Passive joint device, cable guide, and power transmission mechanism

A passive joint device for supporting a rotation-side member rotatably about a horizontal axis in a vertical direction with respect to a fixed-side member, comprising:

• a cylindrical cam member having a cylindrical surface centered on the horizontal axis and fixed to the fixed-side member, the cam member having a pair of cam surfaces symmetrically arranged on the cylindrical surface about the horizontal axis and formed obliquely along the horizontal axis;
• a pedestal slidably disposed along the horizontal axis within the horizontal axis fixed to the rotation-side member, the pedestal having a pair of cam followers that contact with each of the pair of cam surfaces;
• and
• a spring disposed inside the horizontal axis fixed to the rotation-side member, the spring biasing the pedestal toward the fixed-side member along the horizontal axis,
• wherein the spring force causes the pair of cam followers to come into contact with the pair of cam surfaces, push the pair of cam surfaces, and provide upward rotational force to the rotation-side member to reduce the downward rotational force of the rotation-side member by the weight applied to the rotation-side member.