EP2226287B1 - Method and assembly for influencing the grab fill for two motor gripper hoisting gears - Google Patents

Description

The invention relates to a method for influencing the Greiferfüllvolumens in hoists with Zweimotorengreiferhubwerken (locking and holding work), a corresponding system for data processing for performing the method and a corresponding computer program or a storage medium on which such a program is stored.

In the case of lifting equipment for bulk material, it is important for economically optimal operation that the filling volume of the gripper always corresponds to the maximum filling weight, ie avoiding both underloading and overloading. The factors influencing the degree of filling are, for example, the density of the bulk material and friction-dependent factors (adhesion, cohesion, roughness of the bulk material). The density of the bulk material, even with bulk material of the same kind, for example, is significantly influenced by the granularity or the water content. Tolerances of the bulk density, which lead to a mismatch of the gripper, let the turnover rate decrease by exceeding the allowable load torque and related interruption of the handling process. The reduction or avoidance of these interruptions not only has an impact on the handling capacity, but also on the service life of the crane system. Therefore, various measures have been taken in the past to adapt the gripper to the respective bulk material.

The simplest measure is to adapt the gripper to the respective bulk material by changing the gripper shells, for example in DE 79 10 944 U1 a special gripper has been proposed. The change, however, requires a lot of effort by additional working time, possibly an additional worker and the storage of several grippers. If only a short-term change in the bulk density is foreseeable, you will completely waive a change and take for the resulting under-utilization of the gripper operation in purchasing. Economic constraints limit the variety of variants of the gripper because of the high investment costs, so that the bulk density matched gripper meet only to a certain extent the tolerances of the bulk materials occurring in practice. A compromise between the volume of the gripper and the density of the bulk material is therefore always necessary in practice so far.

To remedy this, measures have become known to make do with a single gripper, the receiving volume is variable. Thus, adjustable edge plates have been proposed on the gripper, which should possibly increase the volume.

Conversely, a reduced absorption of bulk material by limiting the opening angle of the gripper is possible. The opening width is limited by adjustable mechanical limit stops (spread limiters), which, among other things, has the disadvantage that the opening of the gripper is also limited during emptying. All mechanical solutions are also, apart from the amount of work involved in an adjustment, anyway disadvantageous due to the rapid wear occurring the necessary limiting means.

Desirable is a solution that provides a limitation of the filling amount of a designed for full load gripper alone by control measures.

To DE 20 41 393 A1 A solution has also become known in which the opening width of the gripper is to be influenced by the gripper opening time. With twin-engine overhead conveyors of modern design, the opening speed is steplessly regulated by the crane operator. Because of the variability of the speed specifications, there would then be different opening angles.

To DD 288 138 A5 already a method for preventing a gripper overload is known, in each of which the forces acting on the strikers and the tethers force measured and their difference is determined. If the difference exceeds a predetermined limit, the closing operation of the gripper is interrupted and the lifting process is initiated. After initiation of the lifting process, the closing process is then continued until the gripper is closed. so that the further bulk material intake is to be prevented when the differential force, which is a measure of the gripper load, has reached a maximum value. However, it has been shown in practice that the cable forces can not be reliably determined during a closing operation, since the bulk material moves in the gripper and act on the upward movement of the gripper shaking forces on this. The solution has therefore proved to be practically impracticable.

To increase the handling capacity or to fulfill projected handling volumes, the utilization of the permissible load capacity of cranes with consideration of load curves is increasingly important.

The object of the invention is to provide a method by means of which a handling process that reduces envelope load when using a gripper designed for full load alone can be reduced by control measures in order to ensure configured handling quantities, if necessary also for hoists with discharge-dependent load-bearing curves.

According to the invention, in a closing operation of the gripper for a crane operation with a reduced filling volume of the gripper set an adjustable limit of holding the gripper torque (holding), which is higher than the moment that would be necessary only for the taut holding the tethers.

So far, a moment is given during a closing operation of the gripper for the holding, which prevents slack of the tethers. For a crane operation, in which such a density of the bulk material is present that can be used with 100% filling volume, so the amount does not need to be reduced, this holding torque is still sufficient. On the other hand, if there is a higher density of the bulk material, should the amount of bulk material absorbed be reduced, a higher holding torque is given. This already occurs during the closing process of the gripper to increase the gripping curve in the bulk material, which in turn leads to a reduced bulk material intake.

The crane operator specifies a stored value for the respective bulk material for the holding torque and adapts the value if necessary with one or two gripper strokes. The force exerted by the weight of the gripper on the bulk material and in addition the force that allow by the grave curve of the gripper sinking of the gripper, lead for a defined bulk material to calculable filling volumes of the gripper.

Advantageously, the value for the holding torque during the closing operation of the gripper can be changed by the higher-level control. In this way, it is adapted to the lifting height independently of the operator and, on the other hand, it can be readjusted automatically depending on the current load torque.

Since a modified cable force of the holding mechanism counteracts when the lifting height is changed by the shortened or extended cable length, the corresponding filling quantity in the gripper can be increased or lowered unintentionally. In order to prevent this, the existing lifting height is detected by an existing displacement measuring system and compensated by adaptation of the associated rope length influence.

The same applies to the consideration of load curves. The higher-level controller adapts the value for the holding torque in accordance with the current load torque, so that a correspondingly lower value for the gripper filling volume is predetermined given a higher crane discharge and thus reduced carrying capacity of the crane.

Activation of the adapted limit occurs automatically on each gripper stroke after falling below an adjustable load comparator threshold of the weight of the gripper in conjunction with the initiation of the closing process.

With the end of the closing process or the initiation of a lifting movement, the specification of the holding torque is withdrawn and the usual function resumed.

A data processing system, a computer program or a computer-readable storage medium, which contains a program for carrying out the method, are each set up in such a way that they perform the following measure:

In a closing operation of the gripper for a crane operation with reduced filling volume of the gripper, an upper limit of the moment is set for the holding, which is higher than a previously determined moment, which would be necessary only for the taut holding of the tethers.

During the lifting or lowering movement during handling with dual-motor gripper hoists, the torque limits in controlled speed controllers should not be chosen differently due to the approximately equal load distribution.

The method has the advantage that the gripper no mechanical measures to limit or increase the capacity must be made. The filling quantity is set solely by a control technology intervention in the optimum height. Independently of the operator, the filling quantity is automatically adjusted depending on the lifting height and the load torque. In addition, the solution has the advantage that delicate ship floors or wagon floors are spared, since the gripping curve is already raised during closing and thus scrapes the gripper only with desired residual weight on the ground.

The invention will be explained in more detail below with reference to an embodiment. The accompanying drawing shows a block diagram of the control influence of the holding work of a Zweimotorengreiferhubwerkes.

The force of a holding work FH of a Zweimotorengreiferhubwerkes is detected by a load cell 1 and a closing mechanism FS by a load cell 2 in a load detection 3 and evaluated.

The activation of the moment influencing takes place in a data processing system 5 by a load comparator 5a when it falls below an adjustable load threshold as a function of the grab own weight, while the gripper is deposited on the bulk material.

By pre-selected in a unit for torque preselection 4 by the operator gripper capacity, by adapting the Seilgewichtseinflusses and Greiferschließwinkels in a unit for Hubhöhenerfassung 5c and by monitoring the allowable load torque of the hoist the required torque limit for the holding plant is determined in a multiplexer 5b.

The torque-forming torque is in a corresponding speed controller 6 for a holding motor 8 (three-phase motor or DC motor) during the closing process in a torque limiter 6a of the speed controller. 6 according to the invention reduced until the gripper is closed by a closing mechanism motor 10, which is controlled by a speed controller 7 or the lifting operation is initiated. During the unloading process, the actual gripper load is compared with the maximum possible gripper load in the load comparator 5a and optionally adjusted in the multiplexer 5b, the torque limit of the maximum handling capacity of the hoist.

The path detection for lifting height adaptation and subtraction (gripper closing angle) in the unit for lifting height detection 5c is realized by displacement sensors 9 and 11 and the associated evaluation software.

List of reference numbers used

1

Load cell

2

Load cell

3

load detection

4

Unit for torque preselection

5

Data processing system

5a

Lastkomparator

5b

multiplexer

5c

Unit for lifting height detection

6

Speed controller

6a

torque limiter

7

Speed controller

8th

engine

9

displacement sensor

10

engine

11

displacement sensor

FH

Force of the holding work

FS

Power of the locking mechanism

Claims (6)

1. A method for influencing the gripper filling volume of hoists having dual-motor gripper hoisting gears, characterized in that
   during a closing process of the gripper for a crane operation with lowered filling volume of the gripper, an adjustable threshold is set for the torque necessary for holding the gripper, wherein said threshold is higher than the torque necessary just for tightly holding the holding ropes, whereby during the closing process, a gripping curve of the gripper is raised and the filling volume of the gripper is lowered.
2. The method according to claim 1, characterized in that the value for the holding torque is adapted to the actual height by a superordinated control.
3. The method according to claim 1, characterized in that the value for the holding torque is adapted to the actual load torque by a superordinated control.
4. An arrangement for influencing the gripper filling volume of hoists having dual-motor gripper hoisting gears, the arrangement comprising a data processing system which is set up in such a manner that the following measure can be carried out:

   During a closing process of the gripper for a crane operation with lowered filling volume of the gripper, an upper threshold of the torque is predetermined for the holding gear, wherein said threshold is higher than a previously determined torque necessary just for tightly holding the holding ropes, whereby during the closing process, a gripper curve of the gripper is raised and the filling volume of the gripper is lowered.
5. A computer program for influencing the gripper filling volume of hoists having dual-motor gripper hoisting gears, wherein the computer program, after being loaded into the storage of a computer, enables said computer to carry out the following measures:

   During a closing process of the gripper for a crane operation with lowered filling volume of the gripper, an upper threshold of the torque is predetermined for the holding gear, wherein said threshold is higher than a previously determined torque necessary just for tightly holding the holding ropes, whereby during the closing process, a gripping curve of the gripper is raised and the filling volume of the gripper is lowered.
6. A computer-readable storage medium in which a program is stored which, after being stored in a computer, enables said computer to carry out the following measures for influencing the gripper filling volume of hoists having dual-motor gripper hoisting gears:

   During a closing process of the gripper for a crane operation with lowered filling volume of the gripper, an upper threshold of the torque is predetermined for the holding gear, wherein said threshold is higher than a previously determined torque necessary just for tightly holding the holding ropes, whereby during the closing process, a gripping curve of the gripper is raised and the filling volume of the gripper is lowered.

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