Electrical Resistances of Artificial Stone Composition.
Year: 1898

page_text: Date of Application, 24th Aug., 1898-Accepted, 26th Nov., 1898
COMPLETE SPECIFICATION.
Electrical Resistances of Artificial Stone Composition.
We, JOSEF FRANZ BACHMANN, Engineer, of VII Kaiserstrasse 81, ADOLF VOGT,
Engineer, of I Lothringerstrasse 5, CARL CAMILLE WEINER, Gentleman, of I
Elisabethstrasse 3, all of Vienna, Austria, ALBERT KÖNIG, Banker, of Budapest,
Hungary, Dr. JOSEF KIRCHNER, Chemist, of I Elisabethstrasse 3, Vienna, and
Dr. ALEXANDER JÖRG, of I, Opernring 1 Vienna, Austria, Chemist, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed to be particularly described and ascertained in and by the following
statement:-
This invention relates to electrical resistances which are made of an artificial
stone composition which consists essentially of a moulded and burnt mixture of
non-conducting substances such as clay, cement, porcelain, with conducting bodies
such as carbon, metal and the like or may be made of any other electrical resist-
ance material which possesses similar properties enabling it to be applied in the
construction of the electrical resistance hereinafter described.
Examples of such compositions are to be found in the material manufactured
according to the inventions claimed in our previous Patent No. 15238 of 1897
and Vogt's Application for Letters Patent No. 18156 dated August 23rd 1898.
With the aid of such a composition which conducts electricity in varying degree
according to the mode of its production, there can be produced apparatus which
serve for regulating the electric current under various conditions such as regu-
lators for theatre stages, main circuit regulators and shunt circuit regulators,
starting resistances for dynamos, motors, exchanges, electrical railways, are lamps
and the like. The various apparatus serving for regulating the current may be
divided into those-which-when inserted in the circuit constitute a resistance
which cannot be regulated and into those which constitute resistances which can
be regulated. These latter again may be divided into resistances in which the
length of the current path is altered, (as for instance by rectilinear or curvilinear
motion of the contacts with relation to the resistance body), resistances in which
the cross-sectional area of the conductor is altered, whilst the length of the
current path remains constant; and resistances in which both the length and the
cross-sectional area of the current path is altered.
The accompanying drawing illustrates various modes of construction according
to our invention of electrical resistances. It will be understood that the forms
themselves can be modified in many ways.
Figures 1 and 2 are longitudinal sections through resistances which when
included in the circuit need not be regulated. They can however be regulated
when so included, by shifting the contact collars or screw nuts on the body a.
The resistance body a consists of a tube or rod which is either provided at both
ends with collars 6 which serve as contacts as shewn in Figure 1, or is provided
with external screw thread upon which the contact nuts bare screwed as shewn in
Figure 2. The resistance tubes a can be made with right and left handed screw
threads so that by turning the tubes a the contact nuts or collars are caused
077

page_text: to approach or recede from each other. The adjustment of the resistance may be
effected by shifting the collars or nuts, which latter may also be screwed into the
tube ab, in which case the resistance body is provided with internal screw threads.
The cross sectional form of the tubes a may be of any desired shape as shewn
in Figures 3, 4 and 5, in which as shewn, there may be also provided cooling
surfaces in the forms of ribs on the tubes. The resistances may be attached to
suitable supports or carriers in any desired suitable manner.
Resistances which are capable of better regulation when included in the circuit,
and in which the length of the current path is varied, are illustrated in
Figures 6-24; Figures 6-15 shew such resistances with rectilinear regulating
movement.
Figure 6 is a longitudinal section of a resistance tube a with internal screw
thread in which the piston-like contact b is adapted to be moved with the aid of
a rotary spindle d. The latter is, like the piston, provided with screw thread of
equal pitch and passes through a nut by tightening which after the contact b
has been adjusted, the latter is fixed and at the same time, even in the case of
wear of the screw thread of the tube, is kept in contact with the latter, on at
least one side, so as thereby to form a secure contact.
In Figure 7 two resistance tubes a connected together are shewn which have
a spectacle-like sliding or rubbing contact 6 that is capable of being shifted by
means of the spindle d. These tubes may be coupled up together either in series
or in parallel. As shewn in the cross-sectional Figures 8-11, the resistance bodies
may be made of any desired form in cross-section, and they may offer to the
rubbing contact one or more sliding surfaces of varying dimensions.
Or only
one body a may be employed, and the contact b may also be shifted by hand.
Figures 12 and 13 shew a resistance with piston-like internal contact in longi-
tudinal section and cross-section. For the purpose of cooling, the tube a may
be provided with ribs as shewn in Figure 13 or with passages as shewn in
Figure 14, or with both kinds of cooling surfaces; also the piston b, which may
be adapted to be shifted in any desired manner may be perforated for the purpose
of better circulation of air.
Figure 15 illustrates a rheostat, the resistance body a of which is connected
in the direction of its length at various points by means of leads with needle
contacts b of successively increasing length which dip successively in a vessel b*
that is capable of being raised and that contains mercury; by this means a
gradually increasing resistance can be included.
Figures 16-20 shew several forms of construction of resistances that are capable
of being regulated during their inclusion in the circuit, in which the resistance
body a is of annular shape, and the contact that is formed as a rotary lever
executes a curvilinear movement on the body a The ring a is interrupted at
one place and there is inserted a non-conductor a¹, consisting of marble, slate &c.
When the lever is situated at a³, the resistance is short-circuited. When the lever
is rotated in the direction of the arrow, more and more resistance is gradually
included until, when the lever is in a position a³ the whole of the resistance is
included. For the purpose of better conduction, a metal plate may be screwed
on at a². When the lever b is moved further along. on to the non-conductor a¹,
the resistance is cut out of circuit; and the sparking produced by such interruption
may be rendered harmless for example by means of a spring e, which is provided
on the outer circumference of the ring a for the purpose of preventing the destruc-
tion of the rubbing surfaces.
It is possible to make such bodies with different specific resistances at different
places; it is therefore better in many cases for reasons of construction to make
the ring a closed as shewn in Figure 17, and it may be made at the place a¹ of
non-conducting material, practically speaking.
Since in practice most resistances are more highly tried at their short circuiting
places than at their cutting out places, it is advisable to make the resistance
body whether it be in the form of a rod or of a ring-in its longitudinal direction

page_text: of different specific resistances adapted to the current strength in each case,
whereby the greatest possible uniformity of load on the cross-sectional area is
produced. Figure 18 shews an annular resistance of this kind whose resistance
is stepped, or graduated between a and as in the manner described. It is of
course to be understood that these steps or gradations may be made in any desired
manner and of any desired dimensions. The rubbing contact b may be made with
a smooth rubbing surface as shewn in Figures 16-18 or it may be made with
The
lamellae as shewn in Figure 19 or it may be in any other desired manner.
contact pieces may be on one or more of the flat or curved surfaces of the ring
as may be found most convenient. A number of such rings may be arranged side
by side (as regulators for theatrical stages) or above one another (as starting resist-
ances for polyphase current motors), and inside one another (as starting resistances
and reversing resistances for continuous current motors) which latter case is
illustrated by Figure 20.
In this Figure 20 the one terminal or pole wire of the main circuit is shewn
connected with the lever b, whilst the other wire is connected with the innermost
one of the rings a and with one brush of the motor. The shunt circuit is connected
with the two good conducting segments of the middle ring. When the lever b
is rotated towards the right (into the position shewn in dotted lines) the shunt
circuit current will travel in the direction of from z to y. If the lever be rotated
in the opposite direction, the shunt circuit current will also change its direction
whilst the direction of the main current will of course, always remain the same.
In consequence of the different direction of the current in the shunt circuit, the
direction of the motor will also be different. The contact spring c which is
attached in an insulated manner, connects, according to the direction of the rotation,
one or the other good conducting segment of the middle ring with the inner ring.
The other segment always receives current through the extension 6* of the lever..
If it is desired always to utilise both halves of the starting resistance, the same are
connected together in the manner indicated by dash-dotted lines in Figure 20.
The rings a may be made of rectangular or of one of the cross sectional forms
shewn in Figures 21-24 in which Figure 24 shows a cross-sectional form having
an inclined rubbing surface.
Resistances in which the length of the current path is retained and in which
the cross-sectional area of the conductor is varied, may be constructed according
to one of the arrangements shewn in Figures 25 to 30. In Figures 25. the resist-
ance is varied by the including of the resistance pins a, a, in parallel, for which
purpose there is provided a bar that is studded with contact springs b, and which
is capable of shifting over the pins. In the case of plate-shaped resistance bodies
(Figure 26) one of the surfaces of the same is provided with a metal covering a
whilst on the other surface the contact plate 6 is ground on, and by shifting which
the cross-sectional area of the conductor and consequently the resistance is varied
(Figures 27-30).
The contact bar, as also the contact plate may receive a rectilinear or a curvi-
linear motion. In the case of plate-shaped and annular resistance bodies, the
rubbing surface for the contact is preferably provided with metallic lamellae
which are made by annlying paraffin, paint or other insulator, so as to form linear.
strips or stripes on the rubbing surface and providing the parts of the surface that
have been left uncovered with a galvanic metallic deposit.
in
actually employed
SO
The resistance may also be varied by constructing the conducting resistance
of varying specific resistance and shifting the contacts
as to vary
the specific resistance of the effective portion of the conducting resistance i.e.
that part which is
If
conducting the current.
this mode be adopted it is not necessary to vary either the length
or cross-section of the current path. It is not necessary however to describe in
detail the mode of applying this method to the various forms of resistance as it will
be understood from what is here contained in relation to the other methods.
Resistances in which both the length, as also the cross-sectional area of the

page_text: current path are altered, may be made by constructing their resistance bodies of
varying cross-section.
Figure 31 shews an example of construction with one resistance-cylinder a
which composed of two obliquely cut inter-fitting halves of a cylinder formed
respectively of a conducting mixture, and of a non-conductor. This cylinder
the circular surface of which is shewn developed in Figure 32, is rotatively
mounted in bearings 9 which may also serve as conductors to supply the current.
On the cylindrical surface are adapted to rub the contact pieces b so that when the
cylinder is rotated, the length and cross sectional area of the current path will
be varied simultaneously. The cylinder may also be stationary, in which case
the contacts are arranged to rotate and rub on the outside of the cylinder or in a
recess in the same. Figure 33 illustrates a particular construction of a resistance
box for measuring purposes with bar-shaped, or tube-shaped resistance bodies a
which are included in the circuit in the usual manner by plugging. The resist-
ance bodies may also be composed of a number of parts which are connected
together by cementing screwing or compressing, and which may be galvanised
at the joints, if required. Any recesses which may be provided may serve for
natural circulation of air, or also for cooling by means of compressed air or water.
In the case of the galvanised rubbing contact of lamellar nature of resistance rings
the interrupting strips may be advantageously arranged in such an oblique position
(see Figure 19) that the inner and outer current paths to the short circuiting
contact are of equal or of almost equal length. The resistance bodies already
described may be fixed directly upon base plates of insulating material (marble.
slate, etc.) or insulated upon metallic base plates by means of screws, straps flanged
rings or clamping jaws.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is:
-:
1. Adjustable electrical resistances in which the resistance consists of one or
more rods, plates, tubes or rings of material such as herein specified, mounted
with adjustable contacts so as to vary the resistance, either (1) by varying the
length of the current path or (2) by varying the cross-section of the conducting
resistance, or (3) by varying the specific resistance of the conducting portion of
such resistance or (4) by a combination of two or more of the above modes of
varying the resistance, substantially as described.
2. Adjustable electrical resistances constructed as described and shewn in the
drawings.
Dated this 24th day of August 1898