IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
Year: 1884

page_text: I ROOKES EVELYN BELL CROMPTON of Mansion House Buildings Queen Victoria
Street in the City of London Engineer do hereby declare the nature of my
invention for IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES to be as follows:
:-
My improvements in dynamo electric machines relate more particularly to those
in which the rotating arinature is of ring form. Although some portions of the
invention may be adapted to dynamo machines of other form.
My improved armature consists of an iron ring core formed preferably of a large
number of separate rings or washers stamped out of soft annealed sheet iron.
these washers are mounted in the manner bereafter to be described on longitudinal
spokes or radial bars made of non-magnetizable metal and held in such a manner
that the central hubs carrying these radial bars can be withdrawn leaving the
radial bars on which are mounted the washers-attached firmly to the latter this.
withdrawal of the central hub or hubs (as the case may be) greatly facilitates the
winding of the armature coils on to the core-It also facilitates the insulation of
the wires and afterwards permits of easier access to the internal surface of the
ring core than has hitherto been the case and thus lessens the cost of repair or
renewals of the coils.
One method of carrying this out is to stamp or otherwise cut out dovetail shaped
notches in the inner edge of each of the washers. These notches being all cut by
the same stamping press (or other tool) they must be exactly alike, the radial bars
have correspondingly dovetail projections cut at their outward ends or edges (as the
case may be.)
The inner edges of the radial bars may be of any suitable form-and in turn
are carried by notches or grooves cut in the external periphery of the central hub
or hubs.
To mount the armature core in the first instance the radial bars are placed in
position in their grooves in the central hub and one end washer made thicker than
the rest is slided over the radial bars-the dovetail notches sliding down the
corresponding projections on the bars. This first washer is prevented from sliding:
right over the bars-by their ends being slightly rivetted over, or thickened The
remainder of the washers are then slided on-being insulated one from the other
by asbestos paper or other suitable material,-at intervals the washers may be
-

page_text: spaced by radial strips of insulating material so as to have radial ventilating
channels and so facilitate the ventilation and add to the cooling surface of the
core.
After all the washers have been put onto the radial bars so as to form a sufficient
length of core measured parallel to the axis, or spindle. The last washer being one
of increased thickness similar to the first one I secure the whole by rivetting
down the ends of the radial bars.
The central hub or hubs can now be withdrawn-and the core will be found to
have the radial bars attached to it as radial strips projecting inwards from the
main surface of it but in no way interfering with the process of winding on the
coils.
One way of insulating this core is by lining each of the spaces between the
radial bars with a gridiron or perforated sheet of insulating material-such as
vulcanized fibre-or any other hard insulating material suitable for the purpose.
The perforations must be large in proportion to the remainder of the material.
In this way the insulation of the core will not interfere with the free access of
air to the main surface of the core.
I sometimes arrange the radial ventilating channels in the core in such manner
that they act as fans and to facilitate this action I so curve or fashion the distance
pieces et cetera as to give the necessary resistance to the passage of the air.
In some cases I make these distance pieces take the form of inclined planes so
placed with reference to the direction of rotation that the air is forced inwards i.e
from the periphery towards the centre.
And in some cases I arrange these ventilating spaces alternately one to force
the air outwards and the next space on either side arranged to force the air
inwards.
I
.
By this arrangement I can cool the inner surface of the core-as well as the
outer surfaces of the inner copper coils without the necessity of the air passing
through the latter. And so avoid the waste of space which is necessary if they
have to be spaced apart so to allow room for the air to pass. I form my. coil of far
greater thickness measured radially than has heretofore been the case
width being from 2 to 23 of the external diameter of the core itself.
This radial
This increased thickness of core is attended with difficulties in the winding on of
the copper coils, from the insufficient space for the coils in the small internal
cylindrical passage from which has to be deducted the space taken by the radial
bars carrying the core and the central hubs themselves. To meet this difficulty. I
use copper tape for the winding of the armature coils and pass it through the
central passage on its edge, that is to say with its larger diameter placed radially,
at the ends of the core I twist the tape through a quarter turn and wind it
flatways on the outer periphery and so on. This arrangement permits of a very
close, approach of the core of the armature to the surfaces of the pole pieces of the
field magnets and thus insure that the coils pass through a very intense magnetic
field.
Instead of tape I can use several wires of round or square or rectangular-section
and pass them through the central passage arranged radially-but on leaving the
passage they can be spread out fanwise on the end of the core and then be laid,
side by side, on the outer periphery. I prefer not to entirely cover the external
surface of the core with winding, but to leave sufficient spacing between the
contiguous coils to allow of the air coming from the radial ventilating space before
described, to find its way between the coils.
In cases where it is desired that the air for ventilation should be passed through
and between the inner coils, as is necessary in all cases when the alternate inward
and outward fan arrangement. above described, is not used, I space the inner coils by.
winding on them insulating tape formed of hard material in a spiral form, the
contiguous wires haveing the spirals-formed in opposite directions, so as to avoid the
possibility of contact between the wires at the bare spiral spaces, or alternate

page_text: wires can be left bare of insulation and interposed between pairs of spirally
insulated ones, or short split tubes formed of vulcanized fibre or similar insulating
material may be sprung over the wires, or copper tapes and spaced at suitable
intervals to properly space apart the wires or tapes.
As the proportions of iron in the core are so high it follows that with suitably
formed field magnets, the magnetic field will be intense enough to give the Electro-
motive force required (for working incandescent lamps or similar purposes) with so
few coils on the armature, that in most cases one turn or coil of the copper tape or
bundle of wires between each seginent of the collecting cylinder will be found
sufficient. In all these cases the winding then consists of a number of stirrups or
single loops of copper tape or of a looped bundle of copper wires. All the stirrups
or loops for the armature can be formed away from the core on a suitable former
and, after being insulated can be brought together into groups, each group consisting
of just so many loops as will fill, or correspond to the space between one pair of
radial bars. These groups can be formed by the set of insulated loops being
brought together with the spacing arrangement above described all placed in
correct position. The perforated lining of the core above described or any other
insulation which is intended to be common to the whole group can be applied and
the entire group of coils can then be slided on to the core as one complete segment
of winding, for instance, in the case of a core having six radial bars, there would
be six segments of winding, each of which can be removed as a whole for exami-
nation or repair without interfering with the remaining segments.
3 1001

page_text: I ROOKES EVELYN BELL CROMPTON of Mansion House Buildings, Queen Victoria
Street in the City of London Engineer do hereby declare the nature of my
invention for IMPROVEMENTS IN DYNAMO-ELECTRIC MACHINES and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement:-
==
My improvements in Dynamo-Electric Machines relate more particularly to those
machines in which the rotating armature is of ring form, although some portions of
the invention may be adapted to the armatures of Dynamo-Electric machines of
other form.
The objects of my invention are
1st The better communication of the driving strain from the driving spindle or
axle to the armature core and coils or winding.
2nd The obtaining an intense magnetic field of force through which the armature
coils or winding moves, and hence obtaining high electromotive force with
comparatively few turns of winding and slow surface speed of the armature, by so
proportioning and arranging the iron composing the armature core, and the copper
conductor forming the winding, that the radial depth of this iron core may be as
great as possible.
3rd The arranging of the winding and its insulation as to allow of the free access
of a ventilating current of air to every part of its surface and the providing this
ventilating current by simple means.
4th The simplification of the winding so that every part of it is readily accessible
for examination, repair or renewal.
My improved armature consists of an iron ring core formed preferably of a large
number of separate rings or washers stamped out of soft annealed sheet iron, these
washers are mounted in the manner hereafter to be described, on longitudinal spokes
or radial bars made of non magnetizable metal and held in such a manner that the
central hub carrying these radial bars can be withdrawn leaving the radial bars on
which are mounted the washers attached firmly to the latter this withdrawal of the
central hub or hubs (as the case may be) greatly facilitates the winding of the
armature coils on to the core.
It also facilitates the insulation of the wires and afterwards permits of easier
access to the internal surface of the ring core than has hitherto been the case and
thus lessens the cost of repair or renewals of the coils.
One method of carrying this out is to stamp or otherwise cut out, dovetail shaped
notches in the inner edge of each of the washers, these notches all being cut by the
same stamping press (or other tool) must be exactly alike, the radial bars have
corresponding dovetail projections cut at their outward ends or edges (as the case
may be). The inner edges of the radial bars may be of any suitable form and in
turn are carried by notches or grooves cut in the external surface of the central.
hubs, hub or axle.
"
"
Figures 1 to 4 shew this method of mounting the core. Figure 1 shews a
longitudinal section through the spindle, hubs, radial bars and core Figure 2 shews
a sectional end view through a plain ring or Gramme form of core. Figure 3
shews a sectional end view through a portion of the same to a larger scale and shows
a portion of the winding in position Figure 4 shews a sectional end view through
an indented ring or "Pacinotti form of core with portion of the winding in
position. Figures 5 and 6 s! ew alternative forms of spindle and hubs. In figures 1.

page_text: 2. 3 and 4 a a is the spindle bb the hubs c the commutator dd the radial bars,
d' the dovetail shaped projections fitting into the corresponding notches in the core
rings hhh Figures 23 and 4 shew clearly the mode in which the inner edges of
the radial bars d d are carried by the grooves or keyways in the hubs b.
In figure 1 the hubs are shown as separate from the spindle a a but figure 5
shews 3 hubs forged solid with the spindle, and figure 6 shews the whole of the
central portion of the spindle enlarged or swelled out so as to form one long hub.
Figures 5a and 6a show the end view of these two forms of spindles when 3 radial
bars only are used. I have shown in the drawing 3 radial bars only which for the
smaller sized armatures is a convenient number, but in the larger armatures I employ
any convenient number of radial bars, and the transverse section of the hubs will
be modified to suit this increased number of bars.
To mount the armature core in the first instance the radial bars d d are first
placed in order in their grooves in the hub or hubs, and then one end washer f
inade thicker than the others, is slid over the bars, the dovetail notches sliding
down the corresponding projections d¹ d'. This first washer fis prevented from
sliding right over the ends of the radial bars by their being slightly upset or
rivetted over at e, the notches in the washer f being made larger at the outer side
than at tlie inner one as shewn by the sloping lines at e².
The remainder of the washers are then slid on in order, being insulated from one
another by asbestos paper or by coating them with a suitable insulating material..
At regular intervals as shown at g¹ g² g³ g¹ g³ &c the washers may be spaced from
one another by strips of material which must also insulate them from one another
and thus leave radial ventilating channels or spaces as shewn in figure 2 where i. i
are the spacing strips and g. g the ventilation channels, after all the washers have
been put on so as to form a core of the required length, the last washer put on must
be a thick one made similar to the first one f. This is shewn at f2. the ends of the
radial bars are then rivetted down on to the last washer f¹ as shewn at e¹.
The spindle and hub a and b can now be withdrawn and the core will be left
having the radial bars firmly attached to it as radial strips projecting inwards from
its inner surface, but in no way interfering with the process of winding on the coils
to be hereafter described.
Although I have shown that this object can be obtained by making the outward
edges of the radial bars and the corresponding notches in the washers of dovetail
form, yet I do not confine myself to this precise method of attaching the bars to the
core washers. It is obvious that the same end may be attained in many ways, for
instance another mode of attachment would be to make the notches in all the
washers rectangular, and inserting a pin or key in each of the thicker end washers
in such manner that when the central hub is withdrawn each radial bar will be
held up firmly to the bottom of its notch, or only a part of the washers may be
made with the notches dovetailed, or the end washers only may be so made.
The object in all cases being that when the central hub is withdrawn the radial
bars will still be held so firmly attached to the core washers, that the core as a
whole can be readily handled when passing through the ordinary workshop
processes without fear of its being distorted or losing its correct form.
The insulation of the external periphery of the plain ring core shown in Figure 3
may be carried out in any convenient manner by winding tape or other insulating
on to it so as not to interfere with the openings or channels
material
I¹ g² j³ g¹ &c.
The insulation of the indented ring armature shown in Figure 4 may be carried
out by trough shaped linings of insulating material being inserted in each notch or
indentations of the periphery of the core, the projections of the core between the
notches may be left bare.
But the insulation of the inner cylindrical surface of the core requires that
3 special provision should be made not only to prevent the channels g¹ g² &c being
stopped at their inner edges but also to provide spaces for the air to circulate
between the copper wires or strips forming the winding,

page_text: If as in the case of the smaller class of armatures I use the ordinary cotton or
silk covered wire for the winding, I line each of the are shaped spaces between the
radial bars with a gridiron or perforated sheet of hard insulating material.
Figures 7, 8, 9. 10. 11. and 12 show three forms of this gridiron insulation in
plan and end view.
Figures 7 and 8 show a portion of a gridiron with square perforations. Figures 9
and 10 show similarly a grid with a central back bone. Figures 11 and 12 show
another form made by cutting the material step fashion as at 11 12 13³ and bending
up these steps as shown in the same plan and in the end view m. m² m² &c.
These bent up portions then serve as spacing strips to space the coils apart and
thus allow air to pass between them. This last form of insulation has the advantage
that bare copper wire or strip can be used for the coils, as the equally spaced
strips m1 m² m³ &c by themselves form sufficient insulation.
But in the larger class of armatures or where I prefer to use bare copper wire or
strip whether of cylindrical or other section I sometimes use the spiral arrangement
of winding a strip of insulating material round each coil as shown by Figures 13
& 14.
Another form is shown by Figures 15 and 16 and consists of short lengths of
tube formed of hard insulating material slipped on to the coils or bars in alternate
order as shown in plan Figure 15.
Figure 16 shows end sectional view of one tube to an enlarged scale this tube
being moulded to suit strip of rectangular cross section.
These short spacing tubes also form the insulation of the internal winding, as
shown in end view Figures 3. 4. 24. and 25-in all these figures the tubes are
_arranged alternately as shown in plan by Figure 15-so as to give the required
spaces for the passage of air between the copper wire, strips or bars.
:
When using cores of plain ring form I find it convenient to space the coils by
such tubes on the external periphery of the armature as well as on the internal
one.
In this case the tubes serve not only to insulate the outer coils from each other,
but also to wedge them tightly one against the other in order that each coil may
be firmly held and be able to resist tangential electro magnetic forces when passing
through the strong parts of the field. The tubes are placed so as to touch one
another on the external periphery of the armature and around the whole I put at
intervals hoops of insulating material and over these bindings of wire or other
suitable material wound tightly on só as to prevent the coils from flying outwards
. under the influence of centrifugal force:
I sometimes curve the distance pieces or strips i. i Figure 2 in the manner well
known to Engineers so that these strips act as fan blades of the most efficient form.
I sometimes form these strips as shown at ii figure 17 so curved in relation to
the direction of rotation that they form inclined planes or spiral fan blades drawing
the air from the outward periphery and forcing it inwards.
Figure 18 is a diagram showing on a longitudinal section of the armature core
by arrows, the direction the currents of air will take if g. g² g' &c are formed with
the strips curved as in figure 2 whilst g¹ g³ are formed with the strips curved as in
figure 17.
The currents in the former channels being outwards whilst those in the latter are
inwards.
This last arrangement permits of the coils forming the internal portion of the
winding being placed quite close together or without any spacing strips, thus
heavier section of copper can be used such an arrangement is shown in end
sectional view figure 26.
It will be seen that the circulating currents of air cool the external surfaces of
the inner coils, their inner surfaces nearest the spindle can be cooled by a separate
current of air forced through the inner space by means of a suitably placed fan at
the end of the armature.

page_text: It will be seen from Figures 1, 2, 3 and 4 that I form my core of far greater
depth measured radially than has been heretofore the case I do this for magnetic
reasons in order to approximate more nearly the area of cross section of the iron
forming the core of the armature coils or winding to that of the iron forming
the core of the Field Magnet Coils, but this increased radial depth introduces
considerable difficulty in the winding of the armature.
In the proportion of core shown on the drawings it will be seen from figure 3
that each turn of the winding occupies at n¹ on the outer periphery nearly twice
the width measured tangentially that it does at n on the inner periphery.
To provide for this in one arrangement shown in end section at Figure 3 and by
side view of one turn of the winding at Figure 19 I make the coil of copper strip
of rectangular section as shown and pass it through the inner space on its edge,
that is to say with its larger diameter placed radially as shown at n and twist it
through a quarter turn at n³ Figure 19, so that it passes back on the outer
periphery of the core with its larger diameter placed tangentially or flatways.
In the case of large bars I use copper of varying sections as may be found most
convenient for the inner part of the winding and either braze or autogenously
solder it to copper of any convenient sections to form the outer winding, this is
shown at n Figures 21 and 22.
By these arrangements I can reduce the total thickness of the external part of
winding measured radially far below what has been hitherto attempted and I thus
obtain the result that, whether I use the plain or indented form of ring core, in the
revolution of the armature the surface of its core passes very close to the polar
surfaces of the field magnet cores, the winding therefore passes through a very
intense magnetic field.
Figures 23. 24 and 25 show various methods of winding so as to produce the
same result. In figure 23 the winding is formed of copper wire of ordinary
cylindrical section which may be insulated by being covered with cotton in the
usual manner the turns being arranged side by side on the external periphery but
in double rows on the inner side and being kept spaced apart by some of the
devices before mentioned or other equivalent device-so that the requisite air spaces
are provided Figure 24 shows the same, square or rectangular section of copper
being used.
Figure 25 shows a combination of the arrangement shown on Figures 21 and 22
with multiple, double, treble, or even fourfold strips on the outer periphery.
The object of this last arrangement is to prevent the eddy currents which are
liable to be set up if too broad strips of copper are used in this position.
Figure 26 shows sectional end view of a method of arranging the internal
winding for the larger class of dynomos so as to get the largest possible area of
cross section of the copper combined with the largest amount of cooling surface
exposed to the ventilating currents of air, and consists of bars of wedge formed
section, insulated from one another by continuous ribauds of insulating material
wound alternately over and under them as shown in the figure.
The heavy sections of core and the intense magnetic field which the herein
described methods of winding admit of, renders it possible to obtain electro-
motive force high enough for most commercial purposes with a comparatively
small number of turns on the armature i.e: the winding will consist of one only,
two, or at most three, turns of winding to each section of the commutator.
It follows that all the winding being formed of separate stirrups or loops of
copper as before described that all the soldered joints or connections connecting
these loops together, and to the commutator, may be formed at the commutator
end of the armature, and that any of the loops can be easily disconnected and
drawn off from the core for purposes of repair. It will be seen that for purposes
of convenient manufacture my invention admits of the preparation spacing and
insulation of the copper loops in groups which may consist of any number of the
loops, preferably of such number as will fill the space between two adjoining radial
bars such preparation and grouping may be carried out on a model or former

page_text: apart from the armature core, and the whole may be passed into place on the core
as a complete group or section of winding, and this group can afterwards be
removed as a whole for purposes of examination or repair.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
1 claim is
1st The combination of parts forming the improved armatures substantially as
herein described and for the purposes set forth.
2nd The combination of parts as herein described as methods of attaching the
ring core to its spindle substantially as described and for the purposes set forth.
3rd The improved methods of insulating the internal winding substantially as
described and shown in Figures 7 to 12 and Figures 15 and 16, and for the
purposes set forth.
4th The improved methods of ventilating and cooling the armature substantially
as described.
5th The combination of ventilating spaces with distance pieces arranged so as to
act efficiently as fan blades substantially as described and for the purposes set
forth,
6th The various methods of winding herein described and shown in Figures 19
to 22 and 24 to 26 substantially, as described and for the purposes set forth.
7th The combination of an iron ring core of great radial depth with external
winding of small radial depth and internal winding of great radial depth sub-
stantially as and for the purposes herein set forth.
Dated this 2nd dove of December 1981.