Abstract: The drive of a hydraulic screw press comprises a power cylinder connected with the press slide by its movable member. The chamber of the power cylinder communicates with a pneudraulic accumulator provided with a device for its charging. The device comprises a pneudraulic cylinder with a distributor for communicating its under-piston hydraulic chamber alternately with the source of pressure and a low-pressure hydraulic line, and nonreturn valves for communicating the above-piston pneumatic chamber of the pneudraulic cylinder alternately with the pneumatic line and the pneumatic chamber of the pneudraulic accumulator. This ensures self-sufficiency of the drive of each hydraulic screw press, and the required pressure of gas in the pneudraulic accumulator with a comparatively simple design of the device for charging its pneumatic chamber.

Abstract: A drive of a hydraulic screw press comprises a power cylinder incorporating a movable member connected with the press slide. A limit switch actuated by the downward travel of the slide opens a shutoff valve which permits fluid to flow through an adjustable flow-restrictor to actuate the piston of a pneudraulic cylinder within a preset time period determined by the adjustment of the flow restrictor. At the end of the preset time period, the rod of the piston will have traveled a distance sufficient to actuate a limit switch to control a valve arrangement for discharging the pressure in communication with the power cylinder. The slide is returned to the initial upper position by a cylinder under a constant pressure.