Note: Descriptions are shown in the official language in which they were submitted.
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END ASSEMBLY FOR CONNECTION TO ~ND
OF GROUND WIRE WITH OPTICAL FIBER
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to an end assembly for connection
to an end of an overhead ground wire incorporating an optical
fiber cable therein.
Prior Art
An overhead ground wire of the type described comprises a
protective tube, an optical fiber cable housed in the
protective tube, and a plurality of ground wire elements
helically wound around the protective tube to form a wire
layer of a hollow configuration. One conventional end member
for connection to an end of the ground wire for connecting the
ground wire to a support construction such as a pylon and a
tower, as disclosed in Japanese Utility Model Application
Laid-Open (Kokai) Nos. 56-171523 and 57-15630, comprises a
tubular compression sleeve of metal having a uniform inner
diameter. For connecting the ground wi-re to the support
construction, the compression sleeve is fitted on the end of
the ground wire and is then compressed to be deformed radially
inwardly into firm locking engagement therewith. Then, the
connecting sleeve is connected to the support construction by
a suitable ~astening means to hold the ground wire in the air.
This conventional end member has been found disadvantageous,
however, in that upon compression of the compression sleeve,
the protective tube tends to be deformed or crushed to damage
the optical fiber cable received therein since the protective
tube comprises a relatively thin, soft aluminum tube.
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In order to overcome this difficulty, it has been
proposed in Japanese Utility Model Appl:ication Laid-Open
(Kokai) No. 55-181205 and Japanese Utility Model Publication
No. 58-5~826 to first press-fit a crush-prevention tube oE a
rigid material, such as steel, in between the wire layer and
the protective tube at the end of the ground wire, and to then
fit the tubular compression sleeve on the end of ground wire,
and -to compress the sleeve in a manner described above. With
this method, the protective tube is prevented from becoming
crushed. The hollow wire layer around the protec-tive tube has
a generally uniform outer diameter along its length, and the
compression sleeve to be fitted on the.wire layer also has a
uniform inner diameter along its length. Therefore, it is
necessary that the compression sleeve and the crush-prevention
tube should be long enough to ensure a sufficient locking
engagement of the crushed sleeve with the ground wire. Thus,
the compression of the sleeve of such a length requires
considerable time and labor. In addition, a great pushing
force has to be applied to the crush-prevention tube of such
a length to press-fit it in between the the wire layer and
the protective tube. Therefore, a special tool is required
to push the crush-prevention tube into position.
Another form of the conventional end assembly as
disclosed in Japanese Utility Model Application Laid-Open No.
56-166672 serves as a joint between two ground wires and also
compriseis a con-pression sleeve to be fitted on one ends of the
two ground wire at opposite ends thereof, and a pair of crush-
prevention tubes each to be press-fitted in between the wire
layer and the protective tube at the end of a respective one
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of the two ground wires. For effec-ting the joint, the
compression sleeve is compressed at the opposite ends thereof
in a manner described above. This conventional end assembly
suffers from the same disadvantages as the aforesaid prior art
end assemblies suffer.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide an
end assembly for connection to an end of a ground wire
incorporating an optical fiber therein which assembly, upon
compression, can be easily brought into firm locking
engagement with the ground wire over a relatively short length
thereof.
According to the present invention, there is provided an
end assembly for connection to an end of an overhead ground
wire, the ground wire comprising a protective tube, an optical
fiber cable housed in the protective tube, and a plurality of
ground wire elements helically wound around the protective
tube to form a wire layer of a hollow configuration, the wire
elements being unwound from the protective tube at the end of
the ground wire to provide an exposed end portion thereof,
said end assembly comprising:
(a) a tubular compression sleeve of a plastically
deformable material;
(b) a tubular protective sleeve received in said
compression sleeve and having a central bulged portion
intermediate opposite ends thereof; and
(c) a filler member interposed between said compression
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sleeve and said protective sleeve;
(d) said protective sleeve being adapted to be fitted on
said exposed end portion o~ said protective tube with the
unwound end portions of said wire elements interposed between
said protective sleeve and said filler member, and said
compression sleeve being compressible to be plastically
deformed radially inwardly to firmly hold said unwound end
portions of said wire elements against an outer peripheral
surface of said protective sleeve through said ~iller member.
BRIEF DESCRIPTION_OF THE DRAWINGS
Fig. 1 is a cross-sectional view of an end assembly for
connection to an end of a ground wire which assembly is
provided in accordance with the present invention;
Figs. 2 and 3 are views similar to Fig. 1 but showing
modified end assemblies, respectively;
Fig. 4 is a cross-sectional view -taken along the line IV-
IV of Fig. 3;
Figs. 5 to 7 are views similar to Fig. 1 but showing
further modified end assemblies, respectively; and
Fig. 8 is a cross-sectional view of a ~oint assembly for
connecting one ends of two ground wires together which
assembly is provided in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
The invention will now be described with reference to the
accompanying drawings in which like reference numerals denote
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corresponding parts in several view.
Fig. 1 shows an end assembly 10 for connection to an end
12a of an overhead ground wire 12 for connecting the end of
the ground wire 12 to a support construction 14 such as a
pylon and a tower. The overhead ground wire 12 comprises a
protective tube 16 made of a suitable material such as
aluminum and an aluminum alloy, an optical fiber cable 18
housed in the protective tube 16, and a plurality of ground
wire elements 20 helically wound around the protective tube 16
to form a wire layer 20a of a hollow configuration.
The end assembly 10 comprises a tubular compression
sleeve 22 of plastically deformable metal
such as steel, a tubular filler member 24 of metal such as aluminum
snugly received in the compression sleeve 22, and a protective
sleeve 26 loosely received in the split collar 24, the
protective sleeve 26 being made of metal such as steel harder
than the tubular body 22. The protective sleeve 26 is of a
tubular shape and is adapted to be fitted on the protective
tube 16 of the ground wire 12 at its end 12a. The inner
diameter of the protective sleeve 26 is slightly greater than
the outer diameter of the protective tube 16. The outer
peripheral surface 26a of the protective sleeve 26 is tapering
from its center toward opposite ends thereof to provide a
central bulged portion 26b.
The filler member comprises a tubular split collar 24
composed of a pair of half cylinders 24a and 24b and having a
uniform outer diameter throughout the length thereof. The
inner peripheral surface 24c of the split collar 24 is
tapering from its center toward opposite ends thereof and
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corresponds in shape to the tapered outer peripheral surface
26a of the protective sleeve 26. The protective sleeve 26
extends outwardly from the split collar 24 in a direction away
from the helically wound wire e:Lements 20.
A U-shaped mounting member 30 is fixedly secured by
welding to one end of the compression sleeve 22, and a
connective plate 32 having an aperture 32a is fixedly secured
by welding to the mounting member 30. The end assembly 10 is
connected to the support construction 14 by a bolt 36 passing
through the aperture 32a of the connective plate 32 into the
support construction 14.
For attaching the end assembly 10 to the ground wire 12,
the wire elements 20a are unwound as at 20b from the
protective tube 16 at the end 12a o~ the ground wire 12 to
expose the end of the protective tube 16. Then, the
protective sleeve 26 is fitted on the exposed end of the
protective tube 16 with the unwound end portions 20b of the
wire elements 20a held in contact with the outer peripheral
surface 26a of the protective sleeve 26. When the end
portions 20b of the wire elements 20a are unwound from the end
of the protective tube 16, each of the unwound end portions
20b assumes a curve generally corresponding to the outer
peripheral surface 26a of the protective sleeve 26 when viewed
in a direction transverse to the axis of the protective sleeve
26. Then, the tubular split collar 24 is fitted on the
protective sleeve 26 with the unwound wire end portions 20b
sandwiched therebetween. Then, the compression sleeve 22 is
fitted on the tubular collar 24. Finally, the tubular body 22
is compressed to be deformed radially inwardly, so that the
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tubular collar 24 is also deformed radially inwardly to ~irrnly
hold the unwound wire end portions 20b against the outer
peripheral surface 26a of the protective sleeve 26 and the
tubular collar 24, thereby connecting the end assembly 10 to
the end 12a of the ground wire 12. In this condition, the
protective sleeve 26 of a hard metal is not deformed radially
inwardly to protect the protective tube 16, which houses the
optical fiber cable 18, against crushing.
Since the protective sleeve 26 has the outer peripheral
surface 26a tapering from its center toward the opposite ends
thereof and closely spaced from the correspondingly shaped
inner surface of the tubular split collar 24 through the
unwound wire end portions 20b, upon application of tension or
a pulling force to the ground wire 12 in a direction indicated
by an arrow in Fig. 1, the protective sleeve 26 is axially
urged toward the split collar 24 in the direction of the
arrow, so that the unwound wire end portions 20b are more
firmly held therebetween. Therefore, the length of the
compression tube 22 to he compressed can be reduced
considerably without lowering the ability of the end assembly
10 to hold the ground wire 12.
Fig. 2 shows a modified end assembly 1Oa which differs
from the end assembly 10 of Fig. 1 in that a pair of
peripheral grooves 40 and 40 are formed in the outer
peripheral surface of the tubular split collar 24 adjacent to
the opposite ends thereof and in that a pair of binding wires
42 and 42 are wound around the split collar 24 and received
respectively in the pair of grooves 40 and 40 to tie the half
cylinders 24a and 24b together. With this construction, the
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fitting of the compression sleeve 22 on the split collar 24 is
facilitated.
Figs. 3 and 4 show another modified end assembly 1Ob
which differs from the end assembly 10 of Fig. 1 in that the
protective sleeve 26 has a plurality of registration
projections 46 of a rounded shape formed on the outer
peripheral surface 26a adjacent to one end thereof close to
the mounting member 30 and spaced circumferentially at equal
intervals, the number of the projections 46 corresponding to
lQ that of the wire elements 20a. The unwound end portions 20b
of the wire elements 20a are received at their free ends
respectively in circumferentially spaced recesses 48 defined
by the projections 46. By virtue of the provision of the
registration projections 46, the unwound wire end portions 20b
are uniformly arranged on the protective sleeve 26 and held in
position. With this arrangement, upon installation of the
ground wire 12 in the air, tension is advantageously
exerted on the ground wire 12 along a longitudinal axis
thereofv
Fig. 5 shows a further modified end assembly 10c which
differs from the end assembly 10 of Fig. 1 in that a binding
wire 50 is wound around the protective sleeve 26 at one end
thereof close to the mounting member 30 to hold the unwound
wire end portions 20b in equally circumferentially-spaced
relation.
Fig. 6 shows a still furth~r modified end assembly 1Od
which differs from the end assembly 10 of Fig. 1 in that a
retaining ring 52 is provided for threaded engagement with the
outer peripheral surface 26 of the protective sleeve 26. The
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protective sleeve 26 has an externally-threaded portion 26d on
the ou-ter peripheral surface 26a at one end thereof close to
the mounting member 30. The retaining ring 52 includes an
annular body 52a and a flange 52b flaring from one end of the
body 52, and the annular body 52a has an internally threaded
portion 52c on the inner surface thereof. The re-taining ring
52 is fitted on the protective sleeve 26 with the internally-
threaded portion 52c threadedly engaging the externally-
threaded portion 26d in such a manner that the flaring flange
52b holds the ends of the unwound wire portions 20b against
the outer peripheral surface 26a of the protective sleeve 26.
Fig. 7 shows a further modified end assembly 1Oe which
differs from the end assembly 10 of Fig. 1 in that a band 56
is wound around the helically-wound wire elements 20a adjacent
to the unwound end portions 20b thereof to prevent the
helically-wound wire elements 20a from becoming loose or
released.
Fig. 8 shows a joint assembly 60 for connecting one ends
12a and 12a of two ground wires 12 and 12 together. The joint
assembly 60 comprises a pair of first and second end
assemblies 10' and 10" each similar in construction to the end
assembly 10 of Fig. 1. More specificallyt the first end
assembly 10' comprises a tubular compression sleeve 22 of
metal such as steel having a compression portion 22a and a
greater diameter portion 62 extending from one end of the
compression portion 22a, a tubular filler member or split
collar 24 of metal such as aluminum snugly received in the
compression portion 22a, and a protective sleeve 26 loosely
received in the split collar 24 and adapted to be fitted on
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the protective tube 16 of the ground wire 12 at its end 12a.
the protective sleeve 26 being made of metal such as steel
harder than the compression sleeve 22. As described above for
the end assembly 10 of E`ig. 1, the compression portion 22a is
compressed radially inwardly to Eirmly hold the unwound end
portions 20b of the wire elements 20a between the protective
sleeve 26 and the split collar 24. The protective tube 16 of
the ground wire 12 extends into the greater diameter portion
62 which serves as a connecting portiGn as described later.
The connecting portion 62 has external threads 62a formed on
an outer surface thereof.
The second end assembly 10" is identical in construction
to the first end assembly 10' except that a greater diameter
portion 64 of a compression sleeve 22 is substantially longer
than the greater diameter portion 62 to serve as a housing for
accommodating an optical fiber cable-joint box 66. The
housing 64 has at its free end a further greater diameter
portion 66 having internal threads 66a and serving as a
connectiny portion. The end 12a of the ground wire 12 is
secured to the second end assembly 10" in a manner described
above for the first end asseinbly 10'.
The first and second end assemblies 10' and 10" are
coupled together by threading the connecting portion 62 into
the connecting portion 66. One end of the joint box 66 is
received in the connecting portion 62 and secured thereto by
bolts 70 passing through the connecting portion 62 into the
end of the joint box 66. In this condition, a seal ring 72
made, for example, of chloroprene rubber is interposed between
the free end of the connecting portion 66 and a peripheral
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flange 62b formed on the connecting portion 62 adjacent to the
compression portion 22a. A plurality of bolts 74 extend
through the housing 64 adjacent to the compression portion 22a
in circumferentially spaced relation and are held against the
outer surface of the joint box 66 to hold it against movement.
The two optical fiber cables 18 and 18 of the ground
wires 12 and 12 held respectively by the first and second end
assemblies 10' and lO" extend into the joint box 66 and are
joined together at their free ends to provide a joint 76.
Since the compression sleeves 22 and 22 of the first and
second end assemblies 10' and 10" are detachably connected
together through the above-mentioned threaded engagement, the
two ground wires 12 and 12 can be easily disconnected from
each other and for connection to another ground wire. In
addition, the tension of each of the two ground wires 12 and
12 does not act on the joint 76 between the two optical fiber
cables 18 and 18 since the two ground wires are lockingly held
by the respective end assemblies 10' and 10~o Therefcre,
transmission characteristics of the optical fibers are not
affected for a long period of time.
The greater diameter portions 62 and 64 of the two
compression sleeves 22 and 22 may have the same length. Also,
the compression sleeve 22 of the second end assembly 10" may
be of the same construction as the compression sleeve 22 of
the first end assembly 10' in which case a separate tubular
housing (not shown) is provided for threaded connection
between the two compression sleeves 22 and 22.
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