Abstract: A unitized valve body for use in an automatic transmission includes a plurality of valve bores and a plurality of hydraulic passages. Each valve bore is configured to receive a valve. The plurality of hydraulic passages are in fluid communication with the valve bores and arranged parallel to each other. The plurality of valve bores extend normal to the hydraulic passages and are arranged above and below the hydraulic passages.

Abstract: A hydraulic machine is provided. A boom actuator includes a large chamber and a small chamber. A recovery unit receives fluid discharged from the large chamber and then recovers energy. A recovery line connects the large chamber and the recovery unit. An accumulator is connected to the recovery line. A jack-up assist line connects the accumulator and the small chamber. A jack-up assist valve is disposed on the jack-up assist line to block flow of fluid from the accumulator to the small chamber in a first position and allow the flow of fluid from the accumulator to the small chamber in a second position. A controller controls movement of the jack-up assist valve. The controller may determine whether or not the hydraulic machine is in a jack-up condition, and when the hydraulic machine is determined to be in the jack-up condition, moves the jack-up assist valve to the second position.

Abstract: A hydraulic drive apparatus for an industrial vehicle includes a cargo-handling device, a hydraulic control device, a cargo-handling-device operating member, and a switching member. When a first operation of the cargo-handling-device operating member is performed, an open-close valve is opened to hydraulic oil flowing in a first direction to cause the hydraulic oil to bypass a throttle. When a second operation of the cargo-handling-device operating member is performed while the switching member is in a first state, the open-close valve is closed against hydraulic oil flowing in a second direction to cause the hydraulic oil to flow through the throttle. The throttle provided in a flow route of the hydraulic oil between a main control valve and the cargo-handling device reduces a flow rate of the hydraulic oil to restrict cargo handling.

Abstract: A hydraulic system is provided. The hydraulic system includes a pump, a load sense conduit, a tank conduit, a function workport, and a function control valve. The hydraulic system further includes a function poppet valve arranged between the function workport and the function control valve and having a function poppet vent passage, and a system control valve arranged downstream of the function control valve. The system control valve is biased into a first position where fluid communication between the function poppet vent passage and the tank conduit is prevented and fluid communication between the load sense conduit and the tank conduit is provided. The system control valve is selectively movable to a second position where fluid communication between the function poppet vent passage and the tank conduit is allowed and fluid communication between the load sense conduit and the tank conduit is prevented.

Abstract: A consumer control device, with which an external consumer device can be supplied with compressed air in a controlled manner, contains a compressed air maintenance unit, equipped with a proportional pressure regulating valve that can be electrically actuated, which is connectable via an outlet channel with the consumer device to be actuated. In the outlet channel an electrically controllable shut-off valve and an outlet pressure sensor are connected, both of which communicate with an internal electronic control unit, which is also supplied with information on the air flow in the outlet channel. The consumer control device can be operated according to a similarly proposed method, in that the consumer device in a normal operating phase is supplied with compressed air by the shut-off valve that is in the release position, which is regulated by a proportional pressure regulating valve adopting working mode at a working pressure value.

Abstract: A proportional motion control valve includes an electro-mechanical actuator that provides an infinitely controlled pressure setting in response to an electric signal applied to the electro-mechanical actuator. In another aspect, a proportional motion control valve includes a pilot-operated valve disposed intermediately with respect to a cage and a valve body to fluidly isolate an internal cavity of the valve body from a bore of the cage. The pilot-operated valve is subjected to a hydraulic opening force of pilot fluid that is present in the bore of the cage. A spring is disposed within the internal cavity of the valve body and arranged to subject the pilot-operated valve to a closing spring force.

Abstract: An electrohydraulic control circuit for driving a hydraulically actuated actuating element (5, 6), by means of which a segment (5.3) of a manipulator, in particular of a large manipulator for truck-mounted concrete pumps, can be adjusted in terms of its orientation, wherein there are provided an electrically driven first valve (2.4), which is connected to hydraulic working lines of the actuating element (5.6) for the drive thereof, and leak-free check valves (2.5, 2.6) provided in the working lines of the actuating element (5.6), which valves are arranged on the actuating element (5.6) or on the segment (5.3) associated with this actuating element (5.6) and can be released for the normal operation of the actuating element (5.6), wherein the release of the check valves (2.5, 2.6) is driven by an electronic control unit (ECU) separate from the first valve (2.4) and the check valves (2.5, 2.6).

Abstract: Disclosed is a power conversion system for controlling the flow of a hydraulic power signal between a power source and a hydraulic actuator having first and second ports. The power conversion system includes a control valve that is configured to selectively expose each of the first and second ports to one of the power source and a low pressure reservoir. An enabling valve having a disabled position, a first enabled position, and a second enabled position receives an input from the control valve and provides an output to the hydraulic actuator.

Abstract: A hydraulic control valve for a construction machine is disclosed, which can variably control the flow of hydraulic fluid that is supplied to a hydraulic cylinder to drive a working device. The hydraulic control valve for a construction machine includes a valve block in which an inlet port and an outlet port that communicates with the inlet port is formed, a check valve provided with a first throttling portion to permit the flow of the hydraulic fluid from the inlet port to the outlet port and to variably control the flow of the hydraulic fluid from the outlet port to the inlet port, and a spool provided with a second throttling portion to variably control the flow of the hydraulic fluid from the outlet port to the inlet port through the check valve that is opened when the second throttling portion is shifted by pilot signal pressure.

Abstract: A system for operating a single acting hydraulic cylinder includes a directional valve that has one extreme position in which a workport is connected to a tank return conduit, another extreme position where the workport is connected to a pump supply conduit, and a closed intermediate a position where the workport is disconnected from both the pump and the tank. The directional valve is pilot operated and is biased toward the one extreme position by a spring. An electrically operated primary applies pilot pressure to the directional valve alternately from the pump supply conduit and the tank return conduit. A pilot operated check valve has a first state which restricts fluid flow only from the workport toward the chamber and a second state in which fluid can flows from the chamber to the workport. The system has a pressure compensation that also provides self priming of the directional valve.

Abstract: A hydraulic valve device has a valve housing (10) in which an activating piston (16) is guided in a movable manner. The activating piston (16) is actuatable by an actuating device (18) and activates a pilot valve (20) to connect a fluid port (T) in the valve housing (10) to a fluid chamber (22) of a shut-off piston (24). The shut-off piston (24) activates at least one fluid-conducting connecting line (1, 2) of the valve device and has a fluid conducting control line (26) opening from the connecting line (1, 2) into the fluid chamber (22) of the shut-off piston (24).

Abstract: A balance having at least one adjusting device (2, . . . ) having a drive, wherein the drive of the adjusting device is configured as a fluidic drive (4, . . . ), to which pressure can be applied by a pressure source disposed outside the scales via a pressure connection.

Abstract: A hydraulic system is disclosed. The hydraulic system may have a pump, a hydraulic actuator, and first and second passages fluidly connecting the pump to the hydraulic actuator in a closed-loop. The hydraulic system may also have a control valve, and a load-holding valve configured to selectively lock movement of the hydraulic actuator. The load-holding valve may include a valve block at least partially defining a pump passage, an actuator passage, a control passage, a restricted passage connecting the actuator passage and the control passage, and a bypass passage connecting the actuator passage and the control passage. The load-holding valve may also include a valve element movable between a first position at which flow between the pump and the hydraulic actuator is blocked, and a second position at which fluid is allowed to flow between the pump and the hydraulic actuator, the valve element being spring-biased toward the first position.

Abstract: A hydraulic actuation unit for controlling the starting and stopping of hydraulic motors includes a first main circuit and a second main circuit, a first recirculation circuit and a second recirculation circuit, a counterbalancing valve, which includes a shuttle, and a first discharge channel and a second discharge channel. The shuttle includes a first check valve and a second check valve. The first check valve includes at least one first flow control element that can move from an open position to a closure position. The second check valve includes at least one second flow control element that can move from an open position to a closure position. The first and second check valves respectively are provided with first damping means and second damping means in order to slow down the passage movement respectively of the first flow control element and of the second flow control element.

Abstract: A hydraulic load control valve (10) accommodated between a hand valve (H) and a hydraulic engine (D) has got at least one proportional load control valve (E), controlled by the pump pressure independent of the flow of hydraulic fluid to the engine. The flow to the engine (D) flows via a non-return valve (12), that is prestressed to open at a pump pressure above the upper limit before a given pressure interval, within which the load control valve (E) is adjusted between completely closed and completely open position of the pump pressure.

Abstract: A poppet valve assembly includes a body and first and second check valves. The body includes opposing first and second axial end portions. The first end portion has a first circumferential surface, a first end surface, and a tapered surface, which seals with a main valve seat. The second axial end portion defines at least one metering slot. The body defines first and second internal passages. The first internal passage includes an opening in the first end surface, is in fluid communication with one of the metering slots, and has a first check valve seat. The second internal passage includes an opening in the first circumferential surface, is in fluid communication with one of the metering slot, and has a second check valve seat. The first and second check valves are disposed in the respective internal passages and are adapted for sealing engagement with the respective check valve seats.

Abstract: A fluid control valve wherein a main valve body includes: a high-pressure passage providing communication between a suction port and a sleeve in which a spool is fitted; a tank passage providing communication between a discharge port and the sleeve; a lift lock poppet located between the sleeve and a cylinder port and assuming an open position for providing communication between the sleeve and the cylinder port; a hydraulic fluid discharge passage providing communication between a back-pressure chamber provided within the lift lock poppet and the sleeve; a hydraulic fluid delivery passage located between the sleeve and the lift lock poppet; a cylinder passage located between the lift lock poppet and the cylinder port that communicates with the hydraulic fluid delivery passage when the lift lock poppet is in the open position, and a communication passage providing communication between the hydraulic fluid discharge passage and the hydraulic fluid delivery passage.

Abstract: A method for controlling fluid flow. A valve system may be kept in an open state in response to a fluid being at a selected level of pressure at any of a plurality of ports in a valve. The valve system may be for the valve, and the valve may comprise a housing, the plurality of ports on the housing, and the valve system located inside the housing. The valve system may be configured to be in a closed state when an absence of the selected level of pressure is present at all of the plurality of ports and in the open state when the selected level of pressure is present at any of the plurality of ports. The valve system may be kept in the closed state in response to an absence of the fluid being at the selected level of pressure at all of the plurality of ports.

Abstract: Methods and systems for operating a cylinder lock valve to control fluid flow to a hydraulic cylinder operating a drilling rig sub-system. The lock valve 1) allows fluid flow through the valve if pressure on a main and pilot area overcomes a closing spring force on the valve, or 2) blocks flow through the valve if a loss in charge pressure in the main and pilot area falls below the closing spring force on the valve.

Abstract: A hydraulic system for construction equipment having a float function is provided. The hydraulic system can perform ground leveling as making a boom descend due to its own weight without using hydraulic fluid that is discharged from a hydraulic pump. The hydraulic system includes a holding logic poppet mounted in the float valve to prevent an abrupt descending of the boom due to leakage of the hydraulic fluid through a flow path between the main control valve and the float valve during the operation of the boom cylinders.

Abstract: A hydraulic system has several valve sections, each having a directional valve that controls fluid flow from a pump to a hydraulic actuator. A mechanism senses a greatest pressure among the hydraulic actuators to provide a load sense pressure. One valve sections has a pressure compensation apparatus includes a pressure compensation valve that reduces fluid flow between a given directional valve and an associated hydraulic actuator in response to pressure at a control port, and a pressure regulating valve that responds to the load sense pressure and pressure in the associated hydraulic actuator by selectively applying output pressure from the pump and the load sense pressure to the control port.

Abstract: An improved double check valve for a construction machine is provided, which can greatly reduce noise and hunting phenomenon by making check valves open and close within a predetermined time difference to correspond to pressure drops that occur due to an external load when a dozer blade working device is operated.

Abstract: A hydraulic circuit for a hydraulic working machine is composed of a main pump 21, a boom cylinder 11 arranged for extension or contraction by pressure oil from the main pump 21, a directional control valve 22 for controlling flows of pressure oil to be fed from the main pump 21 to a bottom chamber 11a and rod chamber 12b of the boom cylinder 11, a control unit 23 for performing a change-over control of the directional control valve 22, a pilot pump 24, a jack-up selector valve 25 for controlling a flow of pressure oil delivered from the pilot pump 24, a flow control valve 26 connected on an upstream side of the directional control valve 22 to a meter-in port of the directional control valve 22 such that the flow control valve 26 can be changed over by the jack-up selector valve 25, and a center bypass selector valve 27 connected on a downstream side of the directional control valve 22 to a center bypass port of the directional control valve 22 such that the center bypass selector valve 27 can be changed over

Abstract: A hydraulic control valve with a monolithic body having four sides located between a top and a bottom, and all pilot ports on a body front side, valve work ports on the top side, three bores running within the body from the front side to a rear side, a spool in each bore, and a single three section spool port lock that locks two or three ports at the same time, the pilot ports present machined female quick-connect connections, with spring wet cavities being provided for mechanically operated control spools.

Abstract: A fluid power valve module has a supply port for fluid and at least one fluid power and more especially pneumatic valve able to be controlled via the control interface of the valve module for control of a fluid power instrumentality by way of power ports on the basis of the supplied fluid. There is a provision such that the valve module comprises at least one switching output integrated in its housing for output of a switching signal for switching a switching means for influencing and more especially deactivating the instrumentality.

Abstract: A hydraulic circuit having a holding valve of an external pilot pressure operation type is provided, which can make a double check valve, which is installed to prevent an actuator from being pushed due to leakage of hydraulic fluid of a main control valve, be opened by an external signal pressure being supplied to shift the main control valve. The hydraulic circuit includes a double check valve installed in a flow path between the main control valve and the hydraulic cylinder to be opened by the pilot signal pressure for shifting the main control valve, and preventing the hydraulic cylinder from being moved due to leakage of hydraulic fluid of the main control valve, and a select valve shifted to open the double check valve in response to the pilot signal pressure being supplied in accordance with the manipulation of the joystick.

Abstract: A hydraulic control apparatus 1 includes a switch valve 11, a valve support chamber 35, a flow control valve 12 movable within the valve support chamber 35, an on-off valve 13 movable within the communication path chamber 12a, and a valve control device 14. The flow control valve 12 has a communication path chamber 12a and a back pressure chamber 12d. The on-off valve 13 is capable of opening and shutting off a communication path X between a cylinder line 32 and a switch valve line 33. A restrictor is formed between the flow control valve 12 and a wall defining the valve support chamber 35. The restrictor connects the cylinder line 32 and the communication path chamber 12a to each other. The opening degree of the restrictor is changed in correspondence with movement of the flow control valve 12.

Abstract: A hydraulic control apparatus 1 includes a switch valve 11, an adjustment valve 12, and a valve control device 13. The adjustment valve 12 has a fluid chamber 15, a valve body 14, and a back pressure chamber 17. A restrictor is formed between the valve body 14 and a wall defining the fluid chamber 15 and connects the cylinder line 32 to the switch valve line 33. The opening degree of the restrictor changes in correspondence with movement of the valve body 14. When the switch valve 11 is located at a neutral position or a supply position, the valve control device 13 applies the fluid pressure in the cylinder line 32 to the back pressure chamber 17. When the switch valve 11 is located at a drainage position, the valve control device 13 applies a pilot pressure lower than the fluid pressure in the cylinder line 32 to the back pressure chamber 17.

Abstract: An apparatus for hydraulically adjusting the blades of an impeller of an axial-flow fan, comprising an adjustment cylinder that on both sides of a piston displaceably disposed in the cylinder has a first chamber and a second chamber respectively provided with a connection to control oil lines connected to four-way valves. Not only a feed line leading to one of the control oil lines, but also a return line connected to the other control oil line, is each divided into two parallel branch lines. Two redundant four-way valves are provided, each being disposed in one of the parallel branch lines. Disposed in each branch line of each control oil line, between the respective connection and the respective four-way valve, is a seat valve that closes by spring force.

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: The present invention relates to an arrangement for controlling a hydraulically driven motor, forming part of a hydraulic system in which hydraulic fluid under pressure forms a main flow through a main duct in which the motor is connected. The motor drives a varying load, and one or more valves (7) are adapted for controlling the hydraulic fluid flow through the motor on the one hand during operation and on the other hand for starting and stopping of the motor. One of the valves consists of a flow control valve (7) which is connected in the main duct (1) downstream of the outlet of the motor, and the flow control valve (7) is integrated with the motor housing (50).

Abstract: A hydraulic circuit for a hydraulic working machine is composed of a main pump 21, a boom cylinder 11 arranged for extension or contraction by pressure oil from the main pump 21, a directional control valve 22 for controlling flows of pressure oil to be fed from the main pump 21 to a bottom chamber 11a and rod chamber 12b of the boom cylinder 11, a control unit 23 for performing a change-over control of the directional control valve 22, a pilot pump 24, a jack-up selector valve 25 for controlling a flow of pressure oil delivered from the pilot pump 24, a flow control valve 26 connected on an upstream side of the directional control valve 22 to a meter-in port of the directional control valve 22 such that the flow control valve 26 can be changed over by the jack-up selector valve 25, and a center bypass selector valve 27 connected on a downstream side of the directional control valve 22 to a center bypass port of the directional control valve 22 such that the center bypass selector valve 27 can be changed over

Abstract: A hydraulic circuit controls flow of fluid between first and second ports of a hydraulic actuator, such as a cylinder/piston arrangement and each of a supply conduit and a tank return conduit. The hydraulic circuit operates in standard powered operating modes as well as powered and unpowered regeneration modes. In a powered operating mode, a conventional pressure compensated spool valve determines the velocity of the hydraulic actuator. A workport blocking valve connects one workport of the spool valve to the first port and the other workport is connected to the second port. A regeneration shunt valve is directly connected between the first and second ports of the hydraulic actuator. In a regeneration operating mode or a mix of powered and regeneration modes, a combination of the spool valve, the workport blocking valve, and the regeneration shunt valve determines the velocity of the hydraulic actuator.

Abstract: The present invention relates to an arrangement for controlling a hydraulically driven motor (2), forming part of a hydraulic system in which hydraulic fluid under pressure forms a main flow through a main duct (1) in which the motor is connected. The motor is adapted to drive a load with varying loading, and one or more valves (6, 7) are adapted for controlling the hydraulic fluid flow through the motor on the one hand during operation and on the other hand for starting and stopping of the motor. One of the valves consists of a flow control valve (7) which is connected in the main duct (1) downstream of the motor (2) and is adapted for on the one hand starting/stopping of the motor and on the other hand constant flow control of the hydraulic fluid flow through the motor.

Abstract: An object is to provide a directional control valve device and a fluid pressure cylinder device using the same that can flow a large quantity of fluid without an additional hydraulic source even if a reciprocating pump is used, and that does not add any constraint on design of the fluid pressure cylinder. A directional control valve device includes a moving valve element that can move in a reciprocating manner, a first passage for connecting the second port (PT2) with the first port (PT1) by using a part of a movement path of the moving valve element as a part of the passage when the moving valve element is in a position of a first movable end, a second passage for connecting the second port (PT2) with the third port (PT3) by using an internal passage of the moving valve element as a part of the passage when the moving valve element is in a second movable end, a spring for pressing the moving valve element toward the first movable end.

Abstract: A hydraulic system provides failure protection by incorporating an isolator adjacent a hydraulic actuator. The isolator has a first port connected to the hydraulic actuator and a second port with an electrically operated isolation valve connected between those ports. A pressure relief valve responds when pressure in the hydraulic actuator exceeds a given level by relieving pressure thereby enabling the isolation valve to open without application of electricity and release the pressure in the hydraulic actuator. A control valve assembly is remote from the hydraulic actuator and connected to the second port for metering flow of fluid between a source and the hydraulic actuator.

Abstract: Control device 1 having a changeover valve 5, a pump 4 delivering operating medium, in particular a motor-operated pump or a hand pump, connection devices for connecting the control device 1 to at least two tools, in particular a first lifting cylinder 2 and a second lifting cylinder 3 or the like, the changeover valve 5 being operable in particular by hand; wherein a) the changeover valve 5, when the operator lets go of it, can be brought automatically into a basic position in which no pressure build-up in the region of the tools is possible, b) a control valve 7 is provided between the changeover valve 5 and the tools, and c) the control valve 7 can likewise be operated by hand by an operator.

Abstract: A hydraulic stabilizing device for vehicles having an actuator which can be acted on in opposite directions comprises a switching device, which is formed by a directional control valve, and, in series with the switching device, a switching apparatus, which is formed by two separate directional control valves which are connected in parallel and correspondingly have a blocking position and different pass-through positions.

Abstract: Cushion chambers (8) disposed in the vicinity of both ends of a hydraulic cylinder (1) to throttle inflow or outflow of an operating oil caused by a piston (5) moving close to a piston stroke end, pressure sensors (16, 17) to detect pressures in the cushion chambers (8), and a control valve (13) disposed in a passage to supply/drain the operating oil to and from oil chambers (6, 7) of the hydraulic cylinder (1) for varying a flow amount of the operating oil are provided. A controller (9) varies an opening degree of the control valve (13) within a piston stroke end range based upon outputs of the pressure sensors (16, 17), adjusts a cushion pressure and controls a moving speed of the piston (5). Thereby deceleration degrees of the piston (5) can be freely adjusted within the piston stroke end range based upon a change of the operating conditions of the hydraulic cylinder (1).

Abstract: A hydraulic system provides failure protection by incorporating an isolator adjacent a hydraulic actuator. The isolator has a first port connected to the hydraulic actuator and a second port with an electrically operated isolation valve connected between those ports. A pressure relief valve responds when pressure in the hydraulic actuator exceeds a given level by relieving pressure thereby enabling the isolation valve to open without application of electricity and release the pressure in the hydraulic actuator. A control valve assembly is remote from the hydraulic actuator and connected to the second port for metering flow of fluid between a source and the hydraulic actuator.

Abstract: An hydraulic unit includes a hydraulic cylinder, and a piston retained in the hydraulic cylinder, wherein the piston can be moved from a first end position located at one end of the hydraulic cylinder to a second end position located at the opposite other end position of the hydraulic cylinder. The hydraulic cylinder is hydraulically connected with a delay unit which is equipped with an auxiliary cylinder containing an auxiliary piston, with which a movement of the piston can be delayed in a middle section located between the first and the second end position. The auxiliary cylinder has a first and a second opening for incoming and outgoing hydraulic oil. In order to precisely set an attenuation point, a throttle valve provided on the auxiliary cylinder or piston be connected in the flow path.

Abstract: The invention relates to a method and an apparatus for controlling an actuator (7, 8) of a crane by control means (10) in a situation where the lifting power of the actuator (7, 8) of the crane is increased temporarily by an auxiliary valve arrangement (11). In the invention, control properties of the actuator (7, 8) are changed when the temporarily increased lifting power is applied to limit the speed of the actuator (7, 8).

Abstract: What is disclosed is a hydraulic control arrangement for controlling a consumer, comprising a continuously adjustable directional control valve, an individual pressure compensator associated to the latter, as well as shut-off blocks arranged downstream from the directional control valve. In accordance with the invention, in the case of a insufficient supply of the consumer the pressure compensator is subjected not to the pressure in the supply (load pressure) but to a higher pressure, so that the control pressure difference at the supply control edge is raised.

Abstract: A boom-holding control device brings an excavator boom into a holding condition or a release condition. The device includes a boom-holding valve provided on a fluid pressure line for preventing boom deadweight-caused drainage of a hydraulic flow from a boom cylinder to thereby keep a boom in a holding condition, a boom release valve for releasing the boom from the holding condition in response to at least one of a boom-down pilot signal pressure supplied from a boom cylinder remote control valve and a travel signal pressure fed from a travel control operator-interface device and a solenoid-actuated changeover valve provided on a travel signal line for selectively opening and blocking off the travel signal line. The changeover valve is normally kept in a closing position and will be shifted to an opening position at the time of simultaneous activation of a travel selection switch and a boom release switch.

Abstract: A hydraulic circuit includes a control valve that controls flow of pressure oil from a hydraulic source to work hydraulic cylinders, an operating device that issues a command for drive of the control valve, valve devices each comprising a check valve, each provided in correspondence to one of the plurality of work hydraulic cylinders to allow and prohibit outflow of pressure oil from a work hydraulic cylinder, a commanding device that outputs a command allowing or a command prohibiting extension/contraction for each of the work hydraulic cylinders and a control device that controls each of the valve devices to allow outflow of pressure oil from the work hydraulic cylinder by invalidating a check valve function in response to the command for allowing extension/contraction and to prohibit outflow of pressure oil from the work hydraulic cylinder with the check valve in response to the command for prohibiting extension/contraction.

Abstract: Disclosed is a hydraulic control valve having a holding valve with improved response characteristics.

Abstract: Disclosed is a flow control apparatus for construction heavy equipment capable of maintaining constant set flow rate regardless of changes in load pressure and pump pressure. The flow control apparatus is composed of a control valve, a flow control valve, and a load check valve. The control valve has a parallel passage, a housing provided with a first load passage and a second load passage, and a control spool provided to be movable in the housing. The flow control valve having a logic check valve provided to be openable between the first load passage and the parallel passage, and a logic control valve controlling a flow rate supplied to a back pressure chamber of the logic check valve. The load check valve is provided between the second load passage and the parallel passage to restrict backflow from the second hydraulic cylinder.

Abstract: In the present invention, it is possible to supply hydraulic fluid by the amount needed in an option tool even when a combined work is performed by engaging an option tool having a different operation pressure to a work apparatus. The hydraulic circuit for an option tool of heavy equipment comprises a poppet valve which is openably and closably installed in a flow path of a supply side of the option tool spool, a first spool which is installed in a flow path between the poppet valve and the option tool spool and has an opening portion adapted to maintain a constant pressure difference when the first spool is switched by pilot pressure discharged from the pilot pump, and a second spool which is installed in a down stream side of the poppet valve and is switched when an over load occurs due to an over pressure exceeding the degree set in the option tool for thereby closing the poppet valve.

Abstract: There is provided a hydraulic circuit for an option apparatus of heavy equipment using a boom confluence spool, comprising a poppet valve installed at a flow path of a supply side of a spool for the option apparatus, a boom confluence spool that controls the flow rate supplied to the option apparatus and work apparatus and is installed at a direct upstream of the spool of the option apparatus, a second electromagnetic proportion reducing valve that is installed at a flow path between the pilot pump and the boom confluence spool and outputs a secondary pressure in response to an electric signal from the controller and controls the boom confluence spool, and a first spool that is installed at a downstream of the poppet valve and is switched when a pressure difference between upstream and downstream of the boom confluence spool is larger than a set value.

Abstract: A fluid system is provided wherein two different fluid circuits are connected in parallel with a single source of pressurized fluid and the two fluid circuits can function together even when one of the loads is lighter than the other. This is accomplished by having the lightly loaded circuit having a directional control that when operated in one of its operative positions the flow from the rod end of the cylinder is directed through the directional control valve and combined with the supply flow being directed to the head end of the cylinder. With the other heavier loaded circuit also being actuated, the pressure of the fluid from the rod end of the fluid cylinder is equalized with the pressure of the heavier loaded circuit. Consequently, the speed of the heavier loaded circuit does not stall or slow down relative to the lightly loaded circuit.