Improvements in the Construction of Rheostats or similar Electrical Instruments.
Year: 1891

page_text: Date of Application, 7th May, 1891
Complete Specification Left, 6th Feb., 1892-Accepted, 9th Apr., 1892
PROVISIONAL SPECIFICATION.
Improvements in the Construction of Rheostats or similar
Electrical Instruments.
FRANK BRYAN, Electrical Engineer, of 11 Brackley Terrace, Chiswick,
London, W. and WOODHOUSE & RAWSON UNITED LIMITED, Electrical Engineers
and Contractors, of 88 Queen Victoria Street, London E.C. do hereby declare
the nature of this invention to be as follows:-
This invention relates to electrical instruments by means of which variable
resistances are inserted into any circuit or circuits carrying a current of electricity
and is designed to afford a more perfect and reliable form of instrument for the
said purpose.
It is well known that a wire of some metal or alloy is usually employed to form
the medium of resistance in such instruments but what I prefer to use is a conductor
formed as follows.
I take a tube or cylinder of any suitable metal or alloy, such as German silver.
This tube may either be drawn in the usual manner or may be formed of a flat
sheet of metal bent into a cylindrical form, in which case it is not necessary to
solder or otherwise join together the edges of the said sheet. I may also use a
cylinder formed by casting in a suitable mould the metal I wish to employ.
The cylinder thus obtained is to be arranged in such a manner between suitable
end plates as to be capable of rotation round an axis.
The cylinder must be insulated from the said end plates in any suitable manner,
and must be sawn or otherwise divided in planes preferably parallel with the axis,
in such a manner as to constitute a kind of zig-zag conductor running up and down
from end to end of the said cylinder which must be totally split or separated from
top to bottom at one point.
By this means, if a current is caused to pass between any two points on the
circumference of the said divided cylinder, it must of necessity go up and down
each intervening zig-zag successively, thus being obliged to traverse more or less
resistance according to the less or greater distance apart of the points of contact
or application of the said current.
A convenient mode of applying the said current to cause it to traverse the said
resistance is to connect one end of the zig-zag conductor to the end plate and axis
and to cause a metallic brush or contact device to press against the surface of the
cylinder (which I prefer) or the cylinder may be fixed and the brush caused to
rotate around the same.
Another form of cylinder may be made by casting or otherwise producing two
concentric tubes or cylinders united at both ends.
This may be so sawn or divided as to constitute a conductor in which the course
of the current would be in one direction in the outer sections of the conductor
and returning in the opposite direction in the inner sections and in this manner be
caused to traverse the whole circumference both of the inside and outside concentric
tubes, one of the advantages of this form of cylinder being that more resistance
may be got into the same space than is the case with the first described cylinder.
Another advantage I claim for these modes of construction is that no insulating
material is needed between adjacent portions of the conductors the risk of
damaging the instrument through overheating of the conductors is reduced

page_text: to a minimum thus greatly increasing the current carrying capacity of the
instrument.
Dated this Seventh day of May 1891.
FRANK BRYAN.
WOODHOUSE & RAWSON UNITED, LIMITED,
W. T. Stutchbury, Secretary.
COMPLETE SPECIFICATION.
Improvements in the Construction of Rheostats or similar
Electrical Instruments.
FRANK BRYAN, Electrical Engineer, of 11 Brackley Terrace, Chiswick,
London, W. and WOODHOUSE & RAWSON UNITED LIMITED, Electrical
Engineers and Contractors, of 88 Queen Victoria Street, London E.C. 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:-
Our invention relates to electrical instruments by means of which variable
resistances are inserted into any circuits or circuits carrying a current of electricity,
and is designed to afford a more perfect and reliable form of instrument for the
said purpose.
It is well known that a wire of some metal or alloy is usually employed to form
the medium of resistance in such instruments but what we prefer to use is a
conductor formed as follows:-Having reference to the accompanying drawings,
we take a tube or cylinder A Figs. 2, 3, 4, of any suitable metal or alloy, such
as German silver. This tube may either be drawn in the usual way, in which case
it must be cut right through at one part and slotted up and down in a zig-zag
manner, or we may form it of a flat sheet of metal Fig. 5 with slots 8, s, s sawn or
otherwise cut, this we form or bend into a cylindrical form, in which case it is
not necessary to solder or otherwise join together the edges of the said sheet, we
may also use a cylinder formed by casting in a suitable mould the metal we wish
to employ.
The cylinder thus obtained we fix between two rings I, I Fig. 1 which consist
of any suitable insulating material such as ebonite, which are clamped between two
discs or plates and mounted on an axle E Fig. 1 round which it is capable of
rotation.
The cylinder being split in the manner above described, it is evident that if a
current is caused to pass in at one end of the zig-zag, it must traverse more or
less resistance according to the greater or less distance apart of the points of
contact.
To perform this, to a terminal T Fig. 2 we connect a rubbing contact brush B
Fig. 2, which brush presses on the cylinder A at the point C Fig. 2, so that the
current may be applied to any portion of the cylinder which it must traverse until
it gets to the end of the zig-zag, which end is fastened to the axle E, which is
connected to the other terminal T¹, a convenient means of joining the cylinder to
the axle is shown in Fig. 6, where J is a bracket joining one end of the cylinder
to the plate and axle.
Figs. 3 and 4 show a method in which the cylinder A is fixed, and the arm D,
carrying the rubbing contact brush B, is capable of rotation round the cylinder.
For the purpose of economising space, Figs. 7 and 8 show two concentric rings
united at each end or of a tube flattened out, as shown in section in Fig. 8, which
is sawn or cut in any suitable manner into a continuous spiral or zig-zag, and is
then bent round into a circle, having an opening at one point F, Fig. 7, when it
can be mounted between rings 1, 1, Fig. 1 in the manner above described.

page_text: Having now particularly described and ascertained the nature of our inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is,
An apparatus for the insertion of variable resistances in an electrical circuit or
circuits substantially as described.
Dated this 5th day of February 1892.
WOODHOUSE & RAWSON UNITED, LIMITED,
A. L. Foley, Assist. Secretary.
LA DDVAN

page_text: $ $
FIG 5