Concentric tubes, mounted for relative rotation about their common axis, each include radially extending hinge plates. The tubes carry contra-rotational cam slots through which project the ends of a cross-shaft. Bearings on the ends of the cross-shaft engage the milled cam slots. A cylindrical cross...http://www.google.fr/patents/US4788746?utm_source=gb-gplus-shareBrevet US4788746 - Cam actuated self-locking hinge
