Abstract:
An open ended papermaking fabric comprised of interwoven longitudinal and transverse thread systems which define a paper side, a machine side and a plurality of seaming loops at each open end of the fabric. The seaming loops are formed by the longitudinal thread system and the transverse threads define a seaming zone at each end. The fabric is characterized by at least one additional transverse thread interwoven with the longitudinal threads in the seam zone in a repeat pattern that includes a mid-plane float of at least two threads in the longitudinal yarn system.

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, non-woven 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. At least one additional transverse thread interwoven in at least one seam zone with the longitudinal thread system in a repeat pattern that includes a mid-plane float that extends between at least two pairs of paper side and machine side longitudinal threads. 
    
    
     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. 
     FIG. 16 illustrates the weave repeat for one additional thread in accordance with a fifth embodiment. 
     FIG. 17 illustrates the weave repeat for a second additional thread in accordance with the fifth embodiment. 
     FIG. 18 shows the weave repeats of FIGS. 16 and 17 in combination. 
     FIG. 19 illustrates the weave repeat for one additional thread in accordance with a sixth embodiment. 
     FIG. 20 illustrates the weave repeat for a second additional thread in accordance with the sixth embodiment. 
     FIG. 21 shows the weave repeats of FIGS. 19 and 20 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 seam loops with additional threads woven in accordance with the present invention. The base fabric  1  comprises a top layer of MD longitudinal threads,  10 ,  12 ,  14 ,  16 ,  18 ,  20 ,  22 , and  24 , and a bottom layer of MD longitudinal 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 phantom CMD threads  2 - 5  are interwoven with the top and bottom MD longitudinal threads in a given repeat pattern to form the body of the fabric. The weave of the body of the fabric forms no part of the present invention. A seam zone  40  exists between the final CMD thread  2  and the seam loops  35 - 1  to  35 - 8 . 
     Reference is now made to FIGS. 3,  4  and  5 . Although some benefits will be obtained with a single additional thread, the preferred embodiments employ two additional threads for more uniformity in the paper side surface. The two additional CMD threads  50  and  51  are interwoven in the seam zone  40  with both layers of MD threads  10  through  25 . Additional CMD thread  50  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. 4, the second additional thread  51  is woven in a complementary pattern to that of the thread  50 . The CMD thread  51  weaves in a repeat that passes between thread pairs  10 - 11 ,  12 - 13 , over threads  14 - 15 , under threads  16 - 17 , over threads  18 - 19  and between thread pair  20 - 21 ,  22 - 23 ,  24 - 25 . 
     The complementary pattern of the repeats can be seen from FIG.  5 . From FIG. 5 it can be seen that the shifted weave repeats of threads  50  and  51  result in a transverse weave repeat that appears as a plain weave on the paper side surface of the fabric, and a mid-plane float between each MD pair  10 - 11 ,  12 - 13 ,  14 - 15 ,  16 - 17 ,  18 - 19 ,  20 - 21 ,  22 - 23 , and  24 - 25  of the repeat. Finally, these weave repeats result in minimum interlacings on the machine side of the fabric. This allows the mid-plane floats to migrate relative to one another, thereby effectively creating a virtually continuous mid-plane float across the width of the fabric, see FIG.  6 . This is particularly beneficial in two-layer fabric constructions. 
     With reference to FIGS. 7,  8  and  9 , there is shown a second embodiment of the present invention. In this embodiment, the transverse additional thread  55  weaves between MD threads  10 - 11 , under MD threads  12 - 13 , between MD threads  14 - 15 , over MD threads  16 - 17 , between MD thread pairs  18 - 19 ,  20 - 21 ,  22 - 23  and over MD threads  24 - 25 . The additional transverse thread  56  weaves in a complementary pattern. Thread  56  weaves over MD threads  10 - 11 , between MD thread pairs  12 - 13 ,  14 - 15 ,  16 - 17 , over MD threads  18 - 19 , between MD threads  20 - 21 , under MD threads  22 - 23 , and between MD threads  24 - 25 . As can be seen from FIG. 9, these complementary weave patterns produce a sheet side weave pattern with pairs of transverse weave knuckles alternating with pairs of MD threads that are over both of the additional transverse threads  55  and  56 . In addition to producing long continuous mid-plane floats, these patterns also increase the thread&#39;s transition length as it passes from layer to layer. Here, the threads  55  and  56  transition under three sheet side MD threads while passing under only one machine side MD thread. This embodiment provides minimum machine side surface interlacings, and long transitions that appear to provide a continuous a mid-plane float between six of the eight MD pairs. 
     A third embodiment of the present invention is shown in FIGS. 10-12. The fabric of this embodiment repeats on twenty four MD threads  10 - 33 . The two additional threads  70  and  71  are interwoven in the seam zone  40  with both layers of longitudinal threads  10  through  33 . Additional CMD thread  70  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. 11, the second additional thread  71  is woven in a complementary pattern to that of thread  70 . Additional thread  71  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 between thread pairs  26 - 27 ,  28 - 29 ,  30 - 31 ,  32 - 33 . 
     As can be seen from FIG. 12, two additional threads interwoven in accordance with FIGS. 10 and 11 produce a weave repeat structure having the appearance of a plain weave in the upper layer and two crossover points  73  and  74  which are spaced apart by at least three MD threads. This results from the additional longitudinal thread being in a continuous portion  80  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  70  and  71  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 combined threads provide two mid-plane floats, each floating between five of six MD thread pairs. 
     With reference to FIGS. 13-15, there is shown a fourth embodiment of the present invention. In this fourth embodiment, the first additional thread  75  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  76  weaves in the mirror image of thread  75 . As shown by FIG. 15, the threads  75  and  76  produce a plain weave pattern on the paper sheet side, relatively long transitions which combine in a virtual mid-plane float and widely spaced crossover points  77 ,  78  which encourage migration of the threads relative to each other. As with the prior embodiment, this embodiment provides a continuous portion  81  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 and two mid-plane floats, each floating between five of six MD thread pairs. 
     Referring to FIGS. 16-18, a fifth embodiment is shown. Additional CMD thread  100  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. 17, the second additional thread  101  is woven in a complementary weave pattern to that of thread  100 . Additional thread  101  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. 17 that additional thread  101  forms two mid-plane floats between four pairs of MD threads  16 - 17 ,  18 - 19 ,  20 - 21 ,  22 - 23  and  26 - 27 ,  28 - 29 ,  30 - 31 ,  32 - 33 . 
     As can be seen from FIG. 18, the two additional threads  100 , 101  as interwoven in FIGS. 16 and 17 produce a weave repeat structure having the appearance of an over three, under one repeat in the upper layer. The two crossover points,  103 ,  104  are spaced apart by at least three MD threads. This creates a long continuous portion of the second additional thread  101  which generally forms mid-plane floats that complement the long transition of the first additional thread  100 . 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  100  and  101  tend to act as one thread in a continuous over three, under one weave pattern on the top layer. With reference again to FIG.  16  and additional thread  100 , it can be seen that the weave repeat of thread  100  includes a subrepeat of over three, under one which repeats twice within the pattern. This weave repeat permits the relatively loose interlacing of the thread  101  but enables the pattern to be continued throughout the upper layer when the threads  100 ,  101  are combined in accordance with FIG.  18 . Again, the combined threads  100 ,  101  provide two mid-plane floats, each floating between five of six MD thread pairs. 
     With reference to FIGS. 19-21, there is shown a sixth embodiment of the present invention. In this sixth embodiment, the first additional thread  105  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 two repeats of the subrepeat pattern of over two, under one with upper MD threads  22 ,  24 ,  26 ,  28 ,  30 ,  32 . The second additional thread  106  weaves in the mirror image of thread  105 . As shown by FIG. 21, the threads  105  and  106  produce an over two, under one weave pattern on the paper sheet side, relatively long transitions in virtual five thread mid-plane floats and crossover points  107 , 108  which encourage migration of the threads relative to each other. As with the prior embodiment, this embodiment provides a weave repeat that includes two repeats of the subrepeat in adjacent paper side longitudinal threads between the transitions from the machine or paper side longitudinal threads. 
     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. 
     The additional CMD threads  50 ,  51 ,  55 ,  56 ;  70 ,  71 ,  75 ,  76 ,  100 ,  101 , and  105 ,  106  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.