IMPROVEMENTS IN CONSTRUCTION OF ELECTRIC CABLES AND LINES OF ELECTRIC COMMUNICATION AND PREVENTION OF INDUCTION THEREIN
Year: 1884

page_text: I, SIDNEY FORTESCUE SHELBOURNE of 37 Wall Street, city/ New York, in the
County and State of New York, one of the United States of America, Counsellor
at Law, do hereby declare the nature of my Invention for IMPROVEMENTS IN
CONSTRUCTION OF ELECTRIC CABLES AND LINES OF ELECTRIC COMMUNICATION
AND PREVENTION OF INDUCTION THEREIN and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
"
The chief objects sought to be attained in the manufacture of electric cables, are
to provide an efficient and durable insulation and to lessen or obviate the effects of
induction in the cable conductors. The present Invention sets forth an improve-
ment in both these directions, but its principal object is to overcome the difficulties
of induction. It consists-Firstly, in an improved method of preparing and
insulating the conductors. Secondly, in providing the conductors with shields of
metal or other equivalent coatings and an outer insulation for the same so as to
control and limit inductive action between the conductors. Thirdly, as auxiliary
and necessary to the second step a method of connecting electrically the induction
shields with each other so as to form a system of induction circuits within the
cables, avoiding earth connections. Fourthly, in an improved method of assembling
or laying together the conductors composing the electric cables and; Fifthly, the
electrical combination of such conductors and their induction shields between
different sections of the cables in making up extended lines of communication.
The several improvements in the manufacture of the cables and their arrange-
ment and connection in lines of communication are as follows. Wires of the desired
size, usually of copper, are covered with one or more windings or braidings of fibre
as a part of and a basis for their insulation. The insulation is completed in the
usual manner by immersing the covered wires in liquid or melted insulating
materials, or by causing the several threads of fibre to pass through a holder of
insulating material as they are covered upon the wires, but I employ a method as
follows: The fibres in their natural condition are wound or braided upon the
wires to the required thickness. They contain minute air particles adhering more
or less tenaciously within their substance. The usual saturation with insulating

page_text: material imprisons these air particles within the fibres and the insulation remains
porous. To avoid this I place the fibre covered wires in an air-tight vessel or
chamber and produce a vacuum therein while heated. This deprives the fibres of
their adhering air particles and the insulating material is then introduced under
considerable pressure and penetrates the fibres to the metal surface of the wires and
gives them a dense and efficient insulation. The wires at this stage are passed
'through uniforming dies smoothing them to receive their induction shields or
coatings. I employ for these shields; Firstly, any metal or combination of metals
having the required strength, and ductility to form thin strips or ribbons to be
wound with overlapping edges spirally about and enclose the insulation of the
wires; but the electrical conductivity of the metal or combination of metals is an
element to be regarded in these coatings, being provided for however, within limits
of convenience, by the thickness of the strip. I prefer for these shields thin
ribbons of copper the conductivity of which is modified by percentages of iron, zinc,
tin or other elements of alloy. Copper ribbons as described, if of pure copper, have
a high conductivity and may be of a thickness of onethousandth of an inch or less,
and add but little to the diameter of the insulated conductors or the thickness of
the cables. Where, however, size in the manufacture is not an object, these strips
⚫ can be made of soft malleable iron. Secondly, I employ for counteracting induction
a coating or layer, around the insulation of the wires, of magnetic oxide of iron.
This material, known in nature as the lodestone, is reduced to an impalpable
powder by grinding and, with a suitable agglutinant, formed into a paste, is coated
upon the insulation of the wires and itself protected and enclosed by a further
wrapping of fibre and insulating material. It is well known that this form of iron
will not rust or change by elemental action and each particle being in itself a
magnet, the myriads of them about the insulation of the wires serve to divert and
thwart the passage of lines of magnetic force from an enclosed conductor to its
neighbors, while at the same time by linear conduction these magnetic particles
may serve a like function as the metal shields above described.
Whether the induction shields or coatings are of metal ribbons or of the magnetic
oxide described further windings or braidings of fibre are served upon, enclose, and
insulate them, each laterally, from that of an adjacent conductor in the cable. The
conductor with this outer winding or braiding saturated with insulating material
is uniformed by dies or rollers as before and is then ready to be made into cables.
A good waterproofing insulating material in the preparation of the conductors may
be made by digesting waste rubber in a proper solvent, as a base for a composition
with other hydro-carbons one of which, as distillate from petroleum tar, I have
heretofore described.
In the construction of cables much will depend upon the particular use intended
or the locality of that use. I therefore describe first a cable shown in Figures 6
and 7 of the Drawing composed of a single conductor with a double induction
shield, and a connection forming a complete induction circuit, for use as a submarine
cable. In such case the single copper conductor is usually composed of several
small wires twisted together. This conductor is covered with gutta percha to any
desired thickness. A light single winding of fibre then encloses the gutta percha.
Over this is wound spirally a metal induction ribbon with its edges overlapping
each other. A double braiding or winding of fibre thoroughly saturated with
insulating material is made to enclose the metal shield and over the insulation a
second metal ribbon is wound similar to the first.. Another light winding of fibre
over the second shield is succeeded by as many coatings of gutta percha or other
insulation as may be desired and the cable finished outwardly in the usual manner
with jute and steel wire armor. In this construction the two metal induction
shields are connected electrically at the ends of the cable. A cable with more than
a single conductor but each conductor cord provided with a double induction shield,
as just explained, may serve for long distance telegraphy underground, with any
modification of exterior finish and protection which may be found desirable.
The construction however of cables for ordinary telegraphic and telephonic

page_text: distances through the air or underground, will employ conductors with a single
induction shield and outer insulation as first described. Where the whole number
of conductors in the line required are few, these conductors are assembled six
about one as shown in Figure 8 and the whole heavily covered with braiding
and insulation and then provided with a close fitting and continuous jacket
of lead.
In cases where the number of conductors are eighteen and upwards, as shown in
Figure 9, the cable first commences with a strengthening core of insulated iron or
steel wire which may itself serve as a conductor. The cable is built up around
this core, each outer circle of conductors passing around it in spirals of opposite
direction to those of the circle or series next within and nearer to the core, the
number of the circles or series of conductors being limited only by convenience.
Another construction shown in Figure 10, which is preferred employs the core
of iron wire insulated to the required size. Around it are laid six strands of
conductors, each strand composed of three conductors twisted or spiralled about
each other, the alternate strands being of opposite spirals, that is, any two strands,
side by side will be of differing spirals, and their conductors therefore not parallel
with each other. In this construction the number, of strands in a circle about
the core must be an even number but the number of circles of such strands is
unlimited.
Still another modification of construction makes the strands of each circle
or series about the core to have their three conductors of spirals of the same
direction, but the reverse or opposite to those of the conductors composing the
strands of the next adjacent circle or series, inwardly or outwardly, as shown in
Figure 11 of the Drawing.
The cable comprising the conductors under one of the modifications described
then receives a covering of braided fibre and waterproofing saturation, or a gutta
percha or jute and wire armor protection or may be encased in lead according to
the use intended.
Usually where electric cables are used underground, their length, for convenience,
is limited to a few hundred feet, and extended lines of. these cables are formed by
means of chambers or boxes sunk in the ground to receive the ends of the cables
or sections composing the lines as represented in sectional Figure 12, and in which
the conductors are connected from one section to the succeeding one.
If the cables pass through the air, suitable boxes are located upon the house-
tops or within buildings to afford a convenient means to connect the sectional
parts of the line with each other.
In forming lines of communication the electrical connection of the conductors
and their induction shields at the ends of the cable sections or lines of cables will
be an important feature in avoiding induction in and between the wires. In the
one conductor submarine cable described, when we have connected electrically the
annular induction shields with each other at both ends of the cable, we have
interposed a completed metallic induction circuit between the copper conducting
core of the cable and the earth. The object here is to prevent static charge and
retardation in the conductor core of the cable.
In the cases of telephonic cables where each conductor has but a single induction
shield a corresponding metallic induction circuit will be produced if we electrically
connect, at the ends of the cable sections, or across the connecting boxes and at the
ends of the line of cables, the induction shields of any two of the conductors.
As in these cables there are many conductors, by connecting the induction shields,
in pairs, of any two together, there are formed as many distinct induction circuits
within the cable, as there are pairs of conductors, composing it. Heretofore while
the conductors of electric cables have been provided with metallic induction
coverings, those coverings have been in metallic contact with each other throughout
the whole cable and thus have afforded a multifold condenser effecting a retardation
in the conductor currents of each and all of the conductors alike. Such a result
I have prevented in the cables described, by an outer insulation of each induction

page_text: shield from every other in the cable and by making only two of the induction,
shields to be in circuit relation with each other in the same cable section. In this
case also, where there are many induction circuits, those nearer the surface of the
cable serve to protect those conductors within and nearer the centre of the cable,
both by distance and by metallic interposition, from the earth's inductive
influence.
In the Drawing Figure, 1, is a cross section of one of the conductors shown in
Figure 4, the letter a, representing in both Figures the induction shield of the
conductors, the electrical connection of which shields between any two of the
conductors in a cable being indicated in Figure 4 by the dotted lines d, d.
In Figures 2, and 3, 6 represents the coating of magnetic oxide of iron as
described and is an insulation topping or wrapping to enclose and protect it.
Figure 5 shows two strands, each of three conductors, such conductors being
spiralled about each other in opposite direction in each of the strands respectively,.
and in such relation composing layers of the cable shown in Figure 10.
Figures 6 and 7 represent respectively a longitudinal elevation and cross section
of the one conductor submarine cable described. In these Figures, e, and e¹ are
the two induction shields which are shown connected electrically in Figure 6, by
the dotted line f.
In Figure 8 the seven conductor telephone cable described, is shown, the six
surrounding conductors being of identical construction with the central
conductor g, and the double insulation and lead jacket being indicated at i, i, and k
respectively.
The strengthening core of iron or steel wire in the larger telephone cables
represented in 'Figures 9, 10, and 11, is indicated by the letter, w, in each of these
Figures.
.
Figure 12, shows in section a series of chambers or vaults sunk in the ground,
in and through which the sections composing a line of underground cables are
connected with each other. In these chambers the electrical connection of the
conductors themselves is indicated by the letter m while n represents a like
connection of their induction shields.
An enlarged view of these connections, in line between two conductors and their
shields, is indicated by the same letters respectively in Figure 13. The connection
of the induction shields, across the vaults, may be made ordinarily by copper wire
or by a thin flat strip of such metal, insulated, except at the contact ends as shown
in Figure 14.
Having now particularly described and ascertained the nature of my said
Invention and in what manner the same is to be performed, I declare that what
I claim is:-
1. An induction shield of metal or coating of magnetic oxide of iron surrounding
the insulation of an electric conductor, when composing one of a number or series
within an electric cable, in combination with an outer and enclosing insulation for
such induction shield or coating, by which it is separated laterally from electrical
contact with each and every other like induction shield in the same cable, but
connected electrically in pairs with a like shield at the ends of the cable or line of
cable sections.
2. In an electric cable composed of one or several conductors, a double metallic
induction shield for the said single or each of the several conductors, such double
shield being composed of two layers or windings of metal ribbons, the first upon
and around the insulation of the conductor, and the second, upon and around an
insulation covering the inner shield, with an outer insulation covering and
protecting such second shield, and the two shields connected together electrically
at the ends of the cable.
3. The method of laying together the conductors of electric cables to diminish
parallelism between such conductors, consisting in assemblages or layers of strands
composed of three or more.conductors spiralled about each other, such conductors
being spiralled in opposite directions in strands laterally adjacent to each other and

page_text: in several layers of such strands all the strands of each successive layer being
spiralled about the core or central line of the cable in a reverse direction to the
spirals of the preceding inner layer substantially as described.
4. The combination in an electric cable of insulated conductors, each having a
metallic induction shield, which is also surrounded with an insulation, in layers of
spiral direction about the central line or core of the cable, the spirals of each
succeeding layer being reverse to those of the preceding layer.
5. A line of electric communication of several cables regarded as sections of said
line, in combination with chambers or boxes in which the sections are connected
electrically with each other, such line being composed of cables whose conductors
have induction shields or coatings, and an outer insulation as specified, such
induction shields being connected electrically in line across such chambers or boxes,
each with a successor in line of communication, for the purpose of forming an
extended induction circuit by the electrical connection of any two such extended
induction shields at remote points in such line of cables, substantially as described.
Dated this 22nd day of April 1884.
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