IMPROVEMENTS IN DYNAMO-ELECTRIC MACHINES
Year: 1882

page_text: LETTERS PATENT to Henry Harris Lake of the firm of Haseltine, Lake,
& Co Patent Agents, Southampton Buildings London for an Invention of
"IMPROVEMENTS IN DYNAMO-ELECTRIC MACHINES". communicated to him from
abroad by Richard Henry Mather, of Windsor, Connecticut, United States
of America, Electrician ·
PROVISIONAL SPECIFICATION left by the said Henry Harris Lake at the
Office of the Commissioners of Patents on the 12th December 1882.
HENRY HARRIS LAKE, of the firm of Haseltine Lake and Co, Patent Agents
Southampton Buildings, London "IMPROVEMENTS IN DYNAMO - ELECTRIC
MACHINES [A communication to him from abroad by Richard Henry Mather,
of Windsor, Connecticut, United States of America, Electrician].
"
This Invention relates to dynamo-electric machines and comprises the novel
features of construction hereinafter described.
The improved machine, has a field-magnet in two parts arranged in the same.
general longitudinal line with the armature located and adapted to be rotated
between them.
H
One of the peculiarities of this machine is the armature, the iron core of which
is a flat disc provided with transverse grooves.at regular intervals in its peripheries
to hold the coils of insulated wire; when three coils are used there are six of these
transverse grooves
The magnetic axis of this disc is at right angles to the axis of rotation that is
to say, parallel with the plane of rotation. Magnetism seldom or never extends
far beneath the surface of a mass of iron especially when the iron is in motion;
generally magnetism does not extend more than an inch beneath the surface, hence
an armature, in order to be very effective, that is to say in order to produce a
current of high electro-motive force with a short length of wire on the armature
core, must have a considerable amount of surface as compared with the amount of.
metal contained in it; moreover the shape of the armature must be such that the
wire may be readily coiled upon it.

page_text: It is very important that an armature should require but a small space for its
rotation. Magnetism like heat, tends to a state of diffusion, never to a state of
concentration. If an armature is large it requires a large magnetic field for it to
rotate in, which necessitates the employment of a great deal of iron and copper
in the magnets, it also necessitates a great expenditure of force to produce and
maintain the current used to charge the magnets. On the other hand if a magnetic
field is small it requires but little copper and iron and but little force to maintain
the current that charges the magnet. It is a general law that a small magnetic
field can be more easily maintained than a large, but equally intense, one.
It will
therefore be readily comprehended that an armature in the disc form as above
described meets all these conditions. No part of the disc-armature can escape
magnetization; the large surface combined with the small thickness (this thickness
not exceeding one third of the diameter) ensures complete magnetic saturation;
moreover there is no screening of one part of the armature by another part, such
as is incident to the use of the ring and the cylinder forms of armature, in which
also there is a great deal of space lost within the armature itself owing to its being
made hollow but there would be no use in filling such hollow and making it solid
metal, for the magnetism would not penetrate to such a depth beneath the surface
as to utilize such metal.
There is no such loss of space in a disc armature because the disc is either made
solid or composed of thin plates or lamina separated by non-conducting material,
paper for instance, to prevent the circulation of electric currents within the armature
core itself; as there is no loss of space in this disc armature it occupies *less space
than the armatures heretofore constructed
The number of grooves in the periphery of the; disc is proportional to the
number of coils laid upon the armature, two diametrically opposite grooves to each
coil and the number of coils to be varied according to the purpose for which the
machine is to be applied.
The width of one of these grooves will in general be equal to the distance
between two adjacent grooves. One end of each of the coils communicates with
one of six plates upon the periphery of the commutator hereinafter described and
the other end of each of the said coils communicates with another of the six
commutator plates which (on, the commutator) is diametrically opposite the first-
plate mentioned; as these coils are laid upon the armature core each of them
surrounds a diameter of the core; they are at the periphery of the armature core
at substantially equal distances apart; the Invention is not limited to any specific
number of coils on the armature, I prefer two. In one complete rotation of such
an armature as is herein described, two electric currents are produced in each coil,,
one positive and the other negative; the duration of each of these currents is
slightly less than the duration of a semi-rotation of the armature, in other words
the length of time that the current lasts is almost identical with the time required
by the armature to perform a half rotation; increase of speed increases this
difference but does not increase it greatly when the speed is kept within practical.
limits.
When this armaturé is rotated in a magnetic field the currents 'produced in each
coil have a nearly fixed strength for a considerable portion of each seini-rotation,
that is to say when the armature begins to make a certain semi-rotation the
electric current in one of the armature coils rises from zero to a maximum and
remains constant, or nearly so, until near the end of such semi rotation when it
descends rapidly to zero again; the current' does not pass immediately from zero to
the maximum nor does it pass immediately from the maximum to zero, but an
appreciable time is required for each of these changés.
. J
Each of these currents has a nearly fixed strength during two thirds of a semi-
rotation of the armature, that is to say, during one third of an entire rotation of the
armature.
[
The shape of the armature core before the wire is wound upon it is in
transverse section that of a rectangle, but when the wire' is laid upon it its shape is

page_text: substantially that of an oval or ellipse; this is caused by the coils being laid one
upon another at the centre where they. cross one another; the major axis of the
ellipse is the diameter of the armature.
When the herein described form of armature is situated with regard to the field
magnets, as herein described every part of the wire laid upon the armature suffers
induction; no part can be idle, consequently a very high electro-motive force is
produced by a short length of wire; moreover the wire in the field magnet coils
acts directly upon the wire in the armature producing currents by direct induction
without the intervention of any metal. The armature is moreover removed from
all chance of injury; the poles of the field magnets are enclosed and being within
the coils diffusion is prevented so that the machine does not magnetize every
magnetizable thing in its neighbourhood. The advantages obtained by this form
of construction are numerous and important.
The commutator used with the herein described armature is of peculiar con-
struction. Assuming there are three coils of insulated wire wound upon the
armature core, there will be in all six ends, each of these ends communicates with
an insulated metallic plate on the periphery of the commutator, which plate is
separate and distinct and insulated from the other peripheral plates, it follows
therefore that there are as many peripheral plates on the commutator as there are
ends of the armature coils, that is to say, the number of peripheral plates on the
commutator is double the number of coils in the armature, two for each coil, one
for each end of each coil, and the two appurtenant to a coil are diametrically
opposite each other on the commutator.
.
These commutator plates are peripherally separated from each other by an
interval suitable for purposes of insulation, and together they form a hollow
cylinder, a construction which permits air to have access to all parts and thus tend
to prevent the heating of the commutator plates. These plates are supported upon
a disc preferably bolted thereto and carried on the armature shaft, the rotation of
which shaft and the armature is caused by means of a belt running on a pulley.
The coil ends enter the hollow of the shaft near the armature and run lengthwise
through the same to the commutator.
I provide elastic strips of metal bearing at diametrically opposite points on the
periphery of the commutator as it rotates, these strips are commonly called
brushes." When the armature rotates in a magnetic field and the brushes are
joined by a conductor electric currents are generated in the armature coils. These
currents are continuous and in one direction. It will be observed that the brushes
which collect the currents would bear upon, each set of peripheral commutator
plates when they are six in number, about 1/ or 60° of the circle in each
semi-rotation if the commutator plates were all of the same size (which they
are in this case) and their lines of separation were at right, angles to the plane
of rotation.
Theory and practice both shew that the current in each of the armature
coils is produced or tends to be: produced during about 1, or 120° of the
circle in each semi-rotation, and each set of the commutator plates should be in
contact with the brushes for the same duration in order to attain the full efficiency
of the armature coils. To accomplish this it is necessary that each commutator
plate should extend about. of the entire distance around the circumference
of the commutator, and to permit this the lines of separation between the com-
mutator plates are not at right angles to the plane of rotation but are at some
other angle thereto proportionate to the width of these plates and the width of the
brushes; the one essential condition is that the angle shall be such that each
commutator plate extends substantially around 1, of the entire circumference of
the commutator and this is true whatever be the number of armature coils.
An advantage incident to the construction and operation of the armature and
commutator herein described is that the spark generated when a. brush quits a
commutator plate can be divided between the two brushes and its hurtful influence
greatly diminished.
s

page_text: +
..
Having to some extent described the armature and commutator I shall now
proceed to describe the field magnet of the machine which constitutes an important
feature of the Invention. The field magnet consists mainly of two parts or poles
lying in the same line of direction with the armature between them which in
effect is a part of the field magnet considered as a whole...
Each of the said parts or poles is made up of two or more iron plates disposed
side by side communicating by metallic end and edge attachments, but not in
"direct contact so that air may circulate between the plates. These plates have a
width slightly greater than the diameter of the armature and a length considerably
greater than such width.
.
The length of these plates will vary under different circumstances being
generally from one or one half to two times as great as the diameter of the
armature. The combined thickness of these plates is considerably greater than the
thickness of the armature disc. The ends of these plates next the armature are.
"substantially of the shape of the arc of a circle and in the intermediate circular
space the armature is located and rotates the shaft thereof being carried in suitable
bearings.
Those of the said plates which make up one pole are supported and held in
*communication at the outer end by screws running through an end piece of the
general frame of the machine and on the edges by screws running through the edge
'plates which are of brass or other suitable material. Those of the said plates
which make up the other pole are correspondingly supported and held in com-
munication at the outer end by screws running through an end piece of the
general frame and on the edges by screws running through brass edge plates.
"
I
It is desirable that the figure in transverse section formed by the field magnet
parts other than the armature before the insulated. wire is wound upon them shall
be substantially the same as the transverse section of the armature after the wire is
laid upon it so that the coils on the fixed magnet can be brought very near to the
armature and yet have one shape throughout. For this purpose pieces of wood,
flat or hollow on the inner side and convex or curved on the outer side, are disposed
at the sides of the field magnet and supported by pins with a space between the
said wooden pieces, and the field magnet plates for the circulation of air. Then a
coil (or coils) of insulated wire is wound over substantially the entire outside of
the whole system secluding the armature as well as the field magnet proper except
a small space at the longitudinal centre where the armature shaft emerges.
this way the armature is magnetized directly by the coils of the field magnet as
well as by the core of the field magnet;
In
As herein before stated magnetism tends to a state of diffusion, but a state of
concentration can be brought about by proper means as well as heat can be
concentrated by refraction. The way to prevent diffusion of magnetism is to
prevent the core from projecting beyond the coil magnetizing it. The further the
core projects beyond the coil the more will the magnetism be diffused. To obtain
the best effect the end of the core should be within. the cavity of the coils. When
the parts are arranged in this manner which is substantially the arrangement in
the construction herein described, the magnetism seems to be concentrated to the
very ends of the core. Lengthening the core also has a concentrating effect.
When both of these means are employed the magnetic energy is of very great
intensity. The electric current employed in the coil surrounding the field magnet
may come either from the current generated by the armature or from a distinct
source.
+
Metallic shells connect the end pieces of the frame and protect the enclosed parts,
and cross-bars forming bearings for the armature shell are supported from the
aforesaid edge plates. While the coils are moving in front of the poles of the field
magnet the said coils are active, that is to say they are generating electric currents,
and the commutator plates appurtenant to the coils are so located with reference
to the points of contact with the brushes that the brushes pass from one com-
mutator plate to another while the coils to which the last mentioned plates are
1

page_text: appurtenant are thus active; so that the currents coming off the two contiguous
commutator plates, at the time of the passage of a brush from one to the other, are
moving in the same direction, and flow off together and not from one plate to the
other so as to make a short circuit.
According to a modification of the said Invention the field magnet core is of cast
iron and has a central longitudinal perforation and its outer surface is formed with
longitudinal ribs or corrugations to permit the, free passage of air about the said
core. A sheet of insulating material, such as paper, is first wound about the core
and over that are wound the coils of wire or sheets of copper insulated by
O intermediate sheets of paper.
tt
'
f
. The rapid rotation of the armature, causes a strong draught and rapid circulation.
of air through and around the field magnet core and coils so that the parts are not
liable to become heated sufficiently to be perceptibly warm to the hand
The armature core is formed of a spiral coil of thin ribbon of iron tightly wound
5 upon a spindle that forms the axis of the armature. In order to obtain the highest
efficiency in the operation of the inachine induced currents in the armature core
must be prevented or broken up. The scale formed upon the thin ribbon in the
process of 'rolling it, is a tolerably good non-conductor, this scale forms a material
percentage of the armature core when ready for receiving the coils, and reduces tlie
mass of metal in which currents may be induced in
The said ribbon is wound tightly upon itself and is preferably held in place, that
is to say, each layer upon the one below or preceding it, by punching for example
with a centre punch, small depressions.in the ribbon either along the line of its
centre or at random. The effect of this indentation is carried through several
5 thicknesses of metal without breaking the same and it holds the spiral together
very firmly the outer end' being fastened by a pin driven through it and one or
more, layers beneath it. The said ribbon may be rolled with one or more
longitudinal channels so as to prevent lateral play, but the method just described
is the most 'satisfactory. Soon after winding the core is soaked in Japan varnish
or like substance which hardens under heat and it is then baked! This makes a
core very compact and firm and one that will not perceptibly become heated.
The method of winding the armature coil is as follows, that is to say pins of
metal are driven radially into the core projecting any suitable distance from the
periphery thereof, and between these pins the coils are wound as follows, that is to
say: A wire is wound laterally about the disc or core with all its strands on one
side of the axis or shaft, the positive and negative ends of the wire coming together
or near each other on one side. Another wire is wound between the saine pins but
on the other side of the said shaft and its ends come together nearly opposite to
those of the other wire.
If
Other wires are wound' in a similar manner between the other pins until the
spaces are filled.
.
This method of winding makes a thinner disc than could be obtained by any
öther method and possesses obvious advantages in joining up.
1
It.
1!
+
- ..
-
• 09:
.8 fr
siting m
7.
3
D
ST.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Henry Harris Lake in the Great Seal Patent Office on the
12th June 1883.
HENRY HARRIS, LAKE, of the firm of Haseltine, Lake & Co, Patent Agents,
Southampton Buildings, London "IMPROVEMENTS IN DYNAMO - ELECTRIC 5
MACHINES" a Communication to me from abroad, by Richard Henry Mather,
of Windsor, Connecticut, United States of America, Electrician.
F
This Invention relates to dynamo-electric machines and comprises various
improvements in the construction of such machines as hereinafter described and
illustrated in the accompanying drawing, in which,
Figure 1 is a side elevation of a machine constructed according to the said
Invention
Figure 2 is a front elevation of the same.
Figure 3 is a plan or top view thereof.
Figure 4 is a view of the machine in the same position as in Figure 1, but with 1
the exterior casing and substantially the upper half of the machine represented in
vertical section on the line x, x, Figure 3.
Figure 5 is a vertical section of the machine on the line x, x¹, Figure 3.
Figure 6 is a horizontal section on the line ", " Figure 4.
Figure 7 is a side elevation of the armature.
Figure 8 is a plan or top view of the commutator, drawn to an enlarged scale.
: Figure 9 is a central longitudinal section of the commutator, also drawn to an
enlarged scale, and
Figure 10 is an end view of the same.
Figure 11 is a side elevation of a machine constructed according to a modification 2
of the said Invention, the exterior casing being removed:
Figure 12 is a central vertical section of the same.
Figure 13 is a horizontal. section of one part of the field magnet and the casing
of the said machine:
Figures 14, 15, 16 and 17 are different views, drawn to an enlarged scale, 3
illustrating details of construction of a modified form of armature.
The improved machine has a field magnet in two parts arranged in the same
general longitudinal line, with the armature located and adapted to be rotated
between them.
One of the peculiarities of this machine is the armature, the iron core of which 3
is made in the form of a flat disc provided with, transverse grooves at regular,
intervals around its periphery to hold the coils of insulated wire; when three coils
are used as shown in the drawing, there are six of these transverse grooves, two of
which are shown in Figure 5.
The magnetic axis of the said disc is at right angles to the axis of rotation, that 4
is to say, parallel with the plane of rotation. Magnetism seldom or never extends
far beneath the surface of a mass of iron, especially when the iron is in motion;
generally it does not extend more than one inch beneath the surface, hence an
armature, in order to be very effective, that is to say, in order to produce a current
of high electromotive force with a short length of wire on the core, must have a 4
considerable amount of surface as compared with the amount of metal contained in
it; moreover the shape of the armature should be such that the wire may be
readily coiled upon it.
It is very important that an armature should occupy a small space. Magnetism,
like heat, tends to a state of diffusion, never to a state of concentration. If an 5

page_text: armature is large it requires a large magnetic field in which to rotate, 'this:
necessitates the employment of a large quantity of iron and copper in the magnets
and a great expenditure of force to produce and maintain the current used to
charge the magnets. On the other hand, if a magnetic field is small, it requires
but little copper and iron and only a small force to maintain the current that
charges the magnets. It is a general law that a small magnetic field can be more
easily maintained than a large, but equally intense, magnetic field. It will, there-
fore, be readily comprehended that an armature having the disc form shown in the
drawing fulfils all these conditions. No part of the disc armature can escape
magnetization, the large surface combined with the small thickness (this thickness
not exceeding one third of the diameter) ensures complete magnetic saturation;
moreover there is no screening of one part of the armature by another part, such as
is incident to the use of the ring and the cylinder forms of armature. In these
forms there is a large amount of space lost within the armature itself by reason of
its being made hollow, but there would be no advantage in filling the said space
and making the said core of solid metal, because the magnetism would not
penetrate to such a depth beneath the surface as to utilize the whole of the said
metal. There is no similar loss of space in a disc armature because the disc is
either made solid or it is composed of thin plates or lamina separated by non-
conducting material such as paper to prevent the circulation of electric currents
within the armature core. In Figure 5 I have shown the armature disc made
of metal plates separated by sheets of paper. This disc armature occupies less
space than armatures heretofore constructed for producing currents of the same
strength.
The number of grooves in the periphery of the disc is proportional to the
number of coils laid upon the armature, two diametrically opposite grooves being
formed for each coil; and the number of coils may be varied according to the
purpose for which the machine is to be applied.
'
The width of one of these grooves is usually made equal to the distance between
two adjacent grooves. In Figure 7, b, c and d represent three coils laid upon the
armature core a; one end of each of these coils communicates with one of six
plates upon the periphery of the commutator hereinafter described, and the other
end of each of the said coils communicates with another of the six commutator
plates diametrically opposite the first of the said plates. When these coils are laid
upon the armature core, each of them diametrically surrounds the same; and on
the periphery of the armature core they are at substantially equal distances apart.
In one complete rotation of the armature, two electric currents are produced in
each coil, one positive and the other negative; the duration of each of these
currents is slightly less than the duration of a semi-rotation of the armature, in
other words, the length of time that the current lasts is almost identical with the.
time required by the armature to perform a half rotation; increase of-speed,
increases the difference between these periods of time but does not increase it
greatly when the speed is kept within practical limits.
20
When this armature is rotated in a magnetic field, the currents produced in each
coil have a nearly uniform strength for a considerable portion of each semi-i
rotation, that is to say, when the armature begins to make a certain semi-rotation,
the electric current in one of the armature coils rises from zero to its maximum
strength and remains constant, or nearly so, until near the end of the said semi-
rotation when it falls rapidly to zero again; the current does not rise immediately
from zero to the maximum nor does it fall immediately from the maximum to zero,
but an appreciable time is required for each of these changes.
Each of these currents has a nearly fixed or uniform strength during two thirds
of a semi-rotation of the armature, that is to say, during one third of an entire
rotation of the armature.
>
The shape of the armature core, before the wire is wound upon it, is, in transverse
section, that of a rectangle, but, when the wire is laid upon it, its shape is
substantially that of an oval or ellipse, by reason of the coils being laid one upon-

page_text: .
another at the centre where they cross each other; the, major axis of the ellipse.is,
the diameter of; the armature...
f
When the above described form of armature is situated, with regard to the field.
magnets as herein. described, every part of the wire laid upon the armature core.
is subjected to induction, no part can be inoperative, consequently a very high
electromotive force is produced by a short length of wire; furthermore the wire in.
the field magnet coils acts directly upon the wire in the armature, producing,
currents by direct induction without the intervention of any metal; the armature,
is moreover, removed from all liability to injury, the poles of the field magnets are
enclosed, and, being within the coils, diffusion is, prevented, so that the machine,
does not magnetize articles adjacent thereto. The advantages obtained by this
form of construction are numerous and important.......
The.commutator designed to be used with the herein described armature is of
peculiar construction. As above stated, there are in the machine shewn in the
drawing, three coils of insulated wire wound upon the armature core, there will,
therefore; be in all six ends; each of these, ends communicates with an insulated.
metal plate on the periphery of the; commutator. The said six ends are shown in
Figure, 10, e, e being the two ends of the coil b; ff.the two ends of the coil c;;
and g;g the two ends of the coil d. Each of these ends communicates with, a
peripheral plate of the commutator, which plate is separate. and distinct and
insulated' from the other peripheral plates; it follows, therefore, that, there are as
many, peripheral plates on the commutator as there are ends of the armature.coils,,
that is to say, the number of peripheral plates on the commutator is double the
number of coils in the armature; and the two appurtenant to a coil are
diametrically opposite each other on the commutator. ¡
h, h' are the commutator plates communicating with 'the ends e, elof, the coil b;
are the commutator plates communicating with; the ends f, fl of the coil c
and j, j are the commutator plates communicating with the ends g, g of the, coil. d.
These commutator plates are, separated from each other by an, interval suitable for
purposes of insulation, and together they form a hollow cylinder. This form of
construction permits access for air to all parts of the commutator, and thus, tends to
prevent the heating of the commutator plates. These plates are supported by the
disc, being: preferably, bolted thereto as shown in Figure 9. This disc is
carried by the armature shaft 7, the rotation, of which shaft and of the armature is
caused by means of a belt and a pulley m; the ends of the coils enter the hollow
shaft near the armature and pass longitudinally, through the same to tlie
commutator.
1
ارا
a; a" are elastic strips of metal, commonly called "brushes," bearing at
diametrically opposite. points on the periphery, of the commutator. When the
armature rotates in the magnetic field and the brushes are joined by a conductor,
electric currents are generated in the armature coils. These currents are continuous
in one direction. The brushes which collect the currents will bear upon each set
of peripheral commutator plates (when the latter are six in number) for about one
sixth (%) or sixty degrees (60%) of the circle in each semi-rotation of the commu-
tator, all of the said plates. being of the same size as shown and assuming their
lines of separation to be at right angles to the plane of rotation.
Theory and practice both shew that the current in each of the armature coils is
produced, or tends to be produced, during about one third ('/s) or one hundred and
twenty degrees (120°) of the circle in each semi-rotation, and each set of the com-
mutator plates should be in contact with the brushes for the same length of time
in order to attain the full efficiency of the armature coils. To attain this result it
is necessary that each commutator plate should extend around about one third ('/s)
of the circumference of the commutator; for this purpose the lines of separation
between the commutator plates are not at right angles to the plane of rotation, but
are at some other, angle thereto proportionate to the width of these plates and the
width of the brushes, the essential condition being that the angle must be such.
that each commutator plate, extends substantially around one third (/) of the

page_text: entire circumference of the commutator, and this is true whatever be the number of
armature coils.
J
An advantage incident to the construction and operation of the armature and
commutator as herein' described is that the spark generated when a brush quits à
commutator plate can be divided between the two brushes and its injurious influence
be thereby greatly diminished.
".
Having to some extent described the armature and commutator, I shall now
proceed to describe the field-magnet of the machine which constitutes an important
feature of this Invention, the field magnet consists mainly. of two parts or poles
arranged in line with each other with the armature between them, which armature
is, in effect, a part of the field-magnet considered as a whole.
Each of the said parts or poles is made up of two or more iron plates arranged
side by side and communicating by metallic end and edge attachments, but not in
direct contact, so that air may circulate between them. n, n, are two plates which
make up one of the said parts or poles, and o, o, are two plates which make up the
other of the said parts or poles. These plates have a width slightly greater than
the diameter of the armature and a length considerably greater than such width.
The length of these plates is varied according to circumstances, being generally
from one and a half to two times as great as the diameter of the armature. The
combined thickness of these plates is considerably greater than the thickness of the
armature disc. The ends of these plates next the armature are made substantially
in the form of an arc of a circle, and in the intermediate circular space the
armature is located and rotates, the shaft thereof being carried in suitable
bearings.
The plates n, n are supported and placed in communication with each other at
their outer ends by screws p passing through the end piece r of the frame of the
machine, and on the edges by screws 8 passing through the edge platest which
are of brass or other suitable material. The plates o, o are correspondingly
supported and placed in communication with each other at their outer ends by
screws p' passing through the end piece of the frame, and on the edges by screws
passing through brass edge plates as above described.
It is desirable that the said two parts or poles of the field magnet, before the
insulated wire is wound upon them, shall be of substantially the same shape in
transverse section as the armature after the wire is laid thereon, so that the.coils of
the field magnet can be brought very near to the armature and yet be of the same
configuration throughout. For this purpose pieces of wood u, flat or concave on
the inner side and convex on the outer side, are arranged at the sides of the said
parts or poles and are supported by pins v, a space being left between the said
wooden pieces and the field magnet plates for the circulation of air. One or more
coils of insulated wire w are then wound over the exterior of the field magnet with
the exception of a small space where the armature shaft emerges. In this manner
the armature is magnetised directly by the coils, of the field magnet as well as
by the core of the same.
As herein before stated, magnetism tends to a state of diffusion, but a state of
concentration can be brought about by proper méans, as heat can be concentrated
by refraction. To prevent diffusion of magnetism, the core must be made so.as
not to project beyond the coil magnetizing it. The further the core projects
beyond the coil, the more will the magnetism be diffused. To obtain the best
effect the end of the core should be within the cavity formed by the coils. When
the parts are arranged in this manner, which is substantially the arrangement
herein described, the magnetism appears to be concentrated to the ends of the core;
lengthening the core also has a concentrating effect:
When both of these means are employed the magnetic energy is of very great
intensity. The electric current employed in the coil surrounding the field magnet
may be either the current generated by the rotation of the armature or it may be
obtained from a distinct source.
'
y', y¹ are metallic shells connecting the end pieces r, 71, of the frame and

page_text: protecting the enclosed parts.. 2, 2 are cross-bars forming bearings for the armature
and supported by the edge plates 2,2. While the coils are moving in front of the
poles of the field magnet, the said coils are active, that is so say, they are generating
electric currents, and the commutator plates appurtenant to the coils are so located
with reference to the points of contact with the brushes, that the brushes pass from
one commutator plate to another while the coils to which the last mentioned
plates are appurtenant are thus active; so that the currents coming off the two
contiguous commutator plates. during the passage of a brush from one to the other,
are moving in the same direction, and flow off together and not from one plate to
the other so as to make a short circuit.
:
LLi
"According to the modification of the said invention illustrated in Figures 11
to 17, the field magnet core a is of cast iron and has a central longitudinal
perforation 61; its outer surface is formed with longitudinal ribs or corrugations
to permit the free passage of air about the said core. A sheet c' of insulating
material, such as paper, is first wound about the core, and over the said material
are wound the coils of wire d' or sheets of copper insulated by intermediate sheets
of paper.
The rapid rotation of the armature causes a strong draught and rapid circulation
of air through and around the field magnet.core a¹ and within the coils d¹ so that
the parts are not liable to become heated sufficiently to be perceptibly warm to
the hand.
The armature core e¹ is formed of a coil of thin iron ribbon e² tightly wound
upon a spindle f1 forming the axis of the armature. In order to obtain the
highest efficiency in the operation of the machine, induced currents in the armature
core must be prevented, or. broken up. The scale formed upon the said thin
ribbon in the process of rolling is a tolerably good non-conductor. This scale forms
a considerable percentage of the bulk of the armature core, when ready for receiving
the coils, and reduces the mass of metal in which currents may be induced.
こ
The said ribbon e' is wound tightly upon itself and is preferably held in place,
(that is to say, each layer upon the one below or preceding it) by punching (for
example, with a centre punch) small depressions in the ribbon, either along the line
of its centre or at random as shewn at e³ in Figures:14 and 15: The effect of this
indentation is carried through several thicknesses of metal without breaking the
same and holds the coil together very firmly; the outer end of the coil is fastened
by a pin g² driven through it and one or more of the layers beneath it. The
ribbon e² may be rolled with one or more longitudinal channels so as to prevent
lateral play, but the method above described is the most satisfactory. After
winding the coils upon the core, it is soaked in Japan varnish or like substance
which hardens under the influence of heat, and it is then baked. This makes a
very compact and firm core. that will not become perceptibly heated.
The method of winding the coils on the armature core is as follows; that is to
say-Pins p² of metal, are driven radially into the core e so as to project a
suitable distance from the periphery thereof, and between these pins the coils are
wound, as shewn in Figure 16, that is to say, a wire 2 is wound about the disc
or, core e¹ between the pins p2 with all its strands on one side of the axis or shaft f
the positive (+) and negative (-) ends of the wire coming together or near each
other on one side, as shewn. Another wire is wound between the said pins p²
but on the other side of the said shaft and its ends. + and - come together
nearly opposite those of the wire 12. Other wires are wound in a similar manner
between the other pins until all the spaces are filled:
i
-
I
This method of winding forms a thinner disc than can be obtained by other
'methods and possesses obvious advantages in making the connections,
I sometimes make the armature of a cylinder or drum, of the Siemens type,
wound with two coils of, wire at right angles to each other, the ends of the said
coils being brought out to the commutator which is composed of four insulated
segments of metal, each segment extending ninety, degrees (90°) around the
commutator.
0
.I
t

page_text: Diametrically opposite segments are connected with one coil; one end of the
said coil is connected with one of the segments, and the other end of the said coil
is connected with the diametrically opposite segment; the other coil is connected
with the other pair of diametrically opposite segments, in a similar inanner.
In one type of machine this, armature, as above described is complete and is
connected to the field (magnet, in the ordinary manner, but in another type of
machine a separate wire is wound over each of the coils above described but is not
connected with them.
The wire thus 'wound formis two more coils wound at right angles to each other,
these two coils are connected to a commutator similar to the one above described
and in a similar manner.
One set of coils with its corresponding commutator is used for exciting the field
magnet and the other set of coils and its commutator for supplying the external
circuit.
But when the machine is employed for incandescent electric lighting, it is
preferable to dispense with the commutator and substitute therefor rings of metal
with brushes bearing upon them;' in this case the currents are alternating.
:
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 do not claim the use of a magnetizing coil or coils surrounding both the field
inagnets and the rotating armature; nor do I claim an armature having a core of
circular or similar outline on a shaft transverse to the plane of rotation of the
armature and placed between the parts of the field magnet, the ends of which next
the armature are of corresponding outline; nor a circular armature core wound
with insulated wire and surrounded, as far as practicable, by the field magnet coil
or coils; moreover I do not claim broadly or irrespectively of the improvements
herein described, a field magnet having the core formed with a perforation or
aperture; but I claim: in a dynamo electric machine.
First An armature composed of a disc whose thickness does not exceed one
third of its diameter and having a substantially solid centre or interior, and coils
of insulated wire wound thereon, substantially as, and for the purposes, set forth.
Second A disc armature core having grooves cut in its periphery and coils of
insulated wire wound in the said grooves, substantially as shown and described and
for the purposes specified.
Third The combination of an armature core, two or more coils wound thereon,
and a commutator having peripheral plates two of which plates are connected with
each of the said coils, the said plates each extending substantially around one third
of the circumference of the commutator, all substantially as, and for the purposes,
set forth.
Fourth A field magnet having the core formed with a longitudinal perforation
and with external longitudinal ribs or corrugations, and surrounded by a sheet or
sheets of insulating material over which are wound coils of wire or sheets of copper
insulated by intermediate sheets of paper, as above set forth and for the purposes
specified.
Fifth An armature having the core formed of thin iron ribbon (with or with-
out the longitudinal channels) tightly wound upon the shaft and secured as above
described, and having pins driven radially therein and projecting therefrom, the
coils being wound between the said pins, all substantially as above set forth and
for the purpose specified.
Sixth-The employment of Japan varnish, or similar substance which hardens
under the influence of heat, for consolidating the ribbon armature core, substantially
as, and for the purpose, set forth.
Seventh-An armature having two coils wound at right angles to each other
and connected to a commutator having four segments, one pair of diametrically
opposite segments being connected to one of the said coils and the other pair of
diametrically opposite segments being connected to the other coil, as above set
forth.

page_text: :-
+
Eighth The combination of an armature having two coils wound at right
angles to each other and connected to a commutator having four segments, one
pair of diametrically opposite segments being connected to one of the said coils and
the other pair of diametrically opposite segments being connected to the other coil,
of two coils superposed one upon each of the first pair of coils and connected to a
commutator similar to that used with the first pair of coils, or to metal rings, one
set of coils being used to excite the field magnet and the other set of coils to supply.
the external circuit, as, and for the purposes, set forth.
In witness whereof I the said Henry Harris Lake have hereunto set my
hand and scal this Twelfth day of June in the year of our Lord One
thousand eight hundred and eighty three.