IMPROVEMENTS IN * ELECTRICAL SAFETY PLUGS OR FUSES " PROVISIONAL SP
Year: 1883

page_text: LETTERS PATENT to Charles Vernon Boys of Wing near Oakham in the
County of Rutland and Henry Hardinge Cunynghame of Paper Buildings
Temple in the County of Middlesex for an Invention of "IMPROVEMENTS IN
* ELECTRICAL SAFETY PLUGS OR FUSES
"
PROVISIONAL SPECIFICATION left by the said Charles Vernon Boys and
Henry Hardinge Cunynghame at the Office of the Commissioners of Patents
on the 2nd April 1883.
CHARLES VERNON BOYS of Wing near Oakham in the County of Rutland and
HENRY HARDINGE CUNYNGHAME of Paper Buildings Teinple in the County of
Middlesex IMPROVEMENTS IN ELECTRICAL SAFETY PLUGS OR FUSES
"
"
Our invention relates to electrical safety plugs or fuses, that is to say, portions of
an electrical circuit which shall give way and open the circuit whenever a current
beyond the normal strength passes through them. The object of our invention is
to construct such safety plugs or fuses in a simple and compact form, and in such
a manner that they will immediately act whenever the current becomes too powerful,
and that after one has acted, a fresh plug or fuse can be readily substituted for it.
For this purpose, we make the plug or fuse in two parts, of metal in the form of
thin strip or wire, and we unite these two parts by soft solder, taking care to
make the junction of small extent. We fix the two ends of the plug thus made so
as to connect two points of the circuit to which it is to be applied, securing it by
screws or by merely pushing its ends tightly into holes or slits in suitable terminals,
and we apply to the plug or fuse a spring or springs so as to put a strain on the
junction. These springs may be separate from the plug and may be attached to
the terminals which it joins, or the plug itself may be so bent or twisted before
being fixed in position, that its own elasticity imposes on on the junction the
required strain. When an excess of current passes through the plug, the junction
becomes heated and the solder gives way, permitting the two limbs of the plug to
fly apart in obedience to the springs or to their elasticity, and so opening the
circuit. In many cases, instead of joining the two limbs of the plug or fuse by
melted solder, we join them by a piece of wire made of metal readily fusible, in the
form of a pin or rivet, and inserted in holes or loops presented by the limbs.
:

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Charles Vernon Boys and Henry Hardinge Cunynghame in the
Great Seal Patent Office on the 2nd October 1883.
CHARLES VERNON BOYS of Wing near Oakham in the County of Rutland and
HENRY HARDINGE CUNYNGHAME of Paper Buildings Temple in the County of
Middlesex "IMPROVEMENTS IN ELECTRICAL SAFETY PLUGS OR FUSES
"
Our invention relates to electrical safety plugs or fuses, that is to say, portions
of an electrical circuit which shall give way and open the circuit whenever a
current beyond the normal strength passes through them. The object of our
invention is to construct such safety plugs or fuses in a simple and compact form,
and in such a manner that they will immediately act whenever the current becomes
too powerful, and that after one has acted, a fresh plug or fuse can be readily
substituted for it. For this purpose, we make the plug or fuse in two parts, of
metal in the form of thin strip or wire, and we unite these two parts by soft
solder, taking care to make the junction of small extent. We fix the two ends of
the plug thus made so as to connect two points of the circuit to which it is to be
applied, securing it by screws or by merely pushing its ends tightly into holes or
slits in suitable terminals, and we apply to the plug or fuse a spring or springs so
as to put a strain on the junction. These springs may be separate from the plug
and may be attached to the terminals which it joins, or the plug itself may be so
bent or twisted before being fixed in position, so that its own elasticity imposes on
the junction the required strain. When an excess of current passes through the
plug, the junction becomes heated, and the solder gives way, permitting the two
limbs of the plug to fly apart in obedience to the springs or to their elasticity, and
Bo opening the circuit. In many cases, instead of joining the two limbs of the
plug or fuse by melted solder, we join them by a piece of wire made of metal
readily fusible, in the form of a pin or rivet, or bent wire inserted in holes or
engaging loops presented by the limbs.
The forms of safety plugs or fuses constructed as above described may be very
various. One form which we find convenient is shewn in side view at Fig. 1 and
in plan at Fig. 2 of the accompanying drawings; a a are the two thin strips of
copper or brass narrowed at the ends which are united by solder at b. The other
ends are inserted in split holders d d fixed on a base c of insulating material, each
holder having a spring e which presses against one of the strips a, so that when
there is sufficient heat to melt the solder at b, the two strips a a are forced apart by
the springs e and bent away from each other as indicated by the dotted lines a².
It is convenient to fit in each of the holders d a sliding pin f to which the fingers
can be applied to push the springs e aside while a fresh fuse is being inserted into
the splits of the holders d d. Fig. 3 shews another form of safety plug or fuse
according to our invention. In this case there are two elastic wires g g one end
of each of which is inserted in a holder h, the other end being somewhat hooked.
The wires being bent so that their ends are brought together, they are held by a
bent piece of wire of fusible metal k. When this melts, the wires gg spring apart
as indicated by the dotted lines. According to another form shewn in Fig. 4 two
wires are coiled in the form of helical springs and their ends being flattened
are soldered together at m. When the solder melts, these ends spring apart.
Having thus described the nature of our invention and in what manner the same is
to be performed, we claim:-The construction of electrical safety plugs or fuses by
soldering together or joining together by a rivet or wire of fusible metal two metallic

page_text: strips or wires strained by their own elasticity, or by springs, so as to separate when
their junction is caused to give way by the heat resulting from excess of electricity
passing through it, substantially as herein described.
In Witness whereof I the said Charles Vernon Boys have hereunto set my hand
and seal this twenty-ninth day of September in the year of our Lord One thousand
eight hundred and eighty-three.