| 摘要 |
A venting closure is provided which retains the contents of a screw-top container yet prevents distortion of the latter under the influence of a pressure differential applied from without. It consists of a cap fitted with a gasket which is supported circumferentially around the entire rim of the container by a plurality of flanges which at no point have a pitch greater than that of the screw threads; and which are disposed in relation to one another so as to permit air that has passed from the outside of the container along the container threads to enter the space between the gasket and the underside of the cap. The gasket normally seals against a central boss depending from the cap underside; however when external pressure exceeds that within the container by a predetermined level it momentarily lifts the gasket from its seat, admits air into the container through a central hole in the gasket, and tends to equalize the pressures. |
