Patent Publication Number: US-6213164-B1

Title: Pintle seamed press felt

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed 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 U.S. Pat. No. 4,698,250 to Talonen et al, U.S. Pat. No. 4,824,525 to Penven, and U.S. Pat. No. 4,842,925 to Dufour et al. 
     The instant invention has for its object a seam construction for a papermaking fabric which provides for more uniform cover over its entire support surface. 
     Another object of the invention is a seamed papermaking fabric in which the end most transverse yarns are maintained stable during use. 
     Another object of the invention is a papermaking fabric in which the cover at the seam is substantially uniform of the cover of the remainder of the support surface. 
     Another object of the invention is the provision of a papermaking fabric in which the caliper remains uniform throughout. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a seamed multi-layer press felt for use in a papermaking machine, the 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 form a portion of the needled fibrous layer. The press felt is 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, are juxtaposed, are partially intermeshed, or are intermeshed. 
     The invention is also directed to a multi-layer papermaking fabric, including at least a felt outer surface which is formed endless by a seam, wherein 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. The fabric layers along with the felt are interconnected by needling. 
     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 formed of interconnected coils or they may be selectively formed by any one of these. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The construction designed to carry 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 an example of the invention is shown and wherein: 
     FIG. 1 is a diagrammatic view of the fabric in the press section of a papermaking machine. 
     FIG. 2 is a sectional side view of a seam construction for a first embodiment of the invention; 
     FIG. 3 is similar to FIG. 2 showing a second embodiment of the invention; 
     FIG. 4 is similar to FIG. 2 showing a third embodiment of the invention; and, 
     FIG. 5 is a sectional top view of the seam area of a fabric utilizing the seam construction of the invention. 
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT 
     Turning now to the drawings, the invention will now be described in more detail. 
     FIG. 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. 
     FIG. 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 , 20  and  16  on first and second picks and weft yarn  17  weaving with warp yarns  18  and  20  on third and fourth picks. As weft yarn  20  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 fiber 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 fiber cover may be provided in the area of the seams during the needling operation. The additional fiber 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. Pat. No. 4,883,097 to Dufour shows a preferred construction for yarn K. 
     Turning now to FIG. 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 in 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 fiber 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 fiber batt  32 ′ over the outer surface of the upper fabric. 
     In FIG. 4, the third embodiment is shown as fabric F″. This arrangement is very similar to the arrangement shown in FIG.  3 . Here fabric F″ comprises a carrier fabric  14 ″ formed as described in FIG.  3 . Support fabric  24 ″ is also formed as described in FIG.  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 with 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 FIGS. 2 and 3. 
     FIG. 5 is a sectional top view of the press fabric of the invention. Here fabric F is shown to include the paper support surface formed by fiber 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 fibers of knit yarns K, fibers of the forming yarns of support fabric  24 , and fibers of fiber 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 fiber 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 spirit or scope of the following claims.