Pressure intensifying apparatus for hydraulic cylinder

摘要

There are provided a pressure intensifying cylinder 2a for allowing a pressure intensifying chamber 31 to communicate with a head-side cylinder chamber 22 of a working cylinder 1 and its control hydraulic circuit. When a load and a rated pressure Pp of a hydraulic pump 25 are balanced with each other at the time of inserting and setting a core 41, a check valve 21 is closed and a sequence valve 34 is opened to move the pressure intensifying cylinder 2a forward, so that the pressure of the head-side cylinder chamber 22 is increased. A pressure intensifying ratio of the pressure intensifying cylinder 2a is set such that the pressure of the head-side cylinder chamber 22 is higher than pressure occurring with molding pressure.