A first position detection sensor and a second position detection sensor of a pressure booster detect the position of a first piston or a second piston. A fluid supply mechanism supplies a fluid to a first pressure-boosting chamber and/or a second pressure-boosting chamber. On the basis of the detection results of the first position detection sensor and the second position detection sensor, the fluid supply mechanism switches between performing an operation for supplying fluid to a first drive chamber and discharging fluid from a second drive chamber, and performing an operation for discharging fluid from the first drive chamber and supplying fluid to the second drive chamber.

Disclosed embodiments include travel motor hydraulic circuits for controlling the provision of hydraulic fluid to a travel motor. The travel motor hydraulic circuits include a counterbalance valve configured to block the flow of hydraulic fluid when in a neutral position to prevent unintended movement of a power machine, and an anti-cavitation valve configured to direct flow of hydraulic fluid back to the travel motor to prevent cavitation.

The hydraulic apparatus is set so that the ratio of the pressure-receiving area of the respective bottom oil chambers of the boom cylinder, the arm cylinder and the bucket cylinder to the pressure-receiving area of the respective rod oil chambers matches the ratio of the extruded volume drawn into or discharged from the bottom oil chambers per single rotation by the respective extrusion members of the first hydraulic pump motor, the second hydraulic pump motor and the third hydraulic pump motor to the volume discharged from or drawn into the rod oil chambers.

A hydraulic system, a mobile mining machine and to a method of controlling a hydraulic actuator is provided. The hydraulic system includes two hydraulic pumps (P1, P2) for generating hydraulic power for a hydraulic actuator. The pumps are powered by means of a common electric motor. Operation of the actuator is controlled by controlling speed and direction of the motor, whereby hydraulic lines (19a, 19b) may be without actively controlled control valves.

Disclosed embodiments include travel motor hydraulic circuits for controlling the provision of hydraulic fluid to a travel motor. The travel motor hydraulic circuits include a counterbalance valve configured to block the flow of hydraulic fluid when in a neutral position to prevent unintended movement of a power machine, and an anti-cavitation valve configured to direct flow of hydraulic fluid back to the travel motor to prevent cavitation.

A piston includes a piston housing and a decompression valve disposed in the piston housing. The decompression valve includes a valve housing seated in the piston housing and a valve member moveably received by the valve housing. The valve member has a radially outer surface including an annular shoulder. In addition, the piston includes an end cap secured to the first end of the piston housing. A radially inner surface of the end cap includes an annular valve seat. The decompression valve has a closed position with the annular shoulder of the valve member engaging the valve seat of the end cap and an open position with the annular shoulder of the valve member axially spaced from the valve seat of the end cap. The piston also includes a biasing member configured to bias the decompression valve to the closed position.

The present invention relates inter alia to a hydraulic device which may be used as a hydraulic transformer. The hydraulic device comprising a housing, a first tubular cavity and a second tubular cavity both being provided within the housing. A piston structure is reciprocatable arranged within the housing and comprises a first piston and a second piston; wherein the first piston divides the first cavity into two chambers, and the second piston divides the second cavity into two chambers. Fluid passages for individually exchanging fluid between the chambers and the exterior of the housing are provided and each fluid passage comprising a controllable shut-off valve so as to provide the reciprocating movement of the piston structure by exchanging fluid between exterior and the two chambers of the first cavity, and said hydraulic transformed being configured to control the shut-off valves to selectively be in a closed state or in an open state.

The hydraulic apparatus is set so that the ratio of the pressure-receiving area of the respective bottom oil chambers of the boom cylinder, the arm cylinder and the bucket cylinder to the pressure-receiving area of the respective rod oil chambers matches the ratio of the extruded volume drawn into or discharged from the bottom oil chambers per single rotation by the respective extrusion members of the first hydraulic pump motor, the second hydraulic pump motor and the third hydraulic pump motor to the volume discharged from or drawn into the rod oil chambers.

The present invention relates inter alia to a hydraulic device which may be used as a hydraulic transformer. The hydraulic device comprising a housing, a first tubular cavity and a second tubular cavity both being provided within the housing. A piston structure is reciprocatable arranged within the housing and comprises a first piston and a second piston; wherein the first piston divides the first cavity into two chambers, and the second piston divides the second cavity into two chambers. Fluid passages for individually exchanging fluid between the chambers and the exterior of the housing are provided and each fluid passage comprising a controllable shut-off valve so as to provide the reciprocating movement of the piston structure by exchanging fluid between exterior and the two chambers of the first cavity, and said hydraulic transformed being configured to control the shut-off valves to selectively be in a closed state or in an open state.