Abstract:
A fabric for providing reinforcement and the like which is made from a two dimensional flat fabric which includes portions that the warp and weft fibers are interlocked together and portions that are non-interlocked together that allow the fabric to be folded to create a three dimensional structure without the need for cutting and darting.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation-in-part of U.S. Ser. No. 09/749,318, filed Dec. 27, 2000 entitled “Reinforced Article and Method of Making” the disclosure of which is incorporated herein by reference 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to a textile reinforced substrate which is formed into a three dimensional article by thermoforming or other means suitable for the purpose.  
         BACKGROUND OF THE INVENTION  
         [0003]    Fiber reinforced composite structures enjoy the benefit of being lightweight while providing mechanical advantages such as strength. However, in many applications, molded plastic, wood or metal structures are preferred due to the cost involved, since they are relatively easy to fabricate. Often times however, articles, such as package or storing crates, are prone to damage due to the rough handling involved or are limited in their stacking ability due to weight and strength considerations. While fiber reinforced composite structures would be more desirable, the expense involved in making a somewhat complex three dimensional (3D) structure is a consideration.  
           [0004]    This is because composite structures start off typically with a woven flat substrate of fibers. The substrate then has to be shaped into the form of the article which is then coated with a resin and thermoformed or cured in the desired shape. This may be readily done for relatively flat or smooth surfaces. However, for angled surfaces such as at the junction of the sides, corners and bottoms of a box or crate, cutting or darting is required. This is somewhat labor intensive and adds to the cost of manufacture. For things typically considered to be inexpensive, for example a packaging crate, the added expense may outweigh the benefits of it being reinforced.  
           [0005]    While woven 3D structures may be woven by specialized machines, the expense involved is considerable and rarely is it desirable to have a weaving machine dedicated to creating a simple structure.  
           [0006]    Accordingly, while fiber reinforced articles are desirable in many applications to replace comparable plastic, wood or metal structures, there exists a need to reduce the cost involved in the method of their manufacture. By doing so it may also allow for their relative mass production and wide spread application.  
         SUMMARY OF THE INVENTION  
         [0007]    It is therefore a principal object of the invention to minimize or eliminate the need to cut and dart reinforcing fabrics for 3D structures.  
           [0008]    It is a further object as part of this to simplify the manufacture of such structures and reduce the labor requirement.  
           [0009]    A yet further object of the invention is to avoid the need for special weaving equipment to create 3D structures.  
           [0010]    A still further object is to provide for a method of creating a reinforcing fabric which may be readily adapted to create a wide variety of different 3D structures.  
           [0011]    These and other objects and advantages will be apparent from the present invention. The present invention is directed toward providing a specially designed fabric suitable as the reinforcement for a 3D composite structure. The fiber reinforcement is one that may be woven on conventional weaving machinery. It starts off as a woven 2D structure that is then formed into a 3D structure, particularly one having deep draws. To provide for this, the reinforcing fabric is woven in a manner that, in portions of the weave, the warp and weft or fill fibers are laid on each other and do not interlock. In this portion the fibers can move independently and slide past one another when the fabric is drawn or folded into shape. If the portion is a rectangular or square shape, it can be collapsed in such a manner that both the warp and weft fibers fold upon themselves and each other to align in an unidirectional manner which creates a corner which acts as a compression column in the final structure.  
           [0012]    Another way of creating the reinforcing textile is by way of stitch bonded fabrics. These are fabrics made through a combination of highspeed fiber laying/fiber placement technology and knitting technology. In stitch bonded fabrics, the fibers or yarns in the warp and weft direction are not interlaced. Knitting needles interlock each intersection of warp and weft fibers with a third stitching yarn. The stitching yarns also binds a wale of adjacent stitching yarns. In the present invention, selected regions of the warp and weft yarns are not bound by stitching yarns creating areas similar to the “non-woven” areas in the aforesaid embodiment. Accordingly, in these areas, the fibers can move independently and slide past each other when the fabric is drawn or folded into shape.  
           [0013]    A yet further manner of creating the reinforcing textile is to have two layers of fibers laid at 90 degrees (or other angles) with respect to each other and then, in selected areas, bonded together at the warp and weft intersections. This would require that at least one of the two directions of fibers be comprised of fibers that are thermoplastic or have a thermoplastic coating or component. Those areas that are bonded would act as “woven”. Those which are not bonded would act as “non-woven” areas similar to the earlier embodiment. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    Thus by the present invention its objects and advantages will be realized the description of which should be taken and in conjunction with the drawings wherein:  
         [0015]    [0015]FIG. 1 illustrates the construction of a flat 2D woven fabric incorporating the teachings of the present invention.  
         [0016]    FIGS.  2 A- 2 D illustrates the sequence of folding or drawing down the fabric to produce deep draws.  
         [0017]    [0017]FIG. 3 illustrates a 2D fabric having multiple areas where warp and weft fibers are not interwoven to create a complex structure upon folding or drawing down.  
         [0018]    [0018]FIG. 4 is a perspective view of a 3D structure formed from the fabric shown in FIG. 3.  
         [0019]    [0019]FIG. 5 is a perspective view of a stitch bonded fabric, incorporating the teachings of the present invention.  
         [0020]    [0020]FIG. 6 is a perspective view of a stitch bonded fabric having select areas not bound by stitching yarn, incorporating the teachings of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]    Turning now more particularly to the drawings, like parts will be similarly numbered. In FIG. 1, there is shown a flat 2D woven reinforcement fabric  10  which illustrates the present invention. The fabric  10  may be woven using any conventional textile pattern such as plain, satin, twill, etc. or any other pattern suitable for this purpose. The fiber used can be any fiber that can be woven, synthetic or natural, including for example fibers made from glass, Kevlar®, carbon, nylon, rayon, polyester, cotton, etc. and may be woven on conventional weaving equipment.  
         [0022]    In FIG. 1, the warp fibers are shown in direction A with the weft fibers in direction B. For purposes of this illustration the fabric  10  has been divided into regions  12  through  28  divided along fold lines  30 - 36 . In regions  12 - 18  and  22 - 28  the fibers are woven in a conventional fashion with the warp fibers intersecting with the weft fibers. In region  20  these fibers do not interlock, in other words the weft fibers float beneath the warp fibers. In region  20  the fibers can therefore move independent of one another.  
         [0023]    Once the fabric  10  is constructed, it can then be formed into the desired shape. If it is to act as a reinforcing structure, the fabric can be impregnated with the desired material or resin and then formed or thermoformed into shape. Alternatively, co-mingled tows consisting of a structural fiber and a thermoplastic resin could be woven to produce a preform which is then thermoformed.  
         [0024]    Turning now to FIGS.  2 A- 2 D, shown in FIG. 2A is the flat 2D woven fabric  10 . The fabric  10  is then folded along fold lines  30  and  32  which are parallel to the warp fibers, as shown in FIG. 2B. The fabric  10  is then folded along fold lines  32  and  36  which are parallel to the weft fibers and perpendicular to the warp fibers, as shown in FIG. 2C. In this process since the warp and weft fiber in region  20  are not interlocked, they slide past one another and ultimately accumulate in corner  38  as shown in FIG. 2D. The fibers in corner  38  are now unidirectional and can act as a compression column and increase the strength of the structure being formed. The foregoing can be done automatically by thermoforming equipment having the desired shaped mold, or by other means suitable for this purpose; then the structure heat set or cured.  
         [0025]    The foregoing advantageously avoids the need for cutting or darting, thereby reducing the amount of labor required and the ultimate cost of the article. The present invention allows for the increased automation of the fabrication and therefore broadens the applications for which reinforced structures may be used.  
         [0026]    Turning now briefly to FIG. 3 there is shown a flat woven 2D fabric  110 . Fabric  110  illustrates a plurality of regions  120  wherein in the woven structure, the warp fibers merely lay on the weft fibers. With such a fabric  110 , it may be folded and shaped into a complex reinforced structure  130  as shown in FIG. 4. Of course other shapes can be created by varying the size and location of the regions where the warp and weft fibers do not interlock.  
         [0027]    In another embodiment, there are alternate fabric forming machines to that of conventional weaving looms that have been designed over the years, some of which rely on a combination of high-speed fiber laying/fiber placement technologies and knitting technology. As aforesaid, the fabrics made on such machines are often referred to as “stitch bonded fabrics” or “knitting through” technology. The fibers or yarns in the warp and weft directions of such fabrics do not interlace. They are instead laid down in layers. For example, the warp yarns of fibers would be on one face of the fabric and the weft yarns on the other face of the fabric. As shown in FIG. 5 in the stitch-bonded fabric  200  shown, knitting needles would interlock each intersection of warp  202  and weft  204  yarns with a third stitching yarn  206 . The stitching yarns  206  serve two purposes. First, they bind warp  202  and weft  204  yarns at each intersection  208 . Secondly, the stitching yarns  206  also bind a wale  210  of stitching yarns  206  with the adjacent wale  210  of stitching yarns  206 . Without this interconnection, a fabric would not be formed. The “standard” stitch bonded fabric design, such as that produced by Malimo® technology which is available from Meyer Textile Machine Corporation located in Obertshausen, Germany, results in all yarn intersections being bound by stitching yarns  206 . However, the fabric  200  provided by the present invention as shown in FIG. 6 has selected regions  214  of the fabric  200  that do not have warp and weft yarns bound by stitching yarns  206 . This is accomplished by a redesign of the stitching yarn mechanisms so that the regions where binding is desired and where binding is not desired can be independently controlled so as to create “woven” and “non-woven” areas as previously described which would operate in a similar fashion. It might be noted that the interconnecting of adjacent wales by stitching yarns may not be required in every design due to the existence of weft yarns to stabilize the fabric in that direction.  
         [0028]    In addition, it may be desirable with a stitch bonded fabric to incorporate fibrous mats or veils  214  with the warp, weft and stitching yarns. These mats can be applied to the surface, for example, to enhance a desirable feature such as a smoother surface finish. The fibrous mats may be introduced in such a manner that the knitting needles penetrate the mat and thereby bind it to the fabric by the stitching yarns.  
         [0029]    A yet further way to create a reinforcing textile which would perform in a similar manner to that first described is as follows. This would involve two layers of parallel yarns or fiber laid at 90 degrees (or another angle, if suitable for the purpose) and then bonded to each other in selected areas to fix the fiber locations at warp and weft intersections. The process provides for that at least one of the two directions of fiber be comprised of fibers that are thermoplastic, have a thermoplastic coating or have a thermoplastic component (for example comingled fibers). In this regard, the thermoplastic coating (or component) would be heated to a point where the polymer (thermoplastic material) would melt, adhere to the fiber in contact with it and then be cooled to provide a semi-permanent bond. Other areas would not be bonded. The areas with no bonding would be free to move in a similar fashion to the “non-woven” areas as first discussed. Bonding could be accomplished by an electrically heated contact point, by laser, by ultrasonics or other means suitable for purpose. By this method the speed of fabrication of the reinforcing textile is enhanced.  
         [0030]    Thus by the present invention its objects and advantages are realized and although preferred embodiments have been disclosed and described in detail herein, its scope should not be limited thereby rather its scope should be determined by that of the appended claims.