CRANE

Description

[0001] The present invention relates to a crane with a height-adjustable control or personnel station, which can be raised and lowered by at least two lifting elements, wherein the two lifting elements are articulated on a compensating rocker, which is mounted on a rocker bearing head connected to the control or personnel station so as to be rockable about a horizontal pivot axis, wherein a monitoring and / or safety device is provided for monitoring and / or ensuring the safety of the control station.

[0002] Such a crane is shown, for example, in EP 27 19 652 A1, which discloses the features of the preamble of claim 1, wherein a passenger stand is suspended from two hoist ropes via a balancing rocker. A tension measuring lug is provided between each of the two hoist ropes and the balancing rocker to measure the hoist rope force.

[0003] Height-adjustable control stations can, for example, be mounted on the tower of a crane so that they can be moved longitudinally and thus adjusted in height. Such a crane tower can support a boom in a conventional manner, from which a hoist cable runs to a load hook, possibly via a trolley that can be moved longitudinally along the boom. The tower can be mounted telescopically and / or luffing on an upper carriage, which can be mounted around an upright axis on a ground-moving undercarriage. Such cranes are sometimes referred to as mobile fast-erecting cranes.

[0004] In principle, the control station mentioned can also be provided on a conventional tower crane, or on another type of crane, whereby the control station does not necessarily have to be mounted on a tower in a movable manner, but can also be mounted in another way so that its height can be adjusted.

[0005] The control and / or personnel position is often designed in the form of a cabin or as a crane operator and / or lift cabin, whereby it can be advantageous if such a crane operator cabin can be positioned at different working heights for different lifting tasks of the crane.

[0006] To ensure the safety of height-adjustable control stations or lift cabins, even when people such as the crane operator are transported during the height adjustment process, special safety measures are required. Firstly, this involves providing two parallel lifting elements to achieve the necessary redundancy. Secondly, the proper functioning of these lifting elements and the control station suspension is additionally monitored to detect any malfunction or even breakage in a timely manner.

[0007] By linking the two lifting elements to a compensating rocker, adjustment comfort can be increased, as the compensating rocker balances the lifting forces of the lifting elements and can compensate for a jerky or not entirely synchronized start-up process to a certain extent. These lifting elements can be hoist cables that suspend the compensating rocker and thus the control station from above. In principle, however, it would also be possible to use actuators, for example in the form of pressure cylinders, as lifting elements that can pull or push the compensating rocker into the desired position.

[0008] In order to detect malfunctions such as slack rope, rope breakage, rope elongation, or incorrect spooling on the drive rope drum, it has already been proposed to monitor the angular position of the compensating rocker using mechanical limit switches actuated by a swivel arm of the compensating rocker when the compensating rocker reaches a predetermined swivel or rocking position. The compensating rocker is generally preloaded into a non-deflected neutral position by one or more spring devices, so that the compensating rocker only rocks up or down in the event of significant irregularities in the force applied by the two lifting elements, and is subjected to such a strong rotational deflection that the limit switches are actuated.If, for example, one of the hoist ropes is wound up significantly faster than the other, the compensating rocker will shift increasingly, which can be indicated by a first limit switch, for example, a pre-critical condition. If slack develops on the hoist rope that is wound up more slowly, or if one of the two hoist ropes breaks completely, so that only the other hoist rope supports the compensating rocker and thus the control station, a maximum rotational deflection will occur, which can be indicated by another limit switch.

[0009] On the other hand, "normal" overloading of the elevator car should also be detected, for example, if one person climbs into the car or onto the platform too many times, or if a person carries equipment that is too heavy, so that the permissible load is only slightly exceeded. Since the aforementioned limit switches, which indicate a severe tilting when a hoist rope breaks, do not respond in such cases of slight exceedance, additional sensors must be installed to detect such an overload condition.

[0010] Thus, through the clever arrangement of different mechanical limit switches, different critical conditions can be detected and displayed.

[0011] However, the current safety and / or monitoring devices are relatively complex. Differentiating between different critical states requires various mechanical limit switches, and the spring loading of the compensating rocker must be adjusted accordingly. Furthermore, even with more complex configurations of the safety and / or monitoring devices, it has so far been difficult to monitor with sufficient precision to allow timely intervention in the crane's control system.

[0012] The present invention is therefore based on the object of creating an improved crane of the type mentioned above that avoids the disadvantages of the prior art and advantageously develops them further. In particular, the aim is to achieve sensitive monitoring of the suspension and operation of the height-adjustable control and / or personnel stand using simple means. This monitoring can distinguish between various critical conditions, enabling not only an emergency shutdown but also enabling the crane's control system to take advance measures, such as counteracting the activation of the drives or issuing a maintenance notification.

[0013] According to the invention, the stated object is achieved by a crane according to claim 1. Preferred embodiments of the invention are the subject of the dependent claims.

[0014] It is therefore proposed to integrate the monitoring of the control station suspension into the pivot axis, which pivotably mounts the balancing rocker on the rocker bearing part connected to the control station. The pivot axis serves, on the one hand, to pivotally mount the balancing rocker and, at the same time, to detect the load condition on the rocker bearing, so that the pivot axis fulfills a dual function. According to the invention, the pivot axis is designed as a measuring axis for detecting the load condition of the rocker-like bearing of the balancing rocker and providing a load signal to the monitoring and / or safety device. Said measuring axis can, in particular, be designed as a force measuring bolt, which pivotably connects the balancing rocker to the rocker bearing head and detects at least transverse forces transverse to the pivot axis.

[0015] Because the swivel pin is not a normal axle pin, but also serves as a measuring pin or measuring axis, the control station's suspension can be designed more compactly and requires fewer components. At the same time, this enables sensitive measurement of the forces acting between the compensating rocker and the rocker bearing head.

[0016] In order to be able to distinguish between a normal overload condition, for example too many people in the cabin, on the one hand, and a mechanical irregularity in the lifting elements and the compensating rocker, such as a broken cable or incorrect spooling, on the other, with such a simple measuring axis, an advantageous development of the invention can provide for the compensating rocker and / or the rocker bearing head and / or the measuring axis to be assigned a lever mechanism which converts tilting movements of the compensating rocker and / or the rocker bearing head that exceed a predetermined value into a noticeable or detectable change in the load on the measuring axis or the bearing forces acting on the measuring axis. The said lever mechanism can in particular be designed to compensate for a holding and / or braking torque that arises when stopping and / or braking a relative rotation of the compensating rocker relative to the rocker bearing head.This is necessary for this purpose, and must be converted into a bearing force acting on the measuring axis. If, for example, one of the lifting cables or elements breaks, the compensating rocker would twist until the holding force exerted by the remaining lifting element passes vertically through the measuring axis. However, if the twisting is braked or stopped beforehand, the necessary holding or braking torque can be converted by the aforementioned lever mechanism into a force that significantly changes the load on the measuring axis.

[0017] The said lever mechanism may in particular comprise a pivot limiter which permits a certain pivoting movement between the compensating rocker and the rocker bearing head occurring during normal operation, but limits and / or brakes it when a certain pivoting angle is reached in order to generate the said holding and / or braking torque and to convert it into a change in the measuring axis load.

[0018] In an advantageous development of the invention, pivot stops can be provided on the compensating rocker and the rocker bearing head, which limit the possible pivoting movements of the compensating rocker relative to the rocker bearing head. In particular, the aforementioned pivot stops on the compensating rocker and the rocker bearing head can be arranged such that the pivot stops are disengaged in a non-deflected neutral position of the compensating rocker and only engage when a predetermined pivoting position of the compensating rocker relative to the rocker bearing head is reached, blocking any further pivoting movement beyond this position.

[0019] By means of such swivel stops, larger changes in the load condition can be generated on the measuring axis when the swivel stops engage, since their leverage changes the load condition on the measuring axis.

[0020] In particular, using such pivot stops and the resulting changes in the load on the measuring axis, it is possible to determine which lifting element has failed or is obstructed, or generally, the nature of the fault, even if the measuring axis is not designed to detect the direction of the load, for example, if the measuring axis is not rotationally fixed, which is nevertheless also possible in conjunction with the pivot stops. Due to the known geometry of the pivot stops and the linkage of the lifting elements, as well as the geometry of the compensating rocker, the change in the load state of the measuring axis can be used to determine what change has occurred in the suspension.

[0021] In an advantageous development of the invention, the said pivot stops can be arranged on a partial circle around the measuring axis, in particular arranged directly adjacent to the outer circumference of the said measuring axis, so that larger changes in the load state occur due to a relatively short lever arm with respect to the pivot axis when forces are transmitted via the pivot stops.

[0022] Advantageously, said pivot stops can be arranged on a pitch circle around the measuring axis, the diameter of which is less than 300% or less than 200% or less than 150% of the outer diameter of said measuring axis.

[0023] In an advantageous development of the invention, the pivot stops can be arranged in a horizontal plane extending transversely to the effective axis of the lifting elements. In particular, when viewed in the direction of the pivot axis, the pivot stops can be arranged in the region from approximately 2 o'clock to 5 o'clock or in the region from approximately 8 o'clock to 10 o'clock.

[0024] The arrangement of the swivel stops can be such that the forces transmitted by the swivel stops, when the swivel stops are engaged, run approximately in the direction of the actuating forces of the lifting elements and / or the weight force of the control station.

[0025] In order to be able to distinguish between different critical states, a further development of the invention can provide an evaluation device for evaluating the measurement signal of the measuring axis, which is configured to determine various critical states of the suspension of the control and / or passenger stand based on the height and / or a change in the measurement signal of the measuring axis. In particular, said evaluation device can be designed to compare the measurement signal of the measuring axis with different threshold values ​​in order to determine the load state, depending on which threshold value is exceeded or undershot.

[0026] For example, the evaluation device can operate with a first threshold value that is within the range of the permissible load of the control and / or passenger station, or characterizes a load on the measuring axis below which a normal operating condition can be assumed, and above which a "normal" exceedance of the permissible load can be assumed. In other words, the first threshold value can characterize an operating condition in which a transition occurs between a still-tolerated load and an excessive load, but no abnormal rotation of the compensating rocker relative to the rocker bearing head has yet occurred.

[0027] Alternatively or additionally, the evaluation device can compare the measuring axis signal with a second threshold value that characterizes a load on the measuring axis that only occurs in the event of an abnormal rotation of the compensating rocker relative to the rocker bearing head, in particular due to the aforementioned pivot limitation that limits the pivoting of the compensating rocker relative to the rocker bearing head and multiplies the weight load on the suspension by the weight of the control and / or passenger position including load.

[0028] In a further development of the invention, the said second threshold value can be more than 20% or more than 40% higher than a load on the measuring axis that occurs at the maximum permissible load of the control and / or personnel station with the balancing rocker not deflected or only slightly deflected, or with the lifting elements operating properly. Such a buffer window between the maximum, normal load and excessive loading on the measuring axis due to excessive deflection of the balancing rocker, as occurs in the event of a cable break or incorrect spooling, allows the evaluation device to reliably distinguish between normal overloading caused by too many people on the one hand and damage to the suspension on the other, without requiring additional sensors beyond the said measuring axis.

[0029] The aforementioned evaluation device can be electronically configured, for example, comprising switching elements integrated into the measuring axis sensor system. Alternatively or additionally, the evaluation device can also be part of an electronic control device, which can, for example, have a processor and a memory in which the aforementioned threshold values ​​can be stored. For example, the aforementioned evaluation device can be part of the electronic crane control system.

[0030] The measuring axis mentioned can be designed in different ways to detect the magnitude and / or direction of the transverse forces acting on the measuring axis. For example, a detection device for detecting elastic deformation of the measuring axis can be assigned to the measuring axis. For example, one or more strain gauges can be attached to the measuring axis mentioned to detect deformations of the measuring bolt.

[0031] Alternatively or additionally, the measuring pin can be provided with a surface coating that exhibits a change in electrical resistance when the measuring pin deforms. Such a surface coating can, for example, be in the form of a thin-film coating or a thin-film sensor.

[0032] Alternatively or additionally, a magnetic field-based sensor can be assigned to the measuring axis to detect deformations and / or forces applied, or the stresses acting in the measuring pin. For example, the measuring axis can serve as the iron core of a transformer circuit, so that strains in the measuring axis affect the magnetic properties and thus the voltage on a secondary coil.

[0033] The measuring axis can be non-rotatably mounted to the rocker bearing head, while the compensating rocker can be mounted on the measuring axis so that it can rotate relative to the measuring axis. Alternatively, it would also be possible to non-rotatably mount the measuring axis to the compensating rocker, so that it follows the rocking movements of the compensating rocker and rotates relative to the rocker bearing head.

[0034] By specifying a predetermined rotational position of the measuring axis, it would be possible to determine the direction of the forces acting on the measuring axis and / or to determine which sector of the measuring axis the transverse forces act on, at least predominantly. From the information on the sector on which the transverse forces act, it would be possible to determine the relative rotational or rocking position of the compensating rocker relative to the rocker bearing head. From the aforementioned pivoting position of the compensating rocker and the rocker bearing head relative to each other, conclusions can be drawn about the load condition, in particular unequal positions of the two lifting elements, for example, due to asynchronous adjustment.

[0035] In principle, however, it is not necessary to fix the measuring axis in a rotational direction, for example, if only absolute monitoring of the magnitude of the forces transmitted by the measuring axis between the balancing rocker and the rocker bearing head is required, for example, to implement an overload protection device. Such an overload protection device can be triggered or intervened, for example, if too many people enter the control station or if the guides of the crane operator's cabin jam.

[0036] In an advantageous development of the invention, the rocker bearing head can be rigidly connected to the control station. Advantageously, the rocker bearing head can be attached directly to the chassis of the control station. However, it would also be possible, in principle, to connect the rocker bearing head indirectly to the control station, for example, via a linkage arrangement that holds the rocker bearing head to the control station.

[0037] In a further development of the invention, the lifting elements mentioned are flexible traction elements, particularly in the form of lifting ropes. Traction chains or belts are also conceivable.

[0038] Alternatively, the lifting elements mentioned can also be designed in the form of actuating actuators such as hydraulic cylinders, in which case it would also be possible to apply pressure to the compensating rocker, for example in the form of upward pressure forces.

[0039] The present invention will be explained in more detail below using a preferred embodiment and the accompanying drawings. In the drawings: Fig. 1: a schematic side view of a fast-erecting crane designed as a tower crane according to an advantageous embodiment of the invention, the crane operator's cabin is mounted on the tower of the crane in a height-adjustable manner, Fig. 2: a perspective view of the crane operator's cabin from Figure 1and its suspension, Fig. 3: a perspective view of the suspension of the crane operator's cabin from Figure 2 , which shows the compensating rocker with the two lifting cables hinged to it and the measuring axis by means of which the compensating rocker is pivotally hinged to the rocker bearing head of the suspension, Fig. 4: a plan view of the compensating rocker and the measuring axis of the suspension from the preceding figures, wherein the compensating rocker is shown in an undeflected neutral position in which the pivot stops are disengaged, and Fig. 5: a plan view of the compensating rocker and the measuring axis similar to Figure 4, wherein the compensating rocker is shown in a twisted position due to a break or slack cable in one of the lifting cables, in which the pivot stops have engaged.

[0040] How Figure 1shows, the crane 1 can be designed as a tower crane and have a tower 2 which is upright during operation and carries a cantilevered boom 3. The tower 2 can be seated with its lower end on a slewing platform 4 which is rotatable about an upright axis and supported on an undercarriage 5 which can be designed as a truck or movable in some other way, but can also form a rigid, non-movable support base if necessary.

[0041] A trolley 7 can be mounted on the boom 3 for longitudinal movement, which can be moved back and forth by means of a trolley cable 8. A hoist cable 6 with a load hook can run over the trolley 7.

[0042] The crane 1 comprises a control and / or personnel station 9, which can be designed as a crane operator's cabin or elevator cabin 10. Said control and / or personnel station 9 is mounted so as to be height-adjustable. In particular, said crane operator's cabin or elevator cabin 10 can be mounted on the tower 2 so as to be longitudinally movable, for example, by means of a cabin chassis that is guided along the tower profile, for example, its longitudinal belts.

[0043] As the Figures 2 to 5As shown, the control and / or personnel station 9 can be held by a suspension 11 and adjusted to various height positions, which can engage the chassis, in particular the top of the crane operator's or lift cabin 10. Said cabin 10 can be moved up and down on an outer side of the tower 2, for example, by means of a roller guide or rail guide along the tower. If necessary, the cabin can also be arranged inside the tower profile, for example, if it is only used as a climbing aid to reach the boom or a control station located above, and the tower profile is sufficiently voluminous.

[0044] Said suspension 11 can, in particular, comprise a balancing rocker 12, to which two lifting elements 13 in the form of hoist ropes can be articulated, which can be raised and lowered via a suitable hoist drive. For example, two rope drums can be provided that can wind up and unwind the two hoist ropes.

[0045] The said balancing rocker 12 is pivotally mounted on a rocker bearing head 15 by means of a pivot axis 14 which extends horizontally and engages a central section of the balancing rocker 12, which rocker bearing head 15 can be rigidly connected to the control station 9, in particular fastened to the chassis of the cabin 10.

[0046] As the Figure 3As shown, the rocker bearing head 15 can, for example, form a bearing yoke, between the legs of which the compensating rocker 12 is inserted with a bearing section, wherein the legs of the rocker bearing head 15 and the bearing section of the compensating rocker 12 can have aligned pivot bearing bores through which the pivot axis 14 extends. In principle, however, it would also be possible to reverse the arrangement, for example to provide two yoke legs on the bearing section of the compensating rocker 12, between which the rocker bearing head 15 extends. Other designs, for example in the manner of a cantilevered pivot bearing connection, would also be possible.

[0047] The pivot axis 14 is designed as a measuring axis 16 in order to detect transverse forces acting on the pivot axis 14. The measuring axis 16 can be designed in the manner of a force measuring bolt, wherein a suitable sensor system can be provided on the measuring axis 16, which can detect the aforementioned bearing forces and loads acting on the bolt. As mentioned above, the sensor system 17 can, for example, comprise strain gauges on the measuring axis or a thin-film coating applied thereto in order to measure deformations and thus loads.

[0048] As a comparison of the Figures 4 and 5 As shown, the measuring axis 16 can be mounted in a rotationally fixed manner on the rocker bearing head 15, so that it does not participate in rotational movements of the compensating rocker 12. Alternatively, the measuring axis 16 can also be mounted rotatably relative to the rocker bearing head 15 and / or the compensating rocker 12, so that it does not assume a predetermined rotational position.

[0049] The pivotability of the compensating rocker 12 relative to the rocker bearing head 15 can advantageously be limited by pivot stops 18, which can be provided on the compensating rocker 12 and the rocker bearing head 15. In particular, the aforementioned pivot stops 18 can be arranged around the pivot axis 14 directly adjacent to its outer circumference, i.e., in particular, around the bearing bores through which the pivot axis 14 extends.

[0050] For example, the aforementioned pivot stops 18 may be formed by projections formed on the compensating rocker 12 and the rocker bearing head 15 to collide with each other when the compensating rocker 12 pivots relative to the rocker bearing head 15.

[0051] As the Figures 4 and 5 show, the mentioned swivel stops 18 can be in a non-deflected neutral position of the compensating rocker 12, which in Figure 4shown, be disengaged from each other so that the compensating rocker 12 can rotate freely from the neutral position. On the other hand, the pivot stops 18 engage when the compensating rocker has performed a predetermined pivoting movement, for example, by an angle of approximately + / -10° to + / -20°.

[0052] If the swivel stops 18 engage with each other, as Figure 5shows, for example, because one of the lifting elements 13 has broken or been unwound too far, the load condition on the measuring axis 16 changes significantly. The eccentrically arranged pivot stops 18 and the forces transmitted thereby act on the pivot axis 14, which must compensate for the lever situation. The loads detected on the measuring axis 16, in particular transverse forces and / or bending moments, experience a significant change as soon as the pivot stops 18 engage. This change can fundamentally be a relief or additional load that can be detected on the measuring axis.

[0053] Advantageously, the pivot stops 18 are designed such that engagement forces are generated on the engaged stop surfaces that are eccentric with respect to the pivot axis 14 and / or have a lever arm to generate a reaction in the measuring axis. In particular, a resulting engagement force can act eccentrically to the measuring axis when the pivot stops are engaged.

[0054] As the Figures 4 and 5 As shown, the pivot stops 18 may comprise two pairs of pivot stops 18 arranged on opposite sides of the measuring axis 16, preferably approximately—at least approximately—in a plane extending horizontally through the pivot axis 14. For example, the pivot stops 18 may extend in a range from 2 o'clock to 4 o'clock or 8 o'clock to 10 o'clock when the pivot axis 14 is viewed in its axial direction.

[0055] The pivot stops 18 are advantageously arranged in such a way that, depending on the tilting movement of the compensating rocker, only one pair of stops engages on one side of the pivot axis 14.

[0056] The pivot stops 18 form a lever mechanism that converts the torque or holding torque occurring when limiting the pivoting movement of the compensating rocker 12 into a significant change in the load on the measuring axis 16. In particular, the lever mechanism formed by the pivot stops 18 can multiply the load introduced into the suspension by the cabin, so that the load on the measuring axis 16 increases significantly, in particular, much more than would be the case if the permissible load were only slightly exceeded, for example, if an additional person boarded.

[0057] How Fig. 5shows, when a pair of swivel stops engages with a correspondingly further rotation of the compensating rocker, on the one hand a lever arm of the measuring axis or the cabin load passing through the measuring axis to the engaged pair of swivel stops and on the other hand a lever arm of the still load-bearing cable 13 to the pair of swivel stops 18 arise, wherein the said lever arms can each correspond essentially to the horizontal distance between the center of the measuring axis and the point of engagement of the swivel stops on the one hand or the line of action of the cable tensile force and the point of engagement of the swivel stops 18 on the other hand.

[0058] Since the rope force in the still load-bearing rope 13 corresponds to the load of the cabin including the payload and attachments, so that a vertical force equilibrium can be achieved, the change in the load occurring on the measuring axis can be controlled by the length of the lever arms mentioned.

[0059] For example, the length of said lever arms can be designed by appropriately designing the geometry of the compensating rocker and the rocker bearing head, in particular the articulation point of the lifting elements 13 on the compensating rocker and the arrangement of the pivot stops 18, such that the load occurring and thus measured on the measuring axis 16 increases by 50% or more when the said pivot stops 18 engage due to corresponding pivoting of the compensating rocker 12. For example, if the cabin 10 weighs 1000 kg including the permissible maximum load, the said lever arms can be adjusted such that a load of 1500 kg occurs on the measuring axis 16 when the pivot stops 18 engage.In this respect, it is easy to distinguish between normal overloading and a cable break or incorrect spooling. For example, if a first threshold of 1050 kg is exceeded and a second threshold of, say, 1400 kg is not yet exceeded, then normal overloading can be assumed while the suspension is still functional. If the second threshold of, say, 1400 kg is exceeded, then a cable break or incorrect spooling can be assumed. The values ​​mentioned are merely examples.

[0060] The sensor system 17 assigned to the measuring axis 16 emits a load signal which characterizes the load situation on the measuring axis 16, in particular indicating the transverse forces occurring there in terms of their magnitude and / or their direction.

[0061] The said load signal of the sensor system 17 can be evaluated by a control device 20 of the crane 1, which control device 20 can be electronically designed and can, for example, comprise a microprocessor which can process a control program stored in a memory.

[0062] The control device 20 mentioned can have an evaluation device 19 which evaluates the measurement signal of the measuring axis 16 in the manner mentioned, in particular comparing it with two threshold values ​​which, on the one hand, characterise the normal transition from a normal, permissible load to an overload and, on the other hand, characterise the engagement of the pivot stops 18 and the associated change in the load on the measuring axis.

[0063] The control device 20 can, on the one hand, issue a warning signal and / or stop at least one drive of the crane, in particular the hoist drive for the height adjustment of the control station 9, if the load signal of the sensor system 17 indicates an unusual load condition, for example excessive transverse forces on the measuring axis.

[0064] Alternatively or additionally, the aforementioned control device 20 can also intervene preventively in the control of the drives if necessary. For example, if the sensor system 17 detects that the compensating rocker is tilting too far, the control device 20 can attempt to correct the hoist drive from which the hoist rope, which is too slack or too tight, is running.

[0065] Alternatively or additionally, the control device 20 can also emit a preventive maintenance signal if the load signals of the sensor system 17 do not yet indicate a critical condition, but already show significant changes compared to the original load collective when new.

Claims

1. A crane, in particular fast-erecting crane, comprising a telescopable and / or luffable tower (2), with a height-adjustably mounted control and / or personnel stand (9) that can be lifted and lowered by two lifting elements (13), wherein the two lifting elements (13) are articulated to a balancing rocker (12) that is luffably mounted on a rocker bearing head (15) connected to the control and / or personnel stand (9) about a horizontal pivot axis (14), wherein a monitoring and / or safety device (21) is provided for monitoring the control and / or personnel stand (9), characterized in that the pivot axis (14) is configured as a measurement axis (16) for detecting the load state of the luffable bearing of the balancing rocker (12) and for providing a load signal to the monitoring and / or safety device (21).

2. The crane according to the preceding claim, wherein a lever mechanism for generating a change of the measurement axis load acting on the measurement axis (16) in dependence on a rotation of the balancing rocker (12) relative to the rocker bearing head (15) is associated with the balancing rocker (12) and / or the rocker bearing head (15) and / or the measurement axis (16), wherein said lever mechanism is configured to convert a holding and / or braking moment occurring when limiting and / or braking the rotation of the balancing rocker (12) relative to the rocker bearing head (15) into a load acting on the measurement axis (16).

3. The crane according to any of the preceding claims, wherein pivot stops (18) are provided on the balancing rocker (12) and the rocker bearing head (15), which are out of engagement in a non-deflected neutral position of the balancing rocker (12) and come into engagement when reaching a predetermined swivel position of the balancing rocker (12) and block a further swivel movement of the balancing rocker (12) relative to the rocker bearing head (15), wherein the pivot stops (18) are arranged on a partial circle around the measurement axis (16) and / or adjacent to the outer circumference of the measurement axis (16), wherein said partial circle has a diameter of less than 300% or less than 200% of the outside diameter of the measurement axis (16).

4. The crane according to any of claims 2 to 3, wherein the pivot stops (18) are arranged in a horizontal plane transversely to the luffing axis of the lifting elements (13).

5. The crane according to any of claims 2 to 4, wherein the pivot stops (18) in their engaged position are configured to generate a resultant abutment force that acts eccentrically to the axis of rotation (14).

6. The crane according to any of the preceding claims, wherein an evaluating device (19) is provided for evaluating the measurement signal of the measurement axis (16), wherein said evaluating device (19) is configured to employ a height and / or a change of the measurement signal of the measurement axis (16) to distinguish between an overload of the control and / or personnel stand (9) at a proper operating condition of the lifting elements (13) and the balancing rocker (12) on the one hand and a malfunction of the lifting elements (13) and / or the balancing rocker (12) on the other hand.

7. The crane according to the preceding claim, wherein said evaluating device (19) is configured to compare the measurement signal of the measurement axis (16) with two different threshold values, a first one of which characterizes the load acting on the measurement axis (16) on transition between maximum permissible load and overload of the control and / or personnel stand (9) at a proper operating condition of the lifting elements (13) and the balancing rocker (12), and a second one of which characterizes an increase of the load acting on the measurement axis (16) with an excessive deflection of the balancing rocker (12) from its neutral position.

8. The crane according to any of the preceding claims, wherein the measurement axis (16) is non-rotatably attached to the rocker bearing head (15) and the balancing rocker (12) is retained at the measurement axis (16) so as to be rotatable relative to said measurement axis (16).

9. The crane according to any of the preceding claims, wherein the measurement axis (16) is configured to detect transverse forces acting on the measurement axis (16) in terms of their amount and / or direction.

10. The crane according to any of the preceding claims, wherein the measurement axis (16) is configured to detect bending moments acting on the measurement axis.

11. The crane according to any of the preceding claims, wherein the measurement axis (16) comprises a sensor system (17), at least one strain gauge and / or a strain-sensitive thin-film coating and / or a magnetic field-based sensor array.

12. The crane according to any of the preceding claims, wherein the rocker bearing head (15) is rigidly attached to the control and / or personnel stand (9).

13. The crane according to any of the preceding claims, wherein the at least two lifting elements (13) are each configured as flexurally slack traction elements, in particular lifting cables.

14. The crane according to any of the preceding claims, wherein the balancing rocker (12) defines a triangle with its articulation points of the lifting elements (13) and the pivot axis (14), wherein preferably a straight connecting line is arranged to extend through the articulation points of the lifting elements (13) above the pivot axis (14).

15. The crane according to the preceding claim, wherein in the non-deflected neutral position of the balancing rocker (12) the pivot axis (14) is positioned on the balancing rocker (12) centrally between the articulation points of the lifting elements (13).