Patent ID: 7210514

Claim:
A die casting machine comprising at least a first and second die which are disposed in abutment against each other to define a casting space therebetween, a sleeve mounted on the first die and communicating with the casting space, an injection piston slidably disposed within the sleeve for injecting molten metal supplied into the sleeve into the casting space, drive means for causing the injection piston to reciprocate, and lubricant oil feeding means for feeding a lubricant oil into a clearance between an inner peripheral surface of the sleeve and an outer peripheral surface of the injection piston; the lubricant oil feeding means comprising a lubricant oil feed passage for feeding a lubricant oil into the clearance between the inner peripheral surface of the sleeve and the outer peripheral surface of the injection piston, and an air feed passage for feeding air into a clearance between the inner peripheral surface of the sleeve and the outer peripheral surface of the injection piston, and a groove formed in the inner peripheral surface of the sleeve at a location corresponding to a retreated position of the injection piston so as to form a space with respect to the outer peripheral surface of the injection piston, the lubricant oil feed passage and the air feed passage being opened to the groove, wherein the air from the air feed passage serves as means for pumping the lubricant oil from the lubricant oil feed passage into the clearance between the outer peripheral surface of the injection piston and the inner peripheral surface of the sleeve via the space and the groove is continuous in a circumferential direction and has a center which is offset upwardly from the center of the sleeve.