Mobile crane

Abstract

The invention relates to a mobile crane, in particular an off-road crane, comprising: a boom mounted so as to be pivotable about a horizontal pivot axis; the lifting arm can change the amplitude up and down around the pivoting axis through the hydraulic amplitude changing cylinder; the hydraulic control block is used for controlling the variable amplitude cylinder; and the first safety valve is connected between the control block and the variable-amplitude cylinder and is configured to close a bearing cylinder chamber of the variable-amplitude cylinder in a locking position. The crane also includes a second relief valve connected in series between the first relief valve and the control block and configured to close a load cylinder chamber of the luffing cylinder in a locked position. The crane further comprises a hydraulic damping device through which pitching vibration of the crane can be damped through the suspension arm when the crane moves, and the hydraulic damping device comprises a hydraulic energy accumulator and a first valve, the first valve connects the hydraulic accumulator to a connection line between the first relief valve and the second relief valve in a first switch position and disconnects the hydraulic accumulator from the connection line in a second switch position.

Description

Technical Field

[0001] The invention relates to a mobile crane. Background Art

[0002] Mobile cranes with wheeled chassis are known from the prior art. Such mobile construction machines have a mobile undercarriage, a superstructure mounted on the undercarriage so as to rotate about a vertical axis of rotation, and a boom, usually a telescopic boom, mounted on the superstructure so as to pivot about a horizontal pivot axis. The boom is usually luffed up and down about the aforementioned pivot axis using one or more hydraulic luffing cylinders.

[0003] Rough terrain cranes are specifically configured for use on rough terrain and have a relatively short chassis, which typically has only two axles. This equipment makes rough terrain cranes suitable for use on construction sites, especially on uneven terrain, and in remote areas such as oil and gas projects or the construction of wind turbines.

[0004] This type of off-road crane is prone to pitching during movement due to its long telescopic boom compared to the undercarriage and its typically unsprung axles with large-volume tires. This means that the front and rear of the off-road crane move in anti-phase (i.e. the front moves downwards while the rear moves upwards, or vice versa). These are small movements caused, for example, by the road surface (e.g. small bumps) and / or an unfavorable center of gravity (the center of gravity is not in the middle of the vehicle with a small boom angle, but far away from the front) in combination with the short wheelbase and the acceleration of the off-road crane. Off-road cranes are usually operated at speeds of up to 25 km / h. Even at these relatively low speeds, the aforementioned pitching vibrations may occur. These pitching vibrations are stressful for the driver and the machine and affect the drivability of the off-road crane. Summary of the invention

[0005] It is therefore an object of the present invention to minimize the occurrence of pitch vibrations in general cranes, in particular in the aforementioned rough terrain cranes.

[0006] According to the invention, said object is achieved by a mobile crane according to one aspect of the invention.An advantageous embodiment of the invention is according to another aspect of the invention and is described below.

[0007] Therefore, a mobile crane, in particular an off-road crane, is proposed, comprising a boom, in particular a telescopic boom, which is pivotably mounted about a horizontal pivot axis, and a hydraulic luffing cylinder, by means of which the boom can be luffed up and down about the pivot axis. The crane can have one or more luffing cylinders, for the sake of simplicity only one luffing cylinder will be mentioned below. The mobile crane also comprises a hydraulic control block, by means of which the luffing cylinder can be controlled or extended and retracted (and the pressure maintained). The control block can be the main control block of the crane.

[0008] Due to the high safety requirements of mobile cranes caused by lifting loads, especially at great heights, a first safety valve is arranged between the control block and the luffing cylinder. This is intended to prevent the boom from being accidentally lowered when lifting a load (e.g. due to leakage through the control block) and is therefore configured to close the load cylinder chamber of the luffing cylinder in the blocking position or to prevent hydraulic fluid from flowing back out of the load cylinder chamber. The term "load" is to be understood as meaning the deadweight of the boom, and also means the "load" acting on the cylinder chamber.

[0009] In addition to the control block, a first safety valve is provided, which can also be switched into a blocked position and thus constitutes an additional safety level. The first safety valve can be a seat-sealed valve, for example a lowering brake valve, which has a particularly high level of leak-proofness or tightness, in particular a higher tightness than conventional control blocks. The first safety valve is preferably controlled, for example, by the crane control system, so that it is always switched into the blocked position when the boom has picked up a load and the luffing cylinder is not retracted or extended via the control block, i.e. in particular during crane operation, for example when the crane is not moving and is supported by the supporting device.

[0010] The aforementioned high safety requirements distinguish the luffing cylinders of such cranes from the hydraulic cylinders of other construction machines such as wheel loaders or hydraulic excavators, in which additional safety valves are not mandatory in addition to the normal function of the corresponding control block.

[0011] Due to the arrangement of the first safety valve directly on the luffing cylinder, in particular due to high safety requirements, it is not easy to provide means for hydraulically damping the crane via the luffing cylinder or the boom during travel operation, since the first safety valve completely closes the load-bearing cylinder chamber in the blocked position and it is also not possible to completely open the first safety valve during travel operation due to safety requirements.

[0012] According to the invention, the mobile crane therefore comprises a second safety valve, which is connected in series with the first safety valve, i.e. the second safety valve is located between the control block and the first safety valve. The second safety valve is configured to close the load-bearing cylinder chamber of the luffing cylinder in the blocking position. When the first safety valve is open, the second safety valve thus assumes the above-mentioned additional safety function and prevents a return flow of hydraulic fluid to the control block. The two safety valves are connected to each other via a hydraulic connecting line. This arrangement now makes it possible to connect the damping device to the luffing cylinder without having to compromise safety.

[0013] According to the invention, the mobile crane thus comprises a hydraulic damping device, by means of which pitching vibrations of the crane can be damped or counteracted by the boom when the crane is moved. The damping device comprises a hydraulic accumulator, which is connected to the aforementioned connecting line between the two safety valves via a first valve. In a first switching position, the first valve connects the hydraulic accumulator to the connecting line in a fluid-conducting manner (activated vibration damping), and in a second switching position disconnects the hydraulic accumulator from the connecting line (deactivated vibration damping). In the first switching position, the boom is thus actually supported on the hydraulic accumulator, so that a compensating movement between the superstructure and the boom can be carried out, which counteracts or damps the pitching vibrations of the crane.

[0014] Due to the second safety valve, the first safety valve can be fully opened and the hydraulic accumulator of the damping device can be connected to the load-bearing cylinder chamber in a fluid-conducting manner without a return flow of hydraulic fluid to the control block. In its closed position, the second safety valve separates the area comprising the load-bearing cylinder chamber, the first safety valve and the hydraulic damping device from the control block, so that the area forms a closed system. The term "sealed" is to be understood in particular in a specific way, so that even leaks that each control block typically has can be excluded. This means that the vibration damping can be activated during the load-free movement of the crane without removing the hydraulic fixing of the luffing cylinder or the boom, thus enabling the crane to be moved safely with reduced pitch vibrations. Further hydraulic components can be connected between the safety valve and the control block. It should be noted at this point that the terms "vibration damping" and "vibration absorption" are used synonymously in this document.

[0015] In one possible embodiment, the second safety valve is hydraulically controllable and has a hydraulic control port, which is connected to the control valve via a hydraulic control line. The control valve is preferably electrically controllable, for example by a crane control system. This can be configured so that it automatically switches the second control valve, for example together with the first safety valve (or a further control valve that hydraulically controls the first safety valve) and / or the first valve of the hydraulic damping device (or a control valve that hydraulically controls the first valve).

[0016] Alternatively or additionally, the position of the control valve can be monitored by a position sensor. This can be used, for example, to inform the crane control system whether the control valve is in a certain switching position and therefore whether the second safety valve is in a blocked position or an open position. If an error occurs when the crane is moving on the construction site, such as a partial or complete opening of the second safety valve, the crane control system can take appropriate measures, such as issuing a warning and / or stopping the crane. Of course, alternatively or additionally, the position monitoring of the second safety valve can be performed directly. Alternatively or additionally, the position monitoring of the position of the first safety valve and / or the first valve of the hydraulic damping device can be performed.

[0017] In another possible embodiment, a release device is connected in parallel to the control valve, the release device being configured to release the control line towards the tank. The release device preferably connects the control line to the tank and can, for example, comprise an electrically controllable release valve, which switches accordingly in the event of an error. In the simplest case, the release device can comprise a throttling device and thus permanently release the control line towards the tank. This ensures that in the event of an error in which the control valve is not properly actuated or cannot be properly actuated, the control line is still released and the second safety valve can be reliably moved to the blocking position so that the luffing cylinder is fixed. The control valve or the hydraulic fluid supply device is particularly configured so that when the second safety valve is open, the flow of hydraulic fluid through the throttling device is overcompensated and the second safety valve remains in the open position, for example when the luffing cylinder is retracted and extended.

[0018] In a further possible embodiment it is provided that the first safety valve and / or the second safety valve is switched to the blocking position in the de-energized state. In particular, the second safety valve is in the blocking position when the control valve is not energized. Thus, in the event of an error (e.g. failure of the power supply to the control valve, leakage in the control line, etc.), the load-bearing cylinder chamber is automatically closed so that the boom cannot be unintentionally lowered.

[0019] Alternatively or additionally, the first safety valve and / or the second safety valve may be configured as a seat sealing type and / or a binary shut-off valve.

[0020] The first safety valve and / or the second safety valve may comprise a non-return valve which, in a blocked position, blocks a return flow from the load-bearing cylinder chamber and allows a flow in the direction of the cylinder chamber. Alternatively or additionally, the first safety valve and / or the second safety valve may comprise a throttling element which, in an open position, allows a controlled throttled flow through the valve, so that the boom is lowered in a controlled manner and at a reduced speed.

[0021] In a further possible embodiment it is provided that the first safety valve is directly connected to the load-bearing cylinder chamber. In other words, for safety reasons, there are no further valves or branches between the first safety valve and the load-bearing cylinder chamber. In particular, the first safety valve can be flange-connected directly to the luffing cylinder. Alternatively or additionally, the first safety valve can be hydraulically connected to the load-bearing cylinder chamber via a metal pipe (rather than, for example, via a hydraulic hose).

[0022] In a further possible embodiment, the hydraulic damping device comprises a pressure limiting device, which connects the hydraulic accumulator to the tank, in particular via the tank port of the hydraulic damping device, and limits the maximum pressure in the hydraulic accumulator to a defined limit pressure. The pressure limiting device may comprise a pressure cut-off or pressure limiting valve and protects the hydraulic accumulator from overpressure. The limit pressure may be greater than 100 bar, preferably greater than 200 bar, and depends on the design of the system.

[0023] In a further possible embodiment, the hydraulic damping device has a feed port via which pressure can be applied to the hydraulic accumulator, i.e. the feed pressure, in order to always keep the hydraulic accumulator at a defined pilot pressure. This means that the hydraulic accumulator is always filled in a predefined manner and vibration damping is achieved at any time when required. If the hydraulic accumulator is not always filled in a predefined manner, the boom will first "droop" and fill the hydraulic accumulator. A pressure limiting valve can be provided to define the pilot pressure, as described below.

[0024] The feed port is connected to the first valve via a second valve of the hydraulic damping device. In a second switching position of the first valve, the hydraulic accumulator is connected to the second valve via the first valve, so that the hydraulic accumulator is connected to the feed pressure connection depending on the switching position of the second valve. In the first switching position of the first valve, i.e. when the vibration damping is activated, the hydraulic accumulator is disconnected from the second valve.

[0025] In a further possible embodiment, it is provided that the second valve is configured as a pressure-maintaining valve and is configured to be switched by the feed pressure into an open position in which the feed port is connected to the first valve via a feed pressure connecting line, in particular when the feed pressure drops below a defined pilot pressure. The pilot pressure, which in particular defines the pressure at which the hydraulic accumulator is maintained, is preferably defined by a pressure-limiting valve of the hydraulic damping device, which connects the feed pressure connecting line between the first valve and the second valve to the tank port. In combination with the pressure-limiting valve, the pressure-maintaining valve thus ensures that the hydraulic accumulator always remains at the pilot pressure and can be configured, for example, as a proportional 3 / 3-way valve.

[0026] In a further possible embodiment, it is provided that the first valve of the hydraulic damping device is hydraulically switchable and has a hydraulic control port which is connected via a hydraulic control line to a third valve of the hydraulic damping device acting as a control valve. The third valve is preferably electrically controllable, in particular controlled by a crane control device which also controls the control valve of the second safety valve (and preferably also the first safety valve).

[0027] In a further possible embodiment, it is provided that the third valve connects the hydraulic control port of the first valve to the hydraulic accumulator in the first switching position. In particular, this causes the first valve to move to the first switching position, so that the vibration damping is activated (provided that the first safety valve is open). In the second switching position, the third valve disconnects the control port of the first valve from the hydraulic accumulator and preferably connects it to the tank, so that the first valve moves to the second switching position (vibration damping is deactivated). Preferably, the third valve is pre-biased to the second switching position in the non-energized (i.e., de-energized) state. Therefore, when the third valve is in the de-energized state, the first valve is also pre-biased to the second switching position. This automatically deactivates the vibration damping in the event of an error.

[0028] In a further possible embodiment, the crane comprises a control system, which may be a crane control system or an additional control system communicating with the crane control system. The control system is electrically connected to the control valve of the second safety valve and to the hydraulic damping device, in particular to the aforementioned third valve. Preferably, the first safety valve is also switched via an electrically controllable control valve, which is also controlled by the control system. The control system is configured to switch the second safety valve (via the control valve) to a blocking position and to switch the first valve (in particular via the aforementioned third valve) to a second switching position, so that the first safety valve can be safely opened and the vibration damping can be activated. The boom is secured against sagging by the closed second safety valve.

[0029] As described above, the control system is preferably also connected to the first safety valve (or to the corresponding control valve) and is configured to open the first safety valve when the second safety valve is in the blocking position and in particular the hydraulic accumulator is connected to the first safety valve (i.e. the first valve is in the first switching position). However, the hydraulic accumulator does not necessarily need to be connected to the first safety valve before the first safety valve is opened. Alternatively, the first valve of the hydraulic damping device can also be switched to the first switching position after the first safety valve is opened.

[0030] In a further possible embodiment, the control system is configured to automatically switch the second safety valve to the blocking position and to switch the first valve to the first switching position and to open the first safety valve (activated vibration damping) when the starter moves without the boom picking up an additional load (travel without load). Thus, the control system automatically activates the vibration damping as long as the crane moves without an additional load. This state can be detected, for example, via corresponding sensors on the support means of the crane (which are retracted when the crane moves) and / or pressure sensors on or in the luffing cylinders and / or by recording the travel speed, the engine speed or any other parameter. For this purpose, the crane can, for example, comprise first detection means for detecting the current load picked up via the boom, which first detection means are connected to the control system. In particular, the detection means can comprise a pressure sensor for detecting the current pressure in the load-bearing cylinder chamber.

[0031] Alternatively or additionally, the control system can be configured to automatically close the first safety valve during operation of the crane (i.e. in particular when the crane is supported and a load is attached to the boom, this state being detectable via corresponding sensors on the supporting device and / or pressure sensors on or in the luffing cylinder), so that the vibration damping is deactivated. Preferably, the first valve of the damping device is switched to the second switching position. The second safety valve can also be closed (which further increases safety), but can also be opened, since the safety function has already been performed by the first safety valve.

[0032] In a further possible embodiment it is provided that the control system is configured to activate vibration damping (i.e. the first safety valve is opened and the second safety valve is switched to the blocking position and the first valve is switched to the first switching position) only when the boom is in a defined angle range when the crane is travelling without load. This takes into account the fact that in certain boom positions (e.g. in the case of boom down and / or small boom angles and / or abrupt boom luffing) no or only negligible pitching oscillations occur. Therefore, for such boom positions, it is not necessary to activate vibration damping. For detecting the boom position, the crane can preferably comprise a second detection device for detecting the current boom angle, which second detection device is connected to the control system. If the crane has a folded position, this folded position of the boom can also be detected via corresponding sensors (e.g. contact switches, magnetic switches, etc.).

[0033] Alternatively or additionally, the control system may be configured to maintain vibration damping during the entire travel period if vibration damping is activated during the unloaded travel period, and only when the vehicle comes to a standstill again reassess whether vibration damping should continue (e.g. depending on the boom angle). One possible reason for doing this is that the dynamics prevailing in the system during travel may therefore distort the accurate load calculation.

[0034] It is conceivable that, alternatively or in addition to the boom angle, the control system may take into account other parameters, such as the travel speed (eg vibration damping may only be activated if a certain minimum speed is exceeded).

[0035] In a further possible embodiment, it is provided that the first valve is pre-biased to the second switching position in the non-energized state (ie, in particular when the aforementioned third valve is not energized).

[0036] Alternatively or additionally, the first valve can have at least one transition position between the first switching position and the second switching position, in which a hydraulic accumulator with a reduced flow cross section is connected to the connecting line between the first safety valve and the second safety valve. This can provide a smooth transition between the two final switching positions (activated / deactivated vibration damping) and help avoid pressure fluctuations.

[0037] In another possible embodiment, it is provided that the crane comprises an underframe with a wheeled chassis and a superstructure, which is mounted on the underframe so that it can rotate, on which a boom is mounted. The wheeled chassis can have exactly two axles (for example, in the case of an off-road crane) or more than two axles. The boom can be a telescopic boom with one or more internal telescopic sections. The crane can have a folding boom which, if necessary, can be mounted on the boom and can be stored, for example, at the side of the boom. In this case, the hydraulic damping device is preferably configured to be activated and to eliminate pitching vibrations, even when the folding boom is mounted and the crane is otherwise traveling without load.

[0038] Preferably, it is displayed to the crane operator on a display unit in the operator's cab of the crane when the vibration damping is activated and / or when it is deactivated.

[0039] The above-mentioned hydraulic accumulator of the hydraulic damping device can be a pure hydraulic accumulator or a hydropneumatic accumulator. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Further features, details and advantages of the invention are obtained from the exemplary embodiments explained below with reference to the attached drawings. In the drawings:

[0041] Figure 1a shows a side view of a mobile crane according to the present invention according to an exemplary embodiment;

[0042] Figure 1b Show Figure 1a A view of the rear of the crane is shown;

[0043] Figure 2A schematic diagram showing a hydraulic system supplying a luffing cylinder with a safety valve and a damping device; and

[0044] Figure 3 Shown as Figure 2 An enlarged view of the damping device is shown. DETAILED DESCRIPTION

[0045] Figure 1a and Figure 1b A side view showing an exemplary embodiment of a mobile crane 10 according to the present invention is shown. Figure 1a ) and its rear view ( Figure 1b ). In the exemplary embodiment shown here, the crane 10 is a rough terrain crane having a mobile undercarriage 12 and a superstructure 13, which is mounted on the undercarriage 12 so as to rotate about a vertical rotation axis. The undercarriage 12 here has a wheeled chassis with two axles 11, but more than two axles 11 are also possible.

[0046] A telescopic boom 14 is mounted on the superstructure 13 so that it can be pivoted about a horizontal pivot axis and can be luffed up and down about the aforementioned pivot axis by means of a hydraulic luffing cylinder 15. Furthermore, a superstructure operator's cab is located on the superstructure 13, from which the crane 10 is controlled. In this exemplary embodiment, a folding boom is mounted on the side of the telescopic boom 14 (see Figure 1b : It can be seen on the left side of the boom 14 that the foldable boom can be installed on the boom head of the telescopic boom 14 if necessary.

[0047] Due to its long telescopic boom 14, in particular the unsprung axle 11 and the relatively bulky tires, the off-road crane 10 is susceptible to pitching vibrations when moving, in particular off-road (but sometimes also when driving on the road). In order to eliminate or dampen these pitching vibrations, a hydraulic damping device 30 according to the invention is provided, which comprises a suitably tuned hydraulic accumulator 34, which can be hydraulically connected to the piston chamber or the bearing cylinder chamber 15a of the luffing cylinder 15 as required, so that the boom 14 is supported on the hydraulic accumulator 34 during movement. This makes it possible to compensate for the movement between the frame and the boom 14, which significantly reduces the pitching vibrations.

[0048] Figure 2 An exemplary embodiment of a hydraulic damping device 30 and a hydraulic system of a crane 10 connecting the damping device 30 to the luffing cylinder 15 is shown. Figure 3 An enlarged view of a circuit diagram of the damping device 30 is shown.

[0049] The luffing cylinder 15 comprises a piston and a piston rod emerging from one side of the cylinder housing, the piston rod being connected to the boom 14 (or hinge section). The piston chamber 15a represents the load-bearing cylinder chamber of the luffing cylinder 15, the pressure of which resists the deadweight of the boom 14 including any attached equipment (e.g., the folding boom shown) and the weight of any load lifted via the boom 14.

[0050] The extension and retraction of the luffing cylinder 15 is carried out via a control block 40, which is in particular the main control block of the crane 10. Figure 2 1 is only schematically shown as a box. Due to the high safety requirements for the luffing cylinder 15 in this type of off-road crane 10, the first safety valve 21 is directly connected to the load-bearing cylinder chamber 15a and in particular is directly flange-connected to the luffing cylinder 15 without any other branches. In the exemplary embodiment shown here, the first safety valve 21 is a seat-sealed descent brake valve with two switching positions. In the locked position (the position shown in FIG. 1 ), the first safety valve 21 prevents the hydraulic fluid from flowing back from the load-bearing cylinder chamber 15a to the control block 40, i.e. the load-bearing cylinder chamber 15a is closed. The first safety valve 21 has a high degree of seat sealing, so that leakage as is usual with any control valve is largely excluded. This prevents the boom 14 from being lowered inadvertently. In the open position, the first safety valve 21 allows the hydraulic fluid to flow between the luffing cylinder 15 and the control block 40. This flow can be deliberately reduced, such as Figure 2 The throttle symbol in the figure is indicated in order to achieve a slow descent of the boom, but throttling of the flow is not mandatory.

[0051] The first safety valve 21 is hydraulically controlled via a control valve, not shown, which in turn is electrically actuated by a control system, which may be a crane control system. Figure 2 As indicated in FIG. 1 , the first safety valve 21 may include a check valve which, in a blocked position, blocks flow from the luffing cylinder 15 to the control block 40 and allows flow in the opposite direction.

[0052] In order to be able to connect the hydraulic damping device 30 or its hydraulic accumulator 34 to the load-bearing cylinder chamber 15a without reducing the safety level of the crane 10 (because this requires a direct connection between the hydraulic accumulator 34 and the cylinder chamber 15a, i.e., an open first safety valve 21), according to the present invention, the second safety valve 22 is connected in series between the control block 40 and the first safety valve 21. The second safety valve 22 meets the same safety requirements as the first safety valve 21 and can in particular also be configured as a seat-sealed lowering brake valve with two switching positions, possibly including a check valve and / or a throttle valve.

[0053] The second safety valve 22 is Figure 2The control valve 24 shown in the figure is hydraulically controlled, wherein the control valve 24 is connected to the control port of the second safety valve 22 via a hydraulic control line 25. The control valve 24 can be electrically actuated and controlled via the aforementioned control system, so that the second safety valve 22 is directly opened or closed accordingly. The control valve 24 can be configured as a 4 / 2-way valve. It can include a control pressure port and a tank port, which are connected to the control line 25 according to the switch position.

[0054] In the exemplary embodiment shown, the two safety valves 21, 22 are configured so that each of them is in a blocked position when not actuated (ie, the corresponding control valve is de-energized) (see Figure 2 ). In the event of an error (ie in the event of a power failure), the load-bearing cylinder chamber 15a is thus locked and the boom 14 is fixed. In order to further increase the reliability, an additional release device 26 can be provided, for example Figure 2 In the exemplary embodiment shown, the release device 26 comprises a throttle valve and connects the control line 25 to the hydraulic oil tank of the crane 10, so that in the event of an error, the control line 25 is hydraulically released and the second safety valve 22 can always be safely closed. Preferably, in the de-energized state ( Figure 2 In the position shown), the control valve 24 is in a switching position in which the control line 25 is released toward the tank.

[0055] In addition to the aforementioned hydraulic accumulator 34, the hydraulic damping device 30 comprises a first valve 31 which, in a first switching position, hydraulically connects the hydraulic accumulator 34 to the connecting line 23 which connects the two safety valves 21, 22 to one another and in a second switching position ( Figure 2 In the exemplary embodiment shown here, the first valve 31 is configured as a main sliding method and can have one or more transition positions with a cross-section reduction or throttling in addition to the first switching position (complete connection of the hydraulic accumulator 34) and the second switching position (complete disconnection of the hydraulic accumulator 34) in order to achieve a smooth transition between activating and deactivating the vibration damping and to avoid pressure fluctuations. Figure 2 and Figure 3 Transition positions with several throttle valves and nozzles are shown.

[0056] In the exemplary embodiment shown here, the hydraulic damping device 30 comprises a control block 38, in which, in addition to the aforementioned first valve 31, a second valve 32 and a third valve 33 are integrated, whose functions will be described later. A hydraulic accumulator 34 is connected to the control block 38 and is connected therein to the first valve 31 via a port H, wherein alternatively, the hydraulic accumulator 34 can also be integrated into a component together with the aforementioned components. Alternatively, the aforementioned valves can be arranged in different components or not in a common control block 38.

[0057] The control block 38 has a tank port T, via which it is connected to the hydraulic tank. The pressure cut-off member 36 connects the hydraulic accumulator 34 to the tank port T and thus protects the hydraulic accumulator 34 from overpressure (in the exemplary embodiment, the limit pressure is 250 bar, but other values ​​greater / less than 250 bar are of course conceivable).

[0058] The hydraulic damping device 30 comprises a second valve 32, which in the exemplary embodiment shown here is configured as a hydraulically actuated proportional 3 / 3-way valve. The second valve 32 acts as a pressure maintaining valve and is opened by the feed pressure applied to the feed port S of the control block 38. The output of the second valve 32 is connected to the first valve 31 via a feed pressure connecting line, in which a check valve 39 is arranged, whereby the check valve 39 prevents the flow of hydraulic fluid from the first valve 31 to the second valve 32. The outlet of the second valve 32 is also connected to the tank port T via a pressure limiting valve 37, which always keeps the pressure (pilot pressure) of the hydraulic accumulator 34 provided via the feed port S at a defined value (25 bar in the present case, but other values ​​greater or less than 25 bar are also conceivable here, depending on the design of the system or the luffing cylinder 15 and the hydraulic accumulator 34). This means that the hydraulic accumulator 34 is always filled in a predefined manner and is ready to achieve vibration damping when needed. If not filled in a predefined manner, the boom 14 will first “droop” and fill the hydraulic accumulator 34 .

[0059] The first valve 31 is hydraulically controlled via a third valve 33, which in turn is electrically actuated by the control system. The third valve 33 connects a hydraulic accumulator 34 to the end face of the first valve 31 via a control line 35. The existing control pressure in the control line 35 (which corresponds to the pilot pressure in the hydraulic accumulator 34 when the third valve 33 is open) presses the first valve 31 into the first switching position. The third valve 33 is configured in such a way that in the de-energized state (see Figure 2 ), which is in a switching position in which the control line 35 is connected to the tank port T, whereby the first valve 31 is in a second switching position (vibration damping is deactivated, see Figure 2). If the third valve 33 is energized, the control line 35 is connected to the hydraulic accumulator 34 and the first valve 31 is moved to the first switching position (vibration damping is activated). In the exemplary embodiment shown, the control line 35 extends through the first valve 31, but this is not necessarily the case. The third valve 33 can be configured as a 3 / 2-way valve.

[0060] exist Figure 2 In the second switching position of the first valve 31 shown, the hydraulic accumulator 34 is disconnected from the connecting line 23 between the two safety valves 21 , 22 and is connected to the second valve 32 and to the feed port S if the latter is open.

[0061] In a first switching position of the first valve 31 , the hydraulic accumulator 34 is connected via port Z to the connecting line 23 and is disconnected from the feed pressure connecting line and the second valve 32 or the feed port S. The vibration damping is activated and the boom 14 can vibrate in a direction opposite to the pitch vibrations and counteract or reduce the pitch vibrations.

[0062] Due to the second safety valve 22 provided according to the invention, it is possible to connect the hydraulic damping device 30 directly to the load-bearing cylinder chamber 15a via the opened first safety valve 21. When the second safety valve 22 is closed, the aforementioned cylinder chamber 15a and the hydraulic damping device 30 continue to form a closed system. When vibration damping is activated, the first safety valve 21 is in particular fully opened, since the hydraulic accumulator 34 must be connected directly to the load-bearing cylinder chamber 15a without interfering with the damping in order to damp properly.

[0063] Compared to the prior art, the situation preferably remains unchanged in crane operation: the first safety valve 21 takes on the load (i.e. blocks the load-bearing cylinder chamber 15a). The vibration damping is deactivated and the first valve 31 is preferably switched to the second switching position. The hydraulic accumulator 34 is filled with pilot pressure via the feed port S and the second valve 32. In particular, the second safety valve 22 is fully open and therefore has no effect. Port Z is blocked via the first valve 31. The "luffing jib" crane function is available as usual.

[0064] In a driving mode in which vibration damping is activated, the second safety valve 22 is now closed and the first safety valve 21 is fully opened in order to fluidly connect the hydraulic accumulator 34 to the load-bearing cylinder chamber 15a of the luffing cylinder 15. Vibration damping can now be activated by switching the first valve 31 to the first switching position. Position monitoring of the control valve 24 is preferably performed in order to detect defects.

[0065] The second safety valve 22 is seat-tight, so that a fluid volume remains in the closed system of the hydraulic accumulator 34 and the cylinder piston side. In this closed hydraulic volume, the disengaged telescopic boom 14 can now luff in a damped manner and acts as a shock absorber. It counteracts the pitching vibrations of the rough terrain crane 10 with its counter-rotating vibration behavior and largely cancels them out. In this case, it is not possible to lift the load as usual.

[0066] When the crane 10 is traveling without a load, vibration damping may be automatically activated by the control system. The activity of the damping is preferably displayed to the operator via a display in the crane cab.

[0067] When moving, the rough terrain crane 10 may carry a folding boom (see FIG. Figure 1b ). In addition, hook groups of different weights can be mounted on the crane 10. In principle, the crane operator is allowed to move the rough terrain crane 10 with a load. However, if the vibration damping is activated, the crane can preferably only be moved without a load. The load weighing is preferably realized via the luffing cylinder 15 and comprises, for example, a pressure sensor which detects the existing pressure in the load-bearing cylinder chamber 15a and makes it available to the control system. The mentioned additional components (hook group, folding boom) also act on the luffing cylinder 15 via their own weight.

[0068] In an optional embodiment, the mobile crane 10 includes a load moment limiter (LMB) that compares the detected current load capacity with a stored and / or dynamically calculated limit value and preferably takes appropriate action, such as issuing a visual and / or audible warning and / or intervening the control system (e.g., limiting or stopping the current crane movement) if the limit value is exceeded (or about to be exceeded). An active LMB is not necessarily required to move the rough terrain crane 10, and the crane operator can also move the rough terrain crane 10 without an LMB. For this reason, load weighing by the LMB cannot be used to enable vibration damping. In particular, the setting status cannot be accurately determined.

[0069] The control system can enable vibration damping, depending on the pressure in the luffing cylinder 15 (or in the load bearing cylinder chamber 15a) and the angle of the telescopic boom 14 relative to the horizontal. A threshold value of the pressure can be used as a control variable for switching on the vibration damping. The threshold value must take into account the dependency on the attached attachment (e.g., folding boom). The threshold value can be calculated based on the pressure in the luffing cylinder 15 and the angle of the telescopic boom 14. In an exemplary embodiment, the rough terrain crane 10 can also be moved with the heaviest hook block and folding boom using active vibration damping.

[0070] The decision as to whether to enable vibration damping (the control system preferably enables this function independently) must be made before starting the trip and preferably maintained throughout the trip. A new determination as to whether vibration damping can continue is preferably made when the rough terrain crane 10 stops again.

[0071] If vibration damping is activated, the second safety valve 22 is closed. The switching state of the second safety valve 22 is preferably monitored. The monitoring can be indirect. If the switching position is "closed" (latched position), the first safety valve 21 is open and vibration damping is activated via the first valve 31. If vibration damping is not activated, the second safety valve 22 and the first safety valve 21 remain closed, in particular as long as no luffing movement of the telescopic boom 14 is performed. By adding the second safety valve 22 between the first safety valve 21 and the control block 40 (for luffing of the telescopic boom 14), the control valve 24 must also be energized during luffing. If the control valve 24 is not energized, it is not possible to luff the telescopic boom 14.

[0072] Ends at Figure 2 One or more of the various hydraulic lines on the left side may also be connected to the control block 40. Figure 2 In the figure, for simplicity and for the purpose of illustration, the box 40 is only connected to the hydraulic line, in which the first safety valve 21 and the second safety valve 22 are arranged. However, this should not be understood as limiting.

[0073] Reference numerals list

[0074] 10 Mobile cranes

[0075] 11 Axles

[0076] 12. Base

[0077] 13 Superstructure

[0078] 14 Jib

[0079] 15 Luffing Cylinder

[0080] 15a Load-carrying cylinder chamber

[0081] 21 First safety valve

[0082] 22 Second safety valve

[0083] 23 Connecting pipelines

[0084] 24 Control valve

[0085] 25 Control pipeline

[0086] 26 Release device

[0087] 30 Hydraulic damping device

[0088] 31 First valve

[0089] 32 Second valve

[0090] 33 Third valve

[0091] 34 Hydraulic accumulator

[0092] 35 Control pipeline

[0093] 36 Pressure limiting device

[0094] 37 Pressure limiting valve

[0095] 38 Control Block

[0096] 39 Check valve

[0097] 40 Control Block

[0098] H Port Hydraulic Accumulator

[0099] S Feed Port

[0100] T tank port

[0101] Z-port luffing cylinder.

Claims

1. A mobile crane (10), in particular an off-road crane, comprising: A boom (14) is mounted in a manner that allows it to pivot about a horizontal pivot axis; a hydraulic luffing cylinder (15) by which the boom (14) can be luffed up and down about the pivot axis; a hydraulic control block (40) for controlling the luffing cylinder (15); and a first safety valve (21) connected between the control block (40) and the luffing cylinder (15) and configured to close a bearing cylinder chamber (15a) of the luffing cylinder (15) in a locked position, It is characterized in that a second safety valve (22) connected in series between the first safety valve (21) and the control block (40) and configured to close the bearing cylinder chamber (15a) of the luffing cylinder (15) in a locked position, and A hydraulic damping device (30) by which the pitch vibration of the crane (10) can be damped by the boom (14) when the crane (10) moves, and the hydraulic damping device comprises a hydraulic accumulator (34) and a first valve (31), wherein the first valve (31) connects the hydraulic accumulator (34) to a connecting line (23) between the first safety valve (21) and the second safety valve (22) in a first switching position and disconnects the hydraulic accumulator (34) from the connecting line (23) in a second switching position.

2. Mobile crane (10) according to claim 1, wherein the second safety valve (22) is hydraulically controllable and comprises a connection port, which is connected to a control valve (24) via a hydraulic control line (25), wherein the control valve (24) is preferably electrically controllable and / or position-monitored by a position sensor.

3. Mobile crane (10) according to claim 2, wherein a release device (26) is connected in parallel to the control valve (24), the release device being configured to release the control line (25) towards the tank, wherein the release device (26) preferably comprises a throttling device and permanently releases the control line (25) towards the tank.

4. The mobile crane (10) according to any one of the preceding claims, wherein the first safety valve (21) and / or the second safety valve (22) are switched to the blocking position in a non-energized state and / or are configured as seat-sealed binary shut-off valves.

5. Mobile crane (10) according to any of the preceding claims, wherein the first safety valve (21) is directly connected to the load bearing cylinder chamber (15a), wherein the first safety valve (21) is preferably directly flange-connected to the luffing cylinder (15) and / or hydraulically connected to the load bearing cylinder chamber (15a) via a metal pipe.

6. Mobile crane (10) according to any of the preceding claims, wherein the hydraulic damping device (30) comprises a pressure limiting device (36) which connects the hydraulic accumulator (34) to a tank and limits the maximum pressure in the hydraulic accumulator (34) to a limiting pressure.

7. Mobile crane (10) according to any of the preceding claims, wherein the hydraulic damping device (30) comprises a feed port (S) via which pressure can be applied to the hydraulic accumulator (34), wherein the feed port (S) is connected to the first valve (31) via a second valve (32), wherein the first valve (31) preferably connects the hydraulic accumulator (34) to the second valve (32) in the second switching position and disconnects the hydraulic accumulator from the second valve (32) in the first switching position.

8. Mobile crane (10) according to claim 7, wherein the second valve (32) is configured as a pressure maintaining valve, in particular a proportional 3 / 3-way valve, and is configured to be switched by the feed pressure into an open position, in which the feed port (S) is connected to the first valve (31), wherein the pilot pressure is preferably defined by a pressure limiting valve (37) of the hydraulic damping device (30), which connects the feed pressure connecting line between the first valve (31) and the second valve (32) to the tank port (T).

9. Mobile crane (10) according to any of the preceding claims, wherein the first valve (31) is hydraulically switchable and comprises a control port which is connected via a control line to a third valve (33) of the hydraulic damping device (30), wherein the third valve (33) is preferably electrically controllable.

10. Mobile crane (10) according to claim 9, wherein the third valve (33) connects the control port of the first valve (31) to the hydraulic accumulator (34) in a first switching position and disconnects the control port from the hydraulic accumulator (34) in a second switching position, wherein the third valve (33) is preferably pre-biased to the second switching position in the unenergized state.

11. Mobile crane (10) according to any of the preceding claims, comprising a control system, which is electrically connected to the control valve (24) and the hydraulic damping device (30) and is configured to switch the second safety valve (22) into the blocking position and to switch the first valve (31) into the second switching position, wherein the control system is preferably also connected to the first safety valve (21) and is configured to open the first safety valve (21) when the second safety valve (22) is in the blocking position and in particular the hydraulic accumulator (34) is connected to the first safety valve (21).

12. Mobile crane (10) according to claim 11, wherein the control system is configured to automatically switch the second safety valve (22) to the blocking position and the first valve (31) to the first switching position and to open the first safety valve (21) when the crane (10) moves without picking up a load via the boom, wherein the crane (10) preferably comprises a first detection device for detecting a current load picked up via the boom (14), the first detection device being connected to the control system, wherein the detection device in particular comprises a pressure sensor for detecting a current pressure in the load cylinder chamber (15a).

13. The mobile crane (10) according to claim 12, wherein the control system is configured to open the first safety valve (21) and switch the second safety valve (22) to the blocking position and switch the first valve (31) to the first switching position only when the boom (14) is within a limited angle range during unloaded travel of the crane (10), wherein the crane (10) preferably includes a second detection device for detecting a current boom angle, the second detection device being connected to the control system.

14. The mobile crane (10) according to claim 1 , wherein the first valve (31) is pre-biased to the second switching position in the non-energized state and / or wherein the first valve (31) has at least one transition position between the first switching position and the second switching position, wherein the hydraulic accumulator (32) with a reduced flow cross section is connected to the connecting line between the first safety valve (21) and the second safety valve (22).

15. Mobile crane (10) according to any of the preceding claims, comprising an underframe (12) with a wheeled chassis and a superstructure (14), the superstructure being rotatably mounted on the underframe (12) and on which the boom (14) is mounted, wherein the boom (14) is preferably configured as a telescopic boom.

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