Abstract: A fluid circuit is provided to independently control the flow of fluid into and out of each end of an actuator. This is accomplished by having two different independently controlled valves controlling the flow of fluid into and out of one end of the actuator and by having two other independently controlled valves controlling the flow of fluid into and out of the other end of the actuator. Regeneration of the fluid flow from one end of the actuator to the other end of the actuator is provided by blocking the exhaust flow of fluid to the reservoir by one of the independently controlled valves and redirecting the flow across the other of the independently controlled valves to join with the flow of the pump that is being directed to the other end of the actuator. This arrangement permits a portion or all of the fluid from one end of the actuator to be regenerated to the other end of the actuator.

Abstract: In an excavating/slewing work truck, the boom falls freely at the time of lowering operation without requiring any power but the flow rate of a pump increases excessively when the speed is balanced with other acutuators and power loss is inevitable for enhancing the operability. In order to eliminate this inconvenience, a first oil path (41) connecting a bottom side cylinder port (CB) and a tank port (T2), a second oil path (42) connecting a pump port (P2) and a rod side cylinder port (CR), and a third oil path (43) connecting a pump port (P1) and a tank port (T1) are provided, respectively, with first, second and third restrictors (61), (62) and (63) at the boom down position of a change-over valve (51) for the boom cylinder of an excavating/slewing work truck, wherein the first restrictor (61) restricts by such an amount as the work machine lowers gravitationally an the second restrictor (62) restricts by such an amount as the pressure on the boom side is not exceeded.

Abstract: The present invention relates to a hydraulic circuit for a boom cylinder combination having a float function which is capable of implementing a leveling work in such a manner that a leveling work is performed by lowering a boom based on its self-weight without using an operation oil discharged from a hydraulic pump using an excavator during a leveling work which includes a first inner path which is formed in one side of the boom cylinder combining spool and connects a hydraulic pump and a boom cylinder large chamber in a switching mode, a second inner path which is formed in the other side of the boom cylinder combining spool and connects an operation oil from the hydraulic pump to a hydraulic tank in a switching mode, and a third inner path which is formed in the other side of the boom cylinder combining spool and combines the operation oils from the small chamber and large chamber of the boom cylinder in a switching mode and connects the same to the hydraulic tank.

Abstract: A hydraulic control apparatus for controlling a hydraulic cylinder for an implement selectively mounted to a work vehicle. The apparatus includes a hydraulic power source, a four-position changeover control valve disposed between the hydraulic cylinder and the hydraulic power source, and an operational mechanism for operating the four-position changeover control valve. The four-position changeover control valve has a first position for moving a rod of the hydraulic cylinder in one direction, a second position for stopping the rod of the hydraulic cylinder, a third position for moving the hydraulic cylinder rod at a high speed in the other direction with using a function of a regenerative circuit and a fourth position for moving the hydraulic cylinder rod in the other direction at a standard speed without using the function of the regenerative circuit, in the mentioned order.

Abstract: An insert or cartridge that fits into a cavity in a valve body provides a check valve function and an anti-cavitation function and a pressure relief function. This insert is substantially circular and has an internal cavity with a valve assembly that has two pairs of valve seats, one pair of valve seats providing the anti-cavitation function and the other pair of valve seats providing the pressure relief function. The outside of the insert itself engages with a sealing surface in the cavity in the valve body to provide the check valve function.

Abstract: The present invention relates to a control system and method for a hydraulic working machine characterized by having a construction wherein a flow discharge control valve is disposed in a discharge-side pipe line of a main flow control valve, the amount of operation of an operating lever is converted to a pilot pressure by a remote controlled valve, the pilot pressure is then input to a controller and is calculated into a pressure change speed as operation speed, in a pressure change speed calculator, further, the operation speed is calculated into an electromagnetic valve current in an electromagnetic valve current calculator, then the electromagnetic proportional valve current is output to an electromagnetic proportional valve from a command unit, and the degree of opening of the discharge flow control valve is controlled with a secondary pressure in the electromagnetic proportional valve.

Abstract: A hydraulic control circuit for a hydraulic cylinder is described for the raising and lowering of a boom on a telescopic loader. First and second chambers of the hydraulic cylinder are connected to a control valve over first and second supply lines and are selectively connected to either a hydraulic pressure source or to a hydraulic reservoir. The circuit includes on-off valves for controlling the flow through a first hydraulic line extending between the first chamber of the cylinder and the hydraulic reservoir, and through a second hydraulic line extending between the second chamber and the hydraulic reservoir in such a way that a floating position can be provided. Furthermore, a load-holding valve arrangement is provided in the first supply line at a location between the control valve and the first chamber of the cylinder.

Abstract: A hydraulic valve system (1) has a supply connection arrangement, having a high-pressure connection (P) and a low-pressure connection (T), a working connection arrangement, having two working connections (A, B), which can be connected with a hydraulic motor (2), and a directional valve (4) between the supply connection arrangement (P, T) and the working connection arrangement (A, B), which is connected with the working connection arrangement (A, B) via working lines (17, 18), in which are arranged check valves (21, 22), which can be opened by means of pressure.

Abstract: A hydraulic control apparatus for controlling a hydraulic cylinder for an implement selectively mounted to a work vehicle. The apparatus includes a hydraulic power source, a four-position changeover control valve disposed between the hydraulic cylinder and the hydraulic power source, and an operational mechanism for operating the four-position changeover control valve. The four-position changeover control valve has a first position for moving a rod of the hydraulic cylinder in one direction, a second position for stopping the rod of the hydraulic cylinder, a third position for moving the hydraulic cylinder rod at a high speed in the other direction with using a function of a regenerative circuit and a fourth position for moving the hydraulic cylinder rod in the other direction at a standard speed without using the function of the regenerative circuit, in the mentioned order.

Abstract: A hydraulic system for raising and lowering aircraft landing gear (11, 12) includes an actuator (18) which is extendible and retractable to operate the landing gear, the actuator (18) including a movable member (19) in a casing (20), the movable member (19) being moved relative to the casing (20) in a first direction to extend the actuator (18) when fluid under pressure is supplied to a first side (22) of the movable member (19) while fluid is exhausted from a second side (23) of the movable member (19), and the movable member (19) being moved in a second direction to retract the actuator (18) when fluid under pressure is supplied to the second side (23) of the movable member (19) while fluid is exhausted from the first side (22) of the movable member (19), and there being selector valve (25) selectively to supply pressurized fluid to the first (22) or second (23) side of the movable member (19), and a check valve (40) to permit exhausted fluid from at least one of the first (22) and second (23) sides of the

Abstract: An insert or cartridge that fits into a cavity in a valve body provides a check valve function and an anti-cavitation function and a pressure relief function. This insert is substantially circular and has an internal cavity with a valve assembly that has two pairs of valve seats, one pair of valve seats providing the anti-cavitation function and the other pair of valve seats providing the pressure relief function. The outside of the insert itself engages with a sealing surface in the cavity in the valve body to provide the check valve function.

Abstract: A fluid system includes first and second control valves that control fluid communication with first and second actuators. The first control valve may combine fluid flow from a second end port of the first actuator with fluid flow from a pressurized fluid source when providing a supply of fluid to a first end port of the first actuator. The first and second control valves include first and second signal ports in fluid communication with the supply of fluid to the first and second actuators. A resolver outputs a resolved signal pressure equal to the greater of a first signal pressure output by the first signal port and a second signal pressure output by the second signal port. A compensator in fluid communication with the first control valve and the first actuator controls fluid flow from the first control valve to the first actuator based on the resolved signal pressure.

Abstract: By means of a method and a device for controlling a lift cylinder (2) of working machines, wherein the hydraulic oil from the pressure cylinder space (12) is forced via a control element (3) into the suction cylinder space (11) during lowering by an external force, it is possible in particular to achieve automatic changeover between normal operation and an operating condition in which an additional force in vertical direction can be exerted.

Abstract: A fluid control system includes a pump, a tank, and an actuating cylinder having a rod end chamber and a head end chamber. The fluid control system also includes an independent metering valve arrangement and a pressure sensor configured to sense a pressure of fluid at the head end chamber. A controller communicates with the valve assembly and the pressure sensor. The controller selectively actuates at least one valve of the independent metering valve arrangement based on the sensed pressure at the head end chamber and a mode of operation of the control system.

Abstract: A fluid circuit is provided to independently control the flow of fluid into and out of each end of an actuator. This is accomplished by having two different independently controlled valves controlling the flow of fluid into and out of one end of the actuator and by having two other independently controlled valves controlling the flow of fluid into and out of the other end of the actuator. Regeneration of the fluid flow from one end of the actuator to the other end of the actuator is provided by blocking the exhaust flow of fluid to the reservoir by one of the independently controlled valves and redirecting the flow across the other of the independently controlled valves to join with the flow of the pump that is being directed to the other end of the actuator. This arrangement permits a portion or all of the fluid from one end of the actuator to be regenerated to the other end of the actuator.

Abstract: An insert or cartridge that fits into a cavity in a valve body provides a check valve function and an anti-cavitation function and a pressure relief function. This insert is substantially circular and has an internal cavity with a valve assembly that has two pairs of valve seats, one pair of valve seats providing the anti-cavitation function and the other pair of valve seats providing the pressure relief function. The outside of the insert itself engages with a sealing surface in the cavity in the valve body to provide the check valve function.

Abstract: A hydraulic recovery system for a construction machine comprises a recovery valve for supplying at least a part of a hydraulic fluid from a rod-side line, through which the hydraulic fluid is drained from a rod-side hydraulic chamber of an arm hydraulic cylinder, to a bottom-side line through a variable throttle, and a throttle valve for returning the remaining part of the hydraulic fluid, which is not recovered, from the rod-side line to a hydraulic reservoir through a variable throttle. Opening areas of those variable throttles are controlled depending on an arm flow rate supplied from hydraulic pumps to the arm hydraulic cylinder.

Abstract: An actuation arrangement for displaced components on vehicles, particularly trunk lids, convertible tops, engine hoods or the like, includes at least one supply line for the pressurized medium and one essentially non-pressure connection line to a reservoir for the working medium or a pump arrangement being functionally of the same kind, at least one preferably hydraulic working cylinder, and at least one control valve controlling the supply of a working medium in at least one working chamber of the working cylinder.

Abstract: A hydraulic recovery system for a construction machine comprises a recovery valve for supplying at least a part of a hydraulic fluid from a rod-side line, through which the hydraulic fluid is drained from a rod-side hydraulic chamber of an arm hydraulic cylinder, to a bottom-side line through a variable throttle, and a throttle valve for returning the remaining part of the hydraulic fluid, which is not recovered, from the rod-side line to a hydraulic reservoir through a variable throttle. Opening areas of those variable throttles are controlled depending on an arm flow rate supplied from hydraulic pumps to the arm hydraulic cylinder.

Abstract: A hydraulic drive unit is disclosed which can prevent the occurrence of cavitation at the time of turning OFF of a hydraulic motor without greatly modifying the circuit configuration and the entire system and which, as a result, can improve the deceleration feeling of the hydraulic motor and prevent the occurrence of a low noise.

Abstract: The present invention is concerned with a work machine having a telescopic arm coupled to the front thereof. This arm is used for seating various sorts of frontal attachments and is raised and lowered by means of a hydraulic piston-cylinder unit. Now in order to ensure that an installed frontal attachment always rests on the ground with a pre-selected force, use is made of a pilot controlled seat valve and an adjustable pressure regulating valve which ensure that a constant pressure is maintained in the cylinder chamber formed below the base of the piston in the piston-cylinder unit when a constant supply of oil is fed to this part of the cylinder chamber. In consequence, this means that the installed frontal attachment always rests on the ground with one and the same force independently of whether the ground is flat or uneven. The frontal attachment thus precisely copies the contour of the ground at all times.

Abstract: A hydraulic system for a motor vehicle having a convertible top (2) which can be folded back has a convertible-top control system (1) and further hydraulic control devices (3, 4) which can be activated by a common hydraulic pump (6). In hydraulic lines (8, 9) leading to the convertible-top control system (1) there are arranged hydraulic valves (13, 14) which enable optional operation of the convertible-top control system (1) or of the further control devices (3, 4). Because of this, the hydraulic system turns out to be particularly simple structurally.

Abstract: A recovery check valve 26 and a piston valve 27 are axially slidably disposed within a spool 2 in coaxial relation. An axial fluid passage 32 is formed within a cylindrical portion 27a of the piston valve 27, and a seat portion 33 for the recovery check valve is formed at an open end of the cylindrical portion 27a. The cylindrical portion 37a of the piston valve is formed with a hole 36 through which a hydraulic fluid in the fluid chamber 32 is introduced to a bridge passage 21 when the spool 2 is operated so as to introduce a hydraulic fluid from a hydraulic pump to the bottom side of a hydraulic cylinder. Fluid passages 40, 31 are formed within the spool so that a hydraulic fluid in the bridge passage 21 is introduced to the closed end of the piston valve through the fluid passages when the spool is operated in the opposite direction. With such a structure, the size of the valve apparatus can be set to the same size as the directional control valve not provided with the recovery check valve.

Abstract: An improved method and apparatus utilizing regenerative hydraulic control principles are disclosed. A regenerative valve is operatively connected in a hydraulic control circuit with a primary hydraulic cylinder for controlling the speed at which the piston and attached rod of the hydraulic cylinder operatively move. The regenerative valve and control apparatus and method control speed of operation of the primary hydraulic cylinder when moving in both its power and its return strokes, to significantly reduce the cylinder's cycle time. A unique regenerative valve configuration enables significantly enhanced volumes of hydraulic fluid to be transferred during a regeneration cycle between the rod and blind sides of the hydraulic cylinder.

Abstract: A fluid regeneration circuit for a hydraulic system having at least one hydraulic actuating cylinder associated therewith, the present circuit including a control valve connected in fluid communication with the actuating cylinder for controlling the operation thereof, a regeneration valve connected in fluid communication with the control valve and with the head and rod end portions of the cylinder, a position sensor coupled to the actuating cylinder for sensing the position of the piston within the cylinder during movement thereof, and a controller coupled to the position sensor, the control valve and the regeneration valve for controlling fluid flow to and from the actuating cylinder.

Abstract: A meter-out flow control valve is provided that is compact and possesses a regenerative function. A poppet valve 70 for establishing and blocking fluid communication between a first actuator port 73-1 and a tank port 74 is urged by a spring 71 into a pressure contact with a seat 72. The poppet valve 70 is moved away from the seat 72 under pressure in a first pressure receiving chamber 80-1. A cylindrical valve 103 is fitted with the poppet valve 70 to provide a regenerative switching valve 101 that may establish and block fluid communication between the first actuator port 73-1 and a first regenerative port 100. A meter-out flow control valve having a poppet valve 70 and a cylindrical valve 103 fitted together is thus provided that is compact in form and yet capable of regenerating pressure fluid in a first actuator port 73-1 into a first regenerative port 100.

Abstract: A fluid control system including a control valve providing a simple, easy to use regeneration capability in association with a pump, a tank, and a double acting actuator having a first actuating chamber and a second actuating chamber. The control valve has a first actuating chamber port connected to the first actuating chamber, a second actuating chamber port connected to the second actuating chamber, a tank port connected to the tank, a first pump port and a second pump port. The control valve includes a connecting passage connecting the first pump port and the second pump port to the pump, and is operable in a first position to allow fluid flow from the pump through the first pump port and the first actuating chamber port to the first actuating chamber and fluid flow from the second actuating chamber through the second actuating chamber port and the tank port to the tank.

Abstract: Thick matter and solids are conveyed together and substantially continuously through a conveyor pipeline. The thick matter is forced by a conveyor piston driven by a piston pump from a feed container into a conveyer cylinder. A forward face of the piston has a cutting crown with a cutting edge cooperating with an annular cutting ring to cut off solids projecting beyond an inlet in the conveyer pipeline.

Abstract: A device is disclosed for controlling a double action working cylinder (10) having a piston (11) with a piston rod (12) on a single side by means of a multiple-way valve (19), in which the available forces are to be fully applied at the beginning of the extension of the piston rod (12) and the differential motion becomes effective after a fixed distance of displacement of the piston. The multiple-way valve (19) has seven connection openings (T1, A1, P, B1, A2, T2, B2) for driving the predetermined functions, which can be driven in the individual working position by means of a valve piston (20) provided with seven control edges (1-7).

Abstract: A device is disclosed for controlling a double-effect working cylinder (10) having a piston (11) with a piston rod (12) on a single side by means of a multiple-way valve (19), in which the available forces are to be fully applied in the extended end position of the piston rod (12). The multiple-way valve (19) has seven connection openings (P, A1, A2, B1, B2, T1, T2) for controlling the predetermined function, which can be driven in the individual working position by means of a corresponding valve piston (20).

Abstract: Disclosed is an apparatus for a derrick, including hydraulic piston/cylinder arrangements for raising and lowering a yoke travelling on guide rails attached to the derrick. A hydraulic system having different modes of operation is provided for the operation of the piston/cylinder arrangements. The hydraulic system can operate in a normal mode for raising or lowering the yoke and in other modes by interconnecting upper and lower chambers of the piston/cylinder arrangements and utilizing a differential surface area of the piston exposed to the two chambers for rapidly raising or lowering the yoke.

Abstract: An oil-pressure cylinder in a crushing device is connected to a crushing jaw via a pivot shaft so that the crushing jaw can open and close. The extension of oil-pressure cylinder causes the crushing jaw to close and crush the object to be crushed. Oil-pressure cylinder has a piston with a greater pressure-receiving area on the head side than on the rod side. An acceleration valve serves to switch the extension/retraction operations of the oil-pressure cylinder. During a rod unloaded interval, beginning when the crushing jaw starts to close and ending when the crushing jaw comes into contact with the object to be crushed, the acceleration valve makes communication between a head-side port and a rod-side port in the cylinder continuous, while the oil path from the rod side to a tank is blocked. The oil from the rod side is made to flow to the head side.

Abstract: Thick matter and solids are conveyed together and substantially continuously through a conveyor pipeline. The thick matter is forced by a conveyor piston driven by a piston pump from a feed container into a conveyer cylinder. A forward face of the piston has a cutting crown with a cutting edge cooperating with an annular cutting ring to cut off solids projecting beyond an inlet in the conveyer pipeline.

Abstract: A hydraulically powered tool having a motor, a pump, and a hydraulic directional flow control valve. The valve has a frame and a rotatable spool with flow channels. The valve is provided as a four position, six way valve to provide four operational conditions for the tool including NEUTRAL, DRILL, RETRACT and FAST FORWARD.

Abstract: The present quick drop valve control provides both quick drop and float functions by moving a quick drop valve to a position interconnecting the drop and lift sides of a pair of lift cylinders when a directional control valve reaches a predefined position. The quick drop function valve is established by simultaneously energizing a first solenoid valve to communicate a shift end of the quick drop valve with a resolved pressure port of a resolver connected to the drop and lift sides and a first solenoid of a second solenoid valve to communicate a spring end of the quick drop valve with the drop sides so that the quick drop valve moves to the interconnecting position combining fluid expelled from the lift sides with fluid going to the drop side from a pump.

Abstract: A variable-regeneration directional control valve for construction vehicles is disclosed. The control valve has a pressure control means for controlling the opposite pressure caused by elasticity of a valve spring. The opposite pressure acts on one end of a regeneration switching spool, while a self pressure (hydraulic pressure of pressurized fluid output from a pump) acts on the other end of the regeneration switching spool and thereby moves the spool. In the preferred embodiment, the means is a pressure control piston, which is provided on the end of the valve spring. The pressure control piston receives an outside control signal through an electronic proportional control valve and thereby continuously moves. The electronic proportional control valve outputs pressurized fluid in proportion to a current amount of the outside control signal.

Abstract: A directional control valve unit includes a first actuator port connected to a raising side chamber of a working machine cylinder. In addition, a second actuator port is connected to a lowering side chamber of the working machine cylinder. A regeneration passage makes the second actuator port communicate with a regeneration port through a check valve. A main spool is adapted to supply a pressure oil to the second actuator port and to make the first actuator port communicate with a tank port and the regeneration port by moving the main spool in one direction. The directional control valve unit also includes a switching device for switching the maximum moving distance of the main spool in the one direction in a plurality of stages.

Abstract: In order to improve speed controllability both in low and high speeds, thereby stabilizing the speed of a hydraulic cylinder, both the flow-in amount of hydraulic operating fluid flowing from a hydraulic source to the hydraulic cylinder having a run-around circuit and the flow-in amount of hydraulic operating fluid flowing from the run-around circuit to the hydraulic cylinder are controlled simultaneously by a control valve, so that the speed of the hydraulic cylinder is controlled.

Abstract: Cylinder drift resulting from internal leakage of a recycling circuit, which recycles oil returned from the arm cylinder of a hydraulic shovel to the hydraulic supplying end, is reduced by an hydraulic circuit which includes a recycle valve attached directly to a control valve. When working fluid is returned from a rod chamber of arm cylinder into the control valve, the recycle valve recycles a part of the working fluid through a recycle selector valve to the hydraulic supplying end. A pilot operated check valve is disposed in the oil channel that connects the rod chamber and recycle selector valve together. When extending arm cylinder of the hydraulic shovel, pilot pressure from control valve shifts a pilot selector valve in such a direction as to open pilot operated check valve. When control valve is at the neutral position, pilot selector valve is shifted back to the return position and closes pilot operated check valve so that return oil of arm cylinder is prevented from working on recycle selector valve.

Abstract: A return fluid regeneration device for construction vehicles is provided. The regeneration device includes an orifice disposed on a return-side internal line of a directional control valve of an actuator. A regeneration line is arranged between the return-side internal line and a return line extending to a return tank and is further selectively connected to the return-side internal line during a weight operation of the actuator. A regeneration branch line is branched from the return-side internal line and is connected to a supply-side internal line of the valve, thus selectively feeding the return fluid from the return-side internal line to the supply-side internal line and thereby regenerating the return fluid. First and second check valve are also provided on the regeneration line and branch line, respectively. The regeneration device regulates the moving speed of the actuator while simultaneously preventing the generation of high pressure in a fluid supply line.

Abstract: A hydraulic actuator includes three cylinder spaces: a first cylinder space (6) located between a ring piston and a cylinder; a second cylinder space (7) between the ring piston and an auxiliary piston inside a hollow piston rod connected to the ring piston; and the third cylinder space (8) formed between the ring piston, the cylinder and the hollow piston rod.

Abstract: The use of an accumulator attached to a chamber of a cylinder allows for the reduction in pressure spikes in constant force hydraulic control systems. Constant force hydraulic control systems often use a differential pressure valve that may have a reaction time of up to one second. By using the accumulator, pressure spikes which might have occurred in the past can be smoothed out and reduced, thus preventing damage to a workpiece or agricultural product. Additionally, by using two cylinders of different sizes, in which one of the cylinders has a barrel end with the approximately the same area as the rod end of the larger cylinder, coordination of devices attached to the cylinders can be maintained without a mechanical link when the hydraulic control system is in a manual mode.

Abstract: A motor cavitation prevention device for hydraulic systems is disclosed. The device exerts no influence upon return fluid of any actuators other than the hydraulic motor thereby preventing undesired pressure loss of the return line. The device has valve means installed in a given position of the return line such that the return fluid of the motor necessarily passes the check valve prior to returning to a return tank but the return fluid of the other actuators does not pass the check valve, and a feedback line for feeding the return fluid of the motor back to the motor in the ease of generation of the pressure above tank in the return line, one end of which feedback line is connected to the return line at the front of the check valve but the other end of which feedback line is connected to the motor.

Abstract: A control valve having a regeneration function, including a hollow valve body, a plurality of spaced ports provided at the valve body, the ports including a pump port, an actuator port, a regeneration port and a tank port, a hollow main spool movably disposed in the valve body, a regeneration spool movably disposed in the main spool and adapted to be moved by a flow of fluid delivered from a pump through the pump port, a fluid passage provided at the main spool and adapted to communicate the actuator port and the tank port together, the fluid passage being opened or closed by the movement of the regeneration spool, whereby as the regeneration spool is moved by the fluid flow delivered from the pump, a part, to be fed to the tank port, of a flow of fluid emerging from the actuator port is increased, while a part to be fed to the regeneration port is correspondingly decreased.

Abstract: A hydraulic fluid-loss control valve for preventing uncontrolled load movement in the event of a fluid loss such as from the bursting of a hose and further for allowing an operator to move the load in a controlled way despite the fluid loss. The control valve is situated between a conventional main spool valve and a piston/cylinder hydraulic actuator which powers the load. The control valve has a spool sliding reciprocally in a bore. Grooves and lands on the spool combine with passages in the control valve body to provide alternate fluid paths between a pump and the actuator and between the actuator and a reservoir. Fluid can flow from a controlled chamber of the actuator only when the spool is in a position which provides a fluid path. A passage within the spool provides fluid communication between an input fluid flow and a chamber at one end of the spool. A second passage within the spool provides fluid communication between an actuator chamber and a chamber at the other end of the spool.

Abstract: Disclosed is a stiffness enhanced electrohydrostatic actuator for aircraft flight controls which eliminates the requirement for a central hydraulic system. The actuator replicates the blocked port condition of the central hydraulic system to provide static and dynamic stiffness by the use of valves having a first sleeve and spool and a second sleeve and spool disposed on either side of a valve seat with the first spool biased towards the valve seat.

Abstract: A hydraulic piston machine is disclosed, having a cylinder drum and a control plate, which control plate has at least one high-pressure "kidney" and at least one low-pressure "kidney" and also a contact surface against which the cylinder drum bears in operation, at least the contact surface being provided with a friction-reducing layer. It is desirable for such a machine to have better operational behavior and a longer service life. For that purpose, the contact surface in the region of the low-pressure kidney has a recessed region forming a gap between the cylinder drum and the control plate.

Abstract: Fluid regeneration circuits are useful for filling expanding sides of a hydraulic cylinder with fluid being exhausted from the other side. The currently available circuits pass the excess fluid not needed for filling the expanded side of the cylinder through the directional control valve to the tank such that the directional control valve must be actuated for the regeneration valve assembly to function. A combined meter-out and regeneration valve assembly of the present invention is used in a hydraulic system having a directional control valve for metering in pump to cylinder fluid flow and includes a meter-out valve to meter-out cylinder to tank fluid flow from a head end actuating chamber. The fluid passing through the meter-out valve passes through an exhaust conduit to a tank bypassing the directional control valve. This permits the meter-out valve to be used independently of the directional control valve to retract a hydraulic cylinder.

Abstract: The present invention relates to a hydraulic control valve in a construction machine, wherein a parallel port (20b) and bridge ports (20c) which are provided in a valve body (40) of the hydraulic control valve are formed by machining, cylinder drain ports (20e) are limited to through holes opened on opposite sides of the valve body (40) and caused to join together in a tank port block (39). Accordingly, when the valve body (40) is manufactured by casting, only a main core (19) forming a spool port (13h) need be used, so that the control valve can be made compact in size. Furthermore, portions (20', 21') where a passage of a neutral port of the core has heretofore been formed by jointing the main core (19) to joint cores (20, 21) are formed by machining a manual operation process of jointing can be dispensed with and the working efficiency and casting accuracy are improved.

Abstract: A hydraulic valve assembly comprises a valve body defining first and second valve receptacle bores, a fluid pump, a first fluid passage communicated with the fluid pump, a second fluid passage communicated with a hydraulic load, and a third fluid passage communicated with a fluid reservoir. A first valve sub-assembly including a sleeve enclosing a first valve mechanism therein is disposed within the first valve receptacle body for selectively permitting and blocking introduction of the pressurized working fluid. Also, a second valve sub-assembly including a sleeve enclosing a second valve mechanism therein is disposed within the second valve receptacle bore for selectively establishing and blocking fluid communication between the second and third fluid passage means.