IMPROVEMENTS IN ARMATURES FOR DYNAMO OR MAGNETO ELECTRIC MACHINES
Year: 1882

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake,
"
& Co., Patent Agents, Southampton Buildings, London, for an Invention of
'IMPROVEMENTS IN ARMATURES FOR DYNAMO OR MAGNETO ELECTRIC
MACHINES." A communication from abroad by James John Wood, of
Brooklyn, New York, United States of America.
COMPLETE SPECIFICATION filed by the said William Robert Lake at
the Office of the Commissioners of Patents on the 27th May 1882.
"
WILLIAM ROBERT LAKE of the Firm of Haseltine Lake & Co Patent Agents,
Southampton Buildings London IMPROVEMENTS IN ARMATURES FOR DYNAMO
OR MAGNETO ELECTRIC MACHINES." A communication by James John Wood,
of Brooklyn, New York, United States of America.
This Invention is especially applicable to the well known " Gramme" form of
armature for dynamo electric machines and has for its object to secure the annular
core portion or armature proper to its hub or shaft in a positive and rigid manner
in its direction of rotation so as to obviate the displacement of the armature or its
coils by the strains to which it is subjected when in use.
The "Gramme" armature, as is well known, consists of an annular or cylindrical
coil of iron wire forming a central magnetic core on which the electrical generating
coils of copper wire are wound radially in closely succeeding sections, each of which
is connected to corresponding sections of the commutator. The armature is thus
a complete compound ring of closely wound iron and copper wire, and hence
possesses considerable weight.
Heretofore this ring-armature has been simply placed upon a wooden hub which
is in turn keyed to the shaft, the tight frictional fit of the armature ring on the
said hub being relied upon to prevent its displacement, or in some cases, an
expanding hub has been employed to obtain a better frictional grasp upon the
armature. As the armature is however quite heavy and is revolved at a high speed,
it is subjected to great centrifugal strain, which frequently causes it to expand
.

page_text: appreciably and relax its grasp upon the hub, thus allowing it to slip and become
displaced thereon.
In addition to this centrifugal strain, there exists the radial attraction of the field
magnets, which constantly tends to expand and relax the grasp of the armature on
the hub in the same way.
Again, if the armature is started quickly, or if the circuit of the machine is closed
while the armature is being revolved rapidly in an open circuit, the great inertia
of the heavy armature in the one case, or the sudden resistance offered to its
rotation in the other, tends to make the hub turn in the armature, and thus
relatively displace the said hub and armature or injure some part of the generating
coils or their connections with the commutator; this injury in fact frequently
happens in practice. In addition to these occasional strains there is the steady
and strong attraction of the field magnets when the armature is in action, which
attraction offers a constant resistance to the rotation of the said armature and
tends to hold it stationary, while the tendency of the power driven hub is to turn
within it.
According to my present improvements I introduce at intervals thin plates, or
similar projections, between the coil-sections of the armature; these plates or
projections embrace the iron core and project into or are secured to the hub, thus
producing a positive rotating connection between the armature and its hub so as
to entirely obviate the above mentioned objections or defects.
In the accompanying Drawing,
Figure 1 is a central section of a Gramme armature provided with my
improvement and,
Figure 2 is an end view thereof,
Figure 3 is a plan or top view of the said armature.
a indicates the driving shaft of the armature which is formed, mounted, and
driven in the usual way. To about the middle of this shaft is keyed a hub b
preferably of wood as usual and of such a size as to fit the interior of the annular
armature c. In the present case, however, the hub is made to fit easily within the
armature, instead of being made a tight driving fit as heretofore.
The said armature c is composed as usual of a core d of iron wire wound
preferably in the shape of a hollow cylindrical coil with rounded ends, as clearly
shown in Figure 1. On this core are wound radially the electrical generating
coils e of copper wire which follow each other in closely succeeding radial layers
around the iron core in the usual manner; the opposite ends of these coils are
connected to corresponding sections of the commutator fin the well known manner
as illustrated.
At one or more points, however, in the circumference of the armature, thin
projections or plates g, g, are introduced between the coils, which are wound
tightly on either side of the said plates or projections; these plates project inwardly
toward the hub, and are adapted to lie in and engage with corresponding slots h
cut radially in the periphery of the hub b, thus making a positive rotating or
driving connection between the annular armature and its central hub.
The plates g, g, are made of thin brass or other non-magnetic material and are
preferably so formed as to completely embrace the iron core, and to exactly
correspond, in their external outline, with the external outline of the copper coils
so as to ride flush with the exterior of the armature, or slightly above the same on
the periphery, and they have an inward prolongation or wing which engages with
slots in the hub as above described and as illustrated in Figures 1 and 2.
The plates g, g, are preferably made in halves where they encircle the core d so
that the halves may be readily fitted onto the core, and afterwards soldered together
at the joint, as will be understood by reference to Figure 1. These plates are
preferably three in number as shown in Figure 2, but their number may be more
or less; they are placed upon the core either before or during the operation of
winding the copper coils thereon, and are arranged at the proper intervals apart
and tightly embedded between the succeeding coils as shown, while thin sheets

page_text: of insulating material are placed on either side of the plates to ensure perfect
insulation between the same and the adjacent coils.
The hub b abuts at one end against a collar i fixed on the shaft a and this end
of the hub is formed with a slight enlargement or flange k at its peripheral edge,
against which one end of the annular armature fits as shown in Figure 1, thus
restraining the armature from further end wise movement in this direction. The
opposite end of the hub, as well as the middle portion, fits freely within the interior
of the armature so that when the projecting plates g, g, of the armature are
properly registered with the slots in the hub, the armature may be easily slid upon
the said hub from this end, as will be understood by reference to Figure 1, and
when the commutator is secured on this end of the shaft and forced against the
end of the said hub and the connections are made with the coils of the said
armature, the latter will be secure against longitudinal displacement in either
direction on the hub. When, however, the commutator is loosened, the armature
may be readily slid off the hub when required, as for instance to repair a damaged
or short circuited coil, as will be readily understood.
It will hence be seen that by the above described construction I not only form
a positive rotating connection between the armature and its hub of both a
simple and certain character which, while not interfering with the functions of
the said armature entirely obviates the difficulties before named and enables the
parts to resist the strains to which they are subjected, and completely prevents the
turning or loosening of the hub in the armature, whether by the centrifugal strain
of rotation, the attraction of the field magnets, or the inertia or momentum of the
armature itself, but in addition to this security, the armature is capable of being
easily removed and replaced when required.
When the winding of the coil portion of the armature is completed, the external
periphery of the armature is wound as is now usual, with three parallel bands m
of strong brass wire, as clearly shown in Figures 1 and 3, which bands are soldered
either to the edges of the plates 9 or to a transverse copper strip placed under
them, tapes being previously wound under the wires to ensure insulation.
These brass wire, bands thus serve to bind the armature firmly and protect the
periphery of the coils from any friction or contacts while revolving in the polar or
armature socket of the field magnet.
I prefer to employ the construction already described and illustrated that is to
say, I prefer to use a wooden hub with peripheral slots, and to fix radial plates in,
and to the armature to engage with the slots of the said hub as set forth, as
this construction is efficient and cheap as well as light, by reason of the wooden
hub.
In some cases, however, the hub may be made of brass as in Figure 4 with thin
radial blades or spokes which are embedded between the sections of the armature
in the same way as the plates g, g. The outer ends of these spokes are divided
in a line with the inner periphery of the armature core but connected with the
inner portion of the spokes by screws, so as to permit of the attachment and
detachment of the armature from the hub as will be readily understood.
Having thus fully described the said Invention as communicated to me by my
foreign correspondent, and the manner of performing the same I wish it understood
that I claim,
"
First. An annular or Gramme" armature formed with radial plates or bars,
embedded between its coils, embracing the core, and secured to, or engaged with,
the driving hub or shaft substantially as herein set forth and for the purposes
specified.
Second. The combination with an annular armature and its driving hub, of plates
or projections extending radially from the said armature and engaging with the
said hub, substantially as, and for the purpose, set forth.
Third. An annular armature, formed with one or more radial plates or pro-
jections introduced or embedded between its coils or sections, in combination with

page_text: a central hub formed with corresponding slots to engage therewith, substantially
as, and for the purpose, set forth.
"
Fourth. A "Gramme or annular armature constructed with one or more plates
or projections extending radially therefrom, in combination with a driving hub
adapted to enter the armature from one end, and provided with one or more
peripheral slots or recesses to engage with the said projections, and a projecting
peripheral flange or shoulder on one end, whereby the armature may be easily
placed on or removed from, the hub, but will have a positive driving connection
therewith when placed thereon, substantially as herein shown and described.
In witness whereof I the said William Robert Lake have hereunto set my
hand and seal this Twenty sixth day of May in the year of our Lord One
thousand eight hundred and eighty two.
TIM DODT TAZL
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