Improvements in Safety Fuses for Electric Circuits.
Year: 1899

page_text: COMPLETE SPECIFICATION.
Improvements in Safety Fuses for Electric Circuits.
I, JOSEPH SACHS, residing at No. 220, Collins Street, Hartford, in the County of
Hartford, and State of Connecticut, United States of America, 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 fol-
lowing statement:-
Safety fuses have heretofore been employed in electric circuits, the fuse to be
melted or disrupted by an excess of current so as to prevent injury to translating
devices in the circuit, and such safety fuses have been placed within tubes so as
to prevent injury from the melted metal or from any flame or electric arc that
may exist between the terminals by the passage of the electric current.. But it
has not heretofore been easy to ascertain which safety fuse in the electric circuit
may have been disrupted, because the case has prevented the injured safety fuse
from being noticed.
In carrying out the present invention I make use of two or more metallic con-
ductors in the complete safety-fuse, the, joint capacity of which is such that the
fuse will be melted or disrupted before injury occurs to any of the translating
devices in the. electric circuit, and when the current is in excess so that the safety
fuse is brought into action, one of the wires will be first disrupted and the cur-
rent passing by the second wire prevents the formation of an electric arc.by the
melting or disruption of the first wire. This second wire is fine and is on the
outside of the case holding the main wire, and it is disrupted, broken, melted, or
so rapidly injured that an electric arc is not liable to be formed, and the fact
that the enclosed wire has been disrupted will be appreciated by the visible dis-
rupted condition of the wire on the outside of the case.
In the drawing, Figure 1 represents by a sectional view the fuse in the form
adapted to general use with the main fusible strip within the case, and the fine
fuse outside, and Fig. 2 is a plan view of the exterior of the case showing the
outside fuse wire.
The terminals A and B are of any desired character and the fusible strip C is
of metal and adapted to being melted by the passage of 'the electric current, if
such current is in excess so as to break the circuit before any of the translating
devices in the circuit are liable to injury.
The case D may be of any desired character. I prefer to employ insulating
material and to make the case tubular and to employ end plugs or heads HH
within the open ends of the case, which end plugs or heads are preferably of
vulcanized fibre or cement.
:
The terminals A B are in the form of crossing pins which pass through the
heads and through the tubular casing, and the safety fuse passes centrally through
the case and the respective ends thereof pass into the end plugs or heads and are
electrically connected to the terminals AB..
The second conductor E is preferably a fine wire having a resistance that renders
This second
such wire adapted to act in connection with the fusible strip C.
wire is on the outside of the case and it may be protected by or embedded in a
covering, such as a piece of thin asbestos paper F, which will be torn or injured
by the passage of the current through the second wire E. This thin covering of
asbestos paper or similar material is not shown in Fig. 2 of the drawing. The

page_text: respective ends of the second conductor E are connected to the ends of the ter-
minals A B where they project through the insulated case D.
If now an excess of current passes through the safety fuse, the fusible strip C
is melted or disrupted, but an arc will not be formed in so doing, because the
second route for the electric current exists through the wire E and the current
being concentrated on this thin wire will cause the same to be substantially and
instantly destroyed, but the volume of the same is not sufficient to cause any
risk of fire, but the fact of this second wire E being destroyed is easily visible
on the outside of the case, so that the injured safety fuse may be removed and
another one substituted.
I find a convenient manner of making the exterior conductor is to take a piece
or strip of foil and fasten it to a strip of asbestos or similar paper and apply the
same, with the respective end portions of the foil in contact with the ends of the
terminals A B upon the outside of the tubular case and the passage of the current
disrupts this foil and by breaking the paper renders the injury to the safety fuse
visible.
I do not limit myself to the particular details of the construction of the herein
described device so long as the fuse wire is within a case and there is a second
wire or fusible strip outside the case, so that the disruption of the fuse within
the case is visibly appreciated by the disruption of the strip or wire outside the
case.
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―
:
First The combination with a tubular casing having closed ends and pro-
jecting terminals therein, of two fuse wires between and connecting the terminals,
the one passing longitudinally through and within the casing between the closed
ends and the other extending visibly along the outer surface of the casing between
the terminals, substantially as specified.
Second: An electric safety cut-out having a fusible wire and casing for enclos-
ing the same, a second conductor exterior to the casing and also connecting the
terminals and a covering to the second conductor, substantially as specified.
Third: The combination with a tubular casing having closed ends and pro-
jecting terminals therein, of two fuse wires between and connecting the terminals
and varying in diameter and resistance, the larger being within the casing and
the smaller upon the outer surface of the casing, substantially as set forth.
Fourth-The combination with a tubular casing having closed end plugs
between which and within the casing is a space, projecting terminals passing
through said end plugs or heads, fusible wires between and connecting the ter-
minals, one being wholly within the casing and extending through the space
therein and the other upon the outer surface of the casing, substantially as set
forth.
Fifth The combination with a tubular casing having end plugs therein,
closing the same with a space between the plugs, terminals passing through said
end plugs and the casing and projecting and thus securing the end plugs in the
tubular casing, a low resistance wire wholly within the casing connected to the
terminals and extending through the space within the casing and a high resist-
ance wire connected to the ends of the terminals upon the outer surface of the
casing, substantially as set forth.
Dated this 2fith dov of Oatakan 1900
HARRIS & MILLS,
23, Southampton Buildings, London, W.C., Agents.