Article of Footwear with Lightweight Sole Assembly

Abstract

An article of footwear includes an upper and a sole assembly secured to the upper. The sole assembly includes a first portion having a lower ground engaging surface, an upper surface, and a recess formed in the upper surface. The upper surface of the first portion is in contact with the upper. A second portion is seated in the recess in the first portion and has an upper surface, with the upper surface of the second portion being in contact with the upper. The second portion comprises a foam material having a density less than 0.25 g/cm 3 .

What is claimed is: 
     
         1 . A sole structure for footwear comprising a midsole, the midsole comprising an exterior sidewall having at least one rib formed on the exterior side wall, the midsole further comprising a first foam material having a density less than 0.25 g/cm3 and a resiliency greater than about 40%. 
     
     
         2 . The sole structure of  claim 1  wherein the density is less than about 0.18 g/cm3. 
     
     
         3 . The sole structure of  claim 2  wherein the density is less than about 0.15 g/cm3. 
     
     
         4 . The sole structure of  claim 1  wherein the resiliency is greater than about 45%. 
     
     
         5 . The sole structure of  claim 1  wherein the resiliency is about 50%. 
     
     
         6 . The sole structure of  claim 1  wherein the first foam has a compression set of less than 50%. 
     
     
         7 . The sole structure of  claim 1  wherein the first foam has a hardness of 25 to 45 Asker C. 
     
     
         8 . The sole structure of  claim 1  wherein the first foam has a hardness of 25 to 35 Asker C. 
     
     
         9 . The sole structure of  claim 1  wherein the first foam has a hardness of 35 to 45 Asker C. 
     
     
         10 . A sole structure for footwear comprising a midsole, the midsole comprising an exterior sidewall having at least one rib formed on the exterior side wall, the midsole further comprising a first foam material having a density less than 0.25 g/cm3 and a hardness of 25 to 45 Asker C. 
     
     
         11 . The sole structure of  claim 10  wherein the density is less than about 0.18 g/cm3. 
     
     
         12 . The sole structure of  claim 10  wherein the density is less than about 0.15 g/cm3. 
     
     
         13 . The sole structure of  claim 10  wherein the hardness is 25 to 35 Asker C. 
     
     
         14 . The sole structure of  claim 10  wherein the hardness is of 35 to 45 Asker C. 
     
     
         15 . A sole structure for footwear comprising a midsole, the midsole comprising an exterior sidewall having at least one rib formed on the exterior side wall, the midsole further comprising a first foam material having a density less than 0.25 g/cm3 and an energy loss of less than about 30%. 
     
     
         16 . The sole structure of  claim 15  wherein the density is less than about 0.18 g/cm3. 
     
     
         17 . The sole structure of  claim 15  wherein the density is less than about 0.15 g/cm3. 
     
     
         18 . The sole structure of  claim 15  wherein the density is less than about 0.18 g/cm3. 
     
     
         19 . The sole structure of  claim 15  wherein the energy loss is about 20% to about 30%. 
     
     
         20 . The sole structure of  claim 1  comprising the first foam material, wherein the first foam is flexible, and a stiffer second foam material having a density of 0.25 g/cm3 or greater, wherein the second foam material is in the heel region of the midsole. 
     
     
         21 . The sole structure of  claim 20  wherein the density of the first foam is less than about 0.18 g/cm3. 
     
     
         22 . The sole structure of  claim 21  wherein the density of the first foam is less than about 0.15 g/cm3. 
     
     
         23 . The sole structure of  claim 1  wherein the at least one rib extends on the exterior sidewall from a central portion of a forefoot portion on a medial side rearwardly along the exterior sidewall, around a heel portion, and forwardly on a lateral side to a central portion of forefoot portion. 
     
     
         24 . The sole structure of  claim 1  wherein the midsole comprises a first portion containing the at least one rib and an upper surface, and a second portion seated on the upper surface of the first portion. 
     
     
         25 . The sole structure of  claim 24  wherein the upper surface of the first portion has a recess and the second portion is seated in the recess. 
     
     
         26 . The sole structure of  claim 1  wherein the at least one rib is at least one substantially horizontal rib or a plurality of substantially horizontal ribs. 
     
     
         27 . The sole structure of  claim 10  wherein the at least one rib extends on the exterior sidewall from a central portion of a forefoot portion on a medial side rearwardly along the exterior sidewall, around a heel portion, and forwardly on a lateral side to a central portion of forefoot portion. 
     
     
         28 . The sole structure of  claim 10  wherein the midsole comprises a first portion containing the at least one rib and an upper surface, and a second portion seated on the upper surface of the first portion. 
     
     
         29 . The sole structure of  claim 28  wherein the upper surface of the first portion has a recess and the second portion is seated in the recess. 
     
     
         30 . The sole structure of  claim 10  wherein the at least one rib is at least one substantially horizontal rib or a plurality of substantially horizontal ribs. 
     
     
         31 . The sole structure of  claim 15  wherein the at least one rib extends on the exterior sidewall from a central portion of a forefoot portion on a medial side rearwardly along the exterior sidewall, around a heel portion, and forwardly on a lateral side to a central portion of forefoot portion. 
     
     
         32 . The sole structure of  claim 15  wherein the midsole comprises a first portion containing the at least one rib and an upper surface, and a second portion seated on the upper surface of the first portion. 
     
     
         33 . The sole structure of  claim 32  wherein the upper surface of the first portion has a recess and the second portion is seated in the recess. 
     
     
         34 . The sole structure of  claim 15  wherein the at least one rib is at least one substantially horizontal rib or a plurality of substantially horizontal ribs.