The present invention relates to a hydraulic system for a hydraulically actuable work machine that comprises a switching valve block having a plurality of valve block inputs for a respective connection to a pressure output of one or more hydraulic fluid pumps; having a plurality of valve block outputs for outputting a pressurized hydraulic fluid; and having at least one valve that is arranged between valve block inputs and valve block outputs and that is adapted to selectively produce a fluid connection between a first valve block input and a first valve block output or between the first valve block input and a second valve block output; a plurality of pressure sources, preferably a plurality of separately controllable pressure sources of which each one is connected to a respective valve block input; and a plurality of hydraulic consumers of which each one is connected to a respective valve block output. The system is characterized in that the first valve block output furthermore already has a fixed fluid connection, preferably a fixed exclusive fluid connection, to a second valve block input and in that the steering is connected to the first valve block output.

A hydraulic apparatus comprises first and second manifolds each of which is connected to a plurality of actuators via corresponding actuator valves connected in parallel and operated responsive to inputs to regulate the flow of fluid to the actuators. A plurality of working chambers are connectable to either the first or second manifold and have a net flow which is controlled responsive to a negative feedback signal. The negative feedback signal is determined in response to a calculated pressure or flow rate in virtual fluid flow paths extending from the first and second manifolds.

A pneumatic control device of auto door includes a first directional control valve configured to control a direction of a compressed air supplied to a door cylinder for opening and closing a door, a door detection sensor configured to detect an open/close state of the door, first and second exhaust lines respectively connected to first and second outlet ports of the first directional control valve, and second directional control valves installed in the first and second exhaust lines respectively to operably exhaust the compressed air exhausted from the first and second outlet ports according to an emergency stop signal, and capable of changing positions to reduce an exhaust speed of the compressed air in case that the door is not completely open or closed when an operation signal is generated after the emergency stop signal.

A control valve assembly for indirect pneumatic control and method for controlling a working fluid pressure, which enable precise, sensitive and speed-variable controlling. The assembly includes two valve units, a working fluid inlet, and a control fluid inlet. A working fluid channel connects the working fluid inlet through the two valve units to an outlet. A valve piston arranged within a valve cylinder of the valve units is movable between open and closed positions. A spring element biases the valve piston toward the closed position, and a control pressure chamber applies a control pressure counteracting the spring element's bias. When a control pressure is applied in the first chamber, the first valve piston is moved to the open position. Two opposite valve surfaces form a valve opening opened at varying widths when the valve piston is moved in the valve cylinder because of a changing control pressure, and the working pressure can be finely adjusted corresponding to the valve opening width depending on the control pressure.

A pressure supply device for prioritised volume flow splitting, in particular in mobile working machines, includes at least one adjusting pump (2) controllable by an LS signal as main pump, a constant-displacement pump (4) as an auxiliary pump, and two pressure balances. A system is supplied primarily, in particular in the form of steering hydraulics (PL), which outputs an LS signal. A system is supplied secondarily, which outputs a further LS signal, in particular in the form of working hydraulics (PA). A further system is supplied hydraulically, in particular in the form of brake hydraulics (PB). One pressure balance (DW1) is used to supply the system (PL) to be supplied primarily and/or the further hydraulic system (PB), the other pressure balance (DW2) is used to supply the system (PL) to be supplied primarily and/or the system (PA) to be supplied secondarily, The respective pressure balance (DW1, DW2) can be activated by an LS signal in such a way that the constant-displacement pump (4) is also used to supply the system (PA) to be supplied secondarily.

A hydraulic unit includes a hydraulic circuit fluidly connected to a hydraulic actuator, and a control device to control the hydraulic circuit. The hydraulic circuit includes a hydraulic oil tank, a hydraulic pump that supplies the hydraulic oil to the hydraulic actuator from the hydraulic oil tank, a discharge flow path fluidly connecting a discharge side of the hydraulic pump to the hydraulic actuator, a valve that blocks a flow of the hydraulic oil in the discharge flow path, and a pressure sensor that detects a pressure of the hydraulic oil the discharge flow path. In a pressure holding state, when a rotational frequency of the hydraulic pump exceeds a predetermined first determination rotational frequency or when a discharge flow rate of the hydraulic pump exceeds a predetermined first determination discharge flow rate, the control device determines that the hydraulic circuit is abnormal.

A hydraulic apparatus has a plurality of pump modules each of which is formed by a plurality of working chambers having a common high pressure manifold. A connecting circuit switchably connects pump modules to first and second hydraulic circuit portions to allocate capacity as first and second demands for hydraulic fluid vary. In an apparatus which may have two or more connecting circuit outputs, valves may be controlled or working chamber pumping cycles made inactive to facilitate the reallocation of a pump module from one output to another, and a control strategy addresses pump module allocation when the demands for hydraulic fluid exceed available capacity.

Problem to be solved: To provide a hydraulic circuit for the construction machine which enables to use the relief valve of low capacity in the work tool circuit. Solution: The hydraulic circuit 2 for a construction machine has: a hydraulic pump 4 of variable capacity, a work tool 6 operated by hydraulic oil delivered by the hydraulic pump 4, a work tool operating device 10 to output a signal for operating the work tool 6, a control valve 14 allowing the hydraulic pump 4 to supply the hydraulic oil to the work tool 6 based on the signal output from the work tool operating device 10, a tool's relief valve 44 to release the hydraulic oil flowing between the control valve 14 and the work tool 6, a pressure sensor 46 to detect a pressure of hydraulic oil flowing into the work tool 6, and a controller 48 to reduce a delivery rate from the hydraulic pump 4 when the pressure detected by the pressure sensor 46 exceeds a predetermined value.

A fluid supply system supplying multiple fluid consumers of a vehicle with fluid, the fluid supply system including: a first pump supplying a first fluid consumer, arranged in a first supply circulation of the vehicle, with fluid; a second pump supplying a second fluid consumer, arranged in a second supply circulation of the vehicle, with fluid; and a directional control valve adjustable between a first valve position and at least one other, second valve position and preferably includes an electromagnetic device for adjusting. The directional control valve allows the fluid to be delivered from the second pump into the first supply circulation in the first valve position and separates the first supply circulation from the second pump, or allows the fluid to be delivered from the second pump into the first supply circulation only to a restricted extent as compared to the first valve position, in the second valve position.

A hydraulic unit includes a hydraulic circuit fluidly connected to a hydraulic actuator, and a control device to control the hydraulic circuit. The hydraulic circuit includes a hydraulic oil tank, a hydraulic pump that supplies the hydraulic oil to the hydraulic actuator from the hydraulic oil tank, a discharge flow path fluidly connecting a discharge side of the hydraulic pump to the hydraulic actuator, a valve that blocks a flow of the hydraulic oil in the discharge flow path, and a pressure sensor that detects a pressure of the hydraulic oil the discharge flow path. In a pressure holding state, when a rotational frequency of the hydraulic pump exceeds a predetermined first determination rotational frequency or when a discharge flow rate of the hydraulic pump exceeds a predetermined first determination discharge flow rate, the control device determines that the hydraulic circuit is abnormal.