Patent ID: 7601104

Claim:
An apparatus comprising a plurality of pivotally connected members forming an articulated system for attaching to a person and passively assisting said person to move from a first seated position to a second standing position and vice versa by transferring the combined weight of the articulated system and said person from said person's legs to a primary support, the apparatus comprising: a parallelogram structure connecting a scale length attachment point on each of said plurality of pivotally connected members to a combined center of mass of said plurality of pivotally connected members; a first connecting spring connecting said center of mass to said primary support, and a second connecting spring connecting said center of mass to said plurality of pivotally connected members, wherein said first and second springs are selected such that the total potential energy of the articulated system is invariant with member configuration; and wherein the articulated system comprises three degrees of freedom and is adapted for mounting on a person forming an exoskeleton having pivoting members attached to a person's torso, thigh, and calf and wherein said first supporting point is said person's ankle and said primary point is located external to said exoskeleton.