Abstract:
A fabric for papermaking usable in the forming section of a paper making machine, having a first weft system, a second weft system and a third weft system; and a plurality of warp systems, each warp system having at least one warp yarn, each warp yarn binding with one of the first weft system, the third weft system, the first and second weft systems, and the second and third weft systems; wherein a first warp system is an exchange warp system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not Applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       REFERENCE TO A COMPACT DISK APPENDIX  
       [0003]     Not applicable.  
       BACKGROUND OF THE INVENTION  
       [0004]     1. Field of the Invention  
         [0005]     The invention relates to a fabric used in papermaking. More specifically, the present invention relates to forming fabrics used in the forming section of a papermaking machine.  
         [0006]     2. Description of Background  
         [0007]     In the art of papermaking, multiple steps occur from the introduction of a pulp slurry to the output of a finished paper product. The initial introduction of the slurry is at the portion of a papermaking machine known as the wet end. Here, the slurry, or fiber suspension, is initially dewatered when the slurry is introduced onto a moving forming fabric, in the forming section of the papermaking machine. Varying amounts of water is removed from the slurry through the forming fabric, resulting in the formation of a fibrous web on the surface of the forming fabric.  
         [0008]     Forming fabrics address not only the dewatering of the slurry, but also the sheet formation, and therefore the sheet quality, resulting from the formation of the fibrous web. More specifically, the forming fabric must simultaneously control the rate of drainage while preventing fiber and other solid components contained in the slurry from passing through the fabric with the water. The role of the forming fabric also includes conveyance of the fibrous web to the press section of the papermaking machine.  
         [0009]     Additionally, if the drainage occurs to rapidly or too slowly, the quality of the fibrous web is reduced, and overall machine production efficiency is reduced. Controlling drainage by way of fabric void volume is one of the fabric design criteria.  
         [0010]     Forming fabrics have been produced to meet the needs and requirements of the various papermaking machines for the various paper grades being manufactured. As the needs arises to increase production speed of the papermaking machines and the quality of the paper being produced, the need for improved paper machine clothing allowing for increase production rates and improved quality resulted.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     Accordingly, the present invention is for a fabric used in papermaking, and more particularly, as a forming fabric. In the preferred embodiment, the fabric is a hybrid warp exchange triple layer forming fabric. The fabric has a first weft system, a second weft system and a third weft system, the second weft system between the first and third weft systems. In the finished fabric, the second and third weft systems are preferably in the same plane. The fabric also has a plurality of warp systems, each warp system having at least one warp yarn. Each warp yarn binds with one of the first weft system, the third weft system, the first and second weft systems, and the second and third weft systems. A first warp system is an exchange warp system. Generally, machine direction (MD) yarns are warp yarns, and cross machine direction (CMD) yarns are weft yarns.  
         [0012]     A weft system is a system of wefts that performs a function. As such, the first weft system can be a paper side weft, a wear side weft or and intermediate weft. In the preferred embodiment, the intermediate weft acts as a binding layer. Still further, the mesh density of the first weft system and the second weft system is independent from the mesh density of the third weft system and the second weft system.  
         [0013]     Still further, the first weft system has a first yarn, the first yarn having a first diameter. Likewise, the second weft system has a second yarn, the second yarn having a second diameter, and the third weft system has a third yarn, the third yarn having a third diameter. The weft and warp yarn materials include, but are not limited to mono filament yarns, synthetic or polyester mono filament yarns, twisted mono filament yarns, twisted synthetic or twisted polyester or twisted polyarnide mono filament yarns, twisted multi-filament yarns, twisted synthetic or twisted polyester multi-filament yarns, and others. Various yarn profiles can be employed, including but not limited to yarns having a circular cross sectional shape with one or more diameters, or other cross sectional shapes, for example, non-round cross sectional shapes such as oval, or a polygonal cross sectional shapes, for example diamond, square, pentagonal, hexagonal, septagonal, octagonal, and so forth, or any other shape that the yarns may be fabricated.  
         [0014]     Still further, each warp system can be independent. Each warp layer, has at least one warp yarn, and the at least one warp yarn has a fourth diameter.  
         [0015]     Additionally, each warp system has a predetermined number of warp repeats, ranging from 2-112, preferably 2-28.  
         [0016]     The triple layer forming fabric of the present invention has exchange warps that do not bind with larger diameter bottom wefts. Rather, they bind with a smaller diameter intermediate weft. All of the warp yarns can be the same diameter or there can be two different warp yarn diameters. In contrast, the warp yarns in the prior art fabrics must all be of the same diameter.  
         [0017]     As a result, the exchange points can be spread out farther than the prior art, resulting in a less obvious pattern. This can be done because the bottom warps bind with the intermediate wefts between the exchanges.  
         [0018]     The warp that weaves only on the bottom, or wear side of the fabric can be of a larger diameter than those that weave on the top, or paper side of the fabric. In this manner the modulus of the fabric is enhanced, and allows for larger diameter bottom wefts to be employed.  
         [0019]     In another embodiment, the fabric has a first weft system, a second weft system and a third weft system, the second weft system between the first and third weft systems. The fabric also has a plurality of warp systems, each warp system having at least one warp yarn. Each warp yarn binds with one of the second weft system and one of the first and third weft systems.  
         [0020]     It is also understood that there are no limitations to the paper grades or former types where this invention can be applied. It is also understood that the fabric can be woven utilizing either two or three warp beams.  
         [0021]     These and other features and advantages of this invention are described in or are apparent from the following detailed description of the preferred embodiments. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The preferred embodiments of the present inventions will be described in detail, with reference to the following figures, wherein:  
         [0023]      FIGS. 1A-1B  depict a cross-sectional view of a triple layer fabric having a 2:1 warp ratio and a two shed/three shed arrangement according to the present invention;  
         [0024]      FIG. 2  depicts a forming side plan view of a triple layer fabric having a 2:1 warp ratio and a two/three shed arrangement according to the present invention;  
         [0025]      FIGS. 3A-3B  depict a cross-sectional view of a triple layer fabric having a 2:1 warp ratio and a three shed/three shed arrangement according to the present invention;  
         [0026]      FIG. 4  depicts a forming side plan view of a triple layer fabric having a 2:1 warp ratio and a three/three shed arrangement according to the present invention;  
         [0027]      FIGS. 5A-5C  depict a cross-sectional view of a triple layer fabric having a 2:1 warp ratio and a two shed/four shed arrangement according to the present invention;  
         [0028]      FIG. 6  depicts a forming side plan view of a triple layer fabric having a 2:1 warp ratio and a two shed/four shed arrangement according to the present invention;  
         [0029]      FIGS. 7A-7C  depict a cross-sectional view of a triple layer fabric having a 2:1 warp ratio and a two shed/six shed arrangement according to the present invention; and  
         [0030]      FIG. 8  depicts a forming side plan view of a triple layer fabric having a 2:1 warp ratio and a two shed/six shed arrangement according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]      FIGS. 1A-1B  depict a cross-sectional view of a triple layer fabric  10  having a 2:1 warp ratio and a two shed/three shed arrangement according to the present invention, fabricated on a two beam loom.  FIG. 2  depicts the forming side plan view of the same fabric  10 .  
         [0032]     A first weft system  12  is shown above a second weft system  14 . The first and second weft systems  12 ,  14  are shown above a third weft system  16 . Each weft system  12 ,  14 ,  16  is made up of a plurality of yarns  18 ,  20 ,  22 . First weft yarn  18  has a first yarn diameter, second weft yarn  20  has a second yarn diameter, and third weft yarn  22  has a third yarn diameter. The first, second and third yarn diameters  18 ,  20 ,  22  can be the same or different. Different size numerals for each of the different weft layer yarns  18 ,  20 ,  22  is indicative of a different weft yarn diameter in the preferred embodiment.  
         [0033]     The first, second and third weft systems  12 ,  14 ,  16  are bound together by a plurality of warp systems  24 .  FIGS. 1A-1B  show fifteen warp systems  24  in a repeating pattern. Each warp system  24  has at least one warp yarn  26 , and each warp yarn  26  is woven in a two shed/three shed repetition.  
         [0034]     The weft and warp yarn materials include, but are not limited to mono filament yarns, synthetic or polyester mono filament yarns, twisted mono filament yarns, twisted synthetic or twisted polyester or twisted polyarnide mono filament yarns, twisted multi-filament yarns, twisted synthetic or twisted polyester multi-filament yarns, and others. Various yarn profiles can be employed, including but not limited to yarns having a circular cross sectional shape with one or more diameters, or other cross sectional shapes, for example, non-round cross sectional shapes such as oval, or a polygonal cross sectional shapes, for example diamond, square, pentagonal, hexagonal, septagonal, octagonal, and so forth, or any other shape that the yarns may be fabricated into.  
         [0035]     This first warp yarn  26  binds the top, or first weft  12  with the middle, or second weft  14 . A second warp yarn  30  also binds the top, or first weft  12  with the middle, or second weft  14 . The first and second warp yearns  26 ,  30  form what is called an exchange warp. An exchange warp is, for example, when one member of a pair of warp yarns  26 ,  30  is weaving with the first weft system  12  and the other member of the pair of warp yarns  26 ,  30  is weaving with the second weft system  14 . Stated differently, an exchange warp allows for one warp yarn of a pair of warp yarns to weave in alternate fashion such that when the first warp yarn  26  is weaving with a first weft system  12 , the second warp yarn  30  is not weaving with the first weft system  12 , and both the first and the second warp yarns are not weaving the same weft at the same time.  
         [0036]     In the present invention, while depicting a plurality of warp systems  24 , some yarns of the warp systems form exchange warp pairs and some of the warp systems do not form exchange warp pairs. In  FIG. 1 , for example, the first warp yarn  26  and the second warp yarn  30  form the first warp system  28 , which is an exchange warp pair. In contrast, warp yarn  32  forms a second warp system  34 . Accordingly, warp yarn  32  does not cross the second warp yarn  30  of the first warp system  28 , and no exchange warp is formed.  
         [0037]      FIG. 2  depicts the forming side plan view of the triple layer fabric  10  having a 2:1 warp ratio and a two shed/three shed arrangement according to the present invention. In this example, it can be readily seen that the first and second warp yarns  26 ,  30  form a first warp system, and therefore a warp pair that forms an exchange warp. The x notation marks where the first warp yarn  26  appears in the forming side view forming a knuckle, and y indicates where the second warp yarn  30  appears in the forming side view forming a knuckle. The third warp yarn  32 , since it only binds the second weft system  14  with the third weft system  16 , does not appear in the forming side plan view. The boxes with forward slash fill denote where warps exchange, and boxes with grey fill denote locations of bottom side warp knuckles. Since the invention is directed to a triple layer fabric, the weave has a separate forming or paper side and a wear side.  
         [0038]     This pattern repeats throughout the forming side plan view. For example, a fourth warp yarn  36  forms an exchange warp with a fifth warp yarn  38 . Similarly, a sixth warp yarn  40  forms a warp exchange with a seventh warp yarn  42 . An eighth warp yarn  44  does not form an exchange warp with another yarn.  FIGS. 1A-1B  further show a ninth warp yarn  46 , a tenth warp yarn  48 , and eleventh warp yarn  50 , a twelfth warp yarn  52 , and thirteenth warp yarn  54 , a fourteenth warp yarn  56 , and a fifteenth warp yarn  58 . Accordingly,  FIG. 2  depicts fifteen warp repeats, with six pairs of exchanging warps and 3 bottom warps. The pattern repeats in both the forming side and the wear side layers. The double forward slashed areas in  FIG. 2  show the crossover points of the warp exchange yarns below the forming side surface. The single grey areas in  FIG. 2  show the warp yarn exposure on the wear side, that is, a wear side knuckle, not shown.  
         [0039]     Accordingly, the views in  FIGS. 1A-1B  and  2  show one complete pattern in the machine direction.  
         [0040]      FIGS. 3A-3B  depict a cross-sectional view of a triple layer fabric having a 2:1 warp ratio and a three shed/three shed arrangement according to the present invention.  FIG. 4  depicts the forming side plan view of the triple layer fabric having a 2:1 warp ratio and a three shed/three shed arrangement according to the present invention. As in  FIGS. 1A-1B  and  2 , the first warp yarn  26  forms an exchange warps with the second warp yarn  30 . The difference is that the first and second warp yarns  26 ,  30  have a three shed weave pattern.  
         [0041]      FIGS. 5A-5C  depict a cross-sectional view of a triple layer fabric having a 2:1 warp ratio and a two shed/four shed arrangement according to the present invention, and  FIG. 6  depicts the forming side plan view. Twenty-four warp yarns are shown as  118 ,  120 ,  122 ,  124 ,  126 ,  128 ,  130 ,  132 ,  134 ,  136 ,  138 ,  140 ,  142 ,  144 ,  148 ,  150 ,  152 ,  154 ,  156 ,  158 ,  160 ,  162  and  164 . In this embodiment, an additional warp is added that only binds to the top, or first weft system  112 , and does not bind with the second or third weft systems  114 ,  116 . These top binding only warps are designated  118 ,  126 ,  134 ,  142 ,  150  and  158 . The boxes in  FIG. 6  with the reverse hash fill indicate locations where the bottom warp binds with the binding weft, or the second weft system.  
         [0042]      FIGS. 7A-7C  depict a cross-sectional view of a triple layer fabric having a 2:1 warp ratio and a two shed/six shed arrangement according to the present invention, and FIG.  8  depicts the forming side plan view. Twenty-four warp yarns are shown as  218 ,  220 ,  222 ,  224 ,  226 ,  228 ,  230 ,  232 ,  234 ,  236 ,  238 ,  240 ,  242 ,  244 ,  246 ,  248 ,  250 ,  252 ,  254 ,  256 ,  258 ,  260 ,  262  and  264 . In this embodiment, the fabric  10  is woven using a three beam configuration, and has a different weave pattern than that depicted in  FIGS. 5-6 . This pattern shown in  FIG. 8  has the additional notation of boxes containing horizontal or vertical fill lines, representing locations where an exchanging warp binds at the second weft layer according to the cross-sectional view of  FIGS. 7A-7C .  
         [0043]     The invention has been described that can be fabricated on a three beam loom. Likewise, the triple layer fabric of the present invention can also be fabricated on a four beam loom. Use of four beams could result in similar fabrics, with the addition of at least one of a top only warp, a bottom only warp, a bottom warp that binds at the second weft system, and a top pair that binds with the second weft system.  
         [0044]     While the present invention has been particularly shown and described with reference to the foregoing preferred embodiments, those skilled in the art will understand that many variations may be made therein without departing from the spirit and scope of the invention as defined in the following claims. This description of the invention should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. The foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application. Where the claims recite “a” or “a first” element or the equivalent thereof, such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements.