A hydraulic system, mining machine and method of controlling a hydraulic actuator. The hydraulic system (HS) is provided with a control valve (23) for controlling movement direction and speed of a hydraulic actuator (HA) connected to the system. Generated force of the hydraulic actuator is controlled independently relative to the control valve by means of counterbalance valves (Cb1, Cb2) and servo valves (Sv1, Sv2) controlling their opening pressure. The counterbalance valves and the servo valves operate as a meter-out control assembly which controls flow of hydraulic fluid discharged from working pressure spaces (16a, 16b) of the hydraulic actuator. The disclosed system may be implemented to control a mining boom (3) of a mining machine (1).

The subject matter of this specification can be embodied in, among other things, a method that includes actuating a closure member at a predetermined first velocity a predetermined first number of cycles between a first configuration and a second configuration, actuating the closure member at a predetermined second velocity a predetermined second number of cycles between the first and the second configuration, actuating the closure member at a predetermined third velocity a predetermined third number of cycles and the second configuration, actuating the closure member at a predetermined fourth velocity a predetermined fourth number of cycles and the second configuration, and actuating the closure member to the second configuration at a predetermined fifth velocity for a predetermined flushing period.

A control valve includes a housing formed with first and second supply ports, first and second actuator ports, and a pilot port, and a spool accommodated slidably in the housing, and the spool is configured to allow the first supply port and the pilot port to communicate with each other both at the first communication position and the second communication position.

A control valve assembly for a load handling vehicle such as forklift comprises a valve body having a bore and a spool located within the bore that is axially movable along the bore between at least two operating configurations. The valve body includes a service port connected to a hydraulic actuator, a pressure port connected to a pump, and a tank port connected to a hydraulic tank reservoir. The valve is reconfigurable between first and second operating configurations. In the first operating configuration the spool defines a fluid pathway connecting the pump port, the service port and the tank port such that in a first flow direction fluid is able to flow from the pressure port to the service port and the tank port, and in a second flow direction fluid is able to flow from the service port to the pressure port and the tank port. The spool is also controllable in the first operating configuration to variably restrict flow to the tank port. In the second operating configuration the spool defines a fluid pathway connecting the pressure port and the actuator port, and is controllable to variably restrict flow between the pressure port and the actuator port.

A hydraulic system (1, 50) for a load handling vehicle comprises lifting actuator (2, C1) that operates in a load lifting mode in which a load is induced on the actuator, and a load lowering mode in which the actuator provides hydraulic power PI to the hydraulic system. An auxiliary hydraulic actuator (4, 6, 8, C2) is also provided that has a hydraulic power demand P2. A hydraulic pump (10, 58) directs hydraulic power to the hydraulic lifting actuator and the at least one auxiliary hydraulic actuator. The hydraulic system is configured such that when the hydraulic lifting actuator is in the load lowering mode, it is required to simultaneously actuate the at least one auxiliary hydraulic actuator, and PI is greater than or equal to P2, hydraulic power may be channelled directly to the auxiliary hydraulic actuator from the hydraulic lifting actuator in order that the at least one auxiliary hydraulic actuator is actuated entirely by the hydraulic power from the hydraulic lifting actuator, and without the use of the pump.

1. Control Device

2. A control device for controlling a hydraulic consumer (2), such as a working cylinder, consisting of at least one control valve (18) having a control spool (20), which is guided in a valve housing (22) in a longitudinally movable manner and which can be actuated by means of an electric motor (24) and which can be controlled by means of control electronics (MC), which receive input signals from a sensor device (58, 60, 62), which detects at least one operating state of the consumer (2).

A hydraulic system includes a hydraulic pump to output an operation fluid, first and second hydraulic devices to be operated by the operation fluid, first and second control valves to control the first and second hydraulic device, respectively, first and second communication tubes connecting the first hydraulic device to the first control valve, a supply fluid tube connecting the first control valve to the second control valve, the supply fluid tube being configured to supply the return fluid to the second control valve, first and second connection fluid tubes disposed on the first control valve, a discharge fluid tube connected to the first control valve, first and second branching fluid tubes branched from the first and second connection fluid tubes, respectively, first and second throttles disposed on the first and second branching fluid tubes, respectively, the second throttle being smaller than the first throttle.

The subject matter of this specification can be embodied in, among other things, an electrohydraulic positioning control system that includes a shuttle valve configured to direct fluid flow between a selectable one of a first fluid port and a second fluid port, and a fluid outlet configured to be fluidically connected to a fluid actuator, a first servo valve controllable to selectably permit and block flow between the first fluid port, a fluid source, and a fluid drain, a second servo valve controllable to selectably permit and block flow between the second fluid port, the fluid source, and the fluid drain, a first servo controller configured to provide a first health signal and control the first servo valve based on a second health signal, and a second servo controller configured to provide the second health signal and control the second servo valve based on the first health signal.

The subject matter of this specification can be embodied in, among other things, a method that includes actuating a closure member at a predetermined first velocity a predetermined first number of cycles between a first configuration and a second configuration, actuating the closure member at a predetermined second velocity a predetermined second number of cycles between the first and the second configuration, actuating the closure member at a predetermined third velocity a predetermined third number of cycles and the second configuration, actuating the closure member at a predetermined fourth velocity a predetermined fourth number of cycles and the second configuration, and actuating the closure member to the second configuration at a predetermined fifth velocity for a predetermined flushing period.

A hydraulic system includes a first hydraulic device, a second hydraulic device, a first control valve to control the first hydraulic device, a second control valve disposed on a downstream side of the first control valve and configured to control the second hydraulic device, a communication tube connecting the first hydraulic device to the first control valve, a supply fluid tube connecting the first control valve to the second control valve, a connection fluid tube disposed on the first control valve, the connection fluid tube connecting the communication tube to the supply fluid tube, a discharge fluid tube connected to the first control valve, a setting portion disposed on the discharge fluid tube and configured to increase a pressure in the discharge fluid tube, a branching fluid tube branched from the connection fluid tube and connected to the discharge fluid tube, and a throttle disposed on the branching fluid tube.