Abstract: A flow controller that changes the flow rate of air exhausted from an air cylinder in mid-stroke includes a first switching valve displaced from a first position to a second position under the effect of pilot air, and causing one port of the air cylinder to communicate with a first channel at the first position, exhausting air exhausted from the one port of the air cylinder while reducing the flow rate of the air using a first regulating valve at the second position. Since the pilot air is taken into the first switching valve from a second channel in a system different from the system of the first channel, a second regulating valve can be adjusted without being affected by the degree of opening of the first regulating valve.

Abstract: A control valve has a first and second pilot chambers facing both ends of a spool, a signal pressure passage configured to lead a pilot pressure of the first and second pilot chambers to another device other than the control valve as a signal pressure, a communication groove configured to allow the first pilot chamber and the signal pressure passage to communicate with each other, a communication hole configured to allow the second pilot chamber and the signal pressure passage to communicate with each other, and a check valve interposed in the communication hole, and the check valve has a poppet portion configured to open or close the communication hole and a spacer portion configured to regulate a moving amount of the poppet portion in an open direction, and the control valve further includes a movement regulating portion configured to regulate movement of the spacer portion toward the poppet portion.

Abstract: A hydraulic valve device includes a first and a second engine port to a double acting hydraulic motor, a pump, a hand valve which has two open positions, wherein in the first open position the pump is fluidly connected to the first engine port and the tank is fluidly connected to the second engine port; and wherein in the second open position the pump is fluidly connected to the second engine port and the tank is fluidly connected to the first engine port, with a first nonreturn valve, arranged between the pump and second engine port. A piston which by way of the load pressure in the first engine port via a line governs the first nonreturn valve, and a second nonreturn valve arranged, as long as the hand valve is in its first open position, to connect the first engine port to the second engine port.

Abstract: A hydraulic system and methods for conserving energy in such system is disclosed. The hydraulic system includes a hydraulic actuator having a head end, a rod end and a piston disposed therebetween. The system also includes a pump that pumps fluid to the actuator, a first valve disposed downstream of the rod end, and a second valve disposed between the pump and the head end of the actuator. When the system is in a load overrunning condition, the second valve is partially closed to restrict the flow of a combined fluid. The combined fluid including fluid received from the pump and fluid received from the rod end of the actuator. When the system is in the light resistive load condition, the second valve is open to allow the combined fluid to flow through the second valve.

Abstract: The invention relates to a hydraulic control arrangement for supplying a pressure medium to at least one consumer. The forward line and/or the return line of the consumer comprises a distributing valve that can be continuously controlled and that has two switch positions, and a lowering brake valve that can be placed in an open position due to the pressure in the supply line. The distributing valve is in an open neutral position and can be displaced, electrically or electrohydraulically, from said neutral position into the direction of the second switch position thereof.

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

Abstract: A motor assembly for a pneumatic tool includes: a motor cylinder coaxially secured in a tubular inner housing, which is coaxially secured in a tubular outer housing and has an inlet passage defining a longitudinal axis, including a valve seat, and defining forward and reverse passages that communicate with a motor chamber and extend through the valve seat, and an exhaust port that communicates with the motor chamber, and a throttle passage defined between the inner and outer housings; a motor rotor supported within the motor chamber and rotatable in a forward or reverse direction; and a rotary valve coaxially disposed in the inner housing, supported by the valve seat, and rotatable about the longitudinal axis between forward and reverse positions.

Abstract: A hydraulic control system includes an oil control valve to control oil flow within a valvetrain. The control valve varies the flow rate to actuate an engine component from a first position to a second position based upon fluid pressure from the control valve. Varying the flow rate through the control valve includes increasing the flow rate through the control valve to increase the pressure to a first level to actuate the engine component to the first position. After the engine component is actuated, the flow rate through the control valve is maintained at a level sufficient to maintain the engine component in the first position. To actuate the engine component to the second position the flow rate through the control valve is then decreased. The fluid flow rate through the control valve is then maintained at a level sufficient to maintain the engine component in the second position.

Abstract: A hydraulic control system includes an oil control valve to control oil flow within a valvetrain. The control valve varies the flow rate to actuate an engine component from a first position to a second position based upon fluid pressure from the control valve. Varying the flow rate through the control valve includes increasing the flow rate through the control valve to increase the pressure to a first level to actuate the engine component to the first position. After the engine component is actuated, the flow rate through the control valve is maintained at a level sufficient to maintain the engine component in the first position. To actuate the engine component to the second position the flow rate through the control valve is then decreased. The fluid flow rate through the control valve is then maintained at a level sufficient to maintain the engine component in the second position.

Abstract: An actuation system includes a pump assembly configured to form a pump chamber, an actuator having first and second chambers and a movable member and configured to convert pressures applied to the first and second chambers into a movement of the movable member, and a valve section. The valve section has a plurality of positions set by a controller, and the plurality of positions includes a first position in which the valve section opens the first flow path and closes the second flow path, a second position in which the valve section closes the first flow path and opens the second flow path, and a neutral position in which the valve section closes the first and second flow paths.

Abstract: A system operates a hydraulic actuator, such as a cylinder, in one of several modes that include powered extension and retraction, self-powering regeneration modes in which fluid exhausting from one cylinder chamber is routed into the other cylinder chamber, and cross function regeneration modes wherein the fluid exhausted from one actuator is routed in the supply conduit to power a different actuator. A controller determines which modes are viable based on existing system conditions and selects from among the viable available modes. That determination is a function of the desired velocity for the actuator, the hydraulic load on the actuator, and pressures in the supply and return hydraulic conduits. The system also can recover potential or kinetic energy through pressure intensification which recovered energy can be used to power another simultaneously active hydraulic function or to drive the prime mover via an over-center variable pump/motor.

Abstract: A hydraulic arrangement is provided for a tool locking device of a loader. The hydraulic arrangement comprises a hydraulic cylinder with first and second chambers, which cylinder has a first position for unlocking and a second position for locking, a first supply line hydraulically connected to the first chamber, a second supply line hydraulically connected to the second chamber and a control valve hydraulically connected to the first chamber. So as to prevent the faulty actuation of the hydraulic cylinder, it is proposed that the control valve has a first position and a second position, the control valve in the first position allowing hydraulic fluid to flow only in the direction of the first chamber and in the second position allowing hydraulic fluid to flow both to the first chamber and out of the first chamber and the control valve being controlled such that it assumes the first position when the hydraulic cylinder assumes its first position.

Abstract: The invention relates to a hydraulic actuating device for a movable component of a vehicle, in particular a closure element for closing an opening in a vehicle body, such as for example a movable roof, such as a folding roof or a retractable hard top.

Abstract: A crowd control mechanism for a power shovel includes an extendible dipper handle having an extended position and a retracted position. A double acting hydraulic cylinder having a an extendible ram has one of the cylinder and the ram fixed to the dipper handle and the other of the cylinder and the ram is stationary relative to the dipper handle. At least one of the cylinder and the ram have at least one of a blind end port and a rod end port, and at least one of the cylinder and the ram have the other of the blind end port and the rod end port, wherein hydraulic fluid flowing into the cylinder through the blind end port urges the ram toward an extended position to extend the dipper handle, and hydraulic fluid flowing into the rod end port urges the ram toward a retracted position to retract the dipper handle. Hydraulic fluid flowing into and out of the cylinder is controlled by one or more pilot operated poppet valves.

Abstract: The present invention lowers energy loss while at the same time enhancing the responsiveness of a steering control system. When a steering controller is operated rapidly, the aperture area of a steering flow control valve 4 rapidly increases, and the differential pressure (Pp?-PL) across the steering flow control valve 4 rapidly decreases. When the differential pressure (Pp?-PL) across the steering flow control valve 4 rapidly decreases, a flow control valve 6 is biased by the spring force of a spring 6f and quickly moves to the side of a valve position 6b to increase the differential pressure (Pp?-PL) and make it correspond to a set pressure. Thus, the pressure oil of a surplus flow ?, which up to this point has been flowing to a discharge oil line 7, is quickly supplied from the flow control valve 6 to a steering hydraulic cylinder 5 via the steering flow control valve 4. Thus, an output Q? starts quickly relative to an input St.

Abstract: In the present invention, sensors for cylinder control are connected to a main cylinder which has an internal cylinder chamber which is partitioned by a piston into two chambers, and they detect the operational state of the piston. There are provided accumulators connected to one of said two chambers by connecting conduits and whose interiors are pressurized by hydraulic fluid which is expelled from said one chamber, and also stop signal generation mechanisms which generate signals to stop the driving of said main cylinder by pressure differential between said accumulators and said connecting conduits generated at the instant that increase of pressure from said one chamber stops.

Abstract: A safety device for a moving system with a drive in which a pneumatically operated piston, by linear movement in a cylinder, moves a transported object past a stationary part in at least one direction has the aim of generating a switching signal at every point of a through-opening when an obstacle is located between the moving object and the edge of the through-opening, regardless of the movement direction of the object and the geometrical construction of the through-opening. The cylinder has, at its ends, devices for measuring the pressure of the air flowing out of the cylinder in the movement direction of the piston, wherein a drop in the otherwise substantially constant pressure below a threshold value serves as a switching signal at least for switching off the system. The device is useful for safety purposes during the transport of objects, particularly when the objects form shearing edges with neighboring objects.

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: A high speed safety circuit arrangement is provided for a hydraulic press which is driven by a hydraulic cylinder assembly constituted by a principal cylinder unit and a subsidiary cylinder unit. The circuit arrangement comprises a servo valve disposed in one of at least a pair of conduit lines for supplying a pressure fluid from a source thereof into the principal cylinder unit and the subsidiary cylinder unit, a first logic valve disposed in the other of the conduit lines and switched on and off and by the servo valve and a first electromagnetic valve for opening and closing that other conduit line, a second and a third logic valve of which each is switched on and off, and at least one is selectively actuatable, by a second electromagnetic valve to interconnect an upper and a lower chamber of the principal cylinder unit in a hydraulic circuit.

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: An auto cycle pump in accordance with the invention includes a housing having a reservoir for storing hydraulic fluid. A hydraulic pump in the housing provides hydraulic flow. A directional valve has neutral, advance and retract positions to respectively restrict hydraulic flow, direct hydraulic flow to an advance port and direct hydraulic flow to a retract port, the ports for hydraulic connection to the hydraulic tool, in use. Fluid conduits are provided connecting the pump and reservoir to the directional valve. A flow switch detects return flow from the directional valve to the reservoir. A pressure sensor sense hydraulic pressure from the pump. A dump valve is operatively connected to the pump for directing hydraulic flow back to the reservoir when the directional valve is in the neutral position. A control is operatively connected to the pump, the directional valve, the flow switch and the pressure sensing means for controlling operation of the auto cycle pump in automatic mode of operation.

Abstract: A hydraulic control system for excavators includes a variable displacement pump for producing a variable volume of pressurized working fluid, a hydraulic swing motor rotatably driven by the working fluid and a flow control valve operable to control flow of the working fluid with respect to the swing motor. The first flow control valve comprises a valve body and a valve spool slidably fitted into the valve body for selective shifting movement between a first operative position, a second operative position and a neutral position.

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: A hydraulic device for construction machinery includes a hydraulic pump; a hydraulic actuator having two fluid chambers; actuator fluid lines leading from each of the fluid chambers; pump fluid line leading from the pump; fluid tank fluid line leading to the fluid tank; operating lever to be operated by an operator; a direction switching unit connected to the actuator lines, the fluid tank fluid line, and the pump fluid line, and which is controlled in accordance with the direction of operation of the operating lever; inflow variable restriction located between the pump and the actuator fluid lines and whose restriction area is controlled in accordance with the degree of operation of the operating lever; outflow variable restriction located in between the fluid tank and the actuator fluid lines; and a pressure difference controller for controlling the difference in pressure between the inlet and exit ports of the inflow variable restriction.

Abstract: A hydromechanical differentiating system for actuator dynamic stiffness enhancement and dynamic load damping. A free floating spool valve receives a pressure signal and moves in opposite directions away from a null position. When the valve moves in response to an increase in the pressure signal it compresses fluid in a chamber connected at the opposite end of the cylinder in which the spool moves and simultaneously connects a source of fluid under pressure to the chamber causing the valve to return to its null position. Conversely, if the pressure signal decreases, the spool valve allows the fluid in the chamber to expand moving the valve away from the chamber and simultaneously connecting system return to the chamber to decrease the fluid pressure in the chamber and cause the valve to return to its null position.

Abstract: The hydraulic setting device (10) has a differential cylinder (11) whose pressure spaces (14, 18) can each be acted upon by a pump (17). The pressure conduits (15) and (19) between the pump and the two pressure spaces (14) and (18) are connected to a control valve (31) by means of control conduits (29) and (33). A part pressure can be set in the pressure spaces (14) and (18) by spilling pressure medium by corresponding activation of the control valve.

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 control circuit of a double-acting hydraulic jack (10), consisting of a piston (12) connected to an output rod (18) and separating a cylinder into two chambers (14, 16), comprises a source of fluid under pressure (20, 26), a distribution system (28, 28', 52, 52') alternately putting one of the chambers, or control chamber, in communication with the source of fluid under pressure (20, 26) and the other chamber, or controlled chamber, in communication with a reservoir of fluid under low pressure (25), in order to control the movement of the piston (12) of the jack (10). The jack comprises an auxiliary circuit (50, 120, 122) for preventing communication between the controlled chamber and the reservoir (25), interrupting communication between the control chamber and the source of fluid under pressure (20, 26) and allowing communication between the controlled and control chambers when the pressure of the fluid in the controlled chamber exceeds a predetermined value.

Abstract: Hydraulic control of reversible hydraulic motors typically requires several different valves to provide for the various operating parameters. The subject hydraulic control circuit has only a pair of electrohydraulic control valves to provide all the typical operating parameters. Operation of the control valves is controlled by a microprocessor in response to receiving command signals from a manually controlled command signal outputting device which establishes a desired fluid flow rate and direction of flow through the control valves.

Abstract: A distributor for hydraulic cylinders (2), especially applicable to crane drive cylinders, which comprises an axial sliding runner (4) for selection of the oil circuit. Said runner (4) is hollow, forming two separate chambers (19,20) adjacent to the cylinder chamber supply and return ducts with which it is connected through holes in the wall of the said runner. One of the chambers (19) includes means for varying the degree to which the holes are opened, according to the return oil pressure from the cylinder withdrawal chamber. The other chamber (20) incorporates means for opening or closing the connection through it, according to the pressure being delivered by the pump, to the cylinder withdrawal chamber oil supply duct. Thus it is possible to regulate the flow as an inverse function of the load and to reduce the effect of induced pressure.

Abstract: The drive is controlled such that reduced pressure is applied during a forward motion phase and venting flow from the drive is used as dynamic control pressure to hold off application of full driving pressure until, through physical impediment, piston movement stops. This way rebounding is prevented and strong holding pressure (e.g. on welding electrodes) is made available after a low power motion phase.

Abstract: A spindle carrier, which is movable vertically by an electric servo motor through a relatively long ball screw, has a substantially constant counterbalance force maintained on it irrespective of whether it is moving up or down. This prevents compression or tension of the ball screw. The counterbalance force is maintained substantially constant through sensing the load on the spindle carrier and using the sensed load to vary the hydraulic pressure applied to a piston within a hydraulic cylinder and connected through a chain to the spindle carrier to apply the counterbalance force.

Abstract: A hydraulic elevator up direction control system is provided including a circulating valve connected between the supply and the return of a source that normally supplies pressure to the cylinder of an elevator controlled by a two position switchable setting valve that influences the pilot fluid pressure in the operating chamber of the circulating valve to control the size of opening of the circulating valve and thereby the volume of fluid passing through the circulating valve affecting inversely the volume of fluid passing through a check valve, to provide two distinctive intermediate up speeds of travel in addition to the nominal full speed of travel facilitating a fast, smooth and accurate ride of the elevator car as it approaches a stopping point relative to an upper floor of a building. A three speed down direction control system presents no problems of significance and is not dealt with.

Abstract: A load sensing circuit of a load responsive direction control valve including a device for sensing load pressure signals, identifying those pressure signals as positive or negative and transmitting those identified positive or negative load pressure signals to the throttling compensator controls of the load responsive valve. The load pressure signal identifying circuit responds to the control pressure signals, which determine the desired direction of displacement of the spool of the direction control valve, while those control pressure signals are selectively isolated from the identifying circuit, in response to the direction of spool displacement from its neutral position.

Abstract: A load responsive system is provided with two synchronizing systems for positive and negative load compensation. One of the synchronizing systems varies the flow through a negative load compensator, during control of a negative load, in response to the inlet pressure of a fluid motor which is controlled by a positive load compensator. The other synchronizing system isolates the system pump from the fluid motor during control of the negative load while make-up flow to the fluid motor is supplied from the fluid exhaust system. In a more specific arrangement, the system pump is isolated from the fluid motor through the use of the positive load compensator and totally independent of any negative load compensating action. The synchronizing systems function in response to an external signal(s), which can be a function of any selected specific parameter of the system.

Abstract: A hydraulic motor has its lube drain connected to the motor return line. A motor seal protector valve has a pilot which responds to pressure in the motor return line. Normally, the valve connects system pressure to the motor inlet. High pressure in the return line causes the pilot to move the valve to block the motor feed line and then to connect the motor feed line to sump. In a preferred embodiment, system pressure is connected to the plot to "lock up" the valve in response to return line overpressurization.

Abstract: A load responsive system including individual positive and negative load compensators, for control of positive or negative load and an external logic system for determination of whether the controlled load pressure is positive or negative. The deactivating valve deactivates the positive load compensator, when the negative load pressure exceeds a certain minimum predetermined level, preventing flow of fluid from the system pump to the system actuator controlling a negative load at a pressure higher than a certain predetermined level, and therefore preventing development of excessive pressure in the actuator, while also deactivating the negative load compensator below a certain minimum predetermined negative load pressure level and while the positive load is being controlled by the positive load compensator.

Abstract: The invention relates to a control unit for a hydraulically operated consumer of the type which is used for operating heavily intermittently and loaded machines such as cranes. The consumer is fed in accordance with a load sensing function with pressurized fluid which depends on the opening of the supply valve but is independent of load pressure variations. The invention is directed to minimizing the lagging of the adjustments to different loading conditions to provide more rapid stabilization. This is done by providing the signal conduit with three branches between the inlet and outlet lines to form a pressure dividing arrangement in which the signal pressure is no longer equal to the load pressure but is composed of parts of the load pressure and the output of a pressure regulating valve in the inlet line of the unit. Upon fluctuation in the load the amount of flow is not kept constant but instead decreases with an increasing load and increases with a drop in the load.

Abstract: A load control system is disclosed for preventing the uncontrolled lowering of a load should a line failure occur in a hydraulic system. The system is designed to be used with a hydraulic cylinder having a movable piston therein which divides the cylinder into a head end and a rod end. Attached to the piston and extending out of the hydraulic cylinder is a piston rod which has a load secured to its free end. The load control system includes a source of pressurized fluid, the flow of which is selectively controlled to the hydraulic cylinder by a control valve. Positioned between the control valve and the head and rod ends of the hydraulic cylinder, respectively, are first and second valves each of which is normally biased towards a closed position by a common pressure. The first and second valves are urged toward an open position by fluid pressure taken between the control valve and the first valve and are movable by this fluid pressure in a proportional manner with the second valve being opened first.

Abstract: A load sensing circuit of a load responsive direction control valve including a device for sensing load pressure signals, identifying those load pressure signals as positive or negative and transmitting those identified positive or negative load pressure signals to the throttling compensator controls of the load responsive valve, while also transmitting the positive load pressure signal to the pump control. The identification and distribution of the load pressure signals to the controls of the load responsive circuit can take place with the direction control spool in its neutral position. Therefore such a load pressure sensing and transmitting circuit is capable of anticipating the command signal indicated control function.

Abstract: The invention relates to a compressed fluid saving device positioned between the outlet of a distributor and the admission of a pneumatic jack. The device comprises a valve which is kept open, to allow the flow of driving fluid into one chamber of the jack from the start and right through the stroke, by the exhaust back-pressure escaping from the other chamber of the jack, and acting on the piston of said valve. When the back-pressure disappears, the valve closes under the action of a screw-adjustable spring.

Abstract: A rotary vane air or gas motor is provided with a primary exhaust port having an exhaust fluid throttling valve therein for controlling motor speed. The motor includes a secondary exhaust port for discharging exhaust fluid flow from the motor expansible chambers after cutoff of the primary exhaust port. A flow sensing vane member is movably disposed in a flow passage in communication with the secondary exhaust port and is responsive to flow variations to actuate the exhaust fluid throttling valve by connecting linkage. The interconnected exhaust fluid throttling valve and flow sensing vane function as a motor speed limiting governor.

Abstract: The servo-motor system is provided with an internal control line which communicates one control valve with a cylinder chamber which is connected to a control valve connected with an external control line. The internal control line permits the second valve to be actuated via the externally controlled control valve.

Abstract: The front end of a handgrip mounts an interchangeable tool-holder for pincer type tools whose opening and closing is controlled pneumatically through a cylinder-piston assembly to which a source of compressed air is supplied. Downstream of the compressed-air source there is a pneumatic circuit for the automatic operation, intermittently at adjustable intervals, of the cylinder-piston assembly. The placing in service and the taking out of service of the pneumatic circuit is controlled by simply obturating and freeing, respectively, an aperture provided in the handgrip and communicating with a bypass duct in parallel with the duct that supplies the compressed air to the cylinder-piston assembly.

Abstract: A hydraulic isolation valve (10) will not open if leaks are present in the associated utility subsystem (15). The continuity of the hydraulic fluid circuit actuates the valve (10) to the open position by an energized solenoid operated pilot valve (21) sending a small flow through a fuse (23) and one-way restrictor (24) to the utility function (15). If no leaks are present, the utility function (15) begins to actuate sending return flow through a two-way restrictor (31) and moving a continuity actuation piston (28) to push the shut off spool (16) to the open position so that full flow is admitted to actuate the utility function (15). If the continuity of the hydraulic circuit is broken by leaks, the return flow does not reach the continuity actuation piston and the shut off spool (16) remains in the shut off position, the fuse (23) closing to block further flow and then resetting by spring action when the solenoid operated pilot valve (21) is deenergized so that actuation may be attempted again, if desired.

Abstract: A dual input direction flow control valve responsive to a manual or an electrical control signal for control of positive and negative loads operated by a single pilot valve stage, which automatically maintains a relatively constant pressure differential across valve spool, while controlling positive and negative loads and which permits variation in the level of pressure differential in response to a pulse type control signal, while this pressure differential is maintained constant at each controlled level.

Abstract: A direction flow control valve for control of positive and negative loads operated by a single pilot valve stage, which automatically maintains a relatively constant pressure differential across valve spool, while controlling positive and negative loads and which permits variation in the level of pressure differential in response to an external control signal, while this pressure differential is maintained constant at each controlled level.

Abstract: A fully compensated direction flow control valve for control of positive and negative loads provided with a direction control and flow metering spool and a control which varies the level of the pressure differential controlled across the metering section of the spool in respect to the displacement of the spool from its neutral position.

Abstract: A direction flow control valve responsive to a manual control signal for control of positive and negative loads operated by a single pilot valve stage, which automatically maintains a relatively constant pressure differential across valve spool, while controlling positive and negative loads and which permits independent adjustment in maximum flow level through the valve for positive and negative load control.

Abstract: A direction flow control valve for control of positive and negative loads equipped with a positive and negative load compensator controlled by a single pilot valve stage responsive to positive and negative load pressure signals.