Patent ID: 8534951

Claim:
A joint unit comprising: a cylindrical case; first and second holders arranged at ends of the cylindrical case; first and second arms each having a joint section respectively housed in the first and second holders, and a lock mechanism pressing the joint sections against an inner surface of the first and second holders, the lock mechanism being arranged within the cylindrical case and including: first and second pressing bodies each having a round cross section, the second pressing body contacting and pressing against the first pressing body, first and second pressure blocks, one of the first and second pressure blocks arranged between the first pressing body and the joint section of one of the first and second arms, and another of the first and second pressure blocks arranged between the second pressing body and the joint section of another of the first and second arms, the first and second pressure blocks being movable in an axial direction of the cylindrical case; and a clamp having a bolt extending through a hole formed in the cylindrical case and pressing against the first pressing body, while the first pressing body directly presses against one of the first and second pressure blocks and the second pressing body, and while the second pressing body directly presses against at least another of the first and second pressure blocks, wherein an area inside the cylindrical case housing the first and second pressing bodies has a dimension (S) along the axial direction of the cylindrical case that is smaller than a sum of diameters of the first and second pressing bodies, and a dimension (H) in a direction the bolt presses against the first pressing body that is smaller than the sum of diameters of the first and second pressing bodies.