An object of the present invention is to prevent breakage of a unidirectional filter part for high-pressure oil. A hydraulic device 100 supplies oil to a high-pressure oil channel L1 and a low-pressure oil channel L2 from an oil tank 102 via a supply pump 104. The hydraulic device 100 includes an accumulator 106 capable of accumulating a hydraulic pressure of the oil supplied to the high-pressure oil channel from the supply pump; a filter part 120 disposed between the supply pump and a connection point N1 at which the high-pressure oil channel connects to the accumulator, along a direction in which the oil is supplied; and a check valve 110 capable of preventing a backflow of the oil to the filter part, and disposed between the filter part and the connection point.

When hydraulic fluid discharged from a hydraulic actuator is to be recovered for driving a different hydraulic actuator, the recovery frequency is increased to achieve further energy saving. To this end, a pressure increasing circuit 36 is provided in which a communication pressure increasing valve 12 is disposed in a communication passage 26 that connects a bottom side line 23 of and a rod side line 24 a boom cylinder 4. A recovery control valve 11 is controlled such that, when a first operation unit 5 is operated in a boom lowering direction (own weight falling direction of the boom) and a second operation unit 6 is operated simultaneously, only if the pressure at the bottom side of the boom cylinder 4 is higher than the pressure at the arm cylinder side that is a recovery destination of hydraulic fluid, the recovery control valve 11 is opened to recover the flow rate discharged from the bottom side of the boom cylinder 4 to the arm cylinder side.

A series hydraulic hybrid system for a vehicle may have: a hydraulic circuit with a first hydraulic displacement unit in fluid communication with a second hydraulic displacement unit, a hydraulic actuator, and a hydraulic accumulator assembly. The hydraulic accumulator assembly is selectively in fluid communication with the hydraulic circuit via at least one controllable circuit valve. The hydraulic accumulator assembly is selectively in fluid communication with the hydraulic actuator via at least one controllable actuator valve, such that the hydraulic accumulator assembly is configured to be selectively fluidly connected with and to be selectively fluidly disconnected from the hydraulic actuator via the at least one actuator valve independently of a control position of the at least one circuit valve. A method of operating the system is also described.

A hydraulic control device that reduces the loss of the power of a pump in combined operation of boom lowering and arm pushing. A controller performs single control of increasing capacity of a first pump in accordance with increase in an operation amount of a boom operation member, in a single operation of the boom lowering. On the other hand, the controller restricts the capacity of the first pump compared to capacity in the single control, during a restriction control period when the combined operation of boom lowering and arm pushing is detected, and the operation amount of the boom operation member is a prescribed operation amount or more.

A shuttle valve connects a second flowpath and a drain flowpath when the hydraulic pressure in a first flowpath is greater than the hydraulic pressure in the second flowpath. The shuttle valve connects the first flowpath and the drain flowpath when the hydraulic pressure in a second flowpath is greater than the hydraulic pressure in the first flowpath. The ratio between the pressure receiving area of a first pressure section and the pressure receiving area of a second pressure section is the same as the ratio between the pressure receiving area of a first chamber side and the pressure receiving area of a second chamber side of a cylinder rod.

Provided is a hydraulic shovel capable of moving a boom, an arm, and a bucket at respective adequate speeds even during complex operations thereof, without a significant pressure loss. This hydraulic shovel includes: a first pump (31) connected to a boom actuator (24) and a bucket actuator (28); a second pump (32) connected to an arm actuator (26) and the boom actuator (24); a third pump (33) connect to the arm actuator (26); a boom control valve (54) interposed between the first pump (31) and the boom actuator (24); an arm control valve (56) interposed between the second pump (32) and the arm actuator (26); a bucket control valve (58) interposed between the first pump (31) and the bucket actuator (28); a boom merging valve (55) for speed increase interposed between the second pump (32) and the boom actuator (24); and an arm merging valve (57) for speed increase interposed between the third pump (33) and the arm actuator (26).

A hydraulic drive system raises and lowers an object by supplying and discharging operating oil to and from two ports of an actuator and includes a control device, first to fifth electromagnetic proportional control valves, first and second hydraulic pumps, a first and second control valve, and a lock valve. When a fourth pilot pressure is output, the second control valve causes the operating oil to be discharged from a first port in order to lower the object. The lock valve prevents the operating oil from being discharged from the first port by closing a path between the first port and the second control valve, and when a fifth pilot pressure is output from the fifth electromagnetic proportional control valve per an operating device, discharges the operating oil from the first port by opening the path between the first port and the second control valve, to lower the object.

In a compressed air supply system for a first compressed air consumer circuit such as an air spring system of a vehicle, a first compressed air line leads to the first compressed air consumer circuit and a distribution line leads to further consumer circuits. A priority valve arrangement is disposed between the first compressed air line, wherein the first compressed air line comprises no safety valve. The first compressed air consumer circuit can therefore be filled at a higher priority, and achieve operational readiness quickly in air spring processes such as lifting or raising activities.

To provide a driving device capable of improving the operability of a plurality of single rod hydraulic cylinders. The present invention takes a construction provided with a closed circuit A in which first and third hydraulic pumps 12, 14 and a boom cylinder 1 are connected through selector valves 43a, 45a in a closed-circuit fashion, a plurality of open circuits E, F provided with second and fourth hydraulic pumps 13, 15 and selector valves 44a, 46a that switch the supply destinations of hydraulic oils flowing out from the second and fourth hydraulic pumps 13, 15, and a connection passage 301 connected to sides of the selector valves 44a, 46a from which sides hydraulic oil flows out, and connected to the closed circuit A.

A pump device includes a first pump that includes a first discharge portion and a second discharge portion, a first flow path that connects the first discharge portion and a first chamber of a cylinder, a second flow path that connects the second discharge portion and a second chamber of the cylinder, a second pump that includes a third discharge portion and a fourth discharge portion, a third flow path that connects the third discharge portion and the first chamber, a fourth flow path that connects the fourth discharge portion and the second chamber, a branch path that branches from the third flow path and reaches the tank, and an opening valve that opens the branch path, the opening valve being disposed in the branch path so as to open the branch path when a pressure in the second chamber is higher than a predetermined pressure.