IMPROVEMENTS IN AND RELATING TO MEANS FOR INSULATING AND PROTECTING ELECTRIC WIRES OR CONDUCTORS
Year: 1884

page_text: COMPLETE SPECIFICATION.
I WILLIAM ROBERT LAKE, of the firm of Haseltine, Lake, and Co Patent
Agents, Southampton Buildings, London in the County of Middlesex do hereby
declare the nature of said invention for." IMPROVEMENTS IN AND RELATING TO
MEANS FOR INSULATING AND PROTECTING ELECTRIC WIRES OR CONDUCTORS" 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 means for insulating and protecting electric wires and
conductors and comprises an insulating asphaltic-concrete conduit for the reception
and protection of electric wires of all descriptions and an improved compound for
the said conduit and for insulating electric wires.
.
A thoroughly practicable system of conduits or pipes for an underground electric
system should meet certain requirements, that is to say: The material itself should
be of high insulating capacity and of such character as to furnish all necessary.
protection to the wires without intervention of other protectors such as metal pipes,
or the like.
The conduits should be easy of manufacture and manipulation, economical in
first cost; and durable so as to ensure economy of maintenance and repair. Where
roadways or streets are to be disturbed in laying the conduit it should be of such
character as to create the least disturbance and obstruction during such laying.
Where the top of the conduit or system of conduits is at or near the surface of
the roadway, it should if practicable, be of such material and manufacture as of
itself to form a good and enduring pavement and it should be so constructed as to
be affected in the least possible degree by thermal or hygrometric changes.
The objects of this invention are to furnish a material for a system of under-
ground conduits possessing these qualities in the highest degree, and to utilize the
same in such a conduit or system of conduits and for the insulation of electric
conductors whereever used.
To accomplish this I use an asphaltic concrete, that is a concrete consisting
mainly of asphalte or equivalent hydrocarbons and silicious matters. While the
proper proportions of these ingredients may be determined in any suitable manner;
[Price 6d.1

page_text: to ensure the highest efficiency, it is preferred to ascertain them in the manner
hereinafter set forth.
As is well known, both natural asphalt (which herein may be taken as a type
of similar hydro-carbons, whether natural or derived from oils or fatty substances)
and silica are good insulators, each however having properties which preclude
its use alone for this purpose. What I prefer to use is a compound of asphalt
and silica.
Silicious particles need some binding agent to unite them in a firm homogeneous
mass to prevent movement and saturation which would reduce or destroy the
insulative properties of the mass.
Asphalt and other oxigenated hydro-carbons alone are too readily affected by
thermal changes, expanding or contracting, or becoming soft and malleable, or hard
and brittle, with changes in temperature.
In view of these facts this invention may be said to consist partly in combining
asphalt and silica in such proportions as will furnish only enough cement to fill
the interstices of the silicious matter, and thereby render the combination of the
two as near a perfect solid as it is possible to attain: partly in the utilization of
the matter so prepared as the material from which conduits for underground use.
are to be made; partly in providing conduits, pipes or tubes for an underground
system made as hereinafter set forth from such material, partly in furnishing a
matrix holding and protecting tubes of such materials enclosing wires, when it
is desired to use such tubes; and partly in insulating electric conductors of all
description.
In carrying the said invention into practice what may be called the
voids" of
the silicious matter to be used should be accurately ascertained. Suppose two
degrees of fineness as regards size of such matter are used (the same principles
applying to any number of such degrees) the first being sharp fresh water gravel,
well screened, and of a size not larger than a pigeon's egg, and the second ordinary.
fresh water sand. There are in any given bulk of such material, a number of
interstices between the points of contact of the units of the mass which, are
hereinafter termed "voids."
Starting now with a given bulk of the first element, namely sharp fresh water
gravel. The percentage of these "voids" to the entire mass is ascertained in the
usual manner by the quantity of water which it will hold, and a proper percentage
of fresh water sand is added.
By such experiments the percentage of fine sand which may be mixed with the
coarser materials without increasing the bulk may be ascertained for the several
varieties used, but there yet will remain "voids" between the units of the mass.
The percentage of these "voids" thus ascertained in volume gives the proportional
measure of asphaltic cement (allowance being made for its shrinkage in cooling)
which should be added to the silicious matter to forin, as nearly as can be done by
human agency, a perfect solid, of high insulative capacity, thoroughly waterproof,
durable and not affected by thermal or hygrometric changes.
While the above gives a general description of the method of manufacture of the
improved asphaltic concrete, I have found it preferable in practice to make some
modifications thereof.
When the proportion of sand to be used is ascertained (whether sand alone or in
conjunction with the gravel mentioned) I prefer to add to it from five to ten per
cent. of ground plaster, or carbonate of lime, of the amorphous kind, in order to
partially fill the remaining "voids" to assist in the binding properties of the
asphaltic cement by its affinities and to lessen the tendency of the asphaltic cement
to contract or expand under thermal changes.
In place of sand a greater or less proportion of pulverized silicious stone or stone
dust may be used.
I prefer also not to use the asphalt in its crude or natural state, but to subject it
to the action of heat to such a degree that it will resist a high fire test say 208°

page_text: This eliminates all foreign ingredients, water and the like, and leaves the product
a pure, or sufficiently pure asphaltum.
To this mass is then added, while hot say from 15 to 20 per cent. of what is
known as the residuum of petroleum, that is liquid bitumen, whose density is 14°
to 18° Baumé and which will resist a high fire test.
It follows then that while the asphaltic concrete to be used may be composed of
silicious matters and asphaltic cement whose relative proportions are to be
ascertained as set forth, the preferable concrete is composed of clean sharp fresh
water sand, amorphous carbonate of lime, asphalt and petroleum residuum.
The proportions thereof will vary according to the properties of the materials in
any particular locality, and the shrinkage of the cement in passing from a liquid to
a solid condition but such proportions can be definitely ascertained by the process
hereinbefore described.
These materials are mixed together at a heat which ordinarily should not exceed
the lowest degree at which asphaltic cement is maintained in a liquid condition,
and the composition is laid or moulded while hot, as hereinafter set forth.
Thus prepared, proportioned, and mixed, a concrete is obtained which, when
properly laid, renders the entire conduit solid, so as to prevent the penetration of
water, is of high insulative character, comparatively cheap, ensy of use, and
imperishable by any action of the elements.
In utilizing this concrete for the purpose of an underground electric system,
a ditch is dug, upon the bottom of which is laid a foundation of ordinary good.
hydraulic concrete composed of broken rock, gravel or the like and hydraulic
cement to form a firm unyielding base for the layers of insulating concrete to be
laid thereon.
Upon such or upon any other suitable base is placed a layer of the improved
concrete which is tamped and rammed while hot, it being understood that the
sides are supported while the concrete is being compacted.
Upon such layer, wires either naked or insulated, or tubes for the reception of
wires are placed.
If wires are used they may be placed thereon from reels which run above the
ditch and are so arranged as to lay or reel off the wires, parallel to each other.
If tubes for the reception of wires are to be used, they may be of metal or
wooden or paper tubes of proper size laid thereon parallel to each other, or tubes or
conduits may be formed by laying upon this (or any other layer) mandrils or
formers.
A second layer of the concrete is then placed thereon, rammed and tamped, and
other wires or formed tubes are placed upon the said layer.
If the tubes are to be formed of the material in situ the forming may be done
by the consolidation of the material around the mandrils or formers referred to,
which are withdrawn after the hardening or setting of this second or other layer
leaving a conduit formed of the concrete itself..
In forming tubes around mandrils or formers, the latter, in order that they may
be easily withdrawn after the hardening of the concrete around them, may be oiled
or coated with pariffine, or preferably a tube of paper is formed on the mandril or
former by winding thereon a sufficient quantity of stiff paper, which may itself
have been coated or treated with asphalt. It may be noted that if tubes be used as
mandrils they will cool sooner than the surrounding concrete, owing to air passing
through them, their subsequent contraction enabling them to be readily withdrawn.
Upon and around such tube the concrete will pack firmly and readily, clinging
closely thereto. The interior mandril or former is then withdrawn leaving a
conduit or pipe of the concrete lined with paper.
Additional layers are then 'formed if necessary in the same manner, the result
eventually being a prism of solid concrete containing the desired number of wires
or tubes for the reception of such wires, either singly or in cables. This concrete
prism enclosing the wires is itself of high insulative capacity, economical in first
cost, durable, water repellant and of itself, if needed, a good roadway surface.

page_text: It need not be laid deep as it will not be affected by thermal or hygrometric
changes, and where desired the top layer may itself form the gutter for the roadway
or a portion of the roadway itself.
In laying such a conduit or system, it is to be understood, that it may be laid in
sections, the sections breaking joint with each other, but the sections of each layer
are so laid as to form a continuous homogeneous layer, and the layers united by a
flushing of hot asphalt, so as to form a solid continuous homogenous prism enclosing
the wires or the tubes for the wires and possessing the qualities before mentioned.
Instead of a base of hydraulic concrete, a box of metal or prepared wood or
hydraulic concrete may be used the box forming the limits of and aiding in
supporting the insulating concrete and wires or tubes, which are laid therein as
though upon the hydraulic base. This is preferable where bridges or streams have
to be crossed.
In the accompanying drawing
Figure 1 is a perspective view of a prism in a ditch, containing wires and tubes.
Figure 2 is a section thereof laid at the curb or edge of a road way; while
Figure 3 is a diagram showing large and small tubes enclosed in the prism;
Figure 4 is a view similar to Figure 2, except that the top layer is finished off as
part of the roadway.
Figure 5 is a perspective view of a conduit laid in a containing box.
A indicates the side and the bottom of a ditch whose width is that desired for
the ultimate prism of concrete.
Upon the bottom of this ditch should be laid a foundation B of hydraulic
concrete, to afford a firm unyielding bed for the asphaltic concrete.
Upon this base B is laid the first layer C of the asphaltic concrete made as
described. It is laid hot and tamped solid before cooling. Preferably, while yet
somewhat plastic, wires, as 1, 2, 3, 4, 5, 6, are laid thereon parallel to each other Or
cables containing many wires, or single wires having an insulating and protecting
covering or naked wires may be laid thereon.
The wires may be easily laid in parallel lines by being unwound from a reel on
a carriage whose wheels straddle the ditch, the reel having as many compartments
and rolls of wire as there are wires to be laid.
Upon this first layer C is now laid and tamped into place a second layer D.
Upon the surface of which tubes a a of any suitable configuration in cross section
are laid or formed.
It is to be understood that tubes of wires may be placed or formed between any
layers, the arrangements shewn in the drawing being merely typical.
The tubes to be embedded may be of any desired material. If they are to be
formed or formed and lined say with paper, mandrils or formers are laid in proper
position having around them a wrapping of paper as hereinbefore set forth.
The paper tubes thus formed in situ are rendered continuous by lapping or
passing the end of each over the end of the one in place.
Secured in position a third layer E is placed upon the layer D and thoroughly
tamped. This process, is repeated until the desired number of layers has been
built up.
The joints of the various sections and the lines of union of the layers with each
other are made firm and solid by flushing the exposed joints, ends or surfaces with
hot liquid asphalte just prior to the addition of the material forming the next
section or layer.
The result is a prism of asphaltic concrete, of itself an exceedingly good insulator,
thoroughly waterproof, practically indestructable by natural causes and economical
in material and labor.
•
The prism may be placed in any portion of the roadway. In cities especially
the more desirable location seems to be at the edge of the roadway, and next the
curb, as shewn in Figures 2 and 4 where S indicates the roadway; P the pavement
and T the curb, the prism being buried beneath the gutter G.
.

page_text: In Figure 4 a top layer E¹ is shewn forming the surface of the prism and
finished off to form the gutter for which from its solidity durability and water-
proof nature it is well-adapted. In fact a top or finishing layer of the prism may
well be used as a part of the roadway wherever located.
In Figure 3 is shewn an arrangement typical of the many modifications as to
size and distributions of pipes which may be made, there being a large tube H for
large cables several smaller ones h for smaller cables or collections of wires and
small pipes ii for one or two wires or small cables.
In Figure 5 is shewn a box B, which may be of metal, wood or composition in
which box may be laid the insulating concrete cables, tubes and wires either or all
of such form thereof may be desired.
The prism herein represented may he considered a trunk prism or conduit, from
which branches may be laid at suitable or desirable points and wires or tubes led
off therein from the main prism or conduit.
If desired "man holes" may be made at intervals one end each of two sections
or conduits entering therein so as to afford means for ready inspection of the
conduits and contents.
Having now particularly described and ascertained the nature of my said.
invention and in what manner the same is to be performed I declare that what
I claim is.
First. The method of forming an insulating concrete, consisting in first ascer-
taining the "void" or interstices of the silicious materials used, and then adding a
proper percentage of the binding agent thereto, substantially as set forth.
Second. The insulating concrete hereinbefore described, consisting of silicious
matter, asphaltum and petroleum residuam combined in the proportions ascertained
or determined by the measurement of the interstices or "voids" substantially as
set forth.
Third. The insulating concrete herein before described, consisting of silicious
matter, asphaltum and petroleum residuum combined substantially as described.
Fourth. An insulating asphaltic concrete conduit formed of silicious materials
and tempered asphalt, the percentage of the latter being approximately equal to
the. ascertained "voids" of the silicious material; and containing wires laid in situ
substantially as set forth.
Fifth. An insulating asphaltic concrete conduit formed of silicious materials and
tempered asphalt, the percentage of the latter being approximately equal to the
ascertained voids" of the silicious materials, and containing tubes, substantially
as set forth.
Sixth. An insulating asphaltic concrete conduit formed of silicious materials, and
tempered asphalt combined in the proportions set forth, and having its top finished
off to form part of the street or roadway substantially as described.
Seventh. An insulating asphaltic concrete conduit formed of silicious materials
and tempered asphalt combined in the proportions set forth, and containing pipes
or tubes laid and lined with paper in situ substantially as set forth.
Dated this 12th day of February 1884.
HASELTINE, LAKE & Co.,
For the Applicant.