Abstract: A hydraulic valve assembly includes a pressure compensating valve in which a compensator spool is slideably received in a bore. A pre-compensator gallery connected to a metering orifice, a preload gallery leading to a hydraulic actuator, an auxiliary pump supply passage, and a load sense passage all open into the bore. The compensator spool moves in response to a pressure differential between the pre-compensator gallery and the load sense passage. That movement selectively opens and closes a first path between the pre-compensator gallery and the a preload gallery, and a second path between the auxiliary supply passage and the load sense passage. Control of these paths maintains a constant pressure drop across the metering orifice and generates a pressure signal that is employed to regulate pressure at an outlet of a pump.

Abstract: The invention provides a pumping system for delivering a plurality of different materials serially at a location at substantially the same flow rate wherein the system has a plurality of diaphragm pumps wherein each diaphragm pump has a first chamber for receiving a hydraulic fluid from a first and/or second hydraulic fluid source and a second chamber for receiving a material to be pumped from one of a plurality of pumpable material sources and wherein the system has a sensor for detecting the pressure of the hydraulic fluid in each of the first chambers of the plurality of diaphragm pumps which sensor is operable connected to a source of hydraulic fluid such that the sensor can activate the source of hydraulic fluid to ensure that the hydraulic fluid in each of the first chambers of the plurality of diaphragm pumps has an equivalent pressure at a time when delivery from one of the diaphragm pumps ceases and delivery from another commences; and a method of delivering a plurality of different materials at a lo

Abstract: A hydraulic system for utility vehicles is disclosed for prioritized pressure medium supply to internal and external pressure medium consumers (6, 11, 12), which are fed via load sensing spool valves (20, 26), the external pressure medium consumers (11, 12) being supplied with pressure medium via a priority valve (17). In order to improve the work quality of an implement driven by an external pressure medium consumer, the present invention provides that priority can be selectively assigned to the internal (6) or the external (11, 12) pressure medium consumers. It is thus possible for the driver, in order to ensure optimum operation of the utility vehicle in critical situations, to give priority to external pressure medium consumers. In this way during operation of an implement for dispersion of substances, better work quality can be attained, as a reduced supply and thus slower function of the internal power lift are accepted.

Abstract: A hydraulic control device for an automatic transmission, including: a hydraulic pressure source; a plurality of friction engagement elements; a line pressure regulating valve that regulates hydraulic pressure from the hydraulic pressure source to a predetermined line pressure; a plurality of operation pressure regulating valves that regulate the line pressure as operation pressure for a hydraulic servo operating a friction engagement element; a maximum pressure conducting circuit that feeds a maximum pressure, among the operation pressures, to the line pressure regulating valve, wherein the friction engagement elements are engaged and released to achieve a plurality of forward speeds and a reverse speed, and the line pressure regulating valve regulates the line pressure during forward travel based on the maximum operation pressure, and regulates the line pressure during reverse travel based on the operation pressure input from a specific operation pressure regulating valve.

Abstract: A hydrostatic transmission having a hydraulic pump that is fluidly connected to a hydraulic motor. The transmission also has a pressure control valve that has first and second stages and is fluidly connected to the hydraulic pump. By utilizing the pressure control valve when the first stage of the pressure control is at a minimum pressure the second stage determines the minimum charge pressure setting for the hydrostatic transmission.

Abstract: A hydraulic circuit for a construction machine is disclosed, which can prevent an energy loss of a hydraulic system by automatically reducing revolution of an engine when a working device such as a boom is not driven. The hydraulic circuit includes first to third hydraulic pumps, a first switching valve, a second switching valve, a third switching valve, a confluence switching valve, a first shuttle valve selecting any one of a pressure of a first signal line in which a signal pressure is formed when the third switching valve for working devices connected to the third hydraulic pump is shifted and a pressure of a second signal line in which a signal pressure is formed when a switching valve for traveling devices is shifted, and a second shuttle valve selecting any one of the pressure selected by the first shuttle valve and a pressure of a third signal line in which a signal pressure is formed when switching valves for the working devices connected to the first and second hydraulic pumps are shifted.

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: A hydraulic system includes first and second pumps, first and second motors, and three valves for selectively creating combined and basic hydraulic flow. The arrangement of valves permits combined flow to be provided to both motors in series to cause high speed operation of the motors, and permits combined flow to be provided to one motor and basic flow to the other motor. When applied to a vehicle, the arrangement provides a steerable high speed series arrangement of the vehicle's drive motors.

Abstract: A hydraulic system including a control valve and a steering control assembly. The steering control assembly includes a steering control unit and a priority flow divider contained in a single unitary casing. The steering control assembly is attached adjacently with and directly to the control valve by means of an interface that fluidly connects the control valve with the steering control assembly.

Abstract: The invention relates to a valve arrangement having an adjustable control valve (10), comprising a control slide (12) for actuating at least one consumer connection (A,B), and having an LS control line, wherein the differential pressure of two actuating pressures (Xa, Xb) serves for the actuation of the control slide (12). Due to the fact that the actuating pressures (Xa, Xb) also actuate a logic valve, which in turn influences an additional valve, and/or actuates a pressure scale that is connected upstream to the control valve (10) having the control slide (12), the difference of the two actuating pressures (Xa, Xb) initially displaces the control slide of the control valve, wherein the higher or the lower of the two actuating pressures (Xa, Xb) either actuate the further valve in the form of the additional valve, and/or influences the pressure scale.

Abstract: A hydraulic circuit for an excavator is provided, which includes first to third hydraulic pumps, a first traveling control valve and a first boom control valve successively installed along a first center bypass line from a downstream side of the first hydraulic pump, a second traveling control valve and a second boom control valve successively installed along a second center bypass line from a downstream side of the second hydraulic pump, a swing control valve connected between the third hydraulic pump and a swing motor to control the operation of the swing motor in accordance with an external valve switching signal, and a confluence line connected between a third center bypass line and a flow path of the second boom control valve to make hydraulic fluid from the third hydraulic pump join hydraulic fluid in a neutral position of the swing control valve.

Abstract: A hydraulic actuator for a hydraulic servomotor (4) is disclosed. The hydraulic servomotor (4) is of a kind having at least one defined end position, and has a first chamber (5) and a second chamber (6) associated therewith. The actuator is connected to a fluid source (2) and a fluid drain (3). The actuator comprises a first valve (7) fluidly connected between the fluid source (2) and the first chamber (5), a second valve (8) fluidly connected between the first chamber (5) and the fluid drain (3), and a third valve (9) fluidly connected between the fluid source (2) and the second chamber (6). The actuator further comprises a flow channel (10, 17), preferably comprising a flow restrictor (12, 18), in fluid communication with the second chamber (6). The valves (7, 8, 9) are such that, in the case of a power cut off, they will prevent a fluid flow out of the first chamber (5), and a fluid flow out of the second chamber (6) takes place via the flow channel (10, 17).

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 priority flow rate control valve (4) increases a distribution ratio of pressurized oil to a power steering device (1) of a fork-lift track via a power steering oil passage (9) as a differential pressure between a power steering pressure (PS) in the power steering oil passage (9) and a pilot pressure (LS) decreases. A load signal port (24) which outputs a pressure indicative of a load exerted on the power steering device (1) and the power steering oil passage (9) are connected via two orifices (26A, 26B), and the pilot pressure (LS) pressure is extracted from a point between the two orifices (26A, 26B). By providing a bypass passage (31, 35) which bypasses one of the two orifices (26A, 26B) and a bypass valve (30) which opens and closes the bypass passage (26A, 26B), a response of the priority flow rate control valve (4) can be increased temporarily.

Abstract: A dual mode control system for a hydraulic circuit (200) having a variable displacement pump (216) includes at least two actuators, each controlled by a respective valve. The valves are connected in series with a pressure sensor (250) measuring a pressure of fluid between the first valve (224) and the second valve (234) and relaying a signal to the electronic controller (202). The electronic controller (202) operates in a first mode, varying the displacement of the pump (216) based on a command signal operating at least one of the valves, and operates in a standby mode, varying the displacement of the pump (216) based on the signal from the sensor, when both valves are in their respective neutral positions.

Abstract: An apparatus for fixing hydraulic pipes for construction equipment is provided, which can facilitate joint connection of return pipes having a large size to a hydraulic tank, in an environment where a working space of an upper frame is narrow such as in a small swing radius construction equipment, by a return pipe block for returning hydraulic fluid of a main control valve to the hydraulic tank without being interfered with a swing motor and so on.

Abstract: A steering system includes a fluid pump and an electro-hydraulic steering circuit in selective fluid communication with the fluid pump. The electro-hydraulic steering circuit defines a first flow path having a first proportional valve and a first load-sense passage in selective communication with the first proportional valve. The first proportional valve includes a closed position. A hydrostatic steering circuit is in selective fluid communication with the fluid pump and defines a second flow path having a second proportional valve and a second load-sense passage in selective fluid communication with the second proportional valve. The second flow path is in a parallel flow configuration with the first flow path. An isolation valve is disposed in the first flow path in series with the first proportional valve. The isolation valve includes a closed position and is piloted to the closed position by fluid communicated through the second load-sense passage.

Abstract: A hydraulic system comprises a plurality of primary hydraulic circuits and a secondary hydraulic circuit for satisfying flow continuity of the primary hydraulic circuits.

Abstract: A method for controlling a hydraulically actuated rotor brake for a drive train of a wind energy plant, wherein the rotor brake is realized as an active rotor brake, which exerts a braking moment getting stronger when the hydraulic pressure increases, wherein in a first phase, a brake cylinder is pressurized with a first pressure via a first pressure reducing valve, in a second phase, the brake cylinder is pressurized with a second pressure via a second pressure reducing valve, and a switchover equipment is provided, which switches over from the first pressure to the second pressure.

Abstract: Disclosed is a hydraulic system for utility vehicles, in particular agricultural tractors, for supplying primary and/or auxiliary pressure medium consumers with pressure medium, comprising a pump, sucking from a pressure medium tank, the pump being controlled as a function of the load pressure of the pressure medium consumers and supplying a pump pressure exceeding the load pressure by a predetermined control pressure differential. The hydraulic system produces a first control pressure differential for operating a primary pressure medium consumer and a second higher control pressure differential for operating an auxiliary pressure medium consumer. The hydraulic system obtains rapid response of an actuated primary pressure medium consumer and prevents, under certain conditions due to thermal expansion, pressure medium from flowing to the pressure and flow controller of the pump and possibly causing unwanted restriction of the pump.

Abstract: A hydraulic valve assembly includes a pressure compensating valve in which a compensator spool is slideably received in a bore. A pre-compensator gallery connected to a metering orifice, a preload gallery leading to a hydraulic actuator, an auxiliary pump supply passage, and a load sense passage all open into the bore. The compensator spool moves in response to a pressure differential between the pre-compensator gallery and the load sense passage. That movement selectively opens and closes a first path between the pre-compensator gallery and the a preload gallery, and a second path between the auxiliary supply passage and the load sense passage. Control of these paths maintains a constant pressure drop across the metering orifice and generates a pressure signal that is employed to regulate pressure at an outlet of a 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: The invention relates to a method and a circuit arrangement for controlling and regulating the supply of pressure medium to at least two hydraulic consumers, which are assigned in each case a directional valve for setting the flow and a setpoint signal source, by means of a pump with a variable displacement, which can be regulated by means of a displacement controller. The pump displacement is regulated according to the flow required by the setpoint signals. The individual load pressure of the consumers and of the consumer having the highest load pressure are determined. The directional valve of the highest loaded consumer is controlled to a valve-spool position y1, with y1=K·y1,max=const., which lies by a factor K, with 0<K<1, below the valve-spool position y1,max representing the maximum opening of the directional valve.

Abstract: A hydraulic circuit for heavy equipment is disclosed, which utilizes a hydraulic fluid supplied from a hydraulic pump for driving a cooling fan, as a pilot signal pressure, without installing a separate constant displacement pilot pump for supplying the pilot signal pressure to a control valve for controlling the hydraulic fluid to be supplied to a working device such as a boom.

Abstract: There is provided a hydraulic controller for a working machine in which a pilot hydraulic pressure source is connected in common to a plurality of pilot-operated hydraulic devices each having a pilot pressure input unit, and a common pilot pressure input switching valve is adapted to control the switching between a pilot pressure input from the pilot hydraulic pressure source to each pilot pressure input unit and a relief of the input. The switching control of a pilot pressure input by the pilot pressure input switching valve is performed based on the operating state of the working machine and pilot pressure input conditions of the respective pilot-operated hydraulic devices.

Abstract: An accumulator for a hydraulic system, wherein the accumulator comprises a liner, a piston and a housing, that defines a pressure chamber, for receiving hydraulic fluid at high pressure, wherein the piston is biased towards an end position of the pressure chamber for interacting with the hydraulic fluid in the pressure chamber, and the piston is movable in a predetermined range for accumulating hydraulic fluid. The accumulator has at least one outlet port in a sidewall of the liner, which outlet port is covered by the piston in the predetermined range and is uncovered when the piston has moved a predetermined distance from the end position. A hydraulic system is also provided that comprises the above accumulator and an all-wheel drive system comprising the above hydraulic system. A method for de-airing an accumulator according to above is also provided.

Abstract: There is provided a hydraulic fluid supply structure including: a discharge line fluidly connected to a discharge port of a hydraulic pump body and regulated to have a first pressure value; an external hydraulic fluid extraction line for supplying the hydraulic fluid to an actuator for raising and lowering a working machine, the external hydraulic fluid extraction line being fluidly connected to the discharge line through a resistance valve; a PTO hydraulic fluid line for supplying the hydraulic fluid to a hydraulic operating type clutch mechanism for engaging or disengaging power transmission to the working machine, the PTO hydraulic line being fluidly connected to the discharge line through a throttle valve and regulated to have a second pressure value lower than the first pressure value; and a PTO switching valve interposed in the PTO hydraulic fluid line so as to turn ON/OFF the supply of the hydraulic fluid to the hydraulic clutch mechanism.

Abstract: A hydraulic system has first and second functions in which separate control valves govern the flow of fluid between actuators and both a supply conduit and a return conduit. The second function is connected to a load sense passage. When pressure in the load sense passage exceeds a given level an anti-stall valve opens a restricted path between the supply and return conduits. Fluid flow through that restricted path reduces a likelihood that a prime mover driving the pump of the hydraulic system will stall. When only the first function is active the anti-stall valve is closed and does not affect the supply of fluid to that function.

Abstract: A tree felling machine has a main pump for operating functions of the machine such as the drive wheels or tracks, the steering, the brakes, and the lifting and extension of the boom, and a separate saw pump for driving the cutting element, for example, a circular disc saw driven by a hydraulic motor. Both pumps are driven by the same prime mover, i.e. the same internal combustion engine, and the power division between the two pumps is determined by the operator and by the hydraulic control system. In particular, a control provided in the cab is controllable by the human operator to limit the maximum power that the saw pump can draw from the prime mover. In addition, the power that the saw pump can draw from the prime mover is limited by a combination of the displacement setting of the main pump, the output pressure of the saw pump, and the pressure exerted on the load by the main pump.

Abstract: A circuit or system having application for operating an implement or attachment for a power machine is disclosed. The circuit includes a first or primary valve, a second or auxiliary valve connected in series with the first valve and a supplemental line connected in parallel with the second valve to provide fluid to a supplemental system in parallel with the second valve.

Abstract: A hydrostatic drive system has a consumer (7), in particular a hydraulic motor, located in the open circuit. Associated with the consumer (7) is at least one pressure limiting device (11a; 11b) that can be actuated in the braking phase for the generation of a braking pressure that is present on the discharge side of the consumer (7) from a minimum response pressure in the direction of an increase of the response pressure. A feeder device (12a; 12b) provides a feed of pressure fluid into the admission side of the consumer (7). The pressure limiting device (11a; 11b) and the feeder device (12a; 12b) are integrated into a valve unit (10a; 10b).

Abstract: A hydraulic system includes a first pump that delivers hydraulic fluid to a first load outlet point and to a second load outlet point, a second pump that delivers hydraulic fluid to the second load outlet point, but not to the first load outlet point, a pressure detector for detecting the load pressure at the first load outlet point and a pressure detector for detecting the load pressure at the second load outlet point. The system includes a controller for controlling the first pump on the basis of the detected load pressure at the first load outlet point and the detected load pressure at the second load outlet point, and a controller for controlling the second pump on the basis of the detected load pressure at the second load outlet point but not on the basis of the detected load pressure at the first load outlet point.

Abstract: A hydraulic control system is disclosed, which can minimize the flow rate of a hydraulic fluid being discharged from a variable displacement hydraulic pump by using pilot pressure constantly produced by a pilot pump when a switching valve is in a neutral position, and can adjust the flow rate of the hydraulic fluid being discharged from the variable displacement hydraulic pump by using pressure produced by a pressure generator positioned at the most downstream side of a bypass passage if a separate input signal is applied to the pressure generator when the switching valve is operated.

Abstract: A fluid system comprises a static LS valve, a dynamic LS valve, a priority valve biased to preferentially supply pressurized fluid to both the static LS valve and the dynamic LS valve, and a signal-mimicking device fluidly coupled to a static LS port of the static LS valve, a dynamic LS port of the dynamic LS valve, and a dynamic LS pilot port of the priority valve for mimicking a static LS signal from the static LS port of the static LS valve into a dynamic LS signal from the dynamic LS port of the dynamic LS valve to produce a combined LS signal communicated to the dynamic LS pilot port of the priority valve. Such a fluid system may be applied to a steering system. An associated method is disclosed.

Abstract: A control system for a work machine having a plurality of removably attachable work tools is disclosed. The control system has a tool recognition device configured to generate a recognition signal corresponding to each of the removably attachable work tools, and at least one fluid actuator configured to move at least one of the plurality of removably attachable work tools. The control system also has at least one fluid sensor configured to generate a load signal and at least one operator interface device configured to generate a desired velocity signal. The control system further has a controller in communication with the tool recognition device, the at least one fluid actuator, the at least one fluid sensor, and the at least one input device. The controller is configured to command a velocity for the fluid actuator in response to the recognition signal, the load signal, and the desired velocity signal.

Abstract: The invention relates to a hydraulic control device for a priority, first hydraulic consumer and a subordinate, second hydraulic consumer, pressure medium being deliverable to the first or the second consumer via a first or a second metering diaphragm. A pressure scale which allows a constant pressure difference to be adjusted above the first metering diaphragm is mounted upstream from the first metering diaphragm. For this purpose, said pressure scale is provided with a valve piston encompassing a first control edge, by means of which a first flow area between a feeding duct and the first metering diaphragm can be controlled. A second pressure scale which can be impinged upon in the closing direction by control pressure prevailing in a control chamber while being impinged upon in the opening direction by the pressure applied downstream from the second measuring diaphragm is mounted downstream from the second measuring diaphragm.

Abstract: A user input device is provided for a hydraulic system that has a source of pressurized fluid and a tank. The user input device includes a body with a supply passage for receiving the pressurized fluid, a tank passage for connection to the tank, and a first chamber. A handle is pivotally attached to the body and operates one or more valves within the body. In a preferred embodiment, the handle can be pivoted independently about two orthogonal axis with separate pairs of valves operated by movement about each axis. In response to the position of the handle, each valve connects a separate chamber alternately to either the supply passage or the tank passage and different pressure sensor produces an electrical signal indicating a level of pressure in the chamber of each valve. Thus an electrical signal is produced from each valve to indicate motion of the handle.

Abstract: A hydraulic system comprises a plurality of primary hydraulic circuits and a secondary hydraulic circuit for satisfying flow continuity of the primary hydraulic circuits.

Abstract: Disclosed are a control arrangement and a method for the pressure medium supply of at least two hydraulic consumers that are supplied with pressure medium through the intermediary of a variable displacement pump. In the pressure medium flow path between the consumers and the variable displacement pump a respective meter-in orifice is provided. An adjustment of the variable displacement pump and of the meter-in orifices takes place electronically through the intermediary of a control means in dependence on the target values input by an operator. In accordance with the invention, the meter-in orifice associated with the consumer having the highest load pressure is controlled to open completely, so that the pressure loss across this meter-in orifice is minimum.

Abstract: An anti-saturation valve assembly (51) for use in a hydraulic system having priority (17) and auxiliary (25) load circuits, the priority circuit providing a priority load signal (19). The anti-saturation valve assembly includes a pressure sensor portion (61) which senses a decrease between pump pressure (23) and the priority load signal (19), and generates a force on a pressure reducing portion (63) to reduce, correspondingly, a pilot pressure (59): The reduced pilot pressure to a pilot valve (35) results in reduced flow to a pilot-operated main control valve (27) in the auxiliary load circuit (25), thus providing anti-saturation protection for the circuit, without throttling a main flow path and wasting substantial hydraulic power.

Abstract: A vehicle is disclosed having a hydraulic system. The hydraulic system includes a pressure regulator that maintains the output pressure from a hydraulic pump above a predetermined minimum pressure.

Abstract: Disclosed is a hydraulic system for utility vehicles, in particular agricultural tractors, for supplying primary and/or auxiliary pressure medium consumers (6, 11, 12) with pressure medium, comprising a pump (1), whose pressure and flow are controlled as a function of the load pressure of the pressure medium consumers by a pressure and flow controller (13) to which whenever auxiliary pressure medium consumers (11, 12) are operating, a higher load pressure compared to the actual load pressure is reported through an amplifier device. In order to obtain rapid response of an actuated auxiliary pressure medium consumer it is proposed that the amplifier device (29) consists of a proportionally controllable pressure reducing valve (39).

Abstract: A hydraulic system is disclosed. The hydraulic system includes a source of pressurized fluid, a low pressure source, and a plurality of actuators. The hydraulic system also includes a plurality of valves configured to selectively communicate fluid to and from the plurality of actuators. The hydraulic system further includes a first valve disposed downstream of the plurality of valves. The first valve is configured to communicate fluid from the source of pressurized fluid toward the low pressure source.

Abstract: The flow of fluid to a hydraulic actuator is controlled by a valve assembly which operates in different metering modes at various points in time for energy conservation. The metering mode to use is selected in response to the hydraulic load acting on the hydraulic actuator. Specifically, the present magnitude of hydraulic load is determined and compared to first and second thresholds. Below the first threshold only a first metering mode is activated, and only a second metering mode is activated above the second threshold. A combination of the first and second metering modes is utilized when the hydraulic load is between those thresholds, wherein the metering modes are used in proportion to a proportional relationship of the hydraulic load to the first and second thresholds. Using a metering mode combination in this manner smoothes transitions between the first and second metering modes.

Abstract: A hydraulic circuit 100 having a simple structure can recover energy of fluid. Hydraulic circuit 100 comprises a boom cylinder 22, a hydraulic pump 31, a motion switchover valve 32, a hydraulic pressure regulation system 37 and a recovery pipe 36. Hydraulic pump 31 is driven by a drive source 15 so as to deliver fluid to boom cylinder 22. Motion switchover valve 32 is disposed between boom cylinder 22 and hydraulic pump 31 so as to switch a motion of boom cylinder 22. Hydraulic pressure regulation system 37 adjusts a differential pressure of motion switchover valve 32 between a delivery port 31a of hydraulic pump 31 and a suction port of boom cylinder 22 to a predetermined value. Recovery pipe 36 supplies hydraulic pump 31 with fluid from motion switchover valve 32 to which the fluid is drained from a drain port of boom cylinder 22.

Abstract: A hydraulic control device of an excavator is provided for controlling combined operation of boom-raising and swing on a slope. A swing priority valve (20) is provided on a pressured fluid supply line (8) that connects a first hydraulic pump (1) to a boom high-speed control valve (7). If an excavator performs its tasks on a slope, the swing priority valve (20) is automatically shifted under a control of an electronic controller (28) into a throttling position to thereby restrict hydraulic flow through the boom high-speed control valve (7) so that an increased amount of hydraulic flow can be supplied to a swing motor (14), thus increasing a swing operating pressure more rapidly than a boom operating pressure and consequently facilitating combined operation of boom-raising and swing on a slope.

Abstract: A priority flow rate control valve (30) distributes pressurized working oil discharged from a hydraulic pump (10) driven by an electric motor (11) to a power steering device (20) first, and distributes the residual pressurized working oil to a cargo handling device (19). The rotation speed of the electric motor (11) and the distribution ratio of the pressurized working oil of the priority flow rate control valve (30) vary depending on the operation states of these devices (19, 20). By decreasing the rotation speed of the electric motor (11) at a rate smaller than a normal decrease rate when the cargo handling device (2) stops operation in a state where the power steering device (20) and the cargo handling device (19) are in operation, a kickback in a steering wheel (7) due to a response delay of the priority flow rate control valve (30) can be prevented.

Abstract: A hydraulic system including a first pump, a second pump, an auxiliary passage, and a supplemental apparatus. The first pump is in fluid communication with a first valve, and the second pump is in fluid communication with a second valve. The auxiliary passage is in fluid communication with the first valve and the second valve. The supplemental apparatus is in fluid communication, by way of a supplemental passage, with the second valve and the auxiliary passage.

Abstract: A hydraulic system is provided for an air cart towed by a tow vehicle across a field. The hydraulic system includes a first selector valve configured to selectively communicate a first flow rate regulated by a first control valve to drive a hydraulic-driven auger mechanism at the air cart. The hydraulic system also includes a second selector valve control configured to selectively communicate a second flow rate regulated by a second control valve to drive a hydraulic-driven pressure source at the air cart. The first and second selector valves and first and second control valves are located at the tow vehicle, and are connected via a common hydraulic line to a main selector valve located at the air cart. The main selector valve is connected to selectively communicate the first hydraulic fluid flow rate to a pressure source and the second hydraulic fluid flow rate to the hydraulic-driven auger mechanism.

Abstract: A hydraulic control apparatus is provided to prevent failure that can occur due to hunting, to elevate performance of a hydraulic control valve, and to improve operation efficiency by effectively conducting bleed off. The hydraulic control apparatus can include a first change over valve group that can include a change over valve connected with a first delivery line associated with the variable capacity pump, and arranged to have load sensing function. A second change over valve group can also be provided, and can include at least one change over valve connected with a second delivery line associated with the variable capacity pump. An open and close motion valve and a compensation valve can be configured to constitute a pressure compensation flow control means connected through the second delivery line and the second change over valve group.