Crane

Abstract

The present invention relates to a crane, in particular to a revolving tower crane, having a boom rotatable about an upright slewing gear axis by a slewing gear drive and having an out-of-operation brake which allows and brakes rotary movements of the boom in the out-of-operation state. In accordance with the invention, the out-of-operation brake is configured as working electrodynamically and comprises an electric motor of the slewing gear drive which can be operated as an electric-motor brake.

Claims

1. A revolving tower crane comprising: a boom rotatably supported about an upright axis of rotation by a slewing gear drive, wherein the boom comprises an out-of-operation brake which permits and brakes rotary movements of the boom in an out-of-operation state of the crane under wind loads, wherein the out-of-operation brake is configured to operate electrodynamically, and wherein the out-of-operation brake comprises an electric motor of the slewing gear drive which is operable as an electric-motor brake, wherein the electric motor is configured as an asynchronous motor with which an out-of-operation exciter is connected thereto, and wherein the out-of-operation exciter comprises a capacitor circuit.

2. The crane of claim 1, further comprising a brake circuit connected with the electric motor of the slewing gear drive.

3. The crane of claim 2, wherein the brake circuit comprises at least one series resistance (R.sub.v) which can be activated or connected thereto.

4. The crane of claim 3, wherein the series resistance (R.sub.V) which can be activated is configured as three-phase or comprises three resistance groups of at least approximately the same size with a single-phase configuration.

5. The crane of claim 3, wherein the series resistance (R.sub.V) which can be activated comprises a braking resistance which can be activated in normal operation for taking up a reverse power produced in crane operation.

6. The crane of claim 5, wherein the series resistance (R.sub.V) which can be activated is configured as three-phase or comprises three resistance groups of at least approximately the same size with a single-phase configuration.

7. The crane of claim 2, wherein the brake circuit comprises a short-circuit switch for short-circuiting a motor winding of the electric motor.

8. The crane of claim 1, wherein the capacitor circuit comprises excitation capacitors switchable in parallel with the winding of the asynchronous motor and connected to one another in a star or in a triangle.

9. The crane of claim 1, wherein the out-of-operation brake is configured such that the braking torque is smaller than a predefined torque up to a predefined rotational speed of the boom, said predefined torque being able to be produced by a predefined wind load on the crane and the braking torque only being larger than the predefined torque produced by said wind load on the crane on an exceeding of said rotational speed of the boom.

10. The crane of claim 1, further comprising a cooling apparatus active in electric-motor braking operation, wherein the cooling apparatus is connected with the electric motor.

11. A revolving tower crane comprising: a boom rotatably supported about an upright axis of rotation by a slewing gear drive, wherein the boom comprises an out-of-operation brake which permits and brakes rotary movements of the boom in an out-of-operation state of the crane under wind loads, wherein the out-of-operation brake is configured to operate electrodynamically, and wherein the out-of-operation brake comprises an electric motor of the slewing gear drive which is operable as an electric-motor brake, wherein the electric motor is configured as an asynchronous motor with which an out-of-operation exciter is connected thereto, wherein the out-of-operation exciter comprises a capacitor circuit, and wherein the capacitor circuit comprises excitation capacitors switchable in parallel with the winding of the asynchronous motor and connected to one another in a star or in a triangle.

12. The crane of claim 11, further comprising a brake circuit connected with the electric motor of the slewing gear drive.

13. The crane of claim 12, wherein the brake circuit comprises at least one series resistance (R.sub.v) which can be activated or connected thereto.

14. The crane of claim 13, wherein the series resistance (R.sub.V) which can be activated is configured as three-phase or comprises three resistance groups of at least approximately the same size with a single-phase configuration.

15. The crane of claim 13, wherein the series resistance (R.sub.V) which can be activated comprises a braking resistance which can be activated in normal operation for taking up a reverse power produced in crane operation.

16. The crane of claim 15, wherein the series resistance (R.sub.V) which can be activated is configured as three-phase or comprises three resistance groups of at least approximately the same size with a single-phase configuration.

17. The crane of claim 12, wherein the brake circuit comprises a short-circuit switch for short-circuiting a motor winding of the electric motor.

18. A revolving tower crane comprising: a boom rotatably supported about an upright axis of rotation by a slewing gear drive, wherein the boom comprises an out-of-operation brake which permits and brakes rotary movements of the boom in an out-of-operation state of the crane under wind loads, wherein the out-of-operation brake is configured to operate electrodynamically, and wherein the out-of-operation brake comprises an electric motor of the slewing gear drive which is operable as an electric-motor brake, and a cooling apparatus active in electric-motor braking operation, wherein the cooling apparatus is connected with the electric motor.

19. The crane of claim 18, further comprising a brake circuit connected with the electric motor of the slewing gear drive.

20. The crane of claim 18, wherein the out-of-operation brake is configured such that the braking torque is smaller than a predefined torque up to a predefined rotational speed of the boom, said predefined torque being able to be produced by a predefined wind load on the crane and the braking torque only being larger than the predefined torque produced by said wind load on the crane on an exceeding of said rotational speed of the boom.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The invention will be explained in more detail in the following with respect to preferred embodiments and to associated drawings. There are shown in the drawings:

(2) FIG. 1: a perspective, portion-wise representation of a revolving tower crane in accordance with an advantageous embodiment of the invention which is configured as a top-slewer and which has a slewing gear for rotating the boom relative to the tower;

(3) FIG. 2: an electrical equivalent circuit diagram of an electric motor of the slewing gear drive which is configured as a permanently excited synchronous motor and of the short-circuit switch with series resistances associated therewith;

(4) FIG. 3: a characteristic of the braking torque which can be generated by the electric motor of FIG. 2 over the motor speed when the synchronous motor of FIG. 2 is in the short-circuited state, with the part-view FIG. 3a showing the characteristic curve without series resistances connected in short-circuit and with the part-view FIG. 3b showing the characteristic curves for different series resistances connectable during the short-circuiting;

(5) FIG. 4: an electrical equivalent circuit diagram of a permanently excited synchronous motor similar to FIG. 2, with the braking resistances of a brake chopper present in the inverter circuit being used as series resistances switchable during the short-circuiting;

(6) FIG. 5: an electrical equivalent circuit diagram of the braking resistances which can be connected as series resistances during the short-circuiting similar to FIG. 4, with the braking resistance not being configured as three-phase, but comprising three resistance groups of approximately equal size with a single-phase configuration; and

(7) FIG. 6: an electrical equivalent circuit diagram of a slewing gear drive having two asynchronous motors which can be operated by a common inverter, with capacitors being connected in parallel for the magnetic self-excitation of the asynchronous motors.

DETAILED DESCRIPTION

(8) As FIG. 1 shows, the crane forming the object can be a revolving tower crane 1 configured as a so-called top-slewer whose tower 2 supports a boom 3 and a counter-boom 4 which extend substantially horizontally and which are rotatable about the upright tower axis 5 relative to the tower 2. Instead of the crane configuration shown in FIG. 1, the revolving tower crane 1 can, however, also be configured as a bottom-slewer and/or can comprise a luffable, pointed boom and/or can be guyed via a guying with respect to the tower foot or the superstructure.

(9) To be able to rotate the boom 3, a slowing gear 6 is provided which is provided in the embodiment shown at the upper end of the tower 2 between the boom 3 and the tower 2 and which can comprise a sprocket with which a drive wheel driven by a drive motor 7 can mesh.

(10) An advantageous embodiment of the drive device of the slewing gear 6 can comprise an electrical drive motor 7 which can drive a drive shaft via a slewing gear transmission. Said slewing gear transmission can, for example, be a planetary gear to step the speed of the drive motor 7 up/down into a speed of the output shaft in a suitable manner.

(11) To be able to brake rotary movements of the boom 3 in crane operation and/or to be able to maintain a rotary position of the boom 3 which has been moved to, the slewing gear 6 comprises a slewing gear service brake which can, for example, be arranged on the input side of the slewing gear transmission. The service brake can comprise, for example, in a manner known per se a frictional disk brake device or a multi-disk brake device which is preloaded into the braking position by a preloading device and which can be lifted by an electric adjustment actuator in the form of an electric magnet, for example, to release the brake. Alternatively or additionally to such a mechanical service brake, an electric-motor service brake can also be provided, for example in the form of a brake chopper having connectable braking resistances which can be integrated into or connectable/can be connected with the inverter controlling the electric motor 2, cf. FIGS. 4, 5 and 6.

(12) In addition to this service brake, the slewing gear 6 comprises an out-of-operation brake 10 which is intended to brake, but to allow, the rotary movements of the boom 3 in the shut-down out-of-operation state of the crane in order to enable a self-alignment of the crane or of its boom 3 under wind loads.

(13) Said out-of-operation brake 10 is configured as operating electrodynamically and comprises the drive or electric motor 7 of the slewing gear 6, which electric motor 7 can be operated as the electric-motor brake.

(14) As FIG. 2 shows, said electric motor 7 can in particular be configured as a permanently excited synchronous motor which can be supplied and controlled by an inverter 8. Said inverter 8 can comprise a rectifier 9 and an inverted rectifier 11, cf. FIG. 2, via which the supply voltage can be output to the electric motor 7.

(15) To generate the desired braking torque in the out-of-operation state, a short-circuit switch 12 can be connectable/can be connected with the electric motor 7 and the windings of the electric motor 7 can be short-circuited by means of it.

(16) Said short-circuit switch 12 can be connected to a line disconnector 13 by means of which the electric motor 7 can be disconnected from the supply network on the taking out of operation. Said short-circuit and line disconnection switches 12 and 13 can be integrated into a common switch so that only one switch has to be actuated on the taking out of operation. Alternatively, however, separate switches can also be provided which can be separately operable or which can advantageously be connected to one another such that an actuation of the one switch simultaneously actuates the other switch, preferably such that the electric motor is short-circuited simultaneously or offset in time on the disconnection of the electric motor 7 from the supply network.

(17) As FIG. 2 shows, series resistances R.sub.v can be connectable/connected with the short-circuit switch 12 which can be configured as three-phase and which can be connectable/connected with the motor winding in individual phases when the motor is short-circuited. In general, however, a pure short-circuit switch can also be used without such a series resistance.

(18) As FIG. 3a shows, the electric motor 7 produces a torque or braking torque varying with the speed in the short-circuited state. If the crane is rotated by the wind, for example, the electric motor 7 undergoes a corresponding rotation or speed which rises and falls with the wind-induced rotational speed of the crane. As FIG. 3a shows, on a lack of any rotational speed, no electrodynamic braking torque at all is initially produced, that is the crane can rotate freelyin more precise terms, while only overcoming the mechanical drag resistance. If the rotary speed increases, the braking torque produced electrodynamically by the electric motor 7 also rises progressively until it drops again at the characteristic tilt speed .sub.Kipp.

(19) As FIG. 3b shows, the development of the braking torque curve over the speed can be varied or controlled by switching in the series resistances R.sub.v shown in FIG. 2. The greater the series connected series resistances R.sub.v are, the shallower the increase in the braking torque curve, cf. FIG. 3, so that the maximum braking torque is only reached at a higher speed. The electrodynamically provided braking torque can accordingly be controlled in the desired manner in dependence on the speed by a selection of the series resistance or resistances. While it will be sufficient for a number of cranes only to be able to switch in a series resistance or a series resistance group on the short-circuiting, provision can also be made in a further development of the invention that the crane operator can switch in braking resistances of different magnitudes and can select which of a plurality of braking resistances is activated or connected thereto, for example in that a plurality of short-circuit switches having respectively connectable/can be connected braking resistances can be closed.

(20) As FIG. 2 shows, the series resistances R.sub.v can be separate resistances only provided for the out-of-operation brakes. Alternatively to this, however, an existing braking resistance can also advantageously be used as the series resistance R.sub.v which takes up the reverse power in normal crane operation, that is in the operating state, on the braking of the rotary movement of the revolving deck, for example. As FIG. 4 shows, such a braking resistance can be connectable/connected with a brake chopper which can be provided in the inverter circuit 8. Such a braking resistance can preferably already be of three-phase design, cf. FIG. 4 or can comprise at least approximately three resistance groups R.sub.1, R.sub.2, R.sub.3 of equal sizes with a single-phase design, cf. FIG. 5.

(21) The slewing gear 6 can also comprise one or more asynchronous motors as the electric motor 7 instead of a permanently excited synchronous motor, cf. FIG. 6. Such a plurality of asynchronous motors can advantageously be operated by a common inverter 8, with the inverter circuit in this respect being able to comprise a rectifier 9 and an inverter module 11 in manner known per se, with a brake chopper 14 having connectable/can be connected braking resistances Rv (a braking circuit) also being able to be provided here by which rotary movements can be braked in normal crane operation.

(22) Since such asynchronous motors lack the magnetic excitation in the out-of-operation state without the operating network voltage supply per se, excitation capacitors 15 (a capacitor circuit) can be switched into the asynchronous motors 7, for example via an out-of-operation switch 16. As FIG. 6 shows, the excitation capacitors 15 can advantageously be connected in a triangle and can be switched in parallel. Load resistances can advantageously be connectable/can be connected with the switchable excitation capacitors 15, cf. FIG. 6.

(23) The asynchronous motors 7, which operate as an out-of-operation brake, obtain the required idle power for magnetization required in generation operation from said excitation capacitors 15. In this respect, the idle current, and thus the magnetization, also increases as the speed or frequency rises. The voltage in the three-phase system likewise increases, which results in an increasing power take-up. All the components in the system are in this respect designed for the highest voltage to be assumed.

(24) To avoid inadmissible heating of the electric motor in braking operation, in particular by the short-circuit current after a short-circuit, a cooling apparatus 17 can be connectable/can be connected with the electric motor and can advantageously also be configured as a self-ventilator for cooling in the non-supplied state. A cooling fan driven by the speed of the electric motor can be used, for example.