U.S. patent application number 11/365306 was filed with the patent office on 2006-09-14 for touch fastener element loop retention.
This patent application is currently assigned to Velcro Industries B.V.. Invention is credited to Mark A. Clarner.
Application Number | 20060200952 11/365306 |
Document ID | / |
Family ID | 34465560 |
Filed Date | 2006-09-14 |
United States Patent
Application |
20060200952 |
Kind Code |
A1 |
Clarner; Mark A. |
September 14, 2006 |
Touch fastener element loop retention
Abstract
A male touch fastener component having a sheet-form base and an
array of molded fastener elements having stems and heads having
lower surfaces forming an arched crook for retaining loops. The
crooks have particularly high crook angles, such that a maximum
side angle measured about the crook from a line normal to the
forward edge of the stem at an elevation from the base
corresponding to a lowermost extent of the tip, to a normal to the
lower head surface, is greater than about 180 degrees.
Inventors: |
Clarner; Mark A.; (Concord,
NH) |
Correspondence
Address: |
FISH & RICHARDSON PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
Velcro Industries B.V.
|
Family ID: |
34465560 |
Appl. No.: |
11/365306 |
Filed: |
February 28, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10688029 |
Oct 15, 2003 |
|
|
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11365306 |
Feb 28, 2006 |
|
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Current U.S.
Class: |
24/452 |
Current CPC
Class: |
B29C 2043/465 20130101;
Y10T 24/2792 20150115; A44B 18/0049 20130101; A44B 18/0061
20130101; B29C 43/46 20130101; B29L 2031/729 20130101; B29C
2043/461 20130101; B29C 43/222 20130101 |
Class at
Publication: |
024/452 |
International
Class: |
A44B 18/00 20060101
A44B018/00 |
Claims
1-22. (canceled)
23. A method of forming a touch fastener component having a
sheet-form base and an array of fastener elements, the method
comprising: introducing molten resin to a peripheral surface of a
rotating mold roll defining an array of inwardly-extending cavities
each including a stem region extending inwardly from the peripheral
surface, and a head region extending laterally from a distal end of
the stem region to a blind tip, the head region bounded by an outer
surface forming a crook inward of a forward edge of the stem
region, the crook defining an under crook angle, measured about the
crook in side view from a line normal to the forward edge of the
stem region at a mold roll radius to the tip, to a normal to the
crook-forming outer surface, that is greater than about 180
degrees; applying sufficient pressure to force the resin into the
cavities to mold an array of fastener elements, while forming a
sheet of the resin on the peripheral surface of the mold roll;
cooling the resin in the cavities; and then stripping the sheet of
resin from the surface of the mold roll, thereby pulling heads of
the fastener elements formed in the head regions of the cavities
through the stem regions of the cavities to remove the fastener
elements from the cavities.
24. The method of claim 23, wherein each fastener element has
multiple heads extending in different directions.
25. The method of claim 24, wherein each fastener element has two
heads extending in essentially opposite directions.
26. The method of claim 25, wherein each fastener element defines
an upper well between the two oppositely-directed heads, the well
extending down to a height, measured perpendicularly from a top
surface of the sheet of resin, of at least about 70 percent of an
overall height of one of the two oppositely-directed heads.
27. The method of claim 25, wherein each fastener element has an
overall length between opposite extents of the oppositely-directed
heads, measured parallel to the sheet of resin, of at least 1.8
times an overall height of the fastener element.
28. The method of claim 23, wherein a ratio of an overall height of
each crook, measured perpendicular to the sheet of resin from a
lowermost extent of the tip to an uppermost extent of the crook, to
an entrance height measured perpendicular to the sheet-form base
below a lowermost extent of the tip, is greater than 0.6.
29. The method of claim 23, wherein each head has an overall
thickness, measured parallel to the sheet of resin and
perpendicular to a plane of the crook, that is greater than an
entrance height measured perpendicular to the sheet of resin below
a lowermost extent of the tip.
30. The method of claim 23, wherein each stem and head region has
side surfaces lying in parallel planes.
31. The method of claim 23, further comprising introducing a
backing material such that the backing material becomes laminated
to a side of the sheet of resin opposite the fastener elements.
32. The method of claim 23, wherein the under crook angle is at
least about 190 degrees.
33. The method of claim 32, wherein the under crook angle is about
200 degrees.
Description
[0001] This application is a division (and claims the benefit of
priority under 35 U.S.C. .sctn. 120) of pending U.S. patent
application Ser. No. 10/688,029, filed Oct. 15, 2003, the contents
of which is hereby incorporated by reference herein in its
entirety.
TECHNICAL FIELD
[0002] This invention relates to male touch fastener elements
configured to releasably engage fibrous loops, and more
particularly to such fastener elements with stems formed of molded
resin.
BACKGROUND
[0003] Early male touch fastener products were generally woven
materials, with hooks formed by cut filament loops. More recently,
arrays of very small touch fastener elements have been formed by
molding the fastener elements, or at least the stems of the
elements, of resin forming an interconnecting sheet of
material.
[0004] In most applications, male fastener elements are designed to
releasably engage with a mating female fastener component carrying
a field of loops or fibers. To engage the loops, the male fastener
elements must penetrate the field of fibers at least until the tips
of the engaging fastener element heads have sufficiently extended
beyond some of the fibers, such that the fibers can be engaged
within the crooks of the heads.
[0005] Subsequent to engagement, retention of an engaged fiber or
loop depends, at least for loads within the ability of the loop to
resist breakage, upon resistance of the hook to distention and/or
breakage. Distention is the opening of the crook under load of an
engaged loop. For high cycle life applications, breakage of either
both loops and hooks is undesirable. Thus, the ability of the
fastening to resist peel loads in such applications is generally
limited by the ability of the hook to resist distention.
[0006] Unfortunately, for many applications increasing the rigidity
of hooks designed for maximum loop penetration, to increase their
peel resistance, is either undesirable or impractical. For example,
many applications require a gentle `feel` of the male fastener
element array against the skin.
[0007] Further improvements in the overall design of male fastener
elements, particularly those formed or molded of resin and arranged
in large numbers upon a surface for engaging loops or fibers, are
desired. Preferably, such improved fastener elements will be
readily and efficiently manufacturable without great advances in
manufacturing methods.
SUMMARY
[0008] According to one aspect of the invention, a touch fastener
component has a sheet-form base and an array of fastener elements.
Each fastener element includes a stem extending outwardly from and
integrally with the sheet-form base, and a head extending from a
distal end of the stem to a tip to overhang a forward edge of the
stem, the head having a lower surface forming an arched crook for
retaining loops. Specifically, the crook defines an under crook
angle, measured about the crook in side view from a line normal to
the forward edge of the stem at an elevation from the base
corresponding to a lowermost extent of the tip, to a normal to the
lower head surface, that is greater than about 180 degrees.
[0009] In some embodiments, each fastener element has multiple
heads extending in different directions and forming separate
crooks. For example, each fastener element may have two heads
extending in essentially opposite directions.
[0010] In some cases, each fastener element defines an upper well
between the two oppositely-directed heads, the well preferably
extending down to a height, measured perpendicularly from the base,
of at least about 70 percent of the overall height of one of the
two oppositely-directed heads.
[0011] Each fastener element preferably has an overall length,
between opposite extents of the oppositely-directed heads and
measured parallel to the base, of at least 1.8 times the overall
height of the fastener element.
[0012] A ratio of an overall height of the crook, measured
perpendicular to the sheet-form base from a lowermost extent of the
tip to an uppermost extent of the crook, to an entrance height
measured perpendicular to the sheet-form base below a lowermost
extent of the tip, is preferably greater than 0.6.
[0013] For some applications the head has an overall thickness,
measured parallel to the base and perpendicular to a plane of the
crook, that is greater than an entrance height measured
perpendicular to the sheet-form base below a lowermost extent of
the tip.
[0014] In some instances, the head and stem form a unitary molded
structure, such as with the head having surfaces of resin cooled
against a mold surface. The stem may also have opposing surfaces
defined by severed resin, such as from being formed by a
cut-and-stretch operation.
[0015] In some cases, the stem and head have side surfaces lying in
parallel planes.
[0016] The forward edge of the stem preferably extends at an
inclination angle of between about 20 and 30 degrees with respect
to a normal to the base. For example, in one instance the
inclination angle is about 23 degrees.
[0017] The touch fastener component may have a backing material
laminated to a side of the base opposite the fastener elements. In
some cases, the backing material carries engageable loops.
[0018] The fastener elements are preferably arranged in a density
of at least about 350 fastener elements per square inch of the
base. The fastener elements together preferably cover at least 20
percent of an overall surface area of the base from which the
fastener elements extend.
[0019] For some applications, the under crook angle is preferably
at least about 190 degrees, more preferably at least 200
degrees.
[0020] Another aspect of the invention features a method of forming
a touch fastener component having a sheet-form base and an array of
fastener elements. Molten resin is introduced to a peripheral
surface of a rotating mold roll defining an array of
inwardly-extending cavities each including a stem region extending
inwardly from the peripheral surface, and a head region extending
laterally from a distal end of the stem region to a blind tip, the
head region bounded by an outer surface forming a crook inward of a
forward edge of the stem region. The crook defines an under crook
angle, measured about the crook in side view from a line normal to
the forward edge of the stem region at a mold roll radius to the
tip, to a normal to the crook-forming outer surface, that is
greater than about 180 degrees. Sufficient pressure is applied to
force the resin into the cavities to mold an array of fastener
elements, while forming a sheet of the resin on the peripheral
surface of the mold roll. The resin is cooled in the cavities.
Finally, the fastener elements are freed from the mold cavities by
stripping the sheet of resin from the surface of the mold roll,
thereby pulling heads of the fastener elements formed in the head
regions of the cavities through the stem regions of the cavities to
remove the fastener elements from the cavities.
[0021] The improvements in hook design disclosed herein can provide
a touch fastener product with particularly good peel resistance and
other performance characteristics, and are especially applicable to
hooks (whether J-hooks or multiple-crook hooks) that are molded
contiguously with a sheet form base in accordance with known,
cost-effective manufacturing methods. Increased stem taper,
reflected in increased crook angle, beneficially increases rigidity
of the stem against cross-machine bending and torsion. A large
crook angle is particularly useful for retaining loops of large
fiber diameter, high resiliency and in less dense loop field
distributions, once they are engaged. A large crook angle can also
enhance the potential for engagement and retention of multiple
loops at one time within a single crook.
[0022] The illustrated embodiments are also found to be effective
in retaining high-strength, low-loft loops for high cycle life
fastening applications.
[0023] The details of one or more embodiments of the invention are
set forth in the accompanying drawings and the description below.
Other features, objects, and advantages of the invention will be
apparent from the description and drawings, and from the
claims.
DESCRIPTION OF DRAWINGS
[0024] FIG. 1 is a perspective view of male fastener component with
palm tree-shaped hooks.
[0025] FIG. 2 is an enlarged photograph of an example of the
fastener of FIG. 1.
[0026] FIG. 3 is an enlarged side view of one of the fastener
elements.
[0027] FIGS. 3A and 3B are top and end views, respectively, of the
fastener element of FIG. 3.
[0028] FIG. 4 is a perspective view of an alternate palm tree hook
shape.
[0029] FIGS. 4A and 4B are top and end views, respectively, of the
fastener element of FIG. 4.
[0030] FIG. 5 is an enlarged side view of a J-hook fastener
element.
[0031] FIGS. 6 and 6A illustrate alternate molding processes for
forming the fastener components.
[0032] FIG. 7 is a side view of the J-hook fastener element of FIG.
5, illustrating loop confinement area.
[0033] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0034] Referring to FIGS. 1 and 2, a male touch fastener component
100 includes a field of fastener elements 102 arranged in rows R
extending outwardly from and integrally with a sheet-form base 104.
Spacing S between rows may be controlled by the manufacturing
process and will be discussed further below. Fastener elements 102
are palm tree-shaped hooks and are engageable in two directions
along a plane (i.e., an engagement plane) perpendicular to
sheet-form base 104 the in direction of rows R. Each fastener
element 102 includes two heads 106 extending from a single stem
108.
[0035] Male fastener component 100 is designed to, for example,
strongly engage a low pile height, loop touch fastener component,
particularly a loop component with loops formed of, for example, a
high strength multifilament yarn or a high strength monofilament.
High strength loops are desirable for fasteners for high strength
applications requiring high cycle life, as the resist breakage at
higher peel loads. Typically, high strength yarns and monofilaments
are made by extrusion. Generally, the process includes a drawdown
step to impart orientation on the yarn or monofilament so as to
improve, for example, tenacity of the yarn or monofilament. High
strength fibers may also be formed by other methods, for example,
by solution spinning. Suitable high strength loop filament
materials include, for example, polyamides, polyesters,
polyurethanes, ultra-high molecular weight solution spun
polyethylene (e.g., SPECTRA.RTM. polyethylene), aramids (e.g.,
KEVLAR.RTM.0), acrylics and rigid rod polymers like
poly(p-phenylene-2,6-benzobisoxazole).
[0036] Referring now to FIGS. 3, 3A and 3B, fastener element 102
has a substantially constant thickness from base to tip, and
includes a stem 108 extending outwardly from and molded integrally
with sheet-form base 104. For purposes of the present disclosure,
we refer to the stem 108 as beginning at the upper surface of base
104 and ending at an elevation where the inner crook surface is
perpendicular to the base, an elevation 250 above which the inner
crook surface begins to overhang the stem 108 or sheet-form base.
Fastener element 102 also includes two heads 106 extending in
essentially opposite directions in an engagement plane. Heads 106
extend from distal end 250 of the stem to corresponding,
oppositely-directed tips 252. Thus, fastener element 102 is an
example of what is known in the art as a `palm-tree` fastener
element. The heads 106 have upper surfaces that alone or together
with the stem define a well 254 between the heads. Each head 106
has a lower surface that rises up through an apex 258 and then
falls again, forming an arched crook 256 for retaining loops of a
mating female touch fastener component.
[0037] The overall height A of fastener element 102 is measured in
side view perpendicular to sheet-form base 104 from the top of the
sheet-form base. Under crook height C is the distance measured in
side view, perpendicular to the sheet-form base, between the
lowermost extent of the tip 260 and the apex 258 of the crook.
Entrance height E is the distance measured in side view,
perpendicular to the sheet-form base, from the top of the
sheet-form base to the lowermost extent of tip 260. If part of the
stem is directly below the lowermost extent of the tip 260, then
the distance is measured from that portion of the stem directly
below to the lowermost extent of the tip 260. Head height J of
fastener element 102 is measured perpendicular to sheet-form base
104 from the lowermost extent of tip 260 to the highest elevation
of the head 106 above the base. In general, J will be the
difference between A and E. Well height G is measured in side view
from the lower extent of stem 108 to the lower extent of well 256
defined in the upper surface of the fastener element between the
heads.
[0038] Width L of the fastener element is measured in side view and
is the maximum lateral extent of the fastener element heads 106 as
measured parallel to the sheet-form base. Hook thickness K is the
overall thickness of the fastener element, taken at elevation 250
corresponding to the upper end of stem 108. In most cases other
than instances where the heads have been formed subsequent to stem
molding, the heads will lie completely within this hook thickness
K. In the example shown, hook thickness is the same at all
elevations. The product of head width L and thickness K we call the
footprint of the fastener element, and is related to the area of
contact between the hook product and a mating loop product during
initial engagement, although it will be understood to not be an
exact measure of such contact area. The product of footprint and
head height J (i.e., K.times.L.times.J) we refer to as displacement
volume. For a more detailed explanation of the relevance of hook
volume to fastener performance, see Provost, U.S. Pat. No.
5,315,740, the contents of which are incorporated herein by
reference.
[0039] The front and rear surfaces of the stem define, in side
profile, inclination angles .phi. of about 23 degrees with respect
to vertical, with the width of the stem tapering to narrower away
from the base, both for strength and ease of molding.
[0040] Under crook angle .theta..sub.m is an angle defined in the
crook by inner surfaces of the head and stem, between a pair of
line segments perpendicular to facing surfaces of the fastener
element, in side view. Line segment l.sub.1 is perpendicular to the
forward edge of stem 108 at the elevation of the distal tip 260 of
the head. Line segment l.sub.2 is perpendicular to the under crook
surface of the head at a point of inflection `X` of the under head
surface. In cases where there is not a smooth curvature transition
inside the tip, such as where the underside of the head forms a
sharp corner adjacent the tip, line segment l.sub.2 should be taken
as perpendicular to the underside surface of the head just above
such a corner or discontinuity. As shown, angle .theta..sub.m is
measured from the upper side of line segment l.sub.1, about the
crook, to the upper side of line segment l.sub.2. For this
illustrated example, .theta..sub.m is 201 degrees.
[0041] The linear and radial dimensions of the example illustrated
in FIGS. 3, 3A and 3B are as follows: TABLE-US-00001 Dimension
Inches Millimeters A 0.025 0.635 C 0.0064 0.163 E 0.0105 0.267 G
0.0122 0.310 J 0.0145 0.368 K 0.012 0.305 L 0.0497 1.262 R.sub.1
0.0011 0.279 R.sub.2 0.0090 0.229 R.sub.3 0.0026 0.0660 R.sub.4
0.0040 0.102 R.sub.5 0.0107 0.272 R.sub.6 0.0164 0.417
[0042] These values result in a footprint of 5.96.times.10.sup.-4
square inches (0.00385 cm.sup.2), and a displacement volume of
about 8.65.times.10.sup.-6 cubic inches (0.000142 cm.sup.3). Given
a hook density of 380 fastener elements per square inch, the
overall fastener component has an overall hook footprint of 22.6
percent of the overall array area.
[0043] Further description of the embodiment of FIG. 3 can be found
in an application entitled "MULTIPLE-CROOK MALE TOUCH FASTENER
ELEMENTS," filed concurrently herewith and assigned U.S. Ser. No.
10/688,320, the disclosure of which is hereby incorporated in full
by reference.
[0044] Some examples have varying thickness, and non-planar sides.
For example, the fastener element 102a of FIGS. 4, 4A and 4B has a
greatest thickness at its base, and tapers in thickness to the
distal tips of the heads. However, as seen in side view, fastener
element 102a has the same profile as shown in FIG. 3, and
approximately the same dimensions listed above also apply to this
example.
[0045] Not all palm-tree fastener elements have two identical
crooks. For example, some palm-tree fastener elements are
intentionally formed to have one head extending up higher than the
other, such as to engage loops of differing heights. Also, some
palm-tree hooks are molded to have two identical crooks, but later
processing alters one crook more than the other, such as discussed
below.
[0046] Not all examples are of the `palm-tree` variety. For
example, the fastener element 302 of FIG. 5 defines only a single
crook, and is thus an example of a `J-hook` fastener element. In
this case, head width L is taken from the forwardmost edge of the
hook head 306 to the rearmost extent of the hook stem 308.
Otherwise, with the exception of well height G as inapplicable to
J-hooks, the dimensions provided above with respect to FIG. 3 apply
equally to the J-hook of FIG. 5. Both, for example, exhibit
tapering stem cross-sections that enable demolding from molding
cavities. Fastener elements 302 can be arranged in rows extending
from a sheet-form base 304, with hooks of adjacent rows facing in
opposite directions. Other arrangements of such hooks are also
envisioned.
[0047] The fastener elements of FIGS. 3-5 can be molded in the
shapes shown. Referring to FIG. 6, thermoplastic resin 200 is
extruded as a molten sheet from extruder 202 and introduced into
nip 204 formed between a pressure roll 206 and a counter-rotating
mold roll 208 defining fastener element-shaped cavities in its
surface. Pressure in the nip causes thermoplastic resin 200 to
enter these blind-ended forming cavities to form the fastener
elements, while excess resin remains about the periphery of the
mold roll and is molded between the rolls to form sheet-form base
104. The thermoplastic resin is cooled as it proceeds along the
periphery of the mold roll, solidifying the fastener elements,
until it is stripped by stripper roll 212. The molded fastener
elements distend during de-molding, but tend to recover
substantially their as-molded shape. It is generally understood
that fastener element crooks molded to face downstream tend to
distend slightly more than those molded to face upstream, and can
remain more distended in the final product. The direction of travel
of the material illustrated in FIG. 6 is referred to as the
"machine direction" (MD) of the material and defines the
longitudinal direction of the resulting product, while the
cross-machine direction (CD) is perpendicular to the machine
direction within the plane of the sheet-form base. Further details
regarding processing are described by Fischer, U.S. Pat. No.
4,775,310 and Clune et al., U.S. Pat. No. 6,202,260, the
disclosures of which are hereby incorporated in full by
reference.
[0048] In some embodiments, the mold roll 208 comprises a
face-to-face assembly of thin, circular plates or rings (not shown)
that are, for example, about 0.003 inch to about 0.250 inch (0.0762
mm-6.35 mm) thick, some having cutouts in their periphery defining
mold cavities and others having solid circumferences, serving to
close the open sides of the mold cavities and serve as spacers,
defining the spacing between adjacent fastener element rows. A
fully "built up" mold roll may have a width, for example, from
about 0.75 inch to about 6 inches (1.91 cm-15.24 cm) or more and
may contain, for example, from about 50 to 1000 or more individual
rings. Further details regarding mold tooling are described by
Fisher, U.S. Pat. No. 4,775,310. Additional tooling embodiments
will also be described below.
[0049] The cavities that made the fastener element shown in FIG.
3-3B have sharp edges and straight sidewalls and create fastener
elements with substantially similar cross-sections through the
thickness of the fastener element. Tooling with straight sidewalls
and edges can be made by, for example, laser cutting, wire EDM or
electroforming. Further details regarding laser cutting and wire
EDM mold tooling is described by Fisher, U.S. Pat. No. 4,775,310.
The electroforming process is described by Clarner et al., U.S.
Ser. No. 10/455,240, the disclosure of which is hereby incorporated
in full by reference.
[0050] By contrast, fastener elements formed in cavities that have
been, for example, photochemically etched may have rounded surfaces
in some or all regions, from base to tip, such as those illustrated
in FIGS. 4-4B. For example, surfaces at the top of the heads can be
made to taper to a point to give a wedge effect. A wedge-shape may,
for example, assist the entry of the crook into the face of a
mating female fastener component. Further details regarding
photochemical etching is described in Lacey et al., U.S. Pat. No.
6,163,939, the entire disclosure of which is hereby incorporated in
full by reference.
[0051] An alternate technique for molding fastener elements is
shown in FIG. 6A. The process is similar to that described above
with reference to FIG. 6, except only a mold roll 208 is used,
i.e., no pressure roll 206 is necessary. Here, the extruder 202 is
shaped to conform to the periphery of the mold roll 208 and the
extruded resin 200 is introduced under pressure directly to a gap
214 formed between mold roll 208 and extruder 202. The molded
fastener component is stripped from the mold cavities by a stripper
roll 212 as described above. Further details regarding this process
are described by Akeno, U.S. Pat. Nos. 5,781,969 and 5,913,482, the
disclosures of which are hereby incorporated in full by
reference.
[0052] Referring next to FIG. 7, the space above line segments
l.sub.1 and l.sub.2 forms a confinement space 400 into which loops
402 are drawn for engagement. The profile area of this confinement
space is the area swept by the crook angle. As an engaged loop
pulls upward at the apex 304 of the crook, the head 306 of the hook
will distend, opening up the confinement area and shifting the
orientation of line segment l.sub.2 as the hook tip 308 moves
upward. Eventually, at the limit of the ability of the hook to
retain the loop, the hook distends enough that the loop is
released. Because the crook angle is a function of both the extent
to which the hook tip curves back toward the stem, and the taper
angle of the forward edge of the stem, it is related both to the
degree of hook tip displacement required for disengagement under a
normal separation load, and to the strength of the stem to resist
flexure that would otherwise facilitate such loop release. As both
of these factors are related to the amount of normal force required
for loop release, crook angle is found to be directly related to
the ability of the hook to withstand higher peel loads. In closures
that are `hook limited,` in that the loop strength is stronger than
the load required for hook distention, as is typically desirable
for high cycle life applications, increasing the hook peel
resistance increases the performance of the overall closure.
[0053] As a measure of the `encirclement` of the confinement area
by the hook, crook angle is also related to the ability of the hook
to resist unintended disengagement of loops at low loads. For very
low crook angles, engaged loops can tend to exit the confinement
area through the space between tip and base when the load on the
loop is reduced or reversed.
[0054] A number of embodiments of the invention have been
described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention. Accordingly, other embodiments are within
the scope of the following claims.
* * * * *