US Patent 7341603 Prosthetic foot with energy transfer including variable orifice

A prosthetic foot device with variable stiffness response includes a variable energy transfer mechanism or variable resistance cell disposed between first and second foot members to transfer a variable amount of energy from the second member to the first member during use. The energy transfer mechanism or variable resistance cell includes a variable orifice with variable size to variably resist flow of fluid therethrough, and thus variably transfers energy between the first and second members to vary stiffness of the prosthetic foot device.