A counter pressure valve arrangement for controlling a pressure level of a hydraulic fluid in a return line from a hydraulic actuator arrangement. The counter pressure valve arrangement comprises a counter pressure valve having: a moveable valve member; a counter pressure regulating port configured for being connected to the hydraulic actuator arrangement via the return line; a tank port configured for being connected to a tank or low pressure reservoir for storing low pressure hydraulic fluid; and a pump port configured for being connected to a source of pressurised hydraulic fluid. A first position of the valve member effects fluid communication between the pump port and the counter pressure regulating port for supplying pressurised hydraulic fluid to the return line, and a second position of the valve member effects fluid communication between the counter pressure regulating port and the tank port for discharging hydraulic fluid from the return line to the tank.

A hydraulic machine includes: a power source; an assist motor including comprising an inlet port and an outlet port and assisting a torque of the power source; a tank; a collection line which is connected to the inlet port and allows a fluid to flow to the inlet port; a first return line which is connected to the tank and allows the fluid to flow to the tank; a self-priming line which connects the first return line to the inlet port and allows the fluid to flow from the first return line to the inlet port; and an anti-cavitation line which connects the outlet port to the self-priming line and allows the fluid to flow from the outlet port to the self-priming line.

A reservoir for a hydraulic system has a housing with an interior space and a fluid outlet, a hydraulic driving device coupled to a shaft extending in the housing to introduce a torque, and a separating device in the housing, for dividing the interior space into two separate sections. The fluid outlet is fluidically connected to a first section. The separating device extends along the shaft in the housing and sets the size ratio of the two separate sections by pivoting at least one first surface, coupled to the shaft, of the separating device about an axis defined by the shaft. The separating device is coupled to the hydraulic driving device such that the at least one first surface exerts a pressure on a fluid in the first section which is dependent on a surface area of the first surface and the torque.

A hydraulic circuit is disclosed. The hydraulic circuit may comprise an actuation valve configured to actuate a flow of hydraulic fluid to and from the hydraulic consumer, a first control valve in fluid communication with the actuation valve through a first pilot line and configured to displace the actuation valve to a first position when actuated, and a second control valve in fluid communication with the actuation valve through a second pilot line and configured to displace the actuation valve to a second position when actuated. The first pilot line and the second line may each have a fixed minimum back pressure sufficient to maintain dissolved air in the hydraulic fluid.

A sub-system 200 for an aircraft hydraulic system 20 that includes a first inlet 202 for receiving fluid from a supply 22 of hydraulic fluid, a system valve 210 for controlling fluid flow from the sub-system 200 to a hydraulically-operable system 24 of the aircraft hydraulic system 20, a check valve 220 for permitting fluid flow from the sub-system 200 and preventing or hindering fluid flow into the sub-system 200, a second inlet 240 for receiving fluid from a second supply 28 of hydraulic fluid, and a selector 230. The selector 230 configured to place the system valve 210 in fluid communication with the first inlet 202 when the selector 230 is in a first state, and to place the system valve 210 in fluid communication with the check valve 220 and the second inlet 240 when the selector 230 is in a second state different from the first state.

A work machine including: a hydraulic cylinder 20 configured to drive a work implement 3; a control valve 22 configured to connect a delivery line of a hydraulic pump 21 switchingly to a bottom fluid chamber and a rod fluid chamber of the hydraulic cylinder 20 and a tank; a pilot pump 23 configured to output a pilot pressure to drive the control valve 22; an engine 24 configured to drive the hydraulic pump 21 and the pilot pump 23; and an accumulator 26 configured to accumulate a return hydraulic fluid from the hydraulic cylinder 20 is provided with: a bypass line 41 configured to connect the bottom fluid chamber of the hydraulic cylinder 20 and a delivery line 21a of the hydraulic pump 21 by bypassing the control valve 22 and be provided with the accumulator 26 thereon; a pressure-accumulation control valve 27 provided between the bottom fluid chamber of the hydraulic cylinder 20 and the accumulator 26; a release control valve 28 provided between the accumulator 26 and the delivery line 21a; and a hydraulic system controller 30 configured to open the release control valve 28 if an engine revolution speed N becomes lower than a set value Ns.

A monitoring system for a plurality of pressure pumps may include, for each pump, a strain gauge, a position sensor and a pressure transducer. A strain gauge may be positionable on each pump to generate a strain measurement corresponding to strain in each pump. A position sensor may be positionable on each pump to generate a position measurement corresponding to a position of a rotating member corresponding of each pump. A pressure transducer is positionable on each pump to generate a boost pressure measurement that is usable with the strain measurement and the position measurement to determine a cavitation threshold for each pump.

A fluid container, in particular a hydraulic tank for a motor pump unit, has an equalizing chamber that is adapted to contain a supply of fluid and air, and at least one return chamber into which a return flow of the fluid can flow, a fluid communication being provided between the return chamber and the equalizing chamber. The return chamber is provided with a suction port for a pump, in particular of the motor pump unit.

A hydraulic cylinder assembly comprising: a single-acting hydraulic cylinder; an oil tank; a fluid line fluidically connecting the oil tank with the hydraulic cylinder; and a motor unit comprising a pump disposed in the fluid line and comprising a motor configured to operate the pump to pump fluid from the oil tank to the hydraulic cylinder to extend the hydraulic cylinder, and to permit flow of fluid from the hydraulic cylinder to the oil tank through the pump during retraction of the hydraulic cylinder, a pressure sensor configured to output a pressure signal indicative of pressure of hydraulic fluid in the hydraulic cylinder; and a controller configured to control the motor unit based on pressure signals received from the pressure sensor. The hydraulic cylinder assembly is configured so that oil leaving the hydraulic cylinder, during retraction of the hydraulic cylinder, passes through the pump to the oil tank.

An example valve includes a piston configured to block fluid flow from a first port of the valve to a second port of the valve when the valve is in a closed position; a relief mode spring applying a first biasing force on the piston in a distal direction; a reverse flow spring applying a second biasing force on the piston in a proximal direction, wherein the reverse flow spring is weaker than the relief mode spring; and a pressure setting spring applying a third biasing force on a check element in the distal direction, causing the check element to be seated when the valve is in the closed position.