Year: 1898

page_text: We, GERALD CARLYLE ALLINGHAM and WILLIAM FENNELL, both of 27, Bower
Road, Victoria Park, London, N.E., Electrical Engineers, do hereby declare the
nature of this invention to be as follows:-
This invention relates to a new form of twin electric cable, and consists in making
each of the two conductors in the cable in the form of a flat strip of a rectangular
or oblong cross section. The conductors may be formed of solid strips the edges
of which may be rounded or chamfered or bevelled or not, or of strands either of
circular or of rectangular or of other convenient cross section of equal
area and of similar form laid side by side SO that the centres of
the cross sections in any plane of the strands comprising one of the conductors"
lie in one straight line and the centres of the cross sections of the strands com-
prising the other conductor lie in another straight line parallel to the first.
We prefer in most cases to construct our cables with three circular strands of
equal diameter in each conductor, but we can also construct them with two, four,
or a greater number of strands in each conductor.
We cover each conductor with insulating material by any of the well-known pro-
cesses, we then twist the two conductors together and give the cable so formed a
further coating of insulating material if necessary and then apply a protective
covering, which we usually prefer to make of lead. When the conductors are
composed of strands we pass the strands through a die of the required rectangular
or oblong form, when covering them with the insulating material.
Conductors of the form described are especially adapted for twin cables of small
size and of circular cross-section, for interior electric light wiring, and for service
lines and for arc lamp leads or the like, as they are simple and cheap to manu-
facture, small in size, and easy to splice or joint and to connect to terminals.
1
T
1000
'
G. C. ALLINGHAM.
W. FENNELL.
We, GERALD CARLYLE ALLINGHAM and WILLIAM FENNELL, both of Harrow
Green, Leytonstone, in the County of Essex, late of 27, Bower Road, Victoria Park,
Electrical Engineers, do hereby declare the nature of this invention 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 improvements in electric cables and has particular

page_text: reference to twin cables, that is, cables which comprise two insulated conductors,
one forming a lead and the other a return.
Cables made according to this invention comprise two cores, each core being made
up of a single row of conductors of circular cross section and equal size, covered
with a suitable insulating material such as india rubber, paper, jute, or the like.
The conductors forming, the core are held in position by dies, rollers or
equivalents, while the insulating material is placed around them. Two cores thus
formed are placed together with their major cross sectional dimensions parallel
to one another and a protective covering is applied to the cable thus formed. It
is preferable to put a slight twist in the cable before applying the protective cover-
ing in order that the cores shall maintain their relative positions during subsequent
operations.
If desired, a further insulating covering, common to the two cores may be placed
around them before the protective covering is applied., When the insulation is
of a non-hygroscopic character, such as vulcanised india rubber, the cable, if for
drawing into conduits or pipes, is usually simply protected by tape or braid
saturated with preservative compound, but in other cases or where the cable is
to be placed underground or in similar situations, a lead covering is generally
provided. Sheathing or armour of the usual type may also be provided if desired.
In order that the finished cable shall be approximately circular in cross section
and as small as possible, each core is made so that its major cross sectional
dimension is approximately equal to twice the minor cross sectional dimension,
and thus when, the two cores are placed side by side their shape in cross-section
approximates to a square.
In the accompanying drawings,
Figure 1 shows in side elevation a portion of one form of twin cable according
to this invention, parts of the various coverings being removed for the sake of
clearness.
Figure 2 is a transverse section on the line 2-2 of Figure 1.
Like letters indicate like parts throughout the drawings.
A are circular conductors of equal size, three being placed in a single row with
adjacent conductors in contact with each other. Each row of three conductors is
covered with insulating material as at B, thus forming an insulated core.
The two insulated cores are placed side by side so that their major cross sectional
dimensions are parallel to each other, and the cable thus formed is slightly
twisted in order to maintain the relative position of the two cores.
C is an insulating covering placed around the two cores, and D is a protective
covering of lead surrounding the whole.
The space E may if desired, be filled with packing, but it is found in practice
that with small cables, this space does not exist, being filled up by the spreading
of the insulation during the covering processes.
The "lay" or twist is exaggerated in the drawings for the sake of clearness.
In order that the major cross-sectional dimension L of each core shall be
approximately equal to twice the minor cross-sectional dimension 1, it is necessary
when the core comprises three conductors, that the diameter of each of the con-
ductors A shall be equal to twice the radial thickness of the insulation B. When
the core is formed of four conductors the diameter of each conductor A should be
equal to the radial thickness of the insulation B.
The primary consideration in designing a cable is usually the thickness of
insulation required, and this of course depends upon various conditions such as
the voltage employed and the nature of the insulating material. It will be seen that
for cables having equal total area of conductors the thicker the insulation specified,
the greater will be the number of conductors forming each core in order that the
above conditions as to the relative dimensions of the core may be fulfilled and a
cable produced having a minimum amount of waste space.
Cables made according to this invention occupy a small space for the area of
the conductors which they contain and are very flexible. The conductors being

page_text: circular in cross section may be chosen from stock sizes of wire thus obviating the
necessity of specially drawn or rolled conductors. Further, the conductors being
of equal size are more easily and neatly joined into terminals or to other conductors
than is possible when wires of unequal diameter are used.
It is not essential that the cores should be separately insulated, the two rows of
conductors may if desired be held in position and insulated by material common
to both.
Having now particularly described and ascertained the nature of this said
invention and in what manner the same is to be performed, we declare that what
we claim is:-
1. A twin electric cable in which each core is made up of a single row of con-
ductors of circular cross section and equal size arranged substantially as described.
2. In a twin electric cable of the kind claimed in Claim 1, the combination of
two cores each having its major cross sectional dimension approximately equal to
twice the minor cross-sectional dimension substantially as described.
3. The twin electric cable substantially as described and illustrated in the
accompanying drawings.
Dated this 14th dow of October 1900
GERALD CARLYLE ALLINGHAM,
WILLIAM FENNELL,
Boult & Wade,
Agents for the Applicants.