Support arm

1. A support arm comprising:

a first joint part supported by a base;

a second joint part arranged away from said first joint part;

a first parallel link arranged between said first joint part and said second joint part and coupled pivotally to said first joint part and said second joint part; and

a self-weight compensation device producing a force that cancels a force of gravity acting on said first parallel link,

said first parallel link having a first upper shaft, a second upper shaft, and a lower shaft, said first upper shaft and said second upper shaft being arranged in parallel to said lower shaft with spacing therebetween, the spacing being changed with a pivoting movement of said first parallel link,

said first upper shaft and said second upper shaft being arranged offset from said lower shaft in a direction of an axis on which said first parallel link is pivoted,

when said first parallel link is positioned to extend laterally from said first joint part, said first upper shaft and said second upper shaft being located above said lower shaft,

said lower shaft having a thickness greater than the thickness of said first upper shaft and the thickness of said second upper shaft,

a wiring line extending from said first joint part toward said second joint part being fixed to said lower shaft, said wiring line being directly supported by said lower shaft between said first joint part and said second joint part,

said first upper shaft, said second upper shaft, and said lower shaft being disposed at vertices of a triangle, respectively,

said lower shaft being a hollow tubular member having a substantially rectangular sectional shape, and

said lower shaft having a top surface located on the outer side of the tubular member, said wiring line being fixed to said top surface.

2. The support arm according to claim 1 , wherein

a stored state of the support arm is attained when said first parallel link is positioned to rise upwardly from said first joint part, and

in the stored state, said first upper shaft, said second upper shaft, and said lower shaft are arranged to overlap each other when seen from the direction of the axis on which said first parallel link is pivoted.

3. The support arm according to claim 2 , wherein

in the stored state of the support arm, said first upper shaft, said second upper shaft, and said lower shaft extend in a vertical direction from said first joint part toward said second joint part.

4. The support arm according to claim 1 , wherein

the first upper shafts and the second upper shafts are arranged symmetrically on both sides of said lower shaft in the direction of the axis on which said first parallel link is pivoted.

5. The support arm according to claim 1 , further comprising:

a third joint part arranged away from said second joint part; and

a second parallel link arranged between said second joint part and said third joint part and coupled pivotally to said second joint part and said third joint part, wherein

said second parallel link has a third shaft and a fourth shaft arranged in parallel to each other with spacing, the spacing being changed with a pivoting movement of said second parallel link, and

said third shaft and said fourth shaft are arranged offset with respect to each other in a direction of an axis on which said second parallel link is pivoted.

6. The support arm according to claim 5 , wherein

a stored state of the support arm is attained when said first parallel link is positioned to rise upwardly from said first joint part and said second parallel link is folded toward said first parallel link with said second joint part serving as a fulcrum, and

in the stored state, said first upper shaft, said second upper shaft, and said lower shaft are arranged to overlap each other when seen from the direction of the axis on which said first parallel link is pivoted, and said third shaft and said fourth shaft are arranged to overlap each other when seen from the direction of the axis on which said second parallel link is pivoted.

7. The support arm according to claim 1 , further comprising

a charging connector provided to be connectable to a vehicle, and moving with the pivoting movement of said first parallel link.