Patent ID: 7581465

Claim:
A robot joint structure having a first main link and a second main link connected through a first movable link and a second movable link, and an actuator installed on the first main link and driving the first movable link such that the first main link and the second main link are displaced relative to each other; wherein the improvement comprises: rotation axes A and B each provided at the first main link; rotation axes C and D each provided at the second main link, the rotation axes A, B, C and D forming apices of a quadrangle, and when assuming that rotation axes that are diagonally opposed to each other are A and C, while those that are diagonally opposed to each other are B and D, the rotation axes A and C are connected through the first movable link and the rotation axes B and D are connected through the second movable link such that the first movable link and the second movable link are disposed to cross and that the rotation axis A is driven by the actuator to drive the first movable link, such that the first main link and the second main link are displaced relative to each other, a first plate; and a second plate installed in parallel with the first plate, the first and second plates constituting the first main link, such that the first movable link is rotatably connected to the first plate and the second plate through the rotation axis A, while the second movable link is rotatably connected to the first plate through the rotation axis B.