A New or Improved Method of Insulating Electrical Conductors and Conduits for the same.
Year: 1890

page_text: Date of Application, 9th June, 1890
Complete Specification Left, 12th Aug., 1890-Accepted, 13th Sept., 1890
PROVISIONAL SPECIFICATION.
A New or Improved Method of Insulating Electrical Conductors and
Conduits for the same.
We ALEXANDER MUIRHEAD, of Cowley Street, Westminster, in the County of London,
Doctor of Science, Electrical Engineer, and CHARLES ROMLEY ALDER WRIGHT, of
No. 3 Castellain Road, Maida Vale, in the County of Middlesex, Doctor of Science,
Fellow of the Royal Society, Consulting Chemist, do hereby declare the nature of this
invention to be as follows:-
It is well known that paper treated with certain chemical agents such as sulphuric
acid, cuprammonia solution, and various other substances, becomes more or less
completely parchmentised and that a waterproof cardboard may in certain cases be
built up by soaking paper of suitable quality in the parchmentising fluid and pressing
together two or more thicknesses. Also that canvas and other textile fabrics may be
similarly treated, and that a composite variety of waterproof card may be produced by
pressing together a layer of textile material and one of paper.
We find that such paper, canvas, and cardboard, and especially this composite variety
of card, may be advantageously employed as a coating for electrical conductors, and
as a lining for conduits to contain them, for the purpose of assisting in the insulation
of such conductors and the exclusion of water.
In order to cover a conductor we cut paper or card prepared as above described
into strips and wrap these round the conductor longitudinally or spirally and unite the
or the strips may
edges or junctions of the paper with a suitable cementing material
preferably be brushed over with, or soaked in, the cementing material before wrapping
round. The effect of this is to form a protective sheathing or coating outside the
conductor thus treated. If a thicker coating is required we similarly apply a second
layer outside the first one by brushing it over with cementing material and winding or
wrapping on a second series of strips, and so on.
As cementing materials a variety of substances may be used. For many purposes
a resinous or waxy composition may be employed of such a nature as to be solid when
cold but more or less fluid and adhesive when hot; this is applied with a brush whilst
hot or the strips of paper or card may be immersed in the hot cement and applied
immediately to the conductors to be covered. In other cases an analogous composition
may be used made more or less fluid by means of a volatile solvent or thinning agent
such as spirit, bisulphide of carbon, benzoline, or other suitable liquid; this being
brushed on to the card surfaces to be joined will bring about their adhesion as the
volatile fluid evaporates. In some cases gelatinised cellulose may be employed as the
cementing agent, prepared by acting on cotton, paper-pulp, or other kinds of cellulose
with strong cuprammonia solution; this being a watery substance, it is necessary that
the junctions should dry before complete union takes place; this operation may be
assisted by means of artificial warmth. Whatever the nature of the cementing
material the regulated application of pressure during the setting or drying of the
cement greatly strengthens the joining ultimately effected.
It is well known that gelatine can be rendered insoluble in water by combination
with various kinds of tanning materials; we find that a protective sheathing may be
applied to conductors by soaking either ordinary untreated or more or less parch-
mentised paper, linen, or other similar materials in hot glue or strong size and winding
it round the conductor and subsequently brushing over the whole a strong solution of
some form of tannin such as extract of oak bark, or preferably soaking the coated
conductor in a vat of tanning liquid. After drying, a continuous sheathing or coating
is thus formed which may be thickened and strengthened by repeating the process;
finally the whole may be dried thoroughly and soaked in melted paraffin-wax or other

page_text: similar material to increase its waterproof character and insulating power by filling
up all cracks and crevices.
In order to line tubular conduits we cut a strip of paper or card of such breadth
that when the strip is bent round so that the edges just meet, it forms a hollow cylinder
just capable of sliding inside the tube to be lined. If it is intended that the lining
should be fastened to the inside of the tube we smear a suitable cement over the inner
surface of the tube to be lined, or the outer surface of the card cylinder, or both,
before introducing the cylinder inside the tube. A long smooth rod or mandril is then
introduced inside the card cylinder, and the whole rolled on a suitable table or
otherwise so that the mandril may successively press all parts of the card cylinder into
contact with the inner surface of the tube. In order to render the lining still more
complete we thus similarly introduce a second slightly smaller card cylinder inside the
first one and repeat the operation, taking care that the longitudinal join of this second
cylinder shall not be along the same line as that of the first one. When the lining is
not intended to be fastened to the tube but to be removable if required we prepare
a waterproof tube of cardboard or paper of such diameter as just to slide inside
the tube to be lined. Such a waterproof tube is conveniently made by cutting
a strip of waterproof paper, canvas, card, or composite material of paper
and textile fabric, and rolling this round a rod or mandril SO as to form
a hollow cylinder the edges of which slightly overlap. A layer of cement is then
applied between the overlapping edges so as to convert the whole into a tube.
When the cement has set the mandril is removed. If the walls of the tube are to be
tkickened the same process may be repeated; or the strips of paper, canvas, or other
material used may be brushed over with cement and wound spirally round the tube in
regular fashion so as to build it up to any required thickness. When card prepared with
cuprammonia solution is used as the basis for such a tube, the rolled-up strip may be
conveniently converted into a tube by winding round it paper, calico, or similar
materials soaked in strong cuprammonia solution and allowing to dry, a succession of
such outer coatings being applied if requisite so as gradually to build up the tube to
any required thickness. Instead of cuprammonia solution ordinary glue may be used,
the gelatine of which is subsequently rendered insoluble by an application of tanning
fluid. If required, the tubes, when built up to the desired thickness, may be smoothed
by rolling with a mandril inside, and may be further improved in insulating properties
by immersion in a bath of imelted paraffin-wax or other similar substance or
compositions.
If tubes of sections other than cylindrical, for example rectangular, are to be lined
we proceed in the same way, employing a suitably shaped mandril and developing
pressure when required otherwise than by rolling by well-known means.
If a trough or conduit is to be lined we first prepare a card, or preferably
composite card of paper and textile fabric, of sufficient thickness and suitable
waterproof character, and fold up long strips of this so as just to fit inside the
conduit with the edges projecting upwards to such a distance that if these are
folded over horizontally they may meet and slightly overlap. When the electric
conductors are placed in position in the conduit these edges are folded over and
cemented together.
In certain cases we line tubes by placing a mandril inside so as to leave an
equal interspace between the mandril and the inside of the tube all round; and
we then ram or squirt into this interspace a mass of suitable composition in a
partly plastic state, finally withdrawing the mandril so as to leave the tube.coated.
internally with the composition. Paper pulp more or less dried and mixed up with
a small quantity of fused resinous cementing matter and rammed in hot, or mixed
with strong glue and tanning solution, or with any other convenient cement can
thus be made to form a continuous lining, the non-conducting qualities of which
may be improved by completely drying the coating and then immersing the whole
tube in a bath of melted paraffin-wax or other analogous material so as to fill up
all pores and crevices therewith and so render it completely impervious to water.
In order to splice together consecutive lengths of coated conductors we proceed

page_text: in the ordinary way well known in connection with joining wires covered with
gutta percha and similar insulating materials; the metallic wires being soldered
together, we wrap over the junctions the prepared paper and cement used for
coating the rest of the wires so as similarly to coat the junctions.
In order to connect internally lined tubes or conduits we proceed in much the
same way making an internal splice of the lining by introducing a short length
of connecting pasteboard tube well coated with cement and of about the same
external diameter as the inside of the lining, so as to fit tightly therein.
Dated this 9th day of June 1890
A. F. SPOONER,
9, Warwick Court, High Holborn, W.C., Agent for the Applicants.
A New or Improved Method of Insulating Electrical Conductors
and Conduits for the same.
We ALEXANDER MUIRHEAD, of Cowley Street, Westminster, in the County of
London, Doctor of Science, Electrical Engineer, and CHARLES ROMLEY ALDER
WRIGHT, of No. 3, Castellain Road, Maida Vale, in the County of Middlesex, Doctor
of Science, Fellow of the Royal Society, Consulting Chemist, 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 :-
It is well known that paper treated with certain chemical agents such as sulphuric
acid, cuprammonia solution, and various other substances, becomes more or less com-
pletely parchmentised, and that a waterproof cardboard may in certain cases be
built up by soaking paper of suitable quality in the parchmentising fluid and pressing
together two or more thicknesses. Also that canvas and other textile fabrics may
be similarly treated, and that a composite variety of waterproof card may be
produced by pressing together a layer of textile material and one of paper.
We find that such paper, canvas, and cardboard, and especially this composite
variety of card, may be advantageously employed for insulating electrical conductors,
and as a lining for conduits to contain them for the purpose of assisting in the
insulation of such conductors and the exclusion of water.
In order to cover a conductor we cut paper or card prepared as above described
into strips and wrap these round the conductor longitudinally or spirally and unite
the edges or junctions of the strips with a suitable cementing material; or the strips
may preferably be brushed over with, or soaked in, the cementing material before
wrapping round. The effect of this is to form a protective sheathing or coating
outside the conductor thus treated. If a thicker coating is required we similarly
apply a second layer outside the first one by brushing it over with cementing material
and winding or wrapping on a second series of strips, and so on. Or instead of using
a second layer of chemically prepared paper, canvas, cardboard, or analogous material,
we may impregnate ordinary paper or calico, felt, jute, hemp, or any suitable fibrous,
porous, or cellular substance with cementing material, working this in so as to fill up
the pores and air-spaces, if required, and then apply this by winding or wrapping on
so as to form an outer layer or sheathing.
As cementing materials a variety of substances may be used. For many purposes
a resinous or waxy composition may be employed of such a nature as to be solid
when cold but more or less flaid and adhesive when hot; this may be applied with a
brush whilst hot or the strips of paper or card may be immersed in the hot cement
and applied immediately to the conductors to be covered. In other cases an analogous
composition may be used made more or less fluid by means of a volatile solvent or
thinning agent, such as spirit of wine, bisulphide of carbon, benzoline, or other
suitable liquid; this being brushed on to the card surfaces to be joined will bring
about their adhesion as the volatile fluid evaporates. In some cases gelatinised
cellulose may be employed as the cementing agent, prepared by acting on cotton,

page_text: What-
paper-pulp, or other kinds of cellulose with strong cuprammonia solution; this being
a watery substance, it is necessary that the junctions should dry before complete union
takes place which operation may be assisted by means of artificial warmth.
ever the nature of the cementing material the regulated application of pressure
during the setting or drying of the cement greatly strengthens the joining ultimately
effected.
It is well known that gelatine can be rendered insoluble in water by combination
with various kinds of tanning materials; we find that a protective sheathing may be
applied to conductors by soaking either ordinary untreated or more or less parchmen-
tised paper, linen, or other similar materials in hot glue or strong size, and winding
it round the conductor and subsequently brushing over the whole a strong solution of
some form of tannin such as extract of oak bark, or preferably soaking the coated
conductor in a vat of tanning liquid. After drying, a continuous sheathing or
coating is thus formed which may be thickened and strengthened by repeating the
process; finally the whole may be dried thoroughly and soaked in melted pitch,
paraffin wax, or other similar material to increase its waterproof character and
insulating power, by filling up all cracks and crevices.
In order to line tubular conduits we sometimes proceed as follows:-We cut a
strip of paper or any suitable material prepared in accordance with this invention of
such breadth that when the strip is bent round so that the edges just meet it forms a
hollow cylinder capable of sliding inside the tube to be lined. If it is intended that
the lining should be fastened to the inside of the tube we smear a suitable cement
over the inner surface of the tube to be lined, or the outer surface of the inner
cylinder, or both, before introducing the latter inside the tube. A suitably shaped
rod or mandril is then introduced inside the inner cylinder, and the whole rolled in a
suitable table or otherwise so that the mandril may successively press all parts of
the inner cylinder into contact with the inner surface of the tube. In order to render
the lining still more complete we then similarly introduce a second slightly smaller
cylinder of the same or similar material inside the first one and repeat the operation,
taking care that the longitudinal join of this second cylinder shall not be along the
same line as that of the first one.
Instead of thus building up or thickening from within the lining inside the
conduit, we sometimes find it more convenient to construct the internal tube first of
the required thickness, and of such diameter as to be capable of sliding within the
conduit to be lined; having introduced it within the conduit, we cement it thereto by
introducing suitable cement into the interspace between the interior surface of the
conduit and the exterior surface of the internal tube; for this purpose melted paraffin
wax, pitch, or other analogous resinous substances or compositions rendered fluid by
heat may be conveniently used. If the lining tube is not intended to be permanently
fastened to the conduit but to be removable, if required, instead of cementing the
two together we simply introduce the prepared tube inside the conduit and fix it in
position by wedges or packing of any convenient material. In certain cases two or
more tubes may thus be fitted into one exterior conduit.
Such lining tubes are conveniently made by cutting a strip of waterproof paper,
canvas, card, or composite material of paper and textile fabric and rolling this round
a rod or mandril so as to form a hollow cylinder, the edges of which slightly overlap.
A layer of cement is then applied between the overlapping edges so as to convert the
whole into a tube. When the cement has set, the mandril is removed. If the walls
of the tube are to be thickened the same process may be repeated; or strips of paper,
canvas, or other suitable fibrous, porous, or cellular substance may be impregnated
with cement, worked in if requisite, so as to fill up pores and air spaces, and applied
externally by winding or wrapping on or otherwise so as to build up the tube to any
required thickness. When card prepared with cuprammonia solution is used as the
basis for such a tube, the rolled up strip may be conveniently converted into a tube
by winding round it paper, calico, or similar materials soaked in strong cuprammonia
solution, and allowing to dry, a succession of such outer coatings being applied, if
requisite, so as gradually to build up the tube to any required thickness. Instead of

page_text: cuprammonia solution ordinary glue may be used, the gelatine of which is subse-
quently rendered insoluble by an application of tanning material. If required, the
tubes when built up to the desired thickness, may be smoothed by rolling with a
mandril inside, or by other suitable means, and may be further improved in insulating
properties by immersion in a bath of melted pitch, paraffin wax, or other similar
substance or composition.
Waterproof tubes thus prepared are possessed of sufficient mechanical strength and
insulating power to render them capable of use as insulating conduits or mains for
electrical conductors without any exterior metallic pipe or other sheathing being
requisite, and also for smaller conductors intended for the interior of buildings. On
the other hand when a metal or other external tube is to be lined by placing inside
it a pipe made by building up successive layers of material prepared as above
described, if the layer of cementing material filling up the interspace between the
outer and inner tubes is sufficiently thick and possessed of suitablo water-resisting
qualities, it is not indispensable that the material employed in the construction of the
inner tube should have been treated by chemical processes to render it waterproof;
for we find that effectively lined tubes may be obtained by introducing inside the
larger pipes to be lined smaller tubes prepared of ordinary pasteboard, canvas, and
similar materials by methods well known and then filling up the interspace with
melted paraffin wax, pitch, and such like substances. But we prefer to use for the
innermost layer of the lining tube as tough materials as possible so as to resist
the wear and tear occasioned when the electrical conductors are drawn through the
tubes.
If tubes of sections other than cylindrical, for example rectangular, are to be
lined, we proceed in much the same way as that above described employing a suitably
shaped mandril and developing pressure, when required, by well known means,
otherwise than by rolling.
In some cases, if a trough-shaped conduit is to be lined, we first prepare a card, or
preferably composite card of paper and textile fabric. of sufficient thickness and
suitable waterproof character, and fold up long strips of this, so as just to fit inside
the conduit with the edges projecting upwards to such a distance that if these are
folded over horizontally they may meet and slightly overlap. When the electric
conductors are placed in position in the conduit the edges are folded over and
cemented together.
In certain cases we line tubes by placing a mandril inside so as to leave an equal
interspace between the mandril and the inside of the tube; and we then ram or
squirt into this interspace a mass of suitable composition in a partly plastic state,
finally withdrawing the mandril so as to leave the tube coated internally with the
composition. Paper pulp more or less dried and mixed up with a small quantity of
melted resinous cementing matter, and rammed in hot, or mixed with strong glue and
tanning material or with any other convenient cement, can thus he made to form a
continuous lining, the nonconducting qualities of which may be improved by com-
pletely drying the coating and then immersing the whole tube in a bath of melted
pitch, paraffin wax, or other analogous material so as to fill up all pores and crevices
therewith and so render it completely impervious to water.
In order to space together consecutive lengths of coated conductors, we sometimes
proceed in the ordinary way well known in connection with joining conductors
covered with gutta-percha and similar insulating materials; the metallic con-
ductors after being soldered together, are wrapped over at the junctions with layers
of the prepared material and cement used for coating the rest of the conductors so
as to have the junction similarly coated. In order to connect internally lined tubes
or conduits, we proceed in much the same way making an internal splice of the
lining by introducing a short length of connecting tube well coated with cement and
of about the same external diameter as the inside of the lining, so as to fit tightly
therein. When a number of tubes made in accordance with this invention to be
employed as condnits or mains for electrical conductors without any external protec-
tion of iron or other material are required to be joined into one length, we prefer to

page_text: screw them together in the manner adopted with iron piping, threads being easily
formed in the tubes when the material of which they are made is soft.
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. Electrical conductors covered with a sheathing of paper, canvas, or other
aualogous fibrous, textile, or composite material toughened and rendered waterproof
by chemical processes and externally strengthened and built up to any required
thickness substantially as and for the purposes hereinbefore described.
2. Constructing tubular conduits of paper, canvas, or other analogous fibrous,
textile, or composite material and building them up externally substantially as and
for the purposes hereinbefore described.
3. Tubular conduits of iron or other suitable material lined with an internal
sheathing built up from within substantially as hereinbefore described.
4. Conduits for electrical conductors consisting externally of a sheathing of iron
or other suitable material, and internally of one or more casings of paper, canvas, or
other analogous fibrous, textile, or composite material prepared as above described,
either cemented within or wedged or otherwise fixed in position.
Dated this 19th day of August 1890.
A. F. SPOONER,
9, Warwick Court, High Holborn, W.C., Agent for the Applicants.