Note: Descriptions are shown in the official language in which they were submitted.
CA 0220~617 1997-0~-16
A Coupler for Cables Used in Permafrost Regions
The present invention relates to a coupler with an external shrinkable casing for splices
made in armoured cable, the transmission elements of which are accommodated within a
central tube, these preferably being fibre optics cables, the area of the splice being
10 covered by a spiral cover.
DE-OS 41 26 464-A1 describes a coupler for accommodating splices made in armoured
cable, preferably in fibre optics cables. This couple is flexible in the longitudinal
direction and is resistant to tension. The armouring of the two cables that are introduced
15 into the coupler is removed as far back as the entry point into the coupler, the area of the
splice being covered by a connector spiral once the splicing operation has been
completed; this spiral is fixed on the reduced ends of the cable armouring. Cables of
this kind are particularly well suited for use in a submarine environment.
20 In contrast to the foregoing, however, in permafrost regions it is usual to use cable
couplers that are of a diameter that is three to fifteen times greater than the diameter of
the cable. The maximum size is reached if the actual splice coupler is additionally
enclosed in a protective casing that may be of cast iron, for example. However, the most
frequent type of failure in permafrost regions is in the area that forms the transition
CA 0220~617 1997-0~-16
5 between the cable and the coupler. The failures that occur are caused as a result of the following:
because of the different diameters of the cable and the cable coupler, each displays
different buoyancy characteristics on the change from thawed to frozen conditions, so
that considerable forces may come into play during the transition periods. Taken by and
large, the ground is frozen throughout the whole of the year, although the surface may
10 thaw to a depth of about 1 m. This results in the different behaviours. If the ground
thaws to a marked extent, considerable axial displacement may occur, so that under
certain circumstances the cable coupler, which is of the greater diameter, may be left
h~nging in areas that have not thawed as much, with the result that it may be subjected to
considerable tensile strain.
In order to avoid these effects to the greatest extent possible, up to now the cables have
been laid out at excessive lengths, in curves, before they enter the coupler, so that relative
movements could be evened out. Another solution is to use a coupler in which the cable
ingress point and the cable egress point are located on one side of the coupler.
20 Occasionally, cone-shaped transitions from the coupler to the cable are used. Despite
this, the possibility of failures of this kind occurring in permafrost regions cannot be ruled
out.
It is the task of the present invention to create a flexible and very slim coupler that
25 essentially displays the same characteristics as a cable, so that, from the outside, the same
CA 0220~617 1997-0~-16
5 conditions prevail with respect to the environment. This problem has been solved
according to the present invention with a coupler of the type described in the introduction
hereto, in that the splices are supported within a protective tube; in that the protective
tube is fixed, so as to be resistant to tension and compression, on the ends of the central
tube, the protective tube being of a diameter that is smaller than or equal to the inside
10 diameter of the cable armouring; in that the ends of the cable armouring, which consists
of laid-up single wires, is laid up over the protective tube, each second single wire being
cut out at the ends of the armouring, so that gaps are formed in each section of the
armouring, and then, on altern~lin~ sides, the rem~ining long single wires of each
opposite end of the armouring are so interlaced that once again a closed, laid-up
15 armouring results; and in that the spiral cover is arranged over the cable armouring that is
laid up on altern~ting sides over the protective tube.
An important advantage of the coupler according to the present invention is that it is very
slim and is at most 30 percent thicker than the cable itself. Because of the fact that a
20 spiral cover, which is arranged over the armouring that is on altern~ting sides of the cable
is used, the coupler remains flexible. For the remainder, a good electrically conductive
connection is ensured between the armouring used on both cables and the spiral cover.
This is essential, for there is a great risk of lightning in permafrost regions. The reason
for this is the poor conductivity of the ground. In addition, it is possible to attach a
25 ground line or a measurement line to the armouring or to the spiral cover, and this can
CA 0220~617 1997-0~-16
5 then be led to the outside of the cable. Such a line can be used, for example, for
insulation measurements.
The coupler according to the present invention can be used to accommodate cables that
are of round cross section, in which the transmission elements, for example fibre optics
10 conductors, are accommodated within a central tube. An inner casing is arranged over
the central tube, and the armouring, which is in the form of twisted single wires, is laid up
over this inner casing. The ends of the armouring on the cables that are to be connected
are first curved out from the inner cable casing to the required length. The inner casing is
also removed from a short end section of the cable, so that the central tube is exposed.
15 Once the assembly work has been completed, the protective tube, within which the splice
in the fibre optics conductor is located, is then fixed on this exposed end so that it is
resistant to tension and compression. The single wires of the armouring are similarly
cu~ved upwards at the end of the second cable, this area being greater by the length of the
protective tube. The inner casing is also removed in this assembly area, so that the
20 central tube of this cable is exposed. This means that the protective tube can be slid over
this assembly area during assembly work in the area of the splice, so that the area of the
splice is accessible for m~king the splice. Once the splicing operation has been
completed, the protective tube is slid back as far as the end of the central tube of the first
cable, and in this position it is fixed at both ends to the central tubes of both cables,
25 preferably by c~ pillg, which is to say by squeezing the protective tube onto the central
CA 0220~617 1997-0~-16
5 tube. This means that the area of the splice is protected. The rem~ining assembly area
of the second central tube is filled with a suitable filler substance so that the transitions to
the protective tube or to the inner casing can be made without any steps or ridges. Now
the armouring has to be restored, the ends of the armouring on both cables being
interlaced into each other on altern~ting sides. This is done by shortening a single wire of
10 the armouring, whereas the next single wire is left at its original length. This leaves gaps
in the wire in a section of the armouring, and then the single wires that have been left at
their original length are threaded into the armouring of the second cable and laid up, so
that the desired altern~ting lay-up results. This entails the advantage that continuous
armouring runs across the area of the coupler, the sections or lengths of the single wires
15 being so matched to each other that they abut axially. Next, a spiral cover is drawn over
this altern~ting lay-up of the armouring of both cables, and this ensures that the cable is
resistant to axial tension and compression. An additional effect of this spiral cover is
that is presses the laid-up single wires of the armouring of both cables fLnnly against each
other, thereby producing a good electrical contact.
The spiral cover over the cable armouring on the cable can be covered with quartz sand in
order to increase the amount of friction, at least in some areas. In order to provide
additional assurance of obtaining a good electrical transition, the application of sand in
some areas is such that good electrical transitions are formed in the unsanded areas. In
25 addition, it is possible to mix conductive material such as steel filingcinto the quartz sand,
CA 0220~617 1997-0~-16
5 so that a good transition can be created by this means. If an uncoated spiral cover is used,
electrically conductive material and quartz sand are both applied between the individual
wire turns of the armouring and the spiral cover. If the spiral cover is completely sanded,
care must be taken to ensure that after assembly, the displaced/disarranged individual
wires of the cable armouring are pressed against each other so that an electrical contact is
lo made. In addition, it is also possible to use an additional metal tube or a protective tube
that is of metal, and the armouring wires are pressed against this so as to be electrically
conductive. As has already been pointed out, the protective tube can be of metal so that
only a single element is available for forming the contact.
15 The protective tube can be if desired be provided with openings through which the area of
the splice be filled with the desired filler substance.
A reinforcing tube can be introduced into the end of the central tube of an installed cable;
this supports the central tube at the crimp point, so that compression of the central tube is
20 avoided.
After the protective tube has been f1xed over the area of the splice, the assembly area of
the second cable that is exposed is filled with filler, the half-shells being of any material,
a slit tube, a shrink sleeve, or a similar element being used for this purpose.
CA 0220~617 1997-0~-16
5 A suitable adhesive can be used at the crimp point, between the central tube and the
protective tube, so as to provide additional security.
The coupler according to the present invention can be used for ground-cable systems as
well as for connections on ground or phase cables in high-voltage systems, because these
l o require good linear conductivity. If it is used in ground-cable systems, the cable coupler
is also surrounded by an external shrinkable casing that protects it against corrosion,
although this can be dispensed with in high-voltage systems.
The present invention will be described in greater detail below on the basis of the five
15 drawings appended hereto. These drawings show the following:
Figure 1: The principles of the coupler construction;
Figure 2: The coupler in cross-section;
Figure 3: A cross-section of a fibre-optics cable with a central tube and armouring;
Figure 4: The connection of a measurement line within a coupler;
20 Figure 5: A cross-section through the connection area for a measurement line as in
Figure 4.
Figure 1 shows the construction of a cable coupler according to the present invention.
The two cables Kl and K2 (the outer cable casing is not shown) are to be connected to
25 each other in the coupler according to the present invention. These are cables that
CA 0220~617 1997-0~-16
5 incorporate a central tube ZRl or ZR2, respectively, in which the fibre-optics conductors
LWL are located. These fibre optics conductors LWL of the two cables Kl and K2 are
connected to each other through splices S. These splices S are accommodated within a
protective tube SR that is fixed at both ends on a central tube ZRl or ZR2, respectively.
It is particularly advantageous that this fixing be effected by c~ ing at the crimp point
10 K, although other methods can be used. At the two ends of the cables Kl or K2 the
individual wires of the armouring are bent up, the length being such that the individual
wires each extent across the total connection area. The inner cable casing Ml of the one
cable Kl is moved just far enough away from the central tube ZRl to make it possible to
install and fix the protective tube SR. In contrast to this, the inner cable casing M2 of the
15 cable K2 is moved far enough away in an assembly area MB that the protective tube SR
can be pushed back in the assembly phase. This means that the splice area is readily
accessible when the splice is to be completed. Once the connection has been made, the
protective tube SR is once again slid back over the splice area, until the end is against the
central tube ZRl of cable Kl. Now fixing is effected at both ends of the protective tube
20 SR, this being done by clilllpillg, for example. The protective tube SR can incorporate
openings O through which the area surrounding the splice can be filled. The assembly
area MB is now filled with a filler that can consist, for example, of a half shell, a
wrapping tape, a slotted hose, a shrink tube or a similar element. The filling is effected in
such a way that there are no ridges or steps at ends of the assembly area MB. The
25 armouring is next completed around the protective tube SR; this is achieved by
' CA 0220S617 1997-0~-16
5 interlacing the ends of the individual wires of the ends of the cable Kl and cable K2 on
alternating sides. In order to do this, it is necessary to shorten an individual wire EDKl
or EDK2, respectively, whereas the next individual wire EDLl or EDL2, respectively
(not shown herein), is left long enough to reach across the coupler. This leaves gaps
DLl, DL2 (not shown herein) between the wires of the two sections of armouring B 1,
10 B2, respectively. The same steps are taken with respect to the armouring B2 of the
second cable, so that here, too, gaps DL2 are formed between the individula fibre-optics
conductors EDL2 that similarly reach across the coupler. However, for purposes of
clarity, formation of the armouring B2 in this manner is not shown in the drawing; it is,
however, identical to that at the left-hand side of the drawing. Once the individual wires
15 of the armouring B 1, B2 have been "thinned out" in this way the armouring wires can be
laid up onto the protective tube SR, when the long individual wires of the second section
of armouring are intertwined into the gaps left between the wires of the first section of
armouring. This results in a continuous and complete "lay-up" in the area of the coupler
above the protective tube SR, this resulting in reciprocal electrical contact between the
20 sections of armouring. After production of the alternating intertwined armouring B l/B2,
a spiral cover is drawn onto this area, whereupon the armouring sections B 1 and B2 are
connected so as to be resistant to tension and compression. This also provides for the
necessary contact between the individual sections of the armouring. Finally, anti-
corrosion protection is applied over the whole arrangement, this can be in the form of a
25 shrinkable casing, for example; this is not shown in the drawing.
CA 0220.76 17 1 997 - 0.7 - 1 6
5 Figure 2 is a cross-section through a coupler according to the present invention. The
fibre-optics conductors LWL, which are spliced together here, too, are shown within the
protective tube SR. The armouring B l/B2 on alternate sides, which is formed from the
altern~ting interlacing of the individual wires of the armouring B l/B2 is shown on the
outer periphery of the protective tube SR. The spiral cover DS is then drawn onto the
10 armoured layer Bl/B2, and then this in its turn is enclosed in anti-corrosion protection in
the form of a shrinkable sleeve SU.
Figure 3 shows a cross-section of a cable of the kind that can be used for connection
inside a cable coupling. The fibre-optics conductors LWL are accommodated within a
15 central tube ZRl or ZR2. An inner casing Ml or M2 is drawn onto the central tube ZRl
or ZR2, respectively, and the armouring B 1 or B2 is wound onto this. An outer
protective casing AMl or AM2 is applied over this.
Figure 4 shows how a connection for a measurement line ML can be made to make
20 contact with the armouring, in this case on the spiral cover DS within the cable couple
according to the present invention. To this end, a single wire GDDS in the spiral cover
DS is cut out and the section is removed from the winding so that a gap is created,
through with the measurement line ML can be introduced. This measurement line ML is
fitted with a cable shoe KS, the ends of which fit under the spiral cover DS around the
25 armouring that is prepared on alternating sides, or around and electrically conductive tube
' CA 0220S617 1997-0~-16
5 or around an electrically conductive protective tube. The creates a reliable electrical
connection. The egress point for the measurement line ML can be sealed, preferably by a
protective a&esive, the seal being effected when the shrinkable cover SU is shrunk on.
Figure 5 shows the connection of a measurement line that is fitted with a cable shoe KS
10 The inner ends of this cable shoe fit between the spiral cover DS and the protective tube
SR so as to form a contact. This type of contact can, of course, be effected with an
armour on alternating sides, as has been described in the previous examples.
