Chain with improved rocker pin joint structure

A chain comprising:

• a plurality of interleaved rows of link plates articulately connected together in an endless fashion by means of rocker pin joints, each of said link plates having a pair of pin holes, each of said rocker pin joints being composed of a pair of rocker joint pins inserted through each of said pair of pin holes in one link plate and each of said pair of pin holes in an adjacent link plate;
• said pair of rocker joint pins having a convexly arcuate rolling surface, a back surface opposite to said rolling surface, and a pair of upper and lower flat surfaces formed between said rolling surface and said back surface and extending in a longitudinal direction of the chain;
• and
• each of said pin holes having a seat surface engaged with said back surface and formed on a side located closer to an outer end of each link plate than to a center of the link plate, and a pair of upper and lower pin-position constraining surfaces facing said upper and lower flat surfaces, respectively, of one of said pair of rocker joint pins seated on said seat surface with a very small clearance defined between each of said flat surfaces and a corresponding one of said pin-position constraining surfaces, a bend permitting surface contiguous to said upper pin-position constraining surface and spaced from said upper flat surface of the other rocker joint pin seated on said seat surface of said pin hole in said adjacent link plate, a warp blocking surface contiguous to said lower pin-position constraining surface and facing said lower flat surface of said other rocker joint pin seated on said seat surface of said pin hole in said adjacent link plate with a very small clearance defined therebetween, and a concavely arcuate surface contiguous to said bend permitting surface and said warp blocking surface and spaced from said back surface of said other rocker joint pin seated on said seat surface of said pin hole in said adjacent link plate.