초록 ▼

A method and apparatus for injection molding of thermoplastic material to form a hollow article in a closed mold in which a molten thermoplastic material is introduced from an injection nozzle into a mold cavity through an opening in the mold, and a pressurized gas is introduced together with the mo

A method and apparatus for injection molding of thermoplastic material to form a hollow article in a closed mold in which a molten thermoplastic material is introduced from an injection nozzle into a mold cavity through an opening in the mold, and a pressurized gas is introduced together with the molten thermoplastic material through said opening so that the gas forms a hollow cavity under pressure within the thermoplastic material filling the mold. After the thermoplastic material is solidified to form a hollow article within the closed mold, the gas pressure in the hollow cavity of the article is reduced and the mold is opened. The pressurized gas is introduced into the mold from a gas source and the gas pressure is subsequently reduced by recycling at least a portion of the gas in the hollow cavity to the gas source, thereby avoiding loss of the gas to the surrounding atmosphere.

대표청구항 ▼

A method for injection molding of thermoplastic material to form a hollow article in a closed mold wherein a molten thermoplastic material is introduced through a nozzle orifice into a mold cavity through an opening in said mold; a pressurized gas at an elevated pressure is introduced together with

A method for injection molding of thermoplastic material to form a hollow article in a closed mold wherein a molten thermoplastic material is introduced through a nozzle orifice into a mold cavity through an opening in said mold; a pressurized gas at an elevated pressure is introduced together with said molten thermoplastic material through said opening so that the gas forms a hollow cavity under said elevated pressure within the thermoplastic material filling the mold; the thermoplastic material is solidified to form a hollow article within the closed mold while the gas pressure within said mold is maintained at said elevated pressure; and, thereafter, the pressure of the gas in the hollow cavity is reduced prior to opening the mold; said pressurized gas being introduced into said mold from a first gas source at the elevated pressure and the gas pressure being reduced by recycling at least a portion of the gas in the hollow cavity to another gas source at a gas pressure lower than the elevated pressure of the pressurized gas, said another gas source being connected to said first gas source via means for increasing pressure of the gas from the another gas source to said elevated pressure.