Note: Descriptions are shown in the official language in which they were submitted.
1 0 ~9 ~ i ~
This invention relates to electrical connectors and in
particular to an electrical connector or core reinforced cables.
High tension electrical cable is commonly constructed
with a steel core surrounded by twisted or braided strands of a
conductor metal such as aluminum or copper. The conductor strands
provide both tensile strength and the necessary electrical con-
ductive path, and the steel core gives the cable additional
tensile strength.
In connecting lengths of such cable together or in
affixing cable accessories such as dead ends to such cable, a
connector must serve the dual purposes of providing a joint of
adequate strength and providing an adequate conductive path for
electrical current. Meeting these criteria has usually required
that the connector be firmly affixed to and in intimate direct
contact with both the steel core and the conductor strands. In ;
the field of ACSR (Aluminum Conductor Steel Reinforced) cable,
the above criteria have been met by the use of a two-piece
assembly comprising an aluminum outer sleeve and a steel inner
sleeve Typically the aluminum sleeve is placed over the free
end of one of the cables to be joined and moved along the cable
out of the immediate region of joinder. The free ends of both
cables are stripped of conductor strands to expose a length of
core. These exposed core lengths are disposed in opposite ends
of a steel sleeve and the sleeve is then crimped about the
contained core lengths. Finally the aluminum sleeve is moved
onto the region of joinder, so that the aluminum sleeve extends
over the steel sleeve and over equal lengths of cable on either
side of the steel sleeve. The aluminum sleeve is then crimped
against the conductor strands. Alternatively, a single cable
may be joined to the steel sleeve, aluminum sleeve structure in
a similar manner but with the opposite end of the joinder struc-
ture suitably connected to a cable accessory, such as a dead end.
- 1 -
. . .
. . ........ .
1~ 49 ~ ~
The design of such steel and aluminum sleeve assemblies
is such tha~ a given assembly can accommodate very ew cable sizes.
This has resulted in a proliferation of various assembly units
which a cable accessory manufacturer must make and stock in order
to suit the cable sizes which his various customers utilize. Con-
sequently, a specifically designed assembly is usually required
for each of the many common ACSR sizes. Additionally, it is not
unusual for a particular customer to order cable made to an un-
common or non-standard size cable for a particular application,
and this cable will often require a connector assembly designed
especially for that cable. This wide proliferation of sizes
causes undesirable cost and inventory problems.
The method of application of such assemblies presents
additional undesirable aspects to the user. At least two separate
crimping operations are required to effect a joint, i.e. ~he steel
sleeve must be crimped against the cable core or cores and then
the aluminum sleeve must be crimped against the conductor strands.
Since many cable connectors are applied in the field, this two-
operation crimping is undesirable in terms of time and equipment.
Field crews must have two sets of crimping dies, one for the inner
steel sleeve and another for the outer aluminum sleeve.
In addition, the initial positioning o the aluminum
sleeve on the cable some distance from the free end to allow
positioning and crimping of the steel sleeve may be troublesome.
Steel core reinforced cable generally acquires a set from the
drums on which it is initially wound after manufacture, and the
cable will subsequently tend to assume this set or curvature when
it is not under tension. Since the cable cannot usually be held
in tension at its free end during joining or affixing operations,
this curvature will make it difficult to slide the aluminum
sleeve along the cable away from the free end. Finally, when
such a two-sleeve assembl~ is used to join two core reinforced
-- 2 --
'
\
l~91~L
cables, the insertion o~ the exposed cores may occasion some
difficulty. Both core lengths are inserted into a common sleeve
and this requires at least one of the cables to be manipulated
so as to effect insertion because the sleeve will have been posi-
tioned over the exposed core of the other cable.
Previous attempts to overcome these problems have been
made. For example, U.S. Patent No. Re. 25,698 discloses a con-
nector which is adapted to be crimped in a single crimping
operation in which the outer sleeve is crimped over the inner
member and the cable. The inner member, which grips the cable
core, is cons~ructed of a frangible powdered metal which fractures
upon crimping. As disclosed in the patent, this structure re-
quires a high crimping pressure. This may be troublesome
especially in repair as opposed to original installation appli-
cations wherein the necessary portability of the crimping press
~requently limits the force capability of ~he press. U.S. Patent
No. 3,125,630 discloses a similar frangible metal ferrule, but
comprising a plurality o~ segments with interlocking fingers. Both
patent disclosures appear to contemplate fixing the ferrule in
the outer tube and then inserting the exposed core into the
ferrule which is ~ixed in the tube. This means that in joining
two cables both exposed cores will have to be inserted into what
is essentially a common sleeve with the attendant manipulative
difficulties discussed previously. These inser~ion difficulties
are aggravated in the case when the core is made from multiple
wire strands. Unless such a core is "preformed" (treated in the
manufacture of the cable in such a way as to retain its shape),
the individual strands of the core will tend to unravel and splay
out when the surrounding conductor strands are stripped away to ~ -
expose the core at the free end.
The prior art is lacking in a disclosure of a connector
for electrical cables in which the same connector is adapted for
- 3 -
- , ' ', . ' ' .:, ' . ' , . .
.
.. ,', , .'' ~ '
~ ~9 i ~
joining a wide variety of cable sizes using relatively low levels
of crimping force. There is no prior teaching of how to avoid
the manipulative difficulties of inserting exposed cores of
cables to be joined into a common sleeve.
This invention provides a method and core grip for
connecting core reinforced cable to another cable or ~o a cable
accessory. A core grip is provided which secures the cable core
to an electrically conductive outer sleeve which is, in turn,
directly affixed to the conductor strands of the cable. In
joining two core reinforced cables, a core grip is provided for
each cable, and after a core grip is positioned over the exposed
core at the free end of the cable, the core grip is inserted into
one end of a common compression barrel along with a suitable
length of immediately adjacent cable. In other joining situations
a core grip is prov~ed just for the core reinforced cable and
other suitable means is used to affix the cable or desired cable
accessory to the compression barrel. The core grip is so designed
that when a compression barrel is crimped thereover, the core
grip transmits more compressive force than it would if it were a
simple right cylinder. 'Ehe compression barrel is crimped over
both the contained core grip or grips and the inserted cable
lengths.
The design of the core grip and compression barrel is
such that a single set may accommodate a variety of cable sizes.
In addition, the design allows a single compression barrel to be
used with a number of different sized core grips. Thus with a
limited number of sizes the core grip and compression barrel as-
sembly may serve a wide range of electrical cable sizes.
The core grip may be made of any compressible metal, but
is preferably made of aluminum or an aluminum alloy. It may
conveniently have a configuration such that it can readily be
produced by an economical process such as extrusion. Its hoop
' '' . '
. ,:
~9~1~
strength is such that the assembly in which it is incorporated may be
crimped by pressures within the capabilities of currently utilized field
equipment. Among the objects of this invention is to provide a method and
apparatus for interconnecting core reinforced electrical cables which can
be readily employed in the field to provide a joint having a tensile strength
at least equivalent to 95% of the rated tensile strength of the core
reinforced cable. A further object is to provide a joining device which can
be economically produced, easily assembled and readily adapted to a variety
of cable si~es.
lo Thus, in accordance with the broadest aspect of the invention,
there is provided an elongate core grip of deformable metal adapted to be
mechanically joined to the core member in a reinforced cable by crimping a
surrounding compression barrel inwardly against the core grip, said core
grip comprising a plurality of longitudinally extending radially outwardly
projecting lobes of decreasing circumferential extent toward the axis of the
core grip and comprising 1/3 to 2/3 of the circumference of the core grip~
said lobes being integrally interconnected in spaced relation about a common
axis by a deformable sleeve at the inner edges of the lobes with a central
bore through the sleeve for receiving and confining a projecting length oE
core from a cable to be connected thereby, said sleeve having a wall
thickness less than the arc length of the sleeve between adjacent lobes to
facilitate buckling of the sleeve between the lobes upon crimping of a
compression barrel inwardly against the core grip.
The above and other objects and advantages of this invention will `~
be more fully understood and appreciated by reference to the following
description and the appended drawings in which;
~igure 1 shows the end of a core reinforced cable suitable to be `
co~nected to another cable or to a cable accessory in accordance with this
invention,
r . . .
.. ~
:. .' ~ ' ", ': ~: . . :
.
' ' ' ~ ' ' ' ' ,~ . :
~CI 49~
Figure 2 is a side view of a core grip of this invention;
Figure 3 is a transverse cross-sectional view of the core grip of
Figure 2;
Figure 4 is a fragmentary side view of a compression barrel of
this invention in partial section;
Figure 5 is a view similar to Figure 4 and further showing a core
grip and cable end disposed in the compression barrel;
Figure 6 is a transverse cross-section through a compression
barrel, core grip and cable core as crimped into a joint assembly;
lo Figure 7 is a side view in partial section showing a dead end :~
connected to a core reinforced cable using a connector of this invention; and
Figure 8 is a transverse cross-sectional view of an alternative :
embodiment of a core grip of this invention.
1., ^ .
-5a-
. .
.
.
.
~0~
Re~erring to the drawings, Fig. 1 illustrates an end of
a core reinforced cable 10 which is adapted to be joined to
another cable or to a cable accessory employing the present
invention. The conductor strands 12 have been stripped ~rom the
end of the cable so a length of the core 14 is exposed on the end
of the cable with the core projecting some distance beyond the
termination of the conductor stra~s 12 around the core. A suf-
ficient length of the core 14 should be bared or stripped of the
outer conductor strands to expose a length of core approximately
equal to the length of a core grip which will fit over the cable
core as will be hereinafter described. The core 14 of the cable
10 may comprise a plurality of twisted strands as is illustrated
in Fig. 1, a plurality of parallel strands or a single core strand.
The invention is especially addressed to joining cables having
steel core members, which typically have a zinc or aluminum
coating thereon to protect them against corrosion, but may also
be employed for joining cables having an aluminum core member.
This invention is also particularly addressed to joining cables
having aluminum conductor strands, but may also be used with
2~ cables having copper conductor strands.
Figs. 2 ~d 3 illustrate an exemplary ~ngate core grip 4
of this invention. The core grip 4 has three longitudinally
extending, radially outwardly directed lobes 6 which are integrally
interconnected in spaced relationship about a common a~is by
three deformable webs of metal which, in conjunction with the
lobes, form an integral inner sleeve 8. The outer surfaces 9
of the three lobes 6 preferably all lie in a common circle having
a diameter which is preferably slightly greater than the outer
diameter of the cable 10 which is to be joined. The inner surface
inside the core grip ~ may have an abrasive grit thereon such as
aluminum oxide adhered to the surface with varnish or the like.
Alternatively, transverse or longitudinal serrations or threads
- 6 -
.. . .
' :' ' '.': ' ' ' ' ~ '
may be formed in the inner surface of the core grip.
Fig. 4 shows an exemplary compression barrel 20 which
is adapted to receive and join the ends of two reinforced cables
with core grips thereon. The compression barrel 20 preerably has
a length equal to approximately 4 to 5 or more times the length
of the core grip 4 and has an internal stop member 26 therein at
the center of the barrel. This stop member 26 may be of a variety
of constructions such as an aluminum wafer which has been expanded
into barrel to lock it in the proper location at the midpoint in
the barrel. Joint compound 2~ is provided in the compression
barrel 20 adjacent the stop member and preferably fills approxi-
mately one-fourth of the barrel.
The compression barrel has a substantial wall thickness
since it must form both the mechanical and electrical connection
be~ween cables or between a cable and a cable accessory. For
example, the wall 22 of a compression barrel 20 may have a thick-
ness equal to approximately one-fourth of the internal diameter
of the compression barrel. The compression barrel 20 preferably
has a tapered end surface 24 on each end thereof which serves to
distribute the stresses produced on the conductor strands 12 by
the compression barrel when it is crimped against the conductor
strands, and reduces the tendency of the conductor strands to
fracture or shear at the mouth of the compression barrel 20.
Both the compression barrel 20 and the core grip 4 are
constructed of compressible metals or metal a~oys, and are pre-
ferably ormed from aluminum base alloys. The compression
barrel 20 is preferably formed from a medium strength, deformable
aluminum alloy, and the core grip is preferably formed from a
medium to high strength, deformable aluminum alloy. In one
exemplary construction, -the compression barrel is made of 3003
aluminum alloy (typically by weight 0.2% Cu, 1.2% Mn, balance
Al), and the core grip is made of 6061 aluminum alloy (typically
-- 7 --
~.: ,. ", . .. . .. . .
. ,.. ,, . ~ .., . .,,, -
by weight 0.6% Si, 0.27% Cu, 10% Mg, 0.20% Cr). In this com-
bination, the 3003 alloy pre~erably has a hard temper, e.g. H18,
and the 6061 alloy preferably has an intermediate to hard temper,
e.g. T4 to T6. The alloy and temper designa~ions as used herein
are defined in "Aluminum Standards and Data~, 3rd Edition, 1972,
published by the Aluminum Association.
As stated above, the compression barrel must have a
sufficient length and wall thickness to provide adequate electri-
cal and mechanical strength in the joint to be formed~ For many
applications, the joint should have a mechanical strength of at
least 95% of the rated tensile strength of the cable which is to
be joined. In order to provide an adequate interfacial surface
area between the compression barrel and the cable and core grips,
the compression barrel preferably has a length which is in a
range of four to ten, and preferably seven and one-half, times its
inside diameter.
Fig. 5 shows a compression barrel 20 with the end of a
cable 10 and a core grip 4 disposed in one end of the compression
barrel preparatory to crimping the barrel to form a secure joint.
The core grip 4 preferably has an outer diameter as measured
across the common circle defined by the outer surfaces of the
lobes 6, which is only ~ightly less than the inside diameter of
the compression barrel 20. Any excessive clearance between the
outer surfaces of the core grip and theinner surface of the
compression barrel will mean that part of the crimping action
will be used to close this clearance and that less crimping
action will be available to compress the walls of the barrel
against the core grip, and the core grip against the cable core.
It is therefore preferred that there be no more than a 2.5%
diametric clearance between the outer surfaces 9 on the core
grip and the inner surface of the compression barrel 20. A
clearance o~ between approximately 10% and ~0% may exist between
~ C~4~
the inner bore of the core grip and the core of the cable. A
relatively small clearance is desirable because it will produce
the most effective and efficient mechanical contact and gripping
of the core grip against the conductor core when the assembly is
crimped. However, at least a 10% clearance is desired to
facilitate insertion of the core into the core grip. Additionally,
a single core grip size may be used with a range of conductor
sizes so the clearance between the bore of the core grip and the
conductor wilî vary according to conductor size up to approxi-
mately a ~0% clearance.
Preferably the outer surfaces 9 oi the lobe 6 on coreare of sufficient total area and configuration that the lobes
will not intrude substantially into the wall of the compression
barrel 20 upon crimping. For this reason, the outer surfaces 9
of the lobes 6 comprise approximately one-third ~ two-thirds, and
preferably one-half of the circumference of the common circle
defined by such surfaces. On the other hand, an adequate cir-
cumferential spacing must be maintained between the lobes 6 so that
they will not bind against each other as they are driven radially
inwardly against a cable core when the compression barrel is
crimped against the core grip The greater the spacing between
the lobes, the greater will be the potential for radial inward
travel of the lobes against a cable core contained within the
core grip. The amount of spacing between lobes which is required
will depend upon the diameters of the cores of the cables which
are to be joined by a particular core grip. A core grip having
a relatively large circumferential spacing between its lobes
will accommodate a wider range of core sizes with a given cOre
grip. The lobes are preferably spaced to permit a reduction in
the diameter of the bore in the core grip of at least 20% and
preferably approximately 50% before the adjacent lobes bind
against one another. A reasonable compromise which provides
_ 9 _
.
.
~ ~ ~9 ~ ~ ~
adequate outer surface area 9 on the lobes while also providing
adequate space between lobes, is a core grip in which the lobes
and the spaces therebetween are approximately equal.
Fig. 6 is a cross-section through a connector assembly
after crimping with the lobes 6 of the core grip compressed
radially inwardly into tight engagement against the outer sur-
faces of the conductor core 14. The bore of the core grip does
not retain its cylindrical shape upon crimping, but instead
deforms into a substantially triangular configuration with the
webs of metal between the lobes buckled outwardly. The outer
surfaces of the lobes 6 of the core grip are partially embedded
in the walls of the compression barrel 20 and form a secure
mechanical joint therewith. Joint compound 28 substantially
fills the spaces between the lobes 6 of the core grip 4.
The core grip ~ is preferably constructed with integral
webs of metal therebetween forming continuous sleeve 8 which
serves to locate the lobes 6 and also to contain the strands of
a multistrand core and prevent them from moving radially out-
wardly into the spaces between adjacent lobes. IE the strands
of the cable core were permitted to escape into such spaces, the
lobes might not form a tight and secure joint against the core
strands, This is especially important in joining core reinforced
cable in which the core is not "preformed~' or given a permanent
set. When the overlying conductor strands are stripped of such
a cable to expose the core, the core strands tend to untwist and
splay outwardly. The continuous sleeve of a core grip contains
these unruly strands and prevents them from slipping outwardly
into the spaces between the lobes durin~ crimping.
The webs of metal between the lobes 6 in a preferred
embodiment of a core grip 4 of this invention are preferably
relatively thin to provide a minimum resistance to buckling
during crimping. I the webs are too thick and therefore have
- 10 -
' .
.
1~ ~9 ~ ~1
substantial strength, much of ~he crimping force will be utilized
in buckling the webs rather than moving the lobes radially
inwardly into intimate and secure gripping contact against the
core of a cable. The webs of metal between each of the lobes in
effect is a column which must be buckled during crimping of a
connector assembly. In a preferred embodiment of this invention,
the metal thickness in each such web between the adjacent lobes
is preferably less than 25% of the arc length of such web so the
webs can be deformed using a minimum of the crimping force.
The preferred length of a core grip 4 of this invention
is related to the range of core diameters of the cables which are
to be joined using such core grip. A shorter core grip can be
used when the internal diameter of the core grip is relatively
close to the diame~er of the core of the cable. However, there
is a minimum length of the core grip below which it is virtually
impossible to obtain adequate strength in the joint between the
core grip and the cable core. For example, in the smaller cable
sizes such as a cable having a core diameter of approximately 1/4
of an inch, the core grip should be at least 2 inches long even
when the internal diameter of the core grip is only slightly
larger than the diameter of the cable core. A greater range of
cable core sizes can be accommodated with core grips having
longer lengths which provide more surface area for gripping the
core of the cable. A core grip of this invention preferably
has a length which is at least approximately 8 times the internal
diameter of the core grip.
In the practice of this invention to join two aluminum
conductor steel reinforced (A~SR) cables, the cables are prepared
by stripping the conductor strands from the ends of the cables
to be joined to expose a length of cable core approximately the
length of the core grips to be used. If the cables have non-
preformed multistrand cores, the exposed cores inwardly of the
- 11 -
.
~ 9~
terminal end may be temporarily wrapped with tape or the like to
prevent them from splaying. A core grip is then slipped over the
unwrapped projecting end of a core, and the temporary tape
wrapping is removed from the core. The core grip is then further
slipped over the core until it abuts against the conductor strands
on the cable. Each core grip with a following length of cable
approximately equal in length to the core grip is inserted into
opposing ends of a compression barrel until the core grips abut
against the stop in the middle of the compression barrel. The
compression barrel preferably has a joint compound in it to keep
moisture and other contamination out of the barrel. When the
core grip and cable are inserted into the compression barrel, the
joint compound will be exuded around the core grip and cable and
may ooze from the end of the compression barrel. The stop member
in the compression barrel prevents the joint compound in one
end thereof from being pushed into the other end when the cable
and core grip are inserted into the barrel. The compression
barrel is crimped by commercially available force-operated
crimpers having a force in the range of approximately 12-150 tons
depending on the size of the connector and the crimping dies.
The crimping dies are moved radially inwardly against the outer
surface of the compression barrel around substantially its entire
circumference. The dies of a compression-operated crimping tool
may have a width in a range of approximately one to three inches,
again depending on the diameter of the connector and tha power of
the compressor, and the compression dies are progres.sively crimped
against substantially the entire length of the compression barrel.
The compression barrel is preferably crimped commencing approxi-
mately at its center and moving progressively ou~ward toward the
end thereof. The first bite or crimp is preferably ta~en
adjacent to the inner end of the inserted core grip, but not
directly over the center of the stop within the compression
- 12 -
.
.:
. . . .
~ ~9~ 1
barrel to avoid crimping any portion o~ the compression barrel
which may be unsupported by either a core grip or an inserted
cable. It is believed that crimping an unsupported barrel por-~ion
may cause undue weakening of the barrel.
A joint may also be formed between a core reinforced
cable and a cable accessory. Figure 7 shows a connector of this
invention connecting a dead end 30 and an ACSR cable lO. The
dead end 30 is preferably connected to the connector in the
factory or shop by crimping the compression barrel 20 inwardly
agains~ the corrugated surface or ribs 34 on the shank 32 o~ the
eye of the dead end, and the tongue 36 of the dead end is welded
to the outer surface of the compression barrel. This construc-
tion differq from existing steel sleeve-aluminum sleeve construc-
tions in that the load-bearing eye of the dead end may be directly
affixed to the compression barrel without the need for other
mechanical coL.~ections between the eye and the cable core. This
construction is possible because the compression barrel is
designed to support a load equal to a~ least 95% of the rated
tensile strength of the cable. The connector assembly is attach-
ed to a cable in the ~ield in a manner similar to that describedin the preceding paragraph.
Figure 8 shows an alternative embodiment of a core grip
4' which can be used in this invention. Core grip 4' has four
lobes 6', the outer surfaces 9' of which all lie in a common
circle. The opposite lateral edges of the adjacent lobes 6'
lie on approximately the same chordal line with webs of metal
in the inner sleeve 8' interconnecting the adjacent lobes.
Whi1e preferred embodiments of this invention have been
illustrated and described, this invention is not limited to such
30 embodiments For example, the core grip may have any number of ::
lobes thereon and may have a variety of integral connecting means
between the adjacent lobes. The connecting webs of metal between
- 13 -
~ 9~
the lobes may be discontinuous along the length of the core grip
and may be provided only on the opposite ends of such core grip
with no connecting web between lobes along ~he central portion
of the core grip. The core grip may also be formed with no
connecting web between one pair of adjacent lobes leaving a
slot or opening along the entire length of the core grip. How-
ever, for convenience and ease of use, the core grip and com-
pression barrel are both preferably symmetrical about their
longitudinal axes.
Various modifications may be made in the invention
without departing from the spirit thereo~ or the scope of the
claims, and, therefore, the exact form shown is to be taken as
illustrative only and not in a limiting sense, and it is desired
that only such limitations shall be placed thereon as are
imposed by the prior art, or are specifically set forth in the
appended claims.
. .
