Method and apparatus for controlling a hydraulic screw press

摘要

The ram of the press is accelerated to an acceleration-terminating point whereat it attains a speed providing for the required energy of impact upon the work. During the acceleration, the velocity of the ram is measured, as well as the deviation of the actual point of attaining the required speed relative to the preset acceleration-terminating point. Depending on the value of this deviation, either the extent of the acceleration path is varied, with the acceleration value maintained constant, or else the acceleration rate is varied, with the acceleration path length remaining permanent. To effect control by varying the acceleration path length, the control system is provided with specific electric circuitry controlling a transmitter generating a signal sent to a solenoid-operated valve, to vary the latter's position so as to vary accordingly the approach portion of the ram's stroke, and thus to vary the acceleration path. To effect control by varying the acceleration rate, the control system likewise is provided with specific electric circuitry controlling the value of the pressure of the liquid supplied from a hydraulic accumulator into the hydraulic drive of the press.