IMPROVEMENTS IN DYNAMO-ELECTRIC MACHINES
Year: 1881

page_text: LETTERS PATENT to William Hopkin Akester, of Glasgow, in the County of
Lanark, North Britain, Electrician and Engineer for an Invention of
IMPROVEMENTS IN DYNAMO-ELECTRIC MACHINES
PROVISIONAL SPECIFICATION left by the said William Hopkin Akestor
at the Office of the Commissioners of Patents on the 17th December 1881.
WILLIAM HOPKIN AKESTER, of Glasgow, in the County, of Lanark North Britain,
Electrician and Engineer, "IMPROVEMENTS IN DYNAMO-ELECTRIC MACHINES,"
This Invention has for its object to improve the construction and action of
dynamo-electric machines.
In carrying out the Invention according to one modification two bars of iron or
steel are placed parallel to and on opposite sides of the main rotating shaft to
which the driving power is applied. Pole pieces are fixed to the inner sides of the
bars at the ends of each, the north and south poles of one bar being placed opposite
the south and north poles respectively of the other bar. The inner faces of the
pole pieces are made concave, and they are by preference fixed to their bars so as
to leave spaces between them and the bars except near the outer ends. These
bars with their pole pieces constitute the stationary magnets and are excited by
means of insulated wires wound round the middles of the bars and also round the
parts where there are spaces between the bars and the pole pieces.
The concavities of the pole picces partly enclose cylindrical spaces in which a
number of rings rotate and act as armatures or as a compound armature. These
rings which are fixed on wooden or other suitable bosses on the shaft, are made of
coils of soft iron wire; and each ring has wound round it a number of separate
coils of insulated wire, each such coil of insulated wire consisting by preference of
two or more layers, and binding down upon the iron-wire ring an iron piece
having a projecting part at one end. The projecting parts of the iron plates
nearly touch the concave surfaces of the pole pieces of the stationary magnets as
they are carried round by the rotation of the shaft, and the action produces electric
currents in the coils of insulated wire on the iron-wire or armature rings There

page_text: are several rings on the shaft between each pair of polo pieces and those of each
set are arranged with their projecting parts in helical steps and so that the distance
circularly between a projecting part on the ring at one end of the set and the
corresponding projecting part on the ring at the other end of the set, is about equal
to the distance between the edges of the opposite pole pieces. At the middle part
of the shaft there are commutator details of a well known kind with spring wires for
collecting and convoying from the machine the electric currents produced. The
ends of the wires forming the insulated coils on the iron-wire or armature rings
are connected to metal strips fixed in an insulated manner to the boss on the shaft
forming part of the commutator details. The wires of the armature coils may be
connected in various ways, but in a preferable arrangement the coils forming each
helical series on the several rings of each set are connected to the same boss strips,
whilst the different coils on each ring are connected to different boss strips.
In other modifications of the machine two or more pairs of the magnet bars each
with its pair of pole pieces may be arranged equidistantly round the main shaft,
the north and south pole pieces being arranged alternately in the direction round
the shaft,

page_text: SPECIFICATION, in pursuance of the conditions of the Letters Patent and of
an Order- of the Lord Chancellor filed by the said William Hopkin Akester
in the Great Seal Patent Office on the 18th January 1883.
WILLIAM HOPKIN AKESTER, of Glasgow, in the County of Lanark, North Britain,
Electrician and Engineer "IMPROVEMENTS IN DYNAMO-ELECTRIC MACHINES
F
"
My said Invention has for its object to improve tho construction and action of
dynamo-electric machines
In one modification of my improved machine a horizontal shaft carried in
bearings at its ends has on it two compound rotating armatures, and between them
suitable commutator details. The peripheries of the armatures are nearly in
contact with concave surfaces formed on the inner sides of iron pole pieces, of.
which there are two for each compound armature. The pole pieces are placed two-
on one side of the shaft and two on the other, and on each side the two pole pieces
are fixed at opposite ends of electro-magnet bars placed on opposite sides of and
parallel to the shaft and having upon them coils of insulated copper wire for the
passage of the current by which they are excited. Each armature consists of three
or more rings formed of coils of soft-iron wire, and each ring is encircled by a
number of coils of insulated copper wire, each such coil being made to bend down
and hold upon the iron-wire ring a piece of soft iron shaped with a part fitting on
the iron-wire ring and with a part or parts projecting to the outside of the copper-
wire coils. The copper-wire coils are arranged relatively to each other on the
several rings and are connected to each other and to the commutators in a manner
hereinafter described.
And in order that my said Invention and the manner of performing the same
may be properly understood I hereunto append two sheets of explanatory drawings
to be hereinafter referred to and representing one modification of my improved
machines.
Figure 1, on sheet 1, of the accompanying drawings is a plan of the machine.
Figure, 2, is a sectional side elevation, and figures 3, and 4, are transverse vertical
sections; whilst figure, 5, is a diagram showing the mode of connecting the copper-
wire coils of the armatures. Figures 6 and 7, are a face view and section of one
of the soft-iron pieces held in the armatures by the copper wire coils. In these
drawings the same reference numerals are used to mark the same or like parts
wherever they are repeated.
The bed frame, 8, of the machine has fixed upon it three bearing blocks, 9, which
carry a horizontal shaft, 10, having on it fast and loose pulleys, 11, for a driving
belt, between two of the bearings, 9, at and near one end of the machine. In the
other and longer space between the bearings, 9, the shaft, 10, has fixed on it near
each bearing a boss, 12, formed with spokes, 13, having flanges at their outer ends;
and on these flanged spokes, 13, are fixed the armature rings, there being in the
present example, three separate rings in cach compound armature. The armatures
are fixed securely on the flanged spokes, 13, by means of thin wedges of wood or
other suitable material driven in between the flanges of the spokes and thin metal
plates applied to protect the inner surfaces of the copper-wire coils, 15. One of the
compound armatures is shown in section in figure, 2, the other not being seen in
that figure because of a part of the field magnet which is in front of it being
shown. Each armature ring consists of a ring, 14, of soft iron wire which has wound
round it a number of coils, 15, of insulated copper wire; and each copper-wire
coil, 15, binds down on the iron-wire ring, 14; a soft iron piece, 16, such as is

page_text: shown separately in figures, 6, and 7. Each piece, 16, has at one end a flange or
part projecting outwards so as to have its outer edge flush with the general
peripheral surface formed by the outer parts of the copper-wire coils, 15. The
purpose of the projecting parts of the pieces, 16, is to promote and enhance the
inductive action of the field magnets on the iron parts of the armatures, and their
action in this way is rendered much more effective than that of separate projecting
pieces as hitherto applied or proposed to be applied, by their arc-shaped or
segmental parts which extend through the copper-wire coils and are in contact
with the iron-wire ring over a comparatively large surface. The arrangement of
the pieces, 16, partly within the copper-wire coils in this way also constitutes a
materially improved mode of fixing or holding the pieces, as it avoids lateral
projections and admits of the separate rings of the compound armature being placed
close together. In order to facilitate winding of the copper-wire coils, 15, the
pieces, 16, may be first secured in their places on the iron-wire ring, 14, by means
of fine iron wire. The pieces, 16, may be made with projecting parts at both ends
as partly indicated by dotted lines in figure, 7.
The several rings of each compound armature are placed together so that the
copper-wire coils, 15, may be arranged relatively to each other in a helical manner
which will be understood from the diagram figure, 5, in which the coils, 15, are
shown separated and as in a plane. The ends of the copper-wire coils, 15, are
connected to each other as shown in figure, 5, and this figure also shows the
connection to the metal strips of the commutator which strips are indicated at, 17.
For some purposes however the connections may be made differently; but for the
production of continuous currents of relatively moderate intensity I_prefer_to_make
the connections as shown in figure, 5. The commutator for one of the compound
armatures is shown in section in figure, 3, which also shows the arrangement of the
metal brushes, 18, for collecting and leading the currents to and from the machine.
These brushes, 18, are adjustably fixed to slotted brackets, 19, which are bolted to
a block, 20, of wood or other non-conducting material, and wires, 21, 22, connect
the brushes, 18, to terminals or binding screws, 23, 24, on the sides of the
block, 20.
The field or stationary magnets consist of two horizontal single or compound
bars, 25, 26, of steel or iron, placed parallel to and on opposite sides of the
shaft, 10. Poles pieces, 27, are bolted to the opposite ends of the magnet
bars 25, 26, and are formed with concave cylindrical surfaces placed so that the
peripheries of the rotating armatures move almost in contact therewith. The field
magnets are excited by coils, 28, of insulated copper wire through which is passed
a suitable portion of the current produced by the machine itself according to a
system now well understood; and the two field magnets are magnetized in such a way
that the northward and southward poles of one face the opposite or southward and
northward poles respectively of the other. The pole pieces, 27, are formed (as
seen in the plan figure, 1) with projecting parts for the attachment of the extreme
ends of the bars, 25, 26, in such a way that the exciting coils, 28, may be continued
along those bars to some extent behind the pole pieces 27.
In other modifications of the machine two or more pairs of the magnet
bars (25, 26) cach with its pair of pole pieces (27) may be arranged equidistantly
round the main shaft (10) the northward and southward pole pieces which
encompass each compound armature being arranged alternately in the direction
round the shaft.
Having thus particularly described my said Invention and the manner of
performing the same I have to state that I do not restrict myself to the precise
details herein described or delineated but that what I believe to be novel and
original and claim as the Invention secured to me by and in terms of the herein-
before in part recited Letters Patent is :-
1. The combination of parts hereinbefore described and constituting the improved
dynamo-electric machine.

page_text: 2. The improved compound rotating armature consisting of several rings of soft-
iron wire, and each ring having on it several copper-wire coils combined with
soft-iron pieces having projecting parts and parts extending within the coils and
round upon the ring substantially as hereinbefore described.
3. In combination with the parts forming the subject matter of the second claim,
the mode of arranging the coils and connecting their ends shown in figure, 5, of the
accompanying drawings.
In Witness whereof I the said William Hopkin Akester have hereunto
set my hand and seal this ninth day of January in the year of our Lord
One thousand eight hundred and eighty-three
Witness
EDMUND HUNT
Patent Agent
Glasgow.
W. H. AKESTER. (L.S.)