| 摘要 |
An activity frame comprising a first or outer ring mounted between a pair of opposed bearings in a opposed pair of supports, for example upstanding members of a frame, the first bearings having a having a first common axis; a second or middle ring mounted between opposed bearings on the first ring, the bearings having a second common axis orthogonal to the first common axis; a third or inner ring mounted between opposed bearings on the second ring, the bearings having a third common axis orthogonal to the second axis provided with demountable restraining means to limit the movement of two or more of the rings and demountable bars to fix one or more of the rings to the frame or other fixed object. |
