Prosthetic foot with hybrid layup

Abstract

A prosthetic foot has a plate-like foot member with a core section substantially defined by one or more layers comprising a first material fiber, an upper section disposed above the core section, the upper section substantially defined by one or more layers comprising a second material fiber, and a lower section disposed below the core section, the lower section substantially defined by one or more layers comprising a third material fiber, where the upper, lower and core sections together define a total thickness of the plate-like elongate foot member. An idealized ratio of the cross sectional area of each section can be determined such that under an applied load provided to the hybrid layup, the ratio of maximum stress of a given section over the flexural strength of that given section is approximately equal for all sections of the hybrid layup. The hybrid layup arrangement can be configured to have a greater strength, but generally the same stiffness, as a similar foot member made of carbon fiber.

What is claimed is: 
     
         1 . A prosthetic foot, comprising:
 a plate-like elongate foot member comprising:
 a core section of one or more carbon fiber layers; and 
 one or more outer layers disposed on a top and bottom side of the core section so that the core section is interposed between the outer layers, the one or more outer layers being glass fiber layers. 
   
     
     
         2 . The prosthetic foot of  claim 1 , wherein the number of outer layers on the top side is equal to the number of outer layers on the bottom side. 
     
     
         3 . The prosthetic foot of  claim 1 , wherein the proportion of the carbon fiber layers in the foot member is greater than the proportion of the glass fiber layers. 
     
     
         4 . The prosthetic foot of  claim 1 , wherein the proportion of the carbon fiber layers in the foot member is less than the proportion of the glass fiber layers. 
     
     
         5 . A prosthetic foot, comprising:
 a plate-like elongate foot member comprising at least two sections provided on top of one another, each section comprising one or more layers comprising a fiber material, wherein the one or more layers of each section comprise the same type of fiber material and at least two of the at least two sections comprise a different type of fiber material, wherein each section has a flexural strength, and wherein the at least two sections together define a composite member;   wherein the thickness of each section relative to the total thickness of the composite member is configured such that the ratio of maximum stress of a given section over the flexural strength of that given section is approximately equal for all sections, wherein the maximum stress of a given section is the maximum stress experienced by that section under an applied load provided to the composite member.   
     
     
         6 . The prosthetic foot of  claim 5 , wherein the ratios of maximum stress over the flexural strength of all sections are within 20% of each other when the foot member is comprised of two sections. 
     
     
         7 . The prosthetic foot of  claim 5 , wherein the ratios of maximum stress over the flexural strength of all sections are within 5% of each other when the foot member is comprised of three or more sections. 
     
     
         8 . The prosthetic foot of  claim 5 , wherein the first section comprises carbon fiber and the second section comprises glass fiber and wherein the second section is disposed on top of the first section. 
     
     
         9 . The prosthetic foot of  claim 5 , wherein the first section comprises glass fiber and the second section comprises carbon fiber and wherein the second section is disposed on top of the first section. 
     
     
         10 . The prosthetic foot of  claim 5 , wherein the foot member is further comprised of at least an upper section, a lower section, and a core section and wherein a thickness of the upper section is generally equal to a thickness of the lower section. 
     
     
         11 . The prosthetic foot of  claim 5 , wherein a stiffness of the first section is higher than a stiffness of the second section. 
     
     
         12 . The prosthetic foot of  claim 5 , wherein a stiffness of the first section is lower than a stiffness of the second section. 
     
     
         13 . The prosthetic foot of  claim 5 , wherein the proportion of the first section in the foot member is greater than the proportion of the second section in the foot member. 
     
     
         14 . The prosthetic foot of  claim 5 , wherein the proportion of the first section in the foot member is less than the proportion of the second section in the foot member. 
     
     
         15 . A prosthetic foot, comprising:
 a plate-like elongate foot member comprising at least a first section and a second section provided on top of one another, the first section comprising one or more layers comprising a first fiber material, the second section comprising one or more layers comprising a second fiber material, the first fiber material being different from the second fiber material, the second section disposed on top of the first section, wherein the sections together define a composite member;   wherein the overall strength of the composite member is greater than the strength of a hypothetical single-section plate-like foot member sized to have approximately the same stiffness as the composite member, wherein the hypothetical single-section plate-like foot member is made entirely of only one or more layers comprising either the first fiber material or the second fiber material, and wherein the overall thickness of the composite member is within 50% of the hypothetical single-section plate-like foot member.   
     
     
         16 . The prosthetic foot of  claim 15 , wherein the overall thickness of the composite member is within 25-40% of the hypothetical single-section plate-like foot member. 
     
     
         17 . The prosthetic foot of  claim 15 , wherein the first section comprises carbon fiber and the second section comprises glass fiber. 
     
     
         18 . The prosthetic foot of  claim 15 , wherein the first section comprises glass fiber and the second section comprises carbon fiber. 
     
     
         19 . The prosthetic foot of  claim 15 , wherein the foot member is further comprised of at least a third section disposed on top of the second section, and wherein a thickness of the third section is generally equal to a thickness of the first section. 
     
     
         20 . The prosthetic foot of  claim 15 , wherein a stiffness of the first section is lower than a stiffness of the second section. 
     
     
         21 . The prosthetic foot of  claim 15 , wherein the proportion of the first section in the foot member is greater than the proportion of the second section in the foot member. 
     
     
         22 . The prosthetic foot of  claim 15 , wherein the proportion of the first section in the foot member is less than the proportion of the second section in the foot member. 
     
     
         23 . A prosthetic foot, comprising:
 a plate-like elongate foot member comprising at least a first section and a second section provided on top of one another, the first section comprising one or more layers comprising a first fiber material, the second section comprising one or more layers comprising a second fiber material, the first fiber material being different from the second fiber material, the second section disposed on top of the first section, wherein the sections together define a composite member;   wherein the overall flexibility of the composite member is greater than the flexibility of a hypothetical single-section plate-like foot member sized to have approximately the same strength as the composite member, wherein the hypothetical single-section plate-like foot member is made entirely of only one or more layers comprising either the first fiber material or the second fiber material, and wherein the overall thickness of the composite member is within 10% of the thickness of the hypothetical single-section plate-like foot member.   
     
     
         24 . The prosthetic foot of  claim 23 , wherein the first section comprises carbon fiber and the second section comprises glass fiber. 
     
     
         25 . The prosthetic foot of  claim 23 , wherein the first section comprises glass fiber and the second section comprises carbon fiber. 
     
     
         26 . The prosthetic foot of  claim 23 , wherein the foot member is further comprised of at least a third section disposed on top of the second section, and wherein a thickness of the third section is generally equal to a thickness of the first section. 
     
     
         27 . The prosthetic foot of  claim 23 , wherein a stiffness of the first section is lower than a stiffness of the second section. 
     
     
         28 . The prosthetic foot of  claim 23 , wherein the proportion of the first section in the foot member is greater than the proportion of the second section in the foot member. 
     
     
         29 . The prosthetic foot of  claim 23 , wherein the proportion of the first section in the foot member is less than the proportion of the second section in the foot member. 
     
     
         30 . A prosthetic foot, comprising:
 a plate-like elongate foot member comprising:
 a core section substantially defined by one or more layers comprising a first material fiber; 
 an upper section disposed above the core section, the upper section substantially defined by one or more layers comprising a second material fiber, and 
 a lower section disposed below the core section, the lower section substantially defined by one or more layers comprising a third material fiber; 
 wherein the upper, lower and core sections together define a total thickness of the plate-like elongate foot member; 
 wherein the core section is configured to fail when the plate-like member is subjected to a bending force greater than a flexural breaking force of the plate-like foot member, the core section configured to break and the upper and lower sections configured to remain intact and contain the broken core section to maintain the plate-like foot member as one piece. 
   
     
     
         31 . The prosthetic foot of  claim 30 , wherein the first material fiber is carbon fiber and the second and third material fiber is glass fiber. 
     
     
         32 . The prosthetic foot of  claim 30 , wherein the first material fiber is glass fiber and the second and third material fiber is carbon fiber. 
     
     
         33 . The prosthetic foot of  claim 30 , wherein a thickness of the upper section is generally equal to a thickness of the lower section.