Axles of the two shafts may be
1. Parallel and coincident
2. Parallel and distinct (with eccentricity)
3. Intersecting
4. Skew
It is a constant velocity joint for cases 1, 2 and 3.
For details see:
http://meslab.org/mes/threads/20223-Khop-truc-ngam
STEP files of this video:
http://www.mediafire.com/file/8im5hw8xo1d11ag/UniversalJoint1STEP.zip
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