Hydraulic press with servo-hydraulic ram movement control - has individual cylinders with chambers for press working force, and opposite force

摘要

The press uses pref. a hydraulic pressure fluid to charge simultaneously a cylinder chamber for the working movement of a press ram, and an additional cylinder chamber to operate a force acting in the opposite direction. A reference value transmitter controls the ram movement using a rapid acting servo valve without fixed positions, this forming an integral part of the control circuit. The two cylinder chambers (8, 11, 12) are located in individual cylinders. The controlled opposite force acts onto the ram (6) only during the last part of the working stroke (Y), which is not more than half. There is a common servo valve (25) for the teo forces.