PAPERMAKER'S FORMING FABRIC WITH COMPANION YARNS

Abstract: A papermaker's fabric includes a base fabric structure including machine direction yarns and primary cross machine direction yarns interlacing to form a papermaking surface, wherein the machine direction yarns and primary cross machine direction yarns are interlaced in a pattern having a harness repeat of greater than two. The fabric also includes first and second companion cross machine direction yarns positioned between each pair of adjacent primary cross machine direction yarns. Each first companion cross machine direction yarn has an interlacing pattern relative to the machine direction yarns that is identical to a first of the pair of adjacent primary cross machine direction yarns, and each second companion cross machine direction yarn has an interlacing pattern relative to the machine direction yarns that is identical to a second of the pair of adjacent primary cross machine direction yarns. The first companion cross machine direction yarn is positioned between the second primary and companion cross machine direction yarns. The primary cross machine direction yarns have a first diameter, and the first and second companion yarns have a second diameter, wherein the ratio between the first and second diameters is between about 0.9 and 1.1.

Description: PAPERMAKER'S FORMING FABRIC WITH COMPANION YARNS Field nf the Invention This invention relates generally to woven fabrics, and relates more specifically to woven fabrics for papermakers. fiacl grminri nf the Invention In the conventional fourdrinier papermaking process, a water slurry, or suspension, of cellulosic fibers (known as the paper "stock") is fed onto the top of the upper run of an endless belt of woven wire and/or synthetic material that travels between two or more rollers. The belt, often referred to as a "forming fabric", provides a papermaking surface on the upper surface of its upper run which operates as a filter to separate the cellulosic fibers 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, known as drainage holes, by gravity alone or with assistance from one or more suction boxes located on the lower surface (Le., the "machine side") of the upper run of the fabric. After leaving the forming section, the paper web is transferred to a press section of the paper machine, in which it is passed through the nips of one or more pairs of pressure rollers covered with another fabric, typically referred to as a "press felt." Pressure from the rollers removes additional moisture from the web; the moisture removal is often enhanced by the presence of a "batt" layer on the press felt. The paper is then conveyed to a drier section for further moisture removal. After drying, the paper is ready for secondary processing and packaging. Typically, papermaker's' fabrics are manufactured as endless belts by one of two basic weaving techniques. In the first of these techniques, fabrics are flat woven by a flat weaving process, with their ends being joined to form an endless belt by any one of a number of well-known joining methods, such as dismantling and reweaving the ends together (commonly known as splicing), or sewing a pin-seamable flap on each end or a special foldback, then reweaving these into pin-seamable loops. In a flat woven papermaker's' fabric, the warp yarns extend in the machine direction and the filling yarns extend in the cross machine direction. In the second technique, fabrics are 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. As used herein, the terms "machine direction" (MD) and "cross machine direction" (CMD) refer, respectively, to a direction aligned with the direction of travel of the papermaker's' fabric on the papermaking machine, and a direction parallel to the fabric surface and traverse to the direction of travel. Both weaving methods described hereinabove are well known in the art, and the term "endless belt" as used herein refers to belts made by either method. When tissue paper is being formed, typically a forming fabric with a top surface having a relatively fine mesh is employed. Such a fabric can reduce the tendency of the paper to have "pin holes." Also, because tissue paper is typically formed on paper machines that run at high speeds (as much as feet per minute) with high permeability fabrics, tissue forming fabrics generally are relatively thin (i_e., of low caliper); low caliper fabrics tend to drain quickly (due to a lesser void volume) and are therefore often more effective than thicker fabrics. In addition, the high operating rate of a tissue forming machine can also cause the "sheet release" properties of a tissue forming fabric to be very important. In contrast to forming fabrics for higher grades of paper, such as printer paper, the "coplanarity" of the papermaking surface is generally less critical for tissue forming fabrics, as a fabric having less coplanar surface can produce a softer paper (which is, of course, an important quality in tissue). Further, a typical tissue forming fabric is "CMD-predominant" on its top surface; Ls-, the CMD yams of the top surface tend to comprise more of the top surface than do the MD yams and provide much of the fiber support for the paper stock fibers. The foregoing demonstrates that forming fabrics for tissue paper can have much different performance characteristics than those for forming newsprint, printer paper, and other finer paper grades. As such, forming fabrics suitable for fine paper grades, such as those illustrated in U.S. Patent Nos. 4,987,929; 5,518,042; and 5,937,914 to Wilson, may not be suitable for the formation of tissue paper. Fabrics that are designed for tissue paper formation, such as those illustrated in U.S. Patent Nos. 5,025,839 to Wright and 5,857,498 to Barreto, can have insufficient permeability under certain circumstances. One other proposed tissue forming fabric, that illustrated in U.S. Patent No. 5,421,374 to Wright, addresses the permeability issue by including only one bottom CMD yam for every three top CMD yams, but this fabric can have problems with the top CMD yams bunching together such that there is not uniform spacing between the top CMD yams. Summary of the Invention In view of the foregoing, it is an object of the present invention to provide a papermaker's' fabric suitable for forming tissue paper. It is another object of the present invention to provide a tissue forming fabric that addresses the permeability and top CMD spacing uniformity problems described above. These and other objects are satisfied by the present invention, which includes a papermaker's fabric that can provide suitable permeability, surface structure, and top CMD yam spacing for tissue formation. The papermaker's fabric comprises: a base fabric structure including machine direction yams and primary cross machine direction yams interlacing to form a papermaking surface, wherein the machine direction yams and primary cross machine direction yarns are interlaced in a pattern having a harness repeat of greater than two. The fabric also includes first and second companion cross machine direction yams positioned between each pair of adjacent primary cross machine direction yarns. Each first companion cross machine direction yam has an interlacing pattern relative to the machine direction yams that is identical to a first of the pair of adjacent primary cross machine direction yams, and each second companion cross machine direction yam has an interlacing pattern relative to the machine direction yams that is identical to a second of the pair of adjacent primary cross machine direction yarns. The first companion cross machine direction yam is positioned between the second primary and companion cross machine direction yams. The primary cross machine direction yams have a first diameter, and the first and second companion yarns have a second diameter, wherein the ratio between the first and second diameters is between about 0.9 and 1.1. In this configuration, the companion paper side cross machine direction yarns tend to remain separated from each other, thereby providing a surface structure and a permeability that can suitably produce tissue paper. In another embodiment, a papermaker's fabric of the present invention comprises machine direction yams interwoven with first and second sets of top cross machine direction yams and a bottom set of cross machine direction yams in a repeat unit. The first and second sets of top cross machine direction yams are arranged in alternating fashion such that one of the first set of cross machine direction yams resides between two of the second set of top cross machine direction yams, and one of the second set of top cross machine direction yams resides between two of the first set of top cross machine direction yams. Each of the machine direction yams of the repeat unit passes below at least one of the bottom machine direction yarns, and each of the machine direction yams passes either (a) above two adjacent top cross machine direction yams of the first set and below one of the top cross machine direction yarns of the second set positioned therebetween, or (b) above two adjacent top cross machine direction yarns of the second set and below one of the top cross machine direction yarns of the first set positioned therebetween. This configuration can also provide a surface structure and permeability suitable for forming tissue paper. It is preferred that, in this configuration, the paper side cross machine direction yams comprising the first set be formed of a material that has a different elastic modulus ( e., differs in flexibility) than the material from which the paper side cross machine direction yams are formed. Rrief Desr-.riptinn nf the Figures Figure 1 is a top view of the papermaking surface of a double layer forming fabric of the present invention. Figure 2 is a top view of the bottom layer of the double layer forming fabric of Figure 1. Figures 3A and 3B are section views taken along lines 3A-3A and 3B-3B of Figure 1, respectively, showing the interrelationship between two typical MD yams, primary CMD yarns, companion CMD yams, and machine side CMD yams. Figure 4 is an enlarged partial perspective view of the fabric of Figure 1 showing the interrelationship of companion CMD yams to one another and to their adjacent primary CMD yarns. Figure 5 is a top view of the papermaking surface of an alternative double layer forming fabric embodiment of the present invention. Figure 6 is a top view of the bottom layer of the double layer forming fabric of Figure 5. Figures 7A and 7B are section views taken along lines 7A-7A and 7B-7B of Figure 5, respectively, showing the interrelationship between typical MD yams, primary CMD yams, companion CMD yams, and machine side CMD yams. Figure 8 is an enlarged partial perspective view of the fabric of Figure 5 showing the interrelationship of companion CMD yams to one another and to their adjacent primary CMD yarns. Detailed Desrxiprinn nf the Tnventinn The present invention will now be described more particularly hereinafter with reference to the accompanying drawings, in which present embodiments of the invention are shown. The invention, however, be embodied in many different forms and is not limited to the embodiments set forth herein; rather, these embodiments are provided so that the disclosure will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like components throughout. The dimensions and thicknesses for some components and layers may be exaggerated for clarity. The present invention is directed to papermaker's' woven fabrics. For ease of understanding of the concepts of the invention, the first fabric illustrated herein will be described as if a base fabric layer were initially woven and then additional yams added. The hypothetical base fabric layer includes MD yams and CMD yarns referred to as "primary" CMD yams. The additional yams are referred to as "companion" CMD yams. Of course, this fabric embodiment will typically be woven in a one-step weaving process, with the primary CMD yams and the companion CMD yams being woven in sequence. Turning now to the Figures, a double layer fabric, designated broadly at 50, is illustrated in Figures 1 through 4. In the illustration in Figure 1 that encompasses a repeat unit, the fabric 50 includes MD yarns 52, 54, 56, 58, 60, 62, 64, and 66. Eight primary CMD yams 70, 72, 74, 76, 78, 80, 82, and 84 are interwoven with the MD yams in a twill pattern such that each CMD yam passes over seven MD yams, passes beneath an MD yam, then repeats this pattern; e., the "floats" of the primary CMD yams 70 through 84 (those portions of the primary CMD yams which extend over multiple adjacent MD yams) form a "twill" pattern which extends across the fabric 50 at an angle at approximately 45° to the MD yarns. The eight harness fabric 50 is constructed so that the MD knuckles (locations where an MD yam passes over a single primary CMD yam) of adjacent MD yams are offset in the cross machine direction by three primary CMD yams; for example, MD yam 52 passes over primary CMD yam 70, and MD yam 54 passes over primary CMD yam 76. Figure 2 illustrates the machine side layer of the fabric 50. Machine side CMD yams 90, 92, 94, 96, 98, 100, 102, and 104 are positioned below the primary CMD yams 70 through 84 described above, with each machine side CMD yarn preferably being positioned substantially directly beneath a respective paper side primary CMD yam. In Figures 3A and 3B, typical MD yams 52, 54 are shown passing from the paper side of the fabric 50 to interweave the machine side CMD yarns. Specifically, in this instance, the MD yam 52 passes over the machine side CMD yams 90, 92 and 94, under machine side CMD yam 96, over machine side CMD yam 98, under machine side CMD yam 100, and above machine side CMD yams 102 and 104 (Figure 3A). Adjacent MD yam 54 passes below machine side CMD yam 90, above machine side CMD yams 92-100, below machine side CMD yam 102, and above machine side CMD yarn 104. (Figure 3B). Referring again to Figures 1 and 2, a pair of companion CMD yams is positioned between each pair of primary CMD yams. Each companion CMD yam has the identical weave pattem to a primary CMD yam separated from it by only one other companion CMD yarn. For clarity, the numerical designation of each companion CMD yarn matches that of the primary CMD yam with its identical weave pattern, with an "a" or "b" designation added to indicate a companion CMD yarn. Thus, the companion CMD yarn 70b has the identical weave pattern to primary CMD yam 70, companion CMD yams 72a, 72b have the identical weave pattern of primary CMD yam 72, and companion CMD yams 74a, 74b have the identical weave pattern to primary CMD yam 74. The same is true for companion CMD yams 76a, 76b, 78a, 78b, 80a, 80b, 82a, 82b, 84a, and 84b, each of which has the identical weave pattern as the primary CMD yam with its corresponding designating number (companion CMD yarn 84a is located adjacent primary CMD yam 70 is this repeat unit). In each instance, the companion CMD yarn is separated from its corresponding primary CMD yarn by one other companion CMD yam, which, of course, is also separated from its corresponding primary CMD yam by the first companion CMD yam. In this configuration, the MD yams follow an "over 1 /under 1/over 1/under 1/over 1" sequence as they interweave with two companion CMD yarns, a primary CMD yam, and two more companion CMD yarns. For example, MD yam 58 passes over companion yam 72a, below companion yam 70b, above primary CMD yarn 72, below companion yam 74a, and above companion yam 72b. This sequence can encourage the primary and companion CMD yams to remain relatively uniformly separated from one another, particularly when the companion CMD yams are of a similar diameter as the primary CMD yams and/or are formed of a stiffer material than the primary CMD yams, as is described in greater detail below. Preferably, the companion CMD yams are of a similar, or even essentially identical, diameter as the primary CMD yams in the fabric 50. The selected sizes of the companion, primary and machine side CMD yams and the MD yams are typically governed by the performance requirements of the fabric. Generally, the ratio of the diameters of the companion CMD yams and the primary CMD yams should be between about 0.9 and 1.1, with ratio of between about 0.95 and 1.05 being preferred and a ratio of about 1.0 being more preferred. Suitable yam diameters for the primary, companion and machine side CMD yarns and the MD yams are shown in the following table: The form of the yams utilized in the fabrics of the present invention can vary, depending upon the desired properties of the final papermaker's' fabric. For example, the yams may be multifilament yams, monofilament yams, twisted multifilament or monofilament yams, spun yams, or any combination thereof. Also, the materials comprising yams employed in the fabric of the present invention may be those commonly used in papermaker's' fabric. For example, the yams may be formed of cotton, wool, polypropylene, polyester, aramid, nylon, or the like. The skilled artisan should select a yam material according to the particular application of the final fabric. In particular, round monofilament yams formed of polyester or nylon are preferred. The primary CMD yams may be formed of the same material as the companion CMD yarns or be formed of a different material (and preferably a more flexible material) than the companion CMD yams. For example, the primary CMD yams may be formed of a medium modulus polyester having a relative elongation of 10 to 20 percent at 3 g per denier, and the companion CMD yams may be formed of a medium to high modulus polyester having a relative elongation of 3 to 20 percent at 3 g per denier. In this configuration, the MD yams are more likely to "crimp" as they cross the companion CMD yams (see Figure 4). This crimping in the MD yams as they form single float knuckles (encouraged by the "over 1/under 1/over 1/under 1/over 1" configuration of the MD yams on the top surface) tends to maintain the companion CMD yams in their original "as woven" positions within the papermaking surface (rather than pairs of adjacent companion yams being forced toward each other by uncrimped MD yams - see U.S. Patent No. 5,937,914 to Wilson for an explanation of this effect). In their original (and maintained) positions, the companion CMD yams are relatively uniformly separated from each other, which provides a desirable papermaking surface for forming tissue paper. The MD yam crimping can be further encouraged by weaving the MD yams at a lower tension than is typical. For example, the weaving tension of MD yams having a diameter of 0.15 mm may be lowered to a level of between about 60 and 120 g per yam. In this configuration, the fabric 50 has three paper side CMD yams for every machine side CMD yam. As a result, the fabric should have good permeability compared to fabrics with a lower ratio of paper side CMD yams to machine side CMD yams. However, the fabric 50 can address the absence of paper side CMD yam uniformity often found in other fabrics with this 3:1 ratio. It should also be noted that the fabric 50 is also configured such that all of the floats of each primary and companion CMD yam contribute to the twill line. This twill density can reduce the visual effect of fabric marking on paper produced with the fabric. This concept can be extended to virtually any double layer base fabric, including seven harness double layer fabrics, the structures of which are well-known to those skilled in this art and need not be described in detail herein. Those skilled in this art will appreciate that this concept of companion yams can be applied to virtually any fabric, including plain weaves, twills, satins, and the like. It can be employed as the paper side of single, double and triple layer fabrics, whether interlaced by common MD yarns (such as the fabric 50) or formed as separate fabric layers of a laminated fabric, such as those described in U.S. Patent No. 5,277,967 to Zehle. It is preferred that the fabrics of the present invention have a harness repeat of greater than 2 ( z~, for fabrics other than lxl plain weave fabrics). The positive impact of the "over 1/under 1/over 1" configuration on crimping of MD yams and, consequently, maintenance of separation of paper side CMD yams may also be seen in an alternative fabric embodiment, designated broadly at 200 in Figures 5 through 8. The fabric 200 comprises eight MD yams 202, 204, 206, 208, 210, 212, 214, 216 interwoven with sixteen paper side CMD yams 220, 222, 224, 226, 228, 230, 232, 234, 236, 238, 240, 242, 244, 246, 248, 250 and eight machine side CMD ya s 260, 262, 264, 266, 268, 270, 272, 274. The paper side CMD yams can be subdivided into two sets of alternating yams: one set being paper side CMD yams 220, 224, 228, 232, 236, 240, 244 and 248, and the second set of paper side CMD yams being 222, 226, 230, 234, 238, 242, 246 and 250. As can be seen in Figure 5, each MD yam passes above one paper side CMD yam, below the immediately adjacent paper side CMD, above the next adjacent paper side CMD yam, and below the remaining CMD paper side yams. For example, the MD yam 202 passes over paper side CMD yam 220, below paper side CMD yam 222, over paper side CMD yam 224, and below the remaining paper side CMD yams. The remaining MD yams also have this "over 1/under 1/over 1" pattern with paper side CMD yams. Notably, each MD yam passes over two paper side yams that are either both in the first set or both in the second set of paper side CMD yams, and each MD yam passes under a paper side CMD yam that is not in the set of paper side yams that the MD yams passes over. Again using MD yam 202 as an example, it passes over paper side CMD yams 220 and 224, each of which are in the first set of paper side CMD yams as defined above, and below paper side CMD yam 222, which is in the second set of paper side CMD yams. Adjacent MD yams are offset from each other in the machine direction by either five or seven paper side CMD yams. For example, MD yam 202 first passes over paper side CMD yam 220, while adjacent MD yam 204 first passes over paper side yarn 230, which is five yams away from paper side CMD yam 220 in the machine direction. MD yam 206 first passes over paper side CMD yam 244, which is seven paper side CMD yams away from the paper side CMD yam 230 first passed over by adjacent MD yam 204. This alternating offset of five paper side CMD yarns, then seven paper side CMD yams, for adjacent MD yams continues throughout the repeat unit. As a result of this weave pattern, the "companion" yam concept of the fabric 50 described above is extended to the fabric 200 also. Each paper side CMD yam has the identical weave pattern to another paper side CMD yam separated from it by one paper side CMD yam. For example, paper side CMD yams 220 and 224 both pass under MD yams 202 and 208 and over the other MD yams. This pattern forms the "over 1 /under 1/overl" pattern described above that can encourage desirable crimping in the MD yams. Referring now to Figure 6, the machine side of the fabric is formed by the interweaving of the MD and machine side CMD yams. One machine side CMD yam is positioned generally beneath a respective paper side CMD yam. Each MD yam passes below two machine side CMD yams separated by one machine side CMD yam. For example, MD yam 202 passes below machine side CMD yams 266 and 270 (passing over machine side CMD yam 268 that is positioned between machine side yams 268, 272). Similarly, MD yam 204 passes below machine side CMD yams 272 and 260 and above machine side CMD yam 272 (yam 260 would be the next machine side CMD yam in the repeat unit). Notably, half of the MD yams (exemplified by MD yam 202 in Figure 7A), after passing above a paper side CMD yam, pass above one machine side CMD yam before passing below a machine side CMD yam, while the other half of the MD yams (exemplified by MD yam 204 in Figure 7B), pass above two machine side CMD yams after passing over a paper side CMD yam before passing below a machine side CMD yam. The sizes, materials and configurations of the yams for the fabric 200 can take the form described hereinabove for the fabric 50. An exemplary fabric is formed of MD yams having a diameter of 0.15 mm, paper side CMD yams having a diameter of 0.11 mm, and machine side CMD yams having a diameter of 0.25 mm. Like the fabric 50 described above, it maybe desirable to reduce the typical weaving tension for the MD yams. Also as with the fabric 50, it may be desirable to form some of the paper side CMD yarns of a more flexible material. In this configuration, the fabric 200 can provide a desirable combination of permeability and fiber support for tissue forming fabrics. The top surface of the fabric 200 includes the "over 1/under 1/over 1" MD yam weaving pattern that can encourage MD yarn crimping and, as a result, uniform separation of paper side CMD yams. Accordingly, the fabric can furnish a suitable surface for forming tissue paper. It should also be understood that, although fabrics for forming tissue have been discussed herein, this concept can be extended to fabrics for forming other types of paper. For example, similar weave patterns can be used to form brown paper by increasing yarn size, including one embodiment following the weave pattern illustrated in Figures 1 through 4 in which paper side CMD yams having a diameter of 0.23mm, machine side CMD yams having a diameter of 0.40mm, and machine direction yams having a diameter of 0.27mm are employed. Those skilled in this art will recognize other extensions of this concept can apply to other types of paper. The foregoing embodiments are illustrative of the present invention, and are not to be construed as limiting thereof. The invention is defined by the following claims, with equivalents of the claims to be included therein.

Claims: THAT WHICH IS CLAIMED IS: 1. A papermaker's fabric, comprising: a base fabric structure including machine direction yams and primary cross machine direction yams interlacing to form a papermaking surface, said machine direction yams and primary cross machine direction yams being interlaced in a pattern having a harness repeat of greater than two; first and second companion cross machine direction yams positioned between each pair of adjacent primary cross machine direction yams; wherein each first companion cross machine direction yam has an interlacing pattern relative to said machine direction yams that is identical to a first of said pair of adjacent primary cross machine direction yams, and wherein each second companion cross machine direction yam has an interlacing pattern relative to said machine direction yams that is identical to a second of said pair of adjacent primary cross machine direction yarns, and wherein said first companion cross machine direction yam is positioned between said second primary and companion cross machine direction yams; and wherein said primary cross machine direction yams have a first diameter, and said first and second companion yams have a second diameter, and the ratio between said first and second diameters is between about 0.9 and 1.1. 2. The papermaker's fabric defined in Claim 1, wherein said second companion cross machine direction yam is positioned between said first primary and companion cross machine direction yams. 3. The papermaker's fabric defined in Claim 1, wherein said repeating harness pattern is a twill pattern. 4. The papermaker's fabric defined in Claim 3, wherein said twill pattern is a 2 x 1 twill pattern. 5. The papermaker's fabric defined in Claim 1, wherein said ratio between said first and second diameters is between 0.95 and 1.05. 6. The papermaker's fabric defined in Claim 1, wherein said ratio between said first and second diameters is about 1.0. 7. The papermaker's fabric defined in Claim 1, wherein said primary cross machine direction yams are formed of a first material, and said companion cross machine direction yams are formed of a second material that differs from said first material. 8. The papermaker's fabric defined in Claim 7, wherein said second material has a higher stiffness than said first material. 9. The papermaker's fabric defined in Claim 1, further comprising additional cross machine direction yams interlaced with said machine direction yams to form a machine side surface. 10. A papermaker's fabric, comprising: a base fabric structure including machine direction yams and primary cross machine direction yarns interlacing to form a papermaking surface, said machine direction yams and primary cross machine direction yarns being interlaced in a pattern having a harness repeat of greater than two, said base fabric stmcture further including a second set of cross machine direction yams interlaced with said machine direction yarns to form a machine side surface of said fabric; first and second companion cross machine direction yarns positioned between each pair of adjacent primary cross machine direction yams; wherein each first companion cross machine direction yam has an interlacing pattern relative to said machine direction yams that is identical to a first of said pair of adjacent primary cross machine direction yams, and wherein each second companion cross machine direction yarn has an interlacing pattern relative to said machine direction yams that is identical to a second of said pair of adjacent primary cross machine direction yams, and wherein said first companion cross machine direction yarn is positioned between said second primary and companion cross machine direction yams; and wherein said primary cross machine direction yams have a first diameter, and said first and second companion yams have a second diameter, and the ratio between said first and second diameters is between about 0.9 and 1.1. 11. The papermaker's fabric defined in Claim 10, wherein said second companion cross machine direction yarn is positioned between said first primary and companion cross machine direction yams. 12. The papermaker's fabric defined in Claim 10, wherein said repeating harness pattern is a twill pattern. 13. The papermaker's fabric defined in Claim 12, wherein said twill pattern is a 2 x 1 twill. 14. The papermaker's fabric defined in Claim 10 , wherein said ratio between said first and second diameters is between 0.95 and 1.05. 15. The papermaker's fabric defined in Claim 10, wherein said ratio between said first and second diameters is about 1.0. 16. The papermaker's fabric defined in Claim 10, wherein said primary cross machine direction yams are formed of a first material, and said companion cross machine direction yams are formed of a second material that differs from said first material. 17. The papermaker's fabric defined in Claim 16, wherein said second material has a higher stiffness than said first material. 18. A papermaker's fabric, comprising: machine direction yams interwoven with first and second sets of top cross machine direction yarns and a bottom set of cross machine direction yarns in a repeat unit, said first and second sets of top cross machine direction yams being arranged in alternating fashion such that one of said first set of cross machine direction yams resides between two of said second set of top cross machine direction yams, and one of said second set of top cross machine direction yarns resides between two of said first set of top cross machine direction yams, wherein each of said machine direction yarns of said repeat unit passes below at least one of said bottom machine direction yams, and each of said machine direction yarns passes either (a) above two adjacent top cross machine direction yams of said first set and below one of said top cross machine direction yams of said second set positioned therebetween, or (b) above two adjacent top cross machine direction yams of said second set and below one of said top cross machine direction yams of said first set positioned therebetween. 19. The papermaker's fabric defined in Claim 18, wherein said first and second sets of top cross machine direction yams have, respectively, first and second diameters, and wherein the ratio between said first and second diameters is between 0.9 and 1.1. 20. The papermaker's fabric defined in Claim 18, wherein said ratio between said first and second diameters is about 1.0. 21. The papermaker's fabric defined in Claim 18, wherein said first set of top cross machine direction yams are formed of a first material, and said second set of cross machine direction yams are formed of a second material that differs from said first material. 22.. The papermaker's fabric defined in Claim 21, wherein said second material has a higher stiffness than said first material. 23. A method of making paper, comprising the steps of: providing a papermaker's fabric, said papermaker's fabric comprising: a base fabric stmcture including machine direction yams and primary cross machine direction yams interlacing to form a papermaking surface, said machine direction yams and primary cross machine direction yams being interlaced in a pattern having a harness repeat of greater than 2; two companion cross machine direction yarns positioned between each pair of adjacent primary cross machine direction yarns; wherein each first companion cross machine direction yam has an interlacing pattern relative to said machine direction yams that is identical to a first of said pair of adjacent primary cross machine direction yams, and wherein each second companion cross machine direction yam has an interlacing pattern relative to said machine direction yams that is identical to a second of said pair of adjacent primary cross machine direction yams, and wherein said first companion cross machine direction yam is positioned between said second primary and companion cross machine direction yams; and wherein said primary cross machine direction yams have a first diameter, and said first and second companion yams have a second diameter, and the ratio between said first and second diameters is between about 0.9 and 1.1; applying paper stock to said papermaker's fabric; and removing moisture from said paper stock.

Inventors: TROUGHTON BRIAN H P, WILSON ROBERT G, TROUGHTON, BRIAN, H., P., WILSON, ROBERT, G.
Applicants: TROUGHTON BRIAN H P, WEAVEXX CORP, WILSON ROBERT G, TROUGHTON, BRIAN, H., P., WEAVEXX CORPORATION, WILSON, ROBERT, G.
Application year: 2001
Main classification: D21F1
IPC codes: D21F1