Patent ID: 7913616

Claim:
A ram driving apparatus driving a ram reciprocated by a fluid pressure mechanism, wherein a large-diameter cylinder attached integrally to the ram is divided into a first compartment and a second compartment by a large-diameter piston relatively reciprocably included in the large-diameter cylinder, and one end of a large-diameter piston rod protruding from the large-diameter cylinder integrally with the large-diameter piston is fixed to a fixing unit, a small-diameter cylinder integral with the large-diameter cylinder is divided into a first compartment and a second compartment by a small-diameter piston relatively reciprocably included in the small-diameter cylinder, and one end of a small-diameter piston rod protruding from the small-diameter cylinder integrally with the small-diameter piston is connected to a moving member moved by a motor driving, and the first compartment of the large-diameter cylinder is connected to the first compartment of the small-diameter cylinder via a connection path, and the second compartment of the large-diameter cylinder is connected to the second compartment of the small-diameter cylinder via a connection path, and internal pressures of the first compartment and the second compartment of each of the large-diameter cylinder and the small-diameter cylinder are pressurized to a predetermined pressure equal to or higher than an atmospheric pressure.