Leaf valve

A leaf valve is a one-way valve (check valve) consisting of a diagonal obstruction with an opening covered by a hinged flap.

Patents exist in the United States which specify the mechanical use of leaf valves to control various types of fluids.

United States Patent 4930535 is a folding leaf valve which is described as a valve that, "folds upon itself to provide positive sealing of a pressurized chamber under a variety of pressure conditions. In particular, the valve stem folds to effectively close the lumen and provide a positive seal even at low differential pressure."