Improvements in or relating to Armature and Transformer Cores and the like.
Year: 1892

page_text: Date of Application, 23rd May, 1892
Complete Specification Left, 22nd Feb., 1893-Accepted, 20th May, 1893
PROVISIONAL SPECIFICATION.
Improvements in or relating to Armature and Transformer Cores
and the like.
I, WILFRID L. SPENCE of The Elms, Seymour Grove, Manchester, Civil
Engineer, do hereby declare the nature of this invention to be as follows:-
My invention relates to an improved method of manufacture and construction
of the cores of dynamo armatures, transformers and the like, and it is more
particularly applicable to apparatus of the Pacinotti type, i.e., short, flat-ring
cores with radial slots in which the wire is wound.
Hitherto such cores have been built up on one or other of the following
plans:-
<<
"
(A) A plain strip or ribbon of iron of the full width of the core is wound over
a former until the desired radial depth is obtained, and when complete the
channels are milled out on each side to the required number and size.
(B) A continuous strip, whose width is equal to the thickness of the web only,
is wound as above and at intervals (corresponding to the number of coils in the
apparatus), H shaped stampings are inserted between the layers so as to form
channels for the wire.
The objection to the first method is that so much iron is wasted, and to the
second that so many joints are introduced across which the magnetic flux must
pass.
"
In order to avoid both these objections, and to reduce the cost of construc-
tion I build such cores in the following manner. A continuous strip of sheet metal
of the full width is taken and before being wound on the
former is passed
through a stamping or cutting machine. This tool is regulated to cut the slots at
varying distances apart (according as the core has reached a smaller or larger
diameter) by means of a division plate and engaging lever, or other suitable device,
secured to the shaft which carries the core. Thus suppose an armature is being
constructed for eight coils, a plate having eight slots in its periphery is secured to
and driven by the armature shaft, and every time the core turns through 45 degrees
a projection on the aforementioned lever drops into a corresponding recess in the
division plate or copying device.
This movement of the lever permits to be set in motion the cutting tool (whether
knife-edge or cylindrical) and as the strip is drawn along it is cut exactly at the
place required to form, with the windings already in position, a uniform and regular
slot. A wheel, secured to the shaft, gearing with a pinion, the number of whose
teeth as as eight to one, would effect the same purpose as the division plate and
lever aforementioned.
As the strip would have to be drawn along very slowly indeed, or be stopped
altogether if a stamping machine were used, I prefer to employ a revolving cutter
whose motion may be continuous and which will not interfere with the progress of
the strip.
It will be seen that the principle underlying the foregoing construction is that of
regulating the action of the cutter by the angular position which the slot occupies
in the finished armature, and as this is unvarying no further adjustment is required
whatever be the diameter which the core has reached.
The insulating material which is wound on with the iron may or may not be cut
at the same time. In the latter case the superfluous insulation may be removed
by hand or by the milling tool which may be necessary to trim up the edges of the
channels. If, however, the strip coming from the cutter be passed between two

page_text: closely set rollers the burred edges will be flattened out and no subsequent milling
will be necessary.
An emery wheel may be used for the same purpose.
Dated this 23rd day of May 1892.
WILFRID L. SPENCE.
COMPLETE SPECIFICATION.
Improvements in or relating to Armature and Transformer Cores
and the like.
I, WILFRID L. SPENCE, of The Elms, Seymour Grove, Manchester, Civil
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:―
My invention relates to an improved method of manufacture and construction
of the cores of dynamo armatures, transformers and the like, and it is more
particularly applicable to apparatus of the Pacinotti type, i.e., short flat ring cores
with radial slots in which the wire is wound.
.
"
Hitherto such cores have been built up on one or other of the following plans:
(A) A plain strip or ribbon of iron, of the full width of the core, is wound over a
former
until the desired radial depth is obtained, and when complete the
channels are milled out on each side to the required number and size; or, (B) a
continuous strip whose width is equal to the thickness of the web only is wound as
above and at intervals, (corresponding to the number of coils in the apparatus),
H-shaped stampings are inserted between the layers so as to form channels for the
wire. The objection to the first method is that so much iron is wasted, and to the
second that so many joints are introduced across which the magnetic flux must
pass. In order to avoid both and to reduce the cost of construction I build such
cores in the following manner. A continuous strip of sheet metal of the full
width is taken and before being wound on the foundation ring is passed through a
stamping or cutting machine. This tool is regulated to cut the slots at varying
distances apart (according as the core has reached a smaller or larger diameter) by
means of a division plate and engaging lever or other suitable device secured to
the shaft which carries the core. Thus suppose an armature is being constructed
for eight coils, a plate having eight slots in its periphery is secured to and driven
by the armature shaft and every time the core is turned through an angle of
45 degrees a projection on the aforementioned lever drops into a corresponding
recess in the division plate or copying device. This movement of the lever permits
to be set in motion the cutting tool (whether knife edge or cylindrical) and as
the strip is drawn along it is cut exactly at the place required to form, with the
windings already in position, a uniform and regular slot. A wheel secured to the
shaft gearing with a pinion the number of whose teeth are as eight to one would
effect the same purpose as the division plate and lever aforementioned.
As the strip would have to be drawn along very slowly indeed or be stopped
altogether if a stamping or punching tool were employed I prefer in certain cases to
use a revolving cutter whose motion may be continuous and which will not impede
the progress of the strip.
It will be seen that the principle underlying the foregoing construction is that of
regulating the action of the cutter by the angular position which the slot occupies
in the finished armature, and as this is unvarying no further adjustment is required
whatever be the diameter which the core has reached. It will also be perceived
that the distance between the cutting tool and the point at which the strip just
touches the already completed portion of the core, which I shall hereafter refer to
as the tangent point, influences the character of the channel in the finished armature.
When this distance becomes indefinitely small, i.e., when cutting as well as winding
proceed simultaneously at the tangent point the channel is formed truly radial

page_text: throughout, but as the distance is increased the channel has a curvature imparted
to it sloping away from the radius in the direction in which the core is being turned.
This curvature if moderate in amount is no disadvantage in a dynamo but rather
the reverse especially in machines which, like the Brush, have but few coils and
great tendency to heating in the pole pieces. If considered objectionable, however,
it is avoided by varying during construction the length of the path which the strip
must traverse between the cutting tool and the tangent point. Suppose, for
example a core is being built for 12 inches internal and 24 inches external diameter
and that the distance referred to is, say, 12 inches; the angular lag of the slot
when it reaches the core behind the tangent point at the moment of cutting is
consequently
only, and therefore the angular advance of the finished channel from inside to out
would be 57.3°. If instead of this the winding is started with a 12 inch distance as
before which is continuously and uniformly increased to 24 inches as a maximum
then the lag inside and outside and at all intermediate turns will be 114.7 degrees
and the channels will, consequently, be exactly radial. If for any reason channels
having an exaggerated slope should be required the reverse process only is necessary:
the intervening distance is started large and finished small.
As it is not convenient to alter the distance between centres of the winding and
cutting portions of the machine I arrange that the strip between them shall traverse
a suitable number of guide rollers mounted so that their centres may be altered to
vary the length of iron ribbon passing over them. The adjustment may be made
by hand or by gearing worked from the core or press shafts.
An
By employing this mode of construction the amount of special apparatus necessary
is small. An ordinary form of cutting press may be used with a little modification.
The strip, unrolled from a brake drum on one side, passes through the dies thence
round the adjustable guide rollers and finally on to the foundation ring, a high
degree of tension being maintained throughout in order to compact the mass.
intermittent turning motion, corresponding in periods per revolution to the number
of channels in the core, is transmitted to the ring and this draws the strip along
step-by-step. At each momentary stoppage the press clutch is thrown in and a cut
made in the ribbon, the die then rises and again the band is drawn forward. As
already stated the control of the press tool may be automatic or it may be manual,
and the same applies to the motion of the adjusting rollers, although in this case an
automatic traverse by pall and ratchet wheel or equivalent device is much preferable.
It is, of course, clearly understood that the only feed of the strip is by tension from
the core ring, no positive feeding rollers must be employed.
Where core rings are required to be turned out more rapidly than is possible with
a press tool the strip may be drawn through continuously at a slow rate and a
running cutter used to form the slots. Two plans at least are possible; one involves
a cutter with a cylindrical surface working above the strip and turning on its axis
while cutting. Normally resting clear of the band it will be brought down at the
proper instant by an automatic gear similar to that already described, and whenever
the cut is finished and the tool raised a spring will either draw the cutter back to
its original position ready for the next operation, or, if two or more shearing edges
are applied round the same cylinder it will similarly be carried forward. The
other plan requires two circular cutters shaped somewhat like the saws used for
stone dressing. They are set one on each edge of the strip with their axes parallel
thereto and the cutting teeth project over it on each side a distance equal to the
depth of the required channels. At the appropriate intervals they are quickly

page_text: turned and one tooth goes through slotting out the edge as required; the motion
being an intermittent forward one only no return is necessary as the space between
adjacent teeth clears the strip in its progress.
Alternative machine with the distance between cutter and tangent point zero
and invariable. In this machine cutting and winding occur simultaneously at the
tangent point and the resulting channels are always exactly radial. The core
shaft is guided in a slot in the upper portion of the frame and the winding takes
place at or near the lower end of the vertical diameter. Punching is performed
by dies and bolster plates at the same place and the operation is as follows: The
shaft carrying a foundation ring or former is driven by intermittent gearing so as
to advance at each movement through the angular distance occupied by a single
coil. After this motion is completed the punching tool, which works from inside
to out in the space under the shaft, descends and makes the desired cut, it then
rises sufficiently high to clear all windings already in position and is there locked
until the core has again been advanced through the necessary angular distance.
The cycle of operations is then repeated. The advance motion of the core will be
a positive one capable of drawing through the strip against the tension requisite
for compact winding; it may be either automatic or controlled by hand.
In a machine of this type to be used for building cores of different radial depths
it is necessary owing to the limited space between the shaft and the inside of the
ring, to have a variable stroke motion on the cutting die. This I get in the
following way: The main shaft which receives the driving pulley is in the lower
portion of the machine frame, it carries a wheel gearing with an equal sized one on
a second shaft parallel to the first. One of these gears is secured to its shaft by a
"box-wheel" arrangement which permits of varying their relative positions through
180 degrees. Short connecting rods work over an eccentric on each of these
shafts and their other ends are coupled through a pin so as to form a sort of toggle
motion. The pin of this toggle actuates through a tbird rod the cutting tool. It
will now be seen that when the two eccentrics occupy corresponding positions, as
both up or both down, the maximum stroke will be imparted to the toggle pin,
whereas when owing to the action of the box-wheel they do not correspond the
stroke will be less.
As the cutting stroke so obtained does not always terminate at the same point
it is necessary also to be able to vary the height of the table which carries the
bolsters. This may be done in any suitable way.
It will be understood that at all times the lower part of the periphery of the
core rests on this table and that as the diameter increases the shaft rises in the
guiding slot to compensate therefor. The turning effort transmitted to the core
ring thus encounters considerable frictional resistance which tends greatly to
compact the windings.
Where the number of coils is large it may be convenient to punch the slots out
in sets of two or three at a time. Instead therefore of every coil being indepen-
dently radial there will be nor n separate radii each with two or three coils in
planes parallel thereto. For magnetic reasons this grouping should not be carried
too far. Another method which may be adopted to economise labour is to slot
and wind two or three strips, laid over one another, at the same time. In all cases
suitable insulation is run in between the layers. In order to impart stiffness to
the ring the strip of which the core is made may be grooved or corrugated longi-
tudinally or the separate slots may have their edges dished or bent so as to lock
into one another when wound. Brakes should be applied both to the core shaft
and to the reel from which the strip is being unwound to prevent slackness.
Referring to the drawings:
Figures 1 to 4 show several of the cores which can be made by my improved
machines. The combined cutting and winding machine, Figure 10, arranged as a
punch or with the running cutter, Figure 8, is capable of making all the forms and
the alternative machine, Figures 12 and 13, as well as the saw cutter, Figure 9, will
produce all but the type, Figure 3, in which the channel is completely sunk under

page_text: the surface. A "Brush" core is shown at Figure 1, the strip, A, being spaced as
an outer and, B, as an inner convolution.
Figure 2 is a more or less ironclad design, Figure 3 completely so. The grouping
arrangement is indicated by Figure 4 the three channels in each layer being
punched at one operation.
Figure 5 shows the effect of varying distances between cutter and tangent point,
AR is radial, AB is the result of starting with a distance TC which is uniformly
increased to TC', while AA shows the slope produced by a constant distance TC.
A form of division plate and engaging lever is given at Figure 6, a wheel and
pinion gear for the same purpose at Figure 7, and in both cases the control comes
from the core shaft which is independently driven, the connecting rod in the one
and the lever in the other operating a single stroke clutch on the press shaft.
Cylindrical cutting dies for use with a continuously running strip are shown in
outline at Figure 8, they are not positively driven but rotate only by friction with
the moving strip. The upper cylinder carries the cutting edges and the lower one
the hollow portion of the dies. At each cut the top cylinder is pressed down on
to the moving ribbon which then bears on the lower cylinder and. thus both are
rotated bringing round the cutting edges and punching the holes. As soon as the
cut is made the top cylinder rises and the friction becoming too small for the dies
to be driven they are brought back, by controlling springs, (not shown) to their
starting position ready for the next cut. Friction rollers, as indicated, may be used
for carrying the lower die.
Figure 9 shows the saw type of cutter. Shearing teeth, T, are mounted on the
peripheries of two discs which are set one on either edge of the strip, S, seen in end
elevation. At appropriate intervals the discs are rotated so that one tooth at a
time goes through the strip to form the slot. The control is the same as that
already described.
The machine and mode of operation which I prefer as being the simplest and
capable of the widest application is shown in outline by Figures 10 and 11. The
strip, S, unwound from a brake drum, B, passes through a gap in the frame of the
press; it travels between the dies, D, and then round the adjusting rollers, R, on
to the foundation ring to form the complete core, A. The adjusting rollers as well
as the core ring are advanced by pall and ratchet wheels from the press shaft when
the cutting die is on the upward stroke, (the stroke should be considerably greater
than is necessary for mere clearance). A form of feed for the rollers is shown by
Figure 11. The upper limb of the rocking arm, which is shown on Figure 10 and
which is actuated by a connecting rod from an excentric on the press shaft, gives
motion to a pall which turns a corresponding ratchet wheel. On the spindle of this
wheel a pinion is carried gearing with a spur wheel as shown. On this second
shaft two wheels are mounted one gearing with the rack on each roller carriage.
The pitch line diameters are arranged to cause the right hand roller to descend
somewhat faster than the left hand roller ascends. The actual increase in the
length of the strip between tangent point and the cutting tool depends on the
length of this path to start with, and on the inside and outside diameters of
the armature core..
In an actual case the diameters of the core were 9 and 19 inches respectively.
The strip traversed two rollers as shown, each 4 inches diameter, the distance
(horizontal straight line) between press tool and armature shaft centres was
24 inches. During construction the one roller descended 12 inches and the
other rose (19-9)=5 inches to compensate for the increased diameter. This
gave radial slots in the core.
Figure 12 shows the alternative machine in which cutting and winding proceed
simultaneously at the tangent point, hence no adjusting rollers are necessary. The
shaft carrying the core ring is guided by brasses in slots at each end of the
machine as shown. The advance motion is by worm and wheel, W. The worm,
sliding on a feather key, is carried between two bearings in a bracket supported

page_text: on the shaft, S. This form is desirable because during winding the core shaft
is continually rising with the increase in the diameter of the core.
A pall and ratchet wheel, P, driven from the main shaft gives the intermittent
turning motion. If desirable a hand controlled clutch may be substituted and in
this case each movement of the handle would cause the core to turn through an
angle corresponding to one slot or set of slots. The weight of the core is borne as
will be seen, by the table and the frictional resistance to motion between them may
be utilized to compact the windings. The punching tools, T, are fixed to a sliding
carriage or holder, H.
Cutting is performed on the down stroke and always through the outside, last
wound, layers to the lower portion of the dies. As the successive layers are
added to the core the effective stroke of the punches must be increased to pass
through and clear the slots in the completed portion. If the radial space between
the inside of the core and the boss of the spider is greater than the radial depth of
the core itself, then the full stroke may be given at the outset and it may be kept
constant. But when the depth of the core exceeds the space aforementioned the
stroke, small to begin with, must be increased as winding proceeds. The table
being lowered to corresponding positions.
The variable stroke motion is shown in Figure 13. Two shafts geared together
carry eccentrics and short connecting rods coupled through a pin C. One gear
is mounted with a "box-wheel" arrangement so that the relative positions of the
eccentrics, E, may be varied. As shown they give the maximum stroke, in any
other position the stroke will be less. The pin, C, drives through a third rod the
holder H. The usual flywheel and clutch, F, are carried by one of the press
shafts. This machine is only capable of making radial slots which are open to
the surface.
I am aware that it has on several occasions been proposed to construct armatures
which if actually made would look like one built according to my present inven-
tion, only no one has ever suggested how to do it. A recent inventor says that
the strip is punched so that when wound the slots will register and form regular
channels, but the method is not given, and, indeed, it will be almost impossible to
make the slots register at all if the strip is cut beforehand. It is this practical
difficulty which has hitherto prevented the appearance of a highly efficient and
economical type of armature. I would therefore have it clearly understood that
I make no claim to an armature or other core in which the wire lies in radial
slots on the end faces, whatever be the shape of the cross section of these slots.
Such a design is a decade old.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :
1. Forming armature and transformer cores and the like from a continuous strip
or ribbon slotted or notched on each edge while in the process of being wound
into a core ring, substantially as described.
2. In a machine for building armature and transformer cores and the like of the
types herein described, the combination with an intermittent advance motion for
the core ring, either automatic or hand controlled, of a punching or stamping
tool and gear for operating it either automatic or hand controlled, substantially as
described.
3. In a machine for building armature and transformer cores and the like of
the types herein described, the combination with a continuous advance motion
for the core ring of an intermittently-working, running cutting tool substantially
as described.
4. In a machine for building armature and transformer cores and the like, the
combination with a cutting or a punching tool and clutch or other gear for
operating the same of a division plate and engaging lever, wheel and pinion, or

page_text: equivalent device worked from the core shaft by which the periodic motion of the
cutter is controlled, substantially as described.
5. In a machine for building armature and transformer cores and the like of the
types berein described, so coupling together the punching shaft and the core shaft
by an intermittent locked gear that the latter can only advance when the punch is
raised clear for it to do so, and the punch only descend after the core has been
turned into the right position.
6. In a machine for building armature and transformer cores and the like of the
types herein described, making the strip traverse a finite distance between the
cutter and the tangent point so as to deviate the axes of the channels from
the radial direction.
7. In a machine for building armature and transformer cores and the like of the
types herein described, in which a finite distance intervenes between the cutter and
the tangent point, causing this distance to be continuously and uniformly varied
during the process of construction so that the resultant channels approach as
closely as may be desired to the radial direction.
8. In a machine for building armature and transformer cores and the like of the
types herein described and having radial channels in their end faces, placing the
punch to cut outwards at the tangent point, (along a radius of the ring), so that
the tool shall always have the bolster portion of the dies to work against.
9. In a machine for building armature and transformer cores and the like the
variable stroke motion substantially as described.
10. Armature and transformer cores and the like formed in the herein described
manner and having channels in their end faces which slope away from the radial
direction substantially as described.
Dated this 21st day of February 1893.