Patent ID: 8333615

Claim:
A rotation axis arrangement, comprising a sleeve, an elastic body, an indented washer, a movable support, and a stop ring, wherein: the sleeve comprises a lip and a cylinder; the elastic body, the indented washer, and the movable support are positioned sequentially around the cylinder with the lip adjacent to the elastic body along an axial direction of the cylinder beginning with the lip; a surface of the indented washer that contacts a surface of the movable support is configured with a number of concave indents, wherein the concave indents are distributed in a circle; the surface of the movable support contacting the indented washer is configured with a number of protrusions, wherein the protrusions correspond to the concave indents on the surface of the indented washer; the stop ring is positioned around the cylinder and adjacent to the movable support along an axial direction on the opposite side relative to the indented washer and a stop groove is configured on the stop ring; an end-surface of the movable support that contacts the stop ring is configured with a positioning rod; and the stop groove limits the movement of the positioning rod of the movable support to a predetermined range of angles.