Note: Descriptions are shown in the official language in which they were submitted.
CA 02291459 1999-12-02
2945/005
DYNAMO-ELECTRIC MACHINE STATOR
STACK FORMING METHODS AND APPARATUS
This application claims the benefit of
provisional patent application No. 60/110,994, filed
December 4, 1998 and provisional patent application No.
60/133,169, filed May 7, 1999, which are hereby
incorporated by reference herein in their entireties.
Background of the Invention
This invention relates to methods and
apparatus for forming dynamo-electric machine stators
of the type that are made by helically coiling a
longitudinal strip of ferro-magnetic material.
Barrera U.S. patent 4,512,376 and Cardini et
al. U.S. patent 5,845,392 (both of which are hereby
incorporated by reference herein in their entireties)
show apparatus for applying coils of wire to stator
cores to produce stators that are particularly useful
for making alternators. It is known to produce this
type of stator core by helically coiling a strip of
ferro-magnetic material to produce a hollow cylinder.
The strip is provided with transverse recesses spaced
from one another along one of the strip's longitudinal
edges. The spacing of the recesses and the helical
coiling are such that recesses in successive turns of
the coil become superimposed on one another. In this
CA 02291459 1999-12-02
- 2 -
way the superimposed recesses produce slots in the
stator core that extend parallel to the longitudinal
axis of the hollow cylinder and that are spaced from
one another in the circumferential direction around the
inside of the hollow cylinder. These slots receive the
coils of wire that were mentioned earlier.
The electrical efficiency and thus
performance of stators of a given size of the type
described above can be improved by making them from
thinner strip material. However, to make a stator core
of a given size from thinner material either takes
longer or requires the stator core forming machinery to
operate faster, both of which are undesirable. For
example, to make a stator forming machine operate
faster increases its cost and may also increase the
rate of wear of the machine. More machine cycles may
be required to produce stators of a given size using
thinner strip material, and therefore the number of
stator cores that can be produced during the useful
life of a machine may decrease when thinner strip
material is used.
It is also known that the strip material used
to produce the stator cores can have variations in
thickness, metallurgical and mechanical properties, and
geometrical configuration. These variations can lead
to undesirable variations in the diameter of the
internal surface of the helical stator core.
Variations in the internal surface affect the
performance of the helical stator core. These
variations in the strip material can occur between
reels of strip material and throughout a reel of strip
material. There are also local variations or
deformations that can occur at particular isolated
points on the strip material. It has been found that
CA 02291459 1999-12-02
- 3 -
these local variations can disrupt the electromagnetic
flow within fabricated stator cores and thus hinder the
performance of the stators.
Stator cores can also be made by combining
two helically formed strips from separate stator
forming machines each using a different reel of strip
material. Additional advantages can be achieved by
combining the two helically formed strips with an
additional lamination inserted between the two
helically formed strips. The two helically formed
strips and lamination are combined by aligning their
longitudinal axes and the recesses of each piece.
Differences in the internal diameter of the two
helically formed strips are not desirable.
Strip material that is helically coiled
undergoes deformation. Depending on the dimensions and
properties of the strip material, additional unwanted
deformations may occur. One factor which affects the
occurrence of unwanted deformations is the thickness of
the strip material. Typically, the thinner the strip
material, the more likely unwanted deformations will
occur.
In view of the foregoing, it is an object of
this invention to provide improved methods and
apparatus for making dynamo-electric machine stator
cores.
It is a more particular object of this
invention to provide methods and apparatus for making
stator cores from thinner strip material, which methods
and apparatus avoid the need to operate the stator
forming machinery either longer or faster to produce
stator cores of a given size.
It is also an object of this invention to
provide methods and apparatus for reducing the effect
CA 02291459 1999-12-02
- 4 -
of variations that can occur in the strip material on
the electrical performance of the stator cores. More
specifically, the performance can be increased by
reducing the variations that can occur in the internal
diameter of stator cores and by reducing the effects of
local variations that may be present in the strip
material.
It is another object of this invention to
provide methods and apparatus for reducing unwanted
deformations that can occur when strip material is
coiled.
Summary of the Invention
These and other objects of the invention are
accomplished in accordance with the principles of the
invention by providing methods and apparatus in which,
in at least some embodiments, two relatively thin
strips of stator core material are superimposed on one
another to form a composite strip before the composite
strip is helically coiled to produce the hollow
cylinder of the stator core. In this way each strip
can be half as thick as the single strip used
previously, but the machinery can operate at the same
speed to produce finished stator cores of a given size
at the same rate as the prior art machinery.
The methods and apparatus of at least some
embodiments of the invention typically include
superimposing the two strips so that recesses in those
strips are superimposed on one another to produce
recesses in the composite strip. The composite strip
is coiled so that recesses in successive turns of the
coil are superimposed on one another to produce slots
for receiving wire coils as in prior art stators. The
CA 02291459 1999-12-02
- 5 -
methods and apparatus of the invention may include
shaping (e. g., punching) each of the strips to produce
the above-mentioned recesses. The methods and
apparatus of the invention may also include
periodically severing the coil from the composite strip
to produce end faces of the stator cores. The methods
and apparatus of the invention may still further
include axially compressing the coils (e. g., to square
off the ends of the stator core) and welding the
compressed coils together to rigidify the structure.
The methods and apparatus of the invention may also
include selectively pressure rolling the strips in
order to achieve a more constant internal diameter of
the stator core. The internal diameter of the stator
core can also be measured in order to provide feedback
to adjust the pressure rolling.
Another aspect of at least some embodiments
of the invention includes applying the principles of
selective pressure rolling to alternative methods and
apparatus for forming dynamo-electric machine stator
cores in which the stator cores are fabricated by
combining two helically formed strips from separate
stator forming machines that include selectively
pressure rolling the strips.
An additional aspect of at least some
embodiments of the invention includes coiling strip
material that contains apertures within the strip to
reduce unwanted deformations.
Further features of the invention, its nature
and various advantages will be more apparent from the
accompanying drawings and the following detailed
description of the preferred embodiments.
CA 02291459 1999-12-02
- 6 -
Brief Description of the Drawings
FIG. 1 is a simplified plan view of an
illustrative embodiment of apparatus constructed in
accordance with certain aspects of the invention.
FIG. 2 is a simplified plan view of an
illustrative embodiment of representative strip
material produced in the FIG. 1 apparatus.
FIG. 3 is a simplified elevational view taken
along the line 3-3 in FIG. 1.
FIG. 4 is a simplified elevational view taken
along the line 4-4 in FIG. 1.
FIG. 5 is a more detailed elevational view,
partly in section, taken generally along the line 5-5
in FIG. 1.
FIG. 6 is an enlargement, partly in section,
of a portion of FIG. 5.
FIG. 7 is a plan view, partly in section,
taken generally along the line 7-7 in FIG. 5.
FIG. 8 is a plan view, partly in section,
taken generally along the line 8-8 in FIG. 5.
FIG. 9 is an elevational view of an
illustrative stator core assembly made in accordance
with certain aspects of the invention.
FIG. 10 is an elevational view of the FIG. 9
stator core assembly after further processing in
accordance with certain aspects of the invention.
FIG. 11 is a perspective view of an
illustrative stator core assembly made in accordance
with the invention.
FIG. 12 is a simplified elevational view of
an illustrative embodiment of a pressure device in
accordance with certain aspects of the invention.
CA 02291459 1999-12-02
-
FIG. 13 is a plan view taken generally along
line 13-13 of FIG. 12.
FIG. 14 is a simplified, partly schematic,
elevational view of an alternative embodiment of the
pressure device in FIG. 12 in accordance with certain
aspects of the invention.
FIG. 15 is a simplified, largely schematic,
plan view of another illustrative embodiment of
apparatus constructed in accordance with certain
aspects of the invention.
FIG. 16 is a more detailed elevational view,
partly in section and partly schematic, taken generally
along the line 16-16 in FIG. 15.
FIG. 16A is an enlargement, partly in
section, of a portion of FIG. 16.
FIG. 17 is a simplified, partly schematic,
elevational view of a portion of the FIG. 15 apparatus
and an illustrative workpiece in that apparatus in
accordance with other aspects of the invention.
FIG. 18 is an elevational view, partly in
section, taken generally along the line 18-18 in
FIG. 13 of an alternate embodiment of the apparatus in
FIG. 13.
FIG. 19 is a plan view of an alternate
illustrative embodiment of the apparatus in FIG. 8.
FIG. 20 is an enlargement, partly in section,
of a portion of FIG. 18.
FIG. 21 is an elevational view taken
generally along the line 21-21 in FIG. 19.
Detailed Description of the Preferred Embodiments
Illustrative apparatus 10 constructed in
accordance with certain aspects of the invention is
shown in simplified plan view in FIG. 1 and in
CA 02291459 1999-12-02
g
simplified elevation in FIG. 4. Apparatus 10 includes
two reels 20a and 20b of strip material 22a and 22b,
respectively. Strip material 22a and 22b may be
thinner than the single strip of such material
typically used in prior art stator core coiling
apparatus. For example, each strip 22a and 22b may be
approximately only half as thick as the strip material
conventionally used.
Strips 22a and 22b are fed side by side to
punching structure 30 at the same rate. Punching
structure or punch 30 punches transverse recesses 24 in
one longitudinal edge of each strip 22 at regular
intervals along the length of that strip as shown in
FIG. 2. To distinguish the punched strips from the
unpunched strips, the punched strips are referenced
22a' and 22b' herein.
The punched strips 22a' and 22b' exiting from
punch 30 enter strip storage mechanism or structure 40.
This mechanism forms a plurality of loops in each strip
22' over pulley wheels 42 as shown in FIG. 3 so that
the strips can enter the storage mechanism at a rate
that may sometimes differ from the rate at which the
strips leave that mechanism. For example, the output
of strips 22' from mechanism 40 may occasionally be
halted for certain downstream operations without the
need to similarly halt the operation of punch 30.
Mechanism 40 may automatically accommodate such
differences in input and output rates by changing the
length of the strip loops in the mechanism. Of course,
if all the loops reach a predetermined maximum length,
then mechanism 40 must stop further input from punch 30
because no more strip material can be accommodated in
mechanism 40. Similarly, if all of the loops in
mechanism 40 reach a predetermined minimum length, then
CA 02291459 1999-12-02
- 9 -
mechanism 40 must stop the downstream machinery until
the supply of strip material in mechanism 40 is
replenished. In the same way that punch 30 processes
both strips 22a and 22b at the same rate, mechanism 40
preferably also handles strips 22a' and 22b'
identically in order to help maintain synchronism
between the two strips. This can be done by connecting
the corresponding pulley wheels 42 for respective
strips 22' to the same drive shaft as shown in FIG. 1.
The length of the loops of strip material 22a' and 22b'
between successive pulley wheels 42 can then be varied
together by adjusting the rate of rotation between the
successive pulley wheels 42 that are connected to
respective shafts.
After strips 22a' and 22b' exit from
mechanism 40, they may be given slack before entering
superposition mechanism or structure 50. This causes
strips 22a' and 22b' to form respective loops 48a and
48b before they are brought together and superimposed
on one another by super-position mechanism 50 as shown
in FIGS. 1, 4, and 5. For example, super-position
mechanism 50 may include various passive guide
structures 52a, 52b, and 54 for aligning strip 22a'
over strip 22b' and an active element (i.e., driven
spur gear 56) for pulling both of strips 22a' and 22b'
through guide structures 52 and 54. Passive guide
structure 52a and 52b support loops 48a and 48b and
direct strips 22a' and 22b' together into passive guide
54. As is shown in FIGS. 5-7, teeth 58 on spur gear 56
extend into superimposed recesses 24 in strips 22a' and
22b' in order to maintain precise super-positon of
strips 22a' and 22b' and their recesses. The relative
adjustment that may occur between strips 22a' and 22b'
in order to maintain precise super-position of their
CA 02291459 1999-12-02
- 10 -
recesses is taken into account by the slack present in
loops 48a and 48b. For convenience herein superimposed
strips 22a' and 22b' are sometimes referred to
collectively as composite strip 22". Although FIGS. 5
and 6 continue to show some vertical spacing between
the components 22a' and 22b' in composite strip 22", it
will be understood that the components of strip 22" may
in fact be in contact with one another.
From super-position mechanism 50, composite
strip 22" is supplied to coiling mechanism 60 as shown
in detail in FIGS. 5 and 8. In particular, composite
strip 22" enters the lower portion of mechanism 60 and
first passes through the clearance between rollers 62
and 64. Rollers 62 and 64 are set relative to one
another, relative to composite strip 22", and relative
to the central vertical axis 66 of coiling mechanism 60
so that they bend strip 22" into approximate
concentricity with axis 66. In particular, rollers 62
and 64 preferably cooperate with one another to give
strip 22" a curvature having a radius slightly less
than the desired radius of the finished stator to be
made from strip 22". This helps hold strip 22" against
other components of coiling mechanism 60. For example,
it helps hold composite strip 22" against stationary
arcuate guide 68, which is inside the arc of composite
strip 22" downstream from rollers 62 and 64. Farther
downstream it helps hold composite strip 22" against
the outer surface of rotating drum 90, which is
described in more detail later in this specification.
After passing between rollers 62 and 64,
composite strip 22" passes between the blade 72 and
anvil 74 of cutting mechanism or severing structure 70.
Cutting mechanism 70 is used to sever or cut strip 22"
CA 02291459 1999-12-02
- 11 -
after enough of the strip has passed through the cutter
to form a stator of the desired cylindrical length.
After passing through cutter 70, composite
strip 22" starts up stationary helical ramp 80.
Ramp 80 gradually raises strip 22" into contact with
the lower portion of rotating drum 90. This is
necessary because drum 90 is above roller 64, and so
strip 22" must be raised to the level of drum 90 before
it completes its first wrap or loop around axis 66.
Drum 90 is driven to rotate about axis 66 in the same
direction that strip 22" is moving and with an outer
surface velocity equal to the velocity of strip 22".
The outer surface of drum 90 has radially outwardly
extending teeth 92 that are spaced to enter at least
some of the recesses 24 in strip 22" in order to help
keep the recesses in successive turns of strip 22" on
drum 90 superimposed on one another and to help drum 90
pull strip 22" into the coiling mechanism. The outer
surface of drum 90 has the same radius as the inner
radius of the stators being made by the apparatus.
As additional strip material 22" is supplied
to drum 90, previous turns of the strip material are
forced to move up along the outer surface of the drum.
Accordingly, a helix of strip material 22" gradually
builds up on drum 90 as shown in FIG. 5. Although
FIG. 5 shows space between successive turns in this
helix, it will be understood that in actual practice
the successive turns are typically in contact with one
another.
When sufficient strip material 22" has passed
through cutter 70 to produce a stator of the desired
cylindrical length, cutter 70 is operated to cut
through strip 22". The accumulated strip material
downstream from the cutter is then lifted up off the
CA 02291459 1999-12-02
- 12 -
top of drum 90. Apertures 82 may be provided in
ramp 80 to allow a lifting mechanism (not shown) to
engage the under side of the helix on drum 90.
FIG. 9 shows a typical helix 100 of strip
material 22" after removal from coiling apparatus 60.
A subsequent step in the manufacture of stator cores in
accordance with this invention is to axially compress
helix 100 as shown by arrows 110 in FIG. 10. This
helps make the axial ends of the tubular stator core
more square (i.e., perpendicular) to the central
longitudinal axis of the stator. In addition to
squaring off the axial ends of the helix, the several
turns of strip material in the helix may be welded
together (e. g., along lines 102) to convert the helix
to a rigid, unitary structure 100' usable as a stator
core.
It will be apparent from the foregoing
discussion of the manner in which stator core 100' is
made that recesses 24 in adjacent turns of the helix of
material 22" are aligned with one another along the
entire axial length of the stator. These aligned
recesses therefore produce the longitudinal slots in
the interior surface of the stator core that are used
to receive the coils of wire required to complete the
stator in the conventional manner. In order to ensure
such alignment of the recesses 24 in adjacent turns of
the helix of material 22", the outer circumference of
drum 90 must be an integer multiple of the spacing
between adjacent recesses 24 in the strip material.
It will be understood that the foregoing is
only illustrative of certain aspects of the invention,
and that various modifications can be made by those
skilled in the art without departing from the scope and
spirit of the invention. For example, although only
CA 02291459 1999-12-02
- 13 -
two strips 22a and 22b are processed and superimposed
to produce composite strip 22" in the embodiment shown
and described herein, it will be understood that more
than two strips can be superimposed to produce
composite strip 22" if desired. As another example of
modifications within the scope of the invention, side-
by-side handling of strips 22a/22a' and 22b/22b' is
shown herein and may have the advantage of simplifying
storage mechanism 40. But strips 22a/22a' and 22b/22b'
could be supplied with different positions relative to
one another (e.g., one above the other) if desired. It
may not be necessary in all cases for the apparatus to
include all of the components that have been shown and
described herein. For example, coils 20a and 20b could
be of prepunched strip material, thereby rendering
punch 30 unnecessary. Storage mechanism 40 is also
optional and can be eliminated if there is no need to
adjust production rates between upstream and downstream
components.
Furthermore, pressure device or structure 200
as shown in elevation view in FIG. 12 and in plan view
in FIG. 13 may be included in apparatus 10 as an
additional feature of the invention. Preferably, two
pressure devices 200 would be included in apparatus 10,
each located between storage mechanism 40 and super-
position mechanism 50 and each associated with a
respective one of strips 22a' and 22b'.
Pressure device 200 compresses strip 22a' or
22b' between top roller 201 and bottom roller 202 as
the strip passes through the device in direction 208.
Top roller 201 is free to rotate about shaft 201' which
is mounted between two arms of lever 203. Lever 203 is
pivotably attached to support 206 by pin 203' and is
therefore pivotable in directions 205 and 205'. Top
CA 02291459 1999-12-02
- 14 -
roller 201 presses downward with a force F in direction
210 onto the upper surface of strip 22a' or 22b' and
bottom roller 202 reacts with an equal and opposite
force F upward in direction 220 onto the bottom surface
of strip 22a' or 22b'. The bottom roller 202 is free
to rotate about shaft 202' which is mounted on a
support structure (not shown). Adjustable weight 204
is mounted on the section of lever 203 which extends
out beyond top roller 201 opposite from pin 203'.
Weight 204 is adjustable in its position on lever 203
and in its weight. By adjusting these two factors, the
force exerted on strip 22a' or 22b' can be changed.
More particularly, as each strip 22a' or
22b' exits from storage device 40, each strip will
enter a separate pressure device 200. The strips 22a'
and 22b' will pass between pressure rollers 201 and 202
and experience a pressure P on their respective top and
bottom surfaces in contact with pressure rollers 201
and 202. Pressure P results from the force F exerted
from pressure rollers 201 and 202 to strips 22a' and
22b'. After exiting from pressure rollers 201 and 202,
strips 22a' and 22b' are brought together and
superimposed by super-position mechanism 50. While the
strips are actively driven through pressure devices 200
from further downstream, an active element may be
associated with each pressure device 200. For example,
pressure rollers 201 and 202 may be actively driven or
an additional active spur gear similar to spur gear 56,
designed for a single strip, may be used to help pull
the strips through pressure rollers 201 and 202.
The variations that can exist in the strip
material and the other various processes that the
strips undergo can cause spur gear 56 to feed different
lengths of the strip material to drum 90. Even if spur
CA 02291459 1999-12-02
- 15 -
gear 56 maintains precise alignment of the recesses 24
in strips 22a' and 22b' of composite strip 22",
variations in internal diameter 114 can still occur.
The internal diameter 114 is shown in FIG. 11 as the
distance between diametrically opposite pole extensions
112. (FIG. 11 shows stator core 100' after the slots
produced by axially aligned recesses 24 have been lined
with insulating material, but that insulating material
can be ignored for purposes of the present invention.)
For example, if the spacing of the recesses 24 in
strips 22a' and 22b' is not the same, more material
will be fed to drum 90 from the strip with the larger
recess spacing. Since drum 90 pulls the strips around
with teeth 92 entering at least some of the recesses
24, the strip with larger recess spacing will need to
fit more material between adjacent teeth 92 than the
other strip. This causes the longer strip to spread
radially out from drum 90 in order for the additional
material to fit in the same arc length around drum 90.
This results in a corrugated internal diameter of
stator core 100', wherein each adjacent strip layer in
stator core 100' will alternate between a larger and
smaller internal diameter. Other defects, deviations,
or irregularities in the thickness, recess spacing, or
other properties of one or both strips can produce
other similar imperfections in the internal diameter
114 of a stator core.
By measuring the internal diameter 114 in
stator core 100' and comparing these values to a
nominal value, an adjustment of the weight 204 in the
pressure device 200 for each strip 22a' and 22b' can be
determined. As each weight 204 is moved farther out on
the associated lever 203 or its weight increased,
pressure P increases on the respective strip. This
CA 02291459 1999-12-02
- 16 -
increase in pressure further compresses the strip as it
moves through pressure device 200 and thus decreases
its thickness and elongates its length. Hence, the
internal diameter 114 of stator core 100' for that
strip will increase. Therefore, if the internal
diameter of stator core 100' for a particular strip is
too small, the pressure P should be increased for that
particular strip. Likewise, if the internal diameter
of stator core 100' for a particular strip is too big,
the pressure P should be decreased for that particular
strip. Similarly, both weights 204 may need to be
adjusted if the internal diameter of the stator core as
a whole is too large or too small. Therefore, through
this method, variations in the internal diameter 114 of
stator core 100' can be reduced and possibly
eliminated. For this setup, the appropriate weight 204
is typically adjusted between reels of strip material
and also between fabricated stator cores. An
additional benefit of pressure rolling device 200 is
the flattening of certain types of local variations
that may occur on the strip material.
The adjustment of the weight 204 in each
pressure device 200 may be done manually by an operator
of apparatus 10 or it can be done automatically. In
pressure device 200 as described above, the weight 204
may be moved by a motor drive (not shown) connected
between weight 204 and lever 203 which can vary the
position of weight 204 on lever 203. The automatic
positioning of weight 204 can be determined by
measuring the internal diameter of strips 22a' and 22b'
in stator core 100' (or the internal diameter of stator
core 100' as a whole) and feeding this information
along with the nominal internal diameter to a control
CA 02291459 1999-12-02
- 17 -
unit (not shown) that controls the motor drive for the
weight.
FIG. 14 shows an alternative embodiment of
pressure device 200. Whereas pressure device 200 has
weight 204 to adjust pressure P on a strip, pressure
device 300 has a pressure adjusting structure or
actuator 302 which can vary the pressure P on a strip.
Actuator 302 can be any suitable actuator, such as a
hydraulic or pneumatic cylinder. FIG. 14 shows
actuator 302 as a pneumatic cylinder. After stator
core 100' has been fabricated, it is placed in
measuring station or structure 305 and the internal
diameter 114 is measured (e. g., for each strip or more
generally). This can be done with one or more probes.
While FIG. 14 shows one pressure device 300, it is
understood that there are preferably two pressure
devices 300 used in apparatus of the type shown in
FIGS. 1-8. More particularly with respect to one
pressure device 300, the measured internal diameter 114
for the respective strip 22a' or 22b' is sent to the
appropriate control unit or structure 301 which
compares the measured internal diameter with the
nominal internal diameter. Control unit 301 corrects
for a difference in internal diameter by varying the
pressure in actuator 302 by a certain amount. This
adjustment will affect the strip material used in
subsequent stator cores 100' fabricated from
apparatus 10. Alternatively, internal diameter
measuring structure 305 may measure internal diameter
114 more generally and the pressure devices 300 for
both strips 22a' and 22b' may respond by making
appropriate adjustments to the pressures P applied to
both strips.
CA 02291459 1999-12-02
- 18 -
It will be understood that the foregoing is
illustrative of further principles of the invention,
and that various modifications can be made by those
skilled in the art without departing from the scope and
spirit of the invention. For example, although two
pressure devices 200 or 300 are preferably used in
apparatus 10, it will be understood that there could be
only one pressure device used on only one of the
strips. As an example of another modification, an
additional active element could be used in conjunction
with pressure device 300 to help the strip pass through
pressure rollers 201 and 203.
FIG. 15 shows a simplified plan view of an
alternative embodiment of an apparatus for forming
dynamo-electric machine stators. Apparatus 400
includes two reels 420a and 420b of strip material 422a
and 422b, respectively. Strip material 422a and 422b
may be thinner than the strip material typically used
in the prior art. Strips 422a and 422b initially
undergo the same processes through separate equipment.
Therefore, the process will be described in detail for
strip 422a, and it will be understood that strip 422b
undergoes the same process.
Strip 422a is fed from reel 420a to punch
430a. Punch 430a performs the same function as punch
30. Strip 422a exits from punch 430a and is referenced
as punched strip 422a'. Punched strip 422a' enters
storage mechanism 440a which performs the same function
as storage mechanism 40. Upon exiting storage
mechanism 440a, strip 422a' enters pressure device
300a. Pressure device 300a compresses strip 422a' as
described in the foregoing. Pressure device 300a
selectively varies the pressure P applied to strip
422a' in response to control command 310a from control
CA 02291459 1999-12-02
- 19 -
unit 301. Strip 422a' leaves pressure device 300a and
enters coiling mechanism 460a.
Pressure device 300a and coiling mechanism
460 are shown in more detail in FIG. 16. (The "a"
suffix is not used on the reference numbers in FIG.
16.) Pressure device 300 is shown directly before spur
gear 456. Spur gear 456 is configured to guide a
single strip toward drum 90. With pressure device 300
in such close proximity to spur gear 456 and drum 90,
an additional active element may not be necessary to
help strip 422a' pass through pressure device 300. In
reference to coiling mechanism 460, apart from spur
gear 456 and the use of a single strip, coiling
mechanism 460 performs the same processes as coiling
mechanism 60. Therefore, it will be understood that
both strips 422a' and 422b' are formed into
helixes 100a and 100b, respectively, after processing
from separate coiling mechanisms 460a and 460b.
Helixes 100a and 100b are subsequently placed
into compression and welding station 470 where they are
combined as shown in FIG. 17 by aligning their
longitudinal axes and the their recesses 24. An
additional layer or layers of hollow annular lamination
100c may be inserted between and combined with helixes
100a and 100b by aligning its longitudinal axis and
recesses 24 with those of helixes 100a and 100b. In
station 470 helixes 100a, 100b, and possibly the
additional lamination 100c are consequently axially
compressed by forces F, welded, and thereby converted
to a rigid, unitary structure 100d. The welding can be
performed along lines 102 shown in FIG. 10.
Subsequent to welding, stator core 100d may
be processed in conventional dimensioning station or
structure 480. Station 480 may include apparatus for
CA 02291459 1999-12-02
- 20 -
applying forces) to the inside and/or outside of
stator core 100d to mechanically adjust various
dimensional parameters of the core. For example,
station 480 may force a substantially cylindrical
member axially into the interior of the stator core
100d to ensure that the core is truly circular with the
desired interior diameter 114. While dimensioning
station 480 is able to correct for some deviation in
the parameters of stator core 100d, excessive working
of the material of stator core 100d in station 480 may
not be desirable. For this and other reasons it may be
desirable to use feedback to pressure devices 300 to
reduce the amount of dimensional adjustments that must
be made in station 480.
Stator core 100d is removed from device 480
and placed in measuring station 490. Measuring station
490 measures the internal diameter 114 of each of
helixes 100a and 100b of stator core 100d. This may be
done with one probe or with two probes, each entering
from opposite ends of stator core 100d. The internal
diameters 114 of helixes 100a and 100b are sent to
control unit 301.
Control unit 301, with the measured internal
diameters 114 and the nominal required internal
diameter, determines the required adjustment to
pressure devices 300a and b to correct for any
deviation in the internal diameters 114. Control unit
301 then varies the pressure in actuator 302 by the
determined adjustment. This adjustment will affect the
strip material used in subsequent stator cores 100d.
It will be understood that the foregoing is
illustrative of an alternative embodiment of the
invention, and that various modifications can be made
by those skilled in the art without departing from the
CA 02291459 1999-12-02
- 21 -
scope and spirit of the invention. For example, while
it is shown that helixes 100a and 100b are formed from
separate pieces of equipment, it will be understood
that there could be single puncher 430 or storage
mechanism 440 configured to handle both strips. It may
not be necessary to include all of the components of
the alternative embodiment described herein. For
example, storage mechanism 440 may not be necessary and
punch 430 may not be if coils 420a and 420b are of
prepunched strip material. As another example of
modification within the scope of the invention,
pressure device 200 may be used in place of pressure
device 300. If pressure device 200 is used, then
weight 204 can be manually adjusted without the need
for a control unit or automatically adjusted with a
motor drive connected to the control unit.
Additionally, measuring station 490 may be used to
determine the required adjustment to the pressure
devices and control unit 301 would actuate the pressure
devices. Alternatively, there could be two control
units 301, one for each pressure device. As an example
of another modification, only one pressure device may
be used to match the internal diameters of the two
helixes.
It will be appreciated that the pressure
device aspects of the invention can also be used in
apparatus for making a stator core from a single strip
of material. For example, such apparatus could be as
shown in FIG. 15, but without the elements having
reference numbers having the "b" suffix, and with
compression and welding device 470 and subsequent
stations operating on only a single helix 100a.
An additional aspect of the invention
includes using pressure rollers which are tapered in
CA 02291459 1999-12-02
- 22 -
pressure devices 200 and 300 in place of cylindrical
rollers 201 and 202. The tapered rollers are shown in
FIG. 18 as top tapered roller 207 and bottom tapered
roller 209. The tapered rollers are aligned such that
the axial ends of the tapered rollers with the larger
diameter are aligned symmetrical about the strip
material and apply pressure to the edge of the strip
which forms the external surface of the helical coil.
Pressure rolling the strips with tapered rollers may
help to further reduce the effects of local variations
of the strip material on the performance of stator
cores. When used with apparatus that has a coiling
mechanism configured to coil a single strip, the
pressure device with tapered rollers 207 and 209 may be
located before rollers 62 and 64 of the coiling
mechanism.
A pressure device with tapered rollers 207
and 209 can be used with apparatus 10 with super-
position mechanism 50. The pressure device can be used
on composite strip 22" at any place between super-
position mechanism 50 and rollers 62 and 64 of coiling
mechanism 60. This may be used in addition to or in
place of pressure rolling device 200 or 300 with
cylindrical rollers 201 and 202 which may be located on
at least one strip 22a' or 22b'.
FIG. 19 shows a plan view of an additional
alternative embodiment of an apparatus for helically
coiling strip material to form dynamo-electric machine
stators. FIG. 20 shows a detailed plan view of strip
material 22 in FIG 19. Strip material 22 contains pole
extensions 112 centered on corresponding axes 26.
Strip 22 has a thickness 29 and a width dimension 28.
Dimension 28 has a great influence on the force
required to bend strip 22 into a coil. The magnitude
CA 02291459 1999-12-02
- 23 -
of dimension 28 relates positively to the force
necessary to coil strip 22 and thus to the bending
strength of strip 22. Unwanted deformation of strip 22
can occur when strip 22 is being bent into a coil if
the strip's bending strength is large and thickness 29
is small. The bending of strip 22 causes the inside
portion of strip 22 to undergo compression and the
external portion of strip 22 to undergo tension. The
compression of the internal edge may cause unwanted
deformation in areas 27 of strip 22. The unwanted
deformation can generally be considered buckling of
strip 22 out of the plane shown in FIG. 20 due to the
compression in areas 27. This unwanted deformation may
occur as a series of creases in areas 27.
Strip 22 as shown in FIGS. 19 and 20 contains
internal apertures 25. Apertures 25 are located at the
base of pole extensions 112 and centered about axes 26.
Apertures 25 reduce the occurrence of the unwanted
deformation described in the foregoing. The form of
apertures 25 are also such that solid areas 23 of strip
22 are left for the magnetic flow from operation as a
dynamo-electric machine stator. This allows coiling
mechanism or structure 560 to helically coil thinner
strips of strip material 22 without unwanted
deformation.
Another deformation which may occur in
coiling relatively thin strips with a relatively large
dimension 28 is undulation of strip 22 between spur
gear 456 and drum 90. In order to help prevent strip
22 from undulating, spur gear 456 can be placed in
close proximity to coiling mechanism 560 as shown in
FIG. 19. This decreases the length of the strip which
may deform between spur gear 456 and rollers 62 and 64.
An additional modification which decreases the chance
CA 02291459 1999-12-02
- 24 -
of undulation is to make casing 61, which guides strip
22 from rollers 62 and 64 to cutter 70, close-fitting
to strip 22.
A final modification which can be made to
coiling mechanism 560 to reduce undulation of strip 22
is the addition of roller 65. Roller 65 is located
between spur gear 456 and rollers 62 and 64 and is free
to rotate about axis 67. Roller 65 is shown in
elevational view in FIG. 21. Roller 65 contains a
groove 65' around its circumference with a V-shaped
opening for containing the external edge of strip 22.
In particular, roller 65 prevents unwanted deformation
in direction 69 of strip 22.
The apertured strip 22 shown in FIGS. 19 and
20 can be alternatively described in the following
terms: Strip 22 is a longitudinal strip of
ferromagnetic metal for use in producing cores for the
stators of dynamo-electric machines (e. g., electric
motors, generators, alternators, or any other generally
similar kinds of electrical equipment). Strip 22 has a
plurality of apertures 25 through the material of the
strip between the two major planar surfaces of the
strip, the apertures being spaced from one another
along the length of the strip. Apertures 25 are
configured to deform to relieve stress in strip 22 when
the strip is bent, transverse to its length and at
least approximately in the plane in which the strip
lies where it is bent, to produce the stator core. In
the particular embodiments shown and described herein,
the bending thus referred to is the bending between
rollers 62 and 64 and around drum 90 which forms the
strip into a multi-turn helix. Preferably, the stress
relieved by apertures 25 reduces possible deformation
of the strip perpendicular to the plane of the strip
CA 02291459 1999-12-02
- 25 -
where it is bent as described above. Apertures 25 may
relieve stress, for example, by changing shape and/or
size.
Considering more particularly the features of
the illustrative embodiment of strip 22 which is shown
in FIGS. 19 and 20, strip 22 has a spine portion which
extends continuously along a first side of the length
of the strip, and a plurality of teeth 112 which extend
transverse to the spine portion at respective locations
which are spaced along the length of the spine portion.
Apertures 25 are disposed in the spine portion. Most
preferably, each aperture 25 is disposed adjacent the
base of a respective one of teeth 112 where that tooth
joins the spine portion of the strip. When strip 22 is
bent into a mufti-turn helix with the spine portion of
the strip adjacent a radially outer surface of the
helix and teeth 112 extending radially inward toward a
central longitudinal axis of the helix, apertures 25
change size and/or shape (e.g., reduce in size) to
relieve stress in the strip which might otherwise
produce deformations of the strip perpendicular to its
plane.
It is to be understood that the term
"aperture" is used herein and in the appended claims to
refer to an opening through strip 22 which is
completely surrounded or bounded by material of the
strip. An aperture 25 is therefore different from a
recess (such as a recess 24) in the strip because a
recess is only partly surrounded by the material of the
strip and is therefore open on one side. The use of
closed apertures 25 (as distinct from partly open
recesses) to relieve stress in strip 22 is desirable
for several reasons. Closed apertures 25 tend to
reduce the amount of metal in strip 22 less than partly
CA 02291459 1999-12-02
- 26 -
open recesses would. The presence of more metal tends
to improve the electromagnetic performance of the
finished stator. More metal also improves the heat-
dissipating characteristics of the finished stator.
Closed apertures 25 also give the finished stator a
relatively smooth outer surface which is free of the
undesirable discontinuities that would result from the
use of partly open recesses.
Apertures 25 may be formed in strip 22 in any
suitable way and with any suitable shapes, sizes, and
locations. For example, the punching mechanisms 30/430
that may be provided for producing recesses 24 in
strip 22 may also punch apertures 25 in the strip.
It will be understood that the foregoing is
illustrative of an additional alternative embodiment of
the invention, and that various modifications can be
made by those skilled in the art without departing from
the scope and spirit of the invention. For example,
while coiling mechanism 560 is shown coiling a single
strip of material, it will be understood that two or
more strips may be coiled together as a composite
strip. As another example of a modification, internal
apertures 25 may be not be centered about axis 26. It
may not be necessary to include all of the components
and aspects of the this alternative embodiment. For
example, internal apertures 25 may be sufficient alone
to prevent unwanted deformations.
One skilled in the art will appreciate that
the present invention can be practiced by other than
the described embodiments, which are presented for
purposes of illustration and not limitation, and the
present invention is limited only by the claims which
follow.
