Importance

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Abstract

An injection molding apparatus having movable die operated by a piston and cylinder, includes a hydraulic circuit having a supply line for closing and opening the movable die. A branch line from the supply line leads into a die locking chamber defined between the piston and cylinder, and a first multi-directional control valve is provided for control of the closing mechanism. A second multi-directional valve is located in the branch line for feeding hydraulic fluid into the die locking chamber as sensed by a pressure sensor in the supply line. A threaded spindle meshes with a support for the movable die which feeds back the rate of travel and pressure exerted by the movable die to a stepping motor which varies the spindle rotation in accordance with the rate and the pressure. The first control valve shifts relative to the spindle during its rotation to thereby pressurize the plunger which is sensed at a predetermined value for delivering hydraulic fluid into the die locking chamber when the movable die is closed.

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First Claim