It is used for the control of the hydraulic support Jack in the coal mine, and realizes the locking of the high pressure liquid in the working cavity of the Jack, so that the controlled metal structure of the support plays a supporting role; when the reversing valve is changed, the Jack enters liquid into another cavity, and the working cavity is opened at the same time. 

By setting the opening pressure of the safety valve installed in an one-way two-way lock, the working resistance of the metal structure does not exceed the rated value.