Abstract: A mud saver valve adapted to be connected below a kelly including an elastomeric sleeve that opens and closes within a housing, the sleeve defining a flow passage within it and closing against a barrier located within the flow passage, the sleeve closing against the core at low positive differential pressures.

Abstract: A fluid flow control sleeve valve having a generally concave cylindrical deformable sleeve sealing against a core in the flow passage at rest and defining an annular flow passage in the housing when deformed, including a pressure chamber defined between the sleeve and the valve housing, and preferably including integral longitudinal and circumferential sleeve ribs, a concave sealing surface on the core and fins adjacent the core downstream partially conforming to the shape of a portion of the non-deformed sleeve.