A pilot type switching valve includes: a housing bore formed in a valve body, the housing bore having an opening end; a spool slidably housed in the housing bore, the spool being configured to allow or block a flow of the working fluid to a first relief valve; a pilot chamber to which pilot pressure biasing the spool in the valve opening direction is guided; and a spring configured to bias the spool in the valve closing direction. The spool has a bottom surface on which the pilot pressure acts in such a manner that the spool is biased in the valve opening direction, and the area of the bottom surface is smaller than the sectional area of the housing bore.

A pilot type switching valve includes: a housing bore formed in a valve body, the housing bore having an opening end; a spool slidably housed in the housing bore, the spool being configured to allow or block a flow of the working fluid to a first relief valve; a pilot chamber to which pilot pressure biasing the spool in the valve opening direction is guided; and a spring configured to bias the spool in the valve closing direction. The spool has a bottom surface on which the pilot pressure acts in such a manner that the spool is biased in the valve opening direction, and the area of the bottom surface is smaller than the sectional area of the housing bore.

Systems and methods for auto-commissioning first and second valve assemblies associated with an actuator in an electro-hydraulic system are disclosed. In one method, a controller performs an automatic test protocol to determine a bulk modulus over fluid volume parameter used by the controller to control the valve assemblies. In one aspect, the test protocol can include pressurizing each side of the actuator to two different pressures with one of the first and second valve assemblies and blocking the other side of the actuator with the other of the first and second valve assemblies. The bulk modulus over fluid volume parameter for each valve assembly can be calculated based on recorded fluid pressures at the actuator and consumed flow at the first and second valve assemblies.

A lock valve including a poppet valve element which is disposed within a spring chamber, a spring which biases the poppet valve element leftward, and a valve seat which comes into contact with the poppet valve element is disposed in a cavity formed in a valve body to mount a relief valve therein and is positioned further inward than the sleeve of the relief valve. The outer peripheral portion of the poppet valve element has hole portions formed therein at regular intervals. The outer peripheral portion of the valve seat, too, has hole portions formed therein at regular intervals. The valve portion of a solenoid valve is disposed between a passage which is in communication with the spring chamber and a passage which is in communication with a second flow passage open to a low-pressure region such as a hydraulic tank.

A hydraulic machine, such as a revolving excavator work machine, including a travel-purpose hydraulic motor whose capacity is switchable, in which a work accuracy is obtained by avoiding that a hydraulic motor mainly used for work travel in a large-capacity setting state is affected by an increased traveling speed resulting from a small-capacity setting state of a hydraulic motor. A control device for the hydraulic machine, in driving each of a plurality of hydraulic actuators, corrects a target value for a ratio of a supply flow rate to a required flow rate for each hydraulic actuator in accordance with a change in the engine rotation number and further corrects the target value for the ratio of the supply flow rate to the required flow rate for each hydraulic actuator in accordance with switching of the capacity of the travel-purpose hydraulic motor included in the plurality of hydraulic actuators.

An example valve includes a main stage, a pilot stage, and a solenoid actuator. The main stage includes a sleeve and a piston axially movable within the sleeve. The piston defines a cavity therein. The pilot stage includes a pilot pin received at, and axially movable in, the cavity of the piston, where the piston forms a pilot seat at which the pilot pin is seated when the valve is in a closed state. The solenoid actuator includes a solenoid coil, an armature, and a solenoid spring. The solenoid spring applies a biasing force in a distal direction on the pilot pin to seat the pilot pin at the pilot seat. Energizing the solenoid coil causes the armature to move in a proximal direction, thereby reducing the biasing force that the solenoid spring applies on the pilot pin.

A manipulator for concrete pumps having an articulated boom with at least two boom arms and a hydraulic drive that pivots one or more of the boom arms. A hydraulic cylinder has piston and rod side working volumes. A hydraulic circuit has a first switching state in which the hydraulic circuit connects a first working port for feed or discharge of hydraulic fluid to the rod-side working volume and connects a second working port for feed or discharge of hydraulic fluid to the piston-side working volume. In a second switching state, the hydraulic circuit separates the first working port from the first fluid channel and thereby connects the first fluid channel to the second fluid channel for the feed of hydraulic fluid from the rod-side to the piston side working volume. A sensor acquires an operating state variable based upon which an activation assembly sets the switching state.

A control device for a hydraulic machine such as a revolving excavator work machine having a structure that can cope with such an engine output decreasing environment as a work under a low atmospheric pressure at a high altitude without generating noise caused by engine rotation number increase. The control device corrects a control output value to be applied to an electromagnetic proportional valve for load-sensing valve control in a load-sensing type pump control system, based on a detected state quantity related to the engine output decreasing environment. When an engine speed-sensitive pump control system is adopted, a control output value generated based on a detected decrease in the actual engine rotation number is combined with a control output value generated by the load-sensing type pump control system.

A hydraulic system (600) and method for reducing boom dynamics of a boom (30), while providing counter-balance valve protection, includes a hydraulic actuator (110), first and second counter-balance valves (300, 400), first and second control valves (700, 800), and first and second blocking valves (350, 450). A net load (90) is supported by a first chamber (116, 118) of the hydraulic actuator, and a second chamber (118, 116) of the hydraulic actuator may receive fluctuating hydraulic fluid flow from the second control valve to produce a vibratory response (950) that counters environmental vibrations (960) on the boom. The first blocking valve prevents the fluctuating hydraulic fluid flow from opening the first counter-balance valve. The first blocking valve may drain leakage from the first counter-balance valve.

A linear actuator system includes a linear actuator and at least one integrated pump assembly connected to the linear actuator to provide fluid to operate the linear actuator. The integrated pump assembly includes a pump with at least one fluid driver comprising a prime mover and a fluid displacement assembly to be driven by the prime mover such that fluid is transferred from a first port of the pump to a second port of the pump. The pump assembly also includes two valve assembles to isolate the pump from the system. The linear actuator system also includes a controller that establishes at least one of a speed and a torque of the at least one prime mover to exclusively adjust at least one of a flow and a pressure in the linear actuator system to an operational set point.