U.S. patent application number 10/921973 was filed with the patent office on 2005-04-21 for paper machine belt.
This patent application is currently assigned to VOITH FABRICS PATENT GmbH. Invention is credited to Karlsson, Kjell Anders, Lidar, Vaino Per-Ola.
Application Number | 20050081570 10/921973 |
Document ID | / |
Family ID | 34525028 |
Filed Date | 2005-04-21 |
United States Patent
Application |
20050081570 |
Kind Code |
A1 |
Karlsson, Kjell Anders ; et
al. |
April 21, 2005 |
Paper machine belt
Abstract
A paper machine belt that includes a cross-machine direction
supporting layer providing strength in the cross-machine direction
and at least two additional layers. The two additional layers
include polymeric material and at least one of the additional
layers that includes the polymeric material is positioned on one
side of the cross-machine direction supporting layer and at least
another of the additional layers that includes the polymeric
material is positioned on an opposite side of the cross-machine
direction supporting layer. The cross-machine direction supporting
layer substantially includes cross-machine direction yarns loosely
bound together with very fine machine-direction yarns. A ratio of
mass of the cross-machine direction yarns to the machine direction
yarns being at least 160:1, and mass of the polymeric material of
the additional layer on the one side of the cross-machine direction
supporting layer is substantially the same as a mass of the
polymeric material of the additional layer that is provided on the
opposite side of the cross-machine direction supporting layer.
Inventors: |
Karlsson, Kjell Anders;
(Orebro, SE) ; Lidar, Vaino Per-Ola; (Hogsjo,
SE) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1950 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Assignee: |
VOITH FABRICS PATENT GmbH
Heidenheim
DE
|
Family ID: |
34525028 |
Appl. No.: |
10/921973 |
Filed: |
August 20, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10921973 |
Aug 20, 2004 |
|
|
|
PCT/GB03/00830 |
Feb 24, 2003 |
|
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Current U.S.
Class: |
66/202 |
Current CPC
Class: |
D21F 7/083 20130101;
D21F 7/086 20130101; D21F 1/0036 20130101 |
Class at
Publication: |
066/202 |
International
Class: |
D04B 009/12 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 23, 2002 |
GB |
0204310.7 |
Claims
What is claimed:
1. A paper machine belt comprising: a cross-machine direction
supporting layer providing strength in the cross-machine direction;
and at least two additional layers that include polymeric material
and at least one of said additional layers that includes the
polymeric material is positioned on one side of the cross-machine
direction supporting layer and at least another of said additional
layers that includes the polymeric material is positioned on an
opposite side of the cross-machine direction supporting layer,
wherein the cross-machine direction supporting layer substantially
comprises cross-machine direction yarns loosely bound together with
very fine machine-direction yarns, a ratio of mass of the
cross-machine direction yarns to the machine direction yarns being
at least 160:1, and mass of the polymeric material of the
additional layer on the one side of the cross-machine direction
supporting layer is substantially the same as a mass of the
polymeric material of the additional layer that is provided on the
opposite side of the cross-machine direction supporting layer.
2. The paper machine belt according to claim 1, wherein at least
two of said additional layers that include the polymeric material
comprise different polymers.
3. The paper machine belt according to claim 1 wherein at least one
of the additional layers that include the polymeric material is
provided on a surface of the belt and is structured and arranged to
support a paper web.
4. The paper machine belt according to claim 3 wherein the
additional layer that includes the polymeric material, provided on
the surface of the belt, is water-impermeable.
5. The paper machine belt according to claim 1 wherein at least one
of the additional layers that includes the polymeric material has a
Shore hardness of from 30A to 75D.
6. The paper machine belt according to claim 1 wherein a thickness
of the additional layer that includes the polymeric material is
from 0.4 to 1.0 mm.
7. The paper machine belt according to claim 1 wherein at least one
of the additional layers of polymeric material comprises a
thermoplastic material.
8. The paper machine belt according to claim 7, wherein the
thermoplastic material is a polyether-based polyurethane.
9. The paper machine belt according to claim 1 wherein the
cross-machine direction supporting layer exhibits different
shrinkage to said additional layers of polymeric material.
10. The paper machine belt according to claim 1 wherein at least
two of the additional layers that include the polymeric material
have different colors.
11. The paper machine belt as claimed according to claim 1 wherein
the cross-machine direction supporting layer comprises a plurality
of multi-strand cross-machine direction yarns.
12. The paper machine belt according to claim 1 wherein the belt
further comprises a machine direction supporting layer.
13. The paper machine belt according to claim 12, wherein the
machine direction supporting layer comprises an array of spirally
wound machine direction yarns.
14. The paper machine belt according to claim 1 wherein the belt
further comprises at least one layer of batt.
15. A method of making a paper machine belt comprising: providing a
cross-machine direction supporting layer having strength in the
cross-machine direction; positioning one of at least two additional
layers that include a polymeric material on one side of the
cross-machine direction supporting layer; positioning at least
another of said additional layers that include the polymeric
material on an opposite side of the cross-machine direction
supporting layer; and heating the at least two additional layers
and the cross-machine direction supporting layer, wherein a mass of
the polymeric material of the additional layer on the one side of
the cross-machine direction supporting layer is substantially the
same as a mass of the polymeric material of the additional layer
that is provided on the opposite side of the cross-machine
direction supporting layer.
16. The method according to claim 15 further comprising:
calendering the at least two additional layers and the
cross-machine direction supporting layer.
17. The method according to claim 15, wherein at least two of said
additional layers that include the polymeric material comprise
different polymers.
18. The method according to claim 17, wherein the additional layer
that includes the polymeric material, provided on the surface of
the belt, is water-impermeable.
19. The method according to claim 15 wherein at least one of the
additional layers that includes the polymeric material has a Shore
hardness in the range from 30A to 75D.
20. A paper machine belt that is manufactured according to the
method of claim 15.
21. A paper machine belt comprising: a cross-machine direction
supporting layer; and at least two additional layers that include a
polymeric material and at least one of said additional layers that
includes the polymeric material is positioned on one side of the
cross-machine direction supporting layer and at least another of
said additional layers that includes the polymeric material is
positioned on an opposite side of the cross-machine direction
supporting layer, wherein the cross-machine direction supporting
layer substantially comprises cross-machine direction yarns bound
together with machine-direction yarns, the ratio of a mass of the
cross-machine direction yarns to the machine direction yarns being
at least 160:1, and a mass of the polymeric material of the
additional layer on the one side of the cross-machine direction
supporting layer is substantially the same as a mass of the
polymeric material of the additional laver that is provided on the
opposite side of the cross-machine direction supporting layer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a Continuation in Part of
International Application No. PCT/GB03/00830, filed Feb. 24, 2003,
and claims priority of Great Britain Patent Application No.
0204310.7, filed on Feb. 23, 2002. Moreover, the disclosure of
International Patent Application No. PCT/GB03/00830, filed Feb. 24,
2003, and International Patent Application No. PCT/GB03/00824 filed
Feb. 24, 2003 are expressly incorporated by reference herein in
their entireties.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to paper machine process belts
and particularly, but not exclusively, to belts for transferring
and/or smoothing the paper web within, to and/or from a press
section of a paper machine.
[0004] 2. Discussion of Background Information
[0005] Transfer belts are used for carrying a paper web through a
portion of a paper machine so as to eliminate open draws in which
the paper web is unsupported and is thus likely to break. When the
web breaks the paper machine must be shut down and consequently
this constitutes a serious problem to the papermaker. Such transfer
belts tend to have a smooth surface which can aid smoothing of the
paper sheet and provide an extremely uniform pressure distribution
in a nip with no basecloth mark. The surface should nevertheless
provide for eas sheet release. Furthermore, the belt in use should
be water impermeable.
[0006] In EP 1127976, a transfer belt comprises a base support
having a layer of thermoplastic material formed thereon. A batt of
fibrous material is located on top of this thermoplastic material.
The whole structure is then heated in order to allow the
thermoplastic material to migrate to the surface. It is common for
transfer belts, such as that described in EP 1127976, to suffer
from the drawback of edge curl, i.e., inward curling of the edges
of the belt. In severe cases this can lead to the belt folding over
which would, at the very least, mark the roller and cause
misalignment and damage to the paper sheet.
[0007] Edge curl is caused by differential contraction properties
associated with different materials used within the belt structure,
as well as various finishing processes. For example, polyurethane
film has a much greater shrinkage than the yarns of a woven
structure and so when a film layer attached to a woven base cloth
is partially melted, on cooling, it exerts a contractive force on
the base structure, resulting in curling.
[0008] The present invention has been made from a consideration of
this.
SUMMARY OF THE INVENTION
[0009] According to the present invention there is provided a paper
machine belt having paper machine a layer for providing strength in
the cross-machine direction (hereinafter "the cd supporting layer")
and two or more additional layers, wherein at least two of the
additional layers include a polymeric material and wherein at least
one of the layers of polymeric material is provided on one side of
the cd supporting layer and at least another of the layers of
polymeric material is provided on the obverse side of the cd
supporting layer.
[0010] For example, surprisingly, the provision of a similar mass
of polymeric material on either side, i.e. face of the cd
supporting layer, which gives the cross-machine strength and
rigidity for the belt, results in a balancing effect insofar as the
anticipated differential thermal shrinkage properties of the
polymeric layers are concerned, so as to yield a belt with no edge
curl. Different polymeric materials having different shrinkages may
be used in combination, so that further to exposure to thermal
energy, the shrinkage forces are balanced, eliminating edge
curl.
[0011] Ideally at least one layer of polymeric material is provided
on the paper facing surface of the belt. The polymeric material is
ideally provided as a film, but may, for example, alternatively be
provided as sinterable material or as a fibrous material. This
layer, in the finished product, is ideally water-impermeable.
[0012] Preferably some, and ideally all, of the layers of polymeric
material preferably have a Shore hardness in the range from 30A to
75D, and ideally have a hardness of substantially 90 Shore A.
Ideally, the weight of each polymeric layer is approximately 400
g/m.sup.2. The thickness of each layer of polymeric material is
ideally in the range from 0.4 to 1.0 mm. The preferred polymeric
material is a thermoplastic polymer, such as a polyether based
polyurethane, ideally in film form.
[0013] Polymeric materials having different colors may be used. For
example, if a laminate of two polymeric materials were to be used
in which the individual lamina had different colors then as the
outer layer wears away the lower layer (having a different color)
would become exposed. This would act as wear indicator.
Alternatively, the use of differently colored polymeric materials
might be useful for providing a guiding bar mark across the belt
width. Pigments and additives may be included in the polymeric
material as desired, such as photochromic pigments and/or
ultra-violet fluorescent material.
[0014] The cd supporting layer providing the cross-machine strength
is ideally a structure made up of a plurality of cross-machine
direction yarns, preferably multi-strand (e.g. multifilament or
cabled) yarns, which are laid in close proximity to one another.
However, in order to give ease of handling, the cross-machine
direction yarns may preferably be loosely bound together with very
fine machine-direction yarns. For example, the machine-direction
yarn diameter may be in the order of 0.1 mm and selected for
pliabilty, compared to the stiff cross-machine direction yarn with
a diameter of approximately 0.5 mm. The ratio of the mass of the
cross-machine direction yarns to machine direction yarns is ideally
substantially at least 160:1. The whole layer providing
cross-machine stability has a weight of approximately 200
g/m.sup.2. Ideally, this layer includes approximately 9 to 15
cross-machine direction yarns/cm, preferably 12 cross-machine
direction yarns/cm.
[0015] It was found that this quasi-nonwoven cd supporting layer
embedded between the layers of thermoplastic polymer, further to
heat treatment and calendering, results in a laminated product with
much improved macro-level pressure uniformity, due to the fact that
there was far less chance of sheet marking, as is typical of
substrates containing woven substrates with pronounced warp
knuckles.
[0016] In addition, the belt preferably includes a machine
direction (md) supporting layer to be needled on the roll side of
the structure, to provide strength and md stability. This md
supporting layer may be in the form of a woven, knitted or molded
perforated membrane, for example of the type described in EP
0285376. However, this supporting fabric ideally includes an array
of strong, stable, spirally wound, machine direction yarns. Layers
of fibrous batt can also be needled in order to hold the yarns in
position and to provide a coherent structure. The provision of
additional batt on the roll side can also offer better wear
resistance. In a preferred embodiment, the machine roll side layer
is made up of spirally wound, machine direction, 0.2. mm/2 ply/3
cabled, polyamide yarns, with approximately 7 to 12 yarns/cm. There
is approximately 50-800 g/m.sup.2 of polyamide batt fiber in the
range of 3 to 67 dtex needled thereon. This whole layer preferably
has a weight in-the range from 450 to 480 g/m.sup.2.
[0017] The spirally wound layer of md yarns with batt needled
thereon is the preferred supporting substrate for a number of
reasons. Firstly, marking due to cd/md yarn cross-over knuckles, as
exist in woven substrates, is substantially eliminated.
[0018] Secondly, shrinkage upon heat-setting of a fabric generally
takes place mainly in the cross machine direction because the
machine direction length is held constant between the two rollers
on the stretcher. The spirally wound layer is more yielding than a
woven structure in the cd, due to there being only batt between the
md yarns, which does not prevent the yarns from bunching together
in order to conform to the shrinkage requirements of the
thermoplastic film located thereon.
[0019] It is possible to use, in place of the cd and md supporting
layers, a single base structure, which acts as both a cd and md
supporting layer. This may be, for example, a woven material or
possibly a nonwoven or a film. A preferred example is a double
layer woven fabric with polymeric material on both faces.
[0020] Examples include laminates and integrally woven multiple
layer bases. Yarn sizes would typically be from 0.2 mm to 0.6 mm in
diameter.
[0021] A layer of batt fiber, preferably in the range from 3.1 to
44 dtex, would ideally be needled to this woven base structure.
[0022] The structure as a whole may additionally include separate
layers of batt fibers. The batt is needled to any other layers so
as to mechanically inter-lock them together, as well as providing a
higher level of pressure distribution. The batt used preferably has
a weight in the range from 50 to 800 g/m.sup.2 and ideally in the
order of 300 g/m.sup.2. The total belt thickness is normally
betveen 2.4 and 3.2 mm, with an average weight of between 2600 and
3300 g/m.sup.2.
[0023] The preferred structure of the invention includes at least
five main layers, which working from bottom to top include:
[0024] 1) an md supporting structure,
[0025] 2) a thermoplastic film or films,
[0026] 3) a cd supporting structure,
[0027] 4) a fibrous batt, and
[0028] 5) further thermoplastic film or films, ideally wherein the
mass of thermoplastic material of layer (2) is substantially the
same as that in layer (5).
[0029] The belt is preferably made endless, but could feasibly
include a seam.
[0030] The whole structure is consolidated through needling at
various stages during the manufacturing process. As a result of the
needling stage, the surface is not entirely smooth as there are
around 1 to 200 batt fibers per square cm, and preferably 10-100
batt fibers per square cm protruding through to, and in some
instances standing proud of, the polymer surface. These provide for
good sheet release. The fibers might take the form of loops, that
is the middle of the fiber has been pushed through with both ends
still remaining locked within the structure. If desired, the
protruding fibers may be removed.
[0031] Further to the needling process, the entire structure is
then exposed to sufficient thermal energy to cause the lower melt
point, thermoplastic, polymeric film to melt. This melted polymer
bonds the structure together, embedding the cd supporting layer and
part of the batt in a matrix of molten polymer and forms a very
smooth and well defined impermeable surface., which is resistant to
de-lamination. The belt is then smoothed with a cold polished
cylinder. There is no need to grind the finished product, which is
advantageous because this is extremely difficult to achieve in the
case of low melt polymeric elastomers.
[0032] In an alternative preferred structure the order of layers
"1" and "2" hereinbefore described is swapped around, such that the
structure includes at least five main layers, which working from
bottom to top include:
[0033] 1) a thermoplastic film or films,
[0034] 2) a supporting structure providing machine-direction
stability,
[0035] 3) a structure providing cross-machine stability,
[0036] 4) a fibrous batt, and
[0037] 5) further thermoplastic film or films, wherein the mass of
thermoplastic material of layer (1) is preferably substantially the
same as that in layer (5) to minimize edge-curl. Such an
arrangement helps prevent batt loss and assists with ease of
cleaning.
[0038] Another aspect of the invention includes a paper machine
belt that includes a cross-machine direction supporting layer
providing strength in the cross-machine direction and at least two
additional layers. The two additional layers include polymeric
material and at least one of the additional layers that includes
the polymeric material is positioned on one side of the
cross-machine direction supporting layer and at least another of
the additional layers that includes the polymeric material is
positioned on an opposite side of the cross-machine direction
supporting layer. The cross-machine direction supporting layer
substantially includes cross-machine direction yarns looselv bound
together with very fine machine-direction yarns. A ratio of mass of
the cross-machine direction yarns to the machine direction yarns
being at least 160:1, and mass of the polymeric material of the
additional layer on the one side of the cross-machine direction
supporting layer is substantially the same as a mass of the
polymeric material of the additional layer that is provided on the
opposite side of the cross-machine direction supporting layer.
[0039] Further aspects of the present invention include at least
two additional layers that can include the polymeric material with
different polymers. At least one of the additional layers can
include the polymeric material provided on a surface of the belt
and structured and arranged to support a paper web. Moreover, the
additional layer that includes the polymeric material, provided on
the surface of the belt, can be water-impermeable. Additionally, at
least one of the additional layers that includes the polymeric
material can have a Shore hardness of from 30A to 75D. A thickness
of the additional layer that includes the polymeric material can be
from 0.4 to 1.0 mm. At least one of the additional layers of
polymeric material can comprise a thermoplastic material.
[0040] Further aspects of the present invention include the
thermoplastic material can be a polyether-based polyurethane. The
cross-machine direction supporting layer can exhibit different
shrinkage to the additional layers of polymeric material.
Additionally, at least two of the additional layers can include the
polymeric material with different colors. Moreover, the
cross-machine direction supporting layer can include a plurality of
multi-strand cross-machine direction yarns. Additionally, the belt
further can include a machine direction supporting layer. The
machine direction supporting layer can include an array of spirally
wound machine direction yarns. Moreover, the belt further can
include at least one layer of batt.
[0041] Yet another aspect of the invention includes a paper machine
belt that includes a cross-machine direction supporting layer
providing strength in the cross-machine direction and at least two
additional layers. The two additional layers include polymeric
material and at least one of the additional layers that includes
the polymeric material is positioned on one side of the
cross-machine direction supporting layer and at least another of
the additional layers that includes the polymeric material is
positioned on an opposite side of the cross-machine direction
supporting layer. The cross-machine direction supporting layer
substantially includes cross-machine direction yarns bound together
with machine-direction yarns. A ratio of mass of the cross-machine
direction yarns to the machine direction yarns being at least
160:1, and mass of the polymeric material of the additional layer
on the one side of the cross-machine direction supporting layer is
substantially the same as a mass of the polymeric material of the
additional layer that is provided on the opposite side of the
cross-machine direction supporting layer.
[0042] Another aspect of the invention includes a method of making
a paper machine belt. The method including providing a
cross-machine direction supporting layer having strength in the
cross-machine direction, positioning one of at least two additional
layers that include a polymeric material on one side of the
cross-machine direction-supporting layer, positioning at least
another of the additional layers that include the polymeric
material on an opposite side of the cross-machine direction
supporting layer, and heating the at least two additional layers
and the cross-machine direction supporting layer. Additionally, a
mass of the polymeric material of the additional layer on the one
side of the cross-machine direction supporting layer is
substantially the same as a mass of the polymeric material of the
additional layer that is provided on the opposite side of the
cross-machine direction supporting layer.
[0043] Further aspects of the method can further include
calendering the at least two additional layers and the
cross-machine direction supporting layer. Moreover. at least two of
the additional layers can include the polymeric material include
different polymers. Additionally, the additional layer that
includes the polymeric material, provided on the surface of the
belt, can be water-impermeable. Also, at least one of the
additional layers can include the polymeric material which has a
Shore hardness in the range from 30A to 75D. Additionally a paper
machine belt can be manufactured according to the above-noted
method.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] In order that the present invention may be more readily
understood, a specific embodiment thereof will now be described by
way of example only with reference to the accompanying drawing in
which:
[0045] FIG. 1 is a diagrammatic cross-section of a transfer
smoothing belt in accordance with the present invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0046] Referring to FIG. 1, a transfer and smoothing belt 17 for
use in the press section of a paper machine includes an endless
loop having five layers 11-15.
[0047] The supporting layer 11, includes spirally wound machine
direction yarns 16 into which batt has been needled to hold the
yarns 16 in position. In this embodiment the machine direction
yarns include three pairs of yarns twisted together.
[0048] The second layer 12, located on layer 11, itself includes
two individual layers of thermoplastic polyurethane each having a
weight of 400 g/m.sup.2 and being 0.4 mm thick. On heating these
two polyurethane layers, a single homogeneous layer is formed which
bonds and partially impregnates the md supporting fabric 11 and the
adjacent upper cd supporting layer 13.
[0049] Layer 13 includes a quasi non-woven structure made up of
multifilament, cross-machine direction yarns and extremely fine
machine direction yarns, for loosely holding the cross-machine
direction yarns in position. This layer has a weight of
approximately 195 g/m.sup.2. The mass of material ratio of
cross-machine direction yarns to machine direction yarns is
approximately 160:1. This layer provides cross-machine direction
strength and rigidity.
[0050] A layer 14 of batt is located above the cross-machine
direction supporting structure 13 to facilitate inter-locking of
the various layers by needling. The batt material preferably has a
weight in the order of 300 g/m.sup.2.
[0051] The final layer 15 of thermoplastic material is ideally
identical to the inner thermoplastic material layer 12. On heating,
the constituent polyurethane layers flow and bond the structure
together, embedding the top cd supporting layer and part of the
batt 14, in a polymeric matrix, to form a single homogenous layer.
The belt is cured at a surface temperature of approximately
200.degree. C. with a dwell time of 5 minutes. It is then
calendered at 1 to 40 KN/m at a temperature of less than
200.degree. C.
[0052] Surprisingly, by embedding a cd supporting structure between
layers of melted thermoplastic polymeric material, a balance of
contractive forces is achieved. That is, the relatively stiff, high
bending modulus cross-machine direction orientated yarns, placed in
a position relatively near to the top plane of the fabric, between
the melted polymeric material, can successfully balance the
contractive forces of the melted polymeric material, so as to yield
a belt with no edge curl.
[0053] From recent in-house trials on a pilot machine it has been
found that the belt described above gives excellent transfer at
2000 m/min and the surface has been found, using Martindale
Abrasion testing methods, to exhibit good abrasion resistance. In
particular, the belt was found not to suffer from edge curl.
[0054] It is to be understood that the above-described embodiment
is by way of illustration only. Many modifications and variations
are possible.
* * * * *