Improvements in Electric Cables.
Year: 1893

page_text: Date of Application, 9th Aug., 1893
Complete Specification Left, 6th Nov., 1893-Accepted, 4th Aug., 1894
PROVISIONAL SPECIFICATION.
Improvements in Electric Cables.
A communication by SILVANUS PHILLIPS THOMPSON, F.R.S., D. Sc., of The
Technical College, Finsbury, in the County of London, but at the time of
this communication on board the Cunard Royal Mail Steamship "Campania,"
on the High Seas.
I, GEORGE CECIL DYMOND M. Inst. M.E., of The Agency for Foreign Patent
Solicitors, 6 Lord Street, Liverpool, and 6, Bank Street, Manchester both in the
County of Lancaster, and 323 High Holborn, in the County of Middlesex, Patent
Agent, do hereby declare the nature of this invention to be as follows :-
This invention relates generally to improvements in electric cables primarily for
submarine use, and specifically to cables in which there are provided metallic
return circuits, and has for its objects the production of a greater mutual induction.
than heretofore between the outgoing and returning wires of any such circuit, the
provision of a better anti-inductive protection than heretofore between adjacent
parts of different circuits in the same cable, and at the same time the provision of
an efficient protection against the attacks of the teredo and similar submarine
pests.
For this purpose, the pair of insulated copper conductors which constitute the
outgoing and return wires of one circuit is surrounded with a serving of iron in
the form of a spirally enwrapped ribbon or tape, so wrapped around the gutta-
percha or insulating material beneath as to overlap at the edges and leave no
crevice for the attack of the teredo. The iron, having a great inagnetic perme-
ability, increases the mutual induction between the wires of the pair so enclosed,
and thereby assists the rapidity of signalling through the pair. In all cases, this
inductive sheathing lies within the usual external protective sheathing of hemp
and wires. The object will be attained if the iron wrapping is in the form of a
tube such as may be made in long lengths by laying a long strip along a mandrel
and rolling it around, provided the edges slightly overlap. Or it may be made in
long semi-cylindrical tubes put together over the gutta-percha covered core, and
also slightly overlapping at their edges. The iron may be either plain or tinned;
or protected with lacquer or otherwise. By the term "iron" are included mild
steel and other similar magnetic materials. The said inductive enwrapping of iron
may, for aërial or subterranean purposes, only be of iron wire, or iron gauze,
instead of iron foil or strip or sheet, but the latter will not be an efficient protection
against the teredo for submarine purposes.
In the drawings ;-
Figure 1 represents a two-wire cable for metallic circuit, both wires A and B
being separately insulated, and are both together enclosed in the inductive
sheathing S. The insulating coating of gutta percha or similar material around
the upper conductors, and constituting therewith the core, is denoted G. The
outer serving of hemp or jute or similar material is denoted by H, and the external
protective wires of the ordinary sheathing are denoted by W.
Figure 2 gives a perspective view of the construction with the same lettering,
and shows how the inductive sheathing is wrapped over the core, in the case where
the spiral wrapping is employed, with edges preferably overlapping.
Figure 3 indicates the construction for the case of a cable containing two
separate circuits A B and C D, each of which is separately enclosed within an
inductive sheathing S.

page_text: Figure 4 indicates the way in which a simple tubular inductive sheathing may
be formed and
Figure 5 shows how the sheathing may be made of two slightly overlapping
semi-cylindrical tubes. The construction of the inductive sheathing is not,
however, confined to these special forms. It is necessary for submarine purposes
that this sheathing should constitute practically a continuous metallic coating to
baffle the teredo.
Figure shows a similar construction adapted to a 3-circuit cable having the
conductors in pairs A B, C D and E F, each of which is separately clad in an
inductive sheathing; all being enclosed within the ordinary protective sheathing.
My correspondent is aware that the ordinary iron wires used as a protective
sheathing outside ordinary cables act inductively on the wire within; and in the
particular case of cables with two wires within increase the mutual induction
between the two. Such external iron wire sheathing in the case of four-wire or
six-wire cables does not usefully increase the mutual induction, for it produces
mutual induction between the wires of one pair and those of another, giving rise
to cross-talk and false signals. Internal inductive sheathings around each separate
pair, such as herein described, not only increase the mutual induction for each pair,
but shield each pair against induction from the others.
My correspondent is also aware that internal sheathings of brass foil or strip
wrapped in spirals around the core have been used as protection against the ravages
of the teredo: such brass sheathings, not being magnetic, neither increase the
mutual induction, nor, if they had been placed separately around each pair, would
they be effective in protecting from cross-talk.
Dated this 8th day of August 1893.
WM. P. THOMPSON & Co.,
Agents for the Applicant.
A communication by SILVANUS PHILLIPS THOMPSON, F.R.S., D. Sc., of The
Technical College, Finsbury, in the County of London, but at the time of this
communication on board the Cunard Royal Mail Steamship "Campania," on
the High Seas.
I, GEORGE CECIL DYMOND M. Inst. M.E., of The Agency for Foreign Patent
Solicitors, 6 Lord Street, Liverpool and 6, Bank Street, Manchester both
in the County of Lancaster and 323 High Holborn, in the County of Middlesex,
Patent Agent do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
This invention relates generally to improvements in electric cables primarily for
submarine use, and specifically to cables in which there are provided metallic return
circuits, and has for its objects the production of a greater mutual induction than
heretofore between the outgoing and returning wires of any such circuit, the pro-
vision of a better anti-inductive protection than heretofore between adjacent parts
of different circuits in the same cable, and at the same time the provision of an
efficient protection against the attacks of the teredo and similar submarine pests.
For this purpose the pair of insulated copper conductors which constitute the
outgoing and return wires of one circuit are surrounded with a serving of iron
preferably in the form of a spirally enwrapped ribbon or tape, so wrapped around
the gutta-percha or insulating material beneath as to overlap at the edges and leave
no crevice for the attack of the teredo.. The iron having a great magnetic
permeability increases the mutual induction between the wires of the pair so

page_text: enclosed, and thereby assists the rapidity of signalling through the pair. In all
cases this inductive sheathing lies within the usual external protective sheathing of
hemp and wires. The object will be attained if the iron wrapping is in the form of
a tube such as may be made in long lengths by laying a long strip along a mandril
and rolling it around, provided the edges slightly overlap. Or it may be made in
long semi-cylindrical tubes put together over the gutta percha covered core, and
also slightly overlapping at their edges. The iron may be either plain or tinned,..
or protected with lacquer or otherwise. By the term iron are included mild steel
and other similar magnetic materials. The said inductive enwrapping of iron may
for aërial or subterranean purposes only be of iron wire, or iron gauze, instead of
iron foil or strip or sheet, but the latter will not be an efficient protection against
the teredo for submarine purposes.
In the drawings accompanying the Provisional Specification―
Figure 1 represents a two-wire cable for metallic circuit, both wires A and B.
being separately insulated, and are both together enclosed in the inductive
sheathing S. The insulating coating of gutta percha or similar material around.
the copper conductors, and constituting therewith the core, is denoted G. The
outer serving of hemp or jute or similar material is denoted by H and the external
protective wires of the ordinary sheathing are denoted by W;
Figure 2 gives a perspective view of the construction with the same lettering,
and shows how the inductive sheathing is wrapped over the core, in the case where
the spiral wrapping is employed, with edges preferably overlapping.
Figure 3 indicates the construction for the case of a cable containing two separate
circuits A B and C D, each of which is separately enclosed within an inductive
sheathing S..
Figure 4 indicates the way in which a simple tubular inductive sheathing may
formed, and
be
Figure 5 shows how the sheathing may be made of two slightly overlapping
semi-cylindrical tubes. The construction of the inductive sheathing is not however
confined to these special forms. It is necessary for submarine purposes that this.
sheathing should constitute practically a continuous metallic coating to baffle
the teredo.
Figure 6 shows a similar construction adapted to a 3-circuit cable having the
conductors in pairs AB, CD and E F, each of which is separately clad in an.
inductive sheathing, all being enclosed within the ordinary protective sheathing.
My correspondent is aware that the ordinary iron wires used as a protective
sheathing outside ordinary cables act inductively on the wire within, and in the
particular case of cables with two wires within increase the mutual induction.
between the two. Such external iron wire sheathing in the case of four-wire or
six-wire cables does not usefully increase the mutual induction, for it produce
mutual induction between the wires of one pair and those of another, giving rise
to cross-talk and false signals. Internal inductive sheathings around each separate
pair such as herein described, not only increase the mutual induction for each pair,
but shield each pair against induction from the others.
My correspondent is also aware that internal sheathings of brass foil or strip
wrapped in spirals around the core have been used as protection against the ravages
of the teredo, such brass sheathings, not being magnetic, neither increase the
mutual induction, nor, if they had been placed separately around each pair,.
would they be effective in protecting from cross-talk.
Having now particularly described and ascertained the nature of the said invention
and in what manner the same is to be performed, as communicated to me by my
correspondent, I declare that what 1 claim is-
-
1. In an electric cable containing a pair of conductors for a metallic circuit, the
use of an interior inductive sheathing consisting of magnetic material substantially
as described, enclosing both conductors of the 'pair, and lying within the exterior
protective sheathing or braiding.

page_text: 2. In a. submarine electric cable containing a pair of conductors, for a metallic
circuit, the use of an interior inductive sheathing consisting of a practically con-
tinuous sheet or overlapping strip or tube of iron or similar magnetic material,
substantially as described, the said inductive sheathing enclosing both conductors
of the pair, and lying within the usual exterior protective sheathing.
3. In submarine electric cables containing two, three or more pairs of conductors
for as many metallic circuits, the use of as many inductive sheathings substantially
as described, each separately enclosing its own pair of conductors, the whole lying
within the usual exterior protective sheathings.
Dated this 4th day of November 1893.
WM. P. THOMPSON & Co.,
Of Liverpool, Manchester, Nottingham, and London, Patent Agents.