Abstract:
An open ended papermaker&#39;s fabric of a type woven from a longitudinal thread system and a transverse thread system wherein a plurality of seam loops are formed at each end of the fabric by the threads of the longitudinal thread system. A seam zone exists at each end of the fabric between the respective seam loops and the last thread of the transverse thread system. Two additional transverse threads are interwoven with the longitudinal thread system in at least one seam zone in complementary weave repeat patterns that combine to provide a paper side repeated pattern of over one, under one across the repeat.

Description:
This application claims the benefit of: U.S. Provisional Application Serial No. 60/098,547, filed Aug. 31, 1998; U.S. Provisional Application Serial No. 60/097,831, filed Aug. 31,1998; U.S. Provisional Application Serial No. 60/098,566, filed Aug. 31,1998; U.S. Provisional Application Serial No. 60/098,567, filed Aug. 31, 1998; and U.S. Provisional Application Serial No. 60/098,573, filed August 31, 1998. 
    
    
     BACKGROUND 
     The present invention generally relates to an open ended, woven fabric which is designed for use in a papermaking, cellulose or board manufacturing machine. The fabric has a plurality of loops at each end to form a seam for rendering the fabric endless. 
     As will be known to those skilled in the art, papermaking machines generally include three sections commonly referred to as the forming, press and dryer sections. The present invention finds particular application in the press section of a papermaking machine. 
     Typically, press felts include a supporting base, such as a woven fabric, and a paper carrying or supporting layer. Frequently, the paper support layer is a homogeneous, nonwoven batt that has been affixed to the base. Base fabrics are typically woven fabrics which are used as an endless loop. Such an endless loop fabric may be woven endless with no seam or the fabric may be woven with two ends which are joined by a seam. Typical seams include pin type seams which utilize a pintle inserted through seam loops to close the fabric. 
     Some prior art seams have employed threads in the seam area to increase batt adhesion. However, these efforts have not always produced the desired contact area or the desired interconnection between paper and machine side machine direction threads. 
     As a result, there exists a need in seam loop construction to provide increased surface contact in the seam zone for better batt anchorage and a better interconnection between the paper and machine sides. 
     SUMMARY 
     The present invention relates to an open ended papermaker&#39;s fabric of a type woven from a longitudinal thread system and a transverse thread system. A plurality of seam loops are formed at each end of the fabric by the threads of the longitudinal thread system. A seam zone exists at each end of the fabric between the respective seam loops and the last thread of the transverse thread system. Two additional transverse threads are interwoven with the longitudinal thread system in at least one seam zone in complementary weave repeat patterns that combine to provide a paper side repeated pattern of over one, under one across the repeat. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a portion of the longitudinal seam loops in a fabric having additional cross machine direction threads in accordance with the present invention. 
     FIG. 2 is a front elevation of the seam loops and additional threads shown in FIG.  1 . 
     FIG. 3 illustrates one weave repeat pattern for one of the additional threads. 
     FIG. 4 illustrates one weave repeat for a second additional thread. 
     FIG. 5 shows the weave repeats of FIGS. 3 and 4 combined but without the seam loops as shown in FIG.  2 . 
     FIG. 6 is a top plan view of the combined weave patterns as illustrated in FIGS. 1,  2  and  5 . 
     FIG. 7 illustrates the weave repeat for one additional thread in accordance with a second embodiment. 
     FIG. 8 illustrates the weave repeat for a second additional thread in accordance with the second embodiment. 
     FIG. 9 shows the weave repeats of FIGS. 7 and 8 in combination. 
     FIG. 10 illustrates the weave repeat for one additional thread in accordance with a third embodiment. 
     FIG. 11 illustrates the weave repeat for a second additional thread in accordance with the third embodiment. 
     FIG. 12 shows the weave repeats of FIGS. 10 and 11 in combination. 
     FIG. 13 illustrates the weave repeat for one additional thread in accordance with a fourth embodiment. 
     FIG. 14 illustrates the weave repeat for a second additional thread in accordance with the fourth embodiment. 
     FIG. 15 shows the weave repeats of FIGS. 13 and 14 in combination. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments will be described with reference to the drawing figures wherein like numerals represent like elements throughout. 
     Referring to FIG. 1, it shows a portion of the base fabric seamloops with additional threads woven in accordance with the present invention. The base fabric comprises a top layer of MD longitudinal threads,  10 ,  12 ,  14 ,  16 ,  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30 , and  32 , and a bottom layer of MD longitudinal threads,  11 ,  13 ,  15 ,  17 ,  19 ,  21 ,  23 ,  25 ,  27 ,  29 ,  31  and  33 . It will be understood that the top and bottom layers are essentially continuous threads which are connected through the respective seam loop  35 - 1  through  35 - 12  extending between the top and bottom layers. 
     Typically, the phantom CMD threads  2 - 5  are interwoven with the top and bottom longitudinal threads in a given repeat pattern to form the body of the fabric which forms no part of the present invention. A seam zone  40  exists between the end CMD thread  2  and the seam loops. 
     Reference is now made to FIGS. 3,  4  and  5 . Although some benefits will be obtained with a single additional thread, the preferred embodiments use two additional threads for more uniformity in the paper side surface. The two additional threads  50  and  51  are interwoven in the seam zone  40  with both layers of longitudinal threads  10  through  33 . Additional CMD thread  50  preferably weaves in a repeat pattern that passes between MD threads  10 - 11 , under MD threads  12 - 13 , between MD thread pairs  14 - 15 ,  16 - 17 , and then weaves a continuous portion of plain weave with top layer MD threads  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30  before transitioning down between MD threads  32 - 33 . With reference to FIG. 4, the second additional thread  51  is woven in a complementary pattern to that of thread  50 . Additional thread  51  weaves a plain weave construction with top layer threads  10 ,  12 ,  14  before transitioning into a mid-plane float between MD thread pairs  16 - 17 , 18 - 19 , 20 - 21 , 22 - 23 , weaving under MD threads  24 - 25  and transitioning back to a mid-plane float beneath thread pairs  26 - 27 ,  28 - 29 ,  30 - 31 ,  32 - 33 . 
     As can be seen from FIG. 5, two additional threads interwoven in accordance with FIGS. 3 and 4 will produce a weave repeat structure having the appearance of a plain weave in the upper layer and two crossover points  53  and  54  which are spaced apart by at least seven MD threads. This results from the additional longitudinal thread being in a continuous portion  60  of the weave repeat with seven adjacent MD threads between transitions from the machine or paper side longitudinal threads. Since the repeat pattern extends over twelve pairs of MD threads with only a single interlacing in the machine side MD layer and the additional threads can shift relative to each other, threads  50  and  51  tend to act as one thread in a continuous plain weave on the top layer. As a result of the long transitions and the interlacing patterns, the additional threads can migrate relative to each other to produce the desired sheet side weave pattern while also providing mid-plane floats and long transitions. The result of this weave configuration is illustrated in FIG.  6 . 
     With reference to FIGS. 7,  8  and  9 , there is shown a second embodiment of the present invention. In this second embodiment, the first additional thread  55  weaves between MD thread pairs  10 - 11 ,  12 - 13 , beneath MD threads  14 - 15 , between MD thread pairs  16 - 17 ,  18 - 19 ,  20 - 21 , and then in a plain weave repeat with the upper layer MD threads  24 ,  26 ,  28 ,  30 , 32 . 
     The second additional thread  56  weaves in the mirror image of thread  55 . As shown by FIG. 9, the threads  55  and  56  produce a plain weave pattern on the paper sheet side, relatively long transitions which combine to simulate a mid-plane float and cross over points  57 ,  58  which encourage migration of the threads relative to each other. As with the prior embodiment, this embodiment provides a continuous portion  61  of the weave repeat that extends over at least five adjacent paper side longitudinal threads between transitions from the machine or paper side longitudinal threads. 
     Referring to FIGS. 10-12, a third embodiment is shown. The fabric repeats on sixteen MD threads  10 - 25 . Each additional CMD thread  70  and  71  is interwoven in the seam zone  40  with both layers of MD threads  10  through  25 . Additional CMD thread  70  preferably weaves in a repeat pattern that passes over MD threads  10 - 11 , between MD thread pairs  12 - 13 ,  14 - 15 ,  16 - 17 ,  18 - 19 ,  20 - 21 , over threads  22 - 23  and under MD threads  24 - 25 . With reference to FIG. 11, the second additional thread  71  is woven in a complementary pattern to that of thread  70 . Thus, CMD thread  71  weaves in a repeat that passes over threads  14 - 15 , under threads  16 - 17 , over threads  18 - 19  and between thread pairs  20 - 21 , 22 - 23 , 24 - 25  and  10 - 11 ,  12 - 14 . 
     The complementary pattern of the repeats can be seen from FIG.  12 . It will be noted from FIG. 12 that the weave repeats of threads  70  and  71  result in a transverse weave repeat that appears as a plain weave on the paper side surface of the fabric. Likewise, the mid-plane float repeat produces what is essentially a continuous float through the midplane of the fabric. This is particularly beneficial in two-layer fabric constructions. Finally, the weave repeats result in minimum interlacings on the machine side of the fabric. 
     Referring to FIGS. 13-15, a fourth embodiment of the present invention is shown. Each additional CMD thread  80  and  81  is interwoven in the seam zone  40  with both layers of MD threads  10  through  25 . Additional CMD thread  80  preferably weaves in a repeat that passes over MD threads  10 - 11 , between threads  12 - 13 , over thread  14 , between pairs of threads  16 - 17 ,  18 - 19 , under threads  20 - 21  and between pairs of threads  22 - 23 ,  24 - 25 . 
     With reference to FIG. 14, the second thread  81  is woven in a mirror image to the thread  80 . Thus, CMD thread  81  weaves in a repeat that passes between the pair of threads  10 - 11 , beneath the threads of pair  12 - 13 , between the pairs  14 - 15  and  16 - 17 , over the threads of pair  18 - 19 , under thread  20 , over the threads of pair  22 - 23 , and between threads  24 - 25 . 
     As can be seen from FIG. 15, two threads woven in accordance with FIGS. 13 and 14 produce a weave repeat structure having two crossover points  83  and  84  which are spaced apart by at least three MD threads. It will also be noted that MD thread  16  passes over both additional threads  80  and  81 . Since the repeat pattern extends over eight pairs of MD threads with only a single interlacing in the machine side MD layer and the threads can shift beneath thread  16 , threads  80  and  81  tend to act as one. As a result of the long transition and the interlacing patterns, the threads  80  and  81  can migrate relative to each other so that the resulting sheet side MD and CMD weave repeat appears to be a plain weave across the fabric. 
     In accordance with each of the embodiments of the invention described above, the additional threads  50 ,  51 ;  55 ,  56 ;  70 , 71  and  80 , 81  can be said to repeat on X paper side longitudinal threads  10 ,  12 ,  14 ,  16 ,  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30  and  32 . One of the additional threads weaves in a subrepeat pattern of over one, under one with Y of the paper side longitudinal threads  10 ,  12 ,  14 ,  16 ,  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30  and  32  and the other additional thread weaves in a subrepeat pattern of over one, under one with X minus Y paper side longitudinal threads  10 ,  12 ,  14 ,  16 ,  18 ,  20 ,  22 ,  24 ,  26 ,  28 ,  30  and  32 , where X is an integer and Y is an integer less than X. For example, in FIGS. 13-15, X is equal to eight and Y is equal to four, in FIGS. 2-5, X is equal to twelve and Y is equal to four, and in FIGS. 7-9, X is equal to twelve and Y is equal to six. 
     It will be appreciated that batt adhesion will be most improved on the sheet side surface but that some improvement in machine side surface adhesion will result from the presence of the interlacings and relatively long transitions. 
     The additional CMD threads  50 ,  51 ;  55 ,  56 ;  70 ,  71 ; and  80 , 81  can be multifilament, spun, braided, knitted, or bicomponent. If the thread is of a bicomponent nature, the bicomponent material may have a core material with a higher melting point surrounded by a covering of a lower melting point material. This allows the covering to melt and adhere to the batt material during finishing without affecting the core structure of the thread. Threads may be made from polymeric resins selected from a group consisting of polyamide, polyurethanes, polyesters, polyararnids, polyimides, polyolefins, polyetherketones, polypropylenes, PET, PBT, PTT, phenolics, and copolymers thereof.