Improvements in the Construction of Rheostats or similar Electrical Instruments.
Year: 1887

page_text: Date of Application, 27th Dec., 1887
Complete Specification Left, 27th Sept., 1888
Complete Specification Accepted, 9th Nov., 1888
Improvements in the Construction of Rheostats or similar Electrical
Instruments.
1, FREDERICK LAWRENCE RAWSON, Director of and on behalf of the Woodhouse
& Rawson Electric Manufacturing Company, Limited, of 11 Queen Victoria Street,
in the City of London, do hereby declare the nature of this invention, a communi-
cation to me from abroad by Charles Wirt of 292 Avenue B, New York,
Electrician, to be as follows:-
This invention relates to electrical instruments such as a rheostat, by which variable
resistances are inserted into any circuit, and consists of an improved, simple, and
cheap method of construction of the same.
The medium of electrical resistance applied in the instrument is as usual a wire
conveniently of German Silver, platinoid or other metal, and is applied preferably to a
drum or cylinder in a manner hereinafter more particularly described.
The said cylinder is mounted on a central axis capable of rotation by a handle and
a pointer is affixed, to denote the value of the resistance introduced, in proportion to
the degree of rotation, by means of the usual fixed contact brush.
The wire is applied to the rotating drum as follows:-The wire covered or insulated
between successive coils or uncovered is wound first upon a tube of collapsible
insulating material, such as paper, previously varnished. After winding, the whole is
varnished, so that the wire sticks tightly to the paper. When the varnish is sufficiently
dry, but not quite hard, the paper tube with the wire on it is flattened for some hours
between sheets of soft rubber.
The flat plate of paper and wire, so prepared, is then bent over and attached to the
aforesaid drum or cylinder of the rheostat or similar electrical instrument by being
tightly bound over its whole surface by thread, which is then varnished.
After the varnish is quite hard, the surface of the wire is stripped around the
periphery of the drum in a suitable path for the brush or brushes to make contact
thereon.

page_text: These brushes may be formed by a bundle of wires, resting on two supports, one
in the circuit and the other insulated therefrom. The wires may be thus made to
press by their own transverse clasticity tangentially upon the stripped portion of the
wire-covered resistance-drum.
FELL & WILDING,
1, Queen Victoria Street, London, E.C.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Construction of Rheostats or similar Electrical
Instruments.
I, FREDERICK LAWRENCE RAWSON, Director of, and on behalf of, the Woodhouse
& Rawson Electric Manufacturing Company, Limited, of 11 Queen Victoria Street,
in the City of London, do hereby declare the nature of this invention, a communi-
cation to me from abroad by Charles Wirt of 292 Avenue B, New York, Electrician,
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 eléctrical instruments such as a rheostat, by which variable
resistances are inserted into any circuit, and consists of an improved, simple, and
cheap method of construction of the same.
The medium of electrical resistance applied in the instrument is as usual a wire,
conveniently of German silver, platinoid, or other metal, and is applied in the first
place preferably to a collapsible drum or cylinder in a manner hereinafter more
particularly described.
The said collapsible drum or cylinder is made preferably of paper, which after
collapse and flattening by pressure into an uniform plane surface, presents a con-
tinuous coil or series of coils, wound over both surfaces of the said flattened cylinder,
which may then be used on a plane surface or applied easily to any desired surface,
such as the periphery of a metal drum or cylinder, for the purpose of a rheostat as
hereinafter more particularly described.
In order that this invention may be the better understood, I now proceed to
illustrate one form of a complete instrument, in which the said wound and flattened
paper cylinder is applied to a metallic drum, reference being had to the letters and
figures marked thereon.
Figure 1 is a vertical section of such an instrument,

page_text: Figure 2 is an outside elevation and
Figure 3 is a plan of the same.
The said cylinder A is mounted on a central axis B, and is capable of rotation by a
handle C, and a pointer is affixed, to denote the value of the resistance introduced,
in proportion to the degree of rotation, by means of the usual fixed contact
brush D.
The wire is applied to the rotating drum as follows:-
The wire, covered or insulated between successive coils is wound first upon a tube
or cylinder of collapsible insulating material, such as paper, proviously varnished.
After winding, tho whole is varnished so that the wire sticks tightly to the paper.
When the varnish is sufficiently dry, but not quite hard, the paper tube or cylinder E
with the wire on it, is flattened for some hours between sheets of soft rubber. The
flat plate of paper and wire, so prepared, is then bent over and attached to the
aforesaid drum or cylinder of the rheostat or similar electrical instrument, by being
tightly bound over its whole surface by thread F which is then varnished.
After the varnish is quite hard, the surface of the wire is stripped around the
periphery of the drum in a suitable path for the brush or brushes D to make contact
thercon. The brushes D may be formed by a bundle of wires resting on two
supports HF, one in the circuit leading to the binding screw G, and the other insulated
therefrom. These supports H H. and the frame K and bearing spindle B are attached
to a wooden base plato, so as to be all relatively insulated. The wires forming the
brush D press by their own transverse elasticity, tangentially upon the stripped portion
of the wire-covered resistance drum.
The other terminal L is connected to the socket of the handle C which is electrically
connected with the metallic cylinder A, and thence to one end of the resistance
wire, which is soldered to the cylinder. The other ond of the resistance wire remains
free.
Having now particularly described and ascertained the nature of this said
invention, and in what manner the same is to be performed, I declare that what I
claim is
1st. In a rheostat or resistance regulator, the construction of the resistance coil in
the form of a collapsible tube or core, on which the said wire is wound and after-
wards applied in a flattened condition to a desired surface, on which contact brushes
may make electrical contact substantially as described.
2nd. In a rheostat or resistance regulator the combination of a flattened tube
carrying a continuous coil or series of coils of the resistance wire applied to the
surface of a revolving drum, substantially as and for the purposes described.
3rd. In a rheostat or resistance regulator, the formation and covering of the outer
surface of the resistance coil, so that the metallic surface of the wires is only bared
at such points or in such a path as is necessary to allow contact with a fixed brush
or brushes, substantially as described.
4th. In a rheostat or resistance regulator the construction and combination of
parts to form a complete instrument, substantially as illustrated and described.
Dated this 27th day of September 1888.
FELL & WILDING,
1, Queen Victoria Street, London, E.C.,
Agents for the Applicant.
FELL & WILDING,
1, Queen Victoria Street, London, E.C.,
Agents for the Applicant.