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Патент USA US3095653

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July 2, 1963
E. |. COOKE ETAL
3,095,643
METHOD OF MANUFACTURING SUBMARINE CABLES
Filed Feb. 23, 1960
H6: /
C TAPE
B-POLYTHENE SHEATH'
PREGNATED WITH C0RR0S|ON_7
INHIBITOR, E. 6., BARIUM CHROMATE
ALUMINIUM TAPES-6
POLYTHENE INSULATION~5
COPPER TAPE FORMED
INTO A TUBE OVER THE
HEART AND THEN MECH—
ANICALLY REDUCED IN
DIAMETER.
IN VEA/TORS.
E?u/AR? ZINE/{AM chrrk'
FAME! AxTHu/a Don/ELAN
United States Patent 0 "
1
3,095,643
METHOD OF MANUFACTURING SUBMARINE
CABLES
Edward Ingram Cooke, London, and James Arthur Done
lan, Harrow, England, assignors to Submarine Cables
Limited and Pirelli General Cable Works Limited, both
31,095,643
Eatented July 2, 1963
2
by means of inert gas shielded electric arc welding, and
the tape so welded is reduced in diameter mechanically
to connect the conductor and the heart together and there
by to inhibit relative movement between them. ‘Inert gas
shielded electric arc welding is wholly suitable for the
welding process because the speed and control of Welding
of London, England
obtainable does not cause a stranded high tensile heart
Filed Feb. 23, 1960, Ser. No. 10,311
to be heated suiiiciently for it appreciably to lose any
Claims ‘priority, application Great Britain Feb. 27, 1959
tensile strength.
5 Claims. (Cl. 29-460)
10
By providing a continuous seam weld along the longi
This invention relates to submarine cables and is more
particularly concerned with submarine coaxial cables
having insulation extruded over an inner conductor which
surrounds a stranded metal heater. Submarine cables of
tudinal edges of the folded metal tape, the air in the inter
stices of the stranded heart is prevented from escaping
when expanded by the heating e?ect of extrusion, and
thereby air bubbles in the extruded insulation are avoided.
The conductor may be welded about the stranded heart
this nature are described in British patent speci?cations
as an over-size tube, and subsequently the tube contain
Nos. 703,782 and 740,647 and in an article entitled “A
ing the stranded heart drawn through a die or reducing
New Deep-Sea Coaxial Cable” contained in the Journal
rollers so that the tube is reduced in its cross-sectional di
of The ‘Institution of Electrical Engineers, volume 2 (new
series), pages 572 to 573, October 1956. The above 20 mensions to ?t closely the stranded heart, the grip be
tween the conductor and the stranded heart being there
mentioned references described an armourless submarine
by improved. Additionally, the oversize tube reduces
coaxial cable having an inner conductor which surrounds
risk of damage to the heart during welding.
a stranded heart of high tensile steel but the invention
In a preferred method in accordance with the inven
may also be used for the armoured shore end portions of
tion
of electrically Welding an inner conductor of copper
such cables in which the stranded heart is of steel wires
tape about the stranded heart, which method will now be
to simulate the electrical characteristics of the deep-sea
described by way of example with reference to the ac
portion of the cable.
companying drawings in which FIGURE 1 shows a per
It has already been proposed to use, as an inner con
spective cut back view of a cable and FIGURE 2 shows
ductor for the above mentioned cables, a copper tape
longitudinally folded about the stranded metal heart with 30 a cross section through a swaged steel heart, and FIG
URE v3 shows a view similar to FIGURE 1 embodying a
the longitudinal edges of the tape either abutting, or
modi?ed form of the invention, the argon-arc method of
locked in a box-seam. Further, experiments have been
electric welding is used and a single electrode torch hav
carried outwith the edges overlapping with or without
ing a vertically adjustable electrode fed by direct current
the overlap soldered. The present invention is intended
is provided for welding purposes. One convenient con
to overcome certain of the disadvantages associated with
struction of such a welding torch is described in the com
these prior constructions which disadvantages are enu
plete speci?cation of British Patent No. 722,707.
merated below.
Referring now to FIGURE 1 copper tape of between
An inner conductor comprising a longitudinally folded
0.007 to 0.030 inch thick preferably .015 inch thick, is
tape with its longitudinal edges abutting is easily dam
aged when the cable is bent. Furthermore, a longitudinal 4.0 fed horizontally from a reel to straightening rolls which
also shear the longitudinal edges to provide clean edges
folded tape with its edges abutting cannot grip the heart
for
the argon-arc welding process. The copper tape is
and when it is required to transmit any external grip on
sheared to a width which will provide a folded tube 2
the cable to the heart, there is a danger that slip may
which is greater than that required for a close ?tting tube
occur between the inner conductor and the stranded heart.
around a stranded metal wire heart ‘1. . The copper tape
Also, since the abutting edges are not sealed, it is neces
with its edges sheared is passed between forming rolls for
sary to pass the inner conductor through a vacuum cham—
folding it round the torsionally balanced stranded metal
ber immediately before the insulation is extruded over it.
wire heart comprising four 0.092 inch diameter wires
Although the vacuum removes a large portion of the air
and twenty-six 0.038 inch diameter wires as disclosed in
contained in the interstices of the stranded heart, in cer
the Journal of the Institution of Electrical Engineers, vol
tain cases, the heating effect of the extruded insulation
ume 2 (new series) pages 572 to 573, October 1956,
causes the residual air in the interstices to expand, thus
which may be fed vertically downwards from a supply
producing air bubbles in the extruded insulation. Not
drum and guided so as to ‘feed horizontally into the fold
only does this complicate the extrusion process but it can
ing copper tape. The copper tape when folded into the
also slow down the rate of extrusion of the insulation.
tube 2 completely encloses the stranded metal heart 1
The same disadvantage applies in lesser degree to the
which may be guided so as to press to the side of the
“box-seamed” tape, since the seam is not air tight.
copper tube 2 remote from the butting edges. The but
If an inner conductor is used comprising a longitu—
ting edges of the copper tape are then argon-arc welded
dinally folded copper tape with overlapping edges sol
together
in a continuous seam as by a continuous weld
dered together, it is di?’icult to obtain a tight grip upon
the stranded heart in order that a grip upon the external 60 3 as shown between I——I and II——II, or alternatively as
a stitch weld as shown at 4 between 11-11 and III—III,
surface of the cable may be transmitted to the stranded
and
the copper tube 2 thus welded is passed between one
heart when it is composed of high tensile steel strands.
Furthermore the soldered overlap may be damaged when
the cable is bent.
or more reducing dies or sets of rolls to compress it
tightly upon the stranded metal heart 1. The outer diam
eter
of the argon-arc welded inner conductor is then ap
According to the present invention, a method of man 65 proximately 0.33 inch ‘diameter and polythene insulation
ufacturing a submarine cable having insulation extruded
5 is extruded over it with an outside diameter of ap
over a conductor which surrounds a stranded metal heart,
proximately 1.00 inch. The outer conductor 6 is com
is characterized in that a longitudinally extending tape of
posed of six 0.50 inch wide by 0.018 inch thick aluminium
metal, such as copper, of high electrical conductivity is
tapes and is applied with a long lay to the extruded insu—
folded or applied with its edges abutting around a tor 70 lation 5, a fabric tape 7 impregnated with a corrosion
sionally balanced stranded metal heart, the abutting edges
of the tape are butt welded together in a continuous seam
inhibitor, for example barium chromate, being applied
over the aluminium tapes 6. A polythene outer sheath
3,095,643
ll.
3
8 of approximately ‘0.11 inch thick is extruded over the
tape giving the cable an overall diameter of approximate
ly 1.3 inches.
factor of safety because the stress concentration at the
In some instances it may be desirable to provide pro
tection for the stranded metal wire heart or any insulation
which may surround it, against the heating due to weld
ing the inner conductor. This may be done by includ
which, if the outer return conductor is formed of helical
tapes, results in less cross-talk between turns and layers
when coiled in tanks in the factory or cable ship.
corners of the box-seam are no longer present.
(2) Better concentricity of the inner conductor,
(3) Complete sealing of the joined edges of the con- .
ing a copper foil 9 (see FIGURE 3) between the stranded
ductor.
metal wire heart and the copper tape before the latter is
(4) Better mechanical characteristics when the cable is
folded round it.
10 bent.
In an alternative construction of a submarine cable the
A further advantage of the method ‘according to the
outer conductor may be of copper instead of aluminium;
present invention is that because a torsionally balanced
additionally it may comprise a longitudinally folded cop
stranded metal heart is used, the inner conductor does not
per or aluminium tape having either abutted or over
have to be of suflicient strength to limit or counteract any
lapped edges. If a copper outer conductor is used the 15 torsion produced by the heart and can, therefore, be rela
corrosion inhibitor, with which the fabric '7 is impreg
tively thin-thereby saving material.
‘
nated, may be omitted.
We claim:
If desired the outer sheath of polythene may be re
1. A method of manufacturing a submarine cable, said
placed by an outer sheath of a plastic material having a
method comprising the steps of applying a longitudinally
greater resistance to mechanical damage, such as poly 20 extending tape of copper of high electrical conductivity
propylene.
with its edges abutting around a torsionally balanced
If it is found that the stranded metal wire heart is
stranded metal heart, butt welding the abutting edges of
liable to “bird-caging” even when an over-size copper
the tape together in a continuous impermeable seam by
tube is electrically welded about it, this may be alleviated
means of inert-gas shielded electric arc welding so as to
by passing the stranded metal wire heart through a die, 25 form an ensheathing tube, reducing the diameter of said
which slightly reduces it in diameter by swaging, before
it enters the fold in the copper tape. A cross section of
a metal heart which has been swaged is shown in FIG
URE 2 where it can be seen that the strands are so de
formed as to substantially ?ll the cross-sectional area of
the heart. (To “bird cage” means to have an excessive
tendency for the strands to bow radially outwards when
the stranded heart is subjected to longitudinal com
pression.)
An electrically welded inner conductor for a submarine
coaxial cable manufactured in accordance with the pres
ent invention has the following advantages over known
constructions :
(1) An increased grip is provided between the inner
conductor land'the stranded metal Wire heart. Thus, the
inner conductor and heart are mechanically connected to
gether to inhibit movement between them.
(2) The inner conductor is uniform in cross-section
and it therefore is less likely to be damaged during
bending.
tube so as to tightly compress said tube on the heart and
thus mechanically connect the conductor and the heart
together and thereby to inhibit relative movement be
tween them, and thereafter heat extruding a plastic sheath
over said tube and in contact therewith.
2. A method as set ‘forth in claim -1 which is further
characterized in that the tape is of a predetermined width
so as loosely to surround the core and after welding is
drawn down to eifect the mechanical connection between
the heart and the conductor.
3. A method as set forth in claim 1 which includes the
further step of ‘drawing down the tape into intimate con
tact with the heart.
4. A method as set forth in claim 1 which includes
the further step of providing a metal foil between the
tape and the heart.
5. A method as set forth in claim 1 which includes
the further step of initially completely swaging the
stranded heart.
I
(3) Good electrical conductivity is provided across the
electrical weld.
The method of locking the longitudinal edges of the
copper tape together, which is at present in use, is by
867,659
Hoopes et al. __________ __ Oct. 8, 1907
means of a box-seam and an electrically welded inner
2,308,669‘
Beed ________________ __ Jan. 19, 1943
703,782
1,182,997
Great Britain ________ __ Feb. 10‘, 1954
France ______________ __ Jan. 19', 1959
References Cited in the ?le of this patent
UNITED STATES PATENTS
conductor has the following advantages over this method:
(1) The elimination of the protuberance results in:
(a) A reduction ofapproximately 3% in the capacitance
and a corresponding increase in the inductance and 55
therefore a reduction of approximately 3% in the at
tentuation of the cable.
(b) A greater breakdown voltage and therefore increased
FOREIGN PATENTS
OTHER REFERENCES
Post Of?ce Electrical Engineering Journal (British
publication), vol. 50‘, April 1957, pages 7 and 8.
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