U.S. patent application number 10/528282 was filed with the patent office on 2006-07-27 for papermachine clothing with wear-resistant weave.
This patent application is currently assigned to Voith Fabrics Patent GmbH. Invention is credited to Mack Arthur Vines.
Application Number | 20060162803 10/528282 |
Document ID | / |
Family ID | 9944296 |
Filed Date | 2006-07-27 |
United States Patent
Application |
20060162803 |
Kind Code |
A1 |
Vines; Mack Arthur |
July 27, 2006 |
Papermachine clothing with wear-resistant weave
Abstract
Papermachine clothing having machine direction (MD) yarns and
cross-machine direction (CD) yarns interwoven in a repeat pattern,
wherein the CD yarns are provided in two systems. The first CD yarn
system has upper and lower yarns. The second CD yarn system has a
single yarn. The first and second CD systems are provided
alternatively throughout the fabric. The MD yarns are also provided
in two systems, the first MD yarn system extending in between the
upper and lower yarns of the first CD yarn system and over the
single yarn of the second CD yarn system. Individual yarns of the
second MD yarn system extend over one of the upper of lower yarns
of the first CD yarn system and the single yarn of the second CD
yarn system. Two adjacent machine direction yarns from different MD
yarn systems extend as a pair over the same CD yarn of the second
CD yarn system with one of the pair of MD yarns extending above the
other of the pair such that the other yarn is protected from
abrasion.
Inventors: |
Vines; Mack Arthur;
(Waycross, GA) |
Correspondence
Address: |
VOITH FABRICS
3040 BLACK CREEK ROAD
P.O. BOX 1411
WILSON
NC
27893
US
|
Assignee: |
Voith Fabrics Patent GmbH
Patentabteilung zjpt St. Poeltener Strasse 43
Heidenheim
DE
89522
|
Family ID: |
9944296 |
Appl. No.: |
10/528282 |
Filed: |
September 18, 2003 |
PCT Filed: |
September 18, 2003 |
PCT NO: |
PCT/IB03/05024 |
371 Date: |
March 16, 2005 |
Current U.S.
Class: |
139/383A ;
162/902 |
Current CPC
Class: |
D21F 1/0036
20130101 |
Class at
Publication: |
139/383.00A ;
162/902 |
International
Class: |
D03D 25/00 20060101
D03D025/00; D21F 1/00 20060101 D21F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 18, 2002 |
GB |
0221643.0 |
Claims
1. Papermachine clothing comprising machine direction (MD) yarns
and cross-machine direction (CD) yarns interwoven in a repeat
pattern such that, on at least one side of the fabric, as part of
the weave pattern, two adjacent machine direction yarns extend over
the same CD yarn as a pair with one of said pair of MD yarns
extending above the other of said pair such that said other yarn is
protected from abrasion.
2. Papermachine clothing of claim 1, wherein the CD yarns are
provided in two systems, as a first CD yarn system and a second CD
yarn system.
3. Papermachine clothing of claim 2, wherein the two CD yarn
systems are provided alternately through the fabric.
4. Papermachine clothing as claimed in claim 2, wherein the first
CD yarn system comprises stacked upper and lower yarns.
5. Papermachine clothing of claim 2, wherein the second CD yarn
system comprises a single yarn.
6. Papermachine clothing of claim 4, wherein YARNS of a first MD
yarn system extend inbetween the upper and lower yarns of the first
CD yarn system.
7. Papermachine clothing of claim 6, wherein yarns of a second MD
yarn system extends over one of the upper or lower yarns of the
first CD yarn system and over the yarn of the second CD yarn
system.
8. Papermachine clothing comprising machine direction (MD) yarns
and cross-machine direction (CD) yarns interwoven in a repeat
pattern, wherein the CD yarns are provided in two systems, the
first CD yarn system comprising upper and lower yarns, the second
CD yarn system comprising at least one yarn, the first and second
CD systems being provided alternately throughout the fabric, and
wherein the MD yarns are provided in two systems, the first MD yarn
system extending in between the upper and lower yarns of the first
CD yarn system and over the at least one yarn of the second CD yarn
system and individual yarns of the second MD yarn system extending
around one of the upper or lower yarns of the first CD yarn system
and the at least one yarn of the second CD yarn system, and wherein
two adjacent machine direction yarns from different MD yarn systems
extend as a pair over the same CD yarn of the second CD yarn system
with one of said pair of MD yarns extending above the other of said
pair such that said other yarn is protected from abrasion.
9. Papermachine clothing of claim 8, wherein the MD yarns are flat
in cross-section.
10. Papermachine clothing of claim 9, wherein the dimensions of the
MD yarns are in the range from 0.30-0.45.times.0.50-0.80 mm
11. Papermachine clothing of claim 8, wherein the CD yarns are
round in cross-section.
12. Papermachine clothing of claim 8, wherein the diameter of CD
yarns in the first CD yarn system is in the range from 0.20 to 0.80
mm.
13. Papermachine clothing of claim 8, wherein the diameter of the
CD yarns in the second CD yarn system is in the range from 0.50 to
1.50 mm.
14. Papermachine clothing of claim 8, having a permeability in the
range from 90-300 CM.
15. The use of papermachine clothing of claim 8 as a dryer fabric
in a papermaking machine.
16. Papermachine clothing of claim 1, wherein the MD yarns are flat
in cross-section.
17. Papermachine clothing of claim 16, wherein the dimensions of
the MD yarns are in the range from 0.30-0.45.times.0.50-0.80 mm
18. Papermachine clothing of claim 1, wherein the CD yarns are
round in cross-section.
19. Papermachine clothing of claim 2, wherein the diameter of CD
yarns in the first CD yarn system is in the range from 0.20 to 0.80
mm.
20. Papermachine clothing of claim 2, wherein the diameter of the
CD yarns in the second CD yarn system is in the range from 0.50 to
1.50 mm.
21. Papermachine clothing of claim 1, having a permeability in the
range from 90-300 CM.
22. The use of papermachine clothing of claim 1 as a dryer fabric
in a papermaking machine.
Description
[0001] The present invention relates to papermachine clothing and
more particularly, but not exclusively, to dryer fabrics for use in
the dryer section of a papermaking machine.
[0002] Paper is conventionally manufactured by conveying a paper
furnish, usually consisting of an initial slurry of cellulosic
fibres, from a forming section, through a pressing section and
ultimately around a drying section of a papermaking machine.
[0003] Papermachine clothing is essentially employed to carry the
paper web through these various stages of the papermaking machine.
In the forming section the fibrous furnish is wet-laid onto a
moving forming wire and water is allowed to drain from it. The
paper web is then transferred to a press fabric that conveys it
through the pressing section, where it is usually passed through a
series of pairs of rotating cylindrical press rolls. Water is
squeezed from the paper web and into the press fabric as the web
and fabric pass through the nip together.
[0004] In the final stage the paper web is transferred to a dryer
fabric in the dryer section of the papermaking machine. The dryer
section conventionally includes a number of rotatable dryer drums
or cylinders heated from within by steam. The web is directed over
each of these drums by the dryer fabric which holds the web against
the surface of the heated drums. In this way the majority of the
remaining water is evaporated from the paper web.
[0005] Dryer fabrics are generally formed from materials which are
resistant to hydrolytic degradation under high temperatures.
However, these materials are prone to abrasion. Consequently the
dryer fabrics made from these materials have unacceptably short
lives. Numerous solutions have been proposed to this problem. These
solutions sometimes involve varying the constituent polymer of the
fabric yarns, such as in U.S. Pat. No. 5,692,938 or varying the
weave pattern, such as in U.S. Pat. No. 6,158,478 and U.S. Pat. No.
5,503,196.
[0006] U.S. Pat. No. 6,158,478 relates to a multilayer woven dryer
fabric having a weave pattern in which less knuckles are formed on
the machine-side of the fabric than on the paper-side by reducing
the number of interweavings that each machine direction (MD) yarn
makes with the lowermost cross-machine direction (CD) floats. This
produces a machine-contacting surface dominated by a large number
of CD yarns which are subjected to abrasion from the machine, thus
protecting the strength-providing MD yarns. However, this fabric
potentially suffers from the problem of fabric instability in that
during a prolonged run it is likely that the fabric weave will come
apart at the back.
[0007] U.S. Pat. No. 5,503,196 relates to a multilayer dryer fabric
comprising two layers of CD yarns of round cross-section and two
systems of MD yarns, the first being of round cross-section and the
other consisting of flat yarns. The MD yarns in the first system of
MD yarns are interwoven with the CD yarns in the first and second
layers in a duplex weave and bind the first and second layers of CD
yarns together. The MD yarns in the second system of MD yarns are
interwoven with either the first or second layers of CD yarns.
[0008] The knuckles of the first round MD yarn system are said to
be within the fabric with respect to the planes defined by the
second system of flat MD yarns and as a consequence are said to be
less susceptible to degradation by heat and abrasion.
[0009] However, this fabric would be extremely sleezy and not
particularly stable as the whole structure is bound together by
just the central round MD yarns, as the upper and lower MD yarns
only offer minimal binding and for the most part float on either
external surface. Sleezy fabrics suffer from yarn wear, as a result
of internal friction, and changes in permeability resulting in
undesirable differential dewatering of the paper web.
[0010] According to the present invention there is provided
papermachine clothing comprising machine direction (MD) yarns and
cross-machine direction (CD) yarns interwoven in a repeat pattern
such that, on at least one side of the fabric, as part of the weave
pattern, two adjacent machine direction yarns extend over the same
CD yarn as a pair with one of said pair of MD yarns extending above
the other of said pair such that said other yarn is protected from
abrasion.
[0011] According to a second aspect of the present invention there
is provided papermachine clothing comprising machine direction (MD)
yarns and cross-machine direction (CD) yarns interwoven in a repeat
pattern, wherein the CD yarns are provided in two systems, the
first CD yarn system comprising upper and lower yarns, the second
CD yarn system comprising at least one yarn, the first and second
CD systems being provided alternately throughout the fabric, and
wherein the MD yarns are provided in two systems, the first MD yarn
system extending inbetween the upper and lower yarns of the first
CD yarn system and over the at least one yarn of the second CD yarn
system and individual yarns of the second MD yarn system extending
around one of the upper or lower yarns of the first CD yarn system
and the at least one yarn of the second CD yarn system, and wherein
two adjacent machine direction yarns from different MD yarn systems
extend as a pair over the same CD yarn of the second CD yarn system
with one of said pair of MD yarns extending above the other of said
pair such that said other yarn is protected from abrasion.
[0012] The fabric weave of the invention, in arranging some of the
machine direction yarns in pairs with half of these being higher
than the adjacent yarn in the pair, providing protection against
abrasion for the lower MD yarn. Therefore, a considerable number of
the strength-providing machine direction yarns are protected from
abrasion for a considerable time within a highly stable weave
structure.
[0013] The MD yarns are preferably flat, round or square in
cross-section. In a preferred embodiment of the invention the MD
yarns are flat having preferred dimensions in the range from
0.30-0.45.times.0.50-0.80 mm. The CD weft yarns are ideally round
or flat. In a preferred embodiment of the invention the CD yarns
are round in cross-section. Ideally two systems of CD yarns are
used, the first system preferably comprising upper and lower yarns.
The diameter of the CD yarns of the first CD yarn system is ideally
in the range from 0.20-0.80 mm. The diameter of the CD yarns of the
second CD yarn system is ideally in the range from 0.50-1.50 mm.
The second CD yarn system ideally resides within the fabric with
respect to the top and base of the first CD yarn system.
[0014] The fabric of the invention preferably has a permeability in
the range from 90-300 cfm.
[0015] In order that the present invention may be more readily
understood a specific embodiment thereof will now be described by
way of the accompanying drawings in which:--
[0016] FIG. 1 is a plan view micrograph of one fabric in accordance
with the present invention;
[0017] FIG. 2 is a diagram showing the weave pattern of the fabric
of FIG. 1;
[0018] FIG. 3 is a table showing the weave pattern of the fabric of
FIG. 1;
[0019] FIG. 4 is a series of micrographs showing the results of
abrasion tests on the fabric of FIG. 1;
[0020] FIG. 5 is a graph showing the reduction of caliper and
tensile strength of the fabric of FIG. 1 as a consequence of
abrasion;
[0021] FIG. 6 is a graph comparing the reduction of caliper and
tensile strength of the fabric of FIG. 1 with a prior art fabric as
a consequence of abrasion; and
[0022] FIG. 7 is a graph comparing the reduction of caliper and
tensile strength of the fabric of FIG. 1 with a second prior art
fabric as a consequence of abrasion
[0023] Referring to FIGS. 1-3 a papermakers fabric particularly for
use in the dryer section of a papermaking machine is woven from
flat MD warp yarns (0.36 mm.times.0.67 mm) and two systems of CD
wefts/picks which are round in cross-section. The first system of
CD yarns comprises a pair of vertically stacked CD yarns, i.e. top
(T) and bottom (B) yarns, which are 0.4 mm in diameter. The second
system of CD yarns comprises larger wefts, arranged alone, which
are 0.7 mm in diameter. The two CD yarn systems are arranged
alternately through the fabric.
[0024] FIG. 2 clearly shows that the weave is a four warp yarn
repeat within two warp paths. Warps 1 and 3 follow one path such
that the warps hug the external faces of each of the T, B and C
weft yarns. Warps 2 and 4 follow an alternative path passing
between the upper T and lower B picks of the first CD yarn system
and then around weft C. Warps 1 and 3 of the 2.sup.nd MD yarn
system are protected by warp yarns 2 and 4 of the 1.sup.st yarn
system. It can be seen from FIG. 2 that the weave is symmetrical
about a central horizontal plane.
[0025] FIG. 3 is a table showing the exact weave pattern of the
fabric of FIGS. 1 and 2. In the table "LHS" is the left hand weft
presenter, "RHS" is the right hand weft presenter and "Dir" is the
direction of travel of the weft yarn. As is conventional with
tables of this kind a cross in a box underneath any of the
sheds/warps means that the specific warp extends over the
associated weft.
[0026] Therefore we can follow the path of any given warp with
reference to the table of FIG. 3 and also the drawing of FIG. 2.
For example, the number 1 warp from FIGS. 2 and 3 can be seen to
pass over T & B weft yarns 1, 2, under C weft yarn 3, over T
& B weft yarns 4, 5, under 6, over yarns 7, 8, under 9, over
10, 11 and finally under 12.
[0027] As stated previously, the weave is a four warp repeat; i.e.
after the first four warps, the pattern repeats so warps 5 and 9
follow the same path as warp 1, warps 6 and 10 follow the same path
as warp 2 and so on.
[0028] The woven fabric is clearly identified in FIGS. 1 and 2,
where the abrasion resistance of the fabric is readily apparent.
Warps 1 and 3 are protected from abrasion by warp yarns 2 or 4 from
the other pair, as they extend around pick C. Warps 1 and 3 follow
a convoluted path around the external edges of each of the weft
yarns and become tightly wrapped around these yarns. A combination
of this `hugging` effect and the beat up forces of the loom lead to
a high degree of crimp. In comparison, yarns 2 and 4 extend around
the large weft yarns, but then pass between T and B picks, so
taking a far less severe path and subsequently the yarns are less
crimped and fall outside warps 1 and 3, thereby protecting them
from abrasion. In all cases, warp 3 is protected from abrasion on
the upper surface and warp 1 on the lower surface by warp yarns 2
and 4 alternately. In FIG. 1 it can be seen that the protected yarn
3 is provided to the left of warp 2 and to the right of warp 4.
[0029] During manufacture of the fabric two beams are required to
deliver the warp yarns to the healds due to the difference in the
path lengths of the two warp paths of warps 1 and 3 compared to
that of warps 2 and 4. Also two weft presenters are used. One weft
presenter presents either the top or bottom weft of the first CD
yarn system. The other weft presenter presents the larger central
weft yarn of the second CD yarn system.
[0030] Referring to the table of FIG. 3, looking across the first
row from right to left (i.e. the direction of travel of the weft
yarn), it can be seen that the first weft (top) is fired over warps
12, 11 and 10, under warp 9, over warps 8, 7 and 6, under warp 5,
and as can be seen in FIG. 2, over warps 4, 3 and 2, but below warp
1. The second weft selected is a bottom weft and this is picked up
by the shuttle on the left hand side and taken across the loom. As
can be seen in FIG. 2, weft 2 passes under warps 1 and 2, above 3
and then below 4. It then continues (not visible in FIG. 2), under
warps 5 and 6, over 7, under 8, 9 and 10, over 11 and under 12.
[0031] The protected MD yarns 1,3 are advantageously selected to
form the seam loops or to bind to a jointing means such as a
spiral.
[0032] FIG. 4 is a series of twelve micrographs, taken periodically
after the fabric of FIG. 1 has been subjected to abrasion. The
abrasion story is illustrated from 0 to 1632 hours.
[0033] After 96 hours, it can be seen that the uppermost warp
knuckles have just started to be abraded and this continues
gradually until micrograph 6. After 888 hours (micrograph 7) it can
be seen that the most prominent weft yarn T is beginning to be
abraded. At this point, an interesting phenomenon was observed.
Once the abrasion reaches weft yarn T, it seems to halt at this
point, the weft yarn T thus protecting the second warp of the pair
from further abrasion. The abrasion tests were stopped after 1632
hours. At this point, the abrasion seemed not to be any further
advanced than after 888 hours, and there still appeared to be
plenty of life remaining in the fabric. The micrographs clearly
show that the second warp yarn of each warp pair is entirely free
of abrasion for many hours after the onset of abrasion in its
neighbouring yarn.
[0034] FIGS. 5 to 7 show the results of a number of tests which
were carried out to discover, in the same time frames, how the
tensile strength and caliper of the fabric were affected by the
abrasion. These have been plotted for the fabric of the invention
alone, in FIG. 5, and as compared with two prior art dryer
fabrics--"Art 1" & "Art 2", in FIGS. 6 and 7 respectively.
[0035] In FIG. 5 it can be seen that the caliper of the fabric of
the invention is only reduced by just over 13% of its original
value after 1632 hours, and that the tensile strength until 1392
hours was 70% of its original value, but then fell fairly steeply
to just over 45% at the end of the trial. This value though is well
above the critical tensile value, i.e. the value below which the
fabric is rendered unusable, of just under 30%.
[0036] FIG. 6 shows that the fabric of the invention performs well
against the "Art 1" dryer fabric which only has a lifetime of
around 240 hours, at which point the critical tensile strength had
been surpassed.
[0037] In FIG. 7 the performance of the fabric of the invention is
shown as against the "Art 2" dryer fabric. Here the caliper
percentage figures are very similar until around 1536 hours, at
which time, Art 2 shows a sharper decline in caliper. The tensile
strength of the fabric of the invention is consistently lower that
that of Art 2, but after 1632 hours the Art 2 fabric had surpassed
its critical tensile value and became unusable, whereas the fabric
of the invention still had 45% of its original tensile
strength.
[0038] It is to be understood that the above disclosed embodiment
of the invention is by way of illustration only. Many modifications
and variations are possible.
* * * * *