EP1450048A1 - Valve arrangement - Google Patents

Abstract

Valve arrangement for a hydraulic cylinder (26) comprises a control valve (12) connecting at least one first chamber (28) of the hydraulic cylinder via a first supply line (22) to a hydraulic pressure source (18) or a container (20), and a first switching valve (50) controlling the flow in a first hydraulic line (46) running between the first chamber and the container, and opening on the basis of a switching signal to set a floating position. A valve device (52) controlled according to the flow volume is arranged in the first hydraulic line.

Description

The invention relates to a valve arrangement for a Hydraulic cylinder with a control valve, which at least a first chamber of the hydraulic cylinder over a first Supply line optionally with a hydraulic pressure source or connects a container. Furthermore, a first one Switch valve included, which the flow in a extending between the first chamber and the container controls first hydraulic line, and which due to a Switching signal opens, making a floating position adjustable is.

Valve arrangements with implemented floating positions, thereby free movement of a hydraulic consumer are made possible are known in the prior art. there both connection sides of the hydraulic consumer with each other as well as with or without pressure with one Tank or hydraulic tank connected. such Valve arrangements are found in construction and loader vehicles Use where a boom with a lifting cylinder or a loader arm can be raised or lowered. The Function of the floating position is required, for example, to regardless of the position and location of the vehicle allow a tool on the boom or loader arm of the Can follow the contour of the ground true to the contour. The tool will be there just pressed to the ground by gravity. Valve arrangements of this type do not contain any load holding valves, the for safety reasons when a leak occurs in the Connection between cylinder and control valve on unintentional lowering of the boom or loader arm prevent or slow down strongly. Since it can be opened or Bypassing the load holding valve requires a control pressure a solution for combining a load holding valve with a Floating position, in the depressurized state of the hydraulic consumer and therefore no control pressure is buildable, not known.

DE 101 49 787 A1 discloses a valve arrangement with Floating position to control a double acting Consumer, where a control valve in a Flow position is acted upon and by a pressure-switched valve arrangement a floating position is feasible. About the control edges of the control valve brought about a throttling, changes in the Movement speed of the consumer during the transition to the Floating position should be avoided effectively. adversely this has an effect that the throttling over a complex constructed pressure control of the Control valve takes place, which gives a high tax inertia and it is at high load when switching to one Floating position despite throttling to unwanted or uncontrolled lowering movements can occur. Furthermore the valve arrangement does not contain a load holding valve Protection of the hydraulic operation of the consumer.

DE 100 06 908 A1 discloses a hydraulic one Piston cylinder unit for agricultural machines with a load holding valve in the one working position is achieved in which a constant pressure in the piston chamber side cylinder space is adjustable. This can a boom or a tool attached to it always Lie on the floor with the selected contact force. This Working position is achieved by the pressure chambers of the Piston-cylinder unit are connected to each other and a pressure compensation valve between the both pressure chambers. If the pressure drops below one Preselected value, the pressure control valve closes. A Floating position is only possible if the preselected one Value is set to zero, so no pressure control he follows. The disadvantage is that when switching the load or the tool is uncontrolled under load would sink.

DD 205 471 discloses a hydraulic circuit arrangement, with which a floating position is created at the driver's request can be made by the chambers of a cylinder by means of a 3/2 valve can be connected to a container. About one Throttle check valve is a throttled drain on the Pressure side of the cylinder both in the operating position and in Floating position guaranteed. The disadvantage is that at Switch to the floating position under load on the Operation designed constant cross section of the throttle Lowering the pressure side is not controllable. Of Furthermore, such a throttle check valve does not Load holding valve, which is in the operating position can prevent unwanted sinking.

The object underlying the invention is seen in specify a valve arrangement of the type mentioned at the outset, by which the aforementioned problems are overcome. In particular, a valve arrangement is to be proposed with which a floating position can be realized and at Switch from operating position to floating position controlled sinking or holding the pressure side can. Another object of the task is the Valve arrangement effective with a load holding valve for one Combine operating position.

The object is achieved by the teaching of Claim 1 solved. Further advantageous configurations and further developments of the invention result from the subclaims out.

According to the invention, a valve arrangement of the beginning mentioned type with one in the first hydraulic line arranged valve flow-dependent control device Mistake. A flow-dependent control has the Advantage that regardless of the hydraulic pressure in the Hydraulic line the volume flow is controllable so that with both low and high hydraulic loads only a certain flow rate through the hydraulic line reached and thus a safety function is offered. Becomes for example, while the first chamber of the Hydraulic cylinder is pressurized, the valve assembly brought into floating position by the switching signal Switching valve is switched to the flow position, then ensures the valve device that controls the volume flow, that regardless of the level of pressure, the flow rate can only change within certain limits or a certain value will not exceed.

In a preferred embodiment of the invention, the Valve device changing the flow opening Adjustment means, for example a slide or Closing elements, on the one hand a pressure of the first chamber and on the other hand a pressure of the container as well possibly exposed to a spring force. In Dependence on a pressure difference between the two Flow sides that correspond to a prevailing one Volume flow sets, changes or closes the Flow opening of the actuator.

In a particularly preferred embodiment of the invention contains the valve device means that with increasing (falling) pressure drop across the valve device Reduce (widen) the flow cross-section. This has the Advantage that if due to increasing pressure in the Hydraulic line the volume flow increases, that too Pressure drop between the flow inlet and Flow outlet side rises. At the same time it reduces then the flow cross section over the valve device, so that the pressure drop drops again. As a result of falling pressure drop in turn reduces the Flow cross section of the valve device, so that a controlling or regulating state that the Volume flow in the presence of a pressure drop largely or within certain limits.

In a particularly preferred embodiment of the invention the valve device contains a flow control valve, which the volume flow changes depending on the flow and to one specifiable maximum value limited. Such flow control valves are for example from the company "HYDAC International" offered. A precise description can be found in DIN-ISO 1219 be removed. A flow control valve has one Differential pressure regulator, which depends on the flow rate Control piston, a compression spring, a control orifice and one Set screw to adjust the control pressure difference Flow controls. With increasing volume flow or increasing flow d. H. increasing pressure drop the cross section of the control orifice is increased accordingly Pressure drop reduced until on again There is a balance of forces. Through the continuous Readjustment of the differential pressure regulator, according to the prevailing pressure drop, a constant volume flow in reached a control direction, the control direction preferably the outflow direction of the hydraulic fluid the chamber of the Hydraulic cylinder, preferably the stroke side of the Hydraulic cylinder, corresponds to the direction of the container. In The valve can be flowed through uncontrolled in the opposite direction. Such a valve has the advantage that even with extreme high pressure loads always a the control pressure difference sets the appropriate volume flow, with the Control pressure difference can be specified via the adjusting screw. This has the consequence that when switching from operating position to Floating position under load a controlled decrease in pressure, largely independent of the prevailing level Pressure, takes place and thus a safety precaution with the Switching to the floating position is given.

In a particularly preferred embodiment of the invention the valve device contains a parallel to the Flow control valve arranged check valve, which in Direction of the first chamber opens. This ensures that the flowing towards the container Hydraulic fluid is forced through the flow control valve to flow and accordingly controlled from the high Pressurized chamber flows away, whereas an inflow can take place unhindered from the opposite direction.

In another preferred embodiment of the invention contains the valve device means that when exceeded of a preselectable pressure drop reduce the volume flow or interrupt. This ensures that at Reaching a volume flow that corresponds to the predeterminable pressure drop causes the connection to be broken so that the Pressure in the first chamber under high pressure or is held in the first hydraulic line. The pressure drops again, the connection will be re-established as soon as that Predeterminable pressure drop is reached or a Sets the volume flow, which causes a pressure drop, which is less than or equal to the specifiable pressure drop.

In a preferred embodiment of the invention, the Valve device a raw break protection valve, which at Reaching or exceeding a predeterminable pressure drop closes or when the pressure drop falls below the predefinable pressure drop opens. Such raw breakage protection valves are for example offered by the company "HYDAC International" and are detailed in a company catalog "HYDAC INTERNATIONAL - FLUTEC pipe burst safety devices RBE ". "Flutec" pipe burst safety devices are dependent on the volume flow switching flat seat valves, the impermissible and uncontrolled movements of a person under load Prevent consumers. Has a pipe rupture safety valve a closing element, for example a locking piston in the form a poppet valve, which in normal operating condition has open switch position. The closing element is preferably held in the open state by a spring, as long as the spring force is greater than that by the Flow resistance caused by flow through the closing element or on the plate surface of the Poppet valve. The valve remains open and is in both Directions flowable. If the prevailing Volume flow when flowing through the valve in a predeterminable Direction of the pressure drop defined by the maximum permissible value is determined by the Flow resistance increase overcomes the spring force and that Closing element suddenly pressed onto the valve seat, see above that the flow is interrupted. The valve opens automatically as soon as pressure equalization takes place and the Pressure force in front of the valve resulting from spring force and Compressive force behind the valve below.

In a preferred embodiment of the invention, the Valve device one parallel to the pipe rupture safety valve arranged choke or orifice, which when closed Pipe burst safety valve a reduced volume flow allowed. This ensures that there is always a certain Share of the volume flow is forwarded so that the Can not build up pressure in front of the valve device. The throttle or orifice can be parallel in a bypass line be arranged to the raw break protection valve or for example in the form of a hole directly on Pipe rupture safety valve, especially directly on the poppet valve be trained. At high volume flows ensures that by closing the Pipe rupture valve a large part of the volume flow is intercepted and only a small part of the Hydraulic fluid passes through the throttle so that overall a controlled decrease in pressure when switching over to the floating position is reached.

In a further embodiment of the invention, this connects Control valve over a second chamber of the hydraulic cylinder a second supply line optionally with the Hydraulic pressure source or the container. So both can Chambers of a double-acting hydraulic cylinder with pressure be acted upon, which accelerated emptying of the Enables chambers and thus the extension and retraction of one Hydraulic cylinder piston is made possible at shorter intervals. A second switching valve is preferably included, which the flow in a between the second chamber and the Container-extending second hydraulic line controls, and which is parallel to the first due to the switching signal Switch valve opens, making a floating position adjustable is in which the first chamber and the second chamber directly or communicate indirectly through the container. The hydraulic cylinder can be used in any way Operating position are brought into a floating position or after accidentally switching to a floating position without significant pressure loss immediately back into a Operating position.

In a further embodiment of the invention, the first contains and / or the second supply line a load holding valve arrangement. Load holding valve arrangements are state of the art and are considered in most modern valve arrangements Safety precautions introduced in supply lines to an unwanted pressure drop in the consumer or To prevent hydraulic cylinders. If leaks occur, be it on the control valve, on the connecting lines or on Seals etc., especially under load, can be too fast Pressure losses in the hydraulic chambers of the hydraulic cylinder come, which in turn poses a security risk. Around Preventing pressure drops under load will be such Load holding valve arrangements as close as possible to the Hydraulic cylinder positioned so that between Hydraulic cylinder and load holding valve arrangement as little as possible Components are included that could have leaks. These load holding valve arrangements are usually located directly on the hydraulic cylinder and are part of it Assembly, so that no easily damaged components, such as z. B. hoses must be used. Also allow Load holding valve assemblies have a tightness under load even the smallest pressure drops over a longer period of time prevent. An intended pressure change is achieved by such load holding valve arrangements by hydraulic Circuits are bypassed or opened.

In combination with the first and second hydraulic lines, which the chambers of the hydraulic cylinder in floating position connect to the container can be particularly advantageous On the one hand, an operating position with integrated Load holding valve arrangement can be achieved, but also on the other in a floating position with the described Safety features of a controlled volume flow control can be switched.

As load holding valve assemblies z. B. Pipe rupture protection used, the various components, such as z. B. Lowering brake valves, hydraulically unlockable Check valves, overcenter valves or the like included.

In a particularly preferred embodiment of the invention the load holding valve assembly includes a check valve, for example a hydraulically unlockable check valve, which is in a closed position and in Dependence on the pressure of the first and / or the second Supply line opens. Furthermore, is parallel to Check valve included an additional check valve, where the additional check valve towards the Hydraulic cylinder opens. The load holding valve assembly will preferably arranged on the stroke side of the hydraulic cylinder, d. H. on the usually safety-relevant pressure side of the Lift cylinder on which there is a high operating pressure a load will set. About the corresponding one Supply line can be the first chamber of the hydraulic cylinder be filled by the pump. The check valve prevents an effective escape of the hydraulic fluid this filled chamber. A first pressure line connects the second supply line with the shut-off valve. Should now Chamber is emptied, the second chamber over the second Supply line filled, which creates a pressure in the second supply line that builds the check valve the first pressure line from the closed position to a Pass position moved. The hydraulic fluid can now run out the first chamber into the container. As soon as the Relieves pressure in the second supply line, for example by switching to another operating position, that takes Check valve back to its closed position. Furthermore is on the hydraulic cylinder side in the first supply line second pressure line provided as overload protection, which at excessive pressure conditions on the stroke side of the Hydraulic cylinder, regardless of the switching position of the Control valve that opens the shut-off valve.

In a particularly preferred embodiment of the invention the first and second switching valve as electromagnetic switchable seat valves. This allows through The switching valves generate an electrical switching signal controlled and switched to a floating position at any time become. The use of different types is also conceivable here Switching valves, for example pneumatic, hydraulic or are also mechanically controlled switchable.

Preferably in the various configurations shown valve arrangements for use for a Hydraulic cylinder for lifting and lowering a boom on one Loader or construction vehicle, especially on a telescopic loader used. For example, with a telehandler in in any operating position, even under load when raised Boom can be switched to floating position. A Floating position without described volume flow control would cause that with increasing load the boom more or would shutdown less uncontrollably, which is an increased Represents security risk. At the same time, the Use floating position when working on the ground surface. Furthermore, the possibility is given with integrated Load holding valve, the hydraulic cylinder with the boom raised by appropriate control via the control valve to apply pressure on the vertical side, so that a accelerated boom shutdown entry. In all Operating positions is a secure switchover to one Given floating position.

It is particularly advantageous that the inventive Refinements a floating position for a telescopic loader while maintaining a security-relevant Load holding valve arrangement (pipe rupture protection) is given. Of Furthermore, the realization of a floating position is given, which dispenses with complex construction methods, so that the Mostly lifting sections already present on a telescopic loader the main valve blocks do not need to be changed. Thereby the number of valve blocks can be kept low and also the possibility of retrofitting or upgrading Use of the same lifting cylinder with different Options. There are also other variations conceivable having a floating position function for example combine a hydraulic suspension version so that starting from a basic version with load holding valve arrangement a modular extension with floating position function and in addition a modular extension with suspension function is possible.

Using the drawing, the two embodiments of the Invention shows, the invention and others are below Advantages and advantageous developments and refinements the invention described and explained in more detail.

Fig. 1

einen Schaltplan einer ersten erfindungsgemäßen Ventilanordnung mit einem Stromregelventil,

Fig. 2

einen Schaltplan einer zweiten erfindungsgemäßen Ventilanordnung mit einem Rohrbruchsicherungsventil und

Fig. 3

eine schematische Seitenansicht eines Teleskopladers mit erfindungsgemäßer Ventilanordnung zur Verwendung für einen Hydraulikzylinder.

It shows:

Fig. 1

2 shows a circuit diagram of a first valve arrangement according to the invention with a flow control valve,

Fig. 2

a circuit diagram of a second valve assembly according to the invention with a pipe rupture valve and

Fig. 3

is a schematic side view of a telescopic loader with a valve assembly according to the invention for use in a hydraulic cylinder.

The circuit diagram shown in Fig. 1 shows a Embodiment for a valve assembly 10 for Realization of a floating position. The valve assembly 10 contains a switchable control valve 12, for example a Slider valve, which with hydraulic lines 14, 16 with a pump 18 and a hydraulic tank 20 is connected, the control valve 12 in three operating positions, lifting, Neutral and lower position, is switchable. Switching the Control valve 12 is preferably manually controlled, but can also done electrically, hydraulically or pneumatically.

This is via a first and second supply line 22, 24 Control valve 12 connected to a hydraulic cylinder 26, wherein the first supply line 22 into a first chamber 28 of the Hydraulic cylinder 26 and the second supply line 24 in a second chamber 30 of the hydraulic cylinder 26 leads. The first chamber 28 of the hydraulic cylinder 26 provides the piston chamber side or stroke side chamber, whereas the second chamber 30 the piston rod side or lower side Represents chamber of the hydraulic cylinder.

There is one in the first supply line 22 Load holding valve assembly 32 is provided. The load holding valve assembly 32 contains a pressure and spring controlled Blocking valve 34, as well as one opening to the hydraulic cylinder side Check valve 36, which via a bypass line 38 is arranged parallel to the check valve 34. About a first Pressure line 40 is a pressure connection from the check valve 34 to Hydraulic cylinder-side section of the first supply line 22 manufactured. Via a second pressure line 42 a further pressure connection from the check valve 34 to the second Supply line 24 manufactured. Furthermore, one Spring 44, the check valve 34 in the closed position.

A first hydraulic line 46 connects the first chamber 28 or the first supply line 22 with the hydraulic tank 20, which is not connected to the hydraulic tank 20 End 48 of the first hydraulic line 46 between the first Chamber 28 and the load holding valve assembly 32 is arranged.

A first switching valve is located in the first hydraulic line 46 50 and one in the direction of the hydraulic container 20 in series switched valve device 52 arranged. The first Switch valve 50 represents an electrically switchable seat valve represents which via an adjusting spring 54 in the closed position is held and opened via a magnetic coil 56 Open position can be brought. The switching valve 50 seals in one or both directions without leakage from. The valve device 52 contains a flow control valve 58, which is connected in parallel to a check valve 60 is arranged, the check valve 60 in Hydraulic cylinder direction opens. It is also possible here the valve device 52 in the direction of the hydraulic container 20 to be arranged before the switching valve 50.

A second hydraulic line 62 is also provided, which connects the second supply line 24 to the first Hydraulic line 46 connects, the connection point 64 with the first hydraulic line 46 between the Hydraulic container 20 and the valve device 52 are arranged is.

The second hydraulic line 62 also contains a second one Switching valve 66, which is the first switching valve 50 in construction and function is the same.

The individual operating states can now be done as follows via the Control valve 12 and the switching valves 50 and 66 can be controlled. As shown in Fig. 1, the Control valve 12 by the actuating springs 68, 70 in the neutral position held. The switching valves 50 and 66 are in one Closed position. The control valve 12 is controlled by a control signal by means of an actuating device 72 from the neutral position brought out into the lifting or lowering position. It can manual, electrical, hydraulic or act pneumatic actuator 72.

In the lifting position, the connection of the first Supply line 22 with the pump 18 and the connection of the second supply line 24 with the hydraulic reservoir 20th manufactured. The pump connected to the hydraulic tank 20 18 filled via the first supply line 22 and Check valve 36 of the load holding valve assembly 32 (the Check valve 34 of the load holding arrangement 32 is located in Closed position), the first chamber 28 of the hydraulic cylinder 26. As a result, the piston 74 moves in the direction of the second chamber 30 and presses the oil there through the second supply line 24 out into the hydraulic tank 20. Is now switched back to neutral, so The control valve 12 interrupts the connections to the pump 18 and to the hydraulic tank 20 so that the pressure in the two Chambers 28, 30 of the hydraulic cylinder 26 maintained and the Movement of the piston 74 is canceled. The piston 74 remains stand.

In the lowered position, the connection of the first Supply line 22 with the hydraulic tank 20 and the Connection of the second supply line 24 to the pump 18 manufactured. The pump delivers oil to the second chamber 30 of the Hydraulic cylinder 26, which is in the second Supply line 24 building pressure over the check valve 34 the second pressure line 42 of the load holding valve arrangement 32 opens. At the same time, the piston 74 moves in the direction of the first Chamber 28 moves so that the first chamber 28th flowing oil over the first supply line 22 and over the opened check valve 34 enters the hydraulic tank 20.

The load holding valve arrangement 32 thus ensures that the Hydraulic cylinder 26 in its neutral position maintains or no oil from the pressurized first chamber 28 escape and that in Lowering the oil from the first chamber 28 over the open Check valve 34 can flow. To ensure this should or must the load holding valve arrangement be meaningful like shown on the stroke side of the hydraulic cylinder 26 be arranged, the lifting side being the side of the Hydraulic cylinder 26 is in which a pressure for lifting a load is built up. In the exemplary embodiments shown here the stroke side is the first chamber 28 of the hydraulic cylinder 26, by turning the hydraulic cylinder 26 also the second Chamber 30 could serve as the lifting side. The first pressure line 40 represents an overload protection, so that if the Operating pressures in the first chamber 28 of the hydraulic cylinder 26, which arise, for example, from excessive loads can reach a limit pressure in the first pressure line 40 that opens the shut-off valve 34 for pressure reduction.

The switching valves 50 and 66 can be used in any Operating position can be switched to the floating position. To are the switching valves 50 and 66 by means of a switching signal driven in parallel so that the solenoids 56 of the Counteract the spring force of the springs 54 and the switching valves 50, 66 essentially from the closed position brought into flow position at the same time. This has to Consequence that the first chamber 28 and the second chamber 30 to one with the other and the other with the hydraulic reservoir 20 be related, so that an exchange of Hydraulic fluid or oil take place and the piston 74th can be moved freely. Finds a toggle an operating position under load, the oil flows under increased pressure from the pressurized first chamber 28 out, which leads to accelerated piston movement. Around limit this piston movement in its speed the flow control valve 58 enters into force Volume flow limited or controls the flow of the oil or regulates. If the volume flow exceeds an approved value, the passage cross section of the flow control valve 58 narrows, so that the volume flow does not continue to increase. hereby become uncontrolled movements of the hydraulic cylinder piston 74 effectively avoided. With an opposite pressure effect in the direction of the first chamber 28 enables this Check valve 60 bypassing the flow control valve 58 and thus an unregulated flow in the direction of the first Chamber 28. A switch from the floating position to one Operating position is at any time by switching the switching valves 50, 66 possible in a closed position.

2 shows a second exemplary embodiment described. The same will be the same for similar components Reference numerals as used in Fig. 1. 2 is for the valve device 52 in place of the flow control valve 58 and the check valve 60 a pipe rupture valve 76 in Combination with a choke 78 connected in parallel used. Instead of the throttle 78 can also equivalent aperture are used. Is by switching of the switching valves 50, 66 switched to the floating position the pipe rupture safety valve 76 also one flow-dependent reduction or limitation of the Volume flow. Reaches the volume flow in floating position in the first hydraulic line 46, due to excessive pressure in the first chamber 28, one on the pipe rupture safety valve 76 predeterminable limit value, then one affects from the setting pressure difference resulting force of am Pipe rupture valve 76 acting spring force of a Closing spring 80 counter and closes it Pipe rupture safety valve 76. At the same time, the first chamber 28 flowing oil diverted through throttle 78 so that a greatly reduced, controllable volume flow flows and only low speeds of movement of the piston 74 can be approved. Here it is also possible Valve device 52 in the direction of the hydraulic container 20 to arrange the switching valve 50.

Use for those shown in FIGS. 1 and 2 Exemplary embodiments are illustrated in FIG. 3. Fig. 3 shows a mobile telescopic loader 82 with a on a housing 84 or frame of the telescopic loader 82 pivotally hinged, extendable boom 86, between boom 86 and housing 84 is a hydraulic cylinder 26 for lifting and Lowering the boom 86 is arranged. The hydraulic cylinder 26 is at a first and a second bearing point 88, 90 pivoted, the piston rod side 92 on the second bearing 90 on the boom 86 and the piston crown side 94 is hinged to the housing 84 at the first bearing 88. Furthermore, the hydraulic tank 20, the pump 18 and the valve assembly 10 positioned on or in the housing 84 and connected to one another via hydraulic lines 14, 16, 46, 96. Furthermore, the supply lines 22, 24 are between Valve arrangement 10 and hydraulic cylinder 26 can be seen in FIG. 3. Control or not, control or Switch signals generated with which the control valve 12 and the switching valves 50, 66 (see FIGS. 1 and 2) controlled or be switched. According to the previous one described operating positions, the hydraulic cylinder 26th are operated in such a way that the boom 86 is raised, can be held or lowered. It is also possible in Switch floating position so that the piston can move freely and the boom 86 is floating. Through the Floating position ensures that one is on the boom 86 tool 98 fastened and lowered to the floor floating, following the contour of the ground, over the surface of the ground can be moved. The contact pressure of the tool 98 opposite the soil is essentially determined by the weight of the Boom 86 and the tool 98 determined. A Safety function is given by the fact that a Lowering of boom 86 is volume-controlled under load can, so no unwanted, sudden Changes in movement occur. Is z. B. the boom 86 in the raised position under load and then in Switched floating position, the flow control valve 58 ensures or the pipe rupture safety valve 76 in connection with the Throttle 78 for the boom 86 in a preset, controllable speed lowered becomes. Realized with this by the valve arrangement 10 Safety precaution for a floating position can be taken from anyone Operating position switched out into a floating position be without causing uncontrolled changes in movement on the Boom 86 is coming. Furthermore, a Valve arrangement 10 with integrated floating position in Realized connection with a load holding device 32 with which also involves a pressurized lowering of the boom 86 by switching the control valve 12 in the lowered position closed switching valves 50, 66 is possible.

Even if the invention is only based on two Exemplary embodiments have been described, open up for the expert in the light of the above description and the Drawing many different alternatives, modifications and variants which fall under the present invention. So can, for example, the valve arrangement on others Vehicles are used, for example on excavators or Cranes that have hydraulically actuated components, which have to be raised or how to be lowered and where a floating position seems reasonable.

Claims (14)

Valve arrangement for a hydraulic cylinder (26) with a control valve (12), which connects at least one first chamber (28) of the hydraulic cylinder (26) via a first supply line (22) optionally to a hydraulic pressure source (18) or a container (20), and with a first switching valve (50) which controls the flow in a first hydraulic line (46) running between the first chamber (28) and the container (20) and which opens on the basis of a switching signal, whereby a floating position can be set, characterized in that that a valve device (52) which controls the volume flow and is arranged in the first hydraulic line (46) is included. Valve arrangement according to claim 1, characterized in that the valve device (52) contains an adjusting means (58, 76, 78) which changes the flow opening and which on the one hand a pressure of the first chamber (28) and on the other hand a pressure of the container (20) and optionally one Spring force is exposed. Valve arrangement according to one of the preceding claims, characterized in that the valve device (52) contains means (58, 76, 78) which reduce (expand) the flow cross-section with increasing (falling) pressure drop across the valve device (52). Valve arrangement according to one of the preceding claims, characterized in that the valve device (52) contains a flow control valve (58) which changes the volume flow as a function of flow and limits it to a predeterminable maximum value. Valve arrangement according to claim 4, characterized in that the valve device (52) contains a check valve (60) which is arranged parallel to the flow control valve (58) and opens in the direction of the first chamber (28). Valve arrangement according to one of claims 1 to 3, characterized in that the valve device (52) contains means (76, 78) which reduce or interrupt the volume flow when a predetermined pressure drop is exceeded. Valve arrangement according to claim 6, characterized in that the valve device (52) contains a raw breakage protection valve (76) which closes when a predetermined pressure drop is reached or exceeded or opens when the pressure drop falls below the predetermined pressure drop. Valve arrangement according to Claim 7, characterized in that the valve device (52) contains a throttle (78) or orifice which is arranged parallel to the pipe rupture safety valve (76) and which permits a reduced volume flow when the pipe rupture safety valve (76) is closed. Valve arrangement according to one of the preceding claims, characterized in that the control valve (12) connects a second chamber (30) of the hydraulic cylinder (26) via a second supply line (24) either to the hydraulic pressure source (18) or to the container (20). Valve arrangement according to one of the preceding claims, characterized in that a second switching valve (66) is contained, which controls the flow in a second hydraulic line (62) running between the second chamber (30) and the container (20), and which is based on of the switching signal opens in parallel to the first switching valve (50), whereby a floating position can be set in which the first chamber (28) and the second chamber (30) are connected to one another directly or indirectly via the container (20). Valve arrangement according to one of the preceding claims, characterized in that the first and / or the second supply line (22, 24) contains a load holding valve arrangement (32). Valve arrangement according to claim 11, characterized in that the load holding valve arrangement (32) a shut-off valve (34), which is in a closed position due to spring force and opens depending on the pressure in the first and / or the second supply line (22, 24), and further includes a check valve (36) arranged parallel to the shutoff valve (34), the check valve (36) opening in the direction of the hydraulic cylinder (26). Valve arrangement according to one of the preceding claims, characterized in that the first and / or second switching valve (50, 66) are electromagnetically switchable seat valves. Valve arrangement according to one of the preceding claims for use with a hydraulic cylinder (26) for lifting and lowering a boom (86) on a loader or Construction vehicle, in particular on a telescopic loader (82).

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