Abstract:
The present invention relates a protective element for an athlete. The protective element can include a first flexible support layer, wherein a plurality of substantially hard projections is arranged on the first support layer, and a second flexible support layer, wherein a plurality of substantially hard receiving elements is arranged on the second support layer. The receiving elements and the projections are configured to provide flexible protection to various areas of a user&#39;s body.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application incorporates by reference, and claims priority to and the benefit of, German Patent Application Serial No. 102005010614.5, which was filed on Mar. 8, 2005, and European Patent Application No. 06001524.5, which was filed on Jan. 25, 2006, the entire disclosures of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a protective element for use in, for example, sporting activities. 
     BACKGROUND 
     In many fields of sports, the body of an athlete has to be protected against injuries by suitable devices. For example, when playing ice hockey or football, the athletes wear helmets and thickly padded garments for protection against contact with other players or their sports equipment. Another example is shin guards for soccer players, which protect against injuries to the shin by the shoe and, in particular, the hard studs of an opposing player. Also, a shin guard prevents injuries to the shins by particularly fierce ball shots. 
     Shin guards of the prior art typically have one or more hard plastic plates and an attached cushioning material. Although such a construction generally provides sufficient protection, known shin guards have certain disadvantages. For example, the plates limit the freedom of movement of a player. Furthermore, complex mounting structures are necessary to assure that the shin guard does not change its position during use, which further hinders the player. As a result, many players play without the protection of a shin guard and prefer to take the risk of injuries. Similar problems arise with other protective elements for athletes, such as elbow and knee protectors for inline skaters or snowboarders, which are rejected by many athletes for reasons of comfort, since they also constrict the athlete&#39;s movement. 
     Compared to the design of protective sports devices, the construction of bulletproof vests is a completely different technical field. For example, U.S. Pat. No. 5,364,679, the entire disclosure of which is hereby incorporated herein by reference, discloses a body armor made from several layers of (hemi-) spheres, wherein the surfaces of opposing spheres contact each other at certain points. As a result, the impact force of a bullet hitting the vest is distributed onto a plurality of spheres and the bullet is effectively stopped. The adoption of this design for protective sports elements for athletes would lead to a device having a great thickness and a significant weight. It would, therefore, not improve the wearing comfort of the device. 
     There is, therefore, a need to provide a protective element, for example a shin guard, that overcomes the above mentioned disadvantages of the prior art, leads to a higher wearing comfort, and does not hinder the performance of the athlete. Additionally, there is a need to provide a protective element that can be used in a variety of sports equipment and to prevent injuries to various areas of the body, such as ankles, forearms, knees, the head, etc. 
     SUMMARY OF THE INVENTION 
     This problem is solved by a protective element for clothing, for example a shin guard, including a first flexible support layer onto which a plurality of substantially hard projections are arranged and extend therefrom and a second flexible support layer onto which a plurality of substantially hard receiving elements are arranged and extend therefrom. The combination of flexible first and second support layers on the one hand and hard projections and receiving elements, respectively, on the other hand provides, in accordance with the invention, a protecting surface that can, in contrast to the rigid plates of the prior art, flexibly adapt to the contour of the part of the body to be protected. This allows an individual fit of the protective element. The projections and receiving elements are not intended for attachment of one support layer to the other, but are intended to distribute and dampen (for example frictionally or by compression) impact loading and associated forces arising thereon. Furthermore, due to the flexibility of the support layers, the shape of the protective element can yield to movements of the body part to be protected, which increases the wearing comfort. This is particularly desirable if joints are to be protected, such as the elbow and the knee of an athlete. 
     Furthermore, the projections and the recesses provided by the complementary shaped sections of the receiving elements and/or their arrangement lead to a comparatively reduced thickness of the resulting hard protecting layer. This distinguishes the present protective element from the (hemi-) spheres that contact each other in a point-wise manner, as disclosed in U.S. Pat. No. 5,364,679. 
     In one aspect, the invention relates to a protective element including a first flexible support layer, a plurality of substantially hard projections arranged on the first support layer, a second flexible support layer adjacent the first flexible support layer, and a plurality of substantially hard receiving elements arranged on the second support layer. The receiving elements include either a substantially complementary shape to the projections or a defined spacing from one another to define recesses for receiving the projections, or both. 
     In various embodiments, a shape of the projections and/or the receiving elements is selected from the group consisting of polygonal, arcuate, and combinations thereof. In a particular embodiment, the projections have a rounded shape (i.e., convex) and the receiving elements include sections having a correspondingly rounded shape (also convex; however, a plurality of adjacent receiving elements may form a quasi concave receptacle for receiving a projection). In such an arrangement, the rounded projections can slide within the rounded sections without jamming when the flexible support layer is bent to adapt to the natural contour or to a movement of the body part. The protection provided by the hard layer made from the projections and the receiving elements of the protective element is not reduced in such a situation. In one embodiment, the receiving elements are arranged such that several, for example four, receiving elements define a recess for receiving a projection. A load applied to a certain area on the projection element, for example by a single stud, acting on the outside onto the protective element, is thereby distributed over a greater area and is thus dispersed. At least one of the projections and the receiving elements can be made of a substantially incompressible plastic material. The protective element can also include a coating disposed on an outer surface thereof. 
     In addition, the protective element can include an outer support layer including the first flexible support layer and the projections and an inner support layer including the second flexible support layer and the receiving elements. The first flexible support layer and the second flexible support layer can be arranged such that the plurality of projections is arranged substantially in a plurality of recesses formed by the plurality of receiving elements. The projections can be arranged separately from each other on the first flexible support layer, and the receiving elements can be arranged separately from each other on the second flexible support layer. Such an arrangement facilitates a change of the configuration of the two flexible support layers to adapt to the contour of the part of the body to be protected. The projections and/or receiving elements can be formed on a single substrate mounted on or acting as the respective flexible support layer or be individual pieces mounted on their respective flexible support layer. In the case of a common substrate mounting, the projections and/or receiving elements can be spaced apart to allow for a respective reorientation of the two flexible support layers. 
     In other embodiments, the protective element includes interconnecting ridges arranged between adjacent projections and/or adjacent receiving elements. At least one of the first flexible support layer and the second flexible support layer can include a cloth and/or a cushioning layer. A cloth support layer allows the easy integration of a protective element into a garment, such as the sock of a soccer player. In one embodiment, the cushioning layer can include a plurality of plastic fibers arranged between two fabrics, with the fibers extending substantially perpendicular to a surface of the two fabrics. Such a layer design, which is also designated as “3D-mesh,” permanently provides good cushioning properties at a low weight and good ventilation properties. Contrary to common foamed materials, a 3D-mesh is permeable for air flow through and within the mesh. Alternatively, it is also conceivable to use a layer of foamed material or any other material that provides cushioning. 
     In various embodiments, the invention includes a shin guard or article of clothing including at least one protective element in accordance with the invention. The article of clothing can be selected from the group consisting of a forearm guard, pants, a vest, a jacket, a cap, a glove, an article of footwear, and a sock. In one embodiment, the article of clothing includes a pocket and at least one protective element arranged therein. At least one of the flexible support layers can be integral with a fabric layer of the article of clothing. Furthermore, the protective element can include a contoured shape. 
     These and other objects, along with advantages and features of the present invention herein disclosed, will become apparent through reference to the following description, the accompanying drawings, and the claims. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings, in which: 
         FIG. 1A  is a schematic perspective view of one embodiment of a protective element in accordance with the invention; 
         FIG. 1B  is a schematic representation of a plurality of protective elements disposed proximate various areas of a human body; 
         FIG. 2A  is a schematic plan view of a protective element in accordance with one embodiment of the invention; 
         FIG. 2B  is a schematic cross-section of the embodiment of  FIG. 2A  taken at line  2 B- 2 B; 
         FIG. 3A  is a schematic plan view of a protective element in accordance with an alternative embodiment of the invention; 
         FIG. 3B  is a schematic cross-section of the embodiment of  FIG. 3A  taken at line  3 B- 3 B; 
         FIG. 4  is a schematic cross-section of a protective element in accordance with an alternative embodiment of the invention; 
         FIG. 5  is a schematic top view of the receiving elements in the embodiment of  FIG. 4 ; and 
         FIG. 6  is a schematic cross-section of a 3D-mesh as it may be used in a protective element in accordance with one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following, embodiments of the invention are described with reference to a multi-layer protective element for a shin guard for a soccer player; however, it is to be understood that the present invention can also be used for a variety of other kinds of protection devices for athletes, such as protective elements for elbows, knees, and the head to be used by inline skaters, skateboarders, and snowboarders. Other applications include protective elements for hockey players, for example a goalkeeper, and also for motor-cyclists or downhill mountain bikers. Another application for the protective elements is as shoulder pads for use in rugby or football. The protective element can be integrated directly into an article of clothing or be arranged in a corresponding pocket. Also, mixed designs are possible where only parts, for example the support layer, are integrated into the fabric of the article of clothing and the other components are detachably secured thereto. 
       FIG. 1A  shows a schematic perspective view of one embodiment of a protective element  1 . The protective element  1  may be applied to various areas of the body to protect those areas from injury due to impact. The protective element  1  has an interior side  12 , or inner support layer, that is typically arranged towards the body, and an exterior side  14 , or outer support layer, that is typically arranged away from the body.  FIG. 1B  depicts a plurality of protective elements  1  disposed at various areas of a human body. Some examples of where the elements  1  can be located include: the knee  2 , the shin  3 , the foot  4 , the elbow and forearm  5 , the hip  6 , the back  7 , the shoulder  8 , and the head  9 . 
       FIGS. 2A and 2B  schematically illustrate a general design of one embodiment of a protective element  1  in accordance with the invention. A plurality of projections  20  are attached to a first support layer  10 , for example a suitable fabric or a sufficiently stable foil. In one embodiment, the support layer  10  is directed to the exterior side  14 , when the element  1  is in use, so that the projections  20  are inwardly oriented in the direction of the part of the body to be protected (see  FIG. 1B ). As shown in  FIG. 2A , a portion of the support layer  10  is removed, thereby providing a clearer view of one possible arrangement of the projections  20  and receiving elements  40 . The projections  20  extend into recesses  30  that can be formed by several receiving elements  40 . In the embodiment shown, the projections  20  and receiving elements  40  have the shape of a frustum; however, as discussed hereinabelow, the shape of the projections  20  and the receiving elements  40  can vary. The receiving elements  40  are in turn attached to a second support layer  50 . The support layers  10 ,  50  can be relatively flexible to allow the protective element  1  to conform to the contours of the area to be protected. The flexibility of the support layers  10 ,  50  will vary based on, for example, the materials used, the material thickness, and the number of layers used. The overall flexibility of the protective element  1  can be varied to suit a particular application. 
       FIGS. 3A and 3B  schematically illustrate an alternative embodiment of a protective element  101  in accordance with the invention, where the projections  120  and corresponding support layer  110  are provided as a single piece, for example an injection-molded piece. Similarly, the receiving elements  140  can be integrally manufactured together with the second support layer  150 , again, for example, by injection molding. Manufacturing the projections  120  and the receiving elements  140  together with the respective support layers  110 ,  150 , can significantly reduce manufacturing costs. In a particular embodiment, the integrally formed support layers  110  and  150  are sufficiently thin and/or made from a sufficiently flexible material, such that the shape of the overall protective element  101  can adapt to the outer contour of the area to be protected, for example the shin. As shown in  FIG. 3A , a portion of the support layer  110  is removed, thereby providing a clearer view of another possible arrangement of the projections  120  and receiving elements  140 . 
     The protective element  101  depicted in  FIG. 3B  also includes a 3D-mesh cushioning layer  100 ,  115  arranged under the lower support layer  150 . The 3D-mesh cushioning layer  100 ,  115  will be described in greater detail with reference to  FIG. 6 . Furthermore, there may be one or more additional cushioning layer(s)  118  added below or above the support layers  110 ,  150  made from, for example, a comparatively soft foamed material, such as ethylene vinyl acetate (EVA). 
     To prevent the layer ensembles of  FIGS. 2A ,  2 B,  3 A, and  3 B from disintegrating or otherwise separating, the various layers can be stitched together along the outer edges  17 ,  117  of the protective element  1 ,  101 . The projections  20 ,  120  and the receiving elements  40 ,  140  essentially float with respect to one another in their proper orientation. Additional stitching  19 ,  119  or other attachment means can, however, be added at various locations of the protective element  1 ,  101  to further hold the layers together, since the projections  20 ,  120  and the receiving elements  40 ,  140  provide no mechanical retention between the layers. As mentioned before, such a protective layer ensemble can be integrated into the fabric of a garment or arranged in a suitable pocket of a garment. In one embodiment, the layers can be held together with hook and loop type fasteners, such as the Velcro® brand sold by Velcro Industries B.V. Such an arrangement can allow for interchangeability between support layers to, for example, suit different sports or wearers, or to replace a worn outer layer. Additionally, this releasable arrangement makes the layers repositionable with respect to one another. 
     In the embodiments of  FIGS. 2A ,  2 B,  3 A, and  3 B, when the projections  20 ,  120  are positioned in the recesses  30 ,  130 , they form, together with the receiving elements  40 ,  140 , a substantially closed, hard layer that can not be penetrated by an impinging outer device, such as a pointed stud. As a result, the part of the body arranged below the layer is protected. In one embodiment, the projections  20 ,  120  and the receiving elements  40 ,  140  have sections with substantially complementary shapes, for example the essentially parallel side-surfaces  22  and  41  shown in  FIG. 2B  or the round projections  120  and the round recesses  130  in  FIG. 3B , such that the projections  20 ,  120  and the receiving elements  40 ,  140  can engage each other. Alternatively or additionally, the receiving elements  40 ,  140  can be arranged at a sufficient distance from one another on the support layer, such that the relative positions of the receiving elements  40 ,  140  influence the engagement of the projections  20 ,  120  therewith. 
     In order to provide the desired protection, the projections  20 ,  120  and/or the receiving elements  40 ,  140  are made from a sufficiently hard material, although the exact degree of hardness of the material depends on the loads to be expected. It is also conceivable that the projections  20 ,  120  and/or the receiving elements  40 ,  140  can be deformable, so as to provide an additional cushioning effect to the protective element  1 ,  101 . Since the projections  20 ,  120  only contact the receiving elements  40 ,  140  and are not permanently connected or otherwise secured thereto, the layer ensembles shown in  FIGS. 2A ,  2 B,  3 A, and  3 B can also have a curved shape, if necessary, to match the contour or a movement of the part of the body to be protected. 
     The projections  20  and the receiving elements  40  of  FIGS. 2A and 2B  can be anchored to the support layers  10 ,  50 , respectively, using any suitable method, for example stitching or gluing. In addition to stitching, gluing, or similar methods, it has been found to be particularly advantageous if the plastic material of the projections  20  and the receiving elements  40  is directly molded, injection molded, or flow molded on to a support layer, as this process can be easily automated. In one embodiment, the plastic material can be thermoplastic polyurethane (TPU) or a polyolefin, such as, for example, acryl butadiene styrole (ABS). The individual projections  20  and the receiving elements  40  are preferably separately arranged on their respective support layers; however, as shown in  FIG. 3B , the individual projections  120  and the receiving elements  140  can be integrally manufactured together with their respective support layers  110 ,  150 . 
     Furthermore, it is also possible to provide interconnecting ridges  142  between individual projections  120  or receiving elements  140 , respectively. Use of the interconnecting ridges allows for selectively modifying the possible overall configurations of the protective element  101 . For example, in the case of a protective element  101  embodied in a shin guard, it is possible to provide rows of projections  120  and/or rows of receiving elements  140  with interconnecting ridges  142  disposed between the individual projections  120  or receiving elements  140  in a row extending in a longitudinal direction of the shin guard. Such a shin guard can still be flexibly adapted to the individual curvature of the shin; however, in the longitudinal direction the shin guard is substantially rigid. The interconnecting ridges  142  modify the flexibility of the protective element  1 ,  101  and can be used in any of protective elements described herein. 
       FIGS. 4 and 5  disclose another alternative embodiment of a protective element  201  in accordance with the invention. Similar to the embodiment of  FIGS. 3A and 3B , the projections  220  have a rounded shape in this embodiment, in particular a dome shape. The recesses  230  are each formed by four receiving elements  240  having correspondingly rounded side surfaces  241 , which can be engaged by the rounded projections  220 . Due to the rounded shape of the projections  220  and recesses  230  formed by the receiving elements  240 , the protective elements  201  shown in  FIGS. 4 and 5  can be bent more easily than the protective element  1  of  FIGS. 2A and 2B . A jamming of some projections and receiving elements is excluded. 
     The projections  20 ,  120 ,  220  and receiving elements  40 ,  140 ,  240  can, however, be essentially any size and shape, for example, polygonal, arcuate, and combinations thereof. In the present application, the term polygonal is used to denote any shape including at least two line segments, such as rectangles, trapezoids, triangles, hexagonal, pyramidal, frusto-conical, quadrangles, etc. Arcuate shapes include circles, domes, ellipses, etc. Asymmetrical shapes are also possible. Generally, the receiving elements  40 ,  140 ,  240  have a corresponding shape to the projections  20 ,  120 ,  220  so as to achieve the described protective effect. The receiving elements  40 ,  140 ,  240  can additionally or alternatively have corresponding distances therebetween to also provide an area of contact for the projections  20 ,  120 ,  220  also so as to achieve the described protective effect. In addition, the size and shape of the protective elements  1 ,  101 ,  201  may vary to suit a particular application. The protective element  1 ,  101 ,  201  can have essentially any shape, such as polygonal, arcuate, or combinations thereof, and will be sized based, at least in part, on the area of the body to be protected and the relative size of the wearer. 
       FIG. 4  shows a section through the layer ensemble, where the first support layer  210  and the second support layer  250  are arranged with a distance therebetween, so that the individual projections  220  and the receiving elements  240  can be recognized separately from each other. As previously described, the two support layers  210 ,  250  in the protective element  201  can be interconnected at their side edges, for example by stitching, gluing, or welding; however, such a connection is not necessary, for example, if the protective element  201  is arranged within a pocket. 
     The top view of  FIG. 5  illustrates that the recesses  230  that receive the dome-shaped projections  220  are provided by four adjacent receiving elements  240 . As a result, an impact force exerted onto a certain point of the flat outer surface ( 221  in  FIG. 4 ) of the projection  220 , for example by a pointed stud, is distributed over the overall surface of the four receiving elements  240  and, therefore, has a lesser impact on the part of the body that is arranged below the protective element  201 . 
     Apart from the rounded side surfaces  241 , each receiving element  240  includes in the embodiment shown in  FIG. 5  a star-like central area  243 . For reducing the weight, a hole  244  may be arranged in the center of this area  243 . In a similar manner, the central region of the recess  236  could be free from material, since it is sufficient for the round projection  220  to be maintained in a central position between the four receiving elements  240  by the rounded side surfaces  241 . This leads to a reduced thickness of the overall layer ensemble and to a lower weight. In other embodiments, the recess  230  is not free from material. 
     The overall layer ensemble according to any of the embodiments described herein can be directly integrated into a suitable garment. To this end, the first support layer  10  and/or the second support layer  50  may be part of the cloth used for producing, for example, a sock, trousers and/or a jacket. The cloth can be a textile having natural or artificial fibers and either woven or non-woven. Since the projections  20  engage the recesses  30 , a comparatively thin hard layer is achieved, which is less bulky than protective elements according to the prior art. Alternatively, an insert with the layer ensemble shown in  FIGS. 2 to 5  could be inserted into a pocket or the like of a garment, such as a sock. An example of a support device disposed in a pocket on a garment is described in U.S. Pat. No. 6,715,218, the entire disclosure of which is hereby incorporated herein by reference in its entirety. In addition, it is also possible to form a protective element in a bandage-like configuration that can be wound, like a bandage, around the part of the body to be protected. 
     To avoid a premature wear of the outer support layer  210 , an additional coating  260  may be arranged on its exterior side  214 , which may, for example, include suitable rubber ribs. In the case of a shin guard, the rubber coating  260  provides a better control of the ball in addition to protection against wear and tear in a situation where it is necessary to contact the ball with the shin. Also in the case of other protective elements, as they are in an exemplary manner mentioned above, the additional coating  260  may have other advantages. The coating  260  can, similar to the projections  220  and the receiving elements  240 , be directly molded onto the support layer  210 . Alternatively, it is also possible to directly interconnect the coating  260  and the outside  221  of a projection  220  by, for example, gluing and/or welding through the support layer  210 . It is also conceivable to injection mold the additional coating  260  together with the injection molding of the projections  220  and/or the support layer  210 , to further facilitate production. Alternatively or additionally, the coating  260  can be added for aesthetic purposes, for example, the addition of a team logo or other indicia. Also, the coating  260  can be sprayed on to the exterior side  214  of the protective element  201  to influence other performance characteristics of the protective element  260 , for example, a coating to increase or reduce the frictional properties of the exterior side  214  of the protective element  201 . 
     The arrangements shown in  FIGS. 2 to 5  serve to avoid the penetration of a pointed device into the part of the body to be protected; however, these same arrangements also effectively disperse the hitting shock over a broader surface. For a shin guard, but also for other protective elements, it is additionally desirable to provide a cushioning layer for cushioning the arising impact by a suitable deformation. To this end, an appropriate cushioning material can be arranged in the region of the first support layer  10  and/or the second support layer  50  made, for example, from a foamed material, such as an EVA foam. 
       FIG. 6  depicts one embodiment of a cushioning material  312  for use in a protective element in accordance with the invention. A plurality of plastic fibers  315  is arranged between two fabric layers  300  and extends substantially perpendicularly to the surface of the two fabric layers  300 . When such a 3D mesh type cushioning material is compressed, i.e. when the two fabric layers  300  are moved in the direction of each other, the plurality of plastic fibers  315  must be bent and frictionally pass each other. As a result, the compression movement is effectively cushioned, since the fibers  315  are elastic and try to return to their original configuration. 
     Such a cushioning material is very long-lasting and, therefore, particularly suitable to be used in conjunction with the layer ensemble of  FIGS. 2 to 5 . One of the two fabrics  300  may simultaneously provide the function of one of the two support layers  10 ,  50  so that the resulting layer ensemble provides a protecting function as well as a cushioning function. As already explained, a further advantage of the use of a 3D-mesh are the good ventilation properties provided by this material. Contrary to common cushioning materials, such as, for example, rubber foams, a flow of air can easily pass through a 3D-mesh in all directions. This advantage is desirable, in particular for protective elements integrated into articles of clothing for athletes. 
     Protective elements that are subjected to particularly high loads may include a combination of several protection layers including outer projections  20  and correspondingly shaped receiving elements  40  with the discussed cushioning material. The explained cushioning material can, for example, be arranged between two hard protection layers, where the upper fabric layer  300   a  is the lower support layer of the upper protection layer and the lower fabric layer  300   b  is the upper support layer of the lower protection layer. If used in a shin guard, such a design leads to particularly effective protection against penetration of the pointed studs of an opposing player. 
     Generally, the various components can be manufactured by, for example, molding or extrusion. Extrusion processes may be used to provide a uniform shape. Insert molding can then be used to provide the desired geometry of open spaces, or the open spaces could be created in the desired locations by a subsequent machining operation. Other manufacturing techniques include melting or bonding. For example, the various elements may be bonded to the various layers with a liquid epoxy or a hot melt adhesive, such as EVA. In addition to adhesive bonding, portions can be solvent bonded, which entails using a solvent to facilitate fusing of the portions to be added. The various components can be separately formed and subsequently attached or the components can be integrally formed by a single step called dual injection, where two or more materials of differing densities are injected simultaneously. 
     In addition to the materials described hereinabove, the various components can be manufactured from other suitable polymeric material or combination of polymeric materials, either with or without reinforcement. Suitable materials include: polyurethanes; EVA; thermoplastic polyether block amides, such as the Pebax® brand sold by Elf Atochem; thermoplastic polyester elastomers, such as the Hytrel® brand sold by DuPont; thermoplastic elastomers, such as the Santoprene® brand sold by Advanced Elastomer Systems, L.P.; thermoplastic olefin; nylons, such as nylon 12, which may include 10 to 30 percent or more glass fiber reinforcement; silicones; polyethylenes; acetal; and equivalent materials. Reinforcement, if used, may be by inclusion of glass or carbon graphite fibers or para-aramid fibers, such as the Kevlar® brand sold by DuPont, or other similar method. Also, the polymeric materials may be used in combination with other materials, for example natural or synthetic rubber. Other suitable materials will be apparent to those skilled in the art. 
     Having described certain embodiments of the invention, it will be apparent to those of ordinary skill in the art that other embodiments incorporating the concepts disclosed herein may be used without departing from the spirit and scope of the invention. The described embodiments are to be considered in all respects as only illustrative and not restrictive.