U.S. patent application number 10/547034 was filed with the patent office on 2006-10-19 for composite forming fabric.
Invention is credited to Stewart Lister Hay.
Application Number | 20060231154 10/547034 |
Document ID | / |
Family ID | 37107322 |
Filed Date | 2006-10-19 |
United States Patent
Application |
20060231154 |
Kind Code |
A1 |
Hay; Stewart Lister |
October 19, 2006 |
Composite forming fabric
Abstract
A composite forming fabric comprising a paper side layer having
a paper side surface, a machine side layer having a bottom wear
side surface, and a plurality of pairs of first and second
interchanging yarns, wherein: the paper side layer and the machine
side layer each comprise warp yarns and weft yarns woven together;
said paper side layer and said machine side layer each having a
predetermined repeat of the weave pattern in the
cross-machine-direction; each pair of first and second
interchanging yarns having at least two segments in the paper side
layer within each repeat of the weave pattern, said segments
providing an unbroken weft path in the paper side surface, with
each succeeding segment being separated in the paper side surface
of the paper side layer by at least one paper side layer
transitional warp yarn; at least one pair of first and second
interchanging yarns within each repeat of the weave pattern being
binder yarn pairs, each binder yarn in each binder yarn pair
binding together the paper side layer and the machine side layer,
and at least one pair of first and second interchanging within each
repeat of the weave pattern being top weft/binder yarn pairs for
stiffening the fabric and binding together the paper side layer and
the machine side layer of the fabric.
Inventors: |
Hay; Stewart Lister;
(Lancashire, JP) |
Correspondence
Address: |
VOITH FABRICS
3040 BLACK CREEK ROAD
P.O. BOX 1411
WILSON
NC
27893
US
|
Family ID: |
37107322 |
Appl. No.: |
10/547034 |
Filed: |
February 27, 2004 |
PCT Filed: |
February 27, 2004 |
PCT NO: |
PCT/EP04/50218 |
371 Date: |
June 21, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60451780 |
Mar 3, 2003 |
|
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Current U.S.
Class: |
139/383A |
Current CPC
Class: |
D21F 1/0045
20130101 |
Class at
Publication: |
139/383.00A |
International
Class: |
D03D 25/00 20060101
D03D025/00 |
Claims
1. A composite forming fabric comprising a paper side layer having
a paper side surface, a machine side layer having a bottom wear
side surface, and a plurality of pairs of first and second
interchanging yarns, wherein: the paper side layer and the machine
side layer each comprise warp yarns and weft yarns woven together;
said paper side layer and said machine side layer each having a
predetermined repeat of the weave pattern in the
cross-machine-direction; each pair of first and second
interchanging yarns having at least two segments in the paper side
layer within each repeat of the weave pattern, said segments
providing an unbroken weft path in the paper side surface, with
each succeeding segment being separated in the paper side surface
of the paper side layer by at least one paper side layer
transitional warp yarn; at least one pair of first and second
interchanging yarns within each repeat of the weave pattern being
binder yarn pairs, each binder yarn in each binder yarn pair
binding together the paper side layer and the machine side layer,
and at least one pair of first and second interchanging yarns
within each repeat of the weave pattern being top weft/binder yarn
pairs for stiffening the fabric and binding together the paper side
layer and the machine side layer of the fabric.
2. The composite forming fabric of claim 1, wherein at least 50% of
the interchanging yarn pairs are binder yarn pairs.
3. The composite forming fabric of claim 1, wherein at least 50% of
the interchanging yarn pairs are top weft/binder yarns pairs.
4. The composite forming fabric of claim 1, wherein at least one
pair of first and second interchanging yarns is a weft yarn/weft
yarn pair.
5. The composite forming fabric of claim 1, wherein a plurality of
pairs of first and second interchanging yarns is weft yarn/weft
yarn pairs.
6. The composite forming fabric of claim 2, wherein at least one
pair of first and second interchanging yarns is a weft yarn/weft
yarn pair.
7. The composite forming fabric of claim 2, wherein a plurality of
pairs of first and second interchanging yarns is weft yarn/weft
yarn pairs.
8. The composite forming fabric of claim 3, wherein at least one
pair of first and second interchanging yarns is a weft yarn/weft
yarn pair.
9. The composite forming fabric of claim 3, wherein a plurality of
pairs of first and second interchanging yarns is weft yarn/weft
yarn pairs.
10. The composite forming fabric of claim 1, wherein at least one
of said at least two segments of at least one pair of first and
second interchanging yarns has a different length than at least one
other segment of said at least two segments of said at least one
pair of first and second interchanging yarns.
11. The composite forming fabric of claim 1, wherein at least one
of said at least two segments of each pair of first and second
interchanging yarns has a different length that at least one other
segment of said at least two segments of each pair of first and
second interchanging yarns.
12. The composite forming fabric of claim 1, wherein at least some
of the binder yarns in the pairs of first and second interchanging
yarns float under at least two wear side machine direction yarns in
a region underlying at least one of said at least two segments.
13. The composite forming fabric of claim 12, wherein said at least
two wear side machine direction yarns are adjacent to each
other.
14. The composite forming fabric of claim 12, wherein said at least
two wear side machine direction yarns are spaced apart by at least
one wear side machine direction yarn.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to fabrics with paired,
interchanging yarns, and more particularly, to fabrics employed in
web forming equipment, such as papermaking and non-woven web
forming equipment. More particularly, the preferred fabrics of this
invention are employed as forming fabrics in web forming
equipment.
BACKGROUND OF THE INVENTION
[0002] Papermaking involves the forming, pressing and drying of
cellulosic fiber sheets. The forming process includes the step of
depositing an aqueous stock solution of the fibers, and possibly
other additives, onto the forming fabric upon which the initial
paper web is formed. The forming fabric may run on a so-called Gap
Former machine in which the aqueous stock initially is dewatered,
and the initial paper sheet is formed between two forming
fabrics.
[0003] An effective forming process typically produces a sheet with
a very regular distribution of fibers and with a relatively high
solids content, i.e., a high fiber-to-water weight ratio. In order
to form a fibrous web with a desired uniform, regular distribution
and high fiber-to-water weight ratio, the forming fabric must
possess a number of properties. First, the papermaking surface
should be relatively planar; resulting from the yarn floats in both
the machine direction (MD) and cross-machine-direction (CD) lying
at substantially the same height, to thereby prevent localized
penetration of the fibers into the fabric. Such localized
penetration results in "wire marks" which actually is the result of
fiber density variations throughout the sheet area. In addition,
the MD and CD floats need to be distributed in a regular manner to
avoid introducing undesired wire marks into the formed sheet.
Moreover, these basis weight variations can result in undesired
variations in sheet absorption properties; a property very relevant
to the functionality of quality graphical papers where a consistent
uptake of print ink is necessary to produce a clear sharp
image.
[0004] Other factors also cause the formation of undesired wire
marks. For example, wire marks can be introduced into the sheet by
the flow of water around yarns positioned below the fabric's
papermaking surface. This phenomena, referred to as "strike
through" needs to be taken into account in designing the fabric
construction.
[0005] Importantly, the forming fabric must also possess a high
degree of dimensional stability. This high stability is necessary,
for example, to minimize cyclic variations in fabric width, which
can result in MD wrinkles in the fabric. This, in turn, contributes
to the so-called, streaky sheet, i.e., a sheet with machine
direction streaks created by variations in fiber density.
[0006] Dimensional stability of a fabric typically is obtained by
manufacturing the forming fabric with a relatively high mass of
material. However, the use of thick yarns often causes undesirable
wire marks. Consequently, there has been a trend to providing
composite forming fabrics, that is, "multi-layer" structures,
whereby a high number of relatively thin yarns are distributed
throughout various fabrics layers to facilitate fabric
stability.
[0007] One type of mufti-layer structure is a triple-layer fabric
made by joining two (2) distinct fabrics, each with their own
machine direction (warp) yarns and cross-direction (weft) yarns, by
the use of additional and independent "binding yarns." These
binding yarns can be employed in either the machine direction or
cross-machine-direction, and in this system provide the sole
function of binding the two separate fabrics together. In other
words, these binding yarns are not intended to function as part of
the warp or weft yarn system in either the top fabric or the bottom
fabric of the multi-layer structure. Such a triple-layer fabric is
illustrated in EP 0,269,070 (JWI Ltd.).
[0008] Where the two fabrics of the triple-layer structure are
joined in either the machine direction of cross-machine-direction
by binding yarns that also belong, or form part of the weave
pattern of either, or both, of the paper side or wear side fabrics,
the resulting structures are referred to more specifically as
"self-stitched" triple-layer structures. Such binding yarns are
referred to as intrinsic binding yarns. Self-stitched structures
are taught in a number of prior art patents. For example, U.S. Pat.
No. 4,501,303 (Nordiskafilt A B) discloses a triple-layer structure
wherein paper side yarns are used to bind the paper side and wear
side fabrics into one structure.
[0009] Triple-layer structures, whether employing separate and
distinct binding yarns or intrinsic binding yarns that form part of
the paper side and/or wear side weave structure, allow, to some
extent, for the use of fine machine direction and
cross-machine-direction yarns in the paper side fabric layer for
improved papermaking quality and sheet release. Additionally, the
use of significantly coarser yarns can be employed in the lower
fabric layer, or wear side fabric layer, which contacts the paper
machine elements, to thereby provide good stability and fabric
life. Thus, these triple-layer structures have the capability of
providing optimum papermaking properties in the paper side fabric
layer and optimum mechanical properties in the wear side fabric
layer.
[0010] In the triple-layer and self-stitched fabrics of the prior
art there is typically contact between the internal surfaces of the
paper side and wear side fabric layers. The internal surface of the
wear side fabric layer is dominated by floats of machine direction
yarns in all known commercial embodiments of the triple-layer and
self-stitched fabrics. Where wear side fabric cross-direction yarns
interlace with wear side fabric machine direction yarns, such that
the wear side cross-direction yarns appear in the internal region
between the paper side and wear side fabric layers, relatively
prominent short weft knuckles are formed. The pressure of
relatively stiff wear side machine direction yarns acting on the
wear side cross-direction yarns during the production of the fabric
can cause so-called "knuckle spread," whereby the wear side
cross-direction yarn knuckles are distorted and their width
increased to form a relatively large area. It has been found that
fibrous sheet areas formed on the paper side fabric above such
knuckles are noticeably different in appearance from adjacent sheet
areas. Such sheet differences can contribute to variations in the
quality of print imparted to the fibrous sheet in a subsequent
printing step.
[0011] A further common feature of the known self-stitched and
other triple-layer designs is that they are relatively thick
structures with a high amount of empty space distributed throughout
their thickness. The relatively high "void volume" is typically
associated with sheet rewetting on the paper machine such that the
sheet solids content at transfer to the press section may be
undesirably low. That is, the fibrous web formed on the papermaking
fabric has an undesirably low fiber-to-weight ratio. This can
result in reduced papermaking machine performance through a higher
amount of sheet breaks, reduced running speed and higher drying
costs downstream of initial web formation.
[0012] U.S. Pat. No. 4,636,426, discloses a relatively thin,
forming fabric with reduced rewetting potential. Specifically, this
forming fabric includes two adjacent, monofilaments strands of
conventional circular cross-section glued together using a
heat-activated polymeric adhesive. The joined cylindrical strands
are utilized in either or both of the machine and cross-direction
yarns of the fabric. The adhesive also is used to adhere the
machine direction and cross-direction yarns at their cross-over
points. By this means yarns of smaller than normal diameter can be
used to thereby reduce the overall height of the fabric. However,
fabrics formed in the above way have the disadvantage that an
additional gluing process is required which adds to the
manufacturing cost of the fabric. Moreover, the results may not be
permanent, in that the fabrics are susceptible to separation of the
joined (glued or fused) yarns. Additionally, the reduction in yarn
mass, compared with prior art structures of the type disclosed in
the U.S. Pat. No. 4,636,426, may result in reduced fabric
stability.
[0013] A variety of compromise fabrics employing intrinsic
interchanging yarn pairs have been disclosed to attempt to deal
with the various problems of fabric strength, fabric stability,
e.g., fabric stiffness, desired papermaling side performance and
desired wear side performance. In particular, various different
composite fabric constructions are disclosed in U.S. Pat. No.
4,501,303 (Osterbarg); U.S. Pat. No. 5,152,326 (Voehringer); U.S.
Pat. No. 5,826,627 (Seabrook, et al.); U.S. Pat. No. 5,967,195
(Ward) and International Publication WO 02/14601 A1 (Andreas
Kufferath GMBH&Co. KG).
[0014] Although the aforementioned composite papermaking fabrics
employing intrinsic interchanging yarn pairs have provided improved
structures, applicant believes that there still is a need for
additional, improved composite structures of the type employing
intrinsic interchanging yarn pairs having improved properties, such
as reduced sheet marking potential and/or longer service life
potential and/or higher resistance to layer delamination. It is to
such structures that the present invention is directed.
SUMMARY OF THE INVENTION
[0015] The above and other objects of this invention are obtained
in composite forming fabrics having a paper side layer with a paper
side surface, a machine side layer having a bottom wear side
surface and a plurality of pairs of first and second intrinsic
interchanging yarns. Reference throughout this application to
"intrinsic interchanging yarns" or "interchanging yarns" means
yarns that form a part of the weave structure in at least the paper
side layer of the composite fabric.
[0016] In accordance with a first preferred embodiment of this
invention, the paper side layer and the machine side layer each
comprise machine direction warp yarns and non-interchanging
cross-machine-direction weft yarns woven together; said paper side
layer and said machine side layer each having a weave pattern in
the cross-machine direction with a predetermined repeat; each pair
of first and second interchanging yarns having at least two (2)
segments in the paper side layer within each repeat of the weave
pattern, said segments providing an unbroken weft path in the paper
side surface, with each succeeding segment being separated in the
paper side surface of the paper side layer by at least one paper
side layer transitional warp yarn; at least one pair of first and
second interchanging yarns within each repeat of the weave pattern
being intrinsic top weft/binder yarn pairs for stiffening the
fabric and binding together the paper side layer and the machine
side layer of the fabric.
[0017] The transitional warp yarn defines the length of each
segment made in the paper side layer of the fabric by each
individual yarn of an interchanging yarn pair. Specifically, one
yarn of each pair forms a segment of the paper side weft path and
then drops out of the paper side surface adjacent one side of the
transitional warp yarn, while the other yarn of the pair moves into
the paper side layer adjacent the opposite side of the transitional
warp yarn to begin forming a second segment of the paper side weft
path.
[0018] "Intrinsic weft binder yarns" are weft yarns that are part
of the weave structure of the paper side surface of the paper side
layer and also serve to bind together the paper side layer and
machine side layer within each repeat of the weave pattern. Thus,
each intrinsic weft binder yarn of each pair of first and second
intrinsic weft binder yarns provides two functions within each
repeat of the weave pattern. One function is to contribute to the
weave structure of the paper side surface of the paper side layer,
and the second function is to bind together the paper side layer
and the machine side layer.
[0019] Each intrinsic weft binder yarn within each pair of
interchanging yarns forms the weft path in at least one segment of
the paper side layer within each repeat of the weave pattern, and
then disappears from the paper side surface at a transitional warp
yarn by dropping down to engage at least one warp yarn in the
machine side layer underlying another segment within each repeat of
the weave pattern to thereby bind the machine side layer to the
paper side layer. With respect to the intrinsic binder yarn pairs
employed in this embodiment of the invention, one yarn forms part
of the weft path in a segment of the paper side layer within each
repeat of the weave pattern that is not occupied by the other yarn
of the intrinsic weft binder yarn pair, and then drops down to
engage at least one warp yarn of the machine side layer in a region
underlying the other intrinsic weft binder yarn which is forming
another segment of the weft path of the paper side layer. In other
words, within each repeat of the weave pattern, each of the weft
binder yarns within each pair of intrinsic weft binder yarns
contributes to the weft path in the paper side surface in at least
one segment of the repeat and also drops down to engage at least
one machine direction yarn in the machine side layer in a region
underlying a different segment within said repeat of the weave
pattern.
[0020] In a composite fabric structure including two segments in
the paper side layer within each repeat of the weave pattern, one
of the intrinsic weft binder yarns within each pair of binder yarns
provides a weft path in the paper side surface in one segment while
the second intrinsic weft binder yarn of the pair engages at least
one machine direction warp yarn in the machine side layer
underlying said one segment, and said first intrinsic weft binder
yarn then moves out of the paper side layer and into the machine
side layer to engage at least one machine direction warp yarn of
the machine side layer in the second segment within each repeat of
the weave pattern and said second intrinsic weft binder yarn moves
up into the second segment of the paper side layer to continue the
weft path in the cross-machine-direction of the paper side fabric
layer.
[0021] Most preferably the segments in the paper side layer formed
by pairs of interchanging yarns within each repeat of the weave
pattern provide an unbroken weft path in the paper side surface,
with each succeeding segment being separated in the paper side
surface of the paper side layer by at least one paper side layer
transitional warp yarn. This latter arrangement of intrinsic binder
yarn pairs in a weave pattern having only two segments in the paper
side layer is disclosed in Seabrook et al., U.S. Pat. No.
5,826,627, the subject matter of which is herein fully incorporated
by reference. It should be understood that in the structures
disclosed in the Seabrook et al., '627 patent, all of the
interchanging weft yarn pairs are binder yarn pairs and the
disclosed papermaking fabrics include only two segments in the
paper side layer within each repeat of the weave pattern.
[0022] Reference throughout this application to "intrinsic top
weft/binder yarn pairs" means a pair of yarns wherein one yarn of
the pair; namely the binder yarn of the pair, forms the weft path
in the paper side surface of the paper side layer in at least one
segment of each repeat of the weave pattern and then drops down to
encircle at least one warp yarn in the machine side layer in a
region underlying at least another segment within each repeat of
the weave pattern in the paper side layer. The weft yarn of the
weft/binder yarn pair forms the weft path in a segment in the paper
side layer within each repeat of the weave pattern that is not
occupied by the binder yarn of the pair, and then drops our of the
paper side layer to float between the paper side layer and machine
side layer in one or more other segments within each repeat of the
weave pattern; without in any way binding the paper side layer to
the machine side layer. A "top weft/binder yarn pair" is
illustrated in FIG. 2(b) of International Publication No. WO
02/14601, the subject matter of which is incorporated herein by
reference.
[0023] In a preferred embodiment of this invention the fabric
includes a plurality of intrinsic interchanging binder yarn pairs
and a plurality of intrinsic, interchanging top weft/binder yarn
pairs. In a preferred embodiment of this invention at least 50% of
the interchanging yarn pairs are intrinsic interchanging top
weft/binder yarn pairs.
[0024] In one preferred embodiment of this invention alternate top
weft yarns are provided by interchanging yarn pairs; with alternate
pairs being binder yarn pairs and the other alternate pairs being
top weft/binder yarn pairs. Thus, in this preferred embodiment, 50%
of the top weft yarns are formed by interchanging yarn pairs, with
50% of such interchanging yarn pairs being binder yarn pairs and
the other 50% of such interchanging yarn pairs being intrinsic top
weft/binder yarn pairs.
[0025] In a further embodiment of this invention, the composite
fabric, in addition to including at least one pair of intrinsic,
interchanging binder yarn pairs and at least one pair of intrinsic
interchanging top weft/binder yarn pairs, also includes at least
one pair of intrinsic interchanging weft yarn/weft yarn pairs.
[0026] As used throughout this application, reference to "weft
yarn/weft yarn" in referring to a pair or pairs of yarn(s) refer(s)
to a pair of intrinsic interchanging yarns wherein each yarn forms
the cross direction weave path in alternate segments of the paper
side surface and then drops down to float between the paper side
layer and the machine side layer in the remaining segments within
the repeat, and then, after floating between the paper side layer
and machine side layer, moves back into the paper side layer to
provide a continuation of the weft path in the fabric. One yarn of
the weft yarn/weft yarn pair floats between the paper side layer
and the machine side layer in a region underlying the segment in
which the other weft yarn of the pair forms the weft path in the
paper side surface, and then moves up into the paper side surface
in an adjacent segment to form the weft path in that segment of the
paper side surface overlying the portion of the other waft yarn of
the pair that has moved out of the paper side layer to float
between the paper side layer and machine side layer in such
adjacent segment. Thus, in this embodiment the weft yarn/weft yarn
pair cooperates to provide a continuous unbroken weft path across
the paper side surface and also includes segments that float
between the paper side layer and the machine side layer to stiffen
the fabric. Neither yarn of the weft yarn/weft yarn pair cooperates
to bind the paper side layer and the machine side layer
together.
[0027] In accordance with this invention, segments within each
repeat of the weave pattern may have different lengths, if desired.
That is, one weft yarn of a pair of interchanging yarns interlaces
with a number of adjacent top warp yarns in one segment that is
different from the number of adjacent top warp yarns that interlace
with the other weft yarn of the pair in another segment within each
repeat of the weave pattern.
[0028] In one form of the invention, the paper side layer and the
machine layer together are woven in a predetermined number of sheds
to provide the repeat pattern of the composite fabric. For example,
a twenty (20) shed fabric includes ten (10) machine direction warp
yarns in the paper side layer and ten (10) machine direction warp
yarns in the machine side layer vertically underlying machine
direction warp yarns in the paper side layer.
[0029] In accordance with certain embodiments of the invention at
least some of the binder yarns in the pairs of first and second
intrinsic, interchanging yarns float under at least two adjacent
wear side machine direction yarns, and if desired, under at least
three adjacent wear side machine direction yarns to provide
enhanced binding of the paper side layer to the machine side
layer.
[0030] In addition, by floating the interchanging yarns under two
or more adjacent wear side machine direction yarns, the overall
height and void volume within the fabric is reduced. This reduces
the potential water carrying potential of the fabric; resulting in
the formation of a dryer sheet on the fabric.
[0031] In an alternative structure for providing a thin fabric with
minimal delamination tendency at least some of the binder yarns of
the interchanging binder yarn pairs interlace with a number of
single, non-adjacent wear side MD yarn within each repeat of the
weave pattern.
[0032] In all embodiments of the invention disclosed herein all or
some of the wear side and/or paper side warp yarns can be of a
non-circular cross section but particularly of bi-nodal (e.g.,
dumbbell--or "figure 8" shaped) cross-section. The bi-nodal yarn(s)
is (are) extruded with the bi-nodal cross section and thus
require(s) no bonding process of the type employed in the prior
art, where two adjacent, but separately-formed warp yarns have been
woven to an identical weave repeat. Use of bi-nodal warps, with a
vertical-to-horizontal aspect ratio of at least 1:1.25, allows a
thinner fabric to be provided but with the same overall cross
sectional area as prior art structures. This will reduce the water
carrying capacity of the fabric, thereby resulting in the formation
of a paper sheet with reduced moisture content in the forming
section, which, in turn, reduces production costs. Furthermore,
unlike the use of profiled and flat warp yarns employed in prior
art forming fabrics, the bi-nodal yarns employed in this invention
provide several benefits as follows: (1) each bi-nodal yarn
provides a drainage channel along the center thereof to effectively
direct water through the fabric; (2) the use of bi-nodal yarns
avoids the single large surface of the prior rectangular and ovate
yarns, which could directly or indirectly undesirably mark the
sheet; (3) when used as a wear side warp the bi-nodal yarn is less
likely to cause as severe a distortion of the interlacing weft yarn
knuckles as a yarn of similar cross-sectional area but of a
circular cross section to thereby potentially cause less
strikethrough marking of a paper sheet formed thereon and (4) when
used in the fabric paper side layer in the same number as prior
art, circular cross-section yarns the bi-nodal yarn will double the
MD orientated fiber support points of the fabric due to the two,
generally circular, dumbbell shaped ends forming part of each
bi-nodal yarn; thereby reducing, or minimizing the formation of
undesired wire-marks in the formed paper sheet.
[0033] In accordance with another aspect of this invention, the
binder position relative to the interlacings of the warp and weft
yarns in the wear side layer of the fabric can be selected to
facilitate a significant increase in fabric bending stiffness and
thus the ability of the fabric to control sheet basis weight
profiles in a desired manner.
[0034] The embodiments of the invention illustrated herein
typically have 2:1 ratio of paper side layer
cross-machine-direction weft paths to wear side
cross-machine-direction weft paths. However, it is within the scope
of this invention to provide different ratios of paper side layer
CD weft paths to wear side layer CD weft paths, such ratio being
dictated by the desired use of the fabric. For example, and not by
way of limitation, it is within the scope of this invention to
employ paper side layer to machine side layer CD weft path ratios
of 1:1, 3:2, 4:3, or another ratio.
[0035] Although the preferred embodiments of this invention include
non-interchanging weft yarns in the paper side layer, it is within
the scope of this invention to form the paper side layer with warp
yarns and only interchanging CD yarn pairs.
[0036] Although the preferred embodiments of the inventions employ
a paperside to wearside warp ratio of equal number, specifically
1:1, it is also envisaged that all embodiments can be manufactured
with a different warp ratio, e.g., 2:1 or 3:2.
[0037] Fabrics of the invention may be made on looms such as
Juergen's JP2000 or Jaeger's BK600, which have been fitted with a
suitably high shaft capacity, or may be made on looms which utilize
jacquard control over all or for some of the warp yarns.
[0038] A table showing preferred fabrics combinations and the
required shafts is shown below. It can be seen that there are
generally higher number of weave repeats when using the "high
shaft" technique. This provides a significant benefit by allowing
more randomness and flexibility in distributing binding points in
composite fabrics and in distributing interchange points of
interchanging yarn pairs employed in the fabric. In this way, a
fabric with a reduced tendency to form undesired wiremarks in the
formed paper sheet can be provided compared to the prior art.
TABLE-US-00001 No. of No. of Ratio No. of No. of Paperside No. of
Wearside PS:WS Loom Paperside Paperside Weave Wearside Wearside
Weave Weave Shaft Warps Weave Repeats Warps Weave Repeats Repeats
20 10 Plain(1/1) 5 10 4/1 2 2.50 Prior Art 24 12 Plain(1/1) 6 12
5/1 2 3.00 Prior Art 24 12 2/1 4 12 5/1 2 2.00 Prior Art 28 14
Plain(1/1) 7 14 6/1 2 3.50 28 14 Plain(1/1) 7 14 4/1/1/1 2 3.50 30
15 2/1 5 15 4/1 3 1.67 32 16 Plain(1/1) 8 16 3/1 4 2.00 32 16
Plain(1/1) 8 16 7/1 2 4.00 32 16 Plain(1/1) 8 16 5/1/1/1 2 4.00 36
18 Plain(1/1) 9 18 5/1 3 3.00 36 18 2/1 6 18 5/1 3 2.00 36 18
Plain(1/1) 9 18 8/1 2 4.50 36 18 2/1 6 18 8/1 2 3.00 40 20
Plain(1/1) 10 20 4/1 4 2.50 40 20 Plain(1/1) 10 20 7/1/1/1 2 5.00
40 20 2/2 5 20 9/1 2 2.50 42 21 2/1 7 21 6/1 3 2.33 48 24 1/1 12 24
7/1 3 4.00 48 24 2/1 8 24 7/1 3 2.67 48 24 2/1 8 24 5/1/1/1 3 2.67
56 28 1/1 14 28 6/1 4 3.50
[0039] It should be noted that in some of the identified high shaft
fabrics having 28 shafts or more the number of weave repeats in the
fabric cross-direction of the weft yarns with the warp yarns in the
paper side layer within the repeat pattern of the composite fabric
is greater than the number of weave repeats in the fabric
cross-direction of the weft yarns with the warp yarns in the
machine side layer within the repeat pattern of the composite
fabric by a ratio of more than 3:1. The benefits of this feature
will be described and claimed in a subsequently filed
application.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1, illustrates transverse sectional views between each
weft path in one repeat of a fabric in accordance with this
invention; and
[0041] FIG. 2, illustrates transverse sectional views between each
weft path in one repeat of a fabric in accordance with another
embodiment of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
[0042] The weft paths of the paper side, wear side and
interchanging yarn pairs for one preferred embodiment of a
composite forming fabric 10 in accordance with this invention are
shown in FIG. 1. In accordance with this embodiment, the composite
forming fabric has a 20 shaft-40 pick repeat and includes a paper
side layer 12 having a paper side surface 14, a machine side layer
16 having a bottom wear side surface 18 and a plurality of first
and second interchanging yarns pairs, e.g., 20.
[0043] The paper side layer 12 and the machine side layer 16 each
comprise a plurality of warp yarns 22 in the machine direction and
plurality of non-interchanging weft yarns 24 woven together with
the warp yarns. The paper side layer 12 and the machine side layer
16 each have a predetermined repeat of the weave pattern in the
cross-machine direction. As illustrated, but not by a way of
limitation, the illustrated composite fabric 10 is a twenty (20)
shed-forty (40) pick fabric including ten (10) machine direction
warp yarns 22 in the paper side layer, shown at 1, 3, 5, 7, 9, 11,
13, 15, 17 and 19, and ten (10) machine direction warp yarns 22 in
the machine side layer, show at 2, 4, 6, 8, 10, 12, 14, 16, 18 and
20. The non-interchanging weft yarns in the paper side layer 12 are
designated in FIG. 1 by the prefix "T" and the non-interchanging
weft yarns in the machine side layer 16 are designated in FIG. 1 by
the prefix "B."
[0044] As illustrated in FIG. 1, the first and second interchanging
yarns of each pair of interchanging yarns are designated with the
prefix "I"; a first pair being designated I1, I2; another pair
being designated I3, I4, and so on. Each pair of interchanging
yarns has two segments in the paper side layer within each repeat
of the weave pattern. These segments provide an unbroken weft path
in the paper side surface, with each succeeding segment being
separated in the paper side surface of the paper side layer by at
least one paper side layer transitional warp yarn 22T (e.g., top
warp yarns 5 and 13 are transitional warp yarns for interchanging
binder yarns I9, I10). The pairs of interchanging yarns 20 move out
of and into the paper side layer, respectively, on opposite sides
of each transitional warp yarn. As is shown in FIG. 1, the
interchanging yarns cross each other as they move in opposite
directions in a region generally underlying the transitional warp
yarns.
[0045] Still referring to FIG. 1, the fabric 10 of this invention
includes a first set of alternating pairs of first and second
interchanging yarns within each repeat of the weave pattern
constituting binder yarn pairs 26 for binding together the paper
side layer and machine side layer, i.e., I1-I2; I5-I6; I9-I10;
I13-I14 and I17-I18. The fabric 10 also includes a second,
alternating set of pairs of first and second interchanging yarns
within each repeat of the weave pattern constituting top
weft/binder yarn pairs 28 for stiffening the fabric and binding
together the paper side layer and the machine side layer of the
fabric. This second set of top weft/binder yarn pairs is shown at
I3-I4; I7-I8; I11-I12; I15-I16 and I19-I20.
[0046] In the embodiment illustrated in FIG. 1, the top weft yarn
in each of the top/weft binder yarn pairs floats between the paper
side layer 12 and the machine side layer 16 to provide a stiffening
function. In the embodiment illustrated in FIG. 1, the top weft
yarn of each of the top weft/binder yarn pairs actually floats
between five (5) sets of upper and lower warp yarns in the paper
side layer and machine side layer, respectively, e.g., the top weft
yarn in the top weft/binder yarn pair I3-I4 floats between adjacent
upper and lower warp yarns 13-14; 15-16; 17-18; 19-20 and 1-2.
Moreover, the binder yarn in each of the top weft/binder yarn pairs
forms two knuckles in the paper side layer segment within each
weave repeat, e.g., the binder yarn in the top weft/binder yarn
pair I3-I4 forms knuckles over top warp yarns 15 and 19; the binder
yarn in the top weft/binder yarn pair I7-I8 forms knuckles over top
warp yarns 3 and 7; etc. As will be illustrated and explained
below, both the float distance of the top weft yarn and the number
of formed knuckles of the binder yarn in the paper side layer in
top weft/binder yarn pairs can be varied within each repeat of the
weave pattern.
[0047] Although in a preferred embodiment of the invention the
binder yarn pairs and the weft/binder yarn pairs each constitute
50% of the interchanging yarn pairs in the fabric, in accordance
with the broadest aspects of the invention, the percentage of
interchanging yarn pairs provided by binder yarn pairs and top
weft/binder yarn pairs cam be varied.
[0048] Moreover, it should be apparent that alternate unbroken weft
paths are provided by the pairs of first and second interchanging
yarns, which alternate with non-interchanging, top weft yarns that
weave only with the warp yarns of the paper side layer. In other
words, in the embodiment illustrated in FIG. 1, 50% of the weft
yarn paths in the cross-machine direction of the paper side layer
are provided by interchanging pairs of yarns, and the other 50% are
provided by non-interchanging weft yarns that interweave solely
with the warp yarns of the paper side layer.
[0049] Although, in the preferred embodiment at least some of the
weft yarns in the paper side layer and in the machine side layer
are non-interchanging yarns, i.e., they are disposed only in the
paper side layer and the machine layer, respectively, in accordance
with the broadest aspect of this invention the number of such
non-interchanging weft yarns can be varied within wide limits.
Additionally, the percentage of binder yarn pairs and top
weft/binder yarn pairs also can be varied within wide limits and,
if desired, may form all of the weft paths in the paper side
layer.
[0050] In accordance with the preferred embodiment of the invention
illustrated in FIG. 1, adjacent weft paths in the paper side layer
are provided successively by a non-interchanging top weft yarn, a
pair of interchanging binder yarn pairs, a non-interchanging top
weft yarn and a pair of top weft/binder yarn pairs. These four weft
paths repeat continuously throughout the fabric structure. In this
latter arrangement, one-half of the weft yarn paths in the paper
side layer fabric are provided by non-interchanging weft yarns;
one-quarter of the weft yarn paths in the paper side layer are
provided by binder yarns pairs and the other one-quarter of the
weft yarn paths in the paper side layer are provided by weft/binder
yarn pairs.
[0051] It should be understood that the arrangement and percentage
of each of the different weft yarns in the paper side layer can be
varied within wide limits. In accordance with the broadest aspects
of this invention, within each repeat of the weave pattern there is
included at least one pair of first and second interchanging yarns
in the form of a binder yarn pair and at least one pair of first
and second interchanging yarns in the form of a top weft/binder
yarn pair.
[0052] In accordance with the preferred embodiment of the invention
illustrated in FIG. 1, 50% of the interchanging yarn pairs are
binder yarn pairs and 50% of the interchanging yarn pairs are top
weft/binder yarn pairs. However, it is within the scope of the
invention to include a greater percentage of interchanging binder
yarn pairs; thereby resulting in a reduction of the percentage of
pairs of top weft/binder yarn pairs and/or non-interchanging top
weft yarns. Alternatively, it is within the scope of this invention
to include more than 50% interchanging yarn pairs as top
weft/binder yarn pairs; resulting in a reduction in the percentage
of interchanging binder yarn pairs and/or non-interchanging top
weft yarns.
[0053] Referring to FIG. 2, an alternate embodiment of a fabric of
this invention is indicated at 100. The fabric 100 has a number of
features that are similar to the fabric 10. For example, the fabric
100, like the fabric 10 includes alternating, non-interchanging top
weft yarns and interchanging yarn pairs. Also, every other
interchanging yarn pair is a binder/binder pair and the other
alternate interchanging yarn pairs are top weft/binder yarn
pairs.
[0054] However, the fabric 100 has a 20 shaft-80 pick repeat,
unlike the 20 shaft-20 pick repeat of the FIG. 1 embodiment. The
increase in the pick repeat results from two variations in the
weave pattern of the top weft/binder yarn pairs in the FIG. 2
embodiment.
[0055] First, in the fabric 100, the top weft yarn in adjacent top
weft/binder yarn pairs float, respectively, between five (5) sets
of upper and lower warp yarns and seven (7) sets of upper and lower
warp yarns, e.g., the top weft yarn of the top weft yarn/binder
yarn pair I3-I4 floats between the five (5) sets of upper and lower
warp yarns 13-14, 15-16, 17-18, 19-20 and 1-2, and the top weft
yarn of the adjacent top weft yarn/binder yarn pair I7-I8 floats
between the seven (7) sets of upper and lower warp yarns 9-10,
11-12, 13-14, 15-16, 17-18, 19-20 and 1-2.
[0056] The second variation is that the binder yarn of adjacent top
weft/binder yarn pairs alternately forms two (2) paper side
knuckles and three (3) paper side knuckles within each repeat of
the weave pattern, e.g., the binder yarn in the top weft/binder
yarn pair I3-I4 forms two (2) knuckles over top warp yarns 15 and
19, and the binder yarn in the adjacent top weft/binder yarn pair
I7-I8 forms three (3) knuckles over top warp yarns 11, 15 and 19,
etc.
[0057] The above discussed two variations in the weave pattern of
the top weft/binder yarn pairs accompanied by the fact that
alternate top weft yarns are non-interchanging yarns and the
alternate interchanging yarn pairs are bind/binder yarn pairs
results in a repeat of the weave pattern every eighty (80)
picks.
[0058] It is within the scope of the embodiment of the invention
illustrated in FIG. 2 to make the same modifications as disclosed
for the fabric 10. That is, the percentage of non-interchanging
binder yarn pairs, the percentage of interchanging top weft/binder
yarn pairs and the percentage of interchanging binder yarn pairs
can be varied within wide limits. If desired the interchanging top
weft/binder yarn pairs and interchanging binder yarn pairs can form
all of the weft paths in the structure.
[0059] Applicant has determined that significant advantages may be
obtained in the fabrics 10 and 100 of this invention, as compared
to prior art structures in which all of the interchanging yarn
pairs are binder/binder pairs. In particular prior art structures
and the fabrics 10, 100 were formed with the warp and weft yarns
being of the same diameter and with the same number of warp and
weft paths per unit area. The prior art structures included
alternating weft paths formed by non-interchanging top weft yarns
having a diameter of 0.13 mm and by interchanging binder/binder
yarns with each yarn of the pair having a diameter of 0.13 mm. The
fabrics 10 and 100 included alternating weft paths formed by
non-interchanging top weft yarns having a diameter of 0.13 mm and
by interchanging yarn pairs with each yarn of the pair having a
diameter of 0.13 mm, wherein every other interchanging yarn pair
was a bind/binder yarn pair and a top weft/binder yarn pair,
respectively.
[0060] It was determined that the fabric 10 was approximately 17%
stiffer and the fabric 100 was approximately 19% stiffer than the
prior art structure.
[0061] It was determined that the fabrics 10 and 100 had a higher
air permeability (cubic feet per minute), a greater thickness, or
caliper (millimeters) and a higher void volume (cubic
centimeters/square meter) than the prior art structure.
[0062] Although a higher air permeability and greater void volume
may not be desirable, because of the possibility of greater water
retention in the fabric, it should be understood that these higher
permeability and void volume values were obtained in fabrics of
this invention having the same concentration of warp and weft yarns
as the prior art structure and with the warp and weft yarns having
the same diameter as the prior art structure, and also without a
significant reduction in fabric strength as compared to the prior
art structure. Therefore, improved resistance to undesired water
marks can be obtained in the fabrics of this invention by
increasing the concentration of top weft and/or top warp yarns, and
improvements in mechanical properties can be achieved by increasing
the diameter of the bottom warp and/or weft yarns, while also
achieving a reduction in air permeability and void volume to more
desirable levels. Alternatively, it is possible to reduce yarn
diameter in fabrics of the invention and still get identical CD
stiffness to fabrics of the prior art but with reduced
thickness.
[0063] In accordance with an additional embodiment of this
invention (not illustrated), a composite forming fabric has the
same construction as the forming fabric 10 or 100, with the
exception that one or more weft yarns, e.g., either
non-interchanging weft yarns, interchanging binder/binder weft yarn
pairs and/or interchanging top weft/binder yarn pairs, is (are)
replaced with a fourth type of weft yarn system; namely, an
intrinsic interchanging weft yarn/weft yarn pair. As explained
earlier in the summary of the invention, an intrinsic interchanging
weft yarn/weft yarn pair cooperates to provide a continuous weft
path in the top fabric layer within each repeat of the weave
pattern, just like the interchanging bind/binder yarn pairs and the
interchanging top weft/binder yarn pairs. However, the yarns of the
interchanging weft yarn/weft yarn pairs, when they drop out of the
top surface adjacent a top warp transitional yarn, float between
the top warp yarns and bottom warp yarns without binding to a
bottom warp yarn.
[0064] In one embodiment employing weft yarn/weft yarn pairs,
alternating weft paths in the paper side layer are provided by
non-interchanging weft yarns, and located between each pair of
these non-interchanging weft yarn paths is a binder yarn pair, a
top weft/binder yarn pair and a weft yarn/weft yarn pair,
respectively, in any desired order. As noted, in this embodiment
one half of the weft paths are provided by non-Interchanging top
weft yarns; one-third of the weft paths provided by interchanging
yarn pairs are provided by top weft/binder yarn pairs, one-third of
the weft paths provided by interchanging yarn pairs are provided by
weft yarn/binder yarn pairs and one-third of the weft paths
provided by interchanging yarn pairs are provided by weft yarn/weft
yarn pairs. However, in accordance with the broadest aspect of this
invention, the percentages of each of the different types of
interchanging yarn pairs can be varied within wide limits. In fact,
in accordance with certain aspects of this invention, the composite
forming fabric can include a single pair of first and second
interchanging yarns in the form of weft yarn/weft yarn pairs, with
the remaining interchanging yarn pairs being binder yarn pairs
and/or weft/binder yarn pairs. Moreover, interchanging yarn pairs
of the same or different type can be included adjacent to each
other, in which case at least some of the adjacent
non-interchanging top weft yarns will be spaced apart from each
other by more than one interchanging yarn pair.
[0065] Embodiments of the invention including non-interchanging top
weft yarns in the paper side layer; binder yarn pairs having
segments in the paper side layer providing an unbroken weft path
within each repeat of the weave pattern; top weft/top weft yarn
pairs providing an unbroken weft path within each repeat of the
weave pattern and weft yarn/binder yarn pairs providing an unbroken
weft path with each repeat of the weave pattern have been described
earlier herein. Suffice it to state that the form of the fabrics of
this invention can include a combination of each of the four types
of cross-machine direction weft yarns in the paper side layer. By
varying the structure of the top weft path in the paper side layer
to include different types of interchanging yarns and
non-interchanging yarns, the overall properties of the forming
fabric can be varied within wide limits, as dictated by the
particular application of the fabric.
[0066] As should be noted in the fabrics 10 and 100, segments of
one or more pairs of interchanging yarns can be of a different
length within each repeat of the weave pattern. In accordance with
the broadest aspects of this invention, the paper side segments
provided by either all or some of the interchanging yarn pairs;
whether such interchanging yarn pairs are binder yarn pairs, weft
yarn/binder yarn pairs and/or weft yarn/weft yarn pairs, can be of
different lengths.
[0067] In fabrics of the invention in which the yarns of each
interchanging yarn pair provide segments of different length within
each repeat of the weave pattern it is possible to vary the
sequence in which the pair of yarns are placed in the fabric. For
example, in a first pair of interchanging yarn pairs, the yarn
providing the longest segment may be positioned prior to the other
yarn of the pair, which provides the shortest segment. This
arrangement may be reversed for the yarns of other interchanging
yarn pairs throughout the fabric weave repeat. Furthermore, each
interchanging yarn pair need not provide segments of the same
length as other interchanging yarn pairs. In this case, it may be
that the number of segments in some pairs of interchanging yarn
pairs differs from the number of segments in other pairs of
interchanging yarn pairs. This latter feature will be the subject
of a separate patent application.
[0068] Various modifications can be made to the fabrics of this
invention. For example, and not by way of limitation, the shape of
the warp and weft yarns in both the paper side layer and the
machine side layer can be varied within the broadest aspects of the
invention. As described earlier in the summary of the invention, it
may be desirable to employ top warp yarns having a dumbbell-shaped
("figure 8") cross-section, so that the two bulbous ends of each
warp yarn provide two support point for a fibrous web formed on the
fabric. By increasing the number of support points for the web on
the paper side layer of the fabric, a more planar forming surface
is provided, which should achieve a more uniform formation of the
fibrous web.
[0069] Other modifications include having one or more of the binder
yarns of interchanging binder yarn pairs and/or interchanging top
weft/binder yarn pairs bind to more than one bottom warp yarn. Such
multiple bottom warp yarns can be adjacent to each other or
spaced-apart from each other. In either case the binding preferably
takes place with bottom warp yarns underlying top segments in which
the other yarn of the pair is forming a portion of the top weft
path.
[0070] Yet other modifications include the utilization of a weave
other than a plain weave in the fabric papermaking layer. For
example in a 24 shaft fabric of the invention a suitable paperside
weave could be a 3 shaft twill.
[0071] Although the embodiments of the invention described in
detail herein utilize CD orientated interchanging yarn pairs it is
understood that within the broadest aspects of the invention MD
orientated interchanging yarn pairs can be employed to bind and
stiffen the fabric.
[0072] Without further elaboration, the foregoing will so fully
illustrate our invention that others may, be applying current or
future knowledge, readily adapt the same for use under various
conditions of service.
* * * * *