Abstract:
A footwear article comprising a generally elongate sole for engagement with and support of the foot of a person, said sole having an upper surface, a lower surface, a first portion being for interaction with at least the heel region of the foot of the person and a second portion for interaction with at least the metatarsal region of the foot of the person; and a foot engagement means for securing the footwear article to the foot of a person. The footwear article being characterized in that a first portion of the sole includes a first material having a first material property and the a second portion of the sole includes a second material having a second material property; and said first portion and said second portion extend at least to the upper surface of the sole and first material property provides for dampening of load imparted to the foot of the person upon contact with a surface.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of footwear articles, in particular to footwear of composite form. 
     BACKGROUND OF THE INVENTION 
     It is well known in the art that shock loadings and forces applied to the underside of the foot of a person via the sole of footwear article have long term effects on the integrity of joints of a person, whilst also at times causing pain and discomfort, in particular when wearing footwear for extended periods of time. 
     Furthermore, it is well known that the majority of loading on impact to the foot of a person is imparted to the underside of the heel portion of the foot of a person in use. 
     Footwear articles of the prior art include various manners in which to increase comfort and conformity to the foot of user, including shock absorptive inserts, various types of foam rubber and air cushioning devices. Such footwear articles typically require increased manufacturing costs and tooling, thus increasing complexity of production. 
     The present invention is provides a footwear article which overcomes or at least substantially ameliorates at least some of the deficiencies as exhibited by those of the prior art. 
     SUMMARY OF THE INVENTION 
     In a first aspect, the present invention provides a footwear article comprising:
         a generally elongate sole for engagement with and support of the foot of a person, said sole having an upper surface, a lower surface, a first portion being for interaction with at least the heel region of the foot of the person and a second portion for interaction with at least the metatarsal region of the foot of the person; and   a foot engagement means for securing the footwear article to the foot of a person.   characterised in that a first portion of the sole includes a first material having a first material property and the a second portion of the sole includes a second material having a second material property; and   said first portion and said second portion extend at least to the upper surface of the sole and first material property provides for dampening of load imparted to the foot of the person upon contact with a surface.       

     Preferably the first portion further provides for interaction with and at least partial support of the plantar arch of the user. 
     Preferably the first portion extends substantially laterally across the sole. 
     Alternatively, the first portion is provided as a first part and a second part and laterally spaced apart such that the first part provides for interaction with the lateral inferior of the heel of the person and the second part provides for interaction with the medial inferior aspect of the heel of the user. The first part and the second part of the first portion are preferably sized and selected from a material so as to provide lateral stabilisation and load distribution of the heel of the person. 
     The first material property and the second material property may differ from each other and the first material and the second material may differ from each other, and the first material and the second material have differing densities. 
     The first portion and the second portion are preferably selected from the group including polymeric materials, rubbers, elastomers and organic materials or combinations thereof. 
     Preferably the first material and the second material are selected from the group including thermoplastic polymeric material, co-polymers and mixed polymer blends. 
     The first material and the second material are preferably selected from the group including polyurethane, ethylene vinyl acetate, poly vinyl acetate and the like. 
     The first material and the second material may be provided in the form of expanded form, compact form or gel form of combinations thereof. 
     Preferably the first material is a polyurethane gel and the second material is an expanded poly vinyl acetate material. 
     The engagement means is preferably selected from the group including straps, an enclosure, a buckle or the like. 
     Preferably the sole is formed as a unitary construct by co-molding the first portion and the second portion. The sole is preferably formed as a unitary construct whereby the first portion and the second portion are joined together by an adhesive bonding agent, contact cement pressure or heat activated film or the like. 
     The upper surface of the sole is preferably provided as a substantially continuous surface and formed by at least part of the first portion and the second portion of the sole, and the first portion preferably extends partially towards the lower surface of the sole. Alternatively, the first portion may extend through the sole to the lower surface of the sole. 
     The upper surface is preferably of concave form and the sole includes a peripheral lip extending at least partially along the periphery of the sole so as to provide a contoured upper surface configured to receive the underside of the foot of the person. 
     The footwear article may further include a cushioning member located within the sole. 
     The first portion of the sole may be provided as a multi-layered gel construct. 
     The sole may further include a third portion which extends to the upper surface of the sole and having material property provides for dampening of load imparted to the foot of the person upon contact with a surface, said third portion providing for interaction with at least the metatarsal region of the foot of the person. 
     Preferably the footwear article is provided in the form of a “flip-flop” type footwear article. Alternatively, the article may be provided in the form of a “sandal” type footwear article, or as an at least partially enclosed footwear article. 
     Alternatively, the article may be provided as a heeled article such that the upper surface of the sole is inclined in a direction of from the upper surface towards the lower surface in a direction of from the first portion towards the second portion, and the third portion is located in a portion to substantially prevent or reduce movement of the foot of the person along the upper surface of the sole. The third portion may be located so as to be at adjacent the ball of the underside of the foot of the person. 
     In another aspect, the present invention provides a footwear article comprising:
         a generally elongate sole for engagement with and support of the foot of a person, said sole having an upper surface, a lower surface, a first portion being for interaction with at least the heel region of the foot of the person and a second portion for interaction with at least the metatarsal region of the foot of the person; and   a foot engagement means for securing the footwear article to the foot of a person.   characterised in that a first portion of the sole includes a first material having a first material property and the a second portion of the sole includes a second material having a second material property, first material property providing for dampening of load imparted to the foot of the person upon contact with a surface.
 
Preferably, said first material is a gel type polymeric material and said second material is an expanded polymeric material, the sole is preferably formed as a unitary molded structure, and said first portion and said second portion co-operatively form a flexible sole.
 
Preferably a part of the first portion and a part of the second portion form the upper surface of the sole.
       

     In a further aspect, the present invention provides a footwear article comprising:
         a generally elongate sole comprising a first portion and a second portion and having an upper surface and a lower surface, said first portion being for direct contact and interaction with at least a portion of the underside of the foot of the person and being formed from a first polymeric material having a first density; and said second portion forming substantially the entire lower surface and being for direct contact and interaction with a surface and being formed from a second polymeric material having a second density; and   a generally elongate and flexible foot engagement means for securing the footwear article to the foot of a person, said foot engagement being engaged directly with at least said second portion and configured so as to extend over a portion of the upper side of the foot of the person;   wherein the first polymeric material and the second polymeric material are selected and the first portion and the second portion are sized and arranged such that the sole is substantially flexible and elastic so as to allow for substantial flexion of the sole longitudinally and return, when in use and during ambulation of the person;   wherein the first polymeric material and the second polymeric material are selected and the first portion and the second portion are sized and arranged such that dampening is provided upon load being imparted to the foot of the person upon contact with the surface; and   wherein the sole is formed as a unitary construct by co-molding the first portion and the second portion together, and the first polymeric material and the second polymeric material are suitably selected for said co-molding.       

     The first density is preferably greater than the second density, and the first material is preferably provided in a gel form and the second polymeric material is preferably provided in an expanded form. 
     In a preferred embodiment, the foot engagement means is a “thong” type engagement means, and the footwear article is provided in the form of a “flip-flop” type footwear article. 
     The first polymeric material and the second polymeric material may be selected from the group including thermoplastic polymeric materials, co-polymers and mixed polymer blends, more preferably from the group including polyurethane, ethylene vinyl acetate, poly vinyl acetate and the like. 
     In a preferred embodiment, the first material is a polyurethane gel material and the second material is an expanded polyurethane material. 
     The first portion may extend substantially laterally across upper surface of the sole and substantially form the rear part of the upper surface of the sole, and the second portion may form at least a part of the front part of the upper surface of the sole. 
     Alternatively, the first portion may form at least part of the front part of the upper surface of the sole, and the second portion may form at least a part of the rear part of the upper surface of the sole. 
     In an alternate embodiment, the first portion may form substantially the entire upper surface of the sole 
     The first portion may further provide for interaction with and at least partial support of the plantar arch of the user. 
     In other embodiments, the first portion may be provided as a first part and a second part and laterally spaced apart such that the first part provides for interaction with the lateral inferior of the metatarsal region of the foot of the person and the second part provides for interaction with the medial inferior aspect of the metatarsal region of the foot of the person. The first part and the second part of the first portion may be sized and selected from a material so as to provide lateral stabilisation and load distribution of the heel of the person. 
     In further embodiments, the upper surface may be of concave form and the sole may include a peripheral lip extending at least partially along the periphery of the sole so as to provide a contoured upper surface configured to receive the underside of the foot of the person. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the present invention will be explained in further detail below by way of examples and with reference to the accompanying drawings, in which:— 
         FIG. 1 a    is a plan view of an exemplary embodiment of a footwear article according to the present invention; 
         FIG. 1 b    is an underside view of the embodiment of the invention as depicted in  FIG. 1   a;    
         FIG. 1 c    is a side view of the embodiment of the invention as depicted in  FIGS. 1 a    and  1   b;    
         FIG. 2 a    depicts an inside view of a schematic representation of the present invention; 
         FIG. 2 b    is an underside view of the schematic representation depicted in  FIG. 2   a;    
         FIG. 2 c    is an outside view of the schematic representation of the present invention depicted in  FIGS. 2 a    and  2   b;    
         FIG. 2 d    is a section view through line D-D of  FIG. 2   b;    
         FIG. 2 e    is a plan view of the schematic representation depicted in  FIGS. 2 a    to  2   d;    
         FIG. 2 f    is a section view through line A-A of  FIG. 2   b;    
         FIG. 2 g    is a section view through line B-B of  FIG. 2   b;    
         FIG. 2 h    is a section view through line C-C of  FIG. 2   b;    
         FIG. 3 a    is a plan view of a first schematic representation of an embodiment of the present invention; 
         FIG. 3 b    is a plan view of a second schematic representation of an embodiment of the present invention; 
         FIG. 3 c    is a plan view of a third schematic representation of an embodiment of the present invention; 
         FIG. 3 d    is a plan view of a fourth schematic representation of an embodiment of the present invention; 
         FIG. 3 e    is a side view of a further embodiment of the present invention; 
         FIG. 4 a    is a plan view of a first schematic representation of a further embodiment of the present invention; 
         FIG. 4 b    is a plan view of a second schematic representation of a further embodiment of the present invention; 
         FIG. 4 c    is a plan view of a third schematic representation of a further embodiment of the present invention; 
         FIG. 5 a    depicts another embodiment of a footwear article according to the present invention; 
         FIG. 5 b    depicts a further embodiment of a footwear article according to the present invention; 
         FIG. 6  depicts yet another embodiment of a footwear article according to the present invention; 
         FIG. 7 a    depicts yet a further embodiment of a footwear article according to the present invention; 
         FIG. 7 b    depicts the embodiment of the footwear article of  FIG. 7 a    in a non-flexed state; and 
         FIG. 7 c    depicts the embodiment of the footwear article of  FIG. 7 a    in a flexed state. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 a  to 1 c    and  FIGS. 2 a  to 2 h   , an exemplary embodiment of a footwear article  100  according to the present invention is shown. In the present embodiment, the footwear article  100  is provided in the form of a “flip-flop” type article, however other articles or other or alternate embodiments are also applicable to the invention, such as a sandal, slip-on type shoes or the like. 
     The article  100  is provided as a generally elongate sole  10  which, in the present invention, is provided as two portions, a first portion  16  and a second portion  18 , although those skilled in the art will appreciate that the article  100  may be provided as further portions without departing from the invention. 
     A foot engagement means  20  is provided which is provided so as to co-operatively secure the article  100  to the foot of a person. Although depicted as a typical “flip flop” engagement device, those skilled in the art shall appreciate that other engagement devices such as straps, buckles, cross-overs or the like are equally applicable to the invention. Co-operatively with the sole  10 , the engagement means  20  secures the article  100  to the foot of a person. 
     The engagement means  20  is affixed to the sole  10  of the article via apertures extending through the sole  10 , the engagement means  20  having formations for abutting against and within recesses within the underside  14  of the sole  10 . Again, those skilled in the art will understand that various engagement means may secured to the sole  10  in other manners where applicable. 
     The first portion  16  is positioned and formed from a material suitable for providing cushioning or dampening to the heel of a person when standing or during walking. The second portion  18  provides for support of the front portion or metatarsal portion of the foot of a person. 
     The sole  10  is provided with a concave upper surface  12  which is suitably contoured so as to provide for comfort of fit to the foot of a user when wearing the article  100 . A peripheral lip  13  is provided which extends around the periphery of the sole  10  again providing for comfort to a user and for foot conformity. 
     In the present embodiment, the first portion  16  further extends as a medical portion  19  to provide arch support to the foot of a person. Those skilled in the art will appreciate that other geometries and positioning of the first portion  16  may be provided in other or alternate embodiments so as to provide cushioning to the underside of the foot of a person, without departing from the scope of the invention. 
     The first portion  16  of the sole  10  is formed from a gel-type polymeric material, in the present embodiment a polyurethane gel material, the visco-elastic properties of which provide for cushioning and shock absorption to the heel portion of a user. The second portion  18  of the sole  10  is formed from a further polymeric material, in the present embodiment expanded polyurethane, which is integrally formed with the first portion  10 . The second portion of the present embodiment forms the majority of the sole, the flexural properties in conjunction with suitable sizing provides for significant flexing of the sole when walking and again increases comfort to a use. 
     In the present embodiment of the article  100 , the first portion  16  and the second portion  18  are integrally formed by a co-molding process so as to provide continuity between the portions  16  and  18 . A co-molding process, as will readily be understood by those skilled in the art, is whereby the portions are molded together and are generally formed with a common mold. 
     By being formed as a co-molded sole  10 , the present invention provides for continuity of the sole  10  to be formed as a unitary construct, allowing for ease of form and providing for continuity of the upper surface  12  of the sole, thus allowing for direct contact of the underside of the foot of a user and also provides for ease of formation and manufacturing. Further, by providing a unitary construct such that the sole  10  is substantially formed in total by the first portion  16  and the second portion  18 , ease and simplicity of formation and manufacture is achieved. 
     In other or alternate embodiments, the sole  10  may be formed by adhering the first portion  16  and the second portion  18  together by adhesives, pressure or heat sensitive glues or the like, where applicable. 
     Although in the present embodiment, the first portion  16  and the second portion  18  are formed from a polyurethane gel and expanded polyurethane material respectively, those skilled in the art that other polymer or thermoplastic materials may also be utilised, such as poly vinyl acetate materials or other such suitable polymeric materials. 
     Alternatively, in other embodiments and as would be understood by those skilled in the art, other materials such as rubbers, elastomers, organic materials or combinations thereof, and co-polymer and mixed polymer blends and combinations thereof may also be utilised. Further, materials may be provided in the form of compact polymers, expanded polymeric materials or gel materials or combinations thereof and may be used in various combinations without departing from the scope of the invention. Furthermore, the sole  10  may be provided as a single material having varying densities so as to provide a first portion with appropriate cushioning whilst being of a expanded form for example for other parts of the sole so as to provide for structural integrity. 
     Furthermore, in other or alternate embodiments of the invention, the first portion  16  may be provided so as to provide medial or lateral support to the heel of a user so as to more evenly distribute load to the heel and to prevent exacerbated medial or lateral wear of the rear portion of the sole  10 . In other embodiments, the first portion may be provided as two or more discrete parts spaced laterally apart form each other and suitably located and sized so as to provide for more even loading and increased stabilisation to the underside of the foot of a user. 
     In the present embodiment, the first portion  16  is provided so as to extend partway through the sole  10  towards the lower surface  14 . However, in other embodiments, the first portion  16  may extend to a greater or lesser extent through the thickness of the sole  10 . Further, the first portion  16  is provided so as to extend the full width of the sole  10  in the present embodiment, however again, the first portion  16  may extend partway across the sole  10  in other embodiments. 
     In the present embodiment, the article  100  is depicted as a substantially planar “flip-flop” type footwear article, however, in other or alternate embodiments the article  100  may be provided with a raised heel, such as for women&#39;s type footwear. Further, as will be appreciated, the first portion  16  may be provided as a plurality of layers either in the direction between the upper and lower surface or laterally, and each layer may be provided with differing colours. 
     In other embodiments, cushioning elements such as “air cushioning” elements may be incorporated within the sole to provide for additional cushioning to the foot of a user. 
     Referring to  FIG. 3 a   , there is shown an embodiment  200   a  of the invention whereby a third portion  215   a  is provided towards the metacarpal portion of a user&#39;s foot to provide for cushioning to the front portion of the foot of a user. The third portion may be formed from same of different materials as that of the first portion  216   a.    
     In another embodiment of the footwear article  200   b  as shown in  FIG. 3 b   , the first portion  216   b  and the second portion  216  are integrally formed, and co-operatively provide for lateral support of the underside of the foot of a user. 
     Referring to  FIG. 3 c   , and embodiment of the footwear article  200   c  is shown whereby a portion  219   c  of the first portion provides for medial arch support. 
     In a further embodiment of a footwear article  200   d  according to the present invention as depicted in  FIG. 3 c   , the first portion  216   d  is provided as two separate parts being spaced apart laterally so as to provide for increased medial or lateral support and cushioning to the underside of the heel portion of the foot of a user. 
       FIG. 3 e    depicts yet another embodiment of a footwear article  200   e  according to the present invention whereby the article  200   e  is provided with a raised heel. The first portion  216   e  provides for cushioning of the heel of a user whilst a third portion  215   e  is provided for contact with the ball of the foot of a user, which provides resistance and reduces the incidence or likelihood of the foot of the user sliding down the inclined surface. 
     Referring to  FIGS. 4 a , 4 b  and 4 c   , there are shown embodiments of footwear articles  300   a ,  300   b  and  300   c  having various foot engagement means.  FIG. 4 a    shows a foot engagement means  320  typical of that of a “flip-flop”,  FIG. 4 b    shows an “cross-over” type engagement means and  FIG. 4 c    shows a single-strap type foot engagement means  320   c . Those skilled in the art will appreciate that numerous types of foot engagement means are applicable without departing from the scope of the invention. 
     Referring to  FIG. 5 a   , there is shown another embodiment of a footwear article  400  according to the present invention. In the present embodiment, the first portion  410  extends along the entire length of the article  400  so as to provide the entire upper surface  420 . In this embodiment, the first portion  410  again is formed from a gel material so as to provide dampening to the foot of a user upon impact, in combination with an expanded polymeric foam of which the second portion  420  is formed. 
     Further, in the present embodiment, elongate grooves  440  extend laterally across the upper surface  420  of the article  400 . The grooves  440  allow for localized deformation of the first portion  410 , which provides for additional dampening to the foot of a user during use. Furthermore, the laterally extending grooves  440  also provide a “grip” effect which prevents slippage of the foot of a user against the other surface  420  during use. 
     Referring to  FIG. 5 b   , there is shown a further embodiment of a footwear article  500  according to the present invention. Similarly as in the embodiment depicted in  FIG. 5 a   , the first portion  510  extends the entire length of the footwear article  500  so as to form the entire upper surface  520 . Again, the second portion is provided by an expanded polymeric material  520  of foam form which extends the entire length of the article  500 . 
     In the present embodiment, grooves  540  are provided which, similarly as in the embodiment depicted in  FIG. 5 a   , allow for localized deformation of the first portion  510 , and due to the gel like properties, and further incorporation with the expanded polymeric properties of the second portion  530 , the grooves  540  allow for additional dampening and cushioning to the foot of a user during use. Furthermore, again the grooves  540  provide a “grip” type effect which reduces slippage of the foot of a user on the upper surface  520  of the article  500  during use. 
     Referring now to  FIG. 6 , there is depicted yet a further embodiment of a footwear article  600  according to the present invention. In the present embodiment, the first portion  610 , again formed from a gel material, and in this embodiment is provided towards the front portion of the footwear article  600 . The first portion  610  forms a part of the upper surface  620 , and the second portion  630 , again formed from an expanded polymeric material, forms the remaining portion of the upper surface  520 . 
     In the present embodiment, the first portion  610  provides for dampening and shock absorption at the front portion of the foot of a user in use, and furthermore, the first portion being located in this position provides for grip of the foot of a user and prevents slippage along the upper surface  620  in use. 
     Referring now to  FIGS. 7 a , 7 b  and 7 c   , there is depicted yet a further embodiment of a footwear article  700  according to the present invention. In the present embodiment, the first portion  710  is provided again in a gel material form, and the second portion  730  is provided in an expanded polymeric form. The first portion  710  extends the entire length of the footwear article  700  so as to form the entire upper surface  720  of the article  700 . In the present embodiment and those as depicted in preceding embodiments, the first portion and the second portion are selected from suitable polymeric materials and are suitably sized so as to provide for repetitive flexion of the footwear article as shown in  FIG. 7 b    during use, and so as to provide for resilience or “spring bag” such that the deformation is elastic and the article returns to its rest states as depicted in  FIG. 7 c   . As will be understood and appreciated by those skilled in the art, a footwear article of the type depicted, is exposed to much flexion and bending and thus the first portion and second portion must be able to be maintained together to maintain the structural integrity of the sole. 
     In reference to the embodiments of the invention as depicted in  FIGS. 5 a  to 7 c    and as described in the description above, as will be appreciated by those skilled in the art, the footwear articles are provided such that the sole of the article comprises the entire sole of the device, and the foot engagement means merely hold the sole to the bottom of the foot of the user. Such footwear articles are termed different names in different parts of the world, including terms such as “flip flop”, “thongs” and “jandals”. 
     As will be understood by those skilled in the art, to provide a flip-flop type footwear article, the article must be extremely flexible so as to allow for continual flexing during walking or ambulation of a person. Such a sole is distinctly different from that of traditional footwear articles, whereby a comparatively small amount of flexion is allowable and typically at one portion of the sole, in comparison with that as required and provided by flip-flop type footwear articles. 
     As will also be appreciated by those skilled in the art, it is necessary to provide an article which, after many repetitions of flexion, maintains its structural integrity without the first portion and the second portion separating or delaminating. Furthermore, those skilled in the art will appreciate that the sole of a flip-flop device as claimed and shown in the accompanying drawings in accordance with the present invention, only comprises the upper portion and the lower portion as described, the upper portion (i.e. first portion) providing for direct contact with the underside of the foot of a user most often without a sock, and the lower portion (i.e. second portion) engages directly with the grounds or surface upon which a person walks, without the use of additional outer source or the like. 
     Furthermore, flip-flop type footwear, as will readily be understood and appreciated by those skilled in the art, are often exposed to harsh environmental conditions such as water and long durations of sunlight due to their typical applications, and the materials from which they are formed and the manner in which the portions are joined, must be capable of withstanding such exposure. 
     As such, those skilled in the art will appreciate that a substantial difference exists between the sole of the footwear article in the present invention and those of conventional footwear, for which have in the prior art been described as being formed by multiple layers. 
     It will be appreciated, that as the sole of the present invention is comprised only of the first portion and the second portion, these portions must be securely joined or bonded together securely in a manner, as there exists no outer shoe body whereby an inner sole is still retained within a shoe even if not securely bonded to the inside of a shoe, and also in view of typical applications as discussed above. 
     The present invention has overcome problems of the prior art such as delamination, so as to provide a footwear article having a sole distinctly different from those of conventional footwear, a sole which must endure significantly larger amounts of flexion and strain, whilst maintaining the structural integrity of the sole. By provision of a “co-molding process” whereby a gel material is co-moulded with a polymeric material which is expanded in a manner so as to provide continuity between the gel-type material and the expanded polymeric material. As such, a unitary sole of a unitary construct has been provided that overcomes practical and longevity problems which may be encountered when utilizing bonding techniques such as used in the prior art. The co-molding process provides for structural integrity and also maintains the bond between the materials throughout angles of flexion of the sole well beyond the amount of flexion that conventional footwear are exposed to. Furthermore, the co-molding process simplifies production so as to allow ease of manufacture and reduction in manual labour, and does not require separate formation of the two portions, and does not require a post-fabrication process for joining the portions. 
     Thus, the two portions, by being moulded, provides a unitary structure whereby the sole is formed of a “continuous” polymeric material, without the necessity for adhesive and the like, and thus mitigating the incidence of debonding, even throughout repetitive large amounts of flexing. The co-molding process provides for rapid and cost and time effective manufacture, and reduces the amount of material wastage, thus also providing environmental advantages. 
     While the present invention has been explained by reference to the examples or preferred embodiments described above, it will be appreciated that those are examples to assist understanding of the present invention and are not meant to be restrictive. Variations or modifications which are obvious or trivial to persons skilled in the art, as well as improvements made thereon, should be considered as equivalents of this invention. 
     Furthermore, while the present invention has been explained by reference to “flip-flop” type footwear articles, it should be appreciated that the invention can apply, whether with or without modification, to other footwear articles without loss of generality.