Abstract:
A shoe construction having a sole with an outsole shell that is filled with a filling material, such as polyurethane foam, and secured to the upper by a welt. The sole includes an insole having a downwardly extending rib, an outer shell defining a void containing the filling material, and a welt that interconnects the outsole shell and the insole with the upper. To assemble the construction, the upper is lasted and either stitched or stapled to the insole. The welt is then stitched or stapled to the insole/upper combination. Next, the filling material is poured into the void in the outsole shell and the shell is directly attached by the filling material to the upper/insole/welt assembly. The outsole welt is stitched to the shell around the entire periphery of the sole. The stitch extends between a stitch groove in the welt and a stitch groove in the outsole shell.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to footwear construction, and more particularly to a footwear construction in which the sole is attached to the upper by a welt. 
     A variety of different sole constructions are used by the footwear industry. For the most part, each sole construction has characteristics that make it particularly well-suited for specific applications. For example, some sole constructions are selected for their durability, others for their flexibility and comfort, while still others are selected for their aesthetic appeal. One particularly popular type of sole construction is referred to as a welt construction. Welt constructions are popular because they are durable and are aesthetically desirable. There are a variety of different types of welt constructions, but in each construction a “welt,” for example, a strip of material such as leather or hard rubber, is used to intersecure the sole and the upper. FIG. 1 is an exploded sectional view of a conventional welt construction. This construction includes a welt  150  that interconnects an upper  158  and a sole  172 . The welt  150  includes a base portion  152  with an upwardly extending rib  154  located toward the center of the base portion and a downwardly extending rib  156  located at the inner edge of the base portion  152 . The sole  172  includes an insole  160 , a midsole  168 , and an outsole  170 . The insole  172  includes a downwardly extending rib  164  that is used in interconnecting the insole  160 , upper  158  and welt  150 . 
     Assembly of this construction involves a number of common steps. First, the elements of the upper  158  are cut from the desired material and fit together (typically by sewing). The fitted upper  158  is then wrapped tightly around a foot-shaped form, or last, and secured to the insole  160  by stapling, stitching, or otherwise fastening it to the insole rib  164 . This step gives the upper  158  the desired shape and is commonly referred to as lasting. Once lasted, the welt  150  is stitched or stapled to the upper  158  and insole  160  by stitches or staples that extend through the inner welt rib  156 , the bottom periphery of the upper  158 , and the insole rib  164 . The midsole  168  is stitched, stapled or otherwise secured to the bottom of the upper/insole assembly. Typically, the midsole  168  is attached to the upper/insole assembly by stitching that extends through the base portion  152  of the welt  150  and the midsole  168 . Afterwards, the outsole  170  is secured to the bottom of midsole  168 , typically by cement or other adhesives. Although this construction is durable and aesthetically appealing, it is a relatively heavy construction and it does not provide the flexibility of other constructions. 
     In an effort to improve the flexibility and reduce the weight of the sole, a variety of sole constructions have been developed which incorporate polyurethane. For example, some footwear manufacturers currently sell footwear that incorporates a solid polyurethane outsole. Typically, the polyurethane outsole is either directly attached to the upper or it is attached to a midsole that is in turn attached to the upper. Polyurethane is a relatively soft material and it is not as wear-resistant as many other outsole materials, such as leather and rubber. Also, polyurethane has relatively low tear-resistant characteristics. As a result, it does not hold a stitch or staple well, and is consequently not well suited for use in a welted construction. 
     In an effort to overcome these problems, a number of attempts have been made to enclose the polyurethane in a shell. The shell is relatively wear resistant and it forms the wear surface of the sole. One such construction includes a rubber shell that is filled with polyurethane. The shell is cemented to the upper in a conventional manner. Although this construction provides the improved comfort and weight characteristics of polyurethane, it fails to provide the durability and aesthetic benefits of a welt construction. 
     SUMMARY OF THE INVENTION 
     The aforementioned problems are overcome by the present invention wherein a sole construction is provided which includes a polyurethane filled outsole shell that is secured to the upper by a welt. The sole construction includes a generally conventional insole, an outsole shell manufactured from a durable, wear-resistant material, and a welt that interconnects the outsole shell and the insole with the upper. The outsole shell defines a chamber that contains a polyurethane filling material. The polyurethane filling material fills the chamber and bonds directly to the insole, welt, and outsole. 
     In a preferred embodiment, the welt includes a base portion that is stitched to the shell and a downwardly extending rib that is stitched to both the upper and the insole rib. The shell preferably defines a stitch channel that extends entirely around the circumference of shell to receive the stitches that interconnect the welt and the shell. 
     In a second aspect, the shell includes a plurality of protrusions, such as scallops, that extending into the polyurethane chamber. The polyurethane surrounds and attaches to the protrusions to enhance the connection between the polyurethane and the shell. 
     The present invention also provides a method for manufacturing a shoe. First, the upper is lasted and either stitched or stapled to the insole. The welt is then stitched or stapled to the insole/upper combination. Then, polyurethane is poured into the chamber in the shell and the shell is direct attached to the upper/insole/welt assembly. As the polyurethane cures, it expands to fill the space and bond to the shell, the insole, and the welt. The welt is then stitched to the shell around the entire periphery of the sole. The stitch extends between a stitch channel in the welt and a stitch channel in the shell, and preferably does not extend through the polyurethane. 
     The present invention provides a durable and comfortable sole construction. Because the present invention does not require a midsole, the construction is relatively flexible. The outsole shell provides the sole with excellent wear characteristics. Also, the use of polyurethane makes the outsole lighter and more resilient than a conventional welted construction. In addition, the stitch channel in the shell receives the stitching to protect it from abrasion and wear. The present invention is also easily manufactured using conventional machinery. Further, as the polyurethane cures, it expands into and seals the stitch holes and the seams between the insole, the welt, and the upper. As a result, the present invention allows the possible manufacture of the waterproof welted footwear without the need for a membrane. 
     These and other objects, advantages, and features of the invention will be readily understood and appreciated by reference to the detailed description of the preferred embodiment and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of a welt sole construction according to the prior art; 
     FIG. 2 is a perspective view of an article of footwear incorporating the present invention; 
     FIG. 3 is an exploded perspective view of the article of footwear; 
     FIG. 4 is a sectional view of an article of footwear incorporating the present invention; 
     FIG. 5 is a side elevational view of the shell; 
     FIG. 6 is a top plan view of the shell; and 
     FIG. 7 is sectional view of the shell taken along line VII-VII of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A boot constructed in accordance with a preferred embodiment of the present invention in shown in FIGS. 2 and 3, and generally designated  10 . For purposes of disclosure, the present invention is described in connection with a conventional ¾ height boot. One of ordinary skill in the art will, however, readily appreciate that the present invention is well suited for use with other types of soled footwear. For purposes of this disclosure, the terms inner and outer will be used to denote the directions toward and away from the inside of the boot, respectively. 
     In general, the boot  10  includes an upper  12  that is secured to the sole  14  by a welt  16 . As perhaps best shown in FIG. 3, the sole  14  includes an insole  18  and an outsole shell  20 . The outsole shell  20  defines a void  22  that contains a filling material  24 , such as polyurethane. The welt  16  is attached to and interconnects the upper  12 , insole  18 , and shell  20 . 
     The upper  12  is generally conventional and will not be described in detail. Suffice it to say that the upper  12  includes a quarter  29 , a vamp  28 , and a backstay  30 . The upper  12  terminates in a lower peripheral edge  26  that is attached to the sole  14  as described in detail below. The upper  12  is preferably manufactured from leather, canvas, nylon or other suitable materials, and may include a liner (not shown) or other conventional accessories. 
     The welt  16  extends entirely around the boot  10  to interconnect the upper  12  and the sole  14 . As perhaps best shown in FIG. 4, the welt  12  is also generally conventional. The welt  12  includes a generally horizontal base portion  32  with an upwardly extending upper rib  34  located toward the center of the base portion  32  and a downwardly extending lower rib  36  located at the inner edge of the base portion  32 . The outer surface of the upper rib  34  is rounded to, among other things, reduce the profile of the welt  16 . The lower rib  36  is generally rectangular in cross-section and is of sufficient size to receive staples, stitching or other fastening elements. The horizontal base portion  32  defines an upwardly opening stitch groove  38  that extends around the welt  16  near its outer edge. The stitch groove  38  is adapted to receive the stitching  72  that interconnects the shell  20  and welt  16  as described in more detail below. 
     As noted above, the sole  14  includes an insole  18 , an outsole shell  20 , and a filling material  24 , such as polyurethane. If desired, the sole  14  may also include a shank (not shown), a filler (not shown) or other conventional sole components. The insole  18  is generally conventional and includes a base  42  and a downwardly extending rib  44 . The base  42  is generally planar and corresponds in shape with the outline of a foot. The insole rib  44  extends downwardly from and around the base  42  near its outer edge. The insole rib  44  is of sufficient size to receive staples, stitching or other fastening elements. 
     The outsole shell  20  is preferably manufactured from a relatively hard rubber or other sufficiently durable and wear-resistant material. The outsole shell  20  generally includes a bottom  46  and a peripheral wall  48  extending upwardly from the periphery of the bottom  46 . The bottom  46  includes an inner surface  50  and an outer surface  52 . The outer surface  52  forms the wears surface of the sole  14  and is contoured to define the desired heel and tread pattern. The outer surface  52  may also be textured as desired to improve the traction and aesthetic appeal of the boot. The peripheral wall  48  also includes an inner surface  54  and an outer surface  56 . The outer surface  56  of the peripheral wall  48  may be contoured or textured to provide the desired visual appearance. The outer surface  56  defines an outwardly opening stitch groove  58 . The stitch groove  58  extends around the peripheral wall  48  near its upper edge. The stitch groove  58  is generally rectangular in cross section. However, its shape may vary from application to application. The peripheral wall  48  includes a plurality of scallops  60 , or other protrusions, that extend inwardly near the upper edge of the peripheral wall  48 . The scallops  60  interlock with the filler  24  improve the interconnection of the various sole components. If desired, the scallops  60  may define apertures (not shown) through which the filler  24  can flow to further improve the interconnection of the sole components. Obviously, the scallops  60  can be replaced by other similar protrusions. 
     The filling material  24  is preferably a conventional polyurethane foam. The inner surface  50  of the bottom  46  and the inner surface  54  of the peripheral wall  48  cooperatively define a void  22  that receives the filling material  24 . As described below, the filling material  24  is preferably pour molded into the void  22  during assembly of the boot  10  such that it expands to flow around and interlock the insole  18 , the outsole shell  24 , and the welt  16 . The density and precise chemical make-up of the polyurethane will vary from application to application depending on a variety of factors, including the size of void  22  and the desired cushioning and flexibility characteristics. 
     Manufacture and Assembly 
     The boot  10  is manufactured using generally conventional machinery. The insole  18  is manufactured using conventional techniques and apparatus. The insole base  42  and insole rib  44  are manufactured in a conventional manner. The insole rib  44  is attached to the undersurface of the insole base  42  by cement, adhesives or other conventional methods. Alternatively, the insole  18  can be manufactured with an integral base and rib. The insole  18  is stapled or otherwise secured to the bottom surface of a conventional last (not shown). 
     The upper  12  is manufactured using generally conventional techniques and apparatus. The desired upper material (not shown) is cut to form the various elements of the upper, including the vamp  28 , quarter  29 , and backstay  30 . The elements of the upper  12  are then fitted and sewn together using conventional methods and apparatus. A lining (not shown) may be sewn within the upper during the fitting step. The fitted upper  12  is stretched over a last (not shown) and stapled to insole  18 . The insole rib  44  is stapled directly to the lower peripheral edge  26  of the upper  12  using conventional apparatus and techniques to intersecure the upper  12  and insole  18 . Alternatively, insole rib  44  can be sewn to the upper  12  in a conventional manner. 
     The welt  16  is manufactured using conventional techniques and apparatus. For example, the welt  16  can be extruded from a hard durable rubber. Once the upper  12  is lasted to the insole  18 , the welt  16  is attached to the upper  12  and insole  18 . First, lower welt rib  36  is stitched around the periphery of the upper  12  and insole  18  using conventional apparatus and techniques. This rib stitch  40  preferably extends entirely through the lower welt rib  36 , the lower peripheral edge  26  of the upper  12 , and the insole rib  18 . If desired a filler (not shown), shank (not shown) or other conventional sole component can be cemented to the bottom surface of the insole  18  using conventional adhesive or cement. 
     The outsole shell  20  is manufactured using conventional techniques and apparatus. The outsole shell  20  is preferably injection or pour molded from a hard, durable rubber using conventional molding apparatus. The outsole shell  20  can, however, be manufactured from other durable outsole materials. The stitch groove  58 , scallops  60 , void  22  and desired tread pattern are all formed during the molding operation as an integral part of the outsole shell  20 . 
     Once the outsole shell  20  is manufactured, it is attached to the upper/welt/insole combination using conventional machinery. The machinery preferably includes a conventional die (not shown) that facilitates assembly of the boot  10 . The die includes a top half, which receives the upper/welt/insole combination, and a bottom half, which receives the outsole shell  20 . The die halves are designed such that they can be closed to hold the upper/welt/insole combination in appropriate alignment with the outsole shell  20 . The die holds the bottom surface of the welt  16  directly against the top surface of the peripheral wall  48  firmly enough to prevent the expanding polyurethane from entering the seam during assembly. 
     After the outsole shell  20  and the upper/welt/insole combination are inserted into the appropriate die halves, the appropriate volume of filler material  24 , preferably polyurethane foam, is poured into void  22 . As the polyurethane foam is poured into the void  22 , it begins to expand and cure. The die is immediately closed bringing the upper/welt/insole combination into proper alignment with the outsole shell  20 . The polyurethane foam continues to expand and cure, causing it to surround, entrap, and interlock the various elements, including the insole  18 , welt  16 , and outsole shell  20 . By virtue of its expansion, the polyurethane foam flows into the seams between the welt  16 , upper  12 , and insole  18  and into the stitch holes in these elements. As a result, the polyurethane filling material  24  allows for the possible manufacture of waterproof welted footwear without the need for a conventional membrane. 
     Polyurethane foam is generally well-known in the footwear industry, and therefore will not be described in detail. Suffice it to say that polyurethane foam is typically derived by combining a polyether, such as polypropylene glycol, with a diisocyanate in the presence of water and a catalyst. The resulting chemical reaction produces carbon dioxide which causes the polymer to foam. The rigidity and flexibility of the polyurethane foam can be varied from application to application, as desired, using a variety of well-known techniques, such as by adjusting the type and proportionate amount of the reactants. In addition, the rigidity and flexibility of the polyurethane foam can be varied by adjusting the volume of polyurethane foam deposited in the void  22 . 
     After the filling material  24  is sufficiently cured, the welt  16  is stitched directly to the outsole shell  20  using conventional machinery. This outsole stitch  72  extends around the periphery of the boot  10  through the welt  16  at stitch groove  38  and the outsole shell  20  at stitch groove  58 . The stitches  72  are recessed in the grooves  38  and  58  so that they are protected from abrasion and wear. As shown in FIG. 4, the outsole stitch  72  does not pass through the filling material  24 . 
     Finally, a number of conventional finishing operations are performed on the boot  10 . For example, the edge of the sole  14  is trimmed and shaped; the upper  12  is cleaned, polished, and treated as appropriate and necessary; and the laces are inserted in the eyelets. 
     The above description is that of a preferred embodiment of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents.