An Improvement in Electrical Cut-outs.
Year: 1890

page_text: Date of Application, 6th Sept., 1890
Complete Specification Left, 26th May, 1891-Accepted, 27th June, 1891
PROVISIONAL SPECIFICATION.
[Communicated from abroad by Messrs. SIEMENS & HALSKE, of Berlin, in the
German Empire, Electrical Engineers.]
An Improvement in Electrical Cut-outs.
We, SIEMENS BROTHERS & Co. LIMITED of 12 Queen Anne's Gate, West-
minster, in the County of Middlesex, Electrical Engineers, do hereby declare the
nature of this invention to be as follows:-
Various electrical cut-outs have been constructed with the intention of avoiding
damage on the melting of the lead strip by fire, which might result from the dropping
lead or from the luminous are which is frequently produced. In most of these
known constructions the strip of lead is hermetically sealed in cases made of
insulating fire-proof material.
This is objectionable because a new case is required with each new strip of lead,
and often an explosion occurs on the melting of the lead in a hermetically
sealed casc.
It is found
The object of this invention is to avoid the above mentioned evils.
by experiment that it is unnecessary to hermetically seal in the strip of lead in
order to protect the surrounding space from the effects of its melting. It is
sufficient to introduce the strip into a fire proof chamber through grooves which
must not be too wide, taking care that the strip does not connect the terminals of
the cut out in a straight line, and that the first interruption of the circuit by its
melting must take place in the interior of the chamber. The arc produced between
the terminals naturally disappears without doing any damage, if it is forced to find
a way round the corner or corners of some insulating body.
The fusible strip may have a single bend at right angles round the corner of a
piece of insulating material, or it may have several bends, as for instance, over a
rectangular bar of insulating material, and at one of the bends, the cross section of
the strip is diminished by notching its sides so that it must melt first at this point.
As soon as the arc produced on the melting of the strip becomes lengthened it must
bend round the corner and will immediately disappear.
A compact form of safety fuse embodying the above principles is as follows.
The fusible metal strip is made of approximately semicircular form narrowed about
its middle. Its ends are bent first at right angles and again at right angles so as
to form feet which are pressed on a pair of terminal plates by a circular cap held
to a circular base by a central bolt and nut. Both the cap and the base are made of
earthenware or other suitable insulating material and the cap is chambered so that
the fusible strip is left quite free within it. When fusion of the strip has taken
place it is only necessary to unscrew the nut and raise the cap in order to place a
fresh strip in the chamber.
Dated this 6th day of September 1890.
ABEL & IMRAY,
Agents for the Applicants.
COMPLETE SPECIFICATION.
An Improvement in Electrical Cut-outs.
We, SIEMENS BROTHERS & Co., LIMITED, of 12 Queen Anne's Gate, West-
minster, in the County of Middlesex, 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 :-
Various electrical cut-outs have been constructed with the intention of avoiding

page_text: damage on the melting of the lead strip by fire which might result from the
dropping lead or from the luminous are which is frequently produced. In most
of these known constructions the strip of lead is hermetically sealed in cases made
of insulating fire-proof material. This is objectionable because a new case is
required with each new strip of lead, and often an explosion occurs on the melting
of the lead in a hermetically scaled case.
The object of this invention is to avoid the above mentioned cvils. It is found
by experiment that it is unnecessary to hermetically seal in the strip of lead in
order to protect the surrounding space from the effects of its melting. It is
sufficient to introduce the strip into a fire-proof chamber through grooves which
must not be too wide, taking care that the strip does not connect the terminals of
the cut out in a straight line, and that the first interruption of the circuit by its
melting must take place in the interior of the chamber. The are produced between
the terminals naturally disappears without doing any damage, if it is forced to find a
way round the corner or corners of some insulating body, as shown in Figs. 1 and 2
of the accompanying drawings.
The fusible strip B mng (as shewn in Fig. 1) have a single bend B' at right
angles round the corner of a piece of insulating material, or it may have several
bends (as shewn in Fig. 2) as for instance, over a rectangular bar E of insulating
material, and at one of the bends as shewn in Fig. 14 the cross section of the strip is
diminished by notching its sides so that it must melt first at this point. As soon
as the are produced on the melting of the strip becomes lengthened it must bend
round the corner and will immediately disappear.
A compact form of safety fuse embodying the above principles is shown in section
by Fig. 3 and in plan by Fig. 4. The fusible metal strip 13 is made of approximately
semicircular form narrowed about its middle as shewn at A. Its ends are bent
first at right angles and again at right angles so as to form feet which are
pressed on a pair of terminal plates (to which the conducting wires are connected)
by a circular cap D held to a circular base S by a central bolt and nut M.
Both the cap D and the base S are made of earthenware or other suitable
insulating material and the cap is chambered so that the fusible strip is left quite
free within it. When fusion of the strip has taken place it is only necessary to
unscrew the nut M and to raise the cap D in order to place a fresh strip in the
chamber.
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 an electrical cut-out, arranging within a fire-proof casing or chamber the
fusible metal strip shaped or bent in such manner that it does not form a
straight electrical connection between the terminals, substantially as and for the
purposes set forth.
2. An electrical cut-out constructed substantially as herein described with
reference to the accompanying drawings.
Dated this 26th day of May 1801
ABEL & IMRAY,
Agents for the Applicants.