Improvements in Armatures for Dynamo-electric Machines.
Year: 1888

page_text: COMPLETE SPECIFICATION.
Improvements in Armatures for Dynamo-electric Machines.
I, ALEXANDER WILLIAM MESTON, residing at No. 31 South Compton Avenue, in
the City and County of St. Louis and State of Missouri, one of the United States of
America, Gentleman, do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
This invention relates to improvements in that class of armatures known as ring
armatures, and applies particularly to the flat or Pacinotti type of such armatures.
The objects of the invention are:
1st. To provide means in flat ring armatures whereby sections thereof, comprising
one or more coils, which have become damaged, may be readily replaced by duplicate
and perfect sections, and to have such sections of such dimensions and form as. will
allow of their being revolved in an ordinary lathe or other suitable machine for the
purpose of winding the armature coils, doing away with the slow and laborious method
of hand winding which the form of the ordinary ring armature necessitates.
2nd. Improvement in the construction of laminated Hat ring armatures, whereby,
without materially affecting their strength, and without materially increasing the
magnetic resistance of the core, sections or portions of the ring having one or more
coils wound thereon, can be readily detached and taken out and duplicate sections
inserted.
3rd. Improvement in the construction of laminated sectional ring armature, whereby,
inter-changeability of parts is attained.
4th. To combine with the foregoing features, a perfect insulation of the laminae
composing such armatures and of the sections from each other without materially
affecting the continuity of the core.
5th. To combine in a laminated sectional ring armature, strength, rigidity and
accuracy of structure and cheapness of manufacture.
6th. To provide for the ventilation of such armatures, and
7th. Improvement in the manner of attaching such armatures to the spiders on
which they are mounted, providing at the same time for the insulation of the armature
from the spider.

page_text: Laminated armatures of the flat ring or Pacinotti type have hitherto usually been so
constructed as to form a continuous ring upon which the coils are wound. Their form,
of course, precludes all possibility of winding such armatures otherwise than by hand,
literally winding the wire around the core, which is a slow, tedious and expensive
operation. It thus becomes necessary, should any accident cecur to one or more coils,
to abandon the use of the entire armature until these coils can be laboriously unwound
and rewound in the manner stated, which in large machines is an undertaking
requiring several days to perform, during which time the machine is useless. Such a
loss of time is generally a very serious inconvenience to those operating dynamos or
motors, and often causes grave doubts to be cast upon the reliability of this class of
machinery. It is therefore, chiefly with the object of facilitating and cheapening
their repair and manufacture that I have devised the armature hereindescribed, and
also with the object of improving the construction of sectional laminated ring armatures
as regards efficiency, cost, strength, stiffness, and accuracy.
The methods which I employ to attain these objects are illustrated in the
accompanying drawings, wherein
Figure 1, is a side view of an entire armature without the wire.
Figure 2, is an edge view of the same.
Figure 3, is a sectional view of the same through the line, A, B, in figure 1.
Figure 4, is a like sectional view showing modified form of spiders.
Figure 5, is a side view of a detached section, with the radial pole-piece attached.
Figure 6, an end view of the sections shown in figure 5.
Figure 7, is a top view or plan of same.
Figures 8 and 9, are side and edge views of the radial pole-piece, P.
Figure 10, is a side elevation of a detached section in which provision is made for
ventilating the interior of the core, and in which the wire coils are shown in section
for the purpose of indicating how the coils are wound on the section.
Figure 11, is a sectional view of the same through the line, A, B, in figure 10, the
wire coil omitted.
Figure 12, is a top view or plan of the same.
Figure 13, is a detached sectional view of the bent plate, M, through the line, A, B,
in figure 10.
Figure 14, is a side view of a modified form of section.
Figure 15, is a sectional view of same through line, C, D, in figure 14.
Figure 16, is a top or plan view of same.
A
The section shown in figures 5, 6, and 7, has a solid core composed of alternate long
and short layers or plates of sheet iron, fastened together by a suitable number of
rivets as, r,, . These plates so arranged form at each end of the section, alternate
tongues, a, a, a, &c., and recesses, b, b, b, &c. The short plates leave recesses into
which the tongues formed by the projecting plates of the adjoining section fit, bringing
the holes, h, k, in the inter-jacent tongues of the two sections opposite each other.
pole-piece, P, is then placed on each side, fitting into the radial recesses formed
between the coils. The whole is then fastened together by counter sunk headed bolts
passing through one of the pole-pieces, through the holes, h, h, in the inter-jacent
tongues of both sections, and screwed into the pole-pieces on the opposite side. The
lug of the pole-piece which projects inward is then bolted to the spider, as shown in
figures 1, 3, and 4. The remaining sections are mounted and fastened together in the
same manner, until the ring is completed. The complete ring mounted on the shaft
is shown in figures 1, 2, 3, and 4. The two outside plates of each section are of a
suitable shape and are bent up at the ends to a right angle to form the flanges, f, f
between which the armature coils, s, are wound, and which keep the coils in position
when the section is detached from the armature. The coils, s, are insulated from the
core in the usual way.
The plates composing the sections may be insulated from one another by any suitable
material to prevent the generation and flow of Foucault currents. To make the
insulation of these plates perfect the rivets by which they are held together, and the
bolts passing through the pole-pieces and holding the sections together, may,be

page_text: insulated from the core by means of fibre or other non-conducting bushings as, e, c, r, &c.
The pole-pieces may be insulated from the spider by means of non-conducting washers,
as shown by, d, d, in figures 3 and 4, and by insulating the bolts with bushings as, e, e,
in the same figures. The spider should be made of brass, gun-metal, bronze, or other
non-magnetic material that it may not form a conductor by which the magnetic lines
of force can escape across from one pole of the field to the other, without being
traversed by the wire of the armature coils.
The pole-piece, P, shown detached in figures 8 and 9 I prefer to make of separate
plates of soft sheet-iron, (as indicated in the drawings) which may be insulated and
riveted in the same manner as the sections. By doing this and using dies to stamp
out the sheets and holes, perfect uniformity of shape and also in the position of the
holes is attained. This could not be done if they were cast or forged in one piece
without much skilled and correct labor. A better quality of iron, more perfectly
annealed, can also be secured by this means.
In the section shown in figures 10, 11, and 12, provision is made for ventilating
the interior of the core. It is constructed in the same general way as the solid
section, with the exception that several of the plates, preferably several near the out-
side of the core are omitted, and their places occupied by the detached washers, w, w, w,
or other pieces suitably shaped to allow a free circulation of air, as shown in the
drawings. In this construction the outside plates which are bent up to form the
flanges, ff, are cut somewhat narrower than the other sheets of the core. This
leaves a shallow recess or groove along each corner of the core, into which the bout
shield plates, M, M, fit. These plates cover the edges of the core, and being a short
distance from said core, leave an air space, allowing a free circulation of air between
said plate and core, and communicating with the spaces in the interior of the core
kept open by the washers, w, 1, 10. When the armature revolves a current of air is set
up, flowing in under the shield plate, M, covering the inner edge of the core, up
through the space of the core, and out under the shield plate, M, covering the outer
edge of said core, as indicated by arrows in the drawing.
In the construction of the section illustrated by figures 14, 15, and 16, the bent
shield plate, M, is employed as in figures 11, 12, and 13, but merely for the purpose
of covering the sharp edges of the plates of the core to prevent abrasion of the
insulation between them and the wire of the coils, s. It may however, be placed
some distance from the core, as in figures 11, 12, and 13, to allow a partial ventilation
of the coil.
If as many tongues and recesses as there are plates in the section are not desired,
two or more plates may be used for each tongue and recess. While the joining is
not so strong nor so perfect magnetically as if every plate formed a recess or tongue,
still, where the core has considerable thickness and is composed of many plates, the
sirength and magnetic intimacy would be ample. It will be seen that this method of
inter-leaving the plates gives great strength, as the bolt holding the sections together
would have to be sheared as many times as there are tongues before the sections could
be pulled apart.
The armature may be mounted upon two separate spiders, as shown in figure 4,
instead of one, as shown in figure 3. This provides means of adjustment for various
thickness of cores.
The flange shown on the bent shield plate, M, forming a continuation of the
flange, may or may not be used as desired. Neither need the flange, f, extend
further than the edge of the core.
If the armature is not required for heavy duty, or where high efficiency is not
important, it is not necessary to insulate the laminae of the sections, nor to use the
method of ventilation hereindescribed, but it is desirable to do so where these conditions
do not exist, to prevent the armature from heating by breaking up the Foucault current
circuits in the interior of the core, and also by the cooling influence of air currents.
I consider that the best method of insulating the laminae is to to cover them, either
in the sheet, or after they have been cut to shape, with a thin coating of some insulating
compound, such as Japan, asphaltum varnish, or other suitable mixture.

page_text: I attain several desirable advantages in sectional armatures by the construction
hereindescribed.
By building the sections up of alternate long and short sheets of iron, so that the
same sheet forms the tongue at both ends, great strength and safety, and also accuracy
and uniformity of dimensions are secured, as the long plates form a continuous ring
when joined together and neither the strength nor the length of the section depends
upon the screws or rivets which hold the plates together. Where inter-changeability
of sections is desired the last mentioned feature is very important.
The form and strength of the ring are preserved entirely independent of the spider
upon which it is mounted, and the joining of the sections is separate from and in no
way connected with their fastenings to the spider.
The non-magnetic spider does not extend into the magnetic core of the sections, but
is wholly within the internal diameter of said core." I am aware that sectional
armatures have been devised wherein the sections are bolted or otherwise fastened
directly to projecting arms or lugs of the non-magnetic spider which extend out into
the magnetic core of the sections for the purpose. These non-magnetic arms or lugs
occupy space which might otherwise be filled to advantage with iron, and decrease the
magnetic conductivity of the core. This is a grave disadvantage which I obviate in
my construction, as the sectional ring is mounted upon the spider by means of the
magnetic pole-pieces, extending inward to said spider which is wholly within the
inner circumference of the magnetic ring. In this way I get a maximum amount of
iron in the core and pole-picces which greatly increase the efficiency of the armature
by lowering its magnetic resistance and preserving throughout the magnetic section
of the core.
By this method of mounting I am also enabled to get the greatest possible amount
of wire on the sections, as the necks of the magnetic pole-pieces by which the ring is
mounted upon the spider emerge from between the coils at the outside where, by
reason of the curved form of the coils there is always an opening even when the coils
are close together at their inner edges.
The most serious fault which has heretofore existed in sectional armatures is the
imperfectness of the magnetic connection and intimacy of the sections. None of the
armatures of which I have knowledge combine a perfect insulation of the sections
from each other and at the same time maintain the magnetic continuity of the ring.
By making a great many laminations in the core so that the greatest possible number
of tongues and recesses is formed, I am enabled to break up the induced currents by
insulating the laminae and the sections from one another, without decreasing the
magnetic conductivity of the ring, because by so doing a very large surface of tho
plates of the adjacent sections is brought into close proximity, thus almost eliminating
the magnetic resistance of the insulation.
I am aware that sectional ring armatures have heretofore been made, and I have no
intention of broadly claiming such a construction. I am not aware, however, of any
armatures embodying the improvements and advantages possessed by the armature
herein described. Nor am I aware of any laminated flat ring armature having
detachable sections.
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. A flat ring armature composed of laminated sections, having one or more coils of
wire wound on each section, any of such sections being detachable, said sections
composed of alternate long and short plates fitting and joined together by means of
the fongues and recesses formed thereby, substantially as and for the purposes
specified.
2. A flat ring armature composed of laminated sections, the laminae thereof being
insulated from each other, having one or more coils of wire wound on each section,
any of such sections being detachable, said sections composed of alternate long and
short plates fitting and joined together by means of the tongues and recesses formed
thereby, substantially as and for the purposes specified.

page_text: 3. A flat ring armature composed of laminated sections, having one or more coils of
wire wound on each section, any of such sections being detachable, said sections fitting
together by means of tongues and recesses in combination with a spider and detachable
magnetic pole-pieces by means of which the armature ring is mounted on the spider,
substantially as and for the purposes specified.
4. A flat ring armature composed of laminated sections, the laminae thereof being
insulated from each other, having one or more coils of wire wound on each section,
any of such sections being detachable, said sections fitting and joined together by
tongues and recesses, in combination with a spider, and detachable magnetic pole-
pieces, substantially as and for the purposes specified.
5. A flat ring armature composed of laminated sections, having one or more coils of
wire wound on each section, any of such sections being detachable, said sections fitting
and joined together by tongues and recesses, in combination with a spider, and
detachable magnetic pole-pieces, said pole-pieces being insulated from the spider,
substantially as and for the purposes specified.
6. A flat ring armature composed of laminated sections, the laminae thereof being
insulated from each other having one or more coils of wire wound on each section,
any of such sections being detachable, said sections fitting and joined together by
tongues and recesses, in combination with a spider and detachable magnetic pole-
pieces said pole-pieces being insulated from the spider, substantially as and for the
purposes specified.
7. A flat ring armature composed of laminated detachable sections having flanged
outer plates and having one or more coils of wire wound thereon, said sections fitting
and joined together by tongues and recesses, substantially as and for the purposes
specified.
8. A flat ring armature composed of laminated detachable sections, the laminao
thereof insulated from each other, provided with flanged outer plates, having one or
more coils of wire wound thereon, said sections fitting and joined together by tongues
and recesses, substantially as and for the purposes specified.
9. A flat ring armature composed of laminated detachable sections provided with
flanged outer plates and having one or more coils of wire wound thereon, said sections
fitting and joined together by tongues and recesses, in combination with a spider, and
detachable magnetic pole-pieces by means of which the ring is mounted on the spider,
substantially as and for the purposes specified.
10. A flat ring armature composed of laminated detachable sections, the laminae
thereof insulated from each other, and the outer plates flanged, said sections fitting
and joined by tongues and recesses, and having one or more coils of wire wound
thereon in combination with a spider, and detachable magnetic pole-pieces by means
of which the ring is mounted on the spider, substantially as and for the purposes
specified.
11. A flat ring armature composed of laminated detachable sections fitting and
joined together by tongues and recesses, having flanged outer plates, one or more
coils of wire wound thereon, in combination with a spider and detachable magnetic
pole-pieces by means of which the ring is mounted on the spider, said pole-pieces
being insulated from the spider, substantially as and for the purposes specified.
12. A flat ring armature composed of laminated detachable sections joined and
fitted together by tongues and recesses, the laminae thereof insulated from each other,
the sections having flanged outer plates and having one or more coils of wire wound
thereon, in combination with a spider, and detachable magnetic pole-pieces, said pole-
pieces being insulated from the spider, substantially as and for the purposes specified.
13. In a flat ring armature the combination of detachable laminated core sections, a
spider, and detachable laminated pole-pieces by means of which the ring is mounted
on the spider, substantially as and for the purposes specified.
14. A dynamo armature section composed of laminae, the outer plates of the laminae
being flanged, and shield plates which are arranged between the flanged plates and
cover the edges of the laminae, substantially as and for the purposes specified.
15. A dynamo armature section composed of laminae, having its outer plates flanged

page_text: for the coil, and flanged shields to cover the edges of the laminae and complete the
coil flanges, substantially as and for the purposes specified.
16. The combination of an armature, of a laminated core, two independent or
separate spiders and two independent sets of pole-pieces which connect the respective
spiders with opposite sides of the laminated core, substantially as and for the purposes
specified.
17. The combination in an armature of laminated core sections, two independent or
separate spiders, and two independent sets of laminated pole-pieces which connect the
opposite sides of the core sections with their respective spiders, substantially as and
for the purposes specified.