GB2353513A

GB2353513A - Crane lifting capacity optimisation

Info

Publication number: GB2353513A
Application number: GB0016455A
Authority: GB
Inventors: Peter Abel; Neithard Conradt; Helmut Spaeth
Original assignee: Liebherr Werk Ehingen GmbH
Current assignee: Liebherr Werk Ehingen GmbH
Priority date: 1999-07-07
Filing date: 2000-07-04
Publication date: 2001-02-28
Anticipated expiration: 2020-07-04
Also published as: FR2796060B1; DE19931303A1; FR2796060A1; GB2353513B; DE19931303C2; GB0016455D0

Abstract

The invention relates to a method for the performance of movements of a crane having at least two moving elements (1, 2, 3, 6, 7), with the at least two moving elements of the crane being moved in such a way that the crane is maintained in the region of optimum maximum loadability; and to an apparatus for the performance of movements of a crane having a first movement apparatus for a first moving element (1, 2, 3, 6, 7); a second movement apparatus for a second moving element (1, 2, 3, 6, 7); and a control apparatus with which the first and second movement apparatuses can be controlled in such a way that the crane is maintained in the region of optimum maximum loadability. Preferably, the crane has a main jib 1, a fly jib 2, a counter jib 3 and an adjustable counterweight 7. The crane may be provided with a rotary encoder(s) to detect the main and fly jib positions, a load sensor or other position sensors to determine the current luffing or inclination angles whereby the current jib and hence applicable load limits can be determined. Preferably the counterweight is continually moved to balance the continual movement of the main and fly jibs to adjust their position for maximum loading.

Description

2353513 Lifting Capacily Optimisation when making Crane Movements The

present invention relates to a method and an apparatus for the optimisation of lifting capacity when making crane movements. If a load slung on a crane having different individually adjustable jib elements such as a main jib, a jib extension and a derrick or counter jib (all termed jibs hereinafter) is to be brought into a different position, usually a movement type is selected by the crane operator to move the load. This can be done, for example, by the luffing angle of the jib extension being changed in order to thus transport the load in a horizontal and simultaneously vertical direction. The maximum permitted lifting capacity for the crane in the respective operation position will, as a rule, not remain constant, that is will increase or decrease during such an individual luffing movement of the jib extension. That is, the crane was either in a configuration with a higher permitted lifting capacity prior to the performance of the luffing movement or it is moved by this luffing movement from a less favourable position to a more favourable one at which it can take up a bigger load.

It is the object of the present invention to provide a method and an apparatus with which a crane can be employed in a larger load region.

This object is solved by a method in accordance with claim I and by an apparatus in accordance with claim 5. Advantageous embodiments result from the dependent claims.

In accordance with the invention, movements of a crane, during which a load can be slung on, are performed in such a way that the crane comprising at least two movable elements is roughly in the range of optimum loadability at all times. If, for example, a crane having a main jib and a jib extension is to be travelled with a slung load from a first position to a second position, this is not simply done by, for example, only luffing the jib extension. In accordance with the invention, in such a case, for example, the main jib and the jib extension are moved respectively so that the total arrangement of main jib and jib extension is roughly in the region of optimum lifting capacity. The case may occur, for example, where it is advantageous for reasons of optimum lifting capacity of the crane to first increase the luffing angle of the jib extension by a certain amount, whereupon subsequently the luffing angle of the main jib is increased and the luffing angle of the jib extension remains constant. The individual moving elements of a crane should therefore be moved so that for any element taking up a load that position or crane position is selected which roughly allows the optimum loadability or maximum lifting capacity of the crane as a whole.

In accordance with the invention, lifting capacity optimisation can be effected by, for example, the angles being deter-mined for the individual jibs of the crane at which a load can be lifted at a preset distance from the crane location with maximum lifting capacity. A maximum lifting capacity curve can be calculated which results from certain luffing angles of the individual crane jibs. With the method in accordance with the invention for the optimisation of lifting capacity when making crane movements, it is also possible to travel a preset load out as far as possible. The crane is here always moved in a safe operating status, i.e. below the respective limit load data. The individual crane jibs or their luffing angles are coordinated with one another in such a way that the crane is operated in the region of the most favourable lifting capacity curves.

For this purpose, it is advantageous to preset a limit value curve or limit data for the permitted load in at least one luffing position of the crane jib when adjusting a crane having at least one luffable jib, in particular under load. These data indicate which loads the crane can be exposed to at the certain luffing position. From this preset limit value curve for a certain luffing position of a crane jib, possible permitted load statuses or working load limit values for further luffing positions of the crane jib are calculated which state how large the loads can be for each individual luffing position for a continuously luffable crane jib. In this way, it is possible to luff a crane jib continuously also under load as the respective working load upper limits can be determined for every individual luffing status. With the method in accordance with the invention, the crane driver can move the load by free luffing of, for example, the main jib or the needle-type jib in the whole working radius. A simultaneous luffing of the main jib and needle-type jib is naturally also possible.

It is, for example, possible for the main jib and the jib extension to be moved under load from their respective steepest operation positions, e.g. main jib angle = 87% jib extension angle 77' to their respective most plane operating position, e.g. main jib angle = 67% jib extension angle = 10% with it being able to be determined in each case with the method in accordance with the invention how large the maximum permitted lifting capacity of the crane can be. It is not necessary here to switch over a crane status fixed at an overload cut-out so that, for example, a lifting capacity display and a load monitoring can be performed during the whole luffing procedure. New load limit values for the current main jib position can be calculated from the load limit values stored for different positions of the crane jib such as the main jib and from the current position of the main jib.

At least one limit value curve is advantageously provided for one jib position, with it naturally also being possible to store in memory a larger number of load limit values, in each case for a certain position of a crane jib such as the main jib. The load limit values for the respective positions can then be calculated using suitable calculation methods, for example by interpolation or extrapolation, for each status of the crane, i.e. any luffing angle of the main jib or the jib extension or counter-jib, from the data stored for one or more luffing positions of the crane jib.

At least one sensor is preferably disposed on the crane with which the current position or configuration of the crane can be determined. For this purpose, a rotary encoder can, for example, be provided on the main jib to detect the current main jib position. It is naturally also equally possible to provide a corresponding sensor for the jib extension. It is also possible to provide other sensors such as load sensors or position sensors with which the momentary position of the individual crane jib(s), in particular their luffing or inclination angles, can be determined.

The signals received from the sensor(s) serve to determine the current position of a crane jib for which the applicable load limit values should be determined.

The possible liffing capacities are preferably calculated for each operating position of the main jib so that load limit values can be determined for the crane for any position with a continuous luffing of the main jib. It is naturally also possible to use this method on the jib extension or on the jib extension and main jib together so that both can be luffed under load, with a load monitoring being performed at all times. This is equally possible for a counter-jib. In accordance with the invention, any crane jib, such as the main jib, can preferably be adjusted infinitely under load.

In accordance with the invention, an adjustable ballast element can be provided with which it can be ensured, particularly with a load slung on a crane jib, that the ballasting or the momentary position of the ballast corresponds to the current load status of the crane. If, for example, the main jib is luffed infinitely under load, ballasting exactly adjusted to the respective operating status can be performed by means of a corresponding infinite and simultaneous adjustment of the ballast element. By means of an infinite adjustment of the ballast element, it can be ensured that each luffing status of the crane jib(s) is matched by a coordinated or optimum counter ballasting. The ballast element here preferably has an adjustable distance to the lower luffing axle or the slewing platform of the main jib.

A counter-jib or derrick jib, on which a ballast element is slung, can, for example, be provided as the infinitely adjustable ballast element. To design the counter-ballasting infinitely, the derrick jib can be either infinitely luffed or, for example, telescoped out. If, for example, a crane having a main jib and possibly a jib extension should be moved under load from a steep operating position to a flatter operating position, then, for example, the derrick jib can also be moved from a steep to a flatter operating position for the coordinated counter- ballasting in order to increase the counter-load acting on the main jib or the slewing platform by means of the ballast element by increasing the lever arm.

It is also equally possible to provide the ballast element on a suspension load or ballast trolley, for example, with controllable wheels, with the ballast element preferably being able to be travelled out infinitely in a horizontal direction so that a coordinated ballasting for the current load status of the crane can be effected by a corresponding travelling or telescoping of the ballast element.

Here, it is advantageous to provide at least one sensor element to detect the current configuration of the crane. For this purpose, as already described above, rotary encoders can, for example, be provided on the respective crane jibs to detect the operating status. Equally, corresponding sensor elements can be disposed, for example, on the derrick jib or the ballast element which can determine the momentary position of the ballast element.

With the methods given above, it is advantageous to perform a load monitoring, it being monitored for each crane status and the currently lifted load that the crane is still in a safe operating range. As with the infinite adjustment of the individual crane jib(s) or the ballast element, the applicable load limit values are calculated at all times for every operating status, it is also possible to determine in each case during the luffing of the crane from a first position to a second position whether the currently occurring load is still in the permitted range or where the limits of the maximum permitted load of the crane are. As already stated above, this can be done by using load limit values or a limit value curve for a given fixed status of the crane, with a limit value curve or suitable load limit values being able to be determined for any configuration of the crane, i.e. any luffing angle of the individual crane jib(s), by means of a calculation method, e.g. interpolation or extrapolation.

It is of advantage to display the permitted maximum load calculated in each case, with the momentarily occurring load, which is measured for example by means of a load sensor, being equally advantageously shown. This allows a crane operator or a suitable control to judge how large the safety reserves of the crane still are.

Various operating modes for the optimisation of the crane position or for the maximisation of the permitted working load can be provided. For this purpose, for example, corresponding function buttons can be fitted to the crane monitor with which one of the following operating modes is set.

In accordance with an advantageous embodiment, it is preset by the crane operator, for example by means of a manual control lever movement, that the load should be luffed up. It is then automatically selected whether it is more advantageous with regard to the maximum lifting capacity to luff up, for example, the main jib or the jib extension. That luffing movement is performed which is related to the greatest increase or to the lowest reduction of the maximum load capacity of the crane as a whole. It may occur here that first the jib extension is luffed up to a certain position, with subsequent to this the jib extension position being maintained and the main jib being luffed up. In this process, the crane operator does not have to perform a separate control movement as this lifting capacity optimisation can be performed automatically.

The crane control can compute from the stored lifling capacity and from signals made available from suitable sensor elements to determine the current position or configuration or load situation of the crane which movement should be performed for the individual adjustable elements of the crane or crane jibs to always remain roughly in the region of the optimum lifting capacity of the crane.

It is naturally also possible for two or more moving elements of the crane to be moved simultaneously. It can, for example, be advantageous to luff up the main jib, with tile needle-type jib being simultaneously luffed down a little if a load is to be taken up or transported.

The counter-jib or derrick jib can preferably also be controlled during the performance of a crane movement so that it is travelled to a position suitable for an optimum lifting capacity. Here, the derrick jib can, for example during the luffing of the main jib or the needle-type jib or during the lifting or lowering of the load hook, be automatically luffed up or down in such a way that the maximum lifting capacity of the crane remains constant or is optimised. The derrick jib here can either be moved separately from other crane elements or together with them so that, for example, the main jib, jib extension or derrick jib can be moved or adjusted simultaneously with a load slung on the crane. Here, the crane control can calculate for a preset crane movement whether it is more advantageous in the momentary position of the crane to luff the derrick jib up or down.

It is also possible to provide a ballast element on the crane in such a way that this is adjustable by a ballast trolley or a suspension ballast. Such a ballast element can be adjusted horizontally and/or vertically, e. g. hydraulically telescoped out or in to perform lifting capacity optimisation with respect to the crane. The ballast element can be automatically adjusted during luffing, e.g. of the main jib or the jib extension, and during lifting or lowering of the load hook so that the maximum lifting capacity of the crane remains constant or is optimised.

Depending on the application case, it can be provided that only certain crane elements are used for optimising lifting capacity such as only the simultaneous or alternate control of the main jib and the jib extension, with other activating elements of the crane remaining in a fixed position. All elements activatable for the crane control can naturally be involved in the lifting capacity optimisation.

In accordance with the invention, it is also possible to move the crane from a position not optimised for liffing capacity to a position with optimum lifting capacity. For this purpose, for example, a switch can be provided for the crane operator which, when activated, causes the crane to be moved into the optimum position with regard to maximum lifting capacity with the load remaining in a fixed position. This can be done, for example, by the main jib being luffed up and the jib extension being luffed down if in this way a better lifting capacity of the crane can be achieved, with the load remaining in a fixed position.

The apparatus in accordance with the invention for the control of a crane has a first movement apparatus for a first moving element such as the main jib, a second movement apparatus for a second moving element such as the jib extension and a control apparatus with which the first and second movement apparatuses can be selected so that the crane is roughly in the region of optimum lifting capacity. For this purpose, suitable sensor elements such as rotary encoders, winch incremental encoders or linear encoders or a load sensor to determine the momentary position or load situation of the crane can be provided.

The invention is described below by means of two figures in which Fig. 1 shows a crane; and Fig. 2 shows a family of characteristics for a crane having a main jib and a jib extension.

Fig. 1 shows a crane having a main jib 1, a jib extension 2 and a counterjib 3, with an infinitely adjustable ballast element 7 being slung on the counter-jib 3. The main jib 1, jib extension 2, counter-jib 3 and ballast element 7 can be adjusted independently of one another - also under load. In addition, a further ballast element 6 can be provided. A load sensor 5 can be provided on the extension of the jib extension 2 or any other suitable position and angle sensors 4, 4' can be provided on the crane jibs to determine the current crane position or the momentary load. When a load is taken up on the load hook 8, for example the main jib 1 and the jib extension 2 can be luffed up or down in coordination with to each other to move the load in order to transport the load slung on the load hook 8 always in the region of the optimum lifting capacity of the crane.

Fig. 2 shows a family of characteristics for the liffing capacity of a crane having a main jib 1 and a jib extension 2. Curve A shows the lifting capacity of a crane in dependence on the angle position of the continuously adjustable jib extension 2 for a first given fixed position of the main jib 1. In this position of the main jib 1, the optimum angle for the jib extension 2 results in the marked position WA. If the main jib 1 is luffed to a second position, the curve B drawn in Fig. 2 results as the new lifting capacity. Here, the optimum lifting capacity of the crane is operative when the jib extension 2 is travelled to a position having the luffing angle WB. With a continuously adjustable main jib 1 and jib extension 2, a family of characteristics results, with in accordance with the invention the crane always having to be moved to that position in which the optimum lifting capacity is roughly present. In Fig. 2, therefore, the jib extension 2 should always be luffed up or down so that the optimum lifting capacity is achieved for a certain position of the main jib 1.

If a plurality of adjustable elements of the crane jib are taken into account, for example in addition to the given jibs also the derrick jib as another, third jib, then multi-dimensional characteristic families result, with the maximum characteristic family being selected or calculated in each case and with the crane being travelled to the corresponding position if, for example, a load is to be moved to the corresponding position.

1

Claims

Claims

A method for the performance of movements of a crane having at least two moving elements (1, 2, 3, 6, 7), with the at least two moving elements of the crane being moved alternately or simultaneously so that the crane is roughly in the region of optimum loadability.
2. A method in accordance with claim 1. wherein the main jib (1) and/or the jib extension (2) is controlled in such a way that that luffing movement or those luffing movements with the greatest increase or the lowest reduction in the maximum lifting capacity of the crane can be performed.
3. A method in accordance with either of claims I or 2, wherein the counter-jib (3) is luffed in such a way that the maximum lifting capacity of the crane remains constant or is optimised.
4. A method in accordance with any of the preceding claims, wherein at least one ballast element (6, 7) is adjusted so that the maximum lifting capacity of the crane remains constant or is optimised.
5. An apparatus for the performance of movements of a crane having a) A first movement apparatus for a first moving element (1, 2, 3, 6, 7); b) A second movement apparatus for a second moving element (1, 2, 3, 6, 7); and c) A control apparatus with which the first and second movement apparatuses can be controlled in such a way that the crane is roughly in the region of optimum loadability.
6. An apparatus in accordance with claim 5, wherein sensor elements (4, 5) to determine the momentary position or load situation of a crane are provided.
7. A method for the performance of movements of a crane substantially as hereinbefore described with the reference to and as illustrated in the accompanying drawings.
8. An apparatus for the performance of movements of a crane substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.