Patent Grant
6860969
This invention relates generally to woven fabrics, and relates more specifically to woven fabrics for papermakers.
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 (i.e., 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, typically 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.
Effective sheet and fiber support and an absence of wire marking are typically important considerations in papermaking, especially for the forming section of the papermaking machine, where the wet web is initially formed. Wire marking is particularly problematic in the formation of fine paper grades, as it can affect a host of paper properties, such as sheet mark, porosity, “see through” and pin holing. Wire marking is typically the result of individual cellulosic fibers being oriented within the paper web such that their ends reside within gaps between the individual threads or yarns of the forming fabric. This problem is generally addressed by providing a permeable fabric structure with a coplanar surface that allows paper fibers to bridge adjacent yarns of the fabric rather than penetrate the gaps between yarns. As used herein, “coplanar” means that the upper extremities of the yarns defining the paper-forming surface are at substantially the same elevation, such that at that level there is presented a substantially “planar” surface. Accordingly, fine paper grades intended for use in quality printing, carbonizing, cigarettes, electrical condensers, and like grades of fine paper have typically heretofore been formed on very finely woven or fine wire mesh forming fabrics.
Typically, such finely woven fabrics include at least some relatively small diameter machine direction or cross machine direction yarns. Regrettably, 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 effect the mechanical stability of the fabric (especially the skew resistance, propensity for narrowing and stiffness), which may negatively impact both the service life and the performance of the fabric.
To combat these problems associated with fine weaves, multi-layer forming fabrics have been 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 which employ one set of machine direction yarns which interweave with two sets of cross machine direction yarns to form a fabric having a fine 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 have been constructed which include two sets of machine direction yarns and two sets of cross machine direction yarns that form a fine mesh paper side fabric layer and a separate, coarser machine side fabric layer. In these fabrics, which are part of a class of fabrics generally referred to as “triple layer” fabrics, the two fabric layers are typically bound together by separate stitching yarns. As double and triple layer fabrics include additional sets of yarn as compared to single layer fabrics, these fabrics typically have a higher “caliper” (i.e., they are thicker than) comparable single layer fabrics. An illustrative double layer fabric is shown in U.S. Pat. No. 4,423,755 to Thompson, and illustrative triple layer fabrics are shown in U.S. Pat. No. 4,501,303 to Osterberg, U.S. Pat. No. 5,152,326 to Vohringer, U.S. Pat. Nos. 5,437,315 5,967,195, and 6,145,550 to Ward, and U.S. Pat. No. 6,244,306 to Troughton, the disclosures of which are hereby incorporated by reference in their entirety.
Although these fabrics have performed successfully, they have some potential shortcomings that may relate to the inclusion of the stitching yarns, for example, problems with interlayer wear. As the fabric is used on a paper machine, the top and bottom layers tend to shift relative to one another, both in the machine direction and the cross machine direction, due to the tension imparted to the fabric by the rolls. This effect is exacerbated on paper machines, such as the so-called “high-wrap” machines, that include multiple rolls, including some which contact the top layer of the fabric. This shifting can cause the fabric to wear and decrease in thickness, which can adversely affect the drainage of the fabric and, accordingly, its performance in papermaking. In many instances, it is this interlayer wear, rather than the wear of the machine side surface of the fabric machine against the paper machine, that determines the longevity of the fabric.
Also, the stitching yarns of a triple layer fabric should be sufficiently strong and durable to bind the top and bottom layers and to resist the wear and abrasion conditions that the bottom layer experiences while in contact with the paper machine, yet should be delicate enough to produce high quality paper. This balance can be difficult to strike.
The present invention is directed to papermaker's fabrics that can address some of the wear and abrasion issues noted above. In certain embodiments according to the present invention, a papermaker's fabric includes top MD yarns, top CMD yarns, bottom MD yarns, bottom CMD yarns and stitching yarns. The fabric is formed in a plurality of repeating units, each of the repeating units including a set of top MD yarns, a set of top CMD yarns interwoven with the set of top MD yarns to form a top fabric layer, a set of four bottom MD yarns, a set of bottom CMD yarns interwoven with the set of four bottom MD yarns to form a bottom fabric layer and a set of stitching yarns interwoven with the top and bottom fabric layers. The bottom MD yarns and the bottom CMD yarns are interwoven in a series of repeat units in which each of the bottom MD yarns passes below two nonadjacent bottom CMD yarns to form bottom machine direction knuckles, each bottom machine direction knuckle being separated from one adjacent knuckle formed by that bottom machine direction yarn by two bottom CMD yarns and separated from another adjacent knuckle also formed by that bottom MD yarn by four bottom CMD yarns. In this configuration, the bottom MD yarns present stitching locations for the stitching yarns that can be very favorable for avoiding abrasion and wear. The stitching locations form a symmetrical pattern that may be easier to manufacture.
In other embodiments according to the present invention, the papermaker's fabric discussed above includes pairs of first and second stitching yarns positioned between pairs of top CMD yarns. The first and second stitching yarns of each pair are interwoven with the top and bottom MD yarns such that, as a fiber support portion of the first stitching yarn is interweaving with the top MD yarns, a binding portion of the second stitching yarn is positioned below the top MD yarns, and such that as a fiber support portion of the second stitching yarn is interweaving with the top MD yarns, a binding portion of the first stitching yarn is positioned below the top MD yarns. The first and second stitching yarns cross each other as they pass below a transitional top MD yarn, and each of the binding portions of the first and second stitching yarns passes below at least one of the bottom MD yarns.
In other embodiments of the present invention, embodiments of the papermaker's fabrics described above may be used to make paper. A paper stock may be applied to a papermaker's fabric as described above, and moisture may be removed from the paper stock to produce paper.
The present invention will now be described more particularly hereinafter with reference to the accompanying drawings, in which preferred 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 elements and the spacing between elements may be exaggerated for clarity.
An eight harness triple layer forming fabric, generally designated at 10, is illustrated in
Referring now to
The bottom CMD yarns follow an “over 1/under 3” pattern that is repeated twice within the repeat unit. The bottom layer 80 has a repeat unit of four bottom MD yarns. For example, bottom CMD yarn 85 passes over bottom MD yarn 61, under bottom MD yarns 63, 65, and 67, over bottom MD yarn 69 and under bottom MD yarns 71, 73 and 75, while bottom CMD yarn 87 passes over bottom MD yarn 65, under bottom MD yarns 67, 69, and 71, over bottom MD yarn 73, and under bottom MD yarns 75, 61 and 63.
Referring back to
As can be seen in FIGS. 3 and 4A-B, stitching yarns interweave with the top MD yarns and bottom MD yarns in the following pattern. Each of the stitching yarns of the repeat unit can be subdivided into two portions: an upper portion which interweaves with the top MD yarns, and a lower portion which interweaves with a bottom MD yarn. As discussed above, the bottom MD yarns form an “under 1/over 4/under 1/over 2” weave pattern. Thus, the bottom MD yarns form knuckles under nonadjacent bottom CMD yarns such that each knuckle is separated from adjacent knuckles by two bottom CMD yarns one side and four bottom CMD yarns on the other. For example, in
The stitching yarns are interwoven relative to the bottom MD yarns such that the lower portion of each stitching yarn forms a binding knuckle with the bottom MD yarn between the second and third of the four bottom CMD yarns separating two adjacent bottom MD knuckles. For example, bottom MD yarn 63 forms knuckles with CMD yarns 81 and 91. The knuckles are separated by four bottom CMD yarns 83, 85, 87 and 89. A stitching yarn 53 forms a knuckle with the bottom MD yarn 63 between the second and third of the four bottom CMD yarns, that is, bottom CMD yarns 85 and 87 (e.g., FIG. 3). It has been discovered that, in this configuration, the stitching yarns may be better protected from wear. The bottom MD yarn 63 “floats” between the bottom CMD yarns 81 and 91 and arches somewhat above the four bottom CMD yarns 83, 85, 87 and 89. Thus, placing the stitching yarn 53 in a position that is central to the “arch” of the bottom MD yarn 63 (between bottom CMD yarns 85 and 87) may allow protection from wear because stitching yarn 53 is then located some distance from the lower surface of the bottom layer 80, thereby reducing wear on the stitching yarn 53. Each of the other stitching yarns 51, 53, 55, 57 also binds below a bottom MD yarn between the second and third yarns of a four yarn float found by that bottom MD yarn.
The bottom layer 120 includes eight bottom MD direction yarns 131, 133, 135, 137, 139, 141, 143 and 145 interwoven with eight bottom CMD yarns 111, 113, 115, 117, 119, 121, 123, and 125. The weaving pattern of the bottom MD yarns relative to the bottom CMD yarns is identical to that described above for the fabric 10, namely, each bottom MD yarn follows an “under 1/over 4/under 1/over 2” pattern relative to the bottom CMD yarn, and adjacent bottom MD yarns are offset from one another by two bottom CMD yarns. As a result, the characteristic bottom MD knuckles formed under bottom CMD yarns are separated from one another by, alternately, four bottom CMD yarns on one side of a knuckle and two bottom CMD yarns on the other side of a knuckle, similar to fabric 10 discussed above.
As with fabric 10, the stitching yarns are interwoven with bottom MD yarns to form binding knuckles between the knuckles formed by the bottom MD yarns and the bottom CMD yarns. However, the binding knuckles formed by the stitching yarns and bottom MD yarns in fabric 100 are formed between two bottom CMD yarns that separate two bottom MD yarn knuckles. For example, in
The performance advantages discussed above for fabric 10 may also be achieved with fabric 100. Specifically, the binding knuckles are located between two bottom CMD yarns, which in turn separate two bottom CMD/MD yarn knuckles. Thus, the bottom CMD yarns on either side of the binding knuckle can protect the stitching yarns from contact with the paper machine and from the resulting wear. By being so located, the binding knuckles are located at the apex of the float that the bottom MD yarns form over the bottom CMD yarns. Therefore, the binding knuckles are positioned away from the lower surface of the bottom layer 120, and are less susceptible to contact with the paper machine and the resulting wear.
As would be appreciated by those of skill in the art, various top fabric layer configurations and weave patterns may be substituted for the top layers 60 and 110 discussed above. For example, in fabrics 10 and 100, when either of the bottom layers 80 and 120 are joined with the respective top layers 60 and 110, each of the bottom CMD yarns is positioned substantially directly below a corresponding top CMD yarn. There is no bottom CMD yarn positioned substantially directly below the stitching yarn, thereby providing a space in which the stitching yarns can stitch below a bottom CMD yarn. Of course, those skilled in this art will appreciate that the fabric may have differing numbers of top and bottom CMD yarns in a repeat unit; for example, there may be 1.5, two or three times as many top CMD yarns as bottom CMD yarns, or there may be a CMD yarn below each stitching yarn. Also, the top layers 60 and 110 may vary from plain weave patterns illustrated herein; for example, the pattern of the top layer may be satin, twill, broken twill, or the like.
Those skilled in this art will appreciate that, although the illustrated fabrics employ a single stitching yarn, stitching yarn pairs may also be employed. Stitching yarn pairs can be incorporated into the paper making surface of the fabric as is disclosed in U.S. Pat. No. 6,145,550 to Ward. Examples of triple layer fabrics using stitching yarn pairs is illustrated are
One example of a triple layer fabric, designated 170, is shown in
The bottom layer 200 of the fabric 170 is substantially identical to the bottom layers 80 and 120 illustrated in
Corresponding pairs of stitching yarns in fabric 170 interweave with the top MD yarns and bottom MD yarns in the following pattern. Each of the stitching yarns of the repeat unit can be subdivided into two portions: a fiber support portion which interweaves with the top MD yarns, and a binding portion which interweaves a bottom MD yarn. These are separated at “transitional” top MD yarns, below which one stitching yarn of a pair crosses the other stitching yarn of the pair. The stitching yarns of each pair are interwoven relative to one another such that the fiber support portion of one yarn of the pair is positioned substantially above the binding portion of the other yarn of the pair. The fiber support portion of the stitching yarn of each pair designated with an “A” (e.g., 187A, 189A, 191A, 193A) interweaves in an alternating fashion with three top MD yarns in an over/under pattern as the other stitching yarn of the pair (for purposes of this example, designated with a “B”) forms a binding knuckle with one bottom MD yarn.
For example, in
As can be seen, for example, in
Another example of a triple layer fabric 250 having pairs of stitching yarns is shown in
The bottom layer 300 in
The stitching yarn pairs follow a pattern similar to that described with respect to fabric 170. As can be seen in
As an example and as shown in
The stitching yarn pairs shown in fabrics 170 and 250 in
Other stitching yarn configurations can be used. For example, the stitching yarns may be “pseudo-stitching” yarn pairs. In a pseudo-stitching yarn configuration, only one of the yarns in a stitching yarn pair forms a knuckle with the bottom MD yarns. Referring to
As would be understood by those of ordinary skill in the art, the weave patterns described with reference to
Although illustrated embodiments employ plain weave pattern top layers, the fabrics of the present invention may also employ other top layer weave patterns; for example, satins, broken twills, and the like may also be employed. The stitching yarns may comprise an integral portion of the top surface weave or may not.
The form of the yarns utilized in the fabrics of the present invention can vary, depending upon the desired properties of the final papermaker's fabric. For example, the yarns may be multifilament yarns, monofilament yarns, twisted multifilament or monofilament yarns, spun yarns, or any combination thereof. Also, the materials comprising yarns employed in the fabric of the present invention may be those commonly used in papermaker's fabric. For example, the yarns may be formed of polypropylene, polyester, aramid, nylon, or the like. The skilled artisan should select a yarn material according to the particular application of the final fabric. In particular, round monofilament yarns formed of polyester or nylon are preferred.
Yarn sizes should also be selected according to the desired papermaking properties of the fabric. As an example, generally, for fine paper applications, top MD yarns have a diameter of between about 0.13 mm and 0.17 mm, top CMD yarns have a diameter of between about 0.13 mm and 0.20 mm, stitching yarns have a diameter of between about 0.11 mm and 0.15 mm, bottom MD yarns-have a diameter of between about 0.17 mm and 0.25 mm, and bottom CMD yarns have a diameter of between about 0.20 mm and 0.35 mm.
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.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2172430 | Barrell | Sep 1939 | A |
| 2554034 | Koester et al. | May 1951 | A |
| 3094149 | Keily | Jun 1963 | A |
| 3325909 | Clark | Jun 1967 | A |
| 4093512 | Fleischer | Jun 1978 | A |
| 4182381 | Gisbourne | Jan 1980 | A |
| 4244543 | Ericson | Jan 1981 | A |
| 4289173 | Miller | Sep 1981 | A |
| 4290209 | Buchanan et al. | Sep 1981 | A |
| 4414263 | Miller et al. | Nov 1983 | A |
| 4438788 | Harwood | Mar 1984 | A |
| 4452284 | Eckstein et al. | Jun 1984 | A |
| 4453573 | Thompson | Jun 1984 | A |
| 4501303 | Osterberg | Feb 1985 | A |
| 4515853 | Borel | May 1985 | A |
| 4529013 | Miller | Jul 1985 | A |
| 4564052 | Borel | Jan 1986 | A |
| 4592395 | Borel | Jun 1986 | A |
| 4592396 | Borel et al. | Jun 1986 | A |
| 4605585 | Johansson | Aug 1986 | A |
| 4611639 | Bugge | Sep 1986 | A |
| 4621663 | Malmendier | Nov 1986 | A |
| 4633596 | Josef | Jan 1987 | A |
| 4636426 | Fleischer | Jan 1987 | A |
| 4642261 | Fearnhead | Feb 1987 | A |
| 4676278 | Dutt | Jun 1987 | A |
| 4705601 | Chiu | Nov 1987 | A |
| 4709732 | Kinnunen | Dec 1987 | A |
| 4729412 | Bugge | Mar 1988 | A |
| 4731281 | Fleischer et al. | Mar 1988 | A |
| 4739803 | Borel | Apr 1988 | A |
| 4755420 | Baker et al. | Jul 1988 | A |
| 4759975 | Sutherland et al. | Jul 1988 | A |
| 4815499 | Johnson | Mar 1989 | A |
| 4815503 | Borel | Mar 1989 | A |
| 4909284 | Kositzke | Mar 1990 | A |
| RE33195 | McDonald et al. | Apr 1990 | E |
| 4934414 | Borel | Jun 1990 | A |
| 4941514 | Taipale | Jul 1990 | A |
| 4942077 | Wendt et al. | Jul 1990 | A |
| 4945952 | Vöhringer | Aug 1990 | A |
| 4967805 | Chiu et al. | Nov 1990 | A |
| 4987929 | Wilson | Jan 1991 | A |
| 4989647 | Marchand | Feb 1991 | A |
| 4989648 | Tate et al. | Feb 1991 | A |
| 4998568 | Vohringer | Mar 1991 | A |
| 4998569 | Tate | Mar 1991 | A |
| 5022441 | Tate et al. | Jun 1991 | A |
| 5025839 | Wright | Jun 1991 | A |
| 5067526 | Herring | Nov 1991 | A |
| 5074339 | Vohringer | Dec 1991 | A |
| 5084326 | Vohringer | Jan 1992 | A |
| 5092372 | Fitzka et al. | Mar 1992 | A |
| 5101866 | Quigley | Apr 1992 | A |
| 5116478 | Tate et al. | May 1992 | A |
| 5152326 | Vohringer | Oct 1992 | A |
| 5158118 | Tate et al. | Oct 1992 | A |
| 5219004 | Chiu | Jun 1993 | A |
| 5228482 | Fleischer | Jul 1993 | A |
| 5238536 | Danby | Aug 1993 | A |
| 5277967 | Zehle et al. | Jan 1994 | A |
| 5358014 | Kovar | Oct 1994 | A |
| 5421374 | Wright | Jun 1995 | A |
| 5421375 | Praetzel | Jun 1995 | A |
| 5429686 | Chiu et al. | Jul 1995 | A |
| 5449026 | Lee | Sep 1995 | A |
| 5454405 | Hawes | Oct 1995 | A |
| 5456293 | Ostermayer et al. | Oct 1995 | A |
| 5465764 | Eschmann et al. | Nov 1995 | A |
| 5482567 | Barreto | Jan 1996 | A |
| 5487414 | Kuji et al. | Jan 1996 | A |
| 5518042 | Wilson | May 1996 | A |
| 5520225 | Quigley et al. | May 1996 | A |
| 5542455 | Ostermayer et al. | Aug 1996 | A |
| 5555917 | Quigley | Sep 1996 | A |
| 5564475 | Wright | Oct 1996 | A |
| 5641001 | Wilson | Jun 1997 | A |
| 5651394 | Marchand | Jul 1997 | A |
| 5709250 | Ward et al. | Jan 1998 | A |
| RE35777 | Givin | Apr 1998 | E |
| 5746257 | Fry | May 1998 | A |
| 5826627 | Seabrook et al. | Oct 1998 | A |
| 5857498 | Barreto et al. | Jan 1999 | A |
| 5881764 | Ward | Mar 1999 | A |
| 5937914 | Wilson | Aug 1999 | A |
| 5967195 | Ward | Oct 1999 | A |
| 5983953 | Wilson | Nov 1999 | A |
| 6123116 | Ward et al. | Sep 2000 | A |
| 6145550 | Ward | Nov 2000 | A |
| 6148869 | Quigley | Nov 2000 | A |
| 6158478 | Lee et al. | Dec 2000 | A |
| 6227255 | Osterberg et al. | May 2001 | B1 |
| 6244306 | Troughton | Jun 2001 | B1 |
| 6253796 | Wilson et al. | Jul 2001 | B1 |
| 6276402 | Herring | Aug 2001 | B1 |
| 6354335 | Taipale et al. | Mar 2002 | B1 |
| 20040020621 | Heger et al. | Feb 2004 | A1 |
| Number | Date | Country |
|---|---|---|
| 1115177 | Dec 1981 | CA |
| 2-277848 | Apr 1998 | CN |
| 454 092 | Dec 1927 | DE |
| 33 29 740 | Mar 1985 | DE |
| 0 048 962 | Sep 1981 | EP |
| 0 158 710 | Oct 1984 | EP |
| 0 185 177 | Oct 1985 | EP |
| 0 224 276 | Dec 1986 | EP |
| 0 264 881 | Oct 1987 | EP |
| 0 269 070 | Nov 1987 | EP |
| 0 284 575 | Feb 1988 | EP |
| 0 283 181 | Mar 1988 | EP |
| 0 350 673 | Jun 1989 | EP |
| 0 048 849 | May 1990 | EP |
| 0 048 849 | May 1990 | EP |
| 0 672 782 | Mar 1995 | EP |
| 0 794 283 | Sep 1997 | EP |
| 2 597 123 | Apr 1986 | FR |
| 8605115 | Apr 1986 | FR |
| 2157328 | Oct 1985 | GB |
| 2245006 | Feb 1991 | GB |
| 8-158285 | Dec 1994 | JP |
| 9-41282 | Jul 1995 | JP |
| 9-87990 | Sep 1995 | JP |
| WO 8600099 | Jan 1986 | WO |
| WO 8909848 | Apr 1989 | WO |
| WO 9310304 | Nov 1992 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20040149342 A1 | Aug 2004 | US |
