Abstract:
The invention comprises an item of footwear, comprising: a) an upper sole, shaped to receive a user&#39;s foot, and including a toe cap portion, a heel portion, and a sole portion, which is formed from a lightweight, thermally insulative plastics material; b) a lower sole, formed from a resilient plastics material, the lower sole attached to and at least partially covering the sole portion of the upper sole and operative to protect the upper sole from direct physical contact with the ground and to minimize wear on the upper sole; and c) an upper attached to the upper sole.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the field of footwear, and more particularly, to boots and shoes having soles produced by injection molding techniques. 
       BACKGROUND OF THE INVENTION 
       [0002]    The manufacture of footwear, particularly more rugged footwear such as winter boots, work boots and athletic shoes, represents an ongoing balance between weight and durability. To reduce weight and to cut costs therein, it has become common to use lighter weight foamed or expanded plastics materials in the production of such footwear. For example, blown polyurethane has become commonly used as a mid-sole material for winter boots and athletic shoes. It is not only lighter than other plastics or synthetic rubbers (e.g. polyethylene) previously used, but exhibits good thermal insulative properties. 
         [0003]    As a general rule, however, such lighter plastics materials are less durable, which makes them unsuitable for applications, such as lower soles, involving contact with the ground or other ambient surroundings. For children&#39;s footwear, this is not as significant a problem, as children are lighter, resulting in less wear of the item of footwear. Children&#39;s footwear also frequently require replacement of the footwear due to growth, which tends to be as rapid, if not more, than the need to replace the footwear due to wear. However, for adults, who are no longer growing, replacement is driven primarily by wear. 
         [0004]    EVA (Ethylene Vinyl Acetate) is another inexpensive, lightweight plastics material with good insulation properties that is often used to form the insole or midsole of footwear, such as winter boots. However, EVA is also not very wear-resistant and, as such, has not been applied to forming portions of such footwear designed to be in contact with the ground, as the footwear will become unwearable due to abrasion quite rapidly. EVA has been used to make footwear for small children, as their light weight reduces the wear, and their rapid growth means the item of footwear will need to be replaced in a larger size before becoming too worn to wear. 
         [0005]    It is an object of this invention to partially or completely fulfill one or more of the above-mentioned needs by providing an item of footwear that is not only cost-effective to mass manufacture, but which is also lightweight and resistant to undue wear through abrasion, whilst at the same time offering good thermal insulative properties. 
       SUMMARY OF THE INVENTION 
       [0006]    The invention comprises an item of footwear having: a) an upper sole, shaped to receive a user&#39;s foot, and including a toe cap portion, a heel portion, and a sole portion, which is formed by injection molding of a lightweight, thermally insulative plastics material; b) a lower sole, formed by injection molding of a resilient plastics material, the lower sole being attached to and at least partially covering the sole portion of the upper sole and being operative to protect the upper sole from direct physical contact with the ground and to minimize wear on the upper sole; and c) an upper attached to the upper sole. 
         [0007]    Preferably, the lower sole completely covers the sole portion of the upper sole and optionally, the toe cap portion and heel portion of the upper sole. 
         [0008]    Preferably, the resilient plastics material from which the upper sole is molded is EVA (ethylene vinyl acetate). 
         [0009]    It is thus an object of this invention to obviate or mitigate at least one of the above mentioned disadvantages of the prior art. 
         [0010]    Other advantages, features and characteristics of the present invention, as well as methods of operation and functions of the related elements of the structure, and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following detailed description and the appended claims with reference to the accompanying drawings, the latter of which is briefly described hereinbelow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    A preferred embodiment of the invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which like numbers refer to like elements, and wherein: 
           [0012]      FIG. 1  is a front side perspective view of a preferred embodiment of a item of footwear, constructed according to the present invention; 
           [0013]      FIG. 2  is an exploded perspective view of the item of footwear of  FIG. 1 , with the upper removed for simplicity of illustration; 
           [0014]      FIG. 3  is a partially exploded perspective view of the item of footwear of  FIG. 1 , with the upper and upper sole attached to one another and tilted to better illustrate the upper sole to lower sole attachment interface; 
           [0015]      FIG. 4  is bottom plan view of the item of footwear of  FIG. 1 ; 
           [0016]      FIG. 5  is a cross-sectional view along line  5 - 5  of  FIG. 4 ; 
           [0017]      FIG. 6  is a front side perspective view of the lower sole of the item of footwear of  FIG. 1 ; 
           [0018]      FIG. 7  is a side elevational view of the lower sole of  FIG. 6 ; and 
           [0019]      FIG. 8  is a cross-sectional view along line  8 - 8  of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    Referring now to  FIG. 1  of the drawings, there will be seen a preferred embodiment of footwear according to the present invention. The item of footwear illustrated herein is a winter boot  10 , but the invention is not so restricted; rather other items of footwear, such as, for example, safety boots, safety shoes and athletic shoes are equally well within the scope of the present invention. The boot  10  is formed from three parts: an upper sole  100 , a lower sole  200 , and an upper  300 . 
         [0021]    As shown in  FIG. 2 , the upper sole  100  is a molded piece of plastic or thermoplastic which is molded in a shape designed to receive a wearer&#39;s foot through an opening  102 . The upper sole  100  conforms approximately to the shape of the wearer&#39;s foot in standard shoe sizes. The upper sole is comprised of a toe cap portion  104 , a heel portion  106 , and a sole portion  108 . 
         [0022]    Similarly, the lower sole  200 , as shown in  FIGS. 6 and 7 , is a shaped or molded piece of resilient plastic, rubber or a similar material. Lower sole  200  is comprised of a sole portion  208 , and optionally a toe cap portion  204  and a heel portion  206 . The sole portion  208  of the lower sole  200  is shaped so as to adhere to and at least partially cover the sole portion  108  of upper sole  100 . If present, the toe cap portion  204  and heel portion  206  adhere to and at least partially cover the corresponding toe cap portion  104  and heel portion  106 . The bottom surface of the lower sole  200  is covered with a footwear tread pattern to provide traction in accordance with the purpose of the item of footwear  10 . 
         [0023]    The upper  300  (shown in  FIG. 1 ) is attached to upper sole  100  along the edge of opening  102  by an adhesive or by thermal welding or a similar method that provides a watertight seal. 
         [0024]    As shown best in  FIG. 3 , the upper sole  100  and lower sole  200  preferably have complimentary tabs and recesses, or similar interdigitating surface features  110  and  210 , respectively, which are used to align their respective sole portions  108  and  208  for assembly. Other potential types of surface features include a lower surface extension  112  of the upper sole  100  which fits into a corresponding aperture  212  in the lower sole  200 . Ideally, the lower surface extension  112  extends only as far as the bottom surface  203  of the lower sole  200 , as shown in cross-section in  FIGS. 5 and 8 , so as to limit the ground contact and resulting wear of lower surface extension  112 . 
         [0025]    The lower sole  200  is adhered or thermally welded to the upper sole  100  and acts to protect the upper sole  100  from wear, allowing for a lightweight and less abrasion resistant material to be used in the upper sole construction without concerns about premature wear. Similarly, if present, the toe cap portion  204  and heel portion  206  of the lower sole  200  provide additional protection for their counterpart portions  104  and  106  of the upper sole  100 , as the toe and heel portion of footwear can be subject to wear from surface contact in much the same manner as the sole portion. 
         [0026]    Thus, the upper sole  100  is made from a lightweight material, preferably a plastic or thermoplastic, with good thermal insulative properties, and is also sufficiently rigid to be capable of maintaining the internal shape of the item of footwear. The resilience (wear resistance) of the upper sole material is not essential, as the sole portion  108  of the upper sole  100  is covered and protected by the resilient material of the sole portion  208  of the lower sole  200 . A preferred material for forming the upper sole  100  is EVA (ethylene vinyl acetate). 
         [0027]    The lower sole  200  is made of a resilient material to resist wear. Preferably, the resilient material is also flexible, to allow the lower sole  200  to more easily conform to the contours of the upper sole  100  during assembly, although a rigid material can alternatively be used. A preferred material for forming the lower sole  200  is natural rubber or synthetic rubber, such as, for example, and without limitation, polyvinyl chloride, polyurethane, polyethylene and nylon. 
         [0028]    As best seen in  FIG. 1  and in the longitudinal cross-section of  FIG. 5 , along sight line  5 - 5  of  FIG. 4 , the upper sole  100  makes up a significantly greater volume of the item of footwear  10  than does the lower sole  200 , with the result that the selection of a less dense material for construction of the upper sole  100  will typically have a greater impact on the combined weight of the upper  100  and lower  200  sole assembly than would the selection of the material for construction of the lower sole  200 . To further reduce weight, the lower sole  200  can include cutout areas, such as the aperture  212 , which further acts to reduce the total weight of the item of footwear  10  while still ensuring that the upper sole  100  does not come in to regular contact with the ground. The cutouts can additionally reflect arch supports or decorative designs for the item of footwear  10 . Upper sole  100  can additionally include an insole  400  for additional comfort and conformity to the user&#39;s foot. 
         [0029]    Additionally, upper sole  100  can include cut-outs or channels  500 , as shown in  FIG. 5 , which further can add engineered resiliency in supporting the user&#39;s foot and which can reduce the weight of upper sole  100  without unduly reducing structural stability. The exact number and location of such channels can vary significantly based on the material used for upper sole  100  and the intended application for the item of footwear  10 . 
         [0030]    To assemble the item of footwear  10 , the upper sole  100  and lower sole  200  are formed as discussed above, preferably using known injection molding techniques. The lower sole  200  is then adhered to the upper sole  100  by contact along their respective sole portions  208 ,  108 , as well as toe cap portions  204 ,  104  and heel portions  206 ,  106 , if present. Preferably, the lower sole  200  is thermally welded to the upper sole  100 , if their respective materials are compatible with the process. Alternatively, an adhesive substance can be used. 
         [0031]    Once the upper sole  100  and lower sole  200  are bonded together, the upper  300  is attached to upper perimeter of the upper sole  100 . Again, thermal welding is a preferred method of securing the upper  300  to the upper sole  100 , if possible, with stitching and/or adhesives being viable alternatives. 
         [0032]    As an alternative order of assembly, first, upper  300  can be attached to upper sole  100  as described above, and then lower sole  200  adhered to upper sole  100  as described above. 
         [0033]    While the above invention has been presented in the context of a boot type of footwear, the structure and assembly method is equally applicable to other forms of footwear. 
         [0034]    This concludes the description of a presently preferred embodiment of the invention. The foregoing description has been presented for the purpose of illustration and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching and will be apparent to those skilled in the art. It is intended the scope of the invention be limited not by this description but by the claims that follow.