Patent ID: 7971599

Claim:
An air-operated valve comprising: a piston; a cylinder in which the piston is allowed to slide; a valve section to be driven by sliding movement of the piston, wherein: the cylinder includes: an outer member having a hollow portion; and an inner member loaded in the hollow portion of the outer member, defining a piston chamber in which the piston is allowed to slide, the air-operated valve is adapted to be selectively constructed in one of a normally closed configuration and a normally open configuration, the piston has a piston assembly comprising a first piston rod, a second piston rod and a piston portion, the first piston rod and the second piston rod are arranged in opposite directions to each other with respect to the piston portion so that the first piston rod is movable toward and away from the valve section in the normally closed configuration and the second piston rod is movable toward and away from the valve section in the normally open configuration, the first piston rod and the second piston rod include an air passage axially extending in a center of the first piston rod and the second piston; rod, and the piston assembly is arranged such that a seal member is attached to each of the first piston rod and the second piston rod when the air-operated valve is in the normally closed configuration, while the seal member is attached to the second piston rod but no seal member is attached to the first piston rod when the air-operated valve is in the normally open configuration; and a closing plate provided with an air port for air supply, the closing plate being used in both the normally closed configuration and the normally open configuration.