Patent ID: 7521016
Filing Date: 2009-04-21
Classification: B29C

Abstract:
1. An injection molding method for producing a molded article having a hollow portion by injecting a molten resin into a cavity provided in a mold and introducing a pressurized gas into the molten resin in the cavity, said method comprising: providing an apparatus for introducing a pressurized gas, which comprises: coupling the first pressurized-gas supply-line to the first end of each measuring tank and coupling the second pressurized-gas supply-line to the second end of each measuring tank; determining a combination of the measuring tanks in advance on a basis of an amount of pressurized gas to be required for forming the hollow portion in the molded article; bringing the pressurized-gas discharge-control valve into a closed state and bringing the pressurized-gas supply valve into an open state to supply the pressurized gas to the determined combination of measuring tanks, and then bringing the pressurized-gas supply valve into a closed state; injecting the molten resin into the cavity provided in the mold; and bringing the pressurized-gas discharge-control valve disposed in the second pressurized-gas supply-line into an open state on the basis of said determining operation, to introduce the pressurized gas into the molten resin in the cavity for forming the hollow portion, wherein the pressurized-gas discharge-control valve comprises a plurality of pressurized-gas discharge-control valves that are not simultaneously brought into an open state.