Patent ID: 7419052

Claim:
A conveyor chain comprising a number of chain links including a plurality of hinge portions zigzag protruding from front end edges and rear end edges, adjacent ones of said links being connected to each other in the longitudinal direction of the chain through a hinge pin, and free ball elements which are free to rotate in any direction protruding from both surface and back sides of said chain, wherein each of said chain links has a U-shaped mounting region forming a ball-receiving channel extending longitudinally of the chain from the middle of the link through one of said front end edge and rear end edges to provide an open end for said channel in said one end edge, and a pair of ball-holding retainer elements rotatably sandwiching one of said free ball elements therebetween in the channel of one of said mounting regions of said chain links, said channel open end being closed by said hinge pin to capture the ball-holding retainer elements characterized in that one of said free ball element and said pair of ball holding retainer elements comprising polyacetal and the other comprising polyamide or polyester.