Patent ID: 8794099

Claim:
A weight compensation mechanism installed at a robot arm of which one end is rotatable with three degrees of freedom and the other end is rotatable with two degrees of freedom, wherein a first rotation of one end of the robot arm is a yaw rotation aligned with a direction of gravitational pull of earth, and second and third rotations of one end of the robot arm are respectively a roll rotation and a pitch rotation, wherein the second and third rotations of one end of the robot arm are restrained by a plurality of differential bevel gears, wherein a pair of first cam plates is fixed to shafts of a pair of first rotary bevel gears in the plurality of differential bevel gears, and a one-degree-of-freedom weight compensator is provided to be connected to the first cam plates, and wherein a second rotary link as an output link of the two-degree-of-freedom rotation of the other end of the robot arm is restrained by the second and third rotations of one end of the robot arm to move in parallel to one end of the robot arm.