Method for monitoring load on crane with two load suspension means

Abstract

To allow two hook operation with load monitoring function on a crane.SOLUTION: A crane 10 comprises a boom 16 and two load suspension means for lifting one common load 40 or different individual loads. First load suspension means 21 carries a load introduced to the boom 16 at a first load location 01 and second load suspension means 22 carries a load introduced to the boom 16 at a second load location 02 remote from the first load location 01. First and second loads currently introduced to the boom 16 at the first and second load locations 01, 02 are detected.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The invention relates to a method for monitoring the load (payload, load capacity, load rating) of a crane according to the preamble of claim 1, to a crane according to the preamble of claim 13 and to a computer program product according to claim 15. [Background technology]

[0002] To lift and move very large loads, it is known to suspend the loads simultaneously from several cranes and move them in a coordinated lift with a tandem or multi-crane. However, with certain crane types, it is also possible to lift the loads simultaneously using two lifting ropes of only one crane. Such a two-hook operation allows, in addition to lifting and moving one common load, also the lifting and moving of two different loads by only one crane.

[0003] One typical application of lifting and moving common loads in a two-hook operation is to rotate and reorient objects or loads when they are transported in a different position from the one in which they must later be used and assembled in the installed position. The loads must be lifted and rotated in the air with as little diagonal pulling force as possible. When there are no further cranes on the construction site or the available space is limited, the controlled rotation of such loads may be performed in a two-hook operation by only one crane.

[0004] One example of a crane type that allows such a two-hook operation is a travelling crane with a hoistable main boom and a luffing jib attached to it. The main boom has a boom head through which the lifting ropes are guided. A luffing jib is pivotally attached to the boom head, which also has a boom head through which further lifting ropes are guided. The main boom is typically supported by an adjustable mast (guy block) or derrick boom and is hoistable about a hoisting axis, and the luffing jib is supported by its own guying mechanism and is pivotable.

[0005] The boom areas where the lifting ropes (or generally the load suspension means) are connected to the boom and introduce the respective acting loads into the boom structure, i.e. in the above mentioned example at the main boom and luffing jib, are referred to below as load positions. The current load introduced into the boom by the lifting ropes at the corresponding load positions results on the one hand from the lifted loads suspended on the lifting ropes (which may be individual loads or in the case of one object lifted jointly the partial loads received by the respective lifting ropes) and on the other hand from the static load of the lifting ropes (which will be ignored in the following discussion).

[0006] Cranes with only one lifting rope (one-hook operation) use a load monitoring or load torque limiting function as standard equipment to prevent the crane from tipping or the crane components from being damaged. Here, the load monitoring function typically compares the load currently being experienced at a particular crane position with a corresponding limit value (allowable load), which is often taken from a load table stored in the control mechanism or in some cases dynamically calculated by a model. If the current load reaches or exceeds the allowable load, the crane operation is usually stopped. A corresponding warning can also be issued to the crane operator before the allowable load is reached.

[0007] A problem or feature of two hook operation is that the load applied at one load location affects the maximum allowable load at the other load location and vice versa. If the load factor (load utilization factor) at one load location increases, for example due to a change in radius (load radius) or a shift in the center of gravity, the maximum allowable load at the other load location must be reduced. Therefore, normal load monitoring or load torque limiting cannot be used with two hook operation.

[0008] For this reason, conventional crane operation (one hook operation) always allows only one load lifting means, i.e. one load position, while the other load lifting means or the other load position must be unloaded, only in that way can a sufficiently accurate load indication and load factor indication or monitoring be given.

[0009] Currently, there is no safe method for two-hook operation that is monitored by the control computer. If one common load or two separate loads are nevertheless lifted using two hooks in two loading positions, this is usually done at the crane operator's own risk, without monitoring on the crane. Therefore, the crane operating manuals only provide references to operational flows where two-hook operation is prohibited or at best is performed. Summary of the Invention [Problem to be solved by the invention]

[0010] It is therefore an object of the present invention to enable two-hook operation with load monitoring on a crane. [Means for solving the problem]

[0011] According to the invention, this problem is solved by a method with the features of claim 1, a crane with the features of claim 13 and a computer program product with the features of claim 15. Advantageous embodiments of the invention emerge from the dependent claims and the following description.

[0012] Thus, a method for monitoring the load of a crane is proposed. The crane monitored by the method according to the invention comprises a boom, which may in particular be a tiltable boom. The crane further comprises two load suspension means for lifting and moving one common load or two separate loads (two-hook operation). The load suspension means may in particular comprise a lifting rope and a load hook, respectively, but other suspension means such as eye bolts or cross beams may also be provided.

[0013] In a two hook operation with supervision, each of the two load suspension means can carry a load and introduce it onto the boom. The load of the first load suspension means is introduced onto the boom at a first load location and the load of the second load suspension means is introduced onto the boom at a second load location remote from the first load location. The introduced load can be a partial load of one load or one object lifted together, or the loads of loads or objects lifted individually (as already mentioned, the static load of the load suspension means contributes to the introduced load as well, but this will not be mentioned explicitly below).

[0014] Since the two load positions are spatially separated from one another and in particular have different load radii, preferably different permissible load ranges or maximum permissible loads are applied for them. In order to take this into account during the load monitoring, it is conceivable according to the invention that a first load currently introduced on the boom is detected at a first load position and a second load currently introduced on the boom is detected at a second load position. The detection can take place, for example, by corresponding sensors on the guy ropes of the boom and / or on different boom heads of the boom. The detected loads are transmitted to a control unit on which the load monitoring according to the invention is based or is performed.

[0015] The load monitoring according to the invention is based on a calculation method based on a set of load position related variables. These are defined in a special coordinate system in which two load positions are defined along a first axis (e.g. horizontal axis) and a second axis (e.g. vertical axis) perpendicular to the first axis represents the load. Here, the two load positions are defined by two points or areas separated from each other on the first axis. Here, the distance between the two load positions selected in the display along the first axis is not of particular importance, since the distance is irrelevant. Preferably, the distance can be chosen arbitrarily (e.g. it can be set to 1 and / or be unitless) to appropriately simplify the calculations.

[0016] In this coordinate system, a first correlation (first deterministic correlation) is defined between the maximum (i.e. maximum permissible) load at the first load position and the maximum permissible load at the second load position at the maximum load (maximum load rate) at the first load position. In the following, the latter (maximum permissible load at the second load position at the maximum load at the first load position) is called the "residual maximum load". Thus, a maximum permissible load is generally defined for the first load position, which must not be exceeded regardless of the load rate at the second load position. If the current load at the first load position corresponds to this maximum load (= maximum load rate), then the load at the second load position must not exceed the defined remaining maximum load.

[0017] In said coordinate system, a second correlation (second deterministic correlation) is further defined between the maximum (i.e. maximum permissible) load at the second load position and the maximum load still permissible at the first load position at the maximum load (maximum load rate) at the second load position (hereinafter also referred to as the "remaining maximum load"). The above details regarding the remaining maximum load at the second load position also apply here.

[0018] Furthermore, a first intersection point is defined where the first and second correlations are simultaneously satisfied. In particular, these determined correlations represent a functional relationship in the coordinate system (in the simplest case, a linear relationship) that intersects at the first intersection point in the coordinate system. In the simplest case, the functional relationship can be defined by only two points in the coordinate system (e.g., the maximum allowable load at one load location and the maximum remaining load at the other load location).

[0019] The above-mentioned variables defined in the coordinate system can be calculated or determined in advance and stored in the control unit or in a data memory, for example in the form of tables for various boom positions, crane configurations, etc. For this purpose, known load tables for one-hook operations can be used. Alternatively, it can be envisaged that the above-mentioned variables are calculated by the control unit within the scope of the method according to the invention, for example as a function of the current boom position. Thus, for example, the maximum load in the first loading position depends on the swivel angle of the jib, since in the case of a swiveling luffing jib, the swivel angle defines the load radius, the larger the load radius, the lower the permissible load.

[0020] According to the invention, a third correlation (third deterministic correlation) between the first detected load and the second detected load is determined in a defined coordinate system, which is in particular a functional relationship in said coordinate system (in the simplest case a linear relationship, which can be determined only by two points in the coordinate system, i.e. the two detected loads).

[0021] Further, a second intersection is determined where the third correlation and the first intersection have the same value on the first axis. In other words, the second intersection is a point of intersection between the third correlation and a perpendicular line passing through the first intersection to the first axis. Therefore, when the first axis is the horizontal axis, the second intersection is below or above the first intersection, or overlaps with the first intersection.

[0022] According to the invention, the positions of the first intersection point along the second axis and the determined second intersection point (i.e. their load values) are compared with each other. If the load value of the second intersection point is greater than the load value of the first intersection point, the crane is in an unacceptable load range and appropriate measures are automatically taken.

[0023] This action may include issuing a warning, such as an acoustic and / or visual warning to the crane operator indicating that an unacceptable load range has been reached for the current two crane operations. Alternatively or additionally, an automatic intervention in the current operation of the crane may be performed by the control unit, in particular stopping the current crane operation or performing a reverse or compensating movement that brings the crane back into the permissible load range where the load value of the second node is less than or equal to the load value of the first node. The control unit may be a crane control mechanism or a separate control unit.

[0024] The method according to the invention can be implemented with a conventional load torque limiting function which, given the detected first and second loads, determines itself (e.g. from a corresponding stored load table or by a model taking into account in particular the current crane configuration and position) the above-mentioned variables defined in the coordinate system (maximum load value, remaining maximum load value, first intersection point) or is likewise given them as input variables.

[0025] The above first, second and third correlations are preferably mathematical relationships taking into account the respective load values, in particular in the form of functions intersecting or including the respective load values ​​in a coordinate system.

[0026] The distance between the load positions on the first axis, or the midpoint between the load positions, is not of particular importance since the first axis includes the two load positions and is particularly dimensionless. Therefore, it is especially the load values ​​at the intersection of the two load positions (i.e. the values ​​on the second axis) that are of importance for the calculation method according to the invention.

[0027] The calculation method according to the invention is based on the knowledge that the loads at the two load locations can be considered as a whole system, i.e. as a load combination, and that different load combinations can be converted into each other by appropriate mathematical transformations.

[0028] The first limit load combination occurs when the load at the second load position is fully utilized (i.e. the load acting corresponds to the maximum load at the second load position). This is accompanied by a certain maximum remaining load at the first load position. This can have a value equal to or greater than 0 (i.e. no load acts at the first load position or no load is lifted by the first load suspension means), especially if the first load position corresponds to a larger load radius than the second load position. The second limit load combination occurs when the load at the first load position is fully utilized (i.e. the load acting corresponds to the maximum load at the first load position). This is accompanied by a certain maximum remaining load at the second load position. This can have a value equal to or greater than 0 (i.e. a certain load may still act at the second load position or a load may be lifted by the second load suspension means), especially if the first load position corresponds to a larger load radius than the second load position.

[0029] Based on a first intersection between the limit positions, limit values ​​for the loads at the first and second load positions (i.e., current maximum loads) can be determined, which correspond to current load combinations that do not reach the maximum load rate at either the first or second load positions.

[0030] A second intersection point, determined from the detected loads currently acting on the two load locations, gives information as to whether the current load combination corresponds to an admissible load combination that is between the aforementioned limit load combinations. Furthermore, a comparison of the intersection points gives information as to the overall load factor of the crane at the current load combination.

[0031] This allows load monitoring or load torque limiting in two hook operation, which ensures compliance with critical, co-acting load limits of the entire system or the implementation of appropriate measures if unacceptable load ranges are reached, thus enabling a continuously monitored and safe two hook operation.

[0032] Furthermore, optionally a display of the current load and the load limits related to the current total load situation or load combination can be provided, for example on a display unit in the crane cab of the crane.

[0033] In addition to monitoring the individual loads at each load location, a load monitoring is preferably performed based on the load values ​​of the first and second intersections, in other words, preferably by comparing the values ​​of the first and second intersections, the exceeding of the current maximum load at the first load location by the detected first load and the exceeding of the current maximum load at the second load location by the detected second load are further monitored and appropriate measures are taken in case of exceedance.

[0034] Optionally, a predictive calculation can be made assuming the current crane movement continues. For example, when the boom and / or the load suspension means moves, the above defined variables (maximum load, remaining maximum load, first intersection) may change. This will cause the ratio or distance between the first intersection and the second intersection to change. Furthermore, when the boom and / or the load suspension means moves, the first and / or second loads may also change, which will further result in a change in the second intersection. The predictive calculation assuming the boom and / or the load suspension means movement continues allows an early warning to be given before an unacceptable load range is reached and / or measures can be taken, such as slowing down or stopping the crane movement.

[0035] In one possible embodiment, it is considered that the maximum permissible load at the first load position at the maximum load (maximum load rate) at the second load position, i.e. the remaining maximum load at the first load position, is zero. That is, if the maximum load is reached at the second load position, no load should be hoisted at the first load position. Preferably, the remaining maximum load at the second load position is greater than zero, i.e. even if the full load is utilized at the first load position, a load may still be hoisted at the second load position. The above-mentioned method is carried out, for example, in a crane comprising a hoistable main boom with a boom head having a lifting rope and a second load position, and a boom tip assembled to the main boom, with the boom head having a lifting rope and a first load position. The maximum load at the first load position is lower than the maximum load at the second load position, since the first load position has a longer distance from the pivot point of the main boom or a larger load radius.

[0036] In a further possible embodiment, it is envisaged that the first, second and third correlations are linear relationships, which simplifies the calculation method according to the invention, since the first and second intersection points are obtained by intersecting straight lines, in particular in the abovementioned coordinate system.

[0037] Here, the lines are each defined by two points (connecting lines representing the respective limit load combinations, the respective maximum loads and the remaining maximum loads of the load combinations representing the two points that mathematically uniquely define the respective connecting lines) and do not necessarily have to exist as real functions in the control unit. However, as an alternative, it is also possible to define the lines as a function of values ​​along a first axis and to assign specific values ​​of the first axis (e.g. 0 and 1) for the two load positions. As already mentioned, the spacing of the load positions along the first axis does not affect the load value of the intersection point. However, the intersection point may also have a specific value on the first axis and the lines may also be defined as a function of the value of the first axis.

[0038] This leads, inter alia, to the following simplifications:

[0039] The first linear relationship represents a first connecting line between the maximum load at the first load location and the remaining maximum load at the second load location in the above coordinate system, while the second linear relationship corresponds to a second connecting line between the maximum load at the second load location and the remaining maximum load at the first load location.

[0040] Here, the third linear relationship corresponds to a third connecting line between the first detected load and the second detected load, and thus this current load combination is represented by the third connecting line that is uniquely defined by the two detected loads (as two points in the coordinate system).

[0041] As a result, the first intersection point is obtained from the intersection point between the first connection line and the second connection line in the coordinate system. The second intersection point is the intersection point between the third connection line and a line that passes through the first intersection point and is perpendicular to the first axis.

[0042] Although the above relationships have been described based on the connecting lines and their intersections, they are naturally expressed by corresponding mathematical relationships. In particular, there are corresponding equations for the load values ​​of the first and second intersections, which include the maximum load and the remaining maximum load at the first and second load positions.

[0043] It is also clear that the distance between the two load positions on the first axis of the coordinate system does not affect the load value and maximum load of the intersection, so it is not included in the calculation and can be set arbitrarily (as long as it is greater than 0).

[0044] In a further possible embodiment, it is considered that for the lifting of one common load, a maximum load is defined for both the first and the second load position, both of which correspond to the load value of the first intersection point. This is based on the knowledge that the defined correlation (which in the simplest case represents a connecting line) always passes through the first intersection point at the maximum common load rate (i.e. individually, neither the first nor the second load position fully utilizes the maximum load, but in combination the full common load is achieved, and the load cannot be increased at either load position without reducing the load at the other load position).

[0045] In the case of a linear relationship, the load combination with the maximum common load factor (= maximum permissible load combination) can be considered as a "seesaw" (a compensator with a variable angle), where the maximum load for the maximum permissible load combination at the two load positions, i.e. the corresponding connecting line, moves like a "seesaw" (changing the angle) around the first intersection. There must therefore be a load combination with the maximum common load factor, where the connecting line passing through the first intersection runs parallel to the first axis. In this situation, the maximum load (= current permissible load) at both load positions is of the same magnitude and corresponds to the load value at the first intersection (i.e. the value on the second axis). That is, from the load value at the first intersection, the current permissible load valid in the case of a joint can be read directly in the case of the same utilization factor at both load positions, which can be used, for example, as an entry in the corresponding load table for a two-hook operation.

[0046] If the detected first load or the detected second load is greater than the current permitted load valid for this operation, an impermissible load range is present and appropriate measures are taken, which preferably include issuing a warning by the control unit and / or automatic intervention in the current operation of the crane, as already mentioned above.

[0047] In a further possible embodiment, it is envisaged that the first load is determined by detecting a first force on a first guy rope of the boom and the second load is determined by detecting a second force on a second guy rope of the boom, the first and second forces being preferably detected by sensors arranged on the first and second guy ropes and transmitted to the control unit. The first guy rope may be an adjustable luffing jib guying and may include a rope adjustment mechanism for raising and lowering the luffing jib. The second guy rope may be, for example, a retractable main boom guying and may include a cable adjustment mechanism for raising and lowering the main boom.

[0048] In a further possible embodiment, it is envisaged that if the load value of the second node is smaller than the load value of the first node, then from the first node and the determined second node a current permissible load at the first load position and a current permissible load at the second load position are calculated. These determined current permissible loads represent load limit values ​​for the current load combination or load distribution. If these load limit values ​​are exceeded, i.e. if the detected first load exceeds the current permissible load determined from the respective node at the respective load position, measures are taken automatically, as already mentioned above, preferably including issuing a warning by the control unit and / or automatic intervention in the current operation of the crane.

[0049] In a further possible embodiment, it is envisaged that said current permissible loads at the first and second load positions are determined by adding the load values ​​of the first and second loads respectively with the difference between the load values ​​of the first and second intersection points, thereby making it possible to reliably determine and monitor the exceedance of the load limits that apply to the current load distribution with respect to the current load situation in a two-hook operation.

[0050] The distance from the first intersection to the second intersection along the second axis, i.e. the load difference between the two intersections, is in particular a measure for the overall load factor due to the current load combination. In particular, the ratio of the load values ​​can be expressed as a percentage load factor, i.e. this is not the individual load utilization rates at the individual load positions, but the overall or combined load factor that looks at the entire load situation at the two load positions.

[0051] In a further possible embodiment, it is envisaged that if the first load is greater than the maximum load at the first load position or if the second load is greater than the maximum load at the second load position, measures are automatically taken, preferably including issuing a warning by the control unit and / or intervening in the current operation of the crane, as described above. That is to say, in addition to monitoring compliance with the currently valid load limits for the current load combination based on the two nodes, an individual load monitoring of the loads acting respectively at the two load positions is performed. This can be done in a conventional manner, e.g. with one-hook operation, based on corresponding load tables.

[0052] In other words, even if the load value of the second intersection is less than or equal to the load value of the first intersection, it is guaranteed that the maximum load at the first load position or the maximum load at the second load position is not exceeded by the first load or the second load.

[0053] In a further possible embodiment, the crane is configured such that the first load position is movable relative to the second load position, in particular by operating a partial boom (e.g. an adjustable luffing jib) including the first load position relative to a main boom including the second load position.

[0054] Alternatively or additionally, the first load location and the second load location may have a fixed distance from each other along the boom (for example, this would be the case if the luffing jib was attached to the main boom because the respective boom heads would have the same distance regardless of the luffing jib's rotation angle or the main boom's hoist angle).

[0055] In a further possible embodiment, it is envisaged that the boom comprises a main boom with a second boom head, pivotable about a horizontal hoisting axis, supported on the transport device of the crane, and a boom tip with a first boom head, fixed to the main boom, either stationary or pivotable about a horizontal pivot axis, the first load suspension means being guided via the first boom head and the second load suspension means being guided via the second boom head. Thus, the first load position is at the first boom head and the second load position is at the second boom head. The boom may be a lattice boom. The boom may be supported by a guy block or a derrick boom. The transport device may comprise a rotatable upper structure to which the main boom is articulated, the upper structure being rotatably supported on a traveling undercarriage.

[0056] In a further possible embodiment, it is envisaged that the first load suspension means is adjustable by a first hoisting winch and the second load suspension means is adjustable by a second hoisting winch, the hoisting winches being controllable by a control unit of the crane. This control unit may be the control unit which executes the calculation method according to the invention or may be a separate control unit. Preferably, the two load suspension means are adjustable independently of each other.

[0057] In a further possible embodiment, it is envisaged that a deviation of the first and / or second load suspension means from the vertical is detected and, if the deviation is recognised, a warning is issued and / or an input request is indicated and / or measures are taken automatically by the control unit. Thus, in addition to the load monitoring according to the invention in a two-hook operation, a diagonal tension monitoring on the two load suspension means is performed, which is preferably carried out by the same control unit (naturally, several separate control units can also be provided). Said measures preferably include a stop in the movement of the boom (e.g. the main boom and / or the luffing jib adjustable relative to the main boom) or an action to compensate for the deviation.

[0058] Here, in particular, both deviations forward / backward (i.e. parallel to the undulating surface) and deviations to the right / left (i.e. sideways or perpendicular to the undulating surface) are measured and analyzed. If a deviation from the vertical is recognized, then a diagonal tension of the load suspension means in question is occurring (in many cases the load suspension means do not both have diagonal tensions or both have diagonal tensions), which is preferably important to compensate for. For this purpose, preferably at least one actuator (e.g. hydraulic cylinder or cable winch of an adjustable guy cable) which actuates the boom or a boom part boom is controlled by the control unit to correct the deviation from the vertical. The correction of the deviation from the vertical can be initiated by input from the crane operator (e.g. after execution of a command prompt) or fully automatically by the control unit.

[0059] As already mentioned, a diagonal pull on one load suspension means is usually accompanied by a corresponding diagonal pull on the other load suspension means, so that in the simplest case it is sufficient to monitor only the diagonal pull on one of the two load suspension means, although it is of course also possible to monitor the diagonal pull on both load suspension means.

[0060] Therefore, preferably, the crane includes at least one measuring device for detecting deviation of the first or second load suspension means from the vertical. Two measuring devices may be provided for detecting diagonal tension forces of both load suspension means.

[0061] The invention further relates to a crane comprising a boom and two load suspension means for lifting a common load or different individual loads, a first load suspension means adjustable by a first hoisting winch being connected to the boom at a first load position and a second load suspension means adjustable by a second hoisting winch being connected to the boom at a second load position remote from the first load position, and a detection device capable of detecting a first load introduced on the boom at the first load position and a second load introduced on the boom at the second load position.

[0062] According to the invention, the crane comprises a control unit adapted to carry out the method according to the invention (i.e. the steps mentioned above which are associated with or executable by the control unit), where the same properties and advantages are obtained as with respect to the method according to the invention, so that a repeated description will not be given. In particular, all the modifications and optional embodiments mentioned above for the method according to the invention also apply, in any combination, to the crane according to the invention.

[0063] The invention further relates to a corresponding computer program product for carrying out the method according to the invention, comprising instructions such that, when the program is executed, the steps of the above-mentioned method (in any embodiment) relating to the control unit are carried out by a control unit of a crane according to the invention. Preferably, the computer program product can be operated with conventional crane control or load torque limiting functions, so that no retrofitting of hardware components is necessary. Here, as mentioned above, a conventional load torque limiting function can be incorporated.

[0064] Further features, details and advantages of the invention emerge from the following description of exemplary embodiments with reference to the drawings. [Brief description of the drawings]

[0065] [Figure 1] FIG. 1 is a side elevational view of an exemplary embodiment of a crane according to the present invention in which a load is lifted jointly by two hook operations. [Diagram 2] FIG. 2 illustrates an exemplary representation of a coordinate system and variables defined therein for load monitoring in accordance with the present invention. [Diagram 3] FIG. 2 illustrates an exemplary representation of a coordinate system and variables defined therein for load monitoring in accordance with the present invention. [Figure 4] FIG. 2 illustrates an exemplary representation of a coordinate system and variables defined therein for load monitoring in accordance with the present invention. [Diagram 5]FIG. 2 illustrates an exemplary representation of a coordinate system and variables defined therein for load monitoring in accordance with the present invention. [Figure 6] FIG. 2 is a side overall view of the crane according to FIG. 1 in a situation where a diagonal pulling force is applied. [Figure 7] FIG. 2 is an enlarged view of a first boom head of a crane according to the invention, comprising a measuring device for determining the verticality of a load suspension means according to an exemplary embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0066] An exemplary embodiment of a crane 10 according to the invention is shown in a side overall view in Figure 1. The crane 10 is a traveling lattice boom crane including an undercarriage 12 having a crawler chassis and an upperworks 14 supported on the undercarriage 12 for rotation about a vertical axis of rotation. However, other embodiments are of course also conceivable, such as, for example, an undercarriage having a wheeled or rail chassis, or a fixed crane having a boom pivotally supported on a tower or a column.

[0067] In the exemplary embodiment shown herein, the crane 10 includes a boom 16 including a main boom 17 mounted to the superstructure 14 so as to be capable of being raised or lowered about a horizontal lifting axis, and a boom tip in the form of a luffing jib 18 assembled to the main boom 17 and pivotable relative to the main boom 17 about a horizontal pivot axis.

[0068] The crane 10 has two load hoisting means 21, 22, which in the illustrated exemplary embodiment each comprise a lifting rope and a load hook fixed thereto. The luffing jib 18 has a first boom head 25 through which the lifting rope of the first load hoisting means 21 is guided. Through the first load hoisting means 21, a first load L1 is introduced to the boom 16 at a first load position O1 at the first boom head 25. The main boom 17 has a second boom head 26 through which the lifting rope of the second load hoisting means 22 is guided. Through the second load hoisting means 22, a second load L2 is introduced to the boom 16 at a second load position O2 at the second boom head 26.

[0069] The luffing jib 18 is supported by a first guy rope 31, which in particular includes an adjustable guy cable between two masts (guy blocks) of the luffing jib 18, and the guy cable allows the luffing jib 18 to rotate relative to the main boom 17. The lifting rope of the first luggage hoisting means 21 is supported by a first hoisting winch so as to be capable of being wound up and unwound. The main boom 17 is supported by a second guy rope 32, which in particular includes an adjustable guy cable arranged between a mast (guy block) articulated to the upper structure 14 and the upper structure 14, and the guy cable allows the main boom 17 to be raised and lowered relative to the upper structure 14 around the hoisting axis.

[0070] In the exemplary embodiment shown in Fig. 1, one common load 40 is suspended from two load suspension means 21, 22. As indicated by the curved arrows, the load 40 can be moved, e.g. rotated, by suitable adjustment of the load suspension means 21, 22. When one load 40 is lifted jointly, a distribution of the load occurs between the two load suspension means 21, 22, and a specific partial load L1, L2 is introduced at each load position O1, O2.

[0071] In two hook operation, two load suspension means 21, 22 are operated while simultaneously carrying loads at two different load positions O1, O2. A feature of two hook operation is that a load applied at the first load position O1 affects the maximum allowable load at the second load position O2 and vice versa. If the load factor at one load position O1, O2 increases, for example due to a change in outreach (radius) or a displacement of the centre of gravity, the maximum allowable load at the other load position O2, O1 must be reduced.

[0072] This can be illustrated by the following example: if a maximum load (e.g. 40t) is applied to the first load location O1, the second load location O2 may only be loaded with the associated minimum load (maximum remaining load). If the first load location O1 is completely unloaded (0t), the load at the second load location O2 may increase to the maximum permissible load, i.e. the maximum load at the second load location O2 (e.g. 100t).

[0073] Here, the load monitoring according to the invention provides calculations for determining the current permissible loads acting jointly for the individual load positions O1, O2. These can be used to monitor the crane operation, but preferably also to display the current load and load factor as well as the permissible load on a display unit (e.g. a crane monitor). This applies independently of the exact implementation of the crane 10. The calculations are now described with reference to specific exemplary embodiments, but the concept according to the invention is likewise independent of the exact configuration of the crane 10.

[0074] The basis for this calculation is the conventional crane load values, i.e. the maximum load L1 at the first load position O1 and the second load position O2. max and L2 maxThese can be stored, for example, in a corresponding load table and can vary depending on the current boom position. Furthermore, in the following exemplary embodiment, at the maximum load rate (first load position O1) of the luffing jib 18, the main boom 17 (second load position O2) may still be structurally loaded, but at the maximum load (maximum load rate) of the main boom 17, the luffing jib 18 (or the second load position O2) may no longer be loaded. In other words, at the maximum load (maximum load rate) at the second load position O2, the maximum allowable load L1 at the first load position O1 may be greater than the maximum allowable load L2 at the first load position O2. v (=maximum remaining load L1 v ) is zero, but at the maximum load (maximum load rate) at the first load position O1, the maximum allowable load L2 at the second load position O2 is v (=maximum remaining load L2 v ) has a value greater than zero, which depends, among other things, on the current boom position.

[0075] In the present invention, the above values ​​are continuously adapted to the current crane position, in particular the boom position, and can be taken from corresponding load tables or can be interpolated, as known for example from conventional one-hook operations.

[0076] Now, in order to determine a common effective load limit for a two-hook operation, i.e. for the particular load combination currently being lifted (which can result from one load 40 being lifted jointly or from two individual loads being lifted), the above load limits are combined to form a limit load combination, defined in a coordinate system including two load locations O1 and O2 at different positions on a first axis and associated load values ​​along a second axis perpendicular to the first axis.

[0077] 2-5 show examples of such coordinate systems, where the first axis is the horizontal axis (x-axis) and the second axis is the vertical axis (y-axis). The load positions O1 and O2 are separated from each other along the horizontal axis, but the distance can be chosen arbitrarily, as it is not important for this calculation.

[0078] In FIG. 2, the maximum load L2 max (=load limit value at the second load position O2 alone) is shown, and the maximum load L1 for the first load position O1 is shown. max (=load limit value at the first load position O1 alone) is shown, where the maximum load L1 at the first load position O1 max is the maximum load L2 at the second load position O2 max Furthermore, the remaining maximum load L2 at the second load position O2 is smaller than the v In this exemplary embodiment, the remaining maximum load L1 at the first load position O1 is v is zero, this lies on the horizontal axis.

[0079] Here, these values ​​are grouped together to form limit load combinations according to the established correlation (see Figure 2: Limit Load Combination 1: L2 max and L1 v =0;Limit load combination 2:L1 max and L2 v ), the exemplary embodiment considered here is a linear relationship. For this reason, the load values ​​of the respective limit load combinations are connected to each other by connecting lines g1 and g2 (see FIG. 2: Limit Load Combination 1: L2 max and L1 v =0 is connected by the first connecting line g1; limit load combination 2: L1 max and L2 v and are connected by the second connecting straight line g2).

[0080] As can be seen from FIG. 3, the connecting lines g1 and g2 of the two limit load combinations intersect at a first intersection point S1. Here, the y value or load value L S1 is L1 max and L1 v =0 and L2 max and L2 v The load value L of the first intersection point S1 is between S1 There are four load limits L1 max , L1 v , L2 max , and L2 v and in the exemplary embodiment considered here, according to the following formula: TIFF2025032983000002.tif13170

[0081] L S1 It can be seen that θ i does not depend on the distance between the first load position O1 and the second load position O2 along the horizontal axis (the distances are chosen arbitrarily in Figs. 2 to 5).

[0082] From this consideration, the maximum allowable load combination behaves like a seesaw (pendulum, compensator) with a fulcrum at the first intersection point S1 between its two limit values ​​(limit load combinations 1 and 2 in FIG. 3).

[0083] From there, the specific maximum permissible load combinations can be directly derived, which are shown in FIG. 4 by the dashed-dotted connecting lines. Since each maximum permissible load combination has a connecting line passing through the first intersection S1 between the current permissible loads effective at the joint, the maximum permissible load combinations having connecting lines running parallel to the horizontal axis correspond exactly to the case of uniform load application. Thus, the current permissible loads effective at the joint Lg associated with this akt,max have values ​​of equal magnitude and neither may be exceeded.

[0084] Therefore, the load value L at the first intersection S1 S1 from the relevant load limit value, i.e. the current permissible load Lg valid for joint lifting of loads with the center of gravity in the center akt,max This load limit value Lg can be determined directly. akt,max can be used as input for the load table for a two hook operation.

[0085] For example, the loads L1 and L2 acting on the two load locations O1 and O2 will be of different magnitudes when different individual loads are lifted by the two load suspension means 21, 22, or when an off-center center of gravity or a diagonal pulling force occurs when one load 40 is lifted jointly. When such a current load combination (i.e., the currently acting loads L1 and L2 and the third connecting line g3 connecting these loads L1, L2) is observed in a coordinate system (see FIG. 5), a second intersection point S2 between this third connecting line g3 and a line gs perpendicular to the horizontal axis and extending through the first intersection point S1 is obtained.

[0086] Here, the load monitoring according to the present invention is performed by detecting the load value L of the second intersection point S2. S2 is the load value L at the first intersection S1 S1 On the other hand, the load value L at the second intersection point S2 is larger than the load value L at the second intersection point S2. S2 is the load value L at the first intersection S1 S1 (See FIG. 5) if the current load combination is less than (or equal to) the current load L1 and L2 (both of the current loads L1 and L2 are below their associated load limit values ​​L1 max and L2 max is within the permissible load range (assuming that the load does not exceed

[0087] For the current load combination (Figure 5), the total load factor A of the crane Kran is the load value L of the first intersection point S1 and the second intersection point S2 S1 and L S2 It is obtained from the ratio of TIFF2025032983000003.tif13170

[0088] Load value L at the first intersection point S1 and the second intersection point S2 S1 and L S2 From the difference between the current load values ​​L1 and L2, the current allowable load L1 applied to the current load combination at the first load position O1 and the second load position O2 is calculated by translating the current load values ​​L1 and L2 along the vertical axis by the above difference. akt,max and L2 akt,max can be calculated (see the double-headed arrow in Figure 5). TIFF2025032983000004.tif8170TIFF2025032983000005.tif8170

[0089] Now, starting from g3, the value The fourth connecting straight line g4 of the calculated maximum allowable load combination, obtained by shifting the axis by TIFF2025032983000006.tif6170, passes through the first intersection point S1.

[0090] Referring to FIG. 5, an additional monitoring criterion L S2 ≦L S1 It is also clear why the maximum load L1 at each load position O1 and O2 is required. max , L2 max If only the loads of ... akt,max and L2 akt,max is the maximum load L1 applied to the load positions O1 and O2 separately. max and L2 max It is much lower than the standard L S2 ≦L S1 This takes into account the actual load situation in two-hook operation where the two loads L1 and L2 influence each other.

[0091] However, preferably, the standard L S2 ≦L S1 In addition to monitoring the load factor at each load position, the load factor is also monitored (i.e., L1 ≤ L1 max and L2≦L2 max ).

[0092] If one of these criteria is not met (i.e., L S2 >L S1 Or L1>L1 max Or L2>L2 max), countermeasures can be taken automatically. For example, a warning can be issued to the crane operator on a display unit and / or an automatic shutdown can be performed.

[0093] Regardless of the specific exemplary embodiment, it should be noted that, alternatively, actions may be taken upon reaching the respective limits.

[0094] Preferably, the current load situation and applicable limit values, and / or the current total load factor A Kran are displayed to the crane operator on a display unit, preferably graphically. The display can be in a form similar to that shown in Figs. 2 to 5, i.e. the current positions of the loads L1, L2, their respective limit values ​​L1, max , L2 max , L2 v , and the corresponding connecting straight lines g1, g2, g3 and the two intersection points S1 and S2. Alternatively or additionally, the respective load values ​​and / or total load factors A Kran can also be displayed numerically.

[0095] The loads L1 and L2 currently acting on the two load positions O1, O2 are detected by a detection device and transmitted to the control device, for example by sensors for detecting the forces on the first and second guy ropes 31, 32.

[0096] The graphical representation of the connecting lines g1, g2, g3, g4 and the coordinate system shown in figures 2 to 5 is only for the purpose of illustrating the calculation method according to the invention. This graphical representation is based on mathematical equations and relations involving the various variables mentioned above. Therefore, it is not necessary to define or provide as functions, for example, the actual connecting lines g1, g2, g3, g4 in the control unit.

[0097] Moreover, when lifting one common load by two hooks at different load positions, the diagonal pull forces must also be taken into account, especially when rotating the jointly lifted load, and must be detected and taken into account in the load factor. Such a situation is shown in Figure 6, where the load suspension means 22 has an "inward" diagonal pull force and the load suspension means 21 has an "outward" diagonal pull force.

[0098] Such diagonal tensions affect the load indication, the load monitoring, the cable tensions and the supporting structure of the crane 10 or the boom 16. Since the load monitoring of the crane 10 is based especially on a vertically suspended load (without diagonal tensions), the control unit calculates erroneous loads L1, L2 from the forces measured by the detection devices, from the current loads L1, L2 which are too low, especially if sensors for determining the forces are arranged in the guy ropes. When a diagonal tension inwards occurs, the actual loads L1, L2 are higher, which has an effect on the actual structural load of the boom 16 and must not be ignored.

[0099] To ensure safety in two-hook operation of a common load, it is necessary to measure or determine the diagonal pull angles of the load suspension means 21 and / or 22. Knowing the diagonal pull angles, the actual loads L1, L2 and the load factor A of the crane 10 can be calculated. Kran can be accurately calculated and displayed to, for example, a crane operator.

[0100] Preferably, the diagonal pull force monitoring is performed by a corresponding support system in the crane 10, which support system may be independent or may be part of the load monitoring according to the invention.

[0101] In an embodiment of the diagonal tension monitoring system, the forward / rearward and lateral diagonal tensions of the lifting ropes of at least one load suspension means 21, 22 are displayed and possibly corrected. The crane operator can thus recognize and prevent lateral and forward tensions. A display unit, e.g. a crane display, preferably indicates to the crane operator (e.g. in the form of a plan view to the respective load position O1, O2 on the boom 16) whether the lifting rope or ropes are in a vertical position. It can be envisaged that, in the event of diagonal tensions being present, the crane 10 automatically corrects the diagonal tensions by means of compensating movements of the boom 16 (e.g. the first and / or second hoisting winch) upon control by the crane operator (e.g. via an input button on the master switch). Alternatively, the corrections can also be made possible automatically (i.e. without the intervention of the crane operator) by the control unit.

[0102] FIG. 7 shows an embodiment of a sensor system 50 for detecting the diagonal tension of the lifting ropes of the first load suspension means 21. The first boom head 25 of the luffing jib 18 with the pulleys along which the lifting ropes are guided can be seen. One of the reevings of the lifting ropes is connected to a measuring device 50 fixed to the first boom head 25, which detects and transmits to the control unit the deviation of the lifting ropes from the vertical to the side (i.e. to the left / right) and parallel to the undulating plane (i.e. to the front / back). Naturally, alternative detection devices are also conceivable. Optionally, the second sensor system 50 can also be provided on the second load suspension means 22 or on the second boom head 26. [Explanation of symbols]

[0103] 10. Crane 12 Lower bogie 14 Superstructure 16. Boom 17 Main Boom 18 Boom tip 21 First luggage suspension means 22 Second luggage suspension means 25 First Boom Head 26 No. 2 boom head 31 No. 1 guy rope 32 No. 2 guy rope 40 Received Baggage 50 Sensor system for detecting diagonal tensile force g1 First connecting line g2 Second connecting line g3 3rd connecting line g4 4th connecting line L1 First detected load L2 Second load detected L1 akt,max Current permissible load in the first load position L2 akt,max Current permissible load in the second load position Lg akt,max Common effective current load capacity L1 max Maximum load in first load position L2 max Maximum load at second load position L1 v Maximum remaining load L2 v Maximum remaining load O1 1st load position O2 2nd load position S1 1st intersection S2 2nd intersection

Claims

1. A method for monitoring a load on a crane (10), said crane (10) comprising a boom (16) and two load suspension means (21, 22) for lifting one common load (40) or different individual loads (40), a first load suspension means (21) carrying a load introduced on said boom (16) at a first load position (O1) and a second load suspension means (22) carrying a load introduced on said boom (16) at a second load position (O2) remote from said first load position (O1), The method comprises: a first load (L1) currently being introduced to the boom (16) at the first load position (O1) and a second load (L2) currently being introduced to the boom (16) at the second load position (O2) are detected; A coordinate system in which two points spaced apart from each other along a first axis represent the two load positions (O1, O2), and a second axis perpendicular to the first axis represents the loads at each of the load positions (O1, O2), and the following variables are defined: The maximum load (L1 ｍａｘ ) and the maximum allowable load (L2) at the second load position (O2) at the maximum load at the first load position (O1). ｖ ) a first correlation between The maximum load (L2) at the second load position (O2) ｍａｘ ) and the maximum allowable load (L1) at the first load position (O1) at the maximum load at the second load position (O2). ｖ ) and a second correlation between a first intersection (S1) where the first correlation and the second correlation are simultaneously satisfied; is defined, A third correlation between the first load (L1) and the second load (L2) is determined in the defined coordinate system; A second intersection point (S2) is determined where the third correlation and the first intersection point (S1) have the same value along the first axis; if the value of the second intersection point (S2) along the second axis is greater than the value of the first intersection point (S1), measures are automatically taken, said measures preferably including issuing a warning and / or intervening in the current operation of the crane (10) by a control unit. A method comprising:

2. At the maximum load at the second load position (O2), the maximum allowable load (L1 ｖ ) is zero, and / or at the maximum load at the first load position (O1), the maximum allowable load (L2 ｖ 2. The method of claim 1 , wherein:

3. The first, second and third correlations are linear relationships, in particular The first linear relationship is the maximum load (L2 ｍａｘ ) and the maximum allowable load (L1) at the first load position (O1) at the maximum load at the second load position (O2). ｖ ) a first connecting line (g1) between A second linear relationship is expressed as the maximum load (L1 ｍａｘ ) and the maximum allowable load (L2 ｖ ) a second connecting line (g2) between a third linear relationship is a third connecting line (g3) between the first load (L1) and the second load (L2); The first intersection point (S1) is an intersection point between the first connecting line (g1) and the second connecting line (g2), The second intersection point (S2) is an intersection point between the third connecting line (g3) and a perpendicular line (gs) passing through the first intersection point (S1) to the first axis. The method according to claim 1 or 2.

4. The maximum load (Lg) for the first and second load positions (O1, O2) for lifting one common load (40) ａｋｔ，ｍａｘ ) is defined, and the maximum load (Lg ａｋｔ，ｍａｘ ) corresponds to the value of the first intersection point (S1) along the second axis, and the detected first load (L1) or the detected second load (L2) corresponds to the value of the maximum load (Lg ａｋｔ，ｍａｘ 4. The method according to claim 1, wherein if the difference between the load and the load is greater than the load, then measures are automatically taken, said measures preferably including issuing a warning by the control unit and / or intervening in a current operation of the crane (10).

5. The method according to any one of claims 1 to 4, wherein the first load (L1) is determined by detecting a first force on a first guy rope (31) of the boom (16) and the second load (L2) is determined by detecting a second force on a second guy rope (32) of the boom (16), the first force and the second force being preferably detected by sensors arranged on the first guy rope (31) and the second guy rope (32) and transmitted to the control unit.

6. If the value of the second intersection point (S2) along the second axis is smaller than the value of the first intersection point (S1), the current allowable load (L1) at the first load position (O1) is calculated from the first intersection point (S1) and the determined second intersection point (S2). ａｋｔ，ｍａｘ ) and the current allowable load (L2 ａｋｔ，ｍａｘ ) is determined, and the first load (L1) is the current allowable load (L1) at the first load position (O1). ａｋｔ，ｍａｘ ), or when the second load (L2) is greater than the current allowable load (L2) at the second load position (O2), ａｋｔ，ｍａｘ 6. The method according to claim 1, wherein if the difference between the maximum and minimum thresholds is greater than 0, then measures are automatically taken, said measures preferably including issuing a warning by the control unit and / or intervening in the current operation of the crane (10).

7. The current allowable load (L1 ａｋｔ，ｍａｘ ) is determined by adding the first load (L1) and the difference between the first intersection point (S1) and the second intersection point (S2) along the second axis, and the current allowable load (L2) at the second load position (O2) is calculated. ａｋｔ，ｍａｘ 7. The method according to claim 1, wherein the second load (L2) is determined by the addition of the difference between the first intersection point (S1) and the second intersection point (S2) along the second axis.

8. The first load (L1) is the maximum load (L1 ｍａｘ ), or when the second load (L2) is greater than the maximum load (L2) at the second load position (O2) ｍａｘ 8. The method according to claim 1, wherein if the difference between the load and the load is greater than the load, then measures are automatically taken, said measures preferably including issuing a warning by the control unit and / or intervening in a current operation of the crane (10).

9. The method according to any one of claims 1 to 8, in particular by moving a partial boom (18) having the first load position (O1) relative to a main boom (17) of the crane (10) having the second load position (O2), wherein the first load position (O1) is movable relative to the second load position (O2) and / or the first load position (O1) and the second load position (O2) have a fixed distance from each other along the boom (16).

10. 10. The method according to claim 1, wherein the boom (16) comprises a main boom (17) with a second boom head (26), pivotably supported on a transport device, in particular a rotatable superstructure (14) of the crane (10) about a horizontal hoisting axis, and a boom tip (18) with a first boom head (25), fixed to the main boom (17) either stationarily or pivotably about a horizontal pivot axis, the first load suspension means (21) being guided via the first boom head (25) and the second load suspension means (22) being guided via the second boom head (26), the first load position (O1) being located at the first boom head (25) and the second load position (O2) being located at the second boom head (26).

11. The method according to any one of claims 1 to 10, wherein the first load suspension means (21) is adjustable by a first hoisting winch and the second load suspension means (22) is adjustable by a second hoisting winch, the hoisting winch being controllable by a control unit of the crane (10), and the two load suspension means (21, 22) are preferably adjustable independently of each other.

12. A method according to any one of claims 1 to 11, wherein a deviation of the first luggage suspension means (21) and / or the second luggage suspension means (22) from the vertical is detected and, if the deviation is recognised, an alarm is issued and / or an input request is indicated and / or measures are automatically taken by the control unit, said measures preferably including stopping movement of the boom (16) or taking action to compensate for the deviation.

13. A crane (10) comprising a boom (16), two load suspension means (21, 22) for lifting one common load (40) or different individual loads (40), a first load suspension means (21) adjustable by a first hoisting winch being connected to the boom (16) at a first load position (O1) and a second load suspension means (22) adjustable by a second hoisting winch being connected to the boom (16) at a second load position (O2) remote from the first load position (O1), and a detection device capable of detecting a first load (L1) introduced on the boom (16) at the first load position (O1) and a second load (L2) introduced on the boom (16) at the second load position (O2), A crane (10), characterized in that it comprises a control unit designed to carry out the steps of the method according to any one of the claims 1 to 12.

14. 14. The crane according to claim 13, wherein the boom (16) comprises a main boom (17) with a second boom head (26), pivotably supported on a transport device, in particular a rotatable upper structure (14) of the crane (10) so as to be pivotable about a horizontal pivot axis, and a boom tip (18) with a first boom head (25), fixed to the main boom (17) so as to be stationary or pivotable about a horizontal pivot axis, the first load hoisting means (21) being guided via the first boom head (25) and the second load hoisting means (22) being guided via the second boom head (26), the first load position (O1) being located at the first boom head (25) and the second load position (O2) being located at the second boom head (26).

15. A computer program product comprising instructions which, when the program is executed, cause the steps of the method according to any one of claims 1 to 12 to be carried out by a control unit of a crane (10) according to claim 13 or 14.

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