Prosthetic foot with tunable performance

Abstract

A prosthetic foot ( 190 ) incorporates a foot keel ( 192 ) and a resilient calf shank ( 193 ) with its lower end connected to the foot keel to form an ankle joint of the prosthetic foot. The calf shank extends upward from the foot keel by way of an anterior facing convexly curved portion ( 195 ) of the shank, and is secured to the foot keel by way of a coupling element ( 194 ). The lower end of the shank is reversely curved ( 196 ) and housed by a reversely curved portion of the coupling element. A posterior calf device ( 191 ) has a cable ( 204 ) which is untensioned in a normal gait cycle but tensioned by a force loading on the prosthesis greater than 120% of body weight of the user to limit, e.g. stop, further anterior motion of the upper end of the shank.

1 . A prosthetic foot comprising: 
 a longitudinally extending foot keel having forefoot, midfoot and hindfoot portions;    a resilient, upstanding calf shank having a lower end connected to the foot keel and an upper end to connect with a supporting structure on an amputee's leg, the upper end being movable longitudinally of the foot keel in response to force loading and unloading of the calf shank during use of the prosthetic foot;    a device to limit the anterior, longitudinal motion of the upper end of the calf shank during use of the prosthetic foot in response to a force loading on the calf shank greater than that encountered in a normal gait cycle.    
     
     
         2 . The prosthetic foot according to  claim 1 , wherein said device limits the anterior, longitudinal motion of the upper end of the calf shank in response to a force loading greater than 120% of body weight of the user.  
     
     
         3 . The prosthetic foot according to  claim 1 , wherein said device includes an elongated member connected with play between the upper end of the calf shank and a lower portion of the prosthetic foot, the elongated member being tensioned during use of the prosthetic foot only when a force loading on the calf shank is greater than that encountered in a normal gait cycle for limiting said anterior, longitudinal motion of the upper end of the calf shank.  
     
     
         4 . The prosthetic foot according to  claim 3 , wherein said device further includes a resilient bumper to absorb shock when the elongated member is tensioned.  
     
     
         5 . The prosthetic foot according to  claim 3 , wherein said device further includes an upper block connected to the upper end of the calf shank, said elongated member being secured to and extending over a posterior surface of said block.  
     
     
         6 . The prosthetic foot according to  claim 5 , wherein said block has a guide for said elongated member on said posterior surface.  
     
     
         7 . The prosthetic foot according to  claim 6 , wherein said guide is a groove in the posterior surface of said block.  
     
     
         8 . The prosthetic foot according to  claim 3 , wherein the upper end of said elongated member has a connector thereon, said block having a recess in which said connector is retained to secure said elongated member to said block.  
     
     
         9 . The prosthetic foot according to  claim 3 , wherein said device further includes a lower block connected to said prosthetic foot, the lower end of said elongated member being connected to said block with play.  
     
     
         10 . The prosthetic foot according to  claim 9 , wherein the lower end of said elongated member extends longitudinally slidably through an aperture in the lower block and below the aperture a connector is provided on said elongated member to prevent withdrawal of the elongated member from said aperture and said block when said member is tensioned.  
     
     
         11 . The prosthetic foot according to  claim 10 , wherein the device further includes a resilient bumper between said connector and said lower block to absorb shock when the elongated member is tensioned.  
     
     
         12 . The prosthetic foot according to  claim 9 , wherein said lower block is pivotably connected to said prosthetic foot.  
     
     
         13 . The prosthetic foot according to  claim 12 , wherein said lower block is pivotably connected to said prosthetic foot by way of a backing plate on a coupling element connecting the calf shank to the foot keel.  
     
     
         14 . The prosthetic foot according to  claim 3 , wherein said elongated member is a cable.  
     
     
         15 . The prosthetic foot according to  claim 1 , wherein said calf shank is connected to the foot keel by way of a coupling element.  
     
     
         16 . The prosthetic foot according to  claim 1 , wherein the lower end of the calf shank is reversely curved.  
     
     
         17 . The prosthetic foot according to  claim 16 , wherein the reversely curved lower end is in the form of a spiral.  
     
     
         18 . The prosthetic foot according to  claim 16 , wherein an end of the reversely curved shank is fastened to a coupling element connecting the calf shank to the foot keel.  
     
     
         19 . The prosthetic foot according to  claim 18 , wherein the coupling element has an anterior facing concavity within which the reversely curved lower end of the calf shank is housed.  
     
     
         20 . The prosthetic foot according to  claim 18 , wherein the coupling element and at least a portion of the foot keel are monolithically formed.  
     
     
         21 . A system for a lower extremity prosthesis comprising: 
 a longitudinally extending foot;    an ankle;    an upstanding shank extending upward from the ankle;    wherein the ankle and shank are formed by a resilient member having a reversely curved lower end secured to the foot and extending upward from the foot by way of an anterior facing convexly curved portion of the member, and    wherein a device is provided to limit the anterior, longitudinal motion of the upper end of the resilient member during use of the prosthesis in response to a force loading on the resilient member greater than that encountered in a normal gait cycle.    
     
     
         22 . The system according to  claim 22 , wherein said device limits the anterior, longitudinal motion of the upper end of the resilient member only when a force loading on the prosthesis is greater than 120% of body weight of the user.