EP1752587B1 - Hydraulic arrangement - Google Patents

Abstract

The hydraulic circuit (10) for the suspension system of a construction vehicle boom has a hydraulic cylinder (26) and a hydraulic tank (20) with a feed (18) and a reservoir (48). A control (12) has a first control pressure pipe (42) between a pipe breakage safety control (32) and a feed (18). The first pressure pipe has a switching valve (58) to vary the pressure in the pipe and operate a pressure limiting valve (34).

Description

The invention relates to a hydraulic arrangement for a suspension system comprising a hydraulic cylinder having at least one first chamber, a hydraulic tank, at least one conveying a hydraulic fluid, a hydraulic accumulator, a first hydraulic line arranged between the hydraulic accumulator and the first chamber, a first switching valve arranged in the first hydraulic line , a first supply line for the first chamber, a control unit having at least three switching positions, which comprise a lifting position, a lowered position and a neutral position for the hydraulic cylinder, and arranged in the first supply line pipe rupture protection device, which closes in the direction of the control valve check valve and a a first control pressure line aufsteuerbares pressure relief valve comprises.

In agricultural machines, such as telescopic loader, wheel loader or front loader on tractors, it is known to use a hydraulic suspension system that cushions the boom or the rocker to achieve overall on the vehicle improved suspension comfort, especially while driving. Here, by means of a suitable hydraulic arrangement of valves, the lifting side of a hydraulic cylinder is connected to a hydraulic accumulator to effect a suspension through the hydraulic accumulator. Further, the lowering side of the hydraulic cylinder is connected to a hydraulic tank to prevent on the one hand cavitation on the lower side and on the other to allow free movement of the piston rod during the suspension process. To increase safety against a sudden drop in the boom or the rocker these suspension systems, to protect the hydraulic cylinder against hose breaks, with Load holding valves or pipe rupture protection devices provided. To lower the hydraulic cylinder, it is then necessary to close the tank connection of the lowering side of the hydraulic cylinder, so that a required pressure can build up to open the load-holding valve. Only when the load-holding valve is opened, oil can flow out of the lift side of the hydraulic cylinder.

A hydraulic arrangement for a suspension system according to the preamble of claim 1 is in the EP 1 157 963 A2 disclosed. It is proposed a suspension system for the boom of a telehandler, which provides for securing the boom against sinking a load-holding valve or a pipe rupture device. On the one hand to obtain a pressurized lowering of the boom, which requires opening the load-holding valve, and on the other hand to provide a suspension function in the neutral position of the hydraulic cylinder, a separate switching valve is arranged. For opening the load-holding valve, a pressure limiting valve is provided which can be opened via a control pressure line connected to the supply line of the lowering side of the hydraulic cylinder. To open the load-holding valve then the separate switching valve must be closed, so that the supply line to the tank is closed and can build up to the opening of the load-holding valve pressure in the supply line. A disadvantage is that the pressure to be applied to open the pressure limiting valve requires a relatively high hydraulic power, which must be applied each time the hydraulic cylinder is lowered under pressure. Furthermore, when the suspension is activated, precise positioning is achieved when the boom is lowered more difficult because the required opening pressure on the lowering side of the hydraulic cylinder also leads indirectly to a pressure load of the hydraulic accumulator, which then then relaxes again, which in turn is associated with a movement of the hydraulic cylinder.

The object underlying the invention is seen to improve a suspension system of the type mentioned in such a way that a pressurized lowering of the hydraulic cylinder can be done at lower hydraulic power and precise positioning of the boom when lowering is enabled with suspension enabled.

The object is achieved by the teaching of claim 1. Further advantageous embodiments and modifications of the invention will become apparent from the dependent claims.

According to the invention a hydraulic arrangement of the aforementioned type is designed such that the first control pressure line extends between the pipe rupture protection device and a conveyor and switching means are arranged in the first control pressure line, so that by switching the switching means, the first control pressure line acted upon by a control pressure and the pressure relief valve aufsteuerbar is. The pipe rupture protection device preferably comprises a check valve closing in the direction of the control device and is arranged in a bypass line bypassing the pressure limiting valve. The pressure limiting valve is via a pressure line from the first supply line forth or via the first control pressure line by means of a control pressure, which by a Pressure generating conveyor is generated, aufsteuerbar. As a control pressure generating conveyor either the supply of the hydraulic cylinder provided funding or a separately provided funding can be used. Characterized in that the pressure relief valve has a first control pressure line, which is not connected to a supply line of the hydraulic cylinder, the pressure relief valve can be operated independently of the pressure prevailing in a second chamber of the hydraulic cylinder pressure, ie be controlled. The separate from a second chamber of the hydraulic cylinder pressurizing the first control pressure line allows a Aufsteuern the pressure relief valve at relatively low hydraulic pressure, so that a pressurized lowering of the hydraulic cylinder can be done at lower hydraulic power, or even without pressurization of a second chamber of the hydraulic cylinder, for example by the Gravity of a boom operated by the hydraulic cylinder. Thus, the hydraulic arrangement according to the invention is also suitable as a hydraulic suspension system for a single-acting hydraulic cylinder. Further, when the suspension is activated, ie when the hydraulic accumulator is switched on, a more precise positioning of the boom allows, since the control pressure generated to open the pressure limiting valve is not established via a second chamber and thus the pressure acting on the hydraulic accumulator pressure is much lower, so that Compression movement (in the hydraulic accumulator) of the hydraulic cylinder during lowering substantially less fails. Not least, a performance advantage is achieved by the required low hydraulic power, since, for example, even at low conveyor power of the boom can be lowered at maximum speed.

The hydraulic arrangement has coupling means which couple the first switching means to the control unit in such a way that a switching position of the first switching means, in which pressurization of the first control pressure line is effected, occurs synchronously with a lowering position of the control unit. This ensures that as soon as the control unit is switched to a lowered position, the pressure limiting valve opens and the hydraulic oil located in the first chamber can escape when the hydraulic cylinder is lowered.

Preferably, the control unit is hydraulically switchable and is also connected via control pressure lines. The coupling means can then be designed as a second control pressure line extending between the first control pressure line and the control device, so that pressurization of the second control pressure line takes place by pressurizing the first control pressure line. Characterized in that the first control pressure line is connected via a second control pressure line to the control unit, the first switching means are coupled to the control unit, so that the control pressure generated to open the pressure relief valve is also the applied to switch the control unit in the lowering position control pressure. By switching the first switching means for controlling the pressure limiting valve, the control unit is simultaneously switched to the lowered position.

The hydraulically switchable control device preferably has a third control pressure line, by means of which it can be switched into the lifting position. For this purpose, second switching means are provided in the third control pressure line, via which the third control pressure line can be acted upon with pressure.

Preferably, the switching means are designed as proportional switching valves, in particular pressure reducing valves, by which either a connection of the control pressure lines to the hydraulic tank or to a conveyor can be produced, wherein the switching means mechanically, electrically, hydraulically or pneumatically actuated or can be controlled and proportional to a control signal From a preferably closed first switching position, are switched or moved in an open second switching position. The second switching position is variable or controllable proportional to the control signal, so that a pressure reduction proportional to the control signal can take place.

In particular, the switching means may also be designed as a hydraulic actuating device in the form of a joystick, wherein a simultaneous hydraulic supply of the first and second control pressure line is established as soon as the joystick is moved into a position provided for the lowering position of the control unit. By moving the joystick into a position provided for the lifting position of the control unit, the third control pressure line of the control unit is pressurized and at the same time the hydraulic supply of the first and second control pressure line is interrupted. By moving the joystick into a position provided for the neutral position of the control unit, the hydraulic supply of the first, second and third control pressure lines is interrupted, so that the control unit can assume the neutral position, for example by prestressed control springs.

In an alternative embodiment, the coupling means comprise an actuator for the first Switching means. The switching means are brought into an open or in a closed position in dependence on the switching position of the control device. Depending on the design of the control unit, it is possible to dispense with a third control pressure line, for example in the case of an electrically or mechanically connected control unit, so that only the switching means for the first control pressure line have to be actuated. The actuating device for the first switching means may be designed, for example, mechanically, via a pushbutton / plunger combination, or also electrically, for example via a switch or sensor. Thus, for example, an angle or position sensor can be used, which detects the switching position of the control device or the hydraulic actuator or a joystick and generates a signal for switching the first switching means. Furthermore, other controls should be considered, which would result for a person skilled in the art of hydraulic controls and cause the first switching means are automatically and synchronously connected to the control unit such that when switched into the lowering position of the control unit, a pressurization the first control pressure line for opening the pressure relief valve of the pipe rupture protection device takes place.

In a further embodiment, the control device is preferably designed as a valve spool exhibiting slide valve having three switch positions, each with two inputs and outputs. In the individual positions, the supply lines in different ways according to the switching positions (lifting, lowering and neutral position (holding)) with the Conveyor or connected to the hydraulic tank or closed. At the same time, the first switching means are switched in response to the switching positions of the control unit via the actuating device. For this purpose, for example, the valve slide may be connected to a switching element, for example with a button, a control arm, a lever, a lock slider or the like, which actuates a switch provided on the first switching means actuating plunger or switch. The switching means can for example also be connected via a cable with the valve spool, through which, when moving the valve spool, the adjusting means from a biased position (for example, by a spring) is moved. It should be pointed out again that the control unit can be designed as a hydraulically, electrically or mechanically operable control device, wherein the valve spool can be hydraulically, electrically or mechanically displaceable in a known manner.

A hydraulic arrangement according to the invention with suspension function is, as already mentioned above, both for a hydraulic cylinder acting on one side, ie for a hydraulic cylinder with only one pressurizable chamber, and for a double-acting or double-acting hydraulic cylinder, ie for a hydraulic cylinder with two pressurizable chambers , advantageously usable.
Thus, the hydraulic cylinder may have a second chamber which is supplied by a second supply line. Preferably, a second hydraulic line is then arranged between the second chamber and the hydraulic tank. In a spring movement of the hydraulic cylinder can then in the second chamber located hydraulic oil flow into the hydraulic tank.

The hydraulic assembly may further include a second switching valve disposed in the second hydraulic line. The second switching valve can be used to close the second hydraulic line to the tank, so that the second chamber can be pressurized by the control unit, both with activated and deactivated suspension. This is advantageous if, for example, one wishes to generate a contact pressure for a working tool fastened to a boom actuated by the hydraulic cylinder or to lower the hydraulic cylinder or the arm under pressure. The first and the second switching valve preferably have a closed position and an open position, wherein the first and the second switching valve close in the closed position in one or both flow directions, but open in the open position in both flow directions, so that a suspension function in conjunction with the Hydraulic accumulator or enters with the hydraulic tank. The first and the second switching valve may be formed such that they close in the closed position only in the direction of the hydraulic accumulator or the hydraulic tank. The first and the second switching valve are preferably electrically actuated. It is of course also conceivable that other types of actuation are used for the first and second switching valve, for example a manual, pneumatic or hydraulic actuation.

A hydraulic arrangement according to the invention with a suspension function is suitable, for example, for lifting and Lowering a boom of a charger, such as a wheel loader, front loader, crane or telescopic loader, such chargers are found in agriculture, construction or in forestry.

Now, if the suspension should be activated, which can be done by means of a switch that operates in the cab of the charger, or for example, by a speed signal, the first and the second switching valve is brought into their open positions to the first chamber of the hydraulic cylinder to connect with the hydraulic accumulator and the second chamber of the hydraulic cylinder to the hydraulic tank. During excitation by the running gear of the working machine, jerky accelerations can be damped by the free swinging of the jib or the rocker, so that an increase in driving comfort can be achieved. If the boom or a loader rocker lowered with activated or not activated suspension, the first control pressure line is automatically pressurized, so that the pipe rupture device or the pressure relief valve is opened, which is essential for lowering the boom or rocker. It is not necessary to close the second switching valve, since the control pressure required for lowering the boom to open the pressure relief valve is not built on the pressure in the second chamber. Even during the lowering a hose rupture protection of the hydraulic arrangement is ensured because the hydraulic fluid always drains controlled via the pressure relief valve. If the boom or the rocker is raised with the suspension of the control unit activated, the second chamber of the hydraulic cylinder with the hydraulic tank is automatically lifted connected so that the displaced by the lifting hydraulic fluid from the hydraulic cylinder can flow to the hydraulic tank. If a shock is transmitted to the boom or the rocker during the raising or lowering process, this or this can deflect without risk of cavitation, since the second chamber is relieved to the tank.

Reference to the drawing, which shows an embodiment of the invention, the invention and further advantages and advantageous developments and refinements of the invention are described and explained in more detail below.

Fig. 1

ein hydraulischer Schaltplan einer erfindungsgemäßen hydraulischen Anordnung für ein Federungssystem eines Hydraulikzylinders,

Fig. 2

eine schematische Darstellung eines Teleskopladers mit einer erfindungsgemäßen hydraulischen Anordnung und

Fig. 3

ein hydraulischer Schaltplan einer alternativen Ausführungsform einer erfindungsgemäßen hydraulischen Anordnung für ein Federungssystem eines Hydraulikzylinders.

It shows:

Fig. 1

a hydraulic circuit diagram of a hydraulic arrangement according to the invention for a suspension system of a hydraulic cylinder,

Fig. 2

a schematic representation of a telescopic loader with a hydraulic arrangement according to the invention and

Fig. 3

a hydraulic circuit diagram of an alternative embodiment of a hydraulic arrangement according to the invention for a suspension system of a hydraulic cylinder.

An in Fig. 1 illustrated hydraulic arrangement 10 shows an inventive embodiment for the realization of a suspension. The hydraulic arrangement 10 comprises a hydraulically switchable control unit 12, which, for example, as a Slider valve formed with a valve spool 13 and is connected via hydraulic lines 14, 16 with a pump 18 and a hydraulic tank 20, wherein the control unit 12 in three operating positions, lifting, neutral and lowered position, can be switched.

Via a first and second supply line 22, 24, the control unit 12 is connected to a hydraulic cylinder 26, wherein the first supply line 22 leads into a first chamber 28 of the hydraulic cylinder 26 and the second supply line 24 into a second chamber 30 of the hydraulic cylinder 26. A piston 29 separates the two chambers 26, 28 from each other. The first chamber 28 of the hydraulic cylinder 26 represents the piston bottom side and the stroke side chamber, whereas the second chamber 30 represents the piston rod side and the lower side chamber of the hydraulic cylinder.

In the first supply line 22, a load-holding valve arrangement or pipe rupture protection device 32 is provided. The pipe burst protection device 32 includes a pressure and spring-controlled pressure limiting valve 34, and a check valve 36 which opens to the hydraulic cylinder side and which is arranged via a bypass line 38 parallel to the pressure limiting valve 34. Via a pressure line 40, a pressure connection from the pressure relief valve 34 to the hydraulic cylinder side portion of the first supply line 22 is made. Via a first control pressure line 42, a pressure connection from the pressure relief valve 34 to the pump 18 is established. Furthermore, a spring 44 holds the pressure relief valve 34 in the closed position.

A first hydraulic line 46 connects the first chamber 28 and the first supply line 22 to a hydraulic accumulator 48, wherein the not connected to the hydraulic accumulator 48 end 50 of the first hydraulic line 46 between the first chamber 28 and the pipe rupture protection device 32 is arranged.

In the first hydraulic line 46, a first switching valve 52 is arranged. The first switching valve 52 is an electrically switchable seat valve, which is held by a spring 54 in the closed position and can be brought via a solenoid 56 in an open position. The first switching valve 52 seals in the closed position in the direction of the hydraulic accumulator 48. Here, the first switching valve 52 may also be designed such that it seals leak-free in both directions. In the open position, a hydraulic flow in both directions is ensured to produce a suspension function between the hydraulic cylinder 26 and the hydraulic accumulator 48.

A second hydraulic line 46 'connects the second chamber 30 and the second supply line 24 to the hydraulic tank 20.

In the second hydraulic line 46 ', a second switching valve 52' is arranged. The second switching valve 52 'is an electrically switchable seat valve, which is held in the closed position by a spring 54' and can be brought into a open position via a magnetic coil 56 '. The second switching valve 52 'seals in the closed position in the direction of the hydraulic tank 20 from. Here, the second switching valve 52 'may also be designed such that it seals leak-free in both directions. In the open position is ensures a hydraulic flow in both directions to establish a connection between the second chamber 30 of the hydraulic cylinder 26 and hydraulic tank 20.

In the first control pressure line 42 formed as a pressure reducing valve first switching means 58 are arranged, which have a first switching position and at least a second switching position, wherein in the at least second switching position, a pressure reduction is infinitely variable. The first switching means 58 are preferably connected electronically, wherein the first control pressure line 42 in the first switching position (as in FIG. 1 shown) with the tank 20 and in the second switching position with the pump 18 is connectable.

The hydraulic arrangement according to the invention also has coupling means which couple or connect the first switching means 58 and the control unit 12 or synchronize their switching operations. The coupling means are in the form of a second control pressure line 60, which extends from the first control pressure line 42 to the control unit 12, so that upon pressurization of the first control pressure line 42 and the second control pressure line 60 is pressurized. The second control pressure line 60 is arranged such that when pressure is applied, the control unit 12 or the valve slide 13 is switched or moved into the lowered position.

The control unit 12 is further provided with a third control pressure line 62. In the third control pressure line 62 formed as a pressure reducing valve second switching means 64 are arranged, which a first Switching position and have at least a second switching position, wherein in the at least second switching position, a pressure reduction is infinitely variable. The second switching means 64 are preferably switched electronically, wherein the third control pressure line 62 in the first switching position (as in FIG. 1 shown) with the tank 20 and in the second switching position with the pump 18 connects. The third control pressure line 62 is arranged such that, when pressure is applied, the control unit 12 or the valve slide 13 is switched or moved into the lifting position.
The individual operating states can now be controlled as follows via the control unit 12 and via the switching valves 52, 52 '. As in Fig. 1 illustrated, the control unit 12 is held in neutral position by adjusting springs 70, 72, wherein the first and second switching means 58, 64 are each in their first switching position. The switching valves 52, 52 'are in a closed position. Via control signals by means of a joystick or by means of an electronic control device 76, the first and / or second switching means 58, 64 and the first and second switching valve 52, 52 'are switched. By actuating the electronic control device 76 or a joystick (not shown) for lifting, lowering or holding (neutral position of the control unit 12) of the hydraulic cylinder 26 corresponding switching signals for the first and second switching means 58, 64 are generated, so that the control unit 12 by means of electronic control device 76 or by means of a joystick from the neutral position out in the lifting or lowering position or from the lifting or lowering position out into the neutral position (holding position) is brought.

In the lifting position (in the FIGS. 1 and 3 the top switching position of the controller 12), the connection of the first supply line 22 to the pump 18 and the connection of the second supply line 24 to the hydraulic tank 20 is made. For this purpose, a corresponding switching signal is generated by the control device 76, whereby the second switching means 64 are switched and a controlled according to the control signal pressurization of the third control pressure line 62 takes place. As a result, the control unit 12 and the valve slide 13 is brought into the lifting position. The first chamber 28 of the hydraulic cylinder 26 is then filled via the first supply line 22 and via the check valve 36 of the pipe rupture protection device 32 (the pressure relief valve 34 of the load-holding arrangement 32 is in the closed position). As a result, the piston 29 moves in the direction of the second chamber 30 and presses the oil present there through the second supply line 24 out into the hydraulic tank 20. By actuating the control device 76, a corresponding switching signal for switching to the neutral position (holding position) can be generated , whereby the second switching means 64 are moved back into their first switching position, a pressure relief of the third control pressure line 62 to the tank takes place and the control unit 12 assumes the neutral position (holding position). At the same time, the controller 12 interrupts the connections to the pump 18 and the hydraulic tank 20, so that the pressure in the two chambers 28, 30 of the hydraulic cylinder 26 is maintained and the movement of the piston 29 is released. The piston 29 stops or is held.

In the lowered position (in the FIGS. 1 and 3 the lowest switching position of the controller 12), the connection of the first supply line 22 to the tank 20 and the connection of the second supply line 24 to the pump 18 is made. For this purpose, a corresponding switching signal is generated by the control device 76, whereby the first switching means 58 are switched and a controlled according to the control signal pressurization of the first and second control pressure line 42, 60 takes place. As a result, the control unit 12 or the valve slide 13 is brought into the lowered position. The second chamber 30 of the hydraulic cylinder 26 is then filled via the second supply line 24. By the simultaneous pressurization of the first control pressure line 42, the pressure relief valve 34 is opened. As a result, the piston 29 moves in the direction of the first chamber 28 and pushes the existing there oil via the open pressure relief valve 34 through the second supply line 22 out in the hydraulic tank 20. By actuating the control device 76, a corresponding switching signal for switching to the neutral position (Stop position) are generated, whereby the first switching means 58 are moved back to their first switching position, a pressure relief of the first and second control pressure line 42, 60 takes place towards the tank and the control unit 12 assumes the neutral position (holding position). At the same time, the controller 12 interrupts the connections to the pump 18 and the hydraulic tank 20, so that the pressure in the two chambers 28, 30 of the hydraulic cylinder 26 is maintained and the movement of the piston 29 is released. The piston 29 stops or is held. The switching operations described above can of course not only be from a lifting or lowering position into a neutral position, but also directly from a lifting position in a lowered position or vice versa.

The pipe rupture device 32 thus ensures that the hydraulic cylinder 26 maintains its position in the neutral position or escape oil in the lifting and neutral position from the pressurized first chamber 28 and that in the lowered position, the oil from the first chamber 28 can flow through the open pressure relief valve 34 , To ensure this, the pipe rupture protection device 32 should or should be arranged on the lifting side of the hydraulic cylinder 26, as shown, with the lifting side being the side of the hydraulic cylinder 26 in which a pressure for lifting a load is built up. In the embodiment shown here, the lifting side is the first chamber 28 of the hydraulic cylinder 26, wherein the second chamber 30 could serve as a lifting side. The excess pressure line 40 is an overload protection, so that at excessive operating pressures in the first chamber 28 of the hydraulic cylinder 26, which may be caused by excessive loads, for example, in the pressure line 40, a limiting pressure is reached, which opens the pressure relief valve 34 to reduce pressure.

Based on a connected to the controller 12 switch or sensor 80, the positions of the controller 12 can be detected and a signal to the electronic control device 76 are sent. The control unit 76 is connected to the first and second switching valves 52, 52 '. The activation of the suspension via an activation switch 82, which outputs an activation signal to the control unit 76.

• In der Senkstellung (unterste Schaltstellung des Steuergeräts in den Figur 1 und 3) wird die erste Versorgungsleitung 22 mit dem Hydrauliktank 20 und die zweite Versorgungsleitung 24 mit der Pumpe verbunden. Gleichzeitig wird das Druckbegrenzungsventil 34 über die erste Steuerdruckleitung 42 geöffnet, so dass Öl aus der ersten Kammer 28 über die erste Versorgungsleitung 22 in den Hydrauliktank 20 abfließen kann. Es kann vorgesehen werden, dass die elektrische Steuereinrichtung in Abhängigkeit eines Sensorsignals des Sensors 80, der die Senkstellung signalisiert, das zweite Schaltventil 52' in eine Schließstellung bringt, was zwar nicht erforderlich ist, um den Hydraulikzylinder abzusenken, jedoch von Vorteil sein kann, wenn man ein möglichst schnelles druckunterstütztes Absenken des Hydraulikzylinders wünscht bzw. einen Anpressdruck durch den Hydraulikzylinder generieren will, beispielsweise wenn ein Arbeitsgerät, welches an einem von dem Hydraulikzylinder bewegten Ausleger befestigt ist, auf den Boden gepresst werden soll. Sollte das zweite Schaltventil 52' geschlossen sein, so wird es, sobald das Steuergerät 12 wieder aus der Senkstellung in Neutral- oder Hebestellung gebracht wird, bei aktivierter Federung geöffnet.
• In der Neutralstellung (mittlere Schaltstellung des Steuergeräts 12 aus den Figuren 1 und 3) werden alle Ein- und Ausgänge am Steuergerät 12 geschlossen, d. h. es kann kein Öl durch die Versorgungsleitungen 22, 24 zum Steuergerät 12 fließen. Bei einer Federbewegung des Kolbens 29 kann dieser sich frei in beide Richtungen bewegen, da zum Einen das Öl aus der ersten Kammer 28 über das geöffnete erste Schaltventil 52 in den Hydraulikspeicher 48 und aus der zweiten Kammer 30 über das geöffnete zweite Schaltventil 52' in den Hydrauliktank 20 fließen kann.
• In der Hebestellung (obere Schaltstellung des Steuergeräts 12 in den Figuren 1 und 3) wird die erste Versorgungsleitung 22 mit der Pumpe 18 und die zweite Versorgungsleitung 24 mit dem Hydrauliktank 20 verbunden. In der ersten Versorgungsleitung 22 bzw. in der ersten Kammer 28 baut sich ein entsprechender Druck auf, durch den der Kolben 29 angehoben wird, so dass Öl aus der zweiten Kammer 30 über die zweite Versorgungsleitung 24 in den Hydrauliktank 20 abfließen kann. Gleichzeitig kann der Kolben 29 federnde Bewegungen ausführen, da eine Verbindung zum Hydraulikspeicher 48 auf der Hubseite und eine Verbindung auf der Senkseite zum Hydrauliktank 20 hergestellt ist.

As soon as an activation signal occurs, the suspension is activated by the control unit 76 by opening the first and second switching valve 52, 52 '. As long as the switching valves 52, 52 'are in the closed position, the hydraulic cylinder 26 is separated on one side from the hydraulic accumulator 48 and on the other side of the hydraulic tank 20 and can not perform any resilient movements. Only by activating the suspension, ie by opening the two switching valves 52, 52 'or by adding the hydraulic accumulator 48 and the hydraulic tank 20, the piston 29 can move resiliently, ie traversing in both directions.
For a suspension function activated by the activation switch 82, the following states result according to the different switching positions of the control unit 12:

• In the lowering position (lowest switching position of the control unit in the FIG. 1 and 3 ), the first supply line 22 is connected to the hydraulic tank 20 and the second supply line 24 to the pump. At the same time, the pressure limiting valve 34 is opened via the first control pressure line 42, so that oil can flow out of the first chamber 28 via the first supply line 22 into the hydraulic tank 20. It may be provided that the electrical control device in response to a sensor signal of the sensor 80, which signals the lowering position, the second switching valve 52 'brings into a closed position, which is not required to lower the hydraulic cylinder, however, may be advantageous if one wants the fastest possible pressure-assisted lowering of the hydraulic cylinder or generates a contact pressure by the hydraulic cylinder, for example, when a working device, which at one of the Hydraulic cylinder moving boom is attached, should be pressed to the ground. If the second switching valve 52 'is closed, it will, as soon as the control unit 12 is brought back from the lowered position in the neutral or lifting position, opened with activated suspension.
• In the neutral position (middle switching position of the controller 12 from the FIGS. 1 and 3 ) All inputs and outputs are closed on the control unit 12, that is, no oil can flow through the supply lines 22, 24 to the control unit 12. During a spring movement of the piston 29, this can move freely in both directions, since on the one hand the oil from the first chamber 28 via the opened first switching valve 52 in the hydraulic accumulator 48 and from the second chamber 30 via the opened second switching valve 52 'in the Hydraulic tank 20 can flow.
• In the lifting position (upper switching position of the controller 12 in the FIGS. 1 and 3 ), the first supply line 22 is connected to the pump 18 and the second supply line 24 to the hydraulic tank 20. In the first supply line 22 and in the first chamber 28, a corresponding pressure builds up, through which the piston 29 is raised, so that oil from the second chamber 30 via the second supply line 24 can flow into the hydraulic tank 20. At the same time, the piston 29 can perform resilient movements, since a connection to the hydraulic accumulator 48 on the lifting side and a connection on the lowering side to the hydraulic tank 20 is made.

When activated suspension function, the piston 29 can spring freely. If it moves downwards by a shock transmitted to it, the oil from the first chamber 28 in the Hydraulic accumulator 48 pushed. The pressure building up in the hydraulic accumulator 48 causes the oil to flow back into the first chamber 28, so that the piston 29 moves upward again. This resilient movement is repeated, if necessary, until the shock has been completely compensated.

A use for that in Fig. 1 illustrated embodiment is shown in Fig. 2 clarified. Fig. 2 shows a mobile telescopic loader 83 with a on a housing 84 or frame of the telehandler 83 pivotally hinged, telescopically extendable, boom 86. Between boom 86 and housing 84, a hydraulic cylinder 26 for raising and lowering of the boom 86 is arranged. The hydraulic cylinder 26 is pivoted to a first and a second bearing 88, 90, wherein the piston rod side 92 is hinged to the second bearing point 90 on the arm 86 and the piston bottom side 94 at the first bearing 88 on the housing 84. Furthermore, the hydraulic tank 20, the pump 18 and the control unit 12 are positioned on or in the housing 84 and connected to each other via hydraulic lines 14, 16, 96. Furthermore, the supply lines 22, 24 between the control unit 12 and hydraulic cylinder 26 in Fig. 2 to see. The pipe burst protection device 32 and the switching valve 52 are located in a common valve block directly on the hydraulic cylinder 26. The hydraulic accumulator 48 is preferably also disposed directly on the hydraulic cylinder 26, so that between the common valve block and the hydraulic accumulator 48, the first hydraulic line 46 can be formed as a rigid connection that does not require a separate breakaway device. According to the switching positions described above, the hydraulic cylinder 26 can be operated such that the boom 86 can be raised, held and lowered and possibly perform resilient movements. When the suspension is activated ensures that during excitation, for example, by the chassis of the telehandler 83, shock-like acceleration due to a free swing of the boom 86 are damped, so that there is an increase in ride comfort, especially when with a working tool 98 loads be recorded and proceed.

In FIG. 3 an alternative embodiment is shown, which, in contrast to the in FIG. 1 illustrated embodiment, an electronically controllable or switchable control unit 112, wherein the control unit 112 also includes a slide valve with a valve spool 113. However, the control unit 112 may also be designed as a hydraulically or mechanically controllable control unit. The control unit can also be actuated here via an electronic control device 76 or via a joystick or a similar control device. The hydraulic arrangement 110 shown here further corresponds to the in FIG. 1 illustrated arrangement 10 described above, unless it is pointed to corresponding differences. In the FIG. 3 also has a first control pressure line 42 which extends between the pressure relief valve 34 of a pipe rupture device 32 and a conveyor or pump 18. In the first control pressure line 42 first switching means 114 are also arranged, which are designed as a switching valve, in particular pressure reducing valve. An essential difference to that in FIG. 1 illustrated embodiment is that in FIG. 3 the first switching means 58 from FIG. 1 be replaced by first switching means 114 and mechanical coupling means between the first switching means 114 and the control unit 112 are arranged. The second switching means 64, and the second and third control pressure line 60, 62 (off FIG. 1 ), since this is an electrically controllable switching valve 112. However, it is also conceivable the control unit 112, according to the in FIG. 1 illustrated control unit 12, hydraulically controllable form and provide the necessary to switch the controller 12 first and second switching means 58, 64, without the first switching means 58 are connected to the control pressure line 42. The coupling means are formed as a mechanical actuator 116 for the first switching means 114, wherein the actuating means 116 bring the first switching means 114 in response to or proportional to the switching position of the controller 112 and the valve spool 113 in a first or second switching position, wherein in the second Switching one of the movement of the controller 112 and the valve spool 113 proportional pressure reduction in the first control pressure line is carried out. In the first switching position, a connection of the control pressure line 42 to the pump 18 is interrupted, in the second switching position, a connection of the control pressure line 42 is made to the pump 18, so that the control pressure line 42 is pressurized. The dependence on the switching position of the controller 112 and the valve spool 113 is such that when the controller 112 and the valve spool 113 is brought into the lowered position (lowermost switching position of the controller 112 in FIG. 3 ), the actuating device 116 brings the first switching means 114 in the second switching position, so that the control pressure line 42 is pressurized and the Pressure relief valve 34 is opened. As soon as the control unit 112 or the valve slide 113 is again moved out of the lowered position, the first switching means 114 are returned to the first switching position. The actuating device 116 has a locking slide 118 which is in contact or interacts with an actuating tappet 120 arranged on the first switching means 114. As soon as the control unit 112 or the valve slide 113 is moved into the lowered position, the actuating push rod 120 is pressed or actuated, whereby the first switching means 114 are brought into the second switching position. As soon as the control device 112 or the valve slide 113 is again moved out of the lowered position, the actuating push rod 120 is relieved of the control slide 118 or moves back again, so that the first switching means 114 again assume their first switching position. By the coupling of the movement or the switching operation of the control device 112 and the valve spool 113, which is given by the actuating device 116, it is thus ensured that, as soon as the lowering position is assumed for the hydraulic cylinder 26, the pressure relief valve 34 synchronous and proportional to the movement the control valve is turned on, so that the oil can escape from the first chamber 28 when lowering the piston 29. At the same time, however, a pipe rupture protection function is ensured. Furthermore, it is conceivable to form the actuating device 116 also electrically. For example, by the sensor 80, the position of the control device 112 and the valve spool 113 can be detected. A corresponding to the position proportional signal can then be generated by the electronic control device 76 and used to control the first switching means 114, wherein the first switching means 114 are then formed as electronically controllable switching means or pressure reducing valve.

Incidentally, the above with respect to in FIG. 1 illustrated embodiment described functions accordingly also for in FIG. 3 illustrated alternative embodiment.

This in FIG. 3 illustrated embodiment may according to the in FIG. 1 illustrated embodiment also on the in FIG. 2 Telehandlers 83 are used.
The inventive arrangement of the first control pressure line 42 for the pressure relief valve 34 of the pipe rupture protection device 32, based on two embodiments with respect to the FIGS. 1 and 3 has been described, it is ensured that the boom can be lowered independently of a pressure prevailing in the second chamber, whereby a better power output, in particular with respect to a hydraulic power at idle speed of the telehandler 83, can be achieved. Furthermore, a more precise positioning can be achieved when lowering the boom when the suspension is activated.

It is again pointed out that the first and second switching means 58, 114, 64 can be actuated or controlled mechanically, electrically, hydraulically or pneumatically and in proportion to a switching signal or control signal from a preferably closed first switching position to an opened second switching position be switched or moved. The second switching position is variable proportional to the switching signal or control signal or controllable, so that a pressure reduction proportional to the switching signal or control signal can take place.

It should also be pointed out again that the embodiments described above have been illustrated using the example of a double-acting hydraulic cylinder 26 which has a first and a second pressurisable chamber 28, 30. However, the hydraulic arrangements 10, 110 illustrated in the exemplary embodiments can also be applied in a corresponding manner to a one-sided hydraulic cylinder 26, which is obvious to a person skilled in the art, so that no further details are given.

Although the invention has been described by way of two embodiments only, many different alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description and the drawings, which fall within the scope of the invention as defined by the claims. Thus, for example, the hydraulic arrangement can also be applied to other vehicles, for example to wheel loaders or front loaders or to excavators or cranes, which have hydraulically actuated components that can be raised or lowered and where a suspension seems useful.

Claims (19)

1. Hydraulic arrangement for a suspension system, comprising a hydraulic cylinder (26) having at least one first chamber (28), a hydraulic tank (20), at least one conveying means (18) conveying a hydraulic fluid, a hydraulic accumulator (48), a first hydraulic line (46) disposed between the hydraulic accumulator (48) and the first chamber (28), a first pilot valve (52) disposed in the first hydraulic line (46), a first supply line (22) for the first chamber (28), a control unit (12, 112) having at least three switch settings, comprising a lifting setting, a lowering setting and a neutral setting for the hydraulic cylinder (26), and a pipe fracture protection device (32), which is disposed in the first supply line (22) and which comprises a non-return valve (36) that closes in the direction of the control unit (12, 112) and a pressure relief valve (34) that can be made to open via a first control pressure line (42), characterized in that the first control pressure line (42) extends between the pipe fracture protection device (32) and a conveying means (18) and in the first control pressure line (42) contains first switching means (58, 114), so that, by switching of the first switching means (58, 114), the first control pressure line (42) can be subjected to a control pressure and the pressure relief valve (34) can be made to open.
2. Hydraulic arrangement according to Claim 1, characterized in that coupling means are provided, which couple the first switching means (58, 114) to the control unit (12, 112) such that a switch setting of the first switching means (58, 114), in which a pressurization of the first control pressure line (42) is effected, occurs synchronously with a lowering setting of the control unit (12, 112).
3. Hydraulic arrangement according to Claim 1 or 2, characterized in that the control unit (12, 112) is hydraulically switchable and the coupling means comprise a second control pressure line (60) extending between the first control pressure line (42) and the control unit (12, 112), so that a pressurization of the second control pressure line (60) is realized by pressurization of the first control pressure line (42).
4. Hydraulic arrangement according to one of Claims 1 to 3, characterized in that the control unit (12, 112) comprises a third control pressure line (62) provided to switch the control unit (12, 112) into the lifting setting, the third control pressure line (62) containing second switching means (64).
5. Hydraulic arrangement according to Claim 4, characterized in that the second switching means (64) comprise a proportional pilot valve, in particular a pressure-reducing valve, by which, selectively, a connection of the third control pressure line (62) to the hydraulic tank (20) or to a conveying means (18) can be established.
6. Hydraulic arrangement according to one of Claims 1 to 5, characterized in that the first switching means (58, 114) comprise a proportional pilot valve, in particular a pressure-reducing valve, by which, selectively, a connection of the first control pressure line (42) to the hydraulic tank (20) or to a conveying means (18) can be established.
7. Hydraulic arrangement according to one of Claims 1 to 6, characterized in that the switching means (58, 114, 64) can be actuated mechanically, electrically, hydraulically or pneumatically.
8. Hydraulic arrangement according to one of Claims 1 to 7, characterized in that the first switching means (58, 114) are configured as a hydraulic joystick, a hydraulic supply to the first and second control pressure lines (42, 60) being able to be established as soon as the first switching means (58, 114) are moved into a position provided for the lowering setting of the control unit (12, 112).
9. Hydraulic arrangement according to one of Claims 4 to 8, characterized in that the second switching means (64) are configured as a hydraulic joystick, a hydraulic supply to the third control pressure line (62) being able to be established as soon as the second switching means (64) are moved into a position provided for the lifting setting of the control unit (12, 112).
10. Hydraulic arrangement according to Claims 2 to 9, characterized in that the coupling means comprise an actuating device (116) for the first switching means (114), which, in dependence on or proportionally to the switch setting of the control unit (112), bring the first switching means (114) into a first or second switch setting.
11. Hydraulic arrangement according to Claim 10, characterized in that the actuating device (116) comprises an angle or position sensor.
12. Hydraulic arrangement according to Claim 10 or 11, characterized in that the control unit (112) comprises a valve slide (113) and the actuating device (116) comprises a switching element (118) connected to the valve slide (113) and an actuating tappet (120) configured on the first switching means (114), the actuating tappet (120) being able to be actuated by the switching element (118) through displacement of the valve slide (113).
13. Hydraulic arrangement according to one of Claims 1 to 12, characterized in that the hydraulic cylinder (26) has a second chamber (30) and a second supply line (24) is provided for the second chamber (30), and in that between the second chamber (30) and the hydraulic tank (20) there is disposed a second hydraulic line (46').
14. Hydraulic arrangement according to Claim 13, characterized in that a second pilot valve (52'), disposed in the second hydraulic line (46'), is provided.
15. Hydraulic arrangement according to one of Claims 1 to 13, characterized in that the first and the second pilot valves (52, 52') have a closing setting and an opening setting.
16. Hydraulic arrangement according to one of Claims 1 to 15, characterized in that the first pilot valve (52), in the closing setting, closes in the direction of the hydraulic accumulator (48).
17. Hydraulic arrangement according to one of Claims 14 to 16, characterized in that the second pilot valve (52'), in the closing setting, closes in the direction of the hydraulic tank (20).
18. Hydraulic arrangement according to one of Claims 14 to 17, characterized in that means (76, 80) are provided, which bring the second pilot valve (52') into a closing setting when the control unit (12, 112) assumes a lowering setting.
19. Loader, in particular a telescopic loader (83), comprising a boom (86) and a hydraulic arrangement (10, 110) according to one of the previous claims for lifting and lowering the boom (86).

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