Improvements in and connected with Electric Safety Fuses.
Year: 1899

page_text: Date of Application, 6th May, 1899-Accepted, 10th June, 1899
COMPLETE SPECIFICATION.
Improvements in and connected with Electric Safety Fuses.
I, JAMES GRAY, of 5, Allan Street, Dalmarnock, in the County of Glasgow,
North Britain, Electrical Engineer 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, that is to say:-
My said invention has for its object to improve the construction of electric
safety-fuses and their holders of the kind having bridge pieces for carrying the
fuse wire, my improvements relating to the bridge piece itself, to the means of
making contact with the "bus" bar or main conductor block and opposite
terminal block and to means for fixing the terminals to the slate or other
insulating base combined with means for securing the branch wire.
And in order that my said invention and the manner of performing the same
may be properly understood I hereunto append a sheet of explanatory drawings to
be hereinafter referred to and showing my improvements.
Figure, 1, on the accompanying sheet of drawings is a plan showing a part of a
safety-fuse board sufficient to hold two of my improved bridge pieces and parts
connected therewith. Figures, 2, and 3, are, respectively, a longitudinal vertical
section, and an end elevation partly in section, of same. Figures, 4, and 5, are
respectively, a partial plan and side elevation of a second modification.
In the modification shown in Figures, 1, 2, and 3, I employ a bridge piece, A,
of ceramic ware or other suitable insulating material this piece, A, instead of
having an open space between it and the slate, marble, or other suitable
insulating base, B, is, according to my invention, made to extend down to or near
to the base and a groove or channel, C, is made in this lower part as shown in
Figures, 2, and 3. A small projection, D, extends down from the upper part of
the bridge, A, into the channel, C, and the fuse wire, E, (the ends of which are
secured as hereinafter described) extends along in the channel, C, the part at the
middle lying in a small groove in the projection, 1). The fuse wire, E, is
thus entirely under cover and in the event of it becoming fused from any cause
the broken pieces are prevented from flying out and possibly causing one or more
of the other fuse wires on the board to become fused also. An opening, F, may
be formed as shown through the bottom edge of the lower part of the bridge on
each side leaving a space to allow for the expansion of volatile gases produced in
the event of the wire, E, fusing, or holes, G, (shown by dotted lines in Figure, 2)
may be formed for the same purpose; or both the openings, F, and holes, G,
may be used. A hole is formed through each outer projecting end, H, of the
bridge piece, A, to receive a screw, J, of special construction serving not only
to hold the ends of the fuse wire, E, but to act as improved forms of contacts with
both a "bus" bar K, and an opposite terminal block, L. Each end of the fuse
wire, E, is passed more or less round one of the screws, J, and pinched between two
nuts, M, on the screw. The lower end, N, of each screw, J, has a saw draft cut in
it and a hole or socket is formed in both the busbar, K, and the terminal
block, L, these sockets being tapered if desired, so that after the fuse wire, E,

page_text: has been secured as herein before described, the lower end, N, of one
screw, J, is inserted like a plunger in the socket in the bus bar, K, and the lower
end, N, of the other screw, J, in the socket in the terminal block, L, thus not only
holding the bridge piece, A, securely in position but effecting perfect electrical
contact. In some cases the saw draft may be dispensed with. The "bus"
bar, K, and terminal block, L. is recessed to receive the binding nuts, M, so that
when the bridge screw piece, A, and "bus" bar, K, and terminal, L, are in
good contact there is no intervening space between the bridge piece and both the
bus bar and terminal block. My improved form of wire fixing and contact
screw, J, may be employed in connection with any known form of bridge piece (A),
and the improved form of bridge piece having the longitudinal channel (C) in
which to lay the fuse wire (E) may also be employed in connection with other
known means of securing the ends of the wire and making electrical contact with
the "bus" bar (K) and terminal block (L).
An
hollow
The main conductor, P, is shown as attached in the usual manner to the
"bus" bar, K, and this bar is secured to the insulating base, B, as in other fuse
boards, by a number of screws, Q, inserted from the underside of the base.
improved form of fixing is provided for securing the opposite terminal block, L,
for each branch wire, to the base, B, this fixing serving also in securing.
the branch wire to its terminal. As shown in the drawings (Figure, 2)
the terminal block, L, is secured to the base, B, by means of a
screw, R, inserted from the underside through holes in the base so that the
upper end of the screw, R, projects above the base and is screwed into the
terminal block, L, thus holding the terminal in position. If desired small
steadying pins, S, may be formed on the underside of the terminal so as to project
into holes formed for them in the upper side of the base, B. A hole, T, is
formed through the terminal block, L, opposite the end of the hollow screw, R,
and the end of the branch wire, U, is passed up from the underside of the base, B,
through the hollow screw, R, so as to project into this hole, T, where it is securely
held by a pinching screw, V, entered from the outer end of the terminal
block, L.
This improved form of fixing and direct wiring by use of a hollow screw may
also be used for the "bus" bar instead of the ordinary method shown and
described, and instead of there being one continuous "bus" bar, K, as shown the
main conductor, P, may be connected to a separate terminal block or blocks
similar to, L.
Figures, 4, and 5, show the application of my improved form of bridge piece, A,
to a terminal block, L, which is secured to the base, B, in the usual manner by
means of ordinary screws, W, passed up through holes from the underside of
the base, the branch wire, U, being also secured in the usual manner by being
inserted in a hole, X, and held by a pinching screw, Y.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
:-
"
1. In and connected with an electric safety-fuse, a bridge piece made with a
longitudinal channel forming an isolating chamber in which the fuse wire lies
and with or without openings or holes in the sides of the channel, the ends of
the fuse wire being held between nuts on screws projecting through the ends of
the bridge piece and inserted into sockets formed for them in a
main conductor block and opposite terminal block, a hollow screw inserted from
bus" bar or a
the underside through the base into the terminal, a vertical hole formed through
the terminal and a pinching screw entered into this hole from the end of the
terminal block the parts being combined and operating all substantially as and
for the purposes hereinbefore described and as shown in Figures, 1, 2, and 3 of
the accompanying drawings.
2. A carrier for an electric safety fuse consisting of a bridge piece made with a

page_text: longitudinal channel forming an isolating chamber in which the fuse wire lies
and with or without openings or holes in the sides of the channel combined with
means for securing the ends of the fuse wire and effecting electrical contact
between a "bus" bar or a main conductor block, and an opposite terminal block
substantially as and for the purposes hereinbefore described.
bus
"
3. In and connected with an electric safety-fuse a bridge piece carrying a fuse
wire the ends of which are secured between nuts on screws projecting through the
ends of the bridge piece and inserted into sockets formed for them in a
bar or a main conductor block and opposite terminal block substantially as and
for the purposes hereinbefore described.
4. In and connected with an electric safety-fuse, a hollow screw inserted from
the underside through the insulating base into a terminal block or bus bar or
main conductor block a vertical hole formed through the terminal block or bus
bar or main conductor block and a pinching screw entered into this hole sub-
stantially as and for the purposes herein before described. .
Dated this Fifth day of May 1899.
EDMUND HUNT,
Applicant's Agent.