Patent ID: 8827562

Claim:
A mud-lubricated bearing assembly comprising: a generally cylindrical housing; an elongate mandrel having a longitudinal bore, said mandrel being coaxially disposed within the housing and being rotatable relative to the housing; a thrust bearing configured to transfer axial on-bottom loads and off-bottom loads from the mandrel to the housing; a radial bearing disposed within the annular space between the mandrel and the housing and configured to maintain coaxial alignment of the mandrel and the housing; an annular lower seal ring coaxially and non-rotatably secured to a lower region of the mandrel, said lower seal ring having an annular upper seal surface in a plane perpendicularly transverse to the longitudinal axis of the mandrel; and an annular upper seal ring mounted to a lower region of the housing such that the upper seal ring is non-rotatable relative to the housing and axially movable relative to the housing within a defined range of travel, said upper seal ring having an annular lower seal surface matingly engageable with the upper seal surface of the lower seal ring; wherein the mandrel includes one or more fluid ports configured to allow fluid flow into the mandrel bore from an annular space between the mandrel and the housing.