Importance

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Abstract

A valve which is primarily useful in avoiding liquid being held or trapped around the exterior of a closure member used to close off the flow from an inlet to an outlet cavity through an opening after having been positioned so as to permit such flow can be constructed so that the terminal surface on the closure member appears as a continuation of the internal surface of the outlet cavity around the opening when the closure member is in this closed position. Preferrably, the outlet cavity is a cylindrical bore and the terminal surface of the closure member is a cylindrical surface having the same diameter as the bore. When the outlet cavity and the terminal surface are so shaped, a guide structure is used to control the movement of the valve closure member so that it can only be located in a closed position in which the cylindrical surface appears as a part of the cylindrical bore. Preferrably, the valve seat and the closure member are formed of different inert polymer materials having different hardnesses and a spring is provided for biasing the closure member against the valve seat when it is in the closed position so that some cold flow will take place in the softer of the two materials in order to achieve an acceptable seal.

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First Claim