IMPROVEMENTS IN INSULATORS FOR TELE- GRAPH WIRES
Year: 1860

page_text: LETTERS PATENT to William Andrews, of Woburn Chambers, Henrietta
Street, Strand, and of 58, Threadneedle Street, in the City of London,
PROVISIONAL SPECIFICATION left by the said William Andrews at the
Office of the Commissioners of Patents, with his Petition, on the 18th
October 1860.
I, WILLIAM ANDREWS, of Woburn Chambers, Henrietta Street, Strand,
and of 58, Threadneedle Street, in the City of London, do hereby declare
the nature of the Invention for "IMPROVEMENTS IN INSULATORS FOR TELE-
GRAPH WIRES," to be as follows:-
According to this Invention I take a bar of wood or other suitable non-
conducting material; I then bore round or square holes into the wood, and from
top to bottom perpendicularly, or at right angles to the horizontal line of the
bar when fixed. These holes are wide at the top and for a short distance down
the wood; there they are narrowed to about two-thirds, more or less, of the
original width, and afterwards they are again widened out for the remaining
distance through the bar to about the former dimensions, or rather larger. The
bottom part of the bar is then grooved out lengthways in a half circle.

page_text: take hollow tubes, square or round, or of other convenient shape, but larger
externally and internally for some distance from the top than at the bottom, or
about half way up; they are made of vulcanite, gutta percha, india-rubber,
porcelain, earthenware, glass, or other good insulating material; these tubes I
drop down into the holes before mentioned, and they rest on the material of the
bar where the hole is of small diameter. I place a ring of rubber, vulcanised
or otherwise, or of other soft and elastic material between the rim of the tube
and the material of the bar. I now take a bolt made of iron, wood, vulcanite,
or other strong material, preferably of the same shape as the tube, but smaller
and considerably narrower where it remains in the smaller part of the tube,
and this I drop down into the insulating tube previously named. The bolt
is made with a rim to set firmly on to the narrow part of the tube, where there
is also a rim of vulcanised india-rubber or other soft material; I now prefer,
although it is not essential, to pour a non-conducting material, such as marine
glue, or tarry and resinous or other suitable compounds, between the bolt and
the tube, and fill these in in the widest part, the rim of the tube preventing
the further descent of the material. I cover the bolt completely with this
compound, the bolt being below the top of the tube. The top of the tube
which projects above the bar of wood is provided with a screw, and I now take
a vulcanised band of rubber or other suitable material which I place round the
outside of the tube and rest on the bar. A cover or cap made of insulating or
other material provided with a female screw is then screwed down tightly on
to the tube, and the thread of the tube extending below the top surface of the
bar; the cap or cover can be screwed tightly down on to the vulcanised band.
I also fill in between the exterior of the tube and the bar with an insulating
compound. If the bolt from which the wire is suspended be of vulcanite or
other plastic material, I can then make the bolt and tube in one mass provided
with a rim and vulcanised band at the top of the tube and bottom when the
weight of the wire brings it firmly against the wood; I also pour in compound
between the vulcanite and the wood as before described. I also make double
tubes to extend the insulating surface, or triple tubes, and so on, or I make
only the bottoms of the tubes double. I also paint or prepare or cover the
wooden bar with a coating impervious to moisture, or I roof over the wooden
bar or arm to protect it from the effects of the weather and to render it a
better non-conductor. By these means I gain very great advantages over the
ordinary methods. I dispense with all metal fastenings or supports, the only
metal being, perhaps, but not necessarily, the bolt supporting the wire. The
insulator is enclosed, hermetically sealed at top, and perfectly protected all

page_text: round by a comparatively good insulating substance. The strain is borne by the
mass of the arm, and the composition used to fill in between the bolt and
insulating tube may be poured in at a very low temperature, and be more
harmless in its effects than sulphur and other materials at present employed.
The insulator extending only to about the level of the external flanges of the
wood in the longitudinal groove before mentioned is absolutely preserved from
accidental damage from stones or otherwise. The insulating substance is
shielded from the sun, wet, and ordinary effects of the weather. Any moisture
working downwards drops harmlessly to the ground instead of saturating the
arms or posts. Skeleton iron or other arms may be used; in such case the
iron at the point of support of the insulator being cast in a tube of the saine
shape as the holes in the wooden arms, or of other convenient shape. In
some cases I use the insulator with an ordinary bracket or support.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Andrews in the Great Seal Patent Office on the 18th
April 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
ANDREWS, of Woburn Chambers, Henrietta Street, Strand, and of 58, Thread-
needle Street, in the City of London, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Eighteenth day of October, in the year of our Lord
One thousand eight hundred and sixty, in the twenty-fourth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me,
the said William Andrews, Her special licence that I, the said William
Andrews, my executors, administrators, and assigns, or such others as I,
the said William Andrews, my executors, administrators, and assigns, should
at any time agree with, and no others, from time to time and at all times
thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN INSULATORS FOR TELEGRAPH WIRES," upon the condition
(amongst others) that I, the said William Andrews, my executors or
administrators, by an instrument in writing under my, or their, or one of
their hands and seals, should particularly describe and ascertain the nature
of the said Invention, and in what manner the same was to be performed,

page_text: and cause the same to be filed in the Great Seal Patent Office within
six calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said William Andrews, do hereby declare
the nature of the said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the follow-
ing statement thereof, that is to say :-
According to this Invention I take a bar of wood or other suitable non-
conducting material; I then bore round or square holes into the wood, and
from top to bottom perpendicularly or at right angles to the horizontal line of
the bar when fixed. These holes are wide at the top and for a short distance
down the wood; there they are narrowed to about two thirds, more or less, of
the original width, and afterwards they are again widened out for the remaining
distance through the bar to about the former dimensions or rather larger.
The bottom part of the bar is then grooved out lengthways in a half circle. I
now take hollow tubes square or round, or of other convenient shape, but
larger externally and internally for some distance from the top than at the
bottom, or about half way up; they are made of vulcanite, gutta percha, india-
rubber, porcelain, earthenware, glass, or other good insulating material; these
tubes I drop down into the holes before mentioned, and they rest on the
material of the bar where the hole is of small diameter; I place a ring of rubber,
vulcanised or otherwise, or of other soft and elastic material, between the rim
of the tube and the material of the bar. I now take a bolt made of iron,
wood, vulcanite, or other strong material preferably of the same shape as the
tube, but smaller and considerably narrower, where it remains in the smaller
part of the tube, and this I drop down into the insulating tube previously
named. The bolt is made with a rim to set firmly on to the narrow part of
the tube where there is also a rim of vulcanized india-rubber, or other soft
material. I now prefer (although it is not essential) to pour in non-conducting
material, such as marine glue, or tarry and resinous or other suitable compounds
between the bolt and the tube, and fill these in, in the widest part, the rim of
the tube preventing the further descent of the material. I cover the bolt
completely with this compound, the bolt being below the top of the tube. The
top of the tube which projects above the bar of wood is provided with a screw,
and I now take a vulcanized band of rubber or other suitable material, which
I place round the outside of the tube and rest on the bar. A cover or cap
made of insulating or other material provided with a female screw is then
screwed down tightly on to the tube, and the thread of the tube extending

page_text: 0
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it to form an elastic bed for the tube to rest on where it bears on the shoulder
a; f is the bolt; it is formed at the lower end with a hook or scroll f' to
receive the telegraph wire, and at its upper end with a head f²; a washer of
vulcanized india-rubber 9 is placed under the head of this bolt, and the bolt
is then dropped into the tube d, as is shown, and descends through it till the
head is stopped by the shoulder in the tube. The tube d is fixed securely in
its place by cement run it at h, h. This cement I prefer, if the tube d is of a
material other than vulcanite, to be of marine glue or hard bituminous
material; but if the tube d is of vulcanite (the material I prefer) then sulphur
is as good a cement as can be employed. I employ this material also to fix
the bolt f in the tube d, the cement completely covering the head of the bolt.
The top of the tube d has a screw thread formed on it, and receives a screw
cap i, which being screwed down on the vulcanized india-rubber ring j makes
a tight joint. The bar a is grooved along the bottom, so that any water
running down the sides of the bar may drip off at the lower edges, and not
run along the under part of the bar. In place of vulcanized india-rubber
rings or washers, rings or washers of other elastic material may be employed,
and more especially when the tube d is of vulcanite, or of a material in itself
elastic. The use of such rings or washers is by no means essential. Figure 4
is a vertical transverse section of an arrangement in which no rings or washers
are employed, and.in which the form of the parts is in some respects slightly
inmodified. The cap at the top of the tube d is in this arrangement secured by
cement in place of by a screw. Figure 5 is à transverse vertical section of
another arrangement, by which many of the advantages of the arrangements
before described are attained in a somewhat simpler form. This form, how-
ever, is not so advantageous as those before described, in cases in which the
insulators are exposed to a more than ordinary strain. In this arrangement
there is for each insulator a vertical hole bored in the bar a. This hole is
smaller at the top than elsewhere; into it is dropped a tube d of vulcanite or
other material, secured as before by sulphur or other cement; the vulcanite
tube is closed at the top, and has an enlarged head which rests on the top of
the bar; f is the bolt, as before; it is fixed in its place by sulphur or cement
which will hold it securely in cases where the strain s not very severe. If a
more than ordinarily good insulation is required, I cover the bar a with an
insulating material, by preference, marine glue. Roofing over the bar also
improves the insulation.
In some cases in place of the wooden bar a I employ an iron bar (a wooden
bar is, however, generally preferable). The bar is made much smaller in size

page_text: than that shewn, and has bosses at intervals, in which the holes for the tubes d
are formed. In place of mounting a number of insulators on one bar, it is
evident that each may be mounted on a separate bracket of its own, if
desired.
In witness whereof, I, the said William Andrews, have hereunto set
my band and seal, this Eighteenth day of April, in the year of our
Lord One thousand eight hundred and sixty-one.