Adjustable stiffness spring

Abstract

A mechanical arm comprises a forearm, a spring, and an upper arm disposed between the forearm and the spring, wherein the forearm applies a moment to the upper arm. A translation device associated with the upper arm translates a force associated with the moment to the spring. The spring is adapted to apply a counter-force resisting at least a portion of the moment to reduce a torque for urging the forearm.

1 . An adjustable stiffness spring comprising:
 a cable adapted to be connected to a load;   a constant torque mechanism;   said cable connected to said constant torque mechanism;   said constant torque mechanism including a spring with an adjustable spring constant; and   a spring constant adjustment mechanism that when adjusted changes the spring constant of said spring.   
     
     
         2 . The adjustable stiffness spring of  claim 1  wherein:
 adjusting the spring constant with the spring constant adjustment mechanism adjusts the stiffness in said cable. 
 
     
     
         3 . The adjustable stiffness spring of  claim 1  wherein:
 said constant torque mechanism includes a spiral pulley connected to said cable; 
 a capstan connected to said spiral pulley; and 
 said spring connected to said capstan. 
 
     
     
         4 . The adjustable stiffness spring of  claim 1  wherein:
 said constant torque mechanism includes a spiral pulley connected to said cable; 
 a capstan connected to said spiral pulley; 
 said spring connected to said capstan; 
 a dual spiral pulley; 
 a cable connecting said dual spiral pulley to said capstan; 
 and another spring connected to said dual spiral pulley. 
 
     
     
         5 . The adjustable stiffness spring of  claim 1  wherein:
 said constant torque mechanism is a rotary counterbalance mechanism. 
 
     
     
         6 . The adjustable stiffness spring of  claim 1  wherein:
 said constant torque mechanism includes a spiral pulley connected to a dual capstan; 
 said cable is connected to said spiral pulley; 
 said spring is connected to said dual capstan; 
 a dual spiral pulley that is connected to said dual capstan; and 
 another spring that is connected to said dual spiral pulley. 
 
     
     
         7 . The adjustable stiffness spring of  claim 6  wherein:
 a first spiral of said dual spiral pulley is connected to said dual capstan; and 
 a second spiral of said dual spiral pulley is connected to said another spring. 
 
     
     
         8 . The adjustable stiffness spring of  claim 7  wherein said another spring is anchored to said constant torque mechanism. 
     
     
         9 . The adjustable stiffness spring of  claim 1  wherein said constant torque mechanism is connected to a load with an idler pulley. 
     
     
         10 . The adjustable stiffness spring of  claim 1  wherein said spiral pulley convert a force from said spring into a constant torque. 
     
     
         11 . The adjustable stiffness spring of  claim 1  wherein a stiffness of a force in said cable can be adjusted by adjusting said constant torque mechanism. 
     
     
         12 . The adjustable stiffness spring of  claim 1  wherein a stiffness of a force in said cable can be adjusted by adjusting said spring constant of said constant torque mechanism. 
     
     
         13 . The adjustable stiffness spring of  claim 1  wherein said load is a link. 
     
     
         14 . The adjustable stiffness spring of  claim 1  including a mechanism for adjusting the position of said constant torque mechanism relative to said load. 
     
     
         15 . The adjustable stiffness spring of  claim 14  wherein said mechanism is a pantograph mechanism. 
     
     
         16 . An adjustable stiffness spring comprising:
 a cable adapted to be connected to a load;   a constant torque mechanism;   said cable connected to said constant torque mechanism;   said constant torque mechanism including a spring with an adjustable spring constant;   a spring constant adjustment mechanism that when adjusted changes the spring constant of said spring.   wherein adjusting the spring constant with the spring constant adjustment mechanism adjusts the stiffness in said cable.   said constant torque mechanism includes a spiral pulley connected to said cable;   a capstan connected to said spiral pulley;   said spring connected to said capstan;   a dual spiral pulley;   a cable connecting said dual spiral pulley to said capstan; and   and another spring connected to said dual spiral pulley.   
     
     
         17 . The adjustable stiffness spring of  claim 16  wherein:
 a first spiral of said dual spiral pulley is connected to said dual capstan; and 
 a second spiral of said dual spiral pulley is connected to said another spring. 
 
     
     
         18 . The adjustable stiffness spring of  claim 16  wherein a stiffness of a force in said cable can be adjusted by adjusting said spring constant of said constant torque mechanism. 
     
     
         19 . The adjustable stiffness spring of  claim 16  including a mechanism for adjusting the position of said constant torque mechanism relative to said load. 
     
     
         20 . An adjustable stiffness spring comprising:
 a cable adapted to be connected to a load;   a constant torque mechanism;   said cable connected to said constant torque mechanism;   said constant torque mechanism including a spring with an adjustable spring constant;   a spring constant adjustment mechanism that when adjusted changes the spring constant of said spring.   wherein adjusting the spring constant with the spring constant adjustment mechanism adjusts the stiffness in said cable.   said constant torque mechanism includes a spiral pulley connected to said cable;   a dual capstan connected to said spiral pulley;   said spring connected to said dual capstan;   a dual spiral pulley with a first spiral and a second spiral;   a cable connecting said first spiral of said dual spiral pulley to said capstan; and   and another spring connected to said second spiral of said dual spiral pulley.