Year: 1891

page_text: Date of Application, 29th June, 1891
Complete Specification Left, 28th Mar., 1892-Accepted, 30th Apr., 1802
No text detected.

page_text: off from the rest, as, for instance, by glands at junction or splice boxes, the
interruption can be bridged over by a sinall pipe connecting the main pipes on each
side of it.
Dated this 20th 1 of 11001
ABEL & IMRAY,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements in the Preparation and Laying of Electrical Mains on
the Brook's System.
We WALTER CLAUDE JOHNSON, and SAMUEL EDWARD PHILLIPS, both of
14 Union Court, Old Broad Street, in the City of London, Telegraph 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 :-
Our improvements relate to the preparation and laying of electrical conductors
for telegraphic or telephonic circuits, or for electric lighting or transmission of
power, or for any other purpose for which an electric circuit may be employed, on
what is known as the "Brook's" system, in which one or more conductors with a
fibrous or other covering are drawn into metal pipes, the pipes being filled with an
insulating substance, which is sufficiently fluid for flowing into the pipes when it is
heated, and remains fluid or becomes semi-fluid or solid at ordinary temperatures.
According to our invention, we draw or force dry air through the pipes after
they, together with their junction or draw-in boxes are properly connected up in
the position and situation which they are to occupy.
We also draw or force the
heated fluid dielectric into the system of pipes and boxes before or after the cable
or cables have been drawn in, thus ensuring that all air and moisture are removed
from the pipes and boxes and that they are completely filled with the dielectric.
For the purpose of aiding the complete removal of all traces of moisture from the
pipes, boxes, and cables, we draw or force dry air through the system after the
cables have been drawn in but before the dielectric is introduced; and, to facilitate
the drying and subsequently the filling in with the heated dielectric, we heat the
cables or conductors by passing a sufficiently large electric current through them,
or we apply a current sufficient to heat smaller conductors which may be drawn
into the pipes with the main cables and which may be afterwards used as potential
wires, or for other purposes. In this way by electrically heating the dielectric,
which may be, before such heating, too viscous or too adhesive to allow of easy
withdrawal or introduction of cables, we render such dielectric perfectly fluid by
the heat, and are thus enabled to effect such change in, or addition to the number
of cables.
Thus the system becomes what is technically known as a "draw-in" and "draw-
out system.
"
The conductors are prepared for drawing into the pipes by covering them with a
fibrous covering or separator or by applying other means for holding them in
position in the pipe, and they are heated in an insulating mixture so as to expel all
air or moisture, and, until the time for drawing them into the pipe, they are kept in
a hermetically sealed vessel, so as to exclude moisture, the vessel being preferably
scaled up with fluid dielectric.
When the pipes have been thoroughly dried as above described, the vessel is
opened and the cable is drawn directly from it into the pipe, the heated dielectric
being afterwards introduced.
The conductor, after being covered with the fibrous coating and heated in hot
dielectric, as above described, may be armoured with metallic tape or wire, the
metal being preferably laid on under considerable strain so as to compress the
fibrous covering. Each cable may be so covered, or several cables may be laid up

page_text: together and the whole armoured. This armouring serves to protect the cables from
abrasion during the drawing-in or out of the pipes or when additional cables are
drawn in.
At convenient places in the line of pipes we provide closed cavities charged with
air which becomes compressed or dilated when the contents of the pipe expand or
contract, thus avoiding risk of leakage of the dielectric from or leakage of water
or air into the pipes. When such a cavity has to serve for parts of the pipe cut off
from the rest, as, for instance, by glands at junction or splice boxes, the interruption
can be bridged over by a small pipe connecting the main pipes on each side of it.
The accompanying drawing shews by way of example an arrangement of
electrical main and apparatus in connection therewith for carrying out our above
described invention.
Fig. 1 shews an elevation, Fig. 2 a plan, Fig. 3 an enlarged sectional plan of one
of the junction or draw-in boxes with by-pass, and Fig. 4 shews a still further
enlarged cross section of the main with the electrical conductors contained
therein.
box.
AA is the underground main having the junction or draw-in boxes B at suitable
distances apart. C is a hermetically sealed vessel into which has been inserted at
the works a reel D containing a coil of the cable or conductor E to be introduced
into the main. For the purpose of sealing the vessel effectually against moisture
from the atmosphere the air may be exhausted, or the vessel may be filled with a'
liquid, by preference dielectric, the cable being made to pass out through a stuffing
At any desired point of the main A, it is connected by a branch pipe F to
an air
pump G by means of which either the main is exhausted of air for
facilitating the introduction of the liquid dielectric, or it is made to draw a supply
of dry air through the main previous to the introduction of the dielectric such air
supply being dried and if necessary heated by any suitable known means before
passing into the main. The cable or conductor E may either be introduced before
or after such passage of dried air through the main, but preferably after, and to
facilitate the removal of moisture by such means, we in some cases pass sufficiently
large electric currents through the conductors to heat them and thus drive off any
moisture from the cable and from the interior of the main, such moisture being then
carried off by the current of dried air. Instead of heating the main conductors by
the currents for this purpose, we in some cases provide special conductors such as
are indicated at H H in Fig. 4 which are heated to the requisite degree for the
above named purpose, and which also serve to liquefy the viscous or solid dielectric
when it is desired to draw the conductors out of the main. Such special
conductors may be enclosed in the outer sheathing of the cable as shewn.
The cable having been introduced and the moisture expelled from the main as
described, heated dielectric is then introduced, for which purpose a heated
cauldron is connected by a pipe J with the main and the dielectric is either
forced into the same by a force pump or other suitable means, or it is drawn in hy
exhausting the air from the main at the other end of the section which is to be
charged with the dielectric, by means of the air pump G, the flow of the dielectric
past the intermediate junction boxes B being effected by means of by-pass pipes A'
connecting the main A on each side of the box. The charging having been
completed in this manner, the pump G and vessel I are disconnected, and are
connected to the next following section.
At any desired points on the main A may be provided closed air vessels such
as K communicating with the main by a branch opening, so that when the dielectric
with which the main is charged, expands or contracts by variations of temperature,
the air in the air vessel will be compressed or expanded and thus any leakage of
dielectric from or of air or moisture into the main will be prevented.
At Fig. 4 is shewn a cable E consisting of several separate groups or smaller
cables of conductors, each of which is secured with fibrous coating with or without
a metallic coating. HH are the before mentioned special conductors which are
heated by currents for the above named purposes, and which may be bound up

page_text: with the other conductors by a fibrous or other covering and if necessary armoured
with metallic tape or wire.
The conductors may of course be otherwise constructed for the purposes of our
invention and be supported centrally in the main by any suitable insulating
supports.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that
what we claim is :--
1. The method of preparing and laying electrical mains consisting in first drying
the tubular conduit either before or after the introduction of the electric conductors,
by drawing or forcing dry air through the main, and then charging the main, so
prepared, with heated liquid dielectric, the conductors being if necessary heated by
the passage of an electric current for facilitating such operation substantially as
described.
2. The method of preparing and laying electrical mains consisting in first drying
the tubular conduit either before or after the introduction of the electric conductors
by drawing dried air through the main by means of air pumps connected to the
main at one point and then charging the main with heated dielectric, by connecting
it at another point with a heated vessel containing the dielectric which is then
either forced into the main by suitable means, or which is drawn into the main by
exhausting the air therefrom by incans of the said air pump, a by-pass being
provided at the junction or drawing-in boxes for allowing of the flow of the
dielectric past such boxes, substantially as described.
3. In electric mains prepared as set forth in the preceding claims, providing
special conductors which are heated by electric currents for the purpose both of
expelling moisture from the main, and when necessary for liquefying the dielectric
when it is desired to withdraw the main conductors or cable, substantially as
described.
4. In preparing and laying electric mains in the manner referred to in the
preceding claims, the use of a closed receptacle containing the coil of the electrical
conductors to be introduced into the main and hermetically sealed for the exclusion
of moisture substantially as described.
5. In preparing and laying electric mains in the manner referred to in the first
claim, the use in combination with a main A having junction or drawing-in boxes B
and by-pass pipes A', of a receptacle C containing a coil of the conductors to be
laid in the main and sealed with liquid, an air pump G for drawing air through the
main and for exhausting air therefrom, and a heated vessel I, charged with liquid
dielectric and connected with the main for charging the same with such liquid
dielectric substantially as described.
6. The use in combination with electric mains charged with dielectric, of air
vessels such as K for allowing of the expansion and contraction of the dielectric
without causing leakage, substantially as described.
Dated this 28th day of March 1892.
ABEL & IMRAY,
Agents for the Applicants.