An electrohydraulic control circuit for driving a hydraulically actuated actuating element (5, 6), by means of which a segment (5.3) of a manipulator, in particular of a large manipulator for truck-mounted concrete pumps, can be adjusted in terms of its orientation, wherein there are provided an electrically driven first valve (2.4), which is connected to hydraulic working lines of the actuating element (5.6) for the drive thereof, and leak-free check valves (2.5, 2.6) provided in the working lines of the actuating element (5.6), which valves are arranged on the actuating element (5.6) or on the segment (5.3) associated with this actuating element (5.6) and can be released for the normal operation of the actuating element (5.6), wherein the release of the check valves (2.5, 2.6) is driven by an electronic control unit (ECU) separate from the first valve (2.4) and the check valves (2.5, 2.6).

The present invention relates to a hydraulic control valve for construction machinery that is used to maintain secondary pilot pressure which is formed proportionally to the switching of a switching device so as to be equal to or below a setting pressure of a pilot pump. The hydraulic control valve of the present invention includes: a port of the pilot pump into which the pilot pressure flows; a tank port to which the pilot pressure is drained; a valve body at which a secondary pilot pressure port that selectively communicates with the port of the pilot pump and the tank port is formed; the switching device that is pivotally mounted on the valve body; a pilot control valve that is linked through pressurization of the switching device and has a spool which forms the secondary pilot pressure proportional to the amount of switching of the switching device by communicating the port of the pilot pump and the secondary pilot pressure port with each other during the switching; a valve spring that elastically supports the spool so as to communicate the secondary pilot pressure port and the tank port with each other; and a check poppet that is disposed in an openable and closable manner at a pilot passage whose inlet side communicates with the secondary pilot pressure port and whose outlet side communicates with the port of the pilot pump.

A self-contained pressure compensation system and a control method thereof are provided, wherein the self-contained pressure compensation system comprises an oil supply device, a pressure compensation device, a power unit associated with the pressure compensation device, and a switch control device, the pressure compensation device supplies oil to the power unit and detects a change in a chamber pressure of itself in real time, the switch control device triggers the oil supply device to supply oil to the pressure compensation device if the chamber pressure is less than a predetermined first threshold and triggers the oil supply device to stop supplying oil to the pressure compensation device if the chamber pressure is greater than a predetermined second threshold. The invention can detect a chamber pressure of the pressure compensation device in real-time and can achieve automatic oil refilling, and can provide pressure compensation for the power unit effectively.

A hydraulic lifting device for a chassis of a mobile device has a valve block, a pump, a tank, a first cylinder device and a second cylinder device. The first cylinder device and the second cylinder device can be selectively pressurized by the pump or connected to tank via the valve block. The first cylinder device is connected to the pump via at least one primary non-return valve disposed in the valve block. The second cylinder device is connected to the pump via at least one secondary non-return valve disposed in the valve block. The valve block has at least one pressure accumulator downstream of the at least one secondary non-return valve in the flow direction from the pump to the second cylinder device. Furthermore, a chassis with such a lifting device and to a mobile device with a chassis is provided.

A method is provided for the simultaneous detection, localization, and quantification of leaks and obstructions in a gas network under pressure or vacuum. The gas network includes: one or more sources of compressed gas or vacuum; one or more consumers or consumer areas of compressed gas or vacuum applications; pipelines or a network of pipelines to transport the compressed gas or vacuum from the sources to the consumers, consumer areas or applications; a plurality of sensors providing one or more physical parameters of the gas at different times and locations within the gas network. The gas network is further provided with controllable or adjustable relief valves, controllable or adjustable throttle valves and possibly one or a plurality of sensors capable of monitoring the status or state of the relief valves and/or throttle valves.

The invention relates to a hydraulic cylinder, for example for use with a hydraulic tool, which hydraulic tool is provided with a frame and an element which is movable with respect to the frame by means of the hydraulic cylinder.

A hydraulic tool which is operated by means of a hydraulic cylinder as described above is known from, for example, European patent no. 0641618. This patent discloses a frame which is coupleable to a jib of an excavator or the like and to which an assembly of two jaws can be coupled. One of the jaws is pivotable with respect to the other jaw by means of a hydraulic adjusting cylinder (a double-acting piston/cylinder combination).

A diagnosis method for continuous function monitoring of a process valve during normal operation. The diagnosis method includes the steps of determining process set data (S) with discrete-time process set values from an input signal supplied to the process valve, b) determining process actual data (s) with discrete-time process actual values using a displacement-measurement system assigned to the process valve, and c) analyzing the process actual data (s) dependent on the process set data (S) by comparing the process set data (S) and the process actual data (s) with each other to detect defined error states.

A fluid leakage detection system includes: a measurement unit configured to detect leakage of working oil in a hydraulic cylinder; and a controller configured to acquire a measurement result from the measurement unit, wherein the controller diagnoses that a battery depletion has been caused in a battery in a case in which it is determined that a data from the measurement unit has not been acquired and it is determined that the battery of the measurement unit has been in a low-remaining-battery-level state, and the controller diagnoses that a communication abnormality has been caused in a first communication part of the measurement unit in a case in which it is determined that the data from the measurement unit has not been acquired and it is determined that the battery has not been in the low-remaining-battery-level state.

An accumulator includes: a main cylindrical housing having a closed first axial end and a second axial end; a piston arranged in the main cylindrical housing and sealed to an inner surface of the main cylindrical housing, which piston is movable in an axial direction and provides with the main cylindrical housing and the closed first axial end of the main cylindrical housing a variable accumulating space; an urging device arranged between the piston and the second axial end of the main cylindrical housing for urging the piston towards the first axial end of the main cylindrical housing; a fluid supply opening arranged in the first axial end of the main cylindrical housing, which fluid supply opening is in fluid connection with the variable accumulating space; and a protective cylindrical housing having a first and a second axial end, the protective cylindrical housing being arranged concentrically.

Disclosed are seal arrangements in a hydraulic device. The seal arrangement includes a seal channel defining a loop. A seal is seated within the seal channel. A coolant flow passage has a first part intersecting with the seal channel at a first point and a second part intersecting with the seal channel at a second point. The first part of the coolant flow passage is configured to provide hydraulic fluid to the seal channel such that, at the first point, a first portion of the hydraulic fluid flows in a first direction around the loop and a second portion of the hydraulic fluid flows in a second direction opposite to the first direction around the loop. At the second point, the first portion of hydraulic fluid and the second portion of hydraulic fluid are configured to flow into the second part of the coolant flow passage.