Improvements in or connected with Electric Cables or Conductors.
Year: 1896

page_text: This Print is in accordance with the Original Specification as it stands after
Amendment (under Section 11 of the Patents, &c., Act, 1883) as required by
the decision of the Comptroller General of the 14th day of July 1897.
Date of Application, 11th Apr., 1896
PROVISIONAL SPECIFICATION.
Improvements in or connected with Electric Cables or Conductors.
I, HENRY EDMUNDS, of 39 Victoria Street, in the City of Westminster,
Electrical Engineer, do hereby declare the nature of this invention to be as
follows:-
It is known that low capacity is most important in conductors especially when
used for telegraphic, telephonic, and the like purposes and it is known that dry
atmospheric air next the conductor aids in the obtainment of a low capacity. In
cases where the conductor has to be insulated the contact of the insulating material
with the wires increases the capacity of the conductor. Attempts have been made
to overcome this by winding paper or like insulating material spirally round the
conductor so as to leave a certain amount of space between the insulating material
and the conductor. An object of my invention is to provide a conductor so formed
that this space is largely increased and the capacity of the conductor correspond-
ingly decreased. I have further discovered that a vacuum or a rarified atmosphere
in this space gives a still lower capacity. According to my invention and to obtain
the aforesaid increased space I use wires or conductors which are of a section such
as will make the points of contact of the insulating material with the wire or
conductor as small as possible so as to give a correspondingly increased space
between the wire or conductor, and insulating material. This can be effected by
providing the wires or conductors with longitudinal grooves in them so that the
said wires or conductors are say somewhat of a star shape in cross section with
three or more rays so as to leave considerable spaces between the surface of the
wire or conductor, and the insulating material. To prevent the insulating material
from obstructing these grooves it is advisable to twist the wire or conductor thus
causing the rays to take a helical direction and making them capable of supporting
the insulating covering at the proper distance from the centre of the wire or
conductor. The wires or conductors thus formed may be covered with insulating
material of any suitable description such for example as paper with resinous or
other matter applied thereto, and then they may be stranded or cabled in the
ordinary or any suitable manner. The rays of the wires or conductors make the
only contact between the insulating material and the wire or conductor thereby
reducing the surface of contact between the wires or conductors and the insulating
material; and therefore also the capacity to a minimum. From cables having
spaces between the conductors or wires and the surrounding insulating material
and enclosed in a tube (of lead rubber or paper treated with air proof cementing
material for example) the air, and any moisture that may be present may be with-
drawn or expelled from the said spaces in any convenient way for example by an

page_text: exhauster, or by applying heat; closure being effected by plugs or otherwise so
that air and moisture cannot again enter the spaces.
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 understood that
I make no general claim to electric cables having a wire or conductor surrounded,
or wires or conductors each surrounded, by insulating material, and of such a cross
section that a space is, or spaces are, formed between the wire or conductor and
the insulating material, but I declare that what I claim is:-
Electric cables having a wire or conductor surrounded, or wires or conductors
each surrounded, by insulating material, and of such a cross section that a space is,
or spaces are, formed between the wire or conductor and the insulating material,
the air and a moisture that may be present being removed from the said space or
spaces substantially as, and for the purposes, hereinbefore described.
Dated this 11th day of January 1897
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.