Mobile crane and methods for reducing the load on its boom

Abstract

Mobile crane (1) with a boom (2) that can be raised and lowered and is non-telescopic by means of at least one main traction element (7) and a counter boom (6, 6'), the main traction element (7) running between a first attachment point (7a) in the area of ​​a head (2b) of the boom (2) and a second attachment point (7b) in the area of ​​a head (6b, 6b') of the counter boom (6, 6'), the boom (2) having a third attachment point (8a) located between the first attachment point (7a) and its foot (2a) opposite the head (2b), characterized in that a secondary traction element (8) runs between the third attachment point (8a) via a seventh attachment point (8c) on the main traction element (7) and an eighth attachment point (8d) in the area of ​​the foot (2a) of the main boom (2).

Description

[0001] The invention relates to a mobile crane with a boom that can be erected and lowered and non-telescopically supported by at least one main traction mechanism, and a counter-jib. The main traction mechanism extends between a first connection point in the region of a head of the counter-jib and a second connection point in the region of a head of the counter-jib. Furthermore, the invention relates to a method for reducing a load occurring in the boom during operation and / or during erection and lowering.

[0002] In addition to the type of undercarriage (wheeled or crawler), mobile cranes differ primarily in the design of their boom, which can be vertically luffed around the base support. Telescopic designs, i.e., length-adjustable designs, typically feature a luffing mechanism, where the luffing is based on a linear drive generating a compressive force. Non-telescopic designs, such as those based on truss or lattice girders, usually have guying, where the deadweight component of a tensile force transmitted in the area of ​​the boom head by a main traction device enables the boom to be raised and lowered.

[0003] For long lengths, the deadweight of such a boom leads to high loads even during its erection and lowering phases. The unsupported section between its base and the main tension member acting in the head area creates a corresponding bending moment. Added to this is the normal force component from the main tension member, which extends obliquely to the boom's longitudinal axis, which adversely adds to the compressive force component of the bending moment and actually increases it due to the deflection.

[0004] German patent application DE 10 2018 114 832 A1 describes a large crane for the assembly of wind turbines. For a hub height of 200 m on a wind turbine, a hook height of 210 m is required for the large crane. The large crane is designed as a crawler crane with a main boom luffing from a superstructure, which is divided approximately in the middle into a first section and a second section. The first and second sections are hingedly connected to each other for raising and lowering the main boom. A long auxiliary jib is also luffing from the main boom. For raising, lowering, and luffing the main boom, a main traction mechanism is attached to the end near a boom head of the first section of the main boom. Opposite, the main traction mechanism is supported by a counter-jib head, which is pivoted on the superstructure of the large crane, which can pivot about a vertical axis.A tensile force applied to the main traction device causes the first section of the main boom to be raised, lowered, or luffed accordingly. Auxiliary traction devices are also provided, spaced apart between the first section of the main boom and the main traction device. The arrangement of the auxiliary traction devices counteracts the sagging caused by the boom's own weight and the associated bending load on the main boom. The fixed position and length of the auxiliary traction devices represents a compromise between the load cases occurring during operation and during the erection and lowering phases of the main boom. An increase in boom length means that its own weight inevitably increases, and the resulting loads reduce the remaining load capacity for operation.In view of the increasing demand for ever larger working radii and increasing boom lengths, the currently known designs cannot adequately meet the aforementioned load cases.

[0005] Furthermore, a comparable mobile crane with a so-called superlift device is already known from German patent application DE 101 55 006 A1. A superlift device essentially consists of a load-increasing additional counterweight suspended from the head of the counterjib. The horizontal distance between the rotation axis of the superstructure and the center of gravity of the additional counterweight is referred to as the additional counterweight radius. Similarly, the horizontal distance between the rotation axis of the superstructure and the center of gravity of a load to be handled is the load radius. When performing a lifting task, the load radius when picking up a load is usually different from the load radius when setting the load down. To respond to this, the additional weight radius can be adjusted, for example, by retracting or extending a telescopic rod between the additional weight and the superstructure.To complete an upcoming lifting task, the crane operator receives support via a display of the load radius, the additional counterweight radius, the currently loaded load, and the load capacity table corresponding to the mobile crane's setup status. This load capacity table, or load capacity diagram, shows the permissible upper and lower limits of the load to be handled for a given load radius and specified size of the additional counterweight, depending on the additional counterweight radius.

[0006] In view of these observations, such a mobile crane and such a large crane still offer room for improvement with regard to their booms.

[0007] Furthermore, German utility model DE 202 15 179 U1 discloses a crawler crane with a main boom and a counter-boom, each designed as a lattice boom. An adjustable main guy wire runs between the upper ends of the main boom and the counter-boom. In one embodiment, an additional adjustment cable runs in a zigzag pattern between the main guy wire and the main boom, with two pivot points on each of the main guy wire and the main boom. Neither of these pivot points is located near the base of the main boom.

[0008] In the case of comparable cranes known from the German laid-open specifications DE 10 2017 117 121 A1 and DE 10 2010 022 256 A1, one or more central support ropes are shown between the main boom and the main guying.

[0009] Furthermore, German patent application DE 25 06 914 A1 already shows a telescopic boom of a crane with a multitude of holding ropes. The telescopic boom typically consists of a base box and several retractable and extendable telescopic boxes. A retractable support is hinged to one foot of the base box, from whose head the holding ropes run to the heads of the base box and each of the telescopic boxes.

[0010] Furthermore, Japanese Patent Application JP 2011 - 219 213 A discloses another crawler crane with a lattice boom main boom and a lattice boom counter jib, between whose respective heads a main traction device is tensioned. A secondary traction device is tensioned parallel to this, which is attached to the main boom and the counter jib at a distance from the respective heads of the main boom and the counter jib.

[0011] The present invention is therefore based on the object of further developing a mobile crane to further reduce the loads acting on its non-telescopic boom, particularly during erection and lowering, and to increase its overall load capacity. Furthermore, a method is to be presented to reduce the loads occurring in the boom during operation and / or during erection and lowering.

[0012] The device part of this object is achieved by a mobile crane having the features of claim 1 and claim 2. The solution to the method part of this object consists in a method having the features of claim 14. Advantageous embodiments of the invention are specified in the respective dependent claims 3 to 13 and 15.

[0013] Thus, the invention proposes a mobile crane with a boom that can be erected and lowered and non-telescopically by at least one main traction means and with a counter-jib, the main traction means runs between a first connection point in the region of a head of the boom and a second connection point in the region of a head of the counter-jib, wherein the boom has a third connection point located between the first connection point and its foot opposite the head and a secondary traction means runs between the third connection point and a fourth connection point in the region of the head of the counter-jib and the region for the third connection point, seen in the longitudinal direction of the boom, lies between 40% and 60% of the length of the boom or, alternatively, the secondary traction means runs between the third connection point via a seventh connection point on the main traction means and an eighth connection point in the region of the foot of the main boom.The secondary traction device is designed to transmit a compensating force to the boom. In other words, the boom is connected to the counter-boom or the boom foot via an additional secondary traction device. By coupling this to a section of the boom located between the foot and the first connection point, the deflection of the boom due to its own weight can be at least partially compensated.

[0014] The resulting advantage is that the additional connection of the boom to the counter-jib or the boom base via the secondary traction device leads to a beneficial reduction in bending loads. In particular, the critical phase during erection and lowering of the boom into a substantially horizontal orientation, in which the unsupported length of the boom is at its greatest, is significantly relieved. As a result, the invention enables easier erection and lowering of long and / or heavy booms, with further increases in the boom length being achievable. Furthermore, the load capacity for operating the mobile crane can be further increased in this way.

[0015] Determining the exact location of the third tie-down point between the base and the first tie-down point, fifth tie-down point, sixth tie-down point, seventh tie-down point, and eighth tie-down point of the boom is the responsibility of the specialist, who will make the appropriate specifications based on measurements and / or calculations. Despite the sometimes highly individual designs of mobile crane booms, it can be assumed that the third tie-down point will usually be located in a section of the respective boom centrally between the base and the first tie-down point.This non-limiting assessment is based on the assumption that the weight of the boom per meter is essentially constant between its base and the first tie-in point, so that the section of the boom extending between the base and the third tie-in point and the section extending between the third and first tie-in points have approximately the same weight. Any differences in the weight and the resulting normal force distribution of the boom and / or the bending moment resulting from the overhang from the first tie-in point to its free head end will be taken into account by the expert when determining the position of the third tie-in point, fifth tie-in point, sixth tie-in point, seventh tie-in point, and eighth tie-in point in order to achieve the lowest possible load on the boom, particularly from bending moments.

[0016] According to a preferred development of the basic inventive concept, the main traction means and also the secondary traction means can be variable in length. This means both the ability to change its length only in sections, for example, and its overall length. Thus, the main traction means or secondary traction means could be designed, at least in part, in the manner of a pulley system to enable inherent length variation. In this context, for example, a fixed connection at one of its ends to the first or third connection point of the boom, or the second or fourth connection point, would be conceivable. Alternatively or additionally, the connection of the main traction means and the secondary traction means to the counter-boom could be designed to facilitate deflection thereon, whereby the length variation could then be based, for example, on shortening by winding.

[0017] In addition to keeping the main tension member and the secondary tension member under tension during a change in the boom's alignment, the aforementioned length-adjustable secondary tension member offers the possibility of adapting the desired compensation for deflection caused by the boom's dead weight and normal force to changing conditions. These can include, for example, the boom's alignment and the height of the attached load. Using appropriate control, it is then possible to transmit the compensation force, which can be adjusted for optimal load relief, via the secondary tension member in order to effectively counteract the respective deflection of the boom.

[0018] The invention provides that the boom can preferably extend without joints between its base and its head. In this context, the boom according to the invention itself is understood as the main boom and thus not as a collective term for a combination of such a boom and a jib. Even if the boom according to the invention can be equipped with an additional and articulated jib, the inventive designs and arrangements of the main traction means and the secondary traction means fundamentally relate to the boom in the sense of a jointless main boom. In principle, it is also conceivable to equip the jib additionally or only with the secondary traction means according to the invention.

[0019] In principle, it is envisaged that the boom can be constructed in one or more parts. The boom is particularly preferably designed to be non-telescopic, so that its length cannot be changed via a corresponding drive. Any changes to its length due to the attachment or removal of individual sections or segments do not fall under telescoping within the meaning of the invention. For example, the boom can have a single and therefore one-piece support which extends between the base and the head of the boom. Alternatively, the boom can also have a series of at least two supports. The at least one support can be, for example, a box girder in the sense of a hollow body or a lattice girder with a correspondingly open or closed framework. Furthermore, mixed forms and combinations of the above are also conceivable.

[0020] In order to achieve the greatest possible flexibility in use, it is provided that the mobile crane according to the invention can have an upper carriage arranged rotatably on an undercarriage, wherein the boom is then supported on the upper carriage via its base in a luffing manner.

[0021] Based on this, it is considered advantageous if the counter-jib is supported on the superstructure. Preferably, this support is movable, allowing for appropriate adjustments to the counter-jib's alignment.

[0022] With a view to the advantageous length adjustment of the main traction device and the secondary traction device, the superstructure or the base of the counter-jib can be equipped with a winch drive, to which the main traction device and the secondary traction device are then operatively connected. This means, for example, that the secondary traction device can be at least partially wound up and unwound, in particular to vary the level of the required compensation force.

[0023] As a further option for compensating for deflection due to the dead weight and normal force of the boom, it is considered advantageous within the scope of the invention if, in addition to the first connection point for the main traction means and the third connection point for the secondary traction means, the boom also has at least a fifth connection point, which can then be coupled to an auxiliary traction means. Said auxiliary traction means is then connected to the main traction means at its opposite end. Preferably, the fifth connection point can be located between the first connection point and the third connection point, so that the auxiliary traction means extends in a region between the boom head and the secondary traction means, between the boom and the main traction means.

[0024] It is advantageous that the fifth tie-in point is located between the first tie-in point and the third tie-in point on the boom.

[0025] In one design of the mobile crane, an additional counterweight is suspended from the counter jib.

[0026] Depending on the configuration of the mobile crane, the counter jib is either a superlift jib or an A-frame. Typically, an A-frame is used on a mobile crane alone without a superlift jib, or a superlift jib is used only in conjunction with the A-frame. When an A-frame is configured without a superlift jib, the main traction device and, depending on the design, the secondary traction device are connected to the head of the A-frame. When a superlift jib is configured with an A-frame, the main traction device and, depending on the design, the secondary traction device are connected to the head of the superlift jib.

[0027] The mobile crane according to the invention now presented allows for trouble-free erection and lowering despite its extremely long and / or heavy boom. In particular, the design and arrangement of the auxiliary traction device contributes to a highly advantageous reduction in load on the boom. By changing the compensation force transmitted via the auxiliary traction device, adaptation to all operating and / or setup conditions of the mobile crane is possible, in which optimal support of its boom can always be achieved. Furthermore, the invention leads to an increase in the load capacity of the mobile crane, thus expanding its overall range of applications.

[0028] Furthermore, the invention is directed to a method with which the load occurring in the boom of a mobile crane having a counter-jib can be reduced during its operation and / or during the raising and lowering of the boom. In addition to a first connection point located in the area of ​​a head opposite its base and coupled to a main traction device, The boom is connected via a third connection point located between the first connection point and its base. According to the invention, a compensating force, in particular a controllable one, is transmitted to the boom by a secondary traction device coupled to this third connection point. The mobile crane can particularly preferably be the mobile crane according to the invention described above.

[0029] The resulting advantages have already been explained in more detail in connection with the mobile crane according to the invention, so that in order to avoid repetition, reference is made here to the corresponding explanations.

[0030] The method according to the invention further provides for a control of the tensile force to be introduced, which can be carried out in at least one of the following ways: - force-controlled, - path-controlled, - continuously, - constant, - linear, - gradually.

[0031] In other words, the tensile force to be applied can be controlled or adjusted, for example, by detecting the changing force on the secondary traction device from the boom. This way, an increasing force can be compensated for by a counteracting tensile force, while a decreasing force reduces the tensile force accordingly. Similarly, the movements resulting from a change in force can be used to determine a level of tensile force to compensate for and apply it accordingly. This control system can react linearly to any change with a change in the tensile force, or it can only change the level of the tensile force to be applied if the measured parameters move outside a certain range.Overall, the control can preferably be constant and / or continuous in order to achieve the shortest possible response times to changing influences. Alternatively or in addition to the above, at least one of the following features of the mobile crane can be taken into account when controlling the pulling force: - load points, - load radius, - Counterweight radius, - Load curve.

[0032] This essentially means taking into account the load capacity of the mobile crane depending on the orientation of its boom in a vertical plane and around a vertical axis relative to the undercarriage.

[0033] An embodiment of the invention is explained in more detail in the following description. The schematic drawings show: Fig. 1 a mobile crane in a starting position of its boom in a side view, Fig. 2 the mobile crane Fig. 1 in an upright position of its boom compared to the initial position in an otherwise unchanged representation, Fig. 3 the mobile crane Fig. 1 and Fig. 2 in load operation in otherwise the same representation, Fig. 4 the mobile crane Fig. 1 in a first alternative embodiment in otherwise the same representation, Fig. 5 the mobile crane Fig. 1 in a second alternative embodiment in otherwise the same representation, Fig. 6 the mobile crane Fig. 1 in a third alternative embodiment in otherwise the same representation and Fig. 7 the mobile crane Fig. 2 in a fourth alternative embodiment in otherwise the same representation.

[0034] The Fig. 1 shows a mobile crane 1 according to the invention standing on a base U, which comprises a long boom 2 extending in its longitudinal direction X. The boom 2 shown here as an example is clearly designed as a jointless lattice mast girder, the telescoping of which gives it a fixed length. The boom 2 can be composed of a single girder or several girders rigidly connected to one another. The mobile crane 1 also has an undercarriage 3, which in the example shown here has a crawler track 4. Arranged on the undercarriage 3 is an upper carriage 5 which supports the boom 2 and is rotatable about a vertical axis Z relative to the undercarriage 3.The boom 2, which extends in its longitudinal direction X, is supported by its base 2a on the superstructure 5 and is pivoted vertically via a horizontal luffing axis Y in order to erect, lower, or luff the boom 2 during operation. A first attachment point 7a is arranged in the area of ​​a head 2b opposite the base 2a of the boom 2, which is coupled to a main traction mechanism 7. Depending on the design, such a coupling can be a fastening, a deflection, or a combination thereof. The main traction mechanism 7 is coupled opposite to a head 6b of a counter-boom 6 at a second attachment point 7b. This counter-boom 6 is also referred to as a superlift boom or derrick mast. Here, too, depending on the design, such a coupling can be a fastening, a deflection, or a combination thereof. The counter boom 6 is usually also designed as a lattice mast girder and is mounted on the superstructure 5 in a luffing manner.A further third connection point 8a is arranged in a region of the boom 2 located between the first connection point 7a and the base 2a, which is coupled, i.e., fastened and / or deflected, to a secondary traction means 8. The region for the third connection point 8a lies, viewed in the longitudinal direction X of the boom 2, between 25% and 75%, preferably between 40% and 60%, of the length of the boom 2. The secondary traction means 8 is coupled, i.e., fastened and / or deflected, opposite the head 6b of the counter-boom 6 in a fourth connection point 8b. Thus, the main traction means 7 and also the secondary traction means 8 each extend between the boom 2 and the counter-boom 6. The counter-boom 6 is connected via a rear guy 9 to the superstructure 5 or to a conventional additional counter-boom 6' which is hinged thereon and is referred to as an A-frame or support frame.In the setups with counterjib 6 and counterjib 6', the secondary traction device 8 is attached only to the head 6a of the counterjib 6. At its end opposite the boom 2, the superstructure 5 carries a counterweight 10. An additional counterweight 12, also referred to as a superlift, is also suspended from the head 6b of the counterjib 6 via a suspension 13.

[0035] In order to erect the boom 2, luff it during operation, and later lower it, the main traction means 7 and the secondary traction means 8 are designed to be adjustable in length with respect to the section between the head 2b of the boom 2 and the head 6b of the counter-boom 6. Pulley-type reeving is usually provided for this purpose. Accordingly, the main traction means 7 and the secondary traction means 8 are thus each fastened and deflected at their second and fourth connection points 7b, 8b, respectively. For erection, luffing, and lowering, the counter-boom 6 is fixed in its operating position at a preselected angle to the superstructure 5 via the guying 9 and a support. The length of the main traction means 7 and the secondary traction means 8 is changed via winches arranged on the superstructure 5 or on the base 6a of the counter-boom 6.The boom 2, extending in its essentially horizontal starting position S1, can be vertically erected, luffed, and lowered again by a corresponding change in the length of the main traction mechanism 7. Parallel to this, a tensile force in the form of a compensation force K is transmitted to the boom 2 by the secondary traction mechanism 8 in order to reduce or compensate for the loads, in particular bending moments, resulting from the dead weight of the boom 2, which is otherwise unsupported between the first connection point 7a and its base 2a. The control required for this can be implemented in a variety of ways, including, for example, force- or displacement-controlled, continuous, constant, linear, or stepped. The control can take into account other features, such as the individual load points and / or load curves of the mobile crane, along with the respective rotation of its superstructure 5 relative to the undercarriage 3.

[0036] This tensile force is preferably applied to the secondary traction device 8 via a tensioning winch. For this purpose, the tensioning winch is electrically or hydraulically driven. It is also conceivable that hydraulic tensioning cylinders could be used for this purpose, acting directly, via cable drives, or by clamping the secondary traction device 8.

[0037] In the context of the present invention and with all exemplary embodiments, the area of ​​the base 2a of the boom 2 is understood to mean the lower end of the boom 2 with a length corresponding to 10% of the length of the entire boom 2. In the case of a boom 2 designed as a lattice mast, the lower end of the boom 2 thus comprises at least the so-called base section, with which the boom 2 is articulated to the superstructure 5, and the adjoining so-called first intermediate section, to which the sequence of lattice mast sections of the boom 2 then adjoins. Even if, in the case of a short boom 2, the base section and the first intermediate section exceed the defined 10% of the length of the entire boom 2, they still form the area of ​​the base 2a of the boom 2.

[0038] In the Fig. Figure 2 shows one of the erection positions S2 of the mobile crane 1, whose boom 2 was erected via the main traction mechanism 7 and the secondary traction mechanism 8 in the manner described above. Due to the relative length of the boom 2 changing parallel to the ground U, the resulting changing bending moments were taken into account by the control system, whereupon a corresponding adjustment of the compensation force K was made via the secondary traction mechanism 8 in a manner not further discernible.

[0039] The Fig. 3 illustrates an operating position S3 of the mobile crane 1, in which its boom 2 has been erected in a relatively steep position in order to transport a picked-up load L. In the operating position S3, the boom 2 has a significantly shorter unsupported length, particularly compared to the initial position S1, whereby the compensation force K transmittable via the secondary traction device 8 is now primarily used to increase its load capacity.

[0040] The Fig. 4 shows the mobile crane 1 again in its already Fig. 1. The mobile crane 1 has an alternative configuration in which its boom 2 has a further fifth connection point 11a, which is located in an area between the first connection point 7a and the third connection point 8a. To further relieve the load on the boom 2, an auxiliary traction means 11 is coupled to the fifth connection point 11a, which is connected at its opposite end to the main traction means 7 at a sixth connection point 11b. Starting from the sixth connection point 11b, the auxiliary traction means 11 extends at a suitable angle, in particular at a right angle, to the main traction means 7.The auxiliary traction means 11, which thus extends between the fifth connection point 11a and the sixth connection point 11b on the main traction means 7, essentially suspends the dead weight of the boom 2 acting between the first connection point 7a and the third connection point 8a from the main traction means 7, which, despite its natural flexibility with respect to the load thus introduced into it, contributes to a further partial compensation of the bending moments in the boom 2. In principle, it is also possible to use an auxiliary traction means 11 at a different location or to use more than one auxiliary traction means 11 arranged at intervals along the boom 2. A first alternative could provide for the third connection point 8a for the individual secondary traction means 8 to be moved closer to the head 2b of the boom 2 and for the fifth connection point 11a to be provided in an area between the third connection point 8a and the foot 2a of the boom 2.

[0041] The Fig. 5 shows the inventive mobile crane 1 from Fig. 1 in a second alternative embodiment in otherwise the same representation. In comparison to the Fig. 1, the course of the secondary traction element 8 has been chosen differently. The secondary traction element 8 is at a comparable location as in the Fig. 1 is attached to the boom 2 in its third connection point 8a. From here, the secondary traction device 8 is not directed towards the head 6b of the counter boom 6 as in the Fig. 1, but as from the auxiliary traction device 11 Fig. 4 is guided at an angle of less than 90°, which is inclined in the direction of the counter-jib 6, to a seventh connection point 8c on the main traction means 7. This angle can also be 90° if required. At the seventh connection point 8c on the main traction means 7, the secondary traction means 8 is deflected and guided further towards the base 2a of the boom 2, where it is coupled in the area of ​​the base 2a at an eighth connection point 8d. Starting from the eighth connection point 8d, the secondary traction means 8 also forms an angle of less than 90° to the boom 2.Since here too, in order to adjust the length of the secondary traction device 8, the secondary traction device 8 is designed like a pulley block with a corresponding reeving at least between the seventh connection point 8c and the eighth connection point 8d, the secondary traction device 8 is deflected in the eighth connection point 8d on the one hand and guided back once or multiple times in the direction of the seventh connection point 8c on the one hand, and on the other hand further in the direction of the associated winch on the superstructure 5 or on the base 6a of the counter jib 6. In principle, it is also possible to arrange a winch in the area of ​​the base 2a in order to adjust the length of the secondary traction device 8 and thus replace the previously described pulley block-like design.

[0042] In the Fig. 6 is the inventive mobile crane 1 from Fig. 5 in a third alternative embodiment, which is essentially the same as the embodiment according to Fig. 5. In order to achieve a further relief of the boom 2, comparable to the Fig. 4 an auxiliary traction means 11 is coupled between a fifth connection point 11a on the boom 2 and an opposite sixth connection point 11b on the main traction means 7. The auxiliary traction means 11 extends from the sixth connection point 11b at right angles to the main traction means 7. The fifth connection point 11a is located in the area between the third connection point 8a and the foot 2a of the boom 2. Compared to the Fig. In the alternative shown in Figure 5, the third connection point 8a has been shifted further toward the head 2b of the boom 2. In principle, it is also possible to use an auxiliary traction device 11 at a different location or more than one auxiliary traction device 11 arranged at intervals along the boom 2.

[0043] The Fig. 7 shows the mobile crane 1 according to the invention from Fig. 2 in a fourth alternative embodiment in otherwise the same representation. Contrary to the representation in the Fig. 1 to 6, the mobile crane 1 is equipped without a counter jib 6 designed as a superlift jib and thus only with a counter jib 6', also referred to as an A-frame, with a base 6a' and a head 6b'. Here, too, the main traction device 7 runs, as in the previous Fig. 1 to 6 starting from the area of ​​the foot 2a of the boom 2 to the opposite head 2b of the boom 2. The course of the secondary traction means 8 is that from the Fig. 5. The secondary traction device 8 is in a comparable position as in the Fig. 1 is attached to the boom 2 at its third connection point 8a. From here, the secondary traction means 8 is not guided in the direction of the head 6a' of the counter-boom 6', but at an angle of less than 90°, which is inclined in the direction of the counter-boom 6', to a seventh connection point 8c on the main traction means 7. This angle can also be 90° if required. At the seventh connection point 8c on the main traction means 7, the secondary traction means 8 is deflected and guided further towards the foot 2a of the boom 2, where it is coupled at an eighth connection point 8d. Starting from the eighth connection point 8d, the secondary traction means 8 also forms an angle of less than 90° to the boom 2.Since here too, in order to adjust the length of the secondary traction means 8, the secondary traction means 8 is designed like a pulley with a corresponding reeving at least between the seventh connection point 8c and the eighth connection point 8d, the secondary traction means 8 is deflected in the eighth connection point 8d on the one hand and guided back once or several times in the direction of the seventh connection point 8c on the one hand and on the other hand further in the direction of the associated winch on the superstructure 5 or on the foot 6a' of the counter boom 6'.

[0044] In the context of the invention, the main traction means 7 and also the secondary traction means 8 can each be articulated at the tip of the head 2b of the boom 2 or the head 6b, 6b' of the counter-boom 6, 6', or in the area thereof. The term "area" is understood here as a section extending from the respective outer end of the boom 2, 6, 6' inwards with a length of up to 10% of the total length of the respective boom 2, 6, 6'. The same applies to the connection points on the base 2a, 6a, 6a' of the boom 2, 6, 6'.

[0045] In connection with the previously described embodiments according to the Fig.In Figures 1 to 7, the third connection point 8a for the secondary traction device 8 is always shown in the area of ​​an upper chord of the boom 2 designed as a lattice mast. In principle, it is also conceivable for this third connection point 8a to be arranged in the area of ​​a lower chord of the boom 2 or in its so-called system centerline. List of reference symbols 1 mobile crane 2 booms 2a Foot 2b Head 3 undercarriage 4 crawler track 5 superstructures 6 counter jib 6' counter jib 6a, 6a' foot 6b, 6b' head 7 Main traction means 7a first tie-up point 7b second tie-up point 8 secondary traction devices 8a third tie-up point 8b fourth tie-up point 8c seventh tie-up point 8d eighth tie-up point 9 guy wire 10 Counterweight 11 Auxiliary traction devices 11a fifth tethering point 11b sixth tethering point 12 Additional counterweight 13 Suspension K Compensation force L Load S1 starting position S2 upright position S3 operating position Underground X Longitudinal direction Y rocker axis Z vertical axis

Claims

[1] Mobile crane (1) with a boom (2) which can be erected and lowered and non-telescopically by at least one main traction means (7) and a counter-jib (6, 6'), the main traction means (7) runs between a first connection point (7a) in the region of a head (2b) of the boom (2) and a second connection point (7b) in the region of a head (6b, 6b') of the counter-jib (6, 6'), the boom (2) has a third connection point (8a) located between the first connection point (7a) and its foot (2a) opposite the head (2b), characterized by that a secondary traction means (8) runs between the third connection point (8a) via a seventh connection point (8c) on the main traction means (7) and an eighth connection point (8d) in the region of the foot (2a) of the main boom (2). [2] Mobile crane (1) with a boom (2) which can be erected and lowered and non-telescopically by at least one main traction means (7) and a counter-jib (6, 6'), the main traction means (7) runs between a first connection point (7a) in the region of a head (2b) of the boom (2) and a second connection point (7b) in the region of a head (6b, 6b') of the counter-jib (6, 6'), the boom (2) has a third connection point (8a) located between the first connection point (7a) and its foot (2a) opposite the head (2b), characterized by that a secondary traction means (8) runs between the third tying point (8a) and a fourth tying point (8b) in the region of the head (6b, 6b') of the counter-jib (6, 6') and the region for the third tying point (8a) lies between 40% and 60% of the length of the boom (2) as seen in the longitudinal direction (X) of the boom (2). [3] Mobile crane (1) according to claim 1 or 2, characterized bythat the main traction means (7) is variable in length at least in sections. [4] Mobile crane (1) according to one of the preceding claims, characterized by that the secondary traction means (8) is variable in length at least in sections. [5] Mobile crane (1) according to one of the preceding claims, characterized by that the boom (2) extends jointlessly between its foot (2a) and its head (2b). [6] Mobile crane (1) according to one of the preceding claims, characterized by that the boom (2) has several or a single support, in particular lattice girders and / or box girders, extending between its base (2a) and its head (2b). [7] Mobile crane (1) according to one of the preceding claims, characterized by that it has an upper carriage (5) which is rotatably arranged on an undercarriage (3) and on which the boom (2) is supported in a luffing manner via its base (2a). [8] Mobile crane (1) according to claim 7, characterized by that the counter boom (6, 6') is supported on the superstructure (5). [9] Mobile crane (1) according to claim 7 or 8, characterized by that the superstructure (5) or the base (6a, 6a') of the counter-jib (6, 6') has winch drives, wherein the main traction means (7) and secondary traction means (8) are each operatively connected to the winch drive. [10] Mobile crane (1) according to one of the preceding claims, characterized by that the boom (2) has a fifth connection point (11a) to which an auxiliary traction means (11) connected to the main traction means (7) at a sixth connection point (11b) is coupled. [11] Mobile crane (1) according to claim 10, characterized by that the fifth tying point (11a) is located between the first tying point (7a) and the third tying point (8a) on the boom (2). [12] Mobile crane (1) according to one of the preceding claims, characterized bythat an additional counterweight (12) is suspended from the counter jib (6). [13] Mobile crane (1) according to one of the preceding claims, characterized by that the counter jib (6) is a superlift jib and the counter jib (6') is an A-frame. [14] Method for reducing the loads occurring during operation and / or during erection and laying down of the boom (2) of a mobile crane (1) having a counter-jib (6) according to one of the preceding claims, wherein the boom (2) which is supported in a luffing manner via its base (2a) and is coupled to a main traction means (7) via a first connection point (7a) in the region of its head (2b) opposite the base (2a) has a third connection point (8a) located between the first connection point (7a) and the base (2a), via which third connection point a, in particular controllable, compensation force (K) is transmitted to the boom (2) by a secondary traction means (8) coupled to the third connection point (8a). [15] Method according to claim 14, characterized bythat the control of the compensation force (K) to be transmitted takes place in at least one of the following ways: force-controlled, path-controlled, continuous, constant, linear, step-wise, and / or at least one of the following features of the mobile crane (1) is taken into account: load points, load radius, counterweight radius, load curve.

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