Patent ID: 6883518

Claim:
A undirectional valve comprising: a valve body including a frame, a valve opening through the frame, and a valve seat extending from the frame and at least partially surrounding the valve opening; and a valve flap having a first portion attached to the frame and an adjacent second portion free to move from a first position where the second portion is in contact with at least a part of the valve seat to a second position where at least part of the second portion is spaced from the valve seat, wherein the second portion of the valve flap comprises a first side spaced from a second side and a first end proximate the first portion and a second end spaced from the first end, wherein the valve flap further comprises a top surface and at least one rib extending from the top surface of the valve flap, and further wherein the valve flap thickness of a base part of the valve flap outside of the at least one rib decreases when moving from the first end to the second end or from the second end to the first end.