Check valve

A check valve including a generally tubular housing formed with a conical valve seat, a valve member having a semi-spherical seating surface and being selectively movable longitudinally of said housing between a first closed position at which said semi-spherical seating surface engages said conical valve seat and a second open position at which said semi-spherical seating surface is located in longitudinally spaced relation to said conical valve seat, and a valve member support element extending longitudinally of said housing, said valve member being formed with a longitudinally extending opening for receiving said valve member support element, said opening having a cross-sectional area significantly greater than the cross-sectional area of said support member to permit predetermined pivotal movement of said valve member with respect to said support element, said valve member support element, said valve member and valve member longitudinal opening being dimensioned such that the center of said semi-spherical seating surface is longitudinally spaced in one direction from the effective center of support of said valve member on said support element at said closed position of said valve member, and is longitudinally spaced in the opposite direction from the effective center of support of said valve member at said open position of said valve member.