Improvements in Rheostats for the Graduated Control of Electrical Resistance, particularly applicable to the Production of Theatrical Luminous Effects.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in Rheostats for the Graduated Control of Electrical
Resistance, particularly applicable to the Production of Theatrical
Luminous Effects.
I, CLAUDE EDOUARD CLEMANGON, of 23, Rue de Lamartine, Paris, in the Republic
of France, Engineer, do hereby declare the nature of my invention to be as
follows:-
In a great many cases it is useful to be able to vary in a progressive and im-
perceptible manner a resistance placed in series in a fixed electric circuit in such
a manner as to vary in an imperceptable manner the difference of potential at the
terminals of the circuit. Among such examples can be cited the excitation of shunt
dynamos electrotyping, and in particular, the circuits of incandescent lamps for
lighting theatres, lamps, the light of which is required to be varied in an
imperceptible manner so as to give to the spectator the complete illusion of the
fall of night or the break of day.
The principle generally adopted for the construction of rheostats for varying
resistance is the following;-
An index is arranged over a certain number of blocks connected to the different
points of the wire or conductor forming the resistance, enabling one to place in
circuit either the whole or part of this resistance, but doing so in a discontinuous
manner, that is to say that there always exists a certain difference of potential
between one block and the next when the rheostat is in the circuit of a current.
It is possible to diminish the difference of potential between two adjacent blocks
by increasing the number of blocks, but a limit is soon reached in this method by
the difficulties of construction. In general, it is impossible, by this means to obtain
a continuous variation of the resistance inserted in the circuit and in particular
the apparatus actually employed in the production of theatrical effects produces
jumping in the light which is disagreeably noticeable by the spectator.
My invention has for its object the construction of a rheostat consisting
essentially of a drum, on which is placed or wound a conducting wire forming
the resistance, and a liquid or solid contact, the drum, or the contact, or both,
being movable in such a manner that the point of application of the contact can
be slid in a continuous manner along the conductor forming the resistance.
In the accompanying drawings.
Figs. 1 & 2 show modifications of my rheostat with a liquid contact;
Figs. 3 to 7 represent different ways of practically constructing my rheostat
with a solid contact;
Fig. 8 is a diagram illustrating the application of my continuous electrical
rheostat to theatrical illummating devices.
Fig. 9 is a view of a detail.
In these figures like letters refer to like parts.
As the Figures 1 & 2 show in principle; the wire a, constituting, the resistance
is placed on a cylindrical drum b, forming on the surface of this drum a zig-zag
path (Fig. 1). It can equivalently be wound round a rim in the form of a gramme

page_text: When the needle touches the index g, set by the electrician, a current is sent
round the electromagnet E3 which breaks the communication between the minus
terminal B and the switch T so that the motor stops.
The electrician can also stop the rheostat at a determined point and always
reproduce the effects of illumination under the same conditions.
The finger e being on one of the pieces d, it might accidently happen that the
indicator of the dial would be operated several times in a contrary direction to
that given by an action of the reversing switch I which would destroy the corres-
pondence between the position of the rheostat and that of the indicating needle;
the electromagnet E, prevents this accident from taking place. In fact as soon
as there is contact between the finger and the piece d, the electromaget E, comes
into action, the finger, the end of which has forced a spring aside before touching d,
is raised and the end of the spring slides under that end and prevents the finger
from falling again on d, as long as the rotation has not continued long enough to
sufficiently remove the piece d.
Such a combination, composed of the six elements enumerated and described
above, forms a unit corresponding with a single circuit in a switch-board for the
production of theatrical effects. In order to complete such a switch-board as
many of these units are brought together as there are circuits to serve. The
rheostats can be set in motion either all together or separately, and thus all the
various combinations necessary for theatrical effects can be obtained.
Dated this 25th day of April 1898.
FELL & JAMES,
Agents for the Applicant.
Improvements in Rheostats for the Graduated Control of Electrical
Resistance, particularly applicable to the Production of Theatrical
Luminous Effects.
I, CLAUDE EDOUARD CLEMANÇON, of 23, Rue de Lamartine, Paris, in the Republic
of France, 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:---
In a great many cases it is useful to be able to vary in a progressive and im-
perceptible manner a resistance placed in series in a fixed electric circuit in such
a manner as to vary in an imperceptible manner the difference of potential at the
terminals of the circuit among such examples can be cited the excitation of shunt
dynamos, electrotyping, and in particular the circuits of incandescent lamps for
lighting theatres, lamps the light of which is required to be varied in an
imperceptible manner so as to give to the spectator the complete illusion of the
fall of night or the break of day.
The principle generally adopted for the construction of rheostats for varying
resistance is the following:-
An index is arranged over a certain number of blocks connected to the different
points of the wire or conductor forming the resistance, enabling one to place in
circuit either the whole or part of this resistance, but doing so in a discontinuous
manner, that is to say, that there always exists a certain difference of potential
between one block and the next when the rheostat is in the circuit of a current.
It is possible to diminish the difference of potential between two adjacent blocks
by increasing the number of blocks, but a limit is soon reached in this method by
the difficulties of construction

page_text: In general it is impossible, by this means to obtain a continuous variation of
the resistance inserted in the circuit and in particular the apparatus actually
employed in the production of theatrical effects produces jumping in the light
which is disagreeably noticeable by the spectator.
My invention has for its object the construction of a rheostat consisting
essentially of a drum on which is placed or wound a conducting wire forming
the resistance, and a liquid or solid contact, the drum or the contact or both,
being movable in such a manner that the point of application of the contact can
be slid in a continuous manner along the conductor forming the resistance.
On Sheet 1 of the drawings accompanying the Provisional Specification
Figs. 1 and 2 show modifications of my rheostat with a liquid contact.
Figs. 3 to 7 represent different ways of practically constructing my rheostat
with a solid contact.
On the accompanying Sheet 2 Fig. 8 is a diagram illustrating the application
of my continuous electrical rheostat to theatrical illuminating devices.
Fig. 9 is a view of a detail.
In these figures like letters refer to like parts.
As the Figs. 1 and 2 show in principle the wire a constituting the resistance is
placed on a cylindrical drum b, forming on the surface of this drum a zig-zag
path (Fig. 1). It can equivalently be wound round a rim in the form of a
gramme ring (Fig. 2).
The sliding contact consists of a pool of mercury c contained in a trough, in
which the drum is very slightly immersed.
When the drum is made to rotate on its axis, the different parts of the wire
are plunged successively into the mercury, in such a manner that the resistance
varies in an absolutely continuous manner.
The sliding contact can equivalently consist of a piece of metal other than
mercury (Figs. 3 to 7), the relative movement of the contact with respect to the
wire, which is along the path of this wire, can be obtained, either by revolving
the drum alone or by displacing the contact at the same time that the drum is
made to revolve.
Figure 3 shows a form of my rheostat in which the wire a is wound helically
round the drum b which receives a longitudinal motion as well as a motion of
rotation by means of a screw on the axis of said drum so that the contact c is
continuously in contact with the moving wire.
In Figure 4 a form is shown in which the drum revolves and at the same time
by means of gearing causes a screwed spindle to revolve, whereby the contact c
fastened on a block engaging with the screw has a longitudinal displacement given
to it, so that the contact c travels along the wire continuously.
Figure 5 shows a form in which the wire which is helically wound round a drum
as before, fits into a groove in a stationary block carried by the contact spring c,
so that as the drum revolves the coaction of the stationary block with the revolv-
ing wire helix, gives to the said drum a longitudinal displacement.
Figure 6 shows a form in which the drum 6 receives only a motion of rotation
while the contact e receives longitudinal displacement by means of a frame carry-
ing said contact which engages with a screw thread on a portion of the spindle
of the drum.
Figure 7 shows a form in which the contact c is caused to revolve, the block on
which said contact is mounted being rigidly attached to a driving pulley which is
prevented from moving longitudinally by means of stops. The drum is sup-
ported on a horizontal bar capable of sliding longitudinally in square guides and
also having a screw-thread cut on a portion of it, which coacts with and supports
the driving pulley as shown in the drawing. The drum thus receives a longitudinal
displacement and the contact as it revolves moves continuously along and in
contact with the wire.
My electrical rheostat with continuous resistance is suitable for all kinds of
industrial application, it can be notably applied in the production of theatrical

page_text: effects for the purpose of varying in an imperceptible manner the difference of
potential at the terminals of a circuit containing incandescent lamps used as
footlights, in such a way as to vary the light of these lamps in an insensible
manner and thus give to the spectator the complete illusion of the fall of night
and break of day.
The rheostat being inserted in the incandescent lamp circuit, the next matter
is to give to it a variable velocity. The driving gear can be worked, either by
hand, or mechanically, or by transmission to a distance by means of an inter-
mediate agent such as electricity, gas or hydraulic power &c.
In the case where the driving gear is worked electrically, I apply by preference
the following arrangement of the whole which besides can be modified according
to the necessities of the installation. My apparatus consists of a switch A where-
by the lamps can be inserted between the terminals of the supply circuit to give
their full light and can be suddenly disconnected to give sudden extinction, or on
the other hand the rheostat can be inserted in circuit so as to obtain continuous
variations in the brightness of their light.
a
The negative supply main is connected with the rheostat.
C
The rheostat consists of the zig-zag conducting wire a forming the resistance
carried by two discs of insulating material, and of a liquid contact formed by
pool of mercury contained in a basin c in which the wire just dips so that the
point of contact can be displaced in a continuous manner along the conductor
forming the resistance. The insulating discs b are carried by two metallic rings d
which with the frame of the rheostat, the basin and the mercury constitute the part
in connection with the negative supply main.
'
One of the metallic rings d carries a series of contact clocks e, the use of which
are hereinafter described.
The rheostat inserted in the incandescent lamp circuit should be capable of
being driven at a variable velocity. It is driven either by an electric motor f
or by a clutch permitting engagement with an auxiliary motor.
My arrangement contains a polarised relay g, a reversing switch h, a position
indicating dial, a magnetic interrupter ; and a switch k with finger contact
levers. The electric motor f is set in motion by moving the switch k which
introduces the resistances into the motor circuit and consequently regulates
the speed. One can thus cause the rheostat to revolve at variable speeds and
consequently cause the duration of the illuminating effects to vary.
The reverser h allows the current to pass in the armature of the motor in either
direction and consequently the excitation remaining the same causes the rheostat
to revolve, either in one direction to increase the resistance of the circuit (to imitate
night), or in the other direction to diminish the resistance (to imitate day), this
resistance being in series with the lamps.
The drum b turning in one or other direction, it is necessary to be able to stop
it at any point whatever in its rotation, so as to produce at will illumination
suitable for the nature of the scene and also to register the position of the switch
in order to always reproduce the same effects in an invariable manner.
For this purpose, the dial i is placed on the switch, which carries a movable
index which the electrician places at a mark corresponding to the effect to be
obtained.
Moreover the rheostat carries a series of contact-pieces e, arranged in a circle
on one end of the drum band with which a finger n comes in contact which finger
can be displaced normally to the plane of contacts under the action of an electro-
magnet E. This finger when it comes in contact with one of the pieces e, closes
by the intermediate action of the polarised relay g the current on one of the
electromagnets E¹ or E3 (one terminal of each being connected to the positive
supply main) which make the needle o of the indicating dial advance one tooth in
the direction of the motion of the rheostat.
When the needle touches the index m set by the electrician a current is sent

page_text: round the electromagnet which opens the motor armature circuit, so that the
motor stops.
The electrician can also stop the rheostat at a determined point and always
reproduce the effects of illumination under the same conditions.
The fingern being on one of the pieces e, it might accidentally happen that the
indicator of the dial would be operated several times in a contrary direction to
that given by an action of the reversing switch h, which would destroy the corre-
spondence between the position of the rheostat and that of the indicating needle.
In other words it is necessary to prevent the finger n, coming several times
into contact with the piece e in consequence of vibrations. To prevent this it is
necessary that the finger immediately after making contact, should be withdrawn
and held by mechanical means at a distance from the piece e, until the latter has
moved on sufficiently so as to be no longer within reach of the finger n. This
result is obtained in the following manner:-Before establishing metallic con-
tact with a piece e, the finger n by means of a projecting piece of ivory pushes
aside the end of a spring p. At the moment of making metallic contact between n
&e, the electromagnet E is excited and operating the finger n removes its ex-
tremity from the piece e at the same time the ivory projection leaves the end of the
spring which returns to its position of equilibrium & rests under this projection.
After this there is no fear of the contact between m & e so long as this spring,
which is carried round by the drum and which is made sufficiently wide, has not
left the ivory projection..
Such a combination composed of the six elements enumerated and described
above forms a unit corresponding with a single circuit in a switchboard for the
production of theatrical effects. In order to complete such a switchboard, as
many of these units are brought together as there are circuits to serve.
The rheostats can be set in motion either all together or separately, and thus
all the various combinations necessary for theatrical effects can be obtained.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I declare that what I claim is:-
1st. An electrical rheostat with graduated resistance consisting of a drum on
which is applied or wound a conducting wire constituting the resistance in com-
bination with a liquid or solid contact, the drum or the contact or both being
movable in such a manner that the point of application of the contact can move
in a continuous manner along the length of the conductor forming the resistance,
substantially as described and illustrated in Figures 1 to 7 of the drawings accom-
panying the Provisional Specification.
2nd. An electrical rheostat as claimed in Claim 1 adapted to be operated
directly by hand in which case the rheostats can be placed close to the operator or
by apparatus controlled by hand such as motors operated at a distance by means
of electricity, gas, water under pressure or other source of power, said "rheostat
and means for operating the same being adapted to the production of theatrical
luminous effects, substantially as described.
3rd. Apparatus for the production of theatrical luminous effects consisting of
the combination of a motor f driving the drum of the rheostat and put in motion
by operating the switch k which permits the introduction of resistance into the
circuit of the motor and consequently of the regulation of the speed, a reversing
switch h allowing the current to pass in the armature of the motor in one direction
or in the other and to cause the rheostat to turn either in a direction to increase
the resistance of the circuit (in order to imitate night), or in the other to diminish
this resistance (in order to imitate day), this resistance being in series with the
lamps, a position indicating dial i designed to allow of the stopping, at any desired
moment, of the rotation of the drum of the rheostat, the rheostat carrying on one
of the faces of the drum b a series of contact pieces e on which a finger makes
contact; capable of being displaced normally to the plane of these contacts under
the action of an electromagnet, this finger, on making contact with one of the

page_text: pieces of contact e, closing, by the intermediate means of a polarised relay 9 the
current on one of the electromagnets E¹ or which cause the needle of the
indicating dial to advance one tooth in the direction of the motion of the rheostat
until this needle meets an index placed at the point desired by the electrician, the
contact of the needle with the index having the effect of sending the current round
the electromagnet E3 which breaks the communication between the minus terminal
and the switch k so that the motor stops substantially as described and illustrated
in Figures 8 and 9 of the accompanying drawings.
D I
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