Year: 1895

page_text: Date of Application, 13th May, 1895
Complete Specification Left, 13th Feb., 1896-Accepted, 14th Mar., 1896
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 Mulheim-on-the-Rhine, in the German Empire, Cable Mann-
facturers,) to be as follows
-
"
This invention relates to the insulation of electric conductors on the "air spico'
system, especially those of the type referred to in the Specification to Letters
Patent granted to me 12th April, 1892, No. 7029, and in which there are two
conductors separated from one another by an insulating medium, such as one of
more strips of paper or the like: the said invention comprising improved means for
forming the air-spaces about the conductors, for the better conservation of the air-
spaces, and for protecting the walls of the latter against crushing.
The insulating material constituting each tubular air-space may be circular in
cross-section, semicircular, triangular, quadrangular or polygonal. The angular
form is preferred, as offering considerably greater resistance to external pressure
than is presented by a cylindrical tube, thereby better conserving the au-spaces,
the triangular form presenting the additional advantage of economising space.
The strip of insulating material is laid between and about the wires, so as to enclose
them; and its edges are then bent mwards, so that they occupy a position in the
centre of the "double-barrelled " tube when completed.
If it be desired to have a metallic strip between the conductors, two insulating
strips are by preference used and tho metallic strip interposed, contact between the
wires and the metallic strip being thereby prevented. Or the metallic strip may
be laid in a special fold formed in the insulating strip. In this case, and where
contact with an earth conductor is desired the metallic strip may be arranged so as
to project a little at the side.
In the production of an insulated conductor according to this invention, a forming
tool is employed, the delivery extremity whereof corresponds in shape with that
which the insulating strip is desired to assume, and may, for example, be S-shaped,
C-shaped or W-shaped. On opposite sides of the forming tool, two ears are
provided, which serve to force the wires in the proper direction. The insulating
strip then passes through a die or folding instrument, the walls of which force it to
a-sume the desired shape, whilst the wires respectively traverse the centres of the
two compartments into which the die is divided. The die tapers towards the exit
end where each of the compartments assume a form corresponding with that desued
for each member of the duplex usulating tube. When in operation, the die
1s caused to rotate and thereby to impart a twist to the entire product. The
air-spaces or passages, each enclosing one of the conductors, thus acquire a
spiral form.
The conductors thus susulated may be provided with an outer protective sheathing
01 several conductors may oe assembled to form a cable
The insulating strip may be folded about the wires by means other than those
described, provided its edges be bent so as to lie in the interior of the duplex tube.
For instance, one edge of the stup might be laid about bath conductors so as to

page_text: cover them and be then forced between them, so as to occupy a central position in
the interior of the completed product.
Dated this 13th day of May 1895.
Dating Flectric Conductors.
I, GEORGE GATTON MELHUISHI 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 cominunication to me from the Firm of Felten &
Guilleaume, of Mulheim-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 the insulation of electric conductors on the "air-space"
system, especially those of the type referred to in the Specification to Letters
Patent granted to me 12th April, 1892, No. 7029; and in which there are two
conductors separated from one another by an insulating medium, such as one
or more strips of paper or the like; the said invention comprising improved means
for forming the air-spaces about the conductors, for the better conservation of the
air-spaces, and for protecting the walls of the latter against crushing.
In the accompanying drawings,
Figs. 1, and 3 represent in transverse section couductors insulated according to
the improved method; Fig. 1 showing circular envelopes, Fig. 2 quadrangular
envelopes, and Fig. 3 triangular envelopes.
Fig. 4 illustrates a type of construction in which the insulating material is in two
thicknesses and which a metallic strip is introduced. According to Fig. 5,
a metallic strip is also interposed, but the entire envelope is formed of a
single strip.
Figs.6 and 7 are transverse sections at the entering and delivering ends respectively
of the forming tool employed in the initial stage of the manufacture of the improved
insulated conductor, and Fig. 8 is an elevation thereof drawn to a reduced scale.
Figs 9 and 10 are views similar to Figs. 6 and 7 illustrating the entering and
delivering ends of the die which produces the finished envelope. Fig. 11 is an
elevation of this die.
Fig. 12 illustrates in transverse section a strip of insulating material folded
according to a modified method. Fige. 13, 14 and 15 illustrate, in transverse
section, similar constructions in which three and four conductors, are respectively
embodied and insulated according to the improved method.
The insulating material a constituting each tubular air-space may be circular in
cross-section, semicircular, triangular, quadrangular or polygonal. The angular
form is preferred, as offering considerably greater resistance to external pressure
than is presented by a cylindrical tube, thereby better conserving the air-spaces;
the triangular form presenting the additional advantage of economising space.
The strip of insulating material a is laid between and about the wires bb, so as to
enclose them; and its edges are bent inwards at a* a*, so that they occupy a position
in the centre of the "double-barielled " tube when completed.
If it be desired to have a metallic strip between the conductors, two insulating
stips aure by preference used as shown in Fig. 4 and the metallic strip c
interposed; contact between the wires bb and the metallic stripe being thereby
prevented. On the metallic stripe may be laid in a special fold a° formed in the
insulating stup a (see Fig. 5). In this case, and where contact with an earth
conductor 18 desired, the metallic strip e may be arranged so as to project a little at
the side and be folded against the insulating strip.

page_text: In the production of an insulated conductor according to this invention, a forming
tool of the general character illustrated in Figs. 6, 7 and 8 is employed, the
delivery extremity whereof (Fig. 7) approximately corresponds in shape with that
which the insulating strip (a, a', a) is desired to assume, and may, for example,
be S-shaped, C-shaped or W-shaped. On opposite sides of the forming tool A,
Iwo ears d d are provided, which serve to force the wires bb in the proper direction
The insulating strip a, on leaving the forming tool A, enters and passes through a
die or folding instrument B, Figs. 9, 10 and 11, the walls of which force it to
assume the shape desired for the finished product; whilst the wires bbiespectively
traverse the centres of the two compartments C C into which the die is divided.
The forming tool A and die or folding instrument 13 may be connected by any
suitable means; a sufficient interval being left between the two parts to allow the
insulating strip, in its passage from the one part to the other, to assume the
required form for entering the folding instrument without difficulty, whereby
the progress of the operations in both the forming tool and the die are carried on
uninterruptedly. The die B tapers towards the exit end where each of the
compartments C C assume a form coresponding with that desired for each member
of the double-barrelled insulating tube. When in operation, the forming tool and
the die are caused to rotate in unison, each on its centre, as an axis, and thereby to
impart a twist to the entire product. The an-spaces or passages e e, each enclosing
one of the wires bb, thus acquie a spial form.
The improved conductors insulated as herein described may be provided with an
outer protective sheathing or several such conductors may be assembled to form
a cable.
The insulating strip a may be folded about the wines bb by means other than
those described, provided its edges be bent so as to lie in the interior of the duplex
or double-barrelled tube. Referring to Fig. 12, for instance, one edge of the
strip a might be laid about both wes or conductors bb so as to cover them, and,
with the other edge, be then forced between them, so that both edges occupy
a central position in the interior of the completed product
For the purpose of illustrating the manner in which the invention 18 or may be
carried into effect, the description has for the sake of simplicity been confined to
constructions in which there are two conductors respectively arranged in two
compartments of a duplex tube It will, however, be obvious that the method of
construction employed may be extended and rendered applicable to cables comprising
three, four or more conductors respectively enclosed within three, four or more
spiral air-spaces, the folding instrument being appropriately modified; and I would
have it known that I regard such variations as obvious developments of the
Invention for which Letters Patent are now sought. Fig. 13 illustrates a mode in
which three conductors may be arranged in a triple compartment tube; whilst
Figs. 14 and 15 illustrate types in which four conductors are enclosed in
the four passages of a quadruple compartment tube produced from a single strip of
insulating material.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I claim .-
"
1. The herein described method of insulating electic conductors ou the "air-space
system, consisting in enclosing the several conductors in separate air-compartments
of a tube of non-conducting material produced from a single strip (which may be in
one or more thicknesses) and having its edges folded inwards to constitute or form
part of a central wall which divides the compartments and separates the
conductors; the tube and enclosed conductors being ultimately twisted about their
common axis with the effect that each compartment assumes the form of a spiral
passage.
2. In an electric cable, a tube, produced from a single strip (in one or more
thicknesses) of non-conducting material, the edges of the stup being turned inwards
and constituting or forming pait of a central partition which divides the tube into

page_text: compartments; the tube being, moreover, twisted about its axis so as to form spiral
air-spaces within which the conductors are enclosed, substantially as herein
described.
3. An electric cable comprising naked conductors and a tube of non-conducting
material formed with separate air compartments, the tube enclosing the several
conductors each in a separate compartment and being produced from a single strip,
of non-conducting material; the tube and the conductors being ultimately twisted
about their commion axis with the effect that each compartment assumes the form of
a spiral passage within which the conductor lies almost entirely surrounded
by air
4. An electric cable comprising two naked conductors enclosed in the two
compartments of a duplex tube produced from a single stip (in one on more
thicknesses) of non-conducting material, portions of the strip in conjunction with
a metallic strip forming a wall to separate the two conductors, and at the same time
serving to insulate the metallic strip which is inserted in the thickness of the said
wall, the whole being twisted about its common axis 80 as to convert the
compartments within which the conductors are enclosed into spiral air-spaces,
substantially as herein described.
5. The combiuntion with two naked electric conductors bb, of a twisted duplex
enclosing tube a (or a' a²) produced from a single strip (in one or more thicknesses)
of non-conducting material, the edges (ax) of the strip being turned inwards to form
a wall to separate the two conductors, substantially as set forth
6. In the manufacture of "air-space" cables, such as herein referred to, the
employment of forming and finishing tools substantially as described and arranged
to rotate in unison; the forming tool having a straight slot at its entering end which
gradually assumes an S-shape, a C-shape or a W-shape, and being provided on
opposite sides with ears for guiding the conductors; the finishing tool having two
circular compartments C, CT which gradually contract and assume a triangular or
other form corresponding with that required for the finished product.
Dated this 13th day of Febuary 1896
G. G. M. HARDINGHAM.