Gas control unit and process for gas-assisted injection molding

A gas-assisted injection molding system for introducing a predetermined mass of a gas into a mold cavity in combination with a quantity of plastic material, said gas-assisted injection molding system comprising:

• fixed volume means for accumulating a predetermined constant mass of said gas;
• means in fluidic communication with said fixed volume accumulating means for charging said fixed volume accumulating means with said predetermined constant mass of said gas;
• passage means in fluidic communication with said fixed volume accumulating means for communicating said predetermined constant mass of said gas to said mold cavity such that said predetermined constant mass of said gas is distributed between said fixed volume accumulating means, said passage means and said mold cavity whereby said predetermined constant mass of said gas remains substantially contained within said gas-assisted injection molding system;
• means in communication with said fixed volume accumulating means for sensing a pressure of said gas within said fixed volume accumulating means after said gas is communicated to said mold cavity;
• and
• control means in communication with said pressure sensing means for comparing said sensed pressure with a predetermined pressure;
• whereby said control means determines whether said predetermined constant mass of said gas in said fixed volume accumulating means has fully expanded throughout said injection molding system.

A method for introducing a volume of a gas into a mold cavity in combination with a quantity of plastic material, said method comprising the steps of:

• accumulating a predetermined mass of said gas within a fixed volume accumulator;
• communicating said predetermined mass of said gas from said fixed volume accumulator to said mold cavity such that said predetermined mass of said gas is distributed between said fixed volume accumulator and said mold cavity;
• sensing a pressure of said gas in said fixed volume accumulator after said predetermined mass of gas is communicated to said mold cavity;
• and
• comparing said sensed pressure to a predetermined pressure so as to determine whether said mold cavity has been properly filled with said predetermined mass of said gas.

A method for introducing a predetermined mass of a gas into a mold cavity in combination with a quantity of plastic material, said method comprising the steps of:

• supplying said gas from a pressurized source to a fixed volume accumulator having a fixed reservoir volume;
• sensing a reservoir pressure of said gas within said fixed volume accumulator;
• accumulating said gas within said fixed volume accumulator until said reservoir pressure corresponds to a predetermined mass of said gas;
• communicating said predetermined mass of said gas from said fixed volume accumulator to said mold cavity such that predetermined mass of said gas is distributed between said fixed volume accumulator and said mold cavity;
• sensing a final pressure in said fixed volume accumulator of said gas after said gas is communicated to said mold cavity;
• and
• comparing said final pressure to a predetermined pressure which corresponds to said predetermined volume so as to determine whether said mold cavity has been properly filled with said predetermined mass of said gas.