Osmotic membrane and vacuum system for artificial limb

Abstract

A hypobarically-controlled artificial limb for amputees includes a single socket with a volume and shape to receive a substantial portion of the residual limb. A liner with a volume less than the residual limb is donned over the residual limb, with the liner tensioned into a total contact relationship with the residual limb. A sealed cavity is formed between the socket and the liner. A vacuum source is connected to the socket cavity thereby drawing the residual limb and liner into firm and total contact with the socket. To compensate for some air leakage past the seal, there is a mechanism to maintain the vacuum in the cavity. An osmotic membrane encases the residual limb and creates a space between the residual limb and the liner. The osmotic membrane allows passage of water only in one direction: from the residual limb toward the liner. Vacuum may be applied to the space between the osmotic membrane and the liner to assist in wicking perspiration away from the residual limb.

What is claimed:  
     
         1 . In an artificial limb for amputees who have a residual limb, the residual limb being encased in a liner, the residual limb and liner being inserted into the artificial limb socket, an apparatus for wicking away perspiration from the residual limb, the apparatus comprising: an osmotic membrane encasing the residual limb and lying between the residual limb and the liner, thereby creating a space between the residual limb and the liner, the membrane being adapted to allow the passage of water vapor in one direction only, from the residual limb towards the liner.  
     
     
         2 . The apparatus of    claim 1   , further comprising: 
 a) a vacuum source connected to the space between the liner and the residual limb, wherein application of the vacuum source to the space between the liner and the residual limb lowers the partial water vapor pressure in the space, allowing water vapor to pass more readily through the osmotic membrane; and    b) a seal means for sealing the space.    
     
     
         3 . The apparatus of    claim 2   , further comprising a means to maintain a vacuum in the space, in the presence of some air leakage past the seal means.  
     
     
         4 . The apparatus of    claim 2   , wherein the seal means further comprises a nonfoamed, nonporous polyurethane suspension sleeve for rolling over and covering the socket and a portion of the residual limb.  
     
     
         5 . The apparatus of    claim 3   , wherein the vacuum source is a vacuum pump and the means to maintain the vacuum in the cavity is a regulator, and further comprising a power source for the vacuum pump and the regulator.  
     
     
         6 . The apparatus of    claim 3   , wherein the vacuum source and the means to maintain the vacuum in the cavity further comprise a weight-actuated vacuum pump.  
     
     
         7 . A method of wicking away perspiration from a residual limb in an artificial limb, comprising the steps of: 
 a) inserting the residual limb into an osmotic membrane adapted to allow the passage of water vapor in only one direction away from the residual limb;    b) inserting the residual limb and osmotic membrane into a flexible liner wherein a space is created between the osmotic membrane and the liner;    b) inserting the residual limb and liner into a socket having a volume and shape to receive the residual limb and the liner, the socket having a cavity into which the residual limb and liner are inserted;    c) sealing the socket cavity;    d) applying a vacuum to the socket cavity between the liner and the socket, thereby drawing the residual limb and liner into firm and total contact with the socket; and    e) applying a vacuum to the space between the osmotic membrane and the liner.    
     
     
         8 . The method of    claim 7   , further comprising the step of: 
 f) maintaining a vacuum in the socket cavity, in the presence of some air leakage into the socket cavity.    
     
     
         9 . The method of    claim 7   , wherein the liner is of a non-foamed, non-porous polyurethane.  
     
     
         10 . The method of    claim 7   , wherein a vacuum of at least ten inches of mercury is maintained in the cavity.