| 摘要 |
<p>A downhole drive shaft (11) and bearing structure having a unitary, generally cylindrical housing (13) with a radial bearing surface (57) affixed to its interior; a drive shaft having a radial bearing surface (55) affixed to its exterior and thrust bearing inserts (41) mounted at the bit end (15) thereof; and a drive shaft cap (19) affixed to the drive shaft and carrying thrust bearing inserts, the thrust bearing inserts of the cap (19) and drive shaft (11) interfacing with oppositely disposed inserts (37, 39) mounted in the housing (13).</p> |
