Improvements in Electric Conductors or Cables.
Year: 1890

page_text: COMPLETE SPECIFICATION.
[Communicated from abroad by JOHN ARNOLD BARRETT, of 189, Montague Street,
Brooklyn, New York, United States of America, Electrician.]
Improvements in Electric Conductors or Cables.
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co., Patent Agents,
Southampton Buildings, in the County of Middlesex, 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 the manufacture of insulated electrical conductors, being
more particularly designed for application to that class which may be termed lead
covered cables.
In cables of this character it is important to separate the several conductors by a
dielectric of the lowest practicable specific inductive capacity. The separating medium
in such cables is usually of a composite character and though various methods of
manufacture have been proposed the following method is the most commonly practised.
commercially. The wires which are to form the conductors are severally covered to
a prescribed thickness with a wrapping or braid or web of cotton or jute or other
similar material. These covered conductors are then bunched together in any desired
number or arrangement, and bound together by a fibrous or meshed wrapping of
any convenient nature or material to form the so-called core of the cable.
The core thus constructed is usually placed in a hot air chamber for the purpose
of expelling the moisture present in the fibrous material. The dry core is then
commonly treated to a penetrating bath of heated wax or gum or oil, or to heated
compounds of wax, resin, asphalt or similar materials with oil, for the purpose of
filling the fibrous structure of the core where applied with such a material as will to
some degree remove its hygroscopic nature and seal it against the subsequent
absorption of moisture.
Finally the cable core having been prepared and treated with the sealing material
substantially as above described is furnished with a protecting covering as nearly as
possible impervious to water in order to preserve the insulating properties of the core;
and of such a chemical and mechanical nature as to resist decay and damage from
the external conditions to which it may be subjected. At present lead pipe is.
extensively employed as the external imperious protecting sheath.
Various incidental modifications of this process may exist but the product in all
cases is essentially the same. The non-conducting material which separates the
several conductors is composed chiefly of the fibrous covering first placed upon the
wires and the so-called insulating compound or sealing material which has by any of
several well known methods been caused to penetrate and fill up to a great extent
the pores and interstitial spaces throughout the fibrous material.
I proceed in the construction of a cable according to my invention upon different
principles from the foregoing. It is well known that dry air is very much lower in
specific inductive capacity than any of the solids which are generally used as the
sealing material in this class of cables, and if the air which is already enclosed can
be retained and not expelled by the sealing material in applying the latter, the
desired reduction in specific inductive capacity will be secured.
There are well known instances where to meet special conditions cables have been
constructed and used, in which dry cotton-insulated cores have been placed in a
sheath of lead pipe without other filling than the air which surrounds and penetrates
the core, the sealing material being left entirely absent. In these cases the inductive
capacity between the wires is found to be low, But such cores are found in practice

page_text: to be generally unserviceable, chiefly from the fact that any defect or opening in
the protecting sheath even of a very minute character, renders a considerable length
of the core liable to the intrusion of moisture and the consequent loss of insulating
properties.
It has also been proposed to introduce at intervals in the lead pipe containing
such dry cores, plugs or lengths of sealing material for the purpose of confining any
damage from access of water or moisture within the limits of the section of cable
between two adjacent plugs of sealing material.
I have devised a form of electrical conductor in which a considerable quantity.of
air is retained in the insulating spaces at the same time that the sealing material is
applied throughout the entire length of the cable.
Accordingly my invention consists primarily in an electrical conductor so covered
with a fibrous or other separating medium as to afford in the covering numerous
interstitial air spaces, around which is placed a non-conducting envelope capable of
confining the air in such spaces and of retarding or preventing the application of
the sealing material from driving out the air originally enclosed within the insulating
structure. The invention further consists in two or more wires made up in a group,
each wire being covered with fibrous or meshed material containing air with a non-
conducting envelope surrounding the group capable of retarding or preventing the
expulsion of the air by the sealing material when it is applied in the manufacture of
the cable. The invention further consists in a cable in which are assembled the
individual conductors or groups of conductors independently covered as above
described, by a fibrous meshed or honeycombed covering surrounded by a non-
conducting envelope, whether or not an external armor of lead or other material
is employed.
In the drawings which form part of this specification Figs. 1, 2 and 3 are views
illustrating the invention in several modifications;
Fig. 4 is a transverse section of one modification ;
Fig. 5 is a transverse section of a bunched cable showing a number of separate
wires, each insulated according to my invention, and all laid into a bunch and an
external covering of moisture-proof material;
Fig. 6 is a section showing a pair of air-spaced wires having a single moisture-
proof sheath j
Fig. 7 is a transverse section showing a cable composed of a number of pairs of
wires, each pair being arranged and insulated as shown at Fig. 6.
In Figs. 1, 2 and 3, I have shown common methods by which the conductor may
be surrounded by fibrous or meshed material in such manner as to embody with it a
considerable proportion of air, together with a non-conducting envelope, capable of
preventing the sealing material, when applied, from expelling the air contained
within the fibrous or meshed structure. In Fig. 1, a is the conductor, b and bare.
double layers of the fibrous material wrapped thereon, and c is a spirally applied
tape of non-conducting material of such a nature, paper for instance, as to prevent or
retard the free penetration of the sealing material. In Fig. 2 the conductor a has
the braided covering b surrounded by the above described tape of non-conducting
material c. In Fig. 3 a single wrapping b is used.
In the transverse section Fig. 4 the conductor a is shown surrounded by a
covering 6 of fibrous or meshed material, and enclosed by an envelope of non-
conducting material to which the sealing material has been applied externally..
Fig. 5 shows a complete_bunched_cable_having_the-conductors-a,-each-insulated-in-
accordance with the above description by the fibrous air-containing covering b
enclosed in envelope c, and the whole enclosed in the lead sheath d, between which
and the cable structure is placed the filling of sealing material e, so that the latter
surrounds individually all the wires of the core without penetrating into the fibrous
covering of each conductor.
Fig. 6 shows a group_of_two_wires_a, each having the fibrous air-containing

page_text: covering b, and the envelope c of non-conducting material surrounding the group to
which the sealing material may be applied.
Fig. 7 shows a telephone cable made up of groups, each composed of two wires,
arranged as described with reference to Fig. 6.
In carrying my invention into practical effect I prefer first to serve the wire with
a hard cord strip or string of non-conducting material preferably of low hygroscopic
quality, in whatever manner and to whatever thickness may be required for the
particular purpose to which the conductor is to be devoted, provided only that a
sufficient volume of air is embodied with this covering, and I wrap about this one or
more thicknesses of a close covering, such, for instance, as paper, so as to give the
whole structure the requisite smoothness and roundness, and to prevent the sealing
material, such as oil, wax, gum, rubber, gutta percha or other material or compound,
from penetrating in such a manner as to drive out the air from the interior spaces,
when such substances are applied to the structure for the purpose of insulating and
protecting the interior from the admission of moisture.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, as communicated to me by
my foreign correspondent I declare that what I claim is :—
1. In electric cables of that class in which the conductor is surrounded by a non-
conducting covering and a sealing or filling material, the combination of an electrical
conductor, a fibrous or meshed air-containing covering for the same, a surrounding
non-conducting envelope adapted to confine the contained air, and a sealing material
applied to the exterior of the envelope.
2. In electric cables of that class in which the conductor is surrounded by a non-
conducting covering and a sealing or filling material, the combination of two or more
electrical conductors each surrounded by a fibrous or meshed air-containing covering,
a non-conducting envelope surrounding the group of such wires and adapted to
confine the contained air, and a sealing material applied to the exterior of the
envelope.
3. In electric cables of that class in which the conductor is surrounded by a non-
conducting covering and a sealing or filling material, a cable consisting of a group
of electrical conductors, each of which is surrounded, first, by a fibrous or meshed
air-containing covering, and second, by a non-conducting envelope adapted to confine
the contained air, and a sealing material applied to the exterior of each one of the
group constituting the cable.
4. In electric cables of that class in which the conductor is surrounded by a non-
conducting, covering and a sealing or filling material, a cable composed of separate
groups, each group containing two or more wires, each wire surrounded by a fibrous
or meshed air-containing covering, and each group of wires surrounded by a non-
conducting envelope adapted to confine the contained air, and a sealing material
applied to the exterior of each group of wires constituting the cable.
5. In electric cables of that class in which the conductor is surrounded by a non-
conducting covering and a sealing or filling material, the combination of a group of
electrical conductors, each surrounded by a fibrous or meshed air-containing covering,
a non-conducting envelope surrounding the group of such wires and adapted to
confine the contained air, a sealing material applied to the exterior of the envelope,
and a surrounding sheath of lead.
6. In electric cables of that class in which the conductor is surrounded by a non-
conducting covering and a sealing or filling material, a cable consisting of a group of
electrical conductors, each of which is surrounded, first, by a fibrous or meshed air-
containing covering, and second, by a non-conducting envelope adapted to confine the
contained air, a sealing material applied to the exterior of the envelope of each of
the wires constituting the cable, and a surrounding sheath of lead.
7. In electric cables of that class in which the conductor is surrounded by a non-
conducting covering and a sealing or filling material, a cable composed of separate

page_text: groups, each group containing two or more wires, each wire surrounded by a fibrous
or meshed air-containing covering, and each group of wires surrounded by a non-
conducting envelope adapted to confine the contained air, a sealing material applied
to the exterior of the envelope of each group of wires constituting the cable, and, a.
sheath of lead surrounding the core thus constructed.
Dated this 26th day of March 1894).
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.