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 circle drive system with clutch protection in motor graders is disclosed. The circle drive system includes a hydraulic motor that is configured to receive a pressurized fluid and generate a torque for a rotation of a circle and a moldboard. The circle drive system also includes a gearbox to transfer the torque generated by the hydraulic motor to the circle. Further, the circle drive system includes a clutch connected to the hydraulic motor at one end and to the gearbox at another end. In addition, the circle drive system also includes a hydraulic circuit having a pressure relief valve to relieve the pressurized fluid supplied to the hydraulic motor when a pressure of the pressurized fluid exceeds a predefined threshold. The pressure relief valve thereby, limits the torque generated by the hydraulic motor to less than or equal to a torque capacity of the clutch.

A hydraulic system for a working machine, the system comprising: an electric machine connected to a first hydraulic machine and to a second hydraulic machine via a common axle, an output side of the second hydraulic machine being connected to an input side of the first hydraulic machine, wherein the first hydraulic machine is a variable displacement hydraulic machine with unidirectional flow; at least one hydraulic consumer hydraulically coupled to an output side of the first hydraulic machine via a supply line and configured to be powered by the first hydraulic machine; a first return line hydraulically coupling the hydraulic consumer to the input side of the first hydraulic machine.

Provided is a hydraulic circuit, for a construction machine, which drives an actuator by merging pressure oil from a fixed-volume pump into a center bypass oil path from a variable-volume pump to an oil tank, wherein the flow rate of flow from the fixed-volume pump to the center bypass oil path can be controlled in accordance with a requested flow rate of the actuator. A distribution direction-switching valve, which has a first oil path from a fixed-volume pump to an oil tank and a second oil path from the fixed-volume pump to a first center bypass oil path, has a first signal reception unit which causes a spool to slide in a direction in which the first oil path is formed, and a second signal reception unit which causes a spool to slide in a direction in which the second oil path is formed, and determines a distribution ratio of pressure oil flowing to the first oil path and the second oil path in accordance with the difference in size of the signals received by the first signal reception unit and the second signal reception unit, the first signal reception unit receiving a signal based on a negative control signal.

A direction control valve group for a construction machine that controls an amount of pressure oil supplied to a hydraulic actuator from a hydraulic pump that discharges the pressure oil is provided. The direction control valve includes a cylinder port that supplies the pressure oil to the hydraulic actuator, a bridge passage that is switchably connected and disconnected to the cylinder port according to a change in position of a first spool, and an internal passage that supplies the pressure oil discharged from the hydraulic pump to the bridge passage. The first spool is provided in the internal passage.

A drive control method of a hydraulic actuator of a construction machine includes: determining whether a rotation operation lever and a working device operation lever are operated; calculating the required pressure of a hydraulic cylinder fix a working device according to the operation amount of the rotation operation lever; calculating the required flow rates of a swing motor and the hydraulic cylinder for the working device, the required flow rates corresponding to the operation amounts of the working device operation lever and the rotation operation lever; calculating the opening areas of the first and second proportional solenoid valves of an inlet side and an outlet side by using the calculated required pressure and required flow rates of the hydraulic cylinder for the working device and the swing motor; and calculating current values to be inputted into the first and second proportional solenoid valves of the inlet side and the outlet side according to preset data values or a table in comparison with the calculated opening areas of the first and second proportional solenoid valves of the inlet side and the outlet side.

A hydraulic control system includes a flow rate control valve; a variable displacement hydraulic pump which is connected to the flow rate control valve and discharges hydraulic pressure to the flow rate control valve; a pump discharge pressure detector which is installed in a section where the flow rate control valve and the variable displacement hydraulic pump are connected, and detects the discharge pressure of the hydraulic pressure discharged from the variable displacement hydraulic pump to the flow rate control valve; and a hydraulic controller including a detection unit which is connected to the pump discharge pressure detector, detects the discharge pressure of the variable displacement hydraulic pump and converts the discharge pressure to a pump discharge pressure value, a comparison unit which receives the pump discharge pressure value from the detection unit, compares the pump discharge pressure value with a pre-stored lowest recognition pressure value, and determines whether the pump discharge pressure value is greater or less than the lowest recognition pressure value, and a calculation unit which, by interworking with the comparison unit, if the pump discharge pressure value is less than the lowest recognition pressure value, calculates a control pressure by recognizing the control

Disclosed are a damping system for a movable arm of a loading machine and an operation machinery, which comprise a multi-way valve, a movable arm oil cylinder, a movable arm damping valve, and a damping lock. The multi-way valve comprises a movable arm valve core and a bucket valve core, a first movable arm oil port of the movable arm valve core communicates with a rod cavity of the movable arm oil cylinder, a second movable arm oil port of the movable arm valve core communicates with a rodless cavity of the movable arm oil cylinder, the rod cavity of the movable arm oil cylinder communicates with the movable arm damping valve, the rodless cavity of the movable arm oil cylinder communicates, via the damping lock, with the movable arm damping valve; a switching oil port of the damping lock communicates with an unloading position of the bucket valve core.

A remote wireless hydraulic frame preferably includes a frame member, a frame transceiver, a frame bridge controller and an electro-hydraulic conversion valve. The frame bridge controller receives signals from a cab bridge controller through a cab transceiver and the frame transceiver. The frame member preferably includes a frame support, an engine, a hydraulic pump, at least one electrical component and a plurality of hydraulicly operated components. The electro-hydraulic conversion valve preferably includes a valve block and a plurality of proportioning valves. The plurality of proportioning valves receive a hydraulic electrical signal from a hydraulic control device located in a remote wireless hydraulic cab through the cab bridge controller. Hydraulic fluid is sent from the valve block to a plurality of hydraulic operated components on the frame support. Control electrical signals are also received from the cab bridge controller to operate at least one electrical component on the frame support.

A hydraulic system includes: a boom cylinder to move a boom; a working tool cylinder to move a working tool attached to the boom; a boom control valve to control the boom cylinder; a working tool control valve to control the working tool cylinder; a horizontal control valve having: an activating position to allow a horizontalizing operation of the working tool; and a stopping position to stop the horizontalizing operation; and a controller device having: a first information obtaining portion to obtain permission and non-permission to the horizontalizing operation; a second information obtaining portion to obtain at least one of upward operation and upward movement of the boom; and a horizontal controller to set the horizontal control valve to the stopping position when the first information obtaining portion obtains the non-permission and the second information obtaining portion obtains one of the upward operation and the upward movement.