CA2673846A1 - Method of manufacturing industrial textiles by minimizing warp changes - Google Patents

Abstract

A wide variety of industrial fabric structures, each of which previously utilized differing warp yam materials, cross-sectional areas and shapes from the others, can now be woven using as few as one but no more than four warp sizes, material compositions, cross--sectional shapes and meshes by careful initial selection of that warp material, and by subsequent adjustment of the cross-sectional area, shape, material composition and knocking (number of yarns per unit length) of the weft yarns in combination with the basis weight of the product to be manufactured using the fabric. Single and multiple layer fabric structures, requiring either single or multiple beam loom arrangements configured for weaving fabrics according to patterns requiring integer multiples of 2, 3, 4, 6, 8, 12, 16 and 24 sheds, or other numbers of sheds, can thus be made from a single warp "platform"
thereby greatly reducing loom set up and material requirements and thus optimize fabric production.

Description

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:

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 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 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 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 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 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 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 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 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 (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 (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.

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 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:

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:

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

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 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.

Claims (13)

CLAIMS:

1. A method of manufacturing woven fabrics from warp yarns and weft yarns 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 yarns 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 yarns for the selected weave design.

2. A method according to Claim 1, further comprising step (f) for each of the at least one group of fabrics determined in step (a), providing a loom and installing warp yarns on the loom having the optimal properties identified in step (c) for the respective group.

3. A method according to Claim 2, wherein step (o further comprises, for at least one determined group, weaving a fabric on the respective loom to the design selected in step (e) using weft yarns having the optimal properties selected in step (e).

4. A method according to Claim 2 or Claim 3, wherein step (f) comprises providing a loom equipped with a number of back beams selected from one, two and three.

5. A method according to Claim 4, wherein the loom is equipped with two back beams.

6. A method according to any one of Claims 2 to 5, wherein in step (f) the installed warp yarns are constructed of a polyester material selected from polyethylene terephthalate (PET), polyethylene naphthalate (PEN) and blends and copolymers thereof.

7. A method according to Claim 3, wherein in step (f), the weft yarns are constructed of a material selected from PET, polybutylene terephthalate (PBT), a polyamide selected from polyamide 6, 6/6, 6/10, and 6/12, and blends of thermoplastic polyurethane and PET.

8. A method according to Claim 1, wherein step (a) comprises determining a single group of fabrics, and the optimal properties identified for the warp yarns in step (c) comprise a single warp material, size, cross-sectional shape and mesh for each fabric in the group.

9. A method according to Claim 1, wherein step (a) comprises determining a maximum of four groups of fabrics, and the optimal properties identified for the warp yarns in step (c) comprise a single warp material, size, cross-sectional shape and mesh for each fabric within a respective one of the groups.

10. A method according to Claim 3, wherein the selecting of optimal properties in step (e) comprises selection of adjustable properties selected from at least one of weft yarn material, cross-section shape, size and knocking.

11. A method according to Claim 10, wherein the selecting of adjustable properties is performed in accordance with the basis weight of the fabric.

12. A method according to any one of Claims 1 to 11, wherein the identified optimal properties for warp yarns includes warp sizes in ranges between about 0.8mm and about 0.30mm.

13. A method according to any one of Claims 1 to 12, wherein the preparing a weave design in step (d) comprises modifying an existing design.