Abstract: A chuck drive system, especially for a rotating clamping device of a machine tool, includes a rotating chuck cylinder, a stationary frame positioned adjacent the chuck cylinder, and a piston which subdivides the cylinder into two pressure chambers and is formed with a piston rod having one end rotatably supported in the stationary frame. Fluid under pressure is supplied to the pressure chambers, whereby check valves are positioned in the passageways to the pressure chambers to maintain the fluid pressure in the pressure chambers. In order to monitor the fluid pressure in the pressure chambers, a pressure monitoring unit is provided which includes pressure sensors that are respectively assigned to the pressure chambers for determining the fluid pressure in the pressure chambers separately and independently from one another.

Abstract: A hydraulic system with a pressure source controllable via a load sensing signal, a pressure sink, at least two working sections, each having a hydraulic consumer and a control valve with a load sensing signal connection and at least one back-pressure valve arranged in a tank pipe between the control valve and the pressure sink. In such a system the pressure required from the pump in the neutral position must be as low as possible. On the other hand, however, oscillations should not occur, when an external force acts on another hydraulic consumer in the neutral position of a control valve. In the neutral position of the control valves the load sensing signal connection is therefore connected with the pressure sink via an auxiliary tank pipe by-passing the back-pressure valve.

Abstract: A device and method for suppressing vibration of a working machine in which residual vibration produced immediately after an operation is completed can be suppressed well without degrading the response. The device comprises a working machine acceleration detecting means (11H, 11B), a lever turning degree coefficient calculating means (17) for calculating coefficient in accordance with a lever turning degree, an acceleration compensating value operating means (13) for performing an operation from the acting force calculated from the acceleration of the working machine and a lever turning degree coefficient, and a feedback command means (18) for calculating an acceleration feedback command value from an acceleration compensating value and a lever operation command value and for outputting the acceleration feedback command value to electromagnetic proportional pressure control valves (22, 23).

Abstract: A flotation control system for controlling the boom of a tractor or brush cutting machine. Three hydraulic valves operate together and work in conjunction with the existing main valve of the tractor or brush cutting machine to provide flotation control or automatic movement up and down of the boom in response to ground surface variations. The system also allows the amount of weight that the cutter or other attachment exerts against the ground to be increased or decreased. The first valve is a flow control valve or a flow restricting or dividing valve that divides hydraulic flow from the pump of the tractor to the flotation control system. The second valve is a pressure reducing valve that provides the general operation of the flotation control system. The third valve is a directional valve and functions as an on/off for the flotation control system.

Abstract: A control system (10) for a limited stall load actuator (60) comprises a servo pressure regulator (20), solenoid valve (40), relief valve (30) and a shuttle valve (50) connected with a piston actuator 60 such that when source pressure P1 is declining the servo pressure regulator (20) will open to permit more flow and maintain a minimum actuation force effected by the actuator (60), and should there occur a failure of the servo pressure regulator (20) that would permit high source pressure to be communicated to the control system (10), the relief valve (30) will operate to limit the amount of high pressure communicated to the control system (10) such that the actuator (60) will attain no greater than a predetermined maximum output force.

Abstract: Although a workpiece can be elevated or lowered according to the invention, the workpiece is prevented from rising or falling abruptly. When the workpiece is elevated with an external force, air supplied from the side of an auxiliary air supply chamber pushes down a pressure control piston. Since a difference in pressure between the side of a piston pressure chamber and the side of an auxiliary air supply chamber is small, air is prevented from flushing from the side of the auxiliary air supply chamber into the piston pressure chamber. When the workpiece is lowered with an external force, the pressure control piston is pushed up, thereby increasing the pressure in the piston pressure chamber. At the same time, a relief valve is opened and the piston pressure chamber is exhausted. By the provision of a relief valve, excess air is not exhausted from the piston pressure chamber. The pressure control piston is prevented from rising abruptly, and the workpiece can be gradually raised or lowered.

Abstract: A controlled proportional valve is provided, with a main slide valve section (4) containing a main slide valve, which section controls a flow of fluid between a pump connection (P) connected to a pump (2) and a tank connection (T) connected to a tank (6) and two work connections connected to a load (5) and which generates a load-sensing signal (LS.sub.INT) in dependence on the pressures at the work connections (A, B), and with a compensating slide valve section (3) which controls the pressure across the main slide valve section (4) in dependence on the load-sensing signal (LS.sub.INT). It is desirable to achieve a more rapid response time in a proportional valve of that kind, wherein the control means should be capable of being retrofitted to existing proportional valves. To that end, a control arrangement (10) which controls the pressure of the load-sensing signal (LS.sub.INT) to influence the actual volume flow and/or the actual pressure in the work connections (A, B) is provided.

Abstract: A proportional solenoid valve for regulating pressure of fluid supplied to a system. The solenoid valve has high-pressure inlet (1), a low-pressure inlet (2) and an outlet (3) through which fluid under controlled pressure is supplied to the system. The solenoid valve has a body (4) with bore (5) therein for retaining a regulating slide valve (9). The regulating slide valve (9) is subjected to a pressure acting on a cross-section (S), to the force of a spring (10) and to a force exerted by an electromagnet (14,15). Movement of the slide valve brings about a communication between the high-pressure inlet (1) and the outlet (3) and communication between the low-pressure inlet (2) and the outlet (3) as a function of a control valve (16). The control valve (16) is located between the high-pressure inlet (1) and the outlet (3) and the high-pressure inlet (1) and low-pressure inlet (2) are isolated from one another by the slice valve (9) as long as said control valve is not open.

Abstract: A pressure regulating circuit in which the piston of a pneumatic cylinder can attain a balanced condition without requiring any adjustment to a workpiece. In the pressure regulating circuit, the pressure in an oil pressure chamber of a pressure reducing valve equals the pressure in a pressure sensitive oil chamber of a workpiece retention member. The pressure in a pressure sensitive chamber of the pressure reducing valve equals the pressure in the oil pressure chamber. Therefore, the pressure in a piston pressure chamber of a main valve connected to the pressure sensitive chamber equals the pressure in the pressure sensitive oil chamber. When the pressure in a control chamber of the main valve and the pressure in a working chamber of a pneumatic cylinder are respectively balanced with the pressure in the piston pressure chamber, the piston P can attain a balanced condition.

Abstract: In a hydraulic device at least one control valve with at least three control positions is connected with a variable capacity pump, whereby the controlling device of the variable capacity pump is connected with the supply line downstream the control valve via a feedback line with the purpose of adjusting the pump output so as to maintain a constant operational pressure gradient. The back flow pipe is conducted over the control valve, which is connected with the consumers by connecting valves associated to mentioned consumers, whereby a transducer is associated to the back flow pipe, which together with the transducer of the supply line constitutes a regulating variable for a control unit. This way a precise and energy saving regulation or control of the consumers in both flow directions by a control valve at a reasonable price is achieved.

Abstract: A hydraulic control valve formed as a magnet valve with several connections and switching positions, comprises a housing provided with several connections, a valve slider displaceable in the housing, an electromagnet provided with an extensible plunger for controlling the valve slider, a valve seat provided in the housing, a ball movable between a closing position and an opening position with respect to the valve seat, a closing spring which urges the ball to the closing position. The ball is bringable by the valve slider to the opening position under the action of a force of the electromagnet, a valve body is firmly but exchangeably inserted in the valve housing so that the valve slider is guided in the valve body. The valve body accommodates the valve slider, the ball and a closing spring which presses the ball against the valve seat. A plurality of conduits are provided, including a pressure conduit, a control conduit and a consumer conduit.

Abstract: A device for the control of a hydraulic slide valve. The hydraulic valve being put into motion by a motor and by a draw-back spring, the device including structure for controlling the rotational direction of the motor as a function of its positional error, the control structure being, in turn, controlled by a signal given by a correction circuit, the transfer function (K(s)) of which corrects a jet effect that is exerted on the slide valve. The device has application to hydraulic systems requiring large passbands.

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 two stage electrohydraulic pressure control valve includes a pilot stage for providing regulated pressure at lower flows to a larger main stage that handles the higher control flows to and from a pressure applied clutch or pressure released brake. The regulated pressure from the pilot stage acts on an end of the main stage for controlling the position of the main stage. An energy storage device in the form of either an accumulator or a load piston device is connected to the end of the main stage to permit instantaneous independent movement of the main stage relative to the pilot stage. The energy storage device quickly provides for or accepts displaced fluid from the main stage much faster than the limited flow capacity and response time of the pilot stage. This permits the main stage to quickly adjust to flow changes to the clutch or brake with minimal change in pressure until the pilot stage can respond.

Abstract: A two stage valve assembly responsive to signals from a control system for supplying pressurized fluid to two load lines. The first stage includes a motor that directs pressurized fluid from a jet pipe toward a receiver assembly having two receiver ports and a bleedoff area disposed between and separating the receiver ports. The second stage assembly includes two spool/sleeve assemblies that control the flow of pressurized fluid to and from the two load lines. A drain line from the receiver assembly includes a pressure relief valve, which insures that both spool/sleeve assemblies will be servo-controlled at all times. Cartridges may be inserted in the spool/sleeve assemblies to linearize the relationship between input current from the control system and the output force of an unequal area actuator connected to the load lines.

Abstract: An air lifting and balancing unit including a cylinder, a piston in the cylinder, a ball screw affixed to the piston, a ball nut mounted for rotation on the ball screw, a drum mounted on the ball nut, a chain driven by the drum, and centrifugally actuated brakes mounted on the drum for stopping rotation of the drum when the drum exceeds a predetermined acceleration either due to a loss of load or to a loss of air pressure applied to the piston, and a pneumatic circuit in communication with the cylinder for providing air pressure thereto which applies a force on the piston which is at a substantially constant incremental value in opposition to the force exerted by the load applied to the piston through the chain and the drum and the ball screw regardless of variations in said air pressure to thereby cause the speed of the chain to remain substantially constant.

Abstract: The invention relates to a pressure regulation device for a hydraulic system comprising at least one generator (30) of fluid under pressure, a hydraulic actuator (28) and a reservoir (32) of fluid under low pressure, and including an electrovalve controlled by a computer and comprising in a casing (9) an electrical coil (10) and a sliding magnetic core (12) controlling a slide valve (16) sliding in a bore provided in a body (18), the slide valve (16) determining two chambers (22, 36) arranged on either side of the slide valve (16) in the bore, the slide valve comprising a hydraulic chamber (40) communicating with the hydraulic actuator (28) and determining a reaction force adding itself to the force produced by the coil (10), against a prestressed resilient means (20). The hydraulic chamber (40) is delimited by a bore (41) made in the slide valve (16), an end part (43a) of a sleeve (43), a rod (42) and a cup (60) for leaktightness between the rod (42) and the bore (41) of the slide valve (16).

Abstract: A control for a hydraulic propeller pitch actuator includes a low power pilot valve responsive to digital electronic input signals to control movement of a hydraulic servomotor driving a higher power servovalve. Negative feedback motion is delivered from the servomotor to both the pilot valve and the servovalve.

Abstract: The invention relates to a solenoid valve, in particular for a hydraulic braking circuit of a motor vehicle with a wheel antilockup device, the solenoid valve being disposed between at least a pressurized fluid source (52) and at least a pressure receiver (56) and comprising, in a body (10), a piston mechanism (24) which can be displaced between a rest position, in which it permits communication between the pressurized fluid source (52) and the pressure receiver (56), and a work position, in which it permits communication between the pressure receiver (56) and a low-pressure fluid reservoir (66). According to the invention, the piston mechanism (24) is permanently stressed toward the rest position by a constant force.

Abstract: A flow compensator valve for use in a hydraulic system which includes a cylindrical body having inlet and outlet ports, and a slidable, spring-biased hollow piston insert disposed within a center bore of the body, which insert has a plurality of ports for flow control depending on the position of the insert as it reciprocates axially within the center bore of the valve body. In a preferred embodiment, the valve is used in connection with a hydraulically actuated lift which is particularly useful for assistance of handicap persons for vans and mass transit vehicles. The axially-reciprocable, spring-biased flow rate controlling insert has a small central axial bore for slow lift movement in the loaded condition and at least one larger transverse bore, which when exposed, permits flow therethrough for faster movement of the lift in the unloaded condition.

Abstract: This invention relates to a pressure reducing valve wherein a spool is driven axially by a first plunger which moves according to the magnetization state of a first solenoid, and a control port is connected to a supply port and a tank port according to the axial position of this spool. The pressure of the control port acts on the spool in the opposite direction to that of the plunger via a feedback passage, and the pressure increases or decreases according to the current flowing through the first solenoid. According to this invention, a second plunger is arranged in series with the first plunger, and a spring tends to push the second plunger toward the first plunger. A second magnetized solenoid however keeps the second plunger held back against the restoring force of the spring so that it is not in contact with the first plunger, and releases the second plunger so that it pushes the first plunger when the current fails.

Abstract: A counterforce cylinder and piston exert an upward force on the vertically movable slide of a machine. The cylinder pressure line handles reverse flows during operations of the slide. A pilot-operated checkvalve (normally closed) is inserted in the cylinder line between a pressure source and the counterforce cylinder, and is held open during usual operation of the machine. An accumulator is branch-connected to the cylinder line, at a point between the checkvalve and counterforce cylinder. During machine operations, the accumulator stores pressurized fluid; at shutdown of power, the fast-acting checkvalve closes and reliably seals the cylinder line while the accumulator provides pressure to maintain the counterforce cylinder and slide in a substantially constant holding position for several days.

Abstract: An apparatus for controllably actuating a hydraulic actuator is provided. The apparatus is connected between a source of pressurized hydraulic fluid and the hydraulic actuator. The apparatus controllably provides pressurized hydraulic fluid to the hydraulic actuator. The apparatus includes a controller for receiving an operating signal and a load pressure signal and responsively actuating the hydraulic actuator.

Abstract: A pressure control valve for adjusting a controlled pressure supplied to an actuator includes first and second valves. The first valve serves to modify a pressure level of a working fluid supplied from a fluid pressure source to a preselected level and provides it to the actuator. The second valve is responsive to a control signal commanding elevation or reduction in the controlled pressure from a controller to adjust a supply pressure level from the fluid pressure source to provide a pilot pressure, elevated or reduced to a preselected level, to the first valve for activating same. When elevating or reducing the pilot pressure, the second valve decreases the supply pressure level from the fluid pressure source by a preselected degree, for balancing a flow gain when elevating the pilot pressure with that when reducing the pilot pressure, for providing uniform response for elevation and reduction of the controlled pressure to the actuator.

Abstract: A directional control valve for a pneumatic cylinder in which a piston of the cylinder can be lowered and elevated in a high speed with a minimum air consumption and the lowering/rising speed of the piston can be controlled before it reaches the upper/lower end portions to prevent bounding of the piston.

Abstract: A pressure control valve assembly is provided with a valve spool which is formed integrally with a plunger of an electromagnetic solenoid so that the electromagnetic force generated by the solenoid is directly active on the valve spool. By integration of the valve spool and the plunger of the solenoid, axial length can be reduced. Furthermore, with this construction, the set springs can be axially oriented outside of the solenoid to make it easy to adjust the set load to be exerted on the valve spool.

Abstract: An improved two-stage servovalve (70) has a pilot-stage and an output-stage. A torque motor (16) produces pivotal movement of a flapper (18) in response to a supplied electrical current. The pilot-stage produces a flow which is used to selectively displace a second-stage spool (61) relative to a body bore. The servovalve has a hydromechanical pressure feedback loop closed about the load and second-stage spool. The pressure feedback loop is intertwined with an electrical spool position feedback loop closed about the spool and driver. The command to the pressure loop is a function of the error of the spool position loop. The gain of the spool position loop dominates that of the pressure loop. The valve has pressure-flow characteristics approximating those of a "flow-control" servovalve but affords access to an electrical signal substantially proportional to the load pressure differential.

Abstract: In a position independent locking of a hydraulic cylinder/piston mechanism, a pressure limiting member is provided in the supply pipe for the hydraulic medium, with the pressure limiting member being open during the hydraulic displacement of the piston and is closed during lack of hydraulic pressure. The pressure limiting member opens starting from a specific pressurization of the hydraulic medium as a result of a force generated by means of the piston and is located in a related working chamber.

Abstract: The invention relates to a pressure-regulating device for a hydraulic circuit comprising at least one generator (30) of pressurized fluid, a hydraulic motor (28) and a reservoir (32) of fluid under low pressure, and including an electrovalve controlled by a calculator and comprising, in a yoke (8), an electric coil (10) and a sliding magnetic core (12) controlling a slider (16) sliding in a bore provided in a body (18), the slider (16) defining two chambers (22, 36) arranged on either side of the slider (16) in the bore, the slider comprising a hydraulic enclosure (40) communicating with the hydraulic motor (28) and defining a reaction force supplementing the force generated by the coil (10), counter to a prestressed resilient mechanism (20), the enclosure (40) consisting of a blind bore made in the slider (16), a needle (42) closing the enclosure (40) in a substantially leaktight manner, while a radial pierced hole (44) connects it to a groove ( 34) provided at the periphery of the slider (16).

Abstract: A hydraulic control system for controlling the motion of a double acting hydraulic actuator determines the flow to and from the actuator in accordance with1. the desired movement of the actuator2. the measured hydraulic pressures on opposite sides of the piston of the actuator3. a selected, predefined model of the system of which the actuator forms a partand sets the valves controlling the flows accordingly.

Abstract: A hydraulically operated device including a single-acting cylinder having a piston for operating a working tool, a pressure chamber for applying a hydraulic pressure to the piston from an original position to an operated position, and a return spring for biasing the piston toward the original position. The device includes a hydraulic pump for delivering a pressurized fluid to be fed into the pressure chamber of the cylinder, and an automatic drain valve for inhibiting the pressurized fluid from being discharged from the pressure chamber while a difference by which a delivery pressure of the pump is higher than a pressure in the pressure chamber exceeds a predetermined value. When the difference becomes smaller than the predetermined value, the automatic drain valve is operated to allow the pressurized fluid to be discharged from the pressure chamber. Thus, the automatic drain valve automatically drains the pressure chamber when the pump is turned off.

Abstract: The pressure-regulating system for a hydraulic circuit, comprises at least one generator (22) of fluid under pressure, a hydraulic motor (20) and a reservoir (24) of fluid under low pressure. It further includes a solenoid valve controlled by a computer and comprising an electrical coil (1) and a sliding magnetic core (3) controlling a slide (7) sliding in a bore provided in a body (9). The slide (7) defines two chambers (11, 15) arranged on either side of the slide (7) in the bore. The slide (7) comprises a hydraulic cell (26) determining a reaction force opposing the force generated by the coil (1), the cell (26) being connected to one of the chambers (11, 15) as long as the solenoid valve is not energized, while it is connected to the hydraulic motor (20) after energization. An elastic mechanism (13) returns the slide (7) and the core (3) to the rest position.

Abstract: The pressure-regulating system for a hydraulic circuit, comprises at least one generator (22) of fluid under pressure, a hydraulic motor (20), a reservoir (24) of fluid under low pressure and a solenoid valve controlled by a computer and comprising an electrical coil (1) and a sliding magnetic core (3) controlling a slide (7) which slides in a bore provided in a body (9). The slide (7) defines two chambers (11, 15) arranged on either side of the slide (7) in the bore, and it comprises a hydraulic cell (26) communicating with the hydraulic motor (20) and determining a reaction force added to the force generated by the coil (1), counter to a prestressed elastic means (131) and to a return spring (132) returning the slide (7) and the core (3) to the rest position.

Abstract: The invention relates to an integrated pressure amplification and modulation system for a hydraulic brake circuit, comprising at least one master cylinder (10), a hydraulic motor, a source of fluid under high pressure (48) and a reservoir of fluid under low pressure (14), a computer-controlled solenoid (32) modulating by way of a magnetic core (30) the position of a slide (22) which slides in a bore (20). According to the invention, the fluid under pressure coming from the master cylinder (10) is applied to one face (24) of the slide (22), the other face of which bears on the magnetic core (30l ) and receives the force exerted by a spring (34) for return to rest. A reaction chamber (40) formed in the slide (22) is connected permanently to the hydraulic motor (38), and the hydraulic motor (38) is connected either to the reservoir (14) or to the source of fluid under pressure (48), depending on the position of the slide (22).

Abstract: A speed control device for a pneumatic cylinder of the invention is characterized in that a speed control of the pneumatic cylinder can be changed from air pressure to air mass flow by a two-way valve and an airflow control valve. Therefore, an ordinary and low moving speed of a load is maintained even if the load changes its speed or stops moving, and thus any accidents caused by a change of the moving speed of the load are prevented beforehand. Additionally, since in this invention only a two-way valve and an airflow control valve are added to a conventional pneumatic cylinder and high relief type pressure reducing valve, the device of the invention is simply constructed and has a wide variety of usage. Furthermore, since the device of the invention is provided with a pressure accumulator and a checking valve, the pneumatic cylinder can be stably controlled even when the load moves at a high speed.

Abstract: The stem of an inching valve for a power-shift transmission, particularly for lift trucks, is controlled by a hydraulically-operated piston whose axis is distinct from and parallel to the axis of the stem and which is connected to the stem by means of a mechanical transmission. The risk of contamination of the fluid used for operating the piston (which is the fluid of the vehicle's braking circuit) by the oil used in the power-shift transmission is thus avoided.

Abstract: A pressure control valve and transducer package for use in combination with a pneumatic actuator which incorporates a double acting pneumatic cylinder includes, in a single multi-component unit, a valve assembly constructed for direct coupling into the pneumatic pressure loop for operating the actuator, and a second component which comprises a fixture housing one or more continuously operating sensors for measuring the pressures supplied to the opposite ends of the cylinder in the actuator and transmitting appropriate signals conveying that information to a microprocessor which in turn regulates the supply flow rate of pressure gas to the cylinder through a closed loop feedback system.

Abstract: A device for the control of a double-acting hydraulic jack (10) comprises in a main circuit, a distributor assembly (28, 28', 34, 34') electrically controlled and commanding the putting of each of the two chambers (14, 16) of the jack selectively in relation with a source of fluid under high pressure (20, 26) or with a reservoir of fluid at low pressure (24), and an auxiliary circuit controlled by a mechanism (76) sensitive to the position of the piston (12) of the jack (10). The auxiliary circuit comprises a slide distributor (50) which ensures the return of the piston (12) of the jack (10) into a rest position in the event of a failure of the electrical control mechanism by governing the distributor assembly (34, 34') of the main circuit.

Abstract: A directional control valve for a pneumatic cylinder in which a piston of the cylinder can be lowered and elevated in a high speed with a minimum air consumption and the lowering/rising speed of the piston can be controlled before it reaches the upper/lower end portions to prevent bounding of the piston.

Abstract: A method and an arrangement for positioning accurately the piston of a load-carrying pressure-fluid piston-cylinder device, in which the fluid is a compressible gas and the cylinder device is double-acting. A variable operating pressure (P1) acts on one side of the piston, and an applied pressure (P2) of constant value acts on the other side of the piston. The pressures (P1,P2) can be relieved alternately by evacuation, for movement of the piston in the cylinder device. A pressure regulator is provided which functions to detect the load acting on the cylinder device from an external load (F) and which includes a pressure chamber having a movable wall supporting the cylinder device, and in which the operating pressure (Pi) is applied via a valve, the opening and closing movements of which are determined by movements of the movable wall.

Abstract: An air spring apparatus has quick pressure release, and rapid air exhaust, capability by means of a relatively large diameter exhaust port in a larger, primary air spring which is controlled by the action of a smaller, secondary air spring. The secondary air spring is equipped with a check valve which controls the flow of air into the primary air spring. The rapid exhaust of the primary air spring is effected by triggering the removal of air pressure from the secondary air spring through a plurality of orifices in a centrally disposed guide tube which permits the collapse of the smaller air spring and the accompanying removal of a valve plate from a relatively large diameter exhaust port of the primary air spring.

Abstract: A bifluidically controlled distributor of a fluid coming from a first source (11) of fluid under high presure, comprises, in a blind bore (1) made in a body, a sliding piston (3) defining, with a plug of the bore, a first control chamber (5) connected to a first source of control fluid, a slide (9) ensuring communication between the first source (11) of fluid under high pressure or a reservoir (13) of fluid under low pressure, and an outlet conduit (15) for the distributed fluid. The bore (1) and the piston (3) are stepped correspondingly so as to determine between them a reaction chamber (25) connected permanently to the outlet conduit (15) and a second control chamber (21) is formed between the slide (9) and the piston (3) and is connected to a second source of control fluid.

Abstract: The invention relates to a braking valve arrangement for a hydrostatic drive operated in open circuit, in particular for vehicle drives, wherein a hydraulic pressure medium is supplied to the hydraulic motor from the hydraulic pump via a reversing directional control valve as desired through one of two branches each containing a pressure limiting valve and a braking control valve, and the pressure medium is discharged to the tank through the respective other of the two branches. The braking control valve controls the flow of hydraulic medium through the respective branch depending on the pressure in the respective other branch and has parallel with it a non-return valve opening into the hydraulic motor.

Abstract: Device in a hydraulic power system connected to load driving hydraulic motor (18; 32), comprising a pilot controlled flow regulating directional valve (1; 29) for alternative connection of the service ports of the motor (18; 32) to a pressure medium source and a tank. The directional valve (1; 29) comprises two opposite and by a pilot pressure activatable activating means (3, 4), and a pilot pressure means (84) is arranged to pressurize and activate the activating means (3, 4), alternatively, and drain one of the activating means to the tank through a flow restriction (6, 7) at activation of the other activating means (3, 4).

Abstract: A directional control valve for a pneumatic cylinder in which a piston of the cylinder can be lowered and elevated in a high speed with a minimum air consumption and the lowering/rising speed of the piston can be controlled before it reaches the upper/lower end portions to prevent bounding of the piston.

Abstract: A hydraulic control valve is controlled and changed over by a hydraulic pressure output from a remote control valve. A change-over valve is provided between an output port of the remote control valve and a pilot port of the hydraulic control valve. The change-over valve connects the output port of the remote control valve to the pilot port of the hydraulic control valve when the remote control valve is operated, and it connects the pilot port of the hydraulic control valve to a tank when the remote control valve is set to the neutral position. The change-over valve comprises a hydraulic change-over valve capable of establishing the above states of connection by the hydraulic pressure output from the remote control valve, or an electromagnetic change-over valve capable of establishing the above states of connection by electrically detecting the operation of the remote control valve.

Abstract: A directional control valve for a penumatic cylinder in which a piston of the cylinder can be lowered and elevated in a high speed with a minimum air consumption and the lowering/rising speed of the piston can be controlled before it reaches the upper/lower end portions to prevent bounding of the piston.

Abstract: A remote controlled individually pressure compensated hydraulic valve assembly includes a directional valve having an inlet, a load holding check valve, an outlet passage, at least one outlet or cylinder port, and a tank or drain port. The valve defines a bore within which a spool is moveably disposed. A control device includes hydraulic remote actuators or an electro magnetic device to generate a command signal. The control device compares the command signal to an output of a flow measuring device to position the valve spool so that a desired flow rate at the valve cylinder command signal. The load holding check valve is used as the flow measuring device. The check valve includes a valve element and a spring selected so that the differential pressure across the valve element is proportional to flow rate.

Abstract: There is disclosed a system for controlling the operation of a ram of a subsea blowout preventer connected to a piston shiftable between alternate positions within a cylinder. The system includes valve apparatus for so shifting the piston which includes an outlet connected to the cylinder, a first passageway through which hydraulic fluid may be supplied to the outlet, a second passageway through which hydraulic fluid may be vented from the outlet, and a valve member movable between positions alternately connecting the outlet with the first and second passageways, respectively, so as to selectively supply hydraulic fluid to or vent hydraulic fluid from the cylinder.

Abstract: The present invention provides an apparatus for controlling a hydraulic pressure usable for a clutch wherein the apparatus is employed for a transmission mounted on a construction machine or the like in such a manner that it is provided separately for a plurality of clutches and it is controlled individually. The apparatus includes a first valve for allowing a large amount of hydraulic oil to flow in the clutch and a second valve for electronically controlling a clutch pressure so that the termination of filling and the clutch pressure are detected by a simple structural arrangement on the basis of a displacement of a spool for the first valve and a separately disposed piston. In addition, appearing of an overshoot pressure on the termination of filling is prevented by providing a difference in pressure receiving areas on the spool for the first valve.