Note: Descriptions are shown in the official language in which they were submitted.
CA 02673846 2009-07-24
Our File: 01204PO541 CA01
METHOD OF MANUFACTURING INDUSTRIAL TEXTILES BY MINIMIZING
WARP CHANGES
FIELD OF THE INVENTION
This invention relates to the manufacture of industrial textiles, and in
particular to a
method of operating looms in such manufacture. More particularly, the
invention relates
to a method of improved manufacturing of such textiles by reducing the warp
yarn
changes required for such looms so as to minimize down time.
BACKGROUND OF THE INVENTION
Industrial fabrics such as are used in papermaking, filtration and like
applications are
generally woven structures made using very wide industrial looms which can be
30 ft.
(l Om) in width or wider. Certain of these fabrics, particularly those used in
papermaking
to initially form and drain the sheet (referred to as forming fabrics), are
frequently woven
at very high mesh counts, meaning that the number of warp yams per unit of
fabric width
is relatively high in comparison to other papermaking fabrics, and can be in
the range of
up to 200 yarns per inch (78.7 yarns/cm) or more. These yams can be very small
in size,
with diameters ranging from as low as about 0.08mm or less up to about 0.30mm
or
more; other fabrics, such as those used in the press or dryer sections of
papermaking
machines, or in similar industrial filtration applications, may have warp yam
sizes in the
range from about 0.3mm up to about 0.7mm or higher. These larger yams are
frequently
woven to provide a mesh of from 20 yams/inch (7.87 yarns/cm) up to about 70
yarns/inch
(27.6 yarns/cm). Selection of appropriate weave designs for these industrial
fabrics, and
selection of warp and weft yarn diameters and cross-sectional shapes for use
in these
industrial fabrics is generally based on the type of product to be made, the
environment in
which the fabric is to be used, and characteristics of the machine for which
the fabric is
intended.
Industrial fabrics such as papermakers forming fabrics are currently woven to
provide
one of the following well-known textile structures:
1
CA 02673846 2009-07-24
a. Single layer fabrics, woven using one warp yarn system and one weft yarn
system;
b. Semi duplex fabrics, woven with one warp yarn system and two layers of well
yams, which yarns are not stacked directly over each other;
c. Double layer fabrics, woven with one warp yarn system and two layers of
well
yarns which are arranged so that each well yarn in the top surface is
vertically
stacked so as to be directly above a corresponding well yarn in the lower
surface;
d. Extra support double layer fabrics, similar to double layer fabrics but
with
additional well yarns woven into the top surface;
e. Triple well fabrics, woven using one warp yarn system and three well yarn
systems arranged so that the well yams are vertically stacked over each other;
f. Standard triple layer fabrics, woven using two warp yarn systems and two
well
yarn systems to provide two independent fabric structures which are frequently
tied together during weaving by means of an additional well yam system;
g. Triple laver sheet support binder (SSB) fabrics, woven using two systems of
warps and two systems of well yarns; a selected number of the well are woven
into the fabric as exchanging, interchanging yarn pairs so that as one yarn of
the
pair is being woven into e.g. the top surface the other is woven into the
bottom;
h. Triple layer "warp tie" fabrics, woven using two well (CD) yarn systems and
two warp (MD) yarn systems; at least a portion of the warp yarns are woven as
interchanging pairs so that as one yarn of the pair is being woven into e.g.
the
top surface the other is woven into the bottom; in certain designs, some of
the
warp yarns of each of the two systems will be interwoven exclusively with well
yarns of one of the top or bottom systems of well yarns;
i. Triple la ear warp integrated sheet support binders (WISS), woven using two
well (CD) yarn systems and two warp (MD) yarn systems in which all (100%) of
the warp yarns are woven as interchanging pairs so that as one yarn of the
pair is
being woven into e.g. the top surface the other is woven into the bottom
2
CA 02673846 2009-07-24
Industrial fabrics such as papermakers forming fabrics are currently
manufactured using
carefully selected yarn sizes and materials which, when woven according to
provide one
of the above fabric structures, with a chosen mesh and knock (number of weft
yarns per
unit length of fabric), are intended to best suit the grade or type of product
that is to be
manufactured on a specific papermaking machine having unique performance
characteristics. Each papermaking machine and each type of stock (that is, the
highly
aqueous mixture of water, papermaking fibers and chemicals) have, in
combination, a
unique set of operating parameters which the papermaking fabric manufacturer
will strive
to accommodate so as to optimize the quality of the paper product to be made.
In
addition, the fabric itself must be extremely rugged and provide a stable
structure which
will withstand, without distorting or catastrophically failing, the speeds and
environmental conditions in which it is expected to operate.
The fabric surface upon which the papermaking fibers are deposited, referred
to as the
paper side or PS, must be constructed so as to uniformly support the fibers
and form the
sheet, while providing adequate drainage of fluid from the papermaking stock
deposited
thereon. The opposite fabric surface, referred to as the machine side or MS,
must be
rugged and dimensionally stable so as to provide a secure and robust platform
to which
the fine papermaking surface is attached. While in operation, the fabric will
be running
in an endless loop through the papermaking machine at speeds as high as 1,500
m/min or
more and will be in moving contact with various stationary dewatering devices
(such as
blades, foils and suction box covers) in the machine.
Given these differing requirements, the fabric manufacturer must strike a
balance
between the papermaking properties (e.g.: fiber support and drainage
capabilities of the
PS layer), and the mechanical properties of the fabric (e.g.: elastic modulus,
shear
stability, caliper and seam strength) while providing a textile product which
is suitable for
the manufacture of a particular grade of paper on the machine for which it is
intended. In
the past, this was frequently done by changing one or more of the fabric mesh,
knock,
yarn size and structure.
3
CA 02673846 2009-07-24
Woven industrial textiles are typically manufactured from polymeric
monofilament or
multifilament yarns as each of the warp and weft materials. During weaving,
the warp is
paid off from a yarn supply at the back of the loom (from what is referred to
as a back
beam), passed through reed openings mounted in the loom heddles, and then
around a
take-up roll at the front of the loom. As the heddles are moved up and down,
the
individual warp yarns are thus moved to create so-called shed openings. The
weft yarns
are shot or carried across the shed openings from one side of the fabric to
the other by
means of a shuttle, rapier or similar mechanism, depending on the loom type.
These weft
yarns are paid off from a storage canister or bobbin located at each side of
the fabric. The
weave pattern of the fabric is created by controlling the movement of the
heddles and
thus the individual warp yarns so that selected ones are positioned either
above or below
a specific weft yarn, thereby creating interlacing locations across the width
of the fabric.
Changes to the weft yarn size and density (i.e. number of yarns per length of
fabric) are
easily made by canister changes and frequently such changes are an integral
part of the
fabric manufacturing process. However, warp yarn changes are much more
difficult and
time consuming to make, particularly on wide industrial looms such as those
used for the
manufacture of papermaking fabrics, as they require changing one or both of
the back
beam and the heddles, and re-threading of each of the thousands of individual
warp yarns
through both the heddles and reeds.
Industrial fabric manufacturers typically wind thousands of feet or meters of
warp yarn
onto large individual spools (referred to as "cans") which are about 3 ft (1
m) in diameter
and range from about 4 to 12 inches (10cm to 30.5cm) in width. These cans are
usually
made of steel or a similar rugged material and, when full of yarn (which has
been
carefully wound onto the can at predetermined tension) they are then mounted
in
succession along the back beam of the loom to provide the supply of warp
material for
the fabrics that are to be woven. For example, a l Om wide loom equipped with
4 inch
(10.2cm) wide cans might have more than 100 of such cans mounted in succession
along
its back beam. If the loom is a double beam loom, meaning it is equipped with
two such
4
CA 02673846 2009-07-24
back beams, then the number of cans would be double that of a single beam
loom, or 200
such cans or more.
Warp changes on a loom are typically made to accommodate fabrics having either
different fabric structures or meshes, or both, than those made previously on
the same
loom. The warp change will usually be made to allow the manufacturer to weave
other
fabrics having differing mechanical properties and constructions than those
previously
produced. For example, a warp change would be made to allow the production of
a fabric
with a larger or smaller warp yarn size so as to provide a different mesh, or
a different
cross-sectional shape, or made from a different material, than was previously
made on the
same loom. Alternatively, a warp change will be made when the manufacturer
wishes to
weave a different fabric construction on the same loom previously used to
weave another
fabric construction (e.g. a triple layer fabric where previously a semi-duplex
fabric was
woven). Such changes are usually made to optimize the fabric for its intended
end use,
whether for papermaking properties or mechanical properties. Because of the
difficulties
associated with changing the warp material, fabric manufacturers will
frequently devote
one or more looms to a particular warp size and fabric type or style, and will
then
carefully schedule fabric production so that the same loom is devoted to
making as many
of that style using that same warp as are required before a further and very
time
consuming warp change is necessary.
A simple warp change (that is, one that does not require a mesh change) is
effected as
follows when there is no fabric structure change. The original warp yarns are
cut before
(i.e. on the can side of) the heddles so as to leave trailing ends, and the
cans containing
the old warp material are removed from the back beam; cans containing the new
warp
material are then mounted onto a new or the existing back beam at the back of
the loom.
The old beam or cans are removed from the loom and the new beam or cans are
then
suitably positioned. The trailing ends of the existing warp yarns are then
joined onto
those from the new beam and the loom is advanced (i.e. the take-up roll is
advanced so
that the existing warp is wound onto it) and the yarns from the new beam are
passed
through the heddles following the previous ones. Weaving can then re-commence
once
5
CA 02673846 2009-07-24
all of the new yarns are in position and placed under suitable tension. This
relatively
simple change can be executed quickly compared to a complete warp and mesh
change.
However, when the warp change is required due to a fabric mesh change, or the
number
of sheds required to weave the new fabric is different from that needed to
weave the
previous fabric, or if the new fabric has a different structure (i.e. single
layer, double
layer, triple layer, etc.) from that previously woven, then the loom must be
completely re-
drawn or re-threaded, meaning that the old warp must be removed and the new
warp must
be individually and manually threaded through the eyelets of each of the
heddles. It will
be appreciated that when 100 or more warp yams/inch (39/cm) must be threaded
through
the heddles of a loom used to produce a l Om wide fabric, this threading can
be a very
time consuming process. Other loom components may also need to be changed.
Following the warp change, the loom must then be re-set so as to establish
appropriate
weaving tensions and other parameters so as to produce the fabric according to
the
required specifications. Depending on the width of the loom and the warp yarn
size, this
entire process can remove the loom from production for several weeks and
require the
assistance of numerous skilled employees; while re-threading is occurring, the
loom is
unable to produce any fabric. It will thus be appreciated that a warp change
can be a very
expensive and time consuming process.
Efforts have been made by various loom and textile manufacturers to reduce the
time
taken for the warp changing process, by improving the efficiency of steps
within the
process. Examples of attempts to address the mechanical aspects of the steps
in warp
changing include US 6,314,628 to Crook; US 7,178,558 and US 7,318,456 both to
Nayfeh et al.; US 5,775,380 to Roelstraete et al.; US 5,394,596 and EP 592807
both to
Lindenmuller et al.; and US 4,910,837 to Fujimoto et al.;
However, none of these disclosures address the distinct and fundamental issue
of the
desirability of minimizing the number of warp changes that must be made to
accommodate a variety of fabric meshes, structures and designs.
6
CA 02673846 2009-07-24
It would be highly advantageous to develop a production means to reduce the
number of
warp changes necessary to manufacture a wide range of industrial textile
products such as
identified above, thereby reducing production costs while increasing
efficiency.
SUMMARY OF THE INVENTION
The invention seeks to provide a method for optimizing industrial fabric
production by
reducing or minimizing the number of times the warp yarn material on a loom
must be
changed, by providing a manufacturing method whereby a number of different
textile
products, having some equivalent or closely related characteristics, can be
made in
sequence using the same loom and warp yarn material, thus minimizing the
number of
warp changes necessary between production of the different fabrics, in
comparison to the
prior art. At the same time, the physical characteristics of the fabrics can
be selected to
closely match the requirements necessary for the end consumer to manufacture a
range of
cellulosic products whose basis weights range from at least 15 to 80 gsm
(grams per
square meter) or more.
Pursuant to the invention, a single loom including a chosen warp material
having a
specified cross-sectional shape and size, threaded to a chosen mesh, is used
to weave
fabrics having differing structures each of which is intended for use in the
production of
paper products having differing basis weights. In order to do this, one or
more of the weft
size, cross-sectional shape, polymer composition and weft yarn density
(knocking) is
adjusted in the design of the fabric so as to provide a textile product with
both adequate
papermaking properties including drainage area, fiber support and air
permeability, and
mechanical properties including elastic modulus, shear stability and stiffness
sufficient to
accommodate the production of paper products having differing basis weights.
The
fabrics woven using the warp on that one loom will, of necessity, all have the
same mesh
(this is a constant except for single layer fabrics where the warp can be
split to weave
upper and lower fabrics each having half the mesh of a single fabric) and will
be woven
using the same number of sheds in the loom. Adjustments to physical properties
are then
made by changing the weft yarn material
7
CA 02673846 2009-07-24
Whereas in the past it was necessary to have, for example, as many as ten
looms (and
warp size and mesh combinations) or more, each devoted to the production of a
single
product having a specific design and mesh so as to minimize warp changes on
the
individual looms, it is now possible by means of the present invention to
reduce the
number of warp changes significantly, generally to no more than four, and
possibly as
few as one, depending on the papermaking and mechanical requirements of the
textile
products to be made. This rationalization process can be described as a
"single warp
platform" (or SWP) approach, meaning that all fabrics previously made using a
variety of
warp sizes and meshes can now be modified so that the warps can be selected
from no
more than four configurations. Adjustments to fabric properties are then made
by
selection of any or all of the weft yarn size, shape, material and density
(knocking) prior
to and during weaving.
Conventionally, industrial textile manufacturers have diversified the number
of warp
sizes, meshes, materials and cross-sectional shapes used to make fabrics for
their
customers in the belief that, in this manner, the fabrics could be optimized
for the grade
of product to be manufactured and machine for which the fabric was intended.
However,
it has been found from recent experience and experimentation that this
diversification is
not necessary, and that, by means of the present invention, it is now possible
to
accommodate almost all papermaking (and similar fabric) requirements by
reducing the
number of warp meshes, yarn sizes, and cross-sectional shapes to as few as
one, but no
more than four types, thus minimizing the number of different warp used to
weave the
fabrics and thus the number of warp changes required to produce fabrics
adequate to meet
almost all of those needs.
This understanding is based on the discovery that fabric manufacturers have
over-
diversified their production in the past, and have been producing fabrics
within the same
design "family" (e.g. double layer, triple layer) which may utilize a warp
yarn size
difference of as little as 0.02mm, using differing meshes, for different
applications or
customers. In other words, two fabrics within the same design would
conventionally be
manufactured on different looms employing differing meshes and warp yarns
whose
8
CA 02673846 2009-07-24
diameter differed by as little as 0.02mm so as to meet customer-specific or
basis weight
requirements. The invention is thus predicated on the understanding that there
are more
warp sizes in use than are justified by the difference in basis weight between
the products
being manufactured using the fabrics.
The invention therefore seeks to provide a method of manufacturing woven
fabrics from
warp yams and weft yams for industrial uses, the method comprising the steps
of:
(a) identifying optimal fabric characteristics to correspond with at least one
selected
industrial use to determine at least one group of fabrics suitable for each
selected
industrial use;
(b) identifying selected fabric properties to produce the characteristics for
the at least
one determined group;
(c) identifying optimal properties for warp yams for fabrics to be woven for
the at
least one determined group;
(d) preparing a weave design for each fabric to be woven; and
(e) selecting one of the prepared weave designs and selecting optimal
properties for
weft yams for the selected weave design.
DETAILED DESCRIPTION OF THE INVENTION
The invention provides the important advantage that all, or substantially all,
fabrics
presently manufactured from a multiplicity of differing warp types targeted
for a generic
paper grade (e.g.: tissue and towel, printing and writing, packaging and
linerboard) can
now be made using a minimal number, possibly only one, warp type, whose yam
size is
selected from the range of from 0.10mm to about 0.25mm such as would be
optimal for a
range of these textile products. Selection of a specific warp size and mesh is
determined
primarily by the basis weight of the products to be manufactured, and
characteristics of
the papermaking machine for which the fabric is intended. It has also been
found that
fabric production can be further diversified by warp yam size and intended use
as
determined by the basis weight of the product to be manufactured as shown in
Table 1
below:
9
CA 02673846 2009-07-24
TABLE 1
General Grade Basis Weight Warp Yarn Size Optimized Warp
Designation (gsm*) Range of Range (mm) Yarn Size (mm)
Product
Packaging/Linerboard 80+ 0.15-0.25 0.22
Printing / Writing 35 - 80 0.10-0.17 0.15
Towel / Tissue 15 - 35 0.10-0.13 0.11
* = grams per square meter
In Table 1, a wide range of paper products have been grouped by basis weight
into three
general grade designations: packaging and linerboard which are generally
heavier
products and require a high basis weight of about 80 gsm or more; printing and
writing
grades such as newsprint, magazine and similar papers intended for the
application of ink
and which have a lower basis weight range of between about 35 and 80 gsm; and
towel
and tissue which are relatively light basis weight products ranging from about
15 to
35 gsm. Each of these products will require a fabric whose papermaking and
mechanical
properties are optimized for the manufacturing requirements and machine
conditions to
which they will be exposed. In the past, fabric manufacturers would produce
differing
fabrics for a much smaller range of basis weights so that within each of the
above general
grade designations, multiple fabrics would exist to satisfy a narrower basis
weight range.
The present inventors have discovered that this is no longer necessary, and it
is possible
to provide acceptable fabric suitable for the production of all products
within each of the
above grade designations, in other words, one warp will provide fabrics which
will
satisfy the requirements of each grade.
If this is done, then the weft yarn size and knocking (number of weft yarns
per unit length
of fabric) used in combination with the warp will be selected from the range
of from
about 0.08mm to about 0.45mm, with the actual size selected in combination
with the
warp yarn mesh, size and cross-sectional shape available. For example, a round
cross-
section warp yarn having a diameter of about 0.11 mm intended for a fabric for
the
manufacture of low basis weight products such as tissue would generally
utilize a weft
yarn size of from about 0.08 to 0.20 at a PS knocking of from about 50 to 100
yarns/inch
CA 02673846 2009-07-24
(19.7 - 39.4 yarns/cm). Selection of an appropriate weft yarn size, shape,
material and
knocking will provide a fabric having the necessary physical and mechanical
properties
within the range appropriate for the product to be made. The warp yarn size
range in
Table 1 would be appropriate for any of the aforementioned fabric structures
and designs,
and such fabrics could be woven on a loom provided with one, two or three
beams as
required.
The invention is based on the understanding that selection of a preferred
mesh, warp size
and cross-sectional shape appropriate for a range of fabrics is made by
evaluating the
mechanical properties requirements of the resulting fabrics in combination
with the
papermaking properties of the fabric. The fabric must provide adequate
physical
properties appropriate for the environment for which it is intended which are
primarily
dictated by the elastic modulus of the warp materials and the resulting
stability (as
dictated by the shear values of the fabric). Additional important mechanical
properties
include lateral contraction (the narrowing of a fabric as it is tensioned) and
fabric caliper.
These mechanical requirements are then considered in combination with the
desired
papermaking properties of the fabric.
Conventionally, a major constraint when changing from one product at one warp
size and
mesh to another at a different warp size and mesh was the necessity to match
the new
warp cross-sectional area to the old. Mechanical properties of a fabric are
dictated mainly
by cross-sectional area of the warp used in the fabric (it r2 x mesh = warp
cross-sectional
area in fabric). When changing production from a fabric employing a relatively
larger
warp size (e.g. 0.25mm) to smaller (e.g. 0.21mm), the manufacturer had to
increase the
mesh to ensure the same amount of warp cross-sectional area was available to
meet the
target elastic modulus of the fabric.
It has been found that the use of high modulus warp yarn materials,
particularly
polyethylene naphthalate (PEN) and blends thereof such as are described for
example in
PCT/US2009/034850 which is assigned to the present assignee, or high molecular
weight
polyethylene terephthalate (PET) allows use of smaller diameter warp at lower
mesh
11
CA 02673846 2009-07-24
(number of warp per unit width of fabric) while still maintaining adequate
elastic
modulus and is thus particularly suitable. If warp yarns having a smaller
cross-sectional
area can provide adequate elastic modulus for the intended product, then
greater freedom
is available for the selection of an appropriate weft yarn size and knocking
which will, in
turn, allow for a wider variety of paper grades to be manufactured using
fabrics produced
from the same warp. Monofilaments formed from PEN may be more suited for use
in
fabrics where the chosen warp yarn size is relatively small or which may be
subjected to
higher than normally expected linear tensions. Yarns made from polymers such
as
polyetheretherketone (PEEK), polyphenylene sulphide (PPS), various polyamides
or
similar materials may also be used.
The chosen weft yarn can be any of the thermoplastic polymeric monofilaments
or
multifilaments currently employed in the manufacture of industrial textiles.
While
polymers such as PET and polybutylene terephthalate (PBT), polyamides such as
polyamide 6, 6/6, 6/10, 6/12, and blends of thermoplastic polyurethane and PET
such as
are described in US 5,169,711 or US 5,502,120 both of which are commonly
assigned to
the present assignee may be suitable; others may be effective as well and the
invention is
not limited in this way. Similarly, the weft yarns used in fabrics made
according to this
invention will frequently have a round cross-sectional shape, but it could
also be
generally rectangular, square, ovate or otherwise depending on the desired
fabric
properties and its operating environment.
Drainage area as well as other papermaking properties of the PS including FSI
can be
adjusted by appropriate selection of weft size. Weft material used in the
fabrics of this
invention can be of any size, shape or composition appropriate for the
application. To
meet or match fabric specifications (e.g. fiber support or drainage area) when
moving
from one warp size to another, it is necessary to increase/decrease knocking
(number of
weft per unit length of fabric) or increase/decrease weft size. For example, a
larger warp
will reduce drainage area; therefore, this must be accommodated by decreasing
the weft
size to provide both adequate support for the papermaking fibers and drainage
area.
12
CA 02673846 2009-07-24
Preferably, the warp should not be larger than about 0.20 - 0.25mm so as to
provide
adequate PS surface properties and the PS weft should not be smaller than the
warp by a
difference of greater than 0.05mm, to ensure that on heatsetting the weft
provides
sufficient crimp to the warp, as otherwise the warp will be unduly straight
and the
resulting fabric may lack required stability. Subject to this constraint, the
weft can be as
large as necessary or practical to provide the required properties.
The following steps describe the process of consolidating products with
differing warp
diameters and meshes (warp platforms) into a product line consisting of a
single warp
diameter, i.e. a single warp platform (SWP).
Step 1: Select products to consolidate to a single warp platform (SWP) for a
target paper
grade:
a. Number of sheds in weave pattern - the SWP platform loom must have a
number of sheds that is an integer multiple of the existing products to be
consolidated. For example: a 24 shed SWP platform can produce 2, 3, 4, 6, 8,
12 and 24 shed weave designs, but cannot produce 7 shed designs;
b. Warp Count - should be within a range of approximately 10% of the
average warp count of the products to be consolidated into the SWP;
c. Total Warp Cross-Sectional Area - should be within a range of 15% of the
total warp cross-sectional area of the products to be consolidated into the
SWP; and
d. Warp Diameters - should be within a range of 25% of the warp diameter of
the products to be consolidated into the SWP
Step 2: Calculate a table of viable warp cross-sectional areas
a. Create a table of viable warp diameters and warp count combinations using
the criteria in Step 1;
b. The warp cross-sectional areas of the existing product should fall within
the
range of values in the table; and
13
CA 02673846 2009-07-24
c. Identify the cells where the calculated warp cross-sectional areas is
within
-25% of the existing product line warp cross-sectional areas.
Step 3: Calculate a table of viable paper side (PS) warp fill
a. Create a table of viable warp diameter and warp count combinations using
the criteria in Step 1;
b. The existing product PS warp fills should fall within the range of values
in
the table; and
c. Identify the cells where the calculated PS warp fill is within -10% of the
existing product line PS warp fills.
Step 4: Find the logical intersection of the warp cross-sectional areas and PS
warp fill
tables
a. Find the overlap region of the cells of viable values from the warp cross-
sectional area table and those cells of viable values form the PS warp fill
tables. This overlap region will define the range of warp diameters and warp
counts appropriate for the SWP product.
Step 5: Assign weightings to the relative importance of selected fabric
properties
a. A range of viable warp diameters and count combinations for the SWP
product has now been determined that will satisfy the basic mechanical and
drainage requirements of the fabrics intended for the target paper grade, and
also fit within the construction parameters of existing products;
b. List the effect of the warp diameter and mesh for each fabric property;
optionally assign a weighting (e.g. Low, Medium, High) to the importance of
each property for the target paper grade. An example is shown in Table 2 for
Packaging grades:
14
CA 02673846 2009-07-24
Table 2: Fabric Property Weightings
Property Warp Diameter Mesh Weighting /
Comments
Drainage Area Smaller is better Lower is better Medium
Fibre Support Index Smaller is better Higher is better Low
Sheet Smoothness Smaller is better Higher is better Low
Frame Length Smaller is better Lower is better Medium
Air Permeability Smaller is better Lower is better High
Weft Count Range Smaller is better Lower is better High
Shear Stability Larger is better Higher is better High
Stiffness Larger is better Higher is better High
Cloth Caliper Smaller is better No effect Medium
Seam Strength Larger is better Higher is better High
c. In Table 2 above, there are 5 parameters with High weightings; 3 of the 5
call for larger warp diameters and higher mesh counts, the remaining call for
smaller warp diameters and lower mesh counts. Thus, the choice leans
slightly towards choosing as large a warp diameter as possible with as high a
warp mesh as possible.
Step 6: Calculate Weft Diameters and Weft Counts of SWP Products
a. Using suitable calculation tools, calculate the weft yarn diameters and
knocking of the SWP analogues for each fabric design to achieve the best
compromise of fabric properties to match the existing product lines. An
example is shown below in Table 3 below in which existing products
previously woven on separate looms have been converted into SWP
versions:
CA 02673846 2009-07-24
Table 3: Comparison of Properties of Existing Products and SWP Versions
Existing SWP Existing SWP
Product Version Product Version
Weave Type ESDL* ESDL* SSB** Weft SSB** Weft
Tied Tied
Yarn Count 1/in.
Total 112x105 124x105 126x108 126x108
Paper Side 112x70 124x70 63x54 63x54
Machine Side 112 x 35 124 x 35 63 x 36 63 x 36
Yarn Diameters
(mm)
Paper Side MD 0.25 0.22 0.20 0.22
Machine Side MD 0.27 0.22
Paper Side CD 0.26 0.25 0.19 0.18
Paper Side Tie 0.15 0.17 0.19 0.18
Strand
Machine Side CD 0.45 0.45 0.40 0.40
Fabric
Characteristics
Paper Side 40.0% 45.9% 30.0% 28.0%
Drainage Area
Frames Count 1470 /in .2 1085 /in? 3402 /in .2 3402 /in.2
Fibre Support Index 95 88 114 114
(F.S.I
Maximum Frame 0.576 mm 0.556 mm 0.280 mm 0.290 mm
Length
Air Permeability 370 365 450 470
cfm 125Pa cfm 125Pa cfm 125Pa cfm 125Pa
New Cali er 0.05069 0.050 " 0.051 " 0.04869
Drainage Index 21.0 20.2 24.3 25.4
Elastic Modulus 11400 pli 12000 phi 9800 ph 8600 li
Lateral Contraction 0.0019 %/pli 0.0010 %/pli 0.0022 %/pli 0.0037 %/pli
Wear Volume 105 cm3/m2 110 cm3/m2 101 cm3/m2 105 cm3/m2
* ESDL = Extra Support Double Layer
** SSB = Sheet Support Binder
In Table 3 above, a comparison of the papermaking and mechanical properties of
an
Extra Support Double Layer (ESDL) fabric and a triple layer sheet support
binder (SSB)
fabric before and after conversion to the SWP approach is provided. For the
ESDL fabric,
it can be seen that the yarn count was increased from 112 to 124, and the PS
MD
16
CA 02673846 2009-07-24
diameter was decreased from 0.25 to 0.22mm. However, the PS CD weft size was
only
decreased marginally from 0.26mm to 0.25mm and there was no change in the MS
CD
yam size. The resulting fabric had a higher drainage area of 45.9% compared to
40.0%,
but the frame count decreased from 1470/in2 to 1085/in2. The frame length
decreased
from 0.576mm to 0.556mm, the air permeability was marginally decreased from
370 to
365, but the caliper was unchanged. Drainage Index decreased from 21.0 to 20.2
but
elastic modulus increased by 600 pli from 11,400 to 12,000 as did wear volume,
from
105 to 110 cm3/m2. In summary, there were minimal changes to papermaking or
mechanical properties of the fabric as a result of the SWP change.
For the SSB fabric, the yam count was unchanged, and the PS MD diameter was
increased from 0.20 to 0.22mm. As a result of the application of the SWP
process, it will
be noted that the MS MD diameter is the same as the PS MD yarn diameter, and
there
was a small downsizing of the PS CD (weft) size from 0.19 to 0.18; the MS weft
size did
not change. The resulting fabric had a lower PS drainage area of 28.0%
compared to
30.0%, but the frame count and FSI were both unchanged. The frame length
increased
from 0.280mm to 0.290mm, the air permeability increased from 450 to 470, and
the
caliper decreased from 0.051 inches to 0.048 inches. Drainage Index increased
from 24.3
to 25.4 and elastic modulus decreased by 800 pli from 9,800 to 8,600pli but
the wear
volume increased from 101 to 105 cm3/m2. As in the previous ESDL case, there
were
minimal changes to papermaking or mechanical properties of the fabric as a
result of the
SWP change and, in fact, some property improvements were observed.
As discussed above, the method of this invention is directed to looms equipped
with at
least one back beam; it can also be used in looms equipped with two or three
back beams
so as to accommodate differing warp path lengths in the fabric due to
differing weave
designs on each of the paper and machine side surfaces of the fabric. Further,
the
invention is directed to fabric designs which are woven using any number of
sheds in the
loom as are required to weave the chosen design; however fabric designs woven
according to patterns requiring 2, 3, 4, 5, 6, 8, 10, 12, 16, 20, 24, 32, 36
and 48 sheds are
particularly preferred. However, the invention is in no way limited to numbers
of sheds
17
CA 02673846 2009-07-24
required to weave a given fabric design, or to fabric structure (i.e. single,
double, triple
layer, etc.). The invention is also directed at fabrics whose structure
requires the use of
two warp yarn systems, such as triple layer sheet support binder fabrics and
warp tie
fabrics where the size and mesh of the warp on one fabric surface is different
from that
used on the other, however it is not so limited and has applicability to any
industrial
textile structure.
It has been found that the novel fabric manufacturing process of this
invention is able to
produce substantially all fabric structures (single, double, triple, etc) able
to meet the
manufacturing requirements of a given range of basis weights using one warp
(size,
material and shape) by adjusting one or more of the weft size, materials and
knocking
(number of weft per unit fabric length) so as to provide the desired fiber
support
characteristics, open area, air permeability, elastic modulus, dimensional
stability, caliper
and other properties desired in the final product. Alternatively, the number
of warp used
to accommodate all fabric designs and types (i.e. those produced specifically
to match
paper grade and paper machine type or configuration) is no more than four.
18
