Constant velocity universal joints

A constant velocity ratio universal joint for transmission of rotational motion between two shafts adapted to run at a variable angle between one another, comprising two main parts each mounted for rotation with one of the shafts to be coupled, at least two pairs of balls for torque transmission between the main parts, each of said balls being guided along two associated arcuate cross-sections rolling surfaces each of which is provided on one of said main parts, said rolling surfaces being parts of surfaces of revolution, the cross-sections centerlines of which defining two associated guiding paths each of which being oriented to cut its associated guiding path at an angle of 2.alpha. and to make an angle .alpha. with the longitudinal axis of the shafts at the point of intersection between said associated guiding paths when said shafts are in alignment, each main part having one longitudinal plane of symmetry on both sides of which each guiding path for a given pair of balls is symmetrically located with a guiding path for the other pair of balls and vice versa, lines tangent to the guiding paths on one main part at the points of intersection of said guiding paths with their associated guiding paths on the other main part being parallel for a given pair of torque transmitting balls, characterized in that the axis of revolution of the rolling surfaces on each main part for a given pair of balls cut the longitudinal plane of symmetry of that main part, the points of intersection of said axis of revolution with said plane being located on a straight line passing through the longitudinal axis of said main part and equidistant with the point of intersection of said straight line with said longitudinal axis.