Patent ID: 6257859
Filing Date: 2001-07-10
Classification: B29C

Abstract:
A hydraulic circuit of an injection molding machine permitting selection of either a regular mode, in which all drain oil ejected from a front oil chamber of an injection cylinder during injection is returned to an oil tank, or a differential mode, in which all or a portion of the drain oil is supplied to a rear oil chamber of said injection cylinder during injection, said hydraulic circuit comprising:a 4-port servo valve having A, B, P, and T ports and adapted to drive and control said injection cylinder, the A and B ports being connected to the front oil chamber and the rear oil chamber, respectively, of said injection cylinder, and the P port being connected to a hydraulic power unit;a shutoff valve for selecting the regular mode or the differential mode, the T port of said servo valve being connected to said oil tank via said shutoff valve; anda logic valve, via which the T port of said servo valve is connected to the rear oil chamber of said injection cylinder.