Method for monitoring the load on a 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 present invention relates to a method for monitoring the load (payload, load capacity, load rating) of a crane according to the preamble of claim 1, a crane according to the preamble of claim 13 and 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 from multiple cranes simultaneously and move them in a coordinated tandem or multi-crane operation. However, with certain crane types, it is also possible to lift loads simultaneously using two lifting ropes on only one crane. Such a two-hook operation allows for the lifting and moving of two different loads by only one crane, in addition to the lifting and moving of one common load.

[0003] One typical application of a two-hook lifting and moving machine is to rotate and reorient objects or loads when they are transported in a different position from the position where they will later be used and assembled at the installation site. The load must be lifted and rotated in the air with as little diagonal pulling force as possible. When there are no additional cranes on the construction site or the available space is limited, such load rotations can sometimes be performed in a controlled manner with only one crane in a two-hook operation.

[0004] One example of a crane type that allows such 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, while 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 hereinafter referred to as load locations. The current load introduced into the boom by the lifting ropes at the corresponding load location 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, from the partial loads received by each lifting rope), and, on the other hand, from the dead load of the lifting ropes (which will be ignored in the following discussion).

[0006] Cranes with only one lifting rope (one-hook operation) typically use a load monitoring or load torque limiting function 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 obtained 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 to 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, to be lifted, while the other load lifting means or the other load position must be unloaded, only in this way can a sufficiently accurate load indication and load factor indication or monitoring be provided.

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

[0010] SUMMARY OF THE INVENTION 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] That is, 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, and other suspension means may also be provided, such as eyebolts or crossbeams.

[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 loads can be partial loads of a single load or object lifted together, or the loads of loads or objects lifted individually (as already mentioned, the static loads of the load suspension means also contribute to the introduced load, but this will not be explicitly mentioned below).

[0014] Since the two load positions are spatially separated from one another and, in particular, have different load radii, different permissible load ranges or maximum permissible loads are preferably applied to the load positions. To take this into account during load monitoring, the present invention provides for detecting a first load currently applied to the boom at a first load position and detecting a second load currently applied to the boom at a second load position. 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 that forms the basis for or performs load monitoring according to the present invention.

[0015] The load monitoring according to the present invention is based on a calculation method based on a series 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., the horizontal axis) and a second axis (e.g., the 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 is irrelevant, so the distance between the two load positions selected in the display along the first axis is not particularly important. Preferably, the distance can be selected arbitrarily (e.g., the distance can be set to 1 and / or be unitless) to appropriately simplify the calculation.

[0016] In this coordinate system, a first correlation (first deterministic correlation) is defined between the maximum (i.e., maximum allowable) load at the first load position and the maximum allowable load at the second load position at the maximum load (maximum load rate) at the first load position. In the following, the latter (maximum allowable load at the second load position at the maximum load at the first load position) is called the "residual maximum load". Thus, a maximum allowable 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), the load at the second load position must not exceed the defined remaining maximum load.

[0017] In the above coordinate system, a second correlation (second deterministic correlation) is also defined between the maximum (i.e., maximum allowable) load at the second load position and the maximum load (hereinafter also referred to as the "remaining maximum load") still allowable at the first load position at the maximum load (maximum load rate) at the second load position. 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 correlation and the second correlation are simultaneously satisfied. In particular, these determined correlations represent a functional relationship (in the simplest case, a linear relationship) in the coordinate system 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, for example, known load tables for one hook operation can be used. Alternatively, it is conceivable that the above-mentioned variables are calculated by the control unit within the scope of the method according to the invention, for example, depending on the current boom position. Thus, for example, the maximum load in the first load 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, and 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 by only two points in the coordinate system, i.e. the two detected loads).

[0021] Furthermore, 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 the intersection of the third correlation and a perpendicular line to the first axis that passes through the first intersection. 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 present invention, the positions (i.e., their load values) of the first intersection point and the determined second intersection point along the second axis 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] The 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 operation. Alternatively or additionally, the control unit may perform an automatic intervention in the current operation of the crane, in particular stopping the current crane operation or performing a reverse or compensating movement that brings the crane back into an acceptable 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 the 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 the above-mentioned variables (maximum load value, remaining maximum load value, first intersection point) defined in the coordinate system itself (e.g. from a corresponding stored load table or by a model taking into account in particular the current crane configuration and position), 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 that intersect or include the respective load values ​​in a coordinate system.

[0026] Since the first axis includes the two load positions and is dimensionless, the distance between the load positions on the first axis or the midpoint between the load positions is not of particular importance. Therefore, it is primarily the load values ​​at the two load positions, especially the intersection (i.e., the values ​​on the second axis), that are important 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 location is fully utilized (i.e., the applied load corresponds to the maximum load at the second load location). This is accompanied by a certain maximum remaining load at the first load location. This can have a value equal to or greater than 0 (i.e., no load is applied at the first load location or a load cannot be lifted by the first load suspension means), especially if the first load location corresponds to a larger load radius than the second load location. The second limit load combination occurs when the load at the first load location is fully utilized (i.e., the applied load corresponds to the maximum load at the first load location). This is accompanied by a certain maximum remaining load at the second load location. This can have a value equal to or greater than 0 (i.e., a certain load can still be applied at the second load location or a load can be lifted by the second load suspension means), especially if the first load location corresponds to a larger load radius than the second load location.

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

[0030] A second intersection point determined from the detected loads currently acting on the two load locations provides information on whether the current load combination corresponds to an allowable load combination that is between the aforementioned limit load combinations. Furthermore, a comparison of the intersection points provides information on 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, cooperating load limits of the entire system or the implementation of appropriate measures if unacceptable load ranges are reached, allowing for continuously monitored and safe two-hook operation.

[0032] Furthermore, optionally a display of the current load and the load limits associated with 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, 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, exceeding of the current maximum load at the first load location by the detected first load and 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 performed assuming the current crane operation continues. For example, when the boom and / or load suspension means moves, the above-defined variables (maximum load, remaining maximum load, first intersection) may change. This will cause a change in the ratio or distance between the first intersection and the second intersection. Furthermore, when the boom and / or 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 load suspension means continues to move can provide an early warning before an unacceptable load range is reached and / or allow action to be taken, such as slowing down or stopping the crane movement.

[0035] In one possible embodiment, the maximum allowable load at the first load position at the maximum load (maximum load rate) at the second load position, i.e., the maximum remaining load at the first load position, is considered to be zero. That is, if the maximum load is reached at the second load position, a load should not be hoisted at the first load position. Preferably, the maximum remaining load at the second load position is greater than zero, that is, 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-described method is implemented, for example, in a crane including a hoistable main boom with a boom head having a lifting rope and a second load position, and a boom tip attached to the main boom, the boom head having a lifting rope and a first load position. Because the first load position has a longer distance or a larger load radius from the main boom pivot point, the maximum load at the first load position is lower than the maximum load at the second load position.

[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 above-mentioned coordinate system.

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

[0038] This leads to the following simplifications, among others:

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

[0040] Here, the third linear relationship corresponds to the 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] This gives the first intersection point from the intersection point of the first connecting line and the second connecting line in the coordinate system. The second intersection point is the intersection point of the third connecting 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 intersection points, they are naturally expressed by corresponding mathematical relationships. In particular, there are corresponding equations for the load values ​​at the first and second intersection points, which include the maximum load and the remaining maximum load at the first and second load positions.

[0043] This also makes it 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 at 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 envisaged that for the lifting of one common load, maximum loads are defined for both the first and second load locations, both of which correspond to the load value of the first node. This is based on the knowledge that the defined correlation (representing a connecting line in the simplest case) always passes through the first node at the maximum common load rate (i.e., individually, neither the first nor the second load location fully utilizes the maximum load, but in combination the full common load is achieved, and the load at either load location cannot be increased without reducing the load at the other load location).

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

[0046] If the detected first load or the detected second load is greater than the current permissible load in effect at the time of this operation, an unacceptable load range exists 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, the first load is determined by detecting a first force on a first boom guy rope, and the second load is determined by detecting a second force on a second boom guy rope, the first and second forces preferably being detected by sensors disposed on the first and second guy ropes and transmitted to the control unit. The first guy rope may be an adjustable luffing jib guying mechanism 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 mechanism 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, a current allowable load at the first load position and a current allowable load at the second load position are calculated from the first node and the determined second node. These determined current allowable 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 allowable 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 automatically intervening in the current operation of the crane.

[0049] In a further possible embodiment, it is envisaged that the above-mentioned current permissible loads at the first and second load positions are determined by adding the load values ​​of the first and second loads respectively to the difference between the load values ​​at the first and second intersection points, thereby making it possible to reliably determine and monitor the load limits that apply to the current load distribution for the current load situation in 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 a measure of the overall load factor due to the current load combination. In particular, the ratio of the load values ​​can be expressed as a percentage. This means that this is not the individual load utilization at each load location, but the overall, or combined, load factor that observes the entire load situation at the two load locations.

[0051] In a further possible embodiment, 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 the issuance of a warning by the control unit and / or intervention in the current operation of the crane, as described above. That is, in addition to monitoring compliance with the currently valid load limits for the current load combination based on the two nodes, separate load monitoring of the loads acting at each of the two load positions is performed. This can be done in a conventional manner, for example, by 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 will not be 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) comprising the first load position relative to a main boom comprising 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 is the case when a luffing jib is assembled to the main boom because the respective boom heads have the same distance regardless of the luffing jib's swivel angle or the main boom's hoist angle).

[0055] In a further possible embodiment, the boom may include a main boom with a second boom head, the main boom being pivotally supported on the crane's transport device around a horizontal pivot axis, and a boom tip with a first boom head, the boom tip being fixed to the main boom either stationary or pivotally supported around a horizontal pivot axis, with 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 location is at the first boom head and the second load location is at the second boom head. The boom may be a lattice boom. The boom may be supported by guy blocks or a derrick boom. The transport device may include a rotatable upper structure to which the main boom is articulated, and the upper structure may be 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 that 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 automatically taken by the control unit. Thus, in addition to the load monitoring according to the invention in two-hook operation, diagonal tension force monitoring on the two load suspension means is carried out, which is preferably carried out by the same control unit (although of course several separate control units can also be provided). Such measures preferably include stopping the boom (e.g. the main boom and / or the luffing jib adjustable relative to the main boom) or taking 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 detected, a diagonal tension of the load suspension means in question is occurring (in many cases, the load suspension means do not both have diagonal tension or both have diagonal tension), which is preferably important to compensate for. For this purpose, preferably, at least one actuator (e.g., a hydraulic cylinder or a cable winch of an adjustable guy cable) that actuates the boom or boom sub-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 tension on one load suspension means is usually accompanied by a corresponding diagonal tension on the other load suspension means, so that in the simplest case it is sufficient to monitor the diagonal tension on only one of the two load suspension means. Naturally, it is also possible to monitor the diagonal tension 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 the diagonal tension of both load suspension means.

[0061] The invention further relates to a crane comprising a boom, two load suspension means for lifting one common load or different individual loads, the first load suspension means being adjustable by a first hoisting winch and connected to the boom at a first load position, and the second load suspension means being adjustable by a second hoisting winch and 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 configured to carry out the method according to the invention (i.e. the steps mentioned above that are associated with or executable by the control unit), where the same properties and advantages are obtained as with the method according to the invention, and therefore a repetitive description will not be given. In particular, all 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 which, when executed, cause the steps of the above-mentioned method (in any embodiment) associated with the control unit to be carried out by the control unit of the crane according to the invention. Preferably, the computer program product can be operated with conventional crane control or load torque limiting functions, and therefore no retrofitting of hardware components is required. Here, as mentioned above, conventional load torque limiting functions can be incorporated.

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

[0065] [Figure 1] 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; FIG. [Figure 2] FIG. 2 illustrates an exemplary representation of a coordinate system and variables defined therein for load monitoring in accordance with the present invention. [Figure 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. [Figure 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] 2 is a side view of the crane according to FIG. 1 in a diagonal tension situation. FIG. [Figure 7] 1 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; FIG. DETAILED DESCRIPTION OF THE INVENTION

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

[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 able to hoist about a horizontal hoisting 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 suspension means 21, 22, which in the illustrated exemplary embodiment each include a lifting rope and a load hook secured thereto. The luffing jib 18 has a first boom head 25 through which the lifting rope of the first load suspension means 21 is guided. A first load L1 is introduced to the boom 16 at a first load location O1 at the first boom head 25 via the first load suspension means 21. The main boom 17 has a second boom head 26 through which the lifting rope of the second load suspension means 22 is guided. A second load L2 is introduced to the boom 16 at a second load location O2 at the second boom head 26 via the second load suspension means 22.

[0069] The luffing jib 18 is supported by first guy ropes 31, which in particular include adjustable guy cables between the two masts (guy blocks) of the luffing jib 18, and the guy cables allow the luffing jib 18 to be rotated 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 able to be wound up and unwound. The main boom 17 is supported by second guy ropes 32, and in particular include adjustable guy cables arranged between the masts (guy blocks) articulated to the upper structure 14 and the upper structure 14, and the guy cables allow the main boom 17 to be raised and lowered relative to the upper structure 14 around a hoisting axis.

[0070] 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, for example rotated, by appropriate adjustment of the load suspension means 21, 22. When one load 40 is jointly lifted, a load distribution occurs between the two load suspension means 21, 22, and specific partial loads L1, L2 are introduced at each load position O1, O2.

[0071] In two-hook operation, two load suspension means 21, 22 are operated while simultaneously receiving loads at two different load locations O1, O2. A characteristic of two-hook operation is that a load applied at the first load location O1 affects the maximum allowable load at the second load location O2, and vice versa. If the load rate at one load location O1, O2 increases, for example due to a change in outreach (radius) or a shift in the center of gravity, the maximum allowable load at the other load location O2, O1 must be reduced.

[0072] This can be illustrated by the following example: if a maximum load (e.g. 40 t) 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 (0 t), the load at the second load location O2 may increase up to the maximum permissible load, i.e. the maximum load at the second load location O2 (e.g. 100 t).

[0073] Here, load monitoring according to the present invention provides calculations for determining the current allowable loads acting together for the individual load positions O1, O2. These can be used to monitor crane operation, but preferably also to display the current load and load factor, as well as the allowable load, on a display unit (e.g., a crane monitor). This applies independently of the exact implementation of the crane 10. Here, the calculations will be described with reference to specific exemplary embodiments, but the concept according to the present 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 may be stored, for example, in a corresponding load table and may vary depending on the current boom position. Furthermore, in the following exemplary embodiment, at the maximum load rate of the luffing jib 18 (first load position O1), 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 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 L1 at the first load position O1. 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 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 interpolated, as known for example from conventional one-hook operations.

[0076] Now, to determine a common effective load limit for a two-hook operation, i.e. for the particular load combination currently being lifted (which may 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] Figures 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 locations O1 and O2 are spaced apart 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 is max (=load limit value at the second load position O2 alone) is shown, and the maximum load L1 max (=load limit value at the first load position O1 alone) is shown, and here, 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 v In this exemplary embodiment, the maximum remaining load L1 at the first load position O1 is v is zero, so it lies on the horizontal axis.

[0079] Here, these values ​​are grouped together to form a limit load combination 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 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 line g2).

[0080] As can be seen from Figure 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 of the first intersection point S1 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 The four load limits L1 max , L1 v , L2 max , and L2 v and in the exemplary embodiment considered here, according to the following equation: TIFF0007804018000001.tif13170

[0081] L S1 It can be seen that σ ≡ ...

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

[0083] From this, a specific maximum allowable load combination can be directly derived, which is shown in Figure 4 by the dashed-dotted connecting lines. Since each maximum allowable load combination has a connecting line passing through the first intersection S1 between the current allowable loads effective at the joint, the maximum allowable load combination with a connecting line running parallel to the horizontal axis corresponds exactly to the case where uniform loads are applied. Therefore, the current allowable load Lg effective at the joint associated with this maximum allowable load combination is akt,max have values ​​of the same 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 allowable load Lg valid when lifting a load 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, when different individual loads are lifted by the two load suspension means 21, 22, or when a single load 40 is lifted jointly with an off-center center of gravity or a diagonal pulling force, the loads L1 and L2 acting on the two load locations O1 and O2 will have different magnitudes. 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 and L2) is observed in a coordinate system (see FIG. 5), a second intersection point S2 is obtained between this third connecting line g3 and a line gs that is perpendicular to the horizontal axis and extends through the first intersection point S1.

[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 S2 is the load value L at the first intersection S1 S1 (See Figure 5), the current load combination is max and L2 max is within the allowable load range (assuming that the load does not exceed

[0087] For the current load combination (Fig. 5), the total load factor A of the crane Kran is the load value L of the first intersection S1 and the second intersection S2 S1 and L S2 is obtained from the ratio of TIFF0007804018000002.tif13170

[0088] Load value L at the first intersection S1 and the second intersection 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 difference. akt,max and L2 akt,max can be calculated (see the double-headed arrow in Figure 5). TIFF0007804018000003.tif8170TIFF0007804018000004.tif8170

[0089] Now, starting from g3, the value The fourth connecting line g4 of the calculated maximum allowable load combination, obtained by shifting the line by TIFF0007804018000005.tif6170, passes through the first intersection point S1.

[0090] Referring to FIG. 5, in the two-hook operation, 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 load ranges shown in Figure 5 are taken into account, the impermissible load ranges for the current load combinations shown in Figure 5 will not be recognized. Even in the limit case (maximum permissible load combination with connecting line g4), the limit value L1 applied in the joint akt,max and L2 akt,max is the maximum load L1 applied to the load positions O1 and O2 individually. max and L2 max It is much lower than the standard L S2 ≦L S1 This takes into account the actual load situation in a 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, the individual load factors at each load position are 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 the 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 when the respective limits are reached.

[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 similar to that shown in FIGS. 2 to 5, i.e., the positions of the current loads L1 and L2, their respective limit values ​​L1 and L2, max , L2 max , L2 v , and the corresponding connecting 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 merely for the purpose of illustrating the calculation method according to the invention. This graphical representation is based on mathematical equations and relationships involving the various variables mentioned above. Therefore, it is not necessarily necessary to define or provide as functions, for example, the actual connecting lines g1, g2, g3, g4 in the control unit.

[0097] Furthermore, when a common load is lifted by two hooks at different load positions, the diagonal tension must also be taken into account, especially when rotating the jointly lifted load, and this 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 tension and the load suspension means 21 has an "outward" diagonal tension.

[0098] Such diagonal tensions affect the load indication, load monitoring, cable tensions, and the supporting structure of the crane 10 or boom 16. Since the load monitoring of the crane 10 is based, inter alia, on a vertically suspended load (without diagonal tensions), the control unit calculates erroneous loads L1, L2 from the forces measured by the detection devices, particularly from current loads L1, L2 that are too low if sensors for determining the forces are located in the guy ropes. When a diagonal inward tension 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 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 may be independent or may be part of the load monitoring according to the invention.

[0101] In one embodiment of the diagonal tension monitoring system, forward / backward 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 whether one or more lifting ropes are in a vertical position (e.g., in the form of a plan view of the respective load positions O1, O2 on the boom 16). If a diagonal tension is present, it is conceivable that the crane 10 automatically corrects the diagonal tension by 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 be performed automatically by the control unit (i.e., without the intervention of the crane operator).

[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 is visible, equipped with sheaves along which the lifting ropes are guided. 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 any deviation of the lifting rope from the vertical to the side (i.e., left / right) and any deviation parallel to the undulating surface (i.e., forward / backward). Naturally, alternative detection devices are also conceivable. Optionally, a 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 Second Boom Head 31 First guy rope 32 Second guy rope 40 Received Baggage 50 Sensor system for detecting diagonal tensile force g1 First connecting line g2 Second connecting line g3 Third connecting line g4 4th connecting line L1 First detected load L2 Second detected load L1 akt,max Current permissible load at the first load position L2 akt,max Current permissible load at the second load position Lg akt,max Common effective current load capacity L1 max Maximum load at 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), the 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 to the boom (16) at a first load position (O1) and a second load suspension means (22) carrying a load introduced to the boom (16) at a second load position (O2) remote from the 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 load at each of the load positions (O1, O2), and the following variables are used: The maximum load (L1) at the first load position (O1) ｍａｘ ) and the maximum allowable load (L2) at the second load position (O2) at the maximum load rate 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 rate 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) in the defined coordinate system is determined; 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, preferably including issuing a warning and / or intervening in the current operation of the crane (10) by a control unit; A method characterized by:

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

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 rate at the second load position (O2). ｖ ) is a first connecting line (g1) between A second linear relationship is ｍａｘ ) and the maximum allowable load (L2 ｖ ) and 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) to the first axis that passes through the first intersection point (S1). The method of claim 1.

4. For the lifting of one common load (40), the maximum load (Lg 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) is greater than the maximum load (Lg ａｋｔ，ｍａｘ 2. The method of claim 1, wherein if the difference is greater than 0.5, action is automatically taken, said action preferably comprising issuing a warning by the control unit and / or intervening in the current operation of the crane (10).

5. 2. The method of claim 1, 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 detected by sensors preferably 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 ａｋｔ，ｍａｘ ), measures are automatically taken, 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) at the first load position (O1) 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 ａｋｔ，ｍａｘ 2. The method of claim 1, wherein the second load (L2) is determined by adding 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 ｍａｘ 2. The method of claim 1, wherein if the difference is greater than 0.5, action is automatically taken, said action preferably comprising issuing a warning by the control unit and / or intervening in the current operation of the crane (10).

9. 2. The method according to claim 1, wherein the first load position (O1) is movable relative to the second load position (O2), in particular by operating 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), 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. 2. The method according to claim 1, wherein the boom (16) comprises a main boom (17) having a second boom head (26), the main boom (17) being supported on a transport device, in particular a rotatable upper structure (14), of the crane (10) so as to be pivotable about a horizontal luffing axis, and a boom tip (18) having a first boom head (25), the boom tip (18) being fixed to the main boom (17) either stationary or pivotably about a horizontal pivot axis, the first load suspension means (21) being guided via the first boom head (25), the second load suspension means (22) being guided via the second boom head (26), the first load location (O1) being located at the first boom head (25), and the second load location (O2) being located at the second boom head (26).

11. 2. The method of claim 1, 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 winches being controllable by a control unit of the crane (10), and the first and second load suspension means (21, 22) are preferably adjustable independently of each other.

12. 2. The method of claim 1, wherein a deviation of the first load suspension means (21) and / or the second load suspension means (22) from the vertical is detected and, if the deviation is recognized, 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), wherein a first load suspension means (21) adjustable by a first hoisting winch is connected to the boom (16) at a first load position (O1), and a second load suspension means (22) adjustable by a second hoisting winch is 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 onto the boom (16) at the first load position (O1) and a second load (L2) introduced onto the boom (16) at the second load position (O2), A crane (10) comprising a control unit designed to carry out the steps of the method according to claim 1.

14. 14. The crane according to claim 13, wherein the boom (16) comprises a main boom (17) with a second boom head (26), the main boom (17) being supported on a transport device, in particular a rotatable upper structure (14) of the crane (10) so as to be pivotable about a horizontal hoisting axis, and a boom tip (18) with a first boom head (25), the boom tip (18) being fixed to the main boom (17) either stationary or pivotable about a horizontal pivot axis, the first load suspending means (21) being guided via the first boom head (25), the second load suspending 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. When the program is executed, the method of claim 1 The method is carried out by a crane (10) comprising a boom (16), two load suspension means (21, 22) for lifting one common load (40) or different individual loads (40), wherein a first load suspension means (21) adjustable by a first hoisting winch is connected to the boom (16) at a first load position (O1), and a second load suspension means (22) adjustable by a second hoisting winch is 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 onto the boom (16) at the first load position (O1) and a second load (L2) introduced onto the boom (16) at the second load position (O2). A computer program containing instructions to

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