Patent ID: 7758020

Claim:
A valve in which a valve disc and a valve seat are brought into close contact via an annular sealing member composed of an elastic material and provided at said valve disc or said valve seat, wherein the valve is substantially circular in structure about the central axis; said valve disc comprises a first surface that is orthogonal to the central axis facing said valve seat and a first peripheral surface connected to said first surface, said valve seat comprises a second surface that is orthogonal to the central axis facing said first surface and an annular protrusion protruding from said second surface toward said first peripheral surface in a position facing said first peripheral surface, the annular protrusion has a second peripheral surface that is connected to the second surface and is configured to face the first peripheral surface, the first peripheral surface is composed of a tapered peripheral surface, the second peripheral surface is composed of an inversely tapered peripheral surface, said sealing member is provided at one of said first surface and said second surface and configured so that said sealing member can be brought into close contact with the other of said first surface and said second surface, the sealing member is positioned radially inward of the tapered peripheral surface and the inversely tapered peripheral surface in the direction of the central axis of the valve and is wholly integrated into the first or second surface, the sealing member is positioned at a downstream side from the tapered peripheral surface and inversely tapered peripheral surface in a flow direction of fluid, and a flow passage between said first peripheral surface and said annular protrusion comprises a flow passage that is set to have a cross section area that is preferentially reduced with respect to that of a flow passage between said first surface and said second surface during the closing of the valve.