Patent Publication Number: US-11661682-B2

Title: Fabric and belt containing it for shear stressing applications

Description:
TECHNICAL FIELD 
     The present application relates to fabric containing conveyor belts and to uses of such conveyor belts in applications where shear stress is applied to the belt. 
     PRIOR ART 
     Conveyor belts generally consist of a base fabric and top layers adhering to the base fabrics. The top layers may be of rubber, elastomer, thermoplastic and thermoset materials which are either/or chemically or physically attached to the base fabric which is usually of polyester or aramid. Conveyor belts have to be highly flexible to successfully work within a conveyor application. For ease of end-joining by welding together of the open ends it is preferred that the top layers consist of a thermoplastic or thermoplastic elastomer which upon such end-joining may act as the hot-melt adhesive and weldable/joinable to make into an endless belt. The belt design must be able to resist liquids, solvents, oils and wide variety of other chemicals, with abrasion resistance to solid materials, whist subjected to external/internal longitudinal, lateral and surface tensions/contractions, such as shear, under various operating and environmental conditions, with multiple, repetitive impacts whist simultaneously maintaining a good degree of dimensional stability. Such operational forces can damage interplay adhesion (embedded or laminated weaker adhesive forces between the fabric and polymer). 
     DE2234915 discloses a conveyor belt with two individual fabrics, each of the fabrics having a first and second layer of uncrimped weft filaments and second crimped warp filaments passing over uncrimped weft filaments of the first layer, then passing between uncrimped weft filaments of the first and second layer, then passing below uncrimped weft filaments of the second layer and then passing between uncrimped weft filaments of the first and second layer. None of the two fabrics has uncrimped warp filaments passing between the uncrimped weft filaments of the first and second layer. This publication aims to reduce elongation of the belt and to improve its lateral stiffness or transverse rigidity (“Quersteifigkeit”). 
     U.S. Pat. No. 4,877,126A discloses a conveyor belt wherein the fabric has a first and second layer of uncrimped weft filaments; both first crimped warp filaments passing in alternating manner over uncrimped weft filaments of the first layer and below uncrimped weft filaments of the second layer and second crimped warp filaments of the type as described above for DE2234915. This fabric however has no uncrimped warp filaments passing between the uncrimped weft filaments of the first and second layer. 
     GB2101643 discloses a belting fabric having a first, second and third layer of uncrimped weft filaments; crimped warp filaments passing, not necessarily in alternating manner, over uncrimped weft filaments of the first layer and under uncrimped weft filaments of the second layer, or passing, not necessarily in alternating manner, over uncrimped weft filaments of the second layer and under uncrimped weft filaments of the third layer; and uncrimped warp filaments passing between the first and second layer, or between the second and third layer, of uncrimped weft filaments. This fabric does however not contain any second crimped warp filaments of the type described above for DE2234915. This belting fabric is first impregnated and then covered, either on one or both sides of the fabric and if desired along the edges, with elastomeric material. 
     GB1273528 discloses a fabric having a first, second and third layer of uncrimped weft filaments; crimped warp filaments passing in alternating manner over uncrimped weft filaments of the first layer and under uncrimped weft filaments of the second layer, or passing in alternating manner over uncrimped weft filaments of the second layer and under uncrimped weft filaments of the third layer; and uncrimped warp filaments passing between the first and second layer, or between the second and third layer, of uncrimped weft filaments. This fabric does however not contain any second crimped warp filaments of the type described above for DE2234915. This fabric is preferably impregnated with vulcanisable or thermoplastic elastomer, e.g. rubber or PVC. 
     All four above mentioned publications are silent as to the behaviour of their belts under shear stress in longitudinal direction of the belt. 
     The present invention aims to provide an improved conveyor belt in view of its use under shear-stressing applications. 
     SUMMARY 
     The present invention provides a woven fabric comprising: 
     a) A first layer (A) of first uncrimped weft filaments running essentially in parallel to each other and being spaced apart from each other by a distance D; 
     b) a second layer (B) of second uncrimped weft filaments running essentially in parallel to each other and being spaced apart from each other by said distance D; 
     
         
         
           
             wherein for each of the first uncrimped weft filaments there is one corresponding second uncrimped weft filament, and vice versa, to form successive filament pairs, each such successive filament pair being designable with a unique and ascending integer index N;
 
c) crimped warp filaments having one of the following weave types c1-c4:
 
             c1—entwine around first uncrimped weft filaments of all filament pairs with indexes N fulfilling (N mod 4)=0, such indexes N being designated as N A ; pass between first and second uncrimped weft filaments of all filament pairs with indexes N fulfilling (N mod 4)=1, such indexes N being designated as N B ; entwine around second uncrimped weft filaments of all filament pairs with indexes N fulfilling (N mod 4)=2, such indexes N being designated as N C ; and pass between first and second uncrimped weft filaments of all filament pairs with indexes N fulfilling (N mod 4)=3, such indexes N being designated as N D ; or 
             c2—entwine around second uncrimped weft filaments of all filament pairs with said indexes N A ; pass between first and second uncrimped weft filaments of all filament pairs with said indexes N B ; entwine around first uncrimped weft filaments of all filament pairs with said indexes N C ; and pass between first and second uncrimped weft filaments of all filament pairs with said indexes N D ; or 
             c3—pass between first and second uncrimped weft filaments of all filament pairs with said index N A ; entwine around first uncrimped weft filaments of all filament pairs with said indexes N B ; pass between first and second uncrimped weft filaments of all filament pairs with said indexes N C ; and entwine around second uncrimped weft filaments of all filament pairs with said indexes N D ; or 
             c4—pass between first and second uncrimped weft filaments of all filament pairs with said indexes N A ; entwine around second uncrimped weft filaments of all filament pairs with said indexes N B ; pass between first and second uncrimped weft filaments of all filament pairs with said indexes N C ; and entwine around first uncrimped weft filaments of all filament pairs with said indexes N D ;
 
and
 
d) uncrimped warp filaments passing between first and second uncrimped weft filaments of all filament pairs;
 
wherein the fabric does not comprise crimped warp filaments which entwine around first and second uncrimped weft filaments in alternating manner.
 
           
         
       
    
     Preferred embodiments of the fabric are according to the description and dependent claims. 
     The invention furthermore provides belts containing such fabrics and applications of such belts wherein shear stress between the belt&#39;s top surface and the belt&#39;s bottom surface may occur. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIGS.  1 - 3    are schematic representations of the fabric of GB1273528, namely  FIG.  1    as a cross-sectional view,  FIG.  2    as a top view, and  FIG.  3    again as cross-sectional view, but with only one crimped warp filaments, either under unsheared condition (top of  FIG.  3   ) or under 20° shear (bottom of  FIG.  3   ). 
         FIGS.  4 - 6    are schematic representations of the fabric of the invention, namely  FIG.  4    as a cross-sectional view,  FIG.  5    as a top view, and  FIG.  6    again as cross-sectional view, but with only one crimped warp filaments, either under unsheared condition (top of  FIG.  3   ) or under attempted 20° shear (bottom of  FIG.  6   ). 
         FIG.  7    is a schematic cross-sectional view of a belt of the invention with the fabric of  FIG.  4   . 
         FIGS.  8  and  9    illustrate a test setup for testing against delamination under “wear and tear” conditions and under shear stress, respectively. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This development intends to use a thermoplastic polymer matrix flooded directly into unidirectional reinforced multi-layer woven polyester fabric component woven joined layers, providing a fully impregnated, physical entanglement of thermoplastic polymer (preferred TPU) to form an embedded and entangled polymer/fabric matrix. Such entanglement to minimise layer separation, improves the polymer matrix bonding/adhesion characteristics and resistance to product ingress/commination issues and generally improves belt performance and service life, through good wear characteristics whilst providing good integral and dimensional flexibly. 
     The fabric according to the invention has advantages in shear-intensive applications over the fabric of FIG. 1 of GB1273528, believed to be one closest prior art. This will be explained in detail with reference to  FIGS.  1 - 6   . 
       FIG.  1    (cross-sectional view) and  FIG.  2    (top view) show said prior art fabric of FIG. 1 of GB1273528. This weave has central uncrimped warp filaments (one designated with numeral  1 ), uncrimped weft filaments (shown in cross-section in  FIG.  1   , some designated with numerals  201 - 216 ) and crimped warp filaments (the upper ones designated with numerals  31  and  32 ). The centres of adjacent uncrimped weft filaments (e.g.  212 ,  213 ) are spaced apart in warp direction of the fabric by a distance D which here is equal to the half-pitch distance L of the weave in warp direction, as shown in  FIG.  3   . Adjacent uncrimped weft filaments in vertical direction are matched in corresponding pairs (e.g.  208 / 216 ) the centres of which uncrimped weft filaments within a pair are separated in unsheared state by a vertical distance H. The crimped warp filaments  31 ,  32  entwine around the first uncrimped weft filaments  501 ,  502 ,  503 ,  504 ,  505 ,  506 ,  507 ,  508  and the second uncrimped weft filaments  509 ,  510 ,  511 ,  512 ,  513 ,  514 ,  515 ,  516  in alternating manner. 
       FIG.  3    is a schematic side view of the crimped warp filament  31  of  FIGS.  1  and  2   , once (upper part of  FIG.  3   ) without shear and once (lower part of  FIG.  3   ) at 20° shear. This filament  31  has, when seen in the fabric&#39;s warp direction from left to right, falling filament portions (one indicated with numeral  311 ) and rising filament portions (one indicated with numeral  312 ). When the fabric is sheared by 20° to the right (bottom part of  FIG.  3   ) the rising filament portions  312  of the crimped warp filament  31  are under tensile stress. If the crimped warp filament  31  is assumed to be of reasonable tenacity then its rising filament portions  312  do not elongate noticeably under that tensile stress. The uncrimped warp filament  1  is of high tenacity (GB1273528 designates these central uncrimped warp filaments as “strength giving”) and does not elongate noticeably under any tensile stress either. This means that the half-pitch L of the overall fabric and the length W of the rising filament portions  312  remain essentially constant in both unsheared and sheared state of the fabric, as shown in  FIG.  3   . The falling filament portions  311  of the crimped warp filament  31 , however, are under compressible stress when the fabric is sheared by 20°. The presumed reaction of these falling filament portions  311  to such compressible stress is (for monofilaments) some bulging outwards from their longitudinal axis or (for multifilaments) some fluffing up of the individual filaments contained therein or some bulking up of the multifilament. This presumed reaction of the falling filament portions  311  to the compressible stress is believed to be a major reason for possible delamination of an impregnation adhering to these falling filament portions  311 , and thus for delamination of such impregnation adhering to the warp filament  31 . This presumed reaction of the falling filament portions  311  to compressible stress cannot be adequately shown in  FIG.  3   . Instead  FIG.  3    shows a schematic shortening of the length of the falling filament portions  311  from V, unsheared state, to V′, sheared state. 
     This schematic shortened length V′ of the falling filament portions  311  is exactly calculable based on the shear angle, the filament diameters and the interfilament distances, and under said assumptions of L and W remaining constant as follows: 
                     V   ′     =         W   2     +     4   ⁢   L   ⁢           ⁢     sin   ⁡     (   δ   )       ⁢     (       L   ⁢           ⁢     sin   ⁡     (   δ   )         -           L   2     ⁢       sin   2     ⁡     (   δ   )         +     H   2           )                   (   1   )               
wherein W is said length of the rising filament portions  312  (being equal in unsheared state and sheared state, being furthermore equal in unsheared state to the length V of the falling filament portions  311 ), this W being calculable as follows:
 
 W =√{square root over ( L   2   +H   2 −( X+Y ) 2 )}  (2);
         wherein L and H are as defined above; X is the diameter of the uncrimped weft filament(s)  201 - 216 ; Y is the diameter of the crimped warp filament  31 ; and δ is the shear angle.       

     For meaningful shear angles δ the sin(δ) is greater than or equal zero. Furthermore, since L and H are always greater than zero, then always
 
 L  sin(δ)&lt;√{square root over ( L   2  sin 2 (δ)+ H   2 )}
 
This means that the term in brackets in (1) is always smaller than zero. V′ calculated by (1), at meaningful shear angle δ greater than zero, is then always smaller than W appearing in (1). Since W is equal to V, the length of the falling filament portions  311  in unsheared state, it follows that for any meaningful shear angle δ greater than zero the ratio V′:V is smaller than 1. In the exemplary embodiment of  FIGS.  1 - 3   , wherein L=H=15 units, X=4.35 units, Y=4.35 units and 6=20°, one obtains with the above formulae: W=V=19.35 units, V′=12.42 units and V′:V (=V′:W)=0.642. This corresponds to a schematic shortening of the falling filament portions  311  at 20° shear of 35.8%. This is indicative of a significant bulging outwards from their longitudinal axis (if the crimped warp filament  31  is a monofilament) or of a significant fluffing up or bulking up (if the crimped warp filament  31  is a multifilament), and thus to a significant tendency of an impregnation adhering to these falling filament portions  311  to delaminate under shear.
 
     The above considerations were made specifically for the crimped warp filament  31  appearing in  FIGS.  1 - 2   , but can be applied to any of the other crimped warp filaments shown therein, since they all have the same alternating entwinement with the uncrimped weft filaments. 
     However at given H and δ, the term
 
4 L  sin(δ)( L  sin(δ)−√{square root over ( L   2  sin 2 (δ)+ H   2 )})
 
appearing in (1) becomes closer to zero with increasing half-pitch L. This means that for increasing half-pitch L, the V′ calculated with (1) at given H, X, Y, and  6  becomes closer to W appearing in (1). Accordingly, the ratio of V′:V (=V′:W) becomes closer to unity with increasing half-pitch L.
 
       FIG.  4    (cross-sectional view) and  FIG.  5    (top view) show an exemplary fabric of the instant invention. This fabric also has uncrimped warp filaments  4 , first uncrimped and second weft filaments (shown in cross-section in  FIG.  4   ), designated with numerals  501 - 508  and  509 - 516 , respectively, and crimped warp filaments  61 - 64 . To each of the first uncrimped weft filaments  501  resp.  502  resp.  503  resp.  504  resp.  505  resp.  506  resp.  507  resp.  508  there is one corresponding second uncrimped weft filament  509  resp.  510  resp.  511  resp.  512  resp.  513  resp.  514  resp.  515  resp.  516 , and vice versa, to form successive filament pairs  501 / 509 ,  502 / 510 ,  503 / 511 ,  504 / 512 ,  505 / 513 ,  506 / 514 ,  507 / 515 ,  508 / 516 . Each of these successive pairs is designable with an integer index; e.g. according to the following Table 1: 
                         TABLE 1               filament pair   Exemplary index N for filament pair                  501/509   239 (= N D , because (N mod 4) = 3)       502/510   240 (= N A , because (N mod 4) = 0)       503/511   241 (= N B , because (N mod 4) = 1)       504/512   242 (= N C , because (N mod 4) = 2)       505/513   243 (= N D , because (N mod 4) = 3)       506/514   244 (= N A , because (N mod 4) = 0)       507/515   245 (= N B , because (N mod 4) = 1)       508/516   246 (= N C , because (N mod 4) = 2)                    
The index N assigned to each of the successive filament pairs is arbitrary, provided that it increases with the order of the successive filament pairs in warp direction. The index N may be in a range of N min  to N max , wherein N min  is the lowest possible index typically assigned to the first filament pair of the specimen of fabric in question, and wherein N max  is the highest possible index typically assigned to the last filament pair of the specimen of fabric in question. Whether a given index N is assigned the designation N A , N B , N C  or N D  depends on the result of the modulo 4 operation performed on N, as evidenced by above Table 1. The modulo 4 operation (N mod 4), as used here, is the remainder obtained by the so-called “Euclidean integer division” of N by 4.
 
     The weave types of the crimped warp filaments  61 - 64  in dependence of the above indexes N A -N D  of the filament pairs are as in following Table 2: 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 filament 
                 N A   
                 N B   
                 N C   
                 N D   
               
               
                   
               
             
            
               
                 61 (weave type c1) 
                 entwine 
                 pass between 
                 entwine 
                 pass between 
               
               
                   
                 around first 
                 first and 
                 around 
                 first and 
               
               
                   
                 uncrimped 
                 second 
                 second 
                 second 
               
               
                   
                 weft filament 
                 uncrimped 
                 uncrimped 
                 uncrimped 
               
               
                   
                 of such 
                 weft filaments 
                 weft filament 
                 weft filaments 
               
               
                   
                 filament pairs 
                 of such 
                 of such 
                 of such 
               
               
                   
                   
                 filament pairs 
                 filament pairs 
                 filament pairs 
               
               
                 64 (weave type c4) 
                 pass between 
                 entwine 
                 pass between 
                 entwine 
               
               
                   
                 first and 
                 around 
                 first and 
                 around first 
               
               
                   
                 second 
                 second 
                 second 
                 uncrimped 
               
               
                   
                 uncrimped 
                 uncrimped 
                 uncrimped 
                 weft filament 
               
               
                   
                 weft filaments 
                 weft filament 
                 weft filaments 
                 of such 
               
               
                   
                 of such 
                 of such 
                 of such 
                 filament pairs 
               
               
                   
                 filament pairs 
                 filament pairs 
                 filament pairs 
               
               
                 62 (weave type c2) 
                 entwine 
                 pass between 
                 entwine 
                 pass between 
               
               
                   
                 around 
                 first and 
                 around first 
                 first and 
               
               
                   
                 second 
                 second 
                 uncrimped 
                 second 
               
               
                   
                 uncrimped 
                 uncrimped 
                 weft filament 
                 uncrimped 
               
               
                   
                 weft filament 
                 weft filaments 
                 of such 
                 weft filaments 
               
               
                   
                 of such 
                 of such 
                 filament pairs 
                 of such 
               
               
                   
                 filament pairs 
                 filament pairs 
                   
                 filament pairs 
               
               
                 63 (weave type c3) 
                 pass between 
                 entwine 
                 pass between 
                 entwine 
               
               
                   
                 first and 
                 around first 
                 first and 
                 around 
               
               
                   
                 second 
                 uncrimped 
                 second 
                 second 
               
               
                   
                 uncrimped 
                 weft filament 
                 uncrimped 
                 uncrimped 
               
               
                   
                 weft filaments 
                 of such 
                 weft filaments 
                 weft filament 
               
               
                   
                 of such 
                 filament pairs 
                 of such 
                 of such 
               
               
                   
                 filament pairs 
                   
                 filament pairs 
                 filament pairs 
               
               
                   
               
            
           
         
       
     
     That is, the above weave types c1, c4, c2 and c3 differ only in that their entwining around first uncrimped weft filaments, their passing between first and second uncrimped weft filaments, their entwining around second uncrimped weft filaments and their passing between first and second uncrimped weft filaments is permutated cyclically over the indexes N A , N B , N C  and N D  when going from c1 to c4 to c2 to c3. 
       FIG.  6    is a schematic side view of the crimped warp filament  61  of the inventive fabric of  FIGS.  4 - 5   , once (upper part of  FIG.  6   ) without shear and once (lower part of  FIG.  6   ) at attempted 20° shear. 
     Analogously as the fabric of  FIGS.  1 - 3   , this crimped warp filament  61  has again falling filament portions (one indicated with numeral  611 ) of length V and again rising filament portions (one indicated with numeral  612 ) of length W, wherein W=V in the unsheared state. Again here, if the fabric is sheared, the rising filament portions  612  come under tensile stress. As in the fabric of  FIGS.  1 - 3   , the half pitch L and the length W of the rising filament portions  612  may be assumed unchanged in unsheared and sheared state if the uncrimped warp filaments  4  and the crimped warp filaments  61 - 64  are assumed of reasonable tenacity. Again analogously as in the fabric of  FIGS.  1 - 3   , the falling filament portions  611 , when under shear, come under compressible stress and their length V′ becomes schematically shorter under that compressible stress. That length V′ is again calculable by above formula (1) and W contained therein again is calculable by above formula (2). The shortening of V′ is again indicative of some bulking up or fluffing up of these falling filament portions  611 , and thus of some tendency of an impregnation to delaminate under shear stress. 
     However, unlike to the fabric of  FIGS.  1 - 3   , in the fabric of  FIGS.  4 - 6    the half pitch L of the weave in warp direction is not equal to the distance D between centres of adjacent uncrimped weft filaments; it its about twice that distance D. This is is because in the inventive fabric there are always extra filament pairs which allow passing of the crimped warp filaments  61 - 64  between their first and second uncrimped filaments. The half-pitch L in the inventive fabric is thus generally longer, typically about twice as long, as the half pitch L of the fabric of  FIGS.  1 - 3    under otherwise identical features. 
     In keeping with the above explanation for to the behaviour of formula (1) with increasing half pitch L it is possible to predict that, at a given shear angle δ with otherwise identical parameters H, X, and Y (and thus W), the shortening of V′ will be less pronounced with the fabric of  FIGS.  4 - 5    than with the fabric of  FIGS.  1 - 3   , and that the ratio of V′:V (=V′:W) will generally be more close to unity than with the fabric of  FIGS.  1 - 3   . In the exemplary embodiment of  FIGS.  4 - 6   , wherein L=30 units, H=15 units, X=4.35, Y=4.35 units and 6=20°, one obtains with the above formulae: W=V=32.39 units, V′=26.29 units, and V′:V (=V:W)=0.831. 
     This corresponds to a schematic shortening of the falling filament portions  611  at attempted 20° shear of only 16.9%. This schematic shortening is considerably less than the abovementioned 35.8% schematic shortening observed for the fabric of  FIGS.  1 - 3    under 20° shear. By the less pronounced schematic shortening of the falling filament portions  611  of  FIG.  6    with respect to the schematic shortening of the falling filament portions  311  of  FIG.  3   , it is possible to predict that the falling filament portions  611  of  FIG.  6    will in reality not bulge outwards, bulk up or fluff up as strongly as the falling filament portions  311  of  FIG.  3   . 
     It is therefore firstly possible to predict that the fabric of  FIGS.  4 - 6    under shear will have a lower tendency to delaminate an impregnation adhering to its falling filament portions  611  than the fabric of  FIGS.  1 - 3    will have under the same shear for its falling filament portions  311 . 
     Furthermore, in the fabric of  FIGS.  4 - 6    there are the mentioned extra filament pairs (e.g.  503 / 511  or  508 / 516  in  FIG.  6   ) which allow passing of the crimped warp filaments (e.g.  61  in  FIG.  6   ) between their first and second uncrimped filaments. The formula for calculating the schematic distance H′ between the centres of first uncrimped weft filament (e.g.  503  or  508  in  FIG.  6   ) and second uncrimped weft filament (e.g.  511  or  516  in  FIG.  6   ) in any such filament pairs in sheared state of the fabric is:
 
 H′=L   2  sin 2 (δ)+ H   2   −L  sin(δ)  (3)
 
     wherein H, L and δ are as defined above. 
     Since L and H are always greater than zero, and since for meaningful shear angles δ the sin(δ) is greater than or equal zero, the H′ calculated with formula (3) becomes smaller with increasing half-pitch L. The H′ by formula (3) is equal to H when the shear angle δ is zero and becomes smaller than H when δ is greater than zero. 
     By the behaviour of above formula (3) it is therefore secondly possible to predict that, by virtue of H′ becoming smaller with increasing shear angle δ, the said extra filament pairs (e.g.  503 / 511  in  FIG.  6   ) will start to laterally compress the falling filament portions  611 , which will partially counteract their said bulging outwards, bulking up or fluffing up, thus furthermore preventing delamination of the impregnation adhering to these falling filament portions  611 . 
     By the behaviour of above formula (3) it is therefore thirdly possible to predict that, by virtue of H′ converging towards zero with increasing half pitch L, the reduction of the distance H′ will be more pronounced in the fabric of  FIGS.  4 - 6    than in the fabric of  FIGS.  1 - 3   , because in the former fabric the half-pitch L is about twice the distance D between adjacent uncrimped weft filaments, whereas in the latter the half-pitch L is only equal to that distance D. Accordingly it its predicted that the fabric of  FIGS.  4 - 6    cannot be sheared as strongly as the fabric of  FIGS.  1 - 3   , because of the stronger tendency of the former to become compressed (the more pronounced reduction of H′). The schematic representation in the lower part of  FIG.  6    actually predicts that the fabric of  FIGS.  4 - 6    resists a shearing to 20°, in view of the graphical overlap of the uncrimped weft filaments  501 - 516  with the crimped warp filament  61  and with the uncrimped warp filament  4 . In contrast thereto, the fabric of  FIGS.  1 - 3    can schematically be sheared to 20° without graphic overlap of any filaments. 
     The above considerations were made specifically for the crimped warp filament  61  appearing in  FIGS.  4 - 5   , but can be applied to any of the other crimped warp filaments  62 ,  63  and  64  shown therein, since they all have the same weaving type as crimped warp filament  61 . 
     In view of the foregoing the fabric of  FIGS.  4 - 6   , when included into a belt and impregnated, is predicted to be less prone to shear delamination of that impregnation than the fabric of  FIGS.  1 - 3    in an analogously impregnated belt. A suitable practical test setup for testing for resistance to delamination under shearing stress is described in the below examples. 
     Essential for this improved resistance to shear delamination is thus that the fabric of the invention contains both crimped warp filaments  61 - 64  of the weave type discussed for  FIGS.  4 - 5    and contains uncrimped warp filaments  4 , but does not contain any alternatingly entwining crimped warp filaments of the type discussed for  FIGS.  1 - 3   . 
     In keeping with the foregoing considerations, the inventive fabric may optionally contain, as shown in  FIG.  4   , a third layer (C) of uncrimped third weft filaments  517 - 524  running essentially in parallel to each other and being spaced apart from each other by said distance D. For each of the second uncrimped weft filaments ( 509  resp.  510  resp.  511  resp.  512  resp.  513  resp.  514  resp.  515  resp.  516  resp.  517 ) there is one corresponding uncrimped third weft filament  517  resp.  518  resp.  519  resp.  520  resp.  521  resp.  522  resp.  523  resp.  524 , and vice versa, to form successive further filament pairs  509 / 517 ,  510 / 518 ,  511 / 519 ,  512 / 520 ,  513 / 521 ,  514 / 522 ,  515 / 523 ,  516 / 524 . Each successive further filament pair comprising a given second uncrimped weft filament  509  resp.  510  resp.  511  resp.  512  resp.  513  resp.  514  resp.  515  resp.  516  resp.  517  is designable with the same index N as the successive filament pair comprising that same second uncrimped weft filament  509  resp.  510  resp.  511  resp.  512  resp.  513  resp.  514  resp.  515  resp.  516  resp.  517 , as exemplified by above Table 1. There are then crimped further warp filaments  71 - 74  having one of the weave types c1-c4 discussed above for the crimped warp filaments  61 - 64 . However, in these above weave descriptions, any reference to a “first uncrimped weft filament” needs to be replaced by a reference to a “second uncrimped weft filament” and any reference to a “second uncrimped weft filament” needs to be replaced by a reference to a “third uncrimped weft filament”, in order to obtain the weave type description for the further crimped warp filaments  71 - 74 . 
     It is preferred for the fabric of the invention that crimped warp filaments of above weave types c1 and c2 always appear pairwise and immediately adjacent to each other, and that crimped warp filaments of above weave types c3 and c4 always appear pairwise and immediately adjacent to each other. It is more preferred for the fabric of the invention that the crimped warp filaments  61 - 64  and the uncrimped warp filaments  4  are present in repetitive units in weft direction, wherein the order in which crimped warp filaments  61  (with weave type c1), crimped warp filaments  62  (with weave type c2), crimped warp filaments  63  (with weave type c3), crimped warp filaments  64  (with weave type c4) and uncrimped warp filaments  4  are arranged in weft direction is always the same. If a third layer C of uncrimped weft filaments  517 - 524  is present, then it is again preferred that the further crimped warp filaments  71 - 74  and the further uncrimped warp filaments  8  are present in repetitive units, wherein the order in which crimped further warp filaments  71  (with weave type c1), crimped further warp filaments  72  (with weave type c2), crimped further warp filaments  73  (with weave type c3), crimped further warp filaments  74  (with weave type c4) and uncrimped further warp filaments  8  appear is always the same, and is the same as the order within the repetitive units of crimped warp filaments  61 - 64  and uncrimped warp filaments  4 . 
     In one preferred embodiment of the fabric the ratio of crimped warp filaments  61 - 64  to uncrimped warp filaments  4  may be 4:1. If therein these warp filaments occur in repetitive units, wherein the order of the filaments in these repetitive units is always the same, then exemplary such orders (filament numbers and, where applicable, weave types in parentheses) are  61 ( c 1)- 62 ( c 2)- 4 - 63 ( c 3)- 64 ( c 4) or any cyclic permutation thereof. Analogously, if a third layer C of further uncrimped weft filaments  71 - 74 , further crimped warp filaments  517 - 524  and further uncrimped warp filaments  8  are present, then the order of these filaments would accordingly be  71 ( c 1)- 72 ( c 2)- 8 - 73 ( c 3)- 74 ( c 4) or the cyclic permutation thereof that corresponds to the above cyclic permutation. 
     In another preferred embodiment of the fabric the ratio of crimped warp filaments  61 - 64  to uncrimped warp filaments  4  may be 12:1. If therein these warp filaments occur in repetitive units, wherein the order of the filaments in these repetitive units is always the same, then exemplary such orders (filament numbers and, where applicable, weave types in parentheses) are  63 ( c 3)- 64 ( c 4)- 61 ( c 1)- 62 ( c 2)- 63 ( c 3)- 64 ( c 4)- 4 - 61 ( c 1)- 62 ( c 2)- 63 ( c 3)- 64 ( c 4)- 61  (c1)- 62 ( c 2) or any cyclic permutation thereof. Analogously, if a third layer of further uncrimped weft filaments  71 - 74 , further crimped warp filaments  517 - 524  and further uncrimped warp filaments  8  are present, then the order of these filaments would accordingly be  73 ( c 3)- 74 ( c 4)- 71 ( c 1)- 72 ( c 2)- 73 ( c 3)- 74 ( c 4)- 8 - 71 ( c 1)- 72 ( c 2)- 73 ( c 3)- 74 ( c 4)- 71 ( c 1)- 72 ( c 2) or the cyclic permutation thereof corresponding to the above cyclic permutation. 
     If the warp filaments occur in repetitive units, wherein the order of the filaments in these repetitive units is always the same, and antistatic filaments are also present, then preferably again these antistatic filaments are included always at the same position within a repetitive unit. Apart from that, their number and position(s) in a repetitive unit is arbitrary. Preferably there is one such antistatic filament per repetitive unit. 
     It is preferred for the fabric of the invention that all uncrimped weft filaments  501 - 524  are monofilaments, more preferably such monofilaments having a diameter in the range of 0.05 to 2 mm, preferably of 0.25 to 0.45 mm. The uncrimped weft filaments are preferably made of polyester, such as PET. The titer of the uncrimped weft filaments is preferably in the range of 670 to 2100 dtex. 
     It is preferred for the fabric of the invention that all crimped warp filaments  61 - 64 ,  71 - 74  are multifilaments, spun yarns or a combination of multifilament yarns and staple fibres spun together by the commonly known “core-spinning” process. Any such crimped warp filaments are preferably devoid of natural fibres, such as cotton, jute, hemp or cellulose-based fibres. The impregnation adheres sufficiently to the inventive fabric even in the absence of such natural fibres. The crimped warp filaments are preferably made of polyester such as PET. The titer of the crimped warp filaments is preferably in the range of 500 to 2000 dtex, particularly if made from polyester such as PET. Also preferably, the tenacity of the crimped warp filaments is preferably in the range of 15 to 250 cN/tex, more preferably in the range of 15 to 40 cN/tex and most preferably of 20 to 30 cN/tex. Also preferably, their heat shrinkage (percentual length reduction under heating for 2 min at 180° C.) is in the range of 0.5 to 15%, more preferably of 5 to 15% and most preferably of 8 to 12%. Also preferably, if the crimped warp yarns are spun yarns, then they may preferably have a number of turns per metre preferably being in the range of 0 to 400, more preferably of 250 to 400 and most preferably of 300 to 400 
     It is preferred for the fabric of the invention that all uncrimped warp filaments  4 ,  8  are multifilaments, or a plurality of such multifilaments, e.g.  3 - 8  such multifilaments, arranged in parallel and immediately adjacent to each other. The uncrimped warp filaments are preferably made of polyester, in particular PET, or aramid. The titer of the uncrimped warp filaments (or, if there is a plurality of multifilaments, the sum of the titer of all them) is preferably in the range of 500 to 5000 dtex. More preferably, if the uncrimped warp filaments are of polyester such as PET, their titer (or, if there is a plurality of multifilaments, the sum of the titer of all them) is in the range of 550 to 2000 dtex; if they are of Aramid, then their titer is more preferably in the range of 440 to 3500 dtex. Also preferably, the tenacity of the uncrimped warp filaments (or, if there is a plurality of multifilaments, the overall tenacity of the entire plurality) is preferably in the range of 15 to 250 cN/tex, more preferably in the range of 30 to 100 cN/tex and most preferably of 60 to 80 cN/tex. Also preferably, their heat shrinkage (percentual length reduction under heating for 2 min at 180° C.) is in the range of 0.5 to 15%, more preferably of 0.5 to 5% and most preferably of 1 to 2%. Also preferably, the uncrimped warp multifilaments may preferably have an S- or Z-twist, with the number of turns per metre preferably being in the range of 0 to 400, more preferably of 50 to 300 and most preferably of 70 to 140. 
     The fabric of the invention may optionally furthermore comprise crimped antistatic filaments, as known in the prior art. These crimped antistatic filaments then have one of the weave types c1-c4 exemplified above. These antistatic filaments preferably are spun yarns, e.g. of carbon fibres, or are conductive polyester, cotton, nylon or aramid fibres having a metallic conductor adhered thereto, coated thereonto or embedded therein. Such conductive fibres are as such conventional. The tenacity of the crimped antistatic filaments is preferably in the range of 15 to 250 cN/tex, more preferably in the range of 15 to 40 cN/tex and most preferably of 20 to 30 cN/tex. Also preferably, their heat shrinkage (percentual length reduction under heating for 2 min at 180° C.) is in the range of 0.5 to 15%, more preferably of 5 to 15% and most preferably of 8 to 12%. Also preferably, the crimped antistatic filaments may preferably have an S- or Z-twist, with the number of turns per metre preferably being in the range of 0 to 400 and more preferably of 100 to 400. More preferably there is exactly one crimped antistatic filament separated by every four consecutive uncrimped warp filaments. 
     The belt of the invention is made by providing a fabric of the invention, as described above, and impregnating this according to standard procedures, such as melt coating, calendering, rotocure, etc., with an impregnation of an elastomer (rubber), a thermoplastic or a thermoplastic elastomer. By “impregnation” is meant that the fabric is completely embedded into the impregnation, with no filament segments protruding from the top and bottom surfaces of the belt. “Impregnation” may also mean that the belt may have a top and a cover layer each consisting only of the impregnation, and providing said top and bottom surfaces, respectively, of the belt. In one preferred embodiment, this top layer is relatively thick, such as about 10 to 30% of the belt&#39;s overall thickness, and the bottom layer is relatively thin, such as about 1 to 5% of the belt&#39;s overall thickness. In this preferred embodiment, the top layer&#39;s top surface is the one where goods are conveyed, and the bottom layer&#39;s bottom surface is the one that comes into contact with a support and/or rollers. The thin bottom layer minimizes abrasion of impregnation material when being in contact with the support and/or the rollers, which is advantageous when there is shear between the top and bottom surfaces. In another preferred embodiment, both the top layer and the bottom layer are relatively thick, such as about 10 to 30% of the belt&#39;s overall thickness, and then either of the top and bottom layers may serve to convey goods or to be in contact with the support and/or the rollers. More preferably then, both the top and the bottom layers have the same thickness. This allows the belt&#39;s orientation to be inverted, if one of the top or the bottom layer should have become too strongly abraded, thus extending the belt&#39;s service life. 
     The elastomer (rubber) as the impregnation may preferably be selected from natural rubber, polyisoprene, polybutadiene, styrene-butadiene rubber (SBR), nitrile-butadiene rubber (NBR), ethylene-propylene-diene rubber (EPDM) and acrylate rubber. It is preferably impregnated into the fabric in unvulcanised or uncrosslinked state and subsequently vulcanized or crosslinked according to customary procedures. 
     The thermoplastic as the impregnation may preferably be selected from the group consisting of thermoplastic polyolefins (such as polyethylene or polypropylene), substantially random ethylene/C3-12-α-olefin copolymers (examples of the α-olefin being 1-propene, 1-butene, 1-pentene, 1-hexene and 1-octene), thermoplastic polyamides, ethylene-vinylacetate copolymers, poly(vinylacetate) and PVC. 
     The thermoplastic elastomer as the impregnation may preferably be selected from the group consisting of thermoplastic elastomeric block copolymers (such as styrenic block copolymers, in particular styrene-butadiene-styrene, styrene-isoprene-styrene, styrene-ethylene/butylene-styrene and styrene-ethylene/propylene-styrene block copolymers), copolymers of hard blocks of medium density polyethylene and of soft blocks of ethylene/α-olefin copolymers, thermoplastic polyurethanes (such as copolymers of polyester diols or polyether diols with diisocyanates), polyether-/ester block amides and thermoplastic elastomeric ionomers. 
     The impregnation is preferably made of a thermoplastic elastomer, more preferably of a TPU. Suitable TPU&#39;s may be obtained by reacting diisocyanate-containing hard block segments with polyester diol soft block segments. Preferably the impregnation is applied to the fabric without the aid of any adhesion promoters. That is, both the inventive fabric before impregnation and the impregnating composition itself are devoid of such adhesion promoters. The impregnation adheres to the inventive fabric even in the absence of such adhesion promoters. Exemplary customary adhesion promoters that are preferably absent are halogenated polymers, in particular chlorinated polyolefins, comprising a crosslinking agent. 
     The belt of the invention may optionally be coated on its top and/or bottom surfaces with customary coatings, e.g. which enhance resistance against solvents, or which contain antibacterial agents. 
       FIG.  7    is a schematic cross-sectional view of a belt of the invention containing the fabric of the invention, along its longitudinal direction, cutting through the uncrimped warp filament  4  and the first uncrimped and second weft filaments  501 - 508  and  509 - 516 , respectively. The longitudinal direction of the belt is for the purposes of the invention also considered to be the belt&#39;s travel direction. Accordingly the fabric&#39;s warp direction (along the crimped warp filament&#39;s  61 - 64 ) coincides with the belt&#39;s longitudinal direction. The first uncrimped and second weft filaments  501 - 508  and  509 - 516 , respectively, are monofilaments made of polyester and in the exemplified embodiment have a thickness of 0.25-0.45 mm. The uncrimped warp filament  4  is typically a multifilament made of polyester or, more preferable, of Aramid. In the exemplified embodiment it may either be one single Aramid multifilament of 440 to 3500 dtex, or a plurality of such multifilaments, e.g.  3 - 8  such filaments, arranged in parallel and immediately adjacent to each other. The crimped warp filament&#39;s  61 - 64  are typically multifilaments made of polyester and in the exemplified embodiment have a titer of 550 to 2000 dtex. There are typically 4 or 12 crimped warp filaments  61 - 64  per uncrimped warp filament  4 , wherein the latter ratio of 12:1 applies in particular to the above mentioned embodiment of the uncrimped warp filament  4  being a plurality of filaments arranged in parallel and immediately adjacent to each other. This belt of the invention has an overall thickness of typically in the range of 1 to 3 mm. The two arrows indicate the opposite directions of frictional forces that act onto the belt&#39;s top side  9  and on the belt&#39;s bottom side  10  and which cause a shear inside the belt. This is the shear that would typically occur in an application according to the invention of such belt. This belt has an impregnation  11  made of a thermoplastic or thermoplastic elastomer, in particular a TPU, such as of Lubrizol&#39;s Estane® TPU types. This exemplary impregnated conveyor belt is considered as an example of a light conveyor belt. 
     Exemplary uses of the belt of the invention where a shear between the belt&#39;s top surface and bottom surface in the belt&#39;s longitudinal direction occurs or is expected to occur are now described. 
     A first such use is in food processing. There the belt&#39;s top surface is intermittently cleaned in running operation from debris, dust or dirt using a knife which grates along the top surface. The grating knife exerts a shear onto the belt. 
     A second such use is in treadmills. There the belt runs over a fixed supporting board, whereas the runner exercising on the treadmill accelerates the belt&#39;s top surface with his feet while running on the section of the belt lying on said supporting board. The shear occurs between the belt&#39;s bottom side lying on the fixed board and the belt&#39;s top side being accelerated by the runner&#39;s feet. 
     A third such use is in mail sorting machines. There are driven belts which convey a piece of mail by cooperating with a fixed support or by cooperating with a non-driven belt. The fixed support does not move at all. Therefore the piece of mail exerts a braking, thus shearing, action onto the driving belt&#39;s top surface while being conveyed by the driving belt. Similarly a shear occurs in the non-driven belt because it is accelerated over its top surface by the the conveyed piece of mail. Details of such mail sorting machines and of the above two mail conveying methods are disclosed in  FIGS.  3 - 5    and the associated description of WO 2015/011090 A1. 
     Further to improved resistance to delamination under shearing stress, as discussed above with reference to  FIGS.  1 - 6   , the inventive belt also exhibits improved resistance to delamination under so called “wear and tear” conditions, namely under prolonged cycling with bending over pulleys of small diameter. This was determined experimentally and is described in the below examples, also with reference to  FIGS.  8 - 9   . 
     The invention will now be illustrated by the following non-limiting examples. 
     EXAMPLES 
     Example 1: Test Setup for Testing for Resistance to Delamination Under “Wear and Tear” Conditions or Under Shearing Stress 
     The test setup allows for testing for susceptibility to delamination under either predominantly “wear and tear” conditions ( FIG.  8   ) or under predominantly “shearing” conditions ( FIG.  9   ). In both setups the endless belt (inventive or comparative) is cycled in a loop comprising at least a driving pulley  12  and idler pulleys  13 , 14  which all impart the belt a convex bend. 
     In the “wear and tear” setup ( FIG.  8   ) there is a further idler pulley  15  which imparts the belt a concave bend. The idler pulleys  13 , 14 , 15  are of sufficiently small diameter (typically 30-40 mm at the most) such as to cause, by the repeated bending around these small diameter pulleys, a fatigue in the interface between fabric and impregnation. 
     In order to account for having two convex bending pulleys  13 , 14  and only one concave bending pulley  15  it is possible to choose the diameter of the latter smaller than the diameter of the two former, to have the same “wear and tear” effect in both convex and concave bending directions. 
     In the “shearing” setup ( FIG.  9   ) there is however a further concave bending braking pulley  16 . This pulley  16  counteracts by a braking torque T B  [Nm] exerted onto its axle  161  or onto its surface (the figure shows an exemplary shoe brake  17  acting onto the braking pulley&#39;s surface) the driving torque T D  [Nm] exerted by the driving pulley  12 . The driving torque T D  acts on the belts interior (pulley) surface, whereas the braking torque T B  acts on the belt&#39;s exterior (conveying) surface. These two torques produce in the belt longitudinal forces in opposing directions, namely a driving force F D  and a braking force F B , and thus a shear in the belt. T D  must be greater than T B  so that the belt keeps looping. Furthermore the coefficients of friction between belt surfaces and pulley surfaces, the forces inside the belt (produced by T D , T B  and Fw) and the angles by which the belt sweeps over the driving pulley  12  and the braking pulley  16  must be such as that no slipping over either of these two pulleys occurs. This can however be easily be determined either over the Eytelwein formula or by experiment. 
       FIG.  9    shows the driving pulley  12  and braking pulley  16  rotating counterclockwise, accordingly the said forces in opposing directions and the shear, again designated by  6 , arise mainly on the right side of the belt loop, as shown in the figure. 
     If driving pulley  12  and braking pulley  16  rotated clockwise, then the opposing forces and the shear would arise mainly on the left side of the belt loop. 
     In the “shearing” setup of  FIG.  9    all pulleys are of sufficiently large diameter (typically at least 100 mm, preferably 130 mm or more) so as to minimise the “wear and tear” effects by the bending over the pulleys. 
     In both setups of  FIGS.  8  and  9    the concave bending pulleys (idler pulley  15  and braking pulley  16 ) are located on an axle  151  or  161 , respectively, which can be displaced vertically (double arrows in both  FIGS.  8  and  9   ) and which, by an appropriate tensioning force Fw, can impart the belt the required tensioning. Fw [N] is calculated according to the formula:
 
 Fw= 2× k   1%   ×b×ε   0  
 
wherein:
         k 1%  is the tensile force needed to achieve 1% elongation per unit of belt width [N/mm], determined after relaxation according to EN ISO 21181: 2013 (light conveyor belts—determination of the relaxed elastic modulus), which
           in the “wear and tear” setup of  FIG.  8    is determined on the open belt before any cycling;   in the “shearing” setup of  FIG.  9    is determined on the re-opened belt, after “running in” in endless form by cycling 10′000 times on that test setup;   
           b is the width of the belt [mm], which can be arbitrarily chosen, but is typically in the range of 10 to 50 mm; and   ε 0  is the belt elongation [%] that is intended in the test setup after relaxation, normally 0.5%.       

     The Fw is applied perpendicularly to the axle  151  or  161 , e.g. by means of a counterweight or by means of a spring scale. 
     Example 2: Comparative Test of an Inventive Belt and a Prior Art Belt for Resistance to Delamination Under “Wear and Tear” Conditions 
     An inventive belt, containing a fabric construction similar as the one of  FIG.  4    was compared with a prior art belt marketed by the applicant under the code EMB-12EMCH, having two discrete layers of plain weave PET. The test setup was similar to the one of  FIG.  8   , to show improvement of the inventive belt with respect to delamination susceptibility under “wear and tear” conditions. The parameters of the belt and of the test setup were as in following Table 3: 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                   
                 EMP-12EMCH 
               
               
                   
                 Inventive belt 
                 (prior art) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 overall belt thickness 
                 1.2 
                 1.7 
               
               
                 [mm] 
               
               
                 k 1%  (measured after 
                 11 
                 13 
               
               
                 relaxation before any 
               
               
                 looping) [N/mm] 
               
               
                 Diameter of driving 
                 130 
                 130 
               
               
                 pulley 12 [mm] 
               
               
                 Diameter of idler 
                 30 
                 40 
               
               
                 pulleys 13, 14, 15 
               
               
                 [mm] 
               
               
                 b [mm] 
                 40 
                 40 
               
               
                 ε 0  [%] 
                 0.5 
                 0.5 
               
               
                 Fw [N] 
                 440 
                 520 
               
               
                 Number of cycles by 
                 5 million 
                 5 million 
               
               
                 which belt was looped 
               
               
                 over the test setup 
               
               
                 cycling speed [m/s] 
                 10 
                 10 
               
               
                 Impregnation material 
                 thermoplastic 
                 thermoplastic 
               
               
                   
                 polyurethane (TPU), 
                 polyurethane (TPU), 
               
               
                   
                 Estane type 
                 Estane type 
               
               
                 end joining type to make 
                 finger end, using TPU 
                 finger end, using TPU 
               
               
                 belt endless for looping 
                 impregnation as 
                 impregnation as 
               
               
                   
                 hotmelt adhesive 
                 hotmelt adhesive 
               
               
                   
               
            
           
         
       
     
     The assessment of the two belts was as follows:
         Inventive belt: There was no peeling off of the impregnation after the test. Neither were there any cracks or disruptions visible on either of the two belt sides, whether outside of the finger end joint are or at the finger end joint area. It was not possible to peel the impregnation layer off the double layer fabric, neither before nor after the test; the adhesion of the impregnation to the double fabric was always higher than the adhesion within the impregnation layer itself.   Prior art belt: The belt showed after the test several types of defects, among which cracks and disruptions in longitudinal and/or transversal direction (both outside and inside the finger end area). It was possible to peel the impregnation layer off the fabric. Before the test the required force for peeling off the impregnation was in the range of 30-50 N per cm of belt width; after the test the required force was lowered to less than 10 N per cm of belt width. Sometimes the two individual fabrics could be peeled off from each other.