Midsole structure of athletic shoe

Abstract

A midsole structure for an athletic shoe includes a midsole ( 3 ) formed of a soft elastic material and extending from a shoe heel region through a midfoot region to a forefoot region and a plastic shank member ( 10 ) or shankpiece and provided at regions that cover a midfoot portion (B) of the midsole ( 3 ) and having an oblong cross sectional shape where a dimension (W) in a shoe elongated direction is greater than a dimension (h) in the vertical direction. Thus, flexural rigidity of the midfoot portion (B) of the midsole ( 3 ) increases. When a bending moment is applied to themidsole ( 3 ), the shankmember ( 10 ) effectively exercises a so-called “shank effect” and thus, bending deformation can be prevented from occurring at the midfoot portion (B) of the midsole ( 3 ). As a result, flexibility or bendability of the forefoot portion (C) of the midsole ( 3 ) can be relatively advanced.

What is claimed is:  
     
         1 . A midsole structure of an athletic shoe comprising: 
 a midsole formed of a soft elastic material and having a heel portion, a midfoot portion and a forefoot portion and extending from heel region of said shoe to a forefoot region through a midfoot region; and    a shank member formed of plastics and provided at regions that cover said midfoot portion of said midsole and having an oblong cross sectional shape where a dimension in a shoe elongated direction is greater than that in a vertical direction.    
     
     
         2 . The midsole structure of  claim 1 , wherein a front end edge of said shank member is disposed at a rear end portion of said forefoot portion of said midsole and a rear end edge of said shank member is disposed at a front end portion of said heel portion of said midsole.  
     
     
         3 . The midsole structure of  claim 2 , wherein said shank member is a tubelike member that has a hole extending in a shoe width direction.  
     
     
         4 . The midsole structure of  claim 3 , wherein said shank member has a flat annular shape in cross section.  
     
     
         5 . The midsole structure of  claim 3 , wherein said shank member is generally D-shaped or semicircular in cross section.  
     
     
         6 . The midsole structure of  claim 5 , wherein said shank member is formed of an upper portion and a lower portion, said upper portion being convexly curved upwardly and having a central curved face that extends in a shoe width direction, said lower portion being convexly curved upwardly and having a central curved face that extends in a shoe elongated direction, or said lower portion extending in a flat shape, a front and rear end of said upper portion being connected to a front and rear end of said lower portion.  
     
     
         7 . The midsole structure of  claim 6 , wherein said upper portion of said shank member has a pair of flanges that extend upwardly at opposite end edges thereof and that sandwich opposite side f aces of said midfoot portion of said midsole.  
     
     
         8 . The midsole structure of  claim 6 , wherein said lower portion of said shank member has a pair of flanges extending upwardly at opposite end edges thereof, a top portion of each of said flanges being connected to said upper portion, said flanges closing a portion of an opening of said hole in said shank member.  
     
     
         9 . The midsole structure of  claim 6 , wherein said lower portion of said shank member has a pair of flanges extending upwardly at opposite end edges thereof, a top portion of each of said flanges being connected to said upper portion, said flanges closing the whole portion of an opening of said hole in said shank member.