Improvements in Electric Cables.
Year: 1892

page_text: Date of Application, 12th Apr., 1892
Complete Specification Left, 12th Jan., 1893-Accepted, 8th Apr., 1893
PROVISIONAL 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,) to be as follows:-
This invention relates to electric cables or conductors, particularly such as are
intended for use in telephonic transmission, where reduction of 'capacity' to the
utmost degree is highly advantageous; the objects of the present improvements
being to reduce the capacity by means of comparatively large air spaces, to simplify
the construction and to obtain compactness.
According to the preferred mode of carrying out this invention, two conductors
are separated by a strip of non-conducting material, which may be paper of the
required thickness. The strip of non-conducting material, with the two conductors,
disposed one on either side thereof, are then twisted together; the two conductors
being thereby insulated from one another and protected from contact with any
other body, owing to the manner in which the edges of the strip of non-conducting
material project. The twisting of the flat strip causes two spiral grooves to be
formed, one on each side of the strip; the conductors lying in these grooves. The
greater part of the insulation of the conductors consequently consists of the air
contained in the grooves.
The strand, group or core thus produced may be further protected by a layer or
layers of insulating material; for instance, by a strip of paper wound round the
twisted strip. It may also be provided with a metallic or other protective covering.
Several strands, groups or cores such as above described may be united to form
a cable in the usual way. The twist of the several strands when laid up to form a
cable may be right-hand and left-hand alternately.
The twisted insulating strip may be furnished on one or both edges with a pro-
jecting part which, during or after the twisting operation, may be laid over the
grooves or air-spaces for the purpose of closing them.
Instead of a flat strip of insulating material with a conductor on each side, a
strip cross-shaped in transverse section, having a conductor in each of its grooves,
may be employed. One or more or each of the edges of this strip may have a pro-
jecting part for covering the grooves.
Dated the 12th day of April 1892.
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 statement :-
This invention relates to electric cables or conductors for general use, and
particularly to such as are intended for employment in telephonic transmission

page_text: .2
where reduction of 'capacity' is advantageous; the objects of the present improve-
ments being to reduce the capacity by means of comparatively large air-spaces, to
simplify the construction and to obtain compactness.
In the accompanying drawings, which serve to illustrate this invention,
Fig. 1 is a transverse section of a strand at an initial stage of manufacture, and
comprising two conductors separated by a strip of non-conducting material.
Figs. 2 and 3 represent, in elevation and transverse section respectively, the same
parts after having been twisted together.
Figs. 4, 5, 6, 7 and 8 illustrate the manufacture in various forms of development,
but embodying the same invention; Figs. 5 and 6 shewing strands or cables having
four and six wires respectively, Fig. 7 a cable having eighteen wires disposed in
two concentric groups, and Fig. 8 a cable composed of seven pairs of wires or units
of the type illustrated by Fig. 2.
According to one mode of carrying out this invention, two conductors a and a'
are separated by a strip 6 of non-conducting material, preferably paper; but any
other flexible insulating material of the required thickness may be employed. The
strip of non-conducting material and the two conductors, disposed one on each side
thereof as shewn in Fig. 1, are twisted together as represented in Figs. 2 and 3;
the two conductors a and a¹ being thereby insulated from one another and protected
from contact with any other body, owing to the manner in which the edges of the
strip 6 of non-conducting material project. The twisting of the flat strip about its
own axis causes two spiral grooves to be formed by the strip, one on each side
thereof; the conductors lying securely in these grooves. The greater part of the
insulation of the conductors consequently consists of the air contained in the
grooves.
The strand, group or core, thus produced may be further protected by a layer or
layers of insulating material; for instance, by a strip of paper wound round the
twisted strip. Or the insulating strip 6 may be furnished on one or both edges
with a projecting part b' (Fig. 4), which, during or after the twisting operation,
may be laid over the grooves or air-spaces for the purpose of closing them. The
strand or group may also be provided, if desired, with a metallic or other protective
covering.
Several strands such as above described may be united and laid up in the usual
way to form a cable, as represented in Fig. 8. The direction of twist of the several
strands when laid up may be right-hand and left-hand alternately.
Instead of a flat strip of insulating material with a conductor on each side, a
strip 6* (Fig. 5) cross-shaped in transverse section and affording four longitudinal
grooves, or a strip 6" (Fig. 6) star-shaped in transverse section and affording six
(or other convenient number of) longitudinal grooves, may be twisted with the
conductors a, a', a³, etc., lying one in each of the several grooves. One or more or
each of the edges of the cross- or star-shaped strip may have projecting parts, such
as 6 (Fig. 4), for covering the grooves.
Or the cable or strand may be formed as illustrated in Fig. 7, where a central
strand, comprising six wires arranged as previously described with reference to
Fig. 6, is surrounded by a group of twelve conductors d, d', d, etc., arranged in the
longitudinal grooves of the insulating material c and twisted therewith; the
direction of twist being preferably opposed to that of the central group.
It will
be observed that the outer group is a repetition of the inner group, but on an
extended scale and having an enlarged central space. These groups may, if
desired, be surrounded by a third group of conductors, similarly arranged, insulated,
and twisted in the reverse direction to the second layer, and may ultimately be
provided with a metallic or other protective covering.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I claim :-
1. An electric cable or strand, consisting of two or more naked conductors, each.

page_text: conductor being separated from the other or others by a strip of non-conducting
material; the conductors and the non-conducting material being twisted together,
so that spiral air-spaces are formed in which the conductors lie, substantially as
herein described.
2. In an electric cable, a strip of flat or channelled non-conducting material
twisted about its own axis to form spiral air-spaces in which conductors may lie,
substantially as herein described.
3. In an electric cable, a strip of non-conducting material twisted about its own
axis to form spiral air-spaces and provided with a radially-projecting part, or parts,
which can be laid over to close the same, substantially as herein described.
4. In an electric cable, a central group and a surrounding group of conductors,
arranged substantially as described with reference to Fig. 7, and wherein each wire
lies in a separate air-space formed as a spiral groove.
5. The manufacture of cables substantially as herein described and illustrated in
the accompanying drawings.
Dated the 10th dow of Jan1002
G. G. M. HARDINGHAM.