Variable stiffness midsole for article of footwear

Abstract

A sole structure for an article of footwear includes a bladder having a first barrier element attached to a second barrier element to define a chamber including an interior void containing a compressible fluid, a pressure of the compressible fluid being adjustable to selectively adjust a position of the first barrier element relative to the second barrier element. In addition, the sole structure includes a first plate attached to the first barrier element and a second plate attached to the second barrier element on an opposite side of the bladder than the first plate.

What is claimed is: 
     
         1 . A sole structure for an article of footwear, the sole structure comprising:
 a bladder including a first barrier element attached to a second barrier element to define a chamber having an interior void containing a compressible fluid, a pressure of the compressible fluid being adjustable to selectively adjust a position of the first barrier element relative to the second barrier element;   a first plate attached to the first barrier element; and   a second plate attached to the second barrier element on an opposite side of the bladder than the first plate.   
     
     
         2 . The sole structure of  claim 1 , wherein the chamber includes a valve in fluid communication with the interior void. 
     
     
         3 . The sole structure of  claim 1 , wherein each of the bladder, the first plate, and the second plate extends from a forefoot region of the sole structure to a heel region of the sole structure. 
     
     
         4 . The sole structure of  claim 1 , wherein a stiffness of the first plate is different than a stiffness of the second plate. 
     
     
         5 . The sole structure of  claim 1 , wherein the bladder includes a tensile element disposed within the interior void. 
     
     
         6 . The sole structure of  claim 5 , wherein the tensile element includes a first tensile layer attached to the first barrier element, a second tensile layer attached to the second barrier element, and a plurality of connecting members extending between and joining the first tensile layer and the second tensile layer. 
     
     
         7 . The sole structure of  claim 1 , wherein each of the first plate and the second plate includes a laminate fiber structure including a plurality of fiber layers consolidated by a resin. 
     
     
         8 . The sole structure of  claim 7 , wherein at least one of the first plate and the second plate includes at least four of the fiber layers. 
     
     
         9 . The sole structure of  claim 7 , further comprising a pump in fluid communication with the interior void. 
     
     
         10 . The sole structure of  claim 1 , wherein the bladder, the first plate, and the second plate include the same size and shape. 
     
     
         11 . A sole structure for an article of footwear, the sole structure comprising:
 a bladder including a first barrier element attached to a second barrier element to define a chamber having an interior void;   a first plate attached to the first barrier element; and   a second plate attached to the second barrier element on an opposite side of the bladder than the first plate, a distance between the first plate and the second plate being selectively adjustable by varying a volume of fluid contained within the interior void.   
     
     
         12 . The sole structure of  claim 11 , wherein the chamber includes a valve in fluid communication with the interior void. 
     
     
         13 . The sole structure of  claim 11 , wherein each of the bladder, the first plate, and the second plate extends from a forefoot region of the sole structure to a heel region of the sole structure. 
     
     
         14 . The sole structure of  claim 11 , wherein a stiffness of the first plate is different than a stiffness of the second plate. 
     
     
         15 . The sole structure of  claim 11 , further comprising a tensile element disposed within the interior void. 
     
     
         16 . The sole structure of  claim 15 , wherein the tensile element includes a first tensile layer attached to the first barrier element, a second tensile layer attached to the second barrier element, and a plurality of connecting members extending between and joining the first tensile layer and the second tensile layer. 
     
     
         17 . The sole structure of  claim 11 , wherein each of the first plate and the second plate includes a laminate fiber structure including a plurality of fiber layers consolidated by a resin. 
     
     
         18 . The sole structure of  claim 17 , wherein at least one of the first plate and the second plate includes at least four of the fiber layers. 
     
     
         19 . The sole structure of  claim 17 , further comprising a pump in fluid communication with the interior void. 
     
     
         20 . An article of footwear incorporating the sole structure of  claim 11 .