Prevent Damage, and also for Stopping the Motor Driving a Dynamo when its Circuit is thus. or otherwise Opened.
Year: 1885

page_text: Prevent Damage, and also for Stopping the Motor Driving a
Dynamo when its Circuit is thus. or otherwise Opened.
I THORSTEN NORDENFELT of 53 Parliament Street in the City of Westminster
Civil Engineer do hereby declare the nature of my invention for "IMPROVEMENTS
IN APPARATUS FOR OPENING ELECTRIC CIRCUITS TO PREVENT DAMAGE AND ALSO FOR
STOPPING THE MOTOR DRIVING A DYNAMO WHEN ITS CIRCUIT IS THUS OR OTHERWISE
"
OPENED a communication to me from abroad by Oscar Fredrik Jönsson of
Stockholm Sweden Engineer to be as follows :-
This invention relates to apparatus to open an electric circuit when from any
cause the strength of the current increases to an extent likely to cause damage and
also to stop the motor driving the dynamo when its circuit is thus or otherwise
opened.
The automatic apparatus is interposed in the circuit of the dynamo machine near
the motor. The current in passing through this apparatus divides and passes
simultaneously through two electro magnets and joining again passes through three
insulated rails. One of these rails is fixed and the circuit between it and another
moveable rail is completed by each rail having on its end a piece descending into a
vessel containing mercury. This vessel is mounted on the top of a vertical sliding
bar. A spring tends to draw the bar down but it rests on a piece connected with
the armature of one of the magnets. This armature is held back by a spring
sufficiently strong to overpower the attraction until the current has increased to
such a degree that danger is imminent both to the dynamo machine and the circuits.
The armature of the other electro magnet consists of a double armed lever provided
with metal screws in front of the poles of the electro magnet in order to diminish
the effect of the residual magnetism. A hook is provided in order to retain the
lever in its position when no current is passing through the apparatus. On the
opposite end of the lever a weight is suspended and from the weight a string passes
over pulleys to a wheel which is keyed on to the spindle of the stop valve of the
motor in such a manner that the weight when free in falling closes the valve.

page_text: The apparatus works in the following manner: When the current passes through
the last mentioned electro maguet the armature is attracted so that the hook which
is not further wanted becomes disengaged. If any interruption now occurs in the
circuit the maguetism ceases instantly, the consequence of which is that the weight
depresses the shorter end of the lever and glides off and in falling stops the motor.
If this apparatus did not exist the dynamo machine and the motor would in the
event of an interruption in the circuit increase their rapidity in consequence of
motive power being no longer transformed into electricity and owing to the great
speed the machine might be damaged.
Another danger for the dynamo machine may arise in the event of short circuiting
a portion of the main circuit. In such an event the resistance diminishes and the
power of the current increases so that the insulation of the machine and the circuit
may be destroyed. When with this arrangement short circuiting has taken place
and consequently the current has increased the attractive power of the first
mentioned magnet will likewise be increased and its armature is attracted and
moves to its magnet allowing the bar with the vessel of mercury to fall down and
open the circuit.
T
1

page_text: Improvements in Apparatus for Opening Electric Circuits to
Prevent Domage, and also for Stopping the Motor Driving Я
Dynamo when its Circuit is thus or otherwise Opened.
I THORSTEN NORDENFELT of 53 Parliament Street in the City of Westminster
Civil Engineer do hereby declare the nature of this invention (a communication
from abroad by Oscar Fredrik Jönsson of Stockholm Sweden Engineer) 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 apparatus to open an electric circuit when from any cause
the strength of the current increases to an extent likely to cause damage and also
to stop the motor driving the dynamo when its circuit is thus or otherwise opened.
The automatic apparatus is interposed in the circuit of the dynamo machine
near the motor.
The apparatus is represented in the annexed drawing which shows a side view of
the stop apparatus.
The apparatus is interposed in the circuit of the dynamo machine by connecting
its pole screws A and B in the main circuit. At the pole screw A the current
divides and passes simultaneously through two electro magnets C and D and joins
again at E and the whole passes through the insulated rails F and G and to the
pole screw B.
The circuit between the rails F and G is completed by each rail having on its
end a piece H descending into a vessel I containing mercury. The vessel I is
mounted on the top of a vertical bar K. This bar passes through and is guided by
two cars L and is at its lower end provided with a plate M the edge of which
comes against a screw head N on the armature O of the electro magnet D. This
armature is held back by a spring P from the magnet the spring being sufficiently
strong to overpower the attraction until the current has increased to such a degree
that danger is imminent both to the dynamo machine and the circuits. The
armature of the electro magnet C consists of a double armed lever Q provided with
metal screws R in front of the poles of the electro-magnet in order to diminish the
effect of the residual magnetismi-a hook S is provided in order to retain the lever
in its position when no current is passing through the apparatus. On the opposite
end of the lever a weight J is suspended and from the weight a string passes over
pulleys to the wheel V which is keyed on to the spindle of the stop valve of the
motor in such a manner that the weight when free in falling closes the valve.
The apparatus works in the following manner. When the current passes through
the electro magnet C the armature Q is attracted so that the hook S which is not
further wanted becomes disengaged. If any interruption now occurs in the circuit,
the magnetism ceases instantly, the consequence of which is that the weight J
depresses the shorter end of the lever Q and glides off thus stopping the motor. If
this apparatus did not exist the dynamo machine and the motor would in the event
of an interruption in the circuit, increase their rapidity in consequence of motive
power being no longer transformed into electricity and owing to the great speed,
the machine might be damaged.

page_text: Another danger for the dynamo machine may arise in the event of short circuiting
a portion of the main circuit. In such an event the resistance diminishes and the
power of the current increases so that the isolation of the machine and the circuit
may be destroyed. When with this arrangement short circuiting has taken place
and consequently the current has increased, the attractive power of the magnet D
will likewise be increased and the armature O is attracted and moves to its magnet
allowing the bar K with its vessel of mercury I to fall down and disconnect the
rails F and G. The electro magnet C then loses its magnetism and the weight J
falls down and stops the motor.
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.) Automatic stop apparatus for motors driving dynamo machines, consis'in
of two electro magnets C and D in the main circuit acting each upon its lever
armature in combination with a string and weight J rails F and G and moveable
vessel I which contains mercury and is controlled by one of the electro-magnets
the said stop apparatus effecting in an automatic manner the stopping of the motor
driving the dynamo machine in the event of interruption of the circuit or short
circuiting substantially as described.
(2.) Automatic stop apparatus for motors driving dynamo machines consisting of
two electro magnets in the main circuit one releasing its armature and liberating a
weight connected with the stopping gear of the motor when the circuit is inter-
rupted and the other moving its armature when the power of the current unduly
increases and thereby opening the circuit substantially as described.