US3673313A - Electrical junction for high-current conductors and connector and method suitable for making same - Google Patents

Abstract

In a junction of the type in which two high-current conductors are bridged by an external sleeve crimped to the exterior of both conductors, additional axially-overlapping connecting elements are employed to provide connection between interior portions of said conductors, the axially-overlapping portions of said connecting elements being held in stable intimate contact with each other by crimping applied to the exterior of said sleeve member. A preferred connector for use in making such a junction comprises a conductive sleeve for receiving the high-current conductors at its opposite ends and a pair of conductive prongs supported axially therein by a conductive support secured conductively to the interior of said sleeve, said prongs being oppositely directed to fit within corresponding recesses in said high-current conductors, whereby the prongs provide stable electrical connection to said high-current conductors after the exterior sleeve has been crimped.

Description

United States Patent Pickett et a1.

[54] ELECTRICAL JUNCTION FOR HIGH- CURRENT CONDUCTORS AND CONNECTOR AND METHOD SUITABLE FOR MAKING SAME [72] Inventors: Wiley J. Pickett, Moorestown, N.J.;

Bynum E. Smith, Richmond, Va.

[73] Assignee: Utility Industries Inc., Westmont, N..l.; by

said Bynum E. Smith 22 Filed: April 23, 1970 21 Appl. No.: 31,226

2,882,333 4/1959 Berteaux "174/90 3,046,514 7/1962 Brackett ..339/100 3,347,977 10/1967 Hus et a1. ..339/100 X June 27, 1972 3,479,445 11/1969 Jerome ..174/90 X 3,517,112 6/1970 Wahl ..l74/84 C X FOREIGN PATENTS OR APPLICATIONS 584,912 1/1947 Great Britain ..l74/84 C Primary ExaminerDarrell L. Clay Attorney-Howson and Howson [57] ABSTRACT In ajunction of the type in which two high-current conductors are bridged by an external sleeve crimped to the exterior of both conductors, additional axially-overlapping connecting elements are employed to provide connection between interior portions of said conductors, the axially-overlapping portions of said connecting elements being held in stable intimate contact with each other by crimping applied to the exterior of said sleeve member. A preferred connector for use in making such a junction comprises a conductive sleeve for receiving the high-current conductors at its opposite ends and a pair of conductive prongs supported axially therein by a conductive support secured conductively to the interior of said sleeve, said prongs being oppositely directed to fit within corresponding recesses in said high-current conductors, whereby the prongs provide stable electrical connection to said high-current conductors after the exterior sleeve has been crimped.

2 Claims, 20 Drawing Figures Patented June 27, 1972 5 Sheets-Sheet 1 TH n TE NK ECS V m M u mm L B W ATTYS- Patented June 27, 1972 3,673,313

5 Shoots-Shoot z INVENTOR s; WILEY J. PICKE'TT BYNUM E.SMITH BY WW Patented June 27, 1972 5 Sheets-Sheet 5 fxx FIGIB.

ATTYS.

ELECTRICAL JUNCTION FOR HIGH-CURRENT CONDUCT ORS AND CONNECTOR AND METHOD SUITABLE FOR MAKING SANIE BACKGROUND OF THE INVENTION This invention relates to electrical junctions between highcurrent conductors, and to connectors and methods for fabricating same.

In the field of conductors for the transmission of high-currents for power distribution purposes, it is often necessary to provide suitable electrical and mechanical connection between two or more high-current conductors, for example between such conductors of the same or different sizes or between such a conductor and a terminal, typically comprising a lug of generally rectangular cross-section. Furthermore, particularly in field operations such as the outdoor laying or repairing of underground cables, it becomes important to be able to provide such junctions quickly, without elaborate equipment, without the use of equipment which requires specialized skills or critical or dangerous operations, or which is unsuited to outdoor use. In addition, it is generally desirable that such junctions be as short as possible, not only from considerations of expense of material and space required, but also because the conductor normally must be electrically insulated and the junction must therefore be thoroughly covered with insulating material such as electrical tape or other suitable insulating material; the time and materials required for the necessary thorough taping or other insulating procedure becomes greater the greater the length of the junction region.

it is of course also desirable that the junction have good mechanical properties, particularly with respect to the pullout force required to pull the two high-current conductors apart or to interfere with their mechanical or electrical stability.

An important operational characteristic of such junctions is the extent to which they become overheated by the passage of high currents through them. With conductors of relatively small size, junctions operated at rated, or even twice rated, current values do not generally produce a degree of overheating which presents a serious problem. However, when the larger conductors needed for high-current use, typically of sizes from about 350 MCM upwards, are operated at high currents, such as twice rated current or at even higher overload currents which sometimes occur unavoidably from time to time, overheating of junctions between conductors presents a serious problem; not only is the resultant temperature rise undesirable in itself because of its effect on surrounding materials and because of the voltage drop and power dissipation which occurs, but also, importantly, because of the effects of such overheating on the junction itself, which typically may degenerate in its characteristics and ultimately fail completely due to overheating. This tendency toward overheating generally becomes particularly disadvantageous for conductors sizes of 350 MCM and above, and the usual covering of the junction with insulating tape tends further to accentuate these harmful effects of overheating.

Also importantly, in certain conductor materials such as aluminum, repeated cycling of the temperature of the junction due, for example, to varying load-current demands causes a relaxation effect in the conductor material which tends to produce progressively looser components in the junction, and hence a hotter junction; under extreme conditions, complete failure of the junction may then occur.

It is possible to make a crimped-sleeve type of junction between high-current conductors using a relatively long sleeve within which the ends of the conductor are inserted, after which a power tool applies crimps to the exterior of the sleeve to crimp it to both conductors; this process often involves careful wire brushing or sanding of each individual strand of a stranded conductor, and in many cases involves also the application of special anti-oxide inhibitors, in order to approach satisfactory results. The latter preparation procedures typically involve special training of personnel, close supervision of the operation, and the ever-present hazard of human failure; in addition, to reduce the undesired and even debilitating effects of overheating of the junction by large currents, the sleeve and junction must be made quite long. This increases the installation costs not only because more material is used but also because more hours are required to perform the greater amount of taping or other insulating procedure required for a longer junction.

It is also known to join high-current conductors by buttwelding of their adjacent ends. While such welding tends to permit use of shorter junctions for the same maximum current, welding often involves so many problems and safety hazards that such procedures are usually considered very undesirable, particularly in field service or installation applications. For example, in a typical power-distribution system so many primary and secondary splices of largediameter conductors need to be made that the wide-spread use of welding equipment entails not only costly investment in the equipment but also troublesome problems with scheduling the use of the equipment; additionally, skilled welders are generally in short supply. importantly also, the use of welding equipment (particularly in the presence of moisture due, for example, to rain, wet working areas, and wet conductors, etc.) creates substantial problems of fire and explosion hazard.

Accordingly it is an object of the invention to provide new and useful junctions between high-current conductors, particularly conductors exceeding a size of about 350 MCM, and to provide methods and connector means for fabricating such junctions.

It is also an object to provide such methods, connector means and junctions in which the temperature rise of the junction above the temperature of the conductor remote from the junction is reduced for a given length of junction.

Another object is to provide such method, connecting means and junction which can be made or used easily, safely and without elaborate special equipment or training procedures for operating personnel.

Another object is to provide such a junction, connector means and method which are applicable to the connection of conductors of a variety of materials andintemal forms, including but not limited to conductors of copper, aluminum or sodium of a large range of diameters, and cables such as class A, B, and C stranded, compact stranded, solid, segmented, ACSR, etc.

Another object is to provide such a junction, connector means and method which are applicable to the connection of conductors of difierent exterior sizes and fonns, for example to provide connection between a generally cylindrical highcurrent conductor and a high-current terminal lug of generally rectangular cross-section.

A further object is to provide such a junction, connector means and method resulting in a connection in which high local concentrations of current in difierent parts of the crosssection of the junction are reduced.

It is also an object to provide a junction, and a method and connector for making same, by means of which the normally degenerative or debilitating efi'ects of cycling of the temperature of the junction are mitigated.

SUMMARY OF THE INVENTION In accordance with the invention, these and other objects are achieved by means of an electrical junction of high-current conductors comprising an outer sleeve member surrounding axially-overlapping connecting elements disposed so as to interconnect interior portions of the high-current conductors, said outer sleeve member having one or more crimps thereon to provide stable intimate electrical connection between the overlapping regions of said connecting elements. In the preferred form of the method of the invention, the overlapping portions of the electrical connecting elements are placed in closely-confronting relation to each other within said sleeve member, and crimping is thereaiter applied to the exterior of the sleeve member with sufficient force to provide the desired stable intimate electrical connection between the axially-overlapping surfaces of the electrical connecting elements. In some forms of the invention the electrical connecting elements are formed by modifying end regions of the two high-current conductors, for example by forming an end of one conductor into a prong and forming an end of the other conductor into a socket for receiving said prong, or by forming other complimentary end structures on the two high-current conductors which can be fitted together to provide the desired axially-overlapping configuration of connecting elements. In other forms of the invention a separate electrical connecting element is placed between the two high-current conductors, for example in the form of an axial rod member extending into a corresponding recess in one or both of the high-current conductors to be joined. In some instances, such an axial rod member may be a permanent integral part of, and

in continuous metallic connection with, the outer sleeve member. The junction connector and method of the invention may be applied also to more complex interconnections of high-current conductors, such as Y connections, T connections or terminal lug connections, for example.

In accordance with one aspect of the invention, a new and useful form of connector for high-current conductors comprises an outer sleeve portion of conductive material having at least one open end adapted to receive and fit closely about one end of a high-current conductor, a conductive prong portion mounted within said sleeve portion, and a conductive prong-support portion holding said prong portion fixed with respect to said sleeve portion and in electrical connection therewith, said prong portion being configured to be inserted into a corresponding recess in said high-current conductor. When two high-current conductors are to be spliced together, this connector preferably is open at both ends to receive an end of each of the conductors, and said prong portion extends in both axial directions to mate with axial recesses in each of said high-current conductors.

In a junction constructed in accordance with the invention, no welding or other difficult, complex or hazardous procedure is required. Furthermore, compared with prior crimped-sleeve junctions and methods, the provision, and crimping together, of axially-overlapping connecting element extending between interior portions of the two high-current conductors results in less diversion of the current flowing through the junction from its normal direction parallel to the axis of the conductors, and thereby reduces the tendency toward production of high nonuniform current densities in or near the junction and the resultant hot-spots often found in prior-art constructions.

BRIEF DESCRIPTION OF FIGURES These and other objects and features of the invention will be more readily understood from a consideration of the following detailed description, taken in connection with the accompanying drawings, in which:

FIG. 1 is an elevational section, partly in full, showing one form of completed junction constructed in accordance with the invention in one of its aspects;

FIGS. 2 and 3 are cross-sectional views taken along lines 22 and 3-3 respectively of FIG. 1;

FIG. 4 is an elevational sectional view, partly in full illustrating one preferred method of construction of the junction of FIG. 1;

FIG. 5 is a view taken along lines 5-5 of FIG. 4;

FIG. 6 is an elevational sectional view, partly in full, showing another form of electrical junction in accordance with the invention;

FIG. 7 is a view taken along lines 7-7 of FIG. 6;

FIG. 8 is an elevational sectional view of another form of junction constructed in accordance with the invention;

FIG. 9 is a sectional view taken along lines 99 of FIG. 8;

FIG. 10 is an elevational view, partly in section, of a connector constructed in accordance with the invention in one of its aspects and useful in making the junction of FIG. 8;

FIG. 11 is an elevational sectional view, partly in full, of a further embodiment of a junction in accordance with the invention;

FIG. 12 is a view taken along lines l2--l2 of FIG. 11;

FIG. 13 is an elevational sectional view showing a terminal junction constructed in accordance with the invention in one of its forms;

FIG. 14 is a sectional view taken along lines 14-14 of FIG. 14;

FIG. 15 is an elevational sectional view of a Y connection employing electrical junctions constructed in accordance with the invention;

FIG. 16 is an elevational sectional view of a T connection employing electrical junctions constructed in accordance with the invention;

FIG. 17 is an elevational view, partly in section, showing a terminal connector suitable for producing the terminal junction illustrated in FIG. 13;

FIGS. 18 and 19 are elevation views, partly in section, illustrating Y and T connectors suitable for use in providing the Y and T interconnections shown in FIGS. 15 and 16 hereof, and constructed in accordance with the invention; and

FIG. 20 is a graphical representation to which reference will be made in explaining certain advantages of the invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS Referring now by way of example only to the particular embodiment of the invention illustrated in FIGS. 1 thru 5, in which corresponding numerals designate corresponding parts, there are shown two high-current single- conductor cables 10 and and 12 electrically and mechanically joined to each other by the junction 14. In this example the cables 10 and 12 are provided with outer insulation layers 16 and 18 respectively, the latter layers having been removed for a distance extending back from the end of each cable to the sloped shoulders 22 and 24 formed on the respective insulation layers. End portions of the high- current conductors 26 and 28 of the two cables are thereby freed of their insulating layers, and in this example the extreme adjacent ends of the two high-current conductors are modified to form axially-overlapping electricalconductive elements interconnecting interior portions of the two high-current conductors.

More particularly, metallic material has been removed from the outer periphery of the end portion of high-current conductor 28 to form an axially-extending cylindrical prong 32 thereon, which fits within a corresponding axial recess or bore 34 extending inward from the end of conductor 26. Generallycylindn'cal axially-overlapping surface regions are thereby provided at 36 between the prong 32 and the interior of the hollow cylinder 37 formed by bore 34. A generally-cylindrical metal outer sleeve member 38 surrounds the axially-overlapping surface regions of the two electrically conductive elements 32 and 37, and extends on opposite sides thereof so as to overlap adjacent portions of each high-current conductor. Five adjacent annular crimps 40, 42, 44, 46, and 48, formed in the outer sleeve member 38 in a manner to be described hereinafter produce a stable intimate mechanical and electrical crimped connection between the sleeve member 38 and the exterior surfaces of the two conductors 26 and 28; an intimate, stable mechanical and electrical crimped connection is also thereby formed between the exterior surface of the prong 32 and the adjacent overlapping interior surface of the cylinder 37. A generally-cylindrical layer of wound electrically-insulating tape 50 extends around the junction and between the insulation layers 16 and 18 on cables 10 and 12 respectively. In this example the fulldiameter portions of the cable conductors as at 26 and 28 may be considered as the high-current conductors, the exteriors of which are joined by the sleeve member 38, and interior portions of which are joined by the electrically-conducting elements comprising the prong 32 and the cylinder 37 formed integrally with, and at the ends of, the two high-current conductors.

As shown in FIG. 2, it is assumed in this specific example that the high- current conductors 26 and 28 are both of the compact stranded type, composed of a plurality of compacted strands such as 52 positioned closely adjacent each other within a generally cylindrical outer periphery and extending helically along the axis of the cable, except for the axially-central strand which in this case is straight. As shown in FIG. 3, the outer sleeve member 38 is in intimate, stable, crimped mechanical and electrical contact with the outer surface of high-current conductor 26 and the outer surface of the highcurrent conductor 28. In addition, an intimate, stable, electrical and mechanical crimped connection has been formed between the overlapping portions of connecting elements 32 and 37, so much so that, as represented in FIG. 3, there is no clear line of demarcation between the outer periphery of the prong 32 and the inner surface of the cylinder 37.

FIGS. 4 and 5 make clear certain of the steps employed in one procedure for fabricating the junction of FIG 1 in accordance with the invention. In this example it is understood that an appropriate cutting tool has been applied to the periphery of the end of high-current conductor 28 in its original unmodified form to cut away the outer two rows of strands for a distance extending back to the shoulder 54 from the end of the conductor, which may be readily accomplished by merely applying to the butt end of conductor 28 any convenient, preferably portable, cutter of known type suitable for this purpose. The conductor 26 in its original unmodified form may be inserted into any convenient, preferably portable, type of axial boring jig, and the center of the conductor bored out to remove the center strand and the first two inner layers of strands of the conductor, and to produce the modified end structure shown in FIG. 2. The depth of the resulting bore 34 is preferably about the same as the length of the prong 32. The bored-out end of conductor 26 is then slid into the sleeve member 38 along the direction shown in FIG. 4, until it reaches the position shown in FIG. I, and the conductor 28 is slid into the opposite end of the sleeve member along the direction shown in FIG. 4 until prong 32 enters bore 34 and is positioned also as shown in FIG. 1. A power crimping tool 56 is then used to apply appropriate crimps to the exterior of sleeve member 38. This crimping tool may be of no known hydraulic form, utilizing a pair of opposed substantially hernispherical dies 58 and 60 of an appropriate size and shape to provide the desired crimping. The crimping tool is aligned in the axial position along the length of the sleeve member at which a crimp is desired and then manually actuated, automatically to provide the desired crimp. In the present case, the preferred order of providing the five crimps shown in FIG. 1, is the same as the order of the numerals designating them in FIG. 1, that is, the first crimp 40 is preferably provided directly redially outwardly from the overlapping portions of the two conductive elements 32 and 37, initially to fix them mechanically with respect to each other; the next crimp 42 is preferably made directly outwardly from the full-diameter portion of high-current conductor 28 adjacent shoulder 54; and the remaining crimps 44, 46, and 48 are preferably made alternately on opposite sides of center, progressively further along the sleeve member, as shown in FIG. 1.

In one typical case, each of the two cables may be 1,000 MCM compact stranded aluminum about 1.06 inches in diameter, prong 32 may have an outer diameter of about ninesixteenths inch and each crimp may be about one-half inch in width. The outer sleeve member 38 may be of aluminum with a diameter of about 1 a inches, a wall thickness of about onefourth inch, and an overall length of about 3 inches, in which case the crimps may be typically formed by a standard 5,000-lb. hydraulic power crimper such as has been used for making conventional crimped junctions.

With this construction, it has been found that the elevation in temperature of the junction with respect to the temperature of the high- current conductors 26 and 28 remote from the junction, when high current of the order of one or two thousand amperes is passed through it, is substantially less than for prior-art crimped sleeve junctions of the same length, and even than for substantially longer conventional junctions. This advantage of the junction of the invention has been found to exist even though the prior-art crimped sleeve may have a cross-sectional area equal to that of the high-current conductors themselves.

Without wishing to be limited by the details of any specific theory, we believe that this improvement is the result of the following characteristics. In crimped junctions of the prior art constructed like the junction shown in FIG. 1 but without the prong and bore arrangement of the invention, and in which the two flat ends of the conductors are merely placed adjacent each other or adjacent opposite sides of an intervening plug within the sleeve member prior to crimping, there is no provision for producing satisfactory electrical contact between the adjacent butt ends of the conductors, and, in fact, during crimping they will tend to move further apart than they were previously. Accordingly there is then a gap between the end portions of the high-current conductors, as a result of which substantially all of the current flowing between the high-current conductors must turn and flow outwardly from one conductor into the sleeve member, along the sleeve member, and thence back again into the other conductor. This deviation of the current from a flow parallel to the axis of the conductors results in a highly non-uniform distribution of current density across the conductors near the gap between them, as well as in the portions of the sleeve member making contact thereto, whereby the current is concentrated in the outer portions of the high-current conductors near the air gap. Such nonuniforrnity results in excessive temperature rise in the junction, with respect to the temperature of the conductors remote from the junction. When the junction and the sleeve in the prior-art structure are made sufficiently long, the sleeve itself may exert a heat-sink effect, reducing the maximum temperature reached by any part of the junction, and may also tend to produce more uniform current densities. However, when one attempts to make the sleeve member reasonably short, particularly for conductors of larger diameter, the dispersion of the current from its axial direction becomes greater and causes the above-mentioned undesired excessive heating of the junction.

In the junction of the invention, on the other hand, excellent electrical connection is provided not only between the exterior of the two high-current conductors but also between interior or more central portions of the high-current conductors due to use of the electrically-conductive elements with their axially-overlapping contact surfaces. A low-resistance path is provided by these electrically-conductive elements along a direction more nearly parallel to the conductor axis than it is in the case with the prior-art crimped sleeve junction, with a resultant reduction in the degree of non-uniformity of current distribution across the cross-section of the junction, and in the extent of overheating. Typical improvements in these temperature characteristics obtained with the junction of the invention will be discussed in detail hereinafter with reference to the graphs of FIG. 20.

FIG. 6 shows an embodiment of the invention in which parts corresponding to those in FIGS. l-5 are designated by corresponding numerals. The cables 10 and 12 and the outer sleeve member 38 may be as in FIG. 1. However, in this example not only is the axial bore 34 provided in the end of highcurrent conductor 26, but an identical axial bore 64 is provided in the corresponding end of high-current conductor 28, and an axial cylindrical rod 66 is positioned to extend at one end into bore 34 and at its opposite end into bore 64. The axially-bored ends of the two high- current conductors 26 and 28 and the rod 66 thereby provide axially-overlapping electrically-conductive elements interconnecting interior portions of high- current conductors 26 and 28, and the five crimps 40 thru 48 applied to the exterior of sleeve member 38 again provide stable, intimate mechanical and electrical contact between the interior surface of the sleeve member 38 and the outer surfaces of the bored portions of conductors 26 and 28,

while at the same time providing similar intimate stable electrical and mechanical connection between the interiors of the two bores 34 and 64 and the exterior surfaces of the rod 66. Again, in this construction it is not necessary for electrical current to pass in its entirety through the outer sleeve member 38, and instead the current may pass, for example, from highcurrent conductor 28 into the adjacent end of rod 66, through rod 66 to the bored-out end of high-current conductor 26, and thence to the main portion of high-current conductor 26, some current also of course flowing through the sleeve member 38. Again, the divergence or dispersion of the current from its paths parallel to the conductor axis is less than in prior-art arrangements in which only the external sleeve member is utilized. The assembly procedure is merely to bore the ends of the two high-current conductors, slip the sleeve 38 over one high-current conductor, insert the rod 66 in one bore, slip the other bore over the other end of rod 66, position sleeve 38 as shown, and apply the five crimps with the power crimping tool.

FIG. 8 illustrates one preferred embodiment having certain advantages over some of the other embodiments with respect to ease of assembly. Again, parts corresponding to those of the previously-discussed embodiments are indicated by corresponding numerals. In this embodiment, the outer sleeve member 38A supports the rod 66 coaxially and is electrically connected thereto by means of the internal metallic transverse rod support 68, which is disposed at right angles to the axis of sleeve member 38A with the rod 66 extending axially through the center of it. This connector is shown in FIG. 10 as it appears before the high-current conductors have been inserted and the crimping operation formed. To use this connector, appropriate axial bores are again formed in the ends of the two high- current conductors 26 and 28 to receive the opposite ends of the rod 66, and the ends of the two high-current conductors are slipped into sleeve member 38 from opposite sides until they abut opposite surfaces of the support 68; power crimping may then be applied, in this case in the form of the four crimps 70, 72, 74, and 76, preferably applied in that order. In this case crimping along the center of the connector is preferably not applied, since the support 68 may tend to oppose such crimping; however, the four crimps employed are positioned radially directly outward from the axially-overlapping surface regions on the exterior of rod 66 and on the interiors of the bores 69, 69A in the conductors 26 and 28 respectively.

The sleeve 38A, the support 68 and the rod 66 may be made separately and assembled into the complete connector shown in FIG. 10, but is convenient to mold the complete connector as a single integral metal piece, for example of aluminum. It will be understood that in this embodiment, as in others where appropriate, insulation in the form of wound electrical insulating tape, or in any other convenient form, is typically applied around the exterior of the junction where such electrical insulation is desirable or necessary.

The junction of FIGS. 6 and 8 is particularly effective where rod 66 is made of a solid metal since, after crimping, the rod then exerts an outward force on the overlapping portions of the high-current conductors while the sleeve member exerts a radially-inward force on them, thus enhancing the squeezing of the intervening material into a compacted mass of metal in excellent bonded relation both to the interior of the sleeve member and to the exterior of the rod 66, with resultant low electrical contact resistance.

FIG. 11 shows still another embodiment of the invention in which the two high- current conductors 26 and 28, which may be solid rather than stranded, are provided with an electrical connection by way of the axially-overlapping regions formed by shaping the ends of the two conductors into semi-cylinders and placing the flat surfaces of the semi-cylinders in overlapping engagement within the sleeve member 38, after which the crimps such as 40 thru 48 are applied. The crimping action is again effective not only between the inner surface of the sleeve member 38 and the outer surfaces of the high-current conductors, but also provides a sufficient degree of crimping and excellent electrical connection between the overlapping surfaces of the two semi-cylinders, i.e. along the line 80.

FIG. 13 illustrates the manner in which the invention may be applied to making appropriate connection between a highcurrent conductor of normal cylindrical form and a terminal connector 83 having a flat terminal lug 84 of generally rectangular cross-section provided with appropriate holes such as 86 for making external connection thereto. The terminal connector 83 is similar to some known in the prior art, with the important exception that a generally-cylindrical prong 88 is provided along the axis of the sleeve portion 90 of the connector. The end of the high-current conductor 82 is provided with an axial bore 92 so that it can be slipped inside the sleeve portion 90 and over the prong 88, in relatively closely-fitting engagement therewith, after which two crimps 94 and 96 are applied to the exterior of the sleeve portion 90 to provide excellent and stable intimate electrical and mechanical contact between the inner surface of the sleeve portion 90 and the outer surface of the cylinder 99 formed by bore 92, as well as between the inner surface of cylinder 99 and the outer surface of the prong 88; as a result, current is not required to flow only through the outer sleeve portion of the connector as in priorart devices, but also readily flows through the more central path including prong 88, with resultant reduction in the temperature rise of the completed junction when high currents are passed through it. The prong 88 and the cylinder 99 therefore serve as electrically-conductive elements in axially-overlapping relation, providing connection between interior portions of conductors 82 and 84.

FIG. 15 shows an arrangement for providing a Y connection between three difierent high-current conductors, utilizing the same type of junction as is employed in the embodiment of FIG. 13, and accordingly corresponding parts are indicated by corresponding numerals with different letter suffixes. In this construction, electrical connection for high currents is provided between the high-current conductor 82A, the high-current conductor 82B axially-aligned therewith, and the highcurrent conductor 82C aligned along an axis parallel to, but displaced from, that of the other two conductors. To accomplish this, there is provided a connector comprising a generally Y-shaped or branched solid metal connector body 100 having three arms terminating in the outer sleeve portions 90A, 90B and 90C, each of the latter sleeve portions containing a corresponding conductive coaxial prong integral therewith designated respectively as 88A, 88B and 88C. The ends of the conductors 82A, 82B and 82C are bored out to form end cylinders 99A, 99B and 99C, and are such as to be readily slipped into the interiors of the corresponding sleeve portions and over the corresponding prongs, prior to crimping. Two crimps are applied to the exterior of each of the sleeve portions 90A, 90B and 90C, thereby to provide a crimped stable intimate electrical and mechanical connection between the interior surfaces of the sleeves and the exteriors of the cylinders at the ends of the high-current conductors, as well as between the prongs and the interior surface of the end cylinders. Again, the connection thereby provided between interior portions of the high-current conductors and the high-current carrying Y body 100 results in reduced junction heating.

FIG. 16 illustrates how a similar junction may be used in a T joint, there being provided in this instance metallic connector body portion 104 in the shape of a T whereby the junctions 106, 108 and 110 are electrically interconnected, each of these junctions suitably being identical with the three shown in FIG. 15, except that in this case the axis of junction 110 is at right angles to the axis of the junctions 106 and 108.

FIG. 17 illustrates a connector suitable for use in forming the crimped connector junction illustrated in FIG. 13, and FIGS. 18 and 19 illustrate, respectively, suitable forms of connectors for producing the junctions illustrated in FIGS. 15 and 16, respectively, and corresponding parts are indicated by corresponding numerals. In each case a suitably-bored conductor is slipped into its position over its corresponding prong, and

crimping is applied to the exterior of the corresponding sleeve portion, as described previously. Each of these connector structures may, if desired, be molded as a single integral metal piece.

Without thereby in any way limiting the scope of the invention, FIG. 20 illustrates tests which were made with four particular types of junctions, two of which were constructed in accordance with the invention and two of which were constructed in accordance with the prior art. More particularly, FIG. 20 is a graph in which abscissae represent time in minutes and ordinates represent the rise in temperature in degrees Centigrade of the junction above the temperature of the two high-current conductors joined by the junction, as measured at points in the conductors remote from the junction. Across the top of the graph are indicated the temperatures in degrees Centigrade of these conductors at points remote from the junction, at the different indicated times during the tests.

In these tests, a series circuit was made comprising high-current conductors of 1,000 MCM compact stranded aluminum inter-connected by two junctions fabricated in accordance with the invention and two fabricated in accordance with the prior art, and high currents were passed through this series circuit while the temperatures of the conductors remote from the junctions and the temperatures of each junction were measured. One of these junctions was like that shown and described with reference to FIG. 1, using a sleeve member 3 as inches in length, crimped five times as shown in FIG. 1, and curve A of the graph shows the temperature rise for that junction. A second junction, from which the data of curve B of FIG. 20 were obtained, was constructed like the junction shown in FIG. 8, with a sleeve member 38 four inches in length. One of the junctions constructed in accordance with the prior art, providing the data shown in graph C of FIG. 20, was provided by butt-ending the two ends of the 1,000 MCM compact stranded aluminum conductor within a sleeve of 7 inches length, to the exterior of which 8 crimps like those applied to the junctions of the invention were applied. The other of the prior-art junctions, from which the data plotted in curve D in FIG. 20 were obtained, was like the previously-described prior-art junction with the exception that it was only four inches long, with 4 crimps on its exterior.

At the time indicated as in the graph, a current of 1,350 amperes was passed through all four junctions in series and continued for 30 minutes, after which the current was increased to 1,800 amperes; the latter current level was maintained during the remainder of the tests, i.e. for a total of 76 minutes. During this time, the temperature of the conductor at points remote from the junctions increased as shown along the top of the graph, from room temperature (R.T.) to 121.1 l. The four curves in the graph represent plots of the amount by which the temperature of each of the corresponding junctions exceeded the simultaneous temperature in the remote portions of the conductors. It will be seen that the temperature of the conductors at points remote from the junction increased with time as the current was passed through the circuit, and that for about the first 45 minutes of the test the elevation of the temperatures at each junction generally increased also. After 45 minutes, a door of the test room leading to a colder exterior ambient was opened briefly and then reclosed, with the result that the temperature elevation of each junction momentarily decreased and then resumed its increase.

From FIG. 20 it will be appreciated that the temperature elevation (approximately 8 to 10 maximum) of the two junctions fabricated in accordance with the invention was substantially less than that (about 23) for the two prior-art types of junctions, and typically was about one-half or less than that for the prior-art junctions. It is noted that this improvement existed even with respect to the 7-inch long prior-art junction, corresponding to graph C, so that a very substantial improvement in excess temperature rise was obtained by the junction of the invention even when compared with a prior-art junction of twice the length. The junctions of the invention not only proved superior in their temperature characteristics, but they were also very readily made in the manner set forth hereinbefore, and were of good electrical and mechanical properties and longevity.

It will be understood that the junction, connector and method of the invention may in each instance be varied substantially from those particularly shown and described. Many different types of metals may be used for the high-current conductors connected by the junctions, and many different metals may be used for the junction elements themselves. The shapes, sizes and arrangements, as well as the crimping arrangements, may be varied substantially while still retaining the advantages of the invention. The nature and degree of crimping applied to the exterior of the sleeve member, and the dimensions and strength of the various elements subjected to crimping, should be selected so that good bonding and electrical contact is provided not only between the sleeve portion and the exterior of the conductors, but also between the more centrally-located axially-overlapping portions of the two conductive elements within the sleeve member. In any given application, these various parameters may be varied to obtain the desired result, which can be readily determined by mechanical and electrical tests, particularly in conjunction with appropriate sectioning of the finished devices to inspect the cross-sectional configurations obtained.

Thus while the invention has been described in the interest of definiteness with particular reference to specific embodiments thereof, it will be understood that it may be embodied in a variety of forms diverse from those specifically shown and described without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

l. A low-resistance, low temperature-rise electrical junction between a first high-current capacity stranded power-line conductor and a second high-current capacity stranded powerline conductor, comprising:

a metallic connector comprising an outer generally cylindrical sleeve portion of crimpable metal, one end of which fits closely over and around one end of said first conductor and the other end of which fits closely over and around one end of said second conductor; a first solid, generally-cylindrical, rigid, rod-like metal core portion extending substantially along the axis of said sleeve portion, said first core portion fitting closely within a corresponding bore in said one end of said first conductor; a conductive support portion of metal extending generally across the interior of said sleeve portion and physically and electrically connected to said sleeve portion and to said first core portion supporting said core portion and providing low-resistance electrical connection between said first core portion and said sleeve portion; and a second solid, generally cylindrical, rigid, rod-like metal core portion connected to and supported on said support portion and extending therefrom substantially along the axis of said sleeve portion in the opposite direction from said first core portion and fitting closely within a corresponding bore in said one end of said second conductor; the exterior of said sleeve portion being crimped on to said first and second conductors providing stable intimate physical and electrical connection between said connector and said first and second conductors.

2. The junction of claim 1, in which said metallic connector is formed of a single continuous substantially homogeneous body of metal selected from the group of copper or aluminum or alloy thereof.

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Claims (2)

1. A low-resistance, low temperature-rise electrical junction between a first high-current capacity stranded power-line conductor and a second high-current capacity stranded power-line conductor, comprising: a metallic connector comprising an outer generally cylindrical sleeve portion of crimpable metal, one end of which fits closely over and around one end of said first conductor and the other end of which fits closely over and around one end of said second conductor; a first solid, generally-cylindrical, rigid, rod-like metal core portion extending substantially along the axis of said sleeve portion, said first core portion fitting closely within a corresponding bore in said one end of said first conductor; a conductive support portion of metal extending generally across the interior of said sleeve portion and physically and electrically connected to said sleeve portion and to said first core portion supporting said core portion and providing low-resistance electrical connection between said first core portion and said sleeve portion; and a second solid, generally cylindrical, rigid, rod-like metal core portion connected to and supported on said support portion and extending therefrom substantially along the axis of said sleeve portion in the opposite direction from said first core portion and fitting closely within a corresponding bore in said one end of said second conductor; the exterior of said sleeve portion being crimped on to said first and second conductors providing stable intimate physical and electrical connection between said connector and said first and second conductors.

2. The junction of claim 1, in which said metallic connector is formed of a single continuous substantially homogeneous body of metal selected from the group of copper or aluminum or alloy thereof.

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