TOWER CRANE WITH ADJUSTABLE COUNTERBALISM

Description

[0001] The invention relates to a tower crane with a rotating platform, a tiltable boom hinged to the rotating platform and counter ballast mounted on the rotating platform.

[0002] Luffing jib cranes are known in which the counterballast is coupled to the jib via a fixed kinematics. The kinematics transfer the movement of the jib to the counterballast, which is then displaced on the slewing platform depending on the jib angle. The aim of these designs is, on the one hand, to reduce the power required by the adjustment mechanism to move the jib. On the other hand, the aim is to optimize the load on the crane tower by shifting the counterballast, particularly for different conditions and load cases. A key commonality of such designs is that the load on the jib can be relieved and the tower load optimized exclusively for a specific crane type by shifting the counterweight depending on the jib length.

[0003] Figure 1shows, as an example, the course of the deadweight moment, in particular of the moving parts of the upper crane (line 1, line 2), with the aim of optimizing the deadweight moment of the upper crane without payload (line 4). If the crane were equipped with immovable counterballast, line 4 would run parallel to line 1 (jib deadweight moment). However, with movable counterballast (line 2), it is possible to adjust the deadweight moment of the upper crane (line 4) so ​​that it is almost constant. With the sketched payload curve (line 0), a likewise almost constant top crane moment (line 5) results for a boom angle of 15 degrees (maximum radius) to approximately 50 degrees (inflection point of the payload curve), which is approximately the same magnitude as the deadweight moment of the upper crane without payload (line 4).

[0004] However, if the crane configuration changes, e.g., if the length of the adjustable boom changes, this optimum cannot be achieved with a constant top crane deadweight moment due to the fixed mechanical kinematics. Line 4 will be inclined depending on the boom angle alpha. A change in the counterweight merely causes a parallel shift of line 4.

[0005] If, in addition to this optimization task, the influence of the wind load on the upper crane and crane tower for an in- or out-of-service position is also taken into account, the task becomes even more complex. The optimization solution described was considered sufficient in the past because the out-of-service wind load (storm out-of-service) was almost uniform worldwide. With the recent introduction of wind zones, combined with the requirement to adapt the out-of-service wind load to the crane's location of use, the optimization task has become even more complicated. In addition, in the past, the relevance of the in-service load to the out-of-service load has always shifted with increasing crane size, from the out-of-service load cases to the in-service load cases. Conversely, the smaller the crane, the more significant the out-of-service load cases become for the crane tower.

[0006] A tower crane of this type is also known from CN 207 209 812 U.

[0007] The object of the present application is to modify a crane of this type in such a way that the position of the counter ballast can be optimized depending on the crane condition, the crane configuration and the operating conditions.

[0008] This object is achieved by a crane according to the features of claim 1. Advantageous embodiments of the crane are the subject of the dependent claims.

[0009] According to the invention, it is proposed to provide an adjustment mechanism for the tower crane that allows a change in the position of the counterballast independent of the luffing angle of the adjustable boom. The adjustment mechanisms already mentioned always provided a mechanical coupling between the adjustable boom and the counterballast, which is why a change in the position of the counterballast could only be achieved by changing the luffing angle of the adjustable boom. The present application departs from such a solution and instead proposes an independent adjustment mechanism to enable a change in the position of the counterballast independent of an actuation, i.e., a luffing movement, of the adjustable boom.

[0010] For the basic concept of the invention, it is irrelevant whether a kinematic coupling exists between the adjustable boom and the counterballast. However, it is essential to the invention that the position of the counterballast can be changed even when the luffing angle remains constant. However, it does not contradict the inventive concept if a change in the luffing angle of the adjustable boom also leads to a coupled change in the counterballast position.

[0011] According to an exemplary design variant, a complete decoupling of the counterballast and adjustable boom is proposed, meaning that the position of the counterballast remains constant when the luffing angle changes and can only be varied by the adjustment mechanism. A concrete example of an implementation of the adjustment mechanism could be a movable ballast handling device for receiving the counterballast. Ideally, the ballast handling device is designed as a trolley mounted on the crane's slewing platform so that it can move relative to it.

[0012] A horizontal movement of the ballast handling device or trolley is preferred in order to minimize the load on the trolley drive during movement and the associated energy consumption. The use of a cable drive or a spindle drive for moving the ballast handling device or trolley is possible.

[0013] According to the invention, a mechanical kinematic coupling is provided between the adjustable boom and the counterballast. For example, the use of an articulated linkage for the coupling is possible. In particular, a 4-bar kinematics is conceivable, which provides a coupling between the counterballast and the boom by means of a rocker-coupling rod combination. Through this linkage, a change in the luffing angle of the adjustable boom is transmitted to the counterballast, which triggers a positional shift of the counterballast. As the luffing angle of the adjustable boom increases, the distance of the counterballast from the crane tower decreases. The type and extent of the positional shift of the counterballast depends on the kinematics of the linkage used, in particular on the position of the pivot and articulation points as well as the length dimensions of individual rods. Against this background, it is proposed to equip at least one of these coupling rods with the adjustment mechanism according to the invention.The adjustment mechanism allows the axial length of at least one rod to be changed, thereby influencing the position of the counter ballast, even without changing the luffing angle of the adjustable boom.

[0014] The change in length of at least one rod of the linkage can be effected by means of an integral hydraulic cylinder or alternatively by means of a spindle drive.

[0015] It is also conceivable that an adjustment mechanism, e.g. hydraulic cylinder, is provided to change the position of at least one articulation and / or pivot point of the rod.

[0016] As an alternative to using an articulated rod for the mechanical coupling between the adjustable boom and the counterballast, it can also be provided to use a coupling cable instead, which usually creates a mechanical connection between the adjustable boom and the counterballast via one or more deflection pulleys. Here, too, a change in the luffing angle of the adjustable boom leads to a shift in the position of the counterballast, whereby the type and extent of the position change depends significantly on the length of the coupling cable and the position of the deflection pulleys. In this sense, it is proposed that a change in the length of the coupling cable and / or alternatively a change in the position of at least one deflection pulley is brought about by means of the adjustment mechanism according to the invention. By intervening in the kinematics of the cable mechanism, a change in the position of the counterballast can also be achieved without changing the luffing angle of the adjustable boom.

[0017] Further advantages and features of the invention will be explained in more detail below using an exemplary embodiment illustrated in the figures. They show: Figure 1: a diagrammatic representation of the dead weight progression of movable parts of an overhead crane as a function of the boom angle, Figure 2: a first embodiment of the crane according to the invention with 4-joint kinematics, Figure 3: a second embodiment of the crane with a rope hoist system, Figure 4: a third embodiment of the tower crane with a rigid coupling between the boom and counter-jib, Figure 5: a slightly modified version of the tower crane according to Figure 4 and Figure 6: another embodiment of the invention with a fully variable coupling between boom and counter boom.

[0018] Figure 2shows a luffing jib crane. The tower crane comprises a crane tower, at the top of which a slewing platform 1a is mounted for rotation by means of the slewing bearing support 11 and the slewing bearing 10. The slewing boom is mounted on the slewing platform 1a so that it can be luffed about a horizontal axis. The luffing angle α can be adjusted using the adjustment mechanism 8 and the adjustment cable 9. For the lifting work, the hoist cable 7 runs from a hoist mechanism 6 mounted on the slewing platform 1a to the boom tip.

[0019] The adjustable boom 2 is mechanically coupled to the counterballast 5 via a four-link transmission, which consists of the rocker formed by the adjustable boom 2, the coupling rod 3, the counterballast rocker 4, and the connecting element 13. The two rockers 2, 4 are articulated via their articulation points C, D to the turntable 1a and the A-frame 1b of the adjustment mechanism, respectively. The coupling rod 3 is articulated to the rockers 2, 4 via articulation points A, B. The connecting element 13 can also be articulated to the rocker 4 and the ballast 5.

[0020] The displacement of the counterballast 5 when the angle α changes depends on the lengths of the two rockers 2, 4, the length of the coupling rod 3, and the position of the bearing points C, D of the two rockers 2, 4 on the crane structure 1a, 1b. The distance of the counterballast 5 from the crane rotation axis 20 is a non-linear function of the boom angle α, which is specified by the adjustment mechanism 8.

[0021] The deadweight moment of the movable counterballast 5 can now be adjusted by changing the deadweight and by changing the parameters of the 4-bar linkage. According to the invention, an adjustment mechanism for changing the length of the coupling rod 3 is therefore provided. This can be achieved by integrating a hydraulic cylinder or spindle drive, the actuation of which influences the length of the coupling rod 3. It is also conceivable for the coupling rod 3 to be constructed similarly to a turnbuckle in order to be able to manually change the length of the coupling rod 3. The coupling rod can equally well be provided with several bearing bores offset in the axial direction. By appropriately selecting the bearing bore for mounting at the articulation or articulation points A, B, the effective length of the coupling rod can be changed.

[0022] It is also possible to intervene in the kinematics by changing the length of the two rockers 2, 4, e.g. by shifting the two bolting points A, B along the structural components of the two components 2, 4 in the direction of the indicated arrows.

[0023] A second embodiment of the crane according to the invention is shown in Figure 3 Identical components are marked with identical reference symbols. Compared to the crane from Figure 2Here, the mechanical coupling between the adjustable boom 2 and counterballast 5 is implemented differently. A trolley 40 is used, to which the counterweight 5 is attached and which is moved on an inclined plane by means of a cable pull system 30a. The displacement of the counterballast 5 depends on the length of the boom rocker 2, the length of the coupling cable 30a, the inclination of the track of the trolley 40 and the position of the bearing points of the deflection pulleys 30b, 30c as well as the position of the boom rocker 2 on the frame 1a. The distance of the counterballast 5 from the crane rotation axis 20 is a non-linear function of the boom angle α, which is specified by the adjustment mechanism 8.

[0024] The deadweight moment of the movable counterballast 5 can be adjusted by changing the deadweight and by changing the parameters of the cable pull system 30a. This can be achieved by changing the length of the coupling cable 30a. A corresponding adjustment mechanism, e.g., a hydraulic cylinder, can change the cable length during ongoing crane operation.

[0025] However, an intervention in the kinematics and thus a change in the counterballast position can also be achieved by shifting the bolting point A of the coupling cable 30 to the boom rocker 2 along the structural components of the boom 2 in the direction of the indicated arrows. This could also be done automatically using a suitable adjustment mechanism.

[0026] It is also conceivable to shift the position of the deflection pulley 30b along the structural components of the A-frame 1b in the direction of the indicated arrows or to shift the position of the deflection pulley 30c along the structural components of the turntable 1a. The displacement of the deflection pulleys can also be implemented using a suitable adjustment mechanism, e.g., a hydraulic cylinder.

[0027] A third embodiment is the Figure 4can be seen. In this crane, an adjustment cylinder 8a is used to change the angle α of the adjustable boom 2. The adjustable boom 2 is not mounted on the slewing platform 1a, but instead on the A-frame 1b. This solution also uses a rigid coupling between the counterballast 5 and the boom 2. A movable rocker 4 is used, to which the counterweight 5 is attached and which can be adjusted using a coupling rod 3. The pivot point of the rocker 4 is joint A. The pivot points of the coupling rod 3 are labeled B, C. The movement occurs relative to the boom 2 (not to the frame (1b)). The distance of the counterballast 5 from the crane rotation axis 20 is a function of the boom angle α, which is predetermined by the stroke of the adjustment cylinder 8a.

[0028] The dead weight moment of the movable counter ballast 5 can be achieved by changing the dead weight and by changing the length of the coupling rod 3, similar to the solution of the Figure 2 is proposed. Specifically, the length of the coupling rod 3 can be adjusted using an integral hydraulic cylinder or spindle drive. Manual adjustment of the coupling rod length is also conceivable if it is designed similarly to a turnbuckle or is provided with several bearing bores offset in the axial direction.

[0029] Especially with the Figure 4In the crane configuration shown, it is advisable to change the length of the coupling rod 3 when switching to the out-of-service state. With luffing jib cranes, the jib 2 is moved into a relatively steep position (α = approx. 70°) when decommissioning. As a result, with this solution, the counterballast 5 moves relatively close to the crane's rotation axis 20, preventing it from developing an excessive deadweight moment. However, this would be helpful in counteracting the out-of-service wind load in the event of a rearward approach.

[0030] A variation of this solution is in Figure 5shown. In this variant, the coupling rod 3 is divided into two subcomponents 3a, 3b. The coupling and corresponding movement of the counterballast 5 is adapted to the movement of the boom 2 in a suitable ratio by means of a gear 3c. To obtain the necessary relative movement, the coupling rod 3a is no longer connected to the boom 2 but to the frame 1b. The pivot point of the rockers 2, 4 is designated by A. The pivot point of the coupling rod 3a is designated by B, and the pivot point of the coupling rod 3b is designated by C. The pivot points C, D also represent the pivot points of the adjustment cylinder 8a.

[0031] The previous solutions are characterized by the fact that the movement of the counterballast 5 is mechanically coupled to the movement of the boom 2. If the unloading of the adjustment drive can be dispensed with, the counterballast 5 can also be moved directly by a separate drive-based adjustment mechanism according to one embodiment of the invention. The optimization task is thus limited exclusively to minimizing the tower load.

[0032] To minimize the load on this drive and the associated energy consumption, counterweight 5 should be moved as horizontally as possible. This can be achieved with a powered trolley 40 (see Figure 6) to which the counterweight 5 is attached and which is moved, for example, by means of a cable drive comprising the cable 41d and the required rollers 41a, 41b, 41c. Alternatively, a spindle drive could also be used. By means of the cable drive, the trolley 40 and thus the counterweight 5 can be displaced horizontally on the rotating platform 1a, whereby the distance of the counterballast 5 from the crane rotation axis 20 can be adjusted completely independently of the angle α.

[0033] This solution has the advantage that the position of the counter ballast 5 in the "crane in operation" state would be independent of the position in the "out-of-operation" position, the position of the counter ballast 5 in the "crane in operation" state could be adjusted in any ratio to the boom angle α and the position of the counter ballast 5 could be optimally and individually adapted to each boom length.

Claims

1. Tower crane having a slewing platform (1a), an adjustable boom (2) articulated in a derricking manner on the slewing platform (1a), and a counter-ballast (5) mounted on the slewing platform (1a), wherein an adjusting mechanism is provided, which permits a positional change to the counter-ballast (5) independent of the luffing angle of the adjustable boom (2), characterised in that the counter-ballast (5) is coupled to the adjustable boom (2) by means of an articulated linkage, and the length of at least one of the rods (3, 4) of the linkage and / or the position of at least one hinge point (A, B, C) of the linkage can be changed by means of the adjusting mechanism (8).

2. Tower crane according to claim 1, characterised in that the length of the at least one rod (3, 4) or the location of a hinge point (A, B, C) can be set by means of an integral hydraulic cylinder (8a) or a spindle drive.

3. Tower crane according to claim 1, characterised in that the counter-ballast (5) is coupled to the adjustable boom (2) by means of a coupling rope (30), wherein the length of the coupling rope (30) and / or the position of at least one of the deflecting rollers (30b, 30c) for the coupling rope (30) can be changed by means of the adjusting mechanism.

4. Tower crane according to claim 3, characterised in that a hydraulic cylinder (8a) is provided as an adjusting mechanism for changing the rope length or the position of a deflecting roller (30b, 30c).