US Patent 9611885 Lubricated superhard bearing assemblies

Embodiments to bearing apparatuses for placement into a borehole containing a drilling fluid in which the apparatus is configured for transferring heat to the drilling fluid from a lubricating fluid substantially sealed within the apparatus. The apparatus includes a substantially sealed housing, first and second bearing assemblies disposed about a rotatable shaft extending through the housing, where the bearing assemblies are within the substantially sealed housing. Each bearing assembly includes superhard bearing elements. One bearing assembly is fixed relative to the shaft so as to rotate therewith, while another bearing assembly is fixed relative to the housing. In an embodiment, a lubricating fluid for lubricating the superhard bearing elements may circulate from within a circulation cavity of the housing or shaft between the superhard bearing elements, and be recirculated back into the circulation cavity. In other embodiments, the lubricating fluid may not be recirculated.