UNLOCKABLE FLAP VALVE PARTICULARLY FOR USING AS RECOVERY AND PRESTRESSING VALVE FOR PROPS OF MINES OF UNDERGROUND EXPLOITATION

摘要

An improved valve in use for underground mining in connection with a piston cylinder unit, such as a hydraulic prop, is disclosed. The valve includes a piston member within a control chamber which is operative to terminate fluid communication between the hydraulic prop and a hydraulic fluid source. The piston is pressure-equalized in a neutral position when the hydraulic prop is set.