Patent ID: 8128058

Claim:
A valve comprising: a housing defining an internal chamber with an inlet port and an outlet port; a flapper within the chamber, the flapper being configured to pivot to a first closed position to seal the inlet port against flow between the outlet port and the inlet port, and to pivot to a second open position to permit fluid flow between the inlet port and the outlet port; a limiting element within the chamber, the limiting element being adjustably positionable in relation to the flapper to limit the amount by which the flapper pivots including to prevent the flapper from pivoting at all and wherein a leaf spring having a first end and a second end biases the flapper toward the closed position, and further wherein the valve includes a rod extending within the chamber, and the flapper includes a cylindrical portion for receiving the rod and pivoting about the rod, and further wherein the cylindrical portion defines at least one cam protrusion extending from the cylindrical portion, the at least one cam protrusion being configured to engage the leaf spring whereby the leaf spring applies a force to the protrusion and biases the flapper toward the closed position.