Note: Descriptions are shown in the official language in which they were submitted.
CA 02042253 1999-10-21
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METHOD OF MAKING A TRANSFORMER
CORE COMPRISING STRIPS OF AMORPHOUS
STEEL WRAPPED AROUND THE CORE WINDOW
This invention is related to the subject
matter disclosed and claimed in the following
patents:
U.S. P,atent 4,734,975 - Ballard & Klappert
U.S. Patent 4,741,096 - Lee & Ballard
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TECHNICAL
This invention relates to a method of making a
core for an electric transformer that comprises a
plurality of strips of amorphous steel wrapped in
superposed relationship about the window of the core
and, more particularly, relates to a method of this type
that employs a belt nester for wrapping packets made
from groups of such strips about a rotatable arbor that
is rotated as the packets are wrapped thereabout.
BACKGROUND
A type of core-making machine that has been used
for many years for making transformer cores is the belt
nester. Typically, a belt nester comprises a rotatable
arbor about which sections of magnetic strip steel of
controlled length are wrapped in superposed relationship
as the arbor is rotated, thereby building up a core form
that increases in diameter as additional strips are
wrapped about those previously wrapped. Wrapping of the
strips is effected by use of a flexible belt that
encircles the arbor and is driven to cause rotation of
the arbor and any strips previously wrapped about the
arbor. Strips are fed into the belt nester in such a
manner that they enter between the arbor and the
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encircling belt; and as the belt and arbor move
together, each entering strip, or group of strips, is
forced by the belt to tightly encircle the arbor or any
core form already built up upon the arbor. An example
of a belt nester of this type is disclosed in U.S.
Patent 3,049,793-Cooper.
Belt nesters of the above type have heretofore
been used for making cores that comprise strips of
amorphous steel that are wrapped about the rotating
arbor. Because the amorphous strips are very thin
(e.g. , typically only about 1 mil in thickness) , it is
customary and highly desirable to feed them into the
belt nester in groups, each group being at least ten
strips in thickness. But one problem that is present
when a belt nester is used with groups of amorphous
steel strips is that during the nesting process the -
strips tend to slide about within the group and on the
rotatable arbor or on the rotating partially-built up
core form, and this is a serious problem because these
strips must be precisely and predictably located. To
overcome this problem, the assignee of the present
invention has covered the strips, just prior to belt
nesting, with a volatile liquid such as
perchloroethylene that is capable of holding the strips
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together in the manner required for effective belt
nesting. The liquid later evaporates. This, however,
is not an entirely satisfactory approach because the
perchloroethylene is expensive, is environmentally
undesirable, and can produce rust or corrosion problems.
OBJECTS
An object of our invention is to provide, for
making a transformer core of amorphous steel strips
extending about the core window, a method that is
capable of being effectively carried out with a belt
nester having a rotatable arbor about which are wrapped
amorphous steel strips fed into the belt nester in
groups.
Another object is to carry out the immediately-
preceding object by providing a method that requires no
liquid for holding the amorphous steel strips together
while they are being wrapped about the arbor.
SUb~iARY
In carrying out our invention in one form, we
assemble a plurality of packets of amorphous steel
strips, each packet being made up of superposed groups
of amorphous steel strips and each group being made up
of at least one section of multiple-layer amorphous
steel strip. The sections of amorphous steel strips
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are derived by cutting to controlled lengths a composite
strip of amorphous steel strip that has been made up by
combining multiple-layer thickness strips derived from a
plurality of master spools. The multiple-layer
thickness strip in each of these master spools is made
by a pre-spooling operation in which a, pre-spooling
machine takes a plurality of mill-wound spools of single
layer thickness strip and combines strips from such
mill-wound spools to form said multiple-layer thickness
strips in said master spools.
We have found that when this process comprising
pre-spooling is used for making the aforesaid composite .
strip, the strips in each section cut from the composite
strip, even though essentially dry, adhere to juxtaposed
strips almost as if a glue is present between them.
This adhesive effect enables us to make up cohesive
packets from these sections and to feed such packets
into the belt nester without the necessity of relying
upon the previously-used liquid for holding the strips
against displacement during the nesting operation.
BRIEF DESCRIPTION OF FIGURES
For a better understanding of the invention,
reference may be had to the following description taken
in connection with the accompanying drawings, wherein:
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Fig. 1 is an enlarged side elevational view of a
packet of amorphous steel strips representative of many
such packets that are used in carrying out our method.
Fig. 2 is a plan view of the packet shown in Fig.
1.
Fig. 3 is a partially schematic side elevational
view of a belt nester used for building up a core form
from a plurality of packets of the type depicted in
Figs. 1 and 2. A portion of one of the guide flanges of
the belt nester is broken away.
Fig. 4 is a sectional view along the line 4-4 of
Fig. 3.
Fig. 4A is an enlarged view of a portion of Fig. 3
without any breaking away of the guide flange.
Fig. 5 is a sectional view along the line 5-5 of
Fig. 3.
Fig. 6 is a schematic showing of a pre-spooler in
which single layer thickness strip is unwound from five
starting spools of amorphous steel strip and combined
into multi-layer thickness strip that is wound onto a
master spool.
Fig. 7 is a schematic showing of apparatus that
combines multiple-layer thickness strip unwound from
four master spools into a composite strip that is fed
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forward and sheared into lengths of composite strip.
The apparatus of Fig. 7 receives the master spools from
the pre-spooler of Fig. 6.
Fig. 8 is a sectional view along the line 8-8 of
Fig. 3.
DETAILED DESCRIPTION OF EMBODIMENTS
THE PACKETS
Referring first to Figs. 1 and 2, there is shown a
packet 110 that is representative of a large number of
packets that are used for constructing a transformer
core in accordance with the method of our invention.
The packet of Figs. 1 and 2 is formed from many
superposed elongated strips 112 of amorphous steel, each
having a thickness of only about 1 mil, which is very
small in comparison to the 7 to 12 mils typical of the
thickness of the grain-oriented silicon steel that is
most commonly used for distribution transformer cores.
Each strip comprises two lateral edges 114 extending
along its length and transversely-extending edges 116 at
opposite ends of the strip. 'Phe superposed strips are
arranged in groups 120 each comprising a large number of
strips, e.g., 10 to 36. In each group, the lateral
edges 114 of the strips at each side of the strips are
substantially aligned, and the transversely-extending
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edges 116 of the strips at each end of the strips are
substantially aligned.
Packet 110 comprises a plurality of superposed
groups 120 of strips. In each packet, the lateral edges
(114) of all the groups are substantially aligned but
the transversely-extending edges (116) of the groups at
the ends of the packet are staggered with respect to
each other longitudinally of the packet. Within each
packet, the ends of successive groups, considered from
the inside I to the outside O of the packet, overlap at
one end of the packet and underlap at the opposite end
of the packet. All the packets used in a given
transformer core are preferably of the same basic
construction and the same width, but the packets
(assembled for being successively wrapped about the
window of the core) are made of progressively increasing
length to accommodate the increasingly greater
circumference of the core form as it is built up by the
successive wrapping of packets about its outer
periphery. In carrying out the method of our invention,
the packets 110 and their components~are produced in a
special manner that will be described in more detail
hereinafter.
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THE HELT NESTER 12S
For building up a core form from packets such as
shown at 110 in Figs. 1 and 2, we utilize a type of
wrapping machine commonly referred to as a belt nester.
Referring to Figs. 3 and 4, this belt nester, designated
128, comprises a rotatable arbor 130 that comprises a
steel hub 131 having a circular outer periphery 132 and
two guide flanges 134 and 136 removably attached to the
hub at its respective opposite sides. Each guide flange
134 and 136 extends radially outward beyond the circular
outer periphery 132 of the hub so that there is a space
137 of U-shaped cross-section present at the outer
periphery of the arbor. Preferably, each of the flanges
134 and 136 is made primarily of. aluminum, but each
flange includes a thin sheet 138 of wear-resistant
stainless steel on its inner face adhesively bonded to
the remainder of the flange. As will soon be explained,
in more detail, a plurality of packets such as shown at
110 in Figs. 1 and 2 are successively wrapped about the
hub 131 of the arbor in. the space 137 between the
flanges 134 and 136. The flanges serve as guides
cooperating with the lateral edges 114 of the packets to
assure that the packets are tightly wrapped about the
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outer periphery 132 of the hub with their lateral edges
114 at each side of the packet in substantial alignment.
The wear-resistant coating 138 on each flange
serves to protect the flange against wear or other
damage from the sharp edges of the amorphous steel
strips wrapped within space 137.
For successively wrapping the packets llo about
the hub 131 of the arbor 130, the belt nester 128
employs an endless flexible belt 140 that encircles the
hub 131. This belt extends from a first point 141 on
the front of the arbor about a first front roller 142,
then about three idler rollers 143, 144 and 145, then
about rollers 146, 147 and 148 in a belt-tensioning
device 150, then about three more idler rollers 151, 152
and 153, then about a motor-driven pulley 155, and then w
about a second front roller 156 to a second point 158 on
the front of the arbor spaced from the first point 141,
and then around the hub 131 of the arbor back to the
first point 141.
Each of the above described rollers 142, 143, 144,
145, 147, 151, 152, 153 and 156 is suitable mounted for
free rotation about its own stationarily-located central
axis. The motor-driven pulley 155 is coupled to an
electric motor (not shown) through a rotatable drive
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shaft 157 attached to the pulley and having a stationary
axis. When the motor is operated to drive the pulley,
the pulley drives the belt 140 in the direction of
arrows 160 (Fig.3).
The belt-tensioning device 150 comprises a pair of
rollers 146 and 148 that are mounted on a horizontally-
extending cross-head 162 that is suitably guided for
vertical motion and biased vertically upward by a spring
device 164. Also included within the belt-tensioning
device is a stationary idler roller 147. The belt 140
extends from the idler roller 145 over one of the
movable rollers 146, then underneath the idler roller
147, then over the other movable roller 148 and then
underneath idler roller 152. As the core form on the
arbor is built up, greater effective belt length is
required for the belt 140 to encircle the increasingly
larger periphery of the core form; and the movable
rollers 146 and 148 move downwardly against the bias of
spring device 164 to make available this greater
effective belt length.-The spring device 164 maintains a
substantially constant tension on the belt 14o as the
core form is built up on the arbor.
Each packet 110 that is to be wrapped about the
arbor is fed onto the arbor hub along the upper surface
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of a stationary guide plate 165 that extends between
theof front rollers 142 and 156. This guide plate has a
front portion 167 that is curved gradually upwardly so
that the leading end of the packet entering from the
right is directed upwardly into the space between the
upper run of the belt 140 and the underlying peripheral
portion of the hub of the arbor. ~3hen the belt contacts
the leading end of the entering packet, the belt drive
is started and the leading end of the packet is gripped
between the belt and the hub (or any core form then
present on the hub). As the belt moves in a
counterclockwise direction about the axis 166 of the
arbor, it drives the arbor counterclockwise about this
axis, carrying the leading end of the packet
counterclockwise about the axis 166. As the leading end
of the packet moves in this manner, more and more of the
remaining length of the packet enters the space between
the belt and the. hub and is progressively wrapped about
the hub. This action continues until the trailing end
of the packet is wrapped. The packet is of such length
that its trailing end overlaps its leading end, thereby
producing a lap joint between opposite ends of each
group in the packet. The leading edge of each group
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that is laid down after the first (or radially-
innermost) group is positioned closely adjacent the
trailing edge of the immediately-preceding group.
Accordingly, there are formed between the ends of each
packet distributed lap joints, sometimes referred to
also as step lap joints.
Fig. 3 depicts the belt nester after its arbor 132
has been rotated through almost a single revolution to
almost complete wrapping of a first packet 110 about the
arbor hub. A second packet is depicted at 110a in a
position where it is in readiness to be fed in the belt
nester to be wrapped about the first packet after
wrapping of the first packet is completed.
The arbor must be rotated slightly more than one
revolution 1(i.e., a short distance into a second
revolution) in order to produce the desired overlap at
the packet joint. To restore the arbor to a position to
receive the next packet, this second revolution of the
arbor is completed, and then a new packet (e.g., 110a of
Fig.3) is fed into the belt nester in the same manner as
described above and is wrapped about the outer periphery
of the immediately-preceding wrapped packet in the same
manner as described above.
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Additional packets are successively wrapped about
the outer periphery of the core form in the same manner
until a core form of the desired thickness, or build,
has been developed. The additional packets that are
wrapped after the first two are so positioned that their
lap joints are located generally in radial alignment
with the lap joints of the first two packets. The joint
region of the full-thickness core has a progressively
increasing length proceeding from the window to the
outer periphery of the core form, just as shown in Fig.
2 of the aforesaid U.S. Patent 4,741,096-Lee and
Ballard. '
As shown in Fig. 4A, one of the f langes ( 134 ) on
the arbor has a gap or window 135 therein angularly
registering with the joint region, and through this
window the operator of the belt nester 128 can readily
view the joint developed for each packet. If the amount
of overlap in the joint is not within prescribed limits,
he initiates certain adjustments in the strip-length
control means (soon to be described) which cause the
strip-length control means to appropriately adjust the
length of subsequently-cut strips and thus the groups
and packets assembled from such strips..
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As the core form is built up on the hub 131 of the
arbor, the axis 166 of the arbor is forced to move to
the left, as viewed in Fig. 3, thus providing room for
new packets successively fed onto the outer periphery of
the core form between this outer periphery and the front
roller 142. This leftward movement of the arbor axis is
made possible by horizontally-extending slots 168
provided in the framework 170 that supports the arbor.
The arbor has a horizontally-extending supporting shaft
172 that extends into these slots, and the slots
cooperate with this shaft 172 to guide the arbor for the
desired horizontal movement. The arbor is biased to the
right by the belt-tensioning device 150 supplying
tensioning force to the belt 140. But as additional
packets 110 are fed into the belt nester 128 to increase
the diameter of the core form, the arbor hub 131 is
forced away from the front rollers 142 and 156, thus
gradually moving horizontally to the left against the
rightward bias of the belt-tension. Rightward movement
of the arbor by the above-described biasing force is
limited by the front rollers 142 and 156, wi~ich contact
the belt 140 encircling the core form.
As explained under BACKGROUND hereinabove, onethe
problems encountered when a belt nester is used with
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groups of amorphous steel strips is that during the
nesting process the strips tend to slide about within
the group and on the rotating arbor or on the partially
built-up rotating core form. To overcome this problem,
applicants' assignee has heretofore covered the strips
just prior to belt nesting with a volatile liquid such
as perchloroethylene that is capable of holding the
strips together sufficiently to permit effective belt
nesting. But this approach is nat entirely satisfactory
because the perchloroethylene is expensive, is
environmentally undesirable, and can produce rust or
corrosion problems.
FEATURES CONTRIBUTING TO OUR ABILITY TO BELT
NEST ESSENTIALLY DRY AMORPHOUS STEEL
SHEETS ON A ROTATING ARBOR
Our invention enables us to effectively belt-nest
groups of amorphous steel strips on a rotating arbor
without relying upon any perchloroethylene or similar
liquid for holding the strips together while they are
being wrapped. An important step in enabling us to
achieve this objective is that we feed the groups of
strips into the belt nester in packets instead of in
individual groups. Each packet has enough column
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strength considered laterally of the packet to enable
the guide flanges 134 and 136 of the rotating arbor to
edge-guide the packet laterally, acting upon the lateral
edges of the packet to force the packet to seat squarely
within the U-shaped space 127 at the periphery of the
arbor with its lateral edges at each side of the packet
in alignment with those of the already-seated packets.
In addition, by wrapping in packets instead of in
individual groups, we greatly reduce the number of
revolutions that the arbor is required to make in order
to wrap the strips of an entire core; and this reduces
the likelihood of undesirable displacement of individual
strips or groups on the arbor during wrapping of this
large number of strips.
Another important step in enabling us to achieve
our above objective is that we assemble our packets from
groups of strips derived through a pre-spooling process
corresponding to that disclosed and claimed in the
aforesaid Application S.N. 505,593-Ballard and Klappert.
We have found that when the groups are made by this pre-
spooling process, the strips in each group, even though
essentially dry, adhere to juxtaposed strips almost as
if a glue is present between them. This adhesive effect
enables us to make up cohesive groups and cohesive
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packets from these groups that are both characterized by
a greatly reduced tendency for the strips to slide on
each other while the packets are being fed into the belt
nester 128 and are being wrapped about the arbor 130.
More details on the pre-spooling process are provided
hereinafter.
Another important feature that contributes to our
ability to belt-nest the amorphous steel strips on a
rotating arbor without relying upon a liquid adhering
agent is the tight guidance that we apply to the edge
portions of each packet from the time the packet enters
the belt nester underneath the upper front roller 142.
In this respect, we provide the upper front roller 142
with a pair of edge-guiding infeed rollers 180 that are
mounted on the same rotatable shaft 182 as the upper
front roller 142, as will best seen in Fig. 5. As the
packet enters under the upper front roller 142, the edge
portions of the packet tend to bend, or curl, up and, in
so doing, to develop a strong tendency to roll up on one
or the other of the nesting flanges 134 and 136. The
infeed rollers 180 by bearing against the top of the
packet edge-portions(and thus exerting force on these
portions acting radially inwardly of the arbor hub),
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block those edge-portions from rolling up the flanges
and thus maintain a cylindrical configuration of the
core form as it is built up. For best results, the
spacing (at 189, Fig. 5) between the infeed rollers 180
and their associated flanges 134 and 136 is made quite
small in the range of about .01 to .05 inches. It will
be noted from Figs. 4 and 5 that the belt 140 of the
belt-nester has a width that extends for only a small
portion of the width the amorphous sheets and does not
extend out to the infeed rollers 180. As a result, the
exposed periphery of thse rollers is available to bear
against the edge portions of the amorphous packet to
block these edge portions from climbing up the flanges
134 and 136.
The shaft 182 that carries the infeed rollers 180
and the upper front roller 142 is mounted within axially
spaced apart bearings, schematically shown at 186 and
188. These bearings are fixed to the frame 170 by
suitably mounting structures (not shown).
MAKING GROUPS OF STRIPS BY A PROCESS THAT
COMPRISES PRE-SPOOLING
The above-referred-to process for forming the
packets 110 is illustrated in Figs. 6 and 7, which
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figures are substantially identical to Figs. 1 and 2 of
the aforesaid Application S.N. 505,593-Ballard and
Klappert.
Referring now to Fig. 6, there is shown a pre-
spooler 10 which is adapted to receive five starting
spools 12,14, 16, 18, and 20 of amorphous steel strip.
These starting spools are spools received from the steel
mill, and, accordingly, in each starting spool the strip
is of single-layer thickness. The basic purpose of the
pre-spooler is to combine the single-layer thickness
strips from the starting spools 12, 14, 16, 18, and 20
into multiple-layer thickness strip which is wound onto
a master reel 24 as a master spool 25.
Each starting spool is mounted on a fixed-axis
rotatable spindle 26 which is coupled to the rotor of an
adjustable speed electric motor 27, which motor, when
energized drives the spindle 26 in a counterclockwise
direction (as indicated by arrow x) to effect unwinding
of the associated starting spool. The master reel 24 is
mounted on a fixed-axis rotatable spindle 28, which is
also coupled to the rotor of an electric motor (23),
which normally operates at a substantially constant
speed. The latter motor, when energized, drives the
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spindle 28 in a clockwise direction (as indicated by
arrow y) to wind the multiple-layer thickness strip onto
the master reel 24. The single-layer thickness strip
unwound from each starting spool is directedover a
series of guide rollers onto the master reel 24. These
single-layer thickness strips are designated 29a, 29b,
29c, 29d, and 29e.
The guide rollers for the strip from the first
starting spool 24 are designated 30, 31, and 32. The
guide rollers for the strip from the second starting
spool are designated 34, 35, and 36. Corresponding
guide rollers are present for the strip unwound from
each starting spool.
The single-layer thickness strips from the five
starting spools are combined into a multiple-layer
thickness strip at the periphery of the master spool 25,
and this multiple-layer thickness strip is wound onto
the master spool 25 as the spindle 28 of the master reel
is driven in a clockwise direction.
For maintaining each single-layer thickness strip
under appropriate tension as it is being wound onto the
master reel 24, a tensioner roller 40 is provided
adjacent each starting spool, acting on a downwardly
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extending loop 41 in the associated strip located
between two of the guide rollers for the strip. Each of
these tensioner rollers 40 is mounted in a conventional
manner for vertical motion, being gravity biased in a
downward direction by a suitable weight. This gravity
bias, acting on the strip through roller 40, keeps the
strip taut, thus assuring that the multiple-layer
thickness strip is smoothly and tightly wound onto the
master reel 24. In one embodiment of the inventionm
each tensioner roller 40 is biased downwardly with a
weight of about 1.5 pounds for each inch of strip width.
For controlling the unwinding of the starting
spools as the multiple-layer thickness strip is being
wound onto the master reel 24, a suitable control 31 is
provided for each starting-spool electric motor 27.
This control 31, which is of a conventional form,
operates off a dancer arm, schematically indicated at
33, that moves up and down with the tensioner roller 40.
The control 31 causes its associated motor 27 to operate
at a speed which depends upon the vertical position of
the tensioner roller 40. As the starting spool (e. g.,
12) decreases in diameter through unwinding and the
master spool 25 increases in diameter through winding,
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the amount of unwound strip material between the two
spools (12 and 25) will tend to decrease, thus
shortening the loop 41 and causing the tensioner roller
40 to rise. Control 31 responds to this rise in the
position of the tensioner roller 40 by causing the motor
27 to increase its speed, thereby making available more
unwound strip material and causing the tensioner roller
to descend to its normal vertical position shown. If
the tensioner roller descends beyond its normal vertical
position shown, the control 31 will cause the motor 27
to reduce its speed, thus shortening loop 41 and
returning the tensioner roller 40 to its normal vertical
position shown.
It Will thus be seen that the tensioner roller 40
and control 3i cooperate (i) to maintain substanciai
tension on each of the single-layer thickness strips as
it is being wound onto the master spool 25 and ( ii) to
effect unwinding of the starting spools at appropriate
speeds without requiring all the unwinding forces to be
transmitted through the single-layer thickness strip.
When a master spool 25 of the desired build has
been wound on reel 24, the master spool is removed from
the drive spindle 26 and put aside for subsequent use.
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To make possible removal of the master spool, the
single-layer thickness strips 29a-a are suitably cut at
a location adjacent the master spool just prior to
removal.
After a first master spool has been built up as
above described and then removed from drive spindle 28,
additional master spools are built up in the same manner
on the drive spindle 28, each being removed upon
completion to allow the next one to be built up. Then,
four of the master spools 25 are loaded on the four
payoff reels 50 of the care-making apparatus shown in
Fig. 7.
As further shown in Fig. 7, the multiple-layer
thickness strips 53 in the master spools 25 are unwound
from their respective master spools and combined into a
composite strip 55. This composite strip 55 has a strip
thickness equal to the total number of single-layer
strips in all of the master spools 25 depicted in Fig.
7. In the illustrated embodiment, each of the multi-
layer strips 53 in each of the, master spools 25 is five
layers in thickness, and, accordingly, the composite
strip 55 is 4x5, or 20, layers in thickness.
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In unwinding from their master spools 25 and
traveling into the location where they are combined to
form the composite strip 55, each of the strips 53 of
Fig. 2 passes through a pit 76 common to and beneath all
the master spools 25 and then over a guide roll 74,
where the orientation of each strip is changed from
generally vertical to generally horizontal. After
passing over the guide rolls 74, the strips are directed
in gradually converging relationship into the composite
strip 55. The portion of each multiple-layer thickness
strip 53 between its associated master spool and its
quide roll 74 hangs downwardly in a loop that is located
in the pit 76. The weight of the strip 53 in this loop
75 exerts tensile forces on the associated strip 53 as
it enters the composite strip 55, thus keeping the strip
53 taut just upstream from the location where it is
combined with the other strips, thus reducing the
chances for wrinkles and other irregularities in the
composite strip.
The composite strip 55 is advanced to the right in
Fig. 7 by strip-feeding means 57 comprising a pair of
clamping elements 58 and 60. These clamping elements
are movable toward and away from each other and are also
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movable in unison horizontally. In Fig. 7, the clamping
elements are shown in their extreme left-hand location
and in their minimum spacing position clamping the
composite strip 55 on its upper and lower faces. When
the clamping elements 58 and 60 move to the right from
their position of Fig. 7, they advance the composite
strip to the right between the spaced-apart blades 62
and 64 of a shearing device 65.
Assisting the strip-feeding means 57 is additional
strip-feeding means 70 located downstream from the
blades 62 and 64. When this downstream strip-feeding
means 70 becomes effective, the clamping elements 58 and
60 of the first strip-feeding means 57 are separated
from each other to release the composite strip 55 and
are reset by movement in unison to the left back toward
their initial position of Fig. 7. When the strip-
feeding means 70 has properly positioned the composite
strip by further movement to the right, it also unclamps
the composite strip and returns to the left to its
initial position of Fig ~.
For controlling unwinding of the master spools 25
in the apparatus of Fig. 7, each of the payoff reels 50
is coupled to the rotor of an electric'motor 80. As the
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11DT048~6
composite strip 55 is fed to the right the motor rotates
its associated payoff reel in a counterclockwise
direction, making unwound strip material available for
the composite strip 55. As noted hereinabove, in the
pit 76 beneath each master spool 25 the strip unwound
from each master spool hangs down into a loop 75. Each
of the individual strips forming the multiple-layer
strip hangs down in its own loop, and the vertical
spacing between these loops becomes increasingly larger
as the associated master spool unwinds. A photoelectric
control 81 for each multiple-layer strip 53 is located
within, or adjacent, the pit 76 and operates off the
lowermost loop 75 of each multiple-layer strip 53 (i) to
cause the motor 80 associated with that strip 53 to
start and unwind the strip at gradually increasing speed
if the loop rises above a predetermined upper limit and
(ii) to cause the motor to decelerate to a stop if the
loop falls below a predetermined lower limit.
Referring still to Fig. 7, the two strip-feeding
means 57 and 70, in moving to the right, cause the
composite strip 55 to be intermittently advanced to the
right; and this causes the horizontal portions of the
multi-layer strips 53 to be advanced intermittently to
2 8 (,r . ~'a ; ~ . ' ;
11DT04826
the right. As the horizontal portions of the strips 53
are thus intermittently advanced to the right, the
master spools 25 are unwound by their respective motors
80, making available strip material in the loops 75.
From these loops the multi-layer strip material 53 is
pulled by feed means 57 and 70 and combined into the
composite strip 55. During these operations, the
horizontal portion of each of the multi-layer strips 53
is maintained under tension by the weight of the loops
75 in the pit 76.
When the composite strip 55 of Fig. 2, has been
advanced to the right to the desired position, it is cut
by operation of the shear blades 62 and 64. These shear
blades are preferably constructed as shown and claimed
in Patent Application S.N. 334,248 - Taub et al., filed
on April 6, 1989, and assigned to the assignee of the
present invention.
In operating, the shear blades cut the composite
strip 55 into sections of composite strip having the
desired lengths. These sections constitute the groups
120 of Figs. 1 and 2 described hereinabove. The groups
120 are suitably stacked up to form a packet such as the
packet 110 of Figs. 1 and 2. One automated method for
29
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forming a packet from such groups is disclosed in the
aforesaid Application S.N. 463,697 - Ballard and
Klappert, filed January il, 1990.
We have found that when the pre-spooling process
described above is used for making the composite strip
55 from which the sections, or groups, 120 are cut, the
strips in each group, even though essentially dry, ,
adhere to juxtaposed strips almost as if a glue is
present between them. This adhesive effect enables us
to make up cohesive groups and cohesive packets in which
the strips adhere to each other in much the same way as
if the previously-used perchloroethylene is present.
We believe that this adhesive effect is
significantly influenced by the manner in which the
surfaces of juxtaposed strips seat upon one another. If
these juxtaposed strips were made from adjoining or
nearby segments in the same spool of amorphous strip
material, the high spots often present along the width
of the strip material tend to line up, and this appears
to interfere with achieving the adhesive effect between
juxtaposed strips that we find so.highly desirable. the
pre-spooling process provides a high likelihood that
these high spots will not line up and interfere with
30 ~:~ ;,y ? ~; i.
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11DT04826
this adhesive effect.
FEED NG TH PAC ETS 110 TO THE BELT NESTER 28
Each packet, made up and assembled as described
above, is suitably transferred to a position atop the
upper run of a conveyor belt 200 (Fig. 3). This
conveyor belt 200 extends about two spaced-apart pulleys
202 and 204, each rotatable about a fixed axis. Pulley
202 is a driving pulley coupled to the rotor of a
suitably controlled electric motor (not shown), and the
other pulley 204 is an idler pulley.
Beneath the upper run of the conveyor belt are
stationary permanent magnets 205 that assist in transfer
of the packet to the belt by providing a biasing force
that pulls the packet toward the belt. When the packet
is properly seated atop the belt 200, the belt is driven
in the direction of arrows 206, and the leading end of
the packet moves onto the guide plate 165 and then
gradually upwardly to a position between the upper front
roller 142 and the hub of the arbor. Then the arbor is
rotated counterclockwise as hereinabove described to
effect a wrapping operation.
To assure that the packet is properly seated on
the belt 200 in the correct position considered
31
r:~ ;.' ' 1~J :!~ ~ ~':
11DT04826
laterally of the belt, stationary guides 207 and 208 are
provided at opposite sides of the desired lateral
position of the packet. Referring to Fig. 8, these
guides are mounted on a stationary frame 209 positioned
beneath the upper run of the belt. The guiding, or
inner, surfaces of the guides 207 are located in
substantially the same plane as the inner surface of the
nesting flange 134; and the guiding surfaces of guide
208 are located in substantially the same plane as the
inner surface of nesting flange 136. These guides help
to assure that the packet, when fed into the belt nester
128 by the conveyor belt 200, enters the U-shaped space
137 between the flanges 134 and 136 of the arbor 130
correctly oriented to avoid skewing or telescoping of
the packet as it is wrapped about the arbor.
The guides 207 and 208 are suitably adjustably
mounted on the stationary frame 209 so as to render the
conveyor capable of accommodating strips of different
width when it is desired to construct transformer core
forms of different width from that of the core form
illustrated. For such core forms, a different arbor 130
having an appropriately adjusted spacing between its ,
nesting flanges would also be employed.
32
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11DT04826
STRIP LENGTH CONTROL MEANS
As pointed out hereinabove, the length of each
section, or group, 120 cut from the composite strip 55
must be controlled so that the ends of the group overlap
by the proper amount when the group is wrapped about the
arbor. This length is controlled by controlling the
distance that the composite strip 55 is advanced beyond
the blades 62, 64 before a cutting operation is effected
by the blades. This advancing of the composite strip is
performed by strip-feeding means 70 (Fig. 7), which
includes suitable means (not shown) for controlling its
stroke. After each packet is wrapped around the hub of
the belt nester during build-up of the core form, the
resultant joint at the ends of the packet is viewed to
determine the overlap in the groups of the joint. If
this overlap is not within prescribed limits, an error
signal is supplied to the control for the strip-
advancing means 70 to cause it to appropriately adjust
the stroke of the strip-advancing means and thus the
length of the next sections of strip to be cut. These
viewing and stroke-adjusting operations can be done
either by a human operator or by suitable electro-
optical control means (not shown). Viewing of the joint
takes place through the window 135 in flange 134.
33
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1~- ,. _ . , , ,.
11DT04826
It should be appreciated that it is very
advantageous to have the ability to adjust the length of
the groups as the wrapping operation proceeds since this
allows us to compensate for any unpredictable variations
in overlap at the joint that might develop as the
wrapping operation proceeds. This advantage is not
present in those methods in which all of the strips,
before wrapping, are cut to prescribed lengths. A
method of this type is exemplified in the aforesaid U.S.
Patents 4,734,975 - Ballard and Klappert and 4,741,096-
Lee and Klappert, where the strips are produced by
cutting radially through a pre-wound annulus.
While we have shown and described a particular
embodiment of our invention, it will be obvious to those
skilled in the art that various changes and
modifications may be made without departing from our
invention in its broader aspects; and we, therfore,
intend herein to cover all such changes and
modifications as fall within the true spirit and scope
of our invention.
