Overmold direct attach sole

Abstract

Joining a bottom unit, such as an athletic shoe sole, with an upper is achieved with an over molding process. A midsole core may be formed with a direct attach to an underfoot portion of the upper. The forming of the midsole core may be achieved with open cast molding or injection molding, for example. A shell may encapsulate the midsole core and also mechanically engage with the upper to further join the bottom unit with the upper. The shell and the midsole core may be formed from an elastomeric polymer such as polyurethane, thermoplastic polyurethane, ethyl-vinyl acetate, and/or silicone-based materials.

The invention claimed is: 
     
         1 . A method of forming an article of footwear, the method comprising:
 lasting a footwear upper;   forming a midsole core to at least an underfoot portion of the footwear upper, wherein the midsole core is direct attached to the footwear upper through the forming; and   forming a shell to the midsole core and a portion of the footwear upper concurrently, wherein the shell encapsulates at least a portion the midsole core forming an exterior surface on the midsole core.   
     
     
         2 . The method of forming an article of footwear of  claim 1  further comprising inserting the lasted upper into a first tooling prior to forming the midsole core. 
     
     
         3 . The method of forming an article of footwear of  claim 2  further comprising transferring the lasted upper and the midsole core from the first tooling to a second tooling prior to forming the shell. 
     
     
         4 . The method of forming an article of footwear of  claim 2  further comprising maintaining the lasted upper in the first tooling while forming the shell. 
     
     
         5 . The method of forming an article of footwear of  claim 1 , wherein forming the midsole comprises casting material forming the midsole core. 
     
     
         6 . The method of forming an article of footwear of  claim 1 , wherein forming the midsole comprises injecting material into tooling to form the midsole core. 
     
     
         7 . The method of forming an article of footwear of  claim 1 , wherein forming the midsole core to the at least underfoot portion of the footwear upper comprises the midsole core mechanically engaging with the footwear upper. 
     
     
         8 . The method of forming an article of footwear of  claim 1 , wherein the midsole core is direct attached to the footwear upper without an adhesive. 
     
     
         9 . The method of forming an article of footwear of  claim 1 , wherein the midsole core is comprised of at least one selected from PU, TPU, EVA, and silicone. 
     
     
         10 . The method of forming an article of footwear of  claim 1 , wherein the midsole core has a lower density than the shell. 
     
     
         11 . The method of forming an article of footwear of  claim 1 , wherein the midsole core is comprised of a first material and the shell is comprised of a second material, wherein the first material has a higher resilience than the second material. 
     
     
         12 . The method of forming an article of footwear of  claim 1 , wherein forming the shell comprises casting material forming the shell. 
     
     
         13 . The method of forming an article of footwear of  claim 1 , wherein forming the shell comprises injecting material forming the shell into a tooling. 
     
     
         14 . The method of forming an article of footwear of  claim 1 , wherein the shell is comprised of at least one selected from PU, TPU, EVA, and silicone. 
     
     
         15 . The method of forming an article of footwear of  claim 1 , wherein the shell has a greater abrasion resistance than the midsole core. 
     
     
         16 . An article of footwear comprising:
 an upper having an underfoot portion;   a midsole core adjacent to the upper at the underfoot portion; and   a shell, the shell encapsulating the midsole core and mechanically engaged with the upper, wherein the shell forms a ground-contacting surface of the article of footwear.   
     
     
         17 . The article of footwear of  claim 16 , wherein the midsole core is comprised of at least one selected from PU, TPU, EVA, and silicone. 
     
     
         18 . The article of footwear of  claim 16 , wherein the midsole core has a lower density than the shell. 
     
     
         19 . The article of footwear of  claim 16 , wherein the midsole core is comprised of a first material and the shell is comprised of a second material, wherein the first material has a higher resilience than the second material. 
     
     
         20 . The article of footwear of  claim 16 , wherein the midsole core has a density less than 0.25 grams per cubic centimeter.