US 3798589 A
An electrical lead suitable for use in ignition systems for internal combustion engines including an electrical conductor fully surrounded by insulation with an exposed conductor portion extending from the insulation at one end of the lead; and an electrically conductive termination cap fastened at one end including a closed central portion oriented transversely of the conductor in pressed electrically conductive contact with the exposed conductor portion.
Description (OCR text may contain errors)
United States Patent [1 1 Deardurfi Mar. 19, 1974 ELECTRICAL LEAD  Inventor: Lawrence R. Deardurff, Newark,
 Assignee: Owens-Corning Fiberglass Corporation, Toledo, Ohio  Filed: Sept. 27, 1972  App]. No.: 292,577
 US. Cl 339/223 S, 339/100, 339/256 C, 174/74 R, 338/66  Int. Cl ..l-l01r 15/12  Field of Search 339/223 R, 223 S, 256 C, 339/275 R, 275 T, 276 T, 100, 250; 338/66, 214, 266, 272, 322, 332; 174/74 R; 117/229 [5 6] References Cited UNITED STATES PATENTS 2.969,520 l/l96l Waldo 339/105 3,247,020 4/1966 Shulver et al 117/226 l,()56,65l 3/l9l3 Fuile 339/250 X 2,426,845 9/1947 Rogoff 339/223 S 2,965,871 l2/l960 Seyfarth r 339/l00 2,035,947 3/l936 Davis 339/100 Primary Examiner-Joseph H. McGlynn Assistant Examiner Albert A. Hafe1 Attorney, Ag'h: or F irm-Staelin & Overman; Ronald C. Hudgens 57 ABSTRACT An electrical lead suitable for use in ignition systems for internal combustion engines including an electrical conductor fully surrounded by insulation with an exposed conductor portion extending from the insulation 8 Claims, 11 Drawing Figures PATENTED MR 1 9 I974 .....H wwwmmwmmmwm II! A ELECTRICAL LEAD BACKGROUND OF THE INVENTION In recent years ignition cables used with internal combustion engines in vehicles have used electrical conductors of non-conducting elongated support eIe ments like bundles of glass filaments coated with electrically conductive material such as graphite. Many electrical terminations have been tried with these cables.
But prior termination arrangements have had drawbacks. For example, staple type terminations tend to damage a multifilament conductor. Without great care and proper application this damage tends to develop a high resistance electrical short in a conductor that can be especially detrimental to conductors using material like glass filaments with a conductive coating on them. High resistance shorts develop heat that can melt glass filaments; this heat can cause small insulating glass balls or spheres to be formed that augment the short in the initially damaged region of the conductor.
A similar result can occur when a termination staple makes nonuniform contact with a multifilament conductor.
High resistance shorts are difficult to determine until the ignition cable has been used for some time, for example on automobiles after purchase. Hence, the problem can cause considerable difficulty.
Another type of ignition cable termination, known as strip and fold, does not cause high resistance shorts. But this type of termination requires a considerable length of exposed conductor at each end of an ignition cable; in practice /1 of an inch or more of exposed conductor used at each end of a cable. The exposed conductor is folded back along the cable. A conductive termination cap is clamped onto the cable to effect electrical contact with the conductor along the length of the cable.
'A major drawback to strip and fold type of terminations is economic. Literally millions of ignition cables are produced daily. And the length of exposed conductor required to effect a satisfactory electrical connection is considerable. Accordingly, a satisfactory termination using less exposed conductor would effect considerable savings in material. Furthermore, in production strip and fold type terminations require slow and elaborate production methods to insure electrical contact between the termination cap and the exposed fold-back portion of the conductor.
Hence, there is a commercial need for another type of electrical lead suitable for use in ignition systems.
SUMMARY OF THE INVENTION An object of the invention is an improved electrical lead, especially one suitable for use in ignition systems.
Another object of the invention is an improved electrical lead using a relatively tightly packed bundle of glass filaments coated with electrically conductive material.
Yet another object of the invention is a more economically produced improved electrical lead.
The above and other objects are attained by an electrical lead comprising an elongated body capable of conducting electricity with the body fully surrounded by electrical insulation and having an exposed portion extending from one end of the lead; fastened at the one end is an electrically conductive termination cap that includes a closed end portion in pressed electrical contact with the exposed portion of the body.
The above and other objects and advantages will become more apparent as the invention is more fully described hereinafter with reference made to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view of a automotive distributor using electrical leads according to the invention.
FIG. 2 is an enlarged side elevation viewof a portion of the distributor taken along the lines 2-2 shown in FIG. 1. This section view shows an embodiment of an end of an electrical lead according to the invention in place in the distributor shown in FIG. 1.
FIG. 3 is an exploded view in perspective of the electrical lead shown in FIGS. 1 and 2.
FIG. 4 is a side elevation view of the end region of the insulated conductor shown in FIGS. 1-3. FIG. 4 shows an exposed portion of the conductor projecting a short distance a from the end of the insulation.
FIG. 5 is a side elevation view of the termination cap used with the lead shown in FIGS. 1-3.
FIG. 6 is a side elevation view, partially in section, showing another lead according to the invention.
FIG. 7 is a side elevation view, in section, of the end region of another termination cap according to the invention.
FIG. 8 is a side elevation view in section of the end region of yet another termination cap according to the invention.
FIG. 9 is a side elevation view in section of the end region of still another termination cap according to the invention.
FIG. 10 is a view in perspective of another embodiment of an electrical lead according to the invention.
FIG. 11 is a side elevation view, partially in section, of an electrical lead like the lead shown in FIGS. 1-3 but modified to connect with a spark plug. The lead is shown on a spark plug but without the usual flexible spark plug cover.
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 show an embodiment of the invention used with a conventional distributor 10 in an automotive ignition system. The ignition leads 12 connect the distributor 10 with spark plugs; the lead 14 connects the distributor 10 with a high tension or voltage source such as an ignition coil. In the embodiment shown the leads 12 and 14 use the same termination arrangements with the distributor 10.
As can be more clearly seen from the cross sectional view of FIG. 2 each of the leads 12 and 14 extends into the interior of a tubular sleeve 16 that is integral with the distributor cap 18. A cup-shaped member or insert 20 of conducting metal defines the lower portion of the inner wall of each of the sleeves 16. Each of the members 20 provides an extension 22 that forms an internal distributor contact for engagement with the rotor of the distributor 10. The leads 12 fit in snug-fit relation with the insert 20 within the tubular sleeve 16 to obtain good electrical contact.
Referring more particularly to FIGS. 2 through 4, it can be seen that the lead 12 includes an electrical cable comprising a conductor 30 surrounded along its length by a sheath or coating 32 of insulating material. An electrically conductive cap 34 terminates the lead 12.
As shown the conductor 30 is an elongated bundle of relatively closely or tightly packed together continuous glass filaments 36 having a thin electrically conducting film or coating on them formed of small conductive particles such as graphite. U.S. Pat. No. 3,247,020 discloses a method for adhering electrically conducting materials to glass filaments to form an electrically conductive film.
Besides graphite particles, a number of electrically conductive particles can be used to coat the glass filaments. For example, it is possible to use dispersions or colloidal suspensions of carbon black to form a coating of carbon black particles on the glass filaments. Further, it is possible to use metals and organometallic compositions that decompose under heat to form a metallic electrically conductive coating.
Other non-conducting filaments with an electrically conductive film on them can be used. For example, it is possible to use cotton, rayon, polyester, and various blends or mixtures thereof. Also, it is possible to use filaments or wires of conductive material such as silver, copper, and the like. Moreover, the invention embraces the use of monofilament conductors besides a grouping of elongated conductive elements.
The electrical insulating sheath 32 is a simple conventional single layer of elastomeric electrical insulating material. However, any suitable electrical insulating constructions can be used.
An exposed portion 38 of the conductive bundle 30 projects axially from the insulation 32 at one end of the lead 12. In practice, this portion 38 extends only a short distance beyond the end of the insulation; this distance is indicated as a in FIG. 4. Normally the distance a is not greater than the thickness of the insulating sheath 32 surrounding the conductor 30. In practice, an exposed portion 38 having a length a of from Vs to A of an inch has given good results in ignition systems.
As shown the termination cap 34 is an electrically conductive metal member fastened at the end of the lead 12. The cap 34 includes a closed end portion 40 oriented for extension generally transversely of the cable and arms 42 for extension along the length of the cable (conductor 30). The arms 42 are fashioned with pointed push points 44; the points 44 are embedded in the insulation 32 to fasten the cap 34 in place.
The cap 34 has a central dimpled portion 50 that provides a closed central end portion with a convex surface 52 pressed against the exposed portion 38 of the conductor 30 in electrical conducting communications or contact. And as can be more clearly seen in FIG. 2, the convex surface 52 is pressed or intruded lengthwise into the end of the exposed bundle of glass filaments 36 (portion 38) to establish electrical contact. The filaments 36 are dispersed over the surface 52. And this spread apart relation of the filaments 36 provides a larger electrical contact area between the cap 34 (surface 52) and the coated filaments 36. The surface 52 presses more firmly into the central portion of the bundle 30 located more closely adjacent to the end of the insulation 32.
The convex surface 52 is shown as a spherical surface that defines a circle at its base region; the circle is shown in FIG. 4 as having a diameter d. An annular flange portion 54 is integral with and surrounds the convex surface 52 at its base region. The surface 52 projects a height h above the annular surface 54. Good electrical conduction has resulted with h" smaller than d. Further, good electrical conduction has been obtained with d considerably larger than the diameter of the tightly packed bundle or conductor 30, e.g. two times larger.
FIG. 6 shows another lead, denoted by the reference numeral 12', according to the principles of the invention. The lead 12 uses an electrical termination cap 34 on the insulated conductor shown in FIGS. 1-4. The cap 34 includes a closed end portion 40 and a ferrule 56. The ferrule 56 is crimped onto the lead 12'. The end portion 40' provides an interior central convex surface 52' like the convex surface 52 of the cap 34. The cap 34 (convex surface 52) makes electrical contact with the conductor 30' as explained with respect to the lead 12.
FIGS. 7 through 9 show other termination caps according to the invention. FIG. 7 shows a portion of a cap 60 with a curved end portion 62 and a ferrule 64. The end portion 62 provides a concave conductor contacting surface 66. FIG. 8 shows a cap with an end portion 72 and a ferrule 74. The end portion 72 provides a convex surface 76 that is larger in size than the convex surfaces 52 and 54'. As shown the surface 76 comprises the entire internal end surface of the cap 70. FIG. 9 shows a cap 80 with an end portion 82 and a ferrule 84. The end portion 82 provides a planar conductor contacting surface 86. Like the termination cap 34 these additional termination caps are used with insulated conductors having an exposed conductor portion extending from the insulation at one end thereof. These caps are fastened on the insulated conductor with their closed ends in pressed electrical contact with the exposed conductor portion.
FIG. 10 shows a modified lead 92 according to the invention using the insulated conductor shown in FIGS. l-4. However, in FIG. 10 the embodiment uses an electrically conductive termination cap 94 having a striplike closed end portion 96 and arms 98. The end portion 94 provides a planar conductor contacting surface. And in fastened position at the end of the lead 92, this planar surface is in pressed electrical contact with the coated filaments 36 in the exposed portion 38 of the conductor 30. The arms 98 have pins like the pins 44 fashioned in the arms 42 to fasten the cap 34 to the insulation 32.
FIG. 11 shows an electrical lead 12" according to the invention snapped in electrical contact onto a spark plug 100. The lead 12" uses the insulated conductor shown in FIGS. I-4 and a termination cap 34" fastened at the end of the lead 12". The cap 34" is similar to the cap 34, but is modified to include an extension 102 that effects securement of the lead 12" on the spark plug 100. For clarity the lead is shown without the normal flexible protective cover over the end of the lead and the upper portion of the spark plug.
The electrical lead of the invention has been shown as a lead in an ignition system. But the lead has broader use. Hence, it is apparent that modifications and different arrangements can be made within the scope of the invention other than disclosed herein. The disclosure is merely illustrative, the invention comprehending all variations thereof.
1. An electrical lead comprising:
an elongated bundle of filaments capable of conducting electricity;
electrical insulation fully surrounding the bundle, an exposed portion of the bundle extending from the insulation at one end of the lead; and 5 an electrically conductive termination cap including a portion defining a convex filament contacting surface and means fastening the cap to the lead with the convex filament contacting surface in pressed electrically conductive contact with the exposed portion of the bundle beyond the terminating end surface of the insulation, the filament contacting surface pressing the convex filaments against themselves and directly against the terminating end surface of the insulation.
2. The lead of claim 1 in which the convex filament contacting surface is curved in all directions.
its length, an exposed end of the bundle projecting beyond the insulation at one end of the lead; and an electrically conductive metal cap fastened at the one end including a convex surface pressed generally lengthwise into the end of the exposed bundle portion with at least some of the filaments of the bundle spread in electrically conductive contact with the convex surface, and pressed between said convex surface and said end of the insulation.
4. The electrical lead of claim 3 in which the coating includes electrically conductive particles.
5. The electrical lead of claim 4 in which the electrically conductive particles are graphite.
6. The electrical lead of claim 3 in which the base of the convex surface is larger than the cross sectional area of the closely packed filaments.
7. The electrical lead of claim 6 in which the convex surface is hemispherically shaped.
8. The electrical lead of claim 7 in which the exposed end of the bundle projects beyond the insulation a distance no greater than the thickness of such insulation.