U.S. patent application number 12/018385 was filed with the patent office on 2009-07-23 for multi-layer papermaker's forming fabric with long machine side md floats.
Invention is credited to Jason Goins, Kevin John Ward.
Application Number | 20090183795 12/018385 |
Document ID | / |
Family ID | 40548555 |
Filed Date | 2009-07-23 |
United States Patent
Application |
20090183795 |
Kind Code |
A1 |
Ward; Kevin John ; et
al. |
July 23, 2009 |
Multi-Layer Papermaker's Forming Fabric With Long Machine Side MD
Floats
Abstract
A papermaker's fabric includes: a set of top MD yarns; a set of
bottom MD yarns; a set of top CMD yarns interwoven with the top MD
yarns to form a top fabric layer; a set of bottom CMD yarns
interwoven with the bottom MD yarns to form a bottom fabric layer;
and a set of stitching yarns that interweave with the top and
bottom fabric layers. The top MD yarns and the top CMD yarns are
interwoven in a series of repeat units and the bottom MD yarns and
the bottom CMD yarns are interwoven in a series of corresponding
repeat units. Each of the bottom MD yarns forms a bottom MD float
by passing under three or more consecutive bottom CMD yarns.
Inventors: |
Ward; Kevin John;
(Coldbrook, CA) ; Goins; Jason; (Graham,
NC) |
Correspondence
Address: |
MYERS BIGEL SIBLEY & SAJOVEC
PO BOX 37428
RALEIGH
NC
27627
US
|
Family ID: |
40548555 |
Appl. No.: |
12/018385 |
Filed: |
January 23, 2008 |
Current U.S.
Class: |
139/410 ;
139/383A |
Current CPC
Class: |
D21F 1/0045
20130101 |
Class at
Publication: |
139/410 ;
139/383.A |
International
Class: |
D21F 7/08 20060101
D21F007/08; D03D 11/00 20060101 D03D011/00; D03D 25/00 20060101
D03D025/00 |
Claims
1. A papermaker's fabric, comprising: a set of top machine
direction (MD) yarns; a set of bottom MD yarns; a set of top cross
machine direction (CMD) yarns interwoven with the top MD yarns to
form a top fabric layer; a set of bottom CMD yarns interwoven with
the bottom MD yarns to form a bottom fabric layer; and a set of
stitching yarns that interweave with the top and bottom fabric
layers; wherein the top MD yarns and the top CMD yarns are
interwoven in a series of repeat units and the bottom MD yarns and
the bottom CMD yarns are interwoven in a series of corresponding
repeat units; wherein each of the bottom MD yarns forms a bottom MD
float by passing under three or more consecutive bottom CMD
yarns.
2. The papermaker's fabric defined in claim 1, wherein the bottom
MD floats pass under between three and five consecutive bottom CMD
yarns.
3. The papermaker's fabric defined in claim 1, wherein the bottom
MD yarns comprise monofilament yarns.
4. The papermaker's fabric defined in claim 1, wherein the
stitching yarns are arranged in pairs.
5. The papermaker's fabric defined in claim 4, wherein the
stitching yarn pairs comprise MD stitching yarns.
6. The papermaker's fabric defined in claim 4, wherein the
stitching yarn pairs comprise CMD stitching yarns.
7. The papermaker's fabric defined in claim 1, wherein the top MD
yarns, the top CMD yarns and the stitching yarns combine in the top
fabric layer to form a plain weave top surface.
8. The papermaker's fabric defined in claim 1, wherein each of the
MD yarns of the top layer is also a stitching yarn.
9. The papermaker's fabric defined in claim 4, wherein one of the
stitching yarns of each pair is a phantom stitching yarn.
10. The papermaker's fabric defined in claim 5, wherein each of the
stitching yarns stitches below a bottom CMD yarn that is one of the
consecutive yarns that each of the adjacent bottom MD yarn passes
under in forming the bottom MD float.
11. The papermaker's fabric defined in claim 6, wherein each of the
stitching yarns stitches under a bottom MD yarn that an adjacent
bottom CMD yarn also passes under.
12. The papermaker's fabric defined in claim 1, wherein the top MD
yarns have a first diameter, the bottom MD yarns have a second
diameter, and the first diameter is smaller than the second
diameter.
13. The papermaker's fabric defined in claim 8, wherein the ratio
of MD stitching yarn pairs to bottom MD yarns is 1:1.
14. The papermaker's fabric defined in claim 5, wherein the ratio
of top MD yarns and stitching yarn pairs to bottom MD yarns is
2:3.
15. The papermaker's fabric defined in claim 5, wherein the ratio
of top CMD yarns to bottom CMD yarns is 5:2.
16. The papermaker's fabric defined in claim 6, wherein the ratio
of top CMD yarns to bottom CMD yarns is 1:1.
17. A papermaker's fabric, comprising: a set of top machine
direction (MD) yarns; a set of bottom MD yarns; a set of cross
machine direction (CMD) yarns interwoven with the top MD yarns to
form a top fabric layer; a set of CMD stitching yarn pairs that
interweave with the top and bottom fabric layers; wherein the top
MD yarns and the top CMD yarns are interwoven in a series of repeat
units and the bottom MD yarns and the bottom CMD yarns are
interwoven in a series of corresponding repeat units; wherein each
of the bottom MD yarns forms a bottom MD float by passing under
three or more consecutive CMD stitching yarn pairs.
18. The papermaker's fabric defined in claim 17, wherein the bottom
MD yarns comprise monofilament yarns.
19. The papermaker's fabric defined in claim 17, wherein the top MD
yarns, the top CMD yarns, and the stitching yarns combine in the
top fabric layer to form a plain weave top surface.
20. The papermaker's fabric defined in claim 17, wherein one of the
CMD stitching yarns of each pair is a phantom stitching yarn.
21. The papermaker's fabric defined in claim 17, wherein the ratio
of top MD yarns to bottom MD yarns is 1:1.
22. A papermaker's fabric, comprising: a set of machine direction
(MD) stitching yarns, the stitching yarns being arranged in pairs;
a set of bottom MD yarns; a set of top cross machine direction
(CMD) yarns interwoven with the MD stitching yarns to form a top
fabric layer; and a set of bottom CMD yarns interwoven with the
bottom MD yarns to form a bottom fabric layer; wherein the MD
stitching yarns and the top CMD yarns are interwoven in a series of
repeat units and the bottom MD yarns, the MD stitching yarns and
the bottom CMD yarns are interwoven in a series of corresponding
repeat units; and wherein the MD stitching yarns have a first
diameter, the bottom MD yarns have a second diameter, and the first
diameter is less than the second diameter.
23. The papermaker's fabric defined in claim 22, wherein the ratio
of the first diameter to the second diameter is between about 0.4
and 0.7.
Description
FIELD OF THE INVENTION
[0001] This application is directed generally to papermaking, and
more specifically to fabrics employed in papermaking.
BACKGROUND OF THE INVENTION
[0002] In the conventional fourdrinier papermaking process, a water
slurry, or suspension, of cellulosic fibers (known as the paper
"stock") is fed onto the top of the upper run of an endless belt of
woven wire and/or synthetic material that travels between two or
more rolls. The belt, often referred to as a "forming fabric,"
provides a papermaking surface on the upper surface of its upper
run that 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
forming 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.
[0003] 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 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.
[0004] As used herein, the terms machine direction ("MD") and cross
machine direction ("CMD") refer, respectively, to a direction
aligned with the direction of travel of the papermakers' fabric on
the papermaking machine, and a direction parallel to the fabric
surface and traverse to the direction of travel. Likewise,
directional references to the vertical relationship of the yarns in
the fabric (e.g., above, below, top, bottom, beneath, etc.) assume
that the papermaking surface of the fabric is the top of the fabric
and the machine side surface of the fabric is the bottom of the
fabric.
[0005] Typically, papermaker's 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 now commercially available, which for certain fabrics
may be used to automate at least part of the joining process. In a
flat woven papermaker's fabric, the warp yarns extend in the
machine direction and the filling yarns extend in the cross machine
direction.
[0006] 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.
[0007] 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 forming 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 like) the papermaking surface comprises
a very finely woven or fine wire mesh structure.
[0008] Typically, finely woven fabrics such as those used in fine
paper and tissue applications include at least some relatively
small diameter machine direction or cross machine direction yarns.
Regrettably, however, such yarns tend to be delicate, leading to a
short surface life for the fabric. Moreover, the use of smaller
yarns can also adversely affect the mechanical stability of the
fabric (especially in terms of skew resistance, narrowing
propensity and stiffness), which may negatively impact both the
service life and the performance of the fabric.
[0009] To combat these problems associated with fine weave fabrics,
multi-layer forming fabrics have been developed with fine-mesh
yarns on the paper forming surface to facilitate paper formation
and coarser-mesh yarns on the machine contact side to provide
strength and durability. For example, fabrics have been constructed
which employ one set of machine direction yarns which interweave
with two sets of cross machine direction yarns to form a fabric
having a fine paper forming surface and a more durable machine side
surface. These fabrics form part of a class of fabrics which are
generally referred to as "double layer" fabrics. Similarly, fabrics
have been constructed which include two sets of machine direction
yarns and two sets of cross machine direction yarns that form a
fine mesh paperside fabric layer and a separate, coarser machine
side fabric layer. In these fabrics, which are part of a class of
fabrics generally referred to as "triple layer" fabrics, the two
fabric layers are typically bound together by separate stitching
yarns. However, they may also be bound together using yarns from
one or more of the sets of bottom and top cross machine direction
and machine direction yarns. As double and triple layer fabrics
include additional sets of yarn as compared to single layer
fabrics, these fabrics typically have a higher "caliper" (i.e.,
they are thicker) than comparable single layer fabrics. An
illustrative double layer fabric is shown in U.S. Pat. No.
4,423,755 to Thompson, and illustrative triple layer fabrics are
shown in U.S. Pat. No. 4,501,303 to Osterberg, U.S. Pat. No.
5,152,326 to Vohringer, U.S. Pat. Nos. 5,437,315 and 5,967,195 to
Ward, and U.S. Pat. No. 6,745,797 to Troughton.
[0010] U.S. Pat. No. 5,967,195 to Ward discloses a triple layer
fabric in which pairs of stitching yarns extend in the cross
machine direction and form part of the papermaking surface, in
essence "completing the weave" of the papermaking surface, while
also stitching with the bottom layer. The fabrics disclosed in Ward
have the same number of top machine direction yarns and bottom
machine direction yarns. Such fabrics have proven to provide an
excellent papermaking surface (particularly due to the integration
of the stitching yarns into the weave of the papermaking surface)
and to combat inter-layer wear. U.S. Pat. No. 6,896,009 shows a
similar concept with MD stitching yarns. However, in some
applications (e.g., brown paper), high open area and fiber support
may be desirable. Also, the improvement of other performance
characteristics, such as wear resistance, may be desirable.
SUMMARY OF THE INVENTION
[0011] As a first aspect, embodiments of the present invention are
directed to a papermaker's fabric, comprising: a set of top MD
yarns; a set of bottom MD yarns; a set of top CMD yarns interwoven
with the top MD yarns to form a top fabric layer; a set of bottom
CMD yarns interwoven with the bottom MD yarns to form a bottom
fabric layer; and a set of stitching yarns that interweave with the
top and bottom fabric layers. The top MD yarns and the top CMD
yarns are interwoven in a series of repeat units and the bottom MD
yarns and the bottom CMD yarns are interwoven in a series of
corresponding repeat units. Each of the bottom MD yarns forms a
bottom MD float by passing under three or more consecutive bottom
CMD yarns.
[0012] As a second aspect, embodiments of the present invention are
directed to a papermaker's fabric, comprising: a set of top MD
yarns; a set of bottom MD yarns; a set of CMD yarns interwoven with
the top MD yarns to form a top fabric layer; and a set of CMD
stitching yarn pairs that interweave with the top and bottom fabric
layers. The top MD yarns and the top CMD yarns are interwoven in a
series of repeat units and the bottom MD yarns and the bottom CMD
yarns are interwoven in a series of corresponding repeat units.
Each of the bottom MD yarns forms a bottom MD float by passing
under three or more consecutive CMD stitching yarn pairs.
[0013] As a third aspect, embodiments of the present invention are
directed to a papermaker's fabric, comprising: a set of MD
stitching yarns, the stitching yarns being arranged in pairs; a set
of bottom MD yarns; a set of top CMD yarns interwoven with the MD
stitching yarns to Form a top fabric layer; and a set of bottom CMD
yarns interwoven with the bottom MD yarns to form a bottom fabric
layer. The MD stitching yarns and the top CMD yarns are interwoven
in a series of repeat units and the bottom MD yarns, the MD
stitching yarns and the bottom CMD yarns are interwoven in a series
of corresponding repeat units. The MD stitching yarns have a first
diameter, the bottom MD yarns have a second diameter, and the first
diameter is less than the second diameter.
BRIEF DESCRIPTION OF THE FIGURES
[0014] FIG. 1 is a top view of the top layer of a repeat unit of a
fabric according to embodiments of the present invention.
[0015] FIG. 2 is a top view of the bottom layer of the fabric of
FIG. 1.
[0016] FIGS. 3A and 3B are section views taken along lines 3A-3A
and 3B-3B, respectively, of the fabric of FIGS. 1A and 1B showing
typical MD yarns.
[0017] FIG. 4 is a top view of the top layer of a repeat unit of a
fabric according to additional embodiments of the present
invention.
[0018] FIG. 5 is a top view of the bottom layer of the fabric of
FIG. 4.
[0019] FIGS. 6A and 68 are section views taken along lines 6A-6A
and 6B-6B, respectively, of the fabric of FIG. 4 showing typical
top and bottom CMD yarns (FIG. 6A) and stitching yarns (FIG.
6B).
[0020] FIG. 6C is a section view taken along lines 6C-6C of FIG. 4
showing typical top and bottom MD yarns.
[0021] FIG. 7 is a top view of the top layer of a repeat unit of a
fabric according to embodiments of the present invention.
[0022] FIG. 8 is a top view of the bottom layer of the fabric of
FIG. 7.
[0023] FIGS. 9A-9C are section views taken along lines 9A-9A, 9B-9B
and 9C-9C, respectively, of the fabric of FIG. 7 showing typical
stitching yarns and CMD yarns.
[0024] FIG. 10 is a top view of the top layer of a repeat unit of a
fabric according to additional embodiments of the present
invention.
[0025] FIG. 11 is a top view of the bottom layer of the fabric of
FIG. 10.
[0026] FIGS. 12A-12C are section views taken along lines 12A-12A,
12B-12B and 12C-12C, respectively, of the fabric of FIGS. 10 and 11
showing typical bottom MD yarns (FIG. 12A), stitching yarns (FIG.
12B) and top MD yarns (FIG. 12C).
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0027] The present invention will be described more particularly
hereinafter with reference to the accompanying drawings. The
invention is not intended to be limited to the illustrated
embodiments; rather, these embodiments are intended to fully and
completely disclose the invention to those skilled in this art. In
the drawings, like numbers refer to like elements throughout.
Thicknesses and dimensions of some components may be exaggerated
for clarity.
[0028] Well-known functions or constructions may not be described
in detail for brevity and/or clarity.
[0029] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein.
[0030] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof. As
used herein the expression "and/or" includes any and all
combinations of one or more of the associated listed items.
[0031] Although the figures below only show single repeat units of
the fabrics illustrated therein, those of skill in the art will
appreciate that in commercial applications the repeat units shown
in the figures would be repeated many times, in both the machine
and cross machine directions, to form a large fabric suitable for
use on a papermaking machine.
[0032] Turning now to FIGS. 1-3B, a repeat unit of a forming fabric
according to embodiments of the present invention, designated
broadly at 100, is illustrated therein. The repeat unit 100
includes eight MD stitching yarns 101-108, twenty top CMD yarns
111-130, four bottom MD yarns 141-144, and eight bottom CMD yarns
151-158. The interweaving of these yarns is described below.
[0033] As can be seen in FIGS. 1 and 3A, the MD stitching yarns
101-108 are disposed in pairs, wherein each pair together
interweaves with the top CMD yarns 111-130 in an "over 1/under 1"
sequence. For example, as can be seen in FIGS. 1 and 3A, MD
stitching yarn 101 follows an "over 1/under 1" pattern relative to
the top CMD yarns to form five consecutive MD knuckles (passing
over even-numbered top CMD yarns 116, 118, 120, 122, 124 and below
odd-numbered top CMD yarns 117, 119, 121, 123). MD stitching yarn
101 passes below the remaining top CMD yarns. Paired stitching yarn
102 follows an "over 1/under 1" pattern relative to the top CMD
yarns to form five consecutive MD knuckles (passing over
even-numbered top CMD yarns 126, 128, 130, 112, 114 and below top
odd-numbered CMD yarns 127, 129, 101, 103). MD stitching yarn 102
passes below the remaining top CMD yarns. Thus, together the
stitching yarns 101, 102 pass above all of the even-numbered top
CMD yarns and below the odd-numbered top CMD yarns. The remaining
MD stitching yarn pairs (i.e., MD stitching yarns 103, 104, MD
stitching yarns 105, 106, and MD stitching yarns 107, 108) follow a
similar "over 1/under 1" sequence with the top C MD yarns, with the
result that the MD stitching yarns and the top CMD yarns form a
plain weave top, or papermaking, surface.
[0034] Turning now to FIG. 2 and also to FIG. 3A, the MD stitching
yarns 101-108 also interweave with the bottom CMD yarns 151-158.
Each of the MD stitching yarns 101-108 passes below one bottom CMD
yarn, with the MD stitching yarns of each pair together forming
"over 3/under 1" pattern. For example, and referring to FIG. 3B. MD
stitching yarn 101 passes under bottom CMD yarn 151 and over the
remaining bottom CMD yarns. MD stitching yarn 102 passes under
bottom CMD yarn 155, thus forming the "over 3/under 1" sequence
with the bottom CMD yarns noted above. The remaining MD stitching
yarn pairs similarly form an "over 3/under 1" sequence with the
bottom CMD yarns. Each pair of stitching yarns weaves between two
adjacent bottom MD yarns.
[0035] Referring again to FIG. 2 and also to FIG. 3B, the bottom MD
yarns 141-144 interweave with the bottom CMD yarns in an "under
3/over 1" sequence that repeats twice within the repeat unit. For
example, bottom MD yarn 141 passes below bottom CMD yarns 151-153,
above bottom CMD yarn 154, below bottom CMD yarns 155-157, and
above bottom CMD yarn 158. The other bottom MD yarns 142-144 follow
a similar "under 3/over 1" pattern relative to the bottom CMD
yarns. The result is a series of bottom, or machine, side MD floats
formed by the bottom MD yarns that pass below three bottom CMD
yarns.
[0036] Notably, the MD stitching yarns 101-108 each stitch
underneath the bottom CMD yarns in a location where they can be
protected by two adjacent bottom MD yarn floats. For example. MD
stitching yarns 101, 102 stitch below, respectively, bottom CMD
yarns 151, 155. Adjacent bottom MD yarns 141, 144 pass below both
of these bottom CMD yarns. As such, the bottom MD floats formed by
the bottom MD yarns 141, 144 can protect the MD stitching yarns
from wear, which can increase the life of the fabric 100.
[0037] In addition, it is believed that the presence of the long MD
floats (i.e., floats that pass below three or more bottom MD yarns)
may reduce drag of the fabric on the paper machine. In many
embodiments, the bottom MD yarns comprise monofilament yarns, which
tend to have considerable molecular alignment in the axial
direction (induced during an extrusion process). In MD yarns, this
alignment is substantially parallel with the machine direction.
This molecular alignment may reduce drag of the fabric and the
power requirement on the paper machine. The MD float and the
molecular alignment within the floats may together reduce the wear
rate of the fabric on the paper machine.
[0038] The materials for an exemplary embodiment of the fabric 100
are described in Table 1, with weaving and performance
characteristics of the fabric shown in Table 2.
TABLE-US-00001 TABLE 1 Yarn Type Material Size (mm) MD Stitching
PET 0.15-01.8 Bottom MD PET 0.32-0.36 Top CMD PET 0.16-0.22 Bottom
CMD PET 0.36-0.48
TABLE-US-00002 TABLE 2 Top Mesh (per in.) 38 .times. 76
Permeability (cfm) 593 Top Open Area (%) 34.9 Fiber Support Index
127
[0039] It can also be seen from Table 1 that, in some embodiments,
the MD stitching yarns are of smaller diameter than the bottom MD
yarns (a ratio of top MD yarn diameter to bottom MD yarn diameter
of between about 0.4 and 0.7 is typical). The use of finer MD
stitching yarns can improve the papermaking surface, whereas the
use of larger bottom MD yarns can improve wear.
[0040] The concept can also be applied to fabrics that have CMD
stitching. For example, turning now to FIGS. 4-6C, a repeat unit of
another fabric, designated broadly at 200, is illustrated therein.
The repeat unit 200 includes ten top MD yarns 201-210, ten top CMD
yarns 211-220, ten pairs of CMD stitching yarns 221a, 221b-230a,
230b, ten bottom MD yarns 231-240, and ten bottom CMD yarns
241-250. The interweaving of these yarns is described below.
[0041] As seen in FIG. 4, the top MD yarns 201-210 and the top CMD
yarns 211-220 are interwoven such that each top CMD yarn passes
over and beneath top MD yarns in an alternating fashion, with each
top CMD yarn passing over and under the same top MD yarns. For
example, as shown in FIGS. 4 and 6A, top CMD yarn 211 passes under
odd-numbered top MD yarns 201-209 and over even-numbered top MD
yarns 202-210.
[0042] Still referring to FIG. 4 and also to FIG. 6B, the top layer
of the fabric 200 also includes portions of the CMD stitching yarns
221a-230b, which are positioned in pairs between adjacent top and
bottom CMD yarns; there is no bottom CMD yarn below each stitching
yarn pair so that space is present for the stitching yarns to
stitch. Portions of the stitching yarns 221a-230b interweave with
the top MD yarns 201-210 to form, together with the top CMD yarns
211-220, a plain weave pattern in the top surface of the fabric
200. In the illustrated embodiment, a portion of the stitching yarn
of each pair designated with an "a" (e.g., 221a, 222a, etc.)
interweaves in an alternating fashion with five top MD yarns
(alternately passing over three top MD yarns and under two top MD
yarns), and the other stitching yarn of the pair (those designated
with a "b") passes over two top MD yarns while passing below a top
MD yarn positioned between those two top MD yarns. Thus, together
the stitching yarns of a pair pass over each of the odd-numbered
top MD yarns 201-209 and pass below each of the even-numbered top
MD yarns 202-210 to form an "over 1/under 1" sequence with the top
MD yarns. This arrangement can be seen in FIGS. 4 and 6B, which
shows stitching yarn 211a passing over top CMD yarns 205, 207 and
209 and below top CMD yarns 206 and 208, and further shows
stitching yarn 211b passing over top MD yarns 201 and 203 while
passing under top CMD yarn 202. The other stitching yarns follow a
similar pattern, with adjacent stitching yarn pairs being offset
from each other by two top MD yarns. The result is the
aforementioned plain weave surface.
[0043] Referring now to FIGS. 5 and 6C, the bottom layer of the
repeat unit of the fabric 200 is illustrated therein. Each of the
bottom MD and CMD yarns is positioned substantially directly below
a corresponding top MD or CMD yarn. The bottom MD yarns are
interwoven with the bottom CMD yarns in an "under 4/over 1" pattern
that is repeated twice within the repeat unit. For example, as
shown in FIG. 6C, bottom MD yarn 231 passes below bottom CMD yarns
244-247, above bottom CMD yarn 248, below bottom CMD yarns 249,
250, 241, 242 and above bottom CMD yarn 243. The other bottom MD
yarns follow a similar "over 4/under 1/over 4/under 1" weave
pattern, but are offset from their adjacent bottom MD yarns by two
bottom CMD yarns. The long bottom MD floats formed by the bottom MD
yarns can impart reduced drag and, consequently, improved wear
resistance in the manner discussed above with respect to the fabric
100 shown in FIGS. 1-3B.
[0044] In addition, each of the stitching yarns 221a-230b passes
below one of the bottom MD yarns to form a bottom knuckle, with the
bottom knuckles of the stitching yarns of a pair being separated by
five bottom MD yarns. For example, and as shown in FIG. 6B,
stitching yarn 221a passes below bottom MD yarn 232, and stitching
yarn 221b passes below bottom MD yarn 237. As is the case with the
portions of the stitching yarns that interweave with the top MD
yarns, the portions of the stitching yarns that interweave with the
bottom MD yarns are also separated from each other by two bottom MD
yarns.
[0045] Notably, the stitching points of the stitching yarns are
located immediately adjacent the bottom knuckles formed by the
bottom CMD yarns as they pass below a bottom MD yarn. For example,
as best seen in FIGS. 5, 6A and 6B, both stitching yarn 211a and
immediately adjacent bottom CMD yarn 241 pass below bottom MD yarn
232, and both stitching yarn 221b and bottom CMD yarn 241 pass
below bottom MD yarn 237. As such, the stitching yarns are
protected from wear by the presence of the bottom CMD knuckle
formed by the adjacent bottom CMD yarn.
[0046] It can also be seen in FIGS. 4 and 5 that the stitching
yarns are interwoven with the top and bottom MD yarns as "reversed
picks." This concept is described in detail in U.S. Pat. No.
5,967,195 to Ward and need not be discussed further herein. Those
skilled in this art will appreciate that, although the illustrated
reversed picks configuration is preferred, the present invention
may also be employed with non-reversed picks fabrics.
[0047] As another example of a CMD-stitched fabric, a repeat unit
of another fabric, designated broadly at 300, is illustrated in
FIGS. 7-9C. The repeat unit 300 includes four top MD yarns 301-304,
four top CMD yarns 311-314, four pairs of CMD stitching yarns 321,
321b-324a, 324b, and four bottom MD yarns 331-334. The interweaving
of these yarns is discussed in greater detail below.
[0048] Looking first at FIGS. 7 and 9C, the top MD yarns and top
CMD yarns interweave such that the top CMD yarns 311-314 pass under
each of the odd-numbered top MD yarns 301, 303 and over each of the
even-numbered top MD yarns 302, 304. For example, as shown in FIGS.
7 and 9C, top CMD yarn 311 passes under odd-numbered top MD yarns
301, 303 and over even-numbered top MD yarns 302, 304 to form an
"over 1/under 1" pattern. The remaining top CMD yarns follow a
similar pattern with respect to the top MD yarns.
[0049] Turning now to FIGS. 7, 9A and 9B, the stitching yarn pairs
321a, 321b-324a, 324b interweave with the top MD yarns such that
one of the stitching yarns (the yarns with an "a" designation)
passes over one of the odd-numbered top MD yarns and under the
other top MD yarns. For example, as shown in FIG. 9A, the stitching
yarn 321a passes over the top MD yarn 303 and under the other top
MD yarns. The stitching yarn of a pair with a "b" designation
passes over the odd-numbered stitching yarn in the repeat unit that
the "a" yarn does not; for example, the stitching yarn 321b passes
over top MD yarn 301 and under the remaining top MD yarns (FIG.
9B). Thus, together the stitching yarns 321a, 321b follow an "over
1/under 1" sequence with respect to the top MD yarns. As such, the
top MD yarns, the top CMD yarns, and the stitching yarns combine to
form a plain weave papermaking surface.
[0050] Referring now to FIGS. 8, 9A and 9B, each of the "b"
stitching yarns passes below one of the bottom MD yarns 331-334;
however, the "a" stitching yarns do not (i.e., they are so-called
"phantom" stitching yarns). For example, stitching yarn 321a does
not pass below any of the bottom MD yarns, but stitching yarn 321b
passes below bottom MD yarn 332 (see FIGS. 9A and 9B). The
remaining stitching yarn pairs follow a similar pattern. The result
is that each of the bottom MD yarns 331-334 forms an "under 3/over
1" pattern with the "b" stitching yarns, with the result that the
bottom MD yarns form long MD floats (in this case, floats that are
three CMD yarns in length) on the bottom surface of the fabric (see
FIG. 8).
[0051] It should also be noted in FIGS. 9A-9C that the bottom MD
yarns are staggered relative to the top MD yarns; in other words,
the bottom MD yarns are not positioned directly beneath the top MD
yarns, but are positioned directly below the space between adjacent
top MD yarns.
[0052] Another example of a fabric that is MD-stitched is shown in
FIGS. 10-12C, wherein a repeat unit of another forming fabric
according to embodiments of the present invention, designated
broadly at 400, is illustrated. The repeat unit 400 includes four
top MD yarns 401-404, eight MD stitching MD yarns 411a, 411b-414a,
414b, thirty top CMD yarns 421-450, and twelve bottom MD yarns
451-462, and twelve bottom C MD yarns 471-482. The interweaving of
these yarns is described below.
[0053] As can be seen in FIGS. 10 and 12C, each of the top MD yarns
401-404 interweaves with the top CMD yarns 421-450 in an "over
1/under 1" sequence, in which the top MD yarns 401-404 pass under
the odd-numbered top CMD yarns 421-449 and over the even-numbered
top CMD yarns 422-450. As an example, and as shown in FIG. 12C, top
MD yarn 401 passes over even-numbered top CMD yarns 422-450 and
under odd-numbered top CMD yarns 421-449. This pattern is repeated
for the remainder of the top MD yarns 402-404.
[0054] Referring now to FIGS. 10 and 12B, the MD stitching yarns
411a, 411b-414a, 414b are disposed in pairs, wherein each pair
together interweaves with the top CMD yarns 421-450 in an "over
1/under 1" sequence. For example, as can be seen in FIGS. 10 and
12B, MD stitching yarn 411a follows an "over 1/under 1" pattern
relative to the top CMD yarns to form seven consecutive MD knuckles
(passing over odd-numbered top CMD yarns 421-433 and below
even-numbered top CMD yarns 422-432). MD stitching yarn 411a passes
below the remaining top CMD yarns 434-450. Paired stitching yarn
411b follows an "over 1/under 1" pattern relative to the top CMD
yarns to form eight consecutive MD knuckles (passing over
odd-numbered top CMD yarns 435-449) and below even-numbered top CMD
yarns 436-448). MD stitching yarn 411b passes below the remaining
top CMD yarns. Thus together the MD stitching yarns 411a, 411b
follow an "over 1/under 1" pattern relative to the top CMD yarns.
The remaining MD stitching yarn pairs (i.e., MD stitching yarns
412a, 412b, MD stitching yarns 413a, 413b, and MD stitching yarns
414a, 414b) follow a similar "over 1/under 1" sequence with the top
CMD yarns. As a result, the top MD yarns, top CMD yarns, and
stitching yarns combine to form a plain weave surface.
[0055] Turning now to FIG. 11 and also to FIG. 12, the MD stitching
yarns 411a-414b also interweave with the bottom CMD yarns 471-482.
Each of the MD stitching yarns 411a-414b passes below one bottom
CMD yarn, with the MD stitching yarns of each pair together forming
"over 5/under 1" pattern. For example, and referring to FIG. 12B,
MD stitching yarn 411a passes under bottom CMD yarn 479 and over
the remaining bottom CMD yarns. MD stitching yarn 411b passes under
bottom CMD yarn 473, thus combining with MD stitching yarn 411a to
form the "over 5/under 1" sequence with the bottom CMD yarns noted
above. The remaining MD stitching yarn pairs similarly form an
"over 5/under 1" sequence with the bottom CMD yarns.
[0056] Referring again to FIG. 11 and also to FIG. 12A, the bottom
MD yarns 451-462 interweave with the bottom CMD yarns in an "under
5/over 1" sequence that repeats twice within the repeat unit. For
example, bottom MD yarn 451 passes below bottom CMD yarns 471-475,
above bottom CMD yarn 476, below bottom CMD yarns 477-481, and
above bottom CMD yarn 482. The other bottom MD yarns 452-462 follow
a similar "under 5/over 1" pattern relative to the bottom CMD
yarns. Thus, the bottom MD yarns form long MD floats (in this
instance under five bottom CMD yarns) that may have the same drag
reduction and wear resistance discussed above.
[0057] Also, each of the stitching locations is positioned under a
bottom CMD yarn that the adjacent bottom MD yarns do not pass
under. As such, the stitching locations can be protected as
described above.
[0058] The form of the yarns utilized in fabrics of the present
invention can vary, depending upon the desired properties of the
final papermaker's fabric. For example, the yarns may be
monofilament yarns, flattened monofilament yarns as described
above, multifilament yarns, twisted multifilament or monofilament
yarns, spun yarns, or any combination thereof. Also, the materials
comprising yarns employed in the fabric of the present invention
may be those commonly used in papermaker's fabric. For example, the
yarns may be formed of polyester, polyamide (nylon), polypropylene,
aramid, or the like. The skilled artisan should select a yarn
material according to the particular application of the final
fabric. In particular, round monofilament yarns formed of polyester
or polyamide may be suitable, and, as noted, the use of
monofilament yarns as bottom MD yarns may be particularly
suitable.
[0059] Those skilled in this art will appreciate that yarns of
different sizes may be employed in fabric embodiments of the
present invention. As noted above, in embodiments that include both
top and bottom MD yarns, the top MD yarns may be of a smaller
diameter than the bottom MD yarns. For example, the top MD yarns,
top CMD yarns, and stitching yarns may have a diameter of between
about 0.0 and 0.20 mm, the bottom MD yarns may have a diameter of
between about 0.15 and 0.25 mm, and the bottom CMD yarns may have a
diameter of between about 0.20 and 0.30 mm. The mesh of fabrics
according to embodiments of the present invention may also vary.
For example, the mesh of the top surface may vary between about
20.times.30 to 30.times.50 (epcm to ppcm), and the total mesh may
vary between about 60.times.45 to 90.times.75.
[0060] In addition, the numbers of different types of yarns
relative to other types of yarns may vary. For example, in some of
the embodiments shown, the ratio of top MD yarns to bottom MD yarns
is 1:1; in others, the ratio of "effective" top MD yarns (i.e., the
number of top MD yarns plus the number of MD stitching yarn pairs)
to bottom MD yarns is 1:1 or 2:3, but other ratios may also be
employed. In some embodiments, the number of top CMD yarns to
bottom CMD yarns is 1:1; in others, the number of "effective" top
CMD yarns (i.e., the number of top CMD yarns plus the number of CMD
stitching yarn pairs) is 2:1; and in other embodiments, the ratio
of top CMD yarns to bottom CMD yarns is 5:2; however, other ratios
may also be employed.
[0061] Finally, although each of the embodiments include a plain
weave top surface, other embodiments may include a top surface
having a different weave pattern, including twill, satin, or the
like. In addition, the long MD float bottom surfaces of the fabrics
may take other weave patterns, including satin, twill or the
like.
[0062] Pursuant to another aspect of the present invention, methods
of making paper are provided. Pursuant to these methods, one of the
exemplary papermaker's forming fabrics described herein is
provided, and paper is then made by applying paper stock to the
forming fabric and by then removing moisture from the paper stock.
As the details of how the paper stock is applied to the forming
fabric and how moisture is removed from the paper stock is well
understood by those of skill in the art, additional details
regarding this aspect of the present invention need not be provided
herein.
[0063] The foregoing embodiments are illustrative of the present
invention, and are not to be construed as limiting thereof.
Although exemplary embodiments of this invention have been
described, those skilled in the art will readily appreciate that
many modifications are possible in the exemplary embodiments
without materially departing from the novel teachings and
advantages of this invention. Accordingly, all such modifications
are intended to be included within the scope of this invention as
defined in the claims. The invention is defined by the following
claims, with equivalents of the claims to be included therein.
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