Lifting device, in particular a mobile crane or a cable-operated excavator, having an apparatus for monitoring the raising and lowering procedures of a boom system and corresponding method

1. A lifting device ( 1 ), having an apparatus for monitoring raising and lowering procedures of a boom system of the lifting device ( 1 ), the apparatus comprising

a device for detecting loads increasing an overturning moment of the lifting device ( 1 );

a device for detecting loads stabilizing or reducing the overturning moment of the lifting device ( 1 );

a control unit configured to calculate a limit holding force (FGrenz) for a holding line of the boom system of the lifting device ( 1 ) from the detected loads; and

a device for detecting actual holding force of the holding line,

wherein the control unit is configured to compare the limit holding force (FGrenz) and the actual holding force.

2. A lifting device ( 1 ) in accordance with claim 1 , wherein the control unit is configured to output at least one signal in dependence on the comparison between the limit holding force (FGrenz) and the actual holding force.

3. A lifting device ( 1 ) at least in accordance with claim 2 , wherein the at least one signal is a representation of the current utilization with respect to permitted utilization for a machine operator on a monitor of the lifting device and/or for stopping a movement of the lifting device ( 1 ).

4. A lifting device ( 1 ) in accordance with claim 1 , wherein the device for detecting the loads increasing the overturning moment, detects the weight of the boom system and the wind force on a boom system of the lifting device ( 1 ).

5. A lifting device ( 1 ) in accordance with claim 1 , wherein the device for detecting the loads stabilizing or reducing the overturning moment, detects the weight of a carrier unit of the lifting device.

6. A lifting device ( 1 ) in accordance with claim 1 , wherein a sensor system for detecting the current geometry of the lifting device ( 1 ) is provided; and the control unit is a control computer of the lifting device ( 1 ) or an external computer.

7. A lifting device ( 1 ) in accordance with claim 1 , wherein the device for detecting the actual holding force of the holding line, comprises at least one force measurement tab and/or at least one force measurement axis.

8. A lifting device ( 1 ) in accordance with claim 1 , wherein the control unit is configured to calculate the loads increasing the overturning moment simultaneously for a wide range of positions of the boom system in addition to current position of the boom system.

9. A lifting device ( 1 ) in accordance with claim 1 , wherein the control unit is configured not to stop a movement or a direction of movement of the lifting device ( 1 ) as long as the limit holding force (FGrenz) is not exceeded or to selectively release the movement or the direction of movement again after a stop due to an exceeding of the limit load, when maximum permitted load at a lifting hook hook increases with the direction of movement.

10. A lifting device ( 1 ) in accordance with claim 1 , which is a mobile crane or a cable-operated excavator.

11. A method of monitoring the raising and lowering procedures of a boom system of a lifting device ( 1 ), comprising the steps of:

detecting loads increasing overturning moment of the lifting device ( 1 );

detecting the loads stabilizing or reducing the overturning moment of the lifting device ( 1 );

calculating a limit holding force (FGrenz) for a holding line of a main boom ( 2 ) of the lifting device ( 1 ) from the detected loads, by a control unit;

detecting actual holding force of the holding line; and

comparing the limit holding force (FGrenz) and the actual holding force by the control unit.

12. A method in accordance with claim 11 , wherein the lifting device ( 1 ) is a mobile crane or a cable-operated excavator.