Patent ID: 7373995

Claim:
An apparatus for steering an earth-penetrating drill bit, the apparatus comprising: an eccentric sleeve having a cylindrical bore and a piston chamber, the piston chamber having a port; a piston spring engaged with the piston chamber; a piston positioned against the piston spring; a deflection pad mounted to the piston through the port in the piston chamber; a mandrel positioned in the eccentric sleeve, the mandrel having a cylindrical bore, and a mandrel shoulder within the cylindrical bore of the mandrel, and a slot that exposes the cylindrical bore of the mandrel to an external surface of the mandrel; a control spring positioned in the cylindrical bore of the mandrel so that the mandrel shoulder engages an end of the control spring; a control tube positioned in the mandrel so that the control spring engages the control tube and exerts a force on the control tube that urges the control tube vertically downward; wherein the control tube, in response to an increasing back pressure of drilling fluid in the mandrel, moves upwardly against the force of the control spring, thereby exposing the piston to the drilling fluid through the slot in the mandrel and causing the deflection pad to move outward in response to the increasing pressure of the drilling fluid; wherein the increasing back pressure is enabled by a seal between an upper portion and an upper mandrel.