Year: 1888

page_text: Date of Application, 7th Feb., 1888
Complete Specification Left, 10th Oct., 1888
Complete Specification Accepted, 21st Dec., 1888
[Communicated from abroad by LA SOCIÉTÉ ANONYME POUR LA TRANSMISSION DE LA
FORCE PAR L'ELECTRICITÉ, of 1, Boulevard St. Denis, Paris, France, Electrical
Engineers.]
I JOHN CLAYTON MEWBURN, of 169 Fleet Street, in the City of London, Fellow
of the Institute of Patent Agents do hereby declare the nature of this invention to be
as follows:-
In nearly all applications of electricity to industrial purposes it is usual to employ
rheostats essentially composed of more or less resisting conductors in which a part of
the electric energy is expended in heat. When great electric powers are employed
developed by very intense currents the rheostats expend very notable quantities of
energy and it becomes proportionately difficult to construct them with the conducting
bodies usually employed, especially metals. The problem is even more complicated if
the currents employed are of high tension. Powerful high tension currents do not
bear the introduction of rheostats except with special precautions and cannot be
suddenly broken by the ordinary means.
In practice metallic rheostats aro always employed. These act by introducing the
resistances into the current by successive fractions; with currents of high tension this
process produces violent and sudden changes of potential which cause extra currents
and dangerous sparks. On the other hand the currents cannot be broken without
having first reduced them to a very weak intensity without which extra currents ard
sparks which are very prejudicial to the apparatus are engendered. This condition
with high tension currents requires the employment of very high resistances which
never quite fulfil their object when they are obtained with the aid of metals.

page_text: Now the rheostats which form the subject of the present invention permit of
obtaining very easily as high a resistance as is.desired and of introducing it into the
circuit by following a continuous variation, of maintaining it at a determined value
with an absolute pressure and of breaking the current without a sensible spark.
In order to obtain these results I employ liquids as the resisting bodies. This
employment of liquid is not new in principle; it has heen sometimes followed in
laboratories and in experiments but for reasons hereinafter explained liquids have
never been employed industrially and there is no liquid rheostat in current use.
The arrangements hereinafter described have for object to allow of this industrial
use of liquids and to thereby obtain all its advantages.
In all these arrangements there are five general characteristic and novel features
which I will first explain.
The first consists in the nature of the liquid employed. In the laboratory
'experiments above referred to, more or less concentrated saline solutions have been
used. But according to this invention I employ ordinary water, I use saline solutions
only exceptionally in cases where it is necessary to reduce the resistance much as, for
example, when rheostats are applied to currents of relatively weak tension or of great
intensity.
The second characteristic feature is that in order to be able to keep the rheostat
indefinitely in the current I provide for a continuous renewal of the liquid so that the
electrodes are immersed not in a stagnant mass but in a current of liquid; the use of
ordinary water makes this method very simple as it is simply a continuous flow. In
the case of saline solutions the same liquid can be kept circulating through the
rheostat (and through a refrigerator if necessary) by a pump or other analogous
apparatus.
The third characteristic feature is that the electrodes never come in contact in the
liquid; experience has shewn that when there is such contact its rupture in the body
of the liquid is liable to cause voltaic arcs the breaking of which leads to incon-
veniences. It follows that the resistance of the rheostats can never become null.
When it is wished to completely annul it, after having reduced the rheostat to its
minimum resistance an exterior metallic contact is connected. This connection takes
place automatically and by the continuation of the action which has reduced the
resistance to its minimum value. The rheostat is then outside the circuit. Inversely,
when it is desired to reintroduce it the metallic contact is first disconnected and
then the resistance of the rheostat is increased.
The fourth characteristic feature applies to rheostats which are employed as
rheotomes. In this case in order to interrupt the current by one of the arrange-
ments which are hereinafter described, provision is made for the electrodes or one
of them ceasing to be in contact with the liquid. When one of the electrodos has
to leave the liquid before the other it is important for this to be the one which
is connected to the positive polo, that is to say, the one by which the current enters
the rheostat.
The fifth characteristic feature is that the electrodes which conduct the current to
the rheostat and lead it away therefrom are not necessarily formed of metals or
materials which are not attacked under the action of the current (such as carbon
or platinum, for example, which are expensive and fragile); I use on the contrary
ordinary cheap metals such as iron or lead; their waste or wear in the apparatus
is very slow and the renewal by like electrodes is inexpensive.
Having set out the general characteristic features of novelty I will now proceed
to describe the arrangements for carrying them into effect. They are divided
into three classes, viz.: (1) Arrangements in which the electrodes are movable ;
(2) arrangements in which the electrodes are fixed and the liquid is movable; and
(3) arrangements in which neither the destrode or the liquid quid is blo
The most simple arrangement in which the electrodes are movable consists in
placing in a vessel through which a current of liquid flows two, or preferably three,
electrodes the two outer being connected to one pole and the inner to the other

page_text: pole; it suffices to raise one electrode in order to gradually increase the resistance
and to withdraw it from the liquid to break the current without producing extra-
current even by moving the electrode rapidly. Both electrodes may be movable
and rise from the liquid together.
Instead of a narrow vessel which only allows of a vertical movement I can employ
a long vessel or trough which allows of the electrodes being moved away from each
other before withdrawing one of them in order to break the current; the variation of
the resistance is thus more regular. A complete apparatus for effecting this is
described further on.
The plates forming the electrodes have flanges at their lower ends; these flanges by
retaining for an instant a film of liquid when the plates are raised from the rheostat
entirely provent the formation of arcs and sparks when the current is broken. This
provision is useful but is not considered necessary.
In the arrangements above described in which the electrodes are movable in the
liquid, when the electrodes are rising the whole body of liquid continues to conduc
the current, the resistance being reduced only by the diminution of the submerged
surface of the electrodes. But when on the other hand the body of liquid diminishes
at the same time as the submerged surface of the electrodes the resistance diminishes
with greater regularity. In an arrangement in which the body of liquid diminishes,
electrodes are fixed in an insulating vessel; the liquid enters the vessel by an orifice
provided for the purpose and leaves by the orifice of a vertical tube made of non-
conducting material. This tube can be moved endways in a gland or stuffing box and
the height of its upper end determines the level of liquid between the electrodes and
consequently the resistance.
In another arrangement a bell or inverted vessel of insulating material by
descending around an electrode causes the liquid level to be lowered; for more
security this bell can be doubled so as to surround both the electrodes.
The liquid can be moved without moving the bell or inverted vessel either by
blowing into a bell in which the electrodes are or by forcing it by a pressure of air
from a closed reservoir into a vessel in which the electrodes are, or by a simple
plunger of insulating material the lowering of which raises the liquid level and the
raising of which allows the level to go down and thereby breaks the current.
When neither the electrodes nor the liquid are made to move, the variation of the
resistance can be effected by introducing an insulating partition between the electrodes.
This mode can be very efficiently carried out by an arrangement in which the
rheostat is in the form of a flat cylindrical vessel capable of turning upon a horizontal
axis; the vessel is partly divided by a vertical semi-circular partition parallel to the
ends; the electrodes are likewiso semi-circular and are fixed; they are submerged in
the liquid, the renewal of which is effected by connections at the centre of the vessel.
By turning the vessel the insulating partition can be completely disengaged from
or more or less engaged between the electrodes or interposed entirely between them
tbus causing the resistance to vary from the minimum to the maximum by a simple
and rapid operation. With this arrangement the vessel can inversely be fixed the
insulating partition being dispensed with and the clectrodes being movable around the
axis; they could then be more or less submerged in the liquid or be entirely with-
drawn from it; the variation of the resistance would however be less regular than
with the other arrangement.
The arrangement which I will now proceed to describe is a very practical form of
apparatus of the class in which the electrodes or one of them are movable. The
liquid is contained in a vessel or trough of insulating material; it enters and leaves
by suitable orifices. Its level is determined by a partition the height of which can
be varied if necessary. The electrodes are each formed of parallel metallic plates
connected together; one electrode is fixed and receives the current from a binding
screw, the other electrode is movable and suspended from an axis. The plates of
this electrode are parallel with those of the other and can enter between them but
without touching them. The bottom of the vessel is curved the curve being struck
from the axis from which the movable electrode is suspended. The current reaches

page_text: this electrode through this axis. The rod which supports the movable electrode is
connected to a lever and a counterweight tends to keep the rheostat open so as to
avoid accidents if the theostat should by mistake be left to itself. According to the
position given to the lever the movable electrode will either be near the fixed electrode
and the resistance will be very small, or moved away from this electrode the resistance
being proportionately greater, or if the movable electrode be moved quite out of the
water the current will be broken.. On the axis of the lover is a finger connected by a
rod of insulating material to a handle adjoining the lever handle. When the movable
electrode reaches the bottom of the vessel and the lever handle is let go the finger
touches a block and makes a metallic contact putting the rheostat out of circuit ;
inversely if the rheostat is to be used the two handles are grasped together and
consequently the finger is raised and the rheostat is automatically put into the
circuit.
1
1000

page_text: A communication from abroad by LA SOCIETE ANONYME POUR LA TRANSALLIN
DE LA FORCE PAR L'ELECTRICITÉ, of 1, Boulevard St. Denis, Paris, France,
Electrical Engineers.
I, JOHN CLAYTON MEWBURN of 169 Fleet Street, in the City of London, Fellow of
the Institute of Patent Agents, 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 :-
In nearly all applications of electricity to industrial purposes it is usual to employ
rheostats essentially composed of more or less resisting conductors in which a part of
the electric energy is expended in heat. When great electric powers are employed
developed by very intense currents the rheostats expend very notable quantities of
energy and it becomes proportionately difficult to construct them with the conducting
bodies usually employed especially metals. The problem is even more complicated if
the currents employed are of high tension. Powerful high tension currents do not
bear the introduction of rheostats except with special precautions and cannot be
suddenly broken by the ordinary means.
In practice metallic rheostats are always employed. These act by introducing the
resistances into the current by successive fractions; with currents of high tension this
process produces violent and sudden changes of potential which cause extra currents
and dangerous sparks. On the other hand the currents cannot be broken unless they
have been first reduced to a very weak intensity without which extra currents and
sparks which are very prejudicial to the apparatus are engendered. This condition
with high tension currents requires the employment of very high resistances which
never quite fulfill their object when they are obtained with the aid of metals.
Now the rheostats which form the subject of the present invention permit of
obtaining very easily as high a resistance as is desired and of introducing it into the
circuit by following a continuous variation of maintaining it at a determined value
with an absolute pressure and of breaking the current without a sensible spark.
In order to obtain these results 1 employ liquids as the resisting bodies. This employ-
ment of liquid is not new in principle; it has been sometimes followed in laboratories
and in experiments, but for reasons hereinafter explained liquids have never been
employed industrially and so far as I am aware there is no liquid rheostat in current
use. The arrangements hereinafter described have for object to allow of this industrial
use of liquids and to thereby obtain all its advantages.
In all these arrangements there are five general characteristic and novel features
which I will first explain.
The first consists in the nature of the liquid employed. In the laboratory experi-
ments above referred to more or less concentrated saline solutions have been used but

page_text: according to this invention 1 employ ordinary water; I use saline solutions only
exceptionally in cases where it is necessary to reduce the resistance much, as for
example when rheostats are applied to currents of relatively weak tension or of great
intensity.
The second characteristic feature is that in order to be able to keep the rheostat
indefinitely in the current I provide for a continuous renewal of the liquid so that the
electrodes are immersed not in a stagnant mass but in a current of liquid; the use of
ordinary water makes this method very simple as it is simply a continuous flow. In
the case of saline solutions the same liquid can be kept circulating through the
rheostat (and through a refrigerator if necessary) by a pump or other analagous
apparatus.
The third characteristic feature is that the electrodes never come in contact in the
liquid; experience has shown that when there is such contact its rupture in the body of
the liquid is liable to cause voltaic arcs the breaking of which leads to inconveniences.
It follows that the resistance of the rheostats can never become null. When it is
wished to completely annul it after having reduced the rheostat to its minimum
resistance an exterior metallic contact is connected. This connection takes placo
automatically and by the continuation of the action which has reduced the resistance
to its minimum value. The rheostat is then outside the circuit. Inversely, when it
is desired to re-introduce it the metallic contact is first disconnected and then the
resistance of the rheostat is increased.
The fourth characteristic feature applies to rheostats which are employed as
rheotomes. In this case in order to interrupt the current by one of the arrangements
which are hereinafter described provision is made for the electrodes or one of them
ceasing to be in contact with the liquid. When one of the electrodes has to leave the
liquid before the other it is important for this to be the one which is connected to the
positive pole, that is to say, the one by which the current enters the rheostat.
The fifth characteristic feature is that the electrodes which conduct the current to
the rheostat and lead it away therefrom are not necessarily formed of metals or
materials which are not attacked under the action of the current (such as carbon or
platinuin for example which are expensive and fragile); I use on the contrary
ordinary cheap metals such as iron or lead; their waste or wear in the apparatus is
very slow and the renewal by like electrodes is inexpensive.
Having set out the general characteristic features of novelty I will now proceed to
describe the arrangements for carrying them into effect. They are divided into three
classos, viz. (1) Arrangements in which the electrodes are movable, (2) arrangements
in which the electrodes are fixed and the liquid is movable and (3) arrangements in
which neither the electrodes nor the liquid are movable.
The most simple arrangement in which the electrodes are movable is shown in
Figure 1 and consists in placing in a vessel a through which a current of liquid flows
two, or preferably three electrodes F F F the two outer F F being connected to one
pole and the inner F1 to the other pole; it suffices to raise the electrode F in order to
gradually increase the resistance and to withdraw it from the liquid to break the
current without producing extra-current oven by moving the electrode rapidly. Both
electrodes may be movable and rise from the liquid together (see Figure 2). Instead
of a narrow vessel which only allows of a vertical movement I can employ a long
vessel or trough which allows of the electrodes being moved away from each other
before withdrawing one of them in order to break the current; the variation of the
resistance is thus more regular. A complete apparatus for effecting this is described
further on.
The plates forming the electrodes have flanges at their lower ends; those flanges by
retaining for an instant a film of liquid when the plates are raised from the rheostat
entirely prevent the formation of arcs and sparks when the current is broken. This
provision is useful but is not considered necessary.
In the arrangements above described in which the electrodes are movable in the
liquid, when the electrodes are rising the whole body of liquid continues to conduct
the current the resistance being reduced only by the diminution of the submerged

page_text: surface of the electrodes. But when on the other hand the body of liquid diminishes
at the same time as the submerged surface of the electrodes the resistance
diminishes with greater regularity. Figure 3 represents an arrangement in
which the body of liquid diminishes. The electrodes F and F¹ are fixed
in an insulating vessel a. The liquid enters the vessel by an orifice A and
leaves by the orifice B of a vertical tube made of non-conducting material. This
tube can be moved end ways in a gland or stuffing box C and the height of its upper
end determines the level of liquid between the electrodes and consequently the
resistance.
Figure 4 represents another arrangement in which by means of a bell or inverted
vessel of insulating material descending around an electrode F the liquid level can
be lowered; for more security, this bell can be double so as to surround both the
electrodes FF' as seen in figure 5.
The liquid can be moved without moving the bell or inverted vessel either by
blowing into a bell b in which the electrodes are (see Figure 6) or by forcing it by a
pressure of air from a closed reservoir a (Figure 7) into a vessel 6 in which the
electrodes are, or by a simple plunger (Figure 7b) of insulating material the
lowering of which raises the liquid level and the raising of which allows the level to
go down and thereby breaks the current.
When neither the electrodes nor the liquid are made to move the variation of the
resistance can be effected by introducing an insulating partition d between the
electrodes (see figure 8). This mode can be very efficiently carried out by the arrange-
ment shown in Figures 9 and 10 in which the rheostat is in the form of a flat
cylindrical vessel capable of turning upon a horizontal axis o o; the vessel is partly
divided by a vertical semi-circular partition C parallel to the ends; the electrodes F F¹
are likewise semicircular and are fixed; they are submerged in the liquid the level of
which is at N and the renewal of which is effected by connections at the centre of the
vessel. By turning the vessel the insulating partition can be completely disengaged
from, or more or less engaged between the electrodes, or interposed entirely between
them, thus causing the resistance to vary from the minimum to the maximum by a
simple and rapid operation. With this arrangement the vessel can, inversely, be
fixed, the insulating partition being dispensed with and the electrodes being movable
around the axis; they could then be more or less submerged in the liquid or bo
entirely withdrawn from it; the variation of the resistance would however be less
regular than with the other arrangement.
The arrangement which I will now proceed to describe and which is represented in
Figures 11 and 12 is a very practical form of apparatus of the class in which the
electrodes or one of them are movable. The liquid is contained in a vessel or
trough V. of insulating material; it enters by an orifice A and leaves by an orifice B.
Its level is determined by a partition H the hoight of which can be varied if necessary.
The electrodes F F are each formed of parallel metallic plates connected together; the
electrode F is fixed and receives the current from a binding screw a; the electrode F¹
is movable and suspended from an axis o. The plates of this electrode are parallel
with those of the other and can enter between them, as is indicated in Figure 12, but
without touching them. The bottom of the vessel is curved the curve being struck
from the axis from which the movable electrode is suspended. The current reaches
this electrode through this axis. The rod which supports the movable electrode is
connected to a lever G and a counterweight tends to keep the rheostat open so as to.
avoid accidents if the rheostat should by mistake be left to itself. According to the
position given to the lever G the movable electrode F will either be near the
electrode F and the resistance will then be very small, or moved away from this
electrode the resistance being proportionately greater, or if the electrode F" he moved
quite out of the water the current will be broken. On the axis of the lever is a
finger C connected by a rod D of insulating material to a handle m adjoining the
lever handle M. When the movable electrode F' reaches the bottom of the vessel and
the lever handle M is let go the finger touches a block E and makes a metallic
contact putting the rheostat out of circuit; inversely if the rheostat is to be used the
.

page_text: two handles are grasped together and consequently the finger is raised and the
rheostat is automatically pnt into the circuit.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me,
I declare that what I claim is :-
1. In a rheostat or rheotome, a resisting body composed of ordinary water as set
forth.
2. In a rheostat or rheotome in which a liquid forms the resisting body, the com-
bination with the vessel for containing said liquid and with the electrodes, of an inlet
for said liquid and an outlet for same whereby a continuous flow and consequent
renewal of the liquid is maintained as and for the purpose set forth.
3. In a rheostat or rheotome in which a liquid forms the resisting body and in
which the electrodes do not come in contact in the liquid, an external metallic contact
whereby the rheostat circuit can be closed and the resistance of same thereby annulled
as set forth.
4. In a rheostat or rheotome in which a liquid forms the resisting body, the com-
bination with the vessel containing said liquid and with the electrodes of means
whereby contact of one of said electrodes with the liquid can be interrupted and the
current thereby broken as and for the purpose set forth.
5. In a rheostat or rheotome in which a liquid forms the resisting body, the use of
electrodes made of iron or other cheap metal as set forth in lieu of materials such as
are ordinarily employed and which are not attacked under the action of the current.
6. In a liquid rheostat or rheotome, the employment of electrodes formed with flanges
at their lower ends whereby when the electrodes cease to be submerged in the liquid a
film is momentarily retained by the said flanges as set forth.
7. In a liquid rheostat or rheotome, means whereby the submerged electrodes are
relatively displaced in the liquid, and finally moved out of the liquid, so that the
resistance is gradually increased and the current finally interrupted.
8. In a liquid rheostat or rheotome, means whereby the depth of the liquid in which
the electrodes are submerged can be varied so as to vary the resistance as set forth.
9. In a liquid rheostat or rheotome in which the electrodes are not made to move to
vary the resistance, the employment of an insulating partition substantially as and for
the purpose set forth and as represented in Figures 8, 9, and 10.
10. The several arrangements of rheostats and rheotomes herein before described and
represented in the annexed drawings.
Dated thin Thoth dess of October 188N