The results obtained in this paper show that except for the planar or spherical mechanism and the Bennett mechanism non-existance of other 4R mechanism, and besides the planar mechanism there is one, and only one, RPRP mechanism.

• 文中的结果表明；除了平面4R机构、球面4R机构以及Bennett机构外；不存在其它4R机构; 除平面RPRP机构外；还存在且只存在一种RPRP机构.