LIFTING DEVICE AND METHOD FOR STARTING UP THE HOISTING GEAR OF SUCH A LIFTING DEVICE

Abstract

The present invention relates to a lifting device for example in the form of a crane such as a tower crane, with a hoisting gear comprising a hoisting cable which runs off from a drum that can be driven by a hoisting gear drive, and a hoisting gear brake for holding the hoisting cable in a braked position. The invention furthermore relates to a method for starting up the hoisting gear of such a lifting device from the braked position in which the hoisting gear brake holds a hoisting load, wherein a starting torque is built up by a hoisting gear drive against the closed hoisting gear brake, and the hoisting gear brake is released upon or after reaching the starting torque. According to the invention it is proposed that when the hoisting gear brake is closed, the current hoisting load is detected by means of a load detection device and the starting torque is adjusted by the hoisting gear controller with reference to the detected current hoisting load such that the hoisting force provided by the starting torque of the hoisting gear corresponds to the detected, current hoisting load.

Claims

1. A method for starting up a hoisting gear (8) from a braked position in which a hoisting gear brake (9) holds a hoisting load, in which a starting torque is built up by a hoisting gear drive (10) against the closed hoisting gear brake (9) and the hoisting gear brake (9) is released upon or after reaching the starting torque, characterized in that the current hoisting load is detected by means of a load detection device (11) when the hoisting gear brake (9) is closed, and the starting torque is adjusted by a hoisting gear controller (12) with reference to the detected current hoisting load such that the hoisting force provided by the starting torque of the hoisting gear (8) corresponds to the detected current hoisting load.

2. The method according to claim 1, wherein as current hoisting load the sum of attached net load weight, load hook weight and cable weight of the unwound hoisting cable length pulling on the hoisting gear (8) is detected.

3. The method according to claim 1, wherein the current hoisting load is detected by means of a force measurement axis (13) reeved into the hoisting cable (6), with which a load detector (14) of the load detection device (11) is associated.

4. The method according to claim 1, wherein the starting torque is calculated as a fraction of the nominal motor torque of the hoisting gear drive (10) and from the calculated fraction of the nominal motor torque a starting value for a frequency converter (15) actuating the hoisting gear drive (10) is calculated.

5. The method according to claim 1, wherein the starting torque is built up by initializing a speed sensor (16) against the still closed hoisting gear brake (9).

6. The method according to claim 1, wherein the starting torque is variably adjusted in dependence on the detected unwound hoisting cable length and/or an accompanying number of winding layers of the hoisting cable (6) on the hoisting gear drum (17).

7. A lifting device, in particular a crane such as a tower crane or telescopic crane, with a hoisting gear (8) comprising a hoisting cable (6) which runs off from a hoisting gear drum (17) that can be driven by a hoisting gear drive (10), a hoisting gear brake (9) and a hoisting gear controller (12) for actuating the hoisting gear drive (10), wherein the hoisting gear controller (12) includes a start-up control stage (18) for starting up the hoisting gear (8) from a braked position, which is equipped to build up a starting torque at the hoisting gear drive (10) when the hoisting gear brake (9) is still closed, characterized in that a load detection device (11) is provided for detecting a current hoisting load acting when the hoisting gear brake is closed, and said start-up control stage (18) includes a starting torque adjusting device (19) for variably adjusting the starting torque in dependence on the detected current hoisting load such that the hoisting force provided by the starting torque of the hoisting gear (10) corresponds to the detected current hoisting load.

8. The lifting device according to claim 7, wherein the load detection device (11) includes a force measurement axis (14) reeved into the hoisting cable (6), with which a load detector (14) is associated.

9. The lifting device according to claim 8, wherein the reeved force measurement axis (13) comprises a cable deflection pulley (20) whose articulation point is shiftably mounted and is monitored by the load detector (14).

10. The lifting device according to claim 7, wherein the hoisting gear controller (12) includes a frequency converter (15) for actuating the hoisting gear drive (10), wherein the starting torque adjusting device (19) of the start-up control stage (18) is equipped to calculate the starting torque as a fraction of the nominal motor torque of the hoisting gear drive (10) and to calculate a a starting value for the frequency converter (15) from the calculated fraction of the nominal motor torque.

11. The lifting device according to claim 7, wherein the starting torque adjusting device (19) of the actuating control stage (18) includes a lever arm determination device for determining the lever arm of the hoisting cable (6) with respect to the hoisting gear drum (17) and is equipped to determine the starting torque in dependence on the current, determined lever arm, wherein preferably the lever arm determination device calculates the lever arm from the unwound hoisting cable length and/or the detected number of winding layers on the hoisting gear drum (17).

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0014] The present invention will subsequently be explained in detail with reference to a preferred exemplary embodiment and associated drawings, in which:

[0015] FIG. 1: shows a schematic representation of a lifting device in the form of a tower crane whose hoisting gear comprises a hoisting cable guided over a trolley, and

[0016] FIG. 2: shows a schematic representation of the hoisting gear of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0017] As shown in FIG. 1, the lifting device 1 can be configured as a crane such as a tower crane and comprise a tower 2 which carries a boom 3 rotatable about an upright tower axis 4, from which a load hook 7 can be lowered and lifted. Said load hook 7 or a corresponding load harness is articulated to a hoisting cable 6 of a hoisting gear 8, wherein the hoisting cable 6 with the load hook 7 articulated thereto can be guided over a trolley 5 which is traversable along the boom 3.

[0018] As shown in FIG. 2, the hoisting gear 8 comprises a hoisting gear drum 17 around which the hoisting cable 6 is wound in order to be let down and hauled. Said hoisting gear drum 17 can be driven rotatorily by a hoisting gear drive 10 which can be configured to operate electrically, for instance can comprise an electric motor which rotatorily drives the hoisting gear drum 17 via a possibly interposed transmission.

[0019] Said hoisting gear drive 10 advantageously can be actuated by a hoisting gear controller 12 via a frequency converter 15, in particular in order to control or regulate the speed and the torque of the hoisting gear drive 10.

[0020] Furthermore, the hoisting gear 8 comprises a hoisting gear brake 9 by means of which a hoisting load picked up on the load hook 7 can be held. Said hoisting gear brake 9 advantageously can engage the hoisting gear drum 17 or a transmission element connected therewith or can engage the hoisting gear drive 10 itself, wherein the hoisting gear brake 9 can be configured as a friction brake and/or as a locking brake. When the hoisting gear brake 9 is closed, the hoisting gear drum 17 is blocked and hence the load picked up is held stationary.

[0021] To achieve a smooth, jerk-free start-up on release of the hoisting gear brake 9, the hoisting gear controller 12 comprises a start-up control stage 18 which is intended to provide or build up a starting torque at the hoisting gear drive 10 when the hoisting gear brake 9 still is closed, which starting torque then intercepts the hoisting load on release of the hoisting gear brake 9 and at best exactly compensates the same.

[0022] To achieve the smooth, jerk-free start-up independent of the size of the load picked up and the load condition, in particular the hook height in each case, said starting torque is variably and individually adapted to the respective hoisting load condition. For this purpose, a load detection device 11 is provided, by means of which the hoisting load acting on the cable drum 17 when the hoisting gear brake 9 is closed is detected, namely advantageously including the net load attached to the load hook 7, the weight force of the load hook 7 itself, and the weight fraction of the unwound hoisting cable 6, which likewise tugs at the hoisting gear drum 17 and depends on the unwound hoisting cable length or the lowering depth of the load hook 7.

[0023] Said load detection device 11 advantageously comprises a force measurement axis 13 which is reeved into the hoisting cable 6, wherein said force measurement axis 13 can comprise a deflection pulley 20 whose articulation point can be shiftable in the direction of the reeving or the hoisting cable drum running off and can be connected or be operatively connected with a load detector 14. For example, said deflection pulley 20 can be shiftable under spring pretension so that the shifting path is a measure for the hoisting load and the load detector 14 can be a path detector. Alternatively or in addition, however, a direct force meter an also be provided at the force measurement axis 13.

[0024] Said force measurement axis 13 advantageously is associated with a portion of the unwinding path of the hoisting cable 6, which is located closer to the hoisting gear drum 17 than the cable portions running off and pulling on the hoisting gear drum 17 with their weight force, so that the weight force of the cable portions pulling on the hoisting gear drum 17 is included in the force measurement.

[0025] As shown in FIG. 2, the load detection device 11 is connected to the hoisting gear controller 12 which calculates the required starting torque from the currently detected hoisting load value in order to exactly balance out the respective hoisting load. As far as a plurality of layers can be wound on the hoisting gear drum 17 it is conceivable that for the calculation of the required starting torque the currently applicable lever arm of the hoisting cable 6 with respect to the hoisting gear drum 17 is taken into account, namely in particular in the form of the number of winding layers from which the hoisting cable runs off when the brake is to be released.

[0026] The starting torque advantageously is calculated exactly such that from the starting torque via the hoisting gear drum 17 a hoisting force can be induced into the hoisting cable 6, which hoisting force corresponds to the oppositely directed force F of the hoisting load.

[0027] In particular, said start-up control stage 18 of the hoisting gear controller 12 can include a starting torque adjusting device 19 which calculates the required starting torque in the form of a percentage of the nominal motor torque of the hoisting gear drive 10 and from this percentage of the nominal motor torque determines a starting value for the frequency converter 15 so that the frequency converter actuates the hoisting gear drive 10 such that the same builds up the desired starting torque against the closed hoisting gear brake 9. For this purpose, the speed regulator can be pre-initialized for the transmitted torque value so that the torque is still built up against the closed brake. When the starting torque built up is equal to the torque caused by the hoisting load, the brake is opened so that both torques even out and no undesired load hook movement occurs.