Improvements relating to Dynamo-electric Machines and Electric Motors and to Apparatus connected therewith.
Year: 1891

page_text: Date of Application, 30th June, 1891-Accepted, 22nd Aug., 1891
COMPLETE SPECIFICATION.
[Communicated from abroad by THE CROCKER WHEELER ELECTRIC MOTOR
COMPANY, of 430 and 432, West 14th Street, in the City and State of New
York, United States of America.]
Improvements relating to Dynamo-electric Machines and Electric
Motors and to Apparatus connected therewith.
I, HENRY HARRIS LAKE of the firm of Haseltine Lake & Co., Patent
Agents 45 Southampton Buildings in the County of Middlesex 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:-
66
Many attempts have been made heretofore to devise an automatic speed
governing device, or means for automatically maintaining a constant speed under
varying loads in an electric motor operated on a constant current" circuit, and to
accomplish this without the use of cumbersome mechanism and without the loss of
electric energy.
In all such attempts the difficulty has been that the governing mechanism either
responded too tardily to the changes of load, required cumbersome apparatus and
wasted a great deal of electrical energy or involved a great deal of sparking at the
commutators.
111
Attempts have been made to effect the regulation of the power of the motor
so as to maintain a constant speed by mechanism adapted to automatically shift or
rotate the commutator brushies of the machine through a greater or less angle
thereby varying the torque or electro-dynamic moment of the armature
accordance with the demands of the load upon it, but in cases where this has been
tried, the sparking produced at the commutator by shifting the brushes from the
neutral space or region which they normally occupy to a point within and more
or less near the centre of the magnetic field as is necessary to secure the desired
effect has been so serious that the attempts have been abandoned as complete
failures.
By revolving the commutator brushes in the proper direction away from the
neutral position so as to cause the magnetism developed in the armature by the
armature coils to oppose or annul that developed in the pole pieces of the field, and
by constructing the machine on an entirely different principle from that heretofore
employed so that the magnetism in the armature or the magnetising effect of the
armature coils is very intense and that of the field comparatively weak (instead of
having the magnetism of the field completely overpower that of the armature as
heretofore), the armature may be caused to produce such a peculiar effect upon the
distribution of magnetism in the field that practically all sparking is suppressed
and the commutator brushes may be moved to any position necessary to secure the
desired torque or to produce the necessary variation in the counter-electromotive
force developed by the machine.
In the accompanying drawings,
Figures 1, 2 and 3 show the armature and field of an electric motor constructed
in accordance with the invention herein described and representing respectively the
magnetic effects which are produced by moving the brushes to different positions.
Figures 4 and 5, represent an electric motor constructed on the ordinary principles
and show what are the magnetic effects produced by similarly moving the brushes
out of the neutral position in such a machine.
Figure 6, represents a side view of an electric motor provided with an automatic
speed governing apparatus constituting part of the invention and

page_text: mechanism.
respectively decaned cop and end views of the brush rotating
In Figures 1. 2. and 3 is shown a motor so designed and proportioned that the
magnetizing effect of the armature coils is very strong and the magnetizing effect
of the field coils is comparatively weak, or of very much less strength relatively
than is usually the case in the ordinary machine.
This is accomplished in two ways, first by putting upon the armature core a large
amount of conductor or winding considerably greater than is employed in the
ordinary machine, and secondly by constructing the armature on the principle of
sinking the conductors or windings in spaces or slots in the periphery of the core,
one effect of which is to a very largely reduce the amount of magnetizing current
or effect necessary to bring it up to the required degree of strength. The consequence
is that while the magnetizing effect or magnetic moment of the armature is
increased by these means at the same time the magnetizing strength of the field
coils is diminished without materially reducing the strength of the magnetism in the
field; or in other words, without materially reducing the magnetic moment or torque
exerted between the armature and the field.
In the normal position of the brushes, as shown in Figure 1, the current traversing
the armature as is well known, produces magnetic poles in the armature core at the
points N and S within the neutral region. The coil included between two adjacent
commutator sections therefore while passing through this position and under the
brushes has no electromotive force generated in it because while it is in the neutral
region there is no variation of the amount of magnetism or lines of force passing
through it, and consequently no sparking takes place. When, however, a coil is
passing through any other portion of the field it is subjected to a varying amount
of magnetism which gives rise to an electricmotive force and consequently, if the
brushes be placed in any other position than one within the neutral region in the
ordinary machine sparking is produced as the junction between the corresponding
commutator section passes under and leaves the brushes. This however, is not
the case in a machine constructed according to the present invention for reasons
which will now be explained.
In Figure 2, the commutator brushes are shown as shifted to a position which
brings the magnetism developed in the armature by the armature current in direct
opposition to that of the field. By proportioning the comparative strength of the
armature and field windings as already explained, the effect of this is that the poles
of the armature or points opposite the brushes throw out magnetism or lines of force
sufficient to practically or largely annul or neutralize the magnetism or lines of
force thrown into the armature by the field at these points and the consequence is
that no magnetism from the field enters the armature core at these points and the
coils which are under the commutator brushes at these points are not subjected to
any change of magnetism and consequently no sparking is produced as the coil
passes under the commutator brush.
In the drawing the two arrows represent in a general way the magnetic effect or
lines of force thrown out by the armature which are sufficient to neutralise the lines
of force which the field tends to throw into the armature at these points so that
practically no magnetism passes into the armature at the points N and S and
there will be no sparking at the brushes while in this position.
This is also true when the brushes are set in any position intermediate between
that shown in Figure 2, and that shown in Figure 1. the magnetism in the armature
thrown out at the points N and S being sufficient to practically annul or neutralize
that thrown out at the opposite points in the polar faces so that no magnetism or
lines of force enter the armature at these points.
In other words, by properly proportioning the comparative strengths of the
armature and field windings, we are enabled to cause the armature to form what
is in effect a neutral space in the field at the points corresponding with the position
of the brushes and thereby prevent all sparking. With the brushes set in the
position shown in Figure 2, the magnetic effect of the armature being directly

page_text: opposed to that of the field, of course there will be little or no magnetic effect and
no torque produced but in all intermediate positions between this and that shown
in Figure 1, the torque will vary from zero to the full amount while at the same
time the neutral plane or region produced in the field by the armature will follow
the position of the brushes and the sparking will amount to nothing or practically
nothing at all these points.
Figure 3, shows the effect of rotating the brushes in the wrong direction; the
effect of which is that the magnetism in the armature agrees with and reinforces
that of the field strengthening the magnetism which enters the armature at the
points N and S thus producing a maximum variation in the magnetism passing
through any coil as it passes these points, and consequently the greatest amount of
sparking. When the brushes are rotated in the direction shown in Figure 3, the
sparking begins the moment they leave the neutral regions, increasing to a maximum
between that and the position shown in Figure 3.
In practically constructing the machine in order to have the magnetizing effect
of the field coils less comparatively than is the case in the ordinary machine, the
field should be wound with fewer turns of wire and, as already explained, this may
be done without diminishing the general strength of the magnet by employing a
form of armature in which the iron body of the core reaches out to the pole pieces
and the copper wires or conductors are embedded in this core.
Figure 5 illustrates the effect in an ordinary machine of revolving the brushes in
the same direction as that represented in Figure 2 the magnetizing effect of the
armature coils being so much weaker than that of the field coils, the magnetism
thrown out by the armature at the points N and S only partially or immaterially
neutralizes those thrown in from the field at these points and consequently the
coils at these points are subjected to an inductive influence while passing under the
brushes and the sparking is produced. The same is true for the intermediate
positions of the brushes between that shown in Figure 4 and that shown in
Figure 5, the sparking beginning the moment the brushes leave the neutral region
and becoming worse as they are moved further toward the position shown in
Figure 5.
In Figures 6, 7 and 8, A. represents the commutator and B B the brushes of an
electric motor constructed according to this invention. In order to construct an
automatic speed governor operating on this principle, the brushes B B are
mounted upon an ordinary rocking brush holder or support C so that they are
capable of being rotated from their normal or neutral position to an angle of at
least ninety degrees. To enable this to be done with as little friction as possible,
the arm or support C is mounted upon rollers c which travel in a cylindrical
groove forming the bearing between the arm and the journal. Upon the shaft of
the machine is fixed a centrifugal speed governor D D consisting of two centrifugal
arms or weights, pivoted to an arm or disc E rigidly attached to the shaft and
connected by links with a sliding collar F which is connected as clearly shown by
a series of levers with the rocking brush-holder. The sliding collar is held in
its normal position as shown in Figures 7 and 8, by a compression spring which
resists the centrifugal effect of the arms D D more and more as they are thrown
outward. In order to make the governor as nearly isochronous as possible and to
secure the full range of movement for the brushes with a small variation in speed
the arms are made in the forni shown that is so that when they are drawn together
a considerable portion of their weight is in the plane of the axis of the shaft and
consequently this part of the arms has no centrifugal effect in throwing the arms
outward, but as soon as they begin to move outward by an increase of speed this
part of them begins to exert a centrifugal effect sufficient to neutralize the
increasing tension of the spring F. By means of this governor the brushes may
be shifted with a very slight variation in speed from the position shown in
Figure 8 through a series of positions up to ninety degrees or less which will
automatically vary the torque or counter electromotive force produced by the

page_text: motor and consequently the power developed the speed remaining constant within
the limits necessary to cause the governor to operate.
The invention may also be employed for the regulation of the electromotive
force of dynamo electric machines or generators, instead of the regulation of the
counter-electromotive force or the torque in the case of electric motors. By
constructing the dynamo machine as described and rotating the brushes in the
proper direction the electro-motive force developed may be varied from zero to a
maximum, according to the requirements and this may be done either by hand or
by any automatic means of shifting the brushes operated by variations in the
current strength as would be the case in the ordinary are light circuits for
example.
Electric motors have heretofore been devised upon what is known as the
repulsive principle of action; that is to say motors in which the rotation of the
armature is caused by the repulsive action of poles of the same polarity in
the field-magnet and the armature and no claims are made hereinafter broad
enough to include such a construction. It is believed, however, that no one has
heretofore devised an electric motor or a dynamo electric machine in which the
magnetic effect of the armature is substantially equal to that of the field poles, or
in which the magnetic relation of these two parts is such that there is a substantial
magnetic balance between those portions of the field magnet poles and the armature
which lie in alignment with the contacting ends of the commutator brushes; in
other words, it is not believed that any one has heretofore devised a machine of
this type in which there is substantially no magnetic inductive effect felt in those
portions of the armature core which are being energized at the time that the
brushes are passing over consecutive commutator segments connected to coils
surrounding this part of the core.
The claims hereinafter made are directed broadly to the application of this
principle and to the apparatus for practicing the methods claimed.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed as communicated to me
by my foreign correspondents I declare that what I claim is :-
First. The herein described method of preventing injurious sparking at the
commutator brushes of a dynamo electric machine or electric motor, consisting in
producing equal and opposing magnetic effects between the field magnet poles and
those portions of the armature core which are being magnetized, while the brushes
are passing over consecutive commutator segments connected to the coils which
surround the aforesaid portions of the core substantially as described.
Second. The described method of regulating a dynamo electric machine or
electric motor and simultaneously preventing injurious sparking at the commutator
brushes, consisting in producing equal and opposing magnetic effects between the
field magnet poles and those portions of the armature core which are being
magnetized as the brushes pass over consecutive commutator segments connected
to the coils which surround the aforesaid portions of the armature core and
in simultaneously shifting the brushes in proportion to the load, substantially as
described.
Third. A dynamo electric machine or electric motor having the effective
magnetic portions of its field magnets and armature of substantially equal magnetic
capacity and so wound as to produce like polarity and an equal opposing effect
between said field magnet poles and those portions of the armature core which are
being magnetized at the time that the brushes are passing over consecutive
segments of the commutator, substantially as described.
Fourth. A dynamo electric machine or electric motor having the effective
magnetic portions of its field magnets and armature of substantially equal magnetic
capacity and so wound as to produce like polarity, and an equal opposing effect
between said field magnet poles and those portions of the armature core which are

page_text: being magnetized at the time that the brushes are passing over consecutive
segments of the commutator, in combination with means for varying the angular
position of the brushes in accordance with the load and simultaneously maintaining
the aforesaid magnetic balance, substantially as described.
Fifth. A dynamo electric machine or electric motor having the effective
magnetic portions of its field magnets and armature of substantially equal magnetic
capacity and so wound as to produce like polarity and an equal opposing effect
between said field magnet poles and those portions of the armature core which are
being magnetized at the time that the brushes are passing over consecutive
segments of the commutator, in combination with an automatic regulator adapted
to shift the brushes and maintain the aforesaid magnetic balance, substantially as
described.
Sixth. An electric motor or dynamo electric machine possessing the character-
istics above described and provided with an automatic governor such as is shown
in Figure 6, of the drawings for shifting the commutator brushes in order to
prevent sparking and afford the desired regulation.
Dated the 30th day of June 1891.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.