Note: Descriptions are shown in the official language in which they were submitted.
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LAMINATED INTEGRALLY WOVEN PAPERMAKER'S FABRTC
Background of the Invention
1. Field of the Invention
The present invention relates to the papermaking
arts. More specifically, the present invention is
both a papermaker's fabric for use in the press
section of the papermachine, such a fabric being
commonly referred to as a press fabric, as well as for
use on other sections of a papermachine and in other
paper-manufacturing applications, and a method for
manufacturing such a fabric. In particular, the
papermaker's fabric is of the OMS~ (on-machine-
seamable) variety and has a multiple layer laminated
base.
2. Description of the Prior Art
During the papermaking process, a fibrous web is
formed by depositing a fibrous slurry, that is, an
aqueous dispersion of cellulose fibers, on a moving
forming fabric in the forming section of a
papermachine. A large amount of water is drained from
the slurry through the forming fabric during this
process, leaving the fibrous web on the surface of the
forming fabric.
The newly formed cellulosic fiber web proceeds
from the forming section to a press section, which
includes a series of press nips. The cellulosic fiber
web passes through the press nips supported by a press
fabric, or, as is often the case, between two such
press fabrics. In the press nips, the cellulosic
fiber web is subjected to compressive forces which
squeeze water therefrom, and which adhere the fibers
in-the web to one another to transform the cellulosic
fiber web into a paper sheet. The water is accepted
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by the press fabric or fabrics and, ideally, does not
return to the paper sheet.
The paper sheet finally proceeds to a dryer
section, which includes at least one series of
rotatable dryer drums or cylinders, which are
internally heated by steam. The web, or newly formed
paper sheet, itself is directed in a sinuous path
sequentially around each in the series of drums by a
dryer fabric, which holds the web closely against the
surfaces of the drums. The heated drums reduce the
water content of the web to a desirable level through
evaporation.
It should be appreciated that the forming, press
and dryer fabrics all take the form of an endless loop
and function in the manner of conveyors. It should
further be appreciated that paper manufacture is a
continuous process which proceeds at considerable
speed. That is to say, the fibrous slurry is
continuously deposited onto the forming fabric in the
forming section, while a newly manufactured paper
sheet is continuously wound onto rolls after it exits
from the dryer section.
The press fabrics used to clothe the press
section are crucial components in the paper
manufacturing process. One of their functions is to
support and to carry the paper product being
manufactured through the press nips. In this respect,
the fabric serves as a conveyor belt during the
manufacturing process.
The press fabric also take part in the finishing
of the surface of the paper sheet. That is, the
surface of the press fabric is designed to be smooth
and uniformly resilient, so that, in the course of
passing through the press nips, a smooth, mark-free
surface-is imparted to the paper.
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Perhaps most importantly, the press fabrics
' accept the large quantities of water extracted from
the wet paper web in the press nip. In order to
fulfill this function, there literally must be
somewhere in the fabric for the water to go (void
volume), and the fabric must maintain an adequate
permeability to water and an acceptable openness and
void volume for its entire useful life.
Contemporary press fabrics are available in a
wide variety of styles designed to meet the
requirements of the papermachines on which they are
installed for the paper grades being manufactured.
Generally, they comprise a woven base fabric into
which has been needled a batt of fine, nonwoven
fibrous material. The base fabrics may be woven from
monofilament, plied monofilament, multifilament or
plied multifilament yarns, and may be single layered,
multi-layered, multi-plied or laminated. The yarns
themselves are typically extruded from any one of the
synthetic polymeric resins, such as polyamide and
polyester resins, used for this purpose by those of
ordinary skill in the papermachine clothing arts.
In recent years, interest in press fabrics having
laminated base fabrics has been on the increase. Base
fabrics of this type comprise two or more fabric
layers, with one or more endless inner layers being
disposed within an endless outer layer, the inner and
outer layers being joined to one another by the
fibrous material of the batt needled therethrough.
While laminated base fabrics permit the use of a
variety of weave patterns in the individual base
fabric layers, and yield a smoother press fabric with
increased void volume, it is difficult to manufacture
base fabric layers which are adequately matched
dimensionally and in appearance and quality. Further,
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press fabrics having laminated base fabrics comprising
two or more fabric layers are usually stiffer than
their integrally woven counterparts due to the
increased total number of cross-machine direction (CD)
yarns.
The difficulty in producing a press fabric having
a laminated base fabric meeting the requirements of
smoothness, resilience and adequate void volume is
further compounded when one wants to make such a
l0 fabric on-machine-seamable.
At one time, it should be recalled, press fabrics
were supplied only in endless form. One method used
was to weave them in the form of an endless, seamless
loop by a process known as endless weaving. In
addition, conditions in the press section present
additional special requirements that have to be
satisfied to utilize a workable seamed press fabric.
In brief, these special requirements arise because the
seam region must behave under load, that is, under
compression in the press nip or nips, like the rest of
the press fabric, and because the seam region must
have the same permeability to water and to air as the
rest of the press fabric, in order to avoid periodic
marking of the paper product being manufactured by the
seam region.
Despite these considerable obstacles, it remained
highly desirable to develop an on-machine-seamable
press fabric, because of the comparative ease and
safety with which it can be installed on the press
section. Ultimately, these obstacles were overcome
with the development of the OMS° (on-machine-seamable)
and SEAMTECHTM products by Albany International. These
products include a seam formed by providing seaming
loops at the opposite transverse edges at the two ends
of -the fabric. The seaming loops themselves are
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formed by the machine-direction (MD) yarns of the
' fabric. The pin seam is formed by bringing the two
ends of the press fabric together, by interdigitating
the seaming loops at the two ends of the fabric, and
by directing a so-called pin, or pintle, through the
passage defined by the interdigitated seaming loops to
lock the two ends of the press fabric together.
Needless to say, it is much easier and far less time
consuming to install an OMS° press fabric on a
papermachine than it is to install an endless press
fabric there. OMS~ is a registered trademark of
Albany International Corp.
One method to produce a press fabric that can be
joined on the paper machine with a "pin seam" is to
flat-weave the fabric, and then to weave the warp ends
back into the fabric in a direction parallel to the
warp yarns. Another technique, far more preferable,
is a modified form of endless weaving, which normally
provides a continuous loop of fabric. In modified
endless weaving, the weft, or filling, yarns are
continuously woven back and forth across the loom, in
each passage forming a loop on the edges of the fabric
being woven. As the weft, or filling, yarn, which
ultimately becomes the machine-direction (MD) yarn in
the press fabric, is continuous, the seaming loops
obtained in this manner are stronger than any that can
be produced in a flat woven fabric.
While seamed press fabrics have now been
successfully used for a number of years, it has proven
to be difficult to use these seaming techniques in
laminated press felts.
In one prior-art laminated press fabric, a
standard two-layer base fabric with a seam of the on-
machine-seamable type is used. On top of this two-
layer- base fabric, an endless base fabric of a
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different construction is placed. Alternatively, this
additional base may be flat-woven and its edges butted
over the seam area of the two-layer base fabric. The
two base fabric layers are then laminated together by
needling in a staple fiber batt. However, in order to
open the laminated fabric for installation on a paper
machine, one of the final processing steps is to cut
through the needled batt, and the machine-direction
yarns of the top base fabric layer, where the top base
fabric layer is endless.
Because the cross-machine direction yarns of the
top base fabric layer are not perfectly straight
across the top of the laminated fabric, that is,
exactly perpendicular to the seaming loops of the on-
machine-seamable base fabric layer, for the full width
of the fabric, some cross-machine direction yarns will
be cut during this process step. As a consequence,
there will be short machine-direction and cross-
machine direction yarn ends or lengths in the top base
fabric layer which may migrate into the seaming loop
area of the on-machine-seamable base fabric layer.
When the fabric is installed on the paper machine
press, which requires the seaming loops to be meshed
together, these short ends or yarn lengths can get
caught in the seam area and cause difficulties in
meshing the seaming loops. They also can block or
obstruct the path taken by the pin or pintle used to
hold the meshed seaming loops together to close the
seam. This makes installation more difficult and
time-consuming, and more expensive in terms of
increased machine downtime and lost production.
One method used to avoid this problem is to
remove some cross-machine direction yarns from the top
base fabric layer prior to needling. These yarns are
removed from the top base fabric layer in the region
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overlying the seaming loops in the bottom base fabric
layer. While this eliminates the possibility of
accidentally cutting through the cross-machine
direction yarns and causing the problems discussed in
the preceding paragraph, this gives the seam area a
more pronounced mass and caliper difference under load
relative to the rest of the fabric. This difference
can lead to objectionable seam mark, and/or seam
"bounce".
Another way to eliminate this problem is to make
both base fabric layers of the on-machine-seamable
type . Their seams can be aligned one on top of the
other, or offset slightly relative to each other in a
longitudinal direction, and both bases laminated
together during the application of fibrous batt by
needling. While this can be done with multi-layer
bases, it is difficult to do with single-layer bases,
which are difficult to provide with on-machine-
seamable seams having the same openness and thickness
under load as the rest of the fabric. In any case,
each base fabric layer in the laminated press fabric
would have to be separately closed. Not only is it
physically difficult to seam separate, intimately
joined base fabric layers in this manner, but the seam
region so obtained is more susceptible to the
thickness and permeability problems discussed above as
it comprises more than one separate seam.
There is also the problem of base size matching,
even with endless laminated fabrics. Any time two
separate bases are woven, especially of different
construction, chances are that base lengths at the
point of lamination during needling will be different
enough to require one of the bases to be additionally
processed. This costs money and takes time. Often,
one-of-the bases must be discarded and a new one made.
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Accordingly, the provision of a readily on-
machine-seamable, laminated press fabric, whose
individual lamina are well-matched dimensionally and
in appearance and quality, and whose seam may be
readily closed on a papermachine, would fill a great
need in the papermaking industry. The present
invention, which will now be described in the passages
to follow, is submitted to fill this need in the
industry.
Summary of the Invention
The present invention is a laminated, integrally
woven on-machine-seamable papermaker's fabric and a
method for manufacturing the papermaker's fabric.
The papermaker's fabric of the invention includes
a first plurality of warp yarns and a second plurality
of warp yarns interwoven with a continuous weft yarn
by an endless weaving technique. That is to say, the
continuous weft yarn alternately interweaves with the
first plurality of warp yarns to produce a first woven
ply, and with the second plurality of warp yarns to
produce a second woven ply. The continuous weft yarn
alternates between interweaving with the first
plurality of warp yarns and with the second plurality
of warp yarns at each of the two widthwise ends of the
fabric. When so alternating, the continuous weft yarn
forms one of a plurality of seaming loops for use in
joining the fabric into endless form. It will be
appreciated that the continuous weft yarn is the
machine-direction (MD) yarn of the first and second
woven plies when the papermaker's fabric is in its
position of use on the papermachine. The papermaker's
fabric is accordingly a laminated structure having two
woven plies joined to one another by the plurality of
seaming loops along the two widthwise ends.
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The papermaker's fabric may be needled with a
batt of staple fiber material, as is widely done in
the industry. The needling drives the fibers into and
through the two woven plies to further join them
together.
The seaming loops, as noted above, are used to
join the widthwise ends of the fabric to one another
to place the fabric into the form of an endless loop.
Alternatively, a monofilament seaming spiral may be
attached to the seaming loops at each of the two
widthwise ends of the papermaker's fabric either prior
to or following the needling of the fabric with a batt
of staple fibers. The monofilament seaming spirals
are connected to the seaming loops by at least one
connecting yarn. The coils of the spirals at the two
ends of the fabric may then be interdigitated and
joined to one another on the papermachine to form a
seam usually referred to as a spiral seam.
During the weaving of the papermaker's fabric, a
plurality of solvent-removable binder yarns is
interwoven with at least one of the continuous weft
yarn and said first and second pluralities of warp
yarns to bind the two woven plies together. That is
to say, the fabric may include a warp binder, a weft
binder, or binders in both fabric directions.
The binder yarns are made of a material soluble
in a particular solvent not affecting the functional
woven base yarns, that is, the first and second
pluralities of warp yarns and the continuous weft
yarn. Once the fabric is woven, and before or after
it is needled with a batt of staple fiber material,
the binder yarns are removed through dissolution with
the particular solvent to yield a laminated structure.
The present invention is also a method for
manufacturing an on-machine-seamable papermaker's
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fabric comprising the steps of providing the above
mentioned yarns, and of weaving a two-ply fabric with
a binder therefrom by an endless weaving technique
wherein seaming loops are formed at the two widthwise
ends thereof.
In the endless weaving process, the continuous
weft yarn alternates between the first and second
pluralities of warp yarns at the two widthwise ends of
the fabric, .at each alternation providing one of a
plurality of creaming loops for joining the fabric into
endless form.
Concurrently, the plurality of solvent-removable
binder yarns is interwoven with at least . one of the
endless weft ~rarn and the first and second plura ~ ities
of warp yarns to bind the first and second plies
together. Liter, the solvent-removable warp and/or
weft binder yarns are removed by dissolution with the
particular solvent to yield a laminated on-machine-
seamable pape:rmake:r's fabric comprising first and
second plies joined to one another at the widthwise
ends of the fabric by the seaming loops, which
themselves arE~ formE_d by the continuous weft yarn used
to weave the ~~lies.
While the pre~~ent laminated on-machine-seamable
papermaker's fabric is primarily intended for use as
a press fabric, it may also find use as a forming or
dryer fabric, or as a base for a resin polymer-coated,
Paper-Industr~r Process Belt, such as a long nip press
' (LNP) belt, a sheet-transfer belt, or a calender belt.
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ThereforE~, in accordance with the present invention,
there is pr~wided a laminated integrally woven on-
machine-seamable papermaker's fabric, said fabric having
a first end a~.nd a second end and a plurality of seaming
loops at each. of said first and second ends for use in
joining said fabric. into endless form with a pin seam,
said fabric comprising:
a first plurality of warp yarns;
a second plura:Lity of warp yarns; and
a continuous weft yarn,
wherein said continuous weft yarn interweaves with
said f first p~_ural ii:y of warp yarns to produce a f first
woven ply, and with said second plurality of warp yarns
to produce a second woven ply, said continuous weft yarn
alternating from interweaving with said first plurality
of warp yarns to interweaving with said second plurality
of warp yarns at said first end of said fabric, and from
interweaving with said second plurality of warp yarns to
interweaving 'Kith said first plurality of warp yarns at
said second end of said fabric, when so alternating,
forming one of said plurality of seaming loops at said
first and second ends for joining said fabric into
endless form, said fabric thereby being a laminated
structure having two woven plies joined to one another by
said plurality of seaming loops along said first and
second ends.
Also in ~iccordance with the present invention, there
is provided an intermediate on-machine-seamable
papermaker's fabric: product, said intermediate fabric
product having two ends and a plurality of seaming loops
at each of said two ends for use in joining said fabric
into endless form,, said intermediate fabric product
comprising:
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a first plurality of warp yarns;
a second plurality of warp yarns;
a continuous weft yarn; and
a plurality of: solvent-removable binder yarns, said
binder yarns being soluble in a particular solvent not
affecting said first and second pluralities of warp yarns
and said cont__nuous weft yarn,
wherein said continuous weft yarn alternately
interweaves with said first plurality of warp yarns to
produce a fir;~t woven ply, and with said second plurality
of warp yarns to produce a second woven ply, said
continuous weft yarn alternating between interweaving
with said first plurality of warp yarns and with said
second plurality of warp yarns at each of said two ends
of said intermediate fabric product, when so alternating,
forming one of said plurality of seaming loops for
joining said intermediate fabric product into endless
form, and
wherein said plurality of solvent-removable binder
yarns interweaves with at least one of said continuous
weft yarn and said first and second pluralities of warp
yarns to bind said first and second plies together.
Still in. accordance with the present invention,
there is prov_~ded a method for manufacturing a laminated
integrally wo~ren on.-machine-seamable papermaker's fabric
comprising the step: of:
providing a first plurality of warp yarns, a second
plurality of warp yarns, a continuous weft yarn, and a
plurality of :solvent-removable binder yarns, said binder
yarns being soluble in a particular solvent not affecting
said first and second pluralities of warp yarns and said
continuous weft yarn;
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weaving a two-ply fabric from said yarns by an
endless weaving technique, wherein said two-ply fabric
has two ends <~nd wherein seaming loops are formed at said
two ends by weaving said continuous weft yarn around an
edge cord, said weft yarn alternatingly interweaving with
said first plurality of warp yarns and with said second
plurality of warp ~~arns following each alternate passage
around said edge cord to provide a first ply and a second
ply, respectively, while interweaving said plurality of
solvent-remov~~ble binder yarns with at least one of said
continuous weft yarn and said first and second
pluralities o:E warp yarns to bind said first and second
plies together.
The present invention will now be described in more
complete detail with frequent reference being made to the
figures identified as follows.
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Brief Description of the Drawings
Figure 1 is a schematic perspective view of an
on-machine-seamable (OMS°) press fabric;
Figure 2 is a schematic perspective view of the
two ends of the OMS~ press fabric prior to their being
joined to one another;
Figure 3 is a cross-sectional view taken as
indicated by line 3-3 in Figure 2;
Figure 4 is a cross-sectional view, corresponding
to that of Figure 3, following the removal of a
solvent-removable yarn;
Figure 5 is a cross-sectional view taken as
indicated by line 5-5 in Figure 3;
Figure 6 is a cross-sectional view taken as
indicated by line 6-6 in Figure 4;
Figure 7 is a cross-sectional view of the seam of
the OMS° press fabric of the present invention taken
as indicated by line 7-7 in Figure 1;
Figure 8 is a cross-sectional view of the seam of
the OMS° press fabric of the present invention taken
in the same manner as is indicated by line 7-7 in
Figure 1 following the removal of the solvent
removable binder yarns; and
Figure 9 is a cross-sectional view of an
alternate embodiment of the seam taken in the same
manner as is indicated by line 7-7 in Figure 1.
Detailed Description of the Preferred Embodiment
Turning now specifically to the figures, Figure
1 is a schematic perspective view of an on-machine
seamable (OMS°) papermaker's fabric 10. The fabric 10
takes the form of an endless loop once its two ends
12, 14 have been joined to one another at seam 16.
Figure 2 is a schematic perspective view of the
two-ends 12, 14 of the OMS~ fabric 10 prior to their
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attachment to one another: Widthwise across the edges
of each of the two,ends 12, 14 are a plurality of
seaming loops 18. To attach the two ends 12, 14 to
one another, they are brought together, in so doing
5 alternating and intermeshing, or interdigitating, the
seaming loops 18 at each end with one another . The
interdigitated seaming loops 28 define a passage
through which a pin, or pintle, a yarn-like strand or
member, may be directed to secure the ends 12, 14 to
one another to form the seam.
Seaming loops 18 are formed by machine-direction
(MD) yarns of the fabric 10, the machine direction
being the direction of travel of the fabric 10 on a
papermachine. In the weaving of the fabrics 10 of the
15 present invention, the machine-direction (MD) yarns
forming seaming loops 18 axe continuous weft, or
filling, yarns on the weaving loom. These weft yarns
weave endlessly back and forth across the loom in a
process known in the industry as modified endless
20 weaving. At suitable intervals, they weave around an
edge cord, forming a seaming loop 16 for ultimate use
in seaming the fabric during installation on a paper
machine.
25 Several schemes, disclosed and claimed in U.S.
Patent No. 3.815,645 to Codorniu, for
weaving OMS° fabrics by modified endless weaving are
available and may be used in the practice of the
present invention. In one scheme, an edge cord is
30 disposed at one of the two edges of the weaving loom.
The continuous weft yarns weave around the edge cord
alternately forming seaming loops 18 for top and
bottom cloths on the weaving loom. At the othex edge
of the weaving loom, the weft yarns take a continuous
35 path.f-rom the top cloth to the bottom cloth, or vice
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versa, as in traditional endless weaving. As a
consequence, the top and bottom cloths are connected
by a series of continuous weft yarns at this latter
edge of the weaving loom, while they are connected by
two sets of seaming loops 18, one for the top cloth
and the other for the bottom cloth, joined by the edge
cord at the first edge of the weaving loom.
Ultimately, the top and bottom cloths together form an
endless loop of fabric which may be opened by removing
the edge cord.
Figure 3 is a cross-sectional view taken as
indicated by line 3-3 in Figure 2. The cross section
is taken in the cross-machine direction (CD) and, as
a consequence, MD yarns 20, 20', 22 are viewed in
cross section while CD yarns 26, 28 are viewed from
the side. It should be understood that in this and
other figures the scale of and spacing between MD
yarns 20, 20', 22 and CD yarns 26, 28 has been greatly
exaggerated for the sake of clarity.
It will be recognized, bearing in mind that MD
yarns 20, 20', 22 are weft, or filling, yarns, that
the fabric 10 shown in Figure 3 is a two-ply fabric
with a weft binder. CD yarn 26, which is a warp yarn
on the loom used to weave fabric 10, interweaves with
MD yarns 20, 22 to form one of the two plies. CD yarn
28, on the other hand, interweaves with MD yarns 20',
22 to form the other of the two plies. It may also be
described as a 2~-layer fabric. While a specific
weave pattern is shown in Figure 3, it should be
understood that it is shown for the purposes of
illustration alone, and that a two-ply fabric, of any
weave pattern having a warp binder, a weft binder, or
both kinds of binder, may be used to weave the fabric
10 of the present invention.
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It should also be understood that MD yarns 20,
20', 22 and CD yarns 26, 28 may be of any of the yarn
classifications conventionally used by those in the
papermachine clothing industry to weave press fabrics.
That is to say, any of MD yarns 20, 20', 22 and CD
yarns 26, 28 may be monofilament, plied monofilament,
multifilament, plied multifilament, spun, knitted
monofilament, knitted multifilament, braided
monofilament, braided multifilament, polyurethane-
coated monofilament, plied monofilament or
multifilament, bicomponent or any other type of yarn.
MD yarn 22, or, in general, the yarn or yarns
functioning as the binder holding the two plies
together, must, however, be of a soluble material,
such as SOLVRON° (polyvinyl alcohol) or calcium
alginate, which are soluble in water. Alternatively,
certain uncured polymeric resin materials are soluble
in warm water and could be used for MD yarn 22.
Uncured acrylics are an example of such materials. On
the other hand, MD yarns 20, 20' and CD yarns 26, 28
may be of polyamide, polyester, polyaramids,
polyetheretherketone (PEEK) and polyurethanes, or any
other polymeric resin material from which textile
yarns may be extruded or formed.
Figure 4 is a cross-sectional view, corresponding
to that provided in Figure 3, of the fabric 10
following the removal, by dissolution using the
appropriate solvent, of MD yarn 22. Following the
removal of MD yarn 22 in this manner, the two plies
30, 32 are separated from one another. Ply 30 is a
single-layer fabric formed by the interweaving of MD
yarns 20 with CD yarns 26, while ply 32 is a single-
layer fabric formed by the interweaving of MD yarns
20' with CD yarns 28.
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Figure 5 is a cross-sectional view of the fabric
taken as indicated by line 5-5 in Figure 3. Shown
in Figure 5 is the seaming loop 18 formed at the end
12 thereof where MD yarn 20 turns back, by wrapping
5 around an edge cord (not shown? during the weaving
process, and becomes MD yarn 20'. It may now be more
clearly understood that MD yarns 20, 20' are one and
the same continuous weft yarn, weaving back and forth
across the loom and forming a seaming loop 18 when
10 passing around the edge cord at the loop-forming edge
of the weaving loom.
On the other hand, MD yarn 22 need not be
endlessly woven in the same manner as MD yarns 20,
20', but may be woven in a different pattern. In
Figure 5, MD yarn 22 is so shown having an end
adj acent to seaming loop 18 . There is no need to form
such a seaming loop 18 with MD yarn 22, or to weave it
in a modified endless manner, as MD yarn 22, being of
a soluble material, is in any event to be removed by
an appropriate solvent. In general, of course, that
solvent is one which dissolves MD yarn 22 without
dissolving any of MD yarns 20, 20' or CD yarns 26, 28.
Figure 6 is a cross-sectional view of the fabric
10 taken as indicated by line 6-6 in Figure 4, and
corresponds to that provided in Figure 5 following the
removal, by dissolution using the appropriate solvent,
of MD yarn 22.
Following the removal of MD yarn 22 in this
manner, the two plies 30, 32 are joined to one another
only at the seaming loops 18. As a consequence, a
laminated fabric 10, comprising two single-layer plies
30, 32, each being woven from MD and CD yarns, and
joinable into endless form by seaming loops 18, is the
result.
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Figure 7 is a cross-sectional view of seam 16
taken as indicated by line 7-7 in Figure 1 prior to
the removal of MD yarn 22. Seaming loops 18 at ends
12, 14 are interdigitated with one another, as
previously explained, and a pin, or pintle, 34 is
directed through the passage defined by the
interdigitated seaming loops 18 to join ends 12, 14 to
one another. A batt 36 of staple fiber material is
needled through the papermaker's fabric. The staple
fibers may include fibers of polyamide, polyester,
polyimide, polypropylene, polyolefin, polyethylene
terephthalate (PET), polyetheretherketone (PEEK),
polytetrafluoroethylene (PTFE), polyaramid, para-
aramid or meta-aramid. Alternatively, or in addition
to batt 36 of staple fibers, the papermaker's fabric
may be impregnated with a polymeric resin material or
a fiber-reinforced polymeric resin material.
Figure 8 is a cross-sectional view of seam 16
taken in the same manner as is indicated by line 7-7
in Figure 1 following the removal of solvent-removable
MD yarn 22. Seaming loops 18 at ends 12, 14 are again
interdigitated with one another and a pin, or pintle,
34 is directed through the passage defined by the
interdigitated seaming loops 18 to join ends 12, 14 to
one another. A batt 36 of staple fiber material is
needled through plies 30, 32 to join them to one
another. The batt 36 may include staple fibers of any
of the materials noted above. Alternatively, or in
addition to batt 36 of staple fibers, plies 30, 32 may
be joined to one another by impregnating them with a
polymeric resin material or a fiber-reinforced
polymeric resin material.
Solvent-removable MD yarn 22 may be removed at
any time subsequent to weaving, during the
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manufacturing process or after installation on the
papermachine.
Figure 9 is a cross-sectional view of an
alternate embodiment seam 38 taken in the same manner
as is indicated by line 7-7 in Figure 1. In seam 38,
seaming loops 18 are not interdigitated with one
another. Rather, an extruded monofilament seaming
spiral 40 is attached to each end 12, 14 by
interdigitating the monofilament seaming spirals 40
with the seaming loops 18 at ends 12, 14, and by
directing one or more connecting yarns 42 through the
passages defined by the intersecting monofilament
seaming spirals 40 and seaming loops 18. The seam 38
is then formed by interdigitating the individual coils
of the seaming spirals 40, and by directing a pin, or
pintle, 34 through the passage defined by the
intersecting coils. A batt 36 of staple fibers of any
of the polymeric materials noted above is needled
through plies 30, 32 to join them to one another
either before or after the monofilament seaming
spirals 40 are attached to ends 12, 14.
As previously noted, the present papermaker's
fabric may be used as a base for a polymer-coated,
Paper-Industry Process Belt (PIPB), such as a long nip
press (LNP) belt, a sheet-transfer belt, or a calender
belt. In such a case, at least one side of the
papermaker's fabric is coated with a polymeric resin
material, such as polyurethane, after the soluble
binder yarn is removed. Prior to the application of
the coating, the papermaker's fabric may be needled
with a batt of staple fiber material.
The present invention offers several advantages
not afforded by the fabrics of the prior art. First,
and foremost, a laminated OMS~ fabric is produced in
one-operation on the loom with both lamina, or plies,
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being integrally woven. In the preferred embodiment,
the fabric itself comprises two single-layer plies,
which themselves would be difficult to seam, but which
are jointly seamed because the seaming loops
themselves are formed by a yarn serving as the MD yarn
of both plies. Further, the two plies are perfectly
matched in size, obviating the matching problems
endemic to prior-art laminated press fabrics. The
seam formed in the manner of the present invention has
characteristics far more similar to the rest of the
body of the laminated fabric than one resulting from
separately seaming each single-layer ply, and is much
less likely to mark the paper being manufactured.
Finally, because the lamina are integrally woven, the
CD yarn count in each ply can be less than would be
required if they were separately woven. This ensures
that each ply is lighter and more open, and that the
laminated press fabric so obtained is not as heavy,
dense or stiff as those of the prior art.
Clearly, modifications to the above would be
obvious to those of ordinary skill in the art, but
would not bring the invention so modified beyond the
scope of the appended claims.
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