Improvements in Rheostats or Apparatus for Regulating Electric Currents.
Year: 1889

page_text: Date of Application, 5th Oct., 1889
Complete Specification Left, 4th July, 1890-Accepted, 16th Aug., 1890
PROVISIONAL SPECIFICATION.
Improvements in Rheostats or Apparatus for Regulating Electric
Currents.
I JOHN AUGUSTINE KINGDON of 29 Marlborough Hill, St. John's Wood London, in
the County of Middlesex Electrical Engineer do bereby declare the nature of this
invention to be as follows:-
My improved rheostat or apparatus for regulating electric currents consists of a
flexible metallic conductor one end of which is attached to and makes contact with a
fixed terminal and the other end is attached to a rotating drum round which it can be
wound. The flexible conductor is conveniently composed of a strand of fine wires of
iron, steel, German silver or other metal or of flat metallic tape.
One or more pulleys are carried by a block of wood or other suitable insulating
material. A second set of pulleys are carried by a convenient fixed support so as to
be insulated from one another.
The flexible conductor is passed from the terminal round one of the pulleys on the
wooden block, then round one of the fixed pulleys then round a second pulley on
the wooden block then round another fixed pulley and so on until it is brought to the
rotating drum. The second terminal of the rheostat is connected by rubbing contacts
or through the bearings with the last of the fixed pulleys which in this case is of
metal.
The block carrying the pulleys hangs below the set of stationary pulleys being
supported by the flexible cord or conductor.
As the flexible conductor is wound on to the drum the movable block is raised and
the length of the conductor between the contact pulley and the other terminal is
shortened. The resistance between the terminals is consequently decreased.
When the conductor is unwound from the drum the resistance is increased. A
weight is hung on the movable block carrying the pulleys so as to keep the flexible
conductor always stretched tight.
In some cases I use a conductor having a gradually decreasing sectional area the
smaller end being fixed to the drum or I reduce the number of strands in the
conductor. If the electromotive force of the current is constant, as the flexible con-
ductor is unwound from the drum the current is decreased, and the area of the
conductor which is of such size as not to be unduly heated by the current may be
decreased in proportion. A shorter conductor is in this case required to reduce the
current from its maximum intensity to a given amount than would be the case if the
conductor were uniform throughout.
Instead of making contact through one of the pulleys it may be made through the
drum which in this case is of metal.
I sometimes, arrange a switch to short-circuit the apparatus when its resistance is
lowest.
The regulation of electric current is effected by means of my improved rheostat
either by turning the drum by hand or by some automatic apparatus such as an
electromotor controlled by a relay so as to rotate in one direction if the current or
electromotive force which it is desired to regulate is too great and in the other
direction if the current or electromotive force is too small, and to remain at rest when
the current or electromotive force is normal.
Or the drum may be driven from a shaft by means of a clutch controlled by a relay
or other device arranged to produce the desired result.
In some cases I use springs instead of a weight to keep the conductor stretched
tight.
11
1 1
1
1000

page_text: Improvements in Rheostats or Apparatus for Regulating Electric
Currents.
I, JOHN AUGUSTINE KINGDON of 29 Marlborough Hill, St. John's Wood London in
the County of Middiesex 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 :-
My improved rheostat or apparatus for regulating electrical currents consists of a
flexible metallic conductor, conveniently composed of a strand of fine wires of iron
steel German silver or other suitable metal or of flat metallic tape which passes
round one or more pulleys and whose length can be varied preferably by winding
it on a drum.
Fig. 1 of the accompanying drawings is an elevation of my rheostat, and fig. 2 is a
plan of part of the apparatus.
The electric current is regulated by passing it through the flexible metallic con-
ductor F, one end of which is attached to and makes contact with a fixed terminal T
and the other end is attached to a rotating drum D round which it can be
wound.
The flexible conductor F may be composed of fine wires stranded or braided
together. One or more pulleys P P, (fig. 2.) are carried by a block W of wood or
other suitable insulating material. A second set of pulleys QQ, are carried by a
convenient fixed support so as to be insulated from one another. The drum D is
carried on a pin and may be placed at a distance from the pulleys QQ, as con-
venient. A handle H is provided for turning it by hand and a catch K taking
into a ratchet cut on the flange prevents it turning when not desired. The flexible
conductor F is passed from the fixed terminal T round one of the pulleys P, on
the block W then round one of the fixed pulleys Q, then round a second pulley P on
the block W then round another fixed pulley Q then round a guide pulley R and
so to the drum D. The curront enters at the terminal. T and passes through the
metallic conductor F to the pulley Q which is of metal and so to the second
terminal which is in contact with the frame of the pulley Q. In some cases I
arrange a brush to make contact with the flexible conductor F. The block W
carrying the pulleys P P, hangs below the set of stationary pulleys QQ, being
supported by the flexible conductor F. A weight X is attached to the block W
so proportioned as to keep F always stretched tight.
As the flexible conductor F is wound on to the drum D the block W is raised
and the length of the conductor F between the terminal T and the contact pulley Q
is shortened and the resistance of the circuit is reduced. The current is con-
sequently increased by winding the conductor F on to the drum D and reduced
by unwinding it. If the electromotive force of the current is constant so that the
current becomes less as the resistance of the rheostat is increased by unwinding
the conductor F I sometimes use a conductor of decreasing sectional area or of
fewer strands, the sectional area being proportioned so that the conductor is not
unduly heated by the current it has to carry.
I sometimes arrange a switch to shortcircuit the conductor when wound on the
drum.
The regulation may be effected either by hand or by some suitable automatic
apparatus as for example an electromotor, controlled by a relay may be arranged to
rotate in one direction if the current or electromotive force which it is desired to
regulate is too great and in the other direction if the current or electromotive force is
too small and to remain at rest when the current is normal.
In some cases I use springs to keep the flexible conductor tight. This arrangement
is suitable for tramcars or locomotives. The pulleys may be of metal or of china or
other fireproof material.

page_text: The drum may be replaced by any other suitable arrangement for disposing of the
conductor F as for example a second set of fixed and moving pulleys.
The number of pulleys may be varied to suit requirements.
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. A rheostat consisting of a flexible conductor passing round a pulley or pulleys
in combination with a drum or other apparatus for regulating its length.
2. The combination in a rheostat of a flexible conductor with one or more pulleys
carried by a movable block, and one or more pulleys on a fixed block.
3. My improved rheostat substantially as described.
1000
J. A. KINGDON.