Note: Descriptions are shown in the official language in which they were submitted.
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INDUSTRIAL FABRIC INCLUDING SPIRALLY WOUND MATERIAL STRIPS
WITH REINFORCEMENT
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a Continuation-In-Part of U.S. Patent Application No.
12/635,367 filed December 10, 2009, which claims priority of U.S. Provisional
Patent
Application No. 61/246,812 filed September 29, 2009, U.S. Provisional Patent
Application No. 61/246,801 filed September 29, 2009, U.S. Provisional Patent
Application No. 61/147,637 filed January 27, 2009, and U.S. Provisional Patent
Application No. 61/121,998 filed December 12, 2008.
INCORPORATION BY REFERENCE
All patents, patent applications, documents, references, manufacturer's
instructions, descriptions, product specifications, and product sheets for any
products
mentioned herein are incorporated by reference herein, and may be employed in
the
practice of the invention.
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
The present invention is directed to endless fabrics, and particularly,
industrial
fabrics used in the production of nonwoven products. More particularly, the
instant
invention is directed to support members such as belts or sleeves used in the
production
of patterned or marked nonwoven products. Furthermore, the present invention
may be
used as a belt and/or sleeve used in the production of nonwovens by processes
such as
airlaid, melt blowing, spunbonding, and hydroentangling.
2. DESCRIPTION OF THE PRIOR ART
Processes for making nonwoven products have been known for many years. In
one process, a fiber batt or web is treated with water streams or jets to
cause the fibers to
entangle with each other and improve the physical properties, such as
strength, of the
web. Such techniques for treatment by means of water jets have been known for
decades, as may be gathered from the disclosures of U.S. Patent Nos.
3,214,819,
3,508,308 and 3,485,706.
In general terms, this method involves interlacing of elementary fibers with
one
another by means of the action of water jets under pressure, which act on the
fibrous
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structure like needles and make it possible to reorient part of the fibers
forming the web
in the thickness direction.
Such technology has been widely developed at the present time and is used not
only for producing what are known as "spunlaced" or "hydroentangled"
structures for
textile use, such as, in particular for applications in medical fields and
hospitals, for
wiping, filtration and wrappings for teabags, and the articles obtained may be
regular and
homogeneous, as may be gathered from the disclosure of U.S. Patent No.
3,508,308, and
if required, comprise designs resulting from the reorientation of the fibers,
this being
essential for an esthetic purpose, as may be gathered from the disclosure of
U.S. Patent
No. 3,485,706.
As to products of the "spunlace" or "hydroentangled" type, it has been known
for
a very long time that the final properties of the product can be adapted by
producing
mixtures of material, for example by combining a plurality of webs consisting
of fibers
of different types, for example of natural, artificial or synthetic fibers, or
even webs in
which the fibers are previously mixed (webs of the "spunbond" type, etc.) with
reinforcements that can be incorporated into the nonwoven structure.
French patents FR-A-2 730 246 and 2 734 285, corresponding respectively to
U.S. Patent No. 5,718,022 and U.S. Patent No. 5,768,756, describe solutions
which make
it possible to successfully treat hydrophobic fibers or mixtures of these
fibers with other
hydrophilic fibers or even webs consisting entirely of natural fibers by means
of water
jets.
In general terms, according to the teachings of these documents, the treatment
involves treating a basic web composed of elementary fibers of the same type
or of
different types, compressing and moistening this basic web and then
intermingling the
fibers by means of at least one rack of contiguous jets of water under high
pressure
acting on the basic web.
For this purpose, the basic web is advanced positively on an endless porous
support in motion, and it is brought onto the surface of a perforated rotary
cylindrical
drum, to the interior of which a partial vacuum is applied. The basic web is
compressed
mechanically between the porous support and the rotary drum which both advance
substantially at the same speed. Immediately downstream of the compression
zone, a
water curtain is directed onto the web and passes successively through the
porous
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support, the compressed basic web and the supporting perforated drum wherein a
vacuum source removes the excess water.
The elementary fibers are intermingled continuously, still on the rotary
cylindrical drum, by the compressed and wetted web being subjected to the
action of at
least one rack of jets of water under high pressure. In general, bonding is
carried out by
means of a plurality of successive racks of water jets which act either on the
same face or
alternately against the two faces of the web, the pressure within the racks
and the
velocity of the jets discharged varying from one rack to the next and usually
progressively.
It is important to note, as may be gathered from FR 2 734 285, that the
perforated
roller/drum may comprise randomly distributed micro-perforations. If required,
after the
initial bonding treatment, the fibrous nonwoven structure may be subjected to
a second
treatment applied to the reverse face.
In the process of producing spunlaced or hydroentangled nonwoven products, it
is often desired to impart a pattern or mark on the finished product, thereby
creating a
desired design on the product. This pattern or mark is typically developed
using a
secondary process, separate from the nonwoven sheet forming and roll-up
process, where
an embossed/patterned calendar roll is used. These rolls are typically
expensive and
operate on the principle of compressing certain areas of the fibrous web to
create the
required patterns or marks. However, there are several drawbacks of using a
separate
process for creating the pattern or mark on the nonwoven product. For example,
a high
initial investment for calendar rolls would be required, which can limit the
length of
production runs that can be economically' justified by a producer. Second,
higher
processing costs would be incurred due to a separate patterning or marking
stage. Third,
the final product would have a higher than required material content to
maintain product
caliper (thickness) after compression in the calendaring step. Lastly, the two-
stage
process would lead to a lower bulk in the finished product than desired due to
high
pressure compression during calendaring. Prior art nonwoven products made with
these
known patterning processes do not have clear, well defined raised portions and
therefore
the desired patterns are difficult to see. In addition, the raised portions of
prior art
embossed nonwoven products are not dimensionally stable and their raised
portions tend
to lose their three-dimensional structure when stressed after a period of time
depending
on the application.
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U.S. Patent Nos. 5,098,764 and 5,244,711 disclose the use of a support member
in a more recent method of producing nonwoven webs or products. The support
members have a topographical feature configuration as well as an array of
apertures. In
this process, a starting web of fiber is positioned on the topographical
support member.
The support member with the fibrous web thereon is passed under jets of high
pressure
fluid, typically water. The jets of water cause the fiber to intertwine and
entangle with
each other in a particular pattern, based on the topographical configuration
of the support
member.
The pattern of topographical features and apertures in the support member is
critical to the structure of the resulting nonwoven product. In addition, the
support
member must have sufficient structural integrity and strength to support a
fibrous web
while fluid jets rearrange the fibers and entangle them in their new
arrangement to
provide a stable fabric. The support member must not under go any substantial
distortion
under the force of the fluid jets. Also, the support member must have means
for
removing the relatively large volumes of entangling fluid so as to prevent
"flooding" of
the fibrous web, which would interfere with effective entangling. Typically,
the support
member includes drainage apertures which must be of a sufficiently small size
to
maintain the integrity of the fibrous web and prevent the loss of fiber
through the
forming surface. In addition, the support member should be substantially free
of burrs,
hooks or the like irregularities that could interfere with the removal of the
entangled
fibrous nonwoven therefrom. At the same time, the support member must be such
that
fibers of the fibrous web being processed thereon are not washed away (i.e.
good fiber
retention and support) under the influence of the fluid jets.
One of the main problems which arises during the production of nonwovens is
that of achieving the cohesion of the fibers making up the nonwoven in order
to give the
nonwoven products the strength characteristics according to the application in
question,
while maintaining or imparting particular physical characteristics, such as
bulk, hand,
appearance, etc.
The properties of bulk, absorbency, strength, softness, and aesthetic
appearance
are indeed important for many products when used for their intended purpose.
To
produce a nonwoven product having these characteristics, a support member will
often
be constructed such that the sheet contact surface exhibits topographical
variations.
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It should be appreciated that these support members (fabrics, belts, sleeves)
may
take the form of endless loops and function in the manner of conveyors. It
should further
be appreciated that nonwoven production is a continuous process which proceeds
at
considerable speeds. That is to say, the elementary fibers or webs are
continuously
deposited onto a forming fabric/belt in the forming section, while a newly
entangled
nonwoven fabric is continuously being transferred from the support member to a
subsequent process.
SUMMARY OF THE INVENTION
The present invention provides an alternative solution to the problems
addressed
by prior-art patents/patent applications discussed above.
The instant invention provides an improved belt or sleeve that functions in
place
of a traditional belt or sleeve, and imparts desired physical characteristics,
such as bulk,
appearance, texture, absorbency, strength, and hand to the nonwoven products
produced
IS thereon.
It is therefore a principal object of the invention to provide a spunlacing or
hydroentangling support member such as a belt or sleeve that has through voids
in a
desired pattern.
It is a further object to provide a belt or sleeve that may have a topography
or
texture to one or both surfaces, produced using any of the means know in the
art, such as
for example, sanding, graving, embossing or etching. These and other objects
and
advantages are provided by the instant invention. Other advantages such as,
but not
limited to, improved fiber support and release (no picking) over prior art
woven fabrics,
and easier cleanability as a result of no yarn crossovers to trap elementary
fibers are
provided.
If the beltisleeve has a surface texture, then more effective
patterning/texture is
transferred to the nonwoven, and it also results in better physical properties
such as
bulk/absorbency.
The present invention relates to an endless support member such as a belt or
sleeve for supporting and conveying natural, artificial or synthetic fibers in
a spunlace or
hydroentanglement process. The instant porous structures, belts, or sleeves
exhibit the
following non-limiting advantages over calendaring technology: fabric sleeves
are a
relatively less expense item with no large capital investment in fixed
equipment;
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patterning is accomplished during the entangling process itself, eliminating
the need for a
separate calendaring process; lower material content in the final product can
be achieved
as caliper/thickness is not degraded from compression; the finished product
can be
produced with higher bulk as it is not compressed at a calendaring stage. To
the
nonwoven rolled-goods producer, these process advantages further lead to the
end
product advantages of: Lower cost spunlace or hydroentangled webs with desired
patterns, marks, or texture; the ability to customize products as the
size/length of the
production run for particular products is reduced; production of higher
performance
products, such as, products with high bulk imparts the characteristic of
higher
absorbency, which is of great value in consumer applications.
In an exemplary embodiment, the endless belt or sleeve is formed from strips
of
material that are spiral wound around two rolls in a side to side abutting
manner. The
strips are firmly attached to each other by a suitable method to form an
endless loop at
the required length and width for the particular use. In the case of a sleeve,
the strips
may be wound around the surface of a single roll or mandrel which is
approximately the
size of the diameter and CD length of the drum on which the sleeve will be
used. The
strips of material used are commonly produced as industrial strapping
material.
Strapping, especially plastic strapping material, is usually defined as a
relatively thin
plastic band used for fastening or clamping objects together. Surprisingly, it
was
discovered that this type of plastic material has the appropriate
characteristics to be the
material strips to form the inventive belt or sleeve.
The difference in definition between (plastic) strapping and monofilament is
related to size, shape and application. Both strapping and monofilament are
made by
extrusion processes that have the same basic steps of extrusion, uniaxial
orientation and
winding. Monofilament is generally smaller in size than strapping and usually
round in
shape. Monofilament is used in a wide variety of applications such as fishing
lines and
industrial fabrics, including, papermachine clothing. Strapping is generally
much larger
in size than monofilament and always basically wider along a major axis, and
as such,
being rectangular in shape for its intended purpose.
It is well known in the art of extrusion that plastic strapping is made by an
extrusion process. It is also well known that this process includes uniaxial
orientation of
the extruded material. It is also well known that there are two basic
extrusion processes
using uniaxial orientation. One process is the extrusion and orientation of a
wide sheet
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that is slit into individual straps. The other process is the extrusion of
individual
strapping that is oriented. This second process is very much like the process
of making
monofilament as evidenced by the similarity in equipment for both processes.
An advantage of using strapping material versus monofilament is the number of
spiral windings needed to produce a fabric. Monofilaments are usually
considered to be
yarns that are no larger than 5 mm in their largest axis. Uniaxial
monofilament sizes
used for paper machine clothing and the other uses aforementioned seldom
exceed 1.0
mm in their largest axis. The strapping material used is usually at least 10
mm in width
and sometimes exceeds 100 mm in width. It is envisioned that strapping up to
1000 mm
in width could be also used. Suppliers of strapping material which may be used
include
companies such as Signode.
Yet another advantage is thickness versus tensile modulus. Polyester (PET)
films
in the prior art, for example, have a tensile modulus in the long axis (or
machine
direction ¨ MD) of about 3.5 GPa. PET strapping (or ribbon) material has a
tensile
modulus ranging from 10 GPa to 12.5 GPa. To achieve the same modulus with a
film, a
structure would have to be 3 to 3.6 times thicker.
The invention therefore, according to one exemplary embodiment, is a fabric,
belt
or sleeve formed as a single or multi layer structure from these spiral wound
ribbons.
The fabric, belt or sleeve may have planar, smooth top and bottom surfaces.
The belt or
sleeve may also be textured in some manner using any of the means known in the
art,
such as for example, sanding, graving, embossing or etching. The belt or
sleeve can be
impermeable to air and/or water. The belt or sleeve can also be perforated by
some
mechanical or thermal (laser) means so it may be permeable to air and/or
water.
In another exemplary embodiment, the ribbon is formed such that is has an
interlocking profile. The belt or sleeve is formed by spirally winding these
interlocking
strips and would have greater integrity than just abutting parallel and/or
perpendicular
sides of adjacent ribbon strips. This belt or sleeve can also be impermeable
to air and/or
water or perforated to be made permeable.
While the embodiments above are for a single layer of strips of spirally wound
ribbon, there may be advantages to use strips with various geometries that
form a belt or
sleeve of two or more layers. Therefore, according to one exemplary embodiment
the
belt or sleeve may have two or more layers where the strips may be formed such
that the
two or more layers mechanically interlock or are attached together by other
means
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known to those skilled in the art. Again the structure can be either
impermeable or
perforated to be permeable to either air and/or water.
Another exemplary embodiment is a multilayer structure formed using the
concept of a "welding strip" used to further improve the belt or sleeve
integrity. The
structure can be impermeable or perforated to be permeable to either air
and/or water.
The various features of novelty which characterize the invention are pointed
out
in particularity in the claims annexed to and forming a part of this
disclosure. For a
better understanding of the invention, its operating advantages and specific
objects
attained by its uses, reference is made to the accompanying descriptive matter
in which
preferred, but non-limiting, embodiments of the invention are illustrated in
the
accompanying drawings in which corresponding components are identified by the
same
reference numerals.
While the term fabric and fabric structure is used, fabric, belt, conveyor,
sleeve,
support member, and fabric structure are used interchangeably to describe the
structures
of the present invention. Similarly, the terms strapping, ribbon, strip of
material, and
material strips are used interchangeably throughout the description.
Terms "comprising" and "comprises" in this disclosure can mean "including" and
"includes" or can have the meaning commonly given to the term "comprising" or
"comprises" in U.S. Patent Law. Terms "consisting essentially of' or "consists
essentially of' if used in the claims have the meaning ascribed to them in
U.S. Patent
Law. Other aspects of the invention are described in or are obvious (and
within the ambit
of the invention) from the following disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further
understanding of the invention, are incorporated in and constitute a part of
this
specification. The drawings presented herein illustrate different embodiments
of the
invention and together with the description serve to explain the principles of
the
invention. In the drawings:
FIG. 1 is a perspective view of a fabric, belt or sleeve according to one
aspect of
the present invention;
FIG. 2 illustrates a method by which the fabric, belt or sleeve of the present
invention may be constructed;
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FIGS. 3(a) through 3(i) are cross-sectional views taken in a widthwise
direction
of several embodiments of the strip of the material used to manufacture the
inventive
fabric, belt or sleeve;
FIGS. 4(a) through 4(d) are cross-sectional views taken in a widthwise
direction
of several embodiments of the strip of the material used to manufacture the
inventive
fabric, belt or sleeve;
FIGS. 5(a) through 5(c) are cross-sectional views taken in a widthwise
direction
of several embodiments of the strip of the material used to manufacture the
inventive
fabric, belt or sleeve;
FIGS. 6(a) through 6(d) are cross-sectional views taken in a widthwise
direction
of several embodiments of the strip of the material used to manufacture the
inventive
fabric, belt or sleeve;
FIGS. 7(a) through 7(d) are cross-sectional views taken in a widthwise
direction
of several embodiments of the strip of the material used to manufacture the
inventive
fabric, belt or sleeve;
FIGS. 8(a) through 8(c) are cross-sectional views taken in a widthwise
direction
of several embodiments of the strip of the material used to manufacture the
inventive
fabric, belt or sleeve;
FIG. 9 is a bar graph depicting the advantages of using a uniaxially oriented
material (strap/ribbon) over a biaxially oriented material (film) and an
extruded material
(molded part);
FIGS. 10(a) through 10(d) illustrate steps involved in a method by which the
fabric, belt or sleeve of the present invention may be constructed;
FIGS. 11(a) and 11(b) are schematics of an apparatus that may be used in
forming the fabric, belt or sleeve according to one aspect of the present
invention;
FIG. 12 is a schematic of an apparatus that may be used in forming the fabric,
belt or sleeve according to one aspect of the present invention;
FIG. 13 is a cross-sectional view of a fabric, belt or sleeve according to one
aspect of the present invention;
FIG. 14 is an apparatus used in the manufacture of a fabric, belt or sleeve
according to one aspect of the present invention; and
FIGS. 15 and 16 are schematic views of different types of apparatus for
producing nonwoven webs using support members of the present invention.
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DETAILED DESCRIPTION OF THE PREFERED EMBODIMENTS
The instant invention will now be described more fully hereinafter with
reference
to the accompanying drawings, in which preferred embodiments of the invention
are
shown. This invention may, however, be embodied in many different forms and
should
not be construed as limited to the illustrated embodiments set forth herein.
Rather, these
illustrated embodiments are provided so that this disclosure will be thorough
and
complete, and will fully convey the scope of the invention to those skilled in
the art.
The present invention provides a continuous support member such as an endless
belt for use in the apparatus shown in FIG. 15, for example. The nonwoven
support
member functions in place of a traditional woven support member, and imparts
desired
texture, hand, and bulk to the nonwoven products produced thereon. The support
member of the present invention may reduce the manufacturing time and costs
associated
with the production of nonwovens.
FIG. 15 depicts an apparatus for continuously producing nonwoven fabrics using
a support member in accordance with the present invention. The apparatus of
FIG. 15
includes a conveyor belt 80 which actually serves as the topographical support
member
in accordance with the present invention. The belt is continuously moved in a
counterclockwise direction about a pair of spaced-apart rollers as is well
known in the
art. Disposed above belt 80 is a fluid ejecting manifold 79 connecting a
plurality of lines
or groups 81 of orifices. Each group has one or more rows of very fine
diameter orifices,
each about 0.007 inch in diameter with 30 such orifices per inch. Water is
supplied to
the groups 81 of orifices under a predetermined pressure and is ejected from
the orifices
in the form of very fine, substantially columnar, non-diverging streams or
jets of water.
The manifold is equipped with pressure gauges 88 and control valves 87 for
regulating
the fluid pressure in each line or group of orifices. Disposed beneath each
orifice line or
group is a suction box 82 for removing excess water, and to keep the area from
undue
flooding. The fiber web 83 to be formed into the nonwoven product is fed to
the
topographical support member conveyor belt of the present invention. Water is
sprayed
through an appropriate nozzle 84 onto the fibrous web to pre-wet the incoming
web 83
and aid in controlling the fibers as they pass under the fluid ejecting
manifolds. A
suction slot 85 is placed beneath this water nozzle to remove excess water.
Fibrous web
passes under the fluid ejecting manifold in a counter clockwise direction. The
pressure
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at which any given group 81 of orifices is operated can be set independently
from the
pressure at which any of the other groups 81 of orifices is operated.
Typically, however,
the group 81 of orifices nearest spray nozzle 84 is operated at a relatively
low pressure,
e.g. 100 psi. This assists in settling the incoming web onto the surface of
the support
member. As the web passes in the counterclockwise direction in FIG. 15, the
pressures
at which the groups 81 of orifices are operated is usually increased. It is
not necessary
that each succeeding group 81 of orifices be operated at a pressure higher
than its
neighbor in the clockwise direction. For example, two or more adjacent groups
81 of
orifices could be operated at the same pressure, after which the next
succeeding group 81
of orifices (in the counterclockwise direction) could be operated at a
different pressure.
Very typically, the operating pressures at the end of the conveyor belt where
the web is
removed are higher than the operating pressures where the web is initially fed
into the
conveyor belt. Though six groups 81 of orifices are shown in FIG. 15, this
number is not
critical, but will depend on the weight of the web, the speed, the pressures
used, the
number of rows of holes in each group, etc. After passing between the fluid
ejecting
manifold and the suction manifolds, the now formed nonwoven fabric is passed
over an
additional suction slot 86 to remove excess water. The distance from the lower
surfaces
of the groups 81 of orifices to the upper surface of fibrous web 83 typically
ranges from
about 0.5 inch to about 2.0 inches; a range of about 0.75 inch to about 1.0
inch is
preferred. It will be apparent that the web cannot be spaced so closely to the
manifold
that the web contacts the manifold. On the other hand, if the distance between
the lower
surfaces of the orifices and the upper surface of the web is too great, the
fluid streams
will lose energy and the process will be less efficient.
A preferred apparatus for producing nonwoven fabrics using support members of
the present invention is schematically depicted in FIG. 16. In this apparatus,
the
topographical support member is a rotatable drum sleeve 91. The drum under the
drum
sleeve 91 rotates in a counterclockwise direction. The outer surface of the
drum sleeve
91 comprises the desired topographical support configuration. Disposed about a
portion
of the periphery of the drum is a manifold 89 connecting a plurality of
orifice strips 92
for applying water or other fluid to a fibrous web 93 placed on the outside
surface of the
curved plates. Each orifice strip may comprise one or more rows of very fine
diameter
holes or apertures of the type mentioned earlier herein. Typically, the
apertures are
approximately 0.005 inches to 0.01 inches in nominal diameter, for example.
Other
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sizes, shapes and orientations may obviously be utilized, if suitable for the
purpose.
Also, there may be, for example, as many as 50 or 60 holes per inch or more if
desired.
Water or other fluid is directed through the rows of orifices. In general, and
as explained
above, the pressure in each orifice group is typically increased from the
first group under
which the fibrous web passes to the last group. The pressure is controlled by
appropriate
control valves 97 and is monitored by pressure gauges 98. The drum is
connected to a
sump 94 on which a vacuum may be pulled to aid in removing water and to keep
the area
from flooding. In operation, the fibrous web 93 is placed on the upper surface
of the
topographical support member before the water ejecting manifold 89 as seen in
FIG. 16.
The fibrous web passes underneath the orifice strips and is formed into a
nonwoven
product. The formed nonwoven is then passed over a section 95 of the apparatus
95
where there are no orifice strips, but vacuum is continued to be applied. The
fabric after
being de-watered is removed from the drum and passed around a series of dry
cans 96 to
dry the fabric.
Turning now to the structure of the support members, belts, or sleeves, the
support members may have a pattern of through voids. The through voids may
include,
among other things, geometrical characteristics that provide enhanced
topography and
bulk to the nonwoven products or web when produced, for example, on a support
member, belt, or sleeve. Other advantages of the instant support members
include easier
web release, improved contamination resistance, and reduced fiber picking. Yet
another
advantage is that it avoids the constraints of and need for a conventional
weaving loom
since the through voids can be placed in any desired location or pattern. The
support
member may also have a texture on one or both surfaces produced using any of
the
means known in the art, such as for example, by sanding, graving, embossing,
or etching.
It will be appreciated that the term "through void" is synonymous to the term
"through hole" and represents any opening that passes entirely through a
support
member such as a belt or sleeve. A support member as referred to herein
includes, but is
not limited to, industrial fabrics such as belts or conveyors, and sleeves or
cylindrical
belts specifically used in nonwoven production. As mentioned earlier, while
the term
fabric and fabric structure is used to describe the preferred embodiments,
fabric, belt,
conveyor, sleeve, support member, and fabric structure are used
interchangeably to
describe the structures of the present invention.
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FIG. 1 is a perspective view of the industrial fabric, belt or sleeve 10 of
the
present invention. The fabric, belt or sleeve 10 has an inner surface 12 and
an outer
surface 14, and is fashioned by spirally winding a strip of polymeric material
16, for
example an industrial strapping material, in a plurality of abutting and
mutually adjoined
turns. The strip of material 16 spirals in a substantially longitudinal
direction around the
length of the fabric, belt or sleeve 10 by virtue of the helical fashion in
which the fabric,
belt or sleeve 10 is constructed.
An exemplary method by which the fabric, belt or sleeve 10 may be
manufactured is illustrated in FIG. 2. Apparatus 20 includes a first process
roll 22 and a
second process roll 24, each of which is rotatable around its longitudinal
axis. The first
process roll 22 and the second process roll 24 are parallel to one another,
and are
separated by a distance which determines the overall length of the fabric,
belt or sleeve
10 to be manufactured thereon, as measured longitudinally therearound. At the
side of
the first process roll 22, there is provided a supply reel (not shown in the
figures)
rotatably mounted about an axis and displaceable parallel to process rolls 22
and 24. The
supply reel accommodates a reeled supply of the strip of material 16 having a
width of
10 mm or more, for example. The supply reel is initially positioned at the
left-hand end
of the first process roll 12, for example, before being continuously displaced
to the right
or other side at a predetermined speed.
To begin the manufacture of the fabric, belt or sleeve 10, the beginning of
the
strip of polymeric strapping material 16 is extended in taut condition from
the first
process roll 22 toward the second process roll 24, around the second process
roll 24, and
back to the first process roll 22 forming a first coil of a closed helix 26.
To close the first
coil of the closed helix 26, the beginning of the strip of material 16 is
joined to the end of
the first coil thereof at point 28. As will be discussed below, adjacent turns
of the
spirally wound strip of material 16 are joined to one another by mechanical
and/or
adhesive means.
Therefore, subsequent coils of closed helix 26 are produced by rotating first
process roll 22 and second process roll 24 in a common direction as indicated
by the
arrows in FIG. 2, while feeding the strip of material 16 onto the first
process roll 22. At
the same time, the strip of material 16 being freshly wound onto the first
process roll 22
is continuously joined to that already on the first process roll 22 and the
second process
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roll 24 by, for example, mechanical and/or adhesive or any other suitable
means to
produce additional coils of closed helix 26.
This process continues until the closed helix 26 has a desired width, as
measured
axially along the first process roll 22 or the second process roll 24. At that
point, the
strip of material 16 not yet wound onto the first process roll 22 and the
second process
roll 24 is cut, and the closed helix 26 produced therefrom is removed from the
first
process roll 22 and the second process roll 24 to provide the fabric, belt or
sleeve 10 of
the present invention.
Although a two roll set up is described herein, it may be apparent to one of
ordinary skill in the art that the strips may be wound around the surface of a
single roll or
mandrel to form the instant fabric, belt or sleeve. A roll or mandrel of
appropriate size
may be selected based on the desired dimension of the fabric, belt or sleeve
to be
produced.
The present method for producing fabric, belt or sleeve 10 is quite versatile
and
adaptable to the production of nonwoven and/or industrial fabrics or belt or
sleeves of a
variety of longitudinal and transverse dimensions. That is to say, the
manufacturer, by
practicing the present invention, need no longer produce a woven fabric of
appropriate
length and width for a given nonwoven production machine. Rather, the
manufacturer
need only separate the first process roll 22 and the second process roll 24 by
the
appropriate distance, to determine the approximate length of the fabric, belt
or sleeve 10,
and wind the strip of material 16 onto the first process roll 22 and the
second process roll
24 until the closed helix 26 has reached the approximate desired width.
Further, because the fabric, belt or sleeve 10 is produced by spirally
vvinding a
strip of polymeric strapping material 16, and is not a woven fabric, the outer
surface 12
of the fabric, belt or sleeve 10 can be smooth and continuous, and lacks the
knuckles
which prevent the surfaces of a woven fabric from being perfectly smooth. The
fabrics,
belts, or sleeves of the present invention may, however, have geometrical
characteristics
that provide enhanced topography and bulk to the nonwoven product produced
thereon.
Other advantages of the instant support members include easier web release,
improved
contamination resistance, and reduced fiber picking. Yet another advantage is
that it
avoids the constraints of and need for a conventional weaving loom since the
through
voids can be placed in any desired location or pattern. The fabric, belt or
sleeve may
also have a texture on one or both surfaces produced using any of the means
known in
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the art, such as for example, by sanding, graving, embossing or etching.
Alternatively,
the fabric, belt or sleeve may be smooth on one or both surfaces.
FIGS. 3(a) through 3(i) are cross-sectional views, taken in a widthwise
direction,
of several embodiments of the strip of material used to produce the present
fabric, belt or
sleeve. Each embodiment includes upper and lower surfaces which may be flat
(planar)
and parallel to one another, or may have a certain profile intended to suit a
particular
application. Turning to FIG. 3(a), material strip 16 has an upper surface 15,
a lower
surface 17, a first planar side 18 and a second planar side 19, according to
one
embodiment of the invention. The upper surface 15 and the lower surface 17 may
be flat
(planar) and parallel to one another, and the first planar side 18 and the
second planar
side 19 may be slanted in parallel directions, so that the first planar side
18 of each
spirally wound strip of material 16 abuts closely against the second planar
side 19 of the
immediately preceding turn thereof. Each turn of the strip of material 16 is
joined to its
adjacent turns by joining their respective first and second planar sides 18,
19 to one
another by an adhesive, for example, which may be a heat-activated, room-
temperature-
cured (RTC) or hot-melt adhesive, for example, or any other suitable means.
In FIG. 3(b), material strip 16 may have a cross-sectional structure that
enables a
mechanical interlock for joining adjacent strips of material 16 in the
spirally formed
fabric, belt or sleeve. Adjacent strips of material 16 can be the same or
different in size
and/or profile, but each has a locking position, as shown in FIG. 3(b). Other
examples of
mechanical interlock structures are shown in FIGS. 3(c) through 3(g) where the
cross
section of individual strips of material 16 is illustrated. In each case, one
side of the strip
of material 16 may be designed to mechanically interlock or connect with the
other side
of the adjacent strip of material 16. For example, referring to the embodiment
shown in
FIG. 3(g), the strip of material 16 may have an upper surface 42, a lower
surface 44, a
tongue 46 on one side and a corresponding groove 48 on the other side. The
tongue 46
may have dimensions corresponding to those of the groove 48, so that the
tongue 46 on
each spirally wound turn of strip 16 fits into the groove 48 of the
immediately preceding
turn thereof. Each turn of the strip of material 16 is joined to its adjacent
turns by
securing tongues 46 in the grooves 48. The upper surface 42 and the lower
surface 44
may be flat (planar) and parallel to one another, or non-planar and non-
parallel
depending on the application, or even may be convexly or concavely rounded in
the
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widthwise direction thereof, as shown in FIG. 3(0. Similarly, either sides of
the strip
may be cylindrically convex or concave shaped with the same radius of
curvature.
FIG. 3(h) shows another embodiment of the present invention.
In addition to having an extruded strip of material with opposing hemispheres
or
profiles as described above, various other shapes could be extruded or
machined from
rectangular extrusions to have mating edges with raised rails, which may
facilitate
bonding by mechanical and/or adhesive means. One such structure, according to
one
exemplary embodiment of the invention is shown in FIG. 3(i). Alternatively,
the material
strip may not require a right and left side that mate or join together. For
example, as
shown in FIG. 4(a), the cross section of strip of material 16 may have
interlocking
grooves on its upper surface or top side, or material strip 16 may have
interlocking
grooves on its lower surface or bottom side, as shown in FIG. 4(b).
FIG. 4(c), for example, shows the material strips of FIGS. 4(a) and 4(b)
positioned
for interlocking. The arrows in FIG. 4(c) indicate, for example, the direction
that each of
the material strips 16 would have to be moved in order to engage the grooves
and
interlock the two strips. FIG. 4(d) shows the two material strips 16 after
they have been
interlocked or joined together. Although only two of the mating material
strips are
shown in the exemplary embodiments, it should be noted that the final fabric,
belt or
sleeve is formed of several of the material strips interlocked together.
Clearly, if one
interlocks the material strips in a spiral winding process, one can form a
sheet of material
in the form of an endless loop. It should also be noted that while mechanical
interlocks
are shown, the strength of the interlocks can be improved by, for example,
thermal
bonding, especially by a technique known as selective bonding as exemplified
by a
commercial process known as 'Cleanveld' (See www.clearweld.com).
FIG. 5(a) shows a cross-sectional view of a material strip 16 that has grooves
both
on the top side and bottom side thereof. FIG. 5(b) shows how two material
strips 16
having the cross-sectional shape shown in FIG. 5(a) can be interlocked. The
interlocked
structure results in grooves on the top and bottom surface of the end product.
Referring to the embodiment shown in FIG. 5(c), FIG. 5(c) shows the
interlocking
of the two material strips 16 shown in FIG. 5(a) and FIG. 4(b). This results
in a sheet
product that has grooves on the bottom surface with a flat top surface.
Likewise, one
may also form a structure having grooves on the top surface with a flat bottom
surface.
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Another exemplary embodiment is a fabric, belt or sleeve formed from material
strips 16 that have knob-like interlocks or "positive" locks that form
stronger interlocks
due to their mechanical design. The designs have "positive" interlocks in the
sense that
the pins and the receptors for the pins have mechanical interference that
require
considerable force either to join the ribbons together or to separate them.
FIG. 6(a), for
example, illustrates the features of knoblike interlocks in individual ribbon-
like material
strips 16. FIG. 6(b) illustrates the features of knoblike interlocks in
individual ribbon-
like material strips 16 of opposite configuration that are designed to
interlock with the
structure shown in FIG. 6(a). FIG. 6(c) shows the individual ribbon-like
material strips
of FIGS. 6(a) and 6(b) positioned for interlocking. It is to be noted here
that the
staggered position of the top and bottom ribbons is in order to accommodate
another
material strip 16 of opposite configuration. Finally, FIG. 6(d) illustrates
these same
strips after they have been pressed together to form an interlocked structure.
Several
ribbon-like material strips like these may be interlocked together to form the
final fabric,
belt or sleeve.
Another exemplary embodiment is a fabric, belt or sleeve formed from material
strips 16 that have grooves on both the top and bottom sides thereof, for
example, as
shown in FIG. 7(a). These two ribbon-like material strips 16 are designed to
be joined
together to form a positive interlock, as shown in FIG. 7(b). It is to be
noted that the top
and bottom surfaces both retain grooves in their respective surfaces. Also,
looking at
FIGS. 7(a) and 7(b) it may be apparent to one of ordinary skill in the art to
combine three
strips to make a three-layered structure, or if just two strips are used, the
groove profile
of the grooves in the top strip may be different on top versus bottom sides.
Similarly, the
groove profile of the grooves in the bottom strip may be the same or different
on either
sides. As noted earlier, while the embodiments described herein are for a
single layer of
spirally wound ribbons or strips, there may be advantages to use strips with
various
geometries that form a belt of two or more layers. Therefore, according to one
exemplary embodiment the belt may have two or more layers where the strips may
be
formed such that the two or more layers mechanically interlock. Each layer may
be
spirally wound in an opposite direction or angled in the MD to provide
additional
strength.
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FIG. 7(c) shows an interlocked structure that results in a grooved bottom
surface
and a flat top surface, whereas FIG. 7(d) shows an interlocked structure that
results in a
flat bottom surface and a grooved top surface, for example.
As it may be obvious to one of ordinary skill in the art, many shapes may be
considered for making positive interlocks as described above. For example, the
previous
few embodiments focused on round knob-like protrusions and round receptacles.
However, it is also possible to use other shapes such as a trapezoid to
accomplish the
same effect. An example of a positive interlock having such a shape is shown
in FIG.
8(a). Alternatively, one can mix shapes to accomplish a positive interlock. An
example
of mixed shapes is shown in FIGS. 8(b) and 8(c).
The mechanical interlock thus formed between adjacent strips of material as
described in the above embodiments increases the ease with which a spiral
wound base
fabric or structure can be made, because without such a lock, it is possible
for adjacent
strips of material to wander and separate during the process of making the
spirally
wound fabric. By mechanically interlocking adjacent spirals, one may prevent
wandering and separation between adjacent spirals. Additionally, one may not
need to
depend solely on the strength of the mechanical lock for joining strength as
one may also
form thermal welds in the mechanically locked zones of the fabric. According
to one
embodiment of the invention, this can be accomplished by placing a near
infrared or
infrared or laser absorbing dye prior to locking the male/female components
together
followed by exposing the mechanical lock to a near infrared or infrared energy
or laser
source that causes thermal welding of the mechanical lock without melting
material
external to the zone of the mechanical lock.
The strip of material described in the above embodiments may be extruded from
any polymeric resin material known to those of ordinary skill in the art, such
as for
example, polyester, polyamide, polyurethane, polypropylene, polyether ether
ketone
resins, etc. While industrial strapping is attractive as a base material,
given that it is
uniaxally oriented, i.e., it has at least twice the tensile modulus of a
biaxially oriented
material (film) and up to ten times the modulus of an extruded material
(molded), any
other suitable material may be used. That is to say, the structure resulting
from a
uniaxially oriented material requires less than half the thickness of
biaxially oriented
material (film) and less than one-tenth the thickness of an extruded material
(molded).
This feature is illustrated in FIG. 9 where results are shown for designing a
part that has
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been designed for a specific force and strain for a fixed width. The equation
used in this
design problem is the relationship between stress and strain shown as follows:
FORCE = (MODULUS x STRAIN)
(WIDTH x THICKNESS)
The force (or load) is kept constant along with the width and strain in this
illustration. The equation shows that the required thickness is inversely
proportional to
the modulus of the material. This equation is representative of the problem of
designing
nonwoven production machine clothing for dimensional stability, i.e., the load
is known,
the maximum strain is known and the width of the machine is fixed. The result
is shown
in terms of the final thickness of the part required depending upon the
modulus of the
material employed. Clearly, uniaxial materials such as strappings or ribbons
have a
significant advantage over films and molded polymers as shown by FIG. 9. The
instant
support members, belts or sleeves, however, are not limited to uniaxial or
biaxial
orientation of the strapping, in that either or both orientations may be used
in the practice
of the instant invention.
According to one exemplary embodiment, the strip of material or strapping
material described in the above embodiments may include a reinforcing material
to
improve the mechanical strength of the overall structure. For example, the
reinforcing
material may be fibers, yarns, monofilaments or multifilament yarns that can
be oriented
in the MD of the fabric, sleeve or belt, along the length of the strapping
material. The
reinforcing material may be included through an extrusion or pultrusion
process where
the fibers or yarns may be extruded or pultruded along with the material
forming the strip
of material or strapping material. They may be fully embedded within the
material of the
strapping or they may be partially embedded onto one or both surfaces of the
strapping
material, or both. Reinforcing fibers or yarns may be formed of a high-modulus
material, such as for example, aramids, including but not limited to Keviare
and
Nomex , and may provide extra strength, tensile modulus, tear and/or crack
resistance,
resistance to abrasion and/or chemical degradation to the strip of material or
strapping
material. Broadly, the reinforcing fibers or yarns may be made from
thermoplastic
and/or thermosetting polymers. Non-limiting examples of suitable fiber
materials
include glass, carbon, polyester, polyethylene, and metals such as steel.
According to a
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further embodiment the melting temperature of said reinforcing fibers or yarns
may be
higher than the melting temperature of said strip of material or strapping
material or vice
versa.
Strapping is usually supplied in continuous lengths with the product having a
rectangular cross section. It is a tough, general purpose, usually untreated
polyester strip
with excellent handling characteristics, which makes it suitable for many
industrial
applications. It has excellent mechanical strength and dimensional stability
as noted
earlier, and does not become brittle with age under normal conditions.
Strapping has
good resistance to moisture and most chemicals, and can withstand temperatures
of -70
degrees C to 150 degrees C or more. Typical cross-sectional dimensions of a
strapping
material that may be used in the present invention are, for example, 0.30mm
(or more)
thickness and 1 Omm (or more) width. While strapping can be spirally wound,
the
adjacent wraps of strapping that do not have any means of interlocking to be
held
together may need to welded or joined in some manner. In such cases, laser
welding or
ultrasonic welding may be used in to fix or weld the adjacent ribbons or
material strips
together so as to improve cross-machine direction ("CD") properties, such as
strength,
and reducing the risk of separation of neighboring material strips.
While uniaxial strapping is found to have the maximum MD modulus, properties
other than modulus may also be important. For example, if the MD modulus is
too high
for the strapping material, then crack and flex fatigue resistance of the
final structure
may be unacceptable. Alternatively, CD properties of the final structure may
also be
important. For instance, when referring to PET material and material strips of
the same
thickness, non-oriented strips may have a typical MD modulus of about 3GPa and
strength of about 50MPa. On the other hand, a biaxially oriented strip may
have a MD
modulus of about 4.7GPa and strength of about 170MPa. It is found that
modifying the
processing of a uniaxial strip such that the MD modulus may be between 6-10GPa
and
strength may be equal to or greater than 250MPa, may result in a strip with CD
strength
approaching, approximately, 1 OOMPa. Further the material may be less brittle,
i.e. it
may not crack when repeatedly flexed, and may process better when joining the
strips
together. The bond between the strips may also resist separation during the
intended use
on the production machine.
One method to hold together the adjacent strips, according to one embodiment
of
the invention, is to ultrasonically weld adjacent strips edge to edge while
simultaneously
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providing a sideways pressure to keep the edges in contact with each other.
For
example, one part of the welding device can hold one strip, preferably the
strip that has
already been wound into a spiral, down against a supporting roll while another
part of the
device pushes the other strip, preferably the strip being unwound, up against
the strip
being held down. This edge to edge welding is illustrated in FIG. 11(a), for
example.
The application of ultrasonic gap welding results in a particularly strong
bond.
By contrast, ultrasonic welding in either a time mode or energy mode, which is
also
known as conventional ultrasonic welding, results in a bond that can be
described as
brittle. Therefore, it may be concluded that a bond formed via ultrasonic gap
welding is
preferred versus conventional ultrasonic welding.
Another exemplary method to hold together adjacent strips, according to one
embodiment of the invention, is to apply an adhesive 30 to ends 34, 36 of
adjacent strips
16, 16, and joining them is shown in FIGS. 10(a) -I 0(d). It is to be noted
that a filler
material 32, may be used to fill gaps or portions where the strips do not
contact each
other.
Another method to hold together adjacent strips of material or functional
strips,
according to one embodiment of the invention, is to use a "welding strip"
comprised of
the same basic material as the strip of material. For example, this welding
strip is shown
in FIG. 11(b) as a thin material appearing above and below the strips of
material. In such
an arrangement, the welding strip provides a material for the strips of
material to be
welded such that the assembled structure does not depend upon the edge to edge
welding
depicted in FIG. 11(a). Using the welding strip method, edge to edge welding
may
result; however, it is neither required nor preferred. Using the welding strip
method, a
"sandwich" or laminate type of structure may be formed with the horizontal
surface of
the strip of material being welded to the horizontal surface of the welding
strip, as shown
in FIG. 11(b). It is to be noted here that the welding strip does not have to
be located
both above and below the strips of material, in that the welding strip may be
located
either just above or just below the strips of material. According to one
aspect, the
welding strip may also be the central part of the sandwiched structure with
the strip of
material being above and/or below the welding strip. Additionally, the welding
strip is
shown as being thinner than the strip of material and as being the same width
as the strip
of material merely for exemplary purposes. The welding strip may well be
narrower or
broader than the strip of material, and may be of the same thickness or even
thicker than
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the strip of material. The welding strip may also be another piece of strip of
material
rather than being a special material made solely for the purpose of the
welding strip. The
welding strip may also have adhesive applied to one of its surfaces to assist
in holding
the welding strip in place for the welding operation. However, if such an
adhesive is
used, it is preferred that the adhesive be partially applied to the welding
strip versus the
entire surface, because partial application may promote a strong weld between
like
materials (polyester to polyester, for example) of the strip of material and
the welding
strip upon ultrasonic or laser welding.
If the welding strip is made from an extruded polymer with no orientation,
then it
is preferred that the welding strip be much thinner than the strip of
material, because a
non-oriented extruded welding strip is less capable of maintaining the
dimensional
stability of the final structure as illustrated earlier in this disclosure.
However, if the
welding strip is made from an oriented polymer, it is preferred that the
welding strip in
combination with the strip of material be as thin as possible. As noted
earlier, the
welding strip may be another piece of strip of material. However, if this is
the case, it is
preferred that the thickness of the individual materials be selected such that
the total
thickness of the sandwich or laminate can be minimized. As also noted earlier,
the
welding strip may be coated with an adhesive that is used to hold the
structure together
for further processing. According to one aspect, the welding strip with
adhesive may be
used, for example, to create a structure that goes directly to a perforation
step, which
could be laser drilling without any ultrasonic bonding such that the laser
drilling or laser
perforation produces spot welds that can hold the sandwich structure together.
Another method to hold together adjacent strips of material, according to one
embodiment of the invention, is to weld the adjacent strips using a laser
welding
technique.
FIG. 14 illustrates an exemplary apparatus 320 that may be used in the laser
welding process, according to one aspect of the invention. In this process,
fabric, belt or
sleeve 322 as shown in FIG. 14 should be understood to be a relatively short
portion of
the entire length of the final fabric, belt or sleeve. While the fabric, belt
or sleeve 322
may be endless, it may most practically be mounted about a pair of rolls, not
illustrated
in the figure, but known to those of ordinary skill in the art. In such an
arrangement,
apparatus 320 may be disposed on one of the two surfaces, most conveniently
the top
surface, of the fabric 322 between the two rolls. Whether endless or not,
fabric 322 may
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preferably be placed under an appropriate degree of tension during the
process.
Moreover, to prevent sagging, fabric 322 may be supported from below by a
horizontal
support member as it moves through apparatus 320.
Referring now more specifically to FIG. 14, where fabric 322 is indicated as
moving in an upward direction through the apparatus 320 as the method of the
present
invention is being practiced. The laser heads that are used in the welding
process may
traverse across the fabric in a CD or widthwise "X" direction while the fabric
may move
in the MD or "Y" direction. It may also be possible to setup a system where
the fabric is
moved in three-dimensions relative to a mechanically fixed laser welding head.
The advantage of laser welding over ultrasonic welding is that laser welding
can
be accomplished at speeds in the range of 100 meters per minute while
ultrasonic
welding has a top end speed of about 10 meters per minute. The addition of a
light
absorptive dye or ink absorber to the edges of the strips may also assist in
concentrating
the thermal effect of the laser. Absorbers could be black ink or near IR dyes
that are not
visible to the human eye, such as for example those utilized by "Clearweld."
(See
www.clearweld.com)
Once the final fabric, belt or sleeve is made and adjacent strips in the
fabric, belt
or sleeve have been welded or joined in some manner, holes or perforations
allowing
fluids (air and/or water) to pass from one side of the fabric to the other
side of the fabric
can be provided by means such as laser drilling. It should be noted that these
through
holes or perforations that allow fluid to pass from one side of the fabric to
the other can
be made either before or after the spiral winding and joining process. Such
holes or
perforations can be made via laser drilling or any other suitable
hole/perforation making
process, and can be of any size, shape, form and/or pattern, depending on the
intended
use. An exemplary embodiment is shown in FIG. 13, which is a cross section,
taken in a
transverse, or cross-machine, direction, of a fabric 80 of the present
invention, strips of
material 82 are provided along their entire lengths with a plurality of holes
84 for the
passage of air and/or water.
The inventive fabric, as noted earlier, may be used as a process belt or
sleeve
used in airlaid, melt blowing, spunbonding, or hydroentangling processes. The
inventive
fabric, belt or sleeve may include one or more additional layers on top of or
under the
substrate formed using the strips of material, merely to provide
functionality, and not
reinforcement. For example, a MD yarn array may be laminated to the backside
of the
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belt or sleeve to create void spaces. Alternatively, the one or more layers
may be
provided in between two layers of strapping. The additional layers used may be
any of
woven or nonwoven materials, MD or CD yarn arrays, spirally wound strips of
woven
material that have a width less than the width of the fabric, fibrous webs,
films, or a
combination thereof, and may be attached to the substrate using any suitable
technique
known to one of ordinary skill in the art. Needle punching, thermal bonding
and
chemical bonding are but few examples. The inventive fabric, belt or sleeve
may also
have a coating on either side for functionality. The texture on the fabric,
belt or sleeve of
the present invention may be produced before or after applying the functional
coating.
As aforementioned, the texture on the fabric, belt or sleeve can be produced
using any of
the means known in the art, such as for example, sanding, graving, embossing
or etching.
Although preferred embodiments of the present invention and modifications
thereof have been described in detail herein, it is to be understood that the
invention is
not limited to these precise embodiments and modifications, and that other
modifications
and variations may be effected by one skilled in the art without departing
from the spirit
and scope of the invention as defined by the appended claims.
24
