US Patent 7484615 Stopper cylinder

A lever, provided with rollers, is rotatably supported with respect to a lever holder. A lock pin disposed on the lever engages with a lock pawl of a lock mechanism. Accordingly, rotary action of the lever is regulated so as to stop a workpiece that is transported in a predetermined direction. On the other hand, when the workpiece is transported in a direction opposite to the predetermined direction, a second bracket having the lock pawl is rotated due to a pressing action of the lock pin. Accordingly, the lever is released from its rotation-regulated state effected by the lock pin, whereupon the lever is rotated and displaced.