Improvements in and relating to Conduits for Electrical Conductors.
Year: 1895

page_text: Date of Application, 20th Mar., 1895
Complete Specification Left, 20:h Dec., 1895-Accepted, 25th Jan.,
1896
PROVISIONAL SPECIFICATION.
Improvements in and relating to Conduits for Electrical
Conductors.
1, FRANCIS LAUDER, MUIRHEAD, of Princes Street, in the City of Westminster,
lo hereby declare the nature of this invention to be as follows:-
This invention has for its object the improvement of the insulation of the
electrical conductors contained within conduits, the prevention of the accumulation
of gas and water and consequently of explosions in such conduits, and also to
effect certain improvements in the construction and form of conduits.
To effect the said objects my invention consists essentially in filling the
conduit, and completely surrounding the conductors with a hydrocarbon such as
paraffin wax or its hereinafter mentioned equivalents, the conduits being formed
and the electrical conductors being laid in manner hereinafter appearing.
According to my invention the conduits may be of metal or earthenware and
of tubular or trough section, but the latter shape is generally preferred. When
made in accordance with this invention the conduits may, owing to the conductors
being so completely surrounded with insulating material, be considerably smaller
than those now generally in use.. They may be made in the usual lengths and
the joining of such lengths to one another and to the junction boxes may be
When of trough section and
effected in any of the usual or convenient ways.
made of metal the conduits carry at intervals bridge-pieces made of suitable
These bridge-pieces pre-
non-conducting material to support the conductors.
ferably do not abut the internal surface of the conductors at all points and they
as "jockeys" to
are of such shape that by simply reversing them they serve
ride upon the bare conducting strips employed and to maintain them in position.
When earthenware conduits are employed I may form the bridge-pieces in one
with them, preferably thicker at their base and sloping off to a knife-edge at
their slotted parts.
Before placing the conductors in position I may run into the bottom of the
After having placed
conduit a bed of melted paraffin wax or its equivalent.
the conductors in position the lower portion of the conduit is filled up with
similar material, the lid, which may be flanged or otherwise adapted for fixing,
is then secured in position and the whole conduit filled through an opening
provided for that purpose in the lid. In this way the whole of the conduit and
junction boxes may be completely filled with insulating material.
When tubular conduits are employed I may insert the conductors and fill up
each length of such conduits before laying, jointing them together and filling in
the space surrounding such joints after laying.
When using paraffin wax, in order to avoid cracking or unequal contraction of
the mass I may employ a mixture of two kinds of wax of different melting
points and incorporate with the mixture powdered sand, pumice stone or the like
which has been previously thoroughly desiccated. Or a mixture of paraffin wax
and resin may be employed.
The internal surface of the iron or earthenware conduits may sometimes be
thoroughly and securely coated with the insulating material before being laid in
the oth

page_text: In some cases the insulating material might be run into the under part of
conduits previous to laying and grooves for the conductors made in the mass
when cold by means of hot irous or rollers.
I do not limit myself to the use of hydrocarbons as filling-in material, it being
obvious that such combined with other substances, asphalt, rubber insulating
compound, or other material possessing the requisite insulating property and
having a melting point of 100° Centigrade at the least, may be employed.
Dated this 20th day of March 1895.
A. F. SPOONER,
124 Chancery Lane, W.C., Agent for the Applicant.
'
improvements in and relating to Conduits for Electrical
Conductors.
I, FRANCIS LAUDER MUIRHEAD, of Princes Street, in the City of Westminster,
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 :―
ค
This invention has for its object the improvement of the insulation of the
'electrical cables or conductors contained within conduits, and the prevention of
the accumulation of gas and water in such conduits and the consequent liability of
explosions therein; it also comprises the various other improvements hereinafter
indicated.
In the accompanying drawings which illustrate this invention,
Figure 1 is a transverse section, and
Figure 2 is a vertical longitudinal central section on the line x, x of Figure 1
the electrical conductor being left in elevation.
Like letters indicate corresponding parts throughout the drawings.
A is a trough, channel, or U-shaped conduit made of earthenware, stoneware,
metal or other suitable material and closed at its upper part by means of plates or
covers A¹ preferably made of wood. The conduit A may be made in convenient
lengths and connected together by spigot and socket joints in a similar manner to
ordinary channel drain pipes or otherwise. B represents the electrical cables or
conductors which in the drawings are shown as being made up of a number of bare
thin metal strips or ribbons. C, C are bridge or distance pieces of earthenware or
other suitable material for keeping the strips or ribbons forming the conductors
together or in their proper position within the conduit walls to effect which latter
purpose the said bridge or distance pieces are placed alternately above and below
the conductors as shown. D is a filling of insulating material of the nature
bereinafter indicated which is run in a melted or liquid condition into the conduit
so as to completely surround and embed the conductors as shown.
The bridge or distance pieces C are sometimes so constructed that they do not
abut against the conduit at all points and they are preferably of such shape that
by simply reversing them they serve equally well as "jockeys" to ride upon the
bare conducting strips. When earthenware conduits are employed I may form the
bridge-pieces in one with them, preferably thicker at their base and sloping off to
a knife-edge at their slotted parts.
Before placing the cables or conductors B in position I run into the bottom of
the conduit A a bed of melted insulating material suitable for the purpose in order
to fix in position the lower bridge or distance pieces C. After placing the cables
or conductors in position in these lower bridge or distance pieces more of the
insulating material is poured into the conduit until the conductors are covered
after which the covers or plates A¹ are placed in position and the remainder of the

page_text: space in the conduit is filled through one or more apertures provided for that
in the said covers. I am thus enabled to ensure the complete filling up of
purpose
the whole of the conduit and the junction boxes with insulating material, and to
obtain perfect insulation of the cables or conductors. The covers or plates A¹
may be fastened down by pitch, cement or other suitable material.
When made in accordance with my invention the conduits may, by reason of the
conductors being so completely surrounded with insulating material, be con-
siderably smaller than those now generally in use, and being moreover filled up as
already mentioned with insulating material there is no possibility of their becoming
charged with gas or water. The liability to explosions and other inconveniences
is thereby avoided.
Although I have hereinbefore described and illustrated my improved conduit as
being of a trough, channel, or U-shape in transverse section (and I prefer to so
form it) it will be readily understood that I may also construct it of tubular or of
any other convenient form in transverse section.
In order to prevent the mass of insulating material from cracking through
unequal contraction, or from forming undesirable spaces through shrinkage, I in
carrying out this invention employ a mixture of two kinds of paraffin or wax or
other hydrocarbons or other insulating substances having different melting points
and with which has been or may be incorporated finely pulverised sand, pumice
stone or the like, which material has been previously thoroughly desiccated. Or a
mixture of paraffin wax and resin may be used for a like purpose.
I find it advantageous for the purpose of securing thorough adhesion of the filling
of insulating material to the conduit walls and to prevent shrinkage of the mass, to
thoroughly and securely coat the interior of the conduit with insulating material
before it is laid. This may be effected by heating the lengths of conduit and
dipping them into a hot bath of the insulating material or otherwise.
In some cases I may run the insulating material into the under or lower part of
the conduit previous to laying the cables or conductors and allow it to cool and to
harden or solidify, after which grooves may be formed in the said solid mass for
the said cables or conductors by means of hot irons or rollers, or in any convenient
manner.
°
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. A conduit for electrical cables or conductors wherein the latter are completely
embedded in a mass of some suitable insulating material which entirely fills up the
said conduit for the purposes specified.
2. A conduit for electrical conductors or cables wherein the latter are suitably
supported and embedded in a mixture containing paraffin wax or other hydro-
carbons or the equivalent thereof and powdered pumice stone or other pulverized
silicated insulating material, substantially as and for the purposes set forth.
3. The method of coating the interior of the conduit previously to laying the
same substantially as and for the purposes set forth.
4. The improved conduit for electrical conductors or cables made and prepared
substantially as herein described and illustrated in the accompanying drawings.
Tooth dow of December 1895
A. F. SPOONER,
124, Chancery Lane, W.C., Agent for the Applicant.