Year: 1895

page_text: I, GEORGE HINDE NISBETT, of "Ashfield" Huyton, near Liverpool, in the
County of Lancaster Electrical Engineer, do hereby declare the nature of this
invention to be as follows:-
""
My invention has reference to the manufacture of electric cables, and more
especially to those known as air space or "dry core "cables, adapted for use
under water or under other external pressures, and more particularly for telegraph
and telephone purposes.
In order that telegraph and telephone cables may have as low an electrostatic
capacity as possible, it is the practice in insulating the copper conductor to so
arrange the insulating material as to touch the conductor only on a part of its
circumference or at intervals, and in this way the conductor is more or less insulated
and surrounded by air. The electrostatic capacity of air being lower, and the
Insulation resistance higher than that of solid insulators, a conductor is in this way
obtained having both a low electrostatic capacity, and a high insulation resistance.
Such cables are commonly made with paper for subterranean work, and then served
or covered with a sheath of lead to excludo moisture. They can, however, be
insulated with any other suitable materials provided the au space be left. Now,
the presence of the air space before mentioned, more or less surrounding the
conductor, makes the cable very liable to collapse under pressure, as for instance
that to which submarino cables are subjected (this being especially likely when
soft metals, gutta percha, or such substances are used, either for the insulating
material or the waterproof sheathing), and the object and effect of my invention is to
prevent such collapses, and this I do by the construction of cable hereinafter
described. The obvious effect of such a collapso of cable, if it did not result in
the destruction of the cable, would at least be to impair its efficiency by closing
the air space.
In a cable of any of the dry core or air space types, according to my invention,
there is provided over the insulated conductor a cover consisting of a spiral atrip of
metal or other strong substance of any suitable shape in cross section, and so
arranged and applied as not to press upon the insulated conductor within, and to be
mechanically strong enough to withstand a crushing stiain from without. Over
this spiral core a solid sheath of waterproofing material, such as lead, gutta-percha,
or other suitable substance is applied; and this sheath is supported by the spiral
cover before referred to, and therefore cannot collapse.
I may make the supporting spiral of any suitable material, and it may be of any
shape in cross section; and it is airanged in one case in the form of an open spiral
wire round or square in section; while in other cases it is in the form of a flat
strip or strips, adjacent turns overlapping one another, or not, as may be thought
desirable, or arranged in two or more layers so as to break joint.
In the manufacture of the cable, in some cases, the spiral cover is wound on over
the core of the cable; while in other cases, instead of winding the spiral over the
already insulated conductor as before mentioned, the spiral winding or cover is first
made separately, and through and into this I thread the insulated conductor.
]
In some cases prefer to make the spiral cover or winding of an insulating
material having sufficient strength; and in this case the conductor may or may not

page_text: be insulated before the spiral cover or winding is applied. In those cases, in which
the spal cover or winding is alone relied upon to insulate the conductor, the turns
of the spiral are preferably so made as to be as open as possible, consistent with
the necessary strength, and they aic so arranged that the bore of the spiral is larger
in diameter than the conductor, and that the shape of the wire used allows a
minimum of insulating material to touch the conductor. A suitable shape of cross
section for the spiral wie of insulating material would be triangular with the apex
pointing inwards. With this construction of triangular spirals the conductor will
ouly touch the insulating material at a number of points, their frequency depending
upon the "pitch at which the spiral is wound. In this way a conductor 18
completely surrounded by air betweon each turn of the spiral aud so a low capacity
and high insulation obtained.
When I employ an open spiral winding, that is to say, one in which adjacent
turns do not touch each other, in cases where necessary, another layer of a strong
flat strip is wound ou outside it, and so arranged as to prevent the external pressure
from forcing the waterproofing sheathing into the space between the turns of the
open spiral.
When a cable has more than one conductor, I apply the strengthoning spiral as
before described, over the whole of the conductors that there may be in the cable
after they have been insulated and stranded together; or, I may apply it if deemed
desirable over cach individual conductor.
I may also employ the strengthening spiral as before described for cables which
are not built upon the air space principle, but in which by reason either of the
arrangement or nature of the insulating materials employed, such strongthening to
resist external pressures is either desirable or necessary.
Datod this 5th day of October 1895.
CHEESBROUGH & ROYSTON,
15 Water Street, Liverpool, Applicant's Patent Agents.
1, GEORGE HINDE NISHETT, of "Ashfield" Huyton, near Liverpool, in the
County of Lancaster, Electrical Engineci, do hereby declare the nature of this
invention and in what manner the anno is to be performed, to be particularly
described and ascertained in and by the following statement :-
"
"
My invention has reference to the manufacture of electric oables, and more
especially to those known as "air space or "diy core cables, adapted for use
under water or under other external pressures, and more particularly for telegraph
and telephone purposes.
In order that telegraph and telephone cables may have as low an electrostatic
capacity as possible, it is the practice in insulating the copper conductor to arrange
the insulating material as to touch the conductor only on a part of its circumference
or at intervals, and in this way the conductor is more or less insulated and sui-
rounded by air. The clectrostatic capacity of air being lower, and the insulation
resistance higher, than that of solid insulators, a conductor is in this way obtained
having both a low electrostatic capacity, and a high insulation resistance. Such
cables are commonly made with paper for subterranean work, and then served or
covered with a sheath of lead to exclude moisture. They can, however, be
Insulated with any other suitable materials provided the air space be left. Now,
the presence of the air space before mentioned, more or less su rounding the
conductor, makes the cable very liable to collapse under pressure, as fun instance
space

page_text: that to which submarine cables are subjected (this being especially likely when
soft metals, gutta percha, or such substances are used, either for the insulating
material or the waterproof sheathing), and the object and effect of my invention is
to present such collapses; and this I do by the construction of cable hereinafter
described. The obvious effect of such a collapse of cable, if it did not result in the
destruction of the cable, would at least be to impair its efficiency by closing the
air space.
In a cable of any of the dry core air space types, according to my invention,
there is provided over the conductor a cover consisting of a spirel strip or strips
of metal, or other strong substance of any suitable shape in cross section, and 40
arranged and applied as not to press upon the insulated conductor within, and to
be mechanically strong enough to withstand a crushing strain from without.
Over this spiral coil a solid sheath of water proofing material, such as gutta-percha,
or other suitable substance, is applied; and this sheath is supported by the spiral
cover before referred to, and therefore cannot collapse.
Examples of my improved cables are illustrated in the accompanying drawing.
In Figures 1 and 2, (which are respectively longitudinal elevation and cross
section) I show one modification under the invention, the conductor being a single
or stranded wire. The conductor is designated a. brepresents a double covering
of ribbons or strips of metal wound spirally one upon the other, with spaces
between the adjacent couvolutions, and the outer spitals, covering the spaces
between the convolutions of the inner one. a¹ is a long spiral support carrying the
conductor and holding it in the centre of the covering b, and the air space within
it, such support being of any suitable non-conducting material. a³ is a paper
insulation between the inner surface of the metal covers b and the supporting spiral
insulation a¹. c is a waterproof covering on the metal cover b, such covering being
preferably also a non-conductor, as gutta-percha, india rubber, or like material.
dare the outside spiral coils of the cable by which it is given longitudinal strength.
18 an inner layer of jute or like material between tho coils band the insulation c,
and is another jute or like covering outside the coil.
In the cable, it will be seen, in the first place, that the conductor lies within a
tube or tunnel, and has air surrounding it entirely, except at the points or parts at
which it touches its spiral supporting insulation a': then the flat spiral metallic
strips are so arranged-(a) that the cable when completed will bend freely, and 18
well suited to marine work, and (b) that collapse or impairment of the air space
about the conductor, due to external pressure or forcing in of the outer insulation
material is prevented the coating cover the metallic covers is waterproof, and
preferably also an insulator, and prevents the entrance of water or moisture to the
cable or air space round the conductor: and the cable is covered with, and longi-
tudinal strength given it by, external wires or strands as described.
As a modification of the cable just described, in lieu of its being adapted to hold
a single conductor, it may be so made as to hold a number of conductors within
the covering b. Illustrations of modifications of air space cable are shown in the
sections given in Figures 14 1 and 1° of the drawings; but the invention is not
limited to these, or to any particular form or construction of air space cable.
In the modification shewn in Figures 3 and 4, the material next the conductor a
serves both as a support to the conductor in the air space in which it (the conductor)
lies, and as a covering by which the air space is rendered proof against collapse or
impairment by pressure from outside; that is to say, it constitutes the part of the
cable by which the air space is made, which supports the conductor in said air
space, insulates it, and provides the mosus by which the external pressure tending
to collapse the air space is resisted The pait in this case, by which these ends
nie attained, consists of spital convolutions of a suitable non-conducting material
of triangular or equivalent form, the outer edges of which touch or nearly touch
each other, as shewn, while the spaces, or some of thom, of the convolutions stand
apart and come next to the conductor and serve to carry it. This spiral covering b

page_text: may consist of ebonite, or any other convenient, and suitable analogous material.
Outside this covering, the cover c of gutta-percha, or other suitable material, by
which the air space is rendered waterproof, is provided And again outside this
nie the longitudinal strengthening wires d, and coverings of juto of the like. The
conductor a, as will be seen, will only touch its insulating supporting spirals 6 at a
number of points in the direction of its length, their frequency depending upon the
size and shape of the triangula spials, and upon the pitch at which the spirals
are wound.
Another modification under my invention is shewn in Figures 5 and 6. In this
case the insulation support of the conductor within the cable, and the provision of
the means of resistance against collapse or impaument due to outside pressure, is
afforded partly by triangular spiral supports al of insulating material, and partly
by a flat metal spiral ribbon cover b, the convolutions of which are a certain
distance apart, and provide flexibility in the cable. The metal spirals and the
internal triangular spirals al are so disposed in relation to each other that the
opening between the convolutions of the cover b staud over the outside or backs of
the spirals a', and so these openings nie closed. Outside these parts, the water-
proofing coating is applied; and again outside this waterproof coating, the
strengthening outside wires and coverings, as in the cables above described, are
provided.
In cables of the air space type where more than one conductor 18 employed, the
whole of the conductors may be insulated and stranded together and placed or
inclosed within the coveting giving it its power to prevent collapse, and forming
the air space; or, the conductors may be separate, and kept apart within the air
space of the cable with the protective covering suitounding them.
In the manufacture of the cable, in some cases, the spiral protecting cover is
wound on over the core of the cable; while in other cases it may be preferable
that the protective covering be made firet, and the conductor or conductors
threaded through it.
In the apparatus of the invention thus far described, its use in connection only
with cables built on the air space principle has been set forth; but it is to be
stated it may be usefully applied in cables other than these, e, in cables in which
by renson either of the arrangement, or of the nature of the insulating materials
employed, such strengthening to resist or construction of external pressures is
either desirable or necessary.
Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed, I declare that what I
alaim 18-
1. A submarine or analogous electric cable having a conductor or conductors
within same surrounded by a medium which is incapable of resisting substantial
external pressures; a winding or windings of material such as specified around
such medium by which the normal condition of such surrounding medium is
preserved against external pressure, and its derangement prevented; and a water-
proof covering outside such protective covering all substantially as and for the
purposes herein set forth.
2. The air space electric cable set forth with reference to Figures 1 and 2,
comprising a conductor a; an insulating support; motallic spial ribbons
enclosing the air space round said conductor, the waterproofing covering e; and
external strengthoning covering or coils: arranged as and for the purposes set
forth.
3. The air space electric cable set forth with 1oference to Figures 3 and 4,
comprising a conductor a, the combined insulating and anti-collapsing spiral
covering b; the waterproof covering c; and external strengthening coverings or
coils ariauged as and for the purposes set forth.
4. The air space electic cable set forth with reference to Figures 5 and 6,

page_text: comprising a conductor a; insulating and anti-collapsing spiral covering b; the
waterproof covering o; and external strengthening coverings or coils: arranged
as aud for the purposes set forth.
Dated this 6th day of July 1896.
CHEESBROUGH & ROYSTON,
15 Water Street, Liverpool, Applicant's Patent Agents.