Improvements in Dynamo-electric Machines, in part applicable to Electro-motors.
Year: 1889

page_text: Date of Application, 31st Dec.; 1889
Complete Specification Left, 22nd Sept., 1890-Accepted, 15th Nov., 1850
PROVISIONAL SPECIFICATION.
Improvements in Dynamo-electric Machines, in part applicable to
Electro-motors.
1, JAMES JOHN WOOD, of No. 126 Cambridge Place, Brooklyn, in the State of
New York, United States of America, Electrical Engineer, do hereby declare the
nature of this invention to be as follows :-
This invention relates chiefly to dynamo-electric machines, commonly called
“dynamos." It consists in part of improvements in automatic regulators for
governing dynamo machines, in order that they shall generate uniform currents
under all circumstances. Such regulators are most commonly employed with dynamos
of the class generating a constant current of varying electro-motive force, such as is
used for feeding arc lamps in series. This part of the invention is applicable also
to regulators for dynamos generating a constant electro-motive force or difference
of potentials with a current of varying volume, such as are used principally for
incandescent lighting. Another part of the invention consists of improvements in
the armatures of dynamos, the improvements pertaining chiefly to the armature core
and to the supporting spider. This part of the invention is applicable also to electro-
motors.
Figs. 1, 2 and 3 of the accompanying drawings are general views of a dynamo
to which these improvements are applied, Fig. 1 being an elevation of one end showing
the regulating mechanism, Fig. 2 being a vertical section on the line 2-2 in Fig. 3,
showing the commutator brushes and means for moving them, and Fig. 3 being a side
elevation partly in vertical mid-section.
Figs. 4 to 11 inclusive are various views showing the automatic regulator more in
detail; Figs. 12 to 17 inclusive, are views showing the armature, and illustrating in
detail the construction of its core and supporting spider and accessory parts.
The automatic regulator will first be described. This regulator is of that class
wherein the regulation is effected by an adjustment or shifting of the commutator
brushes around the commutator. In dynamo machines having armatures of the
Gramme ring or Siemens drum type, there are two diametrically opposite points
on the commutator where the segments exhibit the greatest difference of potentials,
and when the commutator brushes are applied at these points they take off the
maximum current. This position is hence called the "maximum position," and a line
drawn through it, denoted at x x in Figs. 2, 5 and 7, is called the "maximum line."
By shifting the brushes through an are of about 60 degrees, they are brought to a
position where the current is at the minimum, and which is denoted by the
"minimum "line" y y in Figs. 2 and 5. Whenever, in the operation of the dynamo,
the current rises above or falls below the normal, this can be compensated for by
moving the brushes toward the minimum or toward the maximum position.
Automatic regulators of this class have heretofore been of two kinds: 1st, those in
which the brush-carrier or yoke is connected to the moving member of an electro-
magnet or solenoid, so that the two brushes derive their movements froni, and move
proportionally to, the movements of this member; and 2nd, those in which the
brushes are moved by a shifting mechanism which is driven in either direction from
a source of power, and the clutching of which to the source of power in one direction
or the other is effected by the movements of the armature or, moving member of the
regulating electro-magnet. The present invention is an improvement upon regulators.
of the latter class, and has for its object to render such regulators more sensitive,
more durable, and more easily and perfectly adjustable, and to provide improved
means for preventing the undue action of the regulator when the dynamo is over-
lalal

page_text: The general construction of dynamos shown in, the drawings is of a well-known
type, its field-magnet consisting of upright end frames A A, connected by horizontal
bars constituting the cores of the exciting coils B B, between which, and at the
middle of these bars, are fixed the pole-pieces CC. The armature D and its
commutator E are fixed on a shaft K, which passes through the middle of the end
frames and projects at one end, on which is fixed a driving pulley. F F are the main
commutator brushes, and G G are the auxiliary or supplemental commutator brushes.
M is the regulating electro-magnet. The machine is self-exciting, its field-magnet
coils being wound in series. The circuit extends, as usual in such machines,
from the positive commutator brush or brushes, through the coil of the regulating
magnet M, and thence through the successive field-coils, and out at the positive
binding-post, over the line circuit, and back through the negative binding-post to the
negative brushes.
The main commutator brushes F F are carried as usual in insulated holders
mounted on opposite arms of the brush-carrying yoke or lever H, which turns on an
inward prolongation or boss a formed on or fixed to the inner side of the end
frame A (see Fig. 4), as usual. The supplemental brushes G G are carried by
insulated holders mounted on opposite arms of a supplemental carrier-yoke H¹ mounted
in the same way as the yoke H. These brush-carriers. H and H are formed
respectively with toothed sectors and which mesh respectively with pinions; j
fixed on a shaft J which passes through the main frame A, as shown in Fig. 4.
On the outer end of this shaft is mounted a gear-wheel c connected to the shaft
through a clutch bde, which will presently be described. This gear-wheel c is
geared or connected directly or indirectly to a friction-wheel N. This connection is
preferably made through the medium of a pinion with which the gear c meshes,
and which is fixed to a gear-wheel f, the teeth of which mesh with a pinion f² fixed
on the hub of wheel N.
.
The wheel N has a frictional surface or tread upon its periphery, and close to, but
(preferably) normally just out of contact with, this surface stand two friction
rollers g and i which are revolved continuously in opposite directions from a source
of power, preferably by being geared to the armature-shaft K. A gear-wheel a'
fixed on the end of the armature shaft, drives a gear g¹ fixed to the friction roller g,
which in turn drives a gear fixed to the friction roller i, whereby these two
rollers are driven in opposite directions, as indicated by the arrows marked on
them in Figs. 1 and 6. The rollers and i turn freely on studs projecting from
a lever I fulcrumed at 2 on a screw-stud fixed in the frame A, as best shown
in Fig. 7. The fulcrum of the lever being between the two rollers, the vibrating
of the lever in either direction serves to bring one or other of the two rollers into
contact with the frictional periphery of the wheel N, whereby the latter may
be driven in either direction according as the one or the other of the rollers is
pressed against it.
The lever I is connected by a link to the main operating lever L, which is
pivoted on a screw-stud at its left-hand end, and plays at its right-hand end between
two screw stops b¹ 61. This lever L is acted upon by the regulating electro-
magnet M which is preferably in the form of a solenoid, the movable core M¹ of which
is connected by a link to one side of the lever, while to the opposite side of the
lever is connected a retracting spring S which is adjustable by a screw-stem and nuts
in the usual manner.
The operation is as follows: During the normal running of the dynamo, the
retractive pull of the spring S is exactly counterbalanced by the attraction of the
solenoid M for its core, and the lever L occupies the mid-position shown in Fig. 1.
In case of an increase of resistance on the circuit, the consequent decrease of
current weakens the solenoid M, and the spring pulls the lever L downwardly,
its motion being communicated through the link to the lever I, whereby the
latter is tilted in such direction as to bring the friction roller g against the periphery
of the friction wheel N, whereby this wheel is driven in the direction of the arrow z
in Fig. 6, and its motion is communicated to the wheel c, which is driven in the.

page_text: direction of the arrow ¹ and which turns the shaft J and the pinions jj' in the same
direction, as indicated by the arrow in Fig. 2, whereby the brush-yokes are moved
and the brushes are carried towards the position of maximum current. This move-
ment of the brushes causes them to take off continually a larger current, until the
normal volume of current is restored to the circuit, whereupon the regulating magnet
or solenoid M resumes its normal energy and lifts the lever L again to its mid-position,
thereby moving the friction roller g out of contact with the wheel N and stopping the
further movement of the brushes. Should the momentum of the parts have carried
the brushes too far, or should any change occur in the circuit whereby the current
is too strong, the regulating magnet will be energized to above the normal and its
pull will overcome that of the spring S, so that it will lift the lever L to above its
mid-position and will consequently move the friction roller into contact with the
wheel N, thereby rotating the latter in the opposite direction and communicating this
movement to the brush-yokes, whereby the latter are moved so as to carry the brushes
toward the minimum line yy, which movement continues until the current on the line
is thereby so far decreased as to reduce the regulating magnet M to its normal
excitation, whereupon it relaxes its pull and the lever is restored to its normal
position. The regulator thus compensates for any change occurring in the resistance
of the circuit as well as for variations in the current due to an increase or decrease in
the speed of the machine.
It is more important that an automatic regulator shall act quickly to reduce the
current in case of a considerable reduction in the resistance of the circuit, than that
it shall quickly build up the current in case of a considerable increase in
resistance, since an excessive current is attended with considerable danger to the
dynamo and lamps. For this reason the regulator is constructed to be driven at a
higher speed to cut down the current than to increase it. This result is accom-
plished by driving the friction roller i at a surface-speed faster than that of the
friction roller g.
This may be accomplished either by making the gear smaller
than the gear g¹, or by making the friction roller i larger than the roller g, or by
preference by a combination of both methods, as in the construction shown (see
Figs. 6 and 7).
In case the dynamo is overloaded,-that is to say, in case the resistance on
the circuit is so great that the dynamo at the speed it may be running is unable,
when the brushes are at the maximum position, to generate sufficient electro-motive
force to supply the normal current against this resistance, the regulator will
constantly strive to carry the brushes beyond the maximum position. Since. the
movement of the brushes beyond the maximum would carry them to where they
would take off less current, it is necessary that means shall be provided for pre-
venting this result. This means consists of a separable connection in the shifting
mechanism, or between the shifting mechanism (or the friction wheel N thereof)
and the brushes, constructed to be operated by a stop when the brushes reach the
limit of their movement, and thereby to disconnect the shifting mechanism from
the brushes, so that the subsequent movement of the shifting mechanism shall be
impotent to carry the brushes too far. This disengagement might be effected in
various ways by means of any of several known kinds of clutches or throw-off
movements, but is preferably effected by the constructionof friction-clutch shown. This
clutch consists of a disk 6 fixed on the shaft J, and having two friction-pawls d and e
pivoted to it, which are pressed by a spring, so that their outer ends engage frictionally
a flange c', formed on the gear-wheel c, which wheel turns loosely on the shaft.
The two pawls engage in opposite directions, so that normally the rotation of the
wheel in either direction is transmitted through one pawl or the other to the disk b
and shaft J. The pawls have arms d' e' projecting from them. When the brushes
reach the maximum position the arm d (moving in the direction of arrow ' in
Fig. 6) strikes a stop in (which may be the stud on which the gear, turns, as shown,
or it may be a separate pin), which arrests the pawl and slightly tilts it, so that its
frictional face is disengaged from the inner surface of the Hange c', as shown in
Fig. 7. The continued notion of the wheel c is no longer communicated to the

page_text: disk band shaft J, but so long as the machine remains overloaded the wheels N f
and c continue to revolve freely in the direction of the arrows in Fig. 7, the
flange slipping against the frictional surface of the pawl c. The instant,
however, that the current rises above the normal, so that the wheels Nfc commence
to revolve in the opposite direction, the pawl e bites or engages with the flange c' and
the motion is immediately communicated to the brushes to carry them away from
the maximum position and reduce the current. Hence the disconnection of the
gearing to prevent carrying the brushes bevond the maximum does not prevent
their being instantly shifted in the opposite direction when necessary to reduce the
current.
The proportions of the pinions j j₁ to the sectors h' are such that the shaft J
executes a little less than one revolution in shifting the brushes from the
maximum to the minimum positions; hence when the brushes reach the minimum
position the pawl e is thrown out of engagement by the abutment of its arm e¹
against the stop m, whereby in like manner the regulator is prevented from carrying
the brushes beyond the minimum.
The following adjustments are provided: The friction wheel N is made adjustable
toward and from the friction rollers gi by being mounted on a bracket N', which is
fastened to the end frame A by tap-screws passing through elongated holes or slots
in its base, whereby by loosening these screws the bracket may be moved toward or
from the friction rollers, carrying the wheel N with it. The link is made in two
parts screwing together, so that its length may be adjusted to adjust the relative
positions of the levers L and I, in order to enable the rollers g and i to be adjusted
to positions equally distant from the surface of the wheel N when the lever L is in its
mid-position. In addition there are the usual adjustments for the tension of the
spring S and for the play of the lever L. The adjustment of the bracket N serves to
compensate for wear not only of the friction wheel, but also of the friction rollers if
both wear alike. If they wear differently adjustment therefor may be made by
elongating or shortening the link 1. The adjustment of the bracket N' is in such
direction as to move the pinion f2 tangentially to the gear f so that its mesh therewith
is not impaired.
This improved regulator has the advantages of great simplicity and cheapness of
construction, af perfect accessibility of parts, of abundant provision for all necessary
adjustments both in the original construction and for taking up subsequent wear, of
great lightness of parts, so that their momentum is not liable to carry the brushes too
far, and of providing improved means for preventing the movement of the brushes
beyond the maximum. This last feature is of especial importance, since by the present
invention the liability of injury to the apparatus in the hands of careless and meddlesome
persons is greatly reduced.
In the practical operation of this regulator under some conditions, and notably
when a regulating movement occurs at a time when the dynamo is supplying a much
smaller number of lamps than its full capacity, the regulator, by reason of its great
sensitiveness, will act so quickly and forcibly that the momentum of the shifting
mechanism will carry the brushes not merely to the position at which they will restore
the current to the normal volume, but somewhat beyond that position, thereby
establishing a current fluctuation of opposite character to that which was being com-
pensated for, and which gives rise to a new compensating movement of the regulator
in the opposite direction, and so on. Usually the brushes will come to rest in the
exact position after a very few such "rocking movements," so that these are not
objectionable, but under some circumstances the regulator will maintain an almost
incessant rocking movement of the brushes. This could be avoided by making the
regulator less sensitive, but it is preferable to employ the means shown in Figs. 6
and 9, which consists of a retarding device applied to the shifting mechanism to resist
any undue movements thereof due to its momentum. This retarding device consists
preferably of a fan, O, geared to the friction-wheel N, or other part of the shifting
mechanism, so as to be rotated thereby and so that it applies a certain degree of drag
or retardation to the shifting mechanism. The fan is geared to the shifting mechanism

page_text: through some kind of frictional connection adapted to slip in case of a sudden move-
ment of the shifting mechanism, so that it shall not act to retard the latter when the
regulator acts suddenly to compensate for an extreme change in the circuit. Preferably
the fan-spindle is formed with a friction-roller k, which is pressel into very light
tractive contact with the frictional periphery of the wheel N. The friction-wheel is
elastically mounted, since the fan-spindle turns on an elastic pin k', fixed to a base-
plate 2. The adjustment of the frictional contact is effected by moving this base-plate
toward or from the wheel N by means of the slotted screw holes engaged by its
fastening screws.
While starting the dynamo, and until it attains full speed, it is desirable to throw
the regulator out of action. It is also desirable at times to render it inoperative when
the machine is overloaded, that is, when feeding more than the normal number of
lamps. To this end a movable stop is provided, which can be moved by hand into
such position as to receive the tension of the retracting spring S and prevent it from
throwing the shifting mechanism into action. This stop is constructed preferably as
a pivoted dog, P, shown in Figs. 6 and 9, which normally hangs down, but when the
lever L is lifted and the dog turned up beneath it, it holds the lever in mid-position
against the pull of the spring and prevents the roller y from driving the wheel N.
The regulator will thus be, held out of action as long as the current is beneath the
normal, but as soon as the magnet M attains its normal excitation and lifts the lever L,
the dog P, being thereby freed, falls back and the regulator is automatically put into
normal operation.
The regulating electro-magnet is of novel construction, shown in Figs. 9, 10 and 11.
It is of the type having fixed coils wound on spools and having a U-shaped core, the
legs of which enter the coils and are attracted into them. Whenever a regulating
magnet is placed on or close to the dynamo, as is preferable, its core is magnetized by
induction from the field-magnet, so that one of the poles of the core exhibits a
preponderating polarity as compared with the other, and is more strongly attracted
into the coil, so that the attractive pull of the coils upon the core is unequal and
wanting in sensitiveness. The present invention corrects this defect by reducing the
mass of the pole which exhibits the greatest magnetization sufficiently to compensate
therefor and establish an equilibrium of attraction between the two poles. This
reduction of the mass is preferably effected by boring out the preponderating pole
tubularly, as shown. The sensitiveness of the magnet is also increased by slitting the
polar ends of the core, thereby subdividing each end into two or more poles, which,
being of like polarity, repel each other and thereby tend to demagnetize one another,
so that upon the reduction of the current in the coils, the retraction of the core occurs
more promptly. The sensitiveness of the magnet is further increased by providing
the upper ends of the core with anti-friction wheels or disks pivoted in the slits
therein and projecting slightly beyond the periphery of the core, as shown best in
Fig. 9, so that they roll against the inner surface of the spool and keep the core out of
contact therewith, thereby preventing its displacement and avoiding frictional resistance
to its movement.
The purpose of the supplemental brushes G G will now be explained. In small
dynamos, or those generating a low electro-motive force, these supplemental brushes
with their yoke H and pinion j' may be omitted. But with dynamos generating a
considerable electro-motive force, it is found that with only the single pair of main
brushes, F F, there is an objectionable degree of flashing and burning at the com-
mutator. To prevent this it is essential to enlarge the collecting extent of the brushes
so that they shall bridge over a number of commutator segments. For this purpose
the supplemental brushes are applied in advance of the main brushes and connected
electrically to them, so that the armature coils corresponding to the intervening
seginents, and which are practically out of action during the instant that the segments
pass over the intervening spaces between the brushes, are short circuited. The number
of segments requiring to be thus bridged over is greatest in the maximum and least in
the minimum position, as shown in Fig. 5, where the brushes are shown in full lines
at the minimum and in dotted lines at the maximum position. Heretofore, in practice,

page_text: the main and supplemental brushes have been carried both by one holder, the supple-
mental brushes being movable therein and the attendant being required to slide them
in or out from time to time, whenever he observed any flashing at the commutator.
According to the present invention this relative adjustment of the main and supple-
mental brushes is effected automatically, and always in correct proportion, by reason
of the differential gearing employed, consisting of the pinions jj meshing with the
sectors h h¹.
This automatic and proportional adjustment of the respective pairs of brushes, by
moving them at differential speeds in the same direction, is a novel feature as applied
to dynamos having armatures of the "closed coil" type, such as the Gramme ring or
.Siemens drum armatures. It has been proposed, as applied to armatures of the "open
coil"
type, in which, however, contrary conditions exist, the respective brushes, in
order to prevent flashing, being necessarily moved simultaneously in opposite directions
instead of at differential speeds in the same direction.
To apply this new regulator to dynamos generating constant potential, the supple-
mental brushes G G will be omitted, and the regulating magnet will be shunt-wound
and installed in multiple are or derivation, as will be apparent to those skilled in the
.electrical art.
The part of the invention relating to the construction of the armature will now be
.described.
This part of the invention is applicable to armatures of the Gramme ring type, and
its object is to provide a practical construction which will enable the armature to be
made in sections, whereby are secured the important advantages of greater ease and
cheapness in winding the coils upon the core, and greater facility in repairing or
renewing a defective coil.
To this end the armature-core is divided at intervals into sections which overlap
-one another at their joints, each section being wound with a suitable number of coils,
so that any section may be removed from the armature in order to repair, replace, or
rewind any of the coils. The sections are connected together and mounted upon the
armature-shaft by means of a spider or spiders fixed on the shaft and having carrier
arms engaging the sections at or near their joints.
Fig. 12 is a diametrical section of the armature on the line 12-12 in Fig. 13, which
latter is an end view partly in section on the line 13-13 in Fig. 12, and partly
dissected to show the construction. Figs. 14, 15 and 17 show details of the armature
detached, and Fig. 16 is a perspective view of one of the sections of the core.
R designates the soft iron core of the armature, which is made in the form of a
ring and subdivided into any suitable number of sections or segments rr, six being
shown. These sections or segments are supported on a spider which is fixed on the
armature shaft K, and is constructed preferably in two parts, Q and Q', each of which
has as many radial arms as there are sections rr of the armature core, and their arms
engage the core at or adjacent to the joints between the sections. Each arm is formed
with a head 9 extending longitudinally within the core along the joint between the
sections to support the latter in assembling them, and with a jaw q' extending around
one end of the core and terminating against its exterior with a beveled inner face, as
shown in Fig. 12. The main spider has a long hub which is keyed on the shaft,
and the hub of the spider Q¹ fits over the reduced end of this hub and is fastened
thereon by a nut n. By screwing up this nut the two spiders are drawn together and
the beveled faces of the jaws force the core sections inwardly into intimate contact
with one another at their joints. The heads are turned to a slightly smaller
diameter than the interior of the core to admit of the core sections being thus forced
together.
The core sections rare made to overlap at their joints, or, in other words,
are united by means of scarf joints. The purpose of this is two-fold: first, to afford
an extended bearing surface at the joint in order that the metallic contact of the
two sections may be as complete as possible, whereby the magnetic conductivity
of the core is preserved unimpaired; and second, to provide against the tendency
of centrifugal force to spread the sections apart and thereby impair their magnetic

page_text: contact. To accomplish, the latter purpose it is essential that the sections shall be
supported at or near their junction by means of supports engaging the outer side
of the section whose end laps over and is exterior to the end of the other section.
The hooked jaws q' constitute these exterior supports in the construction shown.
The effect of centrifugal force is to throw the inner overlapping end into firmer
contact with the outer overlapping end, since the outward tendency of the latter
is resisted by its supports.
The preferred form of scarf joint is that shown in Fig. 13, where the end of
each section is formed with a projection p entering a groove in the end of the
adjoining section between a long projections and a short projection s'. The
projections p and overlap for a considerable distance, the outer projection being
supported by the hooked jaws g. The projections brings the joint on the inner
side radially opposite the portion of the outer projections where the support is
applied, so that the heads q on the spider arms, which extend almost uninterruptedly
the entire length of the core, may bridge over the joint between the sections, and
thus support both ends of each section while assembling them.
The core sections might be of solid iron, but preferably they are built up of
insulated laminæ in order to suppress Foucault currents. To this end sheets or
leaves t of the shape shown in Fig. 15, are stamped from thin sheet-iron, an a.
sufficient number of these leaves is superposed, being separated by suitable insulation
such as varnish. or thin paper, or oxide, whereby a sufficient thickness of laminæ
is acquired to impart the desired length to the core. Against the opposite sides
of the laminae are placed iron plates t'', and the laminæ and plates are fastened,
together to form a solid block by passing insulated bolts u u through them, between
the heads and nuts of which the opposite plates t¹ are drawn together and the
intervening laminæ are compressed into a rigid mass. One of the sections thus.
completed is shown in Fig. 16.
The sections thus made are complete except that their opposite ends or sides & th
are angular and consequently unfitted for winding the coils upon. It is customary
to construct Gramme ring cores with their opposite sides or ends rounded in
approximately semi-circular form. To accomplish this, balf-round caps, vv, are.
applied against the opposite sides of the sections. These caps, one of which is
shown detached in Fig. 17, are of arc shape, corresponding in curvature to the
core sections, and are of such length as to extend from one spider arm to the next,
so that when in place their ends abut against the radial side surfaces of the spider
arms. These caps are hollowed out on their flat sides partly to reduce the metal
and prevent Foucault currents, but chiefly to afford room for the heads and nuts.
of the bolts u u. The caps are fastened in place by screws passed through holes
in them and screwing into holes in the plates t¹. One end of each cap is made
solid or flat on its inner side, so that when drawn to place by its screws it overlaps
the side of the projection of the next section. The opposite end of the cap is
thickened at v² on one side to overlap the side of the projection s on the adjoining
section. By constructing the caps to thus partially overlap at either one or both ends
the joints of the sections, the latter are held in proper relative position at their
joints, and their displacement laterally or in direction parallel to the rotative axis
is prevented.
The sections having been provided with their caps v, as described, are covered
with insulation, w, as usual, and the winding W of the armature is then applied
to them either by winding the coils directly on the sections or by winding them
separately and slipping them onto the sections. In the drawing twenty coils are-
shown applied on each section, but this number may be varied as desired: Any
number of coils from one up to the greatest practicable number may be applied.
to each section. The coils having been applied to the sections, insulating plates w
(one of which is shown detached in Fig. 14), are applied on their opposite ends,
and the sections are fitted together end to end to form a complete ring.
spider being in place on the shaft, and the spider Q₁ removed, the armature is
slipped over the spider Q so that its arms enter between the insulating plates w¹ w¹..
The

page_text: The spider Qis then slipped on with its arms entering between the insulating
plates, and the nut is screwed on, which forces this spider toward the spider
and causes the beveled inner faces of the jaws q¹ 9' to engage the sides of the
sections and draw them all powerfully and uniformly toward the centre, thereby
crowding the scarf joints into intimate magnetic contact and drawing the core to a
perfect circle. Subsequently the usual exterior bands of wire p₁ are applied to
prevent displacement of the armature winding by centrifugal force.
The several armature coils are wound with their opposite ends projecting on the
side of the armature towards the commutator E, and when the latter is subsequently
applied these ends are connected to the successive commutator segments in the
usual manner well known in the construction of armatures of the Gramme type.
The construction of the commutator is well known and requires no description.
Attempts have heretofore been made to sub-divide armature cores into sections, but
this has usually been done by radial sub-division, so that the effect of centrifugal force
is to tend to spread the sections apart at their joints when running at high speeds,
thereby imparing the magnetic conductivity of the core and reducing the efficiency
of the armature, as well as causing excessive sparking at the commutator. By the
present invention this defect is entirely overcome by constructing each section to
overlap the next by extending outside of it, and supporting the core at these exterior
overlapping portions.
The several features of this invention are susceptible of considerable modification
in matters of detail or construction, as will be apparent to those skilled in the electrical
and mechanic arts. Obviously such modifications may be made without departing.
from the essential features of the invention. Furthermore, certain parts or features.
of the invention may be omitted in practice, without thereby impairing such other
parts or features as may be retained.
Dated the 31st day of December 1800.
J. C. MEWBURN,
55 & 56, Chancery Lane, London, Patent Agent.
COMPLETE SPECIFICATION.
Improvements in Dynamo-electric Machines, in part applicable to
Electro-motors.
I, JAMES JOHN Wood of No. 126 Cambridge Place, Brooklyn, in the State of New
York, United States of America, Electrical Engineer, 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 chiefly to dynamo-electric machines, commonly called
"dynamos." It consists in part of improvements in automatic regulators for governing
dynamo machines, in order that they shall generate uniform currents under all
circumstances. Such regulators are most commonly employed with dynamos of the
class generating a constant current of varying electro-motive force, such as is used
for feeding arc lamps in series. This part of the invention is applicable also to
regulators for dynamos generating a constant electro-motive force or difference of
potentials with a current of varying volume, such as are used principally for incandescent
lighting. Another part of the invention consists of improvements in the armatures of
dynamos, the improvements pertaining chiefly to the armature core and to the
supporting spider. This part of the invention is applicable also to electro-motors.
Figs. 1, 2 and 3 of the drawings which accompanied my Provisional Specification
and to which I will refer in this Specification are general views of a dynamo to which
these improvements are applied, Fig. 1 being an elevation of one end showing the
regulating mechanism, Fig. 2 being a vertical section on the line 2-2 in Fig. 3,
showing the commutator brushes and means for moving them, and Fig. 3 being a side
elevation partly in vertical mid-section.
Figs. 4 to 11 inclusive are various views showing the automatic regulator more in

page_text: detail; Figs. 12 to 17 inclusive, are views showing the armature, and illustrating in
detail the construction of its core and supporting spider and accessory parts.
The automatic regulator will first be described. This regulator is of that class
wherein the regulation is effected by an adjustment or shifting of the commutator brushes
around the commutator. In dynamo machines having armatures of the Gramme ring
or Siemens drum type, there are two diametrically opposite points on the commutator
where the segments exhibit the greatest difference of potentials, and when the
commutator brushes are applied at these points they take off the maximum current.
This position is hence called the "maximum position," and a line drawn through it,
denoted at in Figs. 2, 5 and 7, is called the "maximum line." By shifting the
brushes through an arc of about 60 degrees, they are brought to a position where the
current is at the minimum, and which is denote: by the "minimum line" y in
Figs. 2 and 5. Whenever, in the operation of the dynamo, the current rises above or
falls below the normal, this can be compensated for by moving the brushes toward the
minimum or toward the maximum position.
Automatic regulators of this class have heretofore been of two kinds: 1st, those in
which the brush-carrier or yoke is connected to the moving member of an electro-
magnet or solenoid, so that the two brushes derive their movements from, and move
proportionally to, the movements of this member; and 2nd, those in which the brushes
are moved by a shifting mechanism which is driven in either direction from a source
of power, and the clutching of which to the source of power in one direction or the
other is effected by the movements of the armature or moving member of the regulating
electro-magnet. The present invention is an improvement upon regulators of the
latter class, and has for its object to render such regulators more sensitive, more
durable, and more easily and perfectly adjustable, and to provide improved means for
preventing the undue action of the regulator when the dynamo is overloaded..
The general construction of dynamos shown in the drawings is of a well-known
type, its field-magnet consisting of upright end frames A A, connected by horizontal
bars constituting the cores of the exciting coils B B, between which, and at the
middle of these bars, are fixed the pole-pieces C C. The armature D and its com-
mutator E are fixed on a shaft K, which passes through the middle of the end frames
and projects at one end, on which is fixed a driving pulley. F F are the main
commutator brushes, and G G are the auxiliary or suppleinental commutator brushes.
M is the regulating electro-magnet. The machine is self-exciting, its field-magnet
coils being wound in series. The circuit extends, as usual in such machines, from the
positive commutator brush or brushes, through the coil of the regulating magnet M,
and thence through the successive field-coils, and out at the positive binding-
post, over the line circuit, and back through the negative binding-post to the negative
brushes.
The main commutator brushes F F are carried as usual in insulate
mounted on opposite arms of the brush-carrying yoke or lever H, which turns
inward prolongation or boss a formed on or fixed to the inner side of the end fra
(see Fig. 4), as usual.. The supplemental brushes G G are carried by insul
holders mounted on opposite arms of a supplemental carrier-yoke H' mounted in
same way as the yoke H. These brush-carriers H and H' are formed respectively w
toothed sectors and h' which mesh respectively with pinions jj' fixed on a shaft
which passes through the main frame A, as shown in Fig. 4. On the outer end
this shaft is mounted a gear-wheel c connected to the shaft through a clutch bde,
which will presently be described. This gear-wheel c is geared or connected directly
or indirectly to a friction-wheel N. This connection is preferably made through the.
medium of a pinion with which the gear c meshes, and which is fixed to a gear-
wheel, the teeth of which mesh with a pinion f2 fixed on the hub of wheel N.
The wheel N has a frictional surface or tread upon its periphery, and close to,
but (preferably) normally just out of contact with, this surface stand two friction
rollers g and i which are revolved continuously in opposite directions from a source of
power, preferably by being geared to the armature shaft K. A gear-wheel a' fixed on
the end of the armature shaft, drives a gear g¹ fixed to the friction roller g, which in
13

page_text: a
turn drives a gear fixed to the friction roller whereby these two rollers are driven
in opposite directions, as indicated by the arrows marked on them in Figs. 1 and 6.
The rollers and i turn freely on studs projecting from a lever 1 fulcrumed at is on a
screw-stud fixed in the frame A, as best shown in Fig. 7. The fulcrum of the lever
being between the two rollers, the vibrating of the lever in either direction serves to
bring one or other of the two rollers into contact with the frictional periphery of the
wheel N, whereby the latter may be driven in either direction according as the one or
the other of the rollers is pressed against it.
The lever I is connected by a link to the main operating lever L, which is pivoted
on a screw-stud at its left-hand end, and plays at its right-hand end between two
screw stops. This lever L is acted upon by the regulating electro-magnet M
which is preferably in the form of a solenoid, the movable core M of which is con-
nected by a link to one side of the lever, while to the opposite side of the lever is
connected a retracting spring S which is adjustable by a screw-stem and nuts in the
usual manner.
The operation is as follows: During the normal running of the dynamo, the
retractive pull of the spring S is exactly counterbalanced by the attraction of
the solenoid M for its core, and the lever Loccupies the mid-position shown in Fig. 1.
In case of an increase of resistance on the circuit, the consequent decrease of current.
weakens the solenoid M, and the spring S pulls the lever L downwardly, its motion
being communicated through the link 7 to the lever I, whereby the latter is tilted in such
direction as to bring the friction roller g against the periphery of the friction wheel N,
whereby this wheel is driven in the direction of the arrow in Fig. 6, and its motion
is communicated to the wheel c, which is driven in the direction of the arrow ¹ and
which turns the shaft J and the pinions jj in the same direction, as indicated by the
arrow in Fig. 2, whereby the brush-yokes are moved and the brushes are carried
towards the position of maximum current. This movement of the brushes causes them
to take off continually a larger current, until the normal volume of current is restored
to the circuit, whereupon the regulating magnet or solenoid M resumes its normal
energy and lifts the lever L again to its mid-position, thereby moving the friction
roller 9 out of contact with the wheel N and stopping the further movement of the
brushes. Should the momentum of the parts have carried the brushes too far, or
should any change occur in the circuit whereby the current is too strong, the
regulating magnet will be energized to above the normal and its pull will overcome
that of the spring S, so that it will lift the lever L to above its mid-position and will
consequently move the friction roller i into contact with the wheel N, thereby rotating
the latter in the opposite direction and communicating this movement to the brush-
yokes, whereby the latter are moved so as to carry the brushes toward the minimum
line y y, which movement continues until the current on the line is thereby so far
decreased as to reduce the regulating magnet M to its normal excitation, whereupon
it relaxes its pull and the lever L is restored to its normal position. The regulator
thus compensates for any change occurring in the resistance of the circuit as well as
for variations in the current due to an increase or decrease in the speed of the
machine.
It is more important that an automatic regulator shall act quickly to reduce the
current in case of a considerable reduction in the resistance of the circuit, than that it
shall quickly build up the current in case of a considerable increase in resistance, since
an excessive current is attended with considerable danger to the dynamo and lamps.
For this reason the regulator.is constructed to be driven at a higher speed to cut down
the current than to increase it. This result is accomplished by driving the friction
roller at a surface-speed faster than that of the friction roller g. This may be
accomplished either by making the gear i¹ smaller than the gear g¹, or by making the
friction roller larger than the roller g, or by preference by a combination of, both
methods, as in the construction shown (see Figs. 6 and 7).
-
In case the dynamo is overloaded, that is to say, in case the resistance on the
circuit is so great that the dynamo at the speed it may be running is unable, when
the brushes are at the maximum position, to generate sufficient electro-motive force to

page_text: supply the normal current against this resistance, the regulator will constantly strive
to carry the brushes beyond the maximum position. Since the movement of the
brushes beyond the maximum would carry them to where they would take off less
current, it is necessary that means shall be provided for preventing this result. This
means consists of a separable connection in the shifting mechanism, or between the
shifting. mechanism (or the friction wheel N thereof) and the brushes, constructed
to be operated by a stop when the brushes reach the limit of their movement, and
thereby to disconnect the shifting mechanism from the brushes, so that the subsequent
movement of the shifting mechanism shall be impotent to carry the brushes too
far. This disengagement might be effected in various ways by means of any of
several. known kinds of clutches or throw-off movements, but is preferably effected
by the construction of friction-clutch shown. This clutch consists of a disk b fixed on
the shaft J, and having two friction-pawls d and e pivoted to it, which are pressed by
a spring, so that their outer ends engage frictionally a flange c', formed on the gear-
wheel c, which wheel turns loosely on the shaft. The two pawls engage in opposite
directions, so that. normally the rotation of the wheel c in either direction is trans-
mitted through one pawl or the other to the disk b and shaft J. The pawls have
arms de projecting from them. When the brushes reach the maximum position
the arm d' (moving in the direction of arrow 2¹ in Fig. 6) strikes a stop m (which
may be the stud on which the gearf turns, as shown, or it may be a separate pin),
which arrests the pawl and slightly tilts it, so that its frictional face is disengaged
from the inner surface of the flange c', as shown in Fig. 7. The continued motion
of the wheel c is no longer communicated to the disk b and shaft J, but so long as the
machine remains overloaded the wheels N and c continue to revolve freely in the
direction of the arrows in Fig. 7, the flange c' slipping against the frictional surface
of the pawl e.
The instant, however, that the current rises above the normal, so that
the wheels Nfc commence to revolve in the opposite direction, the pawl bites or
engages with the flange cand the motion is immediately communicated. to the
brushes to carry them away from the maximum position and reduce the current.
Hence the disconnection of the gearing to prevent carrying the brushes beyond the
maximum does not prevent their being instantly shifted in the opposite direction
when necessary to reduce the current.
"
The proportions of the pinions jj' to the sectors hh' are such that the shaft J
executes a little less than one. revolution in shifting the brushes from the maximum
to the minimum positions; hence when the brushes reach the minimum position the
pawle is thrown out of engagement by the abutment of its arm e' against the stop in,
whereby in like manner the regulator is prevented from carrying the brushes beyond
the minimum.
The following adjustments are provided: The friction wheel N is made adjustable
toward and from the friction rollers gi by being mounted on a bracket N', which is
fastened to the end frame A by tap-screws passing through elongated holes or slots in
its base, whereby by loosening these screws the bracket may be moved toward or from
the friction rollers, carrying the wheel N with it. The link is made in two parts
screwing together, so that its length may be adjusted to adjust the relative positions of
the levers Land I, in order to enable the rollers g and i to be adjusted to positions
equally distant from the-surface of the wheel N when the lever L is in its mid-
position. In addition there are the usual adjustments for the tension of the spring S
and for the play of the lever L. The adjustment of the bracket N' serves to com-
pensate for wear not only of the friction wheel, but also of the friction rollers if. both
wear alike. If they wear differently adjustment therefor may be made by elongating
or shortening the link l. The adjustment of the bracket N¹ is in such direction as to
move the pinion 2 tangentially to the gear so that its mesh therewith is not
impaired.
This improved regulator has the advantages of great simplicity and cheapness of
construction, of perfect accessibility of parts, of abundant provision for all necessary
adjustments both in the original construction and for taking up subsequent wear, of
great lightness of parts, so that their momentum is not liable to carry the brushes too
I

page_text: far, and of providing improved means for preventing the movement of the brushes
beyond the maximum. This last feature is of especial importance, since by the present
invention the liability of injury to the apparatus in the hands of careless and meddle-
some persons is greatly reduced.
In the practical operation of this regulator under some conditions, and notably when
a regulating movement occurs at a time when the dynamo is supplying a much smaller
number of lamps than its full capacity, the regulator, by reason of its great sensi-
tiveness, will act so quickly and forcibly that the momentum of the shifting mechanism
will carry the brushes not merely to the position at which they will restore the
current to the normal volume, but somewhat beyond that position, thereby establishing
a current fluctuation of opposite character to that which was being compensated for,
and which gives rise to a new compensating movement of the regulator in the
opposite direction, and so on. Usually the brushes will come to rest in the exact
position after a very few such " rocking movements," so that these are not objectionable,
but under some circumstances the regulator will maintain an almost incessant rocking
movement of the brushes. This could be avoided by making the regulator less
sensitive, but it is preferable to employ the means shown in Figs. 6 and 9, which
consists of a retarding device applied to the shifting mechanism to resist any undue
movements thereof due to its momentum. This retarding device consists preferably
of a fan, O, geared to the friction-wheel N, or other part of the shifting mechanism,
so as to be rotated thereby and so that it applies a certain degree of drag or retardation
to the shifting mechanism. The fan is geared to the shifting mechanism through
some kind of frictional connection adapted to slip in case of a sudden movement of
the shifting mechanism, so that it shall not act to retard the latter when the regulator
acts suddenly to compensate for an extreme change in the circuit. Preferably the
fan-spindle is formed with a friction-roller k, which is pressed into very light tractive
contact with the frictional periphery of the wheel N. The friction-wheel is elastically
mounted, since the fan-spindle turns on an elastic pin ¹, fixed to a base-plate k².
The adjustment of the frictional contact is effected by moving this base-plate
toward or from the wheel N by means of the slotted screw-holes engaged by its
fastening screws.
While starting the dynamo, and until it attains full speed, it is desirable to throw
the regulator out of action. It is also desirable at times to render it inoperative when
the machine is overloaded, that is, when feeding more than the normal number of
lamps. To this end a movable stop is provided, which can be moved by hand into
such position as to receive the tension of the retracting spring S and prevent it from
throwing the shifting mechanism into action. This stop is constructed. preferably as
a pivoted dog, P, shown in Figs. 6 and 9, which normally hangs down, but when the
lever L is lifted and the dog turned up beneath it, it holds the lever in mid-position
against the pull of the spring and prevents the roller from driving the wheel N.
The regulator will thus be held out of action as long as the current is beneath the
normal, but as soon as the magnet M attains its normal excitation and lifts the lever L,
the dog P, being thereby freed, falis back and the regulator is automatically put into
normal operation.
The regulating electro-magnet is of novel construction, shown in Figs. 9, 10
and 11. It is of the type having fixed coils wound on spools and having a U-shaped
core, the legs of which enter the coils and are attracted into them. Whenever a
regulating magnet is placed on or close to the dynamo, as is preferable, its core is
magnetized by induction from the field-magnet, so that one of the poles of the core
exhibits a preponderating polarity as compared with the other, and is more strongly
attracted into the coil, so that the attractive pull of the coils upon the core is unequal
and wanting in sensitiveness. The present invention corrects this defect by reducing
the mass of the pole which exhibits the greatest magnetization sufficiently to com-
pensate therefor and establish an equilibrium of attraction between the two poles.
This reduction of the mass is preferably effected by boring out the preponderating pole
tubularly, as shown. The sensitiveness of the magnet is also increased by slitting the
polar ends of the core, thereby subdividing each end into two or more poles, which,

page_text: being of like polarity, repel each other and thereby tend to demagnetize one another,
so that upon the reduction of the current in the coils, the retraction of the core occurs
more promptly. The sensitiveness of the magnet is further increased by providing the
upper ends of the core with anti-friction wheels or disks pivoted in the slits therein
and projecting slightly beyond the periphery of the core, as shown best in Fig. 9, so
that they roll against the inner surface of the spool and keep the core out of contact
therewith, thereby preventing its displacement and avoiding frictional resistance to its
movement.
The purpose of the supplemental brushes G G will now be explained. In small
dynamos, or those generating a low electro-motive force, these supplemental brushes
with their yoke H and pinion j¹ may be omitted. But with dynamos generating. a
considerable electro-motive force, it is found that with only the single pair of main
brushes, FF, there is an objectionable degree of flashing and burning at the com-
mutator. To prevent this it is essential to enlarge the collecting extent of the brushes
so that they shall bridge over a number of commutator segments. For this purpose
the supplemental brushes are applied in advance of the main brushes and connected
electrically to them, so that the armature coils corresponding to the intervening
segments, and which are practically out of action during the instant that the segments
pass over the intervening spaces between the brushes, are short circuited. The number
of segments requiring to be thus bridged over is greatest in the maximum and least in
the minimum position, as shown in Fig. 5, where the brushes are shown in full lines
at the minimum and in dotted lines at the maximum position. Heretofore, in practice,
the main and supplemental brushes have been carried both by one holder, the supple-
mental brushes being movable therein and the attendant being required to slide them
in or out from time to time, whenever he observed any flashing at the commutator.
According to the present invention this relative adjustment of the main and supple-
mental brushes is effected automatically, and always in correct proportion, by reason
of the differential gearing employed, consisting of the pinions jj meshing with the
sectors h h¹.
This automatic and proportional adjustment of the respective pairs of brushes, by
moving them at differential speeds in the same direction, is a novel feature as applied
to dynamos having armatures of the "closed coil" type, such as the Gramme ring or
Siemens drum armatures. It has been proposed, as applied to armatures of the "open
coil "
type, in which, however, contrary conditions exist, the respective brushes, in
order to prevent flashing, being necessarily moved simultaneously in opposite directions
instead of at differential speeds in the same direction.
To apply this new regulator to dynamos generating constant potential, the supple-
mental brushes G G will be omitted, and the regulating magnet will be shunt-wound
and installed in multiple arc or derivation, as will be apparent to those skilled in the
electrical art.
The part of the invention relating to the construction of the armature will now be
described.
This part of the invention is applicable to armatures of the Gramme ring type, and
its object is to provide a practical construction which will enable the armature to be
made in sections, whereby are secured the important advantages of greater ease and
cheapness in winding the coils upon the core, and greater facility in repairing or
renewing a defective coil.
To this end the armature-core is divided at intervals into sections which overlap one
another at their joints, each section being wound with a suitable number of coils, so
that any section may be removed from the armature in order to repair, replace, or
rewind any of the coils. The sections are connected together and mounted upon the
armature-shaft by means of a spider or spiders fixed on the shaft and having carrie
arms engaging the sections at or near their joints.
Fig. 12 is a diametrical section of the armature on the line 12-12 in Fig. 13,
which latter is an end view partly in section on the line 13-13 in Fig. 12, and partly
dissected to show the construction. Figs. 14, 15 and 17 show details of the armature
detached, and Fig. 16 is a perspective view of one of the sections of the core.

page_text: .
R designates the soft iron core of the armature, which is made in the form of a
ring and subdivided into any suitable number of sections or segments rr, six being
:shown. These sections or segments are supported on a spider. which is fixed on the
armature shaft K, and is constructed preferably in two parts, Qand Q', each of which
has as many radial arms as there are sections r r of the armature core, and their arms
engage the core at or adjacent to the joints between the sections. Each arm is formed
with a head extending longitudinally within the core along the joint between the
sections to support the latter in assembling them, and with a jaw q! extending around
one end of the core and terminating against its exterior with a beveled inner face, as
shown in Fig. 12. The main spider Q has a long hub which is keyed on the shaft,
and the hub of the spider Q fits over the reduced end of this hub and, is fastened
thereon by a nut n. By screwing up this nut the two: spiders are drawn together
and the beveled faces of the jaws force the core sections inwardly into intimate contact
with one another at their joints. The heads y are turned to a slightly smaller diameter
than the interior of the core to admit of the core sections being thus forced
together.
The core sections are made to overlap at their joints, or, in other words, are
united by means of scarf joints. The purpose of this is two-fold: first, to afford an
extended bearing surface at the joint in order that the metallic contact of the two
sections may be as complete as possible, whereby the magnetic conductivity of the
core is preserved unimpaired; and second, to provide against the tendency of cen-
trifugal force to spread the sections apart and thereby impair their magnetic contact.
To accomplish the latter purpose it is essential that the sections. shall be: supported at
or near their junction by means of supports engaging the outer side of the section
whose end laps over and is exterior to the end of the other section. The hooked
jaws g constitute these exterior supports in the construction shown. The effect of
centrifugal force is to throw the inner overlapping end into firmer: contact with the
outer overlapping end, since the outward tendency of the latter is: resisted by its
supports.
The preferred form of scarf joint is that shown in Fig. 13, where the end of each
section is formed with a projection p entering a groove in the end of the adjoining
section between a long projections and a short projections. The projections p and s
overlap for a considerable distance, the outer projection.being supported by the hooked
jaws q. The projection s¹ brings the joint on the inner side radially opposite the
portion of the outer projections where the support is applied, so that the heads
the spider arms, which extend almost uninterruptedly the entire length of the core,
may bridge over the joint between the sections, and thus. support both ends of each
section while assembling them.
on
The core sections might be of solid iron, but preferably they are built up of
insulated laminæ in order to suppress Foucault currents. To this end. sheets or
leavest of the shape shown in Fig. 15, are stamped from thin sheet-iron, and a
sufficient number of these leaves is superposed, being separated by suitable insulation
such as varnish, or thin paper, or oxide, whereby a sufficient thickness of laminæ is
acquired to impart the desired length to the core. Against the opposite sides of the
laminæ are placed iron plates t¹ t', and the lamina and plates are fastened together to
form a solid block by passing insulated bolts u us through them, between the heads
and nuts of which the opposite plates t' are drawn together and the intervening lamina
are compressed into a rigid mass. One of the sections: thus completed is. shown
in Fig: 16.
The sections thus made are complete except that their opposite ends or sides t t¹ are
angular and consequently unfitted for winding the coils upon. It is customary to
construct Gramme ring cores with their opposite sides or ends rounded. in approxi-
mately semi-circular form. To accomplish this, half-round caps; vv,-are applied
against the opposite sides of the sections. These caps, one of which is shown detached
in Fig. 17, are of arc shape corresponding in curvature to the core sections, and are
of such length as to extend from one spider arm to the next, so that when. in place
their ends abut against the radial side surfaces of the spider arms. These caps are

page_text: hollowed out on their flat sides partly to reduce the metal and prevent Foucault
currents, but chiefly to afford room for the heads and nuts of the, bolts u u. The caps
are fastened in place by screws passed through holes in them and screwing into holes
in the plates t'. One end v¹ of each cap is made solid or flat on its inner side, so that.
when drawn to place by its screws it overlaps the side of the projection p of the next
section. The opposite end of the cap is thickened at v² on one side to overlap the side.
of the projection s on the adjoining section. By constructing the caps to thus partially
overlap at either one or both ends the joints of the sections, the latter are held in
proper relative position at their joints, and their displacement laterally or in direction
parallel to the rotative axis is prevented.
The sections having been provided with their caps v, as described, are covered
with insulation, wr, as usual, and the winding W of the armature is then applied to
them either by winding the coils directly on the sections or by winding them.
separately and slipping them onto the sections. In the drawing twenty coils are
shown applied on each section, but this number may be varied as desired. Any
number of coils from one up to the greatest practicable number may be applied to
each section. The coils having been applied to the sections, insulating plates w¹ (one
of which is shown detached in Fig. 14), are applied on their opposite ends, and the
sections are fitted together end to end to form a complete ring. The spider Q being
in place on the shaft, and the spider Qremoved, the armature is slipped over the
spider so that its arms enter between the insulating plates w¹ w'. The spider Qis
then slipped on with its arms entering between the insulating plates, and the nut n
is screwed on, which forces this spider toward the spider Q and causes the beveled
inner faces of the jaws 'g' to engage the sides of the sections and draw them all
powerfully and uniformly toward the centre, thereby crowding the scarf joints into
intimate magnetic contact and drawing the core to a perfect circle. Subsequently
the usual exterior bands of wire p' are applied to prevent dispiacement of the armature
winding by centrifugal force.
The several armature coils are wound with their opposite ends projecting on the
side of the armature towards the commutator E, and when the latter is sub-
sequently applied these ends are connected to the successive commutator segments
in the usual manner well known in the construction of armatures of the Gramme
type. The construction of the commutator is well known and requires no
description.
.Attempts have heretofore been made to sub-divide armature cores into sections, but
this has usually been done by radial sub-division, so that the effect of centrifugal
force is to tend to spread the sections apart at their joints when running at high
speeds, thereby impairing the magnetic conductivity of the core and reducing the
efficiency of the armature, as well as causing excessive sparking at the commutator.
By the present invention this defect is entirely overc me by constructing each section
to overlap the next by extending outside of it, and supporting the core at these
exterior overlapping portions.
. The several features of this invention are susceptible of considerable modification
in matters of detail or construction, as will be apparent to those skilled in the electrical
and mechanic arts. Obviously such modifications may be made without departing from
the essential features of the invention. Furthermore, certain parts or features of the
invention may be omitted in practice, without thereby impairing such other parts or
features as may be retained.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :
1. In a current regulator, a mechanism for shifting the commutator brushes between
their maximum and minimum positions, and an intervening separable connection -
consisting of a clutch through which said mechanism transmits motion to the brushes,
with a stop.constructed to disconnect said clutch when the brushes reach the limit of
:

page_text: their movement, whereby the mechanism is rendered impotent to carry the brushes
too far, in substantially the manner described.
2. The particular features of construction of said separable connection, consisting
of driving and driven parts, friction pawls carried by the driven part, and through
which the opposite movements are communicated to it from the driving part, and a
stop (or stops) arranged to arrest one or other of said pawls when the driven part
reaches the position corresponding to either limit of movement of the commutator
brushes, whereby the driving connection through the arrested pawl is severed, and
further movement in the same direction is impotent to move the brushes further, but
a movement in the reverse direction is immediately communicated through the other
pawl to the brushes, essentially as described.
3. In a current regulator, the means for giving motion to a shifting mechanism,
consisting of a friction-wheel, two oppositely revolving friction-rollers geared to the
armature shaft and mounted on a lever, so that by moving the lever either roller
can be pressed against the friction-wheel to drive it in one direction or the other,
an electro-magnet and its retractile spring connected to said lever, and suitable means
for relatively adjusting the friction-wheels and rollers, substantially as set forth.
4. Constructing the two friction-rollers to revolve at different surface speeds, the
faster one driving the shifting mechanism in such direction as to move the brushes
away from the maximum position, and the slower one to move them toward the
maximum, for the purpose described.
5. The combination with a current regulator of the class wherein a shifting
mechanism is connected to a source of power by the action of a regulating electro-
magnet, of a retarding device, such as a fan, for resisting undue movements of the
mechanism, in substantially the manner described.
6. The connection of such fan or other retarding device to the shifting mechanism,
by means of a frictional connection, adapted to slip in the case of a quick movement
of the shifting mechanism. for the purposes described.
7. The combination with a current regulator of the class wherein a shifting
mechanism is connected to a source of power by the action of a regulating electro-
magnet against a retractile spring or force, of a movable stop, such as P, constructed
to be applied to receive the tension of the retractile force and prevent the latter
from acting on the mechanism, substantially in the manner described, so that the
regulator can be held out of action when the machine is overloaded or below the
normal speed.
8. Mounting or pivoting the stop P so that when the electro-magnet becomes
strong enough to overcome the retractile force, and set the stop free, it will fall or
move of itself out of engagement, for the purpose set forth.
9. The novel features of construction of the regulating electro-magnet or solenoid M,
comprising the reducing of the mass of the pole which preponderates in polarity by
reason of induction from the field magnet; also the slitting of the polar ends of the
core so that the sub-divisions thereof repel each other and aid the demagnetization of
the core.
10. In a dynamo-electric machine having an armature of the "closed coil" class, the
combination with its commutator and main commutator brushes, and an automatic
regulating mechanism for shifting said brushes between their maximum and minimum
positions to compensate for variations of resistance in the circuit, of supplemental
commutator brushes connected in circuit with the respective main brushes, and the
two sets of brushes geared differentially to the said shifting mechanism, so that the
main and supplemental brushes are moved simultaneously in the same direction but
at different speeds, so as to approach each other in moving away from the maximum
position, and recede from each other in moving toward the maximum, in substantially
the manner and for the purposes set forth.
11. In a dynamo, the construction of the annular armature core of sections over-
lapping at their junction, the end portion of one section extending outside of the other,
and engaged by an external support or spider arm, so that centrifugal action is resisted

page_text: by the said support, and the overlapping ends are pressed thereby into closer contact,
in substantially the manner described.
12. In a dynamo, the construction of the annular armature core of sections
united by scarf joints, and each section built up of laminae superposed in planes
perpendicular to the axis of rotation, with their edges coinciding at the joints, as.
described.
13. An annular armature core consisting of sections built up of laminæ fastened
together, and exteriorly rounded caps fastened against the opposite sides of the sections,
for the purpose set forth.
14. A sectional armature core provided with exterior caps or plates arranged to
partially overlap at their ends the joints of the sections, and thereby prevent their
relative lateral displacement, substantially as described.
15. A sectional armature core, combined with a supporting spider, the arms of
which engage the sections at their joints, and with caps or plates fastened against the
opposite sides of the sections, extending between the spider arms and abutting at their
ends against said arms, for the purpose specified.
16. The combination with an annular armature core divided into sections, of a
supporting spider having arms formed with heads engaging the inner side of the core
at the joints, and with jaws engaging the outer side of the core, and movable to draw
its sections inwardly, substantially in the manner set forth.
17. The combination with an annular armature core divided into sections, of a
supporting spider consisting of two parts, engaging opposite sides of the core,
movable relatively toward and from each other, and each part formed with beveled
jaws overhanging the exterior of the core at its joints, so that by moving the parts
together the sections are drawn inwardly, substantially as described.
Dated this 22nd day of September 1890
J. C. MEWBURN,
55 & 56, Chancery Lane, London, Patent Agent.