Lamina stack with at least one lamina layer having a plurality of discrete segments and an apparatus and method for manufacturing said stack

A laminated stack having a lamina layer comprised of a plurality of discrete lamina segments and which may also have laminas which define a plurality of outer perimeter configurations. The invention provides a method and apparatus for manufacturing such stacks. Lamina layers comprising a plurality of discrete lamina segments are automatically stacked by positioning the uppermost lamina in a choke barrel near the lower die bed surface and engaging the interlock tabs of the discrete lamina segments with the interlock slots of an uppermost lamina layer in the choke barrel prior to the complete separation of the discrete lamina segments from the remaining portion of the strip stock material. Each of the outer perimeter configurations has at least one common choke surface. The common choke surfaces form, when the laminas are stacked, a choke contacting surface on the outer perimeter surface of the lamina stack which extends continuously in the axial direction from the top lamina to the bottom lamina. A die assembly having selectively actuated punches is used to stamp the laminas with a plurality of outer perimeter configurations and the laminas are stacked in a choke barrel with an alignment surface which cooperates with the common choke surface and securely holds the stamped laminas in position while the stack is being formed. Rotation of the choke barrel compensates for strip thickness variations.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to laminated parts. More 
particularly, the present invention relates to lamination stacks formed by 
stamping a plurality of lamination layers from a sheet of stock material 
and the methods and apparatus, i.e., progressive dies, used in the 
manufacture of such laminated parts. 
2. Description of the Related Art 
The manufacture of parts, e.g., stators and rotors for electric motors, 
employing stacked laminas is well known in the art. Typically, the laminas 
are blanked from a continuous strip stock and then stacked and bound 
together to form the completed part. Progressive die assemblies for 
producing laminated stacks wherein a strip of lamination material is fed 
through a sequence of punching steps to progressively form the laminas to 
the desired end configuration are also well known. 
It is also known to form, in the laminas, interlock tabs which extend below 
the generally planar lamina surface and engage slots formed in the next 
lower lamina. In this manner, a plurality of laminas may be stamped from a 
single sheet of strip stock and formed into an interconnected lamina stack 
in the die by means of interlocking tabs and slots. More specifically, to 
form an interconnected lamina stack each lamina, except the bottom lamina 
of the stack, may have a plurality of arcuately spaced interlock tabs 
(typically ranging from 3 to 8 circumferentially disposed tabs) depressed 
from the lamina lower surface adjacent to slots formed in the next lower 
lamina. Each interlock tab engages a corresponding slot in the next lower 
lamina of the stack, generally by the entire thickness of the tab. The 
bottom lamina of the stack may have the interlock tabs blanked and removed 
to avoid interlocking the bottom lamina with the next lower lamina which 
forms the top lamina of the previous stack. In rare instances the tab may 
lock as deeply as two lamina thicknesses, in which case two end 
laminations must be blanked. 
Rotor laminas generally include a plurality of skewed conductor slots which 
are formed around the periphery of the rotor stack in arcuately spaced 
relation to one another by rotationally indexing the laminas with respect 
to the rotor stack. Indexing involves rotating the rotor stack and the 
last produced lamina relative to each other by a predetermined rotational 
increment so that, when the laminas are combined in a stack, the rotor 
conductor bar slot defined by adjacent conductor slots are skewed or 
slanted relative to the stack axis. Stator stacks, on the other hand, 
include winding slots around the inner periphery of the stack which extend 
parallel to the stack axis, without skew, and are shaped to receive the 
stator windings. In some circumstances, however, it may be desired to 
build an "inside-out" motor wherein the outer lamination stack forms the 
rotor and would, thus, require skewed slots. 
Another system of forming a stack involves loosely stacking the laminas as 
they are formed and blanked from the stock material in a progressive die 
assembly. After all the laminas for a given stack are collected, they are 
shuttled to a pressing station and the laminas are pressed together to 
engage the interlock tabs and thereby form the lamina stack. Loosely 
stacking the laminas after they are blanked from strip stock has several 
disadvantages; loose stacking and subsequent pressing does not as 
consistently lock adjacent laminas together; the required handling slows 
production times; and the system lacks a means for automatically 
correcting thickness inconsistencies of the stock material or creating a 
desired skew angle for the conductor slots. A similar process can be 
employed without the use of interlocking features on the laminas. Assembly 
of the non-interlocked laminas requires the welding, keying or riveting 
(or pinning) of the laminas to interconnect the laminas in a stack. 
In response to these problems, an autorotation system for compensating for 
the nonuniform stock thickness was developed which both rotates and 
interlocks the stacked laminas. This system compensates for variations in 
lamina thickness while still properly skewing the conductor slots of rotor 
laminas, as described in U.S. Pat. Nos. 4,619,028; 4,738,020; 5,087,849 
and 5,123,155, all assigned to the assignee of the present invention and 
the disclosures of which are incorporated herein by reference. In the 
system disclosed in the aforementioned patents, the choke barrel holding 
the lamination stack is automatically rotated before each lamina is 
blanked from the strip stock and the lamina's circumferentially disposed 
tabs are interlocked with the slots of the uppermost lamina of the 
incomplete lamination stack within the barrel. 
In the apparatus and method disclosed in the aforementioned patents, the 
individual laminas are typically rotated through an angle of 180.degree.. 
Although the laminas may be rotated through other angles, the angle must 
be at least 360.degree./(number of interlock tabs) so that the 
interlocking tabs and slots are properly aligned. 
The above described improvements have been implemented with rotor 
laminations and stator laminations which have identical outer perimeters 
which enables their insertion into a choke barrel designed to hold a 
lamination having the outer perimeter configuration of the laminations 
being stacked. Many of these improvements require the use of interlock 
tabs in combination with autorotation of a partially formed lamina stack. 
Autorotation requires the use of a rotating choke barrel which firmly holds 
the partially formed lamina stack in position as blanked laminas are 
forced into engagement with the uppermost lamina of the stack. The choke 
barrel is typically configured to match the outer perimeter of the blanked 
lamina and may be slightly undersized, e.g., by 0.001 inch, so that the 
laminas will be firmly held and accurately positioned within the choke 
barrel. The laminas located in the choke barrel thereby provide a back 
pressure or resistance which facilitates the entry of the interlock tabs 
of the next lamina when it is pressed into the choke barrel. 
In certain applications, however, it is desirable to have a lamination 
stack, typically a stator core but also rotor cores in some situations, 
wherein some of the laminations have an outside perimeter which differs in 
shape and/or size from the remainder of the stack of laminations, i.e., 
the laminations in the stack have a plurality of distinguishable 
configurations. For example, the stator core may incorporate a fastening 
feature, such as a projecting flange, to provide a mounting surface which 
is integral with the stator core, or the stator may incorporate a sealing 
feature to provide a seal between the housing of the motor and the stator 
core for motors to be used in environments which include flammable vapors. 
To incorporate such features, a fraction of the laminations in a stack are 
manufactured with integral portions which provide such features. 
Traditionally, the manner in which stator cores having a plurality of outer 
perimeter configurations have been produced is to stamp the differently 
configured laminas in separate dies, i.e., each die provides only a single 
lamina configuration. The plurality of dies produce loose laminations 
having the desired plurality of outer perimeter configurations. The 
laminations must then be manually assembled at a station where laminations 
of the different outer perimeter configurations are placed in the proper 
vertical stack arrangement and are pressed together to interlock the 
laminas. Instead of using interlocking tabs, the laminas may also be 
secured together in some other conventional fashion such as by the use of 
clamps, pins, rivets or welds. 
There are several drawbacks to this manner of manufacturing a lamination 
core having laminations with a plurality of outer perimeter 
configurations. For one, the manufacturing process is relatively expensive 
due to the use of multiple dies and the large amount of labor and handling 
which is required. Additionally, the process does not allow for the 
automatic correction of lamina thickness inconsistencies. 
Another problem with this method of manufacture is that it often produces 
stator cores having winding slots with slight discontinuities and sharp 
edges. Because separate dies are used to form the differently configured 
laminas, the stator winding slots are punched by different dies. Although 
similar in shape, the different punches cannot be precisely identical and 
will generally have minor inconsistencies which, when the differing 
laminas are stacked, cause the slots in adjacent laminations to misalign, 
thereby creating slight discontinuities and sharp edges in the winding 
slots at the points where the two differently configured laminas meet. 
These small discontinuities can scratch and damage the winding coil wires 
which are inserted into the winding slots. 
The discontinuities of the projections which define the winding slots and 
interior surface of the stator core also reduce the efficiency of the 
electric motor or generator which is produced with the stator core. The 
efficiency of the motor or generator may be reduced if the gap between the 
stator core and rotor core is enlarged to account for the discontinuities 
present on the interior surfaces of the stator core because the efficiency 
of the motor or generator is decreased as the gap increases. 
The manufacture of lamina stacks wherein individual laminas are comprised 
of two or more discrete segments also presents significant manufacturing 
difficulties. It is often impractical to manufacture lamina stacks wherein 
one or more of the laminas is formed by at least two discrete lamina 
segments. Laminas comprised of a plurality of discrete segments present 
difficulties in maintaining the proper alignment between the various 
lamina segments which comprise the individual lamina and between the 
lamina segments and the other laminas which comprise the remainder of the 
lamina stack. 
Thus, what is needed is an apparatus and method for producing lamina stacks 
which include laminas comprised of a plurality of discrete lamina segments 
and laminas with a plurality of differently configured outer perimeters. 
SUMMARY OF THE INVENTION 
The present invention provides an apparatus and method for manufacturing 
and automatically stacking a laminated stack which includes a lamina 
comprised of a plurality of discrete lamina segments and which may include 
a plurality of differently configured laminas to thereby produce lamina 
stacks which may include a plurality of slots and windows separating 
individual lamina segments. 
An advantage of the present invention is that it permits the automatic 
stacking of a laminated stack which includes a lamina layer comprised of 
discrete lamina segments thereby providing for the economical manufacture 
of lamina stacks which include a lamina or lamina layer comprising a 
plurality of discrete lamina segments. For example, linear motors which 
require stator cores having slots on opposing sides of the core for 
accommodating supports for an actuator disposed within the stator core may 
be economically manufactured by the present invention. The ability to 
automatically stack a lamina comprised of discrete lamina segments also 
permits the manufacture of a wide variety of laminated stacks for 
applications beyond electrical motor and stator cores which are 
uneconomical or impractical to manufacture using laminated stacks which do 
not include laminas comprising discrete lamina segments. 
Another advantage of the present invention is that the economical 
manufacture of laminated stacks comprising a lamina layer of discrete 
lamina segments permits the manufacture of parts which were previously 
stamped from a single thick sheet material. Manufacturing parts from 
laminas rather than from a single thick sheet material can eliminate 
secondary operations. For example, notches can be placed in selected 
laminas prior to stacking to thereby form a notch or opening in the 
outside edge or wall of the laminated stack which does not extend the 
entire height of the stack and which, if formed in a part stamped from a 
single thick sheet material, would require a secondary machining operation 
after stamping. 
Yet another advantage of the present invention is that it permits the 
automatic stacking of a laminated stack having a plurality of 
distinguishable outer perimeter configurations. The need to manually 
handle and stack laminas to form a lamina stack having a plurality of 
outer perimeter configurations and/or a lamina layer comprising a 
plurality of discrete segments is thereby eliminated. The conveyor, 
pressing and stack securing equipment used in the traditional manual 
assembly method are also eliminated by the present invention. 
The invention comprises, in one form thereof, a die assembly for producing 
a lamina stack including at least one lamina layer which is comprised of a 
plurality of discrete segments. Strip stock is guided through the die 
assembly and a plurality of laminas and discrete lamina segments are 
progressively stamped from the strip stock. The laminas and each of the 
discrete lamina segments have interlock tabs and/or slots punched therein 
and remain attached to the strip stock prior to advancement to the 
blanking station at which the choke barrel is located. At the blanking 
station, the lamina segments have their interlock tabs engaged with the 
interlock slots of the uppermost lamina in the choke barrel immediately 
prior to the complete separation of the lamina segments from the strip 
stock material thereby maintaining the lamina segments in proper alignment 
with each other and the laminas which form the remainder of the lamina 
stack. The choke barrel may also be rotatable whereby the laminas may be 
rotated to correct for thickness inconsistencies in the strip stock 
material. 
The invention comprises, in another form thereof, a die assembly for 
producing a lamina stack including at least one lamina which is comprised 
of a plurality of lamina segments and wherein the laminas forming the 
stack have more than one predetermined outer perimeter configuration. The 
die assembly provides for the alignment, interlocking and stacking of the 
lamina segments as described above and also provides a common choke 
surface on the outer perimeter of each of the lamina segments so that, 
when the lamina stack is completed, the resultant stack comprising 
lamination layers having a plurality of outer perimeters has a plurality 
of common choke surfaces on its outer perimeter which extend continuously 
along the exterior edge of each lamination layer in the stack in a 
direction parallel to the axis of the lamina stack. The laminas are 
stacked within the choke barrel such that the common choke surfaces are in 
registry with an alignment surface of the choke barrel. 
The invention comprises, in another form thereof, a selectively actuated 
die assembly for producing a lamina stack formed from laminas which have 
more than one predetermined outer perimeter configuration. Each of the 
differing outer perimeter configurations has at least one common choke 
surface so that, when the laminas are stacked, the resultant stack has at 
least one choke surface on its outer perimeter which extends continuously 
along the exterior edge of each lamina in the stack in a direction 
parallel to the axis of the lamina stack. The laminas are then stacked in 
a choke barrel with their common choke surfaces being aligned to create a 
lamina stack comprised of laminas having a plurality of outer perimeters 
and at least one choke surface extending continuously in an axial 
direction across a portion of the outer perimeter of each of the laminas. 
The choke barrel, which may be rotatable, includes an alignment surface, 
the common choke surfaces of the laminas being stacked in registry with 
the alignment surface. 
The invention comprises, in another form thereof, a method of manufacturing 
a lamina stack, having at least one lamina layer formed from a plurality 
of discrete segments, in a die assembly having a punch and a choke barrel. 
Strip stock is guided through the die assembly and a plurality of laminas 
are stamped from the strip stock including at least one lamina which is 
comprised of at least two discrete segments. The lamina segments are 
maintained in relative alignment by attachment to the strip stock material 
as they are advanced through the die assembly. During progression of the 
discrete segments through the die assembly interlock tabs and slots are 
stamped into each of the lamina segments. When the lamina segments reach 
the choke barrel, the interlock tabs of each of the lamina segments are 
engaged with the uppermost lamina in the choke barrel prior to separating 
the discrete segments from the strip stock to thereby continuously 
maintain the proper alignment of the lamina segments relative to each 
other and the other laminas which form the remainder of the lamina stack. 
The invention comprises, in another form thereof, a method of manufacturing 
a lamina stack in a die assembly having a selectively actuated punch and a 
choke barrel. Strip stock is guided through the die assembly and a 
plurality of laminas are stamped from the strip stock by the selectively 
actuated punch to form laminas having a plurality of outer perimeter 
configurations. The laminas each have a common choke surface which are 
aligned as the laminas are formed into a stack in the choke barrel. It is 
also possible to autorotate the laminas prior to stacking the laminas.

DESCRIPTION OF THE PRESENT INVENTION 
The embodiments disclosed below are not intended to be exhaustive or limit 
the invention to the precise forms disclosed in the following detailed 
description. 
A strip layout showing a stamping progression in accordance with the 
present invention is shown in FIG. 1. The laminations produced by the 
strip layout of FIG. 1 are used to produce a stator core having projecting 
flanges on only some of the laminations within each stator core as shown 
in FIGS. 2 and 3. 
At Station No. 1, slots 22 which define the outer perimeter of projecting 
flanges for two adjacent laminations are punched. Pilot pin holes 24 used 
to guide and align the strip stock 34 through subsequent stations are also 
punched at Station No. 1. Flange defining slots 22 are punched for each 
lamination, even for those laminations which will have the flanges 
selectively removed at a later station. 
Station No. 2 includes a selectively actuated punch which punches the 
stator bore hole 26 in each lamination. In most cases, this station would 
comprise either a rotor blank out punch or stator bore hole shave punch. 
The flanges 31, 32 and 33 defined by slots 22 are selectively removed from 
some of the laminations at Station No. 2 as shown by outline 27 of the 
selectively actuated flange removal punches. 
At Station No. 3 flange bolt holes 28 and flange slots 30 are punched. The 
strip stock is shown with flanges 31, 32 and 33 at Station Nos. 3-7, 
however, for laminations which do not have flanges 31, 32 and 33 due to 
the actuation of the flange removal punches at Station No. 2, the material 
comprising the flanges would not be present. Thus, the punches at Station 
No. 3 do not have to be selectively actuated. By limiting the use of 
selectively actuated dies to only those situations where they are 
indispensable the cost of the die assembly is minimized. 
The stator winding slots 36 for all of the laminations are punched at 
Station No. 4. The use of a single punch cluster at Station No. 4 to stamp 
the winding slots 36 for each of the laminations produces a winding slot 
in the finished stator core 42 which has fewer discontinuities and sharp 
edges than a stator core comprised of laminations produced by a plurality 
of dies. 
Station No. 5 is a selectively actuated punch station which is actuated for 
the bottom lamination of each stator stack. The material 38 removed at 
Station No. 5 would otherwise be formed into an interlock tab 40 at 
Station No. 6. The punches at Station No. 6 do not have to be selectively 
actuated because if the punches are always operative they would simply not 
create any additional interlock features in the bottom laminations formed 
at Station No. 5. 
At Station 7, all of the laminations are blanked from the remaining strip 
stock 34 by severing the material bridges 41 and are pressed into a choke 
barrel. It is not necessary for the punch to engage the entire surface 
area of flanges 31, 32 and 33. For the present embodiment the choke barrel 
is nonrotatable, however, as will be described below, the choke barrel 
utilized in the present invention may also be rotatable. The material 
bridges 41 are cut at the same location on both the flanged and unflanged 
laminas, thereby creating common choke surfaces 44, as shown in FIGS. 1 
and 3, on the edge of each lamina. 
The choke barrel (shown schematically in FIG. 11) into which the laminas 
are pressed has alignment surfaces which correspond with and engage each 
of the common choke surfaces 44. The alignment surfaces define an outer 
perimeter which is equal to or slightly less, e.g., by 0.001 inch, than 
the outer perimeter defined by the common choke surfaces 44 to thereby 
provide an interference fit engagement with the laminas. This interference 
fit engagement of each of the laminas maintains the laminas in an aligned 
position and also resists the movement of the laminations through the 
choke barrel. This allows subsequent laminations to be pressed into 
interlocked engagement with the laminas already in the choke barrel. 
When the stack has been completed, the individual common choke surfaces 44 
of each lamination form a stack choke surface 45, shown in FIG. 3, which 
extends continuously in an axial direction of the stack across a portion 
of the outer perimeter of each of the laminas which comprise the stack. 
A flanged stator core 42 produced by the laminations punched from the strip 
stock 34 of FIG. 1 is shown in FIGS. 2 and 3. A controller is used to 
selectively actuate the punches at Stations 2 and 5. By actuating the 
punches of Station Nos. 2 and 5 in a controlled sequence, laminations may 
be produced in the order necessary to form flanged stator core 42. 
A second strip layout showing a stamping progression in accordance with the 
present invention is shown in FIG. 4. The laminations produced by the 
strip layout of FIG. 4 are used to produce a stator core having projecting 
flanges on only some of the laminations within each stator core as shown 
in FIGS. 5-7. Prior to reaching Station A, pilot pin holes 46, stator bore 
hole 48, first ribbed slot 50 and second ribbed slot 52 are punched during 
the production of a rotor lamination which is removed from the strip stock 
54 prior to Station A. 
At Station A, two common choke surfaces comprising a circular portion with 
a minor diameter 63 are defined by stamping edge slots 56. Edge slots 56 
are not perfectly symmetrical about centerline 61 but are slightly offset 
and extend further to the left as seen in FIG. 4. 
Station B is a selectively actuated, or cammed, station at which a minor 
circular perimeter 64 having a minor outer diameter 63 is defined by 
triangular punches 58 for certain laminations. Just inside the edges of 
the common choke surfaces 70 defined at Station A, first and second 
rounded corners 60 and 62 project inwardly on the punches and thereby cut 
the common choke surfaces 70 at a roughly 90.degree. angle and avoid the 
difficulties which can arise when attempting to feather a cut into a 
preexisting edge. 
First and second ribbed slots 50 and 52 also have similar rounded corners 
to allow for a cleaner cut. Second ribbed slot 52 is closer to centerline 
51 than first ribbed slot 50; and rounded corners 62 are closer to 
centerline 61 than rounded corners 60 as further explained herein below. 
Station C is idle and the minor circular perimeter 64 is shown in dashed 
outline. The material outside the minor perimeter 64 would not be present 
for those laminations which were stamped by the selectively actuated die 
at Station B. 
The winding slots 66 are stamped at Station D for all of the laminas. At 
Station E the major outside perimeter 67, having a major diameter 69, is 
punched by means of two punches 68 which form an hourglass shape. Station 
E does not have to be selectively actuated and removes no material for 
those laminations which have already had a minor perimeter defined at 
Station B. The hourglass shaped punches 68 do not intersect common choke 
surface 70 on the edge of each lamination but instead leave short and long 
locator ribs 72 and 74, respectively. 
Station F is selectively actuated and punches a tab receiving slot 76 in 
those laminations which will form the bottom lamination of each lamination 
stack 82. A partial cross-sectional view of Station F is shown in FIG. 8 
and illustrates the operation of a selectively actuated punch 85. Piston 
84 is used to control the position of first camming bar 86 which 
reciprocates in the horizontal direction to thereby move camming bar 88 in 
a vertical direction due to the interaction of camming surfaces 87. When 
camming bars 86 and 88 are in the positions shown in solid lines, die 
punches 90 are positioned as shown in FIG. 8. When in this position, die 
punches 90 do not remove material from the strip stock. Die punches 90 are 
allowed to reciprocate vertically with respect to punch block 93 as well 
as move vertically as a unit with upper die assembly 89. 
When piston 84 moves first camming bar 86 into the position shown in dotted 
outline in FIG. 8, the second camming bar 88 is moved into the position 
shown by the dotted outline in FIG. 8 due to the interaction of camming 
surfaces 87. In this actuated position the second camming bar 88 is moved 
downward a short vertical distance 91 and thereby forces punches 90 to 
reciprocate downward distance 92 with respect to punch block 93 and into 
an actuated position. The upper die assembly 89 is shown in its lowermost 
position with respect to die bed 95 in FIG. 8. As seen in FIG. 8, punch 
tips 90A do not punch strip stock 54 during operation of the die when the 
punches 90 are not in an actuated position. When actuated, punch tips 90A 
reach a lowermost position at lines 97 within a cooperating aperture (not 
shown) in the die bed 95 when the upper die assembly 89 is moved downward 
as a unit. Thus, the punches 90 create tab receiving slots 76 in the strip 
stock 54 during operation of the die with the punches actuated but do not 
create tab receiving slots 76 during operation of the die when the punches 
are not actuated. Other cammed or selectively actuated stations operate in 
a similar manner. A center interlock may be alternatively used such as 
described in U.S. patent application Ser. No. 07/966,876 filed Oct. 26, 
1992, assigned to the assignee of the present invention, the disclosure of 
which is expressly incorporated herein by reference. 
At Station G, shown in FIG. 4, interlock tabs 78 are punched. Station H is 
idle, and at Station I the laminations are punched into rotatable choke 
barrel 94 (not shown in FIG. 4). A small carrier strip 80 is cut from one 
end of the lamination defining a common choke surface 71 (shown in FIG. 6) 
and, on the opposing side of the lamination, another common choke surface 
71 is defined along dashed line 81 where the lamination is cut from the 
strip stock. The carrier strip 80 interconnects the laminas allows the 
laminas to be transported as a strip between stations before they are 
blanked into the choke barrel. Other well known means may also be used; 
such as pushback designs, which are generally impractical for stator cores 
because of the increased strip width which is required; and semi-scrapless 
designs, in which only a single cut, severing the lamina from the strip 
stock, is made at the last station. 
Rotatable choke barrel 94 is shown in FIGS. 9 and 10. Common choke surfaces 
71, shown in FIG. 6, are defined by cutting edges 96. Carbide inserts 98 
having aligning surfaces which engage common choke surfaces 70 of each of 
the laminations project into the interior of the choke barrel 94. Similar 
carbide inserts are located below cutting edges 96 and engage common choke 
surfaces 71 of each of the laminations. Carbide inserts 100 engage the 
outer perimeter surface of only those laminations having a major outside 
diameter. 
A servo drive system, mechanical indexer or other means rotates the choke 
barrel 94 by means of a belt 101. The belt, not shown in FIG. 10, is 
located in recess 102. The rotating choke barrel 94 engages the die bed 95 
at surface 104. Punch 106, shown in FIG. 10, presses the individual 
laminations into interlocked engagement with the laminations which are 
already within the choke barrel for those laminations which have interlock 
tabs. The rotation of choke rings is known in the art, as shown for 
example, by U.S. Pat. No. 5,377,115 assigned to the assignee of the 
present invention, the disclosure of which is expressly incorporated 
herein by reference. 
The choke barrel 94 is rotated between each operation of the die assembly, 
for example, by 180.degree. for producing lamination stack 82. Accurate 
rotation of the laminas is important to maintain vertical registry of the 
winding slots 66. The rotation serves several purposes, first it corrects 
for thickness inconsistencies in the strip stock. Second, it prevents 
ribbed slots 50 and 52 and indentations 60 and 62 from being aligned. The 
non-aligned slots and indentations are shown in FIGS. 6 and 7. This allows 
a cup-shaped endshield to be force-fit over the end laminas having a minor 
outside perimeter 64 and to abut the shoulder 65 formed by the laminas 
having a major outside perimeter 67. The endshield thereby hermetically 
seals the interior of the stator core. The hermetic seal would not be 
possible if the laminas were not rotated to prevent alignment of the 
ribbed slots 50 and 52 and rounded corners 60 and 62 on the laminas having 
a minor outside perimeter 64. Providing a hermetically sealed endshield 
allows a motor which incorporates stator core 82 to be safely used in 
environments where flammable vapors are present. Although, the disclosed 
embodiment rotates each lamina 180.degree. with respect to the previous 
lamina, other angles and counts (or frequencies) of autorotation may also 
be used. 
The individual common choke surfaces 70 and 71 disposed on the outer 
perimeter of each lamination form choke surfaces 73 and 75, respectively, 
which extend continuously in an axial direction of the stack across a 
portion of the outer perimeter of each of the laminas which comprise the 
stator stack 82 as illustrated in FIGS. 6 and 7. Common choke surfaces 70 
and 71 are pressed into engaging contact with aligning surfaces 99 of 
carbide inserts 98 when the laminas are blanked into the rotatable choke 
barrel 94. 
FIG. 11 provides a schematic illustration of the die assemblies used to 
manufacture lamina stacks 42 and 82. In FIG. 11, the initial station 112 
corresponds to Stations 1 and A for the embodiments described above while 
the final or blanking station 114 corresponds to Stations 7 and I. FIG. 11 
also includes schematic representations of selectively actuated punch 
stations 85 which correspond to Stations 2 and 5, and B and F, discussed 
above, FIG. 11 does not, however, include representations of each of the 
remaining stations. Choke barrel 94 can be either stationary or rotatable 
and does not require a communications link with controller 108 in all 
embodiments of the invention. 
A controller 108 is used to control the selectively actuated punches 85 and 
may be used to control the autorotation of the choke barrel 94. The choke 
barrel 94 may also be stationary or employ a mechanical indexer, in which 
case the controller 108 would not need to be linked with choke barrel 94. 
The controller can be programmed to produce laminas in the alignment 
necessary to produce the desired stator cores. It is also possible, but 
not required, to employ a measuring device 110, shown schematically in 
FIG. 11, to determine the thickness of the sheet stock at one or more 
points along its width. The measured thickness values would be transmitted 
to the controller 108. The controller 108 would then be used to calculate 
the number of laminations which are required to achieve the desired height 
of the lamination stack, preferably by calculating the number of 
laminations required for each stack segment having a particular outside 
perimeter configuration. 
Instead of measuring the strip stock at two different locations along its 
width and using a measured strip stock thickness inconsistency to 
calculate the amount of rotation required, the irregularities present in 
the strip stock can be evenly distributed about the lamina stack axis by 
rotating all of the laminas a predetermined amount without explicitly 
calculating the thickness inconsistency. 
Autorotation of laminas to correct for thickness variations is known in the 
art and one such method is disclosed in U.S. Pat. No. 5,359,763 assigned 
to the assignee of the present invention, the disclosure of which is 
expressly incorporated herein by reference. Control of the stack height 
can also involve the use of a coreweighing system as disclosed in U.S. 
Pat. No. 5,365,021 assigned to the assignee of the present invention, the 
disclosure of which is expressly incorporated herein by reference. 
In accordance with another embodiment of the present invention, FIG. 12 
illustrates a lamina stack 116 having laminas with a plurality of outer 
perimeter configurations and which includes several laminas or lamination 
layers which are comprised of a plurality of discrete lamina segments. The 
individual lamina layers which are used to form lamination stack 116 are 
illustrated in FIGS. 13A-13E. Lamina 118 is shown in FIG. 13A and has a 
continuous and unbroken outer perimeter. Lamina 118 has its interlock tabs 
144 completely removed thereby leaving only interlock slots 146 and 
forming a bottom lamination 118 of stack 116 which will not interlock with 
a lamina stack positioned immediately below bottom lamina 118 in choke 
barrel 148. Lamina 120, shown in FIG. 13B, is comprised of discrete lamina 
segments 121 and 122, and has an outer perimeter configuration defines 
openings 123B and 124B. Lamina 126, shown in FIG. 13C, is comprised of 
discrete lamina segments 127 and 128, and has an outer perimeter which 
defines openings 123C and 124C. Lamina 134, shown in FIG. 13D, is 
comprised of discrete lamina components 135 and 136, and has an outer 
perimeter configuration which defines openings 123D and 124D. Lamina 134 
also includes projecting flanges 132. Lamina 140 is shown in FIG. 13E and 
has interlock tabs 144 but is otherwise similar to lamina 118. The 
"recipe" for lamina stack 116 from bottom lamination through final 
lamination is lamina 118, lamina 140, lamina 126, lamina 126, lamina 134, 
lamina 120, lamina 120, lamina 140, and lamina 140. 
The various features, including interlock tabs, of laminas 118, 120, 126, 
134, 140 are formed by progressively stamping a length of strip stock 
material by actuating punches in a controlled sequence in a manner similar 
to that described above for forming the laminas of stacks 42 and 82. After 
laminas 118, 120, 126, 134 and 140 have been stacked to form lamina stack 
116, individual lamina openings 123B, 123C and 123D are aligned and form 
opening 123. Likewise, individual lamina openings 124B, 124C and 124D form 
opening 124 in the opposite side of lamina stack 116. 
The bottom lamina 118 is followed by a lamina 140 which has interlock tabs 
144 formed therein which engage bottom lamina 118 and leave corresponding 
interlock slots 146 for engagement by the interlock tabs of the upper 
adjacent lamina. The remaining discrete lamina components 121, 122, 127, 
128, 135 and 136 each have interlock tabs 144 and slots 146 formed 
therein. 
Lamina stack 116 includes laminas which define a plurality of outer 
perimeter configurations and which utilize common choke surfaces 150. 
Common choke surfaces 150 are located on the corners of each of the 
laminas and lamina segments. The locations of common choke surfaces 150 
are shown in FIG. 13E. Common choke surfaces 150 are also shown in the 
perspective view of FIG. 12. The interior of choke barrel 148 includes 
alignment surfaces which engage the common choke surfaces 150 of each of 
the laminas and lamina segments which comprise lamina stack 116 to 
maintain the laminas in an aligned position and resist the downward 
movement of the lamina stack through the choke barrel. Resistance to 
downward movement in the choke barrel provides the back pressure necessary 
to engage the interlock tabs of the laminas when a lamina is pressed into 
engagement with a partially formed stack in choke barrel 148. 
Choke barrel 148 is a steel choke barrel with the alignment surfaces formed 
integrally with the remaining interior surface of choke barrel 148. 
Alternatively, carbide inserts could be used to form the alignment 
surfaces. The remaining interior surface of choke barrel 148 is configured 
to allow all of the lamina configurations used to form stack 116 to enter 
choke barrel 148. The remaining portion of the choke barrel interior 
surface is configured so that the only engagement of the choke barrel 148 
with the individual lamina layers occurs at the alignment surfaces, in 
other words, the interior of the choke barrel, except for at the alignment 
surfaces, does not conform to the outer perimeter of any of the laminas. 
Alternatively, the remaining portion of the choke barrel interior surface 
could engage portions of the laminas along portions of the "larger" outer 
perimeters at locations other than the alignment surfaces. 
The alignment surfaces of choke barrel 148 provide an interference fit with 
the laminas used to form stack 116. Excessively tight interference fits 
are undesirable because they can lead to a bowing of the individual 
laminas which are pressed into the choke barrel. The use of discrete 
lamina segments to form an individual lamina layer, such as laminas 120, 
126 and 134 in stack 116, may increase the susceptibility of a lamina 
layer to undesirable bowing and distortion. The geometric configuration of 
the individual laminas and lamina segments and the physical properties of 
strip stock material 154 are both factors in determining the 
susceptibility of a lamina layer to undesirable bowing or distortion. 
To minimize the risk of undesirable bowing, the alignment surfaces of choke 
barrel 148 utilize a relatively light interference fit which exerts a 
reduced pressure on each individual lamina but which develops that 
pressure over a relatively greater vertical depth 152 to thereby provide 
an adequate total back pressure for engagement of interlock tabs 144. For 
example, in an application wherein a conventional interference fit might 
involve a 0.001 inch interference fit and a choke depth of 1.25 inches, 
the present application might utilize a 0.0002 to 0.0005 inch interference 
fit and a choke depth of 3 inches. Resistance to downward movement within 
the choke barrel is needed to facilitate the engagement of interlock tabs 
144 of the lamina being blanked with the interlock slots 146 of the 
uppermost lamina in the choke barrel. The pressure exerted on the 
individual laminas not only provides resistance to downward motion through 
the choke barrel but also helps maintain the laminas in proper alignment. 
Due to the relatively short height of lamina stack 116, i.e., nine 
laminations, the compounding of the thickness inconsistencies of the 
individual laminas is not likely to create significant variances in the 
final dimensions of lamina stack 116. Thus, illustrated choke barrel 148 
is non-rotatable. However, alternative embodiments could utilize a 
rotatable choke barrel. 
The stacking of a plurality discrete lamina segments to form a single 
lamina layer is schematically illustrated in FIGS. 14-17. FIGS. 14-17 
sequentially illustrate the blanking station, at which discrete lamina 
segments 127, 128 are automatically stacked within choke barrel 148, 
during a single die stroke. 
The laminas and lamina segments which comprise lamina stack 116 are formed 
by stamping various features in strip stock material 154 as it progresses 
through the die assembly prior to reaching the blanking station 
illustrated in FIGS. 14-17. The laminas and lamina segments are attached 
to the strip stock material through strip stock material bridges which are 
severed by blanking punch 156. Strip stock material includes pilot pin 
holes 158 which form apertures in the carrier portion of the strip stock 
material, i.e., that portion of strip stock material which is not used to 
form laminas. Pilot pin holes 158 are used to maintain the strip stock 
material in a desired position relative to the die stations as it is 
stamped during its advancement through the die assembly. As can be seen in 
FIGS. 14-17, pilot pin 160 passes through pilot pin hole 158 and enters 
guide bore 162 to properly locate strip stock material 154 and the laminas 
and lamina segments which are attached thereto by the sheet stock material 
bridges relative to the blanking station prior to stamping the strip stock 
material 154. Although only one pilot pin 160 is illustrated, pilot pins 
are located adjacent each punching station of the die assembly to maintain 
strip stock material 154 in proper alignment during stamping operations. 
FIG. 14 schematically illustrates a portion of upper die assembly 164 and 
lower die bed 166. Upper die assembly 164 reciprocates vertically, 
together with pilot pin 160 and blanking punch 156, to stamp the laminas. 
Blanking punch 156 severs the material bridges connecting the laminas to 
the remainder of strip stock material 154. Blanking punch 156 also pushes 
the laminas into engagement with the uppermost lamina layer disposed in 
choke barrel 148. 
Blanking punch 156 includes staking punch inserts 168 which extend below 
the bottom surface of the blanking punch by a distance designated 170 in 
FIG. 14. Staking punches 168 correspond to the location of interlock tabs 
144 and enter the lamina slot 146 of the lamina or lamina segments being 
blanked from strip stock 154 and positively engage the respective lamina 
tabs 144b of the lamina being blanked with the respective interlock slots 
146u of the uppermost lamina layer disposed in choke barrel 148. 
Staking punches 168 are held in a fixed position relative to blanking punch 
156 and includes a head 169 which is seated in a counterbore in blanking 
punch 156. A grind collar (not shown) may be located below head 169 to 
permit the lowering of staking punch 168 relative to blanking punch 156. 
Lowering of the staking punch might be necessary due to chipping or wear 
of staking punch 168 or to accommodate different interlock tab depths. 
A number of different interlock tab designs are known in the art and the 
tab design will influence the selection of the appropriate tab depth. In 
one design, three of four sides of a tab are severed from the remainder of 
the lamina and the tab may be distended below the bottom surface of the 
lamina by a relatively large distance. In the illustrated embodiment, 
lamina stack 116 utilizes an alternative design in which no portion of 
interlock tab 144 is completely severed from the surrounding lamina 
material. Instead, interlock tab 144 is partially blanked from the 
surrounding material, deforming, but not severing, the material at the 
edges of interlock tab 144. Tabs 144 extend below the bottom of the 
remainder of the lamina by approximately 1/2 to 1/3 the thickness of the 
lamina layer. Alternative embodiments of the present invention may employ 
alternative interlock styles or have the interlock tabs extend a greater 
or less distance below the remainder of the lamina. 
The thickness of the lamina is designated 173 in FIG. 14. The distance by 
which tab 144 extends below the lower lamina surface is designated 172 in 
FIG. 14 and is equivalent to the distance 170 staking punch 168 extends 
below blanking punch 156 and is approximately one half of thickness 173. 
The length designations shown in FIG. 14 are included merely to provide a 
convenient mechanism for graphically identifying the lengths and spatial 
relationships discussed herein and are not necessarily to scale. 
As discussed above, staking punches 168 are used to ensure engagement of 
interlock tabs 144 into interlock slots 146 and to prevent interlock tabs 
144 from being forced upwardly into the horizontal plane of the remainder 
of the lamina when tab 144 engages the uppermost lamina in choke barrel 
148. Staking punches 168 extend a distance 170 below the blanking punch 
156. Distance 170 is equivalent to the depth it is desired to have the 
interlock tab 144 enter the interlock slot 146 of the lower adjacent 
lamina layer. Generally, this distance 170 will be equivalent to the 
distance 172 which the interlock tab 144 extends below the lower surface 
of the strip stock material 154 when tab 144 is formed. 
Each of the laminas and lamina segments of stack 116 has at least one 
interlock feature formed therein. The bottom lamination of each stack, 
however, has its interlock tabs completely blanked, i.e., removed, to 
prevent the bottom lamina 118 from being engaged with the uppermost lamina 
of the previously formed stack when the bottom lamina 118 is separated 
from the strip stock material and pushed into the choke barrel. 
Interlocking the tabs 144 and slots 146 of adjacent lamina layers 
maintains the lamina layers in proper relative alignment both when the 
stack is within choke barrel 148 and after the stack has been removed from 
choke barrel 148. 
Stock lifters 174 are used to prevent interlock tabs 144 from being biased 
upwardly into the horizontal plane of the strip stock material 154 or from 
being snagged on lower die bed 166 during the progressive movement of 
strip stock material 154. Stock lifters 174 are biased upwards by springs 
176 and lift strip stock material 154 above the upper surface of the lower 
die bed 166 when strip stock material 154 is being advanced between die 
stamping strokes. The strip stock material 154 is lifted by the stock 
lifters 174 a distance designated 175 in FIG. 14. Lifter distance 175 is 
often times equivalent to approximately 1.5 times the thickness 173 of the 
strip stock material 154 to provide an ample clearance. The illustrated 
stock lifters 174 are cylindrical. However, other types of stock lifters, 
such as bar type lifters, are known in the art and can also be used with 
the present invention. 
FIG. 14 illustrates the relative positions of upper die assembly 164, 
punches 156, 168, lower die bed 166 and strip stock material 154 at the 
initiation of a stamping stroke at the blanking station of the die 
assembly. FIG. 15 illustrates the die assembly during the downstroke after 
pilot pin 160 has extended through pilot pin hole 158 and has entered 
guide bore 162 to thereby properly locate strip stock material 154 and 
lamina segments 122, 124 which are attached thereto. Shortly after pilot 
pin 160 has properly aligned strip stock material 154, and the laminas and 
lamina segments attached thereto by material bridges, staking punches 168 
enter the interlock slots 146 of the lamina layer which is about to be 
blanked. Shortly after the staking punches 168 enter interlock slots 146, 
blanking punch 156 engages the upper surface of the lamina layer. 
Stock lifter spring 176 has been compressed and strip stock material 154 is 
pressed against the upper surface of lower die bed 166 in FIG. 15. The 
strip stock material 154 may be pressed against the lower die bed 166 by 
engagement with the downwardly moving punches or by another suitable 
mechanism, such as a spring stripper, attached to the upper die assembly 
164 which presses the strip stock material against lower die bed 166 prior 
to the engagement of the punches and strip stock material 154. 
FIG. 16 illustrates the blanking station after the blanking punch has begun 
to sever lamina segments 122 and 124 from the remainder of strip stock 
material 154. As shown schematically in FIG. 16, interlock tabs 144b of 
lamina segments 122, 124 are already partially engaged with interlock 
slots 146u of the uppermost lamina layer in choke barrel 148. The partial 
engagement of interlock tabs 144b and interlock slots 146u occurs prior to 
the complete separation of lamina segments 122, 124 from the remainder of 
the strip stock material. 
Engaging interlock tabs 144b of the discrete lamina segments 122, 124 prior 
to completely severing lamina segments 122, 124 from the remainder of the 
strip stock material 154 permits the aligned stacking of lamina 120 even 
though the segments, once blanked, become separated from each other. The 
proper and positive alignment of discrete lamina segments 122, 124 is 
continuously maintained during the stamping process. Initially, guide pin 
160 maintains the proper alignment of lamina segments 122, 124 by aligning 
strip stock material 154. Prior to completely severing lamina segments 
122, 124 from strip stock material 154, interlock tabs 144b of the 
discrete lamina segments being blanked are engaged with interlock slots 
146u of the uppermost lamina layer in choke barrel 148 to maintain the 
alignment of the discrete lamina segments. 
To accomplish the engagement of interlock tabs 144b and interlock slots 
146u of adjacent laminas prior to the complete severing of the blanked 
lamina layer from the strip stock material 154 the uppermost lamina must 
be positioned in choke barrel 148 near the upper surface of lower die bed 
166. The uppermost lamina is positioned a distance 178 below the entrance 
of the choke barrel located in the upper surface of the lower die bed. 
Distance 178 is determined by the distance blanking punch 156 enters choke 
barrel 148 at the end of the die assembly downstroke as shown 
schematically in FIG. 17. Punch entry distance 178 is typically greater 
than the thickness 173 of the strip stock material in conventional die 
assemblies. For example, for a strip stock thickness 173 equivalent to 
0.025 inch, a conventional die assembly would often have a punch entry 
between 0.030 and 0.035 inch. 
The present invention, however, utilizes a much smaller punch entry which 
ensures that interlock tabs 144 of the blanked lamina layer are engaged 
with the uppermost lamina layer in the choke barrel prior to completely 
severing the lamina layer being blanked. For example, by utilizing a 
distance 178 which is smaller than distance 172, tabs 144b will be 
partially interlocked with slots 146u when the die assembly reaches the 
position shown in FIG. 15. Alternatively, distance 178 can be equivalent 
to distance 170 as shown in FIGS. 14-17 and interlock tabs 144b will be 
engaged with slots 146u as the lamina layer being blanked is being severed 
from the strip stock material 154 but prior to complete separation as 
shown in FIG. 16. It may also be possible to have a distance 178 slightly 
larger than distance 170 and still provide for the partial interlocking of 
tabs 144b and slots 146u prior to complete separation of the lamina layer. 
The partial interlocking in such an arrangement, however, would be 
minimal. 
When a plurality of discrete lamina segments are used to form a single 
lamina layer, the pressure exerted against each common choke surface 150 
by the alignment surfaces of choke barrel 148 will not necessarily be 
counterbalanced by a force created by an opposing alignment surface. 
Interlock tabs 144, however, are disposed near common choke surfaces 150 
and provide resistance to the pressure exerted by the alignment surfaces 
and thereby maintain discrete lamina segments in an aligned position. 
Placing interlock tabs 144 near common choke surfaces 150 also minimizes 
any bowing or distortion of the lamina by limiting the area of the lamina 
which is stressed by the pressure applied by the alignment surfaces. 
The blanking punch 156 severs the material bridges which connect lamina 
segments 122, 124 to the remainder of strip stock material 154 in 
cooperation with cutting edges on the upper lip of choke barrel 148. 
Typically, after blanking punch 156 has sheared the lamina layer to a 
depth which is approximately 1/3 of the lamina thickness, the lower 2/3 of 
the strip stock material will fracture and the lamina layer will be 
completely separated from the strip stock material. The use of a softer, 
more elastic strip stock material, however, would permit the blanking 
punch to enter the strip stock material for more than 1/3 of the lamina 
thickness and produce a lamina with a smaller fracture zone. As discussed 
above, the proper alignment of discrete lamina segments 122, 124 is 
maintained by engagement of interlock tabs 144b prior to the fracturing of 
the strip stock material attaching discrete lamina segments 122, 124 to 
the remainder of strip stock material 154. 
The downstroke is finished by pushing discrete lamina segments 122, 124 
into further engagement with the uppermost lamina in choke barrel 148 and 
pushing lamina segments 122, 124 to a depth 178 below the upper surface of 
lower die bed 166 as schematically illustrated in FIG. 17. After blanking 
punch 156 is retracted, stock lifters 74 elevate strip stock material 154, 
strip stock material 154 is advanced within the die assembly, and the 
stamping cycle is repeated. A die assembly embodying the present invention 
may be operated at speeds which are typical for embodying the present 
invention may be operated at speeds which are typical for interlocked 
laminas, e.g., 300 strokes per minute. The maximum speed of operation of 
any particular die assembly is dependent upon a number of different 
variables relating to the complexity of the die assembly and the material 
handling requirements imposed upon the die assembly by the dimensions and 
configuration of the lamina stack being manufactured. For most lamina 
stack and die assembly designs, however, the stamping and stacking of two 
discrete lamina segments to form a single layer in a lamina stack should 
not, by itself, have a direct impact upon the speed at which individual 
die assemblies are operated. 
The ability to automatically stamp and stack a plurality of laminas which 
include a lamina layer formed by a plurality of discrete lamina segments 
permits the economical manufacture of parts which might otherwise be more 
expensively manufactured from a single layer of material. For example, the 
ability to stack lamina layers having a plurality of discrete lamina 
segments permits the manufacture, in a single operation, of laminated 
parts wherein a plurality of apertures or other discontinuities are 
located in the part so as to prevent the use of an integral lamina for one 
or more layers of the stack. Conventional manufacture of such parts often 
involves the stamping of a single, relatively thick, material layer and 
forming the apertures or other discontinuities with secondary operations 
such as drilling or milling. Additionally, as described in greater detail 
below, a higher quality stamped edge can be realized by utilizing a 
plurality of laminas instead of stamping a single thick material layer. 
FIGS. 18 and 19 schematically, and in exaggerated fashion for the sake of 
clarity, illustrate edges which have been sheared by a stamping process. 
With reference to thick material 180, the process of stamping a part from 
a sheet of stock material with blanking punch 156 will be described in 
greater detail. When punch 156 first engages the material, the material 
will deform plastically before it is sheared. The initial plastic 
deformation results in rounded corner 182. The material will then be 
sheared by the penetration of the punch until the lower portion of the 
strip stock material fractures. Typically, the punch will penetrate 
approximately 1/3 of the lamina thickness before the lower 2/3 of the 
lamina fractures. This leaves a relatively smooth shear cut band 184, 
marked by cross hatching, and a rougher fracture zone 186. Thin laminas 
190 shown in FIG. 19 have rounded corners 192, shear cut bands 194 and 
fracture zones 196 on their cut edges which are proportionally similar to 
those of thick material 180, e.g., shear band 194 is approximately 1/3 the 
thickness of the lamina material. Although proportional, the magnitude of 
the individual edge depressions which are located in the fracture zone 196 
of the thinner laminas 190 are smaller than the depressions located in 
fracture zone 186 of thick material 180. The rounded edge depression 182 
shown in FIG. 19 is also smaller than the depression 192 shown in FIG. 18. 
Thus, by utilizing a plurality of thinner laminas 190 instead of thick 
material 180, one can manufacture a part having an edge wherein the 
magnitude of the roughness is reduced and the clean shear cut band is more 
evenly distributed. For example, a clutch plate having the form of a 
splined disk could be formed by stamping and stacking ten 0.025 inch 
laminas to thereby provide a higher quality edge surface than a single 
0.25 inch layer of stamped material. 
While this invention has been described as having an exemplary design, the 
present invention may be further modified within the spirit and scope of 
this disclosure. This application is therefore intended to cover any 
variations, uses, or adaptations of the invention using its general 
principles. Further, this application is intended to cover such departures 
from the present disclosure as come within known or customary practice in 
the art to which this invention pertains.