Improvements in Dynamo-electric Machines or Electric Motors.
Year: 1890

page_text: COMPLETE SPECIFICATION.
Improvements in Dynamo-electric Machines or Electric Motors.
I, THEODORE MARSHALL FOOTE, of Boston, in the County of Suffolk and State of
Massachusetts, United States of America, Electrician do bereby 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:-
The object of this invention is to obtain simplicity and economy of construction,
increase of electrical efficiency, reduction of the weight of metal required to obtain a
certain out-put, maintenance of the axis of commutation at the point of least sparking
under varying conditions of load and separate and independent circuits in the machine
for the exciting current.
The said invention consists :-
First. In the construction, substantially as hereinafter more fully set forth, of the
field-magnets and their pole pieces.
Second. In the combination, substantially as hereinafter more fully set forth, with
a cylindrical armature rotating between the poles of a cylindrical field-magnet, of
another field-magnet within the armature and having pole-pieces opposite the pole-
pieces of the external field-magnet
Third. In means, substantially as hereinafter more fully set forth, for altering the
position of the pole-pieces of the internal field-magnet relatively to the pole-pieces of
the external field-magnet whereby the effect due to the distortion of the field caused
by the increase of current in the armature is corrected.
In the accompanying drawing
Figure 1 is a plan view of the motor.
Figure 2 is a longitudinal, sectional view through the line y, y Figure 3, and
Figure 3 is a transverse, vertical section through the line a Figure 2.
In these several figures the same letters refer to the same parts.
In order that the sectional views may show all the parts of the machine, the internal
field-magnet is represented as turned into a position in which its axis is at right angles
to the axis of the external field-magnet, but the normal position of the internal field-
magnet is with its axis coincident with the axis of the external field-magnet, except
when it is partially rotated in order to correct the effect due to the distortion of
the field.
The external field-magnet is composed of two semi-cylinders A A', united together
to form a cylinder, enclosing the armature B and having pole-pieces C, C,'on the inside of
the cylinder on opposite sides of the armature. These pole-pieces are provided with
extensions on each side between the armature and the core of the field-magnet, and
are secured to the cores A A¹ by bolts a a, passing through the cores from the outside.
Each pole-piece is united to the opposite ends of the cores, and thus serves to hold
them; the two semi-cylinders forming the cylindrical field-magnet.
The cores of this field-magnet have a series of projections a a¹ on the outside, and
corresponding narrowing projections on the inside, which have the effect of increasing
the magnetic power of the core. The wire is wound between these projections.
The cylindrical field-magnet is supported in a semi-cylinder D, of non-magnetic-
metal, and is secured to the same by bolts b, b, on each side and by a central bolt C
in the bottom of the semi-cylinder A¹. The support is suitably seenred to the bed-
plate of the machine. I have shown this manner of supporting the field-magnet, but
it is obvious that it may be supported in any other manner that may be found
convenient and suitable.
It will be seen that the several parts of the machine are firmly and compactly held
together and that they can be readily separated from one another by removing the

page_text: The armature B, is preferably made of a series of iron rings d, d, placed side by
side and secured together by bolts E between two caps F, of non-magnetic metal, one
on each end. On each of these caps and cast with the same is a sleeve G, G¹.
On one of these sleeves G¹ is keyed the commutator H and brush-holder I, and on
the other sleeve G may be keyed as shown, a magnetic coupling.
This magnetic coupling or electro magnetic friction clutch comprises a loose collar
on the sleeve and a collar fixed to rotate with said sleeve. The loose collar may be in
the form of a pulley, and may be disposed between two collars, all of said collars
being composed of magnetic metal. A wire forming a part of an electric circuit is
wound upon the fixed collars, whereby they may be magnetized. Either the loose
collar or the fixed collars are capable of a slight longitudinal movement on the sleeve G
whereby when one of the fixed collars is magnetized, the adjacent faces of the loose
collar and the magnetized fixed collar will unite, forming a friction clutch transmitting
the power from the sleeve G to the collar or pulley, and thence by a belt to the work.
The current may be conducted to the wire in any suitable manner, as by brushes
bearing upon collars of non-magnetic metal fixed on the sleeve, adjacent to the
magnetizable collars constituting a part of the clutch.
This coupling is shown in order to exhibit the arrangement of the circuit when the
coupling is used with the motor, as will preferably be the case when the motor is used
for street cars, but it forms no part of the present invention, as the motor can be used
equally well with or without the coupling.
Within the sleeves and suitably supported at each end is a non-rotating shaft K,
and on this shaft within the armature is keyed the internal field magnet L, which
magnet consists of a core suitably wound and having pole-pieces curved concentrically
with the armature and as near as possible to its internal walls.
The form of these pole-pieces is, however, not essential to the operation of the
machine, but it is preferable that they should have this form.
The armature shown is a drum armature, and may be wound in any manner that is
adopted for winding drum armatures, and the different sections of the wire are
connected in the usual manner to the sections of the commutator H, which commutator
may be of any desired form.
If desired, the armature may be wound in the same way that a ring armature is
wound.
The brush-holder is mounted upon the sleeve G, and is provided with the arms, one
on each side, to which are secured parallel supports M, M, for the brushes N, N. These
brushes can be adjusted on the face of the commutator by moving the brush-holder on
the sleeve by means of the lever O.
Any other form of brush-holder may be adopted if desired.
The winding of the machine may be series, shunt, or compound, or there may be
separate and independent circuits for the field-magnets and the armature, and these
circuits may be connected together, as may be desired.
In the drawing, the armature and external field-magnets are included in the circuit
which is connected with the commutator, but the independent circuit through the
internal field-magnet includes the magnets of the clutch.
This circuit is as follows:-By the wire 1, which is laid in a channel in the shaft K,
to the internal field-magnet and by another wire also laid in a channel in the shaft K,
to the wire 2, thence by brush R to an insulated collar of metal S, upon the shaft K, and
through the coils of the clutch magnet to another collar S, and brush R¹.
The lines of force produced by the external field-magnet are concentrated by passing
through the iron of the internal field-magnet, and the field in which the armature
rotates is strengthened by the lines produced by the internal field-magnet, so that the
armature rotates in an intense field, and the lines of force constituting the magnetic
circuit are concentrated within this field of force with the result that there is no waste
of force, and the machine is therefore one of high efficiency.
The shaft to which the internal field-magnet is attached is capable of being turned
on its bearings by means of a lever P, so that the position of the pole-pieces of the
internal field-magnet relating to the pole pieces of the external field-magnet can be

page_text: changed as may be desired to correct the distortion of the field, due to any increase of the
armature current caused by variations in the work or otherwise, and the necessity of
any adjustment of the brushes to ensure commutation at the point of least sparking
will be avoided, thus enabling them to be permanently fixed in the most suitable
position.
The same means may be adopted to prevent sparking in case the brushes become
so worn away that the current is not delivered at the proper point on the commutator.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, 1 declare that what I
claim is :-
First A cylindrical field-magnet composed of two semi-cylindrical sections, arc-
shaped pole-pieces within said cylinder at opposite sides thereof and covering the
joints between the semi-cylindrical sections, and bolts passing through the adjacent
ends of said sections into said pole-pieces, substantially as described.
:
Second The combination of a cylindrical field magnet, a cylindrical armature
therein, and a field magnet within said armature, having its pole-pieces adjustable
relatively to the outer field magnet, a semi-cylindrical support for said field-inagnet
and bolts passing through said support near its upper edges and entering said
cylindrical field magnet adjacent to the joints between the sections, substantially as
set forth.
Dated this 12th day of August 1890
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.