IMPROVEMENTS IN THE INSULATION OF ELECTRIC TELEGRAPH WIRES
Year: 1865

page_text: PROVISIONAL SPECIFICATION left by Samuel Alfred Varley at the Office
of the Commissioners of Patents, with his Petition, on the 18th May
1865.
I, SAMUEL ALFRED VARLEY, of 66, Roman Road, Holloway, in the County
of Middlesex, Telegraph Engineer and Contractor, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN THE INSULATION OF ELECTRIC
TELEGRAPH WIRES," to be as follows:-
This Invention has for its object an improvement on the insulator commonly
known as C. F. Varley's double V-insulator; it possesses all the conditions of
that insulator for insuring a high degree of insulation, and at the same time
is more powerful to resist strain, and is consequently not so liable. to receive
damage from the wire breaking or any cause throwing a strain upon the
insulators. This form of insulator is chiefly intended for those cases where
In
an iron hood is placed over the earthenware cups as a further protection.
the double V-insulators usually constructed the upper portion of the inner
cup where it is cemented into the outer earthenware cup, and the upper
portion of the outer earthenware cup where it is cemented into the iron hood,
are generally made taper and grooved both internally and externally, the
effect of this grooving is to very much weaken the strength of the earthenware,
and owing either to the warping of the clay when in the act of drying or
carelessness in their manufacture, this portion of the insulator is often of an

page_text: irregular figure and sometimes barrel-shaped; in consequence of this the
conditions for resisting strain are not nearly so favorable when iron hoods are
placed over the earthenware cups and the telegraph line wire placed in lugs
on the top of the hood, as is frequently done.
My improvement consists in making the earthenware cups with bands at
the top and bottom of the upper portion of the cups. The effect of this is
to counteract any irregularity in the shape, and to insure the full advantage
of the length of the fitting. Any suitable cement may be used for putting
the insulators together, I prefer in certain cases a cement consisting of a certain
description of asphaltum, shellac, and a certain proportion of india-rubber or
gutta percha, and add to this sometimes a certain proportion of very fine sand,
powdered flint, silicate of magnesia, or other suitable powder; this com-
pound requires a very high temperature to melt it and is very fluid when
melted. In some cases I cover the pins with a coating of sulphur and silicate
of magnesia or sulphur and very fine sand or powdered silica and sulphur,
this forms an insulating material which is nearly as effective in practice as
ebonite and much cheaper. I sometimes also coat the earthenware cups with
asimilor material
irregular figure and sometimes barrel-shaped; in consequence of this the
conditions for resisting strain are not nearly so favorable when iron hoods are
placed over the earthenware cups and the telegraph line wire placed in lugs
on the top of the hood, as is frequently done.
My improvement consists in making the earthenware cups with bands at
the top and bottom of the upper portion of the cups. The effect of this is
to counteract any irregularity in the shape, and to insure the full advantage
of the length of the fitting. Any suitable cement may be used for putting
the insulators together, I prefer in certain cases a cement consisting of a certain
description of asphaltum, shellac, and a certain proportion of india-rubber or
gutta percha, and add to this sometimes a certain proportion of very fine sand,
powdered flint, silicate of magnesia, or other suitable powder; this com-
pound requires a very high temperature to melt it and is very fluid when
melted. In some cases I cover the pins with a coating of sulphur and silicate
of magnesia or sulphur and very fine sand or powdered silica and sulphur,
this forms an insulating material which is nearly as effective in practice as
ebonite and much cheaper. I sometimes also coat the earthenware cups with
a similar material
DESCRIPTION OF THE DRAWING.
A, A, represent the pin of the insulator, which I prefer to be. parallel as
shown in the Drawing, this pin may be coated with ebonite or other insulating
material, if a high state of insulation be desired, and may be made of iron, steel,
malleable cast iron, or tempered steel, the lower end of the pin is not shewn
but can be made of any suitable shape. B, B, B, B, represent a section of
the inner earthenware cup; b, b, b, b, represent the two earthenware bands
previously described. C, C, C, C, represent the outer earthenware cup into
which the inuer cup B, B, B, B,,is cemented; c, c, c, c, represent the earthen-
ware bands on the upper portion of the outer cup. The iron hood into which
the outer earthenware cup is cemented is not shown in the Drawing. I
prefer to make all the fittings parallel, as shown in the Drawing, instead of
taper as is frequently done with the ordinary double V-insulator.
A, A, represent the pin of the insulator, which I prefer to be. parallel as
shown in the Drawing, this pin may be coated with ebonite or other insulating
material, if a high state of insulation be desired, and may be made of iron, steel,
malleable cast iron, or tempered steel, the lower end of the pin is not shewn
but can be made of any suitable shape. B, B, B, B, represent a section of
the inner earthenware cup; b, b, b, b, represent the two earthenware bands
previously described. C, C, C, C, represent the outer earthenware cup into
which the inner cup B, B, B, B,,is cemented; c, c, c, c, represent the earthen-
ware bands on the upper portion of the outer cup. The iron hood into which
the outer earthenware cup is cemented is not shown in the Drawing. I
prefer to make all the fittings parallel, as shown in the Drawing, instead of
taper as is frequently done with the ordinary double V-insulator.