U.S. patent application number 12/969806 was filed with the patent office on 2012-02-02 for fibrous web formed on a structured fabric.
This patent application is currently assigned to Voith Patent GmbH. Invention is credited to Scott Quigley.
Application Number | 20120024486 12/969806 |
Document ID | / |
Family ID | 44512849 |
Filed Date | 2012-02-02 |
United States Patent
Application |
20120024486 |
Kind Code |
A1 |
Quigley; Scott |
February 2, 2012 |
FIBROUS WEB FORMED ON A STRUCTURED FABRIC
Abstract
A fibrous web including a fibrous construct having at least one
formed surface feature. The surface feature including a
topographical pattern reflective of a weave pattern in a fabric
used in a papermaking machine. The fabric including a single layer
of yarns arranged in a repeating weave pattern, each weave pattern
including a plurality of warp yarns substantially oriented in a
machine direction (MD) defining MD yarns; and a plurality of weft
yarns substantially oriented in a cross machine direction (CD)
defining CD yarns. The MD yarns each having at least one long float
within the weave pattern. Each long float being adjacent to at
least one other long float of an MD yarn. The weave pattern being a
plain weave apart from the long floats.
Inventors: |
Quigley; Scott; (Bossier
City, LA) |
Assignee: |
Voith Patent GmbH
|
Family ID: |
44512849 |
Appl. No.: |
12/969806 |
Filed: |
December 16, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12847519 |
Jul 30, 2010 |
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12969806 |
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Current U.S.
Class: |
162/109 |
Current CPC
Class: |
D21H 27/002 20130101;
D21F 1/0027 20130101; D21H 27/02 20130101; D21F 11/006
20130101 |
Class at
Publication: |
162/109 |
International
Class: |
D21H 27/02 20060101
D21H027/02 |
Claims
1. A fibrous web, comprising: a fibrous construct having at least
one formed surface feature, said surface feature including a
topographical pattern reflective of a weave pattern in a fabric
used in a papermaking machine, the fabric including: a single layer
of yarns arranged in a repeating weave pattern, each said weave
pattern including: a plurality of warp yarns substantially oriented
in a machine direction (MD) defining MD yarns; and a plurality of
weft yarns substantially oriented in a cross machine direction (CD)
defining CD yarns, said MD yarns each having at least one long
float within said weave pattern, each said long float being
adjacent at least one other long float of an MD yarn, said weave
pattern being a plain weave apart from said long floats.
2. The fibrous web of claim 1, wherein within said weave pattern
said long floats that are adjacent to each other form at least one
MD float pattern within said weave pattern.
3. The fibrous web of claim 2, wherein within said weave pattern
said at least one MD float pattern is a plurality of MD float
patterns.
4. The fibrous web of claim 3, wherein within said weave pattern
said plurality of MD float patterns are each one of identical and
mirror imaged.
5. The fibrous web of claim 4, wherein within said weave pattern
each of said plurality of MD float patterns are surrounded with
said plain weave.
6. The fibrous web of claim 4, wherein within said weave pattern
each of said plurality of MD float patterns touch each other
forming a continuous MD float pattern with said plain weave
defining the balance of said weave pattern.
7. The fibrous web of claim 1, wherein within said weave pattern
each said long float floats across at least 3 CD yarns.
8. The fibrous web of claim 7, wherein within said weave pattern
each said long float floats across at least 4 CD yarns.
9. The fibrous web of claim 8, wherein within said weave pattern
each said long float floats across at least 5 CD yarns.
10. The fibrous web of claim 1, wherein the papermaking machine is
an ATMOS.TM. papermaking machine that includes: a dewatering
fabric, a fibrous web is dewatered through the dewatering fabric,
the dewatering fabric and the fabric being on opposite sides of the
fibrous web; and a permeable belt in contact with a portion of the
fabric, there being an airflow in a direction such that the airflow
first passes through said permeable belt, then the fabric, then the
fibrous web, then said dewatering fabric.
11. A fibrous web obtainable by a process in a papermaking machine,
the process comprising the steps of: discharging a fibrous slurry
between a forming fabric and a structured fabric; and removing
moisture from said fibrous slurry through at least one of said
forming fabric and said structured fabric to thereby form the
fibrous web, said structured fabric being a single layer structured
fabric of yarns arranged in a repeating weave pattern, a fibrous
web being formed between said forming fabric and said structured
fabric, each said weave pattern including: a plurality of warp
yarns substantially oriented in a machine direction (MD) defining
MD yarns; and a plurality of weft yarns substantially oriented in a
cross machine direction (CD) defining CD yarns, each of said MD
yarns having at least one long float within said weave pattern,
each said long float being adjacent at least one other long float
of an MD yarn, said weave pattern being a plain weave apart from
said long floats.
12. The process of claim 11, wherein within said weave pattern said
long floats that are adjacent to each other form at least one MD
float pattern within said weave pattern.
13. The process of claim 12, wherein within said weave pattern said
at least one MD float pattern is a plurality of MD float
patterns.
14. The process of claim 13, wherein within said weave pattern said
plurality of MD float patterns are each one of identical and mirror
imaged.
15. The process of claim 14, wherein within said weave pattern each
of said plurality of MD float patterns are surrounded with said
plain weave.
16. The process of claim 14, wherein within said weave pattern each
of said plurality of MD float patterns touch each other forming a
continuous MD float pattern with said plain weave defining the
balance of said weave pattern.
17. The process of claim 11, wherein within said weave pattern each
said long float floats across at least 3 CD yarns.
18. The process of claim 11, wherein the papermaking machine is an
ATMOS.TM. papermaking machine including a permeable belt in contact
with a portion of said single layer structured fabric, the fibrous
web being between said single layer structured fabric and said
forming fabric, there being an airflow in a direction such that the
airflow first passes through said permeable belt, then said single
layer structured fabric, then the fibrous web, then said forming
fabric.
19. A fibrous web obtainable by a process in a papermaking machine,
the process comprising the steps of: discharging a fibrous slurry
between a forming fabric and a structured fabric; and removing
moisture from said fibrous slurry through at least one of said
forming fabric and said structured fabric to thereby form the
fibrous web, the fibrous web having at least one surface feature,
said surface feature including a topographical pattern reflective
of a weave pattern in said structured fabric used in a papermaking
machine, said structured fabric including a single layer of yarns
arranged in a repeating weave pattern, each said weave pattern
including: a plurality of warp yarns substantially oriented in a
machine direction (MD) defining MD yarns; and a plurality of weft
yarns substantially oriented in a cross machine direction (CD)
defining CD yarns, said MD yarns each having at least one long
float within said weave pattern, each said long float being
adjacent at least one other long float of an MD yarn, said weave
pattern being a plain weave apart from said long floats.
20. The process of claim 19, wherein within said weave pattern said
long floats that are adjacent to each other form at least one MD
float pattern within said weave pattern.
21. The process of claim 19, wherein the papermaking machine is an
ATMOS.TM. papermaking machine including a plurality of pressing
zones through which the fibrous web travels.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a division of U.S. patent application Ser. No.
12/847,519, entitled "STRUCTURED FABRIC", filed Jul. 30, 2010,
which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to papermaking, and
relates more specifically to a fibrous web formed on a structured
fabric employed in papermaking.
[0004] 2. Description of the Related Art
[0005] In a conventional papermaking process, a water slurry, or
suspension, of cellulosic fibers (known as the paper "stock") is
fed into a gap between two endless woven wires that travels between
two or more rolls. At least one of the wires are often referred to
as a "structured fabric" that provides a papermaking surface on the
upper surface of its upper run which operates as a filter to
separate the cellulosic fibers of the paper stock from the aqueous
medium, thereby forming a wet paper web. The aqueous medium drains
through mesh openings of the structured fabric, known as drainage
holes, by gravity or vacuum located on the lower surface of the
upper run (i.e., the "machine side") of the fabric.
[0006] After leaving the forming section, the paper web is
transferred to a press section of the paper machine, where it is
passed through the nips of one or more pairs of pressure rollers
covered with another fabric, typically referred to as a "press
felt." Pressure from the rollers removes additional moisture from
the web; the moisture removal is often enhanced by the presence of
a "batt" layer of the press felt. The paper is then transferred to
a dryer section for further moisture removal. After drying, the
paper is ready for secondary processing and packaging.
[0007] Typically, papermakers' fabrics are manufactured as endless
belts by one of two basic weaving techniques. In the first of these
techniques, fabrics are flat woven by a flat weaving process, with
their ends being joined to form an endless belt by any one of a
number of well-known joining methods, such as dismantling and
reweaving the ends together (commonly known as splicing), or sewing
on a pin-seamable flap or a special foldback on each end, then
reweaving these into pin-seamable loops. A number of auto-joining
machines are available, which for certain fabrics may be used to
automate at least part of the joining process. In a flat woven
papermakers' fabric, the warp yarns extend in the machine direction
and the filling yarns extend in the cross machine direction.
[0008] In the second basic weaving technique, fabrics are woven
directly in the form of a continuous belt with an endless weaving
process. In the endless weaving process, the warp yarns extend in
the cross machine direction and the filling yarns extend in the
machine direction. Both weaving methods described hereinabove are
well known in the art, and the term "endless belt" as used herein
refers to belts made by either method.
[0009] Effective sheet and fiber support are important
considerations in papermaking, especially for the forming section
of the papermaking machine, where the wet web is initially formed.
Additionally, the structured fabrics should exhibit good stability
when they are run at high speeds on the papermaking machines, and
preferably are highly permeable to reduce the amount of water
retained in the web when it is transferred to the press section of
the paper machine. In both tissue and fine paper applications
(i.e., paper for use in quality printing, carbonizing, cigarettes,
electrical condensers, and the like) the papermaking surface
comprises a very finely woven or fine wire mesh structure.
[0010] In a conventional tissue forming machine, the sheet is
formed flat. At the press section, 100% of the sheet is pressed and
compacted to reach the necessary dryness and the sheet is further
dried on a Yankee and hood section. The sheet is then creped and
wound-up, thereby producing a flat sheet.
[0011] In an ATMOS.TM. system, a sheet is formed on a structured or
molding fabric and the sheet is further sandwiched between the
structured or molding fabric and a dewatering fabric. The sheet is
dewatered through the dewatering fabric and opposite the molding
fabric. The dewatering takes place with airflow and mechanical
pressure. The mechanical pressure is created by a permeable belt
and the direction of air flow is from the permeable belt to the
dewatering fabric. This can occur when the sandwich passes through
an extended pressure nip formed by a vacuum roll and the permeable
belt. The sheet is then transferred to a Yankee by a press nip.
Only about 25% of the sheet is slightly pressed by the Yankee while
approximately 75% of the sheet remains unpressed for quality. The
sheet is dried by a Yankee/Hood dryer arrangement and then dry
creped. In the ATMOS.TM. system, one and the same structured fabric
is used to carry the sheet from the headbox to the Yankee dryer.
Using the ATMOS.TM. system, the sheet reaches between about 35 to
38% dryness after the ATMOS.TM. roll, which is almost the same
dryness as a conventional press section. However, this
advantageously occurs with almost 40 times lower nip pressure and
without compacting and destroying sheet quality. Furthermore, a big
advantage of the ATMOS.TM. system is that it utilizes a permeable
belt which is highly tensioned, e.g., about 60 kN/m. This belt
enhances the contact points and intimacy for maximum vacuum
dewatering. Additionally, the belt nip is more than 20 times longer
than a conventional press and utilizes airflow through the nip,
which is not the case on a conventional press system.
[0012] Actual results from trials using an ATMOS.TM. system have
shown that the caliper and bulk of the sheet is 30% higher than the
conventional through-air drying (TAD) formed towel fabrics.
Absorbency capacity is also 30% higher than with conventional TAD
formed towel fabrics. The results are the same whether one uses
100% virgin pulp up to 100% recycled pulp. Sheets can be produced
with basis weight ratios of between 14 to 40 g/m.sup.2. The
ATMOS.TM. system also provides excellent sheet transfer to the
Yankee working at 33 to 37% dryness. A key aspect of the ATMOS.TM.
system is that it forms the sheet on the molding fabric and the
same molding fabric carries the sheet from the headbox to the
Yankee dryer. This produces a sheet with a uniform and defined pore
size for maximum absorbency capacity.
[0013] U.S. patent application Ser. No. 11/753,435 filed on May 24,
2007, the disclosure of which is hereby expressly incorporated by
reference in its entirety, discloses a structured fabric for an
ATMOS.TM. system. The fabric utilizes an at least three float warp
and weft structure which, like the prior art fabrics, is
symmetrical in form.
[0014] U.S. Pat. No. 5,429,686 to CHIU et al., the disclosure of
which is hereby expressly incorporated by reference in its
entirety, discloses structured forming fabrics which utilize a
load-bearing layer and a sculptured layer. The fabrics utilize
impression knuckles to imprint the sheet and increase its surface
contour. This document, however, does not create pillows in the
sheet for effective dewatering of TAD applications, nor does it
teach using the disclosed fabrics on an ATMOS.TM. system and/or
forming the pillows in the sheet while the sheet is relatively wet
and utilizing a hi-tension press nip.
[0015] U.S. Pat. No. 6,237,644 to HAY et al., the disclosure of
which is hereby expressly incorporated by reference in its
entirety, discloses structured forming fabrics which utilize a
lattice weave pattern of at least three yarns oriented in both warp
and weft directions. The fabric essentially produces shallow
craters in distinct patterns. This document, however, does not
teach using the disclosed fabrics on an ATMOS.TM. system.
[0016] What is needed in the art is an efficient effective single
layer fabric weave pattern to be used in a papermaking machine.
SUMMARY OF THE INVENTION
[0017] In one aspect, the invention provides a fibrous web
including a fibrous construct having at least one formed surface
feature. The surface feature including a topographical pattern
reflective of a weave pattern in a fabric used in a papermaking
machine. The fabric including a single layer of yarns arranged in a
repeating weave pattern, each weave pattern including a plurality
of warp yarns substantially oriented in a machine direction (MD)
defining MD yarns; and a plurality of weft yarns substantially
oriented in a cross machine direction (CD) defining CD yarns. The
MD yarns each having at least one long float within the weave
pattern. Each long float being adjacent to at least one other long
float of an MD yarn. The weave pattern being a plain weave apart
from the long floats.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention will be better understood by reference
to the following description of embodiments of the invention taken
in conjunction with the accompanying drawings, wherein:
[0019] FIG. 1 shows a repeating weave pattern having a square shape
of a top side or paper facing side of an embodiment of a structured
fabric of the present invention, each `X` indicating a location
where a warp MD yarn passes over a weft CD yarn;
[0020] FIG. 2 shows the weave pattern of the structured fabric of
FIG. 1;
[0021] FIG. 3 shows a repeating weave pattern having a square shape
of a top side or paper facing side of another embodiment of a
structured fabric of the present invention, each `X` indicating a
location where a warp MD yarn passes over a weft CD yarn;
[0022] FIG. 4 shows the weave pattern of the structured fabric of
FIG. 3;
[0023] FIG. 5 shows a repeating weave pattern having a square shape
of a top side or paper facing side of yet another embodiment of a
structured fabric of the present invention, each `X` indicating a
location where a warp MD yarn passes over a weft CD yarn;
[0024] FIG. 6 shows the weave pattern of the structured fabric of
FIG. 5;
[0025] FIG. 7 shows a repeating weave pattern having a square shape
of a top side or paper facing side of yet another embodiment of a
structured fabric of the present invention, each `X` indicating a
location where a warp MD yarn passes over a weft CD yarn;
[0026] FIG. 8 shows the weave pattern of the structured fabric of
FIG. 7;
[0027] FIG. 9 shows a repeating weave pattern having a square shape
of a top side or paper facing side of yet another embodiment of a
structured fabric of the present invention, each `X` indicating a
location where a warp MD yarn passes over a weft CD yarn;
[0028] FIG. 10 shows the weave pattern of the structured fabric of
FIG. 9;
[0029] FIG. 11 shows a repeating weave pattern having a square
shape of a top side or paper facing side of yet another embodiment
of a structured fabric of the present invention, each `X`
indicating a location where a warp MD yarn passes over a weft CD
yarn;
[0030] FIG. 12 shows the weave pattern of the structured fabric of
FIG. 11;
[0031] FIG. 13 shows a repeating weave pattern having a square
shape of a top side or paper facing side of yet another embodiment
of a structured fabric of the present invention, each `X`indicating
a location where a warp MD yarn passes over a weft CD yarn;
[0032] FIG. 14 shows the weave pattern of the structured fabric of
FIG. 13;
[0033] FIG. 15 shows a repeating weave pattern having a square
shape of a top side or paper facing side of yet another embodiment
of a structured fabric of the present invention, each `X`
indicating a location where a warp MD yarn passes over a weft CD
yarn;
[0034] FIG. 16 shows the weave pattern of the structured fabric of
FIG. 15;
[0035] FIG. 17 shows a repeating weave pattern having a square
shape of a top side or paper facing side of yet another embodiment
of a structured fabric of the present invention, each `X`
indicating a location where a warp MD yarn passes over a weft CD
yarn;
[0036] FIG. 18 shows the weave pattern of the structured fabric of
FIG. 17;
[0037] FIG. 19 shows a repeating weave pattern having a square
shape of a top side or paper facing side of yet another embodiment
of a structured fabric of the present invention, each `X`
indicating a location where a warp MD yarn passes over a weft CD
yarn;
[0038] FIG. 20 shows the weave pattern of the structured fabric of
FIG. 19;
[0039] FIG. 21 shows a repeating weave pattern having a square
shape of a top side or paper facing side of yet another embodiment
of a structured fabric of the present invention, each `X`
indicating a location where a warp MD yarn passes over a weft CD
yarn;
[0040] FIG. 22 shows the weave pattern of the structured fabric of
FIG. 21;
[0041] FIG. 23 shows a repeating weave pattern having a square
shape of a top side or paper facing side of yet another embodiment
of a structured fabric of the present invention, each `X`
indicating a location where a warp MD yarn passes over a weft CD
yarn;
[0042] FIG. 24 shows the weave pattern of the structured fabric of
FIG. 23;
[0043] FIG. 25 shows a repeating weave pattern having a square
shape of a top side or paper facing side of yet another embodiment
of a structured fabric of the present invention, each `X`
indicating a location where a warp MD yarn passes over a weft CD
yarn;
[0044] FIG. 26 shows the weave pattern of the structured fabric of
FIG. 25;
[0045] FIG. 27 shows a repeating weave pattern having a square
shape of a top side or paper facing side of yet another embodiment
of a structured fabric of the present invention, each `X`
indicating a location where a warp MD yarn passes over a weft CD
yarn;
[0046] FIG. 28 shows the weave pattern of the structured fabric of
FIG. 27;
[0047] FIG. 29 illustrates a schematic cross-sectional view of an
embodiment of an ATMOS.TM. papermaking machine;
[0048] FIG. 30 illustrates a schematic cross-sectional view of
another embodiment of an ATMOS.TM. papermaking machine;
[0049] FIG. 31 illustrates a schematic cross-sectional view of
another embodiment of an ATMOS.TM. papermaking machine;
[0050] FIG. 32 illustrates a schematic cross-sectional view of
another embodiment of an ATMOS.TM. papermaking machine;
[0051] FIG. 33 illustrates a schematic cross-sectional view of
another embodiment of an ATMOS.TM. papermaking machine;
[0052] FIG. 34 illustrates a schematic cross-sectional view of
another embodiment of an ATMOS.TM. papermaking machine;
[0053] FIG. 35 illustrates a schematic cross-sectional view of
another embodiment of an ATMOS.TM. papermaking machine; and
[0054] FIG. 36 illustrates a schematic cross-sectional view of
another embodiment of an ATMOS.TM. papermaking machine.
[0055] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplification set out
herein illustrates one embodiment of the invention, in one form,
and such exemplification is not to be construed as limiting the
scope of the invention in any manner.
DETAILED DESCRIPTION OF THE INVENTION
[0056] The particulars shown herein are by way of example and for
purposes of illustrative discussion of the embodiments of the
present invention only and are presented in the cause of providing
what is believed to be the most useful and readily understood
description of the principles and conceptual aspects of the present
invention. In this regard, no attempt is made to show structural
details of the present invention in more detail than is necessary
for the fundamental understanding of the present invention, and the
description is taken with the drawings making apparent to those
skilled in the art how the forms of the present invention may be
embodied in practice.
[0057] The present invention relates to a structured fabric for a
papermaking machine, a former for manufacturing a paper web, and
also to a former which utilizes the structured fabric, and in some
embodiments a belt press, in a papermaking machine.
[0058] The present invention also relates to a twin wire former
ATMOS.TM. system which utilizes the structured fabric which has
good resistance to pressure and excessive tensile strain forces,
and which can withstand wear/hydrolysis effects that are
experienced in an ATMOS.TM. system. The system may also include a
permeable belt for use in a high tension extended nip around a
rotating roll or a stationary shoe and a dewatering fabric for the
manufacture of premium tissue or towel grades. The fabric has key
parameters which include permeability, weight, caliper, and certain
compressibility.
[0059] The structured fabric of the present invention is
illustrated in FIGS. 1-28. FIG. 1 depicts a weave pattern 10 from a
top pattern view of the web facing side of the fabric (i.e., a view
of the papermaking surface). The numbers 1-20 shown on the bottom
of the pattern identify the warp, machine direction (MD) yarns
while the right side numbers 1-20 show the weft, cross-direction
(CD) yarns. The symbol X illustrates a location where a warp yarn
passes over a weft yarn and an empty box illustrates a location
where a warp yarn passes under a weft yarn. As shown in FIG. 1, the
areas that are shaded indicate long float warp yarns, which float
over at least two weft yarns. The shaded areas form a MD float
pattern, while the non-shaded areas represent a plain weave
pattern. In a like manner the weave patterns of FIGS. 3, 5, 7, 9,
11, 13, 15, 17, 19, 21, 23, 25, and 27 illustrate other embodiments
of the present invention.
[0060] FIG. 2 illustrates the weave pattern of the MD yarns
relative to the CD yarns with the CD yarns being represented in
each line as the numbers, with the line being the pattern of the MD
yarn. Each line representing the MD yarn identified along the left
side of the Fig. In a like manner FIG. 4 corresponds to FIG. 3 and
so on with the even numbered figures through FIG. 28, corresponding
to the odd numbered figure that is numerically one less than the
even numbered Fig.
[0061] The embodiments shown in FIGS. 1-28 are illustrative of the
invention and the invention is not limited to the weave patterns
shown therein.
[0062] The fabric of FIGS. 1-28 illustrates a repeating weave
pattern square of the fabric that encompasses twenty MD warp yarns
(yarns 1-20 numbered along the bottom of each pattern) and twenty
weft yarns (yarns 1-20 that are numbered along the right side of
each pattern). There are long floats of the MD warp yarns over the
weft yarns, with the long float being over at least two weft yarns,
and in most patterns over at least three weft yarns. Although in
some patterns the MD warp yarn float is over at least four or even
over at least five weft yarns.
[0063] Where the MD warp yarns have there long float they are
always adjacent to at least one other MD warp yarn that is also
undergoing a long float. The float beginning and ending are offset
in the MD by one weft yarn position. The contiguous adjacent MD
warp yarns form an MD yarn float pattern, with at least one being
present in each weave pattern 10. The MD yarn float patterns are
replicated in weave pattern 10, and includes minor-image or
reflected MD yarn float patterns. The MD yarn float patterns can be
symmetrical or asymmetrical. For example, in FIG. 1 there is one MD
yarn float pattern having a float over five weft yarns that is only
four MD yarns wide and there is another MD yarn float pattern
having a float over five weft yarns that is five MD yarns wide. So,
while the patterns are similar and are a reflection of each other,
they are also asymmetrical.
[0064] Looking at FIG. 3, there are MD yarn float patterns that are
mirror-images and are symmetrical. The MD yarns float over three
weft yarns and are three MD yarns wide. In each case apart from the
MD yarn float patterns the weave of the single layer fabric is a
simple weave pattern. In many cases the plain weave pattern
surrounds the MD yarn float patterns. In some weave patterns, such
as those of FIGS. 17 and 19, the simple weave patterns appear
surrounded by MD yarn float patterns.
[0065] The parameters of the structured fabric shown in FIGS. 1-28
can have a mesh (number of warp yarns per inch) and a count (number
of weft yarns per inch) of any amount. The single-layered fabric
should have a high permeability value due to the nature of a single
layer fabric and the way it is woven. Regarding yarn dimensions,
the particular size of the yarns is typically governed by the mesh
of the papermaking surface and the yarn size can be selected based
upon the intended use. Fabrics employing these yarn sizes may be
implemented with polyester yarns or with a combination of polyester
and nylon yarns.
[0066] The structured fabric can also be treated and/or coated with
an additional polymeric material that is applied by, e.g.,
deposition. The material can be added cross-linked during
processing in order to enhance fabric stability, contamination
resistance, drainage, wearability, improve heat and/or hydrolysis
resistance and in order to reduce fabric surface tension. This aids
in sheet release and/or reduced drive loads. The treatment/coating
can be applied to impart/improve one or several of these properties
of the fabric. As indicated previously, the topographical pattern
in the paper web can be changed and manipulated by use of different
single-layer weaves. Further enhancement of the pattern can be
attained by adjustments to the specific fabric weave by changes to
the yarn diameter, yarn counts, yarn types, yarn shapes,
permeability, caliper and the addition of a treatment or coating
etc. In addition, a printed design, such as a screen-printed
design, of polymeric material can be applied to the fabric to
enhance its ability to impart an aesthetic pattern into the web or
to enhance the quality of the web. Finally, one or more surfaces of
the fabric or molding belt can be subjected to sanding and/or
abrading in order to enhance surface characteristics.
[0067] The characteristics of the individual yarns utilized in the
fabric of the present invention can vary depending upon the desired
properties of the final papermakers' fabric. For example, the
materials comprising yarns employed in the fabric of the present
invention may be those commonly used in papermakers' fabric. As
such, the yarns may be formed of polypropylene, polyester, nylon,
or the like. The skilled artisan should select a yarn material
according to the particular application of the final fabric.
[0068] By way of non-limiting example, the structured fabric is a
single-layered woven fabric which can withstand high pressures,
heat, moisture concentrations, and which can achieve a high level
of water removal and also mold or emboss the paper web. These
characteristics provide a structured fabric appropriate for the
Voith ATMOS.TM. papermaking process. The fabric preferably has a
width stability and a suitable high permeability and preferably
utilizes hydrolysis and/or temperature resistant materials, as
discussed above. The fabric is preferably a woven fabric that can
be installed on an ATMOS.TM. machine as a pre-joined and/or seamed
continuous and/or endless belt. Alternatively, the structured
fabric can be joined in the ATMOS.TM. machine using, e.g., a
pin-seam arrangement or can otherwise be seamed on the machine.
[0069] The invention also provides for utilizing the structured
fabric disclosed herein on a machine for making a fibrous web,
e.g., tissue or hygiene paper web, etc., which can be, e.g., a twin
wire+a permeable belt ATMOS.TM. system. Referring again to the
drawings, and more particularly to FIGS. 29-35, there is a fibrous
web machine including a headbox 22 that discharges a fibrous slurry
between a forming fabric 26 and a structured fabric 28 having a
weave pattern 10. It should be understood that structured fabric 28
is an embodiment of the structured fabric discussed above in
connection with FIGS. 1-28. Rollers 30 and 32 direct fabric 26 in
such a manner that tension is applied thereto, against slurry 24
and structured fabric 28. Structured fabric 28 is supported by
forming roll 34 which rotates with a surface speed that matches the
speed of structured fabric 28 and forming fabric 26. Structured
fabric 28 has peaks and valleys as defined by weave pattern 10,
which give a corresponding structure to web 38 formed thereon.
Structured fabric 28 travels in a web direction, and as moisture is
driven from the fibrous slurry, structured fibrous web 38 takes
form. The moisture that leaves the slurry travels through forming
fabric 26.
[0070] The fibrous slurry is formed into a web 38 with a structure
that matches the shape of structured fabric 28. Forming fabric 26
is porous and allows moisture to escape during forming. Further,
water is removed through dewatering fabric 82. The removal of
moisture through fabric 82 does not cause compression of web 38
traveling on structured fabric 28.
[0071] Due to the formation of the web 38 with the structured
fabric 28 the pockets of the fabric 28 are fully filled with
fibers. Therefore, at the Yankee surface 52 the web 38 has a much
higher contact area, up to approximately 100%, as compared to the
prior art because the web 38 on the side contacting the Yankee
surface 52 is almost flat.
[0072] Referring to FIG. 29, there is shown an embodiment of the
process where a structured fibrous web 38 is formed. Structured
fabric 28 carries a three dimensional structured fibrous web 38 to
an advanced dewatering system 50, past vacuum box 67 and then to a
position where the web is transferred to Yankee dryer 52 and hood
section 54 for additional drying and creping before winding up on a
reel (not shown).
[0073] A shoe press 56 is placed adjacent to structured fabric 28,
holding fabric 28 in a position proximate Yankee dryer 52.
Structured fibrous web 38 comes into contact with Yankee dryer 52
and transfers to a surface thereof, for further drying and
subsequent creping.
[0074] A vacuum box 58 is placed adjacent to structured fabric 28
to achieve improved solids levels. Web 38, which is carried by
structured fabric 28, contacts dewatering fabric 82 and proceeds
toward vacuum roll 60. Vacuum roll 60 operates at a vacuum level of
-0.2 to -0.8 bar with a preferred operating level of at least -0.4
bar. Hot air hood 62 is optionally fit over vacuum roll 60 to
improve dewatering.
[0075] Optionally a steam box can be installed instead of the hood
62 supplying steam to the web 38. The steam box preferably has a
sectionalized design to influence the moisture re-dryness cross
profile of the web 38. The length of the vacuum zone inside the
vacuum roll 60 can be from 200 mm to 2,500 mm, with a preferable
length of 300 mm to 1,200 mm and an even more preferable length of
between 400 mm to 800 mm. The solids level of web 38 leaving
suction roll 60 is 25% to 55% depending on installed options. A
vacuum box 67 and hot air supply 65 can be used to increase web 38
solids after vacuum roll 60 and prior to Yankee dryer 52. Wire
turning roll 69 can also be a suction roll with a hot air supply
hood. As discussed above, roll 56 includes a shoe press with a shoe
width of 80 mm or higher, preferably 120 mm or higher, with a
maximum peak pressure of less than 2.5 MPa. To create an even
longer nip to facilitate the transfer of web 38 to Yankee dryer 52,
web 38 carried on structured fabric 28 can be brought into contact
with the surface of Yankee dryer 52 prior to the press nip
associated with shoe press 56. Further, the contact can be
maintained after structured fabric 28 travels beyond press 56.
[0076] Now, additionally referring to FIG. 30, there is shown yet
another embodiment of the present invention, which is substantially
similar to the invention illustrated in FIG. 29, except that
instead of hot air hood 62, there is a belt press 64. Belt press 64
includes a permeable belt 66 capable of applying pressure to the
machine side of structured fabric 28 that carries web 38 around
vacuum roll 60. Fabric 66 of belt press 64 is also known as an
extended nip press belt or a link fabric, which can run at 60 KN/m
fabric tension with a pressing length that is longer than the
suction zone of roll 60.
[0077] Preferred embodiments of the fabric 66 and the required
operation conditions are also described in PCT/EP2004/053688 and
PCT/EP2005/050198 which are herewith incorporated by reference.
[0078] The above mentioned references are also fully applicable for
dewatering fabrics 82 and press fabrics 66 described in the further
embodiments.
[0079] Belt 66 is a specially designed extended nip press belt 66,
made of, for example reinforced polyurethane and/or a spiral link
fabric. Belt 66 also can have a woven construction. Such a woven
construction is disclosed, e.g., in EP 1837439. Belt 66 is
permeable thereby allowing air to flow there through to enhance the
moisture removing capability of belt press 64. Moisture is drawn
from web 38 through dewatering fabric 82 and into vacuum roll
60.
[0080] Referring to FIG. 31, there is shown another embodiment of
the present invention which is substantially similar to the
embodiment shown in FIG. 30 with the addition of hot air hood 68
placed inside of belt press 64 to enhance the dewatering capability
of belt press 64 in conjunction with vacuum roll 60.
[0081] Referring to FIG. 32, there is shown yet another embodiment
of the present invention, which is substantially similar to the
embodiment shown in FIG. 30, but including a boost dryer 70 which
encounters structured fabric 28. Web 38 is subjected to a hot
surface of boost dryer 70, and structured web 38 rides around boost
dryer 70 with another woven fabric 72 riding on top of structured
fabric 28. On top of woven fabric 72 is a thermally conductive
fabric 74, which is in contact with both woven fabric 72 and a
cooling jacket 76 that applies cooling and pressure to all fabrics
and web 38. The pressing process does not negatively impact web
quality. The drying rate of boost dryer 70 is above 400 kg/hr
m.sup.2 and preferably above 500 kg/hr m.sup.2. The concept of
boost dryer 70 is to provide sufficient pressure to hold web 38
against the hot surface of the dryer thus preventing blistering.
Steam that is formed at the knuckle points of fabric 28 passes
through fabric 28 and is condensed on fabric 72. Fabric 72 is
cooled by fabric 74 that is in contact with cooling jacket 76,
which reduces its temperature to well below that of the steam. Thus
the steam is condensed to avoid a pressure build up to thereby
avoid blistering of web 38. The condensed water is captured in
woven fabric 72, which is dewatered by dewatering device 75. It has
been shown that depending on the size of boost dryer 70, the need
for vacuum roll 60 can be eliminated. Further, depending on the
size of boost dryer 70, web 38 may be creped on the surface of
boost dryer 70, thereby eliminating the need for Yankee dryer
52.
[0082] Referring to FIG. 33, there is shown yet another embodiment
of the present invention substantially similar to the invention
disclosed in FIG. 30 but with an addition of an air press 78, which
is a four roll cluster press that is used with high temperature air
and is referred to as a High Pressure Through Air Dryer (HPTAD) for
additional web drying prior to the transfer of web 38 to Yankee
dryer 52. Four-roll cluster press 78 includes a main roll, a vented
roll, and two cap rolls. The purpose of this cluster press is to
provide a sealed chamber that is capable of being pressurized. The
pressure chamber contains high temperature air, for example,
150.degree. C. or higher and is at a significantly higher pressure
than conventional TAD technology, for example, greater than 1.5 psi
resulting in a much higher drying rate than a conventional TAD. The
high-pressure hot air passes through an optional air dispersion
fabric, through web 38 and fabric structured 28 into a vent roll.
The air dispersion fabric may prevent web 38 from following one of
the cap rolls. The air dispersion fabric is very open, having a
permeability that equals or exceeds that of fabric structured 28.
The drying rate of the HPTAD depends on the solids content of web
38 as it enters the HPTAD. The preferred drying rate is at least
500 kg/hr m.sup.2, which is a rate of at least twice that of
conventional TAD machines.
[0083] Advantages of the HPTAD process are in the areas of improved
sheet dewatering without a significant loss in sheet quality and
compactness in size and energy efficiency. Additionally, it enables
higher pre-Yankee solids, which increase the speed potential of the
invention. Further, the compact size of the HPTAD allows for easy
retrofitting to an existing machine. The compact size of the HPTAD
and the fact that it is a closed system means that it can be easily
insulated and optimized as a unit to increase energy
efficiency.
[0084] Referring to FIG. 34, there is shown another embodiment of
the present invention. This is significantly similar to the
embodiments shown in FIGS. 30 and 33 except for the addition of a
two-pass HPTAD 80. In this case, two vented rolls are used to
double the dwell time of structured web 38 relative to the design
shown in FIG. 33. An optional coarse mesh fabric may be used as in
the previous embodiment. Hot pressurized air passes through web 38
carried on structured fabric 28 and onto the two vent rolls. It has
been shown that depending on the configuration and size of the
HPTAD, more than one HPTAD can be placed in series, which can
eliminate the need for roll 60.
[0085] Referring to FIG. 35, a conventional twin wire former 90 may
be used to replace the crescent former shown in previous examples.
The forming roll can be either a solid or open roll. If an open
roll is used, care must be taken to prevent significant dewatering
through the structured fabric to avoid losing basis weight in the
pillow areas. The outer forming fabric 93 can be either a standard
forming fabric or one such as that disclosed in U.S. Pat. No.
6,237,644. The inner fabric 91 should be a structured fabric that
is much coarser than the outer forming fabric 90. For example,
inner fabric 91 may be similar to structured fabric 28. A vacuum
roll 92 may be needed to ensure that the web stays with structured
fabric 91 and does not go with outer wire 90. Web 38 is transferred
to structured fabric 28 using a vacuum device. The transfer can be
a stationary vacuum shoe or a vacuum assisted rotating pick-up roll
94. The second structured fabric 28 is at least the same coarseness
and preferably coarser than first structured fabric 91. The process
from this point is the same as the process previously discussed in
conjunction with FIG. 30. The registration of the web from the
first structured fabric to the second structured fabric is not
perfect, and as such some pillows will lose some basis weight
during the expansion process, thereby losing some of the benefit of
the present invention. However, this process option allows for
running a differential speed transfer, which has been shown to
improve some sheet properties. Any of the arrangements for removing
water discussed above as may be used with the twin wire former
arrangement and a conventional TAD.
[0086] Referring to FIG. 36 there is illustrated another ATMOS.TM.
system having many elements as discussed above. The ATMOS.TM.
system of FIG. 36, is further described in WO 2010/069695 having a
priority date of Dec. 19, 2008. Belt press 64 constitutes a first
pressing zone where web 38 is pressed. Web 38 proceeds to a second
pressing zone 65 where web 38 is pressed again.
[0087] While this invention has been described with respect to at
least one embodiment, the present invention can be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains and which fall within the limits of
the appended claims.
* * * * *