US3076113A - Spark plug and connector device therefor - Google Patents

Description

Jan. 29, 1963 A. CANDELISE 3,076,113

SPARK PLUG AND CONNECTOR DEVICE THEREFOR Filed March 29, 1961 2 Sheets-Sheet 1 Jan. 29, 1963 A. CANDELISE SPARK PLUG AND CONNECTOR DEVICE THEREFOR Filed March 29, 1961 2 Sheets-Sheet 2 ATTORNEY 3,tl76,lf3 SPARK PLUG AND CONNECTQR BEVIQE THEREFGR Alfred Candelise, Flint, Mich, assignor to General lt'fotors Corporation, Detroit, Mich, a corporation of Delaware Filed Mar. 29, 1961, Ser. No. 99,289 11 Claims. (c1. sis-13s This invention relates to an improved spark plug and connector device therefor incorporating a protective boot to prevent the entrance of water, dirt and the like to the connection. This patent application is a continuation-inpart of my application Serial No. 655,321, filed April 26, 1957.

Heretofore, automotive type spark plugs have been constructed with the electrical terminal located on the top and exterior of the insulator member. By reason of the terminal being so located, such spark plugs must be of considerable length in order to attain sufiicient flashover distance between the terminal and the spark plug shell over the surface of the exposed portion of the insulator. In many instances the length is greater than can be readily accommodated in modern compact engines. Also, while it has been the general practice to protect the electrical connection between the ignition cable and the spark plug terminal with a rubber boot, and very numerous boots have been designed for this purpose, the results obtained thereby have never been fully satisfactory. What usually happens with such construction is that after a period of time the rubber boot loses some of its resiliency by way of its exposure to oil or gasoline fumes and this leads to a looseness of fit between the boot and the spark plug insulator which allows the entrance of dirt, Water vapor and oil fumes to the electrical connection. In aircraft type spark plugs, there has been no such problem because of the particular construction wherein the electrical terminal is located in an insulator well and the insulator is surrounded by a metal shielding barrel threaded at its upper end to thereby allow the ignition cable to be secured into the insulator well by way of a cap which threadedly engages the shielding barrel. However, the shielding barrel type construction, while necessary in aircraft spark plugs for proper radio reception, is unnecessary in spark plugs for automobiles and the like and is, in general, too expensive and therefore unsuited for such use. By the term automotive spark plug as used herein is meant a spark plug having the upper end of its insulator exposed, i.e., not covered by a metal shielding barrel. Such plugs are used not only in passenger car and truck engines but also in outboard and inboard marine engines as well as in small output engines for power lawn mowers and the like.

It has been proposed to provide automotive spark plugs with a terminal located at the bottom of a well in the insulator and then make the electrical connection by inserting the end of the ignition cable into the well, this in order to gain some of the advantages of the aircraft type construction without high cost. However, only partial success has been had in this principally for two reasons. The first of these reasons is that rubber deterioration at the cable connection has led to much the same problems as are encountered with more conventional connector constructions. The second is that even small amounts of gas leakage from the combustion chamber of the engine about the spark plug centerwire tend to move the ignition cable out of the insulator well thereby loosening or completely breaking the electrical connection, this particularly after the rubber has lost some of its resiliency and therefore its ability to resist removal of the cable from the spark plug. Even slight unauthorized pulling of the ignition cable can lead to the same result.

3,076,113 Patented Jan. 29, 1953 ice It is an object of the present invention to provide a spark plug and an electrical connector therefor which serve as a solution to the aforementioned problems. More particularly, it is an object of the present invention to provide a spark plug and electrical connector structure which is inexpensive and yet which provides a tight durable seal for the connection against the entrance of water, dirt and the like. A further object is the provision of automotive spark plug structure and connector structure therefor which allow greatly reduced spark plug length.

Briefly, the above objects are accomplished, in accordance with the invention, by constructing the spark plug with an electrical terminal which extends into a well in the insulator and by constructing the rubber protective boot with an outer skirt portion which tightly engages the external surface of the insulator, with an inner tube which extends into the insulator well, and with a metal conductor extending through the inner tube which is adapted to make electrical contact with the spark plug terminal. The spark plug terminal and the metal conductor in the boot are shaped for mating spring pressed engagement with each other which assures against loosening or breaking of the electrical connection and which assists in maintaining the rubber boot in sealed engagement with the spark plug insulator even after the boot has undergone deterioration and lost some of its elasticity. In order to shorten the portion of the insulator which extends above the shell and yet attain adequate structura rigidity as well as ample flashover distance between the terminal and shell over the surface of the insulator, the well is shaped to extend into the insulator to adjacent the plane of the upper edge of the metal shell.

These and other objects, advantages and features of the invention will appear more fully from the following description of preferred embodiments made with reference to the accompanying drawings in which:

FIGURE 1 is a side view in partial section of a spark plug and electrical connector embodying the invention;

FIGURE 2 is an exploded view of the connector structure shown in FIGURE 1;

FIGURE 3 is a side view in section of another embodiment of the invention;

FIGURE 4 is an exploded perspective view with parts broken away of the embodiment shown in FIGURE 3;

FIGURE 5 is a side view in section of still another embodiment of the invention; and

FIGURE 6 is an exploded perspective view with parts broken away of the embodiment shown in FIGURE 5.

Referring now to the drawings, there is shown in FIG- URE 1 an automotive spark plug which includes a onepiece generally tubular metal shell 4 and a ceramic insulator 6 secured within the metal shell by means of an insulator shoulder section 7 which is tightly engaged within a mating groove in the metal shell, the tight fit being accomplished during manufacture by an operation well known in the art as Cico welding. A centerbore through the insulator accommodates a centerwire 8 the lowermost end of which constitutes the spark plug center electrode 10 and the upper end of which is of reduced diameter and forms the electrical terminal 12. A portion of the centerwire constitutes a conductive glass seal 14 which consists of a fused mixture of glass and conductive powder, preferably copper, and which is bonded to the insulator as well as to the otoher parts of the centerwire to provide a gastight centerwire seal. Such conductive glass seals are shown in detail in United States Patents 2,106,578 Schwartzwalder et al. and 2,248,415 Schwartzwalder et al. Emphasis is placed here on the seal portion of the centerwire because this feature is of importance to optimum functioning of the electrical connector structure in that it prevents gas leakage which would otherwise.

tend to push the connector, to be described in detail hereinafter, out of the spark plug. While the conductive glass seal is preferred, other types may be used such, for example, as that wherein a portion of the centerwire consists of a thin metal wire or rod' which is bonded to the insulator by glass. One example of this type of centerwire seal is shown by United States Patent 2,317,305 Schwa'rtzwalder.

The upper portion of the insulator centerbore is of enlarged diameter and forms a cylindrical Well 16 which communicates with the top of the insulator and which terminates adjacent the plane of the upper edge of the spark plug shell. The outer surface of the insulator at the upper end thereof is formed with a series of four annular ridges as shown at 17 which function as a; part of the connector structure hereinafter described and which also function to lengthen the ins'ulatorsurface or flashover distance from the electrical terminal 12 to the upper edge of the metal shell. Preferably the outer surface of that portion of the insulator which extends above the shell is glazed while the inner surface within the well is left unglazed.

The electrical terminal portion 12 of the centerwire consists of an upwardly extending metal rod which terminates within the well and is tapered at its upper extremity, as shown at 18 in FIGURE 2. An annular groove 20 is formed in the terminal preferably adjacent its upper end as shown; The portion of the rod below the Well 16 is of enlarged section as shown at 21 and forms the inner annular portion of the bottom wall of the well. This enlarged portion which serves as a firm base for the upwardly extending terminal is provided with threads in order to furnish additional surface area for bonding with the conductive glass seal.

By reason of the fact that the bottom wall of the well is located in the plane of the upper edge of the shell, maximum fiashover distance between the terminal and the shell over the surface of the insulator isattained commensurate with the required physical strength. It will be noted that for insulator surface current leakage or fiashover to occur in the spark plug shown, the current would have to pass from the outer periphery of centerwire section 21 up the inner wall cf the insulator and then down the outer Wall of the insuator to the upper edge of metal shell 4; If the insulator well is formed with its bot om wall above the upper edge of the metal shell, then the insulator surface distance from the terminal to ground is decreased. On the other hand, if the well is formed with its bottom wall below the upper edge of the shell, it has been found that considerable structural strength is sacrificed since the high pressure applied to the insulator by way of the press fit between the shell and the insulator requires a thick insulator section at the location of the press fit. 7 It will be seen then, that the spark plug structure of the present invention allows for a considerable reduction inthe length of that portion of the insulator which extends above the shell, and this without any sacrifice in physical strength or resistance to insulator cracking and without any sacrifice in insulator surface flashover distance. This is an important advantage particularly in spark plugs for modern compact engine designs which provide only very limited space for spark plug fitment. r

The rubber protective boot is of one-piece construction and comprises an upper tubular neck portion 22 which divides into an outer tubular shaped skirt portion 24 of larger diameter than theneck portion, and an inner tube portion 26 which is of sma'ler diameter than the neck portion and whch is posiioned c ncentrically within the skirt. The skirt is somewhat thicker than the other portions of the boot. ms for added elasticity and strength, and is shaped to fit over and around the urper end of the insulaor in snugly sealed engagement therewith. The annular ridges 17 on the outer surface of the insulator are helpful in that they a'ssistin providing a sealed fit between the insulator and the skirt and in preventing unauthorized withdrawal of the boot from the spark plug. The inner tube portion 26 extends concentricaly down into the spark plug insulator well 16 and, in the embodiment shown, terminates adjacent the bottom wall thereof. Extending through the neck portion and through the inner tube portion of the boot is an electrical conductor, the upper end of which is formed by the ignition lead cable 28 which fits snugly Within the neck portion 22; To provide a good seal with the cable, it is prefered that the upper endof the neck portion be provided wfth an internal annular raised portion, as shown at St). The lower end of the conductor is formed by a longitudinally split metal tube member 32 which fits over the spark pug terminal. 12 and which-is provided with an internal flange 34'. This flangewhich in the em: bodiment shown is formed by merey indenting the wall of the tube, engages the annular groove 20 on the spark plug terminal with a snap spring pressed fit, the spring action being provided by the resiliency ofthe split metal tube and assisted by the resiliency of the inner tube portion 26 of the boot which fitssnugly around the split metal tube. The top of the split tube communicateswith surfaces 35 which taper outwardly into a portion of large diameter split on only one side thereof to form a pair of jaws 36 and 38 which are clamped tightly aroundtheend of the ignition lead cable 28; A pointed metal tab 40 integral with the jaw portion of the conductor penetrates through the insulation on the cable and forms an electrical connection with the cable. The conductor member 32 can be conveniently and inexpensively made from sheet metal stock. V

The manner of assembling the connector will be apparent from FIGURE 2.. The conductor member 32 is first secured to the endof the ignition lead cable in electrical contact therewith by pushing the tab 40 through the insulation of the cable and pinching the jaws tightly about the end of the cable 28. This assembly is then pushed down: through the neck portion 22 of the pro: tective boot untilthe end of the conductor member 32 extendsto a position adjacent and preferably below the lower end of the inner tube portion 26 of the boot. Then the boot is pushed down into and over the top of the spark plug insulator until the flange 34 snaps into thegroove 20 on the spark plug terminal as shown in FIGURE 1, v One of the important advantages of the construction isthat the permanence and durability of the electrical connection between the cable and the spark plug, while greatly assisted by the resilience of the rubber boot and its tight engagement with the insulator, is not solely dependent on it. Even after considerable rubber deterioration has taken place, the spring pressed engagement between the split metal tube conductor member 32 and the spark plug contact terminal 12 maintains a good electrical connection. Further, this spring pressed engagement assists in the formation of a good seal between the protective boot and the spark plug insulator, and assures a seal between these two members even after some rubber deterioration has taken place. v In this regard itwill be notedthat the surfaces 35 abut the mating tapered wall of the protective boot intermediate its neck and inner tube portions such that there can be no upward movement of the boot with respect to the conductor 32. Thus, the spring pressed mat ng connection between conductor 32 and terminal 12 assists in retaining the boot in'sealed eng"gement with the insulator 6. I r v The protective boot can be made either of natural rubher or of any sui'able synthetic rubber su-h as po ychloroprene, polybutadiene-acrylonitrile, etc. Thus. the termrubber" as used herein is intended to comprehend both; the nau al and the synthetic rubbers. I

Referring now to the embodiment shown in FIGURES, 3 and 4, the spark plug like that previously described; comprises an insulator 40 having an external shoulderpor-. tion tightly secured in metal shell 42 by Cico, welding},

more; 13

i.e., after the insulator and its associated gaskets are positioned in the shell the upper edge of the shell is turned inwardly to form the flange '44 and the thin section 46 is then resistance heated to its softening temperature while axial pressure is applied to thereby cause an extremely tight fit between the shell and insulator. A centerbore through the insulator accommodates the centerwire, the lower end 48 of which constitutes the firing electrode, the center portion of which constitutes the conductive glass hermetic seal 50 and the upper end of which is formed by a rod member 52 which extends into and terminates within the well 54 formed by the enlarged upper portion or the insulator centerbore. The bottom of the rod member 52 is an enlarged section and is provided with an annular flange 56 which forms the bottom wall of the well 54 which is located in the plane of the upper edge of the shell 42. The top of the insulator is formed with a single annular ridge 58 which cooperates with the connector as shown to assist in maintaining the connector assembled to the plug.

The spark plug shown in FIGURE 3 illustrates better than that shown in FIGURE 1 the short insulator but-t length which can be accomplished in accordance with the invention. The length of the insulator portion above the shell 42 is approximately half that which would be required in a conventional spark plug in order to attain the same flashover distance.

The protective boot 60 of the FIGURE 34 embodiment is similar to that of the FIGURE 1-2 embodiment except that it is L-shaped rather than straight and, instead of using a split metal tube as the conductor member, it incorporates a spiral spring 62, the upper end of which terminates in a straight wire 64 which projects into the conductive core of the cable 66. The lower end of the spiral spring surrounds the spark plug terminal 52 in tight spring pressed mating engagement therewith, the inner tube portion 68 of the protective boot serving to compress the spring radially inwardly against the spark plug terminal to thereby further assure good electrical contact.

The embodiment shown in FIGURES 5 and 6 is similar to that shown in FIGURES 3 and 4 except that instead of incorporating a spiral spring as the conductive member for the connector, it utilizes an L-shaped length of wire having an upper end '70 which projects into the conductive core of cable 72 and a single loop 74 at the lower end thereof which surrounds the spark plug terminal 7 6 in tight electrical conductive engagement therewith, the tight engagement being assisted by the inner tube 78 of the protective boot. Also, in the FIGURE 5-6 embodiment the spark plug terminal 76 is formed with a screw thread to thereby provide a plurality of generally annular grooves one of which mates with loop '74 to assist in preventing unauthorized Withdrawal of the connector from the plug. The plurality of grooves provided by the screw thread assures a mating engagement with the wire loop irrespective of the exact downward extent to which the loop projects over the terminal.

It is to be understood that while the invention has been described with reference to particular embodiments thereof, various changes and modifications may be used, all within the full and intended scope of the claims which follow.

I claim:

1. In combination, an ignition cable, a spark plug and a connector device forming a sealed electrical connection between said cable and said spark plug: said cable comprising an electrically conductive core and a sheath of electrical insulating material surrounding said core; said spark plug comprising an insulator having at least one external annular raised ridge at the upper end thereof and having a centerbore therethrough with an upper section of enlarged diameter forming a cylindrical well communicating with the top of said insulator and with a lower section having a centerwire hermetically sealed therewithin, the upper end of said centerwire extending into said well; and said connector device comprising a protective boot having a rubber neck portion fitting snugly around the insulating sheath on said cable, said cable terminating within said neck portion, a rubber skirt portion integral with said neck portion and shaped to fit snugly around the upper end of said spark plug insulator in sealed cooperative engagement with said annular ridge, an inner tube portion integral with said neck portion and said skirt portion and extending into the well of said insulator, said inner tube portion being of smaller diameter than said neck portion, and a metal conductor in said inner tube portion and extending into said neck portion, said conductor having an upper end secured in electrical contact with the conductive core of said ignition cable and a lower and formed as a resilient split portion in surrounding and spring pressed mating engagement with said centerwire, the connection between said centerwire and said resilient portion being encompassed by said inner tube portion and said inner tube portion of said protective boot engaging said resilient split portion to thereby assist in maintaining said resilient split portion in electrical conductive engagement with said centerwire.

2. In combination, an ignition cable, a spark plug and a connector device forming a sealed electrical connection between said cable and said spark plug: said cable comprising an electrically conductive core and a sheath of electrical insulating material surrounding said core; said spark plug comprising an insulator having at least one external annular raised ridge at the upper end thereof and having a centerbore therethrough with an upper section of enlarged diameter forming a cylindrical well communicating with the top of said insulator and with a lower section having a centerwire hermetically sealed therewithin, the upper end of said centerwire extending into said well; and said connector device comprising a protective boot having a rubber neck portion fitting snugly around the insulating sheath on said cable, said cable terminating within said neck portion, a rubber skirt portion integral with said neck portion and shaped to fit snugly around the upper end of said spark plug insulator in sealed cooperative engagement with said annular ridge, an inner tube portion integral with said neck portion and said skirt portion and extending into the well of said insulator, said inner tube portion being of smaller diameter than said neck portion, and a metal conductor in said inner tube portion and extending into said neck portion, said conductor having an upper end secured in electrical contact With the conductive core of said ignition cable and a lower end formed as a resilient annular portion in surrounding and spring pressed mating engagement with said centerwire, the connection between said centerwire and said resilient portion being encompassed by said inner tube portion and said inner tube portion of said protective boot engaging said resilient annular portion to thereby assist in maintaining said resilient annular portion in electrical conductive engagement with said centerwire.

3. An electrical connector device for forming a sealed electrical connection between a cable and a spark plug, said cable comprising an electrically conductive core and a sheath of electrical insulating material surrounding said core and said spark plug comprising an insulator having at least one external annular raised ridge at the upper end thereof and having a centerbore therethrough with an upper section of enlarged diameter forming a cylindrical well communicating with the top of said insulator and with a lower section having a centerwire hermetically sealed therewithin, the upper end of said centerwire extending into said well; said electrical connector device comprising a protective boot having a rubber neck portion shaped to fit snugly around the insulating sheath on said cable with the cable terminating within the neck portion, a rubber skirt portion integral with said neck portion and shaped to fit snugly around the upper end of 7 said spark plug insulator in sealed cooperative engagement withisaid annularridge, an inner tube portion integral with saidneck' portion and said skirt portion and shaped toex'tend into the well of said insulator, said inner tube portion being of smaller diameter thanisaid neck por-; tion, and a me'talconducto'r in'saidiniier tube portion and extending'intosaid neck portion, said conductor having an upper end adapted to besecu'red in electrical contact with the'coriductive core of said ignition cable and a lower end torr'ned as a' resilient portion shaped to abutthe upper" end of said centerwire in pressed engagement therewith, the inner-tube portion of said protective boot fitting'tight- 1y around said resilient portion to thereby assist in maintaiiiin'g' said resilient portion in electrical conductive en gageihent with the upper end of said'centerwire.

4i Ari-'- electrical connector as set forth in claim 3 and wherein the lbwer end of the metal conductor in said inner tube portion is a split tube.

5. Ari electrical connector as set forth in claim 3 and wherein the lower end of the metal conductor in said inner tube portion is a wire formed withat' least one generally annular loop sized to fit snugly around the upper end of the centerwir'e; w

6. An-electrical connector device for forming a sealed en ineer connection between a" cable and aspark pin said cable comprising an electrically conductive core anda sheath off-electrical insulating material surrounding said ears and said spark plug comprising an insulator having at least'ohe external annula-r'raised ridge a'tthe upper end thereof and having acente'rbore therethrough with an" upper section of enlarged diameter forming a cylindrical well communicating withthe top of said insulator and with a lower section having a centerv'vire hermetically sealed therewith'in, the upper end of said c'enterwire errtending into said well and having at least one generally annular groove therein; said electrical connector device comprising a protective boot having a rubber neck portion shaped to fit snugly around the insulating sheath on said cable with the cable terminating within the neck portion, a rubber skirtportion integral with said neck portion and shaped to fit snugly around the upper end of said spark plug insulator in sealed cooperative engagementwith' said annular ridge, an inner tube portion inte'gral with said neck portion and said skirt portion and shaped to extend into the well of said insulator, said inner tube portion being of smaller diameter than said neck portion, and a metal conductor in said inner tube portion and extending into said neck portion, said conductor having an upper end adapted to be secured in electrical contact with the conductive core of said ignition cable and a lower end formed as a resilient annular portion shaped to surround the upper end of said centerwire in pressed mating engagement with the groove therein, the inner tube portion of said protective boot fitting tightly around said resilient annular portion to thereby assist in maintaining said resilient annular portion in electrical conductive en gag'em'ent with the'upperend of said centei'wire.

7. A spark plug. comprising a generally tubular shaped metal shell, a ceramic insulator having an external annular shoulder portion tightly secured in" said shell and an upper portion extending above said shell, said insulator having at least one external annular ridge at the upper end thereofand having a centerbore therethrough with alower section of relatively small diameter and an upper section of enlarged diameter forming a cylindrical Well communicating with the top of the insulator, the bottom or said well being located adjacent the plane of the upper edge ofsaid shell, and a centerwire having an enlarged portion hermetically sealed in the lower section of said centerbore and an upper portion of reduced diameter extending upwardly into said well;

8. A spark plug as set forth in claim 7 wherein the upper portion of'said centerwire terminates within said well.

9. A spark plug as set forth in claim 7 wherein the upper portion of said centerwire has at least one generally annular groove therein.

10. A spark plug as set forth in claim 7 wherein the upper portion'of said eenterwire is screw threaded to thereby provide a plurality of generally annular grooves therein.

11. A spark plug as set forth in claim 7 wherein the upper end of the enlarged portion of said centerwire is provided with an outwardly extending annular flange which forms the bottom wall of said well.

References" Cited inth'e file of this patent UNITED STATES PATENTS 1,795,638 Champion Mar. 10, 1931 2,270,765 Nowosielski Jan. 20, 1942 2,633,116 Ingram Mar. 31, 1953 2,704,355 Holton r Mar. 15, 1955 trim

Claims (1)

1. IN COMBINATION, AN IGNITION CABLE, A SPARK PLUG AND A CONNECTOR DEVICE FORMING A SEALED ELECTRICAL CONNECTION BETWEEN SAID CABLE AND SAID SPARK PLUG: SAID CABLE COMPRISING AN ELECTRICALLY CONDUCTIVE CORE AND A SHEATH OF ELECTRICAL INSULATING MATERIAL SURROUNDING SAID CORE; SAID SPARK PLUG COMPRISING AN INSULATOR HAVING AT LEAST ONE EXTERNAL ANNULAR RAISED RIDGE AT THE UPPER END THEREOF AND HAVING A CENTERBORE THERETHROUGH WITH AN UPPER SECTION OF ENLARGED DIAMETER FORMING A CYLINDRICAL WELL COMMUNICATING WITH THE TOP OF SAID INSULATOR AND WITH A LOWER SECTION HAVING A CENTERWIRE HERMETICALLY SEALED THEREWITHIN, THE UPPER END OF SAID CENTERWIRE EXTENDING INTO SAID WELL; AND SAID CONNECTOR DEVICE COMPRISING A PROTECTIVE BOOT HAVING A RUBBER NECK PORTION FITTING SNUGLY AROUND THE INSULATING SHEATH ON SAID CABLE, SAID CABLE TERMINATING WITHIN SAID NECK PORTION, A RUBBER SKIRT PORTION INTEGRAL WITH SAID NECK PORTION AND SHAPED TO FIT SNUGLY AROUND THE UPPER END OF SAID SPARK PLUG INSULATOR IN SEALED COOPERATIVE ENGAGEMENT WITH SAID ANNULAR RIDGE, AN INNER TUBE PORTION INTEGRAL WITH SAID NECK PORTION AND SAID SKIRT PORTION AND EXTENDING INTO THE WELL OF SAID INSULATOR, SAID INNER TUBE PORTION BEING OF SMALLER DIAMETER THAN SAID NECK PORTION, AND A METAL CONDUCTOR IN SAID INNER TUBE PORTION AND EXTENDING INTO SAID NECK PORTION, SAID CONDUCTOR HAVING AN UPPER END SECURED IN ELECTRICAL CONTACT WITH THE CONDUCTIVE CORE OF SAID IGNITION CABLE AND A LOWER END FORMED AS A RESILIENT SPLIT PORTION IN SURROUNDING AND SPRING PRESSED MATING ENGAGEMENT WITH SAID CENTERWIRE, THE CONNECTION BETWEEN SAID CENTERWIRE AND SAID RESILIENT PORTION BEING ENCOMPASSED BY SAID INNER TUBE PORTION AND SAID INNER TUBE PORTION OF SAID PROTECTIVE BOOT ENGAGING SAID RESILIENT SPLIT PORTION TO THEREBY ASSIST IN MAINTAINING SAID RESILIENT SPLIT PORTION IN ELECTRICAL CONDUCTIVE ENGAGEMENT WITH SAID CENTERWIRE.

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