US Patent 7272922 Articulated chain

A chain has chain links (110) having basically spherical geometry (116) and four flattened surfaces (118) equally distributed in the circumferential direction. A chamber (120) is formed in the chain links (110) in which a connecting member (112) is retained. A back side of the chain links (110) is furnished with a spherical joint surface (124). The connecting member (112) has on its side remote from the said joint surface (124) a head (150) which is furnished with a concave joint surface (162) which runs spaced apart from the outer surface of the chain link (110) and interacts with a complementarily convex joint surface (143) which is carried by the adjacent chain link (110) in the interior of the chamber (120).