The present invention provides a controller for a hydraulic apparatus. The controller is configured to determine (410) that a mode change criteria has been met for the hydraulic apparatus. In response to the determination, the controller is configured to control (420) a valve arrangement to change a first actuator chamber of a hydraulic actuator between being fluidly connected to a hydraulic machine and fluidly isolated from a second chamber of the hydraulic actuator, and being fluidly connected to both the second actuator chamber and the hydraulic machine. Further in response to the determination, the controller is configured to control (430) the hydraulic machine to change a flow rate of hydraulic fluid flowing through the hydraulic machine to regulate a movement of the hydraulic actuator during the control of the valve arrangement.

A hydraulic drive system includes control valve and operating devices, a variable displacement pump, and a flow regulator. When an operating lever inclination angle becomes a value, a control valve opening area becomes a reference. When the operating lever inclination angle maximizes, the opening area maximizes. The flow regulator: until the operating lever inclination angle becomes the value, increases the pump discharge flow rate with the inclination angle, so a differential pressure between pump discharge and actuator load pressures is constant; when the operating lever inclination angle becomes the value, controls the pump discharge flow rate, so a control valve passing flow rate is an actuator maximum flow rate when the differential pressure is constant; and when the operating lever inclination angle is between the value and the maximum, defines a maximum pump discharge flow rate, so the pump discharge flow rate is kept to the actuator maximum flow rate.

A fail-safe actuation system comprising an actuator having first and second chambers, a working circuit with a motor/pump device configured to actuate the actuator in an operative state, and a safety circuit configured to move the actuator into the safety position in a failure state, the safety circuit having a tank that holds pressurized fluid and that, in the failure state, is automatically connected to the first chamber via a switching valve, and having a drain valve that, in the failure state, is moved into a through-flow position in order to drain fluid out of the second chamber, the safety circuit configured such that, in the operative state, an inflow into the actuator—in a manner that is decoupled from the tank—is established by the working circuit, and, in the failure state, an inflow from the tank into the first chamber—in a manner that is completely decoupled from the working circuit—is created by the safety circuit, whereby a short-circuit fluid connection is provided between the first and second chambers that, in the failure state, is through-connected in order to generate a short-circuit flow between the first and second chambers.

The invention concerns a device for the direct recovery of hydraulic energy in a machine, comprising at least one single-acting storage cylinder-piston device with a storage cylinder, a storage cylinder-piston and a storage cylinder chamber, with at least one differential cylinder-piston device with a differential cylinder comprising a separate rod side and base side, and with at least one hydraulic accumulator, which may be connected to the storage cylinder-piston device and/or the differential cylinder-piston device, wherein the potential energy of the storage cylinder-piston device, which retracts under a compressive load, may be at least partially stored in the hydraulic accumulator.

An apparatus for recuperating hydraulic energy in a working machine includes at least one first differential cylinder piston device with a differential cylinder and separate rod and bottom sides, and at least one hydraulic accumulator which is hydraulically connectable with the differential cylinder piston device. The potential energy of the differential cylinder piston device retracting under pressing load is at least partly storable in the hydraulic accumulator. The rod and bottom sides are connectable with each other via at least one brake valve for recirculating hydraulic fluid from the bottom side into the rod side.

There is provided a driving device for a work machine, having a closed hydraulic circuit system for driving cylinders with hydraulic pumps, the driving device making the speed of operation substantially the same in both directions of piston rod extension and contraction. The driving device includes: a first hydraulic pump that has flow rate control device for controlling the flow rate and direction of hydraulic fluid to be delivered; a single rod hydraulic cylinder that is driven with the hydraulic fluid to drive one of work members of a work device on the work machine; a closed hydraulic circuit that connects the first hydraulic pump with the single rod hydraulic cylinder to form a closed circuit using flow lines through which the hydraulic fluid flows; a branch line that branches from the flow line between the first hydraulic pump and the single rod hydraulic cylinder; a first flow line of which one end is connected to the branch line; a tank to which the other end of the first flow line is connected; and a hydraulic fluid flow rate control device attached to the first flow line to control the flow rate of the hydraulic fluid flowing from the branch line to the tank or from the tank to the branch line.

A hydraulic fluid flowpath includes a first flowpath and a second flowpath. The first flowpath connects a first pump port and a first chamber in a hydraulic cylinder. The second flowpath connects a second pump port and a second chamber in the hydraulic cylinder. The hydraulic fluid flowpath forms a closed circuit between a hydraulic pump and the hydraulic cylinder. A bleed-off flowpath bleeds off a portion of the hydraulic fluid from the second flowpath. A control valve connects the second flowpath to the bleed-off flowpath via a throttle when an operation amount of an operating member for lowering a work implement is less than a predetermined operation amount so that a hydraulic pressure in second flowpath is maintained at less than a relief pressure. The predetermined operation amount is less than or equal to the maximum operation amount for lowering the work implement.

A control system for controlling a moveable device includes at least one hydraulic actuator associated with the moveable device, at least one position sensing device to determine the position of the moveable device or the actuator, or both, and a hydraulic control system, including an electronic control unit, for controlling the actuator. For performing a control method, the hydraulic control system is configured to deliver pressurized hydraulic fluid to the actuator, the hydraulic fluid being pressurized at most to a predetermined maximum pressure, and the control system is adapted to regulate the predetermined maximum pressure based on the determined position. According to an example, the moveable device is a boom of a working machine. According to a further example, the actuator is a hydraulic cylinder or motor.

The invention relates to a hydraulic device for driving an actuator to be hydraulically controlled or actuated, comprising a motor arranged in a motor housing, a compensating tank (31) for accommodating hydraulic fluid, and a hydraulic pump, which is arranged in a pump housing and driven by the motor, wherein the hydraulic pump is designed in such a way that the hydraulic pump permits conveyance of hydraulic fluid in two directions, namely in the forward direction and in the backward direction, wherein the hydraulic actuator comprises a drive cylinder, which has a first and a second cylinder chamber and a drive piston (3) arranged therebetween, to which drive piston a drive shaft (2) that can be displaced in the longitudinal direction is attached, wherein the device comprises a loading cylinder for an emergency closing spring (16), in which loading cylinder a loading cylinder chamber (12) and a loading piston (11) that can be coupled to the drive shaft (2) are arranged, wherein the emergency closing spring (16) can be loaded into a loaded or emergency-triggering readiness position by the loading piston (11), wherein the loading cylinder chamber (12) is connected to an outlet of the hydraulic pump in such a way that the loading cylinder chamber (12) can be filled with hydraulic fluid by means of the hydraulic pressure of the hydraulic pump and the loading piston can be transferred into a loading position as the emergency closing spring (16) is compressed and the loading piston can be locked there hydraulically by means of check valves (36, 37), and wherein a controlled seat valve (50) is connected to an inflow/outflow opening of the loading cylinder chamber, by means of which seat valve the emergency closing spring (16) can be transferred from the loaded readiness position into an emergency-triggering opening position, wherein both the hydraulic fluid that is contained in the loading cylinder chamber (12) and holds the emergency closing spring (16) in the readiness position and the hydraulic fluid contained in the first cylinder chamber can be discharged via the controlled seat valve (50).

A downforce control system for an agricultural ground engaging unit provides individual control of each agricultural ground engaging row unit by providing a proportional pressure control valve connected to the retracting chamber of a double acting cylinder which varies the upward force produced by the retracting chamber of the cylinder against a constant counteracting downward force produced by an extending chamber of the cylinder, the valve control based on a comparison of a sensed resultant downward force on the agricultural ground engaging row unit and a predetermined target downward force.