An Improved Electric Spark-fuse.
Year: 1899

page_text: Date of Application, 21st Aug., 1899
Complete Specification Left, 17th Mar., 1900-Accepted, 28th Apr., 1900
An Improved Electric Spark-fuse.
.
I, GEORGE GATTON MELHUISH HARDINGHAM, of Clun House, Surrey Street, in
the County of London, Civil Engineer and Chartered Patent Agent, do hereby
declare the nature of this invention (a communication from abroad from Ottomar
R. Schulz, of 131, Leipziger Strasse, Berlin, in the German Empire, Agent,)
to be as follows:-
This invention relates to electric fuses of the class in which the ignition of
the priming composition is effected by electrical discharges which take place
between two naked metal rods embedded in the composition and respectively
connected with the conductors. With such devices miss-fires" are frequent;
and it is well known that failure is in many instances attributable to the fact that
the electrical discharge in the priming material assumes, as it were, the form of a
thin thread or filament which connects the pole wires at the moment of discharge.
The present invention is designed to avoid this defect and to ensure reliability
in working: same consisting in producing between the ends of the pole wires,
not a spark in the shape of a thread but a sheaf or cluster of sparks. This result
may be accomplished in the following manner:
About the naked ends of the pole wires (which, with the exception of their
ends, are carefully insulated) a narrow strip of paper is wound spirally; the ends
of the latter being attached to the respective wires by means of shellac or the
like. To this strip of paper is attached a strip of tinfoil, preferably of a width
equal to that of the paper; care being taken that the strip of tinfoil nowhere comes
into direct contact with the pole wires. The latter are surrounded in the usual
manner by priming material enclosed in a cylindrical case.
At the moment of discharge, the electric spark in a fuse constructed in this
manner will not flash in a straight line from one pole wire to the other, but it
will select for its passage the line of the spirally arranged strip of tin-foil; and,
inasmuch as sparks flash simultaneously at all the points where the tinfoil
approaches the pole wires, a sheaf of sparks results.
With induction coils as commonly used for operating electric fuses, it is readily
feasible, with the aid of these improved fuses, to bring about explosions at a
distance of upwards of ten miles. As a priming composition fine-grained black
gunpowder would be appropriate; but any other igniting material, susceptible
to the action of electric sparks, may be employed.
In shape, the fuse may be made to accommodate any priming cap; and the
sheaf of sparks may be augmented by increasing the number of convolutions of
the strip of tinfoil.
For the strip of paper, any other good insulating material, such as india-rubber,
animal bladder, properly treated textile fabrics and the like, may be substituted;
and, instead of assuming the form of a strip, the non-conducting material may be
arranged upon the pole ends as rings or plates disposed at convenient distances
apart. Under such circumstances, a strip of good conducting material is stretched

page_text: over the pieces of insulating material. This strip may be connected with one
of the pole-ends.
Instead of the strip of tinfoil being arranged about the pole-ends, means of a
similar character and adapted to distribute or scatter the electrical discharge may
be disposed between the pole-ends. In this case, the strip of conducting material
is wound upon a thin plate of insulating material, such as bone or porcelain, and
this plate is secured between the pole-ends in any manner adapted to ensure its
maintaining its proper position. The strip may consist of a number of separate
pieces; or it may be slotted or perforated so as to produce additional sparking
points.
Datal thin 01at
1000
An Improved Electric Spark-fuse.
I, GEORGE GATTON MELHUISH HARDINGHAM, of Clun House, Surrey Street, in
the County of London, Civil Engineer and Chartered Patent Agent, do hereby
declare the nature of this invention (a communication from abroad from Ottomar
R. Schulz, of 131, Leipziger Strasse, Berlin, in the German Empire, Agent,)
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 electric fuses of the class in which the ignition of
the priming composition is effected by electrical discharges which take place
between two naked metal rods embedded in the composition and respectively
connected with the conductors. With such devices "miss-fires" are frequent:
and it is well known that failure is in many instances attributable to the fact that
the electrical discharge in the priming material assumes, as it were, the form of a
thin thread or filament which connects the pole wires at the moment of discharge.
The present invention is designed to avoid this defect and to ensure reliability
in working; same consisting in producing, between the ends of the pole wires,
not a spark in the shape of a thread but a sheaf or cluster of sparks. This result
may be accomplished in various ways; some examples of the manner in which
my invention may be carried out being illustrated in the accompanying drawings.
Referring to Figs. 1, 2 and 3, whereof Figs. 1 and 2 are elevations of an electric
spark-fuse having the ends of the pole wires exposed and Fig. 3 an elevation of
the completed fuse, a narrow strip of paper e is wound spirally about the naked
ends a, of the pole wires c, d (which, with the exception of their ends, are
carefully insulated); the ends of the stripe or the several convolutions thereof
being attached to the respective wires a, b by means of shellac or the like. To
this strip of paper e is attached a strip of tin foil f, preferably of a width equal
to that of the paper; care being taken that the strip of tin foil nowhere comes into
direct contact with the pole wires a, b. The latter are surrounded in the usual
manner by priming material enclosed in a cylindrical case h.
When, for various reasons, such as the utilisation of longer strips of tin foil
and the augmentation of the number of sparking points, the spirally wound strips
are interlaced about the pole-ends or, in other words, are wound approximately
in the form of the numeral "8," as illustrated in Figs. 4, 5, 6 and 7, the strip of
tin foil f is placed between two strips e el of paper. These three strips may be
secured together. It will be seen that the object in employing two strips of paper is
to ensure that each side of the strip of tin foil shall be insulated from the pole

page_text: wires; this mode of winding or interlacing bringing first one and then the other
side of the combined strip in proximity to the pole-ends.
At the moment of discharge, the electric spark in a fuse constructed in this
manner will not flash in a straight line from one pole wire to the other, but it
will select for its passage the line of the spirally arranged strip of tin foil; and,
where the tin
inasmuch as the sparks flash simultaneously at all the points
foil approaches the pole wires, a sheaf of sparks results. A number of fuses are
usually connected in parallel and may be discharged by means of an electricity
generating machine of low power, without risk of "miss-fires."
With induction coils, as commonly used for operating electric fuses, it is
readily feasible, with the aid of these improved fuses, to bring about explosions
at a distance of upwards of ten miles.
As a priming composition fine-grained black gunpowder would be appropriate,
but any other igniting material, susceptible to the action of electric sparks, may
be employed.
In shape, the fuse may be made to accommodate any priming cap; and the
sheaf of sparks may be augmented by increasing the number of convolutions of
the strip of tin foil f. Instead of a strip, the conducting material may be in the
form of thread or wire.
For the strip of paper, any other good insulating material, such as india-rubber,
animal bladder, properly treated textile fabrics and the like, may be substituted ;
and, instead of assuming the form of a strip, the non-conducting material may
be arranged upon the pole-ends as rings or plates disposed at convenient distances
apart. Under such circumstances, a strip of good conducting material is stretched
over the isolated pieces of insulating material. This strip may be connected
either directly or indirectly with one of the pole-ends.
Iustead of the strip of tin foil being arranged about the pole-ends, means of a
similar character and adapted to distribute or scatter the electrical discharge may
be disposed between the pole-ends. Referring to Fig. 8, the strip f of conducting
material is wound upon a thin plate of insulating material, such as bone or
porcelain, and this plate is secured between the pole-ends a, b in any manner
adapted to ensure its maintaining its proper position. The strip may, moreover,
be of a non-continuous character and consist of a number of separate pieces f*,
Fig. 9, or it may be slotted or perforated so as to produce additional sparking
points.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I claim:-
1. An electric spark-fuse constructed substantially as herein described and
wherein the electric discharge is effected from numerous points distributed about
the pole-ends.
2. An electric spark-fuse in which the electric discharge is effected simul-
taneously from various points evenly or unevenly distributed about the surfaces
of the pole-ends, and whereby clusters of sparks result upon the passage of the
electric current, substantially as herein described.
3. An electric spark-fuse in which an electric conducting strip is disposed in
spiral windings about the naked pole-ends of the fuse, which strip is insulated
from both pole-ends, substantially as herein described.
4. An electric spark-fuse in which an electric conducting strip of ribbon-like
form is wound about the naked pole-ends, such strip being isolated from the one
pole-end and in electrical connection with the other pole-end, substantially as
herein described.
5. An electric spark-fuse wherein a metallic layer is provided between the naked
pole-ends of the fuse, which layer is insulated from the pole-ends and forms a
bridge for the conveyance of electric sparks from one pole-end to the other,
substantially as herein described.
6. In an electric spark-fuse, the employment of a non-continuous conducting

page_text: strip and an insulating medium disposed between the pole-ends, whereby the
passage of the electric current between the pole-ends is interrupted,
sparks
are produced at such points of interruption of the strip, substantially as herein
described.
7. In an electric spark-fuse, the combination, with two naked pole-ends, of a
conductive body and an insulating medium, substantially as and for the purposes
specified.
8. In an electric spark-fuse, the combination, with two naked pole ads, of a
non-conductive plate arranged between the pole-ends, and a conductive strip or
conductive pieces on the said plate, substantially as and for the purposes specified.
Dated this 8th day of March 1900.
For the Applicant,
G. G. M. HARDINGHAM,
Chartered Patent Agent, Clun House, Surrey Street, London, W.C.