4. A Discontinuously Movable Constant Velocity Shaft Coupling of Koenigs Joint Type

Based on the original Koenigs joint, we present a novel discontinuously movable (DM) RC-//-RC parallel mechanism having a bifurcation of motion. At a singular posture of bifurcation, the end effector has locally two degrees of freedom of infinitesimal translation and two working modes happen at the positions of double points on intersections of two congruent revolute cylinders, which are generated by the two RC open sub-chains. In the mode I, two axes of rotations are transmitted by the ratio of minus one and two shafts rotate in an opposite direction. In the model II, angular velocity ratio between two intersecting shafts is positive one and two cranks rotate in the same direction. Moreover, the same type of phenomenon occurs when two RC open chains are displaced by an offset of translation. Last but not least, a further investigation on a general DM chain of RC-//-RC or HC-//-HC type is expected.