Improvements in and relating to Cut-outs and similar Devices for Electric Circuits.
Year: 1896

page_text: Date of Application, 30th Sept., 1896-Accepted, 28th Nov., 1896
COMPLETE SPECIFICATION.
Improvements in and relating to Cut-outs and similar Devices for
Electric Circuits.
I, ARNOLD VON WURSTEMBERGER, Ph.D., of 66 Colonnenstrasse, Schoeneberg,
near Berlin, in the German Empire, 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:-
This invention relates to cut-outs and similar devices for protecting electric
circuits and apparatus against the effects of a too strong current.
The device at present commonly employed consists of a fuse formed of a thin
wire which is placed in the circuit and is of such dimensions and material that it
melts and breaks the circuit upon the passage of an excess of current. Such
fuses, however, are not always satisfactory in action, as damage to the apparatus to
be protected may be caused by the continued passage of a current which is in
excess of the normal but is too weak to melt the fuse. In addition, too, there is
danger after the circuit has been broken as an unsuitable path may be provided
for the current through fragments of the fused metal or through a short circuit to
earth or return.
The objects of the present invention are to provide means for breaking the
circuit either upon the momentary passage of a strong current or the continued
passage of a weaker but still dangerous current; to connect the broken circuit to
earth or return; and in the case of apparatus contained in a building to effect a
cut-out or break of circuit on the outside of the building.
It will of course be understood that although in the following description I
describe my devices as applied to a telephone circuit, they are equally applicable
to any other electric circuit.
The cut-out devices I employ are of two kinds, one, an "Ampere" cut-out
which operates at once upon the passage of a dangerous current, and the other a
"Coulomb" cut-out which operates upon the continued passage of a weaker but
still dangerous current.
The Ampere" cut-out may consist of one of the ordinary fuses at present in
use, but the "Coulomb" cut-out is of special construction and will be hereinafter
described. Both these devices are employed at each station or the like to he
protected, the "Ampere" device being preferably outside the station and the
Coulomb" device within.
The accompanying drawings illustrate in what manner my invention may be
carried into effect and I will now refer to them.
Figure 1 is a diagrammatic view of two telephone circuits and a central station
with my improved devices inserted in the circuits.
Figures 2 to 13 illustrate modified forms of the "Ampere " and "Coulomb "
devices.
Referring to Figure 1, C represents the central station and A and Al two
subscribers stations. L is a simple aerial conductor; K is a cable leading to the
cable box k where the aerial conductor L 1 commences; F and F 1 are the
"Coulomb" devices of the central station; f and f1 are the "Coulomb" devices of
the subscribers' stations; H and H 1 are the "Ampere devices of the central
station; and h 1 are the similar devices of the subscribers' stations; T and T1
are the subscribers' telephones, and M and M1 are the central station
annunciators.
"

page_text: If an excessively strong current-enters or passes through the lines L or L1 at
Jor J1 it passes through the conductors to C and A or A1 respectively. I will
deal with the circuit of which the line L forms part, it being understood, of course,
that the line L1 and its devices would be similarly affected upon the passage of a
dangerous current. The current passes through line L and through and M to
earth. The "Coulomb" device operates as will hereinafter be described and the
line L is cut out and connected directly to earth. The current thus continues and
if sufficiently strong will fuse the "Ampere" device which is outside the building.
In the case of the cable K the device H1 being at the outer end, the cable is
included in the cut-out or protected portion of the circuit.
As before explained the "Ampere " device may consist of a simple fuse protected
by a cover from outside damage, but it may if desired be of any convenient form
such as those illustrated in the drawings.
One arrangement of "Coulomb" device is illustrated in Figure 2. It consists
of a contact arm A which is pulled or pressed in the direction of the arrow by
means of a suitable spring or weight. This arm is retained in the position shown
by a wire d which is connected by a silk thread i with the fuse device S with which
it is also in electrical contact. T is the terminal of the fuse, and is in contact
with the telephone or other apparatus or instrument. The current enters the
circuit from the line through the wire a whence it passes through the arm A, the
wire d, the fuse S, and the terminal T. If a current of excessive strength or
dangerous strength enters the circuit the device S is fused the fusing occupying
more or less time according to the strength of the current. The arm A is thus
released and is pulled against the earth terminal E. A complete circuit is thus
maintained and the telephone or the like is cut out. In the event of a very
excessive current the wire d may fuse before the fuse S has time to act.
Figures 3 and 4 illustrate one form of fuse which may be employed consisting
of two thin pieces of copper foil a, a 1, soldered together at L by some easily
fusible metal. Insulated wire is then coiled round it and connected to the circuit
wires q, q. When the coil is heated by the passage through it of a strong current
the solder is melted.
In Figure 4 the two pieces of foil a, 1 are soldered together and the wires 77
are connected to them by fusible metal at L, L 1.
In the device shown in Figure 5 a coil of wire S is embedded in and surrounded
by sealing wax or some similar suitable substance, which softens or melts when it
is heated. This device may be employed in connection with the arm A, Figure 2,
one end of the coil being connected to the arm. Upon the passage of an excessive
current the wax is softened or melted and the coil S will be extended by the
movement of the arm under its spring until the arm makes contact with the
terminal E. A single stretched wire may of course be employed, but in this case
actual fusing would be necessary before the circuit could be interrupted. A wire
thus insulated acts quite differently to a bare fuse wire exposed to the air. The
latter fuses immediately the current reaches a certain point, whereas the former
only fuses after it has imparted a certain number of heat units to the surrounding
mass which becomes heated and melts. Such an insulated wire forms a "Coulomb
device and may be used in substitution for the device marked S in Figure 2. It
will thus be seen that with the coiled wire actual fusing is unnecessary to enable
the arm to make contact with the earth.
In the modification shown in Figure 6 the coil S is wound round a thin tube P.
One end of the wire, d, is connected to- the arm A. and has attached to it one end
of a cord i the other end of which k is connected by means of resin or the like
to the interior of the tube P. Upon the tube being heated by the passage of a
current of excessive strength the resin melts and allows the wire d and consequently
the arm A to which it is attached to move freely. Instead of one thread two may
be employed if desired.
In the modification shown in Figure 7g is a closed glass tube filled with a
suitable liquid, alcohol for example, and containing, a coiled wire m, n. The

page_text: passage of an excessive current heats the wire and the surrounding liquid until
the tube bursts and the wire is free to move and to fuse. This device may be
constructed to act at any desired temperature by varying the dimensions of the
wire and by charging the tube with different liquids and with different quantities.
If desired the apparatus may be formed like an ordinary thermometer the tube
being empty. Instead of employing alcohol to charge the tube pure water may be
used.
Figure 8 illustrates a device suitable for use with currents of high intensity.
This device when in use is to be placed in a vertical position as shown in Figure 9.
It consists of a charged tube g in which are fused the two wires D and D 1. The
space U between them is bridged by the wires which is fused by an excessive
current. The heat developed will, in most cases, not be sufficient to burst the glass
tube but in the event of a higher intensity being reached an arc will be formed
between the ends of the wires and the glass tube will be immediately broken.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is-
1. The combination with an electric circuit or with electrical apparatus, of two
cut-outs or protecting devices, one of which, the more sensitive, is arranged to
operate to break the circuit and make earth connection upon the passage of a
certain current for a certain time, aud the other of which is arranged to operate
and break the circuit upon the further passage of a stronger current, substantially
as hereinbefore described and as illustrated by the accompanying drawings.
2. A fuse for electric circuits, consisting of two pieces of metal foil soldered
together and provided with a coil of insulated wire, substantially as hereinbefore
described and as illustrated by the accompanying drawings.
3. A fuse for electric circuits, consisting of a coil of conducting wire embedded
in sealing wax or other suitable material which is capable of softening or melting
and allowing the coil to be deformed, substantially as and for the purpose herein-
before described and as illustrated by the accompanying drawings.
4. A fuse for electric circuits, consisting of a sealed glass tube containing a
suitable liquid and provided with a conducting wire or with conducting wires
which upon the passage of an excessive current heat the liquid and fracture the
tube, substantially as hereinbefore described and as illustrated by the accompanying
drawings.
5. A fuse for electric circuits, consisting of a conductor coiled round a tube and
having one of its ends retained by a cord, the cord being released by the heat
generated by the passage of an excessive current through the conductor,
substantially as herein before described and as illustrated by the accompanying
drawings.
Dated this 28th day of Sentember 1806
W. E. HEYS & SON,
Agents for the Applicant.