A regeneration control hydraulic system for an excavator, including at least one hydraulic pump, an actuator, a regeneration oil path, and a regeneration cut-off oil path. The regeneration oil path is configured to send a return oil as a regeneration oil to a cavity having a negative pressure of the actuator. The regeneration oil path is provided with a regeneration valve and a first control valve. The first control valve is configured to control the regeneration oil to enter the cavity having the negative pressure of the actuator when a working device of the excavator retracts inwards, or to control the oil to be discharged from the actuator to the regeneration cut-off oil path when the working device swings outwards. The regeneration cut-off oil path is configured to send the regeneration oil passing through the regeneration valve or the oil discharged from the actuator to other destinations.

A machine is adapted for operation powered by any one of a plurality of interchangeable power sources. The machine may include an undercarriage configured for supporting ground engagement members that propel the machine and an upper structure rotatably supported on the undercarriage. The upper structure may include a swing frame, with the swing frame supporting an operator cab, any one of the plurality of interchangeable power sources, hydraulic components, electrical components, and a counterweight disposed at a first end of the swing frame. The counterweight may include a hollowed out portion facing toward the swing frame. The hollowed out portion of the counterweight may be centrally aligned with a center core portion of the swing frame configured for supporting any one of the plurality of interchangeable power sources, with the one power source being partially accommodated within the hollowed out portion of the counterweight.

A hydraulic drive system for a work machine including a hydraulic energy recovery device that is configured to perform load sensing control and accumulates hydraulic fluid that returns from a hydraulic cylinder in operation of lowering a front work implement into an accumulator includes, in order to prevent, when operation other than operation of lowering the front work implement is to be performed, hydraulic energy accumulated in the accumulator from being consumed uselessly, a regeneration selector valve in a hydraulic line for regenerating the hydraulic fluid accumulated in the accumulator into a hydraulic fluid supply line of a main pump. The regeneration selector valve is controlled such that, only when saturation occurs with the main pump, flow from the accumulator to the hydraulic fluid supply line is permitted.

The object of the present invention is to provide an inventive energy recovery method for a hydraulic system comprising a hydraulic cylinder (1), a pump (2), a tank (3), a supply conduit (4), a return conduit (5), and a hydraulic accumulator (7), the method comprises the steps of charging said hydraulic accumulator (7), and storing fluid in said hydraulic accumulator (7), wherein said energy recovery method comprises the step of directing fluid from said hydraulic accumulator (7) into an expanding chamber (8, 9) of said hydraulic cylinder (1) during an overrunning load condition.

A switching valve includes a spool, a first cylinder port that communicates with the piston side chamber, a second cylinder port that communicates with the rod side chamber, a bridge passage having a first opening which is adjacent to the first cylinder port and a second opening which is adjacent to the second cylinder port, a regeneration passage formed in the spool to connect the second cylinder port communicating with the rod side chamber to the first cylinder port in accordance with a switching position of the spool, and a first communication port and a second communication port formed in the spool to communicate with the regeneration passage. The first communication port communicates with the second opening of the bridge passage, which is adjacent to the second cylinder port, and the second communication port communicates with the second cylinder port in accordance with the switching position of the spool.

Disclosed is a hydraulic system for performing land preparation works by means of a simultaneous boom-up and arm-in operation. The hydraulic system according to the present invention includes: an arm cylinder and a boom cylinder that are connected to first and second hydraulic pumps, respectively; a first boom control valve that is disposed in the discharge flow path of the second hydraulic pump; a second boom control valve that is disposed in the discharge flow path of the first hydraulic pump and causes the working fluid of the first hydraulic pump to converge with the working fluid which is supplied from the second hydraulic pump to the boom cylinder; a first arm control valve that is disposed in the discharge flow path of the first hydraulic pump; a second arm control valve that is disposed in the discharge flow path of the second hydraulic pump and causes the working fluid of the second hydraulic pump to converge with the working fluid which is supplied from the first hydraulic pump to the arm cylinder; a recycle valve that is disposed in the flow path between the working fluid inlet port of the first arm control valve and a hydraulic tank; and a second boom control valve spool having a parallel pressure section in which the boom-up pilot pressure does not increase with respect to the boom-up strokes during the simultaneous boom-up and arm-in operation.

A control system for a hydraulic system including an accumulator and a hydraulic transformer coordinates flow sharing within the hydraulic system. The hydraulic transformer includes first and second variable displacement pump/motor units mounted on a rotatable shaft. The rotatable shaft has an end adapted for connection to a first external load. The first variable displacement pump/motor unit includes a first side that fluidly connects to a pump and a second side that fluidly connects to a tank. The second variable displacement pump/motor unit includes a first side that fluidly connects to the accumulator and a second side that fluidly connects with the tank. A second external load may be hydraulically connected to the hydraulic system. Energy may be transferred to/from the pump, the accumulator, the first external load, and/or the second external load, as directed by the control system.

A power system for a working machine includes a transmission for driving the working machine, the transmission including a continuously variable gear box having a gear unit and a hydraulic variator unit; a work hydraulic circuit for controlling at least one hydraulic actuator of the working machine; wherein the hydraulic variator unit is hydraulically connected to the work hydraulic circuit to hydraulically transfer energy from the hydraulic variator unit to the work hydraulic circuit.

A mobile mining machine includes a plurality of traction elements, a plurality of motors, a power source in electrical communication with the plurality of motors, and an energy storage system in electrical communication with the plurality of motors and the power source. Each of the motors is coupled to an associated one of the plurality of traction elements. Each of the motors is driven by the associated traction element in a first mode, and drives the associated traction element in a second mode. The energy storage system includes a shaft, a rotor secured to the shaft, a stator extending around the rotor, and a flywheel coupled to the shaft for rotation therewith. In the first mode, rotation of the motors causes rotation of the flywheel to store kinetic energy. In the second mode, rotation of the rotor and the flywheel discharges kinetic energy to drive the motors.

A hydrostatic drive includes a hydraulic machine, a hydraulic adjusting device, a high-pressure accumulator, an accumulator-closing valve, and an electronic control unit. The hydraulic machine has a swept volume that is adjustable via the hydraulic adjusting device from a maximum positive swept volume to a maximum negative swept volume via a zero swept volume. The hydraulic machine is operated as a pump with positive swept volume and as a motor with negative swept volume. The high-pressure accumulator supplies the hydraulic machine with pressure medium for operation as a motor via a pressure line. The accumulator-closing valve has a first position and a second position and is arranged in the pressure line. A fluidic connection from the high-pressure accumulator to the hydraulic machine is open in the first position and closed in the second position. The accumulator-closing valve is actuated in accordance with signals from the electronic control unit.