IMPROVEMENTS IN DYNAMO-ELECTRIC MACHINES
Year: 1884

page_text: I Professor GEORGE FORBES of 34 Great George Street in the City of West-
minster do hereby declare the nature of my invention for "IMPROVEMENTS IN
DYNAMO-ELECTRIC MACHINES" to be as follows:-
This invention has for its object the improvement of dynamo-electric machines
and relates especially to machines such as are described in the specification of a
former Patent granted to me No 3115 in the year 1883.
Each iron disc is replaced by a large number of thin discs or rings insulated
from the spindle and from each other. These discs or rings may be clamped
between two thicker insulated discs or rings revolving with them and serving to
solidify the armature by compressing the thin discs tightly. The two sets of thin
discs which replace the two discs of my former specification are connected the first
thin disc of one set with the first thin disc of the other by an insulated bar or
connecting piece and the second with the second and so on. These bars or
connections are within the rings they lie along the axis.
The outer peripheries of the rings are in electrical connection with collectors of
any convenient form, they may be springs, mercury contacts or other; and the
second disc of one set is electrically connected externally with the first of the
second set by the collectors and so also the third of the first set with the second
of the second set and so on. The first disc or ring of the first set and the last of
the second set act as terminals.
The rings may be of iron and the bars of copper, or the rings of copper and bars
of iron, or both may be of iron or other magnetic metal.
I so arrange the connections as to avoid a large difference of potential between
two adjacent bars. This may be done by connecting alternately right and left of
the first bar.
Sometimes in place of electrically connecting the rings to bars as above described
I connect them to the ends of concentric cylinders so that I have as many
cylinders as I have pairs of rings. These concentric cylinders and the rings are of
magnetic metal and insulated from each other.
Sometimes I make a double machine with two armatures on parallel spindles
in which the discs or rings forming the external coatings of the two armatures are
electrically connected by endless inetallic bands passing around them.
These bands may also serve to transmit the motive power from one armature to
the other.

page_text: This method of collecting the current by endless metallic bands from a revolving
surface is applicable to the machine described in the former Patent granted to me
No 3115 in the year 1883 and to dynamo machines generally.
The two discs of the double machine described in my former specification may
be replaced by a single cylinder of iron of length equal to the distance between
the outer faces of the two discs whereby the central portion of the field magnets
projecting into the space between the discs is also replaced and dispensed with.
Sometimes I dispense with the discs or rings and the collectors at both ends of
the bars then consist of a number of springs touching the bars and arranged
round in a circle whose plane is perpendicular to the axis of rotation. Each
spring touches a separate bar and in succession each spring touches every bar
during a rotation of the armature.

page_text: COMPLETE SPECIFICATION.
:-
I Professor GEORGE FORBES of 34 Great George Street in the City of West-
minster do hereby declare the nature of my invention for "IMPROVEMENTS IN
DYNAMO-ELECTRIC MACHINES" and in what manner the same is to be performed
to be particularly described and ascertained in and by the following statement :-
This invention has for its object the improvement of dynamo electric machines
and relates especially to machines such as are described in the Specification of
a former Patent granted to me No 3115 in the year 1883.
In such machines the electro-motive force of one disc at any speed or pair of
discs is limited by the quality of the iron and the diameter of the disc so that in
order to increase the electro motive force of the machine it is necessary to divide
the disc into sections insulated from each other the divisions of the disc being
most conveniently made parallel and perpendicular to the axis of the machine but
they may be made in any directions provided they cut as many of the lines of force
as possible.
When the divisions are planes at right angles to the axis of the machine each
iron disc is divided into or replaced by a large number of thin discs or rings
insulated from the spindle and from each other. These discs or rings may be
clamped between thicker insulated discs or rings revolving with thoin and serving
to solidify the armature by compressing the thin discs tightly.
The two sets of thin discs which replace the two discs of my former Specification
are connected internally as follows-the first thin disc of one set with the first
thin disc of the other by an insulated bar or connecting piece and the second of
one set with the second of the other and so on. These bars or connections are
within the rings they lie along the axis.
The outer peripheries of the rings are in electrical connection with collectors of
any convenient form, they may be springs mercury contacts or any other con-
venient way. By any of these or other means the discs are connected externally
as follows The first disc of one set with the second of the other set and the second
of the first set with the third of the second set and so on. I so arrange the
connections as to avoid a large difference of potential between two adjacent bars.
This may be done by using one of the centre discs of a set as the first or terminal
one and taking discs situated alternately to the right and left of this one in the
succession of connections.
Sometimes in place of electrically connecting the rings to bars as above described
I connect them in pairs to the ends of concentric cylinders so that I have as many
cylinders as I have pairs of rings. These concentric cylinders and the rings are of
magnetic metal and insulated from each other.
When the divisions of the fundamental discs or cylinder are planes parallel to
the axis of the machine it practically takes the form of a cylinder consisting of
a number of separate bars insulated from each other and from the spindle In this
case I sometimes take off the induced current directly from the bars by separate
contact conductors twice as many in number as there are bars and which touch
each bar in succession as the machine revolves. Otherwise I surround the bars
between their poles by a number of concentric conducting rings one of these rings

page_text: being electrically attached to each end of each bar but each ring is insulated from
all the other rings and from all the bars except the one to which it is connected
electrically.
The annexed drawings show some of the forms in which my improvements can
be effected.
Figures 1 and 2 are explanatory diagrams showing how the two discs of the
double machine described in my former Specification may be replaced by a single
cylinder of iron so that the space between the two discs before described is filled
with a mass of iron attached to and rotating with the spindle instead of a stationary
mass attached to the casing the same effect being obtained in each case.
diagrams will assist to a better understanding of my present invention.
In Figures 1 and 2 A A aro two iron discs.
These
a is the central iron mass which may form one solid mass with the discs A. A
or be separate from them as indicated by the dotted lines.
a is part of the outer casing in Figure 1 but which like the centre part may
form part of the revolving armature as in Figure 2.
B is the spindle.
CC is a central mass of soft iron.
DD are two masses of soft iron.
E E are annular spaces between C C and D D. Each of these spaces contains
a magnetizing coil of wire.
The induced current is carried off by contact rings F surrounding the disc A and
by metallic conductors led away from these contact rings through spaces between
the magnetising coils.
The remaining figures show armatures constructed according to my present
invention The armatures shown in these figures are adapted for the machine
shown in Figure 1 but may of course be adapted for the machine shown in
Figure 2.
In Figures 3 and 4 A A are the thin discs or rings which take the place of the
single pair of discs in my former machine.
B B are bars electrically connecting the corresponding discs on either side of the
centre. These may be of iron or copper or any conducting material-Each disc is
connected to one of the bars by a tongue a as shown.
C is an annular mass of soft iron filling up the space between the discs and
being the central pole of the armature.
DD are thick discs of soft iron serving to hold in place and compress the thin
discs F is the spindle.
The discs AA are in the plane of the discs A A shewn in Figure 1 that is in
the same plane as the magnetising coils contained in the annular spaces E shown
in this figure.
In place of the annular mass C of soft iron and the conducting bars B being in
separate pieces the annular mass might be composed of segments forming con-
tinuations of the segmental conducting bara. In this case the segments would be
of soft iron.
Figure 5 shows one arrangement that I use for collecting the induced currents
from the several discs of the armatures.
In this figure G G are rings, the outer circumference of each disc of the two sets
of discs is surrounded by one such ring.
Each ring carries within its interior a number of metallic conducting springs
which bear against the circumference of the disc.
The ring surrounding a disc of one set is connected by a conducting bar H with
a ring surrounding a disc of the other set.
These rings are situated in an annular space between the discs and the
magnetizing coils whilst the bars H which connect the rings one with another may
be outside the magnetizing coils.
The connection between the inner circumference of the several discs A of the
two sets of discs and their outer circumference are so disposed as to couple them

page_text: all in series in one continuous circuit and the conductors led off from the last
ring of each set form the terminals. These conductors may conveniently be led
away between the magnetizing coils as illustrated at Figure 1 and serve to convey
away the current induced in the succession of discs.
In Figures 6 and 7 the construction is the same except that concentric cylinders B
are used to electrically connect the discs in pairs instead of the bars. These
cylinders must be of soft iron or other magnetic material.
In Figure 8 the connecting bars B are of larger size relatively to the rings A
but are connected to them in the same order as in Figures 3 and 4.
In Figures 9 and 10 the rings are dispensed with and the induced current is
carried off from the bars by a number of collectors insulated from each other and
each of which makes contact with each bar in succession as the armature revolves.
There may be two sets of collectors with as many collectors in each set as there are
bars or there may be one less or more than that number in each set.
Figure 11 shews a side elevation one half in section and Figure 12 an end view
one half in section of a dynamo electric machine in which an armature similar to
the armature shewn at Figure 3 is used but in which the fixed magnets in place
of being formed in the manner described in my former Specification and as
illustrated in the diagrams Figures 1 and 2 are formed somewhat in the manner
usually adopted in dynamo machines of the Gramme type. Any of the armatures
herein described may be used with field magnets of this form.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1. The construction of dynamo electric machines of the kind described in the
Specification of my former Patent hereinbefore mentioned or modifications thereof
such as are herein referred to with armatures so divided into separate insulated
parts that the electro motive forces of the separate parts may be added together in
the electric circuit of the machine.
2. The construction of dynamo electric machines substantially as hereinbefore
described and illustrated in the drawings annexed.
3. The combination of discs or rings and connecting bars for this purpose
substantially as described and illustrated in Figures 3 and 4.
4. The combination of cylinders and discs or rings for the same purpose sub-
stantially as described and illustrated in Figures 6 and 7.
5. The combination of bars and rings substantially as described and illustrated
in Figure 8.
6. The compound armature formed by building up a disc or cylinder of insulated
bars substantially as described and illustrated with reference to Figures 9 and 10.
Dated this 10th day of May 190K
CARPMAEL & Co.,
Agents for the Applicant.