Patent ID: 8534155

Claim:
A robot arm assembly comprising: a support arm comprising a mounting base and a connecting portion connected to the mounting base, and the connecting portion defining a hollow portion; a first arm rotatably connected to the support arm; a second arm rotatably connected to the first arm; a first input shaft; a second input shaft coaxial with and rotatable relative to the first input shaft, and the first and second input shafts being rotatably received in the hollow portion; a first gear transmission mechanism coupled to the first input shaft to rotate the first arm, the first gear transmission mechanism comprising a first input gear pair having one gear fixed to the first input shaft, and a first output bevel gear pair having one bevel gear fixed to the first arm; a second gear transmission mechanism coupled to the second input shaft to rotate the second arm, the second gear transmission mechanism comprising a second input gear pair having one gear fixed to the second input shaft, an intermediate bevel gear pair, and a second output bevel gear pair having one bevel gear fixed to the second arm; a first backlash adjust mechanism to move the connecting portion, and the positions of the first and second input shafts relative to the mounting base, thus adjusting the backlash between the first input gear pair and the second input gear pair; and a second backlash adjust mechanism to adjust the backlash between the second output bevel gear pair, wherein the first arm defines a first assembly hole along a central axis thereof, and a second assembly hole extending radially and intersecting with the first assembly hole, the second arm is rotatable received in the second assembly hole, and the first and second output bevel gear pairs are received in the first assembly hole, the second backlash adjust mechanism comprising a first thrust bearing mounted in the second assembly hole and contacting an end of the second arm, an adjust member engaging into the second assembly hole and contacting the first thrust bearing and adjusting the axial position thereof, an elastic member elastically biasing the second arm toward the first thrust bearing, and a second thrust bearing positioned between an inner surface of the first arm and the elastic member.