "5" insert a comma.

Signed and sealed this 7th day of September 1971 (SEAL) Attest:

EDWARD M.FLETCHER, JR.

Attesting Officer ROBERT GOTTSCHALK Acting Commissioner of P:

Claims

1. In spark plug mechanism connected to a spark plug electric current supply wire, an insulating spark plug body having therein a deep cavity opening toward the outer end of the spark plug to receive such wire, an electrode stem extending through the inner end of said insulating spark plug body from the inner portion of its cavity, a metal cup element receiVed within the inner portion of such insulating spark plug body cavity and opening outwardly, a plug element fitted snugly into the opening of said cup element and attached to the end of the spark plug wire, and electrically conducting means connecting said cup element and said electrode stem.

2. In the spark plug mechanism defined in claim 1, the cup element having an open inner end and the electrically conducting means including a plurality of radially projecting vanes carried by the adjacent end of the electrode stem and having their outer edges received within and connected to the inner end of the cup element.

4. In the spark plug mechanism defined in claim 3, the telescoping members being spaced radially from each other, and conductive sealant lodged between and in electrically conducting engagement with both of the two telescoping members.

7. In the spark plug mechanism defined in claim 1, the electrically conducting means including a bonded joint directly connecting the electrode stem and the element to which it is electrically connected.