Air-actuated block valve

To a pneumatic-type shut-off valve, to an intermediate capable of rod member passes through the fluid passage is closed when the shut-off valve of the novel structure. The spool valve comprises a flap seat, radially movable flap, an annular air bag, the flap seal disposed on the inner wall of a rubber membrane and a return spring coil. The rubber sealing film using the tubular structure with flanged ends, which are connected by a rubber membrane sealing flap flange seat; an intake nozzle mounted on the annular balloon. The present invention is the intermediate lever can be realized without the need to dismantle the valve closed. Due to the annular bladder urged by a rubber seal surrounding the membrane flap, to ensure that the circumference of the intermediate link and the sealing force uniform, good sealing effect. Not only simple in structure and operation, and good practical effect. Reactor can be used in engineering or other technical fields having the same or similar construction operating state.