IMPROVEMENTS IN ELECTRIC GENERATORS AND MOTORS
Year: 1884

page_text: We HOLBROOK CUSHMAN Electrician of 72 Great Cheetham Street, Lower
Broughton Manchester in the County of Lancaster, and JOSEPH PLATT HALL
Electrician of 12 Edward Street, Werneth, Oldham, in the County of Lancaster
do hereby declare the nature of our invention for "IMPROVEMENTS IN ELECTRIC
GENERATORS AND MOTORS" and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement :-
The object of our improvements in electric machines is to simplify the construction
and reduce the cost of manufacture. The Invention has also for its object to
expose the conductors in the armature to the inductive influence of the magnetic
field under the most favorable conditions.
To these ends the Invention relates mainly to a novel construction of armature
ensuring great simplicity and economy in manufacture and allowing of the easy
renewal of parts liable to deterioration.
The Invention also relates to the combination of our improved armature, with one
or more pairs of magnets so wound and arranged as to constitute a single magnetic
circuit, or circuits, extending across the machine between the said pair or pairs of
field magnets in such a manner that the said armature may be rotated in a plane
at right angles to a line drawn through the centre of the induced portion of the
magnetic circuit, or in a plane substantially parallel to that in which the exciting
current flows in the convolutions of the wire around the magnets, and that the
radial portions of the conductor shall successively cut through the lines of force at
right angles thereto.
The construction of our improved armature and the relation which it bears to
the field magnets will be understood on reference to the accompanying drawings
in which
Fig 1 is a longitudinal section of a dynamo electric machine, with one pair of
field magnets, constructed according to our Invention.
Fig: 2 is an end elevation showing the method of supporting and staying the
field magnets of the machine, the shaft and armature being removed for the sake
of clearness.
Fig 3 is a front view of the wheel or frame of the armature, on which the
conductor is wound.

page_text: Fig 4 is a front view of one of the cages or frames by which the conductor is
clamped upon the wheel or frame at or around the hub or boss of the armature.
Fig 5 is a side view of the same.
Figures 6 show in side and front views one of the rings by which the conductor.
is clamped upon the frame at or near its rim.
Figures 7, 8 and 9 are diagram views illustrating the principle upon which the
armature is wound.
In these Figures similar parts are designated by similar letters of reference.
A A are the field magnets so wound as to constitute a complete magnetic circuit
or circuits, with poles of respectively opposite polarity in close proximity-In the
machine illustrated in Figures 1 and 2 there is one pair only of field magnets, and
the magnetic circuit is single and complete, and the lines of force induced in the
eores A¹ A¹, as well as those between the poles of the said magnets, are parallel to
the shaft B on which the armature C is mounted.
This armature is of disc form, and is arranged to rotate between the said poles in
a plane at right angles to the line of force passing horizontally and directly across
from the pole of one magnet to the opposite pole of the other magnet.-The
construction of this armature will be fully explained hereafter.
The field magnets A A, each consist of soft iron cores A¹ A¹, formed in one with
or mounted upon a connecting plate or tie piece A' A³, the sectional area of each
connecting plate A³ being approximately equal to that of the said cores.-These
connecting plates A' which form the backs of the magnets are perforated at d to
permit of the free passage of the driving shaft B, and the partial insertion of the
commutator E and boss of the driving pulley, F, which are keyed upon the shaft B
at opposite ends of the machine. The magnets A A are wound to give the polarity
indicated in the Drawings, and are secured upon the bed plate by rigid brackets a a
to which they are bolted.-Other bracket pieces a¹ a¹ are fastened to the tops of
the plates A' A', and extending between them are stay rods a² a as clearly shown
in Figures 1 and 2.-The object of this arrangement of stay rods and brackets is to
counteract the intense attraction due to the close proximity of the poles of the two
magnets, and hold them the required distance apart.
The shaft B of the armature C is mounted in bearings carried by the standards HH,
and tail or centre pins c c are provided for thrusting the shaft end wise and thereby
adjusting the position of the armature mounted thereon with respect to the faces
of the field magnets.
The armature C consists of a wheel or frame C¹ of metal preferably brass mounted
midway of and between, or formed in one with an elongated metal boss G, secured
upon the shaft B by a feather key and set screw.
To prevent this frame C¹ becoming heated by the currents induced in the spokes
or radial portions thereof, when cutting the lines of force, it is necessary to insulate
each spoke at one end.
We preferably form the frame or wheel C¹ by casting boss; spokes and rim in
one, and having divided the rim or outer periphery of the frame by radial saw cuts
between each pair of spokes, remake the joint without metallic connection as shown
in Fig: 3.
The spokes might also be insulated from each other by casting rim and spokes
in one, and making the joint between the inner end of each spoke and the cast iron
boss mounted on the shaft, by insulated set screws; or the boss and spokes might be
cast together and the rim be cast separately, each spoke being insulated at its point
of attachment to the said rim; but the construction shown is preferred.
The rim of the wheel or frame C¹ carries horns or forked extensions c¹ c¹ at regular
intervals around it, to assist in winding and properly disposing the conductor
thereon according to our system of winding which will now be explained.
What we desire to effect in our armature is to dispose a single continuous and
previously insulated wire, or conductor comprising several fine wires, upon a wheel
or frame in such a way that a complete web of radial wires shall fill the space
between the boss and the rim of said frame, and that the current induced in the

page_text: radial portions of the said conductor shall be in such direction as will yield a
continuous current at the terminals of the machine.
The advantages to be derived from such a disposition of a single continuous
conductor are simplicity economy of manufacture, ventilation and generall
efficiency.
In the first place by this arrangement we obviate the necessity for making
repeated connections and joints by solder or otherwise when disposing the copper
conductor in place upon the armature, as nothing can be simpler to use than a
continuous and previously insulated conductor-We also avoid the necessity for
inserting or applying separate insulation in the building up or construction of our
armature, but the main advantage perhaps is due to the peculiar disposition of the
insulated conductor upon the wheel or frame whereby we obtain a web composed
of a single layer or thickness of strands radiating from near the centre to the
circumference, which strands form each an integral part of the conductor and take
a radial direction at such points as will ensure a continuous current in one direction
only being obtained from the armature-This web composed of a single layer of
radial strands occupies but little space widthwise, and hence the faces of the magnets
forming the field through or across which the radial strands are to be moved, can
be set very closely together and the radial portions of the conductor be subjected
to a very powerful inductive action.
There are several ways of disposing the conductor according to the above
principle of winding for one or more magnetic circuits, and in the diagrams,
Figures 7. 8 and 9 we have shewn three methods or arrangements tending to one
common result viz: the disposal of a single conductor or upon an armature in such
a manner that a web composed of radial strands or portions of the said conductor
is formed with the several convolutions so arranged with reference to the field in
which the said armature is to be used, that a current will be produced in one
direction throughout the entire armature.
In the diagram views, Figures 7.8 and 9, the position of the poles of the magnet
or magnets forming one-half of the field, are indicated by fine lines and are marked
N or S according to their polarity, and the several convolutions of wire are
indicated respectively by full lines, fine lines dotted lines or by dots and dashes, for
the sake of clearness in the absence of color It should be noted that although
eight convolutions only are shown in the diagrams, any number may be used.
Referring now to Fig 7 the magnets in which correspond in position and number
with those illustrated in Fig 1, the armature is wound as follows-Beginning at the
boss of the armature we lead the conductor in a radial direction and bending it
over one of the hooks (not shown) on the rim at 2 lay it circumferentially around
the rim for 135° from 2 to 3 returning it over a hook (not shewn) at 3 in a radial
direction to the boss at 4 and there bending it into a loop v of sufficient length to
extend to the commutator, twist the said loop vinto a single cord at right angles
to the radial portion at 4, and lap the free end of the conductor around the boss
for 180° from 4 to 5, thus completing one convolution. The next convolution
begins with a radial portion leading from 5 to the book at 6 next adjacent to that
first above mentioned, the conduction passing circuinferentially around the rim to
a hook at 7, returning radially as before to the boss at 8, being twisted into a
second loop, at 8, extending therefrom at right angles as above described; the free
end being then led around the boss for 180° to 9, and thus completing a second
convolution, and so on following the numbers on the figure until the armature is
fully wound, when the first and last ends of the conductor are permanently con-
nected The ends of wire in the several twisted loops one for each convolution, or
series of convolutions, are bared, and the two portions of the loop connected at the
end near the armature and the opposite ends are joined consecutively to the com-
mutator bars by a soldered, or preferably by a screwed joint. The radial portions
are securely held in place between the spokes of the metal frame by open side
frames or cages H (Figures 1 4 and 5) which fit around and are concentric with

page_text: the boss of the armature, and towards their outer extremities by rings K bolted or
rivetted together, both rings and cages being insulated from the frame as shewn in
the sectional view Fig 1.
To increase the efficiency of this machine by lessening the relative length of
inactive conductor on the rim, in cases where compactness and high electrical
efficiency are demanded, we bolt two extra magnet cores to each of the tie pieces A²,
Fig 1, as indicated in the diagram view Fig 8, and so arranged that the polarity of
each face shall he opposed to that of the faces adjacent on the same side of the
armature, and to that directly opposite to it on the other side. In this case we
wind the same frame as above described in the following manner which is shown
in the diagram Fig 8. Beginning at the rim at 32, the conductor is led in a radial
direction to the boss at 1, where a loop is made as above described. From there it
is laid around the boss for 90° to 2, brought radially to the hook on the rim at 3,
then laid for 90° around the rim to the hook at 4, whence it returns to the boss
and a second loop is made at 5. Thence the conductor is laid 90° around the boss
to 6, then led out to the rim at 7, and then extended around the rim to the hook
next before that at 90° from 7, viz: to 8, thence to the boss at 9 with a third loop,
and then around the boss 90° to 10, out in a radial direction to the rim at 11, and
so on until N° 31 is reached which will be of the same potential as the first end,
and is connected to it-We either wind in this manner with two loops in each
convolution and use two brushes on the commutator or we complete the winding
on the principal shewn in Fig: 8, but symmetrically, except that one loop in each
convolution is omitted, in which case it becomes necessary to use four brushes on
the commutator; or to connect opposite bars of the commutator by conductors
extending around the shaft when two brushes only are required.-This symmetrical
disposition of the single insulated conductor is clearly indicated in the diagram
view Fig: 9.
In this figure it will be seen that the conductor, starting from the circumference
passes in a radial direction to the boss at 1, thence around the boss 90° to 2, where
a loop is made as above described, thence radially to 3. over a hook at that point
and circumferentially for 90° to 4; radially to 5 around the boss for 90° to 6;
radially to 7 and circumferentially for a less angle than 90° to 8, the horn or hook
next before that at the initial end, where a new and precisely similarly wound con-
volution commences, and will be easily traced by following the numbers from 8 to
9, 10. 11. 12. 13. 14. 15 and 16, where convolution number three begins, and passes
through the figures between 16 and 24. and so on around the entire armature.
The commutator bars in these diagrams are numbered to correspond with the
point of the conductor at which a twisted loop of such conductor is formed for the
purpose of connection with its corresponding commutator bar. Thus in digram 9
there are 8 loops, one for each convolution, and 4 brushes touching the bars 10. 26., and
42, 58, those at 10 and 42 being of one electrical sign (say +) and those at 26
and 58 of the opposite electrical sign (say -) If opposite bars had been con-
nected such as 2 and 34, 10 and 42 18 and 50, and 26 and 58, two brushes only
would have been sufficient.
By arranging two brushes or sets of brushes on each side of the commutator in
such a manner that one brush on each side meets the commutor bar connected to
the radial conductor which has just emerged from the magnetic field, such as 4.
and 20 Fig: 7, the other brush to the conductor just entering the opposite field 12
and 28 Fig: 7, we obtain from our simpler form of machine (Fig: 1) a higher
electrical efficiency, both sets of brushes of similar sign being joined, in this manner
cutting out a large portion of the conductor while it is inactive (between 12 and 4,
and between 28 and 20) and thereby diminishing the electrical resistance of the
armature.
By constructing the armature on the principle above set forth ample room is
available around the boss on either side of the spokes of the wheel or frame for the
inner and bent portions of the conductor, and the outer or circumferential portions

page_text: thereof are securely beld within the horns or hooks on the rim, and are drawn
tightly against the rim by the pressure of the clamping frames or rings (Figures 4. 5
and 6) which pressure forces the radial portions of the conductor inwards and holds
them in the plane of the spokes of the wheel or frame.
The armature it will thus be seen has a globular centre or boss and an enlarged
rim and is narrowest in eross section between the said boss and rim, or at that part
where the strands of the conductor are truly radial.
The radial portions of this armature when it is properly mounted and rotated,
are arranged to cut the lines of force in a plane at right angles to the direction in
which they are induced in the magnets, and by this combination and arrangement
of parts, great simplicity and economy of manufacture and efficiency, result.
We are aware that magnets have been arranged to form a field of substantially
the same character as bereinabove set forth, but in such machines armatures of
elaborate construction comprising many separately wound coils or bobbins have
been used.
We are also aware that armatures have been formed with conductors built up of
radial bars and segmental connecting plates, but such armatures have been used in
combination with field magnets whose lines of force are induced by the current in
the convolutions of the wire thereon in a direction parallel to the plane of rotation
of the armature instead of transversely to such plane, as in our machine, and the
radial bars cut the lines of force at a point in the magnetic circuit where they are
diminished by transmission through a length of inactive iron, and by a change of
direction, in order to reach the armature. Moreover such armatures are compli-
cated and expensive to manufacture and require great accuracy in fitting together
the several parts.
Our Invention comprises the advantages of this type of armature with far
greater simplicity of construction, as is above fully explained, and our armature is
mounted in such relation to the field magnets that the lines of force are cut by the
radial portions of the conductors as the armature rotates at right angles to the
direction in which the said lines of force are induced.
By this arrangement we consider that we secure a magnetic field of greater
strength in proportion to the amount of iron and exciting current employed, than
is realized in any other machine with which we are acquainted.
We would remark that we do not claim as original the adaptation of the
Gramme or Siemen's-Alteneck system of winding to the Arago disc machine, but,
Having now particularly described and ascertained the nature of our said
Invention and in what manner the same is to be performed, we declare that what
we claim is:-
1. A dynamo electric machine or electric motor constructed substantially as herein-
above described, and having a disc armature wound with a single continuous
insulated conductor in such a manner that, at intervals the said conductor takes a
radial direction with respect to the boss of the said armature, and so mounted with
respect to the field magnets that when rotating the radial portions of the con-
ductor cut the lines of force passing between the magnets, at right angles thereto,
as set forth.
2. The use in the construction of armatures for electric machines or motors, of a
driving or supporting frame such as C¹, having an elongated boss, and hooks or
horns around its rim, the said frame being rendered proof against the deleterious
action of induced currents in the radial portions thereof by the insertion of insula-
ting divisions substantially as described with reference to the drawings.
3. In an armature for dynamo-electric machines or motors the combination with
a wheel or frame such as C¹ having an elongated boss, insulated spokes and hooks
or their equivalent around its rim, of a single continuous previously-insulated con-
ductor, and side frames or cages and rings such as H and K, for clamping and
retaining the several convolutions of the conductors in position upon the said
frame, substantially as and for the purpose set forth.

page_text: 4. The method of winding armatures with a single, previously-insulated con-
ductor, substantially as hereinabove described with reference to the accompanying
drawings.
5. The use in combination with an armature wound with a single previously-
insulated conductor as above described, of brushes grouped in double, triple or
multiple, series as and for the purpose set forth.