SOUPAPE DE FERMETURE CONSTITUÉE D'UNE FEUILLE ET SAC AVEC SOUPAPE DE FERMETURE

摘要

Provided is a closing valve made of a sheet and a bag that includes the closing valve, the closing valve effectively exerting the function of a check valve when the pressure difference is large and also even when the balanced state where the pressure difference is small continues for a long time. As a valve portion of the closing valve, two valve portions, an upstream valve portion (a) positioned on an upstream side and a downstream valve portion (c) positioned on a downstream side, are provided, and, between the valve portions, a buffer portion (b) in which a fluid in a flow path is retained is provided. Closedness of the flow path in the buffer portion (b) is lower than that of the downstream valve portion (c), and closedness of the flow path in the upstream valve portion (a) is lower than that of the downstream valve portion (c). Also, the length of the buffer portion (b) may be longer than that of at least any one of the upstream valve portion (a) and downstream valve portion (c).