This pump type coupling has the reciprocating action of sliding rods in cylinders.
Centers of spherical joints are always in the plane that bisects the angle α between the two shafts even when α changes so it is a constant velocity joint.
Role of the springs: keeping proper positions of the pistons when two shafts are in line?.
STEP files of this video:
http://www.mediafire.com/file/mbrxohlc93rbtb7/UniversalJoint3STEP.zip
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