IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
Year: 1884

page_text: PROVISIONAL SPECIFICATION.
I, JOHN HAYTON GREENHILL, of 35 Mill Street, Belfast in the County of
Antrim, Electrical and mechanical Engineer do hereby declare the nature of my
invention for IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES to be as follows:-
I employ a species of "spoke" or wheel armature, built up of thin sheets of iron,
which, for the purpose of ventillation and prevention of what are termed Focault
currents, have small air spaces between some or all of the iron sheets or portions of
them, or they may be otherwise insulated in part or in whole. I prefer the
armature to be in the form of a ring with projecting pieces from the periphery,
the projections thus forming the "spokes," all being mounted on brass or other non
magnetic supports, and carried by the revolving shaft; or in a modification, the
iron sheets may be of Disc pattern, with air spaces. Each Wheel or Disc may be
formed in one piece, or cut into segmental sections and built together. The copper
wires or sheets in which the current of electricity is set up are wound either
directly on the spokes, but electrically insulated from them, or they may be coiled
upon "bobbins," and the latter slipped on the spokes and secured.
There may be one wide cylindrical "wheel" (formed by the combination of the
various sheets of iron) or several of them mounted on the revolving shaft which
carries the commutator, the copper coils being connected to the latter in the usual
manner.
The armature revolves in proximity and within the influence of the field
magnets.
$

page_text: I, JOHN HAYTON GREENHILL, formerly of 35 Mill Street Belfast, now of (new)
King street Belfast, in the County of Antrim, Electrical and mechanical Engineer
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 :—
I employ a species of "spoke" or wheel armature, built up of thin sheets of iron,
which for the purpose of ventillation and prevention of what are termed Focault's
currents have small air spaces between some or all of the iron sheets or portions of
them, or they may be otherwise insulated in part or in whole. I prefer the
armature to be in the form of a ring with projecting pieces from the periphery;
the projections thus forming the "spokes," all being mounted on brass or other non-
magnetic supports, and carried by the revolving shaft; or in a modification, the
iron sheets may be of Disc pattern with air spaces. Each wheel or Disc may be-
formed in one piece or cut into sections, and built to-gether. The copper wires or
sheets in which the current of electricity is set up, are wound either directly on
the spokes, but electrically insulated from them, or they may be coiled upon
"bobbins," and the latter slipped on the spokes and secured. There may be one
wide cylindrical wheel (formed by the combination of the various sheets of iron)
or several independent wheels mounted on the revolving shaft which carries the
commutator. The coils of copper may be coupled together, that is, the end of one
coil may be joined to the beginning of the next coil, with a branch connection to
the commutator plate, as in the Gramme armature, or opposite coils may be in
series and their respective free ends joined to commutator plates.
In forming armatures of this class, it is of great importance that the " lines of
.magnetic force " shall be concentrated as much as possible in the immediate vicienity
of the coils, and that ample ventillation is provided. I attain these objects by
having slots or holes in the iron sheets of which the armature is composed or by
building the armature in sets of sections, with air spaces between, shewn in the
drawings herewith annexed.
Fig. 1. represents a wheelarmature with projecting spokes on which the coils (a a a)
are placed. The upper portion of this drawing shews a wheel with twelve pro-
jecting spokes when completed, whereas the lower half indicates an armature with
only eight projections. The number may be more or less according to the diameter
of the wheel. The ventillating apertures are denoted by the letters bbb. This
form of construction requires to be mounted on non-magnetic spokes, discs, drums
or "hubs."
Fig. 2 shews a species of Disc armature with projecting spokes to receive the
coils, (as in Fig. 1.) This arrangement allows the sheets of iron to be mounted
directly on the revolving shaft. The ventillating apertures are also indicated
at bbb, and likewise in Fig 3. which denotes modified projections, of which thero
are only four. The coils on two of the projections are represented by the letters a, a.
By reason of the spokes on the upper half of this drawing being wider at the
periphery than towards the centre, the copper coils must bo wound on them, but
insulated, whereas by the arrangement shewn in the lower half, the coils may be
wound on bobbins, and these slipped on the projecting spokes.

page_text: 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 armatures illustrated in Figs. 1. 2. 3. and sections thereof
with modifications as described.
Dated this 17th day of November 1884.