Patent ID: 8312716

Claim:
A hydraulic drive system comprising: a pressure-regulated hydraulic pump, the pressure-regulated hydraulic pump effective to provide a system pressure; a secondarily regulated hydraulic motor in communication with the pressure-regulated hydraulic pump; and a control in communication with the pressure-regulated hydraulic pump and the secondarily regulated hydraulic motor, the control effective to monitor at least one operating parameter of the hydraulic motor, increase the system pressure for the pressure-regulated hydraulic pump when the at least one operating parameter indicates a need for increased system pressure and decrease the system pressure for the pressure-regulated hydraulic pump when the at least one operating parameter indicates a need for decreased system pressure, set the desired system pressure to at least two different pressure stages, and to change from a normal pressure stage to a high pressure stage when the adjustment angle of the adjustable secondarily regulated hydraulic motor reaches a maximum adjustment angle in a displacement direction.