| 摘要 |
<p>The present invention provides an improved sealing configuration in a downhole drill bit drive apparatus being operable to seal a bearing chamber from drilling fluids in a fluid flow passage and maintain the pressure in the flow passage and in the chamber substantially at equilibrium, The seal configuration includes an annular piston chamber, a housing defining an outer wall of the piston chamber and a mandrel defining an inner wall of the piston chamber, one end of the piston chamber communicating with the fluid flow passage, the other end of the piston chamber communicating with the bearing chamber, an annular piston concentrically disposed within the piston chamber in sealing engagement with the inner and outer walls of the piston chamber, the piston being axially movable in the piston chamber in response to a pressure differential between the fluid pressure in the fluid flow passage and the fluid pressure in the bearing chamber to a position whereat the fluid pressures are substantially equal; and further including a roller bearing for rotatingly mounting the piston on the mandrel to permit rotation of the mandrel with respect to the piston.</p> |
