Abstract
The present invention relates to a crane comprising a main boom and a rearwardly directed derrick boom for bracing the main boom, wherein a suspended ballast is directly or indirectly attached to the derrick head via connecting means, wherein at least one luffable, rearwardly aligned ballast adjusting boom is provided, which acts on the connecting means and influences the suspended ballast radius by its luffing angle.
Claims
1. A crane, comprising a main boom, a rearwardly directed derrick boom for bracing the main boom, a suspended ballast is directly or indirectly attached to a derrick head, connecting means attaching the suspended ballast to the derrick head, and a luffable, rearwardly aligned ballast adjusting boom directly coupled to the connecting means at a point between the derrick head and the suspended ballast, and which acts on the connecting means and influences a suspended ballast radius by a luffing angle thereof, wherein said connecting means comprise a first strand connecting a head of the ballast adjusting boom to the derrick head, and a second strand connecting the suspended ballast to the head of the ballast adjusting boom, and the connecting means comprise a first pulley block connecting the head of the ballast adjusting boom to the derrick head and a second pulley block connecting the suspended ballast to the head of the ballast adjusting boom.
2. The crane according to claim 1, wherein the change of the luffing angle is effected by a change in distance between the derrick head and a ballast adjusting boom head.
3. The crane according to claim 1, wherein an erection cylinder acting independently of the connecting means is provided for the luffing actuation of at least one of the ballast adjusting boom and the derrick boom.
4. The crane according to claim 1, wherein an articulation point of the ballast adjusting boom is located close to a slewing ring of an upper carriage.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Further advantages and properties of the invention will be explained in detail below with reference to the exemplary embodiments illustrated in the Figures, in which:
(2) FIGS. 1a, 1b: show schematic crane representations of a conventional crawler crane,
(3) FIGS. 2a, 2b: show schematic representations of the crane according to the invention comprising a ballast adjusting boom and two connecting means with the main boom put down or erected,
(4) FIG. 3: shows a schematic representation of the crane of FIGS. 2a, 2b to illustrate the occurring transverse and torsional forces,
(5) FIG. 4: shows a modified embodiment of the crane of FIGS. 2 and 3 comprising a shortened ballast adjusting boom,
(6) FIG. 5: shows an alternative embodiment of the crane according to the invention comprising a chain as a continuous connecting means,
(7) FIG. 6: shows another alternative embodiment of the crane according to the invention comprising a bracing element as a continuous connecting means and a deflection pulley as a run-off element,
(8) FIG. 7: shows an embodiment of the crane according to the invention comprising a capstan winch at the ballast adjusting boom, and
(9) FIGS. 8a, 8b, 8c, 8d: show different embodiments of the cable adjuster between ballast adjusting boom and suspended ballast.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
(10) It is the objective of the invention to provide a rather simple constructional solution for the stepless adjustment of the suspended ballast. The fundamental idea of the invention is identical for all exemplary embodiments of FIGS. 2 to 8, namely the installation of a second counter-boom, hereinafter referred to as ballast adjusting boom 10, which in addition to a derrick boom 3 is luffably articulated to the turntable 5 of the crane upper carriage about a horizontal axis. The derrick boom 3 still fulfills the function to increase the lever arm 8 to the main boom 1, in particular when erecting the main boom 1 from a flat position into the working position. By luffing the ballast adjusting boom 10, the radius r of the suspended ballast 7 can be changed from very small to very large. Even with a steep main boom 1 (FIG. 2b) the rearward counter-moment can be reduced or be kept very small without having to put down the ballast 7 for this purpose, i.e. the same can still be suspended on the crane structure.
(11) A first exemplary embodiment of this idea will be explained with reference to FIGS. 2a, 2b. Like in a conventional crane (e.g. as shown in FIGS. 1a, 1b) the derrick boom 3 here as well forms a first counter-boom to the main boom 1. The derrick boom 3 is connected to the main boom 1 via the bracing 2. The bracing 4 extends from the derrick head 3a to the turntable 5 of the crane. The suspended ballast 7 is indirectly connected to the derrick head 3a via the ballast adjusting boom head 10a. Concretely, the suspended ballast 7 is attached to the head 10a of the ballast adjusting boom 10 via a second connecting means in the form of the cable pulley block 12. Via a first connecting means, likewise designed as a cable pulley block 11, the head 10a is connected to the derrick head 3a so that the suspended ballast 7 ultimately engages the derrick boom 3.
(12) The distance between the derrick boom 3 and the ballast adjusting boom 10 thus can be varied via the cable adjuster 11. The distance between ballast adjusting boom 10 and suspended ballast 7 likewise is variable by means of the cable adjuster 12, whereby the hoisting height of the suspended ballast 7 is adjustable. Due to the angular adjustment of the ballast adjusting boom 10 it therefore is possible to change the suspended ballast radius r. The adjustment of the ballast adjusting boom 10 is effected by increasing or reducing the distance between the head piece 3a of the derrick boom 3 and the head piece 10a of the ballast adjusting boom 10.
(13) In the exemplary embodiment of FIGS. 2a, 2b the cable adjustment for the pulley blocks 11, 12 can be effected via two separate winches. The at least one winch for the cable adjuster 11 preferably is mounted on the derrick boom 3, in particular on the articulation piece present there, while the at least one winch for the cable adjuster 12 is seated on the ballast adjusting boom 10 or the articulation piece present there.
(14) For the assembly of the crane shown in FIGS. 2a, 2b an additional actuator (e.g. erection cylinder 22) can be mounted between ballast adjusting boom 10 and turntable 5. By means of the same, the ballast adjusting boom 10 can be urged from the horizontal into an inclined position. Alternatively, an auxiliary crane might of course be used as well. Ideally, the erection cylinder 22 is pressureless in operation, so that no additional moment is introduced into the ballast adjusting boom 10. When the ballast adjusting boom 10 is in an inclined position, the same can be connected to the derrick boom 3 via the bracing 11 and to the suspended ballast 7 via the bracing 12. Subsequently, the derrick boom 3 can be erected via the cable adjuster 11, and the bracing 4 between the head piece 3a of the derrick boom 3 and the turntable 5 can be closed. Thereafter, the main boom 1 can be erected as known by means of the derrick boom 3.
(15) In such an embodiment comprising at least two separate winches as shown in FIGS. 2a, 2b a prior art operating mode with an unguided suspended ballast 7 also is possible, when necessary, or when a crane configuration and a desired operating mode does not require an adjustment of the suspended ballast radius. In this case, the ballast adjusting boom 10′ can be shortened, for example by mounting the head piece 10a directly to the articulation piece without any intermediate pieces. The ballast adjusting boom 10′ in this configuration merely serves as an erection trestle for the derrick boom 3, as this has already been described above with reference to the explained assembly operation. Such a special configuration is depicted in FIG. 4.
(16) Alternatively, the suspended ballast 7 can also be directly attached to the derrick boom 3 via a continuous connecting means. An example of this is shown in FIG. 5, in which the travel adjustment between the head pieces 3a, 10a of the two counter-booms 3, 10 is effected by means of a chain drive. In this solution, a chain 13 concretely is installed between derrick head 3a and suspended ballast 7. The ballast adjusting boom 10 moves along the chain 13 by means of an actuator in the form of a gear wheel or a chain sprocket 14, whereby the distance between the head pieces 3a, 10a of the two counter-booms 3, 10 is changed. Consequently, the distance between the head piece 10a of the ballast adjusting boom 10 and the suspended ballast 7 of course changes as well.
(17) For the height adjustment of the suspended ballast 7 an actuator in the form of the pulling cylinder 20 then can additionally be installed in the chain strand 13. By means of the same, the suspended ballast 7 can be kept at a low height above the ground. The resulting chain drive can be configured by means of a steel chain or also a plastic chain or plastic strap. In addition, a toothed belt drive also is conceivable. Then, the actuator 14 must be adapted corresponding to the plastic chain, the plastic strap or the toothed belt.
(18) The exemplary embodiment of FIG. 6 proves to be an alternative to the chain drive. Here, a cable 15 is stretched between derrick head 3a and suspended ballast 7 instead of a chain. The cable 15 ideally is a bracing cable made of aramide, Dyneema or other plastic fibers. A steel cable also is conceivable. The deflection pulley 16 can be moved along this bracing element 15 and accordingly urges the same away from the crane in a radial direction. An adjusting cable 17, which extends between ballast adjusting boom 10 and suspended ballast 7, serves to luff down the ballast adjusting boom 10. The adjusting cable 17 is actuated via a winch mounted on the articulation piece of the boom 10 and extends over the deflection pulley 16a to the suspended ballast 7, where the same is guided by at least one further deflection pulley 7a back to the deflection pulley 16b or to the head 10a and is firmly fixed there. The function of this construction is based on the fact that the ballast adjusting boom 10 is pressed upwards due to the geometrical conditions, which is prevented by the adjusting cable 17. When the adjusting cable 17 is retracted, the ballast adjusting boom 10 moves downwards and the suspended ballast radius is increased. In the reverse case, the adjusting cable 17 is reeled off and the ballast adjusting boom 10 automatically travels upwards due to the geometrical conditions.
(19) In this embodiment, too, an additional actuator in the form of a pulling cylinder 20 can be installed in the cable strand for the separate height adjustment of the suspended ballast 7.
(20) A modification of the exemplary embodiment of FIGS. 2a, 2b is shown in FIG. 7. In this variant, no separate actuators are installed for the cable adjusters 11, 12, but instead a common capstan winch 21 is used, which provides for a simultaneous adjustment of the ballast adjusting boom 10 and for changing the distance between the head piece 10a of the ballast adjusting boom 10 and the suspended ballast 7. For this purpose, a common cable 18 is drawn into both cable adjusters 11, 12. By means of the capstan winch 21, which for example is arranged on the ballast adjusting boom 10, the cable 18 can be retracted for example from the first cable adjuster 11 and at the same time be lowered into the second cable adjuster 12 so that the ballast adjusting boom 10 is positioned more steeply, while the distance between head 10a and suspended ballast 7 is increased. To better control the height of the suspended ballast 7, in particular to keep the same at a constant height above the ground independent of the luffing angle, a non-illustrated pulling cylinder 20 likewise is installed in the cable strand 18.
(21) Further modifications of the construction as shown in FIGS. 2a, 2b are shown in the representations of FIGS. 8a to 8d. The cable adjuster 12 for the suspended ballast 7 should be configured as broad as possible in order to minimize the risk of torsion of the attached suspended ballast 7. The cable adjuster 12 of the suspended ballast 7 with only one pulley block or only one single cable involves the risk of an inclined position of the suspended ballast 7. For this reason, the modifications of FIGS. 8a to 8d therefore propose two pulley blocks 12a, 12b extending in parallel between head 10a and suspended ballast 7.
(22) The suspended ballast 7 here can be lifted or lowered by an adjuster by means of two synchronously actuatable winches for the Bowden cables 12a, 12b with an alignment as horizontal as possible. Alternatively, a dual winch 23 can be used instead, which winds up the cable ends of the pulley blocks 12a, 12b. The parallel pulley blocks 12a, 12b can share a common cable, as is shown in FIG. 8a. Alternatively, however, it is also possible to use two cables (FIG. 8b) which are connected to each other in a common cable anchorage at the head 10a of the ballast adjusting boom 10.
(23) The solution according to FIG. 8c is regarded as the best solution for reducing the risk of torsion of the suspended ballast 7, in which the cable ends of the two cables of the parallel pulley blocks 12a, 12b are connected to each other via a rocker 24 which itself is suspended on the head 10a of the ballast adjusting boom 10.
(24) According to the further solution of FIG. 8d, the cable ends of the pulley blocks 12a, 12b are fixed to the head 10a of the ballast adjusting boom 10 via separate cable anchorages. At least one of these cable anchorages can be provided with an actuator 20 (e.g. cylinder), via which the cable length can be varied. The suspended ballast pallet 7 thereby can be kept in the horizontal position, even if the cables are wound up differently on the dual winch 23 (tolerances). Furthermore, the suspended ballast pallet 7 can deliberately be put into an inclined position in order to deposit the same on an inclined surface.
(25) The control of the suspended ballast radius can be executed by the crane controller and ideally is identical for all exemplary embodiments. The force present in the bracing 4 between the head piece 3a of the derrick boom 3 and the turntable 5 is used for monitoring the crane stability. This force can furthermore be used to automatically adapt the suspended ballast radius by means of the crane controller, in that the force is kept within a particular force window by adjusting the suspended ballast radius. The controller also can optionally monitor the hoisting height of the suspended ballast 7 and when necessary keep the same at a constant height independent of the radius. For this purpose, the cable paths of the respective adjusters can be detected and be processed by the controller.
(26) For all of the exemplary embodiments set forth here some essential advantages can be summarized. The ballast adjusting boom 10 can be designed very long, which provides for a large suspended ballast radius with the ballast adjusting boom 10 in a horizontal position. The usable range of radii of the ballast 7 is greater than in previous systems. The derrick boom 3 can remain fixed without being moved, and the necessary actuator thereby can be saved. The ballast adjusting boom 10 can be designed straight (not bent like in other systems), so that the same primarily has to absorb compressive forces, which provides for a simpler (less expensive) and lighter construction. The occurring transverse forces F.sub.Q, as shown by way of example in FIG. 3, can be absorbed more easily due to the straight construction. Due to the straight construction of the ballast adjusting boom 10, of the erection cylinder 22 and of the pre-reeved cable adjusters a relatively fast and easy assembly is possible.
(27) To obtain a lifting capacity as high as possible, the articulation point of the ballast adjusting boom 10 preferably is to be arranged as close as possible to the slewing ring 26 (see FIG. 3). When an offset between the slewing ring 26 and the articulation point of the ballast adjusting boom 10 is necessary nevertheless, the turntable 5 should be designed as torsionally rigid as possible in this region. This is helpful to optimally dissipate the transverse forces F.sub.Q which occur at the head 10a of the ballast adjusting boom 10 due to a rotation of the upper carriage (mass inertia of the suspended ballast 7) or due to inclined positions and which act in the turntable 5 as a torsion F.sub.T. The articulation point of the ballast adjusting boom 10, however, can be disposed anywhere at the upper carriage. Hence also at the rear.
