Improvements in Rheostats.
Year: 1899

page_text: Date of Application, 1st June, 1899
Complete Specification Left, 15th Jan., 1900-Accepted, 17th Feb., 1900
Improvements in Rheostats.
We, CARL FLOHR, of 28 Chausséestrasse, Berlin, N., Germany, Engineer, and
REINHARD DIETZE, of 43, Meissnerstrasse, Coswig i/Sa, Germany, Engineer, do
hereby declare the nature of this invention to be as follows:-
-
The rheostats hitherto employed for high-potential currents and comprising
a mass of pulverulent resisting material into which a regulating contact piece
is dipped to a greater or less depth, are attended by the disadvantage that when
they are being operated the metallic powder sticks to the insulating portions of
the apparatus, whereby paths are made for the current that cause short circuits
and disturbances of working. This disadvantage is obviated according to the
present invention by means of a special sliding contact device that is connected
with the regulating contact piece, and by means of which, for the sake of safety,
the circuit is again broken after the regulating contact piece has passed out
of contact with the mass of resisting material.
In an example of rheostat according to this invention, there is journalled in a
closed receptacle containing the pulverulent metallic material, a shaft carrying
a regulating contact arm, which, by rotating the said shaft, can be caused to dip
to a greater or less depth into the said material and also to come into contact
with a suitably curved short-circuiting contact piece. The sliding contact device
through which the current is led into the regulating contact arm, is outside the
receptacle and comprises a fixed contact bar, to which the source of current is
connected and which is curved about the axis of the said shaft as a centre, and
a contact arm fastened on the said shaft.
The sliding contact device is put into circuit by the motion of the regulating
contact arm, during which the contact arm of the sliding contact device comes
into contact with the aforesaid fixed bar, which is in connexion with the source
of current, before the regulating contact arm dips into the mass of resisting
material. On switching off, on the contrary, the sliding contact pieces are not
separated until after the regulating contact arm has left the mass of resisting
material, so that the circuit is broken after the regulating contact arm has
ceased to be in contact with the resisting material.
Dated this 1st day of June 1899
F. WISE HOWORTH,
46, Lincoln's Inn Fields, London, W.C.,
Agents for the Applicants.

page_text: 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: ―
The rheostats hitherto employed for high-potential currents and comprising
a mass of pulverulent resisting material into which a regulating contact-piece is
dipped to a greater or less depth, are attended by the disadvantage that, when
they are being operated, the metallic powder sticks to the insulating portions of
the apparatus, whereby paths are made for the current that cause short circuits
and disturbances of working. This disadvantage is obviated according to the
present invention by means of a special sliding-contact device that is connected 1
with the regulating contact-piece and by means of which, for the sake of safety,
the circuit is again broken after the regulating contact piece has passed out
of contact with the mass of resisting material.
An example of a rheostat according to this invention is shown in the accom-
panying drawings, of which Figs. 1 and 2 are vertical longitudinal sections of
the apparatus with the regulating contact-pieces in two different positions, and
Fig. is a vertical cross-section thereof.
In a closed receptacle A containing the pulverulent metallic material is
journalled a shaft carrying a regulating contact arm B, which, by rotating the
said shaft, can be caused to dip to a greater or less depth into the said material 2
and also to come into contact with a curved short-circuiting contact-piece C. The
sliding-contact device through which the current is led into the regulating
contact arm, is outside the receptacle A and comprises a fixed contact bar a, to
which the source of current is connected and which is curved about the axis of
the said shaft as a centre, and a contact arm c fastened on the said shaft.
2
The sliding-contact device is put into circuit by the motion of the regulating
contact arm B, during which the contact arm c of the sliding-contact device comes
into contact with the fixed bar a, before the regulating contact-arm B dips into
the mass of resisting material. On switching off, on the contrary, the sliding-
contact pieces a and c are not separated from each other until after the regulating 3
contact arm B has left the mass of resisting material, so that the circuit is
broken again after the regulating contact arm B has ceased to be in contact with
the resisting material.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, we declare that s
what we claim is:-
1. A metallic-dust rheostat whose resistance is varied by the dipping into the
resisting material, to a greater or less depth, of a regulating contact-piece, in
which the current is led into the regulating contact piece by a sliding-contact
device, the rotatable arm of which is connected with the regulating contact piece 4
and is so arranged that the parts of the sliding-contact device come into contact
with each other before the regulating contact piece dips into the resisting
material and that, on switching off, the said parts are separated from each other
after the regulating contact piece has left the resisting material.
2. A rheostat constructed, arranged, and operating as hereinbefore described 4
with reference to and shown in the accompanying drawings.
Dated this 15th day of January 1900.
F. WISE HOWORTH,
46, Lincoln's Inn Fields, London, W.C.,
Agents for the Applicants.