Title of Invention

AN IMPROVED MULTI-LAYER WOVEN FABRIC USED IN PAPER MAKING MACHINES

Abstract

An improved multi-layer woven fabric used in paper making machines. The improved fabric comprises one set of top machine direction (MD) yarns and cross machine direction (CMD) yarns from paper side weave and a second set of bottom machine direction (MD) yarns and cross machine direction (CMD) yarns from machine side weave enlaced by interlacing according to desired weave pattern. The paper side is provided with a finer weave with small floats and said machine side is further provided with a coarse weave with longer floats; a set of top CMD yarns being interwoven between said top and bottom layer warps thus binding two different weaves. The binder yarns is formed an integral part of the main fabric; said top weave and the bottom weave being interwoven in a series of repeat units to form the multi-layer woven fabric.

Full Text

Title AN IMPROVED MULTI-LAYER WOVEN FABRIC USED IN PAPER MAKING MACHINES Field of the Invention The present invention relates to an improved multi-layer woven fabric used in paper making machines. The invention particularly relates to a multiple layer woven fabric for paper maker's screen called "wet end" which is used in converting pulp stock to initial paper web in various kinds of paper making machines. Back ground of the invention In the conventional paper making machines, a water slurry or suspension of paper pulp known as paper making "stock" is fed onto the top of upper run of an endless belt of woven wire and / or synthetic material that travels between two or more rollers. This belt is often referred to as "forming fabric", and it provides a paper making surface on the upper surface of its upper run which acts as a filter to separate the fiber pulp of the paper stock from the aqueous medium, thereby forming a wet paper web. The aqueous medium drains through mesh openings of the forming fabric, which are otherwise known as drainage holes, due to gravity alone or with assistance of one or more suction boxes located on the lower face of the upper run of the fabric i.e. machine side of the fabric. In known processes, after leaving the forming section, the paper web is transferred to press section of the paper making machine, where it is passed through the nips of one or more pairs of pressure rollers covered with another type fabric which is ordinarily referred to as a "press felt". Here due to pressure from the rollers, additional moisture from the web is removed. The moisture, removal is often enhanced by the presence of a "Batt" layer of fibers on the press felt. The partially dried paper sheet thus formed is then conveyed to a "Dryer" section for further removal of moisture. After drying the paper is ready for finishing process or is sent straight to packaging. Typically, papermaker's fabrics are manufactured as endless belts by one of two known basic weaving techniques. In one of these techniques fabrics are flat woven by a flat weaving process, and there ends are joined to form an endless belt by any well known joining method, such as dismantling and re-weaving the ends together, commonly known as 'splicing' and 'seaming'. In a flat woven papermaker's fabric, the warp yarns extend in the machine direction and the filling yarn or weft yarn extend in the cross machine direction. As referred to in this specification , the terms "machine direction" (MD) and the "cross machine direction" (CMD) refer, respectively, to a direction aligned with the direction of travel of a papermaker's fabric in a paper making machine, and a direction parallel to the fabric surface and traverse to the direction of travel. According to the other or the second technique, fabric is woven directly in the form of a continuous belt with an endless weaving process. In the endless weaving process, the warp yarns extend in the cross machine direction and the filling yarns extend in the machine direction of the fabric belt. Both the weaving methods described herein above are well known in the art and the term "endless belt" used herein refers to belts made by the unique method. Effective sheet, fiber support and absence of "wire making" are the important considerations in the papermaking process, especially for the formation of section of the papermaking machine where the wet paper web is first formed. The wire marking is particularly problematic in the making of fine grades of paper, as it can affect a host of paper properties responsible for determining the quality of paper in the market such as sheet mark, porosity, uneven formation, pin holes and poor surface quality. Wire marking is typically the result of individual pulp fibers being oriented within the paper web such that their ends reside within gaps between the individual yarns of the forming fabric caused by the weave design on the sheet or web side of the fabric. This problem or disadvantage is generally addressed by providing a monoplanar surface on the sheet side that allows pulp fibers to rest on adjacent yarns rather than penetrate the gaps between the yarns. As used in this specification the term, "monoplanar" means that the upper extremities of the yarns defining the paper forming surface at substantially same elevation such that at that level there is presented a substantially "planar" surface. Accordingly, fine paper grades intended for using in quality printing, carbonizing paper, tissue paper and like grades of fine quality paper need to be formed on very finely woven fabric surface with monoplanar or co-planar property. The applicants have found that such finely woven fabrics include at least some relatively small diameter machine direction or cross machine direction yarns. However, such yarns tend to be delicate, leading to a short surface life for the fabric. Moreover, the use of smaller yarns can also adversely affect the dimensional stability of the fabric, skew resistance and narrowing resistance, which may impact negatively both the surface life and the performance of the fabric. Such forming fabrics with one set of warp i.e., MD yarn and one set of weft i.e., CMD yarn is referred to herein as a single layer forming fabric. To mitigate the above noted problems associated with fine weaves, multi-layer forming fabrics were developed with fine mesh yarns on the paper forming surface to facilitate paper formation and coarser mesh yarns on the machine contact side to provide strength and durability. For example, fabrics have been constructed with one set of machine direction yarns which interweave paper forming surface and a more durable machine side surface. These fabrics form part of a class of fabrics which are generally referred to as "double layer" fabrics. Similarly, fabrics were proposed and manufactured which includes two sets of cross machine direction yarn that form a fine mesh paper side fabric layer and a separate coarser machine side fabric layer, in these fabrics, which are a part of a class of fabrics generally referred to as "triple layer" fabrics, the two fabrics layers are typically bound together by separate woven stitching weft yarns. The multilayer (double and triple layer) fabrics, because of the presence of additional sets of yarns compared to single layer fabrics are of higher "caliper" i.e. thicker and by virtue of their two sided weave for finer paper formation side and coarser machine side for fabric life is found to be superior than single layer fabrics. Although these fabrics have performed successfully, they have some potential shortcomings or disadvantages due to the inclusion of extra stitching weft yarns causing inter-layer wear, de lamination of two fabric layers, fabric layer shifting in high warp - high speed paper machines. This shifting causes the fabric to wear and decrease in thickness, which adversely affects the drainage of the paper making and consequently it affects performance in paper making and ultimately fabric life. More often it is this interlayer wear, rather than the wear on the machine that determines the life of the fabric. It is evident that the stitching weft yarns in such triple layer fabric need to be strong enough to bind the top and the bottom layer fabrics together so that the interlayer wear, shifting and de- lamination of fabric layer is resisted and also need to resist the machine side fabric surface to withstand wear with paper machine yet be delicate enough on the paper side surface to produce high quality finer grade paper. It is quite difficult to strike a balance between the two situations. The applicant's endeavor was to obviate the problem of the prior art and to innovate an improved multi layer fabric which is free from the aforesaid drawbacks. Therefore, one of the objects of the present invention is to mitigate the drawbacks or disadvantages of the prior art. Another object of the present invention is to produce an improved multi- layer fabric used in paper making machine. Yet another object of this invention is to provide stitching weft yarns which is strong enough to bind the top and the bottom layer fabrics and also prevents shifting and delamination of fabric layer. A further object of the present invention is to prevent the interlayer wear to enhance the life of the fabric. A still further object of the invention is to provide a strong multiple layer fabric yet delicate on the paper side surface to produce high quality and finer grade paper. These and other objects of the present invention will be apparent from the description given herein under. According to this invention there is provided a multiple layer paper maker's forming fabric, consisting of one set of top machine direction (MD) yarns and cross machine direction (CMD) yarns form a paper side weave and one set of bottom machine direction (MD) yarns and cross machine direction (CMD) yarns from machine side weave by interlacing according to the desired weave pattern. The paper side has a finer weave with small floats whereas the machine side has a coarse weave with longer floats. The two top and bottom weavers are different by their type. A set of top CMD yarns interweave between top and bottom layer warps thus binding the two different weaves, the binder yarns are also an integral part of the main fabric. The top weave and the bottom weaves are interwoven in a series of repeat units to form a complete woven fabric. A paper stock may be applied to this newly invented fabric as described herein, and pulp and water may be separated from paper maker's stock to produce initial paper web for further processing viz, pressing, drying and other finishing process for producing high quality and fine paper. The present invention provide an improved multi-layer woven fabric used in paper making machines comprising one set of top machine direction (MD) yarns and cross machine direction (CMD) yarns from paper side weave and a second set of bottom machine direction (MD) yarns and cross machine direction (CMD) yarns from machine side weave enlaced by interlacing according to desired weave pattern; said paper side being provided with a finer weave with small floats and said machine side being provided with a coarse weave with longer floats; a set of top CMD yarns being interwoven between said top and bottom layer warps thus binding two different weaves, the binder yarns being formed an integral part of the main fabric; said top weave and the bottom weave being interwoven in a series of repeat units to form the multi-layer woven fabric. The aforesaid multi-layer woven fabric includes a double layer fabric and a three layer fabric. A paper stock is applied to said fabric whereby pulp and water are separated from the paper maker's stock to produce initial paper web for further processing steps namely, pressing, drying and finishing steps for producing high quality fine paper. Detail description of the Invention The present invention will now be explained in detail with reference to the drawings accompanying the provisional specification wherein: Figure 1 illustrates paper side binder having weaving pattern of 24- Sh_4/2_PSB_WnF; Figure 2 illustrates paper side binder of an alternative type having weaving pattern of 24-Sh_4/2-2/4_PSB_WnF. In figure 1 (24-Sh_4/2_PSB_WnF), the intended weave pattern has been constructed on 24 warps i.e., twelve warps 1,3,5,7,9,11,13,15,17,19,21 and 23 make the paper side or top weave and other twelve warps i.e., 2,4,6,8,10,12,14,16,18,20,22 and 24 make the machine side or bottom weave. The total 24 warps make one unit or smallest weave repeat for warp way pattern. The smallest weft way pattern repeats a combination of five wefts as shown in the drawings. Wefts numbered 25,27,28 and 29 are the wefts which constructs the paper side weave and weft numbered 26 form the machine side weave in interweaving with the twelve bottom warps. Wefts 25 and 29 are as shown as in figure 1 make plane weave with the eight top warps and thus form, weave floats or knuckles over and under the top warps. The knuckles over the warps facing and the paper side are meant for sheet support. The wefts 27 & 28 are the binder wefts or stitching wefts. The weft 27 forms a plain weave with top warps 1,3,5,7,9,11 and 13 to dispose four wefts knuckles to the paper side surface for sheet formation and then goes below the rest of the top warp to bind with one or more select bottom warp- as per figure with warp # 20.The next weft # 28 herein called the pair of binder with weft # 27, forms a plain weave with top warps at 23, 21,19 and 1,7 and then goes below rest of the warps to bind with one or more pre- selected bottom warp- as shown in figure 1 of the drawing with warp 10 and 6. Wefts 27 & 28 are called pair because in combination they pass under one common top warp # 15 in combination leave a weave similar to previous and the next top wefts are numbered 25 and 29 and at the same time bind the bottom select warp / warps to bind together both the top and the bottom fabrics. In the smallest weft repeat one machine side weft allowed to form a 5/1 weaves to leave the longer weft float to the machine surface of the fabric. In figure - 02 (24-Sh_4/2-2/4_PSB_WnF) the intended weave pattern has been constructed on 24 warps i.e., twelve warps 1,3,5,7,9,11,13,15,17,19,21 and 23 make the paper side or top weave and other twelve warps i.e., 2,4,6,8,10,12,14,16,18,20,22 and 24 make the machine side or bottom weave. The total 24 warps make one unit or smallest weave repeat for warp way pattern. The smallest weft way pattern repeat is completed by nine wefts as shown in this figure. Wefts numbered 25, 27,28,29,31 and 33 are the wefts which construct the paper side weave and wefts numbered 26 and 30 form the machine side weaves in inter weaving with the twelve bottom warps. Weft number 25, 29 and 33 shown in figure 2 make plain weave with the twelve top warps and thus form weft floats or knuckles over and under the top warps. The knuckles over the warps facing the paper side are meant for sheet support. The wefts numbered 27, 28 and 31, 32 are the two pair of binder wefts or stitching wefts. Weft # 27 forms a plain weave with top warps numbered 1,3,5,7,9,11 and 13 to dispose four weft knuckles to paper side surface for sheet formation and then goes below the rest of the top warp to bind with one or more select bottom warp- as per the drawings with warp # 20. The next weft numbered 28 as herein called the pair of binder with weft 27, forms a plain weave with top warps at 23,21, 19 and 17 and then go below rest of the warps to bind with one or more select bottom warp as shown in the drawings with warp 10 and 6. Wefts 27 and 28 are called pair because in combination they pass under one common top warp # 15 in combination they leave a weave similar to previous and the next top wefts as numbered 25 and 29 and at the same time bind the bottom select warp / warps to bind together both the top and the bottom fabrics. The plain portions on top paper side formed by the pair of binder wefts # 27 and 28 and the longer plain weave portion formed by pick 27 on the left side of the weave pattern as shown herein called "four floats" as it disposes four plain weave weft floats / knuckles to the paper side and similarly the short plain weave portion formed by pick 28 on the right side of the weave 'pattern is herein called "two floats" as it disposes two plain weave weft floats to the paper side, that herein is called "four and two" or "4 and 2" or "4/2" combination of the paper side binder weft's pair. Next weft is a paper side complete plain weave pick which is numbered 29 in the figure and next to this pick # 30 which weaves with the bottom set of warps. Then again one pair of paper side binder wefts #31 and 32 to weave and bind with the bottom warps # 14, 18 and # 4 respectively. Typically this two binder pair of picks have been arranged in weave such that unlike the previous binder pair of pick the short portion of plain weave is formed on left by the weft #31 and the longer portion of plain weave is formed on right by the weft # 32, so as to form the smallest weave repeat with two pair binder or stitching picks disposed in such a fashion, to form a "4/2" and "2/4" weft plain weave portion (as described herein above) on the paper side - which is, by this invention is deemed to be a part of a class of fabrics. To complete the smallest weave repeat a complete plain weave pick #33, which indicates the completion of the weft repeat on paper side with the intended weave pattern, otherwise it is just the repetition of the first pick number 25. In the smallest weft repeat two machine side wefts # 26 and 30 a 5/1 weave to form a 5/1 weave longer weft float on the machine side surface of the fabric. In the improved multi-layer woven fabric as described herein above, each unit of intended weave pattern of a smallest weave repeat for warp way pattern comprises a combination of five wefts as illustrated in the drawings accompanying the provisional specification. In the above mentioned improved multi-layer woven fabric the top weave and the bottom weave are interwoven in a series of repeat units to form a complete woven fabric. In another aspect of the invention of the said improved multi-layer woven fabric, said plain weave pattern said plain weave pattern or paper side surface of the fabric includes other top layer weave pattern namely, satins, broken twills, various types of twill and some derivatives of plain weave. Further the improved multi-layer woven fabric a varied type of yarn is selected from polyester, polyamide, aramid, various co polymers, single or in plurality or in any combination of their position in the fabric mesh and any yarn or raw material is used. Summary of the invention The present invention is intended to weave a multilayer forming fabric comprising one finer top fabric and one coarser bottom fabric inter woven by selected weft of finer top weave to stitch with selected warp of coarser bottom weave and thus constructing a final fabric comprising a top fine plain type weave for good sheet support, while a coarse and sturdy satin weave at bottom side for good resistance to abrasion with paper machine. In one embodiment of the present invention, the new triple layer - a type of paper maker's multiple layer forming fabric includes a set of top MD yarns, top CMD yarns, bottom MD yarns, bottom CMD yarns and stitching CMD yarns or binder CMD yarns to form one certain weave for the paper side and another weave on the reverse side of the fabric herein called the machine side and the both independent weaves are bound together by a plurality of selected CMD yarns of paper side weave herein called binder weft yarns. In another embodiment according to the present invention, the forming fabric discussed above includes a pair of first and second stitching CMD yarns or binders positioned between a pair or more number of paper side weft yarns woven together with the top and bottom MD yarns so that, as a paper side weave part of the first binder weft is inter weaving with the paper side MD yarns and the binding portion of second binde/ weft is positioned below the rest of top MD yarns and such that as a sheet support weave portion of the second stitching yarn is inter weaving with the top MD yarns and a binding portion of the first binder weft is positioned below the top MD yarns. The first and second binder wefts cross each other as they pass below a common top MD yarn and each of the binding portions of the first and second binder wefts pass below one or more number of bottom MD yarn to bind the top and the bottom weaves together to form an integrated woven fabric comprising of two surface weaves for paper formation and machine side weave. In still another embodiment of the present invention and embodiments of paper makers forming fabric described above can be used for making paper. Paper stock may be applied to a paper maker's forming fabric as described above and moisture may be removed from paper stock to produce initial paper web. Although illustrated embodiments employ plain weave pattern for top layer or paper side surface of the fabric, the present invention also includes within its scope the use other top layer weave pattern viz, satins, broken twills, various types of twill and some derivatives of plain weave. The pair of stitching or binder picks weaving style as the main part of the invention. It is possible to obtain varied weave pattern by using this particular stitching weave in combination with changed weave pattern or changed pattern of their position in weave or making a mixture of yarn weave pattern practiced in fabric weaving industry and are within the scope of this invention. The paper maker's fabric defined by 24 Sh_4/2_PSB-WnF in figure 1 and 24-Sh_4/2- 2/4_PSB_WnF in figure 2 can use a varied type of yarn namely, polyester, polyamide, aramid, various co polymers, single or in plurality or in any combination of their position in the fabric mesh and any yarn or raw material those will be introduced for paper maker's forming fabric by the yarn producers in future. The paper maker's fabric as illustrated in Fig.l or figure 2 are manufactured by the applicant in any amount of warp and weft density or fabric mesh as well known in this manufacturing field. Any change in above fabric manufacturing process values on the invented weave designs shall not be deemed as new concept since it is well within the ambit of the present invention as these values are usual day today variations practiced in fabric weaving industry. It should also be understood that the paper maker's fabric as shown in Figs land 2 can also be manufactured by changing or introducing different manufacturing process and / or machine with equipment or different color or hue. In the paper maker's fabric as illustrated in figures 1 & 2, each of the stitching wefts can form one or more binding knuckles or floats with one of the bottom MD yarn. Further a binder weft may not at all make binding with bottom MD yarn as would be required by skilled fabric designer for different application needs. The paper maker's fabric as shown in figure 1 the complete plain weave picks i.e., pick # 25 and 29 are in singular, but such plain picks can be used in any number before and after pair of binder wefts and in any combination of weft weave pattern as would be required by the skill of the fabric designer. The paper maker's fabric as shown in figure 2 illustrates the complete plain weave picks i.e., pick #25, 29 and 33 are in singular, but such plain picks can be used in any number before and after pair of binder wefts and in any combination of weft weave pattern as would be required by a skilled designer according to the requirement. The invention described herein above is only by way of an example without limiting the scope thereof. Any modification or improvement which is well within the knowledge of a person having average skill in the art is intended to be covered within the scope of the present invention. WE CLAIM: 1. An improved multi-layer woven fabric used in paper making machines comprising one set of top machine direction (MD) yarns and cross machine direction (CMD) yarns from paper side weave and a second set of bottom machine direction (MD) yarns and cross machine direction (CMD) yarns from machine side weave enlaced by interlacing according to desired weave pattern; said paper side being provided with a finer weave with small floats and said machine side being provided with a coarse weave with longer floats; a set of top CMD yarns being interwoven between said top and bottom layer warps thus binding two different weaves, the binder yarns being formed an integral part of the main fabric; said top weave and the bottom weave being interwoven in a series of repeat units to form the multi-layer woven fabric. 2. An improved multi-layer woven fabric as claimed in claim 1, wherein said fabric comprises at least a double-layer fabric and includes a triple-layer fabric as described herein. 3. An improved multi-layer woven fabric as claimed in claim 1 or 2, wherein a paper stpck is applied to said fabric whereby pulp and water being separated from the paper maker's stock to produce initial paper web for further processing steps namely, pressing, drying and finishing steps for producing high quality fine paper. 4. An improved multi-layer woven fabric as claimed in anyone of claims 1 to 3, wherein each unit of intended weave pattern is constructed on 24 warps comprising 12 warps, i.e., 1,3,5,7,9,11,13,15,17,19,21 and 23 made on said paper side or top weave and other 12 warps, i.e., 2,4,6,8,10,12,14,16,18,20,22 and 24 made on the machine side or bottom weave. 5. An improved multi-layer woven fabric as claimed in claim 4, wherein each unit of intended weave pattern of a smallest weave repeat for warp way pattern comprises a combination of five wefts as illustrated in the drawings accompanying the provisional specification. 6. An improved multi-layer woven fabric as claimed in any of the preceding claims, wherein said top weave and the bottom weave are interwoven in a series of repeat units to form a complete woven fabric. 7. An improved multi-layer woven fabric as claimed in anyone claims 1 to 3, wherein the intended pattern is constructed on 24 warps comprising 12 warps, i.e. 1,3,5,7,9,11,13,15,17,19,21 and 23 made towards paper side or top weave and remaining 12 warps, i.e. 2,4,6,8,10,12,14,16,18,20,22 and 24 made towards machine side or bottom weave. 8. An improved multi-layer woven fabric as claimed in claim 7, wherein said total twenty four warps make one unit or smallest weave repeat for warp way pattern, the smallest weft way pattern repeats a combination of five wefts. 9. An improved multi-layer woven fabric as claimed in anyone of the preceding claims, wherein said plain weave pattern or paper side surface of the fabric includes other top layer weave pattern namely, satins, broken twills, various types of twill and some derivatives of plain weave. 10. An improved multi-layer woven fabric as claimed in claim 1 or 4 wherein a varied type of yarn selected from polyester, polyamide, aramid, various co polymers, single or in plurality or in any combination of their position in the fabric mesh and any yarn or raw material is used. An improved multi-layer woven fabric used in paper making machines. The improved fabric comprises one set of top machine direction (MD) yarns and cross machine direction (CMD) yarns from paper side weave and a second set of bottom machine direction (MD) yarns and cross machine direction (CMD) yarns from machine side weave enlaced by interlacing according to desired weave pattern. The paper side is provided with a finer weave with small floats and said machine side is further provided with a coarse weave with longer floats; a set of top CMD yarns being interwoven between said top and bottom layer warps thus binding two different weaves. The binder yarns is formed an integral part of the main fabric; said top weave and the bottom weave being interwoven in a series of repeat units to form the multi-layer woven fabric.

Documents:

0003-kol-2007-abstract.pdf

0003-kol-2007-correspondence others.pdf

0003-kol-2007-descriptional (provisional).pdf

0003-kol-2007-drawings.pdf

0003-kol-2007-form1.pdf

0003-kol-2007-form2.pdf

0003-kol-2007-form26.pdf

0003-kol-2007-form3.pdf

03-kol-2007-form 18.pdf

3-KOL-2007-(24-01-2014)-ABSTRACT.pdf

3-KOL-2007-(24-01-2014)-CLAIMS.pdf

3-KOL-2007-(24-01-2014)-CORRESPONDENCE.pdf

3-KOL-2007-(24-01-2014)-DESCRIPTION (COMPLETE).pdf

3-KOL-2007-(24-01-2014)-DRAWINGS.pdf

3-KOL-2007-(24-01-2014)-FORM-1.pdf

3-KOL-2007-(24-01-2014)-FORM-2.pdf

3-kol-2007-abstract.pdf

3-kol-2007-claims.pdf

3-KOL-2007-CORRESPONDENCE 1.1.pdf

3-kol-2007-description (complete).pdf

3-kol-2007-form 2.pdf