Improvements in and relating to Insulators and Insulating Conduits or Tubing for Electrical Purposes.
Year: 1895

page_text: Date of Application, 21st Nov., 1895
Complete Specification Left, 21st Aug., 1896-Accepted, 26th Sept., 1896
Improvements in and relating to Insulators and Insulating Conduits
or Tubing for Electrical Purposes.
I, FREDERICK GWILYM TREHARNE, of Wrangbrook, Llanishen near Cardiff,
in the County of Glamorgan, Analytical Chemist, do hereby declare the nature of
this invention to be as follows:-
My invention relates to insulators and insulating conduits or tubing for electrical
purposes.
My improved insulators are chiefly intended for telephone and telegraph wires
but are also well adapted for carrying conductors through which high voltage
currents are passing.
The said insulator comprises a shell composed of natural silicates of aluminium
or iron or manufactured silicates of these metals such as slag wool, woven into a
suitable shape, and impregnated thoroughly with a non-conducting cement having
for example the following composition, viz. :
Sulphur
Bitumen
Sulphate of barium
Silica
-
21 parts.
10 do.
37 do.
32 do.
In some cases it will be found practicable to omit the bitumen.
This outer shell having been manufactured of the desired shape and impregnated
with the cement is then fitted with a spike or spindle which is fixed to the shell by
being embedded in a composition contained by the shell and similar to that used
for impregnating the shell. One or more cylinders of the same material or of
enamelled iron may be used to increase the surface distance between the spike or
spindle and the shell. The spike or spindle is fixed in position while the cement is
in a plastic condition. The outside of the shell may be burnished smooth or may
be coated with a suitable non-conducting lacquer such as Japan lacquer.
My insulating conduits or tubes are made from steel of suitable dimensions coated
with woven sheets of natural silicates of iron or aluminium or manufactured sheets
of such silicates such as slag wool which sheets are thoroughly impregnated and
coated with the cement above described in a heated state. One two or more of
such woven sheets prepared as above described are used for insulating the conduit
or tube.
The conduits or tubes are made by drawing the metal strips in suitable machinery
to any intermediate shape, then applying the insulating sheets above described and
finally drawing the tube to its finished shape. The tube may have one insulated
channel or two or more channels completely insulated from each other, each of
them being lined throughout with the insulating material. The drawing operation
is conducted at a suitable temperature to facilitate the working of the insulating
material and of the metal plates.
Connecting boxes and joints may be made in the same way, tubes of the
compound sheets herein before described being prepared to completely cover and
insulate the wires passing through the connecting box.
The aforesaid insulating sheets may be sometimes advantageously covered with

page_text: The aforesaid insulating strips may be used for insulating wire without the
external metal tube, the wire being either loose inside the insulating material or
rolled tightly in with the same. The insulating material may be made in the form
of a rope with a conducting wire core through it.
Dated this 21st day of November 1895.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.
Improvements in and relating to Insulators and Insulating Conduits
or Tubing for Electrical Purposes.
1, FREDERICK GWILYM TREHARNE, of Wrangbrook, Llanishen, near Cardiff,
in the County of Glamorgan, Analytical 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 :-
My invention relates to insulators and insulating conduits or tubing for electrical
purposes.
My improved insulators are chiefly intended for carrying telephone and telegraph
wires, but they as well as the conduits are well adapted for carrying conductors
through which high voltage currents are intended to be conveyed.
Referring to the accompanying drawings
Figure 1 is a central longitudinal section of an insulator constructed according to
my invention.
Figure 2 is a similar section illustrating a modification hereinafter described.
Figure 3 is a side view of a further modified form of my insulator.
Figure 4 is a section of another form of my improved insulator suitable for
Bupporting secondary batteries.
Figure 5 is a transverse section illustrating an intermediate stage in the
manufacture of my improved double conduit.
Figure 6 is a section illustrating a later stage in the manufacture of my improved
conduit.
Figure 7 is a section of another double conduit made according to my
invention.
Like letters denote correspording parts in the several figures.
My improved insulator comprises a shell A composed of natural fibrous silicates
of iron magnesium and aluminium or any of them commonly called asbestos or
composed of manufactured silicates commonly known as slag-wool, formed into the
desired shape by moulding or weaving or otherwise and impregnated thoroughly
with a non-conducting cement having for example the following composition
viz. :-
Sulphur
Bitumen
Sulphate of barium
Silica
-
21 parts.
-
10 do.
-
37 do.
-
32 do.
In some cases it will be found practicable to omit the bitumen, and also to
largely reduce the quantity of sulphur present, or even to entirely dispense with
the sulphur but in the latter case the bitumen should not be omitted. I sometimes
also increase the proportions of sulphur and bitumen. The sulphate of barium
may in some instances be substituted by silica or silicate fibre or be substituted by
other salts having no water of crystallization and the proportions may be varied to
suit special requirements. I sometimes incorporate with the cement a small
proportion of india rubber or gutta percha.

page_text: The said shell A formed of the silicate and impregnated with the cement is filled
with a non-conducting composition or cement B similar to that used for impregnating
the shell. Sometimes the shell and interior filling are cast together into the
required shape. The shell is then fitted with a spike or spindle C which is fixed in
position by being embedded in the composition contained in the shell while the said
composition is in a plastic condition. Or a screw thread may be formed in the
cement into which the spike may be screwed, or the spike may be cemented in, in
the usual way after the insulator has been formed. The spike may if desired be
insulated by silicate fibre which is plaited on it and which is impregnated with
non-conducting cement. One or more tubes D of the same material as the shell or
of enamelled iron, may be inserted in the cement as shown to increase the distance
measured along the surface of the non-conducting material between the spike or
spindle and the shell so as to overcome the leakage caused by moisture.
tubular part or parts D may be formed integrally with the shell. The outside of
the shell A and tube D may be burnished smooth or may be coated with a suitable
non-conducting lacquer such as Japan lacquer or gum varnish. In some instances
in lieu of varnishing the finished article incorporate a small quantity of lacquer
or varnish or glue from which the water has been expelled with the compound in
which the shell is soaked.
The
I find that for carrying heavy conductors my insulator is made more effective if
a thin ring of iron or steel F Figure 2 having the shape of the inside of the neck
of the shell and covered either wholly or in part by the natural or manufactured
silicates herein before referred to be introduced into the shell to form a support
therefor. The said ring may have perforations in it to allow the cement to enter
and thereby hold the ring more securely in position. In some instances I provide
the ring with two arms G that project through the shell as shown. The
conductor J is placed between the said arms and is secured by means of a bolt or
screw H which passes through the arms as shown.
The clip formed by the arms G and bolt H is insulated by the fibrous silicates
above referred to. After the bolt or screw has been tightened up to secure the
conductor it is insulated by hot cement applied to it; the cement may if desired be
strengthened by having a little of the silicate fibre embedded in it.
I also make an insulator according to my invention by covering an iron or steel
spike or spindle of the desired form with the silicates above referred to, the same
being more or less tightly plaited or wound on such spike or spindle and
then thoroughly impregnated with the aforesaid non-conducting cement or
composition.
H is a
Such an insulator is shown in Figure 3. The spike ar spindle C is in this
instance bifurcated at the end to form a clip for holding the conductor.
pinching screw or bolt for tightening the clip. K is the insulating silicate fibre
impregnated with the insulating cement or composition. For greater security an
increased thickness of fibre may be applied to the part of the clip which comes in
contact with the conductor.
In order to lessen the danger of leakage due to the presence of a continuous film
of moisture, I fix on such insulator at intervals, discs or curved shields L made of
the same material as the covering of the spike.
Figure 4 shows a form of insulator specially suitable for supporting secondary
batteries. It comprises a shell A and an inner tube E made of the fibrous silicate
above referred to impregnated with the non-conducting cement, and filled with
cement B such as that above described with reference to Figure 1. The tube E
forms a support or foot for the insulator. A'A' are recesses that are advantageous
should this form of insulator be required for carrying conductors.
My insulating single or double conduits or tubes are made from sheets of the
natural silicates above referred to which sheets may be woven, or plaited, or
knitted, or from sheets made of manufactured silicates such as slag wool, or from
tubes which have been prepared by weaving, plaiting or knitting the carded and
spun fibres of such materials, or by pressing or rolling the dehydrated fibre between

page_text: suitable dies or rolls into the required shape, or by moulding, the material in all
cases being thoroughly impregnated with the non-conducting cement above
described. The impregnation is conducted at a temperature sufficiently high to
render the cement plastic enough for the process, and in the case of the tubes,
greased or heated mandrels are placed in them to preserve their shape during the
process of impregnation. When sheets N are used for making double conduits
they are rolled whilst hot to the shape shown in Figure 5, that is to say, each
sheet has two channels N', N₁ formed in it. Greased mandrels M are then placed
in the said channels and the sides of the sheet are then pressed down as indicated
in Figure 6. A hot roll is finally passed over the junction of the two edges in
order to securely seal the edges. The mandrels are then removed.
In some instances I use in combination with the impregnated silicate fibre tubes
a sheet metal covering or a covering of asbestos paper impregnated with a hard
non-inflammable cement, which covering may be applied to the silicate and the two
then rolled together to form the conduit as above described, the metal or
impregnated paper as the case may be being outermost.
I sometimes find it advisable to cover the tubes outside or both inside and outside
with lacquer varnish.
The aforesaid insulating material may be used for insulating wire conductors, the
conductor being tightly rolled in with the same, or the fibrous yarn may be plaited
or rolled on to the conductor and then impregnated with the non-conducting cement
herein above described.
I also make double conduits by taking a tube of woven plaited or knitted silicate
fibre and sewing the same up the centre with silicate fibre in order to form two
tubes of equal size as indicated in Figure 7. I then insert mandrels in the tubes
and impregnate the silicate fibre with the non-conducting cement.
This form may
also be made by moulding or by pressing the impregnated dehydrated fibre with
suitable dies.
Mandrels are placed within the tubes in order to preserve the shape of the tubes
during the impregnation; they are subsequently removed.
Multitubular conduits may be prepared by placing the required number of woven
knitted or plaited silicate tubes impregnated with non-conducting cement within
larger iron, earthenware or wooden or other tubes, at the required distance from each
other, the spaces between them being filled with the non-conducting cement above
described.
Greased or heated mandrels in this case are also placed within the tubes in order
that the shape may be retained during the process of manufacture. Multitubular
conduits may also be made from dehydrated fibre as described for the double
conduit by moulding or otherwise.
For special work when a very high degree of insulation is required, I prepare a
cable as follows, that is to say, I take the metallic conductor and plait, weave or
knit on to it several (as many as are deemed necessary) layers of the silicate fibre
which is then impregnated with the non-conducting cement and if desired is
protected with metal, wood or porcelain or other protective material.
I also prepare a cable in the manner above described and after having woven,
plaited or knitted round it the silicate fibre and impregnated the same, I place it in
a copper, or iron, tube which may be used as another conductor, this being again
insulated in the same way if desired; or copper wire may be wound round the
outside of the first cable and then be insulated as before and protected with any
suitable coating. By these means I form a concentric cable in which the external
conductor may serve as the return.
I find it very advantageous to protect the copper wire conductors used in these
tubes against any possible action of the sulphur by a coating of tin or other suitable
material.
Connecting boxes and joints may be made in the manner above described by
preparing tubes of silicate fibre of suitable size to fit the conduit tube, a little of
the non-conducting cement being used to close the joint by means of a soldering

page_text: cement.
iron, or the tubes may be morticed and joined together by a non conducting
The material in the silicate fibre properly impregnated being of a plastic
nature, I am able to form tubes of any shape or size that may be required.
Connecting boxes may also be made by impregnating dehydrated fibre as above
described and pressing or moulding the same to the required shape.
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. An insulator consisting of a shell made of the natural or manufactured
silicates impregnated with the herein described non-conducting cement and filled
with similar cement, substantially as described.
2. An insulator consisting of a bifurcated spike coated with the natural or
manufactured silicates impregnated with the non-conducting cement herein
described, with or without the discs or shields on the spike, substantially as
set forth.
3. An insulator constructed substantially as described with reference to any one
of Figures 1 to 4 for the purpose specified.
4. A conduit or connecting box formed of the natural or manufactured silicates
impregnated with non-conducting cement substantially as described and for the
purpose specified.
5. A conduit constructed substantially as herein described with reference to
Figure 5 or to Figure 6, for the purposes specified.
Dated this 21st day of August 1896.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.