Input: pink gear.
Output: green gear.
This is a constant velocity joint
The tooth profile dimensions of the semi-spherical gears are varied from bottom to apex of the semi-spherical gear according to sine function.
The spur gear drive (its transmission ratio = -1) ensures the meshing takes place at equal circles of the semi-spherical gears. Centers of the semi-spherical gears lay on axes of spur gears.
Angle between the input and output shafts can be adjusted by turning the yellow carrier.