Abstract: A Hydraulic valve device includes a first engine port and a second engine port to a double acting hydraulic motor, and a pump, a hand valve, which is arranged such that it connects the engine ports to the tank and the pump, and which hand valve has two open positions, wherein the pump in the first open position via a line is connected to the first engine port and the tank via a line is connected to the second engine port, and wherein the pump in the second open position via the line is connected to the second engine port and the tank via the line is connected to the first engine port, and a first nonreturn valve, arranged between the pump and the second engine port and opens towards the second engine port.

Abstract: System for controlling the motion of an actuator of a hydraulic system that may be embodied as a circuit or device that, interposed between a pump and the actuator, controls the motion of the actuator, causing the actuator to follow the movement of the pump. The present invention relates both to a system and a device providing such result just on the basis of the measures of the fluid circulating within the hydraulic circuit or device. The system according to the present invention is suited both with opposing loads and dragging loads.

Abstract: A pump control apparatus for a hydraulic work machine includes: a rotation speed setting device that sets a target rotation speed for an engine; a rotation speed control device that controls an engine rotation speed so as to adjust the engine rotation speed to the target rotation speed; a first variable hydraulic pump used to drive a work hydraulic actuator, driven by the engine; a second variable hydraulic pump used to drive a cooling fan, driven by the engine; and a pump control device that controls an output flow rate of the first variable hydraulic pump and an output flow rate of the second variable hydraulic pump so as to ensure that a sum of an intake torque of the first variable hydraulic pump and an intake torque of the second variable hydraulic pump does not exceed an engine output torque determined in advance based upon the target rotation speed.

Abstract: A counterbalancing arrangement and a method for counterbalancing two mutually movable parts, which is arranged to counteract the gravitational force of at least one of the movable parts. The counterbalancing arrangement includes a gas spring and a compressor system. The compressor system is designed to sense a pressure in the gas spring and to adjust the pressure if the pressure deviates from a predetermined value. The counterbalancing arrangement can be used for counterbalancing an industrial robot arm and is capable of maintaining its working capacity regardless of any gas leakage and variations in the ambient temperature so as to result in very few unwanted stops occasioned by a need for servicing the balancing spring of the counterbalancing arrangement.

Abstract: A case drain circuit particularly well suited for use with a bulk fill subassembly or a vacuum fan assembly of an agricultural implement towed by a tractor or similar vehicle includes a pressure switch that may cause illumination of an in-cab warning light and/or sounding of an in-cab alarm when pressure in the case drain circuit exceeds a predetermined threshold. A fan is driven by a solenoid controlled hydraulic motor which is supplied hydraulic fluid under pressure from a flow control valve to the motor in accordance with electrical signals that are supplied to the solenoid by a controller. The case drain circuit provides a pathway along which leakage fluid from the motor may be delivered to a fluid reservoir, preferably carried by the towing vehicle. During undesirable high pressure conditions in the case drain circuit, the pressure switch provides a corresponding high pressure signal to the controller that in turn cuts electrical current to the solenoid to cut the flow of hydraulic fluid to the motor.

Abstract: An adaptive, low-impact vehicle energy harvester system, and a method of harvesting vehicle energy, is provided. The system includes a plurality of channels disposed longitudinally in a trafficway, wherein each of the plurality of channels includes one or more compressible, elongated hollow bodies such that a movement of a vehicle along the trafficway causes contents in the elongated hollow bodies to be expelled from one end, a motor in communication with the hollow bodies such that the contents expelled from one end of the hollow bodies actuate the motor, and a control unit that varies a resistance to the movement of the contents in the elongated hollow bodies based on at least one of a mass of the vehicle, a velocity of the vehicle, and a rate of change of velocity of the vehicle.

Abstract: A control device for an industrial vehicle including an electric storage device, a load device, a hydraulic pump, and a load motor is disclosed. The electric storage device stores regenerative power generated through regenerative braking performed by the travel motor. The hydraulic pump supplies a hydraulic circuit with hydraulic oil to operate the load device. The load motor drives the hydraulic pump. The control device includes a power control unit and a resistance flow passage. The power control unit executes control for supplying the load motor with the regenerative power when the electric storage device is in a fully charged state during regenerative braking performed by the travel motor. The resistance flow passage is arranged in the hydraulic circuit and enables passage of hydraulic oil while applying flow resistance to the hydraulic oil.

Abstract: The invention relates to a hydraulic control arrangement and to a method for controlling a hydraulic consumer that comprises a pressure chamber on the input side and on the return side, said pressure chamber being connected to an adjusting pump or a tank via a valve device. The valve device is controlled by means of a control unit via which it can be adjusted in a regeneration mode, in which both pressure chambers are connected to the adjusting pump. According to the invention, the adjusting pump is pressure controlled, whereby in the regeneration mode, it is automatically switched to the normal operation in which the supply side of the pressure chamber is connected to the adjusting pump and the return side of the pressure chamber is connected to the tank when the pumping rate falls below the demand for the pressure medium.

Abstract: An apparatus for compensating for fluid contraction in a hydraulic powered telescoping boom may include a monitor determining the elevation angle of the telescoping boom, a supply of hydraulic fluid, and a fluid control responsive to the monitor. The fluid control provides the hydraulic fluid from the supply to a hydraulic cylinder controlling extension of the telescoping boom when the elevation angle exceeds a predetermined threshold angle to compensate for thermal contraction of hydraulic fluid and thus prevent uncommanded boom retraction. A method in accordance with the invention is also disclosed.

Abstract: In a hybrid working machine in which the maximum engine output is set at the average power and the maximum pump input is set to be larger than the maximum engine output in a normal state, in an abnormal state in which the level of charge of a battery decreases and assistance ability of a motor function of a power machine is lost, the minimum pump flow rate is reduced to a value equal to or smaller than a standby flow rate, the standby flow rate being the minimum pump flow rate used in normal state control, and a set value of the maximum pump input is changed such that the maximum pump input is smaller than the maximum engine output.

Abstract: The present invention provides a device and a method for regulating a temperature (T) of hydraulic fluid in at least one hydraulic circuit (2) of an aircraft (1). In this case the temperature (T) of the hydraulic fluid is regulated so that it is above an adjustable minimum temperature limit value {Tmin) of approximately 20° C., for example, at all times.

Abstract: A hydraulic system includes an engine driven adjustable hydraulic pump which supplies fluid to a hydraulic consumer, and an electronic control unit. The adjustable pump includes flow controller for controlling a pressure difference between the consumer and the adjustable pump to a pre-determined control pressure difference. The flow controller includes an actuator controlled by the control unit, through which the pressure difference can be controlled. The electronic control unit receives an engine speed signal and controls the actuator to control the pressure difference, in order to make power delivery of the adjustable pump conform to the operating conditions of a vehicle.

Abstract: The present disclosure relates to a hydraulic system with a hydraulic fluid, with a work element actuable by the fluid, with a fluid pump for the application of a fluid pressure to the fluid, with the fluid pump being operable to generate a reference depression in the system, and with a pressure sensor for the measurement of the fluid pressure which is in communication with a control unit which is designed to carry out a calibration of the pressure sensor with reference to the reference depression. The present disclosure also relates to a method for the calibration of a pressure sensor which is provided for the measurement of the fluid pressure of a hydraulic fluid contained in a hydraulic system.

Abstract: The present disclosure is directed toward a hydraulic control system. The system may have a pump and a tool actuator configured to move a tool with a flow of pressurized fluid provided by the pump. The system may further have a tool control valve configured to control the flow of pressurized fluid to the tool actuator. The system may also have a controller operably connected with the tool control valve and the pump. The controller may be configured to receive a tool movement request. The controller may further be configured to estimate a change in a flow demand across the tool control valve associated with the tool movement request. The controller may also be configured to command adjustment of a discharge flow rate of the pump based on the estimated change in flow demand to satisfy the tool movement request.

Abstract: A motorized hydraulically-operated and driven aircraft loading vehicle is particularly suited for the loading of bombs, which are raised by a pair of hydraulically-operated arms. Vehicle has two selectable operation modes. A first, working mode provides four-wheel hydraulic steering and enables vehicle to be driven at a small turning radius, and at a speed of up to 10 km/h. A second, traveling mode automatically locks the rear wheel steering system allowing vehicle to be driven at a speed of up to 20 km/h, all being computer controlled. Safety devices include an emergency stop switch and a no-driver no-actuation switch, and devices preventing accidents if hydraulic power is lost.

Abstract: A loader includes a hydraulically operated extension arm, a load sensor for monitoring the load condition on the loader and a hydraulic arrangement for actuation of the extension arm and/or an implement attached to the extension arm. The hydraulic arrangement exhibits at least one hydraulic cylinder with one supply line on the piston rod side and one supply line on the piston side. At least one hydraulically switchable control device is coupled between a source of fluid pressure and a hydraulic tank, on the one hand, and the supply lines on the other hand. An actuating device is coupled for routing control pressure to the control device via first and second control pressure lines.

Abstract: A working oil supply flow rate to hydraulic actuators (7-9) is controlled on the basis of target operating speeds (C7-C9). When a state in which one of the hydraulic actuators (7-9) has substantially stopped operating is detected, the target operating speed (C7-C9) of that hydraulic actuator is reset at a smaller value. A required flow rate Qb required of the hydraulic pump 22 is calculated using the reset target operating speed, whereupon the target operating speeds are corrected using a flow distribution factor Qr obtained by dividing a possible supply flow rate Qa by the required flow rate Qb. By controlling the working oil supply flow rate to the hydraulic actuators (7-9) on the basis of the corrected target operating speeds, when one of the hydraulic actuators (7-9) substantially stops operating, the supply of working oil to the other hydraulic actuators can be increased quickly.

Abstract: Adjustable control arms for dual path hydrostatic pumps have first and second arms interconnected by an eccentric mechanism with a common pivot point on a pivotal control input shaft for the pumps. The control arms are adjusted at a minimal pump output such as 500 r.p.m. by varying the eccentric to achieve equal r.p.m. The throw of the pump arms is adjusted at a maximum pump output r.p.m., such as approximately 4000 r.p.m., to achieve uniform tracking, steering, and directional control from the dual path hydrostatic pumps.

Abstract: A double-rod electrohydraulic actuator for the purpose of causing push-pull motion while being part of a structure. Actuator comprises of a piston assembly and an external cylinder. Piston assembly comprises of a piston housing and flanged piston rods on both ends. Piston housing comprises of a cylindrical housing with external sliding seals in sealing contact with the interior surface of the external cylinder. Cylindrical housing contains: pump, motor, relief valves, seals, and porting required for control of fluid flow through the assembly. External cylinder will have sliding seals at both ends in sealing contact with the flanged piston rods of the piston assembly, and hydraulic fluid filling all internal voids. The flanged piston rods will have porting in the flanges for fluid flow and hollow centers for wiring conduit to and through actuator. Relief valves will bypass fluid around the pump section in overload conditions to protect the actuator.

Abstract: A hydraulic system for a machine is disclosed. The hydraulic system has a source of pressurized fluid and a fluid actuator with a first chamber. The hydraulic system also has a first valve configured to selectively fluidly communicate the source with the first chamber. The first valve further includes a first element movable between a flow passing, at which fluid from the source flows to the first chamber, and a flow blocking position, at which fluid from the source is blocked from the first chamber and a second element configured to selectively drain a control passageway associated with the first element to cause the first element to move. The hydraulic system further has a proportional pressure compensating valve configured to control a pressure of a fluid directed between the source and the first valve dependent upon the pressure of the control passageway.

Abstract: A hydraulic circuit for an actuator that has a piston and piston rod that will move a load in a first direction, and which can be externally loaded in an opposite direction, includes a flow compensated valve between the actuator and a control valve. When the piston in the actuator is moved in the second opposite direction under the external load and the rate of flow of fluid out of the actuator through the flow compensated valve exceeds a selected rate, an orifice is introduced in the flow path to restrict flow from the actuator.

Abstract: A system and method for variator control employs positively directed electronic make-up and flushing relief valves for more precise torque control of a hydraulic variator, especially during torque reversal, as well as improved cold weather operation. This can improve machine response during periods of severe torque change. The ability to more tightly control variator torque allows more precise torque management algorithms for power control and engine matching purposes. Moreover, the ability to positively control venting of the hydraulic circuit for purposes of fluid cooling allows for more consistent machine response regardless of ambient temperature.

Abstract: Circuit for controlling a double-action hydraulic drive cylinder includes a directional control valve having working ports A and B, a pump port P, and a tank port T, wherein the directional control valve has a neutral position in which pump port P is blocked and working ports A, B are connected to tank port T. A pressure-limiting valve and a controllable load-holding valve are connected to the piston space in parallel, and a regeneration check valve is connected in series between a connection point for the parallel components and the rod space. A first precharge valve is connected between the working port A and the connection point, and a first bypass check valve is connected anti-parallel parallel with the first precharge valve and the load-holding valve. A second precharge valve is connected in series with the directional control valve between the tank port P and the rod space.

Abstract: A variable rate suspension system for a boom sprayer including a lift assembly and chassis. The suspension system includes a needle valve fluidly connected to a hydraulic accumulator and a first and second lift arm cylinder. A control block provides hydraulic fluid to the system and lift arm cylinders. Dampening of vertical accelerations encountered by the chassis and transmitted to the boom sprayer through the lift assembly is controlled by adjusting the rate hydraulic fluid flows from the cylinders into the accumulator using the needle valve.

Abstract: The present invention provides a construction machine where overheating of mounted electric devices can be prevented properly with a simple structure and a method of controlling the construction machine. For this purpose, a pump target discharge flow rate of a hydraulic pump is calculated based on an operated amount of an operating unit, a temperature of an electric device mounted on the construction machine is detected, an engine minimum speed, which is a minimum possible speed of an engine in carrying out low-speed matching for matching output of the engine and pump absorbing horsepower of the hydraulic pump to each other in a low-speed region where speed of the engine is lower than set speed, is calculated by using the detected temperature of the electric device, and a maximum value out of a corresponding speed of the pump target discharge flow rate and the engine minimum speed is generated as a candidate for an engine target speed.

Abstract: There are provided: control valves 22-24 that control flow of pressure oil from the hydraulic source 21 to the hydraulic actuators 15-17; electric lever devices 51-53 that output electrical operation signals, which are drive instructions for the hydraulic actuators 15-17, in correspondence to lever operation; and a control unit 25-30 and 50 that controls the control valves 22-24 in correspondence to the operation signals. When the determination unit determines that an operation signal is not within the normal range, the hydraulic actuators 15-17 are allowed to be driven with flow of pressure oil to the hydraulic actuators 15-17 limited more significantly than in a case where it is decided that an operation signal is within the normal range.

Abstract: The present invention relates to a hydraulic drive which comprises a hydraulic motor having a first hydraulic connector and a second hydraulic connector, wherein the pressure applied at the first hydraulic connector of the hydraulic motor and the pressure applied at the second hydraulic connector of the hydraulic motor are each separately adjustable.

Abstract: A speed of a hydraulic actuator is matched with that of an electric actuator when the hydraulic actuator and the electric actuator are concurrently actuated. When determination units (71, 72) determine that a boom hydraulic cylinder (31) and a rotation generator motor (11) are concurrently actuated based on a controlled variable of a boom control lever (41) and a controlled variable of a rotation control lever (42), a torque of the rotation generator motor (11) is restricted based on a pump discharge pressure (Pp). Therefore, for example, a torque limit command is generated and output such that a torque limit value (TL2) of the rotation generator motor (11) is decreased with a decrease in discharge pressure (Pp) of a hydraulic pump (3).

Abstract: In an over-loading prevention device including a hydraulic pump, a control valve, and a control lever, a discharge-quantity control unit performs constant-torque control which decreases a discharge quantity in proportion to an increase in a discharge pressure in the pump to control an input torque of the pump uniformly. An operation-state detection unit detects an actuation state of the control lever. A control unit outputs a control signal that sets the pump input torque to a minimum torque according to the constant-torque control, to the discharge-quantity control unit when the control lever is operated over a predetermined speed, and subsequently changes a level of the control signal to a maximum torque according to the constant-torque control in accordance with a predetermined control pattern to raise the pump input torque.

Abstract: A hydraulic circuit that enables smooth absorption of the energy of a return fluid from a hydraulic actuator by means of an energy recovery motor. A return fluid passage to which the fluid discharged from a boom cylinder is branched is provided at the tank passage side of a solenoid valve of a boom control circuit. The return fluid passage comprises two return passages, which are provided with a flow rate ratio control valve for controlling a ratio of fluid that branches off into the return passages. The flow rate ratio control valve is comprised of a solenoid valve disposed in the return passage, which is provided with an energy recovery motor, and a solenoid valve disposed in the return passage, which branches off the upstream side of the solenoid valve.

Abstract: In an actuator control device that controls an expansion/contraction operation of a hydraulic cylinder, when a main spool 52 is switched to a discharge position for discharging working fluid in the hydraulic cylinder, a back pressure chamber 7 communicates with a tank passage 13 via a first port 14, thereby opening an operate check valve 51, and as a result, the working fluid in the hydraulic cylinder flows into a return passage 4 from an actuator port 1 and into a pilot chamber 20 through a second port 15. A pilot spool 53 is maintained in a balanced position by the pressure of the pilot chamber 20, which is caused to act by a front-rear differential pressure of a control throttle 25, and the biasing force of a spring 22 housed in a spring chamber 21, and therefore the opening area of the first port 14 is controlled to and maintained at a fixed level.

Abstract: A concrete agitating drum (1) is driven by a hydraulic motor (81). A connection switch-over valve (20) is arranged to have a function to regulate a flow cross-sectional area of pressurized working oil supplied to the hydraulic motor (81) from a variable capacity hydraulic pump (10). The variable capacity hydraulic pump (10) is driven by a combustion engine (60) together with a charge pump (11). When a discharge pressure of the charge pump (11) is low, the connection switch-over valve (20) maintains a small flow cross-sectional area to rotate the agitating drum (1) at a low rotation speed so that fuel consumption of the combustion engine (60) is suppressed to be small. When the discharge pressure of the charge pump (11) becomes high, the connection switch-over valve (20) enlarges the flow cross-sectional area, thereby realizing a rated rotation speed of the agitating drum (1).

Abstract: An array of valve sections in a hydraulic system are connected to a supply line, a tank return line, and a load sense line. One valve sections includes a control valve with a metering orifice through which fluid flows from the supply line to a valve outlet. A load sense node is coupled by a load sense orifice to the load sense line. A load sense pressure limiter prevents pressure at the load sense node from exceeding a threshold level. A pressure compensator is connected in a fluid path between the valve outlet and one of the hydraulic actuators. The pressure compensator opens and closes the fluid path in response to pressure at the valve outlet and pressure at the load sense node, thereby governing the maximum amount of pressure that the respective valve section can apply to the hydraulic actuator.

Abstract: An exemplary hydraulic system includes a digital valve operable to fluidly connect a hydraulic load to a pressure supply, and an orifice disposed in a flow path between the hydraulic load and the digital valve. A digital controller is operably connected to the digital valve. The digital controller stores a target pressure drop across the orifice and is configured to determine an actual pressure drop across the orifice and formulate a control signal based on the target pressure drop and the actual pressure drop. The controller transmits the control signal to the digital valve for controlling the operation of the valve.

Abstract: An exemplary hydraulic system includes a digital valve operable to fluidly connect a hydraulic load to a pressure supply. A digital controller is operably connected to the digital valve. The digital controller stores a target value of a hydraulic system operating parameter and is configured to formulate a pulse width modulated control signal based on the target value. The digital controller transmits the control signal to the digital valve for controlling the operation of the valve.

Abstract: A priority valve 7 is disposed between a hydraulic pump 2 and a steering valve 4 and is used to supply priority steering cylinders 103a and 103b with pressurized oil discharged from the hydraulic pump 2 by controlling the differential pressure across a meter-in hydraulic line of the steering valve 4 such that the differential pressure is kept at a target value. A pressure sensor 31 for detecting the load pressures of the steering cylinders 103a and 103b is provided. On the basis of the detected load pressures, the target value set for the priority valve 7 is modified by devices including a controller 32, a solenoid valve 33, a pilot hydraulic line 29, and a pressure receiving unit 24c of the priority valve 7. The above configuration enables suppression of a shock occurring at the start of turning of the steering wheel.

Abstract: A hydrostatic drive system has a pump (1) and at least one consumer (5) controlled by a control valve (4) that can be actuated by control signals. A precharge device (10) that generates a precharge pressure is located in a reservoir line (7) that leads from the control valve (4) to a reservoir (2). The precharge device can be pressurized as a function of the control signals of the control valve (4). To make possible a recharge during the deceleration of a consumer, the precharge device (10) can be pressurized in the direction of an elevation of the precharge pressure when there is a decreasing control signal of the control valve (4).

Abstract: A lock valve includes a lock valve body having a bore with a valve spool reciprocatingly received therein. There is a check valve adjacent each end of the bore. Each of the check valves has a check valve member facing the bore and resiliently biased towards a valve seat at each end of the bore. A pressure relief port communicates with the bore near the center thereof and between lands of the valve spool. A pair of spaced-apart grooves are disposed within the spool valve bore. Each groove permits fluid communication past a land of the valve spool when the valve spool is displaced towards one end of the bore by fluid pressure applied to other end of the bore so as to unseat the check valve member adjacent to the one end to the bore and allow pressurized fluid to pass from the one end of the bore, through the groove, and into the relief port.

Abstract: The present invention provides a method of controlling a fluid working machine (12) having a plurality of working cylinders (14) having pistons (16) therein and arranged to drive a shaft (18), in which said cylinders are supplied with pressurised working fluid via a manifold (24), the contents of which may be 5 purged by a de-pressuriser taking one of a number for forms such as to allow re-activation of said machine (10).

Abstract: A pressure selector valve (13) is provided between a hydraulic motor (1) and a directional control valve (5) to connect one of the main conduits (4A), (4B) on a high pressure side to a high pressure conduit (14) while connecting the other of the main conduits on a low pressure side to a low pressure conduit (15). As an inertial body approaches a stop position, a spool valve (16) is switched to an open position (e), bringing a branch passage (14A) of the high pressure conduit (14) into communication with the low pressure conduit. When the pressure difference between the main conduits becomes small, the pressure selector valve is automatically returned to a neutral position to cut off communication between the main conduits, suppressing a reversing movement of the hydraulic motor so that an inertial body can be brought to a stop smoothly.

Abstract: A motor vehicle control device with a digital control loop has an actuator of an electrical actuator device in order to regulate the pressure of the volumetric flow of a motor vehicle hydraulic apparatus. A current limiting unit is provided in the forward path of the digital control loop between the digital controller of the latter and the actuator of the electrical actuator device. The current limiting unit, in order to protect the components of the electrical actuator device, limits the manipulated variable signal from the digital control loop if a predefined permissible current threshold value is exceeded in the electrical actuator device. The digital controller has an additional limiting unit which essentially limits the I component of its manipulated variable signal from the time at which the current limiting unit is activated.

Abstract: The operation control circuit of the present invention reduces the speed of an actuator, such as a rotation motor, according to reduction in the rotational speed of an engine. When the engine rotational speed is at its maximum, a pilot pressure in a pilot conduit is set to a relief pressure of a relief valve. When the engine rotational speed is reduced, the flow rate of pilot pressure hydraulic fluid decreases, and the pressure difference over a throttle section becomes smaller than the relief pressure, so that the pilot pressure is set to the pressure difference. Even if the operator operates an operation lever to a full stroke position the spool valve does not go to the fully opened state, since the pressure is low. As a result, the flow rate of hydraulic fluid supplied to the rotation motor is reduced, so that the speed of rotation is reduced.

Abstract: An electrohydraulic transmission controller (7), a transmission device with an electrohydraulic transmission controller and a vehicle drive train that features an electrohydraulic transmission controller are disclosed. The electrohydraulic transmission controller is constructed with a plurality of electrically actuatable pressure control valves (9 to 16), as well as with a plurality of valve arrangements (17 to 34) that can be acted on in each case by an hydraulic precontrol pressure depending upon the actuation of the pressure valves, by way of which valve arrangements switching elements (A to E) of a transmission device can be acted on in each case with a control pressure to produce a required operating state of the transmission device.

Abstract: A method of allocating hydraulic fluid between two or more actuators in a machine processes a first command intended to provide a first requested fluid flow to a steering actuator for steering the machine, and a second command intended to provide a second requested fluid flow to a non-steeling actuator, such as a lift or tilt actuator. The system modifies the first and second commands to produce modified first and second commands corresponding to modified first and second fluid flows, such that the sum of the adjusted first and second fluid flows is less than or equal to a currently available flow and the modified first fluid flow meets or exceeds the lesser of the first requested fluid flow and a threshold curve that is a function of a machine variable such as engine speed or other variable or parameter.

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 loader and back hoe having circuits to supply the pressure oil from one hydraulic pump P1 to a valve group 150 for back hoe control through a valve group 130 for loader control and the pressure oil from the other hydraulic pump P2 directly to the valve group 150 for back hoe control. The pressure oil is independently supplied from the hydraulic pumps P1 and P2 to valve sections 152 for controlling right and left stabilizer cylinders installed in the valve group 150 for back hoe control.

Abstract: In a hydraulic driving device for an operating machine, when an output value of an operating device is in a first predetermined range, a pump is stopped and each of an open and closed valve and a hydraulic control valve is closed. When the output value goes beyond the first predetermined range, the pump is started and the open and closed valve is opened. When the output value goes beyond a second range greater than the first predetermined range, the hydraulic control valve is opened to supply a hydraulic fluid to an actuator.

Abstract: A flow control apparatus for heavy construction equipment is provided, which can prevent overspeed and abrupt operations of an actuator due to an excessive flow rate during an initial operation of the actuator when a composite work is performed by simultaneously operating an option device and another actuator, and can prevent the cut-off of hydraulic fluid supply to the option device due to an operation inability of a flow control valve when leakage of the hydraulic fluid occurs due to the increase of the temperature of the hydraulic fluid.

Abstract: A method is provided for controlling a hydraulic cylinder, including detecting at least one operating parameter, and variably controlling a communication path between the piston-rod side and piston side of the hydraulic cylinder on the basis of the detected operating parameter.

Abstract: The force feedback poppet valve includes a valve body having a main chamber, a first port, and a second port. The force feedback poppet valve further includes a main poppet disposed within the main chamber and movable between an open position and a closed position to control fluid flow between the first port and the second port. The main poppet forms a control chamber within the main chamber. The force feedback poppet valve further includes a first passage communicating the control chamber with the second port, a second passage communicating the control chamber with the first port, and a pilot valve having a pilot poppet for controlling fluid flow between the control chamber and the first port through the second passage. The force feedback poppet valve further includes a pressure compensator disposed within the main poppet, and fluidly connected to the second port via the first passage.

Abstract: A hydraulic drive system for storing and releasing hydraulic fluid includes a high pressure storage device, a low pressure storage device, and a pump-motor operating at a range of pump-motor speeds for converting between hydraulic energy and mechanical energy. The pump-motor is disposed between the high pressure device and the low pressure device. In normal operation, the hydraulic drive system enters a motoring mode where hydraulic energy is released from the high pressure storage device and converted to mechanical energy using the pump-motor. It also enters a pumping mode where mechanical energy is converted into hydraulic energy. A neutral state exists where hydraulic energy is neither stored nor released from the high pressure storage device. An approach for exiting either the motoring mode or the pumping mode promotes efficiency within the hydraulic drive system.