Underframe structure and crane

Abstract

The utility model relates to the technical field of cranes, and discloses a chassis structure and a crane, the chassis structure comprises a flange fixing box and a support leg fixing box, the flange fixing box comprises an upper panel, a lower panel and a coaming assembly connected between the upper panel and the lower panel, the side end of the coaming assembly is fixedly connected to the side surface of the support leg fixing box, and the side surface of the support leg fixing box is fixedly connected with the lower panel. The side, close to the supporting leg fixing box, of the lower panel extends to the bottom of the supporting leg fixing box and is connected to the bottom of the supporting leg fixing box. The lower panel of the flange fixing box extends to the bottom of the supporting leg fixing box and is fixedly connected with the bottom of the supporting leg fixing box, so that a more complete and stable connecting structure is formed. Compared with a traditional mode that only web plates are connected, the structure enlarges the connection section, optimizes the force transmission path, and effectively improves the rigidity and the fatigue resistance of the chassis under the suspended load working condition.

Description

Technical Field

[0001] This utility model relates to the field of crane technology, and more specifically to a chassis structure and a crane including the chassis structure. Background Technology

[0002] During operation, the crane bears enormous torque from the superstructure and the load. As the key load-bearing structure connecting the chassis and the superstructure, the strength and rigidity of the underframe directly affect the operational safety of the entire vehicle.

[0003] In the prior art, the lower panel of the flange fixing box is usually only connected to the web plate (i.e. the side of the leg fixing box) of the outrigger fixing box, and the upper panel is also mostly connected to the outrigger fixing box through the web plate. This results in discontinuity in the force transmission path of the above structure, which leads to limited joint strength between components. When the underframe is under load, it is prone to problems such as insufficient local stiffness and uneven force transmission. In particular, under lifting load, it is easy to cause structural deformation and stress concentration, which affects the overall stress performance.

[0004] In addition, the installation unit, as a connecting component, is usually set up relatively independently and is not structurally integrated with other main load-bearing components, thus having a limited supporting effect on the overall structural rigidity and load coordination of the base frame.

[0005] Such structural defects can easily lead to problems such as localized fatigue of the underframe, structural loosening, or weld cracks during long-term use, thereby reducing overall durability and operational stability. Therefore, there is still room for further optimization in the connection and coordination between the key load-bearing units in the underframe structure. Utility Model Content

[0006] The purpose of this invention is to overcome the problem of insufficient connection rigidity of the base frame structure in the existing technology, which leads to poor overall stress performance.

[0007] To achieve the above objectives, the present invention provides a base frame structure, which includes a flange fixing box and a leg fixing box. The flange fixing box includes an upper panel, a lower panel, and a surrounding plate assembly connected between the upper panel and the lower panel. The side end of the surrounding plate assembly is fixedly connected to the side of the leg fixing box. The side of the lower panel near the leg fixing box extends to the bottom of the leg fixing box and is connected to the bottom of the leg fixing box.

[0008] Optionally, the base plate of the outrigger mounting box is welded to the lower panel.

[0009] Optionally, the portion of the lower panel that connects to the leg mounting box is dovetail-shaped.

[0010] Optionally, the base frame structure also includes a front mounting bracket fixedly connected to the side of the outrigger mounting box and a rear mounting bracket fixedly connected to the side of the flange mounting box opposite to the front mounting bracket. One side of the upper panel extends along the width direction of the outrigger mounting box to its edge and is fixedly connected to the top of the front mounting bracket at the edge. The other side of the upper panel away from the outrigger mounting box is fixedly connected to the top of the rear mounting bracket.

[0011] Optionally, the bottom of the outrigger fixing box is fixedly connected with a plurality of reinforcing plates spaced apart from each other along the length of the outrigger fixing box, for use with the left and right movable outriggers in the extended state.

[0012] Optionally, the ends of the reinforcing plate are dovetail-shaped.

[0013] Optionally, the flange mounting box further includes a first flange for fixing the outer ring portion of the slewing bearing, and the leg mounting box further includes a second flange concentrically disposed with the first flange for mounting the inner ring portion of the slewing bearing.

[0014] Optionally, the enclosure assembly includes an inner enclosure, an outer enclosure, and several stiffening plates, with the stiffening plates fixed between the inner enclosure and the outer enclosure.

[0015] The second aspect of this utility model provides a crane that includes the aforementioned base frame structure.

[0016] Optionally, the crane also includes a superstructure and a chassis, the superstructure and chassis structure being connected by a slewing bearing, and the chassis structure being fixed to the chassis.

[0017] Through the above technical solution, this utility model extends the lower panel of the flange fixing box to the bottom of the outrigger fixing box and fixes it to the bottom, constructing a more complete and stable connection structure, fundamentally improving the overall load-bearing performance of the underframe structure. This structure, based on the original web connection, adds fixation to the bottom, making the lower panel and the outrigger fixing box form an integrated support, significantly expanding the connection cross-section and effectively improving local stress distribution. Through this optimized design, the path of force transmission from the flange fixing box to the outrigger fixing box is more continuous, resulting in less deformation of the underframe when bearing lifting torque and stronger fatigue resistance. Overall, this structure enhances the rigidity of the connection area, improves the overall strength and stability of the underframe, and meets the higher requirements for structural reliability, such as those for cranes operating under high loads. Attached Figure Description

[0018] Figure 1 This is a top view schematic diagram of the base frame structure of this utility model;

[0019] Figure 2 This is a cross-sectional structural diagram of the base frame structure of this utility model;

[0020] Figure 3This is a bottom view schematic diagram of the base frame structure of this utility model;

[0021] Figure 4 This is a schematic diagram of the overall structure of the base frame of this utility model, in which the upper panel of the flange fixing box has been removed;

[0022] Figure 5 This is a partial structural schematic diagram of the crane of this utility model.

[0023] Explanation of reference numerals in the attached figures

[0024] 1. Flange fixing box; 11. Top panel; 12. Bottom panel; 13. Enclosure assembly; 131. Inner enclosure; 132. Outer enclosure; 133. Rib plate; 14. First flange; 2. Leg fixing box; 21. Reinforcing plate; 22. Second flange; 3. Mounting unit; 31. Front mounting unit; 32. Rear mounting unit; 4. Upper assembly; 5. Slewing bearing; 6. U-bolt. Detailed Implementation

[0025] The embodiments of this utility model will be further described in detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this utility model by way of example, but should not be used to limit the scope of this utility model. This utility model can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0026] These embodiments are provided to make the present invention thorough and complete, and to fully express the scope of the present invention to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​set forth in these embodiments should be interpreted as merely exemplary and not as limiting.

[0027] It should be noted that, in the description of this utility model, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0028] Furthermore, the terms "first," "second," and similar words used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. "Vertical" is not strictly vertical, but within the allowable error range. "Parallel" is not strictly parallel, but within the allowable error range. Words such as "including" or "comprising" mean that the element preceding the word encompasses the element listed after it, and do not exclude the possibility of encompassing other elements as well.

[0029] It should also be noted that, in the description of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0030] All terms used in this invention have the same meaning as understood by one of ordinary skill in the art to which this invention pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0031] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0032] like Figures 1 to 5 As shown, this utility model discloses a base frame structure, which includes a flange fixing box 1 and a leg fixing box 2. The flange fixing box 1 includes an upper panel 11, a lower panel 12, and a surrounding plate assembly 13 connected between the upper panel 11 and the lower panel 12. The side end of the surrounding plate assembly 13 is fixedly connected to the side of the leg fixing box 2. The side of the lower panel 12 near the leg fixing box 2 extends to the bottom of the leg fixing box 2 and is connected to the bottom of the leg fixing box 2.

[0033] Compared with the existing technology where only the lower panel 12 is connected to the web (i.e. its side) of the leg fixing box 2, this base frame structure significantly increases the connection surface and improves the stress concentration area by extending the lower panel 12 to the bottom of the leg fixing box 2, and ultimately effectively improves the deformation resistance and service life of the base frame structure as a whole.

[0034] Specifically, such as Figure 4As shown, the enclosure panel assembly 13 of the base frame structure can be composed of several vertical plates to form a frame structure. The side ends of the enclosure panel assembly 13 can be fixedly connected to the side of the support leg fixing box 2 by welding, bolts or studs. The upper end of the enclosure panel assembly 13 is fixedly connected to the upper panel 11, and the lower end is fixedly connected to the lower panel 12. Preferably, the enclosure panel assembly 13 is made of steel.

[0035] The lower panel 12 extends from the side of the support leg fixing box 2 beyond the boundary of the flange fixing box 1 and extends downward to the bottom of the support leg fixing box 2, where it is fixedly connected to the bottom plate of the support leg fixing box 2. After connection, the flange fixing box 1 and the support leg fixing box 2 can be considered as a double-layered connection structure. The upper layer forms a closed structural unit through the cooperation of the enclosure assembly 13, the upper panel 11, the lower panel 12, and the side of the support leg fixing box 2. The lower layer directly participates in the load-bearing system at the bottom of the support leg fixing box 2 through the extension of the lower panel 12. In this double-layered connection structure, the upper structure enhances the shear, bending, and torsional resistance of the flange fixing box 1, while the lower structure forms a direct load-bearing path with the bottom of the support leg fixing box 2 through the extended lower panel 12, ensuring mutual cooperation between the upper and lower parts under load, thus forming a complete, continuous, and stable load-bearing system between the flange fixing box 1 and the support leg fixing box 2. Furthermore, to enhance corrosion resistance and fatigue resistance, the surfaces of the flange fixing box 1 and the leg fixing box 2 can be treated with sandblasting for rust removal and anti-corrosion coating.

[0036] It should be noted that the base frame structure provided by this utility model can be applied to equipment under high load conditions, such as cranes. Of course, in addition to cranes, it can also be widely used in other large equipment with high requirements for structural rigidity and load-bearing strength, such as vehicle-mounted drilling rigs and engineering operation platforms, and has good versatility and engineering application value.

[0037] Optionally, the base plate of the outrigger fixing box 2 is welded to the lower panel 12. The purpose of welding is to further improve the rigidity and strength of the connection between the two, thereby improving the overall rigidity and strength of the underframe structure, so that the underframe structure has sufficient rigidity and strength to stably withstand, for example, the weight of the equipment on it or the torque generated during hoisting and other operations.

[0038] Optionally, the portion of the lower panel 12 that connects to the leg fixing box 2 is dovetail-shaped.

[0039] Specifically, such as Figure 3As shown, to improve the connection strength and interface stability between the lower panel 12 and the leg fixing box 2, the lower panel 12 is configured with a dovetail structure in the area where it connects to the leg fixing box 2. In the basic structure, the dovetail end forms a widened lap joint with the connecting surface of the leg fixing box 2, resulting in a larger lap area at the connection point. This helps to enhance the tensile and shear resistance of welding or mechanical fixing, thereby improving the overall integrity of the bottom structure.

[0040] Preferably, to achieve a more reliable structural interlock, the bottom plate of the outrigger fixing box 2 may be provided with a structural groove or positioning slot that matches the dovetail end. This groove can be formed by machining or welding, extending along the width direction of the outrigger fixing box 2, and its inner contour is consistent with the shape of the dovetail end of the lower panel 12. During installation, the dovetail end of the lower panel 12 can be directly inserted into or embedded in the groove to form a structural interlocking interface, achieving geometric interlocking. This structure introduces interlocking features on the basis of achieving a wide overlap, significantly enhancing the anti-slip and anti-peeling capabilities of the connection parts, and making the stress on the connection parts more uniform, effectively avoiding stress concentration.

[0041] In particular, in welded joint scenarios, traditional straight-edge structures tend to form sharp stress concentration zones at the weld, especially under heavy or variable load conditions. Long-term use can easily lead to fatigue damage and even crack propagation, affecting structural safety and service life. In contrast, the dovetail structure, with its gradually expanding geometric contour, not only effectively increases the stress path and weld area in the welding region but also achieves smoother force transmission, significantly reducing stress concentration at the weld edge. Through this structural design, the stress distribution at the welded area is more uniform, which helps improve the fatigue strength and overall durability of the joint, thereby enhancing the load-bearing stability and reliability of the underframe structure under high-intensity operating conditions.

[0042] Optionally, it also includes a front mounting bracket 31 fixedly connected to the side of the outrigger mounting box 2 and a rear mounting bracket 32 ​​fixedly connected to the side of the flange mounting box 1 opposite to the front mounting bracket 31. One side of the upper panel 11 extends along the width direction of the outrigger mounting box 2 to its edge and is fixedly connected to the top of the front mounting bracket 31 at the edge. The other side of the upper panel 11 away from the outrigger mounting box 2 is fixedly connected to the top of the rear mounting bracket 32.

[0043] Specifically, such as Figure 1 and Figure 2 As shown, based on the aforementioned base frame structure, it further includes an installation bay for connecting external structures (such as the chassis of a crane). The installation bay mainly consists of two parts: the first part is a front installation bay 31 fixedly connected to the outrigger fixing box 2, and the second part is a rear installation bay 32 fixedly connected to the flange fixing box 1 on the side opposite to the front installation bay 31.

[0044] The front mounting box 31 and / or the rear mounting box 32 can be made of bent structural plates, forming side panels on both sides after bending. The ends of the side panels are fixedly connected to the main structure (leg fixing box 2 or flange fixing box 1), forming a partially enclosed structure after the fixed connection (closed on the connecting side, open in the middle and at the top and bottom). Figure 5 As shown, this enclosed structure is used to fix connectors such as U-bolts 6 to achieve a stable connection between the base frame structure and the aforementioned external structure.

[0045] The upper panel 11 extends along the width of the leg fixing box 2 to the edge of the end where the front mounting box 31 is located, and is fixedly connected to the top of the front mounting box 31 at this edge (the two are fitted together before the fixed connection); the other side of the upper panel 11 (the side away from the leg fixing box 2) is fixedly connected to the top of the rear mounting box 32, thereby constructing an integrated upper structure with complete coverage.

[0046] To achieve the overall construction of the above structure, the installation process of the installation library may include the following steps:

[0047] First, the front mounting bracket 31, which has been bent, is installed on the corresponding side of the outrigger fixing box 2, and its two side plates are fixedly connected to the outrigger fixing box 2 by welding or mechanical fastening. Similarly, the rear mounting bracket 32 ​​is installed on the side of the flange fixing box 1 away from the outrigger fixing box 2 and fixed.

[0048] Subsequently, the upper panel 11 of the flange fixing box 1 is laid out, with one end covering the top area of ​​the front mounting compartment 31 and the other end covering the top area of ​​the rear mounting compartment 32. After all the structures are in place, the upper panel 11 is sequentially fixed to the enclosure assembly 13, the top of the front mounting compartment 31, and the top of the rear mounting compartment 32 by welding or mechanical fastening, thereby achieving a rigid integrated connection between the leg fixing box 2, the flange fixing box 1, the front mounting compartment 31, and the rear mounting compartment 32 in terms of structure, forming a stable load-bearing unit with good integrity and load-bearing capacity.

[0049] The aforementioned integrated structure (i.e., the outrigger fixing box 2, flange fixing box 1, front mounting compartment 31, and rear mounting compartment 32 as a whole) can effectively distribute the load during lifting operations, constructing a continuous and stable force path and avoiding stress concentration caused by isolated local structures. In particular, after the mounting compartment body forms an integrated structure, its load-bearing capacity is significantly improved, effectively enhancing the overall rigidity and strength of the base frame structure, thereby providing safer and more reliable support performance under high load conditions and meeting the stringent requirements of large equipment for stability and durability.

[0050] Preferably, the above-mentioned fixed connection is made by welding to achieve a good rigid connection; in practical applications, high-strength bolts, locating pins or other detachable methods can also be used for assembly according to assembly process or maintenance requirements.

[0051] Optionally, the bottom of the outrigger fixing box 2 is fixedly connected with a plurality of reinforcing plates 21 that are spaced apart from each other along the length of the outrigger fixing box 2, for use with the left movable outrigger and the right movable outrigger in the extended state.

[0052] Specifically, such as Figure 3 As shown, two reinforcing plates 21 are arranged along the length of the outrigger fixing box 2, spaced apart from each other, to enhance the local rigidity and strength of the bottom structure and to effectively cooperate with the left and right movable outriggers installed on both sides of the base frame. The movable outriggers are common key support devices in existing cranes, typically achieving lateral extension and retraction via hydraulic devices. During lifting operations, the movable outriggers fully extend and touch the ground to provide support, forming a stable working platform. The bottom of the outrigger fixing box 2 and its overlapping portion will bear a significant operational load. Therefore, in this structure, a reinforcing plate 21 is provided at this overlapping portion to enhance the load-bearing capacity of this area and improve the safety and stability of the base frame structure in the outrigger operating state. Similarly, the reinforcing plate 21 is preferably welded to the bottom of the outrigger fixing box 2.

[0053] Optionally, the ends of the reinforcing plate 21 are dovetail-shaped. Specifically, the dovetail geometry can effectively avoid stress concentration during loading, delay the initiation and propagation of cracks, thereby improving the fatigue life and overall strength of the structure. Furthermore, the dovetail structure of the reinforcing plate 21, while ensuring the strength and stiffness of the load-bearing area, effectively reduces the use of redundant material through end section optimization, thus achieving a good lightweight effect. This is beneficial for improving the performance of the underframe without significantly increasing the structural weight, meeting the comprehensive requirements of modern lifting equipment for high strength and lightweight design.

[0054] Optionally, the flange mounting box 1 further includes a first flange 14 for fixing the outer ring portion of the slewing bearing 5, and the leg mounting box 2 further includes a second flange 22 concentrically disposed with the first flange 14 for mounting the inner ring portion of the slewing bearing 5.

[0055] Specifically, such as Figure 1 and Figure 4As shown, the second flange 22 can be mounted on a mounting bracket on the top of the outrigger mounting box 2. This mounting bracket is fixedly connected to the main body structure of the outrigger mounting box 2 and has a mounting plate on it. The center of the mounting plate is concentrically arranged with the first flange 14 to ensure the installation accuracy of the slewing bearing 5. The concentric arrangement of the first flange 14 and the second flange 22 helps to prevent damage to the central rotating body caused by shaft offset during the rotation of the upper turntable, thereby improving the stability and service life of the equipment during rotation.

[0056] The slewing bearing 5 can be installed on the first flange 14 and the second flange 22 respectively using standard connecting parts such as bolts, ensuring accurate axial positioning and smooth rotation. The mounting plate can be fixed to the mounting bracket by welding to further enhance the strength, rigidity, and connection stability.

[0057] It is worth noting that in existing technologies, the second flange 22 is often located in the upper structure, belonging to a different mounting platform than the first flange 14. This often leads to misalignment due to machining and assembly errors, causing off-center loading on the slewing bearing and increasing the risk of structural wear and failure. In this embodiment, both the first flange 14 and the second flange 22 are centrally located within the base frame structure, fixed to the flange mounting box 1 and the outrigger mounting box 2 respectively, and are machined and positioned on a unified platform, ensuring their coaxiality from the outset. This structural approach not only improves the installation accuracy and stress uniformity of the slewing bearing but also helps reduce the failure rate and maintenance costs during equipment operation, further enhancing the operational reliability and structural stability of the entire vehicle's slewing system.

[0058] Optionally, the enclosure assembly 13 includes an inner enclosure 131, an outer enclosure 132, and a plurality of stiffening plates 133, the stiffening plates 133 being fixed between the inner enclosure 131 and the outer enclosure 132.

[0059] Specifically, such as Figure 4 As shown, stiffening ribs 133 are used to enhance the overall rigidity and load-bearing capacity of the enclosure assembly 13 in the axial and radial directions. When stiffening ribs 133 are installed below the first flange 14 of the slewing bearing 5, they are used to bear the vertical loads generated by the crane's superstructure and under lifting conditions. By installing multiple stiffening ribs 133, the load-bearing capacity of the first flange 14 can be effectively enhanced, preventing local deformation of the flange due to large loads or off-center loads, thereby improving the installation stability of the slewing bearing and reducing the risk of structural damage to the entire machine during slewing operations.

[0060] In the specific design, the position of the stiffening plate 133 should also avoid the threaded hole of the first flange 14 to prevent interference between the cutting tool and the stiffening plate 133 during flange drilling or threading, ensuring flange machining accuracy and manufacturing efficiency, and preventing damage caused by tool collision. Furthermore, the arrangement of the stiffening plate 133 can be optimized according to the load path, minimizing material usage while meeting strength and stiffness requirements, which helps control the overall structural weight and improves the lightweight level of the base frame structure.

[0061] Another aspect of this utility model discloses a crane that includes the aforementioned base frame structure.

[0062] Optionally, the crane also includes an upper structure 4 and a chassis, the upper structure 4 and the chassis structure being connected by a slewing bearing 5, and the chassis structure being fixed to the chassis.

[0063] Specifically, such as Figure 5 As shown, the chassis structure is preferably fixed to the chassis crossbeam using U-bolts 6. The U-bolts 6 pass through the openings of the front mounting bay 31 and the rear mounting bay 32, and are installed in conjunction with the chassis crossbeam. The clamping and fixing are achieved by tightening the nuts. This design is simple, reliable, and easy to disassemble and maintain. Alternatively, the chassis structure can also be fixed to the chassis crossbeam using bolted connecting plates or clamping connecting structures to adapt to the needs of different vehicle models or installation conditions.

[0064] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including combinations of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A chassis structure, characterized by, The system includes a flange fixing box (1) and a leg fixing box (2). The flange fixing box (1) includes an upper panel (11), a lower panel (12), and a surrounding panel assembly (13) connected between the upper panel (11) and the lower panel (12). The side end of the surrounding panel assembly (13) is fixedly connected to the side of the leg fixing box (2). The side of the lower panel (12) near the leg fixing box (2) extends to the bottom of the leg fixing box (2) and is connected to the bottom of the leg fixing box (2).

2. The undercarriage structure of claim 1, wherein The bottom plate of the outrigger fixing box (2) is welded to the lower panel (12).

3. The undercarriage structure according to claim 1 or 2, characterized in that, The portion of the lower panel (12) that connects to the leg fixing box (2) is dovetail-shaped.

4. The undercarriage structure of claim 1, wherein It also includes a front mounting bracket (31) fixedly connected to the side of the outrigger mounting box (2) and a rear mounting bracket (32) fixedly connected to the side of the flange mounting box (1) away from the front mounting bracket (31). One side of the upper panel (11) extends along the width direction of the outrigger mounting box (2) to its edge and is fixedly connected to the top of the front mounting bracket (31) at the edge. The other side of the upper panel (11) away from the outrigger mounting box (2) is fixedly connected to the top of the rear mounting bracket (32).

5. The undercarriage structure of claim 1, wherein, The bottom of the outrigger fixing box (2) is fixedly connected to a plurality of reinforcing plates (21) that are spaced apart from each other along the length of the outrigger fixing box (2), for use in conjunction with the left movable outrigger and the right movable outrigger in the extended state.

6. The undercarriage structure of claim 5, wherein, The end of the reinforcing plate (21) is dovetail shaped.

7. The undercarriage structure of claim 1, wherein The flange fixing box (1) further includes a first flange (14) for fixing the outer ring portion of the slewing bearing (5), and the leg fixing box (2) further includes a second flange (22) concentrically arranged with the first flange (14) for installing the inner ring portion of the slewing bearing (5).

8. The undercarriage structure of claim 1, wherein, The enclosure assembly (13) includes an inner enclosure (131), an outer enclosure (132) and a plurality of stiffening plates (133), the stiffening plates (133) being fixed between the inner enclosure (131) and the outer enclosure (132).

9. A crane, characterized in that Includes the chassis structure described in any one of claims 1-8.

10. The crane of claim 9, wherein, The crane also includes an upper structure (4) and a chassis. The upper structure (4) and the chassis structure are connected by a slewing bearing (5). The chassis structure is fixed to the chassis.

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