CRANE AND METHOD FOR MONITORING THE OPERATION OF SUCH A CRANE

Abstract

The invention relates to a method for monitoring the operation of a crane, in which an overall center of gravity of the crane, possibly with a load attached thereto, is determined and monitored in terms of its position in relation to a tipping edge of the crane, wherein possible displacements of the overall center of gravity caused by possible changes in different operating and/or influencing variables, which comprise at least different crane movements, and resultant future overall centers of gravity are determined, wherein the most critical overall center of gravity in relation to the tipping edge is determined from the determined plurality of future overall centers of gravity and a possible restriction of crane movements is determined on the basis of the position of this most critical future overall center of gravity in relation to the tipping edge.

Claims

1. A method for monitoring the operation of a crane comprising: determining and monitoring an overall center of gravity of the crane, possibly with a load attached thereto, in terms of its position in relation to a tipping edge of the crane, wherein the possible displacements of the overall center of gravity caused by possible changes in different operating and/or influencing variables, which comprise at least different crane movements, and resultant future overall centers of gravity are determined, wherein a most critical overall center of gravity in relation to the tipping edge is determined from the determined plurality of future overall centers of gravity and a possible restriction of crane movements is determined on the basis of the position of this most critical future overall center of gravity in relation to the tipping edge.

2. The method of claim 1, further comprising selecting the most critical future overall center of gravity on the basis of its distance from the tipping edge, further comprising determining a load reserve and/or stability reserve from the distance of the selected most critical overall center of gravity from the tipping edge, on the basis of which crane movements which increase the tilt behaviour and/or reduce the stability are selectively restricted or released.

3. The method of claim 1, wherein the possible restriction of crane movements comprises switching off and/or limiting a crane movement, reducing the maximum speed or maximum acceleration of a crane movement and/or limiting a crane drive to a single actuation while other crane drives are stopped.

4. The method of claim 1, further comprising determining a possible displacement of the overall center of gravity and an associated therewith possible future overall center of gravity position by a maximum permissible wind load.

5. The method of claim 4, further comprising determining the possible displacement of the overall center of gravity on the basis of the wind load from at least one determined wind direction, in particular a wind direction from behind and/or a wind direction from the side.

6. The method of claim 1, further comprising determining a possible displacement of the overall center of gravity and an associated therewith possible future overall center of gravity position as a consequence of a deformation of the crane.

7. The method of claim 1, further comprising determining a possible displacement of the overall center of gravity and an associated therewith possible future overall center of gravity by the influence of the mass forces from crane movements including rotating, lifting and/or travel of the trolley.

8. The method of claim 1, further comprising determining a possible displacement of the overall center of gravity and an associated therewith possible future overall center of gravity position, wherein this determining comprises taking into account a centrifugal force acting on the crane and/or the hoisting load attached thereto.

9. The method of claim 1, further comprising determining the tipping edge and the position and orientation thereof, relative to the upright crane rotation axis as a function of the extension distance of the supports of a outrigger assembly.

10. The method of claim 1, further comprising determining for a respective hoisting load attached to the lifting hook and/or, respectively, for any hoisting load attached to the lifting hook, in dependence on the tipping edge and the position thereof and in dependence on the determined possible displacements of the overall center of gravity, respectively, an extension state which assumes different values for different rotational positions of the crane.

11. The method of claim 10, further comprising restricting on the basis of the not circularly shaped outreach limit for the respective hoisting load attached to the lifting hook, a movement of the trolley outwards and/or luffing of the boom on the one hand and a rotation of the crane about the upright crane rotation axis on the other hand.

12. A revolving tower crane comprising: drive devices for crane movements and/or load movements; a crane controller for controlling the drive devices, wherein the crane control has a monitoring device for monitoring crane strain and restricting crane movements when critical crane strains are reached, wherein the monitoring device is configured to monitor an overall center of gravity of the crane with a load possibly attached thereto for its position relative to a tipping edge of the crane; wherein the monitoring device is configured to determine displacements of the overall center of gravity as a result of changes in different operating and/or influencing variables which comprise at least different crane movements, and resultant future overall center of gravity positions and to determine from the determined plurality of future overall center of gravity positions the most critical overall center of gravity with respect to the tipping edge and to determine a possible restriction of crane movements on the basis of the position of this future most critical overall center of gravity relative to the tipping edge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The invention is explained in more detail below on the basis of a preferred exemplary embodiment and the corresponding drawings. The drawings show:

[0032] FIG. 1: a schematic side view of a mobile revolving tower crane the tower of which, supported on a rotatable superstructure, carries a boom with trolley and the undercarriage of which is supported on the ground by extendable supports,

[0033] FIG. 2: a top view of the crane of FIG. 1, showing the tipping edges defined by the extended supports of the outrigger assembly, the current center of gravity position and possible future center of gravity positions, and the possible displacement of the payload resulting from the possible future center of gravity positions and the resulting stability reserve,

[0034] FIG. 3: a representation of the permissible outreach or outreach limits resulting for various lifting loads and for different boom positions when the rs of the outrigger assembly are fully extended,

[0035] FIG. 4: a representation of the outreach limits for different lifting loads similar to FIG. 3, but for supports of the outrigger assembly that are not fully extended.

DETAILED DESCRIPTION

[0036] As shown in FIG. 1, the crane 1 may be in the form of a mobile construction crane or mobile revolving tower crane comprising a tower 2 supported on a turntable 3 which sits on an undercarriage 4 and is rotatable about an upright axis of rotation by means of a slewing gear drive device 9. Said undercarriage 4 may be in the form of a truck or otherwise movably configured, but may also be a fixedly anchored or supported support base.

[0037] The tower 2 may support a boom 5 which may be luffed up and down about a horizontal, transverse luffing axis, cf. FIG. 1. A luffing drive device 12 for the boom 5 may, for example, luff the boom 5 via the guy cable construction.

[0038] A trolley 6 may be mounted longitudinally movable on said boom 5, and may be moved by a trolley drive device 11, for example via a corresponding trolley cable. A hoist cable 8 can run over said trolley 6, to which a load rigging, for example in the form of a lifting hook 7, can be attached in order to lift a load in a commonly known manner. A hoisting gear drive device 10 can drive a hoisting cable drum accordingly for this purpose.

[0039] Optionally, and therefore only indicated, the crane may comprise further drive devices, for example a telescopic boom with a telescoping drive device 13, a ballast adjusting drive device 15 for adjusting a ballast or a traversing drive device 14 for traversing the entire crane could be provided, which as a rule shall not be the case in the drawn version of the mobile construction crane, as it is jacked up for lifting loads.

[0040] The different drives are controlled by a central crane controller 16 which, in a commonly known manner known, may provide appropriate operating levers or other input means for a crane operator to control the various axes of movement of the crane. The crane controller 16 comprises a monitoring device 17 which monitors, by means of appropriate sensors, the crane strain acting on the crane, in particular the hoisting load taken up by the lifting hook 7 and the projection which the lifting hook 7 has with respect to the standing base of the crane. Said projection can be determined, for example, by the position of the trolley 6 on the boom 5 and, if necessary, the luffing angle of the boom 5 with respect to the horizontal.

[0041] The position or operating state of said drive devices and/or the crane elements which can be moved by them can be monitored by corresponding sensors, so that the crane controller 16 or the monitoring device 17 knows the respective current crane position, i.e. in particular the angle of rotation about the upright crane axis of rotation 18 and thus the orientation of the boom 5, the position of the trolley 6 in terms of the distance from the tower 2, the lowering depth of the lifting hook 6 and, if necessary, the luffing angle of the boom 5 and the position of the ballast. In addition, a lifting load sensor that measures the load on the hoisting gear 10, for example, can be used to determine the load picked up by the lifting hook 6.

[0042] From these current state variables of the crane 1, the current overall center of gravity of the overall system consisting of the crane 1 and the hoisting load attached to the lifting hook 7 can be determined by the monitoring device 17, in particular with regard to the position of the current overall center of gravity relative to the footprints defined by the outrigger assembly 19, which is shown in FIG. 2.

[0043] In FIG. 2, the current position of the overall center of gravity, which the monitoring device 17 knows or can determine from said state variables, for example can calculate or can read out from a parameter set determined for the crane configuration, is marked with the letter y. The current position of the overall center of gravity is shown in FIG. 2.

[0044] On the other hand, said monitoring device 17 can determine the tipping edges 20 which are connecting lines through the contact points of the outrigger assembly 19. As FIG. 2 shows, the outrigger assembly 19 may comprise, for example, four supports which are extendable in pairs towards opposite sides of the undercarriage 4 and are lowerable to the ground in the respective extended position. As FIG. 2 shows, the supports of the outrigger assembly 19 can be extended to different extents, so that different geometries of the support surface defined by the tipping edges 20 can result. In this respect, it is possible in principle for said supports to be extended in any desired manner, for example steplessly or step-wise, so that any desired multiplicity of differently configured contact or support surfaces can result. In practice, however, it may be useful to allow only several, few extension states for the supports, for example such that each support may be extended 1/4, 2/4, 3/4 and 4/4, or for example 1/3, 2/3 and 3/3 of the width. The resulting tipping edges 20 and their orientation can either be currently calculated by the monitoring device on the basis of sensor signals or can also be read out for the permitted and/or detected extension states in the form of stored values in parameter sets.

[0045] Based on the current overall center of gravity position, which is marked with y in FIG. 2, the monitoring device 17 can determine the displacement of the overall center of gravity and, accordingly, possible future overall center of gravity positions, marked with x in FIG. 2, wherein the possible displacements can be determined for various operating and/or influencing variables and/or changes thereto.

[0046] In particular, for the possible displacement of the current overall center of gravity towards a possible future overall center of gravity, the different crane movements can be taken into account, for example a rotation of the crane about the upright crane rotation axis 18, a lifting or lowering of the load on the lifting hook 7, a movement of the trolley 6, a luffing up or luffing down of the boom 5, possibly inward telescoping and outward telescoping of the boom 5 and/or a movement of the ballast.

[0047] In addition to the possible crane movements and the resulting mass forces, external factors influencing the crane can also be taken into account to determine the possible shifts in the position of the center of gravity. In particular, wind forces or a wind load on the crane 1 can be taken into account.

[0048] In this way, such a wind load can, for example, be taken into account virtually in the form of an additional mass force attached to the lifting hook when the wind pushes against the tower from behind. Alternatively or additionally, however, such a wind force can also be taken into account in the form of an actual displacement of the overall center of gravity, in particular in that the wind deflects the hoisting load attached to the lifting hook, wherein the lowering depth of the lifting hook 7 can be taken into account here if necessary, since the load can be moved further by the wind when the load hook is lowered than when it is moved close to the trolley. Alternatively or additionally, however, a deformation of the crane, in particular a bending of the tower 2 due to a wind load, can also be taken into account, as explained at the beginning. For example, if a wind force pushes against the tower 2 from behind, the tower 2 will deform a little forward towards the boom 3, increasing the outreach of the lifting hook 7 and correspondingly shifting the overall center of gravity of the system.

[0049] For the determination of the possible future total centers of gravity x, in particular also a deformation of the crane 1 can be taken into account, which can occur not only in said manner due to wind loads, but also due to other load variables, in particular the lifting load taken up at the lifting hook 7 and mass forces from a twisting of the crane 1, a movement of the trolley 6, a lifting or lowering of the lifting hook 7 or another of the explained crane movements.

[0050] Since the crane structure and therefore its deformation properties under loads are known, its deformation can be calculated or determined from said mass forces, wind forces and other loads acting on the crane. Such deformations of the crane structure can be determined, for example, on the basis of a model, wherein the deformations occurring for various load variables can be stored as a parameter set and made available to the crane controller 16 or the monitoring device 17 so that they can be provided on demand. Alternatively, said deformations could also be calculated directly on the basis of the influencing variables.

[0051] Proceeding from the current overall center of gravity and its position, the monitoring device 17 acts out, so to speak, the possible operating and influencing variables and their possible changes, in particular possible crane movements, possible wind loads and possible crane deformations, and from this determines different possible displacements and the resulting possible future center of gravity positions, which are marked with the reference variable x in FIG. 2.

[0052] The monitoring device 17 analyses the possible future center of gravity positions x for their relative position to the tipping edges 20, and selects as the most critical future overall center of gravity the one closest to one of the tipping edges 20. In FIG. 2, this critical future total center of gravity is also marked with the parameter x.sub.k in addition to the letter x.

[0053] On the basis of the distance of the critical future total center of gravity x.sub.k from the nearest tipping edge 20, the monitoring device 17 can determine the remaining load or stability reserve, and then determine from said load or stability reserve how far the outreach of the crane can still be increased, for example by moving the trolley 6 outwards or luffing the boom 5 or telescoping the boom 5.

[0054] The possibility of movement or increase of the outreach, which was determined in said manner from the critical future overall center of gravity, while the stability is still ensured, is symbolised in FIG. 2 by the arrow which connects the two trolley positions A and B. The arrow indicates the position of the trolley.

[0055] Taking into account the tilt edges 20 and the respective outreach and position, which may change due to the extension of the supports, the monitoring device 17 can determine the possible new locations of the payload for all boom positions or rotational positions of the crane 1 for a respective hoisting load attached to the lifting hook 7. These possible new locations of the payload for all boom positions are marked in FIG. 2 with the reference numeral 21 and result—approximately, roughly speaking—in a quadrilateral, the main axes of which are approximately oriented to the main axes of the footprint of the outrigger assembly 19, which are determined by the extension states of the supports.

[0056] As FIG. 2 illustrates, this outreach limit 21 is directional for a given hoisting load carried by the lifting hook 6 and varies for different boom positions or as a function of the angle of rotation of the boom 5 about the upright crane rotation axis 18.

[0057] As FIG. 3 shows, for different payloads or different hoisting loads attached to the lifting hook 7, corresponding outreach limits 21 can be determined which, respectively, become larger or smaller, on the basis of which the crane 1 or the monitoring device thereof 17 knows how far a load attached to the lifting hook 7 can still be moved by corresponding crane movements. Since said outreach limits 21 are not circularly shaped around the crane rotation axis 18, but are—approximately, roughly speaking—rectangularly or quadrangularly contoured, said outreach limits 21 can be achieved not only by moving the trolley 6 outwardly or by luffing the boom 5, but also by rotating the crane 1 about its upright crane rotation axis 18.

[0058] Accordingly, the monitoring device 17 can selectively shut down and/or slow down and/or limit the crane movement that would result in reaching or further approaching said outreach limit 21, that is, in particular, an outward movement of the trolley 6 and a corresponding rotational movement about the crane rotation axis 18.

[0059] As a comparison of FIGS. 3 and 4 shows, differently shaped outreach limits 21 result for different extension states of the supports of the outrigger assembly 19.

[0060] Therefore, the described method for monitoring the operation of a crane as well as, concomitantly, the corresponding crane with the monitoring device suitably designed therefore are characterized, inter alia, by the following advantageous aspects:

[0061] The calculation method provides knowledge of all possible center of gravity positions of the entire system, which can arise due to external influences (e.g. wind), mass forces, certain failure states (e.g. rope breakage) or other influences.

[0062] On the basis of the respective crane configuration and load position, all system states with the associated center of gravity positions that could arise during operation are taken into account.

[0063] In the present method, the deformations of the crane system are taken into account when determining the positions of the center of gravity.

[0064] In this way, from all the examined states, those are used which would lead to the smallest safety against tilting of the system or to the exceeding of individual component loads.

[0065] The underlying calculation method is designed in such a way that the calculation regulations and calculation standards specified for the respective existing crane configuration and the current crane application are met.

[0066] The method provides the possible center of gravity positions of the system in advance for all possible system states. From this, the permitted load locations and the associated gradients for all possible directions of movement of the upper crane part and the load can be determined at any time and used to control the crane movements.

[0067] When determining the permissible load size and load position, additional limits stored in the control system are also taken into account. This allows other limiting system states of the assemblies involved to be taken into account.

[0068] Support pressures could be stored with in the controller and used for additional monitoring/redundancy.