EP1574474A2 - Hydraulic arrangement - Google Patents

Abstract

The hydraulic control to provide a floating position for a hydraulic cylinder in a construction vehicle has a switching valve (50) in the hydraulic lines connected to the cylinder and with a control (12) having three positions, one of which provides the floating position. In this a secondary hydraulic feed line (24) is connected to the hydraulic reservoir (20) and both main lines are connected directly to a pump (18).

Description

Hydraulic arrangement for the realization of a floating position for a hydraulic cylinder, with a first and a second chamber having hydraulic cylinder, a Hydraulic tank, one pumping a hydraulic fluid Conveying, one between the first and the second chamber arranged hydraulic line, one in the hydraulic line arranged switching valve, one in the hydraulic line arranged volume flow dependent controlling valve device, a first supply line for the first Chamber, a second supply line for the second chamber, one arranged in the first supply line Pipe burst protection device and a control unit with at least three switching positions, which are a lifting position, a lowered position and a neutral position for the Include hydraulic cylinder.

Hydraulic arrangements with implemented floating positions, whereby a free movement of a hydraulic cylinder allows are known in the art. Both are Connection sides of the hydraulic cylinder with each other as also low pressure or without pressure with a tank or Hydraulic tank connected. Such hydraulic arrangements found in construction or loading vehicles, such. B. Telehandler or front loader vehicles, use in which by means of a Lifting cylinder raised a boom or a rocker or can be lowered. The function of the floating position is for example, needed to be independent of the position and location of the vehicle to allow a tool on Boom or on the rocker of the vehicle, the bottom contour can follow the contour. The tool is just pressed to the ground by gravity.

Hydraulic arrangements with floating positions are taking shape especially then as very expensive if a load-holding valve is provided, which for safety reasons at emergence a leakage in the connection between cylinder and Control unit unintentional lowering of the boom or the swingarm should prevent or slow down much. To the Opening or bypassing the load-holding valve is usually required a control pressure through which the valve is opened. In the Floating position is a non-pressurized state of the hydraulic Consumer, so that without additives no tax pressure is buildable. To build up this control pressure anyway can, such hydraulic arrangements are to additional switching valves and / or hydraulic lines extended. By this extension should then if necessary a Connection of the rod side of the hydraulic cylinder with the Hydraulic tank to be made or separated.

DE 100 06 908 A1 discloses a hydraulic Piston-cylinder unit for agricultural machines with a load-holding valve, in which a working position is reached, in which a constant pressure in the piston bottom side cylinder space is adjustable. This can a boom or a tool located there always rest on the ground with preselected contact force. These Working position is achieved by the pressure chambers of Piston-cylinder unit to be associated with each other And via a pressure control valve, a pressure equalization between the both pressure chambers takes place. If the pressure drops below one preselected value, closes the pressure control valve. A Floating position is only possible if the preselected Value is set to zero, so no pressure control he follows. The disadvantage is that when switching under load, the boom or the tool uncontrolled would sink.

In the German patent application with the file number DE 10307346 a valve assembly is disclosed, which Has load holding valve and a floating position for a Hydraulic cylinder allows. To lower the To allow hydraulic cylinder under load is a separate switching valve in an additional with a Hydraulic tank connected hydraulic line provided. First By closing this switching valve is a structure of the Opening the load holding valve required control pressure allows. Furthermore, it is conceivable that it is at a Such hydraulic arrangement due to complex Switching relationships and / or improper operation of the Operator to unwanted switching states or faulty circuits can come.

The object underlying the invention is seen therein a hydraulic arrangement of the type mentioned to improve that the effort to realize a "lowering function" under load reducible and at the same time a fully functional floating position is feasible. In particular, switching relationships less complex and the risk of incorrect operation and unwanted switching states can be reduced.

The object is achieved by the teaching of Patent claim 1 solved. Further advantageous embodiments and further developments of the invention will become apparent from the dependent claims out.

According to the invention, a hydraulic arrangement of the above mentioned type designed such that the control unit, a has further switching position, which is a floating position represents, in which by the control unit at least the second supply line is connectable to the tank and at the same time connections of both supply lines to Subsidies are interrupted. By doing that, the controller has a fourth switching position, can on a second Switching valve for connecting the second chamber of Hydraulic cylinder with a tank, as in previous ones Solutions provided is waived. With it reduced the technical effort is considerable, especially because of because an additional hydraulic arrangement for the realization one of the "lowering function" under load is eliminated. Thus, will preferably only one switching valve is used with the only the first chamber is connected to the second chamber.

A fourth shift position according to the invention provides the Advantage that in addition to the lifting position and the lowering position furthermore a neutral position for the hydraulic cylinder can be provided in both supply lines are closed. In the neutral position, the connection should between the lower side of the hydraulic cylinder and the Hydraulic tank should preferably be closed, as there are applications with wheel loaders, telescopic loaders and also front loaders are at which a certain contact pressure under one on the boom attached tool is to be produced, resulting in a permanent connection to the tank would not be possible and so on would lead to a disadvantage compared to competing products. It is therefore an advantage of a fourth invention To add switching position and both the lifting and To provide lowering and neutral position.

The control unit may be designed such that in the fourth switching position, the first supply line with the second supply line interconnected and both Supply lines are connected to the hydraulic tank, the second input to the controller being closed, so that there is no supply from the subsidy. A such fourth switching position as floating position is not mandatory, it is sufficient if the fourth Switch position only the second supply line of the Hydraulic cylinder connects to the hydraulic tank.

In the floating position, the control unit connects the second Supply line or the second and the first Supply line directly to the hydraulic tank, i. it No additional valves or means are required (except one) Connecting line from the control unit to the tank). The control unit can be designed manually or electrically operated, Of course, other methods are conceivable are, for example, pneumatic or hydraulic methods, which, however, should not be explained in detail.

The switching valve preferably has a closed position and an open position, wherein the switching valve in the Closing position preferably closes in both flow directions and opens in the open position in both directions of flow, so that a floating position for the hydraulic cylinder entry. The switching valve is preferably electric actuated. It is of course also conceivable that other types of actuation of the switching valve are used, for example, a manual, pneumatic or hydraulic Activity.

If now the floating position to be activated, it will Switching valve in its open position and the control unit in its fourth switching position switched to the first and the second chamber of the hydraulic cylinder with each other and with the Hydraulic tank to connect. So that the hydraulic arrangement as easy to use and the possibilities for a Operator error is minimized the switching valve is preferably always opened automatically, d. H. brought into open position when the control unit in its floating position. Preferably, they are Provided with funds to determine whether the Control unit is in its floating position or not. This can be implemented, for example, in the form of a switch be in connection or depending on the Floating position is switched on the control unit. at electrohydraulically controlled control units is a Such a switch usually not required because this task taken from the software of an electronic control unit can be. It is also irrelevant how and where the switching position of the control unit is detected because only the result as such is of interest. An above This switch can be connected to a joystick, to a Operating mechanism incl. Cable or directly on the Control unit are attached. It is also conceivable here Sensor that receives a proportional signal based on a suitable evaluation an electrical signal generated, which the switching valve in opening or Closed position switches. Also it would be conceivable, a Pressure switch or pressure sensor to use, the Pilot pressure from a hydraulic joystick Control signal is sent to the control unit, determined. It thus arise a variety of ways the To determine the switching position of the control unit and in Dependence of opening or closing the switching valve shut down.

If the boom or swingarm under load or pressure is lowered by adjusting the control unit in the lowering position, and the associated closing of the Switching valve, automatically connect to the two Chambers with each other and closed to the hydraulic tank. Hydraulic fluid flows into the second chamber of the Hydraulic cylinder, where now a sufficiently high pressure can be constructed to open the load-holding valve, what mandatory for lowering the boom or swingarm is required. In the usual hydraulic Arrangements for floating positions with load-holding valve or with a pipe rupture device is a second Switching valve needed, which is the one for a floating position required connection to the tank produces and which must be closed to the required pressure build-up guarantee.

If the boom or the swingarm to be raised, is by adjusting the control unit from the floating position out into the lift position, and the associated one Close the switching valve, automatically connect to the two chambers closed to each other. At the same time a connection through the controller between the second chamber and hydraulic tank created. Hydraulic fluid flows in the first chamber of the hydraulic cylinder and lifts the piston of the hydraulic cylinder, which in the second chamber located hydraulic fluid in the hydraulic tank repressed.

If the boom or the rocker to be fixed, is through Adjusting the control unit from the floating position out in the neutral position, and the associated closing of the Switching valve, automatically connect to the two Chambers closed to each other. At the same time both will Supply lines closed by the control unit. In this Condition can not be hydraulic fluid from the chambers arrive, so that the boom or the rocker is fixed.

Switch now from the lifting, neutral or lowered position in the floating position, the switching valve will automatically opened and the connection to the two chambers produced with each other and to the hydraulic tank.

Furthermore, it is possible, the boom or the rocker to hold under load or with a certain contact pressure. This is from a lifting or lowering position directly into the Neutral position switched and by the lifting or Lowering built contact pressure held. As a result of that the switching valve in the lifting, neutral and lowered position always automatically held in the closed position, no Pressure equalization between the chambers occur. The functions for lifting and lowering of the hydraulic cylinder carried at closed switching valve by switching the control unit in Lifting or lowering in a known manner.

The control device is preferably as a slide valve formed, which four switch positions, each with two Has inputs and outputs. In the individual positions are the supply lines in different ways according to the actuating functions (lifting, lowering, Neutral position (holding) and floating position) of the control unit connected to the conveyor or to the tank or closed.

The pipe rupture protection device preferably comprises a in Direction of the control unit closing check valve and a pressure relief valve, wherein the pressure relief valve through prevailing in the connecting lines pressures is controllable. The control is done by Pilot pressure lines, which of the pressure relief valve in lead the first and the second supply line. The Check valve is in a pressure relief valve arranged bypass bypass, wherein the Check valve opens towards the first chamber. Other Possibilities for pipe burst protection are also conceivable. For example, pressure switches can also be used in case of pressure drop, actuate a switching valve.

Compared to conventional hydraulic arrangements with Floating positions and rupture protection devices results a more cost-effective hydraulic arrangement, since the required second switching valve including its tubing on the side of the second chamber of the hydraulic cylinder omitted and instead a commercially available slide valve can be used with floating position function. By the Elimination of a second switching valve is also the number possible sources of error because one component less is used. Furthermore, there are cheaper creative possibilities, since less space is required becomes.

Especially with tractors with front loader, it is common that the hydraulic and electrical connection between front loader and tractor ensured by means of so-called multi-couplers that is a quick and easy connect and disconnect enable. By using an inventive hydraulic arrangement can maintain these multi-couplers be because no additional hose to connect the Lower side of the hydraulic cylinder with the tank required is. Due to the internal connection of the control unit in his fourth switching position with the tank, the second Chamber of the hydraulic cylinder by means of the already existing second supply hose to be supplied.

A volume flow dependent controlling valve device has the Advantage that regardless of the hydraulic pressure in the Hydraulic line the volume flow is controllable, so that both at low and high hydraulic load only a certain flow through the hydraulic line and thus a security function is offered. Becomes for example, while the first chamber of the Hydraulic cylinder is pressurized, the hydraulic Arrangement brought into floating position by the switching valve by moving the control unit into the floating position in Flow position is switched, then ensures the Volume flow dependent controlling valve device that the flow rate is only in., regardless of the level of pressure does not change certain limits or a certain value will exceed.

The valve device preferably includes a Flow opening changing adjusting means, for example a slider or closing elements, on the one hand a Pressure of the first chamber and on the other hand a pressure of the Container and optionally exposed to a spring force is. Depending on a pressure difference between the two flow sides, which correspond to one prevailing volumetric flow, changed or closes the flow opening of the actuating means.

The valve device preferably has means that with rising (falling) pressure drop over the Valve device reduce the flow area (expand). If due to increasing pressure in the Hydraulic line increases the flow, so does the Pressure gradient between the flow inlet and Flow outlet side on. At the same time then reduces the flow area across the valve means, so that the pressure gradient drops again. As a result of the declining Pressure gradient is reduced again Flow cross-section of the valve device, so that a controlling state that sets the Volume flow in the presence of a pressure gradient keeps as far as possible or within certain limits constant.

The valve device may include a flow control valve, which changes the volume flow as a function of flow and on limits a predefinable maximum value. such Flow control valves are, for example, from the company "HYDAC International. "An exact description of the DIN-ISO 1219 are removed. A flow control valve has via a differential pressure controller, the volume flow dependent on a control piston, a compression spring, a control panel and over a set screw for adjusting the control pressure difference the Flow controls or regulates. With increasing volume flow or increasing flow d. H. increasing pressure gradient is the cross section of the control panel according to the increased Reduced pressure drop until again Force balance is present. By the continuous Readjustment of the differential pressure controller, according to the respective prevailing pressure gradient, will be a constant flow in reaches a control direction, wherein the control direction preferably the outflow direction of the hydraulic fluid the pressurized chamber of the Hydraulic cylinder, preferably the lifting side of the Hydraulic cylinder, in the direction of the container corresponds. In In the opposite direction, the valve can be flowed through unregulated. Such a valve has the advantage that even at extreme high pressure loads always one of the control pressure difference adjusts corresponding volume flow, the Control pressure difference can be specified via the adjusting screw. This As a result, when switching from operating position in Floating position under load a controlled pressure decrease, largely independent of the amount of the prevailing Pressure, takes place and thus a safety precaution in Switching to the floating position is given.

Preferably, the valve means includes a parallel to Flow control valve arranged check valve, which in Direction of the first chamber opens. This will ensure that flowing in the direction of the container Hydraulic fluid is forced through the flow control valve to flow and accordingly controlled from the high Pressure applied chamber drains, whereas an inflow from the opposite direction can take place unhindered.

In another embodiment of the invention contains the Valve means means that when exceeding a predeterminable pressure gradient reduce the volume flow or interrupt. This will ensure that when it reaches a volume flow, the predetermined pressure drop causes the connection is interrupted, so that the Pressure in the pressurized first chamber or is held in the first hydraulic line. If the pressure falls Once again, the connection is restored as soon as that specifiable pressure gradient is reached or a Volume flow that causes a pressure gradient, which is less than or equal to the predeterminable pressure gradient.

Preferably, the valve device includes a Rohbruchsicherungsventil, which when reaching or Exceeding a predefinable pressure gradient closes or falls below the predetermined pressure gradient opens. Such Rohbruchsicherungsventile be for example of offered by the company "HYDAC International" detailed in a company catalog "HYDAC INTERNATIONAL - FLUTEC Pipe Fittings RBE "described." Flutec "Pipe Fuses are volume flow dependent switching Flat seat valves, the impermissible and uncontrolled Avoid movements of a consumer under load. A pipe rupture valve has a closing element, For example, a closing piston in the form of a Poppet valve, which is an open in normal operating condition Has switching position. The closing element is preferably held by a spring in the open state, as long as the Spring force is greater than that through the flow resistance When flowing through force caused on the closing element or on the plate surface of the poppet valve. The valve stays opened and can be flowed through in both directions. exceeds the prevailing volumetric flow when flowing through the valve in a predeterminable direction by the predetermined Pressure drop defined, maximum allowable value is through the flow resistance increase the spring force overcome and the closing element abruptly pressed on the valve seat, so that the flow is interrupted. The valve opens automatically, as soon as a pressure equalization takes place and the Pressure force in front of the valve resulting from spring force and Compressive force behind the valve composing force below.

The valve device has a parallel to the pipe rupture valve arranged throttle or orifice, which allows a reduced volume flow when the pipe rupture valve is closed. This ensures that always a certain proportion of the volume flow is passed on, so that the pressure in front of the valve device can not build up. The throttle or orifice can be arranged in a bypass line parallel to the pipe break safety valve or be formed, for example, in the form of a bore directly on the pipe rupture valve, in particular directly on the poppet valve. At high flow rates is thus ensured that the closing of the pipe rupture valve much of the flow is intercepted and only a small portion of the hydraulic fluid passes through the throttle, so that a total of controlled pressure decrease is achieved when switching to the floating position.
In combination with the first and second hydraulic line, which connect the chambers of the hydraulic cylinder in floating position with the hydraulic tank, can be achieved in a particularly advantageous manner, on the one hand, an operating position with integrated load-holding valve arrangement, on the other hand, in a floating position with the described safety features of a controlled flow control be switched.

Preferably, those in the various embodiments illustrated valve assemblies for use in a Hydraulic cylinder for raising and lowering a boom on a Loader or construction vehicle, in particular on a telescopic loader or used on a front loader vehicle. So can for example, a telescopic loader in each Operating position, also under load with raised boom, in Floating position to be switched. A floating position without described volume flow control would cause with increasing load of the boom more or less uncontrolled Shut down, causing a heightened security risk represents. At the same time, the floating position is made possible to use when working on the soil surface. Furthermore the possibility is given with integrated load-holding valve, the hydraulic cylinder with raised boom through corresponding control via the control valve with the side Pressure to apply, so an accelerated Shutting down the boom entry. In all Operating positions is a secure switch to a Floating position given.

It is of particular advantage that by the inventive Embodiments a floating position for a telescopic loader while maintaining a safety-relevant load-holding valve arrangement (Pipe rupture device) is given. Furthermore, the realization of a floating position given with a design effort compared to previously known hydraulic arrangements can be reduced could.

Reference to the drawing, the two embodiments of Invention shows, the invention and others Advantages and advantageous developments and refinements the invention described and explained.

Fig. 1

einen Schaltplan einer ersten erfindungsgemäßen hydraulischen Anordnung mit einem Volumenstromregelventil als volumenstromabhängig steuernde Ventilvorrichtung,

Fig. 2

einen Schaltplan einer alternativen volumenstromabhängig steuernden Ventilvorrichtung mit Rohbruchsicherungsventil und

Fig. 3

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

It shows:

Fig. 1

3 is a circuit diagram of a first hydraulic arrangement according to the invention with a volume flow control valve as a flow rate-dependent controlling valve device;

Fig. 2

a circuit diagram of an alternative volumetric flow-controlling valve device with Rohbruchsicherungsventil and

Fig. 3

a schematic side view of a telescopic loader with inventive hydraulic arrangement for use for a hydraulic cylinder.

The circuit diagram shown in Fig. 1 shows Embodiment of a hydraulic arrangement 10 for Realization of a floating position. The hydraulic arrangement 10 includes a switchable controller 12, for example a Slide valve, which via hydraulic lines 14, 16 with a pump 18 and a hydraulic tank 20 is connected, wherein the control unit 12 in three operating positions, lifting, neutral and Lowering, switchable. The switching of the control unit 12 is preferably done by hand, but can also electrically, hydraulically or pneumatically.

Via a first and second supply line 22, 24 is the Control unit 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. One Piston 29 separates the two chambers 26, 28 from each other. The first chamber 28 of the hydraulic cylinder 26 provides the piston-side or lift-side chamber, whereas the second chamber 30, the piston rod side and the lower side Represents chamber of the hydraulic cylinder.

In the first supply line 22 is a Pipe breaking device 32 is provided. The Pipe burst protection device 32 includes a pressure and spring-controlled pressure relief valve 34, and a for Hydraulic cylinder side opening check valve 36, which via a bypass line 38 parallel to the pressure relief valve 34 is arranged. About a first pressure line 40 is a Pressure connection from the pressure relief valve 34 to Hydraulic cylinder side portion of the first supply line 22 produced. About a second pressure line 42 is another pressure connection from the pressure relief valve 34 to second supply line 24 made. Furthermore, holds a spring 44, the pressure relief valve 34 in Closed position.

A hydraulic line 46 connects the first chamber 28 and the first supply line 22 to the second chamber 30 and with the second supply line 24, one with the first Supply line 22 connected end 48 of the hydraulic line 46 between the first chamber 28 and the Pipe rupture protection device 32 is arranged.

In the hydraulic line 46 is a switching valve 50 and a in the direction of the second supply line 24 behind the Switching valve 50 connected volume flow dependent controlling Valve device 52 is arranged. The switching valve 50 is turned on electrically switchable seat valve, which has a Stellfeder 54 is held in the closed position and a Solenoid 56 is brought into an open passage position can be. The switching valve 50 seals in both Directions leak-free. The valve device 52 includes a Flow control valve 58, which in parallel to a Check valve 60 is arranged, wherein the check valve 60 opens in the hydraulic cylinder direction. Here it is possible the valve device 52 in the direction of the second Supply line 24 to be arranged in front of the switching valve 50.

The individual operating states can now via the Controlled control unit 12 and via the switching valve 50 become. As shown in Fig. 1, the control unit 12th held in neutral position by adjusting springs 62, 64. The Switching valve 50 is in a closed position. about a control signal or by manual operation is the Control unit 12 by means of an actuator 66 from the Neutral position out in the lifting, lowering or floating position brought. It can be a manual, electrical, hydraulic or pneumatic actuator 66 act.

When switching the controller 12 in the floating position detects a connected to the actuator 66 Switch or sensor 68, the floating position of the controller 12th and sends a signal to a control unit 70. The Control unit 70 is connected to the switching valve 50 and stops or brings the switching valve 50 in the closed position, if the controller 12 is in the floating position.

Is the controller 12 in one of the Floating position deviating switch position, so will the Switching valve 50 automatically by a from the control unit 70th delivered signal closed. The control logic is the Control unit 70 is preferably designed so that at each Switching position of the controller 12 from the floating position deviates a corresponding signal to close the Switching valve 50 is generated, wherein the switch or sensor 68 the switching positions of the control unit 12 detected or detected and a corresponding switching position signal to the Control unit 70 outputs.

In the lifting position (top switch position of the control unit 12 in FIG. 1), the connection of the first supply line 22 with the pump 18 and the connection of the second Supply line 24 made with the hydraulic tank 20. The Switching valve 50 is in the closed position. The with the Hydraulic tank 20 connected pump 18 filled over the first Supply line 22 and the check valve 36 of the Pipe burst protection device 32 (the pressure relief valve 34 is in the closed position), the first chamber 28 of Hydraulic cylinder 26. As a result, the piston moves 29 in the direction of the second chamber 30 and pushes there existing oil through the second supply line 24 out in the hydraulic tank 20. Will now in the neutral position (from above the second switching position of the controller 12 of Figure 1) switched, the controller 12 interrupts the connections to the pump 18 and the hydraulic tank 20, so that the pressure in the retained two chambers 28, 30 of the hydraulic cylinder 26 and the movement of the piston 29 is canceled. The switching valve 50 is closed. The piston 29 stops.

In lowering position (from above the third switching position of the Controller 12 of Figure 1), the connection of the first Supply line 22 to the hydraulic tank 20 and the Connection of the second supply line 24 with the pump 18th produced. The switching valve 50 is closed. The pump delivers oil into the second chamber 30 of the hydraulic cylinder 26, wherein the building up in the second supply line 24 Pressure the pressure relief valve 34 via the second Pressure line 42 of the pipe rupture device 32 opens. At the same time, the piston 29 is in the direction of the first chamber 28, so that the flowing out of the first chamber 28 oil via the first supply line 22 and over the open Pressure limiting valve 34 enters the hydraulic tank 20.

The pipe rupture device 32 thus ensures that the hydraulic cylinder 26 in neutral position maintains or in lifting and neutral position no oil from the pressurized first chamber 28 can escape and that in lowering position, the oil from the first chamber 28 via the opened pressure relief valve 34 can drain. To this, too should or should ensure Pipe rupture device 32 useful way shown on the lifting side of the hydraulic cylinder 26th be arranged, the lifting side of the side of the Hydraulic cylinder 26 is in which a pressure for lifting a load is built. In the embodiments illustrated here the stroke side is the first chamber 28 of the hydraulic cylinder 26, by turning the hydraulic cylinder 26 and the second Chamber 30 could serve as a lifting side. The first pressure line 40 represents an overload protection, so that too high Operating pressures in the first chamber 28 of the hydraulic cylinder 26, for example, caused by excessive loads can, in the first pressure line 40 reaches a limit pressure is that opens the pressure relief valve 34 to reduce pressure.

About the controller 12 can from any Switch position out or in any operating position in the floating position (from above the fourth switching position of Control unit 12 of Figure 1) are switched. It will by the switching signal generated by the control unit 70 Switching valves 50 controlled so that the solenoid 56 of the Spring force of the spring 54 counteracts and the switching valve 50th brought out of the closed position in the open position becomes. This has the consequence that the first chamber 28 and the second chamber 30 with each other and with the other Hydraulic tank 20 can be associated, so that a Replacement of the hydraulic fluid or the oil take place and the piston 29 can be moved freely floating. Finds Switching to the floating position from an operating position under load, the oil flows under elevated pressure from the pressurized first chamber 28 out, resulting in a would lead to accelerated piston movement. Around To limit piston movement in its speed occurs Flow control valve 58 in force, which limits the flow or the flow of the oil controls or regulates. exceeds the volume flow is an approved value, the Passage cross section of the flow control valve 58, so that the Volume flow does not increase any further. This will be uncontrolled movements of the piston 29 effectively avoided.

At an opposite pressure effect in the direction of the first Chamber 28 allows the check valve 60 to bypass the Flow control valve 58 and thus an uncontrolled flow in Direction of the first chamber 28. A switch from the Floating position in an operating position is always through Switch the controller 12 in the lifting, neutral or Lowering possible. Automatically then the switching valve 50th closed.

In Figure 2 is another volume flow dependent controlling Valve device shown, based on an alternative Embodiment will be explained. In place of in FIG. 1 shows the valve device shown in FIG. 2 shown valve device can be used. The rest Components or their functions are according to the in the manner shown in Figure 1 and according to the previous description used. 2 is for the valve means 52 in place of the flow control valve 58 and of the check valve 60 a pipe rupture valve 72 in Combination with a throttle 74 connected in parallel used. In place of the throttle 74 may also be a equivalent aperture can be used. Is through switching of the controller 12 is switched to the floating position causes the pipe rupture valve 72 also a flow-dependent reduction or limitation of the Volume flow. Reaches the volume flow in floating position in the first hydraulic line 46, due to an excessive pressure in the first chamber 28, one on the pipe rupture valve 72nd predeterminable limit, then affects itself from the adjusting pressure difference resulting force of the Pipe rupture valve 72 acting spring force a Closing spring 76 and closes that Pipe rupture valve 72. At the same time that is from the first chamber 28 diverted oil through the throttle 74, so that a greatly reduced, controllable volume flow flows and only low movement speeds of the piston 29 are allowed. Here it is also possible the Valve device 52 in the direction of the second supply line 24 before the switching valve 50 to order.

One use for illustrated embodiments is in Fig. 3 illustrates. FIG. 3 shows a mobile one Telescopic loader 82 with a housing 84 and a frame of the Telescopic loader 82 pivotally hinged, telescopic extendible, cantilever 86. Between cantilever 86 and housing 84 is a hydraulic cylinder 26 for raising and lowering the boom 86 arranged. The hydraulic cylinder 26 is at one first and a second bearing 88, 90 pivotally hinged, wherein the piston rod side 92 at the second Bearing 90 on the boom 86 and the piston bottom side 94 at the first bearing 88 is hinged to the housing 84. Of Further, the hydraulic tank 20, the pump 18 and the Control unit 12 is positioned on or in the housing 84 and over Hydraulic lines 14, 16 connected to each other. In one preferably arranged directly on the hydraulic cylinder 26 Valve block 96 are in particular the pipe rupture protection 32, the Switching valve 50 and the valve device 52 integrated. Furthermore, the supply lines 22, 24 between the Valve block 96 and the hydraulic cylinder 26 in Figure 3 shown. About the actuator 66 and over a not shown electrical or mechanical control Control or switching signals are generated with which the Control unit 12 or the switching valve 50 (see FIG. 1) be operated or switched. By the previous one described operating positions, the hydraulic cylinder 26th be actuated such that the boom 86 is raised, can be kept or lowered. Furthermore, it is possible in Float position to switch so that the piston freely movable and thus also the boom 86 is floating. By The floating position ensures that a on Boom 86 fixed and lowered to the ground tool 98 floating, following the contour of the ground, over the Ground surface can be moved. The contact pressure of the Tool 98 relative to the ground is thereby substantially by the weight of the boom 86 and the tool 98 certainly. A safety function is thereby given, lowering the boom 86 is volume controlled under load can be done so no unintentional, sudden Movement changes occur. Is z. B. the boom 86 in a raised position under load and then in Floating position switched, so provides the flow control valve 58th or the pipe rupture valve 72 in conjunction with the Throttle 74 for the boom 86 in a Presettable, controllable speed lowered becomes. With this by the hydraulic arrangement 10th realized safety precautions for a floating position, can move from any operating position into a floating position be switched without it being too uncontrolled Movement changes on the boom 86 comes. Furthermore, will hereby a hydraulic assembly 10 with integrated Floating position in conjunction with a load-holding device 32 realized, with a pressurized lowering of the Boom 86 by switching the controller 12 in lowered position is possible.

Even if the invention only by way of two Embodiments has been described, opening 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 For example, the hydraulic arrangement on other Vehicles are applied, for example, on excavators or Cranes as well as front loader vehicles that are hydraulically operated have actuatable components which are raised or can be lowered and where a floating position makes sense.

Claims (12)

Hydraulic arrangement for realizing a floating position for a hydraulic cylinder, comprising a first and a second chamber (28, 30) having hydraulic cylinder (26), a hydraulic tank (20), a hydraulic fluid conveying means (18), one between the first and the second chamber (28, 30) arranged hydraulic line (46), a arranged in the hydraulic line (46) switching valve (50) arranged in the hydraulic line (46) volume flow-dependent controlling valve device (52, 76), a first supply line (22) for the first chamber (28), a second supply line (24) for the second chamber (30), a pipe rupture protection device (32) arranged in the first supply line (22) and a control device (12) with at least three switching positions which a lifting position, a lowering position and a neutral position for the hydraulic cylinder (26), characterized in that the control device (12) a further switching position, which represents a floating position, in which by the control unit (12) at least the second supply line (24) to the hydraulic tank (20) is connectable and simultaneously connections of both supply lines (22, 24) to the conveyor (18) are interrupted , Hydraulic arrangement according to claim 1, characterized in that in the floating position, the first and the second connecting line (22, 24) by the control unit (12) with the hydraulic tank (20) are connectable. Hydraulic arrangement according to claim 1 or 2, characterized in that the switching valve (50) has a closed position and an open position. Hydraulic arrangement according to one of the preceding claims, characterized in that means (64, 66) are provided which bring the switching valve (50) in an open position when the control unit (12) is in the floating position. Hydraulic arrangement according to one of the preceding claims, characterized in that means (64, 66) are provided which bring the switching valve (50) in a closed position when the control unit (12) is in the raising, lowering or neutral position. Hydraulic arrangement according to one of the preceding claims, characterized in that the control device (12) is a slide valve having at least two inputs and two outputs for each switching position. Hydraulic arrangement according to one of the preceding claims, characterized in that the pipe rupture protection device (32) in the direction of the control unit (12) closing check valve (36) and a pressure relief valve (34), wherein the pressure relief valve (34) by in the supply lines (22 , 24) prevailing pressures can be controlled. Hydraulic arrangement according to one of the preceding claims, characterized in that the valve device (52) contains a flow opening changing adjusting means (58, 72), on the one hand a pressure of the first supply line (22) and on the other hand, a pressure of the second supply line (24) optionally exposed to a spring force. Hydraulic arrangement according to one of the preceding claims, characterized in that the valve device (52) comprises means (58, 72) which reduce (expand) the flow cross-section with increasing (falling) pressure gradient across the valve device (52). Hydraulic arrangement according to one of the preceding claims, characterized in that the valve device (52) includes a flow control valve (58) which varies the flow rate flow-dependent and limited to a predeterminable maximum value. Hydraulic arrangement according to Claim 9, characterized in that the valve device (52) contains a check valve (60) arranged parallel to the flow control valve (58) and opens in the direction of the first chamber (28). Hydraulic arrangement according to one of the preceding claims, characterized in that the valve device (52) includes means (72, 74) which reduce or interrupt the volume flow when a predeterminable pressure gradient is exceeded.

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