Self-acting fluid non-return valve

Claim 1

In a self-acting non-return heart valve including a ring member defining a smooth bored passage, a flap member mounted in the ring member to turn by pivot means within the passage about a pivoting axis between a closed position, in which the flap member substantially closes the passage to blood flow therethrough in a first back direction, and an open position in which the flap member is substantially aligned with blood flow in a second forward direction being reverse to said first direction, the pivoting axis dividing the flap member into a minor area which is upstream, with reference to blood flow, of the pivoting axis and a major area which is downstream, with reference to blood flow, of the pivoting axis in the open position of the flap member the major area being shaped to provide an aerofoil cross-section to the flap member which generates lift in the direction to urge the flap member into the open position in the face of the second direction flow, wherein the improvement comprises said flap member being a relatively thin flap having at least one thickened localized region in said major area removed from said pivot means responsible for generating the lift, leaving only said pivot means and said localized region thickened while the remaining part of said flap remains relatively thin.