Tower crane

Abstract

The present invention relates to the field of lifting equipment and discloses a tower crane, wherein a boom (2) is hinged to the top of a tower body (1) through a hinge shaft (22a) and comprises a balance arm (21) and a lifting arm (23); the balance arm (23) is provided with a self-unloading counterweight (4) fixed at an installation position through a self-unloading locking mechanism (3); the tower crane is also provided with a trigger device connected to the tower body (1); when the lifting moment of the lifting arm (23) suddenly decreases, the boom (2) can rotate relative to the tower body (1) around the hinge shaft (22a) so that the lifting arm (23) rises relative to the tower body (1), so that the self-unloading locking mechanism (3) is triggered by the trigger device to release the self-unloading counterweight (4) and make it fall off from the installation position, thereby suppressing the upward movement of the boom caused by the drastic change of the instantaneous load it bears, thereby reducing or avoiding the bending moment impact on the tower body, and effectively reducing the risk of overturning accidents.

Description

Technical Field

[0001] The invention relates to lifting equipment, in particular to a tower crane. Background Art

[0002] Tower cranes (also called "tower cranes") have tall towers and are widely used in the construction of housing, bridges, wind power, ports, nuclear power plants, etc. With the development trend of large-scale, modular and intensive construction projects, the development of super-large tower cranes is also required. Super-large tower cranes have the characteristics of high operating height, large lifting weight, and long operating range. Compared with ordinary tower cranes, they are more expensive and bulky, which will significantly increase the property losses and secondary damages caused by overturning accidents.

[0003] In this regard, traditional tower cranes generally improve their anti-overturning performance by enhancing the overall and local structural strength of the tower body or adjusting mass distribution. However, as the weight of the hoisted load increases, this method is difficult to meet the anti-overturning performance requirements of super-large tower cranes, especially in the case of sudden unloading such as the breakage of the wire rope hanging the load, the instantaneous load on the boom changes dramatically, which will produce a huge bending moment impact on the tower body. It is difficult to avoid the crane from overturning accidents by simply relying on enhancing the structural strength and adjusting the mass distribution. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem in the prior art that tower cranes are prone to overturning accidents in the event of sudden unloading, and to provide a tower crane that can be mechanically triggered to release the self-unloading counterweight on the balance arm when the boom is raised relative to the tower body, so as to reduce the risk of overturning accidents by suppressing the rising of the boom.

[0005] In order to achieve the above object, the present invention provides a tower crane, comprising:

[0006] Tower body;

[0007] A boom, which is hinged to the top of the tower body through a hinge shaft and includes a balancing arm extending from a hinge position to one side of the tower body and a lifting arm extending to the other opposite side, wherein the balancing arm is equipped with a self-unloading counterweight fixed at the installation position by a self-unloading locking mechanism; and

[0008] A trigger device is connected to the tower body. When the lifting torque of the boom suddenly decreases, the boom can rotate around the hinge axis relative to the tower body so that the boom rises relative to the tower body, so as to trigger the self-unloading locking mechanism through the trigger device to release the self-unloading counterweight and make the self-unloading counterweight fall off from the installation position.

[0009] Preferably, the self-unloading locking mechanism comprises a load-bearing beam and a supporting mechanism respectively hinged to the balancing arm, and the load-bearing beam is supported by the supporting mechanism to keep the self-unloading counterweight at the installation position.

[0010] Preferably, the trigger device includes a pulling mechanism, which includes a pivot plate hinged to the boom and having a first fulcrum and a second fulcrum, a first pull rod connected at both ends to the first fulcrum and the tower body, and a second pull rod connected at both ends to the second fulcrum and the supporting mechanism. When the boom rotates relative to the tower body so that the lifting arm rises relative to the tower body, the supporting mechanism is pulled to rotate relative to the load-bearing beam around the hinge axis with the boom under the linkage action of the pulling mechanism to a position that is detached from the support of the load-bearing beam, so that the self-unloading counterweight can fall freely from the load-bearing beam.

[0011] Preferably, the pivot plate is formed as a fan-shaped plate, the boom is hinged to the central angle of the fan-shaped plate, and the first fulcrum and the second fulcrum are respectively located at the other two corners; or, the pivot plate is formed as a triangular plate, the boom is hinged to one of the corners of the triangular plate, and the first fulcrum and the second fulcrum are respectively located at the other two corners.

[0012] Preferably, the second tie rod comprises a plurality of tie rod sections connected in sequence, and two adjacent tie rod sections are detachably connected to each other and / or are connected so that the second tie rod has flexibility at the connected position.

[0013] Preferably, the boom comprises a connecting arm connected between the balancing arm and the lifting arm, the hinge shaft is arranged at the lower side of the connecting arm, and the pivot plate is hinged to the center position of the connecting arm.

[0014] Preferably, a support shaft is provided at the lower side of the end portion of the connecting arm connected to the lifting arm, and the connecting arm is supported on the top end of the tower body by the support shaft.

[0015] Preferably, a fixed support is provided at the top of the tower body, a groove for supporting the support shaft is formed on the fixed support, and / or the bottom end of the first pull rod is connected to the fixed support.

[0016] Preferably, one of the load-bearing beam and the supporting mechanism is formed with a groove, and the other is formed with a spherical surface cooperating with the groove, so that the spherical surface can be disengaged from the groove and out of the position supporting the load-bearing beam by rotating the supporting mechanism.

[0017] Preferably, the boom and the load-bearing beam extend in horizontal directions respectively, and the support mechanism is hinged on the bottom beam of the boom. When supporting the load-bearing beam, the angle between the support mechanism and the load-bearing beam facing the self-unloading counterweight is greater than 90°.

[0018] Preferably, the tower crane further comprises a damping device for slowing down the relative rotation speed of the boom and the tower body, or a self-locking device for locking the boom in an extreme upward position, the two ends of which are respectively hinged to the tower body and the boom.

[0019] Through the above technical scheme, the tower crane of the present invention can allow the boom to rotate around the hinge axis relative to the tower body when the boom is suddenly unloaded, and the boom drives the self-unloading locking mechanism to move and the tower body limit trigger device to trigger the self-unloading locking mechanism to release the self-unloading counterweight, thereby suppressing the upward movement of the boom caused by the drastic change of the instantaneous load it bears, thereby reducing or avoiding the bending moment impact on the tower body, and effectively reducing the risk of overturning accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a structural schematic diagram of a tower crane according to a preferred embodiment of the present invention;

[0021] Figure 2 Yes Figure 1 An enlarged view showing the crane arm cut off;

[0022] Figure 3 It is a schematic diagram of the boom after sudden unloading;

[0023] Figure 4 Yes Figure 3 An enlarged view showing the crane arm cut off;

[0024] Figure 5 yes Figure 1 Schematic diagram of the structure of the trigger device of the medium tower crane;

[0025] Figure 6 yes Figure 1 Schematic diagram of the installation structure of the medium dump counterweight on the balance arm.

[0026] Description of Reference Numerals

[0027] 1-tower body; 1a-fixed support; 2-jib; 21-balance arm; 22-connecting arm; 22a-hinge shaft; 22b-support shaft; 23-lifting arm; 3-self-unloading locking mechanism; 31-load-bearing beam; 32-support mechanism; 4-self-unloading counterweight; 5-first tie rod; 6-pivot plate; 7-second tie rod; 8-damping device. DETAILED DESCRIPTION

[0028] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0029] Reference Figures 1 to 4 As shown, a tower crane according to a preferred embodiment of the present invention comprises a tower body 1 and a boom 2 connected to the top of the tower body 1, the boom 2 is hinged to the tower body 1 through a hinge shaft 22a, and comprises a balance arm 21 extending from a hinge position to one side of the tower body 1 and a boom 23 extending to the other opposite side. The boom 23 may be provided with a hanging assembly such as a wire rope, a hook, etc. for connecting to the load being hoisted. A self-unloading counterweight 4 is installed on the balance arm 21, and the self-unloading counterweight 4 is fixed to the installation position by a self-unloading locking mechanism 3. When the boom 23 is suddenly unloaded due to failure of the connection between the hanging assembly and the hoisted load, breakage of the wire rope, etc., the instantaneous load borne by the boom 23 changes dramatically, so that the boom 2 can rotate around the hinge shaft 22a between it and the tower body 1, causing the boom 23 to rise. To this end, the tower crane of the present invention further comprises a trigger device connected to the tower body 1 , which can trigger the self-unloading locking mechanism 3 to release the self-unloading counterweight 4 to inhibit the upward movement of the boom 23 when the boom 23 is rising relative to the tower body 1 .

[0030] Trigger device

[0031] In the tower crane of the present invention, the trigger device can trigger the self-unloading locking mechanism 3 to release the self-unloading counterweight 4 after the lifting arm 23 is lifted, so that the self-unloading counterweight 4 falls off from the counterweight 21. Figure 5 As shown, in a preferred embodiment of the present invention, the trigger device includes a pulling mechanism, which includes a pivot plate 6 hinged to the boom 2, and the pivot plate 6 has a first fulcrum and a second fulcrum, wherein the first fulcrum is connected to the tower body 1 through a first pull rod 5, and the second fulcrum is connected to the self-unloading locking mechanism 3. In the case of sudden unloading of the hanging assembly, the boom 2 can rotate relative to the tower body 1 around the hinge shaft 22a, so that the lifting arm 23 rises relative to the tower body 1, and under the action of the first pull rod 5, the pivot plate 6 remains stationary relative to the tower body 1; at the same time, the self-unloading locking mechanism 3 moves relative to the pivot plate 6 with the rotation of the boom 2, thereby, under the linkage action of the pivot plate 6, the self-unloading locking mechanism 3 can be triggered by pulling, so that it releases the self-unloading counterweight 4 on the balance arm 21, thereby suppressing the upward movement of the boom 2 caused by the drastic change of the instantaneous load it bears, thereby reducing or avoiding the bending moment impact on the tower body 1, and effectively reducing the risk of overturning accidents.

[0032] The second fulcrum of the pivot plate 6 can be connected to the self-unloading locking mechanism 3 in a variety of ways so as to apply a pulling force to the self-unloading locking mechanism 3. In the preferred embodiment shown in the figure, the second fulcrum of the pivot plate 6 is hinged with a second tie rod 7, which extends along the balance arm 21 and is connected to the self-unloading locking mechanism 3 (such as being hinged to the support mechanism 32 of the self-unloading locking mechanism 3 described later). Since the position of the self-unloading locking mechanism 3 will change during the rotation of the boom 2 relative to the tower body 1, the extension path of the second tie rod 7 will also change accordingly. For this reason, in addition to making the two ends of the second tie rod 7 respectively hinged to the pivot plate 6 and the self-unloading locking mechanism 3, the second tie rod 7 can also be made flexible to adapt to the movement of the boom 2. For example, the second tie rod 7 can be configured to include a plurality of tie rod sections connected in sequence to allow the second tie rod 7 to be bent at the connection position. In addition, the plurality of tie rod sections can also be configured to be detachably connected to each other.

[0033] Under normal working conditions, the extension directions of the boom 2 and the tower body 1 are usually arranged to be perpendicular to each other, and the self-unloading trigger device of the present invention needs to use the tower body 1 as a traction basis to trigger the self-unloading locking mechanism 3 on the boom 2, thereby, it is necessary to use the pivot plate 6 hinged to the boom 2 to change the direction of tension transmission. In the self-unloading trigger device provided by the present invention, the pivot plate 6 can be formed as a triangular plate, and is hinged to the boom 2 through one of its corners, and the positions of the other two corners are provided with a first fulcrum connected to the first pull rod 5 and a second fulcrum connected to the second pull rod 7. By arranging the hinge point, the first fulcrum and the second fulcrum at intervals from each other, the tension applied to the pivot plate 6 by the first pull rod 5 can make the pivot plate 6 rotate relative to the boom 2 around the hinge point or have a tendency to rotate relative to the boom 2, thereby applying a tension along the extension direction of the boom 2 to the second pull rod 7, thereby triggering the self-unloading locking mechanism 3 to release the self-unloading counterweight 4 when the boom 2 rotates relative to the tower body 1.

[0034] In another preferred embodiment, the pivot plate 6 can also be formed as a fan-shaped plate, which can be hinged to the boom 2 at its central angle position, and the first fulcrum and the second fulcrum are set at the other two corners close to the top of the arc. It can also trigger the self-unloading locking mechanism 3 by transmitting tension through the first pull rod 5 and the second pull rod 7.

[0035] It should be understood that in the case of sudden unloading, the boom 2 rotates as a whole relative to the tower body 1, resulting in the lifting arm 23 rising. Therefore, the balance arm 21 and the lifting arm 23 described in the present invention are distinguished by different extensions of the boom 2 relative to the tower body 1 only for the convenience of clear description, and they are connected to each other as a whole (that is, the boom 2 can be an integral truss structure). Therefore, the boom 2 also includes a connecting arm 22 connected between the balance arm 21 and the lifting arm 23, and the hinge shaft 22a for hinged connection with the tower body 1 can be set at the lower side of the connecting arm 22.

[0036] In order to avoid interference with related components such as the lifting wire rope, the pivot plate 6 can be hinged to the center position of the connecting arm 22. The center position of the connecting arm 22 here refers to the center position of the connecting arm 22 in the extension direction and the height direction. For example, for a boom 2 with a rectangular cross section, a pair of pivot plates 6 can be provided on two truss planes in the vertical direction thereof, and are respectively connected to the self-unloading locking mechanism 3 through corresponding second pull rods 7.

[0037] Under normal working conditions, the tower body 1 bears the pressure of the boom 2, and therefore needs to provide sufficient support to the boom 2. To this end, a support shaft 22b can be provided at the lower side of the end of the connecting arm 22 connected to the lifting arm 23, and the boom 2 is supported on the top of the tower body 1 through the support shaft 22b.

[0038] As the construction progresses, the height of the tower body 1 will be increased by adding standard sections, etc., so it is usually necessary to set a fixed support 1a for connecting the boom 2 at the top of the tower body 1. The fixed support 1a may be formed with a groove for supporting 22b, which can play a limiting role in the extension direction of the boom 2. In this case, the first pull rod 5 can also be connected to the fixed support 1a at the bottom end, so that there is no need to adjust its connection relationship with the tower body 1 during the construction process.

[0039] Self-unloading counterweight installation structure

[0040] In the tower crane of the present invention, the self-unloading counterweight 4 can be released after the lifting arm 23 is lifted up, so as to fall off from the counterweight 21. The self-unloading counterweight 4 is fixed to the installation position by the self-unloading locking mechanism 3, wherein, as shown in FIG. Figure 6As shown, the self-unloading locking mechanism 3 may include a load-bearing beam 31 and a supporting mechanism 32, one end of the supporting mechanism 32 is hinged on the boom 2, and the other end supports the load-bearing beam 31, so that the self-unloading counterweight 4 can be kept on the boom 2 through the load-bearing beam 31, and the supporting mechanism 32 is arranged to be driven to rotate around the hinge axis between it and the boom 2 until the load-bearing beam 31 is out of the supported state, so that the self-unloading counterweight 4 can fall freely from the load-bearing beam 31. When the tower crane is suddenly unloaded due to failure of the connection between the hanging assembly and the hoisted load, breakage of the wire rope, etc., the boom 2 can be rotated around the hinge axis 22a between it and the tower body 1, causing the boom 2 to rise. During the upward movement of the boom 2, the supporting mechanism 32 will be triggered to rotate around the hinge axis between the boom 2 and the boom 2 until the load-bearing beam 31 is released from the supported state, thereby allowing the self-unloading counterweight 4 to fall freely from the load-bearing beam 31. This can suppress the upward movement of the boom 2 caused by the drastic change in the instantaneous load it bears, thereby reducing or avoiding the bending moment impact on the tower body 1, and effectively reducing the risk of overturning accidents.

[0041] The supporting connection relationship between the load-bearing beam 31 and the support mechanism 32 is achieved through the cooperation of the spherical surface and the groove. For example, a groove is set on the load-bearing beam 31, and accordingly, the end of the support mechanism 32 is designed to be in the form of a spherical surface, so that the spherical end of the support mechanism 32 is located in the groove on the load-bearing beam 31, thereby supporting the load-bearing beam 31. When the support mechanism 32 is driven to rotate a certain angle, the spherical surface is disengaged from the groove, and then the support mechanism 32 is separated from the position of supporting the load-bearing beam 31, so that the load-bearing beam 31 rotates downward around the hinge point between it and the balance arm 21, releasing the self-unloading balance weight. 4, so that the self-unloading counterweight 4 falls off from the balance arm 21; or, a spherical surface can be formed on the load-bearing beam 31, and accordingly, the end of the support mechanism 32 is designed as a groove, so that the spherical surface is located in the groove, and the support mechanism 32 supports the load-bearing beam 31 through the groove. When the support mechanism 32 is driven to rotate a certain angle, the spherical surface is disengaged from the groove, and then the support mechanism 32 is separated from the position of supporting the load-bearing beam 31, so that the load-bearing beam 31 rotates downward around the hinge point between it and the balance arm 21, and the self-unloading counterweight 4 is released, so that the self-unloading counterweight 4 falls off from the balance arm 21.

[0042] The load-bearing beam 31 and the support mechanism 32 constitute a self-unloading locking mechanism 3, which is connected to the transmission mechanism. After the lifting arm 23 is raised, the transmission mechanism triggers the self-unloading locking mechanism 3 to release the self-unloading counterweight 4, so that the self-unloading counterweight 4 falls off the counterweight 21. The self-unloading counterweight 4 is held on the counterweight 21 by the load-bearing beam 31, one end of the load-bearing beam 31 is hinged to the counterweight 21, and the other end is supported by the support mechanism 32 hinged to the counterweight 21. The support mechanism 32 is connected to the transmission mechanism, and the transmission mechanism can be pulled to apply a pulling force to the support mechanism 32 in a direction away from the self-unloading counterweight 4, so that the support mechanism 32 is separated from the position of supporting the load-bearing beam 31.

[0043] Under normal working conditions, refer to Figure 1 and Figure 6 As shown, the extension directions of the boom 2 and the tower body 1 are usually arranged to be perpendicular to each other, the boom 2 extends in the horizontal direction, and accordingly, the load-bearing beam 31 also extends in the horizontal direction, and the support mechanism 32 is hinged on the bottom beam of the boom 2. In the state of supporting the load-bearing beam 31, the angle between the support mechanism 32 and the load-bearing beam 31 on the side facing the self-unloading counterweight 4 is greater than 90°. The transmission mechanism of the present invention needs to use the tower body 1 as a traction basis to trigger the self-unloading locking mechanism 3 on the boom 2, thereby, the direction of tension transmission can be changed through the aforementioned pivot plate 6 hinged to the boom 2.

[0044] Based on the above-mentioned trigger device and the installation structure of the self-unloading counterweight, the tower crane of the present invention can be configured to respectively hinge the two ends of the second pull rod 7 to the second fulcrum of the pivot plate 6 and the support mechanism 32 of the self-unloading locking mechanism 3. When the boom 2 rotates relative to the tower body 1 to make the lifting arm 23 rise relative to the tower body 1, the relative movement of the boom 2 and the tower body 1 is utilized to pull the support mechanism 32 by the trigger device (through the first pull rod 5, the pivot plate 6 and the second pull rod 7 in sequence) to rotate relative to the load-bearing beam 31 around its hinge axis with the boom 2 until it is out of the position of supporting the load-bearing beam 31, so that the self-unloading counterweight 4 can fall freely from the load-bearing beam 31.

[0045] The tower crane of the present invention can be triggered by a self-unloading trigger device to release the self-unloading counterweight on the counterarm to suppress the lifting of the boom. The lifting and resetting of the boom can only enable the boom to realize the mutual conversion between kinetic energy and gravitational potential energy, and these energies always need to be transferred to the tower body or consumed in the lifting process. Therefore, in the case of sudden unloading of the boom, the lifting and resetting of the boom can be effectively controlled to slow down the impact on the tower body, thereby preventing the tower crane from overturning. For this reason, a damping device 8 or a self-locking device can also be connected between the tower body 1 and the boom 23 to slow down the relative rotation speed of the boom 23 and the tower body 1, or the boom 23 is locked in the limit lifting position, thereby effectively supporting the boom when the boom is lifted to the limit lifting position and preventing the boom from freely resetting, so that the kinetic energy of the boom is converted into gravitational potential energy and maintained, avoiding the impact on the tower body caused by the resetting of the boom, so as to effectively prevent the overturning accident. Typically, the damping device 8 or the self-locking device can be set as a hydraulic component (such as a damping cylinder) and can support the boom 23 at the extreme upward position through hydraulic pressure. By controlling the tensile damping and compressive damping of the damping cylinder, the boom 23 can be controllably raised and reset in the event of a sudden unloading of the boom 23, thereby providing higher safety.

[0046] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various specific technical features in any suitable manner. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A tower crane, characterized in that: include: Tower body (1); A boom (2) is hinged to the top of the tower body (1) via a hinge shaft (22a) and comprises a balancing arm (21) extending from the hinge position to one side of the tower body (1) and a lifting arm (23) extending to the other opposite side, wherein the balancing arm (21) is equipped with a self-unloading counterweight (4) fixed at the installation position via a self-unloading locking mechanism (3); and A trigger device is connected to the tower body (1). When the lifting torque of the lifting arm (23) suddenly decreases, the boom (2) can rotate relative to the tower body (1) around the hinge shaft (22a) so that the lifting arm (23) rises relative to the tower body (1), thereby triggering the self-unloading locking mechanism (3) through the trigger device to release the self-unloading counterweight (4) and cause the self-unloading counterweight (4) to fall off from the installation position.

2. The tower crane according to claim 1, characterized in that: The self-unloading locking mechanism (3) comprises a load-bearing beam (31) and a supporting mechanism (32) respectively hinged to the balancing arm (21); the load-bearing beam (31) is supported by the supporting mechanism (32) to keep the self-unloading counterweight (4) at the installation position.

3. The tower crane according to claim 2, characterized in that: The trigger device comprises a pulling mechanism, which comprises a pivot plate (6) hinged to the boom (2) and having a first fulcrum and a second fulcrum, a first pull rod (5) having two ends respectively connected to the first fulcrum and the tower body (1), and a second pull rod (7) having two ends respectively connected to the second fulcrum and the support mechanism (32). When the boom (2) rotates relative to the tower body (1) so that the lifting arm (23) rises relative to the tower body (1), the support mechanism (32) is pulled to rotate relative to the load-bearing beam (31) around its hinge axis with the boom (2) to a position where it is separated from the load-bearing beam (31) under the linkage action of the pulling mechanism. This allows the self-unloading counterweight (4) to fall freely from the load-bearing beam (31).

4. The tower crane according to claim 3, characterized in that: The pivot plate (6) is formed as a fan-shaped plate, the boom (2) is hinged to the central angle of the fan-shaped plate, and the first fulcrum and the second fulcrum are respectively located at the other two corners; or, the pivot plate (6) is formed as a triangular plate, the boom (2) is hinged to one of the corners of the triangular plate, and the first fulcrum and the second fulcrum are respectively located at the other two corners.

5. The tower crane according to claim 3, characterized in that: The second tie rod (7) comprises a plurality of tie rod sections connected in sequence, and two adjacent tie rod sections are detachably connected to each other and / or are connected so that the second tie rod (7) is flexible at the connected position.

6. The tower crane according to claim 3, characterized in that: The boom (2) comprises a connecting arm (22) connected between the balancing arm (21) and the lifting arm (32), the hinge shaft (22a) is arranged on the lower side of the connecting arm (22), and the pivot plate (6) is hinged to the center position of the connecting arm (22).

7. The tower crane according to claim 6, characterized in that: A support shaft (22b) is provided at the lower side of the end of the connecting arm (22) connected to the lifting arm (23), and is supported on the top end of the tower body (1) by the support shaft (22b).

8. The tower crane according to claim 7, characterized in that: A fixed support (1a) is provided at the top of the tower body (1), a groove for supporting the support shaft (22b) is formed on the fixed support (1a), and / or the bottom end of the first pull rod (5) is connected to the fixed support (1a).

9. The tower crane according to claim 2, characterized in that: One of the load-bearing beam (31) and the support mechanism (32) is formed with a groove, and the other is formed with a spherical surface that matches the groove, so that the spherical surface can be disengaged from the groove and out of the position supporting the load-bearing beam (31) by rotating the support mechanism (32).

10. The tower crane according to claim 2, characterized in that: The boom (2) and the load-bearing beam (31) extend in the horizontal direction respectively, and the support mechanism (32) is hinged on the bottom beam of the boom (2). When supporting the load-bearing beam (31), the angle between the support mechanism (32) and the load-bearing beam (31) facing the self-unloading counterweight (4) is greater than 90°.

11. The tower crane according to claim 1, characterized in that: The tower crane also comprises a damping device (8) for slowing down the relative rotation speed of the boom (23) and the tower body (1), or a self-locking device for locking the boom (23) at an extreme upward position, the two ends of which are respectively hinged to the tower body (1) and the boom (23).

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