Abstract:
An open-ended papermaker&#39;s fabric of a type woven from a longitudinal thread system and a transverse thread system and including a plurality of seam loops at each end of the fabric. A seam zone exists at each end of the fabric between the respective seam loops and the last thread of the transverse thread system. At least one additional transverse thread is interwoven in at least one seam zone, with the transverse thread placed in a repeated pattern of over at least three adjacent paper side longitudinal threads, between at least a first pair of paper side and machine side threads, under at least one machine side longitudinal thread, and between at least a second pair of machine and paper side threads.

Description:
This application claims the benefit of: U.S. Provisional Application Ser. No. 60/098,547, filed Aug. 31,1998; U.S. Provisional Application Ser. No. 60/097,831, filed Aug. 31, 1998; U.S. Provisional Application Ser. No. 60/098,566, filed Aug. 31, 1998; U.S. Provisional Application Ser. No. 60/098,567, filed Aug. 31, 1998; and U.S. Provisional Application Ser. No. 60/098,573, filed Aug. 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 and the desired interconnection between paper and machine side machine direction threads. 
     As a result of the seam loop construction, there exists a need to provide increased surface contact in the seam zone for better batt anchorage and a balance 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. At least one additional transverse thread is interwoven in at least one seam zone with the longitudinal thread system in a repeated pattern of over at least three adjacent paper side longitudinal threads, between at least one pair of threads, under at least one machine side longitudinal thread, and between another pair of threads. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic perspective view of a portion of one end of the base fabric of a first embodiment of the present invention. 
     FIG. 2 illustrates one weave repeat pattern for one of the additional threads of the fabric of FIG.  1 . 
     FIG. 3 illustrates one weave repeat pattern for the second additional thread of FIG.  1 . 
     FIG. 4 is an elevation view of the fabric taken along line  4 — 4  in FIG.  1 . 
     FIG. 5 is a top plan view of the two ends of the fabric of FIG. 1 prior to joining together thereof. 
     FIG. 6 is a top plan view of the two ends of the fabric of FIG. 1 joined together. 
     FIG. 7 is a schematic perspective view of a portion of one end of the base fabric of a second embodiment of the present invention. 
     FIG. 8 illustrates one weave repeat pattern for one of the additional threads of the fabric of FIG.  7 . 
     FIG. 9 illustrates one weave repeat pattern for the second additional thread of FIG.  7 . 
     FIG. 10 is an elevation view of the fabric taken along line  10 — 10  in FIG.  7 . 
     FIGS. 11-13 illustrate the weave repeat of the additional threads of a third embodiment of the present invention. 
     FIG. 14 illustrates the weave repeats of the additional threads of a fourth embodiment of the present invention. 
     FIG. 15 a top plan view of one end of the fabric of the embodiment shown in FIG.  14 . 
     FIG. 16 shows a portion of the joined seam loops of the fabric of the embodiment shown in FIG.  14 . 
     FIG. 17 illustrates one weave repeat pattern for one of the additional threads of a fifth embodiment of the present invention. 
     FIG. 18 illustrates one weave repeat for the second additional thread of the fabric of the fifth embodiment. 
     FIG. 19 shows the weave repeats of both additional threads of the fifth embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments will be described with reference to the drawing figures where like numerals represent like elements throughout. 
     Referring to FIG. 1, it shows a portion of one end of the base fabric seam loops with additional threads woven in accordance with a first embodiment of the present invention. The base fabric  1  comprises a top layer of MD threads,  10 ,  12 ,  14 ,  16 ,  18 ,  20 ,  22 , and  24 , and a bottom layer of MD threads,  11 ,  13 ,  15 ,  17 ,  19 ,  21 ,  23  and  25 . It will be understood that the top and bottom layers are essentially continuous threads which form the seam loops  35 - 1  to  35 - 8  between the top and bottom layers. 
     Typically, the body CMD threads  2 - 5 , shown in phantom, are interwoven with the top and bottom MD thread layers in a given repeat pattern to form the body of the base fabric  1 . A seam zone  40  exists between the end CMD thread  2  and the seam loops  35 - 1  to  35 - 8 . The weave pattern of the body CMD threads  2 - 5  can be varied to provide the desired characteristics of the base fabric  1 . 
     Reference is now made to FIGS. 2-4. Although some benefits will be obtained with a single thread, in the preferred embodiments, two additional threads are used for more uniformity in the paper side surface. Additionally, the additional threads may be provided along only one end of the fabric if desired in a particular application. The fabric will be described in terms of the preferred embodiments wherein two additional threads are provided at each end of the fabric. 
     The two additional CMD threads  50  and  51  are interwoven in the seam zone  40  with both layers of MD threads  10  through  25 . As shown in FIG. 2, one additional CMD thread  50  preferably weaves in a repeat that passes over MD threads  10 - 17 , between threads  18 - 19 , under threads  20 - 21 , between threads  22 - 23  and over threads  24 - 25 . With reference to FIG. 3, the second additional thread  51  is woven in a repeat pattern which is shifted four MD thread pairs compared to that of thread  50 . Thus, CMD thread  51  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 over threads  16 - 25 . Each additional thread  50 ,  51  has a sheet side float  54 ,  55  of five top layer MD threads. 
     As can be seen from FIG. 4, two threads  50 , 51  woven in accordance with FIGS. 3 and 4 will produce a weave repeat structure wherein each machine side interlacing  52  and  53 , respectively, is aligned with the paper side float  54  and  55  of the other additional thread  50 ,  51  respectively. As a result, the combined floats  54  and  55  float across each of the top layer MD threads  10 , 12 , 14 , 16 , 18 , 20 , 22 , 24  of the repeat. Since the repeat pattern extends over eight pairs of MD threads with minimal interlacing in the machine side MD layer, the paper side floats  54 ,  55  can shift slightly in the MD over the machine side interlacings  53 ,  52  of the other thread. As a result of the long floats  54 ,  55  and the interlacing patterns, the threads  50  and  51  can migrate relative to each other so that the seam zone  40  has effectively one long float across the width of the fabric. This result is illustrated in FIGS. 5 and 6. This effect may be further enhanced if the additional threads  50 ,  51  are selected from materials with no or low twist. Such material will allow the threads  50 ,  51  to flatten out in the float areas  54 ,  55  to cover more of the seam zone  40 . 
     It is may be desirable, but not necessary, to weave the additional threads at the opposite ends of the fabric in reverse positioning with respect to each other. For example, as illustrated in FIG. 6, on one end of the fabric  1 , additional thread  51  is adjacent the last CMD thread  2  and at the opposite end of the fabric  1 , additional thread  50 ′ is adjacent to the last CMD thread  2 . This allows the two ends of the fabric  1  to complement each other when the fabric  1  is joined. 
     Referring to FIGS. 7-10, a second embodiment  60  which is similar to the first embodiment  1  is shown. In the second embodiment  60 , one of the additional CMD threads  70  weaves between threads  10  and  11 , under threads  12  and  13 , between threads  14  and  15 , under threads  16  and  17 , transitions between threads  18  and  19 , and over threads  20 - 25 . The second additional thread  71  is again offset by four MD thread pairs. As shown in FIG. 9, it weaves between threads  10  and  11 , over threads  12 - 17 , transitions between threads  18  and  19 , weaves under threads  20 - 21 , between threads  22  and  23 , and under threads  24  and  25 . As shown in FIG. 10, the machine side interlacings  72  and  73  for each additional thread  70 ,  71  are aligned with the paper side float  74  and  75  of the other additional thread  70 ,  71  respectively. Although, there is slightly more interlacing points on the machine side MD layer, the paper side floats  54 ,  55  still shift with respect to one another to provide the seam zone  40  with repeating long float across the width of the fabric, as shown in FIGS. 11 and 12. The effective repeat with respect to the top layer MD threads  10 , 12 , 14 , 16 , 18 , 20 , 22 , 24  of the combination of the threads is a pattern of over three and under one. 
     A third embodiment  100  is disclosed with respect to FIGS. 11-13. Additional thread  110  is woven in the same manner as in FIG. 3 with respect to the first embodiment. The weave of additional CMD thread  111  is modified as depicted in FIG.  12 . Thread  111  weaves between MD threads  10 ,  11 , under MD threads  12  and  13 , between MD threads  14 ,  15  and  16 ,  17 , floats over MD threads  18 ,  20 ,  22  and between MD threads  24 , 25 . Referring to FIG. 15, the effective long float over three of four top layer MD threads is maintained across the width of the fabric. 
     With reference to FIG. 14, there is shown a fourth embodiment  150 . In this fourth embodiment  150 , weave repeats of the CMD threads  155  and  156  result in floats over three machine direction threads  10 ,  12  and  14  and over three machine direction threads  18 ,  20 , and  22 . The long transition between pairs of machine direction threads and the interlacing with a single machine side MD thread per repeat is as previously described. Thus, the threads  155  and  156  will migrate relative to each other and produce an effective single thread with floats over three of four top layer MD threads  10 , 12 , 14 , 16 , 18 , 20 , 22 , 24 . FIGS. 15 and 16 illustrate the migration of threads  155  and  156  in a manner similar to that described with respect to FIGS. 5 and 6. 
     Referring to FIGS. 17-19, a fifth embodiment  200  is shown. The fabric  200  repeats on twenty four MD threads  10 - 33 . The two additional threads  210  and  211  are interwoven in the seam zone  40  with both layers of longitudinal threads  10  through  33 . Referring to FIG. 17, additional CMD thread  210  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 , floats over MD threads  18 - 23 , between MD threads  24 - 25 , floats over MD threads  26 - 31  and between MD threads  32 - 33 . 
     With reference to FIG. 18, the second additional thread  211  is woven in a complementary weave pattern to that of thread  210 . Additional thread  211  weaves over MD threads  10 - 15 , between MD thread pairs  16 - 17 ,  18 - 19 ,  20 - 21 ,  22 - 23 , under MD threads  24 - 25  and between MD thread pairs  26 - 27 ,  28 - 29 ,  30 - 31 ,  32 - 33 . It will be noted from FIG. 18 that additional thread  211  forms two mid-plane floats between four pairs of MD threads  16 - 33 . 
     As can be seen from FIG. 19, the two additional threads  210 - 211  as interwoven in FIGS. 17 and 18 produce a weave repeat structure having the appearance of an over three, under one repeat in the upper layer. The two crossover points,  213 ,  214  are spaced apart by at least three MD 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  210  and  211  tend to act as one thread in a continuous three over, one under weave pattern on the top layer. With reference again to FIG.  17  and additional thread  210 , it can be seen that the weave repeat of thread  210  includes a subrepeat of three over, one under which repeats twice within the pattern. This weave repeat permits the relatively loose interlacing of the thread  211 , but enables the pattern to be continued throughout the upper layer when the threads  210 ,  211  are combined in accordance with FIG.  19 . 
     It will be appreciated that batt adhesion to the additional thread(s) of the various embodiments will be most improved on the sheet side surface but that improved machine side batt adhesion will be achieved. 
     As explained above, the additional CMD threads  50 ,  51 ;  70 ,  71 ;  110 ,  111 ;  155 ,  156 ; and  210 ,  211  are preferably manufactured from materials with no or low twist, however, this is not required. The additional threads  50 , 51 ;  70 , 71 ;  110 ,  111 ;  155 ,  156 ; and  210 , 211  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, polyaramids, polyimides, polyolefins, polyetherketones, polypropylenes, PET, PBT, PTT phenolics, and copolymers thereof.