Abstract: A pump drive head backspin retarder includes a vane pump having an impeller with a plurality of spring loaded vanes and a pawl clutch centrally disposed in the impeller and having a hub and a plurality of pawls. Each pawl is pivotally attached to the hub for movement between first and second positions. The impeller includes a plurality of pawl receiving recesses, whereby, for a first direction of rotation, pawls of the pawl clutch pivot to the first position corresponding to a disengaged state for providing no mechanical contact with the impeller and, for a second direction of rotation opposite the first, pawls of the pawl clutch pivot to the second position due to inertia corresponding to an engaged state thereby engaging corresponding pawl receiving recesses.

Abstract: A pump drive head includes a housing, and a main shaft carried on upper and lower bearings disposed in the housing. The main shaft includes an outer torque tube and a liner tube. The outer and liner tubes abut along a first portion of their length and are separated along a second portion of their length forming a double wall with an elongate tubular space in between. A standpipe is coupled at one end to the housing, below the lower bearing, and received by the elongate tubular space an eliminates the need for a lower seal on the main shaft. A hydraulic pump includes a hydraulic pump chamber displosed in the housing and communicating with the main shaft, and first and second gears disposed in the hydraulic pump chamber and the first gear coupled to the main shaft. The second gear intermeshes with the first gear. A suction port is located between the first and second gears and operable when the main shaft is rotated in a reverse direction from the normal pumping direction, during a condition known as backspin.