Abstract: In the oil pressure system, a control unit sets a flow passage changeover valve to be in a merging state, and sets a relief pressure to a low relief pressure via a relief pressure changeover unit in the case that the rotational speed of the engine is lower than a predetermined threshold level. Also, the control unit sets the flow passage changeover valve to be in a branching state, and sets the relief pressure to a high relief pressure via the relief pressure changeover unit in the case that the rotational speed of the engine is the predetermined threshold level or higher.

Abstract: A fixed/variable hybrid system has modified constant flow open center hydraulic valves (“fixed/variable valves”), including an open center core, spools, a power core, and a tank galley. A small fixed displacement pump provides fluid at a constant rate to the open center core. A variable displacement piston pump provides fluid directly to the power core as needed. Activation of spools partially restricts the open center core causing an increase in fluid pressure that is communicated to the variable displacement piston pump's load sense signal port, causing the pump to increase fluid flow and pressure to the power core. Activated spools direct pressurized fluid from the power core to the applications through selected hydraulic ports. Activated spools also direct fluid flow from selected hydraulic ports via the tank galley to a hydraulic tank. Pumping the majority of fluid only on an as-needed basis results in significant efficiencies.

Abstract: A hydraulic traveling vehicle includes a right-travel motor a left-travel motor, a hydraulic pump, a merging/diverging valve and a travel switching unit. The merging/diverging valve is configured to switch between merging and separating a first hydraulic circuit and a second hydraulic circuit. The travel switching unit is configured to switch between a state where sharp turning takes place as a result of one of the right-travel motor and the left-travel motor being stopped and the other being driven, with the merging/diverging valve being in a merging state, and a state where gentle turning takes place as a result of the right-travel motor and the left-travel motor being driven at different rotational speeds, with the merging/diverging valve being in a diverging state.

Abstract: A hydraulic system of a work machine with a hydraulically controlled implement includes: an operating oil flow passage for flowing operating oil from a main pump; a boost flow oil passage for supplying operating oil to the operating oil flow passage; a connection unit for connecting the implement which is provided downstream of the confluence on the operating oil flow passage; a controller for controlling the high-flow valve; and a high-flow switch which is connected to the controller and is configured to effect or cancel a command of the amount increase on a high-flow valve. Annunciation is made when the connection unit is connected to a high-flow actuator for the implement requiring an amount increase of the operating oil, and the amount increase is effected by the high-flow valve in accordance with an operation of the high-flow switch.

Abstract: A hydraulic circuit including a hydraulic swing motor having a first port and a second port. A first motor conduit connected to the first port of the hydraulic swing motor, and a second motor conduit connected to the second port of the hydraulic swing motor. The hydraulic circuit further includes a pump to selectively supply a flow of pressurized hydraulic fluid to the hydraulic swing motor through the first and the second motor conduits. A controller electrically connected to the pump adjusts a torque output of the pump based on a swing speed of the hydraulic swing motor.

Abstract: A hydraulic flow sharing system for excavating and pipe laying work is provided, which can prevent the abrupt change of a traveling speed during traveling through compulsory sharing of the flow rate applied to a working device and a traveling apparatus when a combined operation, in which the traveling apparatus and the working device such as a boom are simultaneously driven, is performed.

Abstract: A hydraulic system with an improved complex operation is provided, which can prevent the generation of shock in a boom by delaying pressure supply during start and end of pilot signal pressure supplied to a spool for controlling an option device when a boom ascending operation and an operation of an option device are simultaneously performed or when such a simultaneous operation of the boom and the option device switches over to an independent operation of the boom.

Abstract: The invention relates to a power train for a hybrid vehicle, comprising two hydraulic machines (20, 22) including variable displacement, both of which are connected to a hydraulic pressure accumulator (24) which stores energy, a first hydraulic machine (20) being permanently connected to an internai combustion traction engine (2), and a second hydraulic machine (22) being connected, also permanently, to drive wheels (8) of the vehicle, characterised in that the two hydraulic machines (20, 22) are also interconnected by a linking means (10) that can be engaged or disengaged.

Abstract: A hydraulic assembly for driving and controlling small hydraulic units, such as hydraulic cylinders of a brake and/or clutch of a forestry winch, is disclosed. The hydraulic assembly includes a means for establishing and also maintaining a pre-determined pressure of a hydraulic media. The hydraulic assembly is characterized by as low as possible hydraulic loss. Also, a quantity of hydraulic media required for a regular operation and maintaining the pressure within the hydraulic assembly is as low as possible.

Abstract: A hydraulic two-circuit system (2, 4) for activating consumers (A1, B1; A2, B2; A3, B3) of a mobile unit, for example a track-laying unit, and an interconnecting valve arrangement (38), which is suitable for a two-circuit system (2, 4) of this type and via which the two circuits (2, 4) can be interconnected so as to add them together, are disclosed. According to the invention, the interconnecting valve arrangement has an interconnecting valve with two pressure connections (P1, P2), two LS input connections (LS1, LS2) and two LS output connections, wherein a valve body of the interconnecting valve is designed with four control surfaces, of which two control surfaces which act in one direction are acted upon by the highest load pressure (LS1) in the first circuit and by the pumping pressure (P2) in the second circuit, and the control surfaces acting in the other direction are acted upon by the highest load pressure (LS2) in the second circuit and by the pumping pressure (P1) in the first circuit.

Abstract: A hydraulic system for an earth-moving vehicle may include first and second hydraulic cylinders, first and second hydraulic pumps and control valves including a combiner valve to modulate hydraulic fluid and pressure from the first and second hydraulic pumps to the first and second hydraulic cylinders as appropriate for the task being performed. If the task is digging, the first and second cylinders may be associated with tilting and lifting, respectively, and the control valves may be oriented so as to make each pump dedicated to one of the cylinders, and if demand is not being met, to then diminish power to the drivetrain to allow the tilting and lifting to be performed. The combiner valve may or may not be open during this time. If the task is not digging, the combiner valve can be opened to allow for cross-flow between the pumps and the cylinders.

Abstract: The invention relates to a shift cylinder including a cylinder element having a working space, a first and a second piston received in the working space displaceably relatively to it, by which the working space is divided in a first working chamber capable of being charged with a working medium through a first port of the shift cylinder, a second working chamber capable of being charged with a working medium through a second port of the shift cylinder and a third working chamber disposed between the first and the second working chamber, including at least one spring member capable of being supported on the first piston on the one hand and on the second piston on the other hand.

Abstract: A valve assembly has a flow summation node coupled to a displacement control port of the first pump. Each valve in the assembly has a variable metering orifice controlling flow from an inlet to a hydraulic actuator and has a variable source orifice conveying fluid from a supply conduit to a flow summation node. The source orifice enlarges as the metering orifice shrinks. Each valve includes a variable bypass orifice and the bypass orifices of all the control valves are connected in series forming a bypass passage between a bypass node and a tank. The bypass node is coupled to the flow summation node and receives fluid from a second pump. At each valve, a source check valve conveys fluid from the supply conduit to the inlet and a bypass supply check valve conveys fluid from the bypass passage to the inlet.

Abstract: The invention relates to a hydraulic system having a pump and at least two working machines, in particular two working machines embodied as hydraulic cylinders. Each working machine is connected by pressure lines to the associated drive machine via two connectors that serve as an inflow or return. At least one valve is associated with each working machine, for adjusting the operating state of the working machine. In the context of an elevating work platform the connector which serves as an outflow in a working state of that working machine that is brought about or at least assisted by gravity is connected via a bypass, circumventing the drive machine, directly to the connector, serving as inflow in the context of a desired operating state, of another working machine, so that the hydraulic fluid flowing out from the first working machine flows for actuation of the other working machine.

Abstract: A fixed/variable hybrid system has modified constant flow open center hydraulic valves (“fixed/variable valves”), including an open center core, spools, a power core, and a tank galley. A small fixed displacement pump provides fluid at a constant rate to the open center core. A variable displacement piston pump provides fluid directly to the power core as needed. Activation of spools partially restricts the open center core causing an increase in fluid pressure that is communicated to the variable displacement piston pump's load sense signal port, causing the pump to increase fluid flow and pressure to the power core. Activated spools direct pressurized fluid from the power core to the applications through selected hydraulic ports. Activated spools also direct fluid flow from selected hydraulic ports via the tank galley to a hydraulic tank. Pumping the majority of fluid only on an as-needed basis results in significant efficiencies.

Abstract: An excavator drive system wherein one of a pair of propulsion motors shares one of a pair of inverter power sources with another of a pair of motors dedicated to crowd and hoist motions. A pair of non-volatile bi-state switches, triggered under control of a controller, allow sharing of inverters between hoist and propel 1 motors. Another pair of switches allows inverter sharing between propel 2 and crowd motors. Each,pair of switches enables change over and power transfer from one of the paired motors to the other motor. The bi-state switches enable quicker transfer of power between motors than transfer switches employing external motor-powered mechanical transfer linkages. Bi-state transfer switches also maintain transfer coupling status in the event of power failure to the switch actuators, allowing an excavator operator to continue the drive function in operation prior to the switch power failure.

Abstract: A traveling device for crawler type heavy equipment is provided, which can improve manipulability by preventing an abrupt decrease/increase of a traveling speed of the equipment when a combined operation, in which a left/right traveling device and a working device are simultaneously driven, is performed. The traveling device for crawler type heavy equipment includes a variable orifice shifted to intercept the supply of the hydraulic fluid toward the traveling device in response to the signal pressure in the combined working mode if a load pressure of the working device is relatively higher than that of the traveling device.

Abstract: A hydraulic circuit for preventing a change of stroke of a boom cylinder or an arm cylinder during transportation. The hydraulic circuit includes first and second hydraulic pumps, a boom cylinder, an arm cylinder, a boom confluence logic valve, a first port connected with a chamber of the boom cylinder in a housing in which a spool for the boom cylinder is shiftably installed, a second port connected with a hydraulic tank in the housing, and a first orifice formed between the housing and a land part of the spool for the boom cylinder located between the first port and the second port. During transportation, a small amount of hydraulic fluid fed from the second hydraulic pump to the large chamber of the boom cylinder drains to the hydraulic tank through the first orifice to prevent a change of stroke of the boom cylinder.

Abstract: A method of combining outputs of a plurality of fluid pumps includes receiving an input signal from an input device. The input signal is adapted to control a function of a work vehicle. An actuation signal is sent to a first direction control device of a first actuator assembly. The first actuator assembly is in selective fluid communication with a first pump assembly. A position of a second direction control valve of a second actuator assembly is received. The second actuator assembly is in selective fluid communication with a second pump assembly. A selector valve that is in fluid communication with a cavity of a poppet valve assembly is actuated so that the second pump assembly is in fluid communication with the first actuator assembly when the second direction control valve is in a neutral position.

Abstract: A hydraulic system for use in a work vehicle with a powered implement is disclosed. In one embodiment, the hydraulic system may include a first hydraulic circuit including a first hydraulic pump with a low pressure and low flow output, switch and valve; a second hydraulic circuit including a second hydraulic pump with a high flow and high pressure output, switch and valve; and a third hydraulic circuit including a third hydraulic pump with a high flow and high pressure output, switch and valve. The first, second, and third circuits each include an output selectively combinable with each other by an operator control which controls the switch and valve configurations. The hydraulic system has several configurations.

Abstract: Systems and methods for efficiently operating a hydraulically actuated device/system are described herein. For example, systems and methods for efficiently operating a gas compression and expansion energy storage system are disclosed herein. Systems and methods are provided for controlling and operating the hydraulic actuators used within a hydraulically actuated device/system, such as, for example, a gas compression and/or expansion energy system, within a desired efficiency range of the hydraulic pump(s)/motor(s) used to supply or receive pressurized hydraulic fluid to or from the hydraulic actuators. In such a system, a variety of different operating regimes can be used depending on the desired output gas pressure and the desired stored pressure of the compressed gas. Hydraulic cylinders used to drive working pistons within the system can be selectively actuated to achieve varying force outputs to incrementally increase the gas pressure within the system for a given cycle.

Abstract: The operability when performing a combined arm-crowd and bucket operation can be improved. A hydraulic drive device for a hydraulic excavator includes: a bucket directional control valve and a second arm directional control valve, which are connected in parallel tandem with a first hydraulic pump; a first arm directional control valve that is connected to a second hydraulic pump; and a flow rate restriction device that restricts the flow rate of pressure oil supplied to the second arm directional control valve, during crowd operation of a bucket. This flow rate restriction device includes a variable throttle whose opening is controlled so as to become smaller as a bucket operating device is operated to the crowd side, the variable throttle being provided in a bypass path connecting to the supply port of the second arm directional control valve.

Abstract: A hydraulic control device of construction machinery is disclosed. The device includes a main merging/diverging valve, operating levers operated to actuate plural actuators, an operating condition judging section, and a pattern collating section. When a load pressure of each actuator is high, a discharge pressure of each discharge oil path is also high, and when a total of the discharge pressures exceeds a predetermined set pressure, the main merging/diverging valve is switched to a diverging position, and when the total of the discharge pressures drops to below the set pressure, the main merging/diverging valve is switched to the merging position.

Abstract: A hydraulic circuit structure of a work vehicle capable of solving a problem in a conventional structure wherein, in a machine attitude control in back hoe operation, pressure oil is preferentially fed to light-loaded machines and some work machines are slowly moved or stopped and, accordingly, the attitudes of the machines cannot be rapidly controlled and work performance is affected. To solve this problem, the hydraulic circuit of the work vehicle comprises two valve groups for a loader and a back hoe having circuits to supply the pressure oil from one hydraulic pump to a valve group for back hoe control through a valve group for loader control and the pressure oil from the other hydraulic pump directly to the valve group for back hoe control. The pressure oil is independently supplied from the hydraulic pumps to valve sections for controlling right and left stabilizer cylinders installed in the valve group for back hoe control.

Abstract: An arrangement for delivering hydraulic fluid to at least one hydraulic actuator of a work vehicle for moving a work implement and/or steering the vehicle includes at least two pumps which are adapted to be operatively driven by a power source and adapted to operatively drive said at least one hydraulic actuator via hydraulic fluid. A first pump is operated with a phase shift relative to a second pump.

Abstract: A hydraulic circuit for construction equipment is disclosed, which can prevent an abrupt rotation of a swing device when a switching valve for the swing device is shifted in a state that switching valves for a traveling device and a working device have been shifted.

Abstract: A system is provided for controllably absorbing energy associated with a machine. The system may include a power source configured to provide power to a hydraulic pump, wherein the hydraulic pump is configured to provide a flow of fluid to a hydraulic dissipation circuit and to one or more implement system hydraulic cylinders, and wherein the hydraulic dissipation circuit is configured to generate a load associated with the hydraulic pump. The system may also include at least one valve configured to provide the flow of fluid to the hydraulic dissipation circuit in response to one or more control signals and a controller configured to receive an input signal from an operator actuated device, and generate the one or more control signals based on the input signal.

Abstract: The dynamic fluid device has a first pumping arrangement and second pumping arrangement arranged in parallel with each other to pump a pressurized fluid to user devices; at least a distributor member interposed amongst the first pumping arrangement, second pumping arrangement and the user devices and connected to them with connection arrangements, the at least a distributor member being arranged to connect singly and/or jointly and/or according to predetermined sequences, the first pumping arrangement and/or the second pumping arrangement to the user devices.

Abstract: The present invention overcomes drawbacks whereby the supply of pressure oil to a hydraulic cylinder for operating a ground working device is temporarily cut, and operation of the ground working device is temporarily stopped when a control valve for the travel device is operated while a control valve for the ground working device is being operated. When control valves (V4, V5) for the travel devices are operated during operation of control valves (V6, V7, V8) for the ground working device, and a first flow channel switching valve (V12) is switched from an operating position (31) to a travel position (34), a second flow channel switching valve (V13) is switched from a non-feeding position (39) to a feeding position (40) before or at the same time as the first flow channel switching valve (V12).

Abstract: A configurable hydraulic system facilitates a variety of oilfield cementing and other oilfield or related applications. The system employs a plurality of prime movers to drive a plurality of loads. The plurality of prime movers and loads are coupled with a configurable hydraulic system that maintains a separate, sealed hydraulic system associated with each prime mover. The configurable hydraulic system also enables the load configuration driven by each prime mover to be changed without losing the benefit of a separate, sealed hydraulic system associated with each specific prime mover.

Abstract: A method for operating a hydraulic system having at least one supply device, in particular a hydraulic pump (39)), which supplies different hydraulic consumers is characterized in that a synchronizing device (33, 35) ensures that, if at least one hydraulic consumer is not supplied sufficiently, the deficit in volumetric flow for said consumer is compensated for in such a way that all the consumers compensate for the deficit equally.

Abstract: A hydraulic two-circuit system (2, 4) for activating consumers (A1, B1; A2, B2; A3, B3) of a mobile unit, for example a track-laying unit, and an interconnecting valve arrangement (38), which is suitable for a two-circuit system (2, 4) of this type and via which the two circuits (2, 4) can be interconnected so as to add them together, are disclosed. According to the invention, the interconnecting valve arrangement has an interconnecting valve with two pressure connections (P1, P2), two LS input connections (LS1, LS2) and two LS output connections, wherein a valve body of the interconnecting valve is designed with four control surfaces, of which two control surfaces which act in one direction are acted upon by the highest load pressure (LS1) in the first circuit and by the pumping pressure (P2) in the second circuit, and the control surfaces acting in the other direction are acted upon by the highest load pressure (LS2) in the second circuit and by the pumping pressure (P1) in the first circuit.

Abstract: A hydraulic circuit of a hybrid type industrial vehicle drivable by an engine and an electric motor is disclosed. A generator motor is driven by the engine and generates electricity. A cargo handling hydraulic pump is actuated in conjunction with an operation of the generator motor and supplies hydraulic oil to a cargo handling circuit. Electricity generated by the generator motor is stored in a battery and drives a steering electric motor. A steering hydraulic pump is actuated in conjunction with an operation of the steering electric motor and supplies hydraulic oil to a steering circuit. A bypass passage connects the cargo handling circuit and the steering circuit to each other, and supplies the hydraulic oil of the cargo handling circuit to the steering circuit. A switching valve is located in the bypass passage.

Abstract: A straight traveling hydraulic circuit is provided. In case of performing a combined operation in which a fine operation of a working device and a fine traveling of a traveling device are simultaneously required, the straight traveling hydraulic circuit can allow the working device and the traveling device to operate independently, and thus prevent a declination or sudden traveling of the equipment. In case of performing the combined operation by simultaneously operating the traveling device and the working device, first and second center bypass shifting valves installed on the lowermost stream side of first and second center bypass passages are shifted by a pilot signal pressure that shifts a straight traveling valve installed on an upper stream side of the second center bypass passage, so that the degree of opening of the first and second center bypass passages is reduced to operate the working device and the traveling device independently.

Abstract: A work machine enabling a hybrid drive system to be directly driven by energy contained in a return fluid discharged from a hydraulic actuator. The work machine includes a hydraulic actuator control circuit and a swing control circuit. The hydraulic actuator control circuit serves to control hydraulic fluid supplied from pumps of a hybrid drive system to travel motors and work actuators. The swing control circuit serves to control a swing motor generator, which functions as an electric motor and, during braking of rotating motion of the upper structure, functions as a generator. The hydraulic actuator control circuit includes an energy recovery motor provided in a return passage, though which return fluid recovered from a work actuator flows. The energy recovery motor is adapted to be driven by return fluid and thereby drive a motor generator of the hybrid drive system.

Abstract: A hydraulic control device for a working machine includes control valves; hydraulic actuators controlled by corresponding control valves and divided into groups; unified bleed-off valves disposed on discharge lines of first and second hydraulic pumps; central bypass paths provided in the control valves, the central bypass paths of each group being connected in tandem so as to form a central bypass line; and bypass-cutting valves disposed on the central bypass lines, the bypass-cutting valves being automatically switched so as to open the central bypass lines when the unified bleed-off valves are not operated.

Abstract: A straight traveling hydraulic circuit is disclosed, which, in the case of performing a combined operation in which working and traveling devices are simultaneously driven, can prevent a declination of equipment due to an overload of the working devices. A straight traveling valve is shifted to supply the hydraulic fluid from the first hydraulic pump to the left and right traveling motors and to supply the hydraulic fluid from the second hydraulic pump to the first and second working devices. A control valve connects inlet and outlet parts of the straight traveling valve, and is shifted, when the combined operation is performed, to intercept a supply of the hydraulic fluid from the second hydraulic pump to the traveling motor.

Abstract: A pilot pressure control valve V17 is provided that is switchable between an operation position 56 where pilot pressure is supplied to a first channel switching valve V12 and a non-operation position 57 where pilot pressure is not supplied to the first channel switching valve V12; this pilot pressure control valve V17 is switched to the non-operation position 57 during a state of non-travel and is switched to the operation position 56 with a pilot pressure established in a travel detection circuit 54, and in the operation position 56, supplies a pilot source pressure to the first channel switching valve V12 from a fourth pump P4 on the upstream side of a pressurized oil introduction orifice 53.

Abstract: A boom control circuit for controlling hydraulic fluid fed to a boom cylinder is provided separately and independently from a travel/stick/bucket control circuit, which serves to control hydraulic fluid fed to travel motors, a stick cylinder, and a bucket cylinder. The boom control circuit includes a boom pump, an energy recovery motor disposed in a return passage through which return fluid from the boom cylinder 8bmc passes, and a boom motor generator connected to the energy recovery motor. The aforementioned boom pump is connected through a clutch to the boom motor generator. The invention is capable of providing a work machine of which a boom control circuit is adapted to function independently so that the flow rate required by the boom control circuit can be easily ensured.

Abstract: A hydraulic control system for a machine is disclosed. The hydraulic control system may have a first fluid actuator, a first pump configured to produce a first stream of pressurized fluid, a second fluid actuator, and a second pump configured to produce a second stream of pressurized fluid. The hydraulic control system may further have a combiner valve, and a controller. The controller may be configured to receive an operator input indicative of a desired velocity for the first fluid actuator, determine a flow rate for the first fluid actuator corresponding to the desired velocity, and determine a flow capacity of the first pump. The controller may also be configured to move the combiner valve to combine the second stream of pressurized fluid with the first stream of pressurized fluid when the determined flow rate for the first fluid actuator is greater than the determined flow capacity of the first pump.

Abstract: An arm direction changeover valve (11) is provided in an arm block (20). A first pilot check valve (18) is provided in a first block (21). A second pilot check valve (19) is provided in a second block (22). The three blocks, i.e., the arm block (20), the first block (21), and the second block (22) are arranged side by side. The first block (21) and the second block (22) are arranged to be contiguous to each other. Accordingly, an increase in size can be prevented even if a float mechanism and a multi-direction changeover valve are formed integrally with each other.

Abstract: An apparatus for increasing an operation speed of a boom on excavators is disclosed, which enables an unskilled operator to conveniently manipulate a working device by decreasing a rotation speed and increasing a lifting speed relatively when the excavator performs combined operation of boom lift and swing drive to improve its working efficiency. The apparatus includes first and second hydraulic pumps, a first actuator, a pair of second actuators, first to third control valves, a block valve installed in a flow path between the selected second actuator and the second control valve, supplying the hydraulic fluid from a second hydraulic pump to the selected actuator only when the second actuators are driven to be switched according to a control signal of boom lift at combined operation in which the first and second actuators are simultaneously driven, to replenish the first actuator with the hydraulic fluid to be supplied to the second actuator.

Abstract: A hydraulic pressure control device of a construction machine enabling an increase in operability and working efficiency by suppressing a fluctuation in flow rates occurring before and after the switching of a merging-separating valve, in energy efficiency by accurately determining the switching timing of the merging-separating valve to suppress the pressure energy loss of a pressure compensating valve, and working efficiency in the compound motion of plural hydraulic actuators. When a controller determines that necessary flow rates of first and second hydraulic actuators are less than maximum discharge flow rate of each of first and second variable displacement hydraulic pumps when the first merging-separating valve is in a merging position, the switching of the first merging-separating valve is controlled so that firstly the first merging-separating valve is switched to a separating position and, after the switching is completed, the second merging-separating valve is switched.

Abstract: A hydraulic system comprising: a first pump, in fluid communication with a first valve; a second pump, in fluid communication with a second valve; an auxiliary passage, in fluid communication with the first valve and the second valve; and a supplemental apparatus, in fluid communication via a supplemental passage with the second valve and the auxiliary passage, wherein the supplemental apparatus comprises a relief valve.

Abstract: A hydraulic circuit for heavy equipment is provided, which can prevent signal pressure exceeding a predetermined pressure from being formed in a pilot signal path provided in a switching valve to sense whether the switching valve has been shifted in a hydraulic system that minimizes the discharge flow rate of a hydraulic pump when a working device such as a boom is not driven.

Abstract: A hydraulic drive system comprises directional flow control valves (10a-f) for selectively supplying a hydraulic fluid from a first hydraulic pump (1a, 1b), inflow control valves (201-203) disposed respectively in branch lines (150A-C) branched from a supply line (100) for supplying a hydraulic fluid delivered from a second hydraulic pump (3a, 3b) to rod pushing-side chambers (5aA, 5bA, 6A, 7A) of hydraulic cylinders, a bypass flow control valve (204) disposed in a line (104) connecting the supply line (100) and a reservoir (2), and a controller (31) for computing control variables corresponding to operation command signals from control levers (32, 33) and controlling the inflow control valves (201-203) and the bypass flow control valve (204) in accordance with the computed control variables. Thus, the number of flow control valves and the length of piping required for their connection can be reduced, and a total pressure loss can be further reduced.

Abstract: A hydraulic traveling vehicle includes a right-travel motor a left-travel motor, a hydraulic pump, a merging/diverging valve and a travel switching unit. The merging/diverging valve is configured to switch between merging and separating a first hydraulic circuit and a second hydraulic circuit. The travel switching unit is configured to switch between a state where sharp turning takes place as a result of one of the right-travel motor and the left-travel motor being stopped and the other being driven, with the merging/diverging valve being in a merging state, and a state where gentle turning takes place as a result of the right-travel motor and the left-travel motor being driven at different rotational speeds, with the merging/diverging valve being in a diverging state.

Abstract: A hydraulic system for use in a work vehicle with a powered implement is disclosed. In one embodiment, the hydraulic system may include a first hydraulic circuit including a first hydraulic pump with a low pressure and low flow output, switch and valve; a second hydraulic circuit including a second hydraulic pump with a high flow and high pressure output, switch and valve; and a third hydraulic circuit including a third hydraulic pump with a high flow and high pressure output, switch and valve. The first, second, and third circuits each include an output selectively combinable with each other by an operator control which controls the switch and valve configurations. The hydraulic system has several configurations.

Abstract: A hydraulic control device of construction machinery having a main merging/diverging valve interposed in a connecting oil path connecting discharge oil paths of first and second hydraulic pumps in a merging position, operating levers for corresponding works operated to actuate plural actuators, an operating condition judging section judging a lever operating condition of each operation lever, a pattern collating section selecting an operating pattern matching an actual operation pattern from set and stored various operation patterns corresponding the operating conditions in a controller. When a load pressure of each actuator is high, a discharge pressure of each discharge oil path is also high, and when a total of the discharge pressures exceeds a predetermined set pressure, the main merging/diverging valve is switched to a diverging position, and when the total of the discharge pressures drops to below the set pressure, the main merging/diverging valve is switched to the merging position.

Abstract: A first group is supplied with hydraulic power from a first hydraulic pump. In the first group, an arm control valve is disposed at the most downstream position. A throttle is provided at the entrance of the arm control valve. Thus, a circuit is configured to give priority to boom raising or bucket excavation. During a combined operation, according to the operation amount of boom pulling or bucket excavation, a controller decreases the upper limit of the discharge amount of the first hydraulic pump determined by the operation amount of arm pulling and increases the recycling rate of oil to the expansion side of an arm cylinder.