Hydraulic control circuit for an injection molding machine

Abstract

An hydraulic control circuit for an injection molding machine feedback-controls the operations of an injection cylinder by connecting an hydraulic source and an oil tank to a hydraulic actuator through a plurality of servo valves. The plurality of servo valves, such as four-port servo valves, are connected in parallel and a servo valve control function unit is used which controls the servo valves preferentially to the feedback control to permit series or parallel control of the servo valves. Thus, even when the specifications of an injection molding machine require a larger size and higher speed, the size of the injection molding machine is prevented from increasing, the cost is decreased, the response speed and the stability are remarkably improved, and fine control is realized over a wide control range.

Dependencies are inferred from the claim text.