Mobile crane and method for reducing the load on its jib

Abstract

To provide a mobile crane capable of further reducing a load acting on a non-telescopic main jib at the time of derricking and increasing an overall support load.SOLUTION: The invention relates to a mobile crane (1) comprising a main jib (2) and a counter-jib (6) which can be moved up and down, but not telescoped, by means of at least one main pulling means (7). The main tensile connector (7) extends between a first connection point (2c) in the region of the head end (7a) of the main jib (2) and a second connection point (6b) in the region of the head end (7b) of the counter-jib (6), wherein a first secondary tensile connector (8) and a second secondary tensile connector (9) are arranged between the main tensile connector (7) and the main jib (2), wherein the first secondary tensile connector (8) has a fixed length. In order to further reduce the loads acting on the main jib, in particular during raising and lowering, and to increase the overall bearing load, it is proposed that the length of at least a part of the second secondary tensioning means (9) is variable.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a mobile crane having a non-extendable jib and a counter-jib, the main tensioning means extending between a first connection point in the head region of the jib and a second connection point in the head region of the counter-jib, and a first secondary tensioning means and a second secondary tensioning means disposed between the main tensioning means and the main jib, the first secondary tensioning means being of fixed length. The present invention also relates to a method for reducing the load on the main jib during operation and / or raising and lowering of such a mobile crane. [Background technology]

[0002] It is commonly known that cranes with long main jibs experience a large bending moment on the main jib when it is raised or lowered from its nearly horizontal mounting position. This bending moment is exacerbated by normal forces from the main guying system, which extend obliquely relative to the main jib's longitudinal axis. These normal forces adversely affect the compressive resistance of the bending moment, increasing the deflection of the main jib. To reduce this bending moment, additional guying systems, also known as secondary tensioning means, are used between the main guying system and the main jib.

[0003] German Published Application DE 10 2010 022 256 A1 already describes a derrick crane with a main jib and a derrick or counter-jib. The derrick crane is designed as a crawler crane with a swiveling superstructure, to which the main jib and counter-jib are luffingly attached. The upper ends of the main jib and counter-jib are connected to each other via a main guying device. The main guying device is designed as a luffing cable with a variable length, which allows the main jib to be raised, lowered, and luffed during operation. The luffing cable is integrated into the main guying device and connected to the counter-jib. The length of the luffing cable can be changed by a winch located on the derrick crane's superstructure. Furthermore, an additional counterweight is suspended from the upper end of the counter-jib. In addition to the main stay system, two or three additional stay systems are provided, each of which has a fixed length and is located outside the luffing cable at the main stay system's fixed position, facing each other at the main jib's fixed position. These additional stay systems, each of which has a fixed length, are said to be disadvantageous compared to additional stay systems of variable length in terms of stay characteristics, but are also said to be advantageous due to structural cost and weight savings. The additional stay systems must be designed to increase or slightly decrease the load capacity of the derrick crane when the main jib is positioned at a steeper slope. The additional stay systems must provide adequate support for the main jib when it is raised.

[0004] Furthermore, German Utility Model DE 202 15 179 ∪1 describes a crawler crane with a main jib and a counter jib, each designed as a lattice mast jib. A main guying device extends between the upper ends of the main jib and the counter jib and is adjustable via a guying cable. In one embodiment, the guying cable of the guying cable device extends further parallel to the main guying device and branches off as an additional guying device to the main jib. The additional guying device is therefore designed to have variable length and tension. Alternatively, two additional guying devices, one fore and one behind, are also described.

[0005] Patent document ∪S 3 072 265 discloses another crawler crane with a main jib and a guy support instead of a counter-jib. In this case, too, the main guy support, including the luffing cable, extends between the end of the main jib and the guy support, and a single additional guy support of variable length is provided. For this purpose, the additional guy cable is led from a winch on the crawler crane's superstructure via a deflection sheave on the main guy support to a fixed point on the main jib. German Published Application DE 36 40 068 A1 describes a similar single additional guy cable of variable length, but this additional guy cable is led from a winch on the crawler crane's superstructure via a deflection sheave on the main jib to a fixed point on the main guy cable. Alternatively, a hydraulic cylinder is provided as the additional guy cable. A further similar single additional guy cable of variable length is disclosed in German Patent No. 10 2017 117 121 B4. In this document, winches for additional stay cables are located either on the main jib foot, on the superstructure, or on the counterjib. Summary of the Invention

[0006] It is therefore an object of the present invention to further develop a mobile crane that further reduces the loads acting on the non-telescopic main jib, particularly during luffing, and increases the overall supporting load. Furthermore, a method for reducing the loads acting on the main jib during operation and luffing has been demonstrated.

[0007] The apparatus part of this object is achieved by a vehicle crane having the features of claim 1. The method part of this object is achieved by a method having the features of claim 14. The dependent claims 2 to 13, 15 and 16 each describe advantageous embodiments of the invention.

[0008] According to the present invention, in a mobile crane having a jib that can be raised and lowered by at least one main tensioning means but is not telescopic, and a counter-jib, the main tensioning means extending between a first connection point at the head region of the jib and a second connection point at the head region of the counter-jib, and a first and second secondary tensioning means disposed between the main tensioning means and the main jib, the length of the first secondary tensioning means being fixed, a reduction in the load acting on the non-telescopic jib, particularly during lifting and lowering, is achieved by making the length of at least a portion of the second secondary tensioning means variable. Overall, this reduction is achieved by the combination of a second secondary tensioning means whose length can be varied and a first secondary tensioning means whose length can be varied. This combination is particularly suitable for tensioning long main jibs with lengths of 150 to 250 meters. Advantageously, one first secondary tensioning means and one second secondary tensioning means are provided. This allows the main jib guying arrangement to be optimized both for the tensioning procedure and for subsequent operations. In the present invention, "secondary tensioning means" means a secondary tensioning means consisting of one strand or multiple strands, which are in most cases parallel and therefore not visible in side view.

[0009] The main tensioning means is tensioned for the main jib's raising and luffing. The first and second secondary tensioning means suppress the main jib's sagging caused by its own weight in the attached position and the resulting bending load on the main jib. The variable position and length of the second secondary tensioning means allow optimal adaptation to the load conditions occurring during operation and the main jib's raising and lowering phases. In particular, the critical phase when the main jib is raised substantially horizontally and when the main jib's unsupported length is at its maximum is significantly alleviated. As a result, the present invention facilitates the raising and lowering of long and / or heavy main jibs, particularly when the main jib's length is further extended. Furthermore, in this way, the supporting load for the mobile crane's operation can be further increased. The loss of supporting load compared to a fixed-length secondary tensioning device is compensated for. A significant increase in supporting load is achieved by optimizing the guying length of the first secondary tensioning means during operation. The optimization of the first secondary tensioning means can be either shortened or extended. It is also possible to adjust the length of the second secondary tensioning means while the mobile crane is in operation.

[0010] According to the invention, the second secondary tensioning means has a variable length, which means that for example only a part of its length can be variable or its entire length can be changed. Thus, the second secondary tensioning means can itself be variable in length, at least in part, for example by being configured as a pulley block.

[0011] Preferably, the second secondary tensioning means is configured to be able to vary its length during main jib raising, main jib lowering and / or main jib operation.

[0012] The second secondary tensioning means is arranged to extend between the sixth connection point of the main jib and the fifth connection point of the main tensioning means, and the first secondary tensioning means is arranged to extend between the fourth connection point of the main jib and the third connection point of the main tensioning means.

[0013] Determining the exact locations of the fourth and sixth connection points on the main jib is the responsibility of those skilled in the art, who will provide corresponding specifications based on measurements and calculations. While the configuration of a mobile crane's main jib is highly individualized, the sixth connection point is typically assumed to be located midway between the foot and head of the main jib. This non-limiting estimate is based on the assumption that the weight per meter of the jib is substantially constant between the foot and head, which is usually not the case because the weight of the main jib decreases toward the head of the main jib. Those skilled in the art should take into account the weight difference of the main jib and the resulting normal force curve when determining the locations of the fourth and sixth connection points, particularly to minimize the load on the jib due to bending moments.

[0014] Preferably, the sixth connection point is configured to be located within a range of 30% to 60%, and more preferably 40% to 60%, of the overall length of the main jib when viewed in the longitudinal direction of the main jib.

[0015] Furthermore, it is preferable that the fourth connection point is located within a range of 50% to 90%, and more preferably 70% to 80%, of the overall length of the main jib when viewed in the longitudinal direction of the main jib.

[0016] To allow the length of the second secondary tensioning means to be varied to maintain tension, an adjustment drive allows the length of the second secondary tensioning means to be varied.

[0017] Structurally, the adjusting drive consists of one or more hydraulic cylinders, or the adjusting drive is preferably an adjusting winch associated with an adjusting rope device, if required.

[0018] In a preferred embodiment, the adjusting drive is arranged in the leg area of ​​the main jib or in the area of ​​the sixth connection point of the main jib. In the context of the present invention, the lower end of the main jib, which has a length corresponding to 10% of the total length of the main jib starting from the leg end, is understood to be in the leg area of ​​the main jib.

[0019] In an advantageous configuration, the main jib is composed of multiple overlapping lattice-like mast sections with no joints between the base and head. Basically, the main jib can be of one-piece or multi-piece construction. In a particularly preferred configuration, the main jib is not telescopic and its length cannot be changed by a corresponding drive. Changing its length by adding or removing individual parts or segments is outside the scope of the telescopic function of the present invention. For example, the jib can have an independent, in this respect, integral girder extending between the base and head of the main jib. Alternatively, the main jib can comprise at least two girders connected together. At least one girder can be, for example, a box girder as a hollow body, or a lattice girder with a corresponding open or closed lattice. Furthermore, mixed forms and combinations of the above are also possible.

[0020] In a known manner, the mobile crane has an upper structure rotatably arranged on a lower carriage, on which the main jib is configured to be luffingly supported via legs.

[0021] The length of at least a portion of the main tensioning means can be changed for the purpose of raising and lowering the main jib.

[0022] Furthermore, the present invention provides a method for reducing loads on the main jib of a mobile crane during operation or lifting, characterized by extending a first length of a second secondary tensioning means between the main jib and the main tensioning means at the mobile crane's mounting position to a second length at the mobile crane's operating position during the lifting process. Of course, this method requires that the length of the second secondary tensioning means be measured in addition to adjustment. In this way, in addition to being able to "keep tension" the main tensioning means and the second secondary tensioning means during changes in the main jib's position, the variable length of the second secondary tensioning means provides the option to adjust the desired compensation for sag caused by the jib's own weight and vertical forces to changing conditions, such as the orientation of the main jib or the height of the suspended load. Using corresponding control means, an adjustable compensation force can be transmitted through the secondary tensioning means to optimally reduce the load, effectively suppressing jib deflection.

[0023] Advantageously, the first length is extended to the second length when the main jib reaches a luffing angle of 75 degrees or more.

[0024] Advantageously, the length of the second secondary tensioning means is varied by force control, path control, continuous, constant, linear, stepped and control taking into account at least one of the following characteristics of the mobile crane: bearing load point, load radius, counterweight radius, bearing load curve.

[0025] In other words, the tension applied to the second secondary tensioning means can be controlled or readjusted, for example, by detecting the changing force on the secondary tensioning means from the main jib. Thus, an increase in force can be compensated for by a counteracting tension, and a decrease in force can be reduced accordingly. Similarly, the movement occurring during a force change can be used to determine and apply a tension level to be used for compensation purposes. This control can react linearly to any changes in tension, or it can change the applied tension level only if the measured parameter goes out of range. Overall, the control is preferably constant and continuous, to minimize the reaction time to changing influences. [Brief explanation of the drawings]

[0026] Exemplary embodiments of the invention will be explained in more detail with reference to the following description, in which: The figures are shown diagrammatically.

[0027] [Figure 1] Figure 1 shows a side view of the mobile crane in its installed position. [Figure 2] FIG. 2 shows the mobile crane of FIG. 1 in a raised operating position. [Figure 3] FIG. 3 shows an enlarged view of a portion of FIG. 1 from the area of ​​the first and second secondary tensioning means in the first embodiment. [Figure 4] FIG. 4 shows an enlarged view of a portion of FIG. 1 from the area of ​​the second secondary tensioning means in the second embodiment. [Figure 5] FIG. 5 shows an enlarged view of a portion of FIG. 1 from the area of ​​the second secondary tensioning means in a third embodiment. [Figure 6] FIG. 6 shows an enlarged view of a portion of FIG. 1 from the area of ​​the second secondary tensioning means in the fourth embodiment. [Figure 7] FIG. 7 shows an enlarged view of FIG. 1 from the area of ​​the second secondary tensioning means in the fifth embodiment.

[0028] FIG. 1 shows a side view of a mobile crane 1 according to the present invention, which is mounted on a ground surface U and has a long main jib 2 extending in its longitudinal direction X. The main jib 2 of the mobile crane 1 is in an attached position extending substantially parallel to and at a fixed distance from the ground surface U. The main jib 2 is approximately 150 to 250 meters long and is designed as a seamless lattice mast or lattice mast girder. This lattice mast or lattice mast girder is not telescopic and has a fixed length when assembled. In a typical configuration, the main jib 2 is composed of multiple lattice mast sections 2a, which are connected to each other in a bending-resistant manner or detachably bolted to each other and arranged one behind the other. Each lattice mast section 2a is typically composed of multiple steel profiles, such as upper chords, lower chords, cross beams, and diagonal beams, welded together, and has a rectangular or triangular cross section.

[0029] Furthermore, in the illustrated embodiment, the mobile crane 1 includes an undercarriage 3 with crawler tracks 4. The mobile crane 1 is therefore a crawler crane. An upper structure 5 supporting the main jib 2 is arranged on the undercarriage 3, and the upper structure 5 is rotatable relative to the undercarriage 3 about a substantially vertical axis Z. The main jib 2, extending in the longitudinal direction X, is supported by its legs 2b on the upper structure 5 and is connected via a horizontal luffing axis Y to the horizontal luffing axis Y for luffing in a vertical plane during operation. Figure 1 shows the mobile crane 1 in a lowered, substantially horizontal mounting position. A first connection point 7a, connected to the main tensioning means 7, is arranged in the region of the tip 2c of the main jib 2, opposite the legs 2b. The first connection point 7a is therefore located in the region of the tip 2c that extends from the outermost end of the tip 2c toward the legs 2b in the longitudinal direction X by a maximum of 2 m, preferably 1 m. Depending on the configuration, this connection of the main tensioning means 7 can be fixed, deflected, or a combination thereof. The main tensioning means 7 is connected to the tip 6b of the counter jib 6 at the second connection point 7b on the opposite side. This counter jib 6 is also called a superlift jib or a derrick mast. Therefore, the mobile crane 1 described here is also called a derrick crane or a derrick crawler crane. In this case, depending on the configuration, the connection of the tensioning means 7 can be fixed, deflected, or a combination thereof. The counter jib 6 is typically designed as a lattice mast girder consisting of the aforementioned lattice mast section 6c, and its legs 6a are attached to the superstructure 5 so that they can luff about a separate horizontal luffing axis W.

[0030] The main tensioning means 7 is further provided with a third connection point 7c. This third connection point 7c is located between the first connection point 7a and a fifth connection point 7d (described later). At this third connection point 7c, a first secondary tensioning means 8 is connected to the main tensioning means 7, i.e., fixed and / or deflected. The main jib 2 is further supported by a support column to the main tensioning means 7 by this first secondary tensioning means 8. For this purpose, the first secondary tensioning means 8 is connected to the opposite side of the main jib 2 at a fourth connection point 2d, i.e., fixed and / or deflected at this position. The connection range of the fourth connection point 2d is 50% to 90%, preferably 70% to 80%, of the length of the main jib 2 in the longitudinal direction X and in the direction of the tip 2c of the main jib 2 (the value indicated in % relates to the length of the main jib 2 starting from the lower end of the leg 2b of the main jib 2). The first secondary tensioning means 8 also extends from the main jib 2 at a substantially right angle in the direction of the primary tensioning means 7. Here, "right angle" refers not only to a right angle but also to an angle ranging from 80 degrees to 100 degrees, preferably from 89 degrees to 91 degrees. Furthermore, the length of the first secondary tensioning means 8 is fixed. This fixed length is designed according to the imminent load case of the mobile crane 1, and is therefore determined and adjusted before operation of the mobile crane 1. The length of the first secondary tensioning means 8 cannot be changed while the mobile crane 1 is in operation.

[0031] This first secondary tensioning means 8 can be designed as a cable made of any material, for example a steel cable, a synthetic cable, a chain, a linkage, or a combination of one, several or all of these elements. Thus, the first secondary tensioning means 8 can be formed continuously from only one of these elements, or from a series of elements of the same or different types, detachably or fixedly connected to one another.

[0032] Furthermore, a fifth connection point 7d is disposed on the main tensioning means 7. This fifth connection point 7d is located between the third connection point 7c and the second connection point 7b. At this fifth connection point 7d, a second secondary tensioning means 9 is connected to the main tensioning means 7, i.e., fixed or deflected. The main jib 2 is further supported by this second secondary tensioning means 9. For this purpose, the second secondary tensioning means 9 is connected to the main tensioning means 7 on the opposite side at a sixth connection point 2e, i.e., fixed or deflected at this position. The second secondary tensioning means 9 therefore extends from the main jib 2 at an approximately right angle to the main tensioning means 7. Here, "perpendicularly" is intended to include not only a right angle but also an angle range of 80 to 100 degrees, preferably 89 to 91 degrees. The connection range of the sixth connection point 2d is 30% to 70%, preferably 40% to 60%, of the length of the main jib 2 when viewed in the longitudinal direction X of the main jib 2 and in the direction of the tip end 2c of the main jib 2 (the values ​​shown in % are the lengths starting from the lower ends of the legs 2b of the main jib 2). In either case, the fourth connection point 2d is located between the sixth connection point 2e and the tip end 2c of the main jib 2. Furthermore, the length of the second secondary tensioning means 9 is variable. This variable length can be changed during the raising of the main jib 2, the lowering of the main jib 2, or the operation of the main jib 2.

[0033] This second secondary tensioning means 9 can be designed as a cable made of any material, for example a steel cable, a synthetic cable, a chain, a linkage, or a combination of one, several or all of these elements. Thus, the second secondary tensioning means 9 can be formed continuously from only one of these elements, or from a series of elements of the same or different types, detachably or fixedly connected to one another.

[0034] The counter-jib 6 is connected to the superstructure 5 via a rear stay system 10 or to a typical additional jib 11, also called A-block or support block, which is connected to this location in the region of the luffing axis W. This additional jib 11 is supported on the superstructure 5 via additional luffing cables, not shown. The superstructure 5 supports a counterweight 12 at the opposite end of the main jib 2. An additional counterweight 14, also called a superlift, is suspended from the tip 6b of the counter-jib 6 via a suspension 13.

[0035] Furthermore, an auxiliary jib 15 is further disposed on the upper end of the tip 2c of the main jib 2. The auxiliary jib 15 can luff relative to the main jib 2, and a luffing support 15a is disposed in the area where the auxiliary jib 15 is connected to the main jib 2. Of course, the auxiliary jib 15 can also be firmly fixed to the main jib 2 at a predetermined angle. Essentially, the auxiliary jib 15 is optional.

[0036] To raise the main jib 2 from its horizontal mounting position shown in FIG. 1 for luffing during operation and then lower it from its substantially vertical operating position to its substantially horizontal mounting position, the main tensioning means 7 is designed to be variable in length relative to the section between the tip 2c of the main jib 2 and the tip 6b of the counter-jib 6, as well as relative to the second secondary tensioning means 9. For this purpose, a pulley-block-like rope system, also including a tensioning cable, called a luffing cable 7e or adjusting drive 9a, is usually provided. To lengthen or shorten the luffing cable 7e or the tensioning cable, a winch (not shown) is usually provided, preferably located on the superstructure 5 or the leg 6a of the counter-jib 6. In a corresponding manner, depending on the configuration of the luffing cable 7e or adjusting drive 9a, the main tensioning means 7 and the second secondary tensioning means 9 are fixed or deflected at the second or fifth connection points 7b and 7d, respectively. For raising, luffing, and lowering, the counter-jib 6 is fixed in an operating position at a predetermined angle on the superstructure 5 via a stay system 10 and an additional jib 11. The main jib 2, extending in a substantially horizontal attachment position S1, can be raised, luffed, and lowered vertically by corresponding changes in the length of the main tensioning means 7, in particular its integral luffing cable 7e. In parallel with the engagement of the main tensioning means 7 with the head 2c of the main jib 2, a tension in the form of a first compensating force K1 is transmitted to the main jib 2 by a first secondary tensioning means 8, and a tension in the form of a second compensating force K2 is transmitted to the main jib 2 by a second secondary tensioning means 9. The two compensating forces K1, K2 serve to reduce or compensate for loads, in particular bending moments, resulting from the weight of the main jib 2 not supported between the first connection point 7a and its foot 2b. The control required for this can be implemented in various ways, for example force control or path control, continuous, constant, linear or stepwise form, and combinations of one, several or all of these elements, etc. In this case, the control can take into account further features such as the individual bearing load points and bearing load curves of the mobile crane 1 and the respectively adopted rotation of its superstructure 5 relative to the undercarriage 3.

[0037] The first compensation force K1 is caused by the preselected fixed length of the first secondary tensioning means 8, the position of the fourth connection point 2d of the main jib 2, the position of the third connection point 7c of the main tensioning means 7, and the tension of the main tensioning means 7.

[0038] The same applies to the second compensating force K2, whose length LM can be varied by its attachment position. The second compensating force K2 is also affected by the position of the sixth connection point 2e of the main jib 2 and the fifth connection point 7d of the main tensioning means 7, as well as the tension of the main tensioning means 7. The desired length LM of the second secondary tensioning means 9, and thus the desired magnitude of the second compensating force K2, is preferably adjusted via an adjusting drive 9a (not shown). The second secondary tensioning means 9 essentially consists of the adjusting drive 9a, a secondary support 9b, and any necessary fixing points and deflectors. In this case, the secondary support 9b can be designed as a cable made of any material, a steel cable, a synthetic fiber cable, a chain, a linkage, or a combination of one, several, or all of these elements. Therefore, the secondary tensioning means 9b can be formed continuously from only one of these elements, or it can be configured as a combination of the same or different types of elements arranged one behind the other, detachably or fixedly connected. The adjusting drive 9a can be designed as a tensioning winch that acts on the secondary rigging device 9b directly, via a deflector, or via a rigging system. In this case, the tensioning winch is electrically or hydraulically driven. It is also possible to design the adjusting drive 9a as a hydraulic piston / cylinder unit or tensioning cylinder that acts on the secondary rigging device 9b directly, via a deflector, or via a rigging system. The adjusting drive 9a, tensioning winch, or tensioning cylinder can be located directly on the main jib 2 in the area of ​​the sixth connection point 2e, on the legs 2b of the main jib 2, or on the superstructure 5.

[0039] In the context of the present invention and all illustrated embodiments, the lower end of the main jib 2, which has a length corresponding to 10% of the overall length of the main jib 2, is understood to be in the region of the leg 2b of the main jib 2. In the case of a main jib 2 designed as a lattice mast, the lower end of the main jib 2 comprises at least a so-called foot piece connecting the main jib 2 to the superstructure 5 and a so-called first intermediate piece adjacent to it and then adjacent to the sequence of further lattice mast parts 2a of the main jib 2, depending on the length of the foot piece.

[0040] FIG. 2 shows the main jib 2 of the mobile crane 1 of FIG. 1 in a very steeply raised operating position for a load-handling operation. Also shown symbolically is a load L being lifted by a lifting cable 16. The main jib 2 is raised from its attached position to its operating position via the main tensioning means 7, first secondary tensioning means 8, and second secondary tensioning means 9 by appropriately shortening the luffing cable 7e of the main tensioning means 7. The second secondary tensioning means 9, which has a variable length, is extended from a length LM at the attached position to a length LB at the operating position during or at the end of the lifting process. During the lifting process of the main jib 2, the relative length between the foot 2b and head 2c of the main jib 2, extending parallel to the ground U, decreases, thereby reducing the bending load on the main jib 2. Therefore, the compensation force K2 can also be reduced by extending the second secondary tensioning means 9 during the lifting process of the main jib 2. The second compensation force K2 is primarily used to increase the supporting load of the mobile crane 1. This extension begins when the main jib reaches a luffing angle of more than 75 degrees from the horizontal, i.e., when the main jib reaches a steep angle. At this time, the adjustment force required is minimized. In theory, it would also be possible to perform the adjustment immediately after the mobile crane 1 stops raising and switches to loading operation.

[0041] By lengthening the second secondary tensioning means 9, the stay length (length LB) of the second secondary tensioning means 9 can be optimally adjusted to suit the respective load case during the loading operation, thereby significantly increasing the supporting load of the mobile crane 1 during the loading operation. Of course, this also involves determining the length LM or LB.

[0042] In parallel with the second secondary tensioning means 9, the main jib 2 continues to be supported at a constant length by the first secondary tensioning means 8.

[0043] In order to lower the main jib 2 from the operating position to the attached position, the second secondary tensioning means 9 must be shortened beforehand to the length LM. The remaining steps are carried out in the same manner as above, but in the reverse order.

[0044] FIG. 3 is an enlarged partial view of the first and second secondary tensioning means 8, 9 in FIG. 1 , showing the second secondary tensioning means 9 in the first embodiment. In this embodiment, the adjusting drive 9a is designed as a hydraulic piston / cylinder unit or hydraulic cylinder. The hydraulic cylinder has one end fixed to the main jib 2 and its longitudinal extension extending toward the main tensioning means 7 at a substantially right angle to the longitudinal direction X of the main jib 2. This right angle includes not only right angles, but also angles ranging from 80 to 100 degrees, preferably 89 to 91 degrees, relative to the longitudinal direction X. The opposite rod end of the hydraulic cylinder is fixed to a secondary guy member 9b of the second secondary tensioning means 9. This secondary guy member 9b is a component of the second secondary tensioning means 9 and can be designed as a cable made of any material, a steel cable, a synthetic fiber cable, a chain, a linkage, or a combination of one or all of these elements. The secondary stay device 9b can therefore be formed continuously from only one of these elements or from a series of elements of the same or different types connected one behind the other in a detachable or fixed manner, so that the length LM or LB of the secondary tensioning means 9 can be adjusted as required by extending or retracting the hydraulic cylinder.

[0045] The secondary stay device 9b of the second secondary tensioning means 9 can be made up of three chain sections arranged one behind the other, while the main tensioning means 7 can be made up of a linkage or rods arranged one behind the other. The hydraulic cylinder of the adjusting drive 9a can be fixed on the housing side and can cross the struts between the lower chords of the main jib 2.

[0046] FIG. 4 shows a further enlarged view of the cross section of FIG. 1 in the region of the second secondary tensioning means 9, which is configured in a second embodiment. In this embodiment, too, the adjusting drive 9a is designed as a hydraulic piston / cylinder unit, i.e., a hydraulic cylinder. However, in this case, the hydraulic cylinder is fixed to the main jib 2 in the region of the housing-side leg 2b and extends with its longitudinal direction approximately parallel to the longitudinal direction X of the main jib 2 toward the head 2c of the main jib 2. The opposite rod-side end of the hydraulic cylinder is fixed to a secondary branch 9b of the second secondary tensioning means 9. This secondary branch 9b is a component of the second secondary tensioning means 9 and is designed as a cable or a steel cable. The secondary stay device 9b, which starts from the rod end of the hydraulic cylinder, first extends parallel to the longitudinal extension line X of the main jib 2 and is deflected by approximately 90 degrees towards the main tensioning means 7 via a deflection pulley at the sixth connection point 2e, where it is fixed to the main tensioning means 7 at the fifth connection point 7d. This allows the length LM or LB of the secondary tensioning means 9 to be adjusted as needed by extending or retracting the hydraulic cylinder.

[0047] Figure 5 shows a further enlarged view of the cross section in the region of the second secondary tensioning means 9 of Figure 1, the second secondary tensioning means 9 being formed in a third embodiment. This third embodiment substantially corresponds to the second embodiment shown in Figure 4 and described above, and reference is made to the above description wherever possible. Whereas in the second embodiment the hydraulic cylinder, the deflecting pulley and the secondary stay device 9b extending therebetween are arranged approximately centrally with respect to the cross section of the main jib 2, in the third embodiment the hydraulic cylinder, the deflecting pulley and the secondary stay device 9b extending therebetween are arranged lower with respect to the cross section of the main jib 2.

[0048] Figure 6 is an enlarged view of a part of Figure 1 in the region of the second secondary tensioning means 9 in a fourth embodiment. In this embodiment, the adjustment drive 9a is designed as a hydraulically or electrically driven adjusting winch. For the points common to the first to third embodiments, please refer to the above explanation. The adjusting winch is fixed in the region of the leg 2b of the main jib 2. The secondary stay rope 9b of the second secondary tensioning means 9 can be wound up and unwound from the winch drum of the adjusting winch and is designed as a cable or steel rope. Starting from the adjusting winch, the secondary stay 9b initially extends parallel to the longitudinal extension X of the main jib 2, is deflected by approximately 90 degrees towards the main tensioning means 7 via a deflection pulley at the sixth connection point 2e, and is then deflected via another deflection pulley to form an adjusting rope 9c between the sixth connection point 2e and the fifth connection point 7d of the main tensioning means 7, which is then secured to the main jib 2 at the sixth connection point 2e after one or more rope passes at the fifth connection point 7d. This allows the length LM or LB of the second secondary tensioning means 9 to be adjusted as required by winding or unwinding the secondary stay 9b. It is obvious that the length of the adjusting rope 9c may be only a part of the adjusted length LM or LB, respectively.

[0049] FIG. 7 is a further enlarged view of the cross section in the region of the second secondary tensioning means 9 of FIG. 1, where the second secondary tensioning means 9 is formed in a fifth embodiment. This fifth embodiment substantially corresponds to the aforementioned fourth embodiment shown in FIG. 6, and reference is made to the above description wherever possible. While in the fourth embodiment the secondary stay device 9b extends from the adjusting winch to the adjusting cable device 9c via the sixth connection point 2e on the main jib 2, in the fifth embodiment the secondary stay device 9b is guided obliquely upward and forward by the adjusting winch via the seventh connection point 2f with the deflecting pulley 9d in the direction of the tip 2c of the main jib 2 and the main tensioning means 7, and extends to the adjusting cable device 9c at the fifth connection point 7d on the main tensioning means 7. Therefore, the seventh connection point 2f is located forward of the sixth connection point 2e when viewed in the direction of the tip 2c of the main jib 2. The secondary stay device 9b terminates at the fifth connection point 7d on the main tensioning means 7. The length of the adjustable rope device 9c can also have an overall length of the adjusted length LM or LB, respectively.

[0050] In this case, the secondary stay device 9b of the second secondary tensioning means 9 can be made up of three chain segments arranged in a row, while the main tensioning means 7 can be made up of a link mechanism or rods arranged in a row, and the adjusting cable device 9c can be fixed to the main jib 2 via three chain segments 9e arranged in a row.

[0051] It is also possible to design the adjusting drive 9a in the form of an electric or hydraulically driven spindle or an electric linear drive. [Explanation of symbols]

[0052] 1. Mobile crane 2 Main jib 2a Lattice mast section 2b Legs 2b Tip 2d Fourth connection point 2e 6th Junction 2F 7th Junction 3 Lower Carriage 4. Crawler Truck 5 Superstructure 6 Counter Jib 6a feet 6b Tip 6c Lattice mast part 7 Main pulling means 7a First connection point 7b Second connection point 7c Third Junction 7d 5th Junction 7e Luffing Cable 8. First secondary tension means 9 Second secondary tension means 9a Adjustment drive 9b Secondary strut arrangement 9c Adjustment cable arrangement 9d deflection pulley 9e Chain part 10 Strapping device 11 Additional Jib 12 Counterweight 13. Suspension 14 Additional counterweight 15 Auxiliary Jib 15a Roughing Support 16 Lifting Cable K1 First compensation force K2 Second compensation force L load LB Length at operating position LM Initial length at mounting position S1 mounting position S2 operating position U Ground W Roughing Axis X Longitudinal direction Y Roughing Axis Z vertical axis

Claims

1. A mobile crane (1) comprising a main jib (2) that can be raised and lowered by at least one main tensioning means (7) but does not extend or retract, and a counter jib (6), the main tensioning means (7) extends between a first connection point (7a) in the area of ​​the tip (2c) of the main jib (2) and a second connection point (7b) in the area of ​​the tip (6b) of the counter jib (6); first and second auxiliary tensioning means (8) and (9) are arranged between the main tensioning means (7) and the main jib (2); the first auxiliary tensioning means (8) has a fixed length, and at least a part of the second auxiliary tensioning means (9) has a variable length. Mobile crane (1).

2. the second auxiliary tensioning means (9) is capable of changing its length during the raising of the main jib (2), the lowering of the main jib (2) and / or the movement of the main jib (2); A mobile crane (1) according to claim 1 or 2.

3. characterised in that the second secondary tensioning means (9) extends between a sixth connection point (2e) on the main jib (2) and a fifth connection point (7d) on the main tensioning means (7). A mobile crane (1) according to claim 1 or 2.

4. characterised in that the first secondary tensioning means (8) extends between a fourth connection point (2d) on the main jib (2) and a third connection point (7c) on the main tensioning means (7), A mobile crane (1) according to any one of claims 1 to 3.

5. the sixth connection point (2e) is located in the range of 30% to 60%, preferably 40% to 60%, of the total length of the main jib (2) in the longitudinal direction (X) of the main jib (2); A mobile crane (1) according to claim 3 or 4.

6. the fourth connection point (2d) is located in the range of 50% to 90%, preferably 70% to 80% of the total length of the main jib (2) in the longitudinal direction (X) of the main jib (2); A mobile crane (1) according to any one of claims 3 to 5.

7. the second auxiliary tensioning means (9) can be varied in length by an adjusting drive (9a), A mobile crane (1) according to any one of claims 1 to 6.

8. The adjusting drive device (9a) is a hydraulic cylinder. A mobile crane (1) according to claim 7.

9. characterised in that the adjusting drive (9a) is an adjusting winch which cooperates, if necessary, with an adjusting rope device (9c), A mobile crane (1) according to claim 7.

10. characterised in that the adjusting drive (9a) is arranged in the region of the legs (2b) of the main jib (2) or in the region of the sixth connection point (2e) of the main jib (2), A mobile crane (1) according to any one of claims 7 to 9.

11. The main jib (2) is characterized in that it consists of a plurality of lattice-like mast sections (2a) arranged back to back with each other, extending seamlessly between its leg sections (2b) and its tip section (2c). A mobile crane (1) according to any one of claims 1 to 10.

12. the crane has a superstructure (5) pivotably arranged on a lower carriage (3) and on which the main jib (2) is supported via its legs (2a) so as to be able to be raised and lowered, A mobile crane (1) according to any one of claims 1 to 11.

13. characterised in that at least a part of the main tension means (7) is variable in length; A mobile crane (1) according to any one of claims 1 to 12.

14. A method for reducing loads acting on the main jib (2) of a mobile crane (1) according to any one of the preceding claims 1 to 13 during the performance of movements and / or lifting / lowering, comprising: a first length (LM) of the second auxiliary tensioning means (9) between the main jib (2) and the main tensioning means (7) in the installation position of the mobile crane (1) is extended to a second length (LB) in the operating position of the mobile crane (1) during the raising of the mobile crane (1); method.

15. the first length (LM) is extended to the second length (LB) when the main jib (2) reaches a hoisting angle of 75 degrees or more; 15. The method of claim 14.

16. the length (LB or LM) of the second auxiliary tensioning means (9) is varied by a control operating according to at least one of the following methods: force control, path control, continuous, constant, linear, stepwise, and / or taking into account at least one of the characteristics of the mobile crane (1), such as the load support point, the load radius, the counterweight radius, the load curve, etc.

16. The method of claim 15.

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