Patent Publication Number: US-6910508-B2

Title: Method for weaving a double layer cloth

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to a method for weaving a double layer cloth and to uses of the method, in particular for manufacturing airbag cloths. 
   U.S. Pat. No. 5,651,395 describes methods for the manufacture of bags for airbags, with double layer cloths being produced for this manufacturing process. In cloths of this kind, two-layered regions can be distinguished from single-layer regions. The inflatable inner spaces of the bags are formed by the two-layered regions, which consist in each case of a lower and an upper cloth. In the single-layer regions, warp threads, which are located separately in the two-layer regions either in the upper or the lower cloth, are made to one another through technical binding measures to form a common partial cloth. The closed seams of the bags can be manufactured from the single-layer regions, which completely surround the two-layered ones. 
   High demands are placed on the quality of the double layer cloths, for example for airbags—i.e. on the so-called product rejection. The warp and weft threads must be uniformly and relatively densely arranged in the cloth. The deviation from a specified air permeability of the lower and the upper cloth respectively should be a minimum. The cloth layers must thus be as uniformly impermeable as possible. The threads used must be able to withstand high stresses in regard to tension and extension. The double layer cloth for airbags is a measured product, namely a cloth which is manufactured to an exact measure. On weaving machines which are equipped in the usual manner, the double layered nature has unfavorable effects on the product rejection when measured products are to be manufactured. 
   During the transport of the cloth by means of a drive roller (or a cloth draw-off beam) away from the location at which the weft threads are inserted and beaten up (beat-up edge, cloth edge), the cloth layers are mutually displaced, which leads to disadvantageous transverse folds. The non-uniform transport of the two layers arises in a so-called bar temple or spreader bar, which is usually used for the positioning of the beat-up edge and the spreading of the cloth. A spreader bar with left-hand/right-hand thread, which is arranged before the drive roller, additionally contributes to the formation of folds. 
   A method is also known from SU-A-1703731 by means of which the formation of folds could be prevented. In this method, however, needles are stuck into the cloth, which would impair the impermeability of the airbag. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to create an improved method for weaving a double layer cloth in which the disadvantageous formation of folds is avoided or lessened. 
   The method for weaving a double layer cloth serves in particular for the manufacture of airbag cloths. It is carried out using a weaving machine which includes, between the weaving sley and the cloth beam, a temple arrangement which is arranged directly after a beat-up edge, a deflection element for the cloth and a drive roller. The produced cloth is transported away from the beat-up edge with the drive roller and using suitable means in such a manner that both layers of the cloth—the lower cloth and the upper cloth respectively—are acted on by largely symmetrical forces. The cloth in the temple arrangement is drawn against frictional resistances through a gap between two stationary surfaces and is at the same time stretched transversely to the transport direction by lateral temple arrangements. The cloth is driven by a rotatable pressing roller, which is used in addition to the drive roller, with the pressing roller, which forms the deflection element, cooperating with the drive roller. 
   The invention will be explained in the following with reference to the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partial, schematic illustration of a weaving machine with a cloth draw-off process being practiced, in which a disadvantageous development of folds arises, 
       FIG. 2  is a cross-section through a bar temple which is used in the weaving machine of  FIG. 1 , 
       FIG. 3  shows two longitudinal sections through airbags which are manufactured of double layer cloth, 
       FIG. 4  shows a cloth draw-off in a weaving machine which uses a temple arrangement in accordance with the present invention, 
       FIGS. 5 ,  6  show two variant forms of the temple arrangement, 
       FIG. 7  is a partial illustration of the weaving machine of  FIG. 4 , 
       FIG. 8  shows a first product made with the method of the present invention, from which rectangular bags or hollow cloth sections can be manufactured, and 
       FIG. 9  shows a second product for the manufacture of round bags or of hollow cloth sections. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  illustrates schematically and only partly a weaving machine in which a cloth draw-off is associated with the occurrence of disadvantageous fold formation. Shown are warp threads  1 ″ for an upper shed and warp threads  2 ″ for a lower shed and a sley  3  for the beating up of non-illustrated weft threads, with which, together with the warp threads  1 ″ on the one hand and the warp threads  2 ″ on the other hand, the upper cloth  1  and the lower cloth  2  are respectively manufactured. Shown in addition are: a beat-up edge  30 ; a bar temple  4 , which is illustrated in more detail in  FIG. 2 ; a bar-shaped deflection element  5 ′ for the cloth layers  1  and  2 ; a drive roller  6  and a pressing roller  7 , following which is a non-illustrated cloth beam (e.g. cloth beam  10  in FIG.  7 ). 
   The bar temple  4 , the cross-section of which can be seen in  FIG. 2 , comprises a rotatable bar  41  which is driven through the cloth layer  1  and a support pan  42  which is composed of two parts  42   a  and  42   b . The warp threads  1 ″ and  2 ″, which are bound in into the cloths  1  and  2 , are indicated by wavy lines  1 ′ and  2 ′. The upper cloth  1  moves with a velocity v 1 , the lower cloth  2  with a velocity v 2 . The cloths  1  and  2  are pressed against the support pan  42  by the bar  41 . Since frictional forces F act between the lower cloth  2  and the support pan  42  and since the bar  41  executes a rotational movement corresponding to the velocity v 1 , v 1  is somewhat greater than v 2 ; there is thus a displacement between the two cloths  1  and  2 . This disadvantageous displacement effect is the most highly pronounced at the deflection points  421  and  422  (“stagnation points”). The deflection element  5 ′ also contributes to the displacement effect at a “stagnation point”  50 . 
     FIG. 3  shows, by means of two longitudinal sections through double layer cloths  1 ,  2 , at the top, a product (airbag) as it should look in the ideal case and, at the bottom, a product (schematically illustrated) as it actually arises as a result of the displacement effects. The warp threads  1 ′ and  2 ′ are made to cross locally through technical binding measures to form common cloth parts  12  for the purpose of producing seams. Zones  101  and  102  in which folds arise can be recognized mainly at the edge of these locations. 
   A cloth draw-off in a weaving machine in which the method in accordance with the invention is used is shown in FIG.  4 . In this method for weaving a double layer cloth, the produced cloth  1 ,  2  is transported away from the beat-up edge  30  with the drive roller  6  and using suitable means in such a manner that the two layers  1  and  2  of the cloth are acted on by largely symmetrical forces. These suitable means consist of special temple arrangement  4  and a deflection element which is formed as a pressing roller  5 . In the temple arrangement  4  the cloth  1 ,  2  is drawn against frictional resistances through a gap  440  between two stationary surfaces. 
   The gap  440  of the temple arrangement  4  lies between a bar  43  and a support pan  44 , which is for example formed in the shape of a trough. The cloth  1 ,  2  is held down by the bar  43  and is pressed onto rounded deflection edges  441  and  442  of the support pan  44 . In the active region of the bar  43  the support pan  44  is shaped concavely and formed in such a manner that its shape fits in a complementary manner with the shape of the bar  43  inclusive of the cloth  1 ,  2  lying thereon. The convexly shaped deflection edges  441  and  442  form the entrance and exit regions respectively of the gap  440 , so that the cloth  1 ,  2  is in each case transported horizontally at the entrance and at the exit. The bar  43 , the position of which can be adjusted (indicated by the double arrow  40 ), is pressed so strongly downwards that the friction which acts between the upper cloth  1  and the bar  43  is approximately of a strength equal to the friction acting between the lower cloth  2  and the support pan  44 . In this the lower cloth  2  need not make contact with the concave middle region of the support pan  44 . 
   The pressing roller  5  is in active contact with the drive roller  6 : The pressing roller  5  is arranged with respect to the drive roller  6  in such a manner that the cloth  1 ,  2  on the pressing roller  5  is in contact with the latter along a wrap-around angle of at least 170°. A torque is exerted by the drive roller  6  on the pressing roller  5  via the cloth  1 ,  2  which lies between them. As a result of this arrangement the pressing roller  5  exerts a drawing force on the lower cloth  2  from a drive point  51 ; the drive roller  6  exerts a drawing force on the upper cloth  1  from a drive point  61 . The pressing roller  5  is advantageously pressed so strongly against the drive roller  6  that the two named drawing forces are largely of equal magnitude. The value of the wrap-around angle at the pressing roller  5  advantageously lies in the range between 170° and 190°. 
     FIGS. 5 and 6  represent two variant forms of the temple arrangement  4 . In these temple arrangements  4  the gap  440  is in each case formed by the bar  43  and a bar section  44 ′ with only one deflection edge  441 ′ or a bar section  44 ″ with a deflection edge  441 ″ respectively. Here as well the bar  43  is disposed in such a manner that its position is adjustable. The adjustment can be made both in the vertical and in the horizontal direction. 
     FIG. 7  is a partial illustration of the weaving machine of FIG.  4 . Here it can be seen that the temple arrangement  4  stretches the cloth  1 ,  2  transversely to the transport direction with lateral temples  45 . The warp threads  1 ″ and  2 ″ are moved by shafts  8 . A double cloth can be produced which has closed regions in the warp direction, on the one hand laterally, and on the other hand at periodic spacings, so that rectangular bags or hollow cloth sections, in particular rectangular airbags, can be manufactured from the product. Folds such as result with the weaving machine of  FIG. 1  do not arise with the weaving machine which is shown in FIG.  7 —when correctly set—or form to a substantially lesser extent. 
   In  FIG. 8  a first product of the method in accordance with the invention, from which rectangular bags or hollow cloth sections can be manufactured, is illustrated in a schematic drawing.  FIG. 9  shows a second product for the manufacture of round bags or hollow cloth sections. In the manufacture of these products the warp threads are moved for example using a Jacquard machine and/or another shed forming device.