Abstract: A power recovery speed control apparatus for use in a system driven by a substantially constant-speed power source driving a turbine type water pump. The system includes a hydromechanical trimmer device controlled by pump output pressure to modify the turbine pump speed over a relatively small range as a function of pump output pressure. In series between the power source output shaft and the turbine pump drive shaft is a mechanical differential gear assembly having input, output and differential (speed difference) shafts. A fixed displacement hydrostatic transmission unit (pump) extracts a fraction of the source power at the differential shaft and applies it through hydraulic feed lines to a variable displacement hydrostatic transmission unit operated as a hydraulic motor. The hydraulic motor unit has its displacement controlled by a pump output pressure sensor and its output torque is introduced into the power train at the power source output or alternatively, at the turbine pump input shaft.

Abstract: Modifying the lands of a control spool of a control valve to provide pressurized fluid to the destroking servo when the land covers the destroking servo port. The lands of a control spool are provided with notches to allow fluid to flow from the control pressure port of the control valve to the servo ports of the valve. These notches ensure that a flow of pressurized fluid will be transmitted from the control pressure port to the destroking servo port during return of the swashplate to its neutral position. By providing the notches, pressurized fluid is directed to the destroking port when the land of the control spool covers the destroking servo port. This pressurized fluid helps force via the destroking servo the swashplate back to its neutral position.