A hydraulic system includes a hydraulic pump to be driven by a prime mover, a first hydraulic actuator, a second hydraulic actuator, a first connecting fluid tube connected to the first hydraulic actuator, a second coupling hydraulic tube connected to the first hydraulic actuator, and a first control valve having a first position and a second position. The hydraulic system includes a second control valve configured to control the second hydraulic actuator, a first fluid tube configured to supply a return fluid to the second control valve, a second fluid tube connected to the first fluid tube, a first communicating-connection tube to be connected to the second fluid tube when the first control valve is in the first position, and a second communicating-connection tube to be connected to the second fluid tube when the first control valve is in the second position.

A hydraulic system in a work machine includes a hydraulic pump to supply pilot hydraulic oil. A work hydraulic actuator is to move a work device of the work machine. A control valve is to control the work hydraulic actuator based on a pilot pressure of the pilot hydraulic oil. A target pilot pressure of the pilot hydraulic oil is input through the work operation device to control, according to the target pilot pressure, the pilot pressure supplied from the hydraulic pump to the control valve. A pilot oil path connects the work operation device and the control valve to supply the pilot pressure to the control valve. A drain oil path is divided from the pilot oil path. A pressure adjustment valve is provided in the drain oil path to adjust the pilot pressure to be less than the target pilot pressure when a condition is satisfied.

A hydraulic driving apparatus that drives a plurality of driving subjects and regenerates energy thereof. This hydraulic driving apparatus includes: a first pump motor; a second pump motor that is switchable between a state of moving a first driving subject by hydraulic oil discharged from the first pump motor and a state of being operated as a pump by means of energy of the first driving subject; a first pump motor line that couples the first and second pump motors with each other; a first accumulator connected to the first pump motor line; a regeneration subject hydraulic actuator that moves a second driving subject; a second accumulator that receives hydraulic oil from the regeneration subject hydraulic actuator; a second pump motor line that couples the second accumulator with the first pump motor; and a pressure release changeover valve that opens/closes the second pump motor line.

There is provided a hydraulic driving device for working machine having operability handling a change in burden weight in a front working device due to a loaded burden and the like when the working machine that accumulates energy in an accumulator and recovers and regenerates the energy performs an operation of lowering the front working device. A hydraulic driving device 5 includes a main pump 101, a boom cylinder 3, a tank 20, a flow rate control valve 6, an accumulator 300, a first differential pressure control valve 201, and a second differential pressure control valve 202. The first differential pressure control valve 201 is located between the boom cylinder 3 and the accumulator 300. The first differential pressure control valve 201 performs control on discharge oil from the boom cylinder 3 such that a differential pressure between before and after the flow rate control valve 6 becomes a target differential pressure. The second differential pressure control valve 202 is located between the accumulator 300 and the tank 20. The second differential pressure control valve 202 performs control on the discharge oil such that a differential pressure between an upstream pressure and a downstream pressure of the flow rate control valve 6 and the first differential pressure control valve 201 becomes the target differential pressure. The first and the second differential pressure control valves 201 and 202 are configured such that the target differential pressure increases according to an increase in pressure of the discharge oil.

A hydraulic apparatus for a hydraulic work vehicle capable of supplying pressure oil to any of a bucket cylinder, an arm cylinder, a boom cylinder, a swing cylinder, a blade cylinder, a turning hydraulic motor, a left traveling hydraulic motor, a right traveling hydraulic motor, and a PTO hydraulic motor by a first hydraulic pump, a second hydraulic pump, or a third hydraulic pump. The pressure oil can be branched off from a discharge oil passage of the third hydraulic pump and supplied through an external pipe to a downstream side of a load check valve disposed on an oil passage communicating with a pump port of a PTO control valve for switching supply of pressure oil from the second hydraulic pump to an external hydraulic work machine.

A hydraulic system in of a work machine includes a hydraulic pump to supply pilot hydraulic oil in a hydraulic oil reservoir. A travel pump is to drive a travel motor according to a pilot pressure of the pilot hydraulic oil. A target pilot pressure of the pilot hydraulic oil is input through a travel operation device to control, according to the target pilot pressure, the pilot pressure supplied from the hydraulic pump to the travel pump. A pilot oil path connects the travel operation device and the travel pump to supply the pilot pressure to the travel pump. A drain oil path is divided from the pilot oil path. A pressure adjustment valve is provided in the drain oil path to adjust the pilot pressure to be less than the target pilot pressure when a condition is satisfied.

A hydraulic system for moving an implement of a working machine includes a hydraulic cylinder with a cylinder and a piston which is adapted to move in the cylinder to thereby move the implement relative to a body structure of the working machine, and an actuator pump arranged to provide hydraulic fluid to the hydraulic cylinder, the hydraulic cylinder having a first port and a second port adapted to be in fluid communication with the actuator pump, the hydraulic cylinder and the actuator pump being arranged so that the hydraulic cylinder is directly controlled by the actuator pump so that the rate of movement of the piston of the hydraulic cylinder is purely pump controlled, the hydraulic system further including a hydraulic accumulator for suspension of the implement, which hydraulic accumulator is arranged to be selectively connectable to the first port, the hydraulic system further including a further pump in addition to the actuator pump, the hydraulic accumulator being arranged to be pressurised by the further pump.

A hydraulic system includes a hydraulic pump to be driven by a prime mover, a first hydraulic actuator, a second hydraulic actuator, a first connecting fluid tube connected to the first hydraulic actuator, a second coupling hydraulic tube connected to the first hydraulic actuator, and a first control valve having a first position and a second position. The hydraulic system includes a second control valve configured to control the second hydraulic actuator, a first fluid tube configured to supply a return fluid to the second control valve, a second fluid tube connected to the first fluid tube, a first communicating-connection tube to be connected to the second fluid tube when the first control valve is in the first position, and a second communicating-connection tube to be connected to the second fluid tube when the first control valve is in the second position.

The present invention relates to a hydraulic system comprising a first actuator and a first pump fluidly connected or connectable to the first actuator via a first circuit and adapted to drive the first actuator. The system further comprises a second pump, a second actuator and a third pump, the third pump being fluidly connected or connectable to the second actuator via a second circuit and adapted to drive the second actuator. To assist the first and third pumps in moving the first and second actuators, the second pump is connectable to the first and second actuators via first and second control valves.

A hydraulic system includes: an arm hydraulic cylinder; a first hydraulic pump and a second hydraulic pump; an arm first direction switching valve; an arm second direction switching valve; and a controller that controls an operation of the arm second direction switching valve when the arm hydraulic cylinder is extended and operated. Further, the arm first direction switching valve incorporates an arm regeneration passage capable of supplying oil when the arm hydraulic cylinder is extended and operated, and the controller monitors a pressure state of the arm hydraulic cylinder, and when determining that oil flow through the arm regeneration passage is possible, the controller blocks oil flow between the arm hydraulic cylinder and the arm second direction switching valve, and otherwise, the controller operates the arm second direction switching valve so that oil can be supplied from the second hydraulic pump to the bottom chamber.