Multi-function machines, hydraulic systems therefor, and methods for their operation

A machine comprising an engine, multiple linear actuators and at least a first rotary actuator that perform functions of the machine, and a hydraulic system for controlling and actuating the linear actuators and the first rotary actuator, the hydraulic system comprising:

• a plurality of first variable displacement pump/motors powered in parallel by the engine, the first variable displacement pump/motors being operable to control flow of a first fluid to control at least some of the linear actuators and the corresponding functions performed thereby;
• a second variable displacement pump/motor connected to the engine in parallel with the first variable displacement pump/motors, the second variable displacement pump/motor drawing power from and delivering power to the engine, drawing power from and delivering power to the at least some of the linear actuators through the first variable displacement pump/motors, and controlling flow of a second fluid to control the first rotary actuator and the corresponding function performed thereby;
• and
• an energy storage device connected in series with the second variable displacement pump/motor and the first rotary actuator, the energy storage device being adapted to accumulate the second fluid pumped thereto by the second variable displacement pump/motor when the second variable displacement pump/motor draws power from the engine or from the at least some of the linear actuators through the first variable displacement pump/motors and being adapted to deliver the second fluid to the second variable displacement pump/motor when the second variable displacement pump/motor delivers power to the engine or to the at least some of the linear actuators through the first variable displacement pump/motors.

An excavator machine comprising an engine, multiple linear actuators that control a first set of multiple implements of the machine, at least a first rotary actuator that controls at least a second implement of the machine, and a hydraulic system for controlling and actuating the linear actuators and the first rotary actuator, the hydraulic system comprising:

• a plurality of first variable displacement pump/motors powered in parallel by the engine, each of the first variable displacement pump/motors controlling flow of a first fluid to control a corresponding one of the linear actuators and a corresponding one of the first set of multiple implements;
• a second variable displacement pump/motor connected to the engine in parallel with the first variable displacement pump/motors, the second variable displacement pump/motor drawing power from and delivering power to the engine, drawing power from and delivering power to the linear actuators through the first variable displacement pump/motors, and controlling flow of a second fluid to control the first rotary actuator and the second implement;
• and
• a hydraulic accumulator connected in series with the second variable displacement pump/motor and the first rotary actuator, the hydraulic accumulator being adapted to accumulate the second fluid pumped thereto by the second variable displacement pump/motor when the second variable displacement pump/motor draws power from the engine or from the linear actuators through the first variable displacement pump/motors, and being adapted to deliver the second fluid to the second variable displacement pump/motor when the second variable displacement pump/motor delivers power to the engine or to the linear actuators through first variable displacement pump/motors.

A method of operating a machine comprising an engine, multiple linear actuators and at least a first rotary actuator that perform functions of the machine, and a hydraulic system for controlling and actuating the linear actuators and the first rotary actuator, the method comprising:

• powering a plurality of first variable displacement pump/motors in parallel with the engine, the first variable displacement pump/motors controlling flow of a first fluid to control the linear actuators and the corresponding functions performed thereby;
• operating a second variable displacement pump/motor connected to the engine in parallel with the first variable displacement pump/motors to draw power from or deliver power to the engine, draw power from or deliver power to the linear actuators through the first variable displacement pump/motors, and control flow of a second fluid to control the first rotary actuator and the corresponding function performed thereby;
• accumulating the second fluid in an energy storage device connected in series with the second variable displacement pump/motor and the first rotary actuator, the energy storage device accumulating the second fluid pumped thereto by the second variable displacement pump/motor when the second variable displacement pump/motor draws power from the engine or from the linear actuators through the first variable displacement pump/motors;
• and
• delivering the second fluid from the energy storage device to the second variable displacement pump/motor when the second variable displacement pump/motor delivers power to the engine or to the linear actuators through the first variable displacement pump/motors.