U.S. patent application number 11/584874 was filed with the patent office on 2007-02-15 for continuous molding of fastener products and the like and products produced thereby.
This patent application is currently assigned to Velcro Industries B.V., a Netherlands corporation. Invention is credited to Richard M. Formato, Andrew C. Harvey, Stephen C. Jens, Howard A. Kingsford, J. Scott Neumann.
Application Number | 20070035060 11/584874 |
Document ID | / |
Family ID | 25276716 |
Filed Date | 2007-02-15 |
United States Patent
Application |
20070035060 |
Kind Code |
A1 |
Harvey; Andrew C. ; et
al. |
February 15, 2007 |
Continuous molding of fastener products and the like and products
produced thereby
Abstract
Improvements are disclosed for an apparatus for continuously
molding small fastener elements integral with a base web from a
flowable resin. The apparatus comprises a cylindrical mold roll
rotatable about an axis and defining small fastener element-shaped
mold cavities in the surface thereof, and pressure-applying means
to apply operating pressure to force the resin into the cavities at
a pressure zone. The pressure-applying means and mold roll define a
mold gap therebetween for forming the base web. The advantageous
use of relatively long mold rolls, to produce a correspondingly
wide web, and the use of higher molding pressures, e.g. to form
very small fastener elements, is enabled by various improvements,
including means to maintain the mold gap at a desired thickness
profile across the length of the molding region of the mold roll
under operating pressure. In some cases the pressure-applying means
includes a pressure roll, in other cases it includes a resin nozzle
assembly or pressure head. In some other cases it includes a belt.
Various control schemes are also disclosed, as are means to provide
cooling. In some particularly useful embodiments, at least one of
the rolls of the apparatus has a resiliently deformable surface.
Methods of molding fastener elements directly on a sheet material,
such as sandpaper, are also disclosed, as well as methods for
laminating.
Inventors: |
Harvey; Andrew C.; (Waltham,
MA) ; Jens; Stephen C.; (Winchester, MA) ;
Kingsford; Howard A.; (Amherst, NH) ; Neumann; J.
Scott; (Natick, MA) ; Formato; Richard M.;
(Shrewsbury, MA) |
Correspondence
Address: |
FISH & RICHARDSON PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
Velcro Industries B.V., a
Netherlands corporation
|
Family ID: |
25276716 |
Appl. No.: |
11/584874 |
Filed: |
October 23, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10720739 |
Nov 24, 2003 |
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11584874 |
Oct 23, 2006 |
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10282716 |
Oct 29, 2002 |
6660121 |
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10720739 |
Nov 24, 2003 |
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09402975 |
Oct 14, 1999 |
6482286 |
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10282716 |
Oct 29, 2002 |
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PCT/US98/07873 |
Apr 16, 1998 |
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09402975 |
Oct 14, 1999 |
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08838279 |
Apr 16, 1997 |
5945131 |
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PCT/US98/07873 |
Apr 16, 1998 |
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Current U.S.
Class: |
264/167 |
Current CPC
Class: |
B29C 43/222 20130101;
B29C 48/92 20190201; B29L 2031/729 20130101; B29C 48/12 20190201;
B29C 2043/465 20130101; A44B 18/0061 20130101; B29C 48/13 20190201;
B29C 59/025 20130101; B29C 48/35 20190201; B29C 59/04 20130101;
A44B 18/0049 20130101; B29C 2043/461 20130101; B29C 48/08 20190201;
B29C 2043/486 20130101; B29C 43/46 20130101 |
Class at
Publication: |
264/167 |
International
Class: |
B29C 47/00 20070101
B29C047/00 |
Claims
1-59. (canceled)
60. A method of forming a fastener product that includes a
plurality of fastener elements integral with a base layer, the
method comprising: providing a rotatable mold roll having an outer
surface and a plurality of inwardly extending cavities shaped to
form at least stem portions of the fastener elements; depositing
molten resin on the outer surface of the cavity roll with an
applicator; and by rotation of the mold roll, carrying the molten
resin on the mold roll a distance from a point at which the resin
is deposited, into a pressure region in which pressure fills the
inwardly extending cavities with some of the resin, other of the
resin forming the base layer on the outer surface of the cavity
roll.
61. The method of claim 60, wherein the mold roll is cooled.
62. The method of claim 60, wherein the applicator generates
sufficient pressure to partially fill the cavities.
63. The method of claim 60, wherein the resin is under
substantially atmospheric pressure conditions as it is carried from
the applicator toward the pressure region.
64. The method of claim 60, wherein the cavities are shaped to form
elements that are loop-engageable.
65. The method of claim 60, wherein the cavities are shaped to form
hooks.
66. The method of claim 60, including introducing a web material to
the pressure region, pressure in the pressure region bonding the
web material to the resin to form a fastener laminate.
67. The method of claim 60, wherein the pressure in the pressure
region is from about 1000 to about 1600 pounds per lineal inch
along the mold roll.
68. The method of claim 60, wherein the mold roll includes an
axially arranged stack of disks, some having mold cavities at their
peripheral surfaces.
69. The method of claim 60, wherein the cavities extend into the
mold roll to a depth of between about 0.004 and 0.035 inch.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to improved equipment and methods for
making continuous fastener products and the like, and to products
produced by the equipment and methods.
[0002] Fastener products, such as hook components of hook-and-loop
fasteners, are manufactured by a continuous molding method
employing a cylindrical mold roll which has fastener-shaped
cavities formed in its periphery. Often the mold roll is formed of
an axially compressed stack of ring-form mold plates. In operation,
molten polymer from an extruder is introduced into a pressure zone
in which the molten polymer is forced under high pressure into the
fastener cavities of the cooled mold roll, to form fastener
elements (e.g. hooks) integrally molded with a base layer. In some
cases the pressure zone is a nip formed by a mold roll and an
adjacent pressure roll. In other configurations the pressure zone
is formed between a conforming stationary pressure head and a mold
roll. Typically, the smaller the fastener elements (or the like),
the faster the optimal production speed. The more viscous the
resin, or the lower the temperature of the cooled roll, the higher
must be the pressure achieved in the pressure zone in order to make
a satisfactory product. Typically, mold rolls of about 10 inch
diameter and 12 inches in axial length have been employed.
SUMMARY OF THE INVENTION
[0003] We have realized that many advantages can be obtained by
employing longer mold rolls and correspondingly wide pressure zones
to form wide products, while providing means to accommodate effects
of the distribution of pressure along the length of the mold roll.
By this means, products molded with wide widths can have uniform
product thickness and other properties previously found only in
narrower materials.
[0004] We also have realized that many advantages can be obtained
by raising the pressure in the pressure zone, with a conventional
roll or a longer roll, to form products having finer features while
providing means to accommodate effects of the distribution of
pressure along the length of the mold roll.
[0005] We have realized that, because of the construction of the
molding region of the mold roll as a stacked series of rings or
plates about a central shaft, the mold roll has limited bending
resistance. As a result, if the molding region of the mold roll is
made long to produce a wide product, or if the pressure of the
resin is increased, the tendency of the mold roll to bend away from
the pressure zone under the extreme molding pressure can cause
small separations between adjacent mold plates and undesirable base
layer thickness variation across the width of the product (i.e. gap
variation along the length of the molding region). Also, we realize
that non-uniform geometry of the pressure zone can produce
detrimental nonuniformity in the pressure distribution across the
pressure zone, which can lead to incomplete filling of some of the
mold cavities.
[0006] According to one aspect of the invention, improvements are
made in an apparatus for continuously molding fastener elements
integral with a base web from a flowable resin. The apparatus
comprises a cylindrical mold roll rotatable about an axis and
defining small fastener element-shaped mold cavities in the surface
thereof, and pressure-applying means to apply elevated operating
pressure to force the resin into the cavities at a pressure zone.
The pressure-applying means and mold roll define a mold gap
therebetween for forming the base web. The provided improvements
include means to maintain the mold gap at a desired thickness
profile across the length of the molding region under operating
pressure that would otherwise tend to produce gap variations.
[0007] The provided improvements are particularly useful if the
molding region of the mold roll is lengthened to about 12 inches or
more or if the operating pressure is raised to higher levels, such
that the mold roll is subject to loads in the range of about 1000
to 1600 pounds per lineal inch along the mold roll.
[0008] In a preferred configuration, the mold roll comprises an
axially arranged stack of a large multiplicity of disks, at least
many of which have mold cavities at their peripheral surfaces.
[0009] In certain advantageous embodiments, the means to maintain
the mold gap comprises a moving support member on the side of the
mold roll generally opposite the pressure-applying means. The
support member is disposed to engage the peripheral surface of the
mold roll with sufficient force to resist radial deflection of the
mold roll. Preferably a support member controller is provided to
vary the amount of engagement between the mold roll and the support
member in response to operating conditions.
[0010] In certain embodiments, the apparatus includes a sensor to
provide operating condition information to a support member
controller. In some cases the sensor is constructed to detect the
presence of molded resin on the peripheral surface of the mold roll
and the controller is constructed to disengage the support member
from the peripheral surface of the mold roll when resin is not
present. In certain arrangements, the sensor is constructed to
respond to a condition of the apparatus that is related to the
pressure in the pressure zone.
[0011] In some preferred embodiments of the invention the depth of
the mold cavities from the surface is between about 0.004 and 0.035
inches, preferably between about 0.005 and 0.020 inches, and more
preferably between about 0.006 and 0.012 inches.
[0012] Broadly, the invention relates to completed fastener
elements and to components or preforms that form a part of, or are
modified to form, a completed fastener. The term "fastener element"
as used herein is intended to include all of these forms.
[0013] In some embodiments, however, the mold cavities preferably
define the shape of functional fastener elements. In some preferred
arrangements the mold cavities at least partially define the shape
of loop or fiber-engaging hook elements, each element having a
pedestal or stem portion and at least one head portion that
projects to a side of the pedestal or stem portion. In other
arrangements, the fastener elements are of mushroom shape or of
stem-shaped preforms that are subsequently processed to form
mushrooms or other elements having flat or rounded heads.
[0014] In some particularly useful embodiments, the support member
that engages the mold roll has a peripheral surface that is
resiliently deformable to conform, in the vicinity of its
engagement with the mold roll, generally to the peripheral surface
of the mold roll. In some of these instances, the portion of the
support member that directly contacts the surface of the mold roll
is of a resilient substance, preferably an elastomeric
material.
[0015] In some preferred embodiments the support member comprises a
generally cylindrical roll arranged to rotate about an axis of
rotation, while in some other embodiments the support member
comprises a belt supported to engage the mold roll with substantial
pressure.
[0016] In some embodiments the means to maintain the mold gap
comprises adjustable structure to elastically deform the shape of
the pressure-applying means, to conform to axial deflection of the
mold roll. In some cases, the pressure-applying means comprises a
pressure roll, the mold gap comprises a nip between the mold roll
and pressure roll, and the means to elastically deform the shape is
constructed to bend the axis of the pressure roll to maintain the
mold gap. In some other cases, the pressure-applying means
comprises a nozzle assembly for introducing the resin to the
pressure zone under pressure, the mold gap comprises a gap between
this nozzle assembly and the mold roll, and the means to
elastically deform the shape is constructed to bend the nozzle
assembly along the length of the mold gap to maintain the mold
gap.
[0017] In some preferred embodiments the pressure-applying means
comprises a pressure roll rotatable about an axis and positioned to
form a nip with the mold roll to provide the mold gap. The means to
maintain the mold gap includes a controller to vary the angle
between the axes of the pressure and mold rolls to introduce skew
to compensate for mold roll deflection under operating
pressure.
[0018] In various arrangements according to the invention, means
are provided to extract heat from the surface of the support member
to cool the support member, thus to withdraw heat from the molding
process.
[0019] According to another aspect of the invention, an apparatus
is provided for continuously molding two streams of fastener
product from flowable resin, each product comprising a base web
with integral fastener elements. The apparatus has a cylindrical
mold roll rotatable about an axis and defining small fastener
element-shaped mold cavities in its surface in a molding region.
The apparatus also has first and second pressure-applying means to
apply operating pressure to force the resin into the cavities of
the mold roll at corresponding first and second pressure zones. The
first and second pressure-applying means and the mold roll define
corresponding first and second mold gaps therebetween for forming
the base webs in the molding region. First and second
product-removing means are included to remove the product from the
mold roll. The first and second pressure-applying means are
advantageously arranged on generally opposite sides of the mold
roll, such that bending loads applied to the mold roll by the
elevated operating pressures of the two pressure applying means are
substantially balanced. Preferably, the mold roll is of extended
length of about 12 inches or more to produce correspondingly wide
webs.
[0020] In some embodiments the first and second pressure-applying
means each comprises a pressure roll and the first and second mold
gaps each comprises a nip between the mold roll and a corresponding
pressure roll.
[0021] In some other embodiments, the first and second
pressure-applying means each comprises a nozzle and shoe assembly
for introducing the resin to the corresponding pressure zone under
pressure and the first and second mold gaps each comprises a gap
between a corresponding nozzle assembly and the mold roll.
[0022] According to another aspect of the invention, an apparatus,
for continuously molding small fastener elements integral with a
base web from a flowable resin, has a cylindrical mold roll
rotatable about an axis and defining fastener element-shaped mold
cavities at its surface in a molding region, and pressure-applying
means are arranged to apply operating pressure to force the resin
into the cavities at a pressure zone. The pressure-applying means
and mold roll define a mold gap therebetween for forming the base
web in the molding region. The apparatus includes a roll arranged
to engage the mold roll with substantial force, and which has a
resiliently deformable surface to conform, in the vicinity of its
engagement with the mold roll, generally to the peripheral surface
of the mold roll along the molding region.
[0023] In some embodiments, the molding region of the mold roll is
of about 12 inches or more in length and the resiliently deformable
roll comprises a pressure roll positioned to form a wide nip with
the mold roll to provide the mold gap, to form a correspondingly
wide web. In these and other embodiments, preferably a
substantially elevated pressure is maintained in the pressure zone
to produce a load of between about 1000 and 1600 pounds per lineal
inch against the mold roll in the molding region.
[0024] In some embodiments, the resiliently deformable roll
comprises a support roll disposed to engage the mold roll on the
side generally opposite the pressure-applying means to resist
deflection of the mold roll.
[0025] In some embodiments useful for producing a laminated
fastener product comprising a molded web and a backing material,
the resilient roll and the mold roll define therebetween a
laminating zone for laminating the molded web to the backing
material.
[0026] According to another aspect of the invention, an apparatus
for continuously molding fastener elements integral with a base web
from a flowable resin has a cylindrical mold roll rotatable about
an axis and defining fastener element-shaped mold cavities at a
surface thereof, pressure-applying means to apply operating
pressure to force the resin into the cavities at a pressure zone
(the pressure-applying means and mold roll defining a mold gap
therebetween for forming the base web), and a belt arranged to
engage the mold roll.
[0027] In some embodiments the belt is arranged to engage the mold
roll on the side generally opposite the pressure-applying means to
resist radial deflection of the mold roll.
[0028] In some embodiments the belt and the mold roll define a
laminating zone therebetween for laminating the molded web to a
backing material.
[0029] In some cases, the belt is constructed to extract heat from
the surface with which it is engaged.
[0030] According to another aspect of the invention, certain other
improvements are provided in an apparatus for continuously molding
fastener elements integral with a base web. The apparatus has a
cylindrical mold roll rotatable about an axis and defining fastener
element-shaped mold cavities in the peripheral surface thereof, and
a nozzle assembly to introduce a flowable resin to the cavities.
The nozzle assembly is constructed and arranged to apply operating
pressure to force the resin into the cavities at a pressure zone,
and the nozzle assembly and mold roll define a mold gap
therebetween for forming the base web, the apparatus including
means to maintain the mold gap at a desired thickness profile
across the width of the wide web under the operating pressure if
the roll is lengthened or if the operating pressure is raised to
higher levels such that the mold roll is subject to loads in the
range of about 1000 to 1600 pounds per lineal inch along the mold
roll.
[0031] In some embodiments the means to maintain the mold gap
comprises a support member disposed to engage the mold roll on the
side generally opposite the nozzle assembly with sufficient force
to resist radial deflection of the mold roll, and a controller
constructed to vary the amount of engagement between the support
member and the mold roll. In some cases the support member is
resiliently deformable.
[0032] In some embodiments the means to maintain the mold gap
comprises an actuator to elastically bend the nozzle assembly to
conform to radial deflections of the mold roll to maintain the mold
gap, and a controller constructed to control the actuator to vary
the amount of bending of the nozzle assembly.
[0033] According to another aspect of the invention, an apparatus
for continuously molding fastener elements integral with a base web
includes a cylindrical mold roll, preferably of extended length to
provide a correspondingly wide web, and a cylindrical pressure
roll. The mold roll is rotatable about an axis and comprises
multiple stacked disks having fastener element-shaped mold cavities
in their peripheral surfaces. The cylindrical pressure roll is
arranged to engage the mold roll at a nip to form a mold gap for
forming the base web. The pressure roll is constructed to apply
operating pressure to force the resin into the cavities. The
apparatus also includes an extrusion die to introduce a flowable
resin to the nip, and means to maintain the mold gap at a desired
thickness profile across the width of the wide web under the
operating pressure, preferably a substantially elevated
pressure.
[0034] In some embodiments the means to maintain the mold gap
comprises a support roll arranged to engage the mold roll on the
side generally opposite the nozzle assembly with sufficient force
to resist radial deflection of the mold roll, and a controller
constructed to control the amount of engagement between the support
roll and the mold roll in response to operating conditions.
[0035] In some embodiments the means to maintain the mold gap
includes a controller to vary the angle between the axes of the
pressure and mold rolls to introduce skew to compensate for mold
roll radial deflection under operating pressure.
[0036] By "radial deflection" as used herein, we mean any lateral
deflection of any portion of the axis of the roll, including
bending or bowing deflections.
[0037] According to another aspect of the invention, an apparatus
for continuously molding fastener elements integral with a base web
includes a cylindrical mold hoop rotatable about an axis and having
fastener element-shaped mold cavities in its peripheral surface.
The apparatus also has at least one driven roll arranged to engage
an inner surface of the mold hoop to drive the hoop and a
pressure-applying means arranged to apply operating pressure to
force the resin into said cavities at a pressure zone.
[0038] In some embodiments of the apparatus of the invention, the
pressure-applying means is constructed to apply first and second
operating pressures at corresponding first and second said pressure
zones at first and second mold gaps, respectively, with the mold
roll. In some instances, the pressure-applying means comprises a
nozzle assembly for introducing resin to the first pressure zone at
the first operating pressure, the first mold gap comprising a gap
between the nozzle assembly and the mold roll. In some cases, the
pressure-applying means also includes a pressure roll, the second
mold gap comprising a nip between the mold roll and pressure
roll.
[0039] According to another aspect of the invention, a method of
continuously molding fastener elements on one broad side of a sheet
product opposite another broad side having surface features, e.g.,
raised or indented portions, is provided. The method comprises
providing an apparatus that includes a mold roll, resiliently
deformable pressure roll, and an extruder die, all as described
above, passing a sheet product having the surface features through
the nip with the molten resin such that the resilient surface of
the pressure roll conforms in the vicinity of the features to
protect the features as they pass through the nip. The method also
includes forming fastener elements integral with a base web on a
broad side of the sheet product.
[0040] In some embodiments, an abrasive sheet product having molded
fastener elements on one side and abrasive particles on the other
side is formed by the in situ laminating method just described, in
which the surface features comprise abrasive particles.
[0041] In some embodiments the surface features comprise a
decorative texture such as an enclosed pattern or decorative fibers
as in grass cloth. In some embodiments, the sheet product comprises
a wall covering covered on its back side with fastener
elements.
[0042] Various aspects of the invention disclosed here enable
cost-effective commercialization of molded fastener products of
extremely wide widths and products having many very small fastener
elements. In particular, fastener products with very thin base
layer thicknesses held to very close dimensional tolerances can be
produced in a practical manner. According to another aspect of the
invention, the contact from loading systems that are provided
according to the invention in the form of load rolls or load belts,
are advantageously employed to extract heat from the back of the
base layer of the product, to enable production of thicker base
layers or to produce a product with a given base thickness at a
much higher production speed than has previously been possible.
[0043] As will be understood from the foregoing and the remaining
description and drawings, various features of the different aspects
of the invention may be advantageously combined in other
embodiments for certain applications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] FIG. 1 shows a molding system with a conformable load roll
according to the invention.
[0045] FIG. 1A shows a molding system similar to FIG. 1 with a
non-conformable load roll.
[0046] FIG. 2 illustrates the use of twin conformable load
rolls.
[0047] FIG. 3 shows a molding system with a load belt.
[0048] FIGS. 4-6 show various methods of cooling a load roll.
(FIGS. 5 and 6 employ cooling belts).
[0049] FIG. 7 is an enlarged view of the contact zone between the
load roll and mold roll of FIG. 1.
[0050] FIGS. 7A and 7B illustrate different conformable load roll
constructions.
[0051] FIG. 7C is an enlarged diagrammatic view of a thermally
conductive, conformable material.
[0052] FIG. 8 illustrates the use of a series of adjustable load
rolls.
[0053] FIG. 9 shows a molding system having two conformable load
rolls.
[0054] FIG. 10 is an enlarged view of the molding nip between a
mold roll and a conformable pressure roll.
[0055] FIG. 11 illustrates a construction of the conformable
pressure roll of FIG. 10.
[0056] FIGS. 12 and 12A show inducing a curvature in, respectively,
a solid and stacked-plate roll.
[0057] FIG. 13 illustrates skewing a pressure roll.
[0058] FIG. 13A is a bottom view of the skewed rolls, taken from
direction 13A-13A in FIG. 13.
[0059] FIG. 13B illustrates an open-loop control system for skewing
a pressure roll.
[0060] FIG. 13C illustrates a closed-loop control system for
skewing and loading a pressure roll.
[0061] FIG. 14 shows a system employing skewing and gross load
control.
[0062] FIG. 15 illustrates the use of a cooling belt for a molding
system.
[0063] FIG. 16 shows a twin molding nip arrangement, according to
the invention.
[0064] FIGS. 17, 17A and 18 through 21 illustrate methods and
systems for forming a laminate product.
[0065] FIGS. 22 and 23 illustrate systems employing a pressure head
and a conformable loading system.
[0066] FIG. 24 shows a system with a pressure head and a cooled,
conformable load roll.
[0067] FIGS. 25 and 26 show control systems for systems with
pressure heads.
[0068] FIG. 27 is of a dual pressure head system.
[0069] FIGS. 28 and 29 illustrate laminating in a pressure head
system.
[0070] FIGS. 30A through 30C illustrate cross-sections of fastener
products.
[0071] FIG. 31 shows an embodiment useful for molding fastener
elements on a backing material.
[0072] FIG. 32 is an enlarged view of part of the nip of FIG. 31,
illustrating an effect of a compliant pressure roll.
[0073] FIGS. 33 and 34 illustrate systems employing a pressure roll
and a pressure head.
[0074] FIG. 35 shows a system with a mold hoop.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0075] Referring to the embodiment of FIG. 1, an extruder 4
delivers a wide extrusion of molten polymer 100 into the nip (i.e.
into the pressure zone) between an elongated mold roll 1 and a
pressure roll 2. The polymer is forced into fastener-shaped
cavities 102 by the pressure of the nip, forming a base layer with
integral fastener elements. The fastener elements are, in some
cases, fully-formed elements capable of snagging loops as molded.
In other cases, the fastener elements are preform elements that are
intended to be subjected to a post-forming operation to form
completed fastener elements. The post-forming operation, in some
cases, forms flat top portions on hook or post preforms. The
fastener elements are very small to engage small loops or fibers on
a surface, and typically are arranged on the web base with a
density of 500 to 2,000 fastener elements per square inch.
[0076] The fastener product 5 is carried on the chilled mold roll 1
a distance sufficient to solidify the fastener elements before
removing the elements from their mold cavities 102. A take-off roll
6 is employed to peel the fastener product 5 from mold roll 1.
Typically the nip pressure is controlled by actuators (not shown)
that force pressure roll 2 against mold roll 1.
[0077] A load roll 3, on the side of mold roll 1 opposite to the
side of the pressure zone, is arranged to engage mold roll 1 to
resist the bending of mold roll 1 that would otherwise occur due to
pressure zone forces. By "engage" we mean that the load roll 3
either directly contacts the load roll surface or resin or other
product layer on the surface of the load roll, with a substantial
contact force. The force exerted by load roll 3 against mold roll 1
is controlled by a control system 7. Control system 7 varies the
position of the load roll to control the load applied to mold roll
1 to result in a more uniform product base layer thickness, and to
protect against accidental contact between the mold roll and
pressure roll. The load applied by the load roll to mold roll 1 is
preferably about the same as the load applied against the mold roll
by pressure roll 2.
[0078] In a preferred embodiment, load roll 3 (a support roll) has
a resilient external layer of thickness t (shown exaggerated in the
figure), such as 0.5 inch of urethane elastomer. The compliance of
the relatively soft external layer of load roll 3 results in a
relatively wide contact area 106 between load roll 3 and mold roll
1 and lower average contact pressures than the pressure in the nip
between mold roll 1 and pressure roll 2. It also provides more
uniform load distribution along the axis of the roll, compensating
for small radial deflections of rolls 1 and 2. The relatively low
contact pressure avoids damage to the delicate mold surface (e.g.
coining or fatigue in the region of the mold cavities) that would
result from high pressure, direct contact with a hard load roll.
The integration of the component of this contact pressure parallel
to the plane of the axes of the mold and pressure rolls 1 and 2
provides a reaction force to balance the bending force applied to
mold roll 1 by nip pressure. Load roll 3 is preferably constructed
and arranged to provide a reaction load substantially equal to the
bending load from the pressure zone, thereby maintaining the
straightness of mold roll 1, and the uniformity of the gap along
the length of the rolls.
[0079] Control system 7 responds to the thickness of the base layer
of the product while on the mold roll, as measured by thickness
sensor 13, and adjusts the reaction load applied by load roll 3
accordingly. In an alternative embodiment, sensor 13 is replaced by
a means to measure the distance between rolls 1 and 2.
[0080] Also shown in FIG. 1, in dashed lines, is an alternative
placement for the take-off roll, shown as take-off roll 6a. In this
alternative embodiment, the product as it cools is carried by mold
roll 1 through a second nip between the mold roll and load roll 3,
and is subsequently peeled away by take-off roll 6a as fastener
product 5a. This alternative embodiment is especially useful when
longer cooling times are desired, as it enables the cooling
fastener product to be carried by chilled mold roll 1 for a longer
time to conduct more heat from the product. Leaving the product in
the mold cavities during contact with load roll 3 also can provide
important protection to the mold cavities from damage when high
loading pressures are employed, as with rolls having a hard outer
layer. In embodiments where load roll 3 is cooled, e.g. by
controlled flow of coolant through its interior, additional heat is
advantageously extracted from the back side of the product as it
passes through the second nip. The relatively wide contact area
between mold roll 1 and load roll 3 can help to promote this heat
transfer.
[0081] The machine and process shown in solid lines in FIG. 1 are
useful when molding delicate products that may tend to be damaged
from travelling through the second nip, whereas the machine and
process shown in dashed lines is useful for more rugged products
and for high speed production.
[0082] As shown in FIG. 1A, passing the cooling product through the
nip between mold roll 1 and load roll 3' enables, in another
embodiment, the use of a non-conformable load roll 3'. In this
embodiment the presence of the resin in the cavities and between
the load roll and the mold roll provides important protection to
the surface of the mold roll and the mold cavities. Without the
product present in the nip between the mold roll and the load roll,
the features of the surface of the mold roll (e.g. mold cavities
102) would be susceptible to damage from high contact or Hertzian
stresses, which can be hundreds of thousands of pounds per square
inch. These high contact stresses can, for instance, deform the
mold roll surface plastically such as by coining or flattening the
tips of some of the fastener-shaped cavities. Even if the mold roll
surface is not deformed instantly, the repeated, localized stress
applied to the metal forming the inside of a hook-shaped fastener
from such hard surface contact can cause fatigue and fracture,
resulting in some of the hooks being deformed and the resulting
product having an unattractive appearance.
[0083] Further features are provided to avoid applying a
substantial load to mold roll 1 by hard load roll 3' of FIG. 1A
when there is not sufficient polymer product in the load roll nip
to protect the mold cavities. In one case, thickness sensor 13 is
adapted to detect an interruption in the flow of product. Control
system 7 is adapted to respond by quickly unloading load roll 3',
thereby avoiding direct contact load against a bare mold roll.
[0084] In FIGS. 1 and 1A the axis of load roll 3 or 3' was
substantially in the plane of the axes of mold roll 1 and pressure
roll 2, all three axes being substantially parallel.
[0085] Referring to FIG. 2, another embodiment has two load rolls
3a and 3b that are generally opposite the pressure zone between
mold roll 1 and the pressure roll, but whose axes are out of the
plane of the mold roll and pressure roll. Load rolls 3a and 3b are
shown to be preferably arranged in a symmetric or balanced manner
about the plane defined by the axis of the upper rolls. The axes of
load rolls 3a and 3b are parallel with each other and substantially
parallel with the axes of the upper rolls. This double load roll
arrangement advantageously results in an even larger net contact
area against mold roll 1 and even lower average contact
pressure.
[0086] Referring back to FIG. 1, one embodiment of the control
system employs manual adjustment by the operator of the pressure
applied by load roll 3. At start up, a release paper is passed with
the extruded polymer through the nip between mold roll 1 and
pressure roll 2, the paper covering cavities 102 so that the
initial melt from the extruder does not enter the cavities. The
release paper continues to pass through the nip until the surface
of mold roll 1 and cavities 102 reach an appropriate operating
temperature and speed. At this point, because of the presence of
the release paper covering the cavities, the product 5 or 5a has no
fastener elements. When operating conditions are reached, but
before applying substantial pressure from either pressure roll 2 or
load roll 3, entry of the release paper into the nip is
discontinued, exposing cavities 102 to the molten polymer, which
begins to flow into the cavities to form partial fastener elements.
The load between pressure roll 2 and mold roll 1 is then increased
by moving the pressure roll closer to the mold roll until there is
enough pressure developed on the melt to completely fill cavities
102 under the desired conditions. At this point, fastener product 5
or 5a has useful, fully-formed fastener elements integrally molded
with the base layer, although the uniformity of the product is
affected by the longitudinal bending of mold roll 1, resulting in a
base layer that is typically thicker in the middle of the product
than on the edges. While measuring the thickness of the base layer
(e.g. by thickness sensor 13), the loads applied by pressure roll 2
and load roll 3 are increased until a desirable product is
produced.
[0087] In a typical operation the load applied by pressure roll 2
is adjusted to produce the desired average or mean product base
thickness, and the load applied by load roll 3 is adjusted to
reduce base thickness variation across the width of the
product.
[0088] In such an arrangement the mold roll may be two feet or
longer in length and the load applied by the pressure rolls may be
as much as 1600 pounds or more per lineal inch of mold nip.
[0089] In a more complex control system 7, signals from thickness
sensor 13 (or multiple sensors arranged to sense various desired
control parameters) are fed into an electronic controller that
contains an algorithm that controls the loading forces or roll
displacements to produce a desired product. Thickness sensor 13 is,
in the presently preferred embodiment, a magnetic reluctance sensor
placed, as shown, to detect base layer thickness near the pressure
zone. Alternatively, sensor 13 (in the form, e.g., of a beta-gauge)
may be placed downstream of the mold apparatus. In some situations
it is desirable to use a scanning sensor 13 that traverses the
width of the product and measures variation in base thickness
across the width. If load roll 3 has a sufficiently compliant
surface and is adjusted to completely balance the load applied by a
sufficiently stiff pressure roll 2, a stationary thickness sensor
13 measuring the thickness at one point along the width of the
product may provide sufficient control feedback, due to the
pressure nip gap remaining even. If the pressure roll is
approximately as flexible as the mold roll, more load must be
applied by the load roll to compensate for the bending of the
pressure roll to maintain an even nip gap by bowing the middle of
the mold roll toward the bowed pressure roll. The stacked plate
structure of the mold roll, however, limits the amount of forced
curvature that can be tolerated before adjacent plates of the mold
roll begin to separate and cause molding flash. Extreme axial
loading of the mold roll (e.g. by tie rods) can extend this limit
and increase the amount of mold roll curvature that can be
tolerated. Furthermore, pressure roll 2 is more readily constructed
to be rigid in bending to address this condition than is the mold
roll.
[0090] Referring to FIG. 3, in another embodiment a load belt
system 108 replaces load roll 3 of FIG. 1 as the means to apply a
reaction load to mold roll 1 to balance the load applied by
pressure roll 2. Load belt system 108 has a load belt 14 and at
least two or more rolls 110 to tension and support belt 14. Belt
system 108 is loaded against mold roll 1 effectively in the plane
of the axes of the mold and pressure rolls.
[0091] An advantage of using a load belt system 108 is that the
contact load against mold roll 1 is spread over a very wide contact
area to make the contact pressure low. In addition, by the
provision of cooling fluid as suggested by arrow A, effective
cooling is achievable. In the case of the arrangement shown in
dashed lines in FIG. 3, contact with the cooling product occurs
over a long length of travel so that even at high speed there is
time to extract heat from the back side of the base layer as it
passes between load belt 14 and the mold roll.
[0092] FIGS. 4-6 show a number of ways, according to the invention,
to cool the molding system. To advantageously remove heat at a
constant rate from either the product or mold roll 1 by a
conformable load roll 3, heat is continuously extracted. Due to the
relatively low thermal transfer characteristics of most durable,
highly compliant materials (as compared to metals), in most
instances it is preferable to transfer heat directly from the load
roll surface rather than transfer it through the outer compliant
layer of the load roll to an internal cooling system. Cooling the
load roll also reduces the amount of heat that otherwise has to
diffuse through the tooling rings or disks of the mold roll to be
extracted by a heat removal means such as circulated water in the
core of the mold roll. This reduces the temperature gradient
between the surface of the mold roll and the cooled core of the
mold roll, which, in turn, improves the assemblability of the mold
roll and helps to keep the mold rings in contact with the central
mold roll shaft, in part because differences in thermal expansion
of the components of the mold roll are reduced due to reduced
temperature gradients.
[0093] In FIG. 4, cold air is blown across the surface of the load
roll from a cold air source 112. In FIG. 5 a moving cooling belt
114 is held in contact with load roll 3. Cooling water (represented
by block 116) is sprayed against the back side of thermally
conductive belt 114, which transfers heat from the surface of load
roll 3. Belt 14 shields load roll 3 from the cooling water, helping
to keep the product dry.
[0094] As shown in FIG. 6, an alternative arrangement is to run
cooling belt 114 through the load roll nip. In the case where the
product remains on mold roll 1 and is peeled off after passing
through the load roll nip (i.e. by take-off roll 6a in FIG. 1),
belt 114 is passed through the load roll nip along with the cooling
product. This arrangement is particularly useful for rapid cooling
of the back side of the base layer, as cooling belt 114 is held in
direct contact with the product through the entire contact area of
the load roll nip. Belt 114 may in turn be cooled (e.g. by water
116 or air) at some distance from the nip.
[0095] Referring to FIGS. 7 and 7A, in the presently preferred
embodiment conformable load roll 3 has a stiff, relatively
non-conformable core 72 (preferably steel), a compliant layer 74
(preferably an elastomer), and an outer sleeve 76 which is formed
of an elastically deformable material with a hard surface,
preferably either hard polymer or metal. In the present embodiment,
the overall diameter of load roll 3 is about 12 inches and
compliant layer 74 has a thickness t of about 0.5 inch. A suitable
material for compliant layer 74 is urethane, due to its stability,
its ability to be sized by grinding, and its relatively low cost.
For higher temperatures, silicone rubber is also acceptable. Outer
sleeve 76 preferably has a smooth exterior and has a high thermal
conductivity to remove heat either out of the back side of a
product with a relatively thick base layer or directly out of the
mold roll itself. Under some temperature and speed conditions,
sleeve 76 may be omitted.
[0096] Referring to FIG. 7B, an alternative embodiment of
conformable load roll 3 is pneumatically inflatable, such as an
automobile tire. As in a tire, a steel reinforcement belt 71 is
preferably employed to stiffen and extend the life of the load
roll.
[0097] Referring to FIG. 7C, in other embodiments designed to
conduct heat through a compliant layer of a roll (e.g. load roll 3
of FIG. 1) particles 80 and 82 of thermally conductive materials
are molded into compliant material 74. Materials such as powdered
aluminum, carbon or powdered copper raise the effective thermal
conductivity of a compliant layer that otherwise consists of
polymers having relatively low thermal conductivity. In general, a
dense distribution of a mixture of rod-shaped particles 82 and
spherical particles 80 provides a higher thermal conductivity at
the same volumetric loading ratio than either of the shapes alone.
This construction is also useful to form the cooling belts of FIGS.
5 and 6.
[0098] The load roll 3 or 3' (or rolls 3a and 3b) of the preceding
figures is (are) configured, in some embodiments, as a series of
independently controllable rolls 120 arranged along the length of
the mold roll, as shown in FIG. 8. Mounted on separate shafts, load
rolls 120a, 120b and 120c are loaded independently against mold
roll 1 to maintain a constant, even gap between the mold roll and
the pressure roll to produce an even thickness product. Instead of
relying on the passive conformability of the load roll to is
maintain gap uniformity, this embodiment enables active control of
gap thickness at distinct points along the width of the product.
For instance, the load roll or rolls 120 near the middle of the
span of the mold roll can be employed to apply a higher load than
the rolls 120 near the edges, if required to optimize or minimize
the curvature of the mold roll. The configuration of FIG. 8 is
particularly applicable for use with a relatively long mold roll 1
or when extremely precise gap control is required. Preferably there
is at least one thickness sensor 13 (FIG. 1) associated with each
load roll 120.
[0099] Referring to FIG. 9, in another embodiment a conformable
roll 122, of similar construction to that previously discussed for
load roll 3, is arranged to load against the back side of pressure
roll 2 opposite mold roll 1. Conformable roll 122 maintains a
desirable degree of curvature (or lack thereof) in pressure roll 2
to control the gap at the pressure zone between pressure roll 2 and
mold roll 1. The compliance of conformable roll 122 reduces the
chance of surface fatigue damage that might be caused by two hard
rolls rolling against each other, and also allows a slight
curvature of pressure roll 2 in some instances where that is
desired. As shown with respect to load roll 3 in FIG. 8,
conformable pressure backup roll 122 can be configured as multiple
rolls 120.
[0100] Referring to FIG. 10, in some embodiments it is desirable to
construct pressure roll 2' with some compliance. FIG. 10
illustrates an enlarged cross section of the pressure zone between
mold roll 1 (with cavities 102) and pressure roll 2', which forces
melt 100 into cavities 102 and counteracts the pressure of forming
base layer 124 of the molded fastener product. High pressures are
developed, illustrated by pressure distribution curve 126, that
push melt 100 into cavities 102. At higher production speeds the
compliance of pressure roll 2' results in a wider pressure zone
area, increasing the length of time that a given portion of melt is
subjected to elevated molding pressures.
[0101] As shown in FIG. 11, pressure roll 2' preferably has a
relatively hard and rigid surface layer, such as a metal sleeve
128, covering a softer, more compliant layer 130. Compliant layer
130 in some embodiments is an elastomeric material, and in other
embodiments is a fluid under pressure.
[0102] In some embodiments it is desirable to actively bend a
rotating roll to create radial deflection. FIGS. 12 and 12A, for
instance, illustrate a method for applying a controllable bending
moment to a roll using secondary bearings or supports 132a and
132b. This is useful, for example, to deform pressure roll 2 to
match the curvature of the mold roll. Spherical journal bearings
that allow a small degree of angular deflection of the shaft of the
roll are suitable for the outer support bearings 134a and 134b.
Between outer bearings 134a and 134b, secondary supports 132a and
132b bear against the roll and produce a constant bending moment
between the secondary supports. Secondary supports 132a and 132b
are, in some cases, large diameter bearings that are nearly the
same diameter as the central portion of the roll. In other cases
fluid film bearings or other rollers are employed to bear on the
surface of the roll.
[0103] FIG. 12A illustrates this bending technique employed to bend
a mold roll 1 comprised of stacked plates or rings. This active
bending helps provide compression between the faces of the tool
rings where the melt is formed into fastener elements, squeezing
the tool rings together to avoid producing molding flash between
them. The molding region L of the mold roll is that part of the
roll comprised of mold plates with molding cavities or which
otherwise forms the molding surface of the roll.
[0104] FIGS. 13 and 13A illustrate another method and system for
controlling the thickness of the molded fastener product base layer
when mold roll 1 is relatively long and therefore tends to deflect
under the pressure of the pressure zone. In operation, nip pressure
between the two rolls tends to cause mold roll 1 to move away from
pressure roll 2 in a bowed manner, causing the nip gap to be
greater near the middle of the span than near the ends, forming a
product base layer that is undesirably thicker at its midspan than
at its edges. In order to compensate for this, the axis of pressure
roll 2 is controllably skewed relative to the axis of mold roll 1,
to provide a more uniform nip gap along the mold roll. Controller
90 controls the amount of skew. By proper adjustment of the skew
angle .alpha. over a practical range, the gap can be made
essentially constant along the length of the nip despite
pressure-induced radial deflection of the mold roll.
[0105] A control method employing an "open" control loop is
illustrated in FIG. 13B. The control technique is called open-loop
because the operator 150 sets the skew between the left and right
sides of pressure roll 2 based on a signal from a downstream device
40. In the present configuration, device 40 is a Beta-gauge mass
sensing device to sense product base layer thickness and thickness
variation across the web. In operation, operator 150 adjusts left
and right skew settings on control panel 42, providing the command
signals to servo controller 44 which controls left and right ball
screws 48. Feedback 50 from ball screws 48 to servo controller 44
informs the servo controller of the current position of the ball
screws. Thus the actual skew position is closed-loop, PID
(Proportional/Integral/Differential) controlled inside the servo
loop, but the position set point is adjusted by an operator.
[0106] In another embodiment illustrated in FIG. 13C, a system
controller 52 replaces the operator for closed-loop control of the
system. System controller 52 determines the desired amount of skew
to produce a constant base layer thickness and produces a command
signal for the ball screw servo controller 44. The system
controller also sends command signals to a hydraulic servo
controller 58 that controls the position of left and right
hydraulic load actuators 152. The hydraulic load actuators adjust
the overall position of pressure roll 2 to provide a desired
average base layer thickness with minimal variation from one edge
to the other.
[0107] The Beta-gauge 40 is a relatively slow method of
measurement. It is a scanning system which travels across the
product at about 3 to 4 inches per second, and in one embodiment is
located about 20 seconds downstream from the nip. The thickness
feedback is therefore delayed by the time required for the product
to travel to gauge 40 and by the time required for the scanning
operation of the sensor. Any corrections made by controller 52
therefore need to be based on average trends to avoid instabilities
caused by immediate real time correction.
[0108] Alternatively, the thickness of the base layer of the
product can be sensed in close proximity to the nip, e.g. by sensor
13. Preferably sensor 13 is a non-contacting sensor (e.g. a
reluctance sensor floating on a gas film bearing on the base
layer), but sensing mechanisms held against the back of the product
with light pressure are also suitable.
[0109] Referring to FIG. 14, a preferred embodiment provides a
useful combination of control techniques, including skew control,
for maintaining constant base layer thickness. Gross (average)
thickness control is provided by a control system 140 controlling
the normal load between mold roll 1 and load roll 3. Fine thickness
control is provided by control system 142 operating actuators at
each end of pressure roll 2 (to adjust for left/right unevenness)
and the skew of pressure roll 2 (to adjust for middle/edge
unevenness). Such combinations are useful when skewing alone
requires impractically large skew angles. By compensating for most
variation with gross variation control system 140, skewing is only
necessary for fine control for automated trimming of thickness
across the width of the product.
[0110] Referring to FIG. 15, a cooling belt 160, similar to the
belt 114 shown in FIGS. 5 and 6, is useful in some embodiments to
cool and support the fastener product through the continuous
molding process. As illustrated, belt 160 is introduced to the nip
between mold roll 1 and pressure roll 2 along with the melt 100.
Belt 160 remains in contact with the cooling product as it is
carried about the mold roll, helping to draw heat out of the base
layer and maintaining continuous pressure against the back side of
the product. The belt continues through the second nip, between
load roll 3 and mold roll 1, and provides additional support for
the product as it is peeled off of the mold roll by take-off roll
6. After passing through a third nip between load roll 3 and
knock-down roll 162, belt 160 is peeled away from product 5.
[0111] The embodiment of FIG. 15 is particularly useful for very
fast production speeds, as the prolonged contact between the
product and belt 160 helps to cool the base layer, so that the
product can be quickly peeled from the mold, without sufficiently
cooling the fastener elements to the point that they can no longer
be easily deformed for removal from the mold cavities.
[0112] Referring to FIG. 16, in some particularly useful
embodiments two continuous streams of fastener product are
simultaneously manufactured with a single mold roll. Mold roll 1 is
arranged between pressure rolls 2 and 2a, defining two pressure
zones. Twin extruders 4 and 4a supply molten resin to the two
pressure zones, and the molded product is peeled away from mold
roll 1 by two take-off rolls 170 and 170a. Arranging the axes of
mold roll 1 and pressure rolls 2 and 2a to lie in substantially the
same plane balances the nip pressure loads exerted on mold roll 1,
greatly reducing the tendency of the mold roll to bend. Any of the
methods previously discussed may be employed, if necessary, to
reduce bending of pressure rolls 2 and 2a or to otherwise maintain
the evenness of the pressure zone gaps. Belt systems 108, as
illustrated in FIG. 3, are useful in place of hard or compliant
pressure rolls.
[0113] One of the advantages of having two, balanced pressure zones
on the same roll, as shown in FIG. 16, is that the amount of
product producible from a single mold roll can be significantly
increased. Another advantage is that the loads on the mold roll are
balanced, enabling less expensive mold roll structures with lower
stiffness requirements. Yet another advantage is that it enables
the production of wider fastener products (i.e. by allowing the use
of longer mold rolls) without compromising the evenness of product
base layer thickness or product quality.
[0114] Referring to FIG. 17, in some useful embodiments an added
material 9 is introduced to a second nip between mold roll 1 and
load roll 3 to form a laminate product 5c with molded fastener
elements on one side and added material 9 on the other. It is
advantageous that this is done on the mold roll while the fastener
elements remain protected from laminating pressure by remaining in
their respective cavities. Preceding the laminating action the back
side of the fastener product is re-softened, if necessary, by a
heat source 10 to enhance the adherence of the base layer to the
added material 9 in the second nip. Added material 9 is introduced
with the molded fastener product into the second nip, which in some
embodiments is defined by a compliant load roll 3. Following the
laminating nip, the molded product is carried around a substantial
arc of the mold roll and cools to the appropriate temperature to
set the bond to the added material. The resulting laminate is
removed from the mold roll by a take-off roll 6a. By bonding the
added material to the fastener product while the latter is still
being carried on the mold roll, the laminate is formed with the
base layer advantageously in a heat-softened, clean condition,
resulting in a sound bond. The freshly molded base layer provides a
very good surface for adhering the added material to form a
laminate. In addition, the product base layer is substantially
supported between fastener elements by the surface of the mold
roll, allowing higher local laminating pressures to be employed
without deforming the fastener elements. This arrangement enables
the laminating of fastener products with relatively thick added
materials that are very difficult to pass through the pressure zone
(i.e. between mold roll 1 and pressure roll 2) without disrupting
the molding process.
[0115] The embodiment of FIG. 17A is similar to that of FIG. 17
except that the load roll 3 that provides the nip where lamination
is performed is a hard roll instead of a compliant one.
[0116] Examples of laminate products that are suitable to being
formed in this manner include carpets and wall coverings. The
second nip (laminating nip) may be maintained at more suitable
temperatures and/or pressures to prevent damaging such products
that would not reliably withstand passage through the molding nip.
Furthermore, the conformability of load roll 3 helps to protect
relatively delicate surface formations (of, e.g., a wall covering)
from undesirable deformation during laminating.
[0117] Referring to FIG. 18, other methods of bonding added
material 9 to form a laminate material 11 with a molded fastener
product include the application of an adhesive with an applicator
12. Suitable methods for applying the adhesive include spraying it
directly on added material 9 or the back side of the unlaminated
base layer prior to the laminating nip, coating the side of added
material 9 with a film layer of adhesive in a previous process,
rolling, doctoring and the like.
[0118] FIG. 19 shows a variation to the lamination method employing
a belt 172 that carries added material 9 into and through the
laminating nip between load roll 3 and mold roll 1. Belt 172
provides extra support for the added material on the way into the
nip and also can provide either heating or cooling, depending upon
whether the belt is heated or cooled. In some embodiments the belt
surface is metallic and of different consistency from the compliant
layer on the load roll. This machine and process is useful for
laminating heavy web materials such as floor mat material and the
like.
[0119] FIG. 20 shows another arrangement useful for forming a
laminate product, employing a belt system 108 (as in FIG. 3) to
provide laminating pressure. Belt system 108 conducts a belt 14 in
close contact with mold roll 1. Both the belt and its roller system
are forced up against the mold roll to provide sufficient pressure
for lamination. This method is most advantageous for laminations
requiring a long time (i.e. a wide contact area in this embodiment)
for proper bonding. Another advantage of employing a belt system to
provide lamination pressure is that microscopic scuffing of a
compliant roll against a hard surface that might damage delicate
laminate materials, such as paper or vinyl wall coverings, is
avoided, without the high contact pressures of a hard load roll.
The laminated product is either removed with the belt system or is
carried further about the mold roll and peeled off by a separate
take-off roll 6a. An optional cooling system is illustrated by box
174.
[0120] FIG. 21 shows a combination of thickness control and
lamination. A skew-controlled pressure roll 2 and controller 176
maintain a constant thickness of molded product base layer. As
described in previous embodiments, load roll 3 compensates for the
load applied by pressure roll 2, minimizing the bending of the mold
roll and thereby minimizing the amount of pressure roll skew
necessary to maintain constant base layer thickness. In addition, a
second load roll 178 bears against load roll 3, helping to maintain
the straightness of load roll 3 and also providing an additional
pressure nip through which the laminate is trained for improved
bonding.
[0121] FIGS. 22-29 illustrate other configurations, equally as
useful as those thus far described, that employ a pressure head 8
fed by an extruder or other source of pressurized molten polymer
resin to both introduce the molten resin that will form the molded
fastener product and to apply the pressure necessary to force the
resin into the fastener-shaped mold cavities. As illustrated by the
common reference numbers in these figures and earlier figures,
other components of the systems that employ a pressure head 8 are
essentially the same as those employing a pressure roll 2. These
additional figures show that the novel features described with
reference to a system with a pressure roll apply equally as well to
a system with the pressure head 8. In this respect, the previous
descriptions of the figures to which FIGS. 22-29 correspond are
also applicable to these embodiments. FIG. 22 corresponds to FIG.
1, FIG. 23 to FIG. 3, FIG. 24 to FIG. 4, FIG. 27 to FIG. 16, FIG.
28 to FIGS. 17, 18 and 19, and FIG. 29 to FIG. 20. From these
examples it should be evident that any of the other embodiments
heretofore disclosed may be adapted to employ a pressure head.
[0122] Pressure head 8 in FIGS. 22-29 comprises an extruder nozzle
assembly fed by an extruder (not shown). In nozzle throat 8a a
sheet form flow of polymer is produced, which is applied to the
mold roll 1. Shoe surfaces 8b of the nozzle assembly that conform
to the curvature of the roll serve to maintain the extruder
pressure against the roll and to define the gap with the mold roll
that defines the thickness of the base layer of the product.
Pressure head 8 thus forces the polymer into the mold cavities in
mold roll 1 and forms a sheet-form film or base layer of polymer on
the surface of the mold roll. As in the previous embodiments, the
polymer is forced into the mold cavities to form fastener elements
or the like under the high pressure of the pressure zone. The
pressure zone forces tend to bend the mold roll away from the
pressure head and are resisted by the methods described above
(with, e.g. a compliant load roll 3 as in FIG. 22 or a belt system
108 as in FIG. 23) to maintain an even gap for forming the base
layer of the fastener product.
[0123] Referring to FIG. 25, an arrangement for controlling the gap
between mold roll 1 and pressure head 8 actively adjusts the shape
and position of the pressure head relative to the mold roll. This
can be done, for instance, in response to thickness sensor 13. The
axis of mold roll 1 is supported on suitable bearings (not shown)
in a load frame 60. An extension 60a of load frame 60 supports a
head loading system 180 (e.g. a number of hydraulic cylinders or
ball screw actuators arranged along the length of the pressure
head). Molten polymer resin is supplied by a melt source or
extruder 61 to head 8 under pressure. Head loading system 180 loads
head 8, by shafts 62, against mold roll 1 through a film of molten
resin, thereby maintaining a controllably constant gap between mold
roll 1 and head 8 for forming the base layer of the fastener
product 5.
[0124] For active bending of the pressure head 8 to contour the
surface of the pressure head along its length to conform to the
surface geometry of the bent mold roll, other means of bending
pressure head 8 include a number of tie bolts between the molding
head and frame 60, arranged along the length of the pressure head,
that are axially adjusted either by rotating a threaded member or
by controlled thermal expansion (i.e. changing the net length of
the tie bolts by changing their temperature). Adjusting the lengths
of individual tie bolts induces bending moments in pressure head 8
that causes its curved surface 182 to also bend along its length to
conform to the curvature of the mold roll.
[0125] Under some circumstances it is desirable for mold roll 1 to
be slightly elastically bent away from pressure head 8 (or pressure
roll 2) by pressure zone forces to increase the axial compression
between the stacked mold plates that form the mold roll in the
vicinity of the high pressure zone. This can reduce the tendency of
the molten resin to form flash between the mold plates. In these
instances it is advantageous to have some intentional bending of
the mold roll away from the pressure source, and to force the
pressure mechanism (e.g., pressure head 8 or pressure roll 2) to
follow that curvature in order to maintain the uniformity of the
gap and of the product. Referring further to FIG. 25, the load
system 180, comprised of several loading rods 62 distributed along
the length of the pressure head, forces head 8 toward mold roll 1
near its midspan to compensate for the curvature of the mold roll.
Rods, 62 are individually controlled by a control system to locally
force pressure head 8 toward or away from mold roll 1 to maintain
the desired gap. This technique is particularly useful to mold
extremely wide widths of product by compensating for the increased
bending of relatively longer rolls subjected to higher overall mold
pressure forces.
[0126] In some instances it is desirable not to have a perfectly
even gap across the width of the pressure zone. For instance, in
some cases it is desirable to have the gap slightly smaller toward
the edges than in the middle, for example when there tends to be
some leakage of polymer material from the edges of the pressure
zone.
[0127] Referring to FIG. 26, use of a load roll 3 with a pressure
head 8 is presently preferred to avoid extreme mold roll curvature
in situations where the flatness of the product is critical.
Molding the product on a bowed mold roll results in a base layer
that has a degree of complex curvature, even after being spooled.
In some cases such a curvature is desirable, but in others it is
not. Some preferred embodiments therefore employ both pressure head
curvature control and a load roll on the side of the mold roll
opposite the pressure head. Controller 182 controls the relative
positions of load roll 3 and pressure head 8 with respect to mold
roll 1. Displacement transducers 184 and 186 and thickness sensor
13 provide feedback. In the embodiment shown, controller 182
controls force F.sub.2 which loads frame 188, to which both mold
roll 1 and load roll 3 are mounted, toward head 8. In addition,
controller 182 controls force F.sub.1 which forces load roll 3
against mold roll 1.
[0128] As shown in FIG. 27, a particularly advantageous embodiment
employs two relatively stiff pressure heads 8 supplying molten
resin to two pressure zones on opposite sides of a single mold roll
1. This produces two continuous streams of product 5 and 5' that
are peeled from mold roll 1 by take-off rolls 6 and 6',
respectively. For the reasons already described, extremely wide
widths of a thin, even product are thus moldable, due to the
balance of forces acting on relatively long mold roll 1.
[0129] FIGS. 30A-30C illustrate some of the web base thickness
profiles that can be maintained by the apparatus and method of the
present invention, shown in cross-section across a portion of the
length of the mold roll. In FIG. 30A, fastener product 5 has a base
web 200 and multiple upstanding fastener elements 202. Maintaining
the thickness of the mold gap that forms base web 200 along its
length produces a product 5 with a base web 200 of generally
consistent thickness t. In another embodiment, shown in FIG. 30B,
tapered regions 204 are provided in the predetermined profile of
base web 200. In some cases, grooves 206 or other indentations are
formed in base web 200, as shown in FIG. 30C. These and other
profiles are advantageously maintained at their predetermined
thicknesses by maintaining the profile of the mold gap as described
above.
[0130] Referring to FIG. 31, in another embodiment a compliant
pressure roll 2' is employed to protect surface features on the
surface of a sheet material 210 introduced to the molding nip
between pressure roll 2' and mold roll 1. These surface features
would tend to be damaged by being passed through a nip formed by
two non-conformable rolls. Hard surface features can also damage
non-conformable roll surfaces. This arrangement is particularly
useful, according to the invention, for continuous molding of
fastener elements on one side of a sandpaper product having surface
features consisting of grains of sand or other abrasive particles
adhered to one broad surface of the paper. It is also useful for
molding fastener elements on wide sheets of material having
delicate surface features, such as fibers or embossed features,
that could be damaged by the extreme pressures of the molding nip.
Examples of these types of materials include upholstery material
with leatherette-grained surfaces and grass-paper wall coverings.
After molding, the finished product is pulled from the mold
cavities of mold roll 1 about a take-off roll 211, which also has a
compliant outer surface.
[0131] FIG. 32, looking in the direction of the flow of material
through the mold nip between compliant pressure roll 2' and mold
roll 1, illustrates the deformation of the surface of the pressure
roll in the vicinity of abrasive grains 212 as a sandpaper product
214 is passed through the nip. Abrasive grains 212 are quite small
in most commercial sandpapers, which have grades from 30 to over
600 for fine polishing applications. The compliant surface of
pressure roll 2', preferably of an elastomeric material of 60 to 70
durometer for use with a medium-grit sandpaper, conforms to
encapsulate the grains 212 and distribute pressure around the
grains. Because there is effectively no surface speed differential
between rolls 1 and 2', grains 212 do not abrade the elastomeric
surface of roll 2'. The resulting abrasive product is "in situ
laminated" to fastener elements such as hooks for hook to loop
fastening. In other words, the forming of the base web integral
with fastener elements and the lamination of the base web and
abrasive paper occur simultaneously in the nip. The resin of the
base web is laminated to the back of the sandpaper to provide a
means for fastening the sandpaper to a sanding block or other
sanding device.
[0132] Referring to the molding system of FIG. 33, in some cases
the system has both a pressure head 8' and a pressure roll 2. The
pressure head 8' preferably applies sufficient pressure in pressure
zone P.sub.1 to partially fill the fastener element cavities in
mold roll 1 and provide a layer of resin on the exterior of the
mold roll. Pressure roll 2 provides a second application of
pressure against the resin in another pressure zone P.sub.2, with
the resin still in a formable condition, to complete the filling of
the cavities in the mold roll and produce a base web with even
thickness. Surface 8b' of pressure head 8' is curved to match the
curvature of the mold roll. For molding systems with two pressure
zones P.sub.1 and P.sub.2, support roll 3 is preferably arranged to
counteract the loads against the mold roll from both pressure zones
(i.e., the three rolls 1, 2 and 3 do not lie in a single plane). By
applying the resin directly against the mold roll, temperature
variations and edge shrinkage can be minimized while, by
subsequently employing the pressure roll, uniform filling of the
mold cavities can be assured under, e.g., high speed
conditions.
[0133] Referring to FIG. 34, in some instances a pressure head 8''
extrudes resin directly onto the surface of a pressure roll 2. The
extruded resin enters the nip between pressure roll 2 and mold roll
1 where it is forced under nip pressure to fill the cavities in the
mold roll. In this case it is not necessary, in most situations,
for the pressure head 8'' to apply substantial pressure, and
therefore the three rolls 1, 2 and 3 are preferably coplanar.
[0134] Referring to FIG. 35, another molding system employs a mold
hoop 220 with fastener element cavities formed in its outer
surface. The mold hoop is held against pressure roll 2 with a
loading roll 222, forming a molding nip and pressure zone between
hoop 220 and roll 2. Loading roll 222 preferably has a conformable
surface, as described above with reference to FIG. 1. Additional
rolls 224a and 224b provide additional support for hoop 220, which
is driven by rotating rolls 2 and 222. The relatively large
diameter of hoop 220 provides room within the hoop for cooling
systems 226 for cooling the hoop. This arrangement is particularly
suitable for molding conditions that require the cooling fastener
elements to remain in their cavities for an extended length of time
for sufficient cooling, or to enable relatively fast line speeds. A
pressure head 228 is shown supplying molten resin to the nip.
Alternatively an extruder 4, as shown in FIG. 1, can be employed.
Hoop 220 is preferably of metal.
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