Check valves

A valve assembly comprising:

• a hollow, main body member disposed on a generally horizontal axis;
• a frusto-conical valve seat disposed interiorly of said main body member;
• and
• a circular closure member having a frusto-conical periphery conforming to said frusto-conical valve seat, said closure member being journalized in said main body member for rotation about a horizontal axis normal to the direction of the axis of said valve seat, said axis of rotation being displaced from a diameter of said closure member a distance less than the radius of said member,
• said closure member having a weight distribution such that the center of gravity thereof remains on one side of a vertical plane including said axis of rotation throughout the entire range of movement of said member and acts through a progressively decreasing moment arm as said member rotates toward a horizontal open position so as to develop a correspondingly decreasing closing, biasing torque.