Year: 1887

page_text: Date of Application, 9th Mar., 1887
Complete Left, 9th Dec., 1887
Complete Accepted, 13th Jan., 1888
I Professor GEORGE FORBES of 34 Great George Street in the City of Westminster
do hereby declare the nature of this invention to be as follows :-
My invention consists in an improved method of laying electrical conductors under-
ground, especially with a view to supplying electricity from a central station to a
town or a district in a town for the purposes of obtaining light and motive power.
In all such systems it is necessary to have some kind of conduit within which the
conductors can be laid. This conduit should be of cheap material and easy to con-
struct without special knowledge or experience on the part of workmen; it ought
also to be watertight, or nearly so, a slight degree of moisture being removable by
forcing dry air through the system of conduits. I attain all these objects by the use of
ordinary cast iron gas pipes, preferably with lead joints using either sockets or faucet
and spigot or other forms serving a like purpose. This conduit forms a metallic line
which may be used for the passage of the roturn currents of electricity, in this case it
will act partially also as an earth plate of enormous surface, thus allowing the return
current of electricity partly to flow into the earth and so to reduce, to a large extent,
the resistance of the whole electric circuit.
The conductors which are inside this conduit must be perfectly insulated from the
cast iron pipes and must be supported in position by a solid material which will not
yield either by time or by the heat generated by the electric current, and they, must
be so adapted that their number can be increased as the requirements of the district
increase. It is also sometimes necessary to be able to carry several sets of conductors
each set being at a different electric potential. Most of the materials at present used
for insulating under-ground conductors of electricity are expensive, and are injured
in their mechanical qualities by the application of heat. To secure rigid and perfect
insulation, I insert insulators of porcelain, glass or other material, in the cast iron
pipes; preferably two in each pipe. These insulators may be of disc form with the
periphery resting in the cast iron pipes, or the periphery may have knobs or pro-
jections which rest on the pipes thus giving a smaller surface of contact for leakage
of electricity. The vacant spaces thus left between the projections at the periphery
are also serviceable for allowing a current of dry air to circulate freely through the
system; each of these discs has one, two, or more, holes in it through which the

page_text: conductors pass, the number of these holes depending upon the number of conductors
of different potential which are in use. Split tubes, which may be of tinned iron,
copper, or other metal, each one a little longer than the cast iron pipes, are passed
through corresponding holes in the insulators contained in each iron pipe. Where
two of the outer pipes are joined together the ends of the split tubes in the interior
of one pipe aro connected to the ends of the split tubes in the other. Preferably to
do this one of them is squeezed at its end to enable it to slip a few inches into the
other one, when, on being released, it springs out and is held firm by the other split
tube. In practice it is most convenient to add each section to the system in the
following order-1st, Fit the additional split tubes into those which are fixed in
position; 2nd, thread the insulators onto the split tubes; 3rd pass a long mandril
through one of the tubes of the new set and partially through the corresponding tube
already fixed in position; the length of mandrel exterior to the split tubes being
about the length of one of the cast iron pipes; 4th, a new cast iron pipe is put over
the exposed part of the mandrel, the end of which is raised by hand so as to support
the now set of split tubes with their insulators and to allow the new cast iron pipe to
pass over the insulators and reach its final position; then, 5th, the lead joint is now
made and the added section is complete.
In this way tubular conduits inside the cast iron conduits pass along their whole
length. At each corner of a street, or other place where a bend occurs in the route,
a manhole is provided, having a watertight cover, this manhole may conveniently have
its bottom deeper in the ground than the pipes so as to act as a sump for the accumu-
lation of small quantities of water, or for the pumping out of larger quantities if any
accident leads to this necessity.
The conductors themselves consist of naked wires without any insulation and are
drawn through the tubular conduits, whose primary purpose is simply to support the
wire conductors. These wires are pulled through the tubes from manhole to man-
hole, and their number is made to suit the requirements of the district and is increased
as the consumption of electricity in the district increases. The corresponding ends in
a manhole are soldered or otherwise joined together.
When it is required to lead the conductors into a house, or other place of direct
supply, a hole, one or two inches in diameter, is tapped in the cast iron pipe and a
small sized gas-pipe containing a copper wire, which is insulated either in the method
above described or by a covering of india-rubber or other material, is screwed into
the hole. Before screwing this, however, it is necessary to attach the end of the wire
to one of the conductors in the cast iron pipe. This end of the wire has soldered to
it a strip of thin sheet copper which is passed into the hole and bent round one of the
split tubes. This strip being already tinned, a copper bolt with a wooden bandle is
introduced through the hole after having been heated to the necessary temperature.
This bolt is so bent that it can be made to encircle the split tube and to grip the
strip of copper against the split tube, when the heat of the bolt completes the joint.
Another method of attachment is to weld the wire to the split tubo by passing a
powerful current of electricity through the point of contact.
When a wire is being drawn out at a manhole it is apt to injure the edge of the
split tube; to prevent this I generally fix a short piece of bell mouthed tube on to the
end of the split tube while drawing the wire out. This bell-mouth is hinged so that
it can be opened, and can be made to encircle the tube conveniently.
It will be noticed that in this system the split tubes perform several functions
(1) as a support for the conductors, (2) as a means of attachment to the wires going
into houses whilst still retaining the power of withdrawing the wires from the tubes
should it be required to do so, and (3) to increase the conductivity of the conducting
system.
CARPMAEL & Co.,
Agents for the Applicant.
5

page_text: Improvements in Laying Electrical Conductors Underground.
I, Professor GEORGE FORBES of 34 Great George Street, in the City of Westminster,
do hereby doclare 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:-
My invention consists in an improved method of laying electrical conductors
underground, especially with a view to supplying electricity from a central station to
a town or a district in a town for the purposes of obtaining light and motive
power.
In all such systems it is necessary to have some kind of conduit within which the
conductors can be laid. This conduit should be of cheap material and easy to
construct without special knowledge or experience on the part of workmen; it ought
also to be watertight, or nearly so, a slight degree of moisture being removable by
forcing dry air through the system of conduits. I attain all these objects by the use
of ordinary cast iron gas pipes; preferably with lead joints using either sockets or
faucet and spigot or other forms serving a like purpose. This conduit forms a
metallic line which may be used for the passage of the return currents of electricity,
in this case it will act partially also as an earth plate of enormous surface, thus
allowing the return current of electricity partly to flow into the earth and so to
reduce, to a large extent, the resistance of the whole electric circuit.
The conductors which are inside this conduit must be perfectly insulated from the
cast iron pipes and must be supported in position by a solid material which will not
yield either by time or by the heat generated by the electric current, and they must
be so adapted that their number can be increased as the requirements of the district
increase. It is also sometimes necessary to be able to carry several sets of conductors
each set being at a different electric potential. Most of the materials at present used
for unsulating underground conductors of electricity are expensive, and are injured in
their mechanical qualities by the application of heat. To secure rigid and perfect
insulation I insert insulators of porcelain, glass or other material, in the cast iron
pipes; preferably two in each pipe. These insulators may be of disc form with the
periphery resting in the cast iron pipes, or the periphery may have knobs or pro-
jections which rest on the pipes thus giving a smaller surface of contact for leakage
of electricity. The vacant spaces thus left between the projections at the periphery
are also serviceable for allowing a current of dry air to circulate freely through the
system. Each of these discs has one, two, or more, holes in it through which the
conductors pass, the number of these holes depending upon the number of conductors
of different potential which are in use. Split tubes, which may be of tinned iron,
copper, or other metal, each one a little longer than the cast iron pipes, are passed
through corresponding holes in the insulators contained in each iron pipe. Where
two of the outer pipes are joined together the ends of the split tubes in the interior of

page_text: one pipe are connected to the ends of the split tubes in the other. Preferably to do
this one of them is squeezed at its end to enable it to slip a few inches into the other
one, when, on being released, it springs out and is held firm by the other split tube.
In practice it is most convenient to add each section to the system in the following
order-1st, Fit the additional split tubes into those which are fixed in position;
2nd, thread the insulators onto the split tubes; 3rd pass a long mandril through one
of the tubes of the new set and partially through the corresponding tube already fixed
in position; the length of mandrel exterior to the split tubes being about the length
of one of the cast iron pipes; 4th, a new cast iron pipe is put over the exposed part
of the mandrel, the end of which is raised by hand so as to support the new set of
split tubes with their insulators and to allow the new cast iron pipe to pass over the
insulators and reach its final position; then, 5th, the lead joint is now made and the
added section is complete.
In this way tubular conduits inside the cast iron conduits pass along their whole
length. At each corner of a street, or other place where a bend occurs in the route, a
manhole is provided, having a watertight cover, this manhole may conveniently have
its bottom deeper in the ground than the pipes so as to act as a sump for the
accumulation of small quantities of water, or for the pumping out of larger quantities
if any accident leads to this necessity.
The conductors themselves consist of naked wires without any
insulation and are
drawn through the tubular conduits, whoso primary purpose is simply to support the
wire conductors. These wires are pulled through the tubes from manhole to manhole,
and their number is made to suit the requirements of the district and is increased as
the consumption of electricity in the district increases. The corresponding ends in a
manhole are soldered or otherwise joined together.
When it is required to lead the conductors into a house, or other place of direct
supply, a hole, one or two inches in diameter, is tapped in the cast iron pipe and a
small sized gas-pipe containing a copper wire, which is insulated either in the method
above described or by a covering of india rubber or other material, is screwed into
the hole. Before serowing this, however, it is necessary to attach the end of the wire
to one of the conductors in the cast iron pipe. This end of the wire has soldered to it
a strip of thin sheet copper which is passed into the hole and bent round one of the
split tubes. This strip being already tinned, a copper bolt with a wooden handle is
introduced through the hole after having been heated to the necessary temperature.
This bolt is so bent that it can be made to encircle the split tube and to grip the strip
of copper against the split tube, when the heat of the bolt completes the joint.
Another method of attachment is to weld the wire to the split tube by passing a
powerful current of electricity through the point of contact.
When a wire is being drawn out at a manhole it is apt to injure the edge of the
spiit tube to prevent this I generally fix a short piece of bell-mouthed tube on to the
end of the split tube while drawing the wire out. This bell-mouth is hinged so that
it can be opened, and can be made to encircle the tube conveniently.
It will be noticed that in this system the split tubes perform several functions (1) as
a support for the conductors, (2) as a means of attachment to the wires going into
houses whilst still retaining the power of withdrawing the wires from the tubes
should it be required to do so, and (3) to increase the conductivity of the conducting
system.
Having now fully described the nature of my invention, I will refer to the annexed
drawings.
In Figure 1a a represent the pipes with a lead joint at b, c c c are the split tubes
making contact with the next set at d; ee are the insulators, shown in the drawing
much closer to each other than they would be in practice.
Figures 2 and 3 represent other joints which might be adopted; Figure 4 shows a
type of man-hole which may be used.
Figures 5, 6, 7 and 8 show different forms of insulators suitable for holding 1, 2, 3
or 4 sets of conductors. Figures 9 and 10 show the bell-mouth and the method of its

page_text: attachment to one of the split tubes.
bolt, and its position relative to the split
shew how branch conductors can be led
conductors.
Figure 11 shows a convenient shape for the
tube and strip of copper. Figures 12 and 13
off from the exterior of any of the tubular
By the system which I have now described I am able to secure my conductors in
a watertight conduit, using the air to insulate them from each other, this being the
cheapest and best insulator known, and using porcelain, or other similar material, to
support them mechanically. The absence of india rubber, or other similar material,
on my wire enables me to pull very great lengths of wire through the tubes and thus
enables me to do all that is required with a sinaller number of man-holes than has
been possible in any other system. I am also enabled at any time easily to increase
the capacity of my conductors by adding to the number of wires..
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to he performed I declare that what
1 claim is
1. The improved method of laying electrical conductors underground substantially
as herein before described.
2. The arrangement of bare wire conductors contained within metallic tubes
surrounded by an outer watertight casing of iron pipe and with the inner tubes kept
apart from one another and from the iron pipe by insulators of porcelain or other
material.
3. The attachment of branch conductors to the exterior of the inner tubes.
4. The employment for the inner tubes of split tube in lengths somewhat exceeding
the length of the outer pipes.