Abstract:
A tubular woven fabric includes fusible warp yarns along with other warp yarns that are substantially unaffected at the temperature at which the fusible yarns melt. The fusible warp yarns are disposed at selected locations in the fabric such that they can be melted by applying heat to them indirectly by a heating element brought into direct contact with the other yarns.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to fabrics, and more particularly to a woven fabric having a feature whereby the fabric can be adhesively attached to another fabric or other object, or whereby one portion of the fabric can be adhesively attached to another portion of the same fabric. 
       BACKGROUND OF THE INVENTION 
       [0002]    An example of a woven fabric having an adhesive feature is the narrow woven fabric commonly used as edging for a metal sifting screen. A typical screen edging fabric is in the form of a narrow woven strip composed of cotton yarns. A coating of low-melting adhesive is provided on one side of the woven strip. The coating can be in the form of two parallel stripes extending lengthwise along the woven strip, separated from each other by an intermediate space located midway between the long edges of the strip. The strip can be bent around an edge of a metal screen, so that the intermediate space is located along the edge of the screen, and the two adhesive stripes are positioned against the screen on opposite sides thereof. By applying heat to the bent strip of fabric using a heating tool, e.g., an iron, the adhesive layers can be made to adhere to the screen and to each other by the formation of adhesive bridges that extend through the apertures of the screen. At the same time, if the adhesive coating is limited to one side of the tube, the adhesive can be melted by the application of heat to the uncoated side of the tube, and exposure of the melted material on the uncoated side can be avoided. Consequently, the melting of the adhesive will neither impair the appearance of the finished article nor cause adhesive to come into direct contact with the heating tool. 
         [0003]    Adhesives have many other applications in fabric products, taking the place of stitching where stitching is not essential, to simplify manufacture and reduce costs. Examples of hot melt adhesives used as coatings on woven fabrics include ethylene-vinyl acetate (EVA), polyolefins (PO), and polyamides (PA). 
         [0004]    In applying stripes of low-melting adhesive to a woven fabric, it is necessary to control the temperature of the adhesive carefully in order to ensure that the adhesive flows properly and is applied uniformly. Other difficulties are encountered in the manufacture of adhesive-coated woven fabrics, including difficulties in feeding and collecting the fabric strip while the adhesive is hot and still in a semi-liquid state. 
         [0005]    This invention addresses problems encountered in the manufacture of adhesive-coated woven fabrics by incorporating yarns composed of a hot-melt adhesive material into the weave. By weaving the fabric as a tube, and limiting the hot-melting yarns to one side of the tube, the woven fabric in accordance with the invention can exhibit many of the same advantages as the conventional adhesive-coated tubular fabrics: avoidance of exposure of melted adhesive, and avoidance of direct contact between the heating tool and the melted adhesive. 
       SUMMARY OF THE INVENTION 
       [0006]    The term “tubular woven fabric” as used herein refers to a woven fabric that is the form of a tube, which has a hollow internal passage extending in the direction of the warp yarn. The tube can be flattened so that it takes the form of two face-to-face layers of fabric connected to each other by folds along opposite side edges. The layers can be connected by interlocking the weft yarn of one layer with one or more warp yarns of the other layer at one or more intermediate locations between the side edges, and if these connections are made, the internal passage is divided into two or more passages. The term “tubular woven fabric” also includes woven fabrics that have, not only one or more tubular woven portions, but an additional woven portion that is in the form of a single, i.e., non-tubular, woven layer. 
         [0007]    The tubular woven fabric in accordance with the invention is composed of at least one continuous weft yarn, and multiple warp yarns. The warp yarns include a first group of fusible yarns composed of a material that melts upon the application of heat at a predetermined temperature, and a second group of yarns composed of a material that is substantially unaffected when raised to the predetermined temperature at which the fusible yarns melt. 
         [0008]    The fusible yarns can be positioned so that they can be melted by heat applied by a heating element to, and conducted through, a layer composed of yarns of the second group. In this way, the melting of the fusible yarns can be utilized to attach the fabric to an object, to another fabric, or to another portion of itself, without exposure of the fusible yarns in such a way that they impair the appearance or function of the fabric, and without having the fusible yarns come into direct contact with the heating element. 
         [0009]    Thus, in a useful embodiment of the invention suitable for applications such as edging for a particle classification screen, if the fusible yarns in the fabric are limited to a area of the fabric having a weft-wise dimension not exceeding one-half the perimeter of the tubular fabric, the tubular fabric can be folded upon itself while in a flattened condition to form a fabric edging having interior and exterior parts. The fusible yarns are opposed to one another in the interior part of the edging, and substantially all of the yarns exposed on the exterior part of the edging are yarns of the second group. 
         [0010]    The tubular woven fabric can be produced so that it is in the form of a tape having opposite flat sides, in which exposure of the fusible yarns is substantially limited to one of the flat sides. 
         [0011]    In a preferred embodiment in which the fabric is in the form of a tape and the fusible yarns are exposed only on one of the flat sides, the fusible yarns are composed of two sets of yarns respectively on opposite sides of a longitudinal centerline, parallel to and located between longitudinal edges of the tape. These two sets of fusible yarns can be spaced from each other so that the tape is formed with a longitudinal hinge along the centerline, about which the tubular woven fabric can be folded. 
         [0012]    In a preferred embodiment, warp yarns on both of the opposite flat sides of the hinged tape can be connected in close relationship to one another by a weft yarn at an intermediate location between the two longitudinal edges, so that the tubular woven fabric is composed of two parallel tubes, ensuring that the tape folds properly so that the fusible yarns are on the inside of the folded tape. 
         [0013]    While the principal advantages of the invention lie in the simplification of manufacture of the fabric, other advantages of the invention will be apparent from the following description when read in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a schematic cross-sectional view of a tubular woven fabric according to a first embodiment of the invention; 
           [0015]      FIG. 2  is a schematic cross-sectional view showing an application of the tubular woven fabric of  FIG. 1 ; 
           [0016]      FIG. 3  is a schematic cross-sectional view illustrating a modification of the tubular woven fabric of  FIG. 1 ; 
           [0017]      FIG. 4  is a schematic cross-sectional view showing a second embodiment of the invention; 
           [0018]      FIG. 5  is a schematic cross-sectional view showing an application of the tubular woven fabric of  FIG. 4 ; and 
           [0019]      FIG. 6  is a schematic cross-sectional view showing an application of a third embodiment of the tubular woven fabric. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    The tubular woven fabric is shown schematically in  FIG. 1  with a very limited number of warp yarns for clarity of illustration, and will ordinarily have many more warp yarns than the limited number shown. The fabric is composed of an upper layer  10  and a lower layer  12 , connected to each other by folds along longitudinal side edges  14  and  16 . The warp yarns consist of two groups. The warp yarns  18 , shown as black dots, located in the lower layer  12 , the folded edges  14  and  16 , and along the right and left sides of the upper layer  10 , can be composed of any conventional yarn material, cotton, polyester, etc. The weft yarn  20  can likewise be composed of any conventional yarn material. 
         [0021]    The warp yarns  22 , shown as circles, which are in the upper layer  10  and not in the folded edges or the lower layer, are fusible yarns composed of a material that melts upon application of heat at a temperature that does not affect the warp yarns  18  or the weft yarn  20 . Preferably, the warp yarns are composed of a low-melting PET (poly (ethylene terephthalate)), which has a melting temperature of approximately 130° C., well below the 218° C. melting temperature of ordinary polyester yarns. Various alternative low-melting warp yarn can be used, such as polypropylene (PP) monofilament yarns, which have a melting temperature of approximately 160° C. The cotton warp yarns do not melt, and can withstand temperatures considerably higher than the melting temperatures of the low-melting warp yarns without deterioration. 
         [0022]    In the process of weaving the fabric shown in  FIG. 1 , the weft yarn  20  is shuttled back and forth while the warp yarns are controlled by the heddles of a loom in such a way that as the shuttle passes weftwise in a first direction, the weft yarn is interlaced with the warp yarns the become part of the upper layer  10 , and as the shuttle passes weftwise in the opposite direction, the weft yarn is interlaced with the warp yarns that ultimately become the lower layer  12  of the fabric. The weft yarn, therefore essentially takes the form of a helix in the final product. 
         [0023]    The fusible warp yarns  22  should be limited to a particular area of the fabric, and preferably to one of the two layers of the tubular fabric when flattened. In this way, heat can be applied to the fusible yarns indirectly, through the yarns of the other layer, the heating element is protected from direct contact with the fusible yarns, and the melted yarn material is not exposed on the side of the fabric opposite from the side having the fusible yarns. 
         [0024]    The weaving pattern can be a plain weave, or any of various other patterns, such as a twill weave, or a herringbone weave. Optionally, the weft can be composed of plural yarns rather than a single weft yarn. 
         [0025]    As shown in  FIG. 1 , the innermost fusible warp yarns  24  and  26 , along a centerline (not shown) midway between the edges of the fabric, are preferably spaced from each other so that the fusible yarns are in two distinct groups on opposite sides of the centerline. When the fabric is folded on itself, the amount of fusible material does not become excessive at the location of the fold. 
         [0026]    In one of its applications, the tubular fabric of the invention is used to form fabric edging for a particle classification screen  28  as shown schematically in  FIG. 2 . The particle classification screen, which can be composed of metal, is typically a rectangular array of evenly spaced, mutually perpendicular elements  26  and  28 , forming a set of openings of uniform size though which only particles smaller than a given size can pass. Grommets (not shown), which are punched through the fabric edging, are used to secure the screen in a machine that causes the screen to vibrate. As the screen vibrates, larger particles are retained on the top of the screen and smaller particles pass through the openings in the screen. The fabric edging defines a rectangular open area of the screen, supports the grommets, and serves as a seal in the vibrating machine. 
         [0027]    The tubular fabric of  FIG. 1  is folded on itself along the centerline so that what was the upper layer  10  in  FIG. 1  becomes two opposed layers  30  and  32  in direct contact respectively with the upper and lower sides of the screen. What was the lower layer  12  then becomes outer layers  34  and  36 . By applying heat to the outer layers using a heating element, the fusible warp yarns  22  ( FIG. 1 ) are melted, and the melted material flows through the apertures of the screen forming bridges  38  of resin which harden when cooled, extending through apertures and securing the layers  30  and  32  to each other and to the screen. Edging fabric can be applied to all four edges of the screen in this manner. 
         [0028]    In weaving the modified tubular fabric shown in  FIG. 3 , the heddles are controlled to cause the weft yarn  40  to become interlaced with one or more warp yarns  42  located midway between the side edges of the fabric, thereby forming a tubular fabric having two, side-by-side openings  44  and  46  instead of a single opening as in  FIG. 1 . Connecting the upper and lower layers at a central location ensures that, when the fabric is folded, it is folded along a central hinge line so that all the fusible yarns are on the mutually opposed inside layers. 
         [0029]    It is also possible, of course, to interlace the weft yarn with warp yarns at two or more intermediate location to form a tubular woven fabric with three or more longitudinally extending openings. 
         [0030]    Advantages of the invention can be realized in various other embodiments such as the second embodiment, shown in  FIGS. 4 and 5 . In this embodiment, the tubular fabric is woven so that a tubular portion  50 , comprising upper layer  52  and lower layer  54 , extends weftwise only part-way across the width of the fabric, the remainder being in the form of a single layer or “flag”  56 . Fusible warp yarns  58  are limited to the upper layer  52  of the tubular part, which preferably includes non-fusible yarns along its side edges. 
         [0031]    As shown in  FIG. 5 , the fabric can be folded over on itself along a fold line  58  at an intermediate location on layer  56 , and formed into a tube by applying heat to the fusible yarns in layer  52  by means of a heating element (not shown) in contact with layer  54 , thereby connecting layer  52  to an opposing part  60  of layer  56  by a layer of resin  62  formed when the melted yarns  58  harden. The final product is a fabric tube having a longitudinally extending opening  64 . 
         [0032]    The fabric tube can have various uses, for example, as a cathodic protector for a pipeline. The cathodic pipe protector can be manufactured using a continuous process in which so the material of  FIG. 4  is fed into a machine in a flat condition and formed into a tube as it enters the machine. A copper wire is fed into the center of the tube and then the tube is filled with a ground carbon material. The adhesive strip formed by the fusible yarns is activated by a heating bar and then cooled, to make the tube permanent. The finished tube is laid into the ground with one or more gas pipes or other pipe lines, and a low current is sent through the copper wire to prevent rusting of the pipes. The cathodic protector can be produced using various materials, depending on the requirements of the end user. For example, a polyester fabric can be used where the end user wants the carbon to remain wrapped within the fabric sheath. A cotton fabric version can be used where the end user wants the material to decay, leaving only the carbon and the copper wire. 
         [0033]    In a third embodiment, shown in  FIG. 6 , the tubular woven fabric is formed with two tubular parts  64  and  66  along opposite edges of a connecting layer  68 . The tubular parts, each of which has upper and lower layers, and the connecting layer, which is a single layer, can be formed by weaving, in a manner similar to the manner in which the fabric of  FIG. 3  is woven. However, the intermediate layer in  FIG. 6  is wider than the central part of the fabric in  FIG. 3 . In this embodiment, the fusible warp yarns on the layers  70  and  72  of the tubular parts, can be used to secure the tubular parts to another fabric layer  74  by means of resin layers  76  and  78  forming a tube having a longitudinal opening  80 , which can receive an object such as a curtain rod, for example. In this embodiment, the use of the tubular woven fabric having fusible warp yarns, can obviate expensive and time-consuming sewing steps while resulting in a durable product having an acceptable appearance. 
         [0034]    The tubular woven fabric of the invention can, of course, have various configurations other than those exemplified by the three embodiments specifically described, and the materials utilized for the yarns can vary, depending on the intended application. For example, in the embodiment shown in  FIGS. 4 , the fusible fibers can be located in layer  54  instead of in layer  52 . Accordingly, the scope of the invention should be understood as limited only by the following claims.