阅读说明：本技术 起重机 (Crane with a movable crane ) 是由 马丁·阿斯法尔格 西蒙·霍尔 于 2020-03-06 设计创作，主要内容包括：本发明涉及一种起重机,其具有高度可调节地安装的控制和/或载人平台,控制和/或载人平台能够通过至少两个提升元件升高和降低,其中,这两个提升元件铰接在平衡摇臂上,该平衡摇臂以能够围绕水平枢转轴俯仰的方式安装在与控制和/或载人平台连接的摇臂轴承头上,其中,设置有用于监测和/或确保控制平台安全的监测和/或安全装置。根据本发明,枢转轴被构造为测量轴,其用于检测平衡摇臂的可俯仰轴承的载荷状态,并向监测和/或安全装置提供载荷信号。(The invention relates to a crane having a height-adjustably mounted control and/or people platform which can be raised and lowered by means of at least two lifting elements, wherein the two lifting elements are articulated on a compensating rocker arm which is mounted in a manner such that it can be tilted about a horizontal pivot axis on a rocker arm bearing head connected to the control and/or people platform, wherein monitoring and/or safety means are provided for monitoring and/or ensuring the safety of the control platform. According to the invention, the pivot shaft is designed as a measuring shaft for detecting the load state of the tiltable bearing of the balance rocker and for providing a load signal to a monitoring and/or safety device.)

1. A crane, in particular a rapid-erection crane, comprising a telescopic and/or pitchable tower (2) having a height-adjustably mounted control and/or people carrier platform (9) which can be raised and lowered by means of two lifting elements (13),

wherein the two lifting elements (13) are hinged to a balance rocker (12) mounted in a manner tiltable about a horizontal pivot axis (14) on a rocker bearing head (15) connected to the control and/or people carrier (9),

wherein monitoring and/or safety means (21) are provided for monitoring the control and/or people carrying platform (9),

characterized in that the pivot shaft (14) is configured as a measuring shaft (16) for detecting the load state of the tiltable bearing of the balance rocker arm (12) and providing a load signal to the monitoring and/or safety device (21).

2. Crane according to the preceding claim, wherein the balancing rocker arm (12) and/or the rocker arm bearing head (15) and/or the measuring shaft (16) are assigned a lever mechanism for generating a change in the measuring shaft load acting on the measuring shaft (16) as a function of the rotation of the balancing rocker arm (12) relative to the rocker arm bearing head (15).

3. Crane according to the preceding claim, wherein the lever mechanism is configured to convert a holding and/or braking torque occurring when limiting and/or braking the rotation of the balancing rocker arm (12) with respect to the rocker arm bearing head (15) into a load acting on the measuring shaft (16).

4. Crane according to any of the preceding claims, wherein a pivot stop (18) is provided on the balance rocker arm (12) and the rocker arm bearing head (15), which pivot stop is disengaged in an undeflected intermediate position of the balance rocker arm (12) and engages and prevents further rotational movement of the balance rocker arm (12) relative to the rocker arm bearing head (15) when a predetermined rotational position of the balance rocker arm (12) is reached.

5. Crane according to the preceding claim, wherein the pivot stop (18) is arranged on a partial circle around the measuring shaft (16) and/or adjacent to the outer circumference of the measuring shaft (16).

6. Crane according to the preceding claim, wherein the diameter of the partial circle is less than 300% or less than 200% of the outer diameter of the measuring shaft (16).

7. A crane according to any one of claims 4 to 6, wherein the pivot stop (18) is arranged in a horizontal plane transverse to the pitch axis of the hoisting element (13).

8. A crane according to any one of claims 4 to 7, wherein the pivot stops (18) are configured to generate a final stopping force acting eccentrically with respect to the pivot axis (14) at their engaged position.

9. Crane according to any of the preceding claims, wherein an evaluation device (19) for evaluating the measurement signal of the measurement shaft (16) is provided, wherein the evaluation device (19) is configured to use the level and/or variation of the measurement signal of the measurement shaft (16) to distinguish between an overload of the control and/or people carrier platform (9) in a normal operating state of the lifting element (13) and the balance rocker (12) and an operational failure of the lifting element (13) and/or the balance rocker (12).

10. Crane according to the preceding claim, wherein the evaluation device (19) is configured to compare the measurement signal of the measurement shaft (16) with two different thresholds, a first of which characterizes the load on the measurement shaft (16) at the transition between the maximum allowed load and the overload of the control and/or people carrier platform (9) in the normal operating state of the lifting element (13) and the balance rocker (12), and a second of which characterizes the increase in the load on the measurement shaft (16) at the excessive deflection of the balance rocker (12) from its neutral position.

11. Crane according to any of the preceding claims, wherein the measuring shaft (16) is fastened to the rocker bearing head (15) in a non-rotatable manner and the balance rocker (12) is held on the measuring shaft (16) in a rotatable manner relative to the pivot shaft (16).

12. Crane according to any of the preceding claims, wherein the measuring shaft (16) is configured to detect the magnitude and/or direction of a lateral force on the measuring shaft (16).

13. Crane according to any of the preceding claims, wherein the measuring shaft (16) is configured to detect bending moments on the measuring shaft.

14. Crane according to any of the preceding claims, wherein the measuring shaft (16) comprises a sensor system (17) comprising at least one strain gauge and/or a thin film coating sensitive to strain and/or a magnetic field based sensor assembly.

15. Crane according to any of the preceding claims, wherein the rocker arm bearing head (15) is rigidly fastened to the control and/or people platform (9).

16. Crane according to any of the preceding claims, wherein the at least two hoisting elements (13) are each configured as a flexible loose traction element, in particular a sling.

17. Crane according to any of the preceding claims, wherein the balance rocker (12) defines a triangle with its hinge point to the lifting element (13) and the pivot axis (14), wherein preferably a connecting straight line passing through the hinge point of the lifting element (13) is arranged above the pivot axis (14).

18. Crane according to the preceding claim, wherein, in an undeflected intermediate position of the balance rocker (12), the pivot axis (14) is positioned centrally on the balance rocker (12) between the hinge points of the lifting elements (13).

Technical Field

The invention relates to a crane with a height-adjustably mounted control or people platform which can be raised and lowered by means of at least two lifting elements, wherein the two lifting elements are hinged to a balancing rocker arm which is mounted in a manner tiltable about a horizontal pivot axis on a rocker arm bearing head connected to the control or people platform, wherein monitoring and/or safety means are provided for monitoring and/or ensuring the safety of the control platform.

Background

For example, the height-adjustable control platform can be mounted on the tower of a crane in a longitudinally movable and thus height-adjustable manner, wherein such a crane tower can carry in a known manner a boom from which a suspension line extends to a load hook, possibly via a trolley that is longitudinally movable on the boom. Here, the tower is telescopically and/or tiltably mounted on a superstructure, which is mountable on a chassis movable on the ground about a vertical axis. Such cranes are sometimes referred to as mobile quick-set cranes.

Basically, however, the control platform can also be provided on a conventional rotating tower crane or another type of crane, wherein the control platform does not have to be movably mounted on the tower, but can also be mounted in another way with a height-adjustable fit.

The control and/or people carrying platform is usually in the form of a car or is designed as a lift operator car and/or an elevator car, wherein such a lift operator car can advantageously be positioned at different working heights for different lifting tasks of the crane.

In order to ensure the safety of the height-adjustable control platform or elevator car, special installation measures need to be taken even if personnel, such as the crane operator, are transported during the height adjustment. On the one hand, two parallel lifting elements are provided in order to be able to achieve the necessary redundancy. On the other hand, however, the proper function of the lifting element and the suspension of the control platform are additionally monitored in order to be able to detect faults or even breaks in time.

By hinging the two lifting elements on the balancing rocker, the adjustment comfort can be increased, since the balancing rocker balances the lifting forces of the lifting elements, or a bumpy or not completely synchronized starting process can be balanced to some extent. The lifting element may be a sling suspending the balance arm and the control platform from above. In principle, however, it is also conceivable to use an adjusting actuator, for example in the form of a pressure medium cylinder, as a lifting element which can pull or push the balance rocker arm into a desired position.

In order to be able to detect functional faults such as cable slackening, cable breakage, cable elongation or erroneous winding on the drive cable drum, it has been proposed to monitor the angular position of the balance rocker by means of mechanical limit switches, which are actuated by the swivel arm of the balance rocker when the balance rocker reaches a predetermined pivot or pitch position. The balance rocker is normally pretensioned by one or more spring devices into a non-deflected neutral position, so that the balance rocker only tilts upwards or downwards and rotationally deflects it to the extent that the limit switch is activated if a greater unevenness of the forces exerted by the two lifting elements occurs. For example, the adjustment range of the balancing rocker will be larger and larger if one of the slings is wound significantly faster than the other, wherein the first limit switch can for example indicate a pre-critical state. If a slack cable is formed on the sling that retracts more slowly, or if one of the two slings breaks completely, so that only the other sling still carries the balance rocker and therefore the control platform, a maximum rotational deflection will occur, which can be indicated by another switch.

On the other hand, a "normal" overload situation of the elevator car should also be detected, for example if someone enters the car or platform too much, or someone carries too heavy equipment, so that the permitted load is exceeded or may only be approached. In this case, the limit switches, which indicate a strong inclination when the suspension cable breaks, do not respond to such an approaching overload, so that additional sensors must be installed in order to be able to detect such an overload situation.

Therefore, by skillfully arranging various mechanical limit switches, various critical states can be detected and displayed.

However, the safety and/or monitoring devices to date are relatively complex. If different critical states are to be distinguished, various mechanical limit switches are required, wherein the spring loading of the balancing rocker must be adjusted accordingly. On the other hand, even if the safety and/or monitoring devices are configured more complex, it has hitherto been difficult to monitor them with sufficient precision in order to be able to intervene in time in the control of the crane.

Disclosure of Invention

It is therefore an object of the present invention to provide an improved crane of the above-mentioned type, which avoids the disadvantages of the prior art and further develops the prior art in an advantageous manner. In particular, a sensitive monitoring of the height-adjustable control and/or the suspension and operation of the people platform should be achieved in a simple manner, which can distinguish between different critical states in order not only to be able to shut down urgently, but also to take precautionary measures by the control device of the crane, for example to prevent the drive from being started or from being notified of maintenance.

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

It is therefore proposed to integrate the monitoring of the control platform suspension into a pivot shaft which mounts the balance rocker in a luffing manner on a rocker bearing part connected to the control platform. The pivot shaft is used here, on the one hand, for the pivotable mounting of the balancing rocker and at the same time for the detection of the load state of the rocker bearing, so that the pivot shaft fulfills a dual function. According to the invention, the pivot shaft is designed as a measuring shaft for detecting the load state of a tiltable bearing (lagerig) of the compensating rocker arm and for providing a load signal to a monitoring and/or safety device. The measuring shaft can be configured in particular as a force measuring bolt which pivotably connects the balance rocker to the rocker bearing head and at least detects a transverse force transverse to the pivot axis.

Since the pivot axis is not a normal axle bolt but is used as a measuring bolt or measuring axle, the suspension of the control platform can be constructed more compactly and requires fewer components. At the same time, the forces acting between the balance rocker and the rocker bearing head can be detected sensitively.

In order to be able to distinguish a normal overload situation (e.g. too many people in the car) from mechanical irregularities on the lifting element and the balance rocker (e.g. cable breaks or false windings) with such a simple measuring shaft, in a modified example of the invention the balance rocker and/or the rocker bearing head and/or the measuring shaft may be assigned a lever mechanism which converts tilting movements of the balance rocker and/or the rocker bearing head which exceed a predetermined amount into a perceptible or detectable change in the load acting on the measuring shaft or in the bearing force acting on the measuring shaft. In particular, the lever arrangement can be designed to convert a holding and/or braking torque, which occurs or is required for preventing and/or braking a relative rotation of the balancing rocker arm with respect to the rocker arm bearing head, into a bearing force acting on the measuring shaft. For example, if one of the slings or lifting elements breaks, the balance rocker will rotate itself until the holding force exerted by the remaining lifting elements passes perpendicularly through the measuring shaft. However, if this rotation is braked or prevented beforehand, the holding or braking torque required for this purpose can be converted by the lever mechanism into a force which significantly changes the load acting on the measuring shaft.

The lever mechanism may in particular comprise a pivot limiter (schwenkbergendenzer) which allows a specific pivoting to occur between the balance rocker arm and the rocker bearing head during normal operation, but limits and/or brakes this pivoting when a specific pivoting angle is reached, in order to generate and convert the holding and/or braking torque into a change in the measured shaft load.

In an advantageous development of the invention, pivot stops can be provided on the balance rocker arm and the rocker bearing head, which limit the possible pivoting movement of the balance rocker arm relative to the rocker bearing head. In particular, the pivot stops on the balance rocker arm and the rocker bearing head may be arranged such that the pivot stops disengage at an undeflected intermediate position of the balance rocker arm and engage and prevent further rotational movement beyond that position only when the balance rocker arm reaches a predetermined rotational position relative to the rocker bearing head.

When the pivot stops are engaged, a greater change in the load state on the measuring shaft can be produced by such pivot stops, since their leverage changes the load state on the measuring shaft.

In particular, by means of such a pivot stop and the resulting change in the load on the measuring shaft, it is possible to determine which lifting element is malfunctioning or blocked, or in general what the malfunction is of, which can be used in conjunction with the pivot stop even if the measuring shaft is not configured for detecting the load direction (for example, if the measuring shaft is not non-rotatable). Due to the known geometry of the pivot stop and the articulation of the lifting element and the geometry of the balance rocker, a change in the suspension arrangement can be inferred from a change in the measured axle load state.

In an advantageous development of the invention, the rotation stop can be arranged on a partial circle (Teilkreis) around the measuring shaft, in particular directly adjacent to the outer circumference of the measuring shaft, so that a relatively short lever arm with respect to the pivot axis results in a greater change in the load state when forces are transmitted via the pivot stop.

Advantageously, the pivot stop can be arranged on a partial circle around the measuring shaft, the diameter of which partial circle is less than 300% or also less than 200% or less than 150% of the outer diameter of the measuring shaft.

In an advantageous refinement of the invention, the pivot stop can be arranged in a horizontal plane which extends transversely to the effective axis of the lifting element. In particular, the pivot stop may be arranged in the range of about 2 to 5 o 'clock or in the range of about 8 to 10 o' clock, seen in the direction of the pivot axis.

The pivot stop may be arranged such that the force transmitted by the pivot stop when the pivot stop is engaged extends substantially in the direction of the driving force of the lifting element and/or the weight of the control platform.

In order to be able to distinguish between the various critical states, in a development of the invention an evaluation device for evaluating the measuring signal of the measuring shaft can be provided, which evaluation device is configured to determine the various critical states of the suspension device of the control and/or people carrying platform from the level and/or the variation of the measuring signal of the measuring shaft. In particular, the evaluation device can be configured to compare the measurement signals of the measuring shaft with different threshold values in order to determine the loading state depending on the exceeding or the failing threshold value.

For example, the evaluation device can use a first threshold value which lies within the permissible load range of the control and/or people carrier or characterizes the load on the measuring shaft, below which a normal operating state can be concluded, and above which a "normal" exceeding of the permissible load can be concluded. In other words, the first threshold value may be characteristic of an operating state in which a transition between a still tolerable load and an excessively high load has taken place, but in which an abnormal rotation of the balance rocker arm with respect to the rocker bearing head has not yet taken place.

Alternatively or additionally, the evaluation device may compare the measuring shaft signal with a second threshold value which characterizes the load on the measuring shaft which occurs only upon abnormal rotation of the balance rocker arm relative to the rocker bearing head, in particular due to said pivot limiter which limits the pivoting movement of the balance rocker arm relative to the rocker bearing head and due to the weight (including the load) of the control and/or people carrying platform increasing the load capacity of the suspension device.

In a modified example of the invention, the second threshold value may be greater than 20% or more than 40% of the load on the measuring shaft which occurs at the maximum permissible load of the control and/or people carrying platform when the balance rocker is not deflected or is deflected only slightly or in normal operating conditions of the lifting element. Due to the presence of such a damping window between the maximum normal load and the excessively high load on the measuring shaft due to excessive deflection of the balance rocker (as occurs in the case of a cable break or a false winding), the evaluation device can reliably distinguish between a normal overload due to too many persons and a damage of the suspension device without the need for further sensors outside the measuring shaft.

The evaluation device may be designed electronically, for example comprising a switching element integrated in the measuring shaft sensor system. Alternatively or additionally, the evaluation device can also be part of an electronic control device, which can comprise, for example, a processor and a memory, in which the threshold value can be stored. For example, the evaluation device may be part of an electronic crane control device.

In principle, the measuring shaft can be configured differently in order to detect the magnitude and/or direction of the transverse forces acting on the measuring shaft. For example, the measuring shaft can be assigned a detection device for detecting an elastic deformation of the measuring shaft. For example, one or more strain gauges may be mounted on the measuring shaft to detect deformation of the measuring bolt.

Alternatively or additionally, the measuring shaft can be provided with a surface coating which exhibits a change in electrical resistance when the measuring bolt is deformed. Such a surface coating can be configured, for example, in the form of a thin-film coating or in the form of a thin-film sensor.

Alternatively or additionally, the measuring shaft can be assigned a magnetic field-based sensor system in order to detect deformations and/or forces or stresses acting in the measuring bolt. For example, the measuring shaft may be used as an iron core of a transformer circuit, and thus the strain of the measuring shaft may affect the magnetic properties and thus the voltage over the secondary coil.

The measuring shaft can be fastened in a rotationally fixed manner on a rocker bearing head, wherein the balancing rocker can be held on the measuring shaft in a rotatable manner relative to the measuring shaft. Alternatively, the measuring shaft can also be fastened to the balance rocker in a rotationally fixed manner, so that it follows the pivoting movement of the balance rocker and rotates relative to the rocker bearing head.

By specifying a predetermined rotational position of the measuring shaft, it is possible to determine the direction of the force acting on the measuring shaft and/or to determine on which section of the measuring shaft the transverse force acts at least predominantly. From the information on which section the transverse force acts on, the relative rotational or rocking position of the balance rocker arm with respect to the rocker arm bearing head can be determined. From the stated rotational position of the balanced rocker arm and the rocker bearing head relative to one another, a load situation can be inferred, in particular the position of the imbalance of the two lifting elements, for example as a result of asynchronous adjustment.

In principle, however, it is not necessary to fix the measuring shaft in a rotationally fixed manner, for example if only the absolute amount of force transmitted by the measuring shaft between the balance rocker and the rocker bearing head is detected or monitored, for example to achieve overload protection. Such overload protection may be triggered or intervened, for example, if too many people enter the control platform or a guide of the crane operator car is jammed.

In an advantageous refinement of the invention, the rocker bearing head can be rigidly connected to the control platform. Advantageously, the rocker bearing head may be fastened directly to the frame of the control platform. In principle, however, it is also possible to hinge the rocker bearing head indirectly on the control platform, for example by means of a link device which holds the rocker bearing head on the control platform.

In a modified example of the invention, the lifting element is in the form of a flexible loose traction element, in particular a sling. Zippers or straps are also contemplated.

Alternatively, the lifting element can also be configured in the form of an actuator, for example a hydraulic cylinder, wherein in this case the balance rocker can also be pressurized, for example in the sense of an upward pressure.

Drawings

The invention is explained in more detail below with reference to preferred exemplary embodiments and the associated figures.

Fig. 1 shows a schematic side view of a fast-erecting crane configured as a rotary tower crane, with a crane operator car mounted on the tower of the crane in a height-adjustable manner, according to an advantageous embodiment of the invention.

Figure 2 shows a perspective view of the jack operator car of figure 1 and its suspension device.

Figure 3 shows a perspective view of the suspension arrangement of the hoist operator car of figure 2 showing a balance rocker arm with two suspension ropes hinged thereto and a measuring shaft by means of which the balance rocker arm is pivotably hinged on a rocker bearing head of the suspension arrangement.

Fig. 4 shows a top view of the balance rocker and the measuring shaft of the suspension of the above figures, with the balance rocker in an undeflected intermediate position with the pivot stops disengaged.

Fig. 5 shows a top view of the balance rocker and the measuring shaft similar to fig. 4, wherein the balance rocker is shown in a position that has been rotated due to a broken or slack one of the slings, in which position the pivot stop has been engaged.

Detailed Description

As shown in fig. 1, the crane 1 may be configured as a rotary tower crane and has a tower 2 which in operation is upright and carries a cantilever boom 3. The tower 2 can be located with its lower end on a rotary platform 4 which can be rotated about a vertical axis and supported on a chassis 5, which chassis 5 can be constructed as a lorry or can be moved in other ways, but can also form a rigid and immovable support base if desired.

A trolley 7, which is movable to and fro by means of a trolley cable 8, can be mounted on the boom 3 in a longitudinally movable manner. The sling 6 with the load hook can be run on a trolley 7.

The crane 1 comprises a control and/or people carrying platform 9 configured as a crane operator or elevator car 10. The control and/or people platform 9 is mounted in such a way that it can be adjusted in height. In particular, the crane operator or the elevator car 10 can be mounted on the tower 2 in a longitudinally movable manner, for example by means of a car chassis guided on a tower profile (for example, its longitudinal chord).

As shown in fig. 2 to 5, the control and/or people carrying platform 9 can be held and brought to different height positions by means of a suspension device 11 which can be engaged with a machine frame (chasis), in particular with the upper side of a crane operator or an elevator car 10. The car 10 can be moved up and down outside the tower 2, for example, by means of roller guides or rail guides along the tower. However, the car can also be arranged inside the tower profile if necessary, for example when it is used only as a lift aid for reaching the boom or as a control platform arranged at the top and the volume of the tower profile is sufficiently large.

The suspension device 11 may in particular comprise a balance rocker 12, to which balance rocker 12 two lifting elements 13 in the form of slings may be articulated, which lifting elements can be raised and lowered by means of a suitable lifting mechanism drive. For example, two cable drums can be provided which can wind and unwind the two slings.

Said balance rocker 12 is pivotally mounted by means of a pivot shaft 14, which extends horizontally and engages a central portion of the balance rocker 12, on a rocker bearing head 15, which can be rigidly connected to the control platform 9, in particular fastened to the frame of the car 10.

As shown in fig. 3, the rocker arm bearing head 15 may, for example, form a bearing yoke between the legs of which the bearing part of the balance rocker arm 12 is inserted, wherein the legs of the rocker arm bearing head 15 and the bearing part of the balance rocker arm 12 may have aligned pivot bearing bores through which the pivot shaft 14 extends. In principle, however, it is also possible to arrange in the opposite way, for example to provide two yoke legs on the bearing portion of the balance rocker arm 12, between which the rocker bearing head 15 extends. Other configurations are possible, such as a cantilevered pivot bearing connection.

The pivot axis 14 is designed as a measuring shaft 16 in order to be able to detect transverse forces acting on the pivot axis 14. The measuring shaft 16 can be designed as a force bolt, wherein a suitable sensor system is provided on the measuring shaft 16, which sensor system can detect the load forces and loads acting on the bolt. As mentioned above, the sensor system 17 may for example comprise a strain gauge on the measuring shaft or a thin film coating applied thereto, in order to be able to measure the amount of deformation and thus the load.

As shown by a comparison of fig. 4 and 5, the measuring shaft 16 can be held on the rocker bearing head 15 in a rotationally fixed manner, so that it does not participate in the rotary movement of the balance rocker arm 12. Alternatively, the measuring shaft 16 may also be mounted in a manner so as to be rotatable relative to the rocker bearing head 15 and/or the balance rocker arm 12, so that it is not in a predetermined rotational position.

Advantageously, the pivotability of the balance rocker arm 12 relative to the rocker bearing head 15 may be limited by pivot stops 18, which may be provided on the balance rocker arm 12 and the rocker bearing head 15. In particular, said pivot stop 18 may be arranged around the pivot shaft 14 near the outer circumference of the pivot shaft 14, i.e. in particular around a bearing hole through which the pivot shaft 14 extends.

For example, the pivot stops 18 may be formed by protrusions formed on the balance rocker arm 12 and the rocker bearing head 15 so that they collide with each other when the balance rocker arm 12 pivots relative to the rocker bearing head 15.

As fig. 4 and 5 show, in the undeflected intermediate position of the compensating rocker arm 12 shown in fig. 4, the pivot stops 18 can be disengaged from one another in this case, so that the compensating rocker arm 12 can be rotated out of this intermediate position without hindrance. On the other hand, the pivot stop 18 engages when the balance rocker has performed a predetermined pivotal movement, for example, pivoting through an angle of approximately +/-10 ° to +/-20 °.

As shown in fig. 5, if the pivot stops 18 engage each other, for example, due to one of the lifting elements 13 breaking or unwinding too much, the load situation on the measuring shaft 16 changes significantly. The eccentrically arranged pivot stop 18 and the forces transmitted thereby exert additional forces on the pivot shaft 14 which have to compensate for the lever situation. Once the pivot stop 18 is engaged, the load, in particular the lateral forces and/or bending moments, detected on the measuring shaft 16 undergo significant changes. This change can in principle be a load reduction (endlastung) or an additional load that can be detected on the measuring shaft.

Advantageously, the pivot stop 18 is configured such that an engagement force is generated on the engaged stop surface, which is eccentric with respect to the pivot axis 14 and/or has a lever arm in order to generate a reaction force on the measuring shaft. In particular, when the pivot stop is engaged, the resulting engagement force may act eccentrically on the measuring shaft.

As shown in fig. 4 and 5, the pivot stops 18 may include two pairs of pivot stops 18 disposed on opposite sides of the measurement shaft 16, preferably substantially (at least approximately) in a plane extending horizontally through the pivot shaft 14. For example, the pivot stopper 18 may extend in a range of 2 to 4 o 'clock or 8 to 10 o' clock when the pivot shaft 14 is viewed in its axial direction.

Here, the pivot stops 18 are advantageously arranged such that, depending on the tilting movement of the balance rocker, only one pair of stops engages on one side of the pivot axle 14.

The pivot stop 18 forms a lever mechanism which converts the torque or holding moment occurring when limiting the pivoting movement of the balance rocker 12 into a significant change in the load on the measuring shaft 16. In particular, the lever mechanism formed by the pivoting stop 18 can multiply the load introduced into the suspension by the car, so that the load on the measuring shaft 16 is increased considerably, in particular more than would be the case if the permissible load were only slightly exceeded (for example if there were an additional person entering the cabin).

If, as shown in fig. 5, the pair of pivot stops engages upon a corresponding further rotation of the balancing rocker, there may be a lever arm of the measuring shaft or of the car load passing through the measuring shaft relative to the pair of engaged pivot stops on the one hand and of the cable 13 still supported relative to the pair of pivot stops 18 on the other hand, wherein said lever arm may correspond substantially to the horizontal distance between the centre of the measuring shaft and the point of engagement of the pivot stops or between the line of action of the cable tension and the point of engagement of the pivot stops 18, respectively.

Since the cable force still in the supporting cable 13 corresponds to the load of the car plus the load and the attachment, there can be a vertical force balance so that the load variations occurring on the measuring shaft can be controlled by the length of the lever arm.

For example, the length of the lever arm can be formed by suitably designing the geometry of the balance rocker arm and the rocker arm bearing head, in particular by suitably designing the arrangement of the pivot point of the lifting element 13 and the pivot stop 18 on the balance rocker arm, such that the load generated on the measuring shaft 16 and thus measured increases by more than 50% when the pivot stop 18 is engaged by a corresponding rotation of the balance rocker arm 12. For example, if the weight of the car 10, together with the maximum allowed load, is 1000kg, the lever arm may be arranged such that a 1500kg load is generated on the measuring shaft 16 when the pivot stop 18 is engaged. In this respect it is easy to distinguish between a normal overload and a broken or wrong winding of the cable, for example if a first threshold value of 1050 kg has been exceeded and a second threshold value of, for example, 1400kg has not been exceeded, so that a normal overload can be concluded, while the suspension device can still function properly, and if said second threshold value of, for example, 1400kg is exceeded, a broken or wrong winding of the cable can be concluded. The values are to be understood as examples only.

The sensor system 17 assigned to the measuring shaft 16 emits a load signal which characterizes the load on the measuring shaft 16, in particular indicates the magnitude and/or direction of the transverse forces occurring there.

Said load signal of the sensor system 17 can be evaluated by a control device 20 of the crane 1, which control device 20 is of electronic design and can comprise, for example, a microprocessor which can process a control program stored in a memory.

The control device 20 may comprise an evaluation device 19 which evaluates the measurement signal of the measurement shaft 16 in the manner described, in particular compares it with two threshold values which, on the one hand, characterize a normal transition from a normal, permissible load to overload and, on the other hand, characterize the engagement of the pivot stop 18 and thus the associated load change on the measurement shaft.

In this case, if the load signal of the sensor system 17 indicates the presence of an abnormal load situation (for example, an excessive transverse force on the measuring shaft), the control device 20 can, on the one hand, issue a warning signal and/or shut down at least one drive of the crane, in particular a lifting mechanism drive for controlling the height adjustment of the platform 9.

Alternatively or additionally, however, the control device 20 can also intervene, if appropriate, preventively in the drive of the drive. If the sensor system 17 determines that, for example, the balance rocker is too large at an incline, the control device 20 can attempt to readjust the hoist drive unwinding the sling too loosely or too tightly.

Alternatively or additionally, the control device 20 may also issue a preventive maintenance signal if the load signal of the sensor system 17 has not indicated a critical state, but has shown a significant change from the original load spectrum in the new state.