US Patent 7780559 Chain transmission

A chain transmission containing two toothed sprockets, a chain and a tensioner where the center (S) of the pitch circle of the driven sprocket (2) lays outside of the circle inscribed by the part of chain (4) mating with the driven sprocket (2). Each link (5,6) of the chain (4) contains plates (7) connected by three pins (8 and 9), while the axis of one of the pin (9) lays outside of the plane determined by axes of the remaining pins (8) of the link (5, 6).