U.S. patent number 3,673,313 [Application Number 05/031,226] was granted by the patent office on 1972-06-27 for electrical junction for high-current conductors and connector and method suitable for making same.
This patent grant is currently assigned to Utility Industries Inc.. Invention is credited to Wiley J. Pickett, Bynum E. Smith.
United States Patent |
3,673,313 |
Pickett , et al. |
June 27, 1972 |
ELECTRICAL JUNCTION FOR HIGH-CURRENT CONDUCTORS AND CONNECTOR AND
METHOD SUITABLE FOR MAKING SAME
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.
Inventors: |
Pickett; Wiley J. (Moorestown,
NJ), Smith; Bynum E. (Richmond, VA) |
Assignee: |
Utility Industries Inc.
(Westmont, NJ)
|
Family
ID: |
21858282 |
Appl.
No.: |
05/031,226 |
Filed: |
April 23, 1970 |
Current U.S.
Class: |
174/90; 174/94R;
29/869; 439/427 |
Current CPC
Class: |
H01R
43/058 (20130101); H01R 4/20 (20130101); Y10T
29/49195 (20150115) |
Current International
Class: |
H01R
43/04 (20060101); H01R 4/10 (20060101); H01R
43/058 (20060101); H01R 4/20 (20060101); H02g
015/08 () |
Field of
Search: |
;174/84C,88R,90,94R,71,72 ;339/100,276T,276R,223R ;29/628 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Clay; Darrell L.
Claims
What is claimed is:
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.
Description
BACKGROUND OF THE INVENTION
This invention relates to electrical junctions between high-current
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 pull-out
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 butt-welding 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
large-diameter 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 and internal 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
different exterior sizes and forms, for example to provide
connection between a generally cylindrical high-current 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 different parts of the cross-section 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 effects 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 thereafter
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 non-uniform
current densities in or near the junction and the resultant
"hot-spots.infin. 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 2--2 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 9--9 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 12--12 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
electrical-conductive 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. Generally-cylindrical
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
full-diameter 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 high-current 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. 1, 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 hemispherical 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 nine-sixteenths 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 1/2 inches, a wall
thickness of about one-fourth inch, and an overall length of about
3 1/2 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 non-uniformity 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. 1-5 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 high-current 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
high-current 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 high-current
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
prior-art 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 different 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 high-current 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 1/2 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 0 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 121.11.degree.. 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.degree. to 10.degree. maximum) of the two
junctions fabricated in accordance with the invention was
substantially less than that (about 23.degree.) 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.
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