METHOD FOR OPERATING A CRANE, AND CRANE

Abstract

A crane, in particular a mobile crane, includes a crane jib which can be moved about a substantially horizontal luffing axis, and a tensioning device for the crane jib. The tensioning device includes two pendants which run from the jib tip to the jib base of the crane jib and tensioning posts each tensioning a respective one of the pendants relative to the crane jib in a triangular configuration. In order to operate the crane, a luffing angle of the crane jib about the luffing axis is measured or recorded, and a spread angle between the tensioning posts while the crane jib is being used is modified depending on the luffing angle.

Claims

1. A method for operating a crane or a mobile crane, the method comprising: providing a crane jib being movable about a substantially horizontal luffing axis, and a crane jib tensioning device including two pendants running from a jib tip to a jib base of the crane jib and tensioning posts each tensioning a respective one of the pendants relative to the crane jib in a triangular configuration; recording a luffing angle of the crane jib about the luffing axis; and modifying a spread angle between the tensioning posts while using the crane jib in dependence on the luffing angle.

2. The method according to claim 1, which further comprises continuously modifying the spread angle.

3. The method according to claim 1, which further comprises increasing the spread angle as the luffing angle increases.

4. The method according to claim 1, which further comprises measuring a length of the crane jib with or without a jib extension, and additionally also modifying the spread angle in dependence on the length of the crane jib.

5. The method according to claim 1, which further comprises measuring a weight of a working load lifted by the crane jib, and additionally also modifying the spread angle in dependence on the weight.

6. The method according to claim 1, which further comprises using a tensioning winch to modify the tension of the pendants in dependence on at least one of the spread angle, the luffing angle, a length of the crane jib or a weight of a working load lifted by the crane jib.

7. A crane or mobile crane, comprising: a crane jib being movable about a substantially horizontal luffing axis, said crane jib having a jib tip and a jib base; a tensioning device for said crane jib, said tensioning device having two pendants running from said jib tip to said jib base and tensioning posts each tensioning a respective one of said pendants relative to said crane jib in a triangular configuration; and a controller configured to detect a luffing angle of said crane jib about said luffing axis and to modify a spread angle between said tensioning posts in dependence on said luffing angle during use of said crane jib.

8. The crane according to claim 7, which further comprises a spreading drive or hydraulic spreading drive configured to continuously vary said spread angle.

9. The crane according to claim 8, wherein said tensioning posts are articulated so as to only permit said tensioning posts to be spread relative to each other within a plane oriented radially relative to said crane jib.

10. The crane according to claim 7, which further comprises a tensioning winch configured to vary the tension of said pendants, said controller configured to control said tensioning winch to vary the tension of said pendants during use of said crane jib.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0030] FIG. 1 is a diagrammatic, side-elevational view of a mobile crane with a crane jib;

[0031] FIG. 2 is a side-perspective view of the crane jib with a jib extension in a first luffed position and a working load which has been picked up;

[0032] FIG. 3 is a partial elevational view of the crane jib taken along a longitudinal axis of the crane jib, in the direction of the jib tip;

[0033] FIG. 4 is a view similar to FIG. 2 showing the crane jib in a second luffed position, with a greater luffing angle than in FIG. 2; and

[0034] FIG. 5 is a view similar to FIG. 3 showing the crane jib in the second luffed position.

DETAILED DESCRIPTION OF THE INVENTION

[0035] Referring now in detail to the figures of the drawings, in which mutually corresponding parts and dimensions are always provided with the same reference symbols, and first, particularly, to FIG. 1 thereof, there is seen a crane, specifically a mobile crane 1, which is diagrammatically illustrated. The crane includes an undercarriage 2 which in turn has a chassis with a plurality of axles carrying wheels 4, and a cab 6. The mobile crane 1 moreover includes a superstructure 8 which is articulated on the undercarriage 2 so that it can be slewed about a vertical axis 10. The mobile crane 1 moreover includes a crane jib 12 which forms a part of the superstructure 8 and is articulated on a mounting of the superstructure 8 so that it can be swiveled (can be “luffed”, i.e. its inclination can be adjusted) about a luffing axis 14. The crane jib 12 is telescopic and for this purpose has a base segment 16 in which a plurality of jib segments 18, each of which has a reduced cross-section, are accommodated so that they can be displaced along a longitudinal axis 20 of the crane jib 12. The “last” or smallest jib segment 18 in this case carries a so-called pulley head 22 on which a plurality of pulley wheels 24 of a pulley block are disposed.

[0036] In proper operation of the crane, a crane cable 26 for lifting a (working) load 28 is guided over the pulley head 22. This is illustrated by way of example in FIG. 2, wherein the crane jib 12 is pictured on its own. The crane jib 12 is in this case inclined upward about the luffing axis 14 by a luffing angle W. Because of its dead weight and the weight of the load 28, the crane jib 12 is subject to a bending moment which causes a deflection in the luffing plane within which the luffing angle W also lies. The crane jib 12 has a tensioning device 30 in order to stabilize the crane jib with respect to this deflection. The tensioning device 30 includes two pendants 32 and two tensioning posts 34. The pendants 32 are attached, at least approximately, to the jib base 36 and to the jib tip, i.e. in the region of the pulley head 22, and are in each case tensioned by the associated tensioning post 34, oriented in this case at right angles to the crane jib 12, with respect to the crane jib 12 in a triangular configuration. A merely diagrammatically indicated tensioning winch 38 for the pendants 32 is disposed in this case at the jib base 36, and through the use of which the tensioning of the pendants 32 can be set.

[0037] The tensioning posts 34 are articulated on the crane jib 12, in the present exemplary embodiment specifically on the base segment 16, in a hinged fashion and so that they can be adjusted relative to each other within a radial plane with respect to the crane jib 12. An actuator 5, which in the present exemplary embodiment is formed by a hydraulic cylinder, is in this case associated with the tensioning posts 34. This actuator 5 effects adjustment, specifically V-shaped spreading between the two tensioning posts 34, illustrated in FIGS. 2 to 5 by a spread angle V. The actuator 5 is therefore referred to as a “spreading drive.” The actuator 5 is in this case configured to enable continuous setting of the spread angle V. For this purpose, the actuator also includes a fixing device which locks the tensioning posts 34 in their current position. They can, for example, in this case be brakes or can define the hydraulic pressure in the above-mentioned hydraulic cylinder, in particular by using a correspondingly controllable blocking valve.

[0038] The mobile crane 1 includes a control unit 3 (also referred to as a “controller”) which is configured to automatically perform a method described in detail below, optionally with the interaction of an operator of the mobile crane 1.

[0039] The control unit 3 in this case calculates the current luffing angle W. The (current value of the) luffing angle W is optionally calculated in this case with the aid of an (extended) position of a (hydraulic) luffing cylinder (not shown), through the use of which the crane jib 12 is inclined, i.e. “luffed.” Alternatively, the mobile crane 1 has an inclination sensor (not shown) on the crane jib 12, through the use of which a value, measured by sensors, for the luffing angle W can be measured.

[0040] In a simple method, the control unit 3 controls the actuator 5 for the tensioning posts 34 in such a way that, while the crane jib 12 is being used (i.e. during the handling of the load 28, the luffing, or the like), as the luffing angle W increases, the spread angle V is likewise increased (see FIGS. 2 to 5).

[0041] The background to this is that the above-described load-induced deflection decreases as the luffing angle W increases because the resulting torque is reduced. In the case of an untentioned jib, the risk of the jib buckling in this case increases, for example according to the known Euler cases, in particular to the side because the crane jib 12 has, as can be seen in FIG. 3, a rectangular cross-section, the long axis of which is oriented in the direction of gravity, i.e. parallel to the luffing plane. This risk can be counteracted by the increasing spreading of the tensioning posts 34 and this advantageously takes place during ongoing operation by the stiffness being reduced within the luffing plane and being increased transversely to the luffing plane.

[0042] In a further exemplary embodiment, the control unit 3 calculates the current length of the crane jib 12 in addition to the luffing angle W. This can usually be read from a memory of the control unit because it is a value which is optionally likewise variable during ongoing operation. Otherwise, the currently configured jib length, i.e. specifically for the current work of the crane, is likewise stored in the memory.

[0043] The control unit 3 moreover also calculates the weight of the lifted load 28. The tensioning posts 34 are adjusted (spread) in this case depending on the luffing angle W, the jib length, and the weight of the load 28.

[0044] For example, where the crane jib 12 is telescoped out to a relatively great length, the tensioning posts 34 are spread only in the case of a relatively high luffing angle W.

[0045] Exemplary values for the spread angle V are 0 degrees in the case of a luffing angle W of 10 degrees, 70 degrees in the case of a luffing angle W of 50 degrees, and 120 degrees in the case of a luffing angle W of 80 degrees.

[0046] In an optional exemplary embodiment, the mobile crane 1 has a wind sensor (not illustrated), through the use of which the control unit calculates the wind load acting on the crane jib 12. The control unit 3 in this case controls the actuator 5 in such a way that the tensioning posts 34 are spread further in the case of a side wind than in the case of wind in the luffing plane.

[0047] The subject of the invention is not limited to the above-described exemplary embodiments. Instead, further embodiments of the invention can be derived from the above description by a person skilled in the art.

[0048] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention.

LIST OF REFERENCE SYMBOLS

[0049] 1 mobile crane [0050] 2 undercarriage [0051] 3 controller [0052] 4 wheel [0053] 5 spreading drive [0054] 6 cab [0055] 8 superstructure [0056] 10 vertical axis [0057] 12 crane jib [0058] 14 luffing axis [0059] 16 base segment [0060] 18 jib segment [0061] 20 longitudinal axis [0062] 22 pulley head [0063] 24 pulley [0064] 26 crane cable [0065] 28 working load [0066] 30 tensioning device [0067] 32 pendant [0068] 34 tensioning post [0069] 36 jib base [0070] 38 tensioning winch [0071] V spread angle [0072] W luffing angle