U.S. patent number RE40,066 [Application Number 09/982,917] was granted by the patent office on 2008-02-19 for multi-layer forming fabric with stitching yarn pairs integrated into papermaking surface.
This patent grant is currently assigned to Weavexx Corporation. Invention is credited to Kevin John Ward.
United States Patent |
RE40,066 |
Ward |
February 19, 2008 |
**Please see images for:
( Certificate of Correction ) ** |
Multi-layer forming fabric with stitching yarn pairs integrated
into papermaking surface
Abstract
A multi-layer papermaker's forming fabric has stitching yarns
integrated into the papermaking surface. Each of a plurality of
repeating units of the fabric comprises: a set of top machine
direction yarns; a set of top cross-machine direction yarns
interwoven with the top machine direction yarns; a set of bottom
machine direction yarns; a set of bottom cross-machine direction
yarns interwoven with the bottom machine direction yarns; and pairs
of first and second stitching yarns. The stitching yarns pairs are
positioned between pairs of top cross-machine direction yarns. The
stitching yarns of each pair are interwoven with the top and bottom
machine direction yarns such that, as a fiber support portion of
the first stitching yarn is interweaving with the top machine
direction yarns, a binding portion of the second stitching yarn is
positioned below the top machine direction yarns, and such that as
a fiber support portion of the second stitching yarn is
interweaving with the top machine direction yarns, a binding
portion of the first stitching yarn is positioned below the top
machine direction yarns. The first and second stitching yarns cross
each other as they pass below a traditional top machine direction
yarn. Also, each of the binding portions of the first and second
stitching yarns passes below at least one of the bottom machine
direction yarns. In this configuration, the stitching yarns are
completely integrated into the top, or papermaking, surface of the
fabric, and therefore do not adversely impact the papermaking
qualities of the fabric.
Inventors: |
Ward; Kevin John (Coldbrook,
CA) |
Assignee: |
Weavexx Corporation (Wake
Forest, NC)
|
Family
ID: |
25420332 |
Appl.
No.: |
09/982,917 |
Filed: |
August 21, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
08905130 |
Aug 1, 1997 |
05967195 |
Oct 19, 1999 |
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Current U.S.
Class: |
139/383A;
139/383R; 139/383AA |
Current CPC
Class: |
D21F
1/0045 (20130101) |
Current International
Class: |
D03D
11/00 (20060101) |
Field of
Search: |
;139/383A,383AA,383R,408,409 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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454 092 |
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Aug 1927 |
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DE |
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454092 |
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0 224 276 |
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Dec 1986 |
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EP |
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0224276 |
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Dec 1986 |
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EP |
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0408040 |
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Nov 1990 |
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EP |
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0 408 849 |
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Nov 1990 |
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EP |
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0 408 849 |
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Nov 1990 |
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EP |
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0408040 |
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Nov 1991 |
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EP |
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0 794 283 |
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Sep 1997 |
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EP |
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0794283 |
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Sep 1997 |
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EP |
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2 597 123 |
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Oct 1987 |
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FR |
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2597123 |
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Oct 1987 |
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FR |
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WO86/00099 |
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Mar 1986 |
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WO |
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WO 86/00099 |
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Mar 1986 |
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WO |
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Other References
International Search Report for PCT Application No. PCT/US97/18629.
cited by examiner.
|
Primary Examiner: Welch; Gary L.
Assistant Examiner: Muromoto, Jr.; Robert H.
Attorney, Agent or Firm: Myers Bigel Sibley &
Sajovec
Claims
That which is claimed:
1. A papermaker's fabric, comprising top machine direction yarns,
top cross machine direction yarns, bottom machine direction yarns,
bottom cross machine direction yarns, and sets of first and second
stitching yarns, said fabric being formed in a plurality of
repeating units, each of said repeating units comprising: a set of
top machine direction yarns; a set of top cross machine direction
yarns interwoven with said set of top machine direction yarns; a
set of bottom machine direction yarns; a set of bottom cross
machine direction yarns interwoven with said set of bottom machine
direction yarns; wherein a pair of first and second stitching yarns
is positioned between each adjacent pair of top cross machine
direction yarns, said first and second stitching yarns of each pair
being interwoven with said top and bottom machine direction yarns
such that, as a fiber support portion of said first stitching yarn
is interweaving with said top machine direction yarns, a binding
portion of said second stitching yarn is positioned below said top
machine direction yarns, and such that as a fiber support portion
of said second stitching yarn is interweaving with said top machine
direction yarns, a binding potion of said first stitching vam is
positioned below said top machine direction yarns, and such that
said first and second stitching yarns cross each other as they pass
below a transitional top machine direction yarn, and such that each
of said binding portions of said first and second stitching yarns
passes below at least one of said bottom machine direction yarns;
wherein each of said top cross machine direction yarns passes over
a first group of alternate top machine direction yarns and under a
second group of alternate top machine direction yarns, with each of
said yarns of said first group being positioned between a pair of
yarns of said second group, and with each of said yarns of said
second group being positioned between a pair of yarns of said first
group, and wherein said fiber support portions of said first and
second stitching yarns pass under said first set of alternate top
machine direction yarns and over said second set of alternate top
machine direction yarns, such that said top machine direction
yarns, said top cross machine direction yarns, and said fiber
support portions of said first and second stitching yarn form a
plain weave pattern; wherein said fiber support portions of said
first stitching yarns pass over a first number of said machine
direction yarns, said fiber support portions of said second
stitching yarns pass over a second number of said machine direction
yarns, and said first number differs from said second number.
2. The papermaker'a fabric defined in claim 1, wherein said first
number is larger than said second number, and wherein said second
stitching yarn has a higher modulus of elasticity than said first
stitching yarn.
3. The papermaker's fabric defined in claim 1, wherein said first
number is three, and second number is two.
4. The papermaker's fabric defined in claim 1, wherein said first
and second stitching yarns are of a smaller diameter than said top
machine direction yarns.
5. A papermaker's fabric, comprising top machine direction yarns,
top cross machine direction yarns, bottom machine direction yarns,
bottom cross machine direction yarns, and sets of first and second
stitching yarns, said fabric being formed in a plurality of
repeating units, each of said repeating units comprising: a set of
top machine direction yarns; a set of top cross machine direction
yarns interwoven with said set of top machine direction yarns; a
set of bottom machine direction yarns; a set of bottom cross
machine direction yarns interwoven with said set of bottom machine
direction yarns; wherein a pair of first and second stitching yarns
is positioned between each adjacent pair of top cross machine
direction yarns, said first and second stitching yarns of each pair
being interwoven with said top and bottom machine direction yarns
such that, as a fiber support portion of said first stitching yarn
is interweaving with said top machine direction yarns, a binding
portion of said second stitching yarn is positioned below said top
machine direction yarns, an such that as a fiber support portion of
said second stitching yarn is interweaving with said top machine
direction yarns, a binding portion of said first stitching yarn is
positioned below said top machine direction yarns, and such that
said first and second stitching yarns cross each other as they pass
below a transitional top machine direction yarn, and such that each
of said binding portion of said first and second stitching yarns
passes beneath only one of said bottom machine direction yarns.
6. A papermaker's fabric, comprising top machine direction yarns,
top cross machine direction yarns, bottom machine direction yarns,
bottom cross machine direction yarns, and sets of first and second
stitching yarns, said fabric being formed in a plurality of
repeating units, each of said repeating units comprising: a set of
top machine direction yarns; a set of top cross machine direction
yarns interwoven with said set of top machine direction yarns; a
set of bottom machine direction yarns; a set of bottom cross
machine direction yarns interwoven with said set of bottom machine
direction yarns; wherein a pair of first and second stitching yarns
is positioned between each adjacent pair of top cross machine
direction yarns, said first and second stitching yarns of each pair
being interwoven with said top and bottom machine direction yarns
such that, as a fiber support portion of said first stitching yarn
is interweaving with said top machine direction yarns, a binding
portion of said second stitching yarn is positioned below said top
machine direction yarns, and such that as a fiber support portion
of said second stitching yarn is interweaving with said top machine
direction yarns, a binding portion of said first stitching yarn is
positioned below said top machine direction yarns, and such that
said first and second stitching yarns cross each other as they pass
below a transitional top machine direction yarn, and such that each
of said binding portions of said first and second stitching yarns
passes below at least one of said bottom machine direction yarns,
wherein said repeat unit includes 10 top machine direction yarns
and 10 bottom machine direction yarns.
7. A papermaker's fabric, comprising top machine direction yarns,
top cross machine direction yarns, bottom machine direction yarns,
bottom cross machine direction yarns, and sets of first and second
stitching yarns, said fabric being formed in a plurality of
repeating units, each of said repeating units comprising: a set of
top machine direction yarns; a set of top machine direction yarns
interwoven with said set of top machine direction yarns; a set of
bottom machine direction yarns; a set of bottom cross machine
direction yarns interwoven with said set of bottom machine
direction yarns; wherein a pair of first and second stitching yarn
is positioned between each adjacent pair of top cross machine
direction yarns, said first and second stitching yarns of each pair
being interwoven with said top and bottom machine direction yarns
such that, as a fiber support portion of said first stitching yarn
is interweaving with said top machine direction yarns a binding
portion of said second stitching yarn is positioned below said top
machine direction yarns, and such that as a fiber support portion
of said second stitching yarn is interweaving with said top machine
direction yarns, a binding portion of said first stitching yarn is
positioned below said top machine direction yarns, and such that
said first and second stitching yarns cross each other as they pass
below a transitional top machine direction yarn, and such that each
of said binding portions of said first and second stitching yarns
passes below at least one of said bottom machine direction yarns;
wherein said top machine direction yarns and said top cross machine
direction yarns are interwoven in a repeating pattern such that
each of said top cross machine direction yarns passes over a first
pair of adjacent top machine direction yarns, under a third top
machine direction yarn adjacent to said first pair, and over a
second pair of top machine direction yarns positioned adjacent said
third top machine direction yarn, and wherein adjacent top cross
machine direction yarns pass over top machine direction yarn pairs
that are offset by two top machine direction yarns; wherein said
stitching yarns are interwoven with said top machine direction
yarns in a repeating pattern such that said fiber support portion
of each of said first and second stitching yarns passes over a
third pair of adjacent top machine direction yarns, under an
adjacent top machine direction yarn, and over a fourth pair of
adjacent machine direction yarns, then passes under said
transitional top machine direction yarn, said third and fourth
pairs of top machine direction yarns being offset from said first
and second pairs by one machine direction yarn, such that said top
machine direction yarns, said cross machine direction yarns, and
said fiber support portions of said first and second stitching
yarns form a 1.times.2 twill pattern.
8. A papermaker's fabric, comprising top machine direction yarns,
top cross machine direction yarns, bottom machine direction yarns,
bottom cross machine direction yarns, and sets of first and second
stitching yarns, said fabric being formed in a plurality of
repeating units, each of said repeating units comprising: a set of
top machine direction yarns; a set of top cross machine direction
yarns interwoven with said set of top machine direction yarns; a
set of bottom machine direction yarns; a set of bottom cross
machine direction yarns interwoven with said set of bottom machine
direction yarns; wherein a pair of first and second stitching yarns
is positioned between each adjacent pair of top cross machine
direction yarns, said first and second stitching yarns of each pair
being interwoven with said top and bottom machine direction yarns
such that, as a fiber support portion of said first stitching yarn
is interweaving with said top machine direction yarns, a binding
portion of said second stitching yarn is positioned below said top
machine direction yarns, and such that as a fiber support portion
of said second stitching yarn is interweaving with said top machine
direction yarns, a binding portion of said first stitching yarn is
positioned below said top machine direction yarns, and such that
said first and second stitching yarns cross each other as they pass
below a traditional top machine direction yarn, and such that each
of said binding portions of said first and second stitching yarns
passes below at least one of said bottom machine direction yarns;
wherein said stitching yarns are interwoven with said top and
bottom machine direction yarns such that adjacent pairs of
stitching yarns cross beneath traditional top machine direction
yarns that are offset by two top machine direction yarns.
9. The papermaker's fabric defined in claim 8, wherein between 25
and 50 percent of said first and second stitching yarns are
interwoven with said top machine direction yarns as reversed
picks.
10. A papermaker's fabric, comprising top machine direction yarns,
top cross machine direction yarns, bottom machine direction yarns,
bottom cross machine direction yarns, and sets of first and second
stitching yarns, said fabric being formed in a plurality of
repeating units, each of said repeating units comprising: a set of
top machine direction yarns; a set of top cross machine direction
yarns interwoven with said set of top machine direction yarns; a
set of bottom machine direction yarns; a set of bottom cross
machine direction yarns interwoven with said set of bottom machine
direction yarns; wherein pairs of first and second stitching yarns
are positioned between pairs of top cross machine direction yarns,
said first and second stitching yarns of each pair being interwoven
with said top and bottom machine direction yarns such that, as a
fiber support portion of said first stitching yarn is interweaving
with said top machine direction yarns, a binding portion of said
second stitching yarn is positioned below said top machine
direction yarns, and such that as a fiber support portion of said
second stitching yarn is interweaving with said top machine
direction yarns, a binding portion of said first stitching yarn is
positioned below said top machine direction yarns, and such that
said first and second stitching yarns cross each other as they pass
below a transitional top machine direction yarn, and such that each
of said binding portions of said first and second stitching yarns
passes below at least one of said bottom machine direction yarns,
and wherein between 25 and 50 percent of adjacent pairs of first
and second stitching yarns are interwoven as reversed picks;
wherein each of said top cross machine direction yarns passes over
a first group of alternate top machine direction yarns and under a
second group of alternate top machine direction yarns, with each of
said yarns of said first group being positioned between a pair of
yarns of said second group, and with each of said yarns of said
second group being positioned between a pair of yarns of said first
group, and wherein a pair of first and second stitching yarns is
positioned between each pair of top cross machine direction yarns,
and wherein said fiber support portions of said first and second
stitching yarns pass under said first set of alternate top machine
direction yarns and over said second set of alternate top machine
direction yarns, such that said top machine direction yarns, said
top cross machine direction yarns, and said fiber support portions
of said first and second stitching yarns form a plain weave
pattern; wherein said fiber support portions of said first
stitching yarns pass over a first number of said machine direction
yarns, said fiber support portions of said second stitching yarns
pass over a second number of said machine direction yarns, and said
first number differs from said second number.
11. The papermaker's fabric defined in claim 10, wherein said first
number is larger than said second number, and wherein said second
stitching yarn has a higher modulus of elasticity than said first
stitching yarn.
12. The papermaker's fabric defined in claim 10, wherein said first
number is three, and second number is two.
13. A papermaker's fabric, comprising top machine direction yarns,
top cross machine direction yarns, bottom machine direction yarns,
bottom cross machine direction yarns, and sets of first and second
stitching yarns, said fabric being formed in a plurality of
repeating units, each of said repeating units comprising: a set of
top machine direction yarns; a set of top cross machine direction
yarns interwoven with said set of top machine direction yarns; a
set of bottom machine direction yarns; a set of bottom cross
machine direction yarns interwoven with said set of bottom machine
direction yarns; wherein pairs of first and second stitching yarns
are positioned between pairs of top cross machine direction yarns,
said first and second stitching yarns of each pair being interwoven
with said top and bottom machine direction yarns such that, as a
fiber support portion of said first stitching yarn is interweaving
with said top machine direction yarns, a binding portion of said
second stitching yarn is positioned below said top machine
direction yarns, and such that as a fiber support portion of said
second stitching yarn is interweaving with said top machine
direction yarns, a binding portion of said first stitching yarn is
positioned below said top machine direction yarns, and such that
said first and second stitching yarns cross each other as they pass
below a transitional top machine direction yarn, and such that each
of said binding portions of said first and second stitching yarns
passes below at least one of said bottom machine direction yarns,
and wherein between 25 and 50 percent of adjacent pairs of first
and second stitching yarns are interwoven as reversed picks;
wherein said repeat unit includes 12 top machine direction yarns
and 12 bottom machine direction yarns.
14. A method of making paper, said method comprising the steps of:
(a) providing a papermaker's fabric comprising top machine
direction yarns, top cross machine direction yarns, bottom machine
direction yarns, bottom cross machine direction yarns, and sets of
first and second stitching yarns, said fabric being formed in a
plurality of repeating units, each of said repeating units
comprising: a set of top machine direction yarns; a set of top
cross machine direction yarns interwoven with said set of top
machine direction yarns; a set of bottom machine direction yarns; a
set of bottom cross machine direction yarns interwoven with said
set of bottom machine direction yarns; wherein a pair of first and
second stitching yarns is positioned between each adjacent pair of
top cross machine direction yarns, said first and second stitching
yarns of each pair being interwoven with said top and bottom
machine direction yarns such that, as a fiber support portion of
said first stitching yarn is interweaving with said top machine
direction yarns, a binding portion of said second stitching yarn is
positioned below said top machine direction yarns, and such that as
a fiber support portion of said second stitching yarn is
interweaving with said top machine direction yarns, a binding
portion of said first stitching yarn is positioned below said top
machine direction yarns, and such that said first and second
stitching yarns cross each other as they pass below a transitional
top machine direction yarn, and such that each of said binding
portions of said first and second stitching yarns passes below at
least one of said bottom machine direction yarns; wherein each of
said top cross machine direction yarns passes over a first group of
alternate top machine direction yarns and under a second group of
alternate top machine direction yarns, with each of said yarns of
said first group being positioned between a pair of yarns of said
second group, and with each of said yarns of said second group
being positioned between a pair of yarns of said first group, and
wherein said fiber support portions of said first and second
stitching yarns pass under said first set of alternate top machine
direction yarns and over said second set of alternate top machine
direction yarns, such that said top machine direction yarns, said
top cross machine direction yarns, and said fiber support portions
of said first and second stitching yarns form a plain weave
pattern; wherein said fiber support portions of said first
stitching yarns pass over a first number of said machine direction
yarns, said fiber support portions of said second stitching yarns
pass over a second number of said machine direction yarns, and said
first number differs from said second number; (b) applying paper
stock to said papermaker's fabric; and (c) removing moisture from
said paper stock.
15. A method of making paper, said method comprising the steps of:
(a) providing a papermaker's fabric comprising top machine
direction yarns, top cross machine direction yarns, bottom machine
direction yarns, bottom cross machine direction yarns, and sets of
first and second stitching yarns, said fabric being formed in a
plurality of repeating units, each of said repeating units
comprising: a set of top machine direction yarns; a set of top
cross machine direction yarns interwoven with said set of top
machine direction yarns; a set of bottom machine direction yarns; a
set of bottom cross machine direction yarns interwoven with said
set of bottom machine direction yarns; wherein a pair of first and
second stitching yarns is positioned between each adjacent pair of
top cross machine direction yarns, said first and second stitching
yarns of each pair being interwoven with said top and bottom
machine direction yarns such that, as a fiber support portion of
said first stitching yarn is interweaving with said top machine
direction yarns, a binding portion of said second stitching yarn is
positioned below said top machine direction yarns, and such that as
a fiber support portion of said second stitching yarn is
interweaving with said top machine direction yarns, a binding
portion of said first stitching yarn is positioned below said top
machine direction yarns, and such that said first and second
stitching yarns cross each other as they pass below a transitional
top machine direction yarn, and such that each of aid binding
portions of said first and second stitching yarns passes below at
least one of said bottom machine direction yarns; wherein said top
machine direction yarns and said top cross machine direction yarns
are interwoven in a repeating pattern such that each of said top
cross machine direction yarns passes over a first pair of adjacent
top machine direction yarns, under a third top machine direction
yarn adjacent to said first pair, and over a second pair of top
machine direction yarns positioned adjacent said third top machine
direction yarn, and wherein adjacent top cross machine direction
yarns pass over top machine direction yarn pairs that are offset by
two top machine direction yarns, and wherein said stitching yarns
are interwoven with said top machine direction yarns in a repeating
pattern such that said fiber support portion of each of said first
and second stitching yarns passes over a third pair of adjacent top
machine direction yarns, under an adjacent top machine direction
yarn, and over a fourth pair of adjacent machine direction yarns,
then passes under said transitional top machine direction yarn,
said third and fourth pairs of top machine direction yarns being
offset from said first and second pairs by one machine direction
yarn, such that said top machine direction yarns, said cross
machine direction yarns, and said fiber support portions of said
first and second stitching yarns form a 1.times.2 twill pattern;
(b) applying paper stock to said papermaker's fabric; and (c)
removing moisture from said paper stock.
.Iadd.16. A papermaker's fabric, comprising top machine direction
yarns, top cross machine direction yarns, bottom machine direction
yarns, bottom cross machine direction yarns, and sets of first and
second stitching yarns, said fabric being formed in a plurality of
repeating units, each of said repeating units comprising: a set of
top machine direction yarns; a set of top cross machine direction
yarns interwoven with said set of top machine direction yarns; a
set of bottom machine direction yarns; a set of bottom cross
machine direction yarns interwoven with said set of bottom machine
direction yarns; and wherein a pair of first and second stitching
yarns is positioned between each adjacent pair of top cross machine
direction yarns, said first and second stitching yarns of each pair
being interwoven with said top and bottom machine direction yarns
such that, as a fiber support portion of said first stitching yarn
is interweaving with said top machine direction yarns, a binding
portion of said second stitching yarn is positioned below said top
machine direction yarns, and such that as a fiber support portion
of said second stitching yarn is interweaving with said top machine
direction yarns, a binding portion of said first stitching yarn is
positioned below said top machine direction yarns, and such that
said first and second stitching yarns cross each other as they pass
below a transitional top machine direction yarn, and such that each
of said binding portions of said first and second stitching yarns
passes below at least one of said bottom machine direction yarns to
form a bottom side stitching yarn knuckle; and wherein each of said
bottom machine direction yarns form bottom side machine direction
knuckles as they interweave with said bottom cross machine
direction yarns, and said bottom side stitching yarn knuckles are
positioned below one of said bottom side machine direction yarns to
be substantially centered between adjacent bottom side machine
direction knuckles on that bottom machine direction
yarn..Iaddend.
.Iadd.17. The papermaker's fabric defined in claim 16, wherein said
repeat unit of said fabric includes 10 bottom machine direction
yarns and 10 bottom cross machine direction yarns..Iaddend.
.Iadd.18. The papermaker's fabric defined in claim 17, wherein each
of said bottom machine direction yarns passes, in order, above four
consecutive bottom cross machine direction yarns, below a bottom
cross machine direction yarn to form a first bottom side machine
direction knuckle, above four consecutive bottom cross machine
direction yarns, and below a bottom cross machine direction yarn to
form a second side machine direction knuckle, and wherein a
stitching yarn forms a bottom side stitching yarn knuckle below
said machine direction yarn between the second and third of each of
said four consecutive bottom cross machine direction
yarns..Iaddend.
.Iadd.19. The papermaker's fabric defined in claim 18, wherein each
bottom machine direction yarn is offset from each adjacent bottom
machine direction yarn by three bottom cross machine direction
yarns, with the result that bottom side machine direction yarn
knuckles are formed below the bottom cross machine direction yarns
that sandwich the stitching yarn pair forming a stitching yarn
knuckle below the bottom machine direction yarn..Iaddend.
.Iadd.20. A papermaker's fabric, comprising top machine direction
yarns, top cross machine direction yarns, bottom machine direction
yarns, bottom cross machine direction yarns, and sets of first and
second stitching yarns, said fabric being formed in a plurality of
repeating units, each of said repeating units comprising: a set of
top machine direction yarns; a set of top cross machine direction
yarns interwoven with said set of top machine direction yarns; a
set of bottom machine direction yarns; a set of bottom cross
machine direction yarns interwoven with said set of bottom machine
direction yarns; wherein a pair of first and second stitching yarns
is positioned between each adjacent pair of top cross machine
direction yarns, said first and second stitching yarns of each pair
being interwoven with said top and bottom machine direction yarns
such that, as a fiber support portion of said first stitching yarn
is interweaving with said top machine direction yarns, a binding
portion of said second stitching yarn is positioned below said top
machine direction yarns, and such that as a fiber support portion
of said second stitching yarn is interweaving with said top machine
direction yarns, a binding portion of said first stitching yarn is
positioned below said top machine direction yarns, and such that
said first and second stitching yarns cross each other as they pass
below a transitional top machine direction yarn, and such that each
of said binding portions of said first and second stitching yarns
passes below at least one of said bottom machine direction yarns to
form a bottom side stitching yarn knuckle; wherein each of said
bottom machine direction yarns form bottom side machine direction
knuckles as they interweave with said bottom cross machine
direction yarns, and wherein each bottom machine direction yarn is
offset from each adjacent bottom machine direction yarn such that,
for each bottom machine direction yarn, bottom side machine
direction yarn knuckles are formed by adjacent bottom machine
direction yarns below the bottom cross machine direction yarns that
sandwich each stitching yarn pair that forms a stitching yarn
knuckle below the bottom machine direction yarn..Iaddend.
.Iadd.21. The papermaker's fabric defined in claim 20, wherein said
repeat unit of said fabric includes 10 bottom machine direction
yarns and 10 bottom cross machine direction yarns..Iaddend.
.Iadd.22. The papermaker's fabric defined in claim 21, wherein said
bottom cross machine direction yarns are offset from one another by
three machine direction yarns..Iaddend.
.Iadd.23. The papermaker's fabric defined in claim 22, wherein each
of said bottom machine direction yarns passes, in order, above four
consecutive bottom cross machine direction yarns, below a bottom
cross machine direction yarn to form a first bottom side machine
direction knuckle, above four consecutive bottom cross machine
direction yarns, and below a bottom cross machine direction yarn to
form a second side machine direction knuckle, and wherein a
stitching yarn forms a bottom side stitching yarn knuckle below
said machine direction yarn between the second and third of each of
said four consecutive bottom cross machine direction
yarns..Iaddend.
.Iadd.24. A papermaker's fabric, comprising top machine direction
yarns, top cross machine direction yarns, bottom machine direction
yarns, bottom cross machine direction yarns, and sets of first and
second stitching yarns, said fabric being formed in a plurality of
repeating units, each of said repeating units comprising: a set of
top machine direction yarns; a set of top cross machine direction
yarns interwoven with said set of top machine direction yarns; a
set of bottom machine direction yarns; a set of bottom cross
machine direction yarns interwoven with said set of bottom machine
direction yarns; wherein pairs of first and second stitching yarns
are positioned between each pair of top cross machine direction
yarns, said first and second stitching yarns of each pair being
interwoven with said top and bottom machine direction yarns such
that, as a fiber support portion of said first stitching yarn is
interweaving with said top machine direction yarns, a binding
portion of said second stitching yarn is positioned below said top
machine direction yarns, and such that as a fiber support portion
of said second stitching yarn is interweaving with said top machine
direction yarns, a binding portion of said first stitching yarn is
positioned below said top machine direction yarns, and such that
said first and second stitching yarns cross each other as they pass
below a transitional top machine direction yarn, and such that each
of said binding portions of said first and second stitching yarns
passes below at least one of said bottom machine direction yarns;
and wherein each of said first stitching yarns passes over a first
number of top machine direction yarns, and each of said second
stitching yarns passes over a second number of top machine
direction yarns, said first number being different than said second
number; and and wherein at least some of the top cross machine
direction yarns are immediately adjacent to either two first
stitching yarns or two second stitching yarns..Iaddend.
.Iadd.25. The papermaker's fabric defined in claim 24, wherein,
beginning with a selected top cross machine direction yarn and
moving in one direction parallel to the machine direction for the
length of the full repeat unit, between 25 and 50 percent of the
first stitching yarns are nearer to said selected top cross machine
direction yarn that the second stitching yarns of their respective
pairs..Iaddend.
.Iadd.26. The papermaker's fabric defined in claim 25, wherein
between 40 and 50 percent of the first stitching yarns are nearer
to said selected top machine direction yarn than the second
stitching yarns of their respective pairs..Iaddend.
.Iadd.27. The papermaker's fabric defined in claim 25, wherein all
of the top cross machine direction yarns are immediately adjacent
to either two first stitching yarns or two second stitching
yarns..Iaddend.
.Iadd.28. The papermaker's fabric defined in claim 25, wherein said
repeat unit includes 10 top machine direction yarns and 10 bottom
machine direction yarns..Iaddend.
.Iadd.29. A papermaker's fabric, comprising top machine direction
yarns, top cross machine direction yarns, bottom machine direction
yarns, bottom cross machine direction yarns, and sets of first and
second stitching yarns, said fabric being formed in a plurality of
repeating units, each of said repeating units comprising: a set of
top machine direction yarns; a set of top cross machine direction
yarns interwoven with said set of top machine direction yarns; a
set of bottom machine direction yarns; a set of bottom cross
machine direction yarns interwoven with said set of bottom machine
direction yarns; wherein pairs of first and second stitching yarns
are positioned between pairs of top cross machine direction yarns,
said first and second stitching yarns of each pair being interwoven
with said top and bottom machine direction yarns such that, as a
fiber support portion of said first stitching yarn is interweaving
with said top machine direction yarns, a binding portion of said
second stitching yarn is positioned below said top machine
direction yarns, and such that as a fiber support portion of said
second stitching yarn is interweaving with said top machine
direction yarns, a binding portion of said first stitching yarn is
positioned below said top machine direction yarns, and such that
said first and second stitching yarns cross each other as they pass
below a transitional top machine direction yarn, and such that each
of said binding portions of said first and second stitching yarns
passes below at least one of said bottom machine direction yarns;
wherein, as stitching yarn pairs pass below transitional yarns,
they form top side transitional stitching yarn knuckles, and in
that, for at least some adjacent top side stitching yarn knuckles,
first stitching yarns extending in one direction parallel to the
cross machine direction from the transitional stitching yarn
knuckles are woven nearer to one another than are the second
stitching yarns of those pairs extending in the opposite direction
parallel to the cross machine direction from the transitional
stitching yarn knuckles..Iaddend.
.Iadd.30. The papermaker's fabric defined in claim 29, wherein said
first stitching yarns are woven nearer to one another as they
extend from adjacent top side transitional stitching yarn knuckles
for at least 50 percent of said top side stitching yarn
knuckles..Iaddend.
.Iadd.31. The papermaker's fabric defined in claim 29, wherein said
first stitching yarns are woven nearer to one another as they
extend from adjacent top side transitional stitching yarn knuckles
for 100 percent of said top side stitching yarn
knuckles..Iaddend.
.Iadd.32. The papermaker's fabric defined in claim 29, wherein a
pair of first and second stitching yarns is positioned between each
pair of adjacent top cross machine direction yarns..Iaddend.
.Iadd.33. The papermaker's fabric defined in claim 29, wherein said
repeat unit includes 10 top machine direction yarns and 10 bottom
machine direction yarns..Iaddend.
.Iadd.34. The papermaker's fabric defined in claim 29, wherein said
repeat unit includes 12 top machine direction yarns and 12 bottom
machine direction yarns..Iaddend.
.Iadd.35. A papermaker's fabric, comprising top machine direction
yarns, top cross machine direction yarns, bottom machine direction
yarns, bottom cross machine direction yarns, and sets of first and
second stitching yarns, said fabric being formed in a plurality of
repeating units, each of said repeating units comprising: a set of
top machine direction yarns; a set of top cross machine direction
yarns interwoven with said set of top machine direction yarns; a
set of bottom machine direction yarns; a set of bottom cross
machine direction yarns interwoven with said set of bottom machine
direction yarns; wherein pairs of first and second stitching yarns
are positioned between pairs of top cross machine direction yarns,
said first and second stitching yarns of each pair being interwoven
with said top and bottom machine direction yarns such that, as a
fiber support portion of said first stitching yarn is interweaving
with said top machine direction yarns, a binding portion of said
second stitching yarn is positioned below said top machine
direction yarns, and such that as a fiber support portion of said
second stitching yarn is interweaving with said top machine
direction yarns, a binding portion of said first stitching yarn is
positioned below said top machine direction yarns, and such that
said first and second stitching yarns cross each other as they pass
below a transitional top machine direction yarn, and such that each
of said binding portions of said first and second stitching yarns
passes below at least one of said bottom machine direction yarns,
said first stitching yarns passing above a first number of top
machine direction yarns, and said second stitching yarns passing
above a second number of top machine direction yarns, said second
number being different from said first number; wherein, as
stitching yarn pairs pass below transitional yarns, they form top
side transitional stitching yarn knuckles, and in that, for at
least some adjacent top side stitching yarn knuckles, first
stitching yarns extending in one direction parallel to the cross
machine direction from the transitional stitching yarn knuckles are
woven nearer to one another than are the second stitching yarns of
those pairs extending in the opposite direction parallel to the
cross machine direction from the transitional stitching yarn
knuckles..Iaddend.
.Iadd.36. The papermaker's fabric defined in claim 35, wherein said
first stitching yarns are woven nearer to one another as they
extend from adjacent top side transitional stitching yarn knuckles
for at least 50 percent of said top side stitching yarn
knuckles..Iaddend.
.Iadd.37. The papermaker's fabric defined in claim 35, wherein said
first stitching yarns are woven nearer to one another as they
extend from adjacent top side transitional stitching yarn knuckles
for 100 percent of said top side stitching yarn
knuckles..Iaddend.
.Iadd.38. The papermaker's fabric defined in claim 35, wherein a
pair of first and second stitching yarns is positioned between each
pair of adjacent top cross machine direction yarns..Iaddend.
.Iadd.39. The papermaker's fabric defined in claim 35, wherein said
repeat unit includes 10 top machine direction yarns and 10 bottom
machine direction yarns..Iaddend.
Description
FIELD OF THE INVENTION
The present invention relates generally to papermaking, and relates
more specifically to fabrics employed in papermaking.
BACKGROUND OF THE INVENTION
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 which operates as a filter to separate the cellulosic fibers of
the paper stock from the aqueous medium, thereby forming a wet
paper web. The aqueous medium drains through mesh openings of the
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.
After leaving the forming section, the paper web is transferred to
a press section of the paper machine, where it is passed through
the nips of one or more pairs of pressure rollers covered with
another fabric, typically referred to as a "press felt." Pressure
from the rollers removes additional moisture from the web; the
moisture removal is often enhanced by the presence of a "batt"
layer of the press felt. The paper is then transferred to a drier
section for further moisture removal. After drying, the paper is
ready for secondary processing and packaging.
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. 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. In the
second 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. 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. Both weaving methods
described hereinbelow are well known in the art, and the term
"endless belt" as used herein refers to belts made by either
method.
Effective sheet and fiber support and an absence of wire marking
are important considerations in papermaking, especially for the
forming section of the papermaking machine, where the wet web is
initially formed. Wire marking is particularly problematic in the
formation of fine paper grades, as it affects a host of paper
properties, such as sheet mark, porosity, see through, and pin
holing. Wire marking is the result of individual cellulosic fibers
being oriented within the paper web such that their ends reside
within gaps between the individual threads or yarns of the forming
fabric. This problem is generally addressed by providing a
permeable fabric structure with a coplanar surface that allows
paper fibers to bridge adjacent yarns of the fabric rather than
penetrate the gaps between yarns. As used herein, "coplanar" means
that the upper extremities of the yarns defining the paper-forming
surface are at substantially the same elevation, such that at that
level there is presented a substantially "planar" surface.
Accordingly, fine paper grades intended for use in quality
printing, carbonizing, cigarettes, electrical condensers, and like
grades of fine paper have typically heretofore been formed on very
finely woven or fine wire mesh forming fabrics.
Regretably, such finely woven forming fabrics often are delicate
and lack dimensional stability in either or both of the machine and
cross machine directions (particularly during operation), leading
to a short service life for the fabric. In addition, a fine weave
may adversely effect drainage properties of the fabric, thus
rendering it less suitable as a forming fabric.
To combat these problems associated with fine weaves, 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 to
include one fabric layer having a fine mesh, another fabric layer
having a coarser mesh, and stitching yarns that bind the layers
together. These fabrics, known as "triple layer" fabrics, are
illustrated in U.S. Pat. No. 4,501,303 to Osterberg, U.S. Pat. No.
5,152,326 to Vohringer, and U.S. Pat. No. 5,437,315 to Ward.
Although these fabrics have performed successfully, they have some
shortcomings that relate to the inclusion of the stitching yarns.
In a typical triple layer forming fabric, one of more stitching
yarns are positioned between some of the CMD yarns of the top and
bottom layers and interwoven with the top and bottom MD yarns. In
such a construction, portions of the stitching yarns form part of
the papermaking surface of the fabric. As a result, the appearance
of paper formed with the fabric can be affected (sometimes
adversely) by the presence of the stitching yarns.
In addition, triple layer fabrics have proven to have problems with
interlayer wear. As the fabric is used on a paper machine, the top
and bottom layers tend to shift relative to one another, both in
the machine direction and the cross machine direction, due to the
tension imparted to the fabric by the rolls. This effect is
exacerbated on paper machines, such as the so-called "high-wrap"
machines, that include multiple rolls, including some which contact
the top layer of the fabric. This shifting can cause the fabric to
wear and decrease in thickness, which can adversely affect the
drainage of the fabric and, accordingly, its performance in
papermaking. In many instances, it is this interlayer wear, rather
than the wear of the machine side surface of the fabric machine
against the paper machine, that determines the longevity of the
fabric.
Further, because the stitching yarns of a triple layer fabric have
a different weave pattern than the top CMD yarns (i.e., they
interweave with the bottom CMD yarns also, whereas the top CMD
yarns to not), there can be differences in tension between the
stitching yarns and the top CMD yarns. These differences can induce
the fabric to distort out-of-plane, which can in turn reduce the
quality of paper produced with the fabric.
Also, the stitching yarns of a triple layer fabric should be
sufficiently strong and durable to bind the top and bottom layers
and to resist the wear and abrasion conditions that the bottom
layer experiences while in contact with the paper machine, yet
should be delicate enough to produce high quality paper. This
balance can be quite difficult to strike.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention
to provide a multi-layer forming fabric construction with little
distortion in the top fabric layer.
It is also an object of the present invention to provide a
multi-layer forming fabric construction that produces a high
quality paper.
It is another object of the present invention to provide a
multi-layer forming fabric construction that maintains the top and
bottom layers in a tightly bound condition.
It is a further object of the present invention to provide a
multi-layer forming fabric that addresses the problem of interlayer
wear.
These and other objects are satisfied by the present invention,
which relates to a multi-layer papermaker's forming fabric with
stitching yarns integrated into the papermaking surface. The fabric
is formed as a plurality of repeating units. Each of the repeating
units comprises: a set of top machine direction yarns; a set of top
cross-machine direction yarns interwoven with the set of top
machine direction yarns; a set of bottom machine direction yarns; a
set of bottom cross-machine direction yarns interwoven with the set
of bottom machine direction yarns; and pairs of first and second
stitching yarns. The stitching yarn pairs are positioned between
pairs of top cross-machine direction yarns. The stitching yarns of
each pair are interwoven with the top and bottom machine direction
yarns such that, as a fiber support portion of the first stitching
yarn is interweaving with the top machine direction yarns, a
binding portion of the second stitching yarn is positioned below
the top machine direction yarns, and such that as a fiber support
portion of the second stitching yarn is interweaving with the top
machine direction yarns, a binding portion of the first stitching
yarn is positioned below the top machine direction yarns. The first
and second stitching yarns cross each other as they pass below a
transitional top machine direction yarn. Also, each of the binding
portions of the first and second stitching yarns passes below at
least one of the bottom machine direction yarns. In this
configuration, the stitching yarns are completely integrated into
the top, or papermaking, surface of the fabric, and therefore do
not adversely impact the papermaking qualities of the fabric. Also,
the relatively large number of stitching yarns provides reliable
binding of the top and bottom layers of the fabric.
In two illustrated embodiments of the fabric, the stitching yarns
are interwoven with the top MD and CMD yarns so that they form a
plain weave papermaking surface. In this embodiment, it is
preferred that the stitching yarns be interwoven as "reverse picks"
(this term is defined in detail hereinbelow). In another
illustrated embodiment, the stitching yarns are interwoven with the
top MD and CMD yarns to form a 1.times.2 twill top surface. In
these embalmments, the integration of the stitching yarns into the
papermaking surface of the fabric addresses many of the problems
associated with prior art triple layer fabrics, such as distortion
of the papermaking surface and inadequate binding of the top and
bottom layers.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1A is a top view of an embodiment of a 20 harness multi-layer
forming fabric of the present invention having a plain weave top
surface.
FIG. 1B is a plan view of the bottom layer of the fabric of FIG.
1.
FIGS. 2A through 2J are section views of the stitching yarns of the
fabric of FIGS. 1A and 1B.
FIG. 3A is a top view of an embodiment of a 24 harness multi-layer
forming fabric of the present invention having a plain weave top
surface.
FIG. 3B is a plan view of the bottom layer of the fabric of FIG.
3A.
FIGS. 4A through 4L are section views of the stitching yarns of the
fabric of FIGS. 3A and 3B.
FIG. 5A is a top view of a 24 harness multi-layer forming fabric of
the present invention having a 1.times.2 twill top surface.
FIG. 5B is a plan view of the bottom layer of the fabric of FIG.
5A.
FIGS. 6A through 6F are section views of the stitching yarns of the
fabric of FIGS. 5A and 5B.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be described more particularly
hereinafter with reference to the accompanying drawings. The
invention is not intended to be to the illustrated embodiments;
rather, these embodiments are intended to fully and completely
disclose the invention to those skilled in this art.
A 20 harness multi-layer forming fabric, generally designated at
20, is illustrated in FIGS. 1A and 1B, in which a single repeat
unit of the fabric is shown. As seen in FIG. 1A, the repeat unit of
the fabric 20 includes a top layer having ten top MD yarns 21-30
and ten top CMD yarns 31-40. These 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, top CMD yarn 31 passes under top MD yarn 21,
over top MD yarn 22, under top MD yarn 23, over top MD yarn 24 and
so on until it passes over top MD yarn 30. Similarly, top CMD yarn
32 passes under top MD yarn 21, over top MD yarn 22, under top MD
yarn 23, over top MD yarn 24 and so on until it passes over top MD
yarn 30.
Referring now to FIG. 1B, a repeat unit of the bottom layer of the
fabric is shown. The repeat unit includes ten bottom MD yarns 41-50
which are interwoven with ten bottom CMD yarns 51-60. The bottom MD
yarns 41-50 are interwoven with the bottom CMD yarns 51-60 in a 1-4
twill type pattern, with each bottom CMD yarn passing above one
bottom MD yarn, below four bottom MD yarns, above one bottom MD
yarn, and below four bottom MD yarns. For example, bottom CMD yarn
51 passes above bottom MD yarn 41, below bottom MD yarns 42-45,
above bottom MD yarn 46, and below bottom MD yarns 47 through 50.
The other bottom CMD yarns follow a similar "over 1/under 4" weave
pattern, but each is offset from its nearest bottom CMD yarn
neighbors by two bottom MD yarns. Consequently, bottom CMD yarn 52
passes below bottom MD yarns 41 and 42, above bottom MD yarn 43,
below bottom MD yarn 44 through 47, above bottom MD yarn 48, and
below bottom MD yarns 49 and 50. Thus the "knuckle" formed by
bottom MD yarn 43 as it passes below bottom CMD yarn 52 is offset
from the "knuckle" formed by bottom MD yarn 41 as it passes over
bottom CMD yarn 51 by two bottom MD yarns.
The top layer (formed by the top MD yarns and the top CMD yarns)
and the bottom layer (formed by the bottom MD yarns and the bottom
CMD yarns) are stitched together with twenty stitching yarns,
designated herein as pairs 61a, 61b through 70a, 70b. The stitching
yarns are positioned in pairs between adjacent CMD yarns. For
example, stitching yarns 61a and 61b are positioned between top CMD
yarns 31 and 32 and between bottom CMD yarns 51 and 52. The
stitching yarns interweave with the top MD yarns and bottom MD
yarns to bind the top and bottom fabric layers together.
As can be seen in FIGS. 2A through 2J, corresponding pairs of
stitching yarns interweave with the top MD yarns and bottom MD
yarns in the following pattern. Each of the stitching yarns of the
repeat unit can be subdivided into two portions: a fiber support
portion which interweaves with the top MD yarns, and a binding
portion which interweaves with a bottom MD yarn. These are
separated at "transitional" top MD yarns, below which one stitching
yarn of a pair crosses the other stitching yarn of the pair. The
stitching yarns of each pair are interwoven relative to one another
such that the fiber support portion of one yarn of the pair is
positioned above the binding portion of the other yarn of the pair.
The fiber support portion of the stitching yarn of each pair
designated with an "a" (e.g., 61a, 62a, 63a) 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 MD yarns. In its fiber support portion, each
stitching yarn passes over top MD yarns that the top CMD yarns pass
beneath, and passes below top MD yarns that each top CMD yarn
passes over. In this manner, the stitching yarns and top CMD form a
plain weave pattern with the top MD yarns (see FIG. 1A). In its
binding portion, each stitching yarn passes below one bottom MD
yarn in the repeat unit such that an "over4/under1" pattern is
established by the pair of stitching yarns on the bottom surface of
the fabric 20 (see FIG. 1B).
The weaving pattern of the stitching yarns is exemplified in FIG.
2D, which illustrates stitching yarns 64a, 64b interweaving with
top and bottom MD yarns. In its fiber support portion, stitching
yarn 64a passes over top MD yarns 21, 23 and 25, and below top MD
yarns 22 and 24. It then passes below transitional top MD yarn 26
and above bottom MD yarn 46. In its biding portion, stitching yarn
64a passes below top MD yarns 27 through 29 while passing above
bottom MD yarns 47 and 49 and below bottom MD yarn 48 to stitch the
bottom layer of the fabric 20. Stitching yarn 64a then passes
between top transitional MD yarn 30 and bottom MD yarn 50. FIG. 2D
also illustrated that stitching yarn 64b is interwoven such that
its binding portion is below that of stitching yarn 64a; stitching
yarn 64b passes below top MD yarns 21 through 25 while passing
above bottom MD yarns 41, 42, 44, 45 and below bottom MD yarn 43.
In its fiber support portion, stitching yarn 64b passes above top
MD yarn 27, below top MD yarn 28 and above top MD yarn 29. As a
result, the fiber support portions of stitching yarns 64a, 64b
combine a form the "over 1/under 1" pattern of a plain weave on the
top layer, and the binding portions of stitching yarns 64a, 64b
combine to form the "over 4/under 1" pattern described above.
As can be seen in FIGS. 2A through 2C and FIGS. 2E through 2J
(which depict the interweaving patterns of the other stitching yarn
pairs with the top and bottom MD yarns), the same pattern described
hereinabove for the stitching yarns 64a, 64b relative to each other
is followed by the other stitching yarn pairs.
Referring back to FIGS. 1A and 1B, pairs of stitching yarns that
are positioned adjacent to and on opposite sides of a top or bottom
CMD yarn are interwoven with the top or bottom MD yarns such that
there is an offset of two MD yarns between such stitching yarn
pairs. For example, stitching yarn 61a passes above top MD yarns
25, 27 and 29 and below bottom MD yarn 42. Stitching yarn 62a
passes above top MD yarns 27, 29 and 21 (with top MD yarn 21 being
a continuation of the pattern on the opposite side) and below
bottom MD yarn 44. Thus, stitching yarn 61a is offset from
stitching yarn 62a by two top and bottom MD yarns. This same two MD
yarn offset is followed for the interweaving of the other stitching
yarns.
It can also be seen in FIGS. 1A and 1B that the stitching yarns are
interwoven with the top and bottom MD yarns as "reversed picks."
This term can be understood by examination of stitching yarn pairs
61a, 61b, 62a, 62b, 63a, 63b. As shown in FIGS. 1A and 2A,
stitching yarn 61a is positioned nearer to top CMD yarn 32 than is
stitching yarn 61b. As seen in FIGS. 1A and 2B, on the other side
of the top CMD yarn 32, stitching yarn 62a is positioned nearer to
top CMD yarn 32 than is stitching yarn 62b. As a result, the fiber
support portions of stitching yarns 61a, 62a are positioned nearer
to top CMD yarn 32 than are the fiber support portions of stitching
yarns 61b, 62b. This relative proximity to the top CMD yarn between
adjacent pairs of stitching yarns is reversed with stitching yarn
pairs 62a, 62b and 63a, 63b. As seen in FIGS. 1A, 2B, and 2C,
stitching yarns 62b and 63b are positioned nearer top CMD yarn 33
than stitching yarns 62a, 63a, with the result again that the fiber
support portions of the nearer stitching yarns are also positioned
nearer to top CMD yarn 33.
It has been discovered that this "reversed picks" configuration is
particularly effective in masking the presence of stitching yarns
in the top surface of the fabric. When a transitional yarn passes
over the stitching yarns of a pair to form a top surface knuckle,
that knuckle tends to receive less upwardly-directed support from
the stitching yarns at that location than other locations on the
top MD yarn where it passes over a stitching yarn or top CMD yarn.
As a result, that knuckle tends to be positioned slightly lower
than the other top MD knuckles. As seen in FIG. 1A, the top MD
knuckles of transitional yarn form a diagonal line; because the
knuckles of this diagonal may all be positioned somewhat lower than
the remaining top MD knuckles, paper formed on such a fabric can
show this pattern, which can in turn affect images printed thereon.
By including the stitching yarns as reversed picks, such as is
illustrated in fabric 20, however, the diagonal formed by the
traditional top MD knuckles is disturbed somewhat and is less
distinctly defined. As such, paper formed on fabric 20 has a less
distinct diagonal pattern due to these knuckles, and printing on
the paper is improved.
Those skilled in this art will appreciate that the aforedescribed
"reverse picks" configuration is created in the fabric by weaving
the stitching yarns into the top and bottom MD yarns so that first
an "a" stitching yarn immediately follows the waving of top and
bottom CMD yarns (followed by a "b" stitching yarn), then a "b"
stitching yarn immediately follows the next set of top and bottom
CMD yarns (followed by an "a" stitching yarn). This pattern can be
repeated throughout weaving. Although it is preferred that all of
the stitching yarn pairs follow this pattern (i.e., that 50 percent
of the stitching yarn pairs be "reversed"), some benefit can be
obtained by reversing only a smaller percentage (for example 25,
33, or 40 percent) of the stitching yarn pairs.
Another embodiment of the present invention is illustrated in FIGS.
3A, 3B and 4A through 4L, wherein a repeat unit of a 24 harness
multi-layer forming fabric designated broadly at 100 is shown. The
fabric 100 comprises top machine direction yarns 101 through 112,
top CMD yarns 121 through 132, bottom MD yarns 141 through 152,
bottom CMD yarns 161 through 172, and stitching yarns 181a, 181b
through 192a, 192b. One pair of stitching yarns is positioned
between each pair of top CMD yarns and each pair of bottom CMD
yarns.
Like the fabric 20, the top MD and CMD yarns of the fabric 100 are
interwoven such that each top CMD yarn passes over and under
alternate MD yarns, and so that every CMD yarn passes over and
under to same MD yarns. These, in combination with the stitching
yarn pairs, form a top papermaking surface that has a plain weave
pattern (FIG. 3A). The bottom MD and CMD yarns are interwoven so
that each bottom CMD yarn follows an "over 1/under 5" pattern
relative to the bottom MD yarns, and so that the knuckles formed by
the bottom MD yarns take a "broken twill" pattern, in which the
knuckles formed under adjacent CMD yarns are first offset by two MD
yarns in one direction, then by three MD yarns in the opposite
direction. Thus, the knuckles form a zig-zag diagonal pattern (see
FIG. 3B).
Each of the stitching yarns of the fabric 100 has a fiber support
portion, which interweaves with the top MD yarns, and a binding
portion, which stitches the bottom layer of the fabric. As in the
fabric 20, these portions of the stitching yarns are separated at
transitional top MD yarns, under which both stitching yarns of a
pair pass under and cross. The fiber support portion of each
stitching yarn is positioned above the binding portion of the other
stitching yarn of its pair.
Each of the stitching yarns of the fabric 100 follows the same
weave pattern in its fiber support portion as it interweaves with
the top MD yarns, with each stitching yarn passing over three top
MD yarns and under two top MD yarns in an alternating fashion. The
stitching yarns pass over the top MD yarns passed under by the top
CMD yarns, then pass over the top MD yarns passed under by the top
CMD yarns, with the result that the top layer of the fabric 100 has
a plain weave surface. Pairs of stitching yarns are interwoven with
the top MD yarns such that each group of four adjacent stitching
yarn pairs falls within a pattern in which the fiber support
portions of three of the four pairs of stitching yarns are not
offset from one another in the MD direction at all; i.e., the fiber
support portions of each pass over the same top MD yarns. The fiber
support portion of fourth pair of stitching yarns of the group is
offset from the others within the group by two top MD yarns. For
the fiber support portions of the next group of four yarn pairs,
the entire group is offset by two top MD yarns in the direction
opposite of the offset of the individual stitching yarn pair.
As an example of this pattern, the stitching yarns 188a, 189a,
190a, and 191a form a group of four stitching yarns in adjacent
stitching yarn pairs. Of these, stitching yarns 188a, 190a, and
191a pass over top MD yarns 105, 107, and 109. Stitching yarn 189a
passes over top MD yarns 107, 109, and 111, which represents a two
MD yarn offset. The next group of four stitching yarn pairs would
then begin with stitching yarn 191a, which passes over top MD yarns
103, 105 and 107; this represents a two top MD yarn offset in the
direction opposite that of the offset of stitching yarn 189a. This
pattern continues for each group of four stitching yarn pairs.
In its binding portion, each stitching yarn passes below five top
MD yarns and above four bottom MD yarns while passing below one
bottom MD yarn to stitch the top and bottom layers together. The
bottom MD yarn stitched by the stitching yarn binding portion
follows one of three different patterns; it is either the second,
third or fourth bottom MD yarn reached by the stitching yarn after
passing below a traditional top MD yarn. For example, stitching
yarn 182a passes below bottom MD yarn 144, the second bottom MD
yarn it approaches after passing below transitional top MD yarn
102. In contrast, stitching yarn 181a passes below bottom MD yarn
147, the third bottom MD yarn it approaches after passing below
traditional top yarn 104, and stitching yarn 183a passes below
bottom MD yarn 146, the fourth bottom MD yarn it approaches after
passing below transitional top MD yarn 102.
Notably, the stitching yarns of each pair follow the same weave
pattern in their binding portions as the other stitching yarn of
that pair (i.e., like stitching yarn 183a, stitching yarn 183b also
stitches the fourth bottom MD yarn it approaches after passing
below a transitional top MD yarn). Also, it can be seen from FIGS.
4A through 4L that the stitching yarn pairs follow a pattern in
which the stitching yarns of the first pair stitch the third bottom
MD yarn they approach, the stitching yarns of the second pair
stitch the second bottom MD yarn they approach, the stitching yarns
of the third pair stitch the fourth bottom MD yarn they approach,
and the stitching yarn of the fourth pair stitch the third bottom
MD yarn they approach. This "third/second/fourth/third" pattern is
repeated three times within the repeat unit.
Like the stitching yarns of the fabric 20, the stitching yarns of
the fabric 100 are also interwoven as "reverse picks." The "reveres
picks" nature of the fabric can be see in FIG. 3B, where a
zig-zagging line indicates the broken twill pattern of knuckles
formed on the bottom layer by the bottom MD yarns and the stitching
yarns. This line indicates locations where a bottom side knuckle
formed by a bottom MD yarn is sandwiched between two stitching yarn
knuckles, each of which is offset from the bottom MD knuckle by one
bottom MD yarn. Following this pattern, it can be seen that
stitching yarns of adjacent pairs within the pattern are both
nearer to the bottom CMD yarn they flank than are their paired
stitching yarns. For those stitching yarn knuckles on the diagonal
line between which there is no bottom MD knuckle, their stitching
yarns are farther from the bottom CMD yarn they flank than are
their paired stitching yarns. Thus, the reversing of the stitching
yarns in this embodiment can be identified by the weave pattern in
the bottom layer of the fabric 100. As with the fabric 20,
reversing of the stitching yarns in the fabric 100 disturbs any
pattern formed by top transitional MD yarn knuckles and, therefore,
provides a fabric that produces a higher quality paper for
printing.
Those skilled in the art will also appreciate that other plain
weave patterns in which the stitching yarns are divided differently
into fiber support portions and binding portions can be
constructed. For example, the fabric can include a top layer in
which each stitching yarn of a pair passes over two or four top MD
yarns in its fiber support portion. As illustrated, the stitching
yarns can pass over different numbers of top MD yarns, or can pass
over the same number. Of course, appropriate adjustment of the
positioning of the bottom knuckles in the binding portions of such
stitching yarns should be made with changes to the stitching yarn
pattern on the top surface.
Another embodiment of a multi-layer forming fabric of the present
invention is illustrated in FIGS. 5A, 5B and 6A through 6F, in
which a repeat unit of a broken twill multi-layer forming fabric,
designated broadly at 200, is illustrated. The repeat unit includes
12 top MD yarns 201 through 212, 6 top CMD yarns 221 through 226,
12 bottom MD yarns 241 through 252, 6 bottom CMD yarns 261 through
266, and 12 stitching yarns 281a, 281b through 286a, 286b.
As shown in FIG. 5A, the top surface of the fabric 200 has a
1.times.2 twill pattern formed by the top MD yarns, the top CMD
yarns and the fiber support portions of the stitching yarns. More
specifically, each top CMD yarn interweaves with the top MD yarns
in an "over 2/under 1" pattern; this is demonstrated by top CMD
yarn 221, which passes over top MD yarns 201 and 202, under top MD
yarn 203, over top MD yarns 204, 205, under top MD yarn 206, over
top MD yarns 207, 208, under top MD yarn 209, over top MD yarns
210, 211, and under top MD yarn 212. The remaining top CMD yarns
follow the same "over 2/under1" pattern, but are laterally offset
from their adjacent CMD yarns by two MD yarns. For example, top CMD
yarn 222 passes over top MD yarn 201, under top MD yarn 202, over
top MD yarn 203 and 204, and under top MD yarn 205 before
continuing in an over 2/under 1 pattern. Thus, the "over 2" portion
of top CMD yarn 222 is first seen as it passes over top MD yarns
203 and 204, which are offset from the top MD yarns 201, 202 passed
over by top CMD yarn 221 by two MD yarns.
Referring now to FIG. 5B, the machine side surface of the fabric
200 formed by the bottom MD and cross MD yarns takes the pattern of
a "broken twill." Each bottom CMD yarn has an "under 5/over 1"
repeat pattern with the bottom MD yarns. For example, bottom CMD
yarn 261 passes over bottom MD yarn 241, under bottom MD yarns 242
through 246, over bottom MD yarn 247, and under bottom MD yarns 248
through 252. This "under 5/over 1" pattern is repeated by the
remaining CMD yarns. However, the bottom side knuckles formed by
the bottom MD yarns as they pass below the bottom CMD yarns are
arranged in a broken twill pattern, with the bottom side knuckles
being formed by bottom MD yarns 241, 243, 245, 242, 246, 244 on
bottom CMD yarns 261 through 266, respectively, and by bottom yarns
247, 249, 251, 248, 252, and 250 on bottom CMD yarns 261 through
266 respectively. As can be seen in FIG. 5B, these knuckles fail to
form a clear diagonal as is characteristic of twill fabrics, but
instead form a "broken twill" pattern.
The top and bottom layers of the fabric 200 are bound together by
the stitching yarns listed above, each of which has both a fiber
support portion and a binding portion. As with the fabrics 20 and
100 described earlier, the fiber support portion and binding
portion of each stitching yarn are divided by traditional top MD
yarns below which stitching yarns of a pair cross each other. The
fiber support portion of each stitching yarn follows an "over
2/under 1/over 2" pattern. In its binding portions, each stitching
yarn passes between the top and bottom MD yarns with the exception
of passing below one bottom MD yarn to stitch the top and bottom
layers together. The bottom MD yarn that is stitched is located
either two or three MD yarns away from the transitional MD yarns
that separate the fiber support and binding portions of each
stitching yarn.
This pattern is exemplified by stitching yarn 285a, the stitching
pattern of which is illustrated in FIG. 6E. Stitching yarn 285a
passes over top MD yarns 201 and 202, under top MD yarn 203, and
over top MD yarns 204, 205 before passing below transitional top MD
yarn 206. In its binding portion, stitching yarn 285a passes above
bottom MD yarns 247 and 248, below bottom MD yarn 249 and above
bottom MD yarns 250, 251 before passing below transitional top MD
yarn 212 and above bottom MD yarn 252.
Pairs of stitching yarns are interwoven with the top MD yarns
relative to one another such that their fiber support portions, the
top MD yarns, and the top CMD yarns form a 1.times.2 twill pattern.
Referring again to FIG. 6E, and as described above, stitching yarn
285a passes above top MD yarns 201, 202 under top MD yarn 203, and
over top MD yarns 204, 205. Both stitching yarns 285a, 285b pass
below transitional top MD yarn 206, after which the fiber support
portion of stitching yarn 285b continues the over 2/under 1 twill
pattern first established by stitching yarn 285a. In doing so,
stitching yarn 285b passes above top MD yarns 207, 208, below top
MD yarn 209 and above top MD yarns 210, 211 before passing below
transitional top MD yarn 212.
FIG. 5A demonstrates that the stitching yarns are interwoven with
the top and bottom MD yarns relative to top CMD yarns such that an
"over 2" segment of each fiber support portion is offset by one MD
yarn from an "over 2" segment of the top CMD yarns that flank that
stitching yarn. For example, the stitching yarn 281a passes over
top MD yarns 202 and 203. The nearest top CMD yarns, which are 221
and 222, pass over top MD yarns 201, 202 and 203, 204 respectively.
Thus, the distinctive diagonal of a twill is formed by the top CMD
yarns and the fiber support portions of the stitching yarns.
FIG. 5B also illustrates how the stitching yarns are stitched into
the bottom MD yarns. It can be seen in FIG. 5B that the knuckle
formed by each stitching yarn as it passes below a bottom MD yarn
is positioned such that, in one direction, two bottom CMD yarns
reside between the stitching yarn knuckle and the knuckle formed by
that bottom MD yarn over a bottom CMD yarn, and in the opposite
direction, three bottom CMD yarns reside between the stitching yarn
knuckle and the next knuckles formed by that bottom MD yarn over a
CMD yarn. For example, stitching yarn 284a forms a knuckle as it
passes under bottom MD yarn 241. The bottom MD yarn 241 forms a
knuckle as it passes under bottom CMD yarn 261, which is separated
from the knuckle formed by stitching yarn 284a by three bottom CMD
yarns (262, 263, 264). Continuing with the pattern in the other
direction, bottom CMD yarns 265 and 266 are positioned between the
knuckle formed by stitching yarn 284a and the knuckle that would be
formed by bottom MD yarn 241 under the next bottom CMD yarn after
bottom CMD yarn 266 (which would have the same weave pattern as
bottom CMD yarn 261). Thus, the stitching yarn knuckle of stitching
yarn 284a is separated from bottom MD yarn knuckles by three bottom
CMD yarns in one direction and by two CMD yarns in the other
direction.
Those skilled in this art will appreciate that fabrics of the
present invention can be construed with other twill patterns in the
top layer. For example, a fabric can have a 1.times.3 or 1.times.4
twill top layer. Any of these twill patterns can be a conventional
twill, such as that of the fabric 100, or can take a broken twill
pattern, such as those embodied in 4 or 5 harness satin single
layer fabrics. Fabrics can also be constructed in which fiber
support portions of stitching yarn pairs pass over different
numbers of top MD yarns. In each instance, the skilled artisan
should understand the appropriate modifications to the binding
portions of the stitching yarns to accommodate differences in the
fiber support portions.
Those skilled in this art will recognize that, although the plain
weave and twill fabrics illustrated and described in detail herein
are preferred, other fabric weaves, such as other twill weaves and
satins, that employ pairs of stitching yarns integrated into the
papermaking surface of a fabric with the top CMD yarns can also be
made. Also, any number of configuration of the bottom layer in
which stitching yarn pairs stitch the bottom MD yarns can be used.
It is also contemplated that, rather than including a pair of
stitching yarns between each pair of top CMD yarns, a fabric in
which a pair of stitching yarns is included between every other
pair of top CMD yarns can be constructed. In addition, although the
illustrated fabrics have equal numbers of top and bottom MD and CMD
yarns, this need not be the case for the present invention; other
ratios, such as two top CMD yarns for each bottom CMD yarn, can
also be employed.
The configurations of the individual yarns utilized in the fabrics
of the present invention can vary, depending upon the desired
properties of the final papermakers' fabric. For example, the yarns
may be multifilament yarns, monofilament 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 papermakers'
fabric. For example, the yarns may be formed of cotton, wool,
polypropylene, polyester, aramid, nylon, or the like. The skilled
artisan should select a yarn material according to the particular
application of the final fabric.
Regarding yarn dimensions, the particular size of the yarns is
typically governed by the size and spacing of the papermaking
surface. Generally, the diameter of the top CMD yarns is about 25
to 75 percent of the diameter of the bottom CMD yarns, and the
diameter of the top MD yarns is about equal to or smaller than the
diameter of the top CMD yarns. In a typical fabric, the diameter of
the top CMD yarns is between about 0.11 and 0.17 mm, the diameter
of the top MD yarns is between about 0.11 and 0.15 mm, the diameter
of the bottom CMD yarns is between about 0.20 and 0.40 mm, and the
diameter of the bottom MD yarns is between about 0.17 and 0.25 mm.
The diameter of the stitching yarns is typically between about 0.11
and 0.17 mm.
Yarns may also vary advantageously in modulus of elasticity. For
example, stitching yarns that interweave with a fewer number of top
MD yarns than its paired stitching yarn (such as the "b" yarns of
fabric 20) may have a higher modulus of elasticity (typically
between about 10 and 50 percent higher) than its paired stitching
yarn.
As the foregoing discussion demonstrates, the fabrics of the
present invention address problems encountered with prior art
triple layer forming fabrics. The fabrics of the present invention
integrate the stitching yarns into the top surface of the fabric,
whether it be a plain weave, a twill, a satin, or other pattern,
and therefore avoid the marring of the papermaking surface that can
accompany stitching yarns that comprise less of the papermaking
surface. The integration of the fabric attributable to the
stitching yarns also greatly reduces (if not eliminating)
interlayer wear. In addition, because the stitching yarns comprise
such a large portion of the papermaking surface, the differences in
tension between the top CMD yarns and the stitching yarns that can
distort the papermaking surfaces of other fabric are less critical
to the fabrics of the present invention. The destiny of the
stitching yarns also provides a tighter and more reliable binding
of the top and bottom layers of the fabric, which can provide the
designer with a wider variety of yarn choices to balance paper
forming properties, durability and wear.
The foregoing embodiments are illustrative of the present
invention, and are not to be construed as limiting thereof. The
invention is defined by the following claims, with equivalents of
the claims to be included therein.
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