IMPROVEMENTS IN INSULATORS FOR TELEGRAPH WIRES
Year: 1867

page_text: PROVISIONAL SPECIFICATION left by George Davies at the Office of
the Commissioners of Patents, with his Petition, on the 7th March
1867. A communication from abroad by David Brooks, of Philadelphia,
Pennsylvania, United States of America.
I, GEORGE DAVIES, of No. 1, Serle Street, Lincoln's Inn, in the County of
Middlesex, and No. 87, St.. Vincent Street, in the City of Glasgow, Civil
Engineer and Patent Agent, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN INSULATORS FOR TELEGRAPH WIRES," (a
communication to me from abroad by David Brooks, of Philadelphia,
Pennsylvania, United States of America,) to be as follows:-
This Invention consists in the employment of paraffine used as an insulating
medium in the construction of insulators, and also of an insulator constructed
as fully described hereafter, which is more efficient and durable than those of
the usual construction. Before applying. the insulator to the post it is
inverted, and the socket as well as the space between the two flanges or cups
is filled with melted paraffine, and then emptied, a portion of the paraffine
remaining as a coating on the entire inner surface of the insulator, which is
then secured to the post in the usual manner. The insulator may be
thoroughly impregnated with the paraffine by leaving the pores of the earthen-
ware open, or removing the usual enamelled surface. It has been ascertained
that paraffine in its natural hard state is such an excellent non-conducting
medium that the thin layer intervening between the post and the insulator
will effectually prevent the transmission of any electric current, while the

page_text: coating of paraffine on the exposed surfaces of the insulator possesses so
little affinity for moisture that such water as adheres to the surface collects in
the form of detached globules; the deposit of a continuous film of water,
which frequently occurs on the surfaces of glass, rubber, or other insulating
materials, and which affords a medium for the escape of electric currents
being thus prevented. Although any of the ordinary insulators may be
rendered much more efficient by the use of the paraffine, as above described,
it is preferable to apply the improvements to insulators made in the following
manner: The stem and inner end of a cast-iron wire holder (having at its
other end two bent arms for retaining the wires) is to be covered with strong
cartridge paper, pasted, glued, or cemented to its place; the stem thus
papered is first slightly heated, and then dipped into molten paraffine, with
which the paper is thus thoroughly impregnated; the papered stem when
cold is then secured by means of sulphur in a glass block or cylinder (about
half the depth of the stem) and closed at one end; the glass block is then
covered with a paper cylinder considerably longer than the block (also closed.
at one end), and pasted, glued, or cemented into its place; the paper
cylinder is then dipped into and thoroughly impregnated with molten paraffine,
and when the latter is hard the whole is secured by means of sulphur into a
cast-iron cylinder or casing; melted paraffine is now poured into the annular
space between the last-named paper cylinder and the papered stem of the
wire holder, and after a short time the greater part is poured out again,
leaving a coating on the interior surface; paper is now pasted over the
greater portion of the exterior surface of the cast-iron cylinder or casing,
which is then dipped into melted paraffine, and when the latter is hard the
instrument is ready to be secured by molten sulphur into an orifice made in
the arm of the telegraph post.