Patent ID: 7530800

Claim:
A drivehead for driving a drive string of a rotary pump or motor, the drivehead comprising: a bearing housing for containing lubricating fluid therein; a driveshaft extending through the bearing housing and connectable into drive communication with the drive string and a pump disposed in the bearing housing concentric about the driveshaft, the pump selected to pump the lubricating fluid through the bearing housing as driven by the driveshaft and such that a fluid pressure output by the pump correlates to the speed of rotation of the driveshaft wherein the driveshaft is driven in a forward direction to drive the drive string and the driveshaft is driven in a reverse direction by release of reactive torque in the drive string and the drive string further comprising a braking assembly including a braking circuit and a hydraulic brake in the braking circuit, the braking assembly operable to brake reverse rotation of the driveshaft and wherein the pump is operable to provide self-regulation of the braking system such that slowing of driveshaft rotation in the reverse direction causes a decrease in the fluid pressure output by the pump to reduce pressure on the hydraulic brake and braking force output by the hydraulic brake.