Patent ID: 7686067
Filing Date: 2010-03-30
Classification: B22D

Abstract:
1. A die casting machine for filling by injecting molten metal into a die cavity, comprising: a pump driven by a drive motor for discharging a hydraulic fluid from a hydraulic fluid tank; a piston for filling by injecting the molten metal in the cavity; an injection cylinder with the piston movably assembled therein and having the internal space thereof divided into two hydraulic chambers by the piston; a hydraulic fluid supply path for supplying the hydraulic fluid discharged by the pump into one of the hydraulic chambers of the injection cylinder; a first logic valve for switching hydraulic fluid paths through which the hydraulic fluid flows, the first logic valve being arranged in a hydraulic fluid path between one of the hydraulic chambers of the injection cylinder and the hydraulic fluid tank, and adapted to be closed during an injection step for injecting molten metal into the die cavity and to be opened during a high pressure holding step for preventing a blowhole from being formed in a die-cast product; a second logic valve for switching the hydraulic fluid paths through which the hydraulic fluid flows, the second logic valve being arranged in a hydraulic fluid path between the other one of the hydraulic chambers of the injection cylinder and the hydraulic fluid supply path, and adapted to be opened during the injection step to form an ejected fluid supply path for supplying the hydraulic fluid ejected from the other one of the hydraulic chambers of the injection cylinder to the hydraulic fluid supply path and to be closed during the high pressure holding step; and a restriction mechanism arranged in the ejected fluid supply path for generating pressure in the hydraulic fluid, which operates depending on the first and second logic valves, wherein the restriction mechanism counteracts a pressure from the filling of the molten metal cavity in order to minimize a decrease in a speed of the piston.