A steering device includes: a cylinder demarcated into first and second chambers by a piston; a main valve having first and second shuttle chambers; a hydraulic source having first and second discharge ports; a first oil passage configured to connect the first chamber and the first shuttle chamber; a second oil passage configured to connect the second chamber and the second shuttle chamber; a third oil passage configured to connect the first shuttle chamber and the first discharge port; a fourth oil passage configured to connect the second shuttle chamber and the second discharge port; and a tank connected to the main valve via the third oil passage and the fourth oil passage. One of the first shuttle chamber and the second shuttle chamber of the main valve is in an opened state when the hydraulic source is stopped.

A prime mover and a plurality of hydraulic actuators, a hydraulic machine having a rotatable shaft in driven engagement with the prime mover and comprising a plurality of working chambers, a hydraulic circuit extending between a group of one or more working chambers of the hydraulic machine and one or more of the hydraulic actuators, each working chamber of the hydraulic machine comprising a low-pressure valve which regulates the flow of hydraulic fluid between the working chamber and a low-pressure manifold and a high-pressure valve which regulates the flow of hydraulic fluid between the working chamber and a high-pressure manifold. The hydraulic machine being configured to actively control at least the low-pressure valves of the group of one or more working chambers to select the net displacement of hydraulic fluid by each working chamber on each cycle of working chamber volume, and thereby the net displacement of hydraulic fluid by the group of one or more working chambers, responsive to a demand signal, wherein the apparatus further comprises a controller configured to calculate the demand signal in response to a measured property of the hydraulic circuit or one or more actuators.

A load sense open center hydraulic system provides efficiency and operator feedback and includes one or more constant flow-open center valves (218); respective one or more parallel power cores (238) operatively coupled to the one or more constant flow-open center valves; a variable capacity pump (246) directly fluidly connected to the one or more parallel power cores; and a pressure compensated flow control fluidly connected between the variable capacity pump and the one or more constant flow-open center valves. The one or more constant flow-open center valves are not fluidly coupled to a fixed capacity pump.

An aircraft assembly having: a first part; a second part, the second part being movably mounted with respect to the first part; an electro-hydraulic actuator coupled between the second part and a first anchor point, the actuator comprising a cylinder defining a bore and a piston and rod assembly slidably mounted within the bore and an active chamber within which an increase in fluid pressure causes the actuator to change during a first phase between first and second extension states to move the second part relative to the first part. The electro-hydraulic actuator further includes a hydraulic fluid supply circuit comprising a piezo-electric pump operable to supply pressurised fluid to the active chamber to change the actuator between first and second extension states.

A hydraulic system including a first cylinder conduit configured to couple to a cylinder, a second cylinder conduit configured to fluidly coupled to the cylinder, and a bypass conduit fluidly coupled both to the first cylinder conduit upstream of the cylinder and to the second cylinder conduit downstream of the cylinder. The bypass conduit is configured to enable intermittent fluid flow of a hydraulic fluid from the first cylinder conduit to the second cylinder conduit while bypassing at least a portion of the cylinder.

Particular embodiments of the inventive technology disclosed herein relate to the use of a dynamic valve to reduce motion caused by impulse force applied to a positioned component. Typically, the inventive technology finds application in an internally pressurized positioning system. At times, use of the inventive technology may lead to cost savings by, e.g., allowing for the use of smaller diameter positioner actuators and/or a reduced internal pressure.

A prime mover and a plurality of hydraulic actuators, a hydraulic machine having a rotatable shaft in driven engagement with the prime mover and comprising a plurality of working chambers, a hydraulic circuit extending between a group of one or more working chambers of the hydraulic machine and one or more of the hydraulic actuators, each working chamber of the hydraulic machine comprising a low-pressure valve which regulates the flow of hydraulic fluid between the working chamber and a low-pressure manifold and a high-pressure valve which regulates the flow of hydraulic fluid between the working chamber and a high-pressure manifold. The hydraulic machine being configured to actively control at least the low-pressure valves of the group of one or more working chambers to select the net displacement of hydraulic fluid by each working chamber on each cycle of working chamber volume, and thereby the net displacement of hydraulic fluid by the group of one or more working chambers, responsive to a demand signal, wherein the apparatus further comprises a controller configured to calculate the demand signal in response to a measured property of the hydraulic circuit or one or more actuators.

In a fluid circuit for an air cylinder connected to a switching valve provided with exhaust ports, a head-side pressure chamber is connected to the switching valve by a first pipe, and a rod-side pressure chamber is connected to the switching valve by a second pipe. A first restrictor is disposed at a connection point between the first pipe and the switching valve or in the vicinity of a first output port of the switching valve, and a second restrictor is disposed at a connection point between the second pipe and the switching valve or in the vicinity of a second output port of the switching valve.

Systems and methods for electrohydraulic valve calibration are provided. In one aspect, a calibration circuit includes a calibration conduit isolated from a supply conduit, a first calibration orifice configured to provide fluid communication between the calibration conduit and a fluid source, and a second calibration orifice arranged in series with the first calibration orifice. The second calibration orifice is on a spool of a electrohydraulic control valve and is configured to selectively provide fluid communication between the calibration conduit and a low pressure source. The calibration circuit further includes a pressure sensor configured to measure a pressure in the calibration conduit between the first calibration orifice and the second calibration orifice. The second calibration orifice is isolated from the at least one workport of the electrohydraulic control valve.

Method for determining the temperature of a fluid in a hydraulic arrangement for a motor vehicle. The hydraulic arrangement has a pump arrangement, which is driven by means of a drive motor, and a pressure sensor, which is connected to a discharge port of the pump arrangement and is used to measure the pressure of the fluid. The pump arrangement is connected to a tank via a leakage point. The temperature of the fluid is determined on the basis of a relationship between a state variable of the drive motor and the temperature of the fluid at a predetermined pressure of the fluid, said relationship being specific to the hydraulic arrangement.