| 摘要 |
PROBLEM TO BE SOLVED: To eliminate gas leakage and to permanently maintain inner pressure by sealing a bung hole from the outside after a required pressure is attained, by using a simply structured valve which can change inner pressure stepwise using room temperature gas. SOLUTION: For gas injection, an inside sheet piece 4 is adhered to the bung hole 3 of this packaging container 1 from its inside face. Then room temperature pressurized gas is injected from the bung hole 3 for raising the inner pressure of the packaging container 1. In a pressurized condition where pressurization is not more than required, the inside sheet piece 4 is pressure welded to the bung hole 3 for making it an apparently sealed condition. Then the outside shape of the packaging container 1 is processed to be formed in a predetermined shape, and then is pressurized to a required level. After that the bung hole 3 is sealed outwardly using an outer seal piece 5 to make it a completely sealed condition.
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