U.S. patent number 3,717,719 [Application Number 05/199,465] was granted by the patent office on 1973-02-20 for coaxial cable inner conductor.
This patent grant is currently assigned to International Standard Electric Corporation. Invention is credited to Norman Stanley Bliss, Colin Francis Greening Smith.
United States Patent |
3,717,719 |
Smith , et al. |
February 20, 1973 |
COAXIAL CABLE INNER CONDUCTOR
Abstract
A laminate structure for the inner conductor of a coaxial cable
includes a thin outer copper layer and an inner aluminum layer over
a central core. The outer layer is used for signal transmission and
the inner layer for direct current, with adhesives bonding the
layers together and to the core. A dielectric layer and outer
conductor and sheath are added to complete the cable structure. Use
of copper in the inner conductor is reduced without increasing high
frequency attenuation and direct current resistance.
Inventors: |
Smith; Colin Francis Greening
(Chandlers Ford, EN), Bliss; Norman Stanley (East
Wellow, EN) |
Assignee: |
International Standard Electric
Corporation (New York, NY)
|
Family
ID: |
22737620 |
Appl.
No.: |
05/199,465 |
Filed: |
November 17, 1971 |
Current U.S.
Class: |
174/107;
174/126.2 |
Current CPC
Class: |
H01B
7/14 (20130101); H01B 11/1826 (20130101) |
Current International
Class: |
H01B
11/18 (20060101); H01B 7/14 (20060101); H01b
005/14 () |
Field of
Search: |
;174/107,16R,126C,126CP,128,131A,130,15R,36 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1,140,207 |
|
Jul 1957 |
|
FR |
|
2,011,085 |
|
Feb 1970 |
|
FR |
|
644,973 |
|
Jul 1964 |
|
BE |
|
Primary Examiner: Gilheany; Bernard A.
Assistant Examiner: Grimley; A. T.
Claims
What is claimed is:
1. A cable comprising a central strength member core and an inner
conductor tape longitudinally wrapped around said core, said inner
conductor tape including a laminate of a first outer metal layer, a
second inner metal layer and an adhesive layer between said first
and second layers, said first outer metal layer being of a material
of lower resistivity than said second inner metal layer and being
adapted for signal transmission, said first outer metal layer being
of a minimum thickness in accordance with the minimum operating
frequency of the cable, said second inner metal layer being adapted
for direct current power transmission and being of a thickness in
accordance with a predetermined voltage drop between intervals
along the length of the cable and being bonded to said core for
interlayer strength.
2. The cable as claimed in claim 1, wherein the first outer metal
layer is of copper and the second inner metal layer is of
aluminum.
3. The cable as claimed in claim 2, wherein said laminate is
wrapped around the core with the longitudinal edges
overlapping.
4. The cable as claimed in claim 2, wherein said laminate is
wrapped around the core with its longitudinal edges abutting.
5. The cable as claimed in claim 2, including an adhesive layer
bonding said second metal layer to said core, said core being of
metal.
6. The cable as claimed in claim 5, wherein said adhesive layer is
of epoxy resin.
7. The cable as claimed in claim 5, including a dielectric layer
over said outer metal layer, an outer conductor tape around said
dielectric layer and an outer insulating sheath around said outer
conductor tape.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to coaxial cables and, in particular, to
inner conductors of submarine cables.
2. Description of the Prior Art
The thickness of the inner conductor of a submarine coaxial cable,
which generally comprises a metal tape wrapped around a central
strength member core, is determined by two factors. Firstly, the
minimum operating frequency of the frequency range, the higher the
frequency the thinner the tape, and secondly the d.c. voltage drop
along the cable. The inner conductor transmits high frequency
signals and also d.c. power to feed the repeaters provided at
intervals along the length of the cable. The higher the frequencies
used, the shorter is the distance between the repeaters, and,
consequently, the lower the d.c. voltage drop required. This is
achieved by utilizing a thicker tape. The two factors governing the
thickness of the inner conductor tape are, therefore, in direct
opposition.
Another requirement for submarine coaxial cables is that it must be
possible to transfer the tension in the strength member core to the
surface of the cable, for example at the point of entry of the
cable into a repeater, by means of the adhesion between the various
layers constituting the cable.
From the signal transmission point of view the best available metal
for the inner conductor is copper. This is, however, wastefully
expensive for the transmission of d.c. power.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide an alternative
less costly more efficient construction for the inner conductor of
submarine coaxial cables.
According to the present invention there is provided a submarine
coaxial cable including a central strength member core and an inner
conductor tape longitudinally wrapped around the core, wherein the
inner conductor tape comprises a laminate of a first metal bonded
to a second metal by an adhesive, the first metal, which is
outermost when the laminate is wrapped around the core, being used
for signal transmission purposes and comprising a metal strip of a
thickness which is the minimum compatible with the minimum
operating frequency of the cable, the second metal being used for
d.c. power transmission and comprising a metal strip of a thickness
dictated by the voltage drop required between repeaters positioned
at intervals along the length of the cable, and wherein the second
metal layer is bonded to the core to transmit interlayer
strength.
BRIEF DESCRIPTION OF THE DRAWING
An embodiment of the invention will now be described with reference
to the accompanying drawing which shows a section (not to scale)
through a submarine coaxial cable employing the inventive form of
inner conductor.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An inner conductor according to the invention basically comprises a
laminate consisting of a layer of a first metal and a layer of a
second metal bonded to one another by a layer of an adhesive
substance. The first metal is suitable for high frequency signal
transmission and it is of the minimum thickness compatible with the
minimum operating frequency for which the cable is intended. The
second metal is suitable for the transmission of d.c. power for
operating the repeaters, and is of a thickness compatible with the
required voltage drop between the repeaters.
In the drawing the laminate, which comprises layers 2, 3 and 4
(layer 2 being the second metal) in the form of a strip, is
longitudinally wrapped around a central strength member core 1,
comprising either a solid rod or a stranded bunch of wires, with
the longitudinal edges of the tape abutting. The laminate is held
in position whilst dielectric 5 is extruded over it in a
conventional manner. After cooling of the dielectric, and core
shaving if necessary, an outer conductor (return) tape 7 is then
longitudinally wrapped with the overlap around the dielectric 5,
and an outer protective insulating sheath 8 extruded over it.
In order for it to be possible to transfer the tension in the
strength member core to the outer surface of the cable there must
be adhesion between the various layers constituting the cable. An
adhesion improving substance, for example an adhesive layer 6 is
thus provided between the metal layer 2 and the core 1, and another
adhesive layer 3 may also be employed between metal layers 2 and 4
of the cable.
In a preferred embodiment the first metal, that is the signal
transmitting layer 4, is copper and the second metal, that is the
d.c. power transmission layer 2, is aluminum, it being cheaper than
copper. A suitable adhesive for bonding the first and second metal
layers together is a copolymer, and a suitable adhesive for bonding
the second metal layer to the strength member core is an epoxy
resin.
Whilst the invention has been described with the laminate tape
wrapped around the core 1 with its longitudinal edges abutting, it
is possible for the laminate tape to be applied with its
longitudinal edges overlapping, or with the butting edges of the
two tape layers displaced circumferentially.
The inner conductor laminate provides a method of reducing the
inner conductor cost without increasing the cable high frequency
attenuation or increasing the inner conductor direct current
resistance.
* * * * *