Method of metering molding compound and a metering system for carrying out the same

A molding compound metering system comprising:

• a stroke detecting mechanism for detecting the backward stroke of the injection plunger of the injection cylinder of an injection molding machine, axially slidably fitted in the injection chamber of the injection barrel of the injection molding machine;
• a molding compound stocker containing a molding compound and connected by a supply line to the injection barre;
• a metering cylinder having a metering plunger axially slidably fitted in the molding compound stocker so as to be advanced to supply the molding compound from the molding compound stocker into the injection chamber of the injection barre;
• and
• an adjustable-pressure relief valve connected to the back working chamber of the injection cylinder to return the working fluid discharged from the back working chamber of the injection cylinder through the adjustable-pressure relief valve into a tank in supplying the molding compound into the injection chamber of the injection barrel;
• wherein the working fluid is supplied into the front working chamber of the injection cylinder through an adjustable pressure reducing valve to apply a pressure to the front working chamber of the injection cylinder when the injection plunger is moved backward by the pressure of the molding compound supplied into the injection chamber of the injection barrel in metering the molding compound, and a pressure sensor is provided on the injection barrel to detect the pressure of the molding compound in the injection chamber of the injection barrel.