Crane with hoisting cable load-dependent load torque equalization

Abstract

A crane includes a jib which is mounted on the crane structure so as to be rotatable about a bearing point, a counterweight arrangement which can be positioned variably in relation to the bearing point, and a hoisting cable which runs out from a hoisting winch and is guided via the jib. A counterweight adjustment device, which is coupled to the counterweight arrangement, includes a lever element mounted rotatably about a pivot point, a hoisting cable guide arranged in the course of the hoisting cable between the hoisting winch and an upper jib section, with a first deflecting pulley arrangement mounted on the jib and a second deflecting pulley arrangement mounted on the lever element, wherein the hoisting cable is guided in an alternating manner via the first and the second deflecting pulley arrangement, and a coupling element acting on the lever element and connected to the counterweight arrangement.

Claims

1. A crane comprising: a. a jib which is mounted on a crane structure so as to be rotatable about a horizontal axis at a bearing point, b. a counterweight arrangement which can be positioned variably in relation to the bearing point, c. a hoisting cable which runs out from a hoisting winch and is guided via the jib, d. a counterweight adjustment device which is coupled to the counterweight arrangement for variably positioning the counterweight arrangement depending on a hoisting cable load, comprising i. a lever element which is mounted rotatably about a pivot point, which is arranged on the crane structure rearwardly with respect to the jib, ii. a coupling element which connects between the lever element and the counterweight arrangement, wherein e. two lever arms extend from the pivot point of the lever element, and the lever element is designed as a balancer, f. the counterweight adjustment device includes a hoisting cable guide which is arranged in a course of the hoisting cable between the hoisting winch and an upper jib section, having a first deflecting pulley arrangement which is mounted on the jib and a second deflecting pulley arrangement which is mounted on the lever element, wherein the hoisting cable is reeved multiple times in the first and the second deflecting pulley arrangement, and therefore a deflection, induced by the hoisting cable load, of the lever element is transmitted to the counter weight arrangement in such a manner that an increase of the hoisting cable load brings about a rearwardly directed change in position and a reduction in the hoisting cable load brings about a forwardly directed change in the position of the counter weight arrangement.

2. The crane as claimed in claim 1, wherein the crane is a mobile crane, with a crane superstructure which is mounted rotatably on a crane truck, and wherein the jib is mounted on the crane superstructure so as to be rotatable about the bearing point.

3. The crane as claimed in claim 2, wherein the lever element is mounted rotatably directly on a bracket belonging to the crane superstructure.

4. The crane as claimed in claim 3, wherein the jib is braced via the hoisting cable guide, wherein an angle (α) between the jib and a stay rack arranged on the crane superstructure is variable and an angle (β) between the stay rack and the crane superstructure is invariable.

5. The crane as claimed in claim 1, wherein the jib is a lattice jib.

6. The crane as claimed in claim 1, further comprising a stay rack which is mounted rotatably on the crane structure, wherein the lever element is mounted rotatably on the stay rack.

7. The crane as claimed in claim 6, wherein the stay rack takes up a fixed angle (a) relative to the jib and a variable angle (β) with respect to a crane superstructure, and wherein a length-invariable jib stay extends between the jib and the stay rack.

8. The crane as claimed in claim 6, wherein the stay rack is mounted rotatably on a crane superstructure.

9. The crane as claimed in claim 1, wherein the lever element has a first lever arm which extends from the pivot point and on which the second deflecting pulley arrangement is mounted, and a second lever arm which extends from the pivot point and on which the coupling element acts.

10. The crane as claimed in claim 9, wherein the first and the second lever arm extend and move in opposite directions.

11. The crane as claimed in claim 10, wherein a counterweight guide is guided on a crane superstructure during the forwardly directed change in position of the counter weight arrangement and the rearwardly directed change in position of the counterweight arrangement.

12. The crane as claimed in claim 10, wherein a counterweight guide is guided in such a manner that, during the rearwardly directed change in position of the counterweight arrangement, the counterweight arrangement is raised in the vertical direction.

13. The crane as claimed in claim 12, wherein at least one coupling of two or more elements of the counterweight adjustment device comprises one or more members adapted to dampen a motion of the two or more elements with respect to each other by increasing friction between the two or more elements.

14. The crane as claimed in claim 1, wherein the coupling element is configured to transmit compressive forces between the lever element and the counterweight arrangement.

15. The crane as claimed in claim 14, wherein the coupling element is designed as a pendulum support.

16. The crane as claimed in claim 1, further comprising a counterweight guide on which the counterweight arrangement is guided during the forwardly directed change in position of the counter weight arrangement and the rearwardly directed change in position of the counterweight arrangement on the crane structure.

17. The crane as claimed in claim 1, wherein at least one coupling of two or more elements of the counterweight adjustment device comprises one or more members adapted to dampen a motion of the two or more elements with respect to each other by increasing a friction between the two or more elements so as to counteract dynamic oscillations of the counterweight adjustment device.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a first embodiment of a mobile crane according to the invention;

(2) FIG. 2 shows a second embodiment of a mobile crane according to the invention;

(3) FIG. 3 shows a first embodiment of a stationary crane according to the invention; and

(4) FIG. 4 shows a second embodiment of a stationary according to the invention.

DETAILED DESCRIPTION

(5) The mobile crane according to a first embodiment that can be seen in FIG. 1 has a crane truck 17 having a crawler track, wherein a crane superstructure 1 is mounted on the crane truck 17 so as to be rotatable about a vertical axis. A hoisting winch 5 and a retracting winch 15, from which a hoisting cable 6 and a cable for the retraction mechanism 16 respectively extend, are arranged inter alia on the superstructure 1.

(6) Furthermore, a lattice jib 3 is connected to the crane superstructure 1 so as to be rotatable via the bearing point 2, and therefore said lattice jib can be tilted down (the angle γ enclosed between the jib 3 and the horizontal plane running through the crane superstructure 1 is reduced) and up (γ is increased). The tilting of the jib 3 down and up is brought about, in the embodiment shown in FIG. 1, by the fact that the cable of the retraction mechanism 16 is unwound from, or wound up by, the retraction winch 15 and, as a result, that end of the stay rack 18 which is remote from the bearing point 2 is moved away from the crane superstructure 1 or toward the crane superstructure 1. Since the jib stay 19 extending in between the tip 10 of the jib 3 and the tip of the stay rack 18 has a fixed length, the angle α enclosed between the jib 3 and the stay rack 18 remains constant while the angle β enclosed between the stay rack 18 and the horizontal plane running through the superstructure 1 has a variable value, complementary to the angle γ.

(7) A counterweight arrangement 4 is provided in the rearward region of the superstructure 1, said counterweight arrangement being braced by the tip of the stay rack 18 and therefore counteracting a tilting moment about the bearing point 2 that is caused by the jib 3 and a load which may be suspended thereon.

(8) In order to be able to vary the position of the counterweight arrangement 4 relative to the bearing point 2 and therefore the generated load equalization torque, in the embodiment of the crane according to the invention that can be seen in FIG. 1, a lever element 9 is connected to the stay rack 18 at a pivot point 8 so as to be rotatable about a horizontal axis. A first lever arm 9a of the lever element 9 is coupled to the jib 3 by the fact that the hoisting cable 6 running out from the hoisting winch 5 is guided in an alternating manner via a first deflecting pulley arrangement 12 arranged on the jib 3 and a second deflecting pulley arrangement 13 arranged on the lever arm 9a before said hoisting cable is guided further via the jib tip 10 to a hook block (not denoted specifically). The lever arm 9b lying opposite the lever arm 9a is coupled to the counterweight arrangement 4 via a pendulum support 14.

(9) It can be understood with reference to FIG. 1 that acting upon the hoisting cable 6 with a load (not shown in FIG. 1) brings about a change in length of the hoisting cable guide 11, specifically depending on the reeving of the hoisting cable 6, in accordance with the number of deflecting pulleys provided for the arrangements 12 and 13. In other words, the hoisting cable guide 11 acts as a block and tackle, and therefore the lever arm 9a is rotated toward the jib 3 depending on the cable load. Conversely, a rearwardly directed shifting of the position of the counterweight arrangement 4 is thereby brought about since the lever arm 9b which is coupled to the counterweight arrangement 4 via the pendulum support 14 also rotates about the pivot point 8. As soon as the counterweight arrangement 4 is moved rearward, it is also raised by a certain amount in the vertical direction because of its length-invariable suspension on the tip of the stay rack 18. By means of the change in the potential energy of the counterweight arrangement 4, in addition to the increase in the load equalization torque with respect to the axis of rotation of the crane superstructure, a resetting torque is also generated which attempts to move the counterweight arrangement 4 in a forward direction again into a position of lower potential energy. A reduction in the cable force in the hoisting cable 6 conversely leads to the counterweight arrangement 4 being moved in a forward direction again.

(10) Since the stay rack 18 and the jib 3 enclose a constant angle α, the mechanism of the counterweight adjustment device 7 remains uninfluenced by the size of the tilting angle γ.

(11) The use of the stay rack 18, which is already structurally provided, as a coupling point for the lever element 9 brings about the advantage of a compact construction of the crawler crane, in particular with respect to the rearward slewing radius of the counterweight arrangement 4. In the embodiment which can be seen in FIG. 1, only the hoisting cable force has a direct influence on the size of the arising counterweight radius if the angle β remains unchanged. The counterweight radius thus arises virtually automatically in a mechanical way corresponding to the hoisting cable force which is present. Actuators and sensors controlled in a complicated manner can thereby be dispensed with apart from the use of displacement sensors, position indicators, load cells or a cable metering means.

(12) FIG. 2 shows a further embodiment of the crane according to the invention which differs from the crane shown in FIG. 1 essentially only by means of a different embodiment of the counterweight adjustment device 7. The lever element 9 is now arranged rotatably about a fixed point relative to the crane superstructure 1, by said lever element being mounted about a pivot point 8 on a bracket 1a of the crane superstructure 1. This has the result that, even a load torque which is variable by tilting of the jib 3 can be equalized in a variable manner by the counterweight arrangement 4. The position of the counterweight arrangement 4 is thus not only dependent on the hoisting cable load, but also on the load radius or on the tilting angle γ.

(13) In the case shown in FIG. 2, the jib stay 19 present in the crane from FIG. 1 can thus also be omitted since the bracing forces are now produced via the hoisting cable loop(s) formed between the deflecting pulley arrangements 12 and 13, and via the lever element 9, the pendulum support 14, the stay (21) of the counterweight arrangement 4 on the stay rack tip, and the stay rack 18. It should be noted in this connection that the stay (21) coupling the stay rack tip to the counterweight arrangement 4 has to be designed in such a manner that it can transmit compressive forces. It is likewise possible for a conventional jib stay to be provided, but this has to be force- and length-variable, in contrast to the length-invariable stay 19 from FIG. 1, since, during the tilting of the jib 3, the angle β remains constant while the angle α is variable. For this purpose, the retraction winch 15 uses the retraction mechanism 16 in the event of the tilting up to pull the stay rack 18 in the direction of the crane superstructure 1 or let same out in the direction of the main jib 3 in the event of the tilting down. A rearward force- and length-variable stay of the stay rack 18 would also be conceivable, which can comprise, for example, a cylinder which brings about a change in force and length.

(14) In the event of hoisting, the tilting up or down of the jib 3 changes the resultant force in the force triangle formed by the stay rack 18, the lever element 9 and the pendulum support 14. In order to produce a horizontal load equalization, and therefore equilibrium between the load side and counterweight side, via the lever element 9, the counterweight arrangement 4 is further deflected. In other words, by means of a stronger force resulting from the hoisting cable force and the stay rack adjustment, a heavy counterweight arrangement 4 can thus be brought onto a greater counterweight radius.

(15) The function of the embodiment shown in FIG. 2 will be outlined briefly below: the load lying on the ground is raised by means of the hoisting cable 6. The load in the hoisting cable 6 increases in the process. Via the hoisting cable loop 11, the force then also acts on the lever element 9 and, by means of the pendulum support 14, pushes the counterweight arrangement 4 rearward, increasing the counterweight radius in the horizontal direction. At the same time, the counterweight arrangement 4 is raised in the circular arc of its suspension, which generates a resetting force in the lever element 9 via the pendulum support 14. If the force in the hoisting cable loop 11 and the force from the linear and/or arcuated adjustment of the counterweight radius are in balance, the load torque being introduced to the structurally defined ratio of the force triangle of stay rack 18, lever element 9, counterweight stay and pendulum support 14, i.e. the counterweight torque, is equalized. The overall system behaves mechanically virtually like a balancer with horizontal load equalization. The depositing of the load proceeds in reverse. Gravity pulls the counterweight arrangement 4 back into its starting position again in proportion to the slackening hoisting cable force in the hoisting cable loop 11 by means of the lever element 9.

(16) FIGS. 3 and 4 show stationary cranes, the lever element of which, as in the case of the crane from FIG. 2 is likewise coupled to a bracket 1a of the crane structure 1. While, in the case of the crane from FIG. 3, the counterweight arrangement 4 is carried by the stay rack 18, on the tip of which said counterweight arrangement is suspended, as already in the case of the cranes from FIGS. 1 and 2, the crane from FIG. 4 additionally has a guide 20 for the counterweight 4. Said guide 20 comprises an arcuate guide rail which is coupled to the counterweight arrangement 4 and is guided on the crane structure by means of running rollers (not denoted specifically). The guide 20 provides an additional safety function in relation to the embodiment shown in FIG. 3. Thus, for example, in the case of a spontaneous “tearing off” of the lifting load, the counterweight arrangement 4 can be guided back in a controlled manner into a position with a lower counterweight torque, while simultaneously avoiding an undamped overswinging of the counterweights 4 suspended on the stay rack tip. For this purpose, the guide 20 can have damping, for example frictional damping between two components moving relative to each other. It can readily be seen both in FIG. 3 and in FIG. 4 that, in the rearwardly deflected state, the counterweight arrangement 4 has a higher level of potential energy which is dissipated when the counterweight arrangement 4 is retracted again in the direction of the rotational center of the crane.