Importance

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Abstract

A slit closure valve for container openings includes a membrane member of flexible material having an at least unidirectionally aligned slit-like outlet opening and a base member peripherally surrounding the membrane member and connected to the membrane member. The outlet opening is held in its closed position by the resilient properties of the material although it is adapted to be moved into its open position against the resilient bias force of the material by a predetermined differential positive pressure exerted on one side of the membrane member. A peripheral wall portion of the base member and an adjacent wall portion of the membrane member include therebetween an acute angle of less than 90'. At least one further, substantially peripherally aligned slit-like passage opening held in its closed position by the resilient properties of the material is provided in the membrane wall portion near the base member, said passage opening being adapted to be moved into its unblocking position by a differential negative pressure exerted on the membrane member from the side thereof subjected to said predetermined differential positive pressure. The valve thereby enables the pressure between the interior of a container and its surroundings to be equalized thus assisting in the restoration of the container after its walls have been pressed-in manually for emptying the contents of the container.

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First Claim