Improvements in Electric Cables.
Year: 1891

page_text: Date of Application, 21st Nov., 1891
Complete Specification Left, 22nd Aug., 1892-Accepted, 1st Oct., 1892
PROVISIONAL SPECIFICATION.
Improvements in Electric Cables.
I, GEORGE GATTON MELHUISH HARDINGILAM, of 191, Fleet Street, in the
City of London, Civil Engineer and Chartered Patent Agent, do hereby declare
the nature of this invention (a communication to me from the firm of Felten &
Guilleaume, of Mülheim on the Rhine, in the German Empire, Cable Manu-
facturers,) to be as follows:-
19
This invention relates to electric cables, particularly such as are intended for use
for telephonic transmission, where reduction of "capacity to the utmost degree is
highly advantageous.
A telephone cable constructed according to this invention may consist of a single
strand, but usually comprises several strands twisted together or laid up in the
ordinary manner. Each strand usually comprises several metallic conductors
twisted together, but each insulated from the other by means of a covering of paper
or other non-conducting material. In the wrapping of the paper or other non-
conducting material about the metallic conductor, it is found advantageous to leave
as much air space as possible between the conductor and the envelope.
accomplish this object, various devices have been resorted to; as, for example, by
crimping the paper or by applying the first covering strip spirally with interstices
between the convolutions.
To
According to the improved method the subject of the present invention, the wire
conductor is rolled or drawn to a rectangular or other regular or to an irregular
shape in cross section. For example, the section may be square, parallelogrammic
or triangular, in which case it is preferred to twist the wire before covering the
same. Or the section may present the appearance of a cross, or instead of four
arns there may be three." Various other forms may be employed and similar
results obtained. In either or any of these cases, the sectional form of the conductor
is of such a character as to prevent its surface being closely wrapped by the paper
or other insulating material; the result being that innumerable air spaces are
formed between the conductor and its envelope.
If it be desired to saturate the paper with a preservative or insulating composi-
tion, this operation is carried out before the wrapping is applied to the wire.
Each bundle of wires when twisted together to form a strand may be served with
a further covering of insulating material, and may then be sheathed with lead. Or
the lead sheathing, or an additional lead or other protective covering, may be
applied after the strands are laid up to form a cable.
Dated the 21st day of November 1891
G. G. M. HARDINGHAM.
COMPLETE SPECIFICATION.
Improvements in Electric Cables.
I, GEORGE GATTON MELHUISH HARDINGHAM, of 191, Fleet Street, in the
City of London, Civil Engineer and Chartered Patent Agent, do hereby declare
the nature of this invention (a communication to me from the firm of Felten &
Guilleaume, of Mülheim on the Rhine, in the German Empire, Cable Manu-
facturers,) and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statenient :-
This invention relates to electric cables, particularly such as are intended for use

page_text: for telephonic transmission, where reduction of "capacity" to the utmost degree is
highly advantageous.
The accompanying drawings represent wire conductors for use in the manufacture
of electric cables made according to this invention.
Fig. 1 is a section of a wire conductor having four concave sides.
Fig. 2 is a corresponding view of a similar conductor; the concavity of the sides
being, however, considerably increased.
Fig. 3 shews a wire conductor having three concave sides. The conductor
illustrated in Fig. 4 has four rounded ribs in Fig. 5, four ribs having flat edges;
in Fig. 6, three ribs having flat edges; and in Fig. 7, five rounded ribs.
Fig. 8 is a cross section of a rectangular conductor, which, prior to the applica-
tion of the insulating material, is twisted, as represented in Fig. 8.
Fig. 9 shews a flat conductor, and Fig. 9^ the same conductor twisted.
In Fig. 10, the conductor has three sides; Fig. 10 being a view of the same
conductor when twisted.
(These illustrations are given by way of example only, as it is obvious that many
other similar designs may be produced.)
Fig. 11 is a transverse section through a telephone cable in which wires of the
type illustrated in Fig. 1 are employed.
The cable may consist of a single strand, but usually comprises several strands.
(as shown in Fig. 11) twisted together or laid up in the ordinary manner.
Each
strand generally contains several metallic conductors a, of the character described
with reference to the drawings, twisted together, but each insulated from the other
by means of a covering b of paper or other non-conducting material.
In the wrapping of the paper or other non-conducting material about the metallic
conductor, it is found advantageous to leave as much air space as possible between
the conductor and the envelope of insulating material. To accomplish this
object, various devices have been resorted to; as, for example, the crimping of the
paper, or the application of a first covering strip arranged spirally with interstices
between the convolutions.
According to the improved method of manufacture, the subject of the present
invention, the wire conductor.a is rolled or drawn to a rectangular or other regular
or to an irregular shape in cross section. For example, the section may be square
(Figs. 8 and 84), parallelogrammic (Figs. 9 and 94), or triangular (Figs. 10 and 10*),
in which case it is preferred to twist the wire, as shewn, before covering the
same. Or, the section may present the appearance of a cross (Figs. 4 and 5), or
instead of four arms there may be three (Fig. 6). Various other forms (Figs. 1, 2, 3
and 7) may be employed and similar results obtained. In either or any of these
cases, the sectional form of the conductor is of such a character as to prevent its
surface being closely wrapped by the paper or other insulating material; the result
being that continuous or innumerable air spaces c are formed between the conductor
and its insulating envelope.
If it be intended to saturate the paper with a preservative or insulating composi-
tion, the operation should be carried out before the wrapping is applied to the
wire.
Each bundle of wires when twisted together to form a strand may be served with
a further covering of insulating material, and may then be sheathed with lead. Or,
the lead sheathing, or an additional lead or other protective covering, may be
applied after the strands are laid up to form a cable.
A wire conductor of a cross section such as shewn in the drawings is particularly
advantageous for use with an insulating envelope of crimped paper or of paper
woven in an open spiral; large air spaces, partly due to the sectional form of the
conductor and partly to the manner in which the first covering strip of insulating
material is applied, being then obtained.
Owing to the impossibility of closely wrapping the surface of a conductor formed
according to this invention, the conductor always has (even when bent to the
utmost) a part of its insulation consisting of air.

page_text: Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I would have it known that I do
not claim an electrical conductor in which a wire is wound with a cord of non-
conducting material and covered with an insulating layer, the cord serving to retain
the insulating layer at a distance from the surface of the wire, and thus to afford air
spaces between the convolutions of the same, as I am aware that such a mode of
construction is described in the Specification to Letters Patent of the United States
granted to McCracken, 8th September, 1891, No. 459,378, but what do
claim is :-
1. In the manufacture of electric cables, the employment of wire conductors
rolled or drawn to a four-sided or other suitable shape in cross section and so formed
that their surfaces cannot be closely wrapped with paper or other non-conducting
material, air spaces being thereby left between the surface of the conductors and the
insulating material, substantially as herein described.
2. In the manufacture of electric cables, the employment of wire conductors
rolled or drawn to a rectangular or other suitable shape in cross section and subse-
quently twisted so that their surfaces cannot be closely wrapped with paper or
other non-conducting material, air spaces being thereby left between the surface
of the conductors and the insulating material, substantially as herein described.
3. In an electric cable, the combination, with a wire conductor rolled or drawn to
a four-sided or other suitable shape in cross section so that its surface cannot be
closely wrapped with paper or other non-conducting material, of an insulating
covering of crimped paper, the air spaces round the conductor being due partly to
the form of the conductor and partly to the manner in which the first covering
strip of insulating material is applied, substantially as herein described.
4. In an electric cable, the combination, with a wire conductor rolled or drawn
to a four-sided or other suitable shape in cross section so that it cannot be closely
wrapped, of a strip of insulating material wound spirally on the conductor with
interstices between the convolutions, the air spaces round the conductor being due
partly to the form of the conductor and partly to the manner in which the first
covering strip is applied, substantially as herein described.
Dated the 16th day of July 1802
G. G. M. HARDINGHAM.