IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
Year: 1884

page_text: 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 what is known as a "ring" armature; built up by preference of thin
iron sheets, which for the purpose of ventillation and the prevention of what are
termed Focault currents have small air spaces between all or some of the iron
sheets, or portions of them, or they may be otherwise insulated in part or in whole.
The ring thus formed is constructed of a number of segmental sections, which have
by preference pieces or "spokes" projecting both towards the centre, and radially,
(outwards.). The copper wires or sheets in which the current of Electricity is set
up are wound circumferentially on the ring in the spaces between the projecting
spokes, but electrically insulated from the iron and each other,
The segmental sections when placed in position and secured form a complete
ring, but each segment, having one or more projecting spokes and coils of copper,
is capable of being removed when desired without disturbing the other segments.
The cylindrical ring or rings (there may be more than one) may be supported by
Crass, or other non magnetic cylinders, spokes or centres, and mounted on a
revolving shaft to which the commutator is attached, the latter being connected to
the copper coils 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 what is known as a "ring" armature, built up by preference of thin
iron sheets or strips, which for the purpose of ventillation and the prevention of
what are termed Focault currents have small air spaces between all or some of the
fron sheets or portions of them, or they may be otherwise insulated in part or in
whole. The ring thus formed is constructed of a number of segmental or laminated
sections, which have in the former method by preference pieces or spokes projecting
both towards the centre and radially, (outwards) or the ring may be without these
projections. The copper wires or sheets in which the current of electricity is set
up are wound circumferentially on the ring in the spaces between the projecting
spokes, but electrically insulated from the iron and each other, or when the ring is
formed without projecting spokes or pieces, the copper may, if desired, be coiled
indepently on bobbins, and the latter afterwards slipped on the ring or sections
thereof.
The segmental sections when placed in position and secured form a complete
ring, but each segment, having one or more projecting spokes and coils of copper
is capable of being removed when desired without disturbing the other segments.
When a plain ring, without projecting spokes is employed, it may be formed of
segmental sections or of laminated strips, the latter being bent round and secured
to form a ring. The ring or rings (there may be more than one) can be supported
by brass or other non-magnetic cylinders, spokes or centres, and mounted on a
revolving shaft to which the commutator is attached, the latter being connected to
the copper coils in the usual manner. The armature revolves in proximity and
within the influence of the field magnets.
In order to more fully indicate the methods of forming armatures described, I
annex drawings.
'
Fig. I illustrates two methods of building a ring armature with projecting pieces
or spokes. The upper portion represents the ring made in four segments with
slots for the T headed arms of the nave to slip endways in. The under portion of
this drawing shews other methods of securing the segments to the arms or spokes.
In order to obtain greater strength and continuity of the iron in the ring, I prefer
forming the segments with overlapping joints, in a manner somewhat similar to
the links in a "Builder's chain," rivets, or bolts or pins being inserted where the
joints overlap, but in order to mitigate, or prevent the evil effects. of Focault's
currents in these rivets, or pins, I prefer to insulate them from the segments of the
rings which they secure, or otherwise building the rings in thin sections, so that
the rivets in one ring do not (electrically) touch those in the other rings. The
dotted lines b. b. in this figure shew where the joints of the segments are in the
next succeeding sections. Some of the copper coils are indicated at a, a, a, a.
In forming rings in this manner, it is evident that air-spaces equal to the
thickness of the iron sheets will be left in portions of the segments; these can,
however, be filled up if necessary by securing shorter segmental pieces, thus giving
greater mass to the entire ring, or the air spaces may only be partly filled up.
Fig. 2 represents a ring, composed of two segments, but without any projecting
pieces. These segments are cut out of thin sheet iron, or forged or bent into the

page_text: semi-circular shape; the ends of these overlap and are secured by rivets or other
fastenings as above explained. The air spaces left by the overlapping of the joints
may, if desired, be filled up in part or in whole by shorter segmental pieces. By
removing one set of rivets, the other set acts as a hinge, and permits the rings to
open sufficiently that the bobbins or coils of copper can be placed thereon.
If as
many bobbins or coils were inserted to entirely fill the ring, it would be impossible
to insert the binding rivets, hence the number of coils and size thereof are so
designed that when all are on the ring, and the latter closed, sufficient space between
a set of coils is left to insert and secure the rivets, pins or screws.
This space is
afterwards utilized by shifting the coils partly over it in order that there may be
other spaces in which the supporting spokes of the nave may be inserted and
secured. These spaces are also beneficial for ventillation of the ring. The letter A
on this drawing denotes a coil or bobbin of copper about to be inserted.
The spokes or arms of the nave are also partly shewn.
Fig. 2B is a plan of Fig. 2 and shews seven rings with air spaces between, but
there may be more or less number of rings and width thereof and consequent
variation in the number and size of the air spaces.
Fig. 3 shews a ring made of sheets of iron placed one above the other, and bent
into a ring; this mode of construction permits the ends to be sprung asunder when
the rivets are removed in order to place the coils on the ring. Fig 3 B is a plan of
Fig. 3, shewing, (as in Fig. 2 B) soven sets of rings, but variable in number and
size as before explained.
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. I, 2. 2 B. 3 and 3B with the
modifications thereof as described.
Dated this 17th day of November 1884.