Improvements in or connected with Electric Mains.
Year: 1898

page_text: Date of Application, 7th Jan., 1898
Complete Specification Left. 7th Nov.. 1898-Accepted. 7th Jan.. 1899
PROVISIONAL SPECIFICATION.
Improvements in or connected with Electric Mains.
I, GEORGE HINDE NISBETT, of Ashfield, Huyton, in the County of Lancaster,
Electrical Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention has reference to electric mains, that is to say, to the mode of
and means for carrying and protecting subterranean electric cables. Of the two
common present known methods of laying electric mains underground, namely,
the drawing in" system, wherein cables are drawn in to pipes or ways, and
the solid" system, in which the cable is permanently buried in the earth, my
present invention has reference more particularly to the latter.
"
Of the "solid" systems, there are several. Probably, the first and best is that
in which iron troughing is used, wherein, electric cables are surrounded with
asphalt composition, pitch, or the like. This system is good mechanically, but
it is relatively expensive, and being of iron, is a conductor itself, which is an
electrical disadvantage. Then according to another method, the cables are
armoured with steel, or laid in the ground without other protection; whilst in
another case, troughing of wood is employed, in which, the cable is surrounded
with asphalt composition, and covered over with a wood cover; and, in some cases,
a layer of bricks or tiles is laid over the top, as a protection against damage from
picks, etcetera. But these systems have serious defects; namely, the armour is
apt to rust away rapidly in many soils; whilst, in the case of wooden troughing,
the wood and the nails of binding perish quickly, and the protection is lost.
Wood also is not a reliable installation, nor a good mechanical protection.
3
Now the chief object of the present invention, amongst other things, is to
obviate these defects, and provide an electric main (taking the word main to
mean the conductor or cable and the covering or part in which it is laid, as one
thing) which shall have none of these defects; and the improvements hereafter
described accomplish these objects, and provide, moreover, a main having special
characteristics, as hereafter specified.
According to this invention, the main is so made and constructed that the con-
ductor or cable within will or may consist of a bare conductor, or of a lightly
covered or insulated conductor; say a conductor served with a thin coating of
india-rubber, or equivalent insulating material, or one having simply a water-
proof paper covering; or again, if a lead or like covering should be deemed
desirable, it may be made very thin, namely, just sufficient to prevent access of
moisture to the insulation, during the process of laying. The conductor or cable
is laid in a troughing and cover of earthenware or stoneware, preferably glazed
inside and out, and is of rectangular, or approximately rectangular, form, the
thickness of material being, say, about " to 3"; and the bottom of the trough is
preferably flat thereby providing a good bed, whilst the corners inside, for con-
venience of manufacture, may be rounded. In each section of length of trough,
a bridge piece or bridge pieces of porcelain or the like, are provided, these being

page_text: adapted to support or keep the conductor or cable in the centre of the trough.
Then asphalt or bituminous filling is poured in into the trough and surrounds
the conductor or cable, forming a complete envelope. In the filling action, the
bridge pieces serve to keep the conductor or cable in the centre of the trough,
and ensure the flow of the filling passing all round the conductor or cable, and
its being completely and equally surrounded. The dimension of the trough
inside should be about an inch or more in each direction, larger than the con-
ductor or cable within it.
The bridge pieces specified may either form part of the troughing, being fixed
in it during manufacture, or, they may be made and supplied separately, and put
in the trough when laid in the trench; and it is preferred that these are made of
similar material to that of the trough.
The covers of the trough are made of the same material as the troughs, in the
form of slabs, and preferably of a thickness to resist blows from picks, or other
tools, used in opening up roads or streets, and from other external actions; and
they may be in length equal to the troughing, or considerably shorter, as may
be deemed desirable. They are joined to the top of the trough by Portland or
bituminous cement, or the like, preferably in continuous lengths; and their
adjacent edges may be rebitted or chamfered to prevent the entrance of picks,
etcetera, into or through the joints.
According to one form, the troughing is quite plain from end to end, and of
the same section throughout; and the lengths are put together, and provided with
a serving of concrete or cement laid round the outside and underneath the joint,
thereby providing a good foundation, and preventing settlement.
According to another construction, one end of the troughing lengths is pro-
vided with a socket; and the lengths are joined by means of such sockets in a
substantially similar manner to that now done, with pipe socket and spigot joints.
In an electric main of the character above described, the materials are all
imperishable, since the conductor or cable is surrounded by a complete envelope
of bitumen, or the like, which is a homogeneous insulating and water-
proof body and this is enclosed and contained within a stone or earthenware
trough, the imperishable and other characteristic qualities of which are well
known; while the conductor or cable may be a bare copper one without other
insulation than the bitumen or the like in the trough. And further, if a separate
trough be used for each conductor, or a trough having two or three ways, with
division strips between them, a short circuit would be practically impossible
between any two conductors; and the worst that could occur would be a small
leakage due to the cracking of the bitumen, and this could be readily repaired
on the spot, and at a minimum cost.
Further, if bare conductors, as referred to, be not used, conductors only lightly
insulated may be employed, that is, served with either a thin coating of india-
rubber, or similar insulating materal; or a waterproof paper covering. Then
again, if a further safe-guard should be required against electrical leakage, à
comparatively thin coating of lead, say just sufficient to prevent access of moisture
to the insulations of the conductor during the process of laying, can be employed.
In cases in which concentric cables are employed, an insulation between the
inner and outer cable only, is provided, the filling of the trough, and the trough
itself, constituting the insulation of the outer conductor from earth. Or, if the
cable be lead covered, the lead covering is directly applied onto the outer con-
ductor, and the copper and lead in parallel, as the return.
When joints or other connections are required after the main has been laid, a
length of earthenware troughing is broken away, and the bitumen removed by
heating or other means; and joint boxes, with sockets, or otherwise constructed,
are arranged in connection with it, in such a manner, that the troughing with its
compound filling, can be brought right up to the outside wall of them.
As a modification of the above construction of troughing, it is in the form of a
complete tube or conduit, or multiple conduit, each way or tube being provided

page_text: with one or more holes at the top, through which the filling of bitumen, or the
like, is poured after the conductors or cables have been drawn into position.
As a further modification, the bitumen filling is dispensed with, and the conduit
or covering will then be such that cables or conductors of kinds suited to these
conditions, may be drawn in or withdrawn at any time; and in such cases, bridge
pieces would be fixed in position in the troughing during manufacture, and so
shaped as to taper towards the top, so as to prevent the cables touching against
them, when being drawn in. In such cases, the cables will only rub on the bridge
pieces, and consequently, they will be more easily drawn in, than in to pipes of
the ordinary form, in which they will bear along the whole bottom of the tube.
As a further modification, the troughing, in lieu of being made of earthenware
or stoneware, as specified, is made of Portland or other suitable cement, or cement
concrete.
1000
Improvements in or connected with Electric MRIDS.
I, GEORGE HINDE NISBETT, of Ashfield, Huyton, in the County of Lancaster,
Electrical Engineer, 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 has reference to electric mains, that is to say, to the mode of
and means for carrying and protecting subterranean electric cables.
Of the two common present known methods of laying electric mains under-
ground, namely, the "drawing in" system, wherein cables are drawn in to pipes
or, ways, and the "solid" system, in which the cable is permanently buried in the
earth, my present invention has reference more particularly to the latter.
Of the solid systems, there are several. Probably, the first and best is that
in which iron troughing is used, wherein, electric cables are surrounded with
asphalt composition, pitch, or the like. This system is good mechanically, but.
it is relatively expensive, and the troughing or casing being of iron, is a con-
ductor. itself, which is an electrical disadvantage. Then, according to another
method, the cables are armoured with steel, or laid in the ground without other
protection whilst in another case, troughing of wood is employed, in which the
cable is surrounded with asphalt composition, and covered over with a wood cover;
and, in some cases, a layer of bricks or tiles is laid over the top, as a protection
against, damage from picks, etcetera. But, these systems have serious defects;
namely, the armour is apt to rust away rapidly in many soils; whilst, in the case.
of wooden troughing, the wood and the nails of binding perish quickly, and the.
protection is lost. Wood also is not a reliable insulation, nor a good mechanical
protection..
"
Now the chief object of the present invention, amongst other things, is to
obviate these defects, and provide an electric main (taking the word "main to
mean the conductor or cable and the covering or part in which it is laid, as one
thing) which shall have none of these defects; and the improvements hereafter
described accomplish this object, and provide, moreover, a main having special
characteristics, as hereafter specified.
According to this invention, the main is so made and constructed that the con-
ductor or cable within will or may consist of a bare conductor, or of a lightly

page_text: covered or insulated conductor; say a conductor served with a thin coating of
india-rubber, or equivalent insulating material, or one having simply a water-
proof paper covering; or again, if a lead or like covering should be deemed
desirable, it may be made very thin, namely, just sufficient to prevent access of
moisture to the insulation, during the process of laying. The conductor or cable
is laid in a troughing and cover of earthenware or stoneware, which, in some cases,
is glazed inside and out, and is of rectangular, or approximately rectangular,
form, the thickness of material being, say, about " to 1"; and the bottom of the
trough is preferably flat, thereby providing a good bed, whilst the corners inside,
for convenience of manufacture, may be rounded. In each section of length of
trough, a bridge piece, or bridge pieces of earthenware or porcelain, or the like,
are provided, these being adapted to support or keep the conductor or cable in
the centre of the trough. Then asphalt or bituminous filling is poured into the
trough and surrounds the conductor or cable, forming a complete envelope. In
the filling action, the bridge pieces serve to keep the conductor or cable in the
centre of the trough, and ensure the flow of this insulating and waterproof
material passing all round the conductor or cable, and its being completely and
equally surrounded.
The bridge pieces specified may either form part of the troughing, being fixed
in it during manufacture; or, they may be made and supplied separately, and put
in the trough when laid in the trench; and it is preferred that these are made of
similar material to that of the trough.
The covers of the trough are made of the same material as the troughs, in the
form of slabs, and preferably of a thickness to resist blows from picks, or other
tools, used in opening up roads or streets, and from other external actions; and
they may be in length equal to the troughing, or considerably shorter, as may
be deemed desirable. They are joined to the top of the trough by Portland or
bituminous cement, or the like, preferably in continuous lengths; and their
adjacent edges may be rebitted or chamfered to prevent the entrance of picks,
etcetera, into or through the joints.
According to one form, the troughing is quite plain from end to end, and of
the same section throughout; and the lengths are put together, and provided with
a serving of concrete or cement laid round the outside and underneath the joint,
thereby providing a good foundation, and preventing settlement.
According to another construction, one end of the troughing lengths is pro-
vided with a socket; and the lengths are joined by means of such sockets in a
substantially similar manner to that now done, with pipe socket and spigot joints.
In an electric main of the character above described, the materials are all
imperishable, since the conductor or cable is surrounded by a complete envelope
of bitumen asphalte, or the like, which is a homogeneous insulating and water-
proof body; and this is enclosed and contained within a stone or earthenware
trough, the imperishable, and other characteristics or qualities of which, are well
known while the conductor or cable may be a bare copper one without other
insulation than the bitumen or the like in the trough. And further, if a separate
trough be used for each conductor, or a trough having two or three ways, with
division strips between them, a short circuit would be practically impossible
between any two conductors; and the worst that could occur would be a small
leakage due to the cracking of the bitumen, and this could be readily repaired
on the spot, and at a minimum cost.
a
Further, if bare conductors, as referred to, be not used, conductors only lightly
insulated may be employed, that is, served with either a thin coating of india-
rubber, or similar insulating materal; or a waterproof paper covering. Then
again, if a further safe guard should be required against electrical leakage,
comparatively thin coating of lead, say just sufficient to prevent access of moisture
to the insulations of the conductor during the process of laying can be employed.
In cases in which concentric cables are employed, an insulation between the
inner and outer cable only, is provided, the envelope round it, filled into the

page_text: trough, and the trough itself, constituting the insulation of the outer conductor
from earth. Or, if the cable be lead covered, the lead covering is directly applied
onto the outer conductor, and the copper and lead in parallel act as the return.
When joints or other connections are required after the main has been laid, a
length of earthenware troughing is broken away, and the bitumen removed by
heating or other means; and joint boxes, with sockets, or otherwise suitably con-
structed, are arranged in connection with it, in such a manner, that the troughing
with its compound filling, can be brought right up to the outside wall of them."
As a modification of the above construction of troughing, it is in the form of a
complete tube or conduit, or multiple conduit, each way or tube being provided
with one or more holes at the top, through which the filling of bitumen, or the
like, is poured after the conductors or cables have been drawn into position.
As a further modification, the bitumen filling is dispensed with, and the conduit
or covering will then be such that cables or conductors of kinds suited to these
conditions, may be drawn in or withdrawn at any time; and in such cases, bridge
pieces would be fixed in position in the troughing during manufacture, and so
shaped as to taper towards the top, so as to prevent the cables touching against
them, when being drawn in. In such cases, the cables will only rub on the bridge
pieces, and consequently, they will be more easily drawn in, than in to pipes of
the ordinary form, in which they will bear along the whole bottom of the tube.
As a further modification, the troughing, in lieu of being made of earthenware
or stoneware, as specified, is made of Portland or other suitable cement, or cement
concrete.
"
The annexed drawings illustrate several modifications of the electric "mains"
under this invention, which are more or less described above. In these drawings,
Figure 1 shews one form or modification of electrical “main,” according to this
invention; and Figures 2, 3, 4 and 5 shew sections of other modifications; whilst
Figure 6 is a side view of the main, the section of which is given in Figure 5,
shewing the construction at the junction of conduits.
Referring, generally, to the drawings, a is the trough of earthenware or stone-
ware i.c. the outer casing of the main-having an upwardly projecting bridge
piece or pieces b on the bottom, for supporting the conductor; c represents the
conductor; and d represents the asphalt or bituminous material-which is poured
into the trough after the conductor is in place within it-constituting a complete
insulating and waterproof envelope to the conductor. e is the cover fitting over
the trough, and the envelope d, this cover being also of earthenware or
stoneware.
These troughings or casings, and covers, can be made of ordinary brick or tile
clay which is preferred, and they can be produced by ordinary tile or brick-
making machinery, in the required lengths; the bridge supporting pieces c being
introduced into the bottom by hand afterwards, and before burning. The
covers e may be simply tiles made in the same way as the troughing, or in any
suitable way.
In Figures 1, 2, 3 and 4, the troughs or casings a are rectangular in form, the
recesses or ways through them being parallel at the upper part, and curved or
rounded at the bottom; whilst the trough shewn in Figures 5 and 6 is of circular
form. In the latter case, the adjacent ends of the lengths of the covers and
bodies of the troughing or casing of the mains are chamfered off at o, providing
an aperture for the introduction of the asphalt or bituminous envelope for the
conductor.
In this case, the troughing or casing-viz., body and cover-may be made in
one operation and together, that is, as a tube, with longitudinal notches a¹ inside
and out; so that after the tube is burned, and turned to earthenware, the upper
part e which is to constitute the cover, can be cracked off in any known way along
these longitudinal nicks a¹.
Regarding Figure 1, the complete main in this case is comprised of the earthen-
ware troughing or casing (a and e), with supporting bridge pieces p for the

page_text: conductor; a bare conductor e resting on the bridge band kept off the bottom
of a by them; and an envelope of asphalt or bitumen constituting the filling of
the troughing.
In Figure 2, the conductor is of the concentric type, and, as shewn in the
drawings, the outer annular return conductor c¹ has in itself no external, insu-
lation, the asphalt or bituminous filling d and the troughing a, serving alone to
insulate the outer return conductor from earth.
In Figure 3, the conductor of the main consists of a wire conductor proper a,
having only an insulating covering of paper a², or a thin coating of india-rubber,
or the like; but the asphalt or bituminous envelope or filling d constitutes a
further insulation and waterproof protection, and the trough a, serving as a
protection for the conductor.
In Figure 4, a lead covered cable is shewn, the lead in this case requiring only
to be thin; and for this purpose it may be merely sufficiently thick to prevent
an access of moisture to the conductor during the process of laying the main.
This provides a further safeguard against electrical leakage.
With regard to the joints between the different lengths of troughs or casings,
any of the modes above described may be employed; and for supporting the
troughing at the joints, one mode is shewn in Figure 6, and consists of a saddle
or socket f, in which the adjacent ends of the tubes or troughs a rest.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The herein described new or improved electric main namely, a main com-
prised of a trough casing of earthenware, stoneware, or the like, having raised
supporting pieces on its bottom inside, a conductor resting on said supporting
pieces, and an envelope of bitumen, asphalt or equivalent material, surrounding
the conductor and filling the trough; substantially as set forth.
2. The electric mains comprising or consisting of the parts, as set forth with
reference to and shewn in the different figures of the drawings, respectively.
3. In or in connection with electric mains, trough casings constructed as and
for the purpose set forth, and shewn in the drawings.
Dated this 5th day of November 1898.
CHEESBROUGH & ROYSTON,
Applicant's Patent Agents, 15, Water Street, Liverpool.