Improvements in Plug Switches or Wall Contacts for Electric Circuits.
Year: 1898

page_text: Date of Application, 1st Nov., 1898-Accepted, 17th Dec., 1898
COMPLETE SPECIFICATION.
Improvements in Plug Switches or Wall Contacts for Electric
Circuits.
We, ALBERT VANDAM, and THOMAS HERBERT MARSH, both of 39, Victoria
Street, Westminster, Electrical Engineers, 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:-
This invention relates to plug switches or wall contacts for electric circuits,
and in particular to switches of the description wherein the leads are connected
to concentric terminals which are insulated from each other by a tubular piece
of non-conducting material and an outer partially tubular piece of the same.
The present invention has for its object to provide for connecting one of the
terminals to its respective lead by means of a fuse wire which is passed round
or over suitable supports projecting from the outer partially tubular non-con-
ducting piece hereinabove mentioned.
The invention will be readily understood by the following description, reference
being had to the accompanying drawing, in which
Figure 1 is a plan of a plug switch or wall contact constructed in accordance
with our invention.
Figure 2 is a side elevation, and
Figure 3 a section on line 3-3, Figure 1.
Figure 4 is a perspective view of the insulating piece which serves to support
the fuse.
A is the base of the switch to which is secured the innermost tubular contact B,
provided with a terminal B¹ to which one of the leads is connected. The outer
terminal C is not directly connected with the other lead, but is provided with
means, such as a screw C¹, to which one end of a fuse wire D is attached the
other end of said fuse wire being connected to a terminal E to which the second
lead is secured. In order to prevent arcing between the various terminals an
insulating piece is provided consisting of an inner tubular portion F, and an
outer partially tubular portion F¹. these portions being preferably connected at
the bottom to form one piece. The fuse wire is supported on projections F2 of
insulating material formed integrally with the outer tubular portion F¹, and
we prefer to provide saw-cuts F3 in said projections to hold the fuse wire as
shewn, so that if breakage of the wire occurs the broken ends will not make
contact with other metallic portions of the device. We sometimes provide other
pieces of insulation F projecting between the terminal B and the base of the
outer terminal C, and also between the terminal B and the terminal E so as to
prevent any possibility of an arc occurring between these parts, but such insula-
tion, while desirable, is not in many cases essential.
The saw-cuts F3 may be of any suitable shane, and we do not restrict ourselves
in respect to the position of such saw-cuts. In certain cases it is convenient to
make them at the top or at the corner of the insulating supports, instead of at
the side as shewn.

page_text: Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is:-
1. In a plug switch or wall contact having concentric terminals, an insulating
piece composed of an inner tubular portion and an outer partially tubular portion
provided with projections for supporting a fuse wire, substantially as described.
2. A plug switch or wall contact constructed substantially as described with
reference to the accompanying drawings.
1000.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicants.