Improvements in Electric Insulators.
Year: 1898

page_text: Date of Application, 5th July, 1898-Accepted, 17th Sept., 1898
COMPLETE SPECIFICATION.
Improvements in Electric Insulators.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of this
invention (which has been communicated to us from abroad by Ben Willard, resid-
ing at Schenectady, in the County of Schenectady, State of New York, United
States of America, Electrical Engineer) and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:-
This invention relates to insulators which are designed to support a conductor
rail, such as that of the well known tramway systems.
The invention has for its object to provide an insulator which is simple in con-
struction, practically indestructible and one which will permit the conductor rail
or its support to move slightly up and down without breaking the insulating
medium employed in the insulator, or being twisted out of position.
It is customary to mount the third rail insulators on the same cross ties which
support the traffic rails, and as the ties move up and down slightly as the trains
pass over them, it causes considerable strain on the insulators since the pressure
on the third rail is so very slight that it does not move up and down in a manner
corresponding to the traffic rails. To provide for this independent movement, one
portion of the insulator is bolted to the cross tie and the other portion is secured
to the conductor rail; the two parts being so related to each other that they are
capable of free independent movement in a vertical plane, but are prevented from
independent movement in a horizontal plane.
In the accompanying drawings, which show an embodiment of the invention,
Fig. 1 is a perspective view of an insulator; Fig. 2 is a plan view of the same,
and Fig. 3 is a side elevation with the cap in section.
The insulator is provided with a rectangular metal cap A, having downwardly
projecting sides B, which are flared at their lower extremity to form a water
shed C, so that water will not run down the sides of the insulating block D, and
cause the current to leak from the conductor rail, L, to ground. In addition to
forming a water shed this construction also increases the creeping surface of
the insulator. On top of the cap, and formed integral therewith, are two lugs E
and F situated at diagonally opposite points and adapted to grip the lower flange L¹
of the conductor rail L. The lugs are cut away slightly on one corner, to permit
the cap to be secured to the rail by a slight rotary movement. The position of
the cap at the time it is to be applied to the rail is shown in dotted lines in Fig. 2.
The shape of the lugs is such that they will grip and securely hold the conductor
rail. It is preferable to make the body D of the insulator of wood, as it is found
that it will stand an almost unlimited amount of abuse without breaking, as well
as the strains to which it is subjected in ordinary use. If desired, however, porce-
lain or vitrified brick may be employed without departing from the invention.
The insulating material is cut away at G so as to increase the outer surface of

page_text: the insulator over which the current must creep in order to form a leak. This
arrangement also possesses the advantage that moisture will collect at the edge G¹
and drop instead of creeping down the entire side. The top of the block and also
the corners are chamfered slightly to compensate for the rounded corners of the
cap. It is intended that the fit between the body of the insulating material and
the cap shall be such that the former is free to move into and out of the cap with-
out binding. Situated on opposite sides of the block and at an angle to each other
are holes H and I, arranged to receive the lag screws J for securing the insulator
to the cross tie. The block is counterbored at K to receive the heads of the lag
screws. By staggering the lag screws and arranging them so that they make an
angle to each other, the insulator can be very firmly secured in place.
The block, if of wood, is preferably, prepared by soaking it in asphaltum and
then coating it with japan; this prevents it from absorbing moisture and also
increases its insulating properties.
The insulator is applied to the rail as shown by the dotted lines in Fig. 2; it is
then swung around. to the position shown by the full lines and secured to the cross
tie M by the lag screws J. The cap is prevented from turning by the angular
surfaces of the insulating block D and, since these surfaces are made large, they
are able to withstand all the strains to which the insulator is subjected. Neverthe-
less, the body of the insulator is free to move up and down within the cap as the
cross tie upon which it is mounted moves. By this arrangement, the insulators
are not subjected to strains as the trains pass by, and a certain amount of freedom
of movement is permitted to all parts.
Having now particularly described and ascertained the nature of our said
invention (as communicated to us from abroad) and in what manner the same
is to be performed, we declare that what we claim is:-
1-In an insulator for an electric conductor, the combination with a body of
insulating material of a metal cap, free to move up and down on the insulating
material, supporting the conductor, and means for preventing the cap from turn-
ing on the insulating material, and means for securing the insulating material
to a support.
2-In an insulator for an electric conductor, the combination of a metal cap
having a receptacle which is other than round, with a body of insulating material
arranged to fit into the cap and be free to move in and out, but prevented from
turning therein, and means for securing the insulator to a support.
3-In an insulator for an electric conductor, the combination of a metal cap,
lugs on the cap for holding the conductor, a receptacle formed on the underside
of the cap which is other than round, a body of insulating material having a
portion formed thereon which corresponds to the receptacle in the cap, the arrange-
ment being such that the cap and insulating material are capable of independent
movement in a vertical plane, but not in a horizontal, and means for securing the
body and insulating material to a support.
4 In a third rail insulator which is arranged to be applied to the rail by a
slightly rotary movement, the combination of a cap having lugs thereon cut away
at an angle for gripping the rail, a receptacle formed on the under side of the cap
and provided with angular surfaces, a body of insulating material adapted to be
secured to the cross tie and provided with angular surfaces corresponding to the
surfaces on the cap, the cap and the body of insulating material being so arranged.
that they are capable of free independent movement in a vertical plane, but not
in a horizontal plane.
5 In a third rail insulator adapted to be secured to the rail by a slight rotary
movement, the combination of a cap having cut-away lugs formed integral there-
with, and a four sided receptacle formed in its under side, a wooden base for
supporting the cap, having a notched or cut-away portion arranged to increase
the creeping surface, and lag screws for securing the wooden base to the cross ties. 5

page_text: 6-As an article of manufacture, an insulating cap comprising a body of metal
having rail securing lugs E and F formed integral therewith, the lugs being cut
away at an angle to receive the rail, a flaring flange C, and a receptacle formed
in the under side of the cap having angular faces to prevent rotation of the insu-
lating support when the insulator is assembled.
Dated this 5th day of July 1898
tn
THE BRITISH THOMSON-HOUSTON CO. LTD.,
J. J. MANHEIM,
ALFRED CLEMENTS,
Directors.
Assistant Secretary.