Abstract:
A blast and fragment resistant polyester or polyether-based polyurethane boot sole includes embedded protective material throughout the entire sole. The embedded protective material consists of one or more layers of woven polyaramid fibers. The polyaramid fibers are thinly coated with polyester or polyether-based polyurethane before they are woven into a layer for incorporation into the sole. This enhances the adhesion between the embedded polyaramid protective material and the polyurethane sole.

Description:
This application is a continuation of Ser. No. 08/894,895 filed Aug. 28, 1997, now abandoned which is a 371 of PCT/SG 96/00001 filed on Feb. 28, 1996. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the construction of a boot sole, and more particularly pertains to a new and improved safety boot sole construction to prevent puncturing of the sole by high energy and high velocity projectiles thus affording greater protection to an individual&#39;s foot without over-restricting movement. 
     DESCRIPTION OF THE PRIOR ART 
     U.S. Pat. No. 5,237,758 to Zachman discloses semi-elliptical sections intersecting at loops with adjacent webs of adjacent loops intersecting with flexible rods directed through the intersecting loops to minimize lateral displacement of adjacent webs. 
     U.S. Pat. No. 5,285,583 to Aleven discloses a protective layer composed of plastic and including a flexible forepart portion having an insole board bonded to its bottom surface and a fabric liner bonded to its top surface during the process of moulding the protective plastic layer. The plastic used by Aleven is molten plastic injected in the final bonding process. 
     International Patent DE 4214802, by ZEPF H, to SPORTARTIKELFABRIK UHL GMBH KARL discloses a multi-layer boot sole having a walking surface, a damping intermediate sole, and an upper insole. The base is a thermo-plastic moulding, or is made of metal, ceramic, or graphite, in which multi-filament organic or inorganic reinforcing fibres are embedded in the form of a mat, or woven or knitted into the structure. The elastic profiled portions are formed on the underside of the base by injection moulding or pressing. The base can contain only a single layer of woven fibres, its total thickness being approximately 0.5 mm. 
     Aleven achieved strength and impact resistance from a plastic plate in the sole, and the use of a fabric mesh was to reinforce the plastic and not to provide impact resistance. ZLPF H could only achieve a single layer of not more than 0.5 mm thickness of woven fibres through injection moulding or pressing. Aleven made no discussion of metal, ceramic, or graphite materials. So far, techniques to use aramid, ceramic, or graphite fibres in the construction of a boot sole in thickness to prevent puncturing of the sole by high energy and high velocity projectiles has not been mentioned or made feasible due to problems in rigidity and bonding. 
     SUMMARY OF THE INVENTION 
     The boot soles described in the prior art are insufficient against blast and projectile protection when it is desired to conserve toe-to-heel flexion in order to enable running, jumping, rope climbing, and to clear obstacles such as rope ladders and small steps, and with sufficient feel or sensitivity to detect edges, pits, and small stones. To attain this, the present invention provides a blast and fragment resistant polyester and/or polyether-based polyurethane boot sole comprising embedded protective material in which the material is embedded throughout the entire sole and is composed of at least one woven polyaramid (Kevlar) layer, the denisity of which is less than or equal to 15 oz per square yard. Increasing density and additional layers of woven polyaramid fibres increases the blast and fragment resistance. 
     It is also an object of the present invention to provide a boot sole with good adhesion between the various polyaramid (Kevlar) layers and/or graphite fibre bundles in spite of the poor intrinsic adhesion between the polyaramid fibres, graphite fibres, and the polyurethane. Due to the extremely thin coating of the various polyaramid (Kevlar) and/or graphite fibre bundles prior to weaving and/or due to the relatively loose or coarse weave of the polyaramid (Kevlar) fibres, the polyurethane is able to penetrate between the fibres, allowing the various layers to be well bonded together, thereby preventing the peeling apart of the sole in subsequent use. 
     Accordingly to the invention, polyaramid (Kevlar) and/or graphite fibres can be coated thinly with polyester or polyether-based polyurethane before they are woven into the required mat form. This will greatly improve adhesion between the polyaramid and polyurethane material . 
     Also according to the invention, polyester fibres, preferably poly(ethylene terephthalate) (PET) fibres, can be interwoven with or between the (coated or uncoated) polyaramid (Kevlar) fibres to improve adhesion between the polyaramid and polyurethane material. 
     Also according to the invention, carbon graphite fibres can be interwoven with or between the polyaramid (Kevlar) layers to further strengthen and to stiffen the sole. 
     Also according to the invention, a woven layer of mineral fibres, notably ceramic fibres or S-Glass fibres, can be included into the boot sole to act as a fire wall for protection against hot gasses with temperatures of between 815 and 1,650 degrees Celsius. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein: 
     FIG. 1 is a vertical cross-sectional view of a boot having a first embodiment of the sole construction according to the present invention; 
     FIG. 1-A is an enlarged view of the sole construction of FIG. 1; 
     FIG. 2 is a vertical cross-sectional view of a boot having a second embodiment of die sole construction according to the present invention; 
     FIG. 2-A is an enlarged view of the sole construction of FIG. 2; 
     FIG. 3 is a vertical cross-sectional view of a boot having a third embodiment of the sole construction according to the present invention; 
     FIG. 3-A is an enlarged view of the sole construction of FIG. 3; 
     FIG. 3-B is an enlarged view of an alternative sole construction to that depicted in FIG. 3-A; 
     FIG. 4 is a vertical cross-sectional view of a boot having a fourth embodiment of the sole construction according to the present invention; 
     FIG. 4-A is an enlarged view of the sole construction of FIG. 4; and 
     FIG. 4-B is an enlarged view of an alternative sole construction to that depicted in FIG.  4 -A. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A boot having a first embodiment of the sole construction according to the present invention generally depicted as  10  in FIGS.  1  and  1 -A. 
     The boot  10  has a standard shaped upper portion  11  and a composite sole  13 . The composite sole  13  comprises an outer polyurethane sole  14  having a tread  17 , an intermediate sole  15  into which is embedded a layer of polyaramid fibres  18 , and optionally, an upper sole  16 . 
     The composite safety boot sole is made in a traditional multi-stage mould which is commonly used in the polyurethane shoe soling industry. 
     The polyester and/or polyether-based polyurethane is first injected into a composite sole mould cavity to form the outer (lower) sole  14  such that its density is typically in the range of 500 to 2000 kg/m 3 . 
     After removal of the top plate of the mould for the outer (lower) sole, one thick layer of polyaramid (Kevlar) woven fibre material  18  is placed onto the outer (lower) sole  14  which remains in the mould cavity. 
     The polyaramid (Kevlar) fibre material can be precoated with polyester and/or polyether-based polyurethane prior to weaving. The coat of polyurethane serves to facilitate good adhesion with and penetration by polyurethane which is injected into the mould cavity. 
     The density of the polyaramid layer  18  is at least 5 oz per square yard, preferably 15 oz per square yard, for each ply of woven polyaramid material. 
     This thick polyaramid layer  18  preferably consists of bundles of polyaramid in crowfoot or leno weave with 70% to 90% in the X to Y direction (that is perpendicular to toe-to-heel), and 10 to 30% in the toe-to-heel direction. 
     The thickness of the layer of the polyaramid layer  18  is at least 0.07 inches, more typically 0.11 inches, using Kevlar  49  in 7100 dernier bundles with tensile strength of 43,000 PSI and modulus 19 million PSI with a 0.07 inch diameter polyaramid fibres. 
     After placement of the polyaramid layer  18 , polyester and/o)r polyether-based polyurethane is injected into the mould cavity containing the outer (lower) sole  14  at the base of the sole to form the intermediate sole  15 . The polyurethane after injection into the mould has a typical density of &lt;1000 kg/m 3  . 
     Due to the penetration of the polyurethane into and though the polyaramid layer  18  good adhesion is achieved between the outer (lower) arid sole  14  and intermediate sole  15 , with the polyaramid layer  18  sandwiched in between. 
     At this stage, the upper portion  11  can be directly attached to the polyurethane composite sole  13  comprising the outer (lower) and intermediate soles  14 ,  15 , or a third, upper sole  16  ran be added on top of the intermediate sole for enhanced comfort. In this latter case, the outer (lower) and intermediate soles  14 ,  15  as described above are left in the mould cavity, and polyester and/or polyether-based polyurethane is injected into the mould cavity, directly on top of the intermediate sole  15 . 
     A shoe sole  13  made according to the above method with the preferred 15 oz per square yard polyaramid layer  18  is effective in providing blast and fragment resistance to a 60 grain projectile with a velocity of 1350 fps. It also conserves good toe-to-heel flexion in order to enable running, jumping, rope climbing, and to clear obstacles such as rope ladder and small steps, while avoiding delamination of the sole in subsequent use. 
     A boot having a second embodiment of the sole construction according to the present invention is depicted as  20  in FIGS.  2  and  2 -A. 
     In this embodiment, where like features have the same reference number as used above, the sole  13  has further layers  18  of polyaramid fibre material incorporated therein. 
     As is depicted in FIG. 2-A, the outer sole  14  can have up to two layers of polyaramid fibre  18 . The intermediate sole  15  would typically have between two to six layers of polyaramid fibre, with three layers being a typical number as is shown in FIG. 2-A. 
     To fabricate the sole, as depicted in FIGS.  2  and  2 -A,  2  layers of the polyaramid woven layers  18  are placed into the mould cavity which forms the outer (lower) sole  14 . 
     The polyaramid layers  18  consist preferably of polyaramid fibres being of 0.01 inch diameter. The fibres are woven together to form a layer less than 0.06 inches thick and, more typically, about 0.04 inches thick. 
     A polyester and/or polyether-based polyurethane is then injected into a composite shoe sole mould cavity to form the outer (lower) sole  14  such that its density is typically in the range of 500 to 2000 kg/m 3 . 
     After removal of the top plate of the mould for the outer (lower;) sole  14 , a further 2 to 6 layers of the same polyaramid (Kevlar) woven material  18  as embedded into the outer (lower) sole  14  are placed onto the outer (lower) sole  14  which remains in the base of the mould cavity. 
     At this stage a polyester and/or polyether-based polyurethane is injected into the mould cavity to form the intermediate sole  15  such that the polyurethane has a typical density of &lt;1000 kg/m 3 . 
     Due to the penetration of the polyurethane into and through the polyaramid layers  18  good adhesion is achieved between the outer (lower) and intermediate soles  14 ,  15  with the polyaramid layers  18  sandwiched in between. 
     At this stage, the upper portion  11  can be directly attached to die polyurethane composite sole  13  comprising of the outer (lower) and intermediate soles  14 ,  15 , or a third, upper polyurethane sole  16  can be included for enhanced comfort. This is achieved by allowing the outer and intermediate soles (made by the process above) to remain in the mould cavity and by injecting polyester and/or polyether-based polyurethane onto the intermediate sole  15 . 
     A shoe sole made according to the above method is even more effective in providing blast and fragment resistance than the first embodiment due to the multiple polyaramid layers. 
     In a third embodiment of this invention, the polyaramid layers  18  as described in relation to soles depicted in FIGS. 1 and 2 are interwoven with polyester (PET) fibres and the boot sole is made in the same manner as described above. 
     The use of interwoven polyaramid and polyester (PET) fibres has the advantage of further increasing the adhesion of the polyurethane material to the embedded layer(s)  18 . This is due to the intrinsically superior adhesion between polyurethane and polyester. 
     In a fourth embodiment of this invention, the polyaramid layers  18  as described in the embodiments above are further interwoven with carbon graphite fibres having 12K TOW and a tensile strength of 470,000 PSI and modulus of 35 million PSI with the boot sole  13  being made in the same manner as described above. 
     The use of interwoven carbon graphite fibres has the advantage of further increasing strength and stiffness and of improving wear resistance. 
     In a further embodiment of the invention depicted generally as  30  in FIGS.  3  and  3 -A boot sole  13  is made as described above except that, in addition, a layer of woven ceramic fibres of composite ceramic/polyaramid fibres  31  is incorporated into the intermediate sole  15 . 
     The woven ceramic fibre layer is preferably comprised of 0.05 inch diameter ceramic fibres with 70% to 90% of the ceramic fibres being woven into a crowfoot or leno weave in the X-Y direction (perpendicular to the toe-to-heel direction) and with 10% to 30% of ceramic fibres in the toe-to-heel direction. This layer is embedded in the intermediate sole above the polyaramid (Kevlar) layer(s)  18  (see FIG.  3 -A). In an alternative arrangement, as depicted in FIG. 3-B, a thin (0.025 inch) composite layer  32  of ceramic/polyaramid fibres preferably consisting of standard bidirectional weave can be embedded in the upper sole  16 . 
     The boot sole incorporating this composite layer of ceramic/polyaramid fibres  32  allows for protection against hot gasses, with a temperature resistance of 1,650 degrees Celsius during the very brief duration of the blast. 
     In a further embodiment  40  of this invention, a layer of composite S-Glass fibres can be added into the middle or upper sole  14 ,  15  (see FIGS. 5,  4 -A and  4 -B). 
     A layer  41  of 0.05 inch diameter ceramic fibres, where 70% to 90% of the S-Glass fibres are woven into a crowfoot or leno weave in the X-Y direction (perpendicular to the toe-to-heel direction) and with 10% to 30% of S-Glass fibres in the toe-to-heel direction, is embedded in the intermediate sole above the polyaramid (Kevlar) layer(s)  18  (FIG.  4 -A). Alternatively, a thinner (0.025 inch) layer  42  of S-Glass fibres preferably having a standard bi-directional satin weave can be embedded in the upper sole  16  (FIG.  4 -B). 
     The boot sole  13  incorporating the layer of S-Glass fibres  41 ,  42  allows for protection against hot gasses with a temperature resistance of 815 degrees Celsius for the very brief duration of the blast. 
     As to the manner of usage and operation of the instant invention, the same should be apparent from the above disclosure and accordingly no further discussion relative to the manner of usage and operation of the instant invention shall be provided. 
     With respect to the above description, it is to be realized that the optimum dimensional relationships and materials for the parts of the invention, to include variations in size, materials, shape, form, function, and manner of operation, assembly, and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. 
     Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art it is not desired to limit the invention to, the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents which may be resorted to fall within the scope of the invention. :