Improvements in Switches for Varying Electrical Resistance.
Year: 1895

page_text: Improvements in Switches for Varying Electrical Resistance.
We, SIEMENS BROTHERS & Co. LIMITED, and EDCARD FRIEDRICH
HERMANN HEINRICH LAUCKERT, of 12, Queen Anne's Gate, Westminster in the
County of Middlesex, Electrical Engineers, do hereby declare the nature of this
invention to be as follows:-
:-
For many purposes, especially for the starting and regulating of motors, it is
necessary to vary the resistance in an electric circuit, and in order to effect this
gradually there are arranged in a switch a considerable number of contact plates
or segments connected through successive resistances, and a brush or rubber
which is moved over these so as to introduce or cut out these resistances step
by step.
This invention relates to the construction of resistance switches and their
brushes in such a manner that, in order to provide for a given number of steps,
the number of contact plates or segments and of the resistances and their
connections may be considerably reduced, or, in other words, that a given number
of plates or segments, resistances and connections may serve for a considerably
greater number of steps. For this purpose, instead of one brush, two or more
brushes insulated from each other are employed; one of these which may be
termed the leading brush, as it is moved over the contact plates or segments brings
them successively into direct connection with the circuit. The second brush as it
is moved, along with the first, brings the successive plates or segments into
connection with a bar or seginent which is connected, not directly, but through a
certain resistance to the circuit. In like manner, there may be a third brush,
moving along with the others and connecting the successive plates or segments to
another bar or segment connected to the circuit through another resistance. The
successive contact plates or segments may be so spaced that only one of the
brushes is on one of them at a time; when the first brush is on, all the resistance
up to that particular plate or segment is in circuit, when the second brush is on, an
additional resistance is included, and when the third brush is on a still greater
resistance is included. In this way the added resistance due to the step from one
contact to the next is divided into three steps, or a certain number of contact
plates and resistances is by the addition of the two brushes and their two
resistances rendered available for thrice the number of steps.
According to a modified arrangement, the leading brush is connected to each of
the others through a resistance.
The contact plates or segments are so arranged that one, two or all of the
brushes may be on one plate or segment at a time, or that one, two or more may be
on one plate, whilst, of the others, one may be over the gap between the plates and
the others on the next plate.
By the parallel routes thus provided for the current, the step from one
resistance to the next in order is subdivided.
In cases where the successive resistances between the plates or segments vary, it
may be of advantage also to vary the resistances between the leading brush an
the others. This can be done by providing each of the brushes with a second

page_text: contact sliding over a separate conducting bar or segment, which may be divided
into sections connected to each other through suitable resistances.
Dated this 2nd day of May 1895.
ABEL & IMRAY,
Agents for the Applicants.
Improvements in Switches for Varying Electrical Resistance.
We, SIEMENS BROTHERS & Co. LIMITED and EDUARD FRIEDRICH
HERMANN HEINRICH LAUCKERT, of 12 Queen Anne's Gate Westminster in the
County of Middlesex Electrical Engineers 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 :-
For many purposes, especially for the starting and regulating of motors, it is
necessary to vary the resistance in an electric circuit, and in order to effect this
gradually there are arranged in a switch a considerable number of contact plates
or segments connected through successive resistances, and a brush or rubber
which is moved over these so as to introduce or cut out these resistances step
by step.
This invention relates to the construction of resistance switches and their
brushes in such a manner that in order to provide for a given number of steps, the
number of contact plates or segments and of the resistances and their connections
may be considerably reduced, or in other words, that a given number of plates or
segments, resistances and connections may serve for a considerably greater number
of steps. For this purpose, instead of one brush, two or more brushes insulated
from each other are employed; one of these, which may be termed the leading
brush, as it is moved over the contact plates or segments, brings them successively
into direct connection with the circuit. The second brush as it is moved, along
with the first, brings the successive plates or segments into connection with a bar
or segment which is connected, not directly, but through a certain resistance to
the circuit.
In like manner there may be a third brush, moving along with the others and
connecting the necessive plates or segments to another bar or segment connected
to the circuit through another resistance, The surce sive contact plates or
opments may he to med that only one of the basis on one of them at a
sh on, il the resistance up to that particular plate up
segment is in circuit; when the sand brush is on, an additional dance is
included, and when the third brush is on a still greater resistance is included.
in this way the added resistance due to the top from one contact to the nest is
divided into three stupe, or a cert: in unter of contact plates and resistance i
by the addition of the two bru he, and their two resistances, rendered available
for thrice the number of steps.
According to a modified arrangement the leading brush is connected to each of
the others through a resistance. The contact plates or segments are so arranged
that one, two or all of the brushes may be on one plate or segment at a time, or
that one two or more may be on one plate, whilst, of the others, one may be over
the gap between the plates and the others on the next plate.
By the parallel routes thus provided for the current, the step from one resistance
to the next in order is subdivided.
In cases where the successive resistaners between the plates or segments very, it
may be of advantage also to vary the resistances between the leading bruck and
the others. This can be done by providing each of the brushes with secon]

page_text: contact sliding over a separate conducting bar or segment, which may be divided
into sections connected to each other through suitable resistances.
Figure 1 is a diagram shewing a series of resistances and contact segments
constituting a switch with two brushes 1 and 2 insulated from each other except
that they bear on conducting bars 10 and 13 connected together through a
resistance 4. When the brushes are in position A the current to be varied in the
circuit 8 passes at 9 to the first segment 6 through brush 1 bar 10 back to 8. By
moving the brushes to a position such as B when the brushes are on two segments,
the current entering at 9 and passing through a number of resistances 7 to the
point 11, divides into two parts, one passing through resistance 12 and brush 1 to
the bar 10 and the other part passing by brush 2 bar 13 resistance 4 to bar 10
where it joins the first part both returning together to 8.
By moving the brushes to such a position as C where brush 2 is over the
interval between two segments the circuit bar 13 and resistance 4 is cut off. At
position D of the brushes the current after having passed through all resistances 7
passes through the brush 2, bar 13, resistance 4 and bar 10 to 8.
Figure 2 is a diagram of a switch with three brushes. In position A the
current passing by 6, 1, and 10 encounters none of the resistances. In position B
brush 1 is on one segment and brushes 2 and 3 on the preceding segment putting
three resistances 4, 5 and 7 in parallel. In position C brush 1 is on one segment
brush 2 is over an interval, and brush 3 is on the preceding segment. In this case
resistance 4 is disconnected and only 5 and 7 are in parallel. In position D the
brushes 1 and 2 are on one segment and brush 3 is over a gap the resistances 7
being only in circuit.
Figures 3 and 4 are diagrams of switches in which the resistance steps 7 are
increased as more resistance is introduced into the circuit. The resistances
between the brushes must also increase and therefore the conducting bar 13 in
Figure 3 and the bars 14 and 15 in Figure 4 are made each in two parts with
resistances 16 connecting the parts which in positions of the brushes at and
beyond G are added to the resistances 4 and 5.
In Figures 1, 2, 3 and 4 the contacts and bar are shewn arranged for rectilineally
sliding brushes. They may be conveniently arranged for brushes moving
circularly.
Figure 5 is a section and Figure 6 a plan of such a circular switch having
13 contact segments S with interposed resistances T which with a single brush in
the usual way would give twelve steps but, by employing a second brush B and
the inner segments C corresponding to divided bars such as 13 or 14 in Figure 4 the
steps are increased to twenty-five. The brush A. is in connection through the axis
with terminal D. The brush B moves over the conducting segments C one
segment of which is connected to brush A through a resistance E. There are
three intervals between the segments Cbridged by resistances F, G, H, so that as
the back part of brush B slides over the segments the resistances F, G, H are
automatically added to the resistance E. When the brushes are in the position
shewn in Figure 6 all the resistances T, E, F, G and H are in circuit. The
current enters at K passes through the twelve resistances T to brush B and the
segment C then through segments C' and resistances H, G, F and E to the axis
and terminal D.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed we declare that what we
claim is:-
1. In a switch for varying electrical resistance, the use of two or more brushes
insulated from each other except through a resistance, these brushes being of
such width and so arranged relatively to the conducting segments over which they
are moved and which are themselves connected through successive resistances so
that in some positions of the brushes they introduce into the circuit the resistances