Seamable, gap-free paper-making fabrics

Abstract

A woven press felt for paper making includes a base weave. A batt layer is disposed on the base weave. The woven press felt includes a seam for joining a first end of the woven press felt with a second end of the woven press felt. The seam receives a pintle inserted through seam loops of a first end of the base weave interdigitated with seam loops of a second end of the base weave. A flap is defined in the batt layer. When the woven press felt is seamed, an edge of the flap extends at an angle relative to a paper side surface of the woven press felt and the flap has a flap height extending beyond a paper side surface of the woven press felt. The flap height is in a range of 10% to 50% of a thickness of the woven press felt.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Patent Application No. 63 / 758,199 filed February 13, 2025, the contents of which are incorporated here by reference in their entirety.TECHNICAL FIELD

[0002] This present disclosure generally relates to fabrics for paper manufacture.BACKGROUND

[0003] During some papermaking processes, after a forming section in which pulp slurry is formed into a sheet, the sheet is processed in a press section. The sheet is supported by a press fabric (or “felt”) that passes through a series of nips formed by rolls. Pressure exerted by the rolls squeezes water out of the sheet and into the press fabric. In other paper making processes, such as crescent forming, pulp slurry is pressed between a forming fabric and a press felt and formed into a continuous paper sheet.

[0004] This mechanical compaction process is known as wet pressing. The press fabric has a “paper side” on which the sheet is supported and a “machine side,” opposite the paper side, in contact with or otherwise adjacent to the machine elements such as rolls. Imperfections such as gaps in the paper side of the press fabric can create imperfections in the sheet during the wet pressing process, which can cause the resulting paper product to have visible and / or structural imperfections.SUMMARY

[0005] Some aspects of this disclosure relate to press fabrics for paper manufacture.

[0006] In one aspect, a woven press felt for paper making includes a base weave. A batt layer is disposed on at least one side of the base weave. The woven press felt further includes a seam for joining a first end of the woven press felt with a second end of the woven press felt. The seam is designed to receive a pintle inserted through seam loops of a first end of the base weave interdigitated with seam loops of a second end of the base weave. A flap is defined in the batt layer. When the woven press felt is seamed, an edge of the flap extends at an angle relative to a paper side surface of the woven press felt and the flap has a flap height extending beyond a paper side surface of the woven press felt. The flap height is in a range of 10% to 50% of a thickness of the woven press felt.

[0007] Embodiments can include one or any combination of two or more of the following features.

[0008] In some implementations, the flap height is greater than zero and less than 3 mm.

[0009] In some implementations, the flap height is in a range of 20% to 40% of the thickness of the woven press felt.

[0010] In some implementations, the flap height is less than a flap length of the flap in the machine direction of the woven press felt.

[0011] In some implementations, a ratio of the flap length to the flap height is in a range of 1 to 3.

[0012] In some implementations, the flap length is in a range of 25% to 125% of the thickness of the woven press felt.

[0013] In some implementations, the flap length is equal to or greater than a seam length of the woven press felt.

[0014] In some implementations, the angle at which the flap extends is in a range of 45º to less than 90º.

[0015] In some implementations, the angle at which the flap extends is in a range of 60º to less than 90º.

[0016] In some implementations, the flap overhangs the paper side surface of the press felt.

[0017] In some implementations, the flap overhangs the paper side surface of the press felt by between 1 mm and 2 mm.

[0018] In some implementations, the flap is installed under tension on a crescent former, no gap exists between the edge of the flap and a second edge of the batt layer opposite the edge of the flap.

[0019] In some implementations, when the flap is installed under tension on a crescent former, the edge of the flap contacts a second edge of the batt layer opposite the edge of the flap.

[0020] In some implementations, the paper side surface of the woven press felt defines a plane, and when the flap is installed under tension on a crescent former, a topmost surface of the flap is 0.6 mm or less above the plane of the paper side surface of the woven press felt.

[0021] In some implementations, when the flap is installed under tension on the crescent former, a topmost surface of the flap is 0.2 mm or less above the plane of the paper side surface of the woven press felt.

[0022] In some implementations, the woven press felt has a permeability in a seam region that is within 10% of a permeability of the woven press felt away from the seam region.

[0023] In some implementations, the woven press felt is capable of use as a press felt in a crescent former.

[0024] In some implementations, when the woven press felt is placed under tension, a pressure characteristic of an area of the press felt at the seam is up to 20% greater than a pressure characteristic of an area of the press felt away from the seam.

[0025] In some implementations, the maximum pressure characteristic at the seam is up to 5 MPa greater than the mean pressure characteristic of an area of the press felt away from the seam.

[0026] In some implementations, the flap height is in a range of 45% to 55% of the thickness of the woven press felt.

[0027] In some implementations, the ratio of the seam loop diameter to the flap height is in a range of 0.65 to 0.75.

[0028] In some implementations, the flap has a flap length extending in the machine direction, and the flap length is in a range of 90% to 100% of the thickness of the woven press felt.

[0029] In some implementations, the ratio of the flap length to the flap height is in a range of 1.95 to 2.0.

[0030] In another aspect, combinable with the first aspect, a woven press felt for paper making includes a base weave. A batt layer is disposed on at least one side of the base weave. The woven press felt further includes a seam for joining a first end of the woven press felt with a second end of the woven press felt. The seam is designed to receive a pintle inserted through seam loops of a first end of the base weave interdigitated with seam loops of a second end of the base weave. A flap is defined in the batt layer. When the woven press felt is seamed, an edge of the flap extends at an angle relative to a paper side surface of the woven press felt and the flap having a flap height extending beyond a paper side surface of the woven press felt. The flap height is in a range of 45% to 55% of a thickness of the woven press felt. The flap height is less than a flap length of the flap in the machine direction of the woven press felt. The flap length is in a range of 90% to 100% of the thickness of the woven press felt. The flap length is in a range of 90% to 100% of the thickness of the woven press felt. The angle at which the flap extends is in a range of 60º to less than 90º.

[0031] In another aspect, combinable with either of the previous aspects, a method of making paper is featured. The method of making paper includes installing, on a paper making machine, a woven press felt. The woven press felt includes a base weave. A batt layer is disposed on at least one side of the base weave. The woven press felt further includes a seam for joining a first end of the woven press felt with a second end of the woven press felt. The seam is designed to receive a pintle inserted through seam loops of a first end of the base weave interdigitated with seam loops of a second end of the base weave. A flap is defined in the batt layer. When the woven press felt is seamed, an edge of the flap extends at an angle relative to a paper side surface of the woven press felt and, the flap having a flap height extending beyond a paper side surface of the woven press felt. The flap height is in a range of 10% to 50% of a thickness of the woven press felt. The method of making paper further includes applying a tension to the woven press felt to draw the first end of the woven press felt apart from the second end of the woven press felt. While tension is applied to the woven press felt, substantially no gap is present between the first end of the woven press felt and the second end of the woven press felt, and the flap protrudes by an amount in a range of 0 mm to 0.2 mm above the paper side surface of the woven press felt.

[0032] The systems and techniques described here may provide one or more of the following advantages. First, the seamable press fabric or felt described here has substantially no gaps or discontinuities at the seam when installed on paper making machinery (e.g., crescent formers) and thereby placed under tension. Second, because of the lack of gap at the seam, the press fabric can be used to produce paper products with fewer defects than a typical press fabric. Third, the press fabric is easier and safer to install in crescent formers than endless or seamless press fabrics. Fourth, because of the easier installation, paper making machinery can have less downtime during press fabric installation than when using conventional press fabrics, enabling a higher production of paper product, e.g., more tons of paper per day or more hours of runtime per day.

[0033] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims.DESCRIPTION OF DRAWINGS

[0034] FIG. 1 is a side view of an example crescent former.

[0035] FIGS. 2 and 3 are schematic views of an example press felt path.

[0036] FIGS. 4A and 4B show cross sectional views of an example prior art press felt.

[0037] FIGS. 5A and 5B show cross sectional views of an example gap-free seamable press felt.

[0038] FIGS. 6A-6B show cross sectional views of an example gap-free seamable press felt.

[0039] FIGS. 7 and 8 show example results of pressure measurement tests performed on several example press felts.DETAILED DESCRIPTION

[0040] This document describes fabrics for use in papermaking, e.g., press fabrics. In the Paper Machine Clothing (PMC) industry, press fabrics (also referred to as press felts) are used to mechanically dewater paper sheets that are formed thereon. During the pressing section of the papermaking process, press felts undergo many millions of cycles of compression and tension during their useful lives. In general, the press fabrics described in this document include seams that can ease their installation on paper making equipment while reducing or eliminating seam gaps that can cause inconsistencies and imperfections in resulting paper products.

[0041] In general, press fabrics for paper manufacture include one or more woven layers that include machine direction (MD) yarns (e.g., yarns that extend in the machine direction) interwoven with a system of cross-machine direction (CD) yarns (e.g., yarns that extend perpendicular to the machine direction), upon which a batt (also called a web cake) is needled to produce a press fabric. The batt is a nonwoven fabric and includes one or more batt yarns. Press fabrics can be flat woven or endless woven. Consistent with standard terminology in the field, “machine direction” and “cross-machine direction” as used herein are with respect to the papermaking rolls with which the fabrics are used, e.g., which may not necessarily correspond to a machine direction and cross-machine direction during weaving of the fabrics.

[0042] These press fabrics are supplied for use in paper making machinery such as crescent formers, which use press fabrics in a wet pressing process. The press fabrics can be used in other paper making machines and processes for various paper grades including tissue, publication, and packaging, including for example, tissue paper making such as toilet paper or napkins, specialty paper making such as filter paper, packaging paper making such as corrugated paper or containerboard, printing paper making, or writing paper making. Press fabrics can also be used in different sections of a paper making machine, including for example, the press section, the forming section, or the pre-press section.

[0043] Seamable press fabrics are installed into the paper making machinery by feeding a flat fabric through and around the various rolls in the machinery, and then the leading edge of the fabric is seamed to the trailing edge of the fabric to form a continuous fabric (e.g., loop). The press fabrics described in this document include features that reduce or eliminate variances in fabric thickness between the body and seam of the fabric. As a result, the press fabric has a substantially flat and uniform surface along its entire length, and is substantially free of variances or discontinuities at the seam that could otherwise create inconsistences and / or flaws in the paper products that are made by using the press fabric.

[0044] FIG. 1 is a side view of an example crescent former 100. FIG. 2 is a schematic view of an example press felt path 200 in a crescent former, and FIG. 3 is a schematic view of components of the example press felt path 200.

[0045] The crescent former 100 includes a wet end 110 and a dry end 170. The wet end 110 includes a headbox 112, a forming part 120, a press part 130, and drainage components. The wet end 110 is where a pulp mixture (e.g., about 0.2% fibers and about 99.8% water and chemicals) is first deposited and begins to form a continuous sheet. The headbox 112 is configured to distribute the pulp mixture (e.g., stock) evenly onto a forming fabric. The headbox 112 is configured to control the flow and consistency of the pulp to ensure uniform sheet formation. The forming part 120 includes a forming roll 122, a forming fabric 124, and the press felt 105. The pulp is trapped between the forming fabric 124 and a press felt 105, and initial water removal occurs here. The forming fabric 124 is a specially designed fabric that supports the pulp as it forms into a sheet. Initial water removal occurs here through gravity and vacuum. The wet end 110 allows water to drain through while retaining the fibers, ensuring a uniform and consistent sheet formation.

[0046] The press part 130 includes a press roll 132 and a large cylinder 134. The press part 130 is configured to remove additional water from the paper sheet by pressing the paper sheet between the press felt 105 and the cylinder 134. The press felt 105 is a highly absorbent fabric that helps remove water from the sheet during the pressing stage. The press felt 105 also provides support and smoothness to the paper sheet as it is pressed against the press roll 132.

[0047] The dry end 170 is where the paper sheet undergoes final drying and is wound onto reels. The dry end 170 includes a drying part 180 and a reeling part 190.

[0048] The drying part 180 includes a large dryer cylinder often called a Yankee dryer 182 and a hot air hood 184 for efficient drying. The drying part 180 also includes doctor blades to remove the dried sheet from the Yankee dryer 182. The hood 184 is an enclosure over the Yankee dryer 182 that directs hot air onto the sheet to aid in drying. The hood 184 helps control the drying process and improves energy efficiency by recirculating hot air.

[0049] The reeling part 190 includes a reel 192 onto which the dried sheet is wound onto reels for further processing or cutting into finished products. Each of these parts plays a role in transforming the pulp mixture into a finished paper product.

[0050] During the press part of a papermaking process, the efficacy of water removal from a paper sheet depends in large part on the characteristics of the underlying press felt. For example, variations in the permeability or openness of the felt can cause variations in the amount of water that is removed from the paper sheet, resulting in the paper sheet having an uneven structure or appearance. Moreover, texture in the press felt can be transferred to the resulting paper sheet. For example, the weave pattern of a press felt can cause a corresponding pattern to be embossed upon the paper sheet during the pressing. Similarly, imperfections in the press felt can cause corresponding imperfections to be formed in the paper sheet. For example, a press felt may include gaps or holes, and when the press felt is pressed against the paper sheet an inconsistent or insufficient level of pressure may be applied to the paper sheet at the locations of the gaps or holes, causing the resulting paper product to include inconsistencies or imperfections that can negatively affect the visual appeal or the structural integrity of the final product.

[0051] Press felts are subject to wear over time as they are used and therefore require replacement after they reach the end of their usable life. Conventional press felts are typically manufactured or woven in two forms: flat, rectangular sheets that are seamed together end-to-end to form a felt, sometimes referred to as flat-woven press felts; or as continuously woven (e.g., endless, seamless, tubular) felts, sometimes referred to as endless or continuous woven press felts. Flat-woven press felts can be installed by feeding the felt into the machinery as a flat felt sheet, and then joining the leading and trailing ends of the flat felt in a seam to form a continuous fabric. When installed under tension, conventional flat felts typically exhibit a gap in the batt between the leading and trailing ends of the felt in the seam region. The gap is at least partly a result of the seam being placed in tension when the leading and trailing ends of the flat felt are joined. Such gaps can cause inconsistencies and imperfections in the resulting paper product. While continuously or endlessly woven press felts do not include the seams of conventional flat press felts that can cause defects in the resulting paper, continuously or endlessly woven press felts can be difficult, time-consuming, and in some circumstances hazardous to install. The machine rolls are cantilevered on one side. The continuously woven press felt is pulled across a width of the machine rolls to install the press felt on the machine from the accessible side. This process is dangerous, time-consuming and requires a lot of human energy.

[0052] The seamable press felts described here are designed such that when they are installed on paper making machines, such as crescent formers, substantially no gap exists in the seam region. This is enabled by forming the press felt such that when it is seamed into a continuous fabric but not under tension, one end of the press felt overhangs the other end of the press felt in the region of the seam. When seamed the press felt is placed into tension, the overhanging portion of the press felt is retracted relative to the other end while maintaining contact with the other end, such that no gap is present between the two ends. Use of seamable press felts without gaps in the seam region is advantageous in papermaking processes, e.g., in avoiding the creation of artifacts and defects in the resulting paper products that would otherwise result from the presence of a gap and allowing for safer installation.

[0053] FIG. 4A shows a cross section of a conventional seamable press felt 400 in a seamed, non-tensioned configuration. The press felt 400 includes a batt 420 that is needled onto a base weave 405. The base weave 405 is formed of a set of machine direction (MD) yarns 410 interwoven with a set of cross machine direction (CD) yarns 412, with the MD yarns forming loops 402, 404 at the two ends of the base weave 405. While loops 402, 404 are shown in the plane of view depicted by FIG. 4A, the press felt includes additional loops (not shown) 402, 404 formed of MD yarns at the two ends of the base weave 405 in other planes of the press felt 400. Loop correctors disposed adjacent to the loops 402, 404 on either side of the base weave 405 help stabilize the loops, e.g., to ensure alignment when seaming the loops.

[0054] To install the press felt 400 on a paper making machine, the flat base weave 405 is folded and the loops 402 are interdigitated with the loops 404, and a cable 456 (e.g., a pintle) is inserted through the interdigitated loops (as shown in FIG. 4A), thereby forming a seam that joins the two ends of the press felt and forming the press felt 400 into a looped fabric. The press felt is then placed under tension (as shown in FIG. 4B) to complete installation.

[0055] A cut through the thickness of the press felt 400 in the vicinity of the seam forms an opening 440 in the batt separating a batt edge 450 of a first side 421a of the fabric from an opposing batt edge 460 of a second side 421b of the fabric. The opening 440 is cut diagonal (e.g., at a non-zero angle) to the thickness of the felt and defines a flap 442 in the first side 421a of the press felt. The flap 442 overhangs the opening 440. For instance, when the felt is installed in a paper making machine, the surface 470 having the flap 442 is the paper side of the felt, and the opposite surface 480 is the machine side of the felt.

[0056] Referring to FIG. 4B, when the conventional seamable press felt 400 is seamed and installed under tension in a paper making machine such as a crescent former, the application of tension to the felt draws the first side 421a of the fabric apart from the second side 421b, widening the opening 440 between the batt edges 450, 460 of the two sides of the fabric. The presence of this discontinuity on the paper side of the seamed felt during the papermaking process can cause irregularities and / or defects in the resulting paper products.

[0057] FIG. 5A shows a cross section of a gap-free seamable press felt 500, e.g., for a crescent former or other type of paper making machine. In FIG. 5A, the seamable press felt 500 is in a seamed, non-tensioned configuration. The gap-free seamed press felt 500 includes a batt 520 that is needled onto a base weave 505. The base weave 505 is formed of a set of machine direction (MD) yarns 510 interwoven with a set of cross machine direction (CD) yarns 512, with the MD yarns forming loops 502, 504 at the two ends of the base weave 505. While loops 502, 504 are shown in the plane of view depicted by FIG. 5A, the press felt includes additional loops (not shown) 502, 504 formed of MD yarns at the two ends of the base weave 505 in other planes of the press felt 500. Loop correctors 612, 614 disposed adjacent to the loops 502, 504 on either side of the base weave 505 help stabilize the loops, e.g., to ensure alignment when seaming the loops.

[0058] To install the press felt 500 on a paper making machine, the loops 502 are interdigitated with loops 504, and a cable 556 is inserted through the interdigitated loops (as shown in FIG. 5A), thereby forming a seam that joins the two ends of the press felt, and forming the press felt 500 into a loop. The press felt is then placed under tension (as shown in FIG. 5B) to complete installation.

[0059] During fabrication of press felt 500, batt 520 is cut through the thickness of the press felt 500 in the vicinity of the seam, forming an opening 540 in the batt 520 separating a batt edge 550 of a first side 521a of the fabric from an opposing batt edge 560 of a second side 521b of the fabric. The opening 540 is cut diagonally (e.g. at a non-zero angle) to the thickness of the felt and defines a flap 542 in the first side 521a of the fabric. The flap 542 extends across and beyond the opening 540 and has an overlap region 630 that overhangs the second side 521b of the fabric. For instance, when the felt is installed in a paper making machine, the surface 570 having the flap 542 is the paper side of the felt, and the opposite surface 580 is the machine side of the felt.

[0060] FIG. 5B shows the gap-free seamable press felt 500 installed under tension in a paper making machine, such as a crescent former. The application of tension to the felt draws the two sides 521a, 521b of the fabric apart from one another. However, because of the length and configuration of the flap 542, even the application of tension to the felt does not result in formation of a significant gap between the batt edges 550, 560 of the first and second sides 521a, 521b of the fabric. Rather, the size of the flap 542 (e.g., the extent of the overlap region 630) is such that even when the press felt 500 is installed under tension, the batt edges 550, 560 remain at least partially in contact with one another, and no gap between the batt edges 550, 560 of the first and second sides 521a, 521b is formed. As a result, the paper side of the press felt 500 is substantially even (e.g., flat) across the seam region, and free of any gap, which allows for the manufacture of high-quality paper with reduced defects.

[0061] FIGS. 6A and 6B show cross sections of the gap-free seamable press felt 500 in a seamed, non-tensioned configuration (FIG. 6A) and under tension (FIG. 6B), annotating various dimensions of the press felt. Relative dimensions of aspects of the seamable press felt 500 are relevant to the ability of the press felt to be placed under tension without creation of a gap between the two sides 521a, 521b of the press felt.

[0062] The seam loop diameter dl (e.g., the diameter of the loops 502, 504) is the vertical distance (i.e., in the direction of the thickness of the fabric) between the inner edges of the MD yarn defining the loop when the press felt 500 is seamed but not under tension. The inner edge of a yarn refers to the edge of the yarn facing the interior of the loop. The seam loop diameter of the loops 502 and the seam loop diameter of the loops 504 are equal in the example gap-free seamed press felt 500.

[0063] In some example press felts, the seam loop diameter dl can be in a range of 0.5 mm to 3.0 mm, e.g., 0.5 mm to 2.0 mm, 0.5 mm to 1.7 mm, 1.0 mm to 1.7 mm, or 1.5 to 2.0 mm, e.g., about 0.5 mm, about 1.0 mm, about 1.5 mm, about 1.7 mm, about 2.0 mm, about 2.5 mm, or about 3.0 mm. For instance, for crescent former fabrics, the seam loop diameter dl can be in a range from 0.5 mm to 1.7 mm.

[0064] The seam length ls represents the lateral extent of the seam region in the machine direction of the fabric when the press felt 500 is seamed but not under tension. In the illustration of FIG. 6A, the seam length ls is the lateral distance between inner edges of the loop connectors defining adjacent seam loops, e.g., the lateral distance between the loop corrector 612 defining the seam loop 502 and the loop corrector 614 defining the adjacent seam loop 504. In fabrics that do not possess loop correctors, the seam length ls is the lateral distance between the inner edges of the CD yarns adjacent to adjacent loops, e.g., the lateral distance between the CD yarn 512a adjacent to the seam loop 502 and the CD yarn 512b adjacent to the seam loop 504.

[0065] In some example press felts, the seam length ls can be in a range of 1.0 mm to 4.0 mm, e.g., 1.0 mm to 3.5 mm, 1.0 mm to 3.0 mm, 1.0 to 2.5 mm, 1.0 to 2.0 mm, 1.2 mm to 3.7 mm, 1.5 to 4.0 mm, 1.5 mm to 3.5 mm, or 1.5 mm to 3.0 mm, e.g., about 1.2 mm, about 1.5 mm, about 1.7 mm, about 2.0 mm, about 2.5 mm, about 3.0 mm, or about 3.7 mm. For instance, for crescent former fabrics, the seam length ds can be in a range from 1.2 mm to 3.4 mm.

[0066] When the seam loop diameter and seam length are within the ranges described above, coupled with a suitably sized flap (discussed below), complete or substantially complete elimination of a seam gap is more effectively achieved when the fabric is installed under tension. For instance, the length l of the flap 542 (e.g., flap length), the flap height h of the flap 542 (e.g., flap height), the length f of the overlap region of the flap, and / or the angle at which the batt is cut to form the flap 542 (e.g., flap angle a) are selected relative to the seam loop diameter, relative to the seam length, and / or relative to one another so that substantially no gap is present in the seam region of the press felt when it is installed under tension on a paper manufacturing machine.

[0067] The flap height h is the maximum vertical distance (i.e., in the direction of the thickness of the fabric) between the paper side surface 570 of the second side 521b of the press felt 500 and the upper surface of the flap 542 when the press felt 500 is seamed but not under tension, as shown by FIG. 6A. The flap height 620 is selected in combination with other aspects of the press fabric, such as the seam loop diameter, seam length, flap length, flap angle, MD yarn diameter, and / or press felt thickness to enable complete or substantially complete elimination of a gap in the seam region of the tensioned press felt 500.

[0068] In some examples, the flap height h generally ranges from greater than 0 mm to about 3 mm, e.g., from about 0.2 mm to about 3 mm, for press felts having a thickness in the range of about 1-6 mm. That is, the flap height can be between about 10% and about 60% of the thickness t of the press felt, e.g., between about 10% and about 50%, between about 10% and about 40%, between about 20% and about 50%, between about 20% and about 40%, between about 30% and about 60%, between about 30% and about 50%, between about 30% and about 40%, between about 40% and about 60%, or between about 50% and about 60%, e.g., about 10%, about 20%, about 25%, about 30%, about 40%, about 50%, or about 60%.

[0069] The ratio of the seam loop diameter to the flap height can impact the ability of the press felt 500 to remain gap-free under tension. A flap with a height that is too short relative to the size of the seam loops may not be large enough to prevent formation of a gap when the press felt 500 is tensioned. A flap with a height that is too large relative to the size of the seam loops may be so large that even under tension, a protrusion of excess flap material may remain in the seam region, which can adversely impact the quality of the resulting paper. Examples of suitable ratios for the seam loop diameter to the flap height can be, e.g., between about 0.5 and about 3, e.g., between about 0.5 and about 2, between about 0.5 and about 1, between about 1 and about 3, between about 1 and about 2, between about 1.5 and about 3, or between about 1.5 and about 2, e.g. about 0.5, about 1, about 1.5, about 2, about 2.5, or about 3.

[0070] The flap length l is the maximum length of the flap 542 in the machine direction between the inner edge of the loop corrector 612 on the side of the fabric housing the flap and the edge 543 of the flap 542 when the press felt 500 is seamed but not under tension, as shown by FIG. 6A. The flap length l is selected in combination with other aspects of the press fabric, such as the seam loop diameter, seam length, flap height, flap angle, MD yarn diameter, and / or press felt thickness to enable complete or substantially complete elimination of a gap in the seam region of the tensioned press felt 500. For instance, the flap length l generally can be in a range of about 1 mm to about 6 mm, for press felts having a thickness in the range of about 1-6 mm. That is, the flap length can be between about 25% and about 125% of the thickness of the press felt, e.g., between 50% and 120%, between 75% and 125%, or between 100% and 125%. In some examples, the flap length is substantially the same as the thickness of the press felt, e.g., within 10% of the thickness of the press felt.

[0071] The ratio of the flap length to the flap height can impact the ability of the press felt 500 to remain gap-free under tension. A flap with a height that is too short relative to its length may result in a depression in the seam region when the press felt 500 is tensioned, which can adversely impact the quality of the resulting paper. A flap with a height that is too large relative to its length may be so large that even under tension, a protrusion of excess flap material may remain in the seam region, which can adversely impact the quality of the resulting paper. In some examples, the flap height is equal to or less than the flap length. Examples of suitable ratios for the flap length to the flap height can be, e.g., between about 1 and about 3, e.g., between about 1 and about 2, between about 1.5 and about 3, or between about 2 and about 3, e.g., about 1, about 1.5, about 2, about 2.5, or about 3.

[0072] The ratio of the flap length to the seam length ls can also impact the ability of the press felt 500 to remain gap-free under tension. A flap with a length that is too short relative to the size of the seam region may not be large enough to prevent formation of a gap when the press felt 500 is tensioned. A flap with a length that is too large relative to the size of the seam region may be so large that even under tension, a protrusion of excess flap material may remain in the seam region, which can adversely impact the quality of the resulting paper. In some examples, the flap length is equal to or greater than the seam length. In some examples, such as when the flap height is greater than the flap length, the flap length can be less than the seam length. Examples of suitable ratios for the flap length to the seam length can be, e.g., between about 1 and about 3, e.g., between about 1 and about 2, between about 1.5 and about 3, or between about 2 and about 3, e.g., about 1, about 1.5, about 2, about 2.5, or about 3.

[0073] The flap angle a is the angle between the overhanging surface of the flap and the paper side surface 570 of the press felt 500 when the press felt 500 is seamed but not under tension. The flap angle a is selected in combination with other aspects of the press fabric, such as the seam loop diameter, flap height, flap length, MD yarn diameter, and / or press felt thickness to enable complete or substantially complete elimination of a gap in the seam region of the tensioned press felt 500. The flap angle a is an acute angle. For instance, the flap angle a generally can be in a range of about 10º to less than 90º, e.g., about 45º to less than 90º or about 60º to less than 90º, e.g., about 45º, about 60º, about 75º, or about 85º.

[0074] The flap length, height, and angle determine an overhang amount f that represents the projection of the flap 542 onto the paper side surface 570 of the press felt 500. The overhang amount f can be, e.g., between about 0.1 mm and about 2 mm. An overhang amount f that is too small may result in a depression in the seam region when the press felt 500 is tensioned, which can adversely impact the quality of the resulting paper. An overhang amount f that is too large may be so large that even under tension, a protrusion of excess flap material may remain in the seam region, which can adversely impact the quality of the resulting paper.

[0075] Referring to FIG. 6B, the relative dimensions of the flap when the press felt 500 is seamed but not under tension impact the configuration of the seam region when the press felt is placed under tension. Specifically, the flap dimensions are selected such that the batt edges 550, 560 of the first and second sides 521a, 521b remain in contact with one another even when the press felt 500 is under tension. For instance, between 50% and 100% of the surface area of the batt edge 550 is in contact with the batt edge 560, e.g., about 50%, about 60%, about 70%, about 80%, about 90%, about 90%, or about 100%. As a result, there is substantially no gap between the first and second sides 521a, 521b. In addition, the flap is substantially flush with the paper side surface 570 of the press felt 500, e.g., such that when the fabric is tensioned, the flap extends to a height of between 0 mm and about 0.6 mm above the plane of the paper side surface 570, e.g., between 0 mm and about 0.2 mm or between 0 mm and about 0.1 mm, e.g., about 0 mm, about 0.1 mm, or about 0.2 mm.

[0076] Tight, gap-free, contact between batt edges 550, 560 during use on the paper making machine prevents paper pulp fibers or other paper materials from inserting into or catching on the seam during paper manufacturing and thereby accumulating in the seam region. As such, paper defects can be reduced and higher operating speeds of the paper making machine can be achieved while still maintaining high yield, quality, and efficiency.

[0077] The MD yarns 510 have any diameter suitable to achieve the desired press felt performance during paper manufacturing. In some examples, the MD yarns 510 have a diameter in a range of about 0.1 mm to about 1.0 mm, e.g., 0.18 mm, 0.20 mm, 0.35 mm, 0.40 mm, or 0.50 mm.

[0078] The pintle 556 can be made of polymeric material, such as one or more of polyester, nylon, or polyether ether ketone (PEEK). In some examples, the pintle 556 can be a pin made of a metallic or inorganic material, such as a stainless steel alloy or other metallic material. In certain examples, the pintle can be a monofilament yarn, a cabled yarn, or multi-component yarn. The pintle material and dimensions are designed to facilitate the creation of the gap-free seam region of the press felt 500. In certain instances, the pintle diameter dp (e.g., the outer diameter of the pintle) is in a range of 0.3 mm to 2.7 mm.

[0079] In a specific example, a new (e.g., not previously used for paper making) gap free seamable press fabric for a crescent former has the following dimensions when seamed but not under tension: a thickness of between 2.5 and 3 mm, loop diameter between about 0.8 mm and about 1.0 mm, seam length between about 2.3 mm and about 2.6 mm, flap height between about 1.2 mm and about 1.4 mm, and flap length between about 2.5 mm and about 2.7 mm. In this specific example, the flap height is between 45% and 55% of the thickness of the press fabric; the ratio of the seam loop diameter to the flap height is between 0.65 and 0.75; the flap length is between 90% and 100% of the thickness of the press fabric; the ratio of the flap length to the flap height is between 1.95 and 2.0; the ratio of the flap length to the seam length is between 1.0 and 1.1. With these dimensions, the flap is sized sufficiently to avoid formation of a gap in the seam region when the press fabric is installed under tension in a crescent former.

[0080] The behavior of the felt, and in particular the seam region, under cycles of applied tension can be used to characterize the felt. For instance, a new (unused) gap-free seamable felt experiences a pressure characteristic at the seam region that is substantially the same as or slightly higher than a pressure characteristic elsewhere on the fabric, e.g., between about 0% and 70%, e.g., between 0% and 50%, between 0% and 20%, or between 0% and 10%, greater than the pressure experienced by the rest of the fabric, e.g., as measured by cyclic tension testing. Moreover, the maximum pressure characteristic of the seam region is within about 10 MPa, e.g., within about 5 MPa, of a mean pressure characteristic of the surrounding fabric. In some examples, the maximum pressure characteristic of the seam region is in a range of about 1 MPa or less than a mean pressure characteristic of the surrounding fabric (e.g., the area of the press felt away from the seam).

[0081] The properties of the gap-free seamable press felt 500, such as pressure characteristics and permeability, are substantially uniform throughout the press felt 500, including in the seam region and in the remaining (e.g., non-seam) regions of the press felt 500. For instance, the permeability in the seam region is within about 10% of the permeability of the press felt 500 away from the seam region. In contrast, conventional press felts that have a gap in the seam region when placed under tension on a paper manufacturing machine can have wide differences in properties between the seam region and the remaining regions of the press felt. For example, when a gap is present, the permeability of the seam region is higher than the permeability of the surrounding fabric. As a result, conventional press felts fail to provide the uniform performance needed to reduce defects during paper manufacturing and extend the operational life of the press felt. The gap-free seamable press felt described herein provides improved performance by delivering uniform permeability within the seam region and the other regions of the press felt.

[0082] FIG. 7 shows example results of pressure measurement tests performed on several example gap-free seamable press felts such as the ones described in this document (e.g., the press felt 500). Three new, unused gap-free seamable press felt samples were placed overnight in a room with constant climate (23 °C, 50 % RH) before measurement. The samples were dry when the impressions were made. Pressure measurements over a seam area were performed. The measurement area was 80x80 mm under an applied pressure of 3.5 MPa. When the imprint pressure was applied, the samples were under a tension of 4 kN / m in the machine direction. Measurements were taken without pre-compaction of the seams. The A-side (flap side) on the seam is to the right in the FIG. 7 images. At each tension, a digital imprint (top- and 3D view) were made together with a blue imprint.

[0083] For sample 1, the press felt sample under test had a seam that is joined by a 6 x 0.30 mm pintle (e.g., a 630 pintle). The press felt was new (e.g., had not been previously cycled through compression) and dry. An imprint 820a shows faint evidence of a seam along a line 822a. A chart 850a of pressure (MPa) versus distance (mm) shows a relative peak 852a corresponding to the location of the seam. In this example, the pressure generally ranges between 4 MPa to 5 MPa, with the peak reaching nearly 7.5 MPa.

[0084] For sample 2, the press felt sample under test had a seam that is joined by a 5 x 0.30 mm pintle (e.g., a 530 pintle). The press felt was new (e.g., had not been previously cycled through compression) and dry. An imprint 820b shows faint evidence of a seam along a line 822b. A chart 850b shows another example of pressure (MPa) versus distance (mm). In this example, the pressure generally ranges around 5 MPa, with no defined peak.

[0085] For sample 3, the press felt sample under test had a seam that is joined by a 4 x 0.30 mm pintle (e.g., a 430 pintle). The press felt was new (e.g., had not been previously cycled through compression) and dry. An imprint 820c shows faint evidence of a seam along a line 822c. A chart 850c shows another example of pressure (MPa) versus distance (mm). In this example, the pressure generally ranges around 4.5 MPa, with no defined peak, but a faint recess 852c corresponding to the seam is visible.

[0086] FIG. 8 shows a blue imprint 920. In the blue imprint 920, darker blue indicates areas of higher pressure, lighter blue indicates areas of lower pressure. The blue imprint illustrates little to no pressure variation in the gap over the seam area.

[0087] A chart 950 of pressure (MPa) versus distance (mm) shows a relative peak 952 corresponding to the location of the seam. In this example, the pressure generally ranges between 4 MPa to 5 MPa, with the peak reaching nearly 7.5MPa.

[0088] In some embodiments, the fabrics described herein can be any suitable fabric formed of a seamable woven base with a web layer, e.g., a flat woven, integrally woven, endless woven, or multiaxial press felt. The lengths of the flaps, angles of flaps, and pressure behaviors of the flaps under load can be selected so as to have a target length, angle, and pressure behavior once installed and put to use in paper-making machines.

[0089] In some examples, such as when the gap-free seamable press felts described herein are configured for use in crescent formers, the batt fibers can have a fineness in a range of approximately 7 decitex (dtex) to 140 dtex. In some examples, the gap-free seamable press felts described herein are configured for tissue paper making on a crescent former paper making machine. In some instances, e.g., for tissue paper making, the batt fibers that form the nonwoven batt can have a fineness in a range of approximately 1.7 dtex to 34 dtex and a weight of about 80grams per square meter (gsm) to about 200 gsm.

[0090] Although the examples in the descriptions above discuss the used to the disclosed press felts in crescent formers, the fabrics described in this document can be used in any appropriate form of paper-making or other equipment, such as equipment for making packaging grade paper, black paper, or other approaches.

[0091] Ranges described herein are inclusive of the endpoints described for the particular range unless otherwise stated. For example, “in a range of x to y” is equivalent to “in a range that is from a value equal to or greater than x to a value that is equal to or less than y” unless otherwise stated. Similarly, a range described herein as “between A and B” is equivalent to “in a range that is from a value equal to or greater than A to a value that is equal to or less than B” unless otherwise stated.

[0092] Although a few implementations have been described in detail above, other modifications are possible. For example, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. In addition, other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Accordingly, other implementations are within the scope of the following claims.

Examples

Embodiment Construction

[0040]This document describes fabrics for use in papermaking, e.g., press fabrics. In the Paper Machine Clothing (PMC) industry, press fabrics (also referred to as press felts) are used to mechanically dewater paper sheets that are formed thereon. During the pressing section of the papermaking process, press felts undergo many millions of cycles of compression and tension during their useful lives. In general, the press fabrics described in this document include seams that can ease their installation on paper making equipment while reducing or eliminating seam gaps that can cause inconsistencies and imperfections in resulting paper products.

[0041]In general, press fabrics for paper manufacture include one or more woven layers that include machine direction (MD) yarns (e.g., yarns that extend in the machine direction) interwoven with a system of cross-machine direction (CD) yarns (e.g., yarns that extend perpendicular to the machine direction), upon which a batt (also called a web ca...

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Patent Application No. 63 / 758,199 filed February 13, 2025, the contents of which are incorporated here by reference in their entirety.TECHNICAL FIELD

[0002] This present disclosure generally relates to fabrics for paper manufacture.BACKGROUND

[0003] During some papermaking processes, after a forming section in which pulp slurry is formed into a sheet, the sheet is processed in a press section. The sheet is supported by a press fabric (or “felt”) that passes through a series of nips formed by rolls. Pressure exerted by the rolls squeezes water out of the sheet and into the press fabric. In other paper making processes, such as crescent forming, pulp slurry is pressed between a forming fabric and a press felt and formed into a continuous paper sheet.

[0004] This mechanical compaction process is known as wet pressing. The press fabric has a “paper side” on which the sheet is supported and a “machine side,” opposite the paper side, in contact with or otherwise adjacent to the machine elements such as rolls. Imperfections such as gaps in the paper side of the press fabric can create imperfections in the sheet during the wet pressing process, which can cause the resulting paper product to have visible and / or structural imperfections.SUMMARY

[0005] Some aspects of this disclosure relate to press fabrics for paper manufacture.

[0006] In one aspect, a woven press felt for paper making includes a base weave. A batt layer is disposed on at least one side of the base weave. The woven press felt further includes a seam for joining a first end of the woven press felt with a second end of the woven press felt. The seam is designed to receive a pintle inserted through seam loops of a first end of the base weave interdigitated with seam loops of a second end of the base weave. A flap is defined in the batt layer. When the woven press felt is seamed, an edge of the flap extends at an angle relative to a paper side surface of the woven press felt and the flap has a flap height extending beyond a paper side surface of the woven press felt. The flap height is in a range of 10% to 50% of a thickness of the woven press felt.

[0007] Embodiments can include one or any combination of two or more of the following features.

[0008] In some implementations, the flap height is greater than zero and less than 3 mm.

[0009] In some implementations, the flap height is in a range of 20% to 40% of the thickness of the woven press felt.

[0010] In some implementations, the flap height is less than a flap length of the flap in the machine direction of the woven press felt.

[0011] In some implementations, a ratio of the flap length to the flap height is in a range of 1 to 3.

[0012] In some implementations, the flap length is in a range of 25% to 125% of the thickness of the woven press felt.

[0013] In some implementations, the flap length is equal to or greater than a seam length of the woven press felt.

[0014] In some implementations, the angle at which the flap extends is in a range of 45º to less than 90º.

[0015] In some implementations, the angle at which the flap extends is in a range of 60º to less than 90º.

[0016] In some implementations, the flap overhangs the paper side surface of the press felt.

[0017] In some implementations, the flap overhangs the paper side surface of the press felt by between 1 mm and 2 mm.

[0018] In some implementations, the flap is installed under tension on a crescent former, no gap exists between the edge of the flap and a second edge of the batt layer opposite the edge of the flap.

[0019] In some implementations, when the flap is installed under tension on a crescent former, the edge of the flap contacts a second edge of the batt layer opposite the edge of the flap.

[0020] In some implementations, the paper side surface of the woven press felt defines a plane, and when the flap is installed under tension on a crescent former, a topmost surface of the flap is 0.6 mm or less above the plane of the paper side surface of the woven press felt.

[0021] In some implementations, when the flap is installed under tension on the crescent former, a topmost surface of the flap is 0.2 mm or less above the plane of the paper side surface of the woven press felt.

[0022] In some implementations, the woven press felt has a permeability in a seam region that is within 10% of a permeability of the woven press felt away from the seam region.

[0023] In some implementations, the woven press felt is capable of use as a press felt in a crescent former.

[0024] In some implementations, when the woven press felt is placed under tension, a pressure characteristic of an area of the press felt at the seam is up to 20% greater than a pressure characteristic of an area of the press felt away from the seam.

[0025] In some implementations, the maximum pressure characteristic at the seam is up to 5 MPa greater than the mean pressure characteristic of an area of the press felt away from the seam.

[0026] In some implementations, the flap height is in a range of 45% to 55% of the thickness of the woven press felt.

[0027] In some implementations, the ratio of the seam loop diameter to the flap height is in a range of 0.65 to 0.75.

[0028] In some implementations, the flap has a flap length extending in the machine direction, and the flap length is in a range of 90% to 100% of the thickness of the woven press felt.

[0029] In some implementations, the ratio of the flap length to the flap height is in a range of 1.95 to 2.0.

[0030] In another aspect, combinable with the first aspect, a woven press felt for paper making includes a base weave. A batt layer is disposed on at least one side of the base weave. The woven press felt further includes a seam for joining a first end of the woven press felt with a second end of the woven press felt. The seam is designed to receive a pintle inserted through seam loops of a first end of the base weave interdigitated with seam loops of a second end of the base weave. A flap is defined in the batt layer. When the woven press felt is seamed, an edge of the flap extends at an angle relative to a paper side surface of the woven press felt and the flap having a flap height extending beyond a paper side surface of the woven press felt. The flap height is in a range of 45% to 55% of a thickness of the woven press felt. The flap height is less than a flap length of the flap in the machine direction of the woven press felt. The flap length is in a range of 90% to 100% of the thickness of the woven press felt. The flap length is in a range of 90% to 100% of the thickness of the woven press felt. The angle at which the flap extends is in a range of 60º to less than 90º.

[0031] In another aspect, combinable with either of the previous aspects, a method of making paper is featured. The method of making paper includes installing, on a paper making machine, a woven press felt. The woven press felt includes a base weave. A batt layer is disposed on at least one side of the base weave. The woven press felt further includes a seam for joining a first end of the woven press felt with a second end of the woven press felt. The seam is designed to receive a pintle inserted through seam loops of a first end of the base weave interdigitated with seam loops of a second end of the base weave. A flap is defined in the batt layer. When the woven press felt is seamed, an edge of the flap extends at an angle relative to a paper side surface of the woven press felt and, the flap having a flap height extending beyond a paper side surface of the woven press felt. The flap height is in a range of 10% to 50% of a thickness of the woven press felt. The method of making paper further includes applying a tension to the woven press felt to draw the first end of the woven press felt apart from the second end of the woven press felt. While tension is applied to the woven press felt, substantially no gap is present between the first end of the woven press felt and the second end of the woven press felt, and the flap protrudes by an amount in a range of 0 mm to 0.2 mm above the paper side surface of the woven press felt.

[0032] The systems and techniques described here may provide one or more of the following advantages. First, the seamable press fabric or felt described here has substantially no gaps or discontinuities at the seam when installed on paper making machinery (e.g., crescent formers) and thereby placed under tension. Second, because of the lack of gap at the seam, the press fabric can be used to produce paper products with fewer defects than a typical press fabric. Third, the press fabric is easier and safer to install in crescent formers than endless or seamless press fabrics. Fourth, because of the easier installation, paper making machinery can have less downtime during press fabric installation than when using conventional press fabrics, enabling a higher production of paper product, e.g., more tons of paper per day or more hours of runtime per day.

[0033] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims.DESCRIPTION OF DRAWINGS

[0034] FIG. 1 is a side view of an example crescent former.

[0035] FIGS. 2 and 3 are schematic views of an example press felt path.

[0036] FIGS. 4A and 4B show cross sectional views of an example prior art press felt.

[0037] FIGS. 5A and 5B show cross sectional views of an example gap-free seamable press felt.

[0038] FIGS. 6A-6B show cross sectional views of an example gap-free seamable press felt.

[0039] FIGS. 7 and 8 show example results of pressure measurement tests performed on several example press felts.DETAILED DESCRIPTION

[0040] This document describes fabrics for use in papermaking, e.g., press fabrics. In the Paper Machine Clothing (PMC) industry, press fabrics (also referred to as press felts) are used to mechanically dewater paper sheets that are formed thereon. During the pressing section of the papermaking process, press felts undergo many millions of cycles of compression and tension during their useful lives. In general, the press fabrics described in this document include seams that can ease their installation on paper making equipment while reducing or eliminating seam gaps that can cause inconsistencies and imperfections in resulting paper products.

[0041] In general, press fabrics for paper manufacture include one or more woven layers that include machine direction (MD) yarns (e.g., yarns that extend in the machine direction) interwoven with a system of cross-machine direction (CD) yarns (e.g., yarns that extend perpendicular to the machine direction), upon which a batt (also called a web cake) is needled to produce a press fabric. The batt is a nonwoven fabric and includes one or more batt yarns. Press fabrics can be flat woven or endless woven. Consistent with standard terminology in the field, “machine direction” and “cross-machine direction” as used herein are with respect to the papermaking rolls with which the fabrics are used, e.g., which may not necessarily correspond to a machine direction and cross-machine direction during weaving of the fabrics.

[0042] These press fabrics are supplied for use in paper making machinery such as crescent formers, which use press fabrics in a wet pressing process. The press fabrics can be used in other paper making machines and processes for various paper grades including tissue, publication, and packaging, including for example, tissue paper making such as toilet paper or napkins, specialty paper making such as filter paper, packaging paper making such as corrugated paper or containerboard, printing paper making, or writing paper making. Press fabrics can also be used in different sections of a paper making machine, including for example, the press section, the forming section, or the pre-press section.

[0043] Seamable press fabrics are installed into the paper making machinery by feeding a flat fabric through and around the various rolls in the machinery, and then the leading edge of the fabric is seamed to the trailing edge of the fabric to form a continuous fabric (e.g., loop). The press fabrics described in this document include features that reduce or eliminate variances in fabric thickness between the body and seam of the fabric. As a result, the press fabric has a substantially flat and uniform surface along its entire length, and is substantially free of variances or discontinuities at the seam that could otherwise create inconsistences and / or flaws in the paper products that are made by using the press fabric.

[0044] FIG. 1 is a side view of an example crescent former 100. FIG. 2 is a schematic view of an example press felt path 200 in a crescent former, and FIG. 3 is a schematic view of components of the example press felt path 200.

[0045] The crescent former 100 includes a wet end 110 and a dry end 170. The wet end 110 includes a headbox 112, a forming part 120, a press part 130, and drainage components. The wet end 110 is where a pulp mixture (e.g., about 0.2% fibers and about 99.8% water and chemicals) is first deposited and begins to form a continuous sheet. The headbox 112 is configured to distribute the pulp mixture (e.g., stock) evenly onto a forming fabric. The headbox 112 is configured to control the flow and consistency of the pulp to ensure uniform sheet formation. The forming part 120 includes a forming roll 122, a forming fabric 124, and the press felt 105. The pulp is trapped between the forming fabric 124 and a press felt 105, and initial water removal occurs here. The forming fabric 124 is a specially designed fabric that supports the pulp as it forms into a sheet. Initial water removal occurs here through gravity and vacuum. The wet end 110 allows water to drain through while retaining the fibers, ensuring a uniform and consistent sheet formation.

[0046] The press part 130 includes a press roll 132 and a large cylinder 134. The press part 130 is configured to remove additional water from the paper sheet by pressing the paper sheet between the press felt 105 and the cylinder 134. The press felt 105 is a highly absorbent fabric that helps remove water from the sheet during the pressing stage. The press felt 105 also provides support and smoothness to the paper sheet as it is pressed against the press roll 132.

[0047] The dry end 170 is where the paper sheet undergoes final drying and is wound onto reels. The dry end 170 includes a drying part 180 and a reeling part 190.

[0048] The drying part 180 includes a large dryer cylinder often called a Yankee dryer 182 and a hot air hood 184 for efficient drying. The drying part 180 also includes doctor blades to remove the dried sheet from the Yankee dryer 182. The hood 184 is an enclosure over the Yankee dryer 182 that directs hot air onto the sheet to aid in drying. The hood 184 helps control the drying process and improves energy efficiency by recirculating hot air.

[0049] The reeling part 190 includes a reel 192 onto which the dried sheet is wound onto reels for further processing or cutting into finished products. Each of these parts plays a role in transforming the pulp mixture into a finished paper product.

[0050] During the press part of a papermaking process, the efficacy of water removal from a paper sheet depends in large part on the characteristics of the underlying press felt. For example, variations in the permeability or openness of the felt can cause variations in the amount of water that is removed from the paper sheet, resulting in the paper sheet having an uneven structure or appearance. Moreover, texture in the press felt can be transferred to the resulting paper sheet. For example, the weave pattern of a press felt can cause a corresponding pattern to be embossed upon the paper sheet during the pressing. Similarly, imperfections in the press felt can cause corresponding imperfections to be formed in the paper sheet. For example, a press felt may include gaps or holes, and when the press felt is pressed against the paper sheet an inconsistent or insufficient level of pressure may be applied to the paper sheet at the locations of the gaps or holes, causing the resulting paper product to include inconsistencies or imperfections that can negatively affect the visual appeal or the structural integrity of the final product.

[0051] Press felts are subject to wear over time as they are used and therefore require replacement after they reach the end of their usable life. Conventional press felts are typically manufactured or woven in two forms: flat, rectangular sheets that are seamed together end-to-end to form a felt, sometimes referred to as flat-woven press felts; or as continuously woven (e.g., endless, seamless, tubular) felts, sometimes referred to as endless or continuous woven press felts. Flat-woven press felts can be installed by feeding the felt into the machinery as a flat felt sheet, and then joining the leading and trailing ends of the flat felt in a seam to form a continuous fabric. When installed under tension, conventional flat felts typically exhibit a gap in the batt between the leading and trailing ends of the felt in the seam region. The gap is at least partly a result of the seam being placed in tension when the leading and trailing ends of the flat felt are joined. Such gaps can cause inconsistencies and imperfections in the resulting paper product. While continuously or endlessly woven press felts do not include the seams of conventional flat press felts that can cause defects in the resulting paper, continuously or endlessly woven press felts can be difficult, time-consuming, and in some circumstances hazardous to install. The machine rolls are cantilevered on one side. The continuously woven press felt is pulled across a width of the machine rolls to install the press felt on the machine from the accessible side. This process is dangerous, time-consuming and requires a lot of human energy.

[0052] The seamable press felts described here are designed such that when they are installed on paper making machines, such as crescent formers, substantially no gap exists in the seam region. This is enabled by forming the press felt such that when it is seamed into a continuous fabric but not under tension, one end of the press felt overhangs the other end of the press felt in the region of the seam. When seamed the press felt is placed into tension, the overhanging portion of the press felt is retracted relative to the other end while maintaining contact with the other end, such that no gap is present between the two ends. Use of seamable press felts without gaps in the seam region is advantageous in papermaking processes, e.g., in avoiding the creation of artifacts and defects in the resulting paper products that would otherwise result from the presence of a gap and allowing for safer installation.

[0053] FIG. 4A shows a cross section of a conventional seamable press felt 400 in a seamed, non-tensioned configuration. The press felt 400 includes a batt 420 that is needled onto a base weave 405. The base weave 405 is formed of a set of machine direction (MD) yarns 410 interwoven with a set of cross machine direction (CD) yarns 412, with the MD yarns forming loops 402, 404 at the two ends of the base weave 405. While loops 402, 404 are shown in the plane of view depicted by FIG. 4A, the press felt includes additional loops (not shown) 402, 404 formed of MD yarns at the two ends of the base weave 405 in other planes of the press felt 400. Loop correctors disposed adjacent to the loops 402, 404 on either side of the base weave 405 help stabilize the loops, e.g., to ensure alignment when seaming the loops.

[0054] To install the press felt 400 on a paper making machine, the flat base weave 405 is folded and the loops 402 are interdigitated with the loops 404, and a cable 456 (e.g., a pintle) is inserted through the interdigitated loops (as shown in FIG. 4A), thereby forming a seam that joins the two ends of the press felt and forming the press felt 400 into a looped fabric. The press felt is then placed under tension (as shown in FIG. 4B) to complete installation.

[0055] A cut through the thickness of the press felt 400 in the vicinity of the seam forms an opening 440 in the batt separating a batt edge 450 of a first side 421a of the fabric from an opposing batt edge 460 of a second side 421b of the fabric. The opening 440 is cut diagonal (e.g., at a non-zero angle) to the thickness of the felt and defines a flap 442 in the first side 421a of the press felt. The flap 442 overhangs the opening 440. For instance, when the felt is installed in a paper making machine, the surface 470 having the flap 442 is the paper side of the felt, and the opposite surface 480 is the machine side of the felt.

[0056] Referring to FIG. 4B, when the conventional seamable press felt 400 is seamed and installed under tension in a paper making machine such as a crescent former, the application of tension to the felt draws the first side 421a of the fabric apart from the second side 421b, widening the opening 440 between the batt edges 450, 460 of the two sides of the fabric. The presence of this discontinuity on the paper side of the seamed felt during the papermaking process can cause irregularities and / or defects in the resulting paper products.

[0057] FIG. 5A shows a cross section of a gap-free seamable press felt 500, e.g., for a crescent former or other type of paper making machine. In FIG. 5A, the seamable press felt 500 is in a seamed, non-tensioned configuration. The gap-free seamed press felt 500 includes a batt 520 that is needled onto a base weave 505. The base weave 505 is formed of a set of machine direction (MD) yarns 510 interwoven with a set of cross machine direction (CD) yarns 512, with the MD yarns forming loops 502, 504 at the two ends of the base weave 505. While loops 502, 504 are shown in the plane of view depicted by FIG. 5A, the press felt includes additional loops (not shown) 502, 504 formed of MD yarns at the two ends of the base weave 505 in other planes of the press felt 500. Loop correctors 612, 614 disposed adjacent to the loops 502, 504 on either side of the base weave 505 help stabilize the loops, e.g., to ensure alignment when seaming the loops.

[0058] To install the press felt 500 on a paper making machine, the loops 502 are interdigitated with loops 504, and a cable 556 is inserted through the interdigitated loops (as shown in FIG. 5A), thereby forming a seam that joins the two ends of the press felt, and forming the press felt 500 into a loop. The press felt is then placed under tension (as shown in FIG. 5B) to complete installation.

[0059] During fabrication of press felt 500, batt 520 is cut through the thickness of the press felt 500 in the vicinity of the seam, forming an opening 540 in the batt 520 separating a batt edge 550 of a first side 521a of the fabric from an opposing batt edge 560 of a second side 521b of the fabric. The opening 540 is cut diagonally (e.g. at a non-zero angle) to the thickness of the felt and defines a flap 542 in the first side 521a of the fabric. The flap 542 extends across and beyond the opening 540 and has an overlap region 630 that overhangs the second side 521b of the fabric. For instance, when the felt is installed in a paper making machine, the surface 570 having the flap 542 is the paper side of the felt, and the opposite surface 580 is the machine side of the felt.

[0060] FIG. 5B shows the gap-free seamable press felt 500 installed under tension in a paper making machine, such as a crescent former. The application of tension to the felt draws the two sides 521a, 521b of the fabric apart from one another. However, because of the length and configuration of the flap 542, even the application of tension to the felt does not result in formation of a significant gap between the batt edges 550, 560 of the first and second sides 521a, 521b of the fabric. Rather, the size of the flap 542 (e.g., the extent of the overlap region 630) is such that even when the press felt 500 is installed under tension, the batt edges 550, 560 remain at least partially in contact with one another, and no gap between the batt edges 550, 560 of the first and second sides 521a, 521b is formed. As a result, the paper side of the press felt 500 is substantially even (e.g., flat) across the seam region, and free of any gap, which allows for the manufacture of high-quality paper with reduced defects.

[0061] FIGS. 6A and 6B show cross sections of the gap-free seamable press felt 500 in a seamed, non-tensioned configuration (FIG. 6A) and under tension (FIG. 6B), annotating various dimensions of the press felt. Relative dimensions of aspects of the seamable press felt 500 are relevant to the ability of the press felt to be placed under tension without creation of a gap between the two sides 521a, 521b of the press felt.

[0062] The seam loop diameter dl (e.g., the diameter of the loops 502, 504) is the vertical distance (i.e., in the direction of the thickness of the fabric) between the inner edges of the MD yarn defining the loop when the press felt 500 is seamed but not under tension. The inner edge of a yarn refers to the edge of the yarn facing the interior of the loop. The seam loop diameter of the loops 502 and the seam loop diameter of the loops 504 are equal in the example gap-free seamed press felt 500.

[0063] In some example press felts, the seam loop diameter dl can be in a range of 0.5 mm to 3.0 mm, e.g., 0.5 mm to 2.0 mm, 0.5 mm to 1.7 mm, 1.0 mm to 1.7 mm, or 1.5 to 2.0 mm, e.g., about 0.5 mm, about 1.0 mm, about 1.5 mm, about 1.7 mm, about 2.0 mm, about 2.5 mm, or about 3.0 mm. For instance, for crescent former fabrics, the seam loop diameter dl can be in a range from 0.5 mm to 1.7 mm.

[0064] The seam length ls represents the lateral extent of the seam region in the machine direction of the fabric when the press felt 500 is seamed but not under tension. In the illustration of FIG. 6A, the seam length ls is the lateral distance between inner edges of the loop connectors defining adjacent seam loops, e.g., the lateral distance between the loop corrector 612 defining the seam loop 502 and the loop corrector 614 defining the adjacent seam loop 504. In fabrics that do not possess loop correctors, the seam length ls is the lateral distance between the inner edges of the CD yarns adjacent to adjacent loops, e.g., the lateral distance between the CD yarn 512a adjacent to the seam loop 502 and the CD yarn 512b adjacent to the seam loop 504.

[0065] In some example press felts, the seam length ls can be in a range of 1.0 mm to 4.0 mm, e.g., 1.0 mm to 3.5 mm, 1.0 mm to 3.0 mm, 1.0 to 2.5 mm, 1.0 to 2.0 mm, 1.2 mm to 3.7 mm, 1.5 to 4.0 mm, 1.5 mm to 3.5 mm, or 1.5 mm to 3.0 mm, e.g., about 1.2 mm, about 1.5 mm, about 1.7 mm, about 2.0 mm, about 2.5 mm, about 3.0 mm, or about 3.7 mm. For instance, for crescent former fabrics, the seam length ds can be in a range from 1.2 mm to 3.4 mm.

[0066] When the seam loop diameter and seam length are within the ranges described above, coupled with a suitably sized flap (discussed below), complete or substantially complete elimination of a seam gap is more effectively achieved when the fabric is installed under tension. For instance, the length l of the flap 542 (e.g., flap length), the flap height h of the flap 542 (e.g., flap height), the length f of the overlap region of the flap, and / or the angle at which the batt is cut to form the flap 542 (e.g., flap angle a) are selected relative to the seam loop diameter, relative to the seam length, and / or relative to one another so that substantially no gap is present in the seam region of the press felt when it is installed under tension on a paper manufacturing machine.

[0067] The flap height h is the maximum vertical distance (i.e., in the direction of the thickness of the fabric) between the paper side surface 570 of the second side 521b of the press felt 500 and the upper surface of the flap 542 when the press felt 500 is seamed but not under tension, as shown by FIG. 6A. The flap height 620 is selected in combination with other aspects of the press fabric, such as the seam loop diameter, seam length, flap length, flap angle, MD yarn diameter, and / or press felt thickness to enable complete or substantially complete elimination of a gap in the seam region of the tensioned press felt 500.

[0068] In some examples, the flap height h generally ranges from greater than 0 mm to about 3 mm, e.g., from about 0.2 mm to about 3 mm, for press felts having a thickness in the range of about 1-6 mm. That is, the flap height can be between about 10% and about 60% of the thickness t of the press felt, e.g., between about 10% and about 50%, between about 10% and about 40%, between about 20% and about 50%, between about 20% and about 40%, between about 30% and about 60%, between about 30% and about 50%, between about 30% and about 40%, between about 40% and about 60%, or between about 50% and about 60%, e.g., about 10%, about 20%, about 25%, about 30%, about 40%, about 50%, or about 60%.

[0069] The ratio of the seam loop diameter to the flap height can impact the ability of the press felt 500 to remain gap-free under tension. A flap with a height that is too short relative to the size of the seam loops may not be large enough to prevent formation of a gap when the press felt 500 is tensioned. A flap with a height that is too large relative to the size of the seam loops may be so large that even under tension, a protrusion of excess flap material may remain in the seam region, which can adversely impact the quality of the resulting paper. Examples of suitable ratios for the seam loop diameter to the flap height can be, e.g., between about 0.5 and about 3, e.g., between about 0.5 and about 2, between about 0.5 and about 1, between about 1 and about 3, between about 1 and about 2, between about 1.5 and about 3, or between about 1.5 and about 2, e.g. about 0.5, about 1, about 1.5, about 2, about 2.5, or about 3.

[0070] The flap length l is the maximum length of the flap 542 in the machine direction between the inner edge of the loop corrector 612 on the side of the fabric housing the flap and the edge 543 of the flap 542 when the press felt 500 is seamed but not under tension, as shown by FIG. 6A. The flap length l is selected in combination with other aspects of the press fabric, such as the seam loop diameter, seam length, flap height, flap angle, MD yarn diameter, and / or press felt thickness to enable complete or substantially complete elimination of a gap in the seam region of the tensioned press felt 500. For instance, the flap length l generally can be in a range of about 1 mm to about 6 mm, for press felts having a thickness in the range of about 1-6 mm. That is, the flap length can be between about 25% and about 125% of the thickness of the press felt, e.g., between 50% and 120%, between 75% and 125%, or between 100% and 125%. In some examples, the flap length is substantially the same as the thickness of the press felt, e.g., within 10% of the thickness of the press felt.

[0071] The ratio of the flap length to the flap height can impact the ability of the press felt 500 to remain gap-free under tension. A flap with a height that is too short relative to its length may result in a depression in the seam region when the press felt 500 is tensioned, which can adversely impact the quality of the resulting paper. A flap with a height that is too large relative to its length may be so large that even under tension, a protrusion of excess flap material may remain in the seam region, which can adversely impact the quality of the resulting paper. In some examples, the flap height is equal to or less than the flap length. Examples of suitable ratios for the flap length to the flap height can be, e.g., between about 1 and about 3, e.g., between about 1 and about 2, between about 1.5 and about 3, or between about 2 and about 3, e.g., about 1, about 1.5, about 2, about 2.5, or about 3.

[0072] The ratio of the flap length to the seam length ls can also impact the ability of the press felt 500 to remain gap-free under tension. A flap with a length that is too short relative to the size of the seam region may not be large enough to prevent formation of a gap when the press felt 500 is tensioned. A flap with a length that is too large relative to the size of the seam region may be so large that even under tension, a protrusion of excess flap material may remain in the seam region, which can adversely impact the quality of the resulting paper. In some examples, the flap length is equal to or greater than the seam length. In some examples, such as when the flap height is greater than the flap length, the flap length can be less than the seam length. Examples of suitable ratios for the flap length to the seam length can be, e.g., between about 1 and about 3, e.g., between about 1 and about 2, between about 1.5 and about 3, or between about 2 and about 3, e.g., about 1, about 1.5, about 2, about 2.5, or about 3.

[0073] The flap angle a is the angle between the overhanging surface of the flap and the paper side surface 570 of the press felt 500 when the press felt 500 is seamed but not under tension. The flap angle a is selected in combination with other aspects of the press fabric, such as the seam loop diameter, flap height, flap length, MD yarn diameter, and / or press felt thickness to enable complete or substantially complete elimination of a gap in the seam region of the tensioned press felt 500. The flap angle a is an acute angle. For instance, the flap angle a generally can be in a range of about 10º to less than 90º, e.g., about 45º to less than 90º or about 60º to less than 90º, e.g., about 45º, about 60º, about 75º, or about 85º.

[0074] The flap length, height, and angle determine an overhang amount f that represents the projection of the flap 542 onto the paper side surface 570 of the press felt 500. The overhang amount f can be, e.g., between about 0.1 mm and about 2 mm. An overhang amount f that is too small may result in a depression in the seam region when the press felt 500 is tensioned, which can adversely impact the quality of the resulting paper. An overhang amount f that is too large may be so large that even under tension, a protrusion of excess flap material may remain in the seam region, which can adversely impact the quality of the resulting paper.

[0075] Referring to FIG. 6B, the relative dimensions of the flap when the press felt 500 is seamed but not under tension impact the configuration of the seam region when the press felt is placed under tension. Specifically, the flap dimensions are selected such that the batt edges 550, 560 of the first and second sides 521a, 521b remain in contact with one another even when the press felt 500 is under tension. For instance, between 50% and 100% of the surface area of the batt edge 550 is in contact with the batt edge 560, e.g., about 50%, about 60%, about 70%, about 80%, about 90%, about 90%, or about 100%. As a result, there is substantially no gap between the first and second sides 521a, 521b. In addition, the flap is substantially flush with the paper side surface 570 of the press felt 500, e.g., such that when the fabric is tensioned, the flap extends to a height of between 0 mm and about 0.6 mm above the plane of the paper side surface 570, e.g., between 0 mm and about 0.2 mm or between 0 mm and about 0.1 mm, e.g., about 0 mm, about 0.1 mm, or about 0.2 mm.

[0076] Tight, gap-free, contact between batt edges 550, 560 during use on the paper making machine prevents paper pulp fibers or other paper materials from inserting into or catching on the seam during paper manufacturing and thereby accumulating in the seam region. As such, paper defects can be reduced and higher operating speeds of the paper making machine can be achieved while still maintaining high yield, quality, and efficiency.

[0077] The MD yarns 510 have any diameter suitable to achieve the desired press felt performance during paper manufacturing. In some examples, the MD yarns 510 have a diameter in a range of about 0.1 mm to about 1.0 mm, e.g., 0.18 mm, 0.20 mm, 0.35 mm, 0.40 mm, or 0.50 mm.

[0078] The pintle 556 can be made of polymeric material, such as one or more of polyester, nylon, or polyether ether ketone (PEEK). In some examples, the pintle 556 can be a pin made of a metallic or inorganic material, such as a stainless steel alloy or other metallic material. In certain examples, the pintle can be a monofilament yarn, a cabled yarn, or multi-component yarn. The pintle material and dimensions are designed to facilitate the creation of the gap-free seam region of the press felt 500. In certain instances, the pintle diameter dp (e.g., the outer diameter of the pintle) is in a range of 0.3 mm to 2.7 mm.

[0079] In a specific example, a new (e.g., not previously used for paper making) gap free seamable press fabric for a crescent former has the following dimensions when seamed but not under tension: a thickness of between 2.5 and 3 mm, loop diameter between about 0.8 mm and about 1.0 mm, seam length between about 2.3 mm and about 2.6 mm, flap height between about 1.2 mm and about 1.4 mm, and flap length between about 2.5 mm and about 2.7 mm. In this specific example, the flap height is between 45% and 55% of the thickness of the press fabric; the ratio of the seam loop diameter to the flap height is between 0.65 and 0.75; the flap length is between 90% and 100% of the thickness of the press fabric; the ratio of the flap length to the flap height is between 1.95 and 2.0; the ratio of the flap length to the seam length is between 1.0 and 1.1. With these dimensions, the flap is sized sufficiently to avoid formation of a gap in the seam region when the press fabric is installed under tension in a crescent former.

[0080] The behavior of the felt, and in particular the seam region, under cycles of applied tension can be used to characterize the felt. For instance, a new (unused) gap-free seamable felt experiences a pressure characteristic at the seam region that is substantially the same as or slightly higher than a pressure characteristic elsewhere on the fabric, e.g., between about 0% and 70%, e.g., between 0% and 50%, between 0% and 20%, or between 0% and 10%, greater than the pressure experienced by the rest of the fabric, e.g., as measured by cyclic tension testing. Moreover, the maximum pressure characteristic of the seam region is within about 10 MPa, e.g., within about 5 MPa, of a mean pressure characteristic of the surrounding fabric. In some examples, the maximum pressure characteristic of the seam region is in a range of about 1 MPa or less than a mean pressure characteristic of the surrounding fabric (e.g., the area of the press felt away from the seam).

[0081] The properties of the gap-free seamable press felt 500, such as pressure characteristics and permeability, are substantially uniform throughout the press felt 500, including in the seam region and in the remaining (e.g., non-seam) regions of the press felt 500. For instance, the permeability in the seam region is within about 10% of the permeability of the press felt 500 away from the seam region. In contrast, conventional press felts that have a gap in the seam region when placed under tension on a paper manufacturing machine can have wide differences in properties between the seam region and the remaining regions of the press felt. For example, when a gap is present, the permeability of the seam region is higher than the permeability of the surrounding fabric. As a result, conventional press felts fail to provide the uniform performance needed to reduce defects during paper manufacturing and extend the operational life of the press felt. The gap-free seamable press felt described herein provides improved performance by delivering uniform permeability within the seam region and the other regions of the press felt.

[0082] FIG. 7 shows example results of pressure measurement tests performed on several example gap-free seamable press felts such as the ones described in this document (e.g., the press felt 500). Three new, unused gap-free seamable press felt samples were placed overnight in a room with constant climate (23 °C, 50 % RH) before measurement. The samples were dry when the impressions were made. Pressure measurements over a seam area were performed. The measurement area was 80x80 mm under an applied pressure of 3.5 MPa. When the imprint pressure was applied, the samples were under a tension of 4 kN / m in the machine direction. Measurements were taken without pre-compaction of the seams. The A-side (flap side) on the seam is to the right in the FIG. 7 images. At each tension, a digital imprint (top- and 3D view) were made together with a blue imprint.

[0083] For sample 1, the press felt sample under test had a seam that is joined by a 6 x 0.30 mm pintle (e.g., a 630 pintle). The press felt was new (e.g., had not been previously cycled through compression) and dry. An imprint 820a shows faint evidence of a seam along a line 822a. A chart 850a of pressure (MPa) versus distance (mm) shows a relative peak 852a corresponding to the location of the seam. In this example, the pressure generally ranges between 4 MPa to 5 MPa, with the peak reaching nearly 7.5 MPa.

[0084] For sample 2, the press felt sample under test had a seam that is joined by a 5 x 0.30 mm pintle (e.g., a 530 pintle). The press felt was new (e.g., had not been previously cycled through compression) and dry. An imprint 820b shows faint evidence of a seam along a line 822b. A chart 850b shows another example of pressure (MPa) versus distance (mm). In this example, the pressure generally ranges around 5 MPa, with no defined peak.

[0085] For sample 3, the press felt sample under test had a seam that is joined by a 4 x 0.30 mm pintle (e.g., a 430 pintle). The press felt was new (e.g., had not been previously cycled through compression) and dry. An imprint 820c shows faint evidence of a seam along a line 822c. A chart 850c shows another example of pressure (MPa) versus distance (mm). In this example, the pressure generally ranges around 4.5 MPa, with no defined peak, but a faint recess 852c corresponding to the seam is visible.

[0086] FIG. 8 shows a blue imprint 920. In the blue imprint 920, darker blue indicates areas of higher pressure, lighter blue indicates areas of lower pressure. The blue imprint illustrates little to no pressure variation in the gap over the seam area.

[0087] A chart 950 of pressure (MPa) versus distance (mm) shows a relative peak 952 corresponding to the location of the seam. In this example, the pressure generally ranges between 4 MPa to 5 MPa, with the peak reaching nearly 7.5MPa.

[0088] In some embodiments, the fabrics described herein can be any suitable fabric formed of a seamable woven base with a web layer, e.g., a flat woven, integrally woven, endless woven, or multiaxial press felt. The lengths of the flaps, angles of flaps, and pressure behaviors of the flaps under load can be selected so as to have a target length, angle, and pressure behavior once installed and put to use in paper-making machines.

[0089] In some examples, such as when the gap-free seamable press felts described herein are configured for use in crescent formers, the batt fibers can have a fineness in a range of approximately 7 decitex (dtex) to 140 dtex. In some examples, the gap-free seamable press felts described herein are configured for tissue paper making on a crescent former paper making machine. In some instances, e.g., for tissue paper making, the batt fibers that form the nonwoven batt can have a fineness in a range of approximately 1.7 dtex to 34 dtex and a weight of about 80grams per square meter (gsm) to about 200 gsm.

[0090] Although the examples in the descriptions above discuss the used to the disclosed press felts in crescent formers, the fabrics described in this document can be used in any appropriate form of paper-making or other equipment, such as equipment for making packaging grade paper, black paper, or other approaches.

[0091] Ranges described herein are inclusive of the endpoints described for the particular range unless otherwise stated. For example, “in a range of x to y” is equivalent to “in a range that is from a value equal to or greater than x to a value that is equal to or less than y” unless otherwise stated. Similarly, a range described herein as “between A and B” is equivalent to “in a range that is from a value equal to or greater than A to a value that is equal to or less than B” unless otherwise stated.

[0092] Although a few implementations have been described in detail above, other modifications are possible. For example, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. In addition, other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Accordingly, other implementations are within the scope of the following claims.

Examples

Embodiment Construction

[0040]This document describes fabrics for use in papermaking, e.g., press fabrics. In the Paper Machine Clothing (PMC) industry, press fabrics (also referred to as press felts) are used to mechanically dewater paper sheets that are formed thereon. During the pressing section of the papermaking process, press felts undergo many millions of cycles of compression and tension during their useful lives. In general, the press fabrics described in this document include seams that can ease their installation on paper making equipment while reducing or eliminating seam gaps that can cause inconsistencies and imperfections in resulting paper products.

[0041]In general, press fabrics for paper manufacture include one or more woven layers that include machine direction (MD) yarns (e.g., yarns that extend in the machine direction) interwoven with a system of cross-machine direction (CD) yarns (e.g., yarns that extend perpendicular to the machine direction), upon which a batt (also called a web ca...

Claims

1. A woven press felt for paper making, the woven press felt comprising:a base weave;a batt layer disposed on at least one side of the base weave;a seam for joining a first end of the woven press felt with a second end of the woven press felt, the seam configured to receive a pintle inserted through seam loops of a first end of the base weave interdigitated with seam loops of a second end of the base weave; anda flap defined in the batt layer, wherein when the woven press felt is seamed, an edge of the flap extends at an angle relative to a paper side surface of the woven press felt and the flap having a flap height extending beyond a paper side surface of the woven press felt,wherein the flap height is in a range of 10% to 60% of a thickness of the woven press felt.

2. The woven press felt of claim 1, wherein the flap height is greater than zero and less than 3 mm.

3. The woven press felt of claim 1, wherein the flap height is in a range of 20% to 40% of the thickness of the woven press felt.

4. The woven press felt of claim 1, wherein the flap height is in a range of 45% to 55% of the thickness of the woven press felt.

5. The woven press felt of claim 1, wherein the flap height is less than a flap length of the flap in the machine direction of the woven press felt.

6. The woven press felt of claim 5, wherein a ratio of the flap length to the flap height is in a range of 1 to 3.

7. The woven press felt of claim 6, wherein the ratio of the flap length to the flap height is in a range of 1.95 to 2.0.

8. The woven press felt of claim 5, wherein the flap length is in a range of 25% to 125% of the thickness of the woven press felt.

9. The woven press felt of claim 8, wherein the flap length is in a range of 90% to 100% of the thickness of the woven press felt.

10. The woven press felt of claim 1, wherein the flap length is equal to or greater than a seam length of the woven press felt.

11. The woven press felt of claim 1, wherein the angle at which the flap extends is in a range of 45º to less than 90º.

12. The woven press felt of claim 11, wherein the angle at which the flap extends is in a range of 60º to less than 90º.

13. The woven press felt of claim 1, wherein the ratio of the seam loop diameter to the flap height is in a range of 0.65 to 0.75.

14. The woven press felt of claim 1, where the flap overhangs the paper side surface of the press felt.

15. The woven press felt of claim 14, wherein the flap overhangs the paper side surface of the press felt by between 1 mm and 2 mm.

16. The woven press felt of claim 1, wherein when the flap is installed under tension on a crescent former, no gap exists between the edge of the flap and a second edge of the batt layer opposite the edge of the flap.

17. The woven press felt of claim 1, wherein when the flap is installed under tension on a crescent former, the edge of the flap contacts a second edge of the batt layer opposite the edge of the flap.

18. The woven press felt of claim 1, wherein the paper side surface of the woven press felt defines a plane, and wherein when the flap is installed under tension on a crescent former, a topmost surface of the flap is 0.6 mm or less above the plane of the paper side surface of the woven press felt.

19. The woven press felt of claim 18, wherein when the flap is installed under tension on the crescent former, a topmost surface of the flap is 0.2 mm or less above the plane of the paper side surface of the woven press felt.

20. The woven press felt of claim 1, wherein the woven press felt has a permeability in a seam region that is within 10% of a permeability of the woven press felt away from the seam region.

21. The woven press felt of claim 1, wherein the woven press felt is capable of use as a press felt in a crescent former.

22. The woven press felt of claim 1, wherein when the woven press felt is placed under tension, a pressure characteristic of an area of the press felt at the seam is up to 20% greater than a pressure characteristic of an area of the press felt away from the seam.

23. The woven press felt of claim 1, wherein the maximum pressure characteristic at the seam is up to 5 MPa greater than the mean pressure characteristic of an area of the press felt away from the seam.

24. A woven press felt for paper making, the woven press felt comprising:a base weave;a batt layer disposed on at least one side of the base weave;a seam for joining a first end of the woven press felt with a second end of the woven press felt, the seam configured to receive a pintle inserted through seam loops of a first end of the base weave interdigitated with seam loops of a second end of the base weave; anda flap defined in the batt layer, wherein when the woven press felt is seamed, an edge of the flap extends at an angle relative to a paper side surface of the woven press felt and, the flap having a flap height extending beyond a paper side surface of the woven press felt,wherein the flap height is in a range of 45% to 55% of a thickness of the woven press felt,wherein the flap height is less than a flap length of the flap in the machine direction of the woven press felt, and the flap length is in a range of 90% to 100% of the thickness of the woven press felt,wherein the flap length is in a range of 90% to 100% of the thickness of the woven press felt, andwherein the angle at which the flap extends is in a range of 60º to less than 90º.

25. A method of making paper, the method comprising:installing, on a paper making machine, a woven press felt comprising:a base weave;a batt layer disposed on at least one side of the base weave;a seam for joining a first end of the woven press felt with a second end of the woven press felt, the seam configured to receive a pintle inserted through seam loops of a first end of the base weave interdigitated with seam loops of a second end of the base weave; anda flap defined in the batt layer, wherein when the woven press felt is seamed, an edge of the flap extends at an angle relative to a paper side surface of the woven press felt and, the flap having a flap height extending beyond a paper side surface of the woven press felt,wherein the flap height is in a range of 10% to 50% of a thickness of the woven press felt; andapplying a tension to the woven press felt to draw the first end of the woven press felt apart from the second end of the woven press felt, wherein while tension is applied to the woven press felt, substantially no gap is present between the first end of the woven press felt and the second end of the woven press felt, and the flap protrudes by an amount in a range of 0 mm to 0.2 mm above the paper side surface of the woven press felt.

Images