Patent ID: 8621955

Claim:
A robot arm assembly, comprising: a first robot arm comprising a first axial sleeve, a hollow first input shaft assembled within the first axial sleeve, and a second input shaft rotatably assembled within the first input shaft via a bearing; a second robot arm rotatably connected to the first robot arm and comprising a second axial sleeve and an output shaft partially received within the second axial sleeve; a first bevel gear and a third bevel gear respectively assembled to the first input shaft and the second axial sleeve so that the first input shaft is configured to rotate relative to the second axial sleeve; and a transmission device assembled within the second axial sleeve so that the output shaft is configured to rotate relative to the second input shaft, wherein the transmission device has a symmetrical quadrangle structure cooperatively formed by a second bevel gear, a pair of fourth bevel gears, and a fifth bevel gear; the second bevel gear is assembled to a distal end of the second input shaft, the fifth bevel gear is assembled to a distal end of the output shaft, the pair of fourth bevel gears are opposite to each other, the second bevel gear engages with the pair of fourth bevel gears on opposite sides thereof, the fifth bevel gear engages with the pair of fourth bevel gears on opposite sides thereof, an alignment post and the third bevel gear are respectively assembled to two sides of an end of the second axial sleeve, and respectively disposed on opposite sides of a rotation axis of the second axial sleeve, the alignment post and the third bevel gear are respectively sleeved on the pair of fourth bevel gears, an axis of the alignment post is perpendicular to the rotation axis of the second axial sleeve.