Hydraulic screw press drive

A drive of a hydraulic screw press comprising:

• a power cylinder;
• a movable member of said power cylinder, connected with a press slide;
• a chamber of said power cylinder;
• a pneudraulic accumulator incorporating a hydraulic chamber communicating with said chamber of the power cylinder, a source of pressure, and a pneumatic chamber;
• an inlet valve which puts said chamber of said power cylinder in communication with the hydraulic chamber of said pneudraulic accumulator;
• a discharge valve through which said chamber of the power cylinder communicates with a low-pressure hydraulic line;
• a control element of said discharge valve;
• a device for actuating said discharge valve comprising a pneudraulic cylinder and a piston rod which incorporates an underpiston pneumatic chamber constantly communicating with a pneumatic line, and an above-piston hydraulic chamber which can communicate alternately with said chamber of the power cylinder and said low-pressure hydraulic line;
• a limit switch of said device for actuating the discharge valve, connected with the control element of the discharge valve and installed in the extreme position of the free end of the pneudraulic piston rod in which its above-piston hydraulic chamber is in communication with the chamber of said power cylinder.