Abstract: Hydraulic valve circuits capable of variably limiting respective maximum hydraulic pressures at which an assembly of bidirectional hydraulic power devices can move respective clamping members, such as forks or clamp arms, selectively in a closing movement toward each other, in an opening movement away from each other, or in a side-shifting movement in unison with each other, so as to provide damage-control capabilities for the control of the clamping members. The circuits preferably include one or more pressure-regulating valves interconnected with the assembly of power devices, and capable of variably limiting a maximum side-shifting pressure, at which said assembly can cause said side-shifting movement, in response to a maximum pressure selection. The circuits preferably include at least one override assembly, capable of overriding the maximum pressure selection to thereby lower the maximum side-shifting pressure automatically irrespective of the maximum pressure selection.

Abstract: What is disclosed is a hydraulic controller arrangement for the pressure medium supply of a hydraulic consumer, e.g., of the rotating gear of a mobile work machine. At low pressure medium flow rates, the pressure medium flow rate draining from the consumer is backed up by means of a drain backup valve having the form of a pressure limiting valve and throttled accordingly, so that a back pressure is generated which is capable of preventing an advance of the mass actuated by the hydraulic consumer.

Abstract: A pressure-compensating directional control valve, for actuating hydraulic actuators, comprising at least one modular valve body, with one through receptacle for a slidable shuttle, a driving fluid delivery port connected to a pump, a discharge fluid port, a first output opening and a second output opening, connected to the first and second chamber, of a hydraulic actuator, at least one bridge for selective communication, by way of the shuttle, of the delivery port with the first or second chambers of the actuator, for actuation thereof, a unidirectional hydrostat connected to the bridge to draw selectively a pressure signal of the load of the actuator, the signal for adjusting selectively the delivery pressure of the pump so as to keep substantially constant the pressure drop between the delivery port and the actuator in any load condition.

Abstract: The invention relates to a hydraulic distributor comprising a casing, a pressurized fluid inlet, a fluid return port, at least two working ports, a slide which is housed in the casing, a passage which is provided in the casing in order to connect the inlet with the working ports, adjustment means which are connected to a load detection line channel, a supply bridge which opens into the slide hole on either side of the inlet chamber, and two main check valves which are borne internally by the slide, The inventive distributor further comprises two secondary check valves which are mounted in the longitudinal channels upstream of the main check valve heads and which are connected to torque slits which open into the hole in which the slide moves.

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

Abstract: A double check valve having a floating function is disclosed, which can prevent construction equipment from overturning through intercepting of a floating function even if a signal pressure is fed to the double check valve to perform the floating function in a state that an excavator is supported by a working device (e.g. a dozer blade), i.e. in a jack-up state, on a sloping site and so on.

Abstract: A flow control apparatus for heavy construction equipment is provided, which can prevent overspeed and abrupt operations of an actuator due to an excessive flow rate during an initial operation of the actuator when a composite work is performed by simultaneously operating an option device and another actuator, and can prevent the cut-off of hydraulic fluid supply to the option device due to an operation inability of a flow control valve when leakage of the hydraulic fluid occurs due to the increase of the temperature of the hydraulic fluid.

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

Abstract: A tank 16 and a main hydraulic pump 17 are connected to head side actuator chambers 13 and rod side actuator chambers 14 of hydraulic actuators 12 via conduits 21, 22. A direction control valve 18 and a quick drop valve 36 are connected to the conduits 21, 22. A hydraulic circuit is provided with an electromagnetic switch valve 42, which switches the quick drop valve 36 from a non-quick drop position 37 to a quick drop position 38. When switching the direction control valve 18 from a neutral position 23 to a lowering operation position 25, if the manipulation speed of a manipulation lever 33 exceeds a criteria speed, an excitation signal is output from a control device 32 to an electromagnetic switch valve 42 to quickly drop a blade 11, and the quick drop valve 36 is switched from the non-quick drop position 37 to the quick drop position 38.

Abstract: A hydraulic system for a machine is disclosed. The hydraulic system has a source of pressurized fluid and a fluid actuator with a first chamber. The hydraulic system also has a first valve configured to selectively fluidly communicate the source with the first chamber. The first valve further includes a first element movable between a flow passing, at which fluid from the source flows to the first chamber, and a flow blocking position, at which fluid from the source is blocked from the first chamber and a second element configured to selectively drain a control passageway associated with the first element to cause the first element to move. The hydraulic system further has a proportional pressure compensating valve configured to control a pressure of a fluid directed between the source and the first valve dependent upon the pressure of the control passageway.

Abstract: An arrangement for controlling two drive units which interact with one another, one of which includes a hydraulically driven motor (2). The motor drives a varying load, and one or more valves (6, 7) control hydraulic fluid flow through the motor during operation and for starting and stopping of the motor. One of the valves is a flow control valve (7) for flow control of the hydraulic fluid flow through the motor. The second drive unit (37) performs a working movement which, under the action of hydraulic flow influences the loading of the motor. The flow of the hydraulic fluid to the second drive unit is controlled in a coordinated way with the control of the flow through the motor.

Abstract: A supply passage 32, a discharge passage 33, an actuator passage 34, and a spool bore 36 are defined in a housing 31. The spool bore 36 accommodates a spool 35 and communicates with the supply passage 32, the discharge passage 33, and the actuator passage 34. Load pressure detection circuit sections 21a, 21b of load pressure detection circuit 21 are provided in correspondence with switch positions 13b, 13c. Each of the load pressure detection circuit sections 21a, 21b detects load pressure when the actuator passage 34 is connected to the supply passage 32. Each load pressure detection circuit section 21a, 21b is defined by a through hole provided in the housing 31 and connected to the spool bore 36. Check valves 22 are each arranged in a corresponding one of the load pressure detection circuit sections 21a, 21b. This simplifies the configuration of each load pressure detection circuit 21 and saves the space for arranging the load pressure detection circuit 21.

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

Abstract: Disclosed is a hydraulic circuit for an option device of heavy construction equipment which can facilitate manipulation of the option device such as a breaker and optionally control a flow rate by supplying hydraulic fluid from a hydraulic pump to the option device at a constant flow rate, regardless of the size of load produced on the option device.

Abstract: A double check valve having a floating function is disclosed, whereby a working device that is operated by a hydraulic cylinder having a double check valve (e.g., a dozer blade) can perform a floating function when the working device performs land readjustment of a work surface. The double check valve having a floating function includes a hydraulic pump, a hydraulic cylinder operating a working device, a control valve controlling a start, a stop, and a direction change of the hydraulic cylinder, and a double check valve installed to open/close flow paths between the control valve and the hydraulic cylinder, and having a pair of plungers dividedly formed to be shifted in opposite directions to each other when a signal pressure is applied thereto, and a pair of check valves being pressed to remove their check functions through a shifting of the plungers.

Abstract: The invention concerns a hydraulic control (1) with a supply connection arrangement (7) having a high-pressure connection (P) and a low-pressure connection (T), a working connection arrangement having two working connections (A, B) connectable with a consumer, a control valve (8) with a valve element (9) between the supply connection arrangement and the working connection arrangement and a compensation valve (11), which is located between the high-pressure connection (P) and the control valve (8) and is acted upon in the closing direction by a pressure between the compensation valve (11) and the control valve (8). It is endeavoured to ensure the most favourable energy consumption possible. For this purpose, in the opening direction the compensation valve (11) is acted upon by a pressure of a selection device (29, 30, 30?, 38), which optionally supplies the compensation valve (11) with a pressure control pressure or a flow control pressure.

Abstract: A two stage pressure regulating device is disclosed. The device is adapted to supply compressed air from a portable container having a pressure of about 150 kg/cm2 to a pneumatic tool by first greatly reducing pressure of compressed air in the container to about 13 kg/cm2 through a pressure-reducing unit and then precisely adjusting same in a low pressure range of about 1-10 kg/cm2 through a fine pressure adjustment unit which is in fluid communication with the pneumatic tool, whereby a user is able to continuously safely operate the pneumatic tool.

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

Abstract: The invention refers to the field of hydraulic control devices and refers to a saturation-proof hydraulic control device with two or more elements; each element is composed of a six-way, two-position spool (4) of the proportional type, a pressure compensator (3), also of the proportional type, notches on the spool for a correct operation and pressure selector members (MS) equipped with spring (M7) that connect the various elements so that the work function at higher pressure sends the pressure to the spring side of its own pressure compensator (3), making it operate as check valve, and sending the pressure existing between spool (4) and pressure compensator (3) to the spring side of the compensators (3) of the other elements and to the pump (P). The spring (M7) must generate a minimum load that is slightly greater than the pressure drop of the maximum flow-rate through the local pressure compensator (3).

Abstract: What is disclosed is a hydraulic control arrangement for controlling a hydraulic consumer, comprising an adjustable supply measuring orifice and an adjustable drain measuring orifice as well as a pressure compensator arranged in a pressure medium delivery. The control arrangement moreover comprises a releasable cut-off block that acts as a check valve in the direction of supply and may be released in the direction of drain by means of a control pressure. In accordance with the invention, the pressure compensator is subjected to a constant force in the opening direction and to the lower one of the pressures downstream from the supply measuring orifice and upstream from the drain measuring orifice in the closing direction.

Abstract: A progressive-starting unit for pneumatic circuits comprises a line inlet and a line outlet interconnected with each other by a regulating valve that is piloted by a pneumatic piloting inlet. The piloting inlet is controlled by the outlet of a progressive-starting device having an inlet connected upstream of said regulating valve. In this manner a progressive-starting unit is obtained which is insensitive to the conditions downstream of its line outlet.

Abstract: A hydraulic system having a source of pressurized fluid and a fluid actuator with a first chamber and a second chamber. The hydraulic system also has a first valve configured to selectively fluidly communicate the source with the first chamber and a second valve configured to selectively fluidly communicate the source with the second chamber. The hydraulic system also has a supply passageway and a signal passageway each disposed between the first and second valves in parallel. The hydraulic system also has a proportional pressure compensating valve configured to control a pressure of a fluid directed between the source and the first and second valves. The hydraulic system further has a fluid passageway disposed between the supply and signal passageways to fluidly communicate the supply and signal passageways.

Abstract: A hydraulic system for a work machine is disclosed. The hydraulic system has a source of pressurized fluid and a fluid actuator with a first chamber and a second chamber. The hydraulic system also has a first valve configured to selectively fluidly communicate the source with the first chamber and a second valve configured to selectively fluidly communicate the source with the second chamber. The hydraulic system further has a proportional pressure compensating valve configured to control a pressure of a fluid directed between the source and the first and second valves.

Abstract: The invention relates to the field of hydraulic directional control valves and refers to an anti-saturation directional control valve (V) composed of two or more sections in each of whom there is a pressure selector compensator with a six-way two-position spool (4) of the proportional type and a compensator (3) performing the function of pressure compensator. The pressure compensator (3) comprises therein a pressure signal selector (S), that is mechanically kept open or not by a piston (5) with a spring (M), of a negligible force, depending on workport pressures. The piston (5) presses against the pressure compensator (3) in the section (E) of the directional control valve (V) that is at a higher pressure, in this case operating as check valve, while in the sections at lower pressure the piston (5) is kept detached from the pressure compensator (3) so that this latter one performs its function of pressure compensator and the inner signal selector (S) by means of the sphere action.

Abstract: A directional control valve for a hydraulic load has, in a piston bore of a valve housing, a control piston which can be displaced axially in opposite directions from a central position and which has first fine control grooves for opening a connection between a load chamber and a feed chamber. There are second fine control grooves for opening a connection between a load chamber and a discharge chamber of the piston bore under control. In its central position, there is a restricted relief connection from a load chamber to the discharge chamber via the control piston. The restricted relief connection is obtained via a recess in the control piston, independently of the second fine control grooves.

Abstract: The invention concerns a hydraulic valve arrangement with a supply connection arrangement, which has a high-pressure connection (P) and a low-pressure connection (T), a working connection arrangement, which has two working connections (A, B), which can be connected with a consumer, a directional valve and a compensation valve arranged between the directional valve and the supply connection arrangement, the pressure outlet of the compensation valve being connected with a pressure inlet of the directional valve. It is endeavoured to avoid dangerous situations, which occur because of uncontrolled pressures. For this purpose, it is ensured that the compensation valve has a relief outlet, which can be connected with the pressure outlet.

Abstract: The present invention relates to a variable flow control apparatus for an actuator of a heavy construction equipment capable of implementing constant flow of hydraulic fluid from a hydraulic pump to an actuator even when a pilot pressure capable of driving a seat valve openably and closably installed in a discharge flow path of the hydraulic pump exceeds a certain pressure level.

Abstract: There is disclosed a stop block for controlling a hydraulic consumer in which a main piston having an advanced opening can be lifted off a valve seat in a return function by means of a push piston. A pressure chamber confined by the main piston on the one hand and by the control piston on the other hand is connected to a tank or low-pressure passage both in the return function and in the non-return function of the stop block so that the change-over from the return function to the non-return function and vice versa can be effected very quickly.

Abstract: A fluid flow control valve assembly that can be actuated using an electrically operated or pneumatically operated flow control valve includes a valve body having a fluid supply passageway, a fluid exhaust passageway, and a fluid bypass passageway. A pilot operated relief valve is disposed in the fluid bypass passageway, wherein the pilot operated relief valve blocks the fluid bypass passageway to create a pressure upstream of the pilot operated relief valve to actuate a different pilot operated device having a pilot line in fluid communication with the fluid bypass passageway upstream of the pilot operated relief valve. Fluid flowing through a venturi nozzle in the fluid bypass passageway that intersects the fluid exhaust passageway lowers the pressure in the fluid exhaust passageway.

Abstract: The flow of fluid to a hydraulic actuator is controlled by a valve assembly which operates in different metering modes at various points in time. The metering mode to use in selected in response to the hydraulic load that acts on the valve associated with the hydraulic actuator. Specifically the load is determined and then compared to threshold levels associated with the different metering modes to choose the metering mode for use a given point in time.

Abstract: A hydraulic control device (10, 90) for load pressure-independent control of a double-acting motor, in which by replacing the pressure balance regulator throttle slide valve element (68, 93) but using the same housing (13), the control device can be converted from a directional-control valve (11) with a primary individual pressure balance regulator (12) for load pressure-independent control to a directional-control valve (91) with a secondary individual pressure balance regulator (92) for an oil flow distribution in the event of undersupply. To this end, in a second longitudinal bore (41) containing the control pressure opening (68, 93), the housing (13) has three axially spaced infeeds of control pressure openings (51, 52, 53), which can be activated differently through interchangeable installation of a sealing plug (66) and a stopper (67) and, together with the respective throttle slide valve element, constitute a primary pressure balance regulator (12) or a secondary pressure balance regulator (92).

Abstract: A directional control valve includes a pressure regulator piston configured as a hollow slide with a radial passage positioned in such a way that a connection from the internal chamber of the pressure regulator piston to a pump pressure annular channel (P) can be regulated by the radial passage and a second radial passage of a directional control valve piston. The second radial passage constitutes a control edge, which is used to regulate the connection from the internal chamber to a load sensing annular channel (LS). An annular groove, which in the neutral position forms a connection from the internal chamber to the load sensing annular channel (LS), is joined to the second radial passage. The pressure regulator is impervious to different flow forces caused by different mass fluxes and ensures that the hydraulic consumer is prevented from moving in the neutral position.

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) connectable with a motor (2), with a directional valve (4), which is arranged between the supply connection arrangement (P, T) and the working connection arrangement (A, B), and with a compensation valve (8), which is acted upon in a first operation direction by a spring (22) and a pressure in a pressure chamber (23), which is connected with a load-sensing line (LS), and in a second operation direction, which is opposite to the first operation direction, by a pressure at the directional valve (4).

Abstract: The present invention intends to improve a hydraulic control unit and prevent the occurrence of hunting as well as to reduce the size of the hydraulic control unit. The hydraulic control unit is used in a several-directional-control-valves-assembled-type hydraulic control system 1 having a load sensing function. The hydraulic control unit has a PLS port. The PLS port is supplied with a maximum load pressure in the hydraulic control system. The compensator of the hydraulic control unit includes a metering orifice imparted with a function equivalent to a check valve. The compensator is imparted with the function of a shuttle valve (directional control valve), and by allowing the shuttle valve to operate independently of the compensator the pressure PLS is adjusted constantly.

Abstract: In an electrohydraulic lifting control device (S) for stacker trucks, which comprises, for lifting control, an electrically operable three-way flow regulator (R1) in a lifting branch (1) between a pressure source (P) and a hydraulic cylinder (Z) as well as, for lowering control, an electrically operable two-way flow regulator (R2) in a lowering branch (2) which branches off from the lifting branch (1) and leads to the reservoir, a redundancy switching element (A) is provided, which is actively electrically operable between closed and open positions, said redundancy switching element (A) being provided between the control pressure circuit of the two-way flow regulator (R2) and/or the control pressure circuit of the three-way flow regulator (R1) and the reservoir (T).

Abstract: An apparatus and method for controlling hydraulic output to a plurality of actuatable devices are disclosed. The apparatus includes a plurality of main valves coupled, respectively, to the actuatable devices and to respective secondary valves, and also an adjustment valve that is coupled between a pressure source and one or more of the secondary valves. The adjustment valve receives a first indication of a pressure at the one or more secondary valves, and a second indication related to a highest load pressure. The adjustment valve allows pressure to be provided from the pressure source to the one or more secondary valves when the second indication exceeds the first indication, such that an equal amount of fluid flow occurs with respect to each of those secondary valves that is reduced in comparison with the fluid flow to any other secondary valves that are not connected to the adjustment valve.

Abstract: A control device for hydraulically operated hoisting mechanisms used to raise and lower loads includes an electrically controllable throttle valve connected to a return line of the hoisting mechanism, and a pressure scale with at least one blocking position and one control position. The pressure scale operates in conjunction with an unblocking mechanism. When in its normal position, the pressure scale blocks the return line. The pressure scale assumes its control position in lowering of a load as a result of triggering of the unblocking mechanism. In the event of failure of the throttle valve, the pressure scale may be moved to its blocking position by the unblocking mechanism. In the event of failure of the pressure scale, the throttle valve assumes its blocking position. The load retention function is performed by two series-connected closed hydraulic actuators which can be electrically controlled individually.

Abstract: A hydraulic control device (10, 90) for load pressure-independent control of a double-acting motor, in which by replacing the pressure balance regulator throttle slide valve element (68, 93) but using the same housing (13), the control device can be converted from a directional-control valve (11) with a primary individual pressure balance regulator (12) for load pressure-independent control to a directional-control valve (91) with a secondary individual pressure balance regulator (92) for an oil flow distribution in the event of undersupply. To this end, in a second longitudinal bore (41) containing the control pressure opening (68, 93), the housing (13) has three axially spaced infeeds of control pressure openings (51, 52, 53), which can be activated differently through interchangeable installation of a sealing plug (66) and a stopper (67) and, together with the respective throttle slide valve element, constitute a primary pressure balance regulator (12) or a secondary pressure balance regulator (92).

Abstract: A control system for operating a hydraulic system includes a user input device which generates an input signal indicating desired movement of a hydraulic actuator. A mapping routine converts the input signal into a velocity command indicating desired actuator velocity. A valve opening routine transforms the velocity command into a flow coefficient which characterizes fluid flow through the valve assembly and from the flow coefficient produces a set of control signals designating levels of electric current to apply to valves within the valve assembly. A pressure controller regulates pressure in the supply line in response to the velocity command. When the hydraulic system has a plurality of functions, the control system adjusts each velocity command to equitably apportion fluid to each function when the aggregate flow being demanded by the functions exceeds the total flow available from a source.

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) connectable with a motor (2), with a directional valve (4), which is arranged between the supply connection arrangement (P, T) and the working connection arrangement (A, B), and with a compensation valve (8), which is acted upon in a first operation direction by a spring (22) and a pressure in a pressure chamber (23), which is connected with a load-sensing line (LS), and in a second operation direction, which is opposite to the first operation direction, by a pressure at the directional valve (4).

Abstract: A hydraulic control system (1) has a hydraulic motor (10), which is connected with a control valve (2) via two working lines (8, 9), the control valve (2) being connected with a low-pressure connection (T) and, via a compensation valve (4), with a high-pressure connection (P), to ensure that a return compensation valve (14, 15) is arranged in each working line, each return compensation valve (14, 15) having a nominal flow line (29), which extends unintersectedly in relation to the nominal flow line (28) of the compensation valve (4).

Abstract: A hydraulic distributor that has a regulating balance including a housing hollowed in the distributor body and containing coaxially a fixed central core. A tubular plunger is interposed sliding freely, coaxially, between the core and the housing and co-operates with a lateral orifice connected to a working orifice. The core and the plunger define between them an annular chamber. The plunger has a first radial annular surface subjected to the highest charge pressure (LS) and a second annular surface subjected to the pressure of the intake fluid. A central passage in the core constitutes a first orifice emerging at one end of the housing exposed to the highest charge pressure (LS). A second orifice emerges in the annular chamber and a third orifice is located opposite the other end of the housing and remains closed by the plunger as long as the charge pressure of the distributor is below the highest charge pressure (LS).

Abstract: An actuator lock switching valve 50 is provided which communicates a drain line 52 and a pilot line 53 with each other when the valve 50 is in a position C, and which communicates pilot lines 51, 53 with each other when it is shifted to a position D. The pilot line 51 is connected to a delivery line 7 of a hydraulic pump 10, and the pilot line 53 is connected to pressure receiving sections 28a, 28b provided at ends of the pressure compensating valves 21a, 21b on the side acting in the closing direction. The actuator lock switching valve 50 has a pressure receiving section 55 connected to the output side of a pilot lock switching valve 43, and is switched over in interlock with shifting of the switching valve 43.

Abstract: In one aspect of the invention, the hydraulic system provided with the hydraulic pressure source and at least one meter-in spool valve. Each Spool valve has an inlet and an outlet. A hydraulic actuator is fluidly coupled with the spool valve outlet. A load hold check valve fluidly interconnects the pressure source with at least one spool valve inlet. The load hold check valve has a pressure control chamber. A three way valve has a first port in fluid communication with the pressure control chamber, a second port in fluid communication with at least one spool valve inlet, and a third port in fluid communication with the pressure source. Proved pressure and flow control to an actuator are provided, and make-up and line relief are provided without the use of an additional spool valve.

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: An actuating device (1) for the rotation of a stand (4) of a vehicle, such as a motorcycle or scooter, between a standing position and a rest position, and allowing also the reverse maneuver in order to rotate the stand from the position of vehicle on the stand up to that in which the vehicle lowers spontaneously. At least one hydraulic actuator (1) is provided that operates, between a first and a second position, an actuating member (7) or piston rod that engages with the stand (4) up to bringing it respectively from the rest position to the standing position. A flow control hydraulic circuit delivers pressurized liquid to the actuator (1) for moving the actuating member (7) from the first to the second position, and allows the back stroke of the actuating member (7) to the first position when the flow of the liquid ceases, whereby the stand (4) can be brought back to said rest position independently from the actuating member (7).

Abstract: In one aspect of the invention, the hydraulic system provided with the hydraulic pressure source and at least one meter-in spool valve. Each Spool valve has an inlet and an outlet. A hydraulic actuator is fluidly coupled with the spool valve outlet. A load hold check valve fluidly interconnects the pressure source with at least one spool valve inlet. The load hold check valve has a pressure control chamber. A three way valve has a first port in fluid communication with the pressure control chamber, a second port in fluid communication with at least one spool valve inlet, and a third port in fluid communication with the pressure source. Proved pressure and flow control to an actuator are provided, and make-up and line relief are provided without the use of an additional spool valve.

Abstract: An actuator lock switching valve 50 is provided which communicates a drain line 52 and a pilot line 53 with each other when the valve 50 is in a position C, and which communicates pilot lines 51, 53 with each other when it is shifted to a position D. The pilot line 51 is connected to a delivery line 7 of a hydraulic pump 10, and the pilot line 53 is connected to pressure receiving sections 28a, 28b provided at ends of the pressure compensating valves 21a, 21b on the side acting in the closing direction. The actuator lock switching valve 50 has a pressure receiving section 55 connected to the output side of a pilot lock switching valve 43, and is switched over in interlock with shifting of the switching valve 43.

Abstract: An arrangement for hydraulic actuation of a movable component on vehicles, particularly a vehicle top, trunk lid, a cover or the like, includes at least one double-action working cylinder (1) whose working chambers are connected to a pressure source (5) via a pressure line (4) or whose working chambers are at least temporarily connectable thereto through a switching valve (11).

Abstract: A hydraulic drive system having a swing control system, includes a pump control unit for controlling a pump delivery rate such that a pump delivery pressure is held a predetermined value higher than a maximum load pressure among a plurality of actuators. Pressure compensating valves are each constructed to set, as a target compensation differential pressure, a differential pressure between a delivery pressure of a hydraulic pump and a maximum load pressure among the actuators. A pressure compensating valve for a swing section is given such a load dependent characteristic that when the load pressure rises, the target compensation differential pressure is reduced, the load dependent characteristic being set so as to provide a flow rate characteristic simulating constant-horsepower control of a swing motor.