IMPROVEMENTS IN APPARATUS FOR THE TRANSMISSION OF POWER BY ELECTRICITY
Year: 1879

page_text: LETTERS PATENT to John Hopkinson, of 4, Westminster Chambers, London,
for the Invention of "IMPROVEMENTS IN APPARATUS FOR THE TRANSMISSION
OF POWER BY ELECTRICITY.”
Sealed the 12th December 1879, and dated the 21st June 1879.
PROVISIONAL SPECIFICATION left by the said John Hopkinson at the
Office of the Commissioners of Patents on the 21st Juno 1879.
"
JOHN HOPKINSON, of 4, Westminster Chambers, London. IMPROVEMENTS IN
APPARATUS FOR THE TRANSMISSION OF POWER BY ELECTRICITY."
My improvement relates to a mode of reversing the direction of rotation of the
armature of a dynamo electric or magneto electric machine when such machine is
used for converting an electric current into mechanical power. Instead of employing
a single pair of copper brushes to admit the current to the commutator of the
armature I employ two pairs of brushes, one pair for each direction of rotation. On
opposite sides of the axis of the armature are two pins insulated from the frame of
the machine and from each other. These pins are connected by a link, or in any
other suitable manner, so that they can be turned simultaneously in the same
direction. Each pin carries two collecting brushes. By turning the two pins in
one direction one of the brushes carried by each pin is brought into contact with
the commutator, the points of contact being opposite to each other and appropriate
to one direction of rotation. By turning the two pins in the opposite direction tho
other brush carried by each pin is brought into contact with the commutator, the
points of contact being appropriate to the opposite direction of rotation.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Hopkinson in the Great Seal Patent Office on the 19th
December 1879.
JOHN HOPKINSON, of 4, Westminster, Chambers, London.
" IMPROVEMENTS IN
APPARATUS FOR THE TRANSMISSION OF POWER BY ELECTRICITY."
My said Invention, relating to improvements in apparatus for the transmission of
power by electricity, has reference to means of reversing the direction of rotation of
the armature of a dynamo electric or magneto electric machine when such machine
is used for converting an electric current into mechanical power.
In carrying out my Invention in lieu of using only a single pair of copper brushes
or equivalent devices as heretofore to admit the current to and conduct it froin the
commutator or collector of the armature two pairs of brushes or equivalent devices,
one pair for each direction of rotation may be employed. These brushes or equi-
valent devices being arranged in the following manner, videlicet:-On opposite
sides of the axis of the armature are two pins which are insulated from the frame
of the machine and from each other, and are coupled together by means of a link
or any other suitable connection, so as to admit of their being turned simultaneously
in the same direction. Each pin carries two collecting brushes or equivalent devices
so placed that when one of the brushes (for example) carried by each pin is in
contact with the commutator or collector the armature will be caused to revolve in
one direction, and that when the other brush carried by each pin is in contact with
the commutator or collector the armature will be caused to revolve in the opposite
direction. By the act therefore of turning the pins in one direction or the other, so_
as to bring one or the other of the brushes of each pin into contact with the com-
mutator or collector, the motion of the armaturó' in the required direction will bo
obtained..
The accompanying Drawing illustrates the application of my said Invention to
the commutator or collector of a Siemens, Gramme, or other machine; in Figure 1
the brushes touch the collector in points appropriate to one direction of rotation;
Figure 2, in points appropriate to the opposite direction of rotation.
in
A represents the commutator or collector when the machine is used as a motor,
and a the axis of tlie armature, the straight arrow through the centre indicating the
direction of the magnetic force of the fixed magnets, and the curved arrow denoting
the direction of motion of the armature. On the opposite sides of the axis a are
two pins B, C, each of which carries two collecting brushes, the brushes carried by
the pin B for admitting the current being marked D, D', and those carried by the
pin C for receiving the current being marked E, E¹. The pins are insulated from
the frame of the machine and from each other as before mentioned, and are coupled
together by a link or other suitable connection (not shewn in my Drawings), so as
to enable them to be turned simultaneously in the same direction. In Figure 1 the
brushes D, E, are represented in contact with the commutator or collector, this
position of the brushes being approprate to the direction of rotation of the armature,
indicated by the curved arrow in that Figure, whilst in Figure 2 the brushes D¹, E¹,
are represented in contact with the commutator or collector, this position of the
brushes being appropriate to the direction of rotation of the armature indicated by
the curved arrow in Figure 2, and which is the opposite of that indicated in Figure 1.
By the act therefore of turning the pins B, C, simultaneously a reversal of the
direction of motion of the armature is obtained.
In my Drawings the brushes are represented in contact with the commutator or
collector at points somewhat behind a plane perpendicular to the direction of
magnetic force of the fixed magnets, this being in general the most suitable position
for the points of contact. The commutator or collector is also shewn as composed

page_text: of sixteen divisions, but any other suitable number of divisions may be used. The
mode of carrying the brushes is indicated in the Drawings in its simplest form, but
it is obvious that the brushes may be pressed against the commutator or collector
by suitable springs; double brushes may also be used in order to avoid sparks; or
in lieu of employing brushes equivalent devices for making contact with the com-
mutator or collector may be used, such, for example, as strips of copper or rollers,
as will be well understood.
Having now described and particularly ascertained the nature of my said Inven-
tion, and a mode in which the same is or may be used or carried into effect, I would
observe in conclusion that I make no claim to the use as motors of dynamo-electric
or magneto electric machines, neither do I confine myself to the use of any particular
construction of dynamo-electric or magneto electric machine, nor to the particular
mode of arranging the parts hereinbefore described, and illustrated in the accom-
panying Drawings, as it is obvious that the same may be varied without departing
from the principle of my said Invention, but what I consider to be novel and
original, and therefore claim as the Invention secured to me by the hereinbefore in
part recited Letters Patent is,-
Effecting the reversal of the direction of motion of the armature or revolving
portion of dynamo-electric or magneto electric machines when used as motors, by
changing the position of the points of contact of the brushes or equivalent devices
and commutator or collector, substantially as hereinbefore described.
In witness whereof, I, the said John Hopkinson, have to this my Specification
set my hand and seal, the Tenth day of December, One thousand eight
hundred and seventy nine.
JOHN HOPKINSON. (L.S.)