Abstract: A hydraulic system for a working machine, includes an operation member, an operation valve to change an output pressure of an operation fluid in accordance with operation of the operation member, a hydraulic device to be activated by the operation fluid outputted from the operation valve, a first fluid tube coupling the operation valve to the hydraulic device, and a bleed circuit connected to the first fluid tube and configured to output the operation fluid in the first fluid tube. The first fluid tube includes a first section fluid tube arranged in a section between the operation valve and a coupling portion coupling the first fluid tube to the bleed circuit, and a second section fluid tube arranged in a section between the coupling portion and the hydraulic device, the second section fluid tube having an inner diameter different from an inner diameter of the first section fluid tube.

Abstract: A hydraulic device includes a braking device to brake a traveling device and release braking of the traveling device, a traveling pump to drive the traveling device with pressure of operation fluid, a brake-operation valve to control operation fluid flowing to the brake device, a traveling operation valve to control operation fluid flowing to the traveling pump, a first discharge fluid tube to discharge operation fluid flowing through the brake-operation valve, the first discharge fluid tube being connected to the brake operation valve, and a second discharge fluid tube to discharge operation fluid flowing through the traveling operation valve, the second discharge fluid tube being connected to the traveling operation valve. The traveling operation valve has a set pressure that is set to be higher than a brake set pressure set by the brake operation valve.

Abstract: A flowmeter test system that tests a test target flowmeter by flowing fluid through the test target flowmeter and measuring the fluid having flowed through the test target flowmeter by a measurement part different from the test target flowmeter is disclosed. The flowmeter test system includes, a storage part to store the fluid, a distribution flow path to distribute the fluid between the storage part and the test target flowmeter, a measurement part introduction path to be connected to the distribution flow path and introduce the fluid into the measurement part, and a flow path switching part to switch between the distribution flow path and the measurement part introduction path. A pressure loss in a flow path from the flow path switching part to the storage part and a pressure loss in a flow path from the flow path switching part to the measurement part are same.

Abstract: A hydraulic system for a work machine includes a first control cylinder to move a boom and a second control cylinder to move a bucket. A body of the first control cylinder has a first fluid chamber and a second fluid chamber. A first control valve is connected to the first fluid chamber via a first fluid path and connected to the second fluid chamber via a second fluid path to control the first hydraulic cylinder. A bucket positioning valve is connected to the second fluid path and a third fluid path to control a second hydraulic cylinder so as to rotate the bucket. A discharge fluid path is connected to the second fluid path between the bucket positioning valve and the first control valve. A discharge control valve is provided in the discharge fluid path to be opened and closed.

Abstract: A hydraulic system for a work machine includes a first control valve to control a first hydraulic actuator, a second control valve to control a second hydraulic actuator, a first fluid tube connecting the first hydraulic actuator to the first control valve, and a second fluid tube connecting the second hydraulic actuator to the second control valve. A level control valve apparatus is connected to the first fluid tube and the second fluid tube. The level control valve apparatus is configured to control a leveling operation for the second hydraulic actuator. An accumulator apparatus is connected to the first hydraulic actuator. The accumulator apparatus communicates with the first fluid tube between the level control valve apparatus and the first control valve. Circuitry is configured to control the level control valve apparatus to stop the leveling operation when the accumulator apparatus is in operation.

Abstract: A hydraulic system for a working machine, includes a hydraulic device to change a flow rate of an operation fluid. The hydraulic device includes a first hydraulic receiver to which the operation fluid is applied, a second hydraulic receiver to which the operation fluid is applied, and a movable portion to be moved by the operation fluid applied to any one of the first hydraulic receiver and the second hydraulic portion. A hydraulic system further includes a differential pressure regulator to supply the operation fluid to the first hydraulic receiver and the second hydraulic receiver, the differential pressure regulator being configured to regulate a differential pressure between a first pressure that is a pressure of the operation fluid applied to the first hydraulic receiver and a second pressure that is a pressure of the operation fluid applied to the second hydraulic receiver.

Abstract: A flowmeter test system that tests a test target flowmeter by flowing fluid through the test target flowmeter and measuring the fluid having flowed through the test target flowmeter by a measurement part different from the test target flowmeter is disclosed. The flowmeter test system includes, a storage part adapted to store the fluid, a distribution flow path adapted to distribute the fluid between the storage part and the test target flowmeter, a measurement part introduction path adapted to be connected to the distribution flow path and introduce the fluid into the measurement part, and a flow path switching part adapted to switch between the distribution flow path and the measurement part introduction path. A pressure loss in a flow path from the flow path switching part to the storage part and a pressure loss in a flow path from the flow path switching part to the measurement part are same.

Abstract: A hydraulic system for a work machine includes a hydraulic bump to output an operation fluid, a hydraulic switch valve to be switched among switching positions in accordance with a pressure of the operation fluid, a proportional valve to change the pressure of the operation fluid applied to the hydraulic switch valve, a travel hydraulic device to change a thrust power in accordance with the switching positions of the hydraulic switch valve. And, the hydraulic system includes a controller to control the proportional valve in accordance with a state of the travel hydraulic device.

Abstract: A hydraulic system for a work machine includes a first control valve to control a first hydraulic actuator, a second control valve to control a second hydraulic actuator, a first fluid tube connecting the first hydraulic actuator to the first control valve, and a second fluid tube connecting the second hydraulic actuator to the second control valve. A level control valve apparatus is connected to the first fluid tube and the second fluid tube. The level control valve apparatus is configured to control a leveling operation for the second hydraulic actuator. An accumulator apparatus is connected to the first hydraulic actuator. The accumulator apparatus communicates with the first fluid tube between the level control valve apparatus and the first control valve. Circuitry is configured to control the level control valve apparatus to stop the leveling operation when the accumulator apparatus is in operation.