Pintle seamed papermaking fabric

Abstract: A multi-layer press felt (F) for use in a papermaking machine which is formed by way of a pintle seam in at least the innermost layer (14). The felt (F) includes a needled fibrous layer (32) on at least its outer surface. Each fabric layer (14, 24) comprises MD monofilament yarns (16, 17, 26) interlaced with CMD yarns (18, 20, 28) forming the plurality of fabric layers each having loops (22, 30) at its opposed MD ends. The loops (22) of the first (14) of the fabric layers are intermeshed to receive the pintle (P) forming the seam which forms the felt (F) endless. Each of the loop portions (30) of the at least second (24) of the fabric layers have a multi-filament stuffer yarn (K) positioned therein.

Description: The present invention is directed to a pintle seamed papermaking fabric and, in particular, to a multi-layered press fabric having a pintle connected seam forming it endless. Seams in multi-layered fabrics which are connected with a pintle are well known throughout the papermaking fabric industry. The problems caused by these seams are also well known. For example, where multiple pintles are used, the problem of uneven compression at the seam due to the presence of the non-compressible pintles is a concern. Pintle seams also produce support surface areas at the seam which have uneven density causing the paper product to be marked. Also, the caliper of fabrics so seamed is sometimes uneven. Various attempts to provide a pintle seam which overcomes some or all of the deficiencies are disclosed in DE 2806742A, U..S. Patent No. 4,698,250 to Talonen et al, U.S. Patent No. 4,842,925 to Dufour et al. GB 2202870A describes a base fabric having two upper layers seamed into endless form at a pintle wire and a lower layer. The present invention has as one of its desired aims a seam construction for a papermaking fabric which provides for more uniform cover over its entire support surface. The invention is also concerned with the provision of a seamed papermaking fabric in which the end most transverse yarns are preferably maintained stable during use. The invention is further directed towards the provision of a papermaking fabric in which the cover at the seam is preferably substantially uniform of the cover of the remainder of the support surface. The invention is also concerned with the provision of a papermaking fabric in which the caliper preferably remains uniform throughout. The present invention provides a multi-layer papermaking fabric comprising first and second interconnected fabric layers, wherein the first layer is seamed into endless form by a pintle seam and wherein the second fabric layer comprises two end portions arranged near to or in contact with one another, each end portion having a plurality of loops and stuffer yarns disposed within said loops. The term "stuffer yarn" appearing in the claims is intended to cover stuffer yarns, filler yarns or yarns or fibres of similar construction. The second layer will usually be the outer layer once the fabric has been made endless and a fibrous layer will usually be attached to that layer, preferably, by needling. The first and second layers will usually be woven layers with machine direction yarns in the second layer forming the loops. The end portions of the second layer may be in close proximity to the pintle seam so that the stuffer yarns improve the uniformity of the papermaking fabric in the region of the pintle seam. Thus, they may be located directly above the pintle seam or, more preferably, slightly to one side of the pintle seam. Preferably, the stuffer yarns are sufficiently close to the pintle seam and sufficiently thick as to allow enough fibre cover to be provided during a needling operation for the transverse seam line to be substantially eliminated. The loops of the respective end portions of the second fibre layer may be fully intermeshed. Alternatively, the second fibre layer may be slightly shorter in length than the first so that the respective sets of loops are only partially intermeshed or are merely disposed closely adjacent each other. In a preferred embodiment, a multi-layer press felt for use in a papermaking machine is formed by way of a pintle seam in at least the innermost layer. The felt includes a needled fibrous layer on at least its outer surface. Each fabric layer comprises MD monofilament yarns interlaced with CMD yarns forming the plurality of fabric layers each having loops at its opposed MD ends. The loops of the first of the fabric layers are intermeshed to receive the pintle forming the seam which forms the felt endless. Each of the loop portions of the at least second of the fabric layers have a multi-filament stuffer yarn positioned therein. The present invention further provides the use in a papermaking fabric comprising a first fabric layer including a pintle seam and an adjacent second fabric layer, of stuffer yarns in looped end portions of the second fabric layer to improve the uniformity of the region of the fabric in which the pintle seam is located. In another preferred embodiment, a seamed multi-layer press felt for use in a papermaking machine has a seam acting to form the felt endless. The felt includes at least first and second interconnected fabric layers and a needled fibrous layer on at least its outer surface. Each fabric layer comprises MD yarns (machine direction yarns) interlaced with CMD yarns (cross machine direction yarns) to form each layer with a body portion having a row of loops at opposed MD ends thereof. The loops of the first or innermost of the fabric layers are intermeshed and receive a pintle forming the seam which interconnects the opposed MD ends of the first fabric layer. Each of the loops of the remaining fabric layers each have a stuffer yarn or filler positioned therein. The stuffer yarn along with the CMD and MD yarns of the upper fabric layer may form a portion of the needled fibrous layer. The press felt is preferably constructed so that each of the at least first and second fabric layers are of different MD length with the first or innermost of the fabric layers being longer than the remaining of the fabric layers. When there are at least three fabric layers, the intermediate layer of the fabric layers may have a MD length greater than the second fabric layer but less than the first fabric layer. In all arrangements each loop of the rows of loops at the opposed MD ends has a stuffer yarn positioned therein with the exception of the loops formed with the first layer. The stuffer yarn may be a multi-filament yarn or a knitted yarn formed of a single multi-filament yarn or of a plurality of multi-filament yarns. The loops of all fabric layers, save the first fabric layer, may be juxtaposed, partially intermeshed, or intermeshed. In a further preferred embodiment a multi-layer papermaking fabric includes at least a felt outer surface. The fabric includes a plurality of superimposed and interconnected fabric layers including at least an inner and outer layer. Each layer has a plurality of transversely spaced seam forming loops (each having an axes) at its opposed longitudinal ends. The loops of the inner layer are intermeshed with their axes aligned forming a channel across the fabric. A pintle is positioned along these aligned axes interconnecting the opposed rows of loops and forming a seam which forms the fabric endless. The loops of at least the outer layer may be in juxtaposed position with their axes misaligned across the fabric width. The loops of at least the outer layer contain a stuffer or filler yarn. This stuffer yarn along with the fabric forming yarns of at least the outer layer contribute to the formation of the felt. Preferably the fabric layers along with the felt are interconnected by needling. In this embodiment, the loops of the inner fabric layer are always intermeshed and formed into a seam. The loops of the remaining fabric layers may be fully intermeshed with their axes aligned, partially intermeshed with their axes misaligned or juxtaposed in end to end engagement. A stuffer yarn is positioned adjacent each of said opposed ends within respective of the loops. The stuffer yarn may be a knit yarn or a multi-filament yarn. All of the fabric layers may be woven or they may be non-woven and formed, for example, of interconnected coils or they may be selectively formed by any one of these. A preferred construction for carrying out the invention will hereinafter be described, together with other features thereof. The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings forming a part thereof, wherein preferred examples of the invention are shown and wherein: Figure 1 is a diagrammatic view of a fabric in the press section of a papermaking machine. Figure 2 is a sectional side view of a seam construction for a first embodiment of the invention; Figure 3 is similar to Figure 2 showing a second embodiment of the invention; Figure 4 is similar to Figure 2 showing a third embodiment of the invention; and, Figure 5 is a sectional top view of the seam area of a fabric utilizing a preferred seam construction according to the invention. Turning now to the drawings, preferred embodiments of the invention will now be described in more detail. Figure 1 shows a general arrangement for a press section D of a papermaking machine. Press fabric F is shown circulating, in the direction of the arrow, about idler rolls 10 and press rolls 12. Seam S is shown where it connects the opposed ends of press fabric F making it endless. Figure 2 shows a first embodiment of the invention. Here, fabric F includes lower carrier fabric 14 which is formed as a two layered fabric. Fabric 14 is formed by weft yarns 16 weaving with warp yarns 18 and 20 on first and second picks and weft yarn 17 weaving with warp yarns 18 and 20 on third and fourth picks. As weft yarn 16 is picked through warp yarns 18 on a first pick, when it approaches outermost warp yarns 18' and 20', at each side of the fabric, it wraps tightly about these outermost yarns and is picked back through the fabric on a second pick. There are no edge loops formed by first weft yarns 16. Weft yarn 17, where it reaches outermost warp yarns 18'and 20', at each side of the fabric, is looped about a stationary edge wire to form loops 22. Loops 22 are spaced transversely of fabric 14 by first weft yarns 16. To form the finished fabric circular or continuous, loops 22 at the opposed ends of the fabric are intermeshed and pintle P is inserted through the aligned openings. Papermaking fabrics formed endless in this manner are well known. An upper or support fabric 24 is positioned over the upper surface of carrier fabric 14. Upper fabric 24 is shown as a single layer fabric formed by weft yarns 26 weaving with warp yarns 28 in a known manner. Loops 30 are formed at opposed ends in the manner earlier described. A knit yarn K which acts as a filler or stuffer is inserted through the aligned openings of loops 30 formed at each end of the fabric. In the arrangement shown, knit yarns K may be formed integral with the fabric during weaving. It is noted that fabric 24 may also be a multi-layer fabric. Upper fabric 24 is formed to be slightly shorter than carrier fabric 14 so that the outer extremities of loops 30 at the opposed ends of the fabric are juxtaposed or in end to end contact. Also, the adjoining ends or loops 30 are preferably, although not necessarily, misaligned vertically of pintle P of the carrier fabric. Upper fabric 24 preferably is united with carrier fabric 14 by needling, although binder yarns or other interlacing techniques may be used. A fibre batt 32 is provided and is secured with at least the outer surface of upper fabric 24 also by needling. Knit yarns K serve two primary functions. First, because of the increased length of yarn within the openings due to the knitted configuration more fibre cover may be provided in the area of the seams during the needling operation. The additional fibre cover essentially eliminates the transverse seam line and forms this portion of the outer surface substantially uniform with the remainder of the outer surface. Secondly, knit yarns K within loop 30 maintain yarns 26, where they cross when forming loops 30, in position. By maintaining yarns 26 in position, outermost warp yarns 28' are maintained in position relative to the adjacent transverse warp yarns 28 during use in the press section. By controlling yarns 26, 28' the support surface is maintained even which allows the drainage over the entire area of the upper fabric to be even. Knit yarns are well known in the art and most constructions are acceptable for use as knit yarn K. U.S. Patent No.4,883,097 to Dufour shows a preferred construction for yarn K. Turning now to Figure 3, a second embodiment in fabric F' is shown. In this arrangement, carrier fabric 14' is formed as a single layer fabric by weaving weft yarns 34 with warp yarns 36 in a desired weave pattern. Loops 38 are formed in alternating sequences at each end of the fabric in the manner earlier described and pintle P is passed through the intermeshed loops 38 to form the fabric endless by way of seam S. Again, this structure is well known. Upper or support fabric 24' is formed as described above and arranged over the outer surface of carrier fabric 14'. In this arrangement, fabric 24' is formed of a length so that loops 30 intermesh completely with the openings of the loops aligned. Again, loops 30 are arranged to be slightly misaligned vertically of loops 38 and pintle P of the carrier fabric. A knit yarn K is positioned through the opening formed by intermeshed loops 30 at each end of the fabric as in the earlier described arrangement. A fibre batt 32' is formed over at least the outer surface of support fabric 24' by needling. The fabrics 14' and 24' are preferably united by needling of fibre batt 32' over the outer surface of the upper fabric. In Figure 4, the third embodiment is shown as fabric F". This arrangement is very similar to the arrangement shown in Figure 3. Here fabric F" comprises a carrier fabric 14" formed as described in Figure 3. Support fabric 24" is also formed as described in Figure 3. In press fabric F", fabric 24" is formed of a length which causes loops 30 at the opposed ends of the fabric to intermesh only slightly with only the outer ends of loops 30 being intermeshed when fabric 24" is positioned over the outer surface of fabric 14". This arrangement provides for the openings in each of loops 30 to be laterally spaced requiring an individual knit yarn K for each of the rows of loops 30. The fabrics are united as described in Figures 2 and 3. Figure 5 is a sectional top view of the press fabric F. Here fabric F is shown to include the paper support surface formed by fibre batt 32 on the outer surface of support fabric 24. Support fabric 24 is supported, united with and carried by carrier fabric 14 by needling as earlier described. Fabric F is made continuous by uniting the opposed ends of carrier fabric 14 by intermeshing loops 22 and positioning pintle P through the aligned loop openings forming seam S. Seam S is substantially obliterated by the cover provided by the needling. The cover includes entangled fibres of knit yarns K, fibres of the forming yarns of support fabric 24, and fibres of fibre batt 32. End loops 30 as well as transverse yarns 28' are maintained in their respective positions by the presence of knit yarns K within loops 30. Knit yarns K also functions to provide a degree of cushion over seam S and particularly over pintle P. When seam S is pressed against one of drums 12, knit yarn K will flatten out and relieve pressure normally caused by the oversized pintle in seam S. This action allows the caliper of the fabric to remain constant throughout. The carrier fabric is normally formed of monofilament warp and weft yarns which are wear resistant and which remain stable when subjected to heat and chemicals. The carrier fabric provides lateral and longitudinal stability for fabric F. The upper or support fabric is formed of mono or multi-filament yarns which, when needled, form a uniform fibre batt surface providing even drainage and cover. While a preferred embodiment of the invention has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the scope of the following claims.

Claims: A multi-layer papermaking fabric (F) comprising first and second interconnected fabric layers (14, 24) wherein the first layer (14) is seamed into endless form by a pintle seam (P) and wherein the second fabric layer (24) comprises two end portions arranged near to or in contact with one another, each end portion having a plurality of loops (30), and characterized in that stuffer yarns (K) are disposed within said loops. A multi-layer papermaking fabric (F) according to claim 1, said fabric being a press felt and having a seam forming said felt endless, said felt including a needled fibrous layer (32) on at least an outer surface thereof, and each said fabric layer comprising MD yarns (16, 17, 26) interlaced with CMD yarns (18, 20, 28) forming each said layer with a body portion having a row of loops (22, 30) at each MD end; wherein said rows of loops (22) of said first (14) of said fabric layers (14, 24) are intermeshed and carry a pintle (P) forming said seam interconnecting said opposed MD ends of said first fabric layer (14) forming said felt endless; and a stuffer yarn (K) is carried by each row of said loops (30) of said at least second of said fabric layers (24). The fabric (F) of claim 2 wherein said stuffer yarn (K) forms a portion of said needled fibrous layer (32). The fabric (F) of any one of claims 1 to 3, wherein said first (14) of said fabric layers (14, 24) comprises an innermost layer of said at least first (14) and second fabric layers (24). The fabric of claim 4 wherein each of said at least first (14) and second (24) fabric layers are of different MD length with said first (14) of said fabric layers (14, 24) being longer than the remaining of said fabric layers (14, 24). The fabric (F) of claim 5 wherein said fabric layers comprise at least three fabric layers with the intermediate fabric layer of said fabric layers having a MD length greater than said second fabric layer of said fabric layers. The fabric (F) of claim 6 wherein each said row of said loops at each of said opposed MD ends of said second and third fabric layers of said fabric layers carries a stuffer yarn (K) positioned therein. The fabric (F) of any one of claims 1 to 7, wherein said stuffer yarn (K) is a multi-filament yarn. The fabric (F) of any one of claims 1 to 7, wherein said stuffer yarn (K) is a knitted yarn formed of at least one multi-filament yarn. The fabric (F) of claim 9 wherein said knitted stuffer yarn (K) is formed of a plurality of multi-filament yarns. The fabric (F) of any one of claims 1 to 10, wherein said stuffer yarn (K) comprises a single stuffer yarn which passes through each said row of said loops (30) at said MD ends of at least said second fabric layer (24). The fabric (F) of any one of claims 1 to 11, wherein there are at least three of said fabric layers and said rows of said loops at said MD ends of at least one remaining fabric layer of said fabric layers are at least partially intermeshed. The fabric (F) of any one of claims 1 to 11, wherein there are at least three fabric layers and said rows of said loops at said MD ends of at least one of said three fabric layers are longitudinally spaced and do not intermesh. The fabric (F) of any one of claims 1 to 13, wherein said fabric layers (14, 24) are interconnected by needling. The fabric (F) of any one of claims 1 to 14, wherein at least said first (14) of said fabric layers (14, 24) comprises a woven fabric. The fabrics (F) of claim 15 wherein said MD yarns (16, 17) of at least said first of said fabric layers comprise weft yarns. A multi-layer papermaking fabric (F) according to claim 1, having at least a felt outer surface, said second layer (24) forming an outer layer relative to said first layers (14) and the multi-layer fabric being formed endless by a seam in which: each said fabric layer has a plurality of spaced seam forming loops (22, 30) at opposed longitudinal ends thereof, said loops (22) at said opposed ends of said first layer being intermeshed and aligned forming a channel through said fabric; a pintle (P) is positioned within said channel for forming said seam; said loops (30) at said opposed ends of at least said second layer (24) are in juxtaposed position with their openings misaligned; said loops (30) at said opposed ends of at least said second layer receive a stuffer yarn (K); and said stuffer yarn (K) and said fabric forming yarns (26, 28) of at least said second layer (24) contribute to the formation of said felt. The fabric (F) of claim 17 wherein said loops (30) at said opposed ends of said at least second layer (24) are intermeshed. The fabric (F) of claim 17 wherein said interconnected fabric layers (14, 24) include an intermediate layer, said loops at said opposed ends of said intermediate layer being intermeshed and misaligned. The fabric (F) of claim 17 wherein said interconnected fabric layers (14, 24) include an intermediate layer, said loops at said opposed ends at each said end of said second (24) and intermediate layers being juxtaposed. The fabric (F) of any one of claims 17 to 20 wherein a stuffer yarn (K) is positioned adjacent each of said opposed ends within respective of said loops (30). The fabric (F) of any one of claims 17 to 21 wherein said stuffer yarn (K) is a knit yarn. The fabric (F) of any one of claims 17 to 21 wherein said stuffer yarn (K) is a multi-filament yarn. A papermaking machine including a fabric (F) as claimed in any one of the preceding claims.

Inventors: OSTERMAYER VOLKER, REUTHER NORBERT, OSTERMAYER, VOLKER, REUTHER, NORBERT
Applicants: GESCHMAY CORP, GESCHMAY CORPORATION
Application year: 2000
Main classification: D21F7
IPC codes: D21F1, D21F7, D21F5