Swing frame assembly of engineering machinery and engineering machinery

Abstract

The utility model relates to a swing frame assembly of an engineering machine and the engineering machine comprising the swing frame assembly. The swing frame assembly comprises a swing frame support, a swing frame body and a gap adjusting assembly. The swing frame support is fixedly connected to a rear frame and comprises a front support arm and a rear support arm which are separated in the longitudinal direction of the engineering machine. The swing frame body is used for installing a rear axle of the engineering machine and comprises a front swing arm and a rear swing arm which are hinged to the front support arm and the rear support arm respectively. The gap adjusting assembly is arranged between the swing frame body and the swing frame support, so that a first gap between the front support arm and the front swing arm is larger than a second gap between the rear support arm and the rear swing arm. The swing frame assembly of the engineering machinery has a better force transmission path, and optimizes longitudinal load distribution of a frame, so that the service life of a rear frame is greatly prolonged.

Description

Technical Field

[0001] The utility model relates to the technical field of parts of engineering machinery, in particular to a swing frame assembly of engineering machinery and engineering machinery comprising the swing frame assembly. Background Art

[0002] In construction machinery such as loaders, the rear frame is connected to the rear axle via a swing frame assembly, and the rear frame is provided with a cab, an engine, a dual-variator assembly, a counterweight and other different components, and the rear drive axle drives the rear frame forward or backward via the swing frame assembly. Therefore, the swing frame assembly is crucial in the power transmission process of the entire loader.

[0003] In the prior art, the swing frame assembly may include a swing frame bracket fixed on the rear frame and a swing frame body connected to the swing frame bracket, and the front and rear sides of the swing frame body are respectively hinged to the swing frame bracket. Due to the influence of installation welding during the manufacturing process or wear and deformation during use, the gaps between the two front and rear connection points of the swing frame bracket and the swing frame body become uncertain, so that when the loader moves forward and backward, a stable force transmission path between the swing frame bracket and the swing frame body cannot be guaranteed, which seriously affects the life of the entire rear frame. Utility Model Content

[0004] The purpose of the present invention is to solve at least one of the above problems and / or other problems existing in the prior art.

[0005] To achieve the above-mentioned purpose, on the one hand, the utility model provides a swing frame assembly of an engineering machinery, the engineering machinery includes a rear frame, and the swing frame assembly includes a swing frame bracket, a swing frame body, and a gap adjustment assembly. The swing frame bracket is fixedly connected to the rear frame, and includes a front support arm and a rear support arm separated along the longitudinal direction of the engineering machinery; the swing frame body is used to install the rear axle of the engineering machinery, and includes a front swing arm and a rear swing arm respectively hingedly connected to the front support arm and the rear support arm; the gap adjustment assembly is arranged between the swing frame body and the swing frame bracket, so that the first gap between the front support arm and the front swing arm is larger than the second gap between the rear support arm and the rear swing arm.

[0006] According to an embodiment of the present invention, the gap adjustment assembly includes a plurality of first gaskets suitable for adjusting the first gap and a plurality of second gaskets suitable for adjusting the second gap.

[0007] According to an embodiment of the present invention, the plurality of first gaskets include gaskets having thicknesses of 1 mm, 1.5 mm and 2 mm, respectively, and the plurality of second gaskets include gaskets having thicknesses of 0.5 mm, 1 mm, 1.5 mm and 2 mm, respectively.

[0008] According to an embodiment of the present invention, the plurality of first gaskets are configured such that the first gap is between 0.5 mm and 1.5 mm, and the plurality of second gaskets are configured such that the second gap is less than 0.5 mm.

[0009] According to one embodiment of the utility model, the front support arm includes two first connecting plates which are parallel and spaced apart in the longitudinal direction, the front swing arm is connected between the two first connecting plates via a first pin shaft, and the first gasket is arranged on the first pin shaft and between the two first connecting plates and the front swing arm, thereby defining the first gap.

[0010] According to one embodiment of the utility model, the plurality of first gaskets are arranged between the front swing arm and the first connecting plate on the front side and / or between the front swing arm and the first connecting plate on the rear side.

[0011] According to one embodiment of the utility model, the rear support arm includes two second connecting plates which are parallel and spaced apart in the longitudinal direction, the rear swing arm is connected between the two second connecting plates via a second pin shaft, and the second gasket is arranged on the second pin shaft and between the two second connecting plates and the rear swing arm, thereby defining the second gap.

[0012] According to one embodiment of the utility model, the plurality of second gaskets are arranged between the rear swing arm and the second connecting plate on the front side and / or between the rear swing arm and the second connecting plate on the rear side.

[0013] According to one embodiment of the utility model, the swing frame body also includes two swing connecting plates which are parallel and opposite to each other in the transverse direction, and the two swing connecting plates are respectively connected to the two ends of the front swing arm and the rear swing arm, and each is provided with a connecting hole for connecting the rear axle.

[0014] On the other hand, the utility model provides an engineering machine, which includes a rear frame and the swing frame assembly as described above. The rear frame includes a left side plate and a right side plate, and the front support arm and the rear support arm are respectively arranged between the left side plate and the right side plate.

[0015] The swing frame assembly of the utility model can ensure that the first gap between the front support arm and the front swing arm is larger than the second gap between the rear support arm and the rear swing arm when the engineering machinery is moving forward or backward, so that the swing frame body and the swing frame support are always in contact between the rear support arm and the rear swing arm, which has a better force transmission path and optimizes the longitudinal load distribution of the frame, thereby greatly improving the life of the rear frame. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The features and advantages of the present invention will be clearly understood through the detailed description provided below with reference to the accompanying drawings. It should be understood that the following drawings are merely schematic and not necessarily drawn to scale, and thus cannot be regarded as limiting the present invention, wherein:

[0017] Figure 1 A schematic diagram showing the installation of a swing frame assembly and a rear frame according to an exemplary embodiment of the utility model;

[0018] Figure 2 Show Figure 1 An exploded schematic diagram of the swing frame assembly and rear frame is shown.

[0019] Description of reference numerals:

[0020] 1. Rear frame; 11. Left side plate; 12. Right side plate; 2. Swing frame bracket; 21. Front bracket arm; 211. First connecting hole; 212. First connecting plate; 22. Rear bracket arm; 221. Second connecting hole; 222. Second connecting plate; 3. Swing frame body; 31. First through hole; 32. Front swing arm; 33. Second through hole; 34. Rear swing arm; 35. Swing connecting plate; 351. Connecting hole; 4. First gap; 5. Second gap; 6. Gap adjustment assembly; 61. First gasket; 62. Second gasket; 7. First pin; 8. Second pin. DETAILED DESCRIPTION

[0021] Embodiments of the present invention are described below with reference to the accompanying drawings. In the following description, many specific details are set forth so that those skilled in the art can more fully understand and implement the present invention. However, it is obvious to those skilled in the art that the implementation of the present invention may not have some of these specific details. In addition, it should be understood that the present invention is not limited to the specific embodiments described. On the contrary, any combination of the features and elements described below may be considered to implement the present invention, regardless of whether they relate to different embodiments. Therefore, the following aspects, features, embodiments and advantages are for illustrative purposes only and should not be regarded as elements or limitations of the claims unless clearly stated in the claims.

[0022] In the following, terms such as "first", "second", etc. are used to describe the elements of the present application. These terms are only used to distinguish the various elements, and are not used to limit the nature, order or number of these elements. The terms "including" and "having" are used to express an open-ended inclusive meaning, and mean that there may be additional elements / components in addition to the listed elements / components.

[0023] As described in the background technology, construction machinery, especially loaders, usually adopt a two-part frame, that is, a front frame (not shown) for connecting the front axle (not shown) and installing working tools such as buckets (not shown) and a rear frame 1 for connecting the rear axle (not shown). The front frame and the rear frame 1 are usually connected by a hinge. For example, the front frame and the rear frame 1 are rotatably connected by a hinge pin perpendicular to the ground, and can deflect relative to each other around the hinge pin. The rear frame 1 is provided with a plurality of different components such as a cab, an engine, a dual-variator assembly and a counterweight, so it can also be called a "main frame". The rear frame 1 can be connected to the rear axle through a swing frame assembly. The power transmission path located at the rear end of the loader is that the power of the engine is transmitted to the swing frame assembly via the rear axle, thereby driving the rear frame forward or backward.

[0024] In the present application, words describing orientation / direction, such as "lateral", "longitudinal", "up", "down", "left", "right", "top", "bottom", "front", "rear", etc., which may be mentioned below, are relative to the engineering machinery normally parked or working on a horizontal plane or the corresponding onboard equipment assembled in place on the engineering machinery. Figure 1 The direction from left to right shown in the stereoscopic view of the construction machine represents the normal forward direction of the construction machine, wherein the direction pointing to the right is the "front" and the direction pointing to the left is the "rear". The direction extending along the front-to-back direction is the "longitudinal" direction of the construction machine. Figure 1 The direction perpendicular to the longitudinal direction is the transverse direction or lateral direction. Figure 1 The direction perpendicular to the rear frame 1 and inward on the paper is the "left" of the construction machinery. Figure 1 The direction perpendicular to the rear frame 1 and out of the paper is the "right" of the construction machinery. Figure 1 The left and right extending direction shown in the figure is called the longitudinal direction of the engineering machine, and the direction extending inside and outside the paper is called the lateral direction of the engineering machine.

[0025] Figure 1 and Figure 2 FIG. 1 shows a schematic diagram of the combination of a swing frame assembly and a rear frame 1 according to an embodiment of the utility model. Figure 1 and Figure 2As shown, the swing frame assembly is arranged below the rear frame 1 and can be used to connect the rear axle. The swing frame assembly according to the utility model can include a swing frame bracket 2, a swing frame body 3 and a gap adjustment assembly 6.

[0026] In the illustrated embodiment, the swing frame bracket 2 may include a front bracket arm 21 and a rear bracket arm 22 that are separately arranged along the longitudinal direction of the engineering machinery. The front bracket arm 21 and the rear bracket arm 22 may each have an overall U-shaped or V-shaped shape, and their respective left and right ends may be fixedly connected to the rear frame 1, for example, by welding, thereby fixing the entire swing frame bracket 2 to the bottom or bottom of the rear frame 1. The swing frame body 3 may have the form of a frame and may include a front swing arm 32 hinged to the front bracket arm 21 and a rear swing arm 34 hinged to the rear bracket arm 22. The gap adjustment assembly 6 may be arranged between the swing frame body 3 and the swing frame bracket 2, so that the first gap 4 between the front bracket arm 21 and the front swing arm 32 is greater than the second gap 5 between the rear bracket arm 22 and the rear swing arm 34.

[0027] The applicant has found in practice that it is more advantageous to make the force transmission path of the loader pass through the rear swing arm 34 and the rear support arm 22 rather than between the front swing arm 32 and the front support arm 21. Based on this, setting the first gap 4 to be larger than the second gap 5 can ensure that when the engineering machine moves forward or backward, the swing frame body 3 and the swing frame support 2 are always in contact between the rear support arm 22 and the rear swing arm 34, which has a better force transmission path, optimizes the longitudinal load distribution of the frame, and thus greatly improves the service life of the rear frame 1.

[0028] According to an exemplary embodiment of the gap adjustment assembly 6, reference Figure 2 , the gap adjustment assembly 6 may include a plurality of first gaskets 61 suitable for adjusting the first gap 4 and a plurality of second gaskets 62 suitable for adjusting the second gap 5. The plurality of first gaskets 61 may include gaskets of various specifications, and may be installed between the front support arm 21 and the front swing arm 32 alone or in combination to adjust and especially reduce the first gap 4. The plurality of second gaskets 62 may also include gaskets of various specifications, and may be installed between the rear support arm 22 and the rear swing arm 34 alone or in combination to adjust and especially reduce the second gap 5. Thus, regardless of the initial size relationship between the first gap 4 and the second gap 5, the first gasket 61 and the second gasket 62 may be used to adjust the first gap 4 to be larger than the second gap 5 and the second gap 5 to reach a preset gap value. Here, it can be understood that when the first gap 4 is smaller than the second gap 5 after the initial assembly of the swing frame bracket 2 and the swing frame body 3, the first gap 4 may be larger than the second gap 5 by arranging a larger number and / or specification of second gaskets 62 between the rear support arm 22 and the rear swing arm 34.

[0029] Preferably, at least some of the plurality of second gaskets 62 have a thickness less than that of the plurality of first gaskets 61, so that the adjustment of the second gap 5 is more precise than the adjustment of the first gap 4. For example, the plurality of first gaskets 61 may include gaskets with thicknesses of 1 mm, 1.5 mm, and 2 mm, respectively, and the plurality of second gaskets 62 may include gaskets with thicknesses of 0.5 mm, 1 mm, 1.5 mm, and 2 mm, respectively. In this way, the second gasket 62 has one more gasket with a thickness of 0.5 mm than the first gasket 61, which is conducive to more precise adjustment of the second gap 5 between the rear bracket arm 22 and the rear swing arm 34, thereby ensuring that the second gap 5 can be adjusted to a gap value smaller than the first gap 4. For example, when the first gap 4 is 2 mm and the second gap 5 is 2.9 mm after initial assembly, a first gasket 61 with a thickness of 1 mm may be provided between the front support arm 21 and the front swing arm 32, and a second gasket 62 with a thickness of 2 mm and 0.5 mm may be provided in combination between the rear support arm 22 and the rear swing arm 34, so that the first gap 4 becomes 1 mm and the second gap 5 becomes 0.4 mm. In some other specific embodiments, the first gasket 61 and the second gasket 62 may each include more gaskets with different thicknesses, such as gaskets with thicknesses of 1.2 mm, 1.4 mm, and 1.7 mm.

[0030] According to a more preferred embodiment, the plurality of first gaskets 61 may be configured to enable the first gap 4 to be adjusted to be between 0.5 mm and 1.5 mm, and the plurality of second gaskets 62 may be configured to enable the second gap 5 to be adjusted to be less than 0.5 mm.

[0031] It can be understood that the first gap 4 and the second gap 5 to be adjusted may be caused by processing errors of related components or deformations produced during the assembly process (such as welding), or may be caused by deformations produced during actual use of the loader.

[0032] According to an exemplary embodiment of the front support arm 21, Figure 2As shown, the front support arm 21 may include two first connecting plates 212 arranged in parallel and spaced apart in the longitudinal direction, and the two first connecting plates 212 may be respectively provided with corresponding first connecting holes 211. The front swing arm 32 may be arranged between the two first connecting plates 212 and provided with a first through hole 31 corresponding to the first connecting hole 211. In this way, the front swing arm 32 may be connected between the two first connecting plates 212 by means of a first pin shaft 7 passing through the first connecting hole 211 and the first through hole 31, and the front swing arm 32 is allowed to rotate, i.e. swing, at a certain angle relative to the two first connecting plates 212. In this case, the first gasket 61 may be installed on the first pin shaft 7 and between the two first connecting plates 212 and the front swing arm 32, thereby defining the first gap 4.

[0033] Specifically, when a single first gasket 61 is used, it can be disposed between the front swing arm 32 and the first connecting plate 212 on the front side, or between the front swing arm 32 and the first connecting plate 212 on the rear side. When a plurality of first gaskets 61 are used in combination, a portion of the first gaskets 61 can be disposed between the front swing arm 32 and the first connecting plate 212 on the front side, and another portion of the first gaskets 61 can be disposed between the front swing arm 32 and the first connecting plate 212 on the rear side. Alternatively, the plurality of first gaskets 61 can also be disposed between the front swing arm 32 and the first connecting plate 212 on the front side (or the rear side).

[0034] Continue to refer Figure 2 , the rear support arm 22 may also include two second connecting plates 222 arranged in parallel and spaced apart in the longitudinal direction, and the two second connecting plates 222 may be respectively provided with corresponding second connecting holes 221. The rear swing arm 34 may be arranged between the two second connecting plates 222 and provided with a second through hole 33 corresponding to the second connecting hole 221. In this way, the rear swing arm 34 may be connected between the two second connecting plates 222 by means of a second pin shaft 8 passing through the second connecting hole 221 and the second through hole 33, and the rear swing arm 34 is allowed to rotate, i.e. swing, at a certain angle relative to the two second connecting plates 222. In this case, the second gasket 62 may be arranged on the second pin shaft 8 and between the two second connecting plates 222 and the rear swing arm 34, thereby defining the second gap 5.

[0035] Specifically, when a single second gasket 62 is used, it can be disposed between the rear swing arm 34 and the second connecting plate 222 on the front side, or between the rear swing arm 34 and the second connecting plate 222 on the rear side. When a plurality of second gaskets 62 are used in combination, a portion of the second gaskets 62 can be disposed between the rear swing arm 34 and the second connecting plate 222 on the front side, and another portion of the second gaskets 62 can be disposed between the rear swing arm 34 and the second connecting plate 222 on the rear side. Alternatively, the plurality of second gaskets 62 can also be disposed simultaneously between the rear swing arm 34 and the first connecting plate 212 on the front side (or the rear side).

[0036] In this case, the first bolt 7 and the second bolt 8 are preferably located on the same straight line, which can extend in particular parallel to the longitudinal direction of the construction machine.

[0037] According to the specific embodiment of the swing frame body 3, refer to Figure 2 The swing frame body 3 may further include two swing connection plates 35 which are parallel and opposite to each other in the transverse direction. The two swing connection plates 35 are respectively located on the left and right sides of the swing frame body 3 and extend in the longitudinal direction, and their front ends are respectively connected to the front swing arms 32, and their rear ends are respectively connected to the rear swing arms 34, thereby forming the swing frame body 3 of a rectangular frame structure.

[0038] Advantageously, the two swing connection plates 35 may each be provided with a connection hole 351. The rear axle may be fixedly connected to the swing frame body 3 as a whole by bolts passing through the connection holes 351. Thus, when the ground on which the loader is traveling has a change in height, the rear axle and the swing frame body 3 may rotate around the first pin shaft 7 and the second pin shaft 8, thereby reducing the impact of terrain changes on the main frame and the hinge pin.

[0039] The utility model also provides an engineering machine including the above swing frame assembly. Figure 1 and Figure 2 As shown, the rear frame 1 of the engineering machinery may include a left side plate 11 and a right side plate 12 , wherein the front support arm 21 is spanned between the left side plate 11 and the right side plate 12 , and the rear support arm 22 is also spanned between the left side plate 11 and the right side plate 12 .

[0040] Industrial Applicability

[0041] The swing frame assembly according to the utility model is suitable for engineering machinery with a two-piece frame, and is particularly suitable for loaders with an articulated frame. However, it should be understood that the swing frame assembly according to the utility model can also be used for other vehicles or equipment with an articulated frame.

[0042] by Figure 1 and Figure 2Taking the embodiment shown as an example, when assembling the swing frame assembly, two first connecting plates 212 can be welded to the rear frame 1 at a predetermined interval to form the front support arm 21, and two second connecting plates 222 can be welded to the rear frame 1 at a predetermined interval to form the rear support arm 22, so that the front support arm 21 and the rear support arm 22 are separated by a certain distance, thereby forming a swing frame bracket 2 fixedly connected to the rear frame 1. Before or after forming the swing frame bracket 2, the swing connecting plate 35, the front swing arm 32 and the rear swing arm 34 are assembled into a swing frame body 3 of a rectangular frame structure by welding or other means. Then, the front swing arm 32 is placed between the two first connecting plates 212, and the rear swing arm 34 is placed between the two second connecting plates 222. Next, the first gasket 61 is placed between the front swing arm 32 and the first connecting plate 212, and the first gap 4 between the front swing arm 32 and the two first connecting plates 212 is adjusted by the first gasket 61, so that the first gap 4 is, for example, between 0.5 mm and 1.5 mm; and the second gasket 62 is placed between the rear swing arm 34 and the second connecting plate 222, and the second gap 5 between the rear swing arm 34 and the two second connecting plates 222 is adjusted by the second gasket 62, so that the second gap 5 is, for example, less than 0.5 mm. After the first gasket 61 and the second gasket 62 are set, the first pin 7 can be passed through the first connecting hole 211 and the first through hole 31 to hinge the front swing arm 32 and the front support arm 21, and the second pin 8 can be passed through the second connecting hole 221 and the second through hole 33 to hinge the rear swing arm 34 and the rear support arm 22. The assembly of the swing frame assembly is thus completed. Finally, the rear axle can be fixed to the swing frame body 3 by passing the bolt through the connecting hole 351. The assembly of the swing frame assembly, the rear frame 1 and the rear axle is then completed.

[0043] As described above, in the swing frame assembly according to the utility model, the first gap 4 between the front swing arm 32 and the front support arm 21 is adjusted to be larger than the second gap 5 between the rear swing arm 34 and the rear support arm 22, so that the swing frame body 3 and the swing frame support 2 always tend to contact between the rear support arm 22 and the rear swing arm 34. Compared with the uncertain gaps at the front and rear ends of the original swing frame body 3 and the swing frame support 2, the swing frame assembly of the utility model can ensure that the force in the longitudinal direction of the engineering machinery is always transmitted at the connection between the rear ends of the swing frame body 3 and the swing frame support 2, thereby having a better force transmission path and optimizing the longitudinal load distribution of the frame. Thereby, the service life of the rear frame 1 is greatly improved.

[0044] For those skilled in the art, various modifications and variations may be made to the embodiments disclosed above without departing from the scope or spirit of the utility model. Other embodiments of the utility model will be apparent to those skilled in the art from the practice of the utility model disclosed in this specification. This specification and the examples disclosed therein should be considered to be illustrative only, and the true scope of the utility model is specified by the appended claims and their equivalents.

Claims

1. A swing frame assembly of an engineering machine, the engineering machine comprising a rear frame (1), characterized in that: The swing frame assembly comprises: A swing frame bracket (2), the swing frame bracket (2) is fixedly connected to the rear frame (1) and comprises a front bracket arm (21) and a rear bracket arm (22) separated along the longitudinal direction of the engineering machine; A swing frame body (3), the swing frame body (3) is used to install the rear axle of the engineering machinery, and comprises a front swing arm (32) and a rear swing arm (34) respectively hingedly connected to the front support arm (21) and the rear support arm (22); and A gap adjustment component (6), wherein the gap adjustment component (6) is arranged between the swing frame body (3) and the swing frame bracket (2), so that a first gap (4) between the front bracket arm (21) and the front swing arm (32) is larger than a second gap (5) between the rear bracket arm (22) and the rear swing arm (34).

2. The swing frame assembly according to claim 1, characterized in that: The gap adjustment assembly (6) comprises a plurality of first shims (61) suitable for adjusting the first gap (4) and a plurality of second shims (62) suitable for adjusting the second gap (5).

3. The swing frame assembly according to claim 2, characterized in that: The plurality of first gaskets (61) include gaskets having thicknesses of 1 mm, 1.5 mm and 2 mm, respectively, and the plurality of second gaskets (62) include gaskets having thicknesses of 0.5 mm, 1 mm, 1.5 mm and 2 mm, respectively.

4. The swing frame assembly according to claim 3, characterized in that: The plurality of first spacers (61) are configured such that the first gap (4) is between 0.5 mm and 1.5 mm, and the plurality of second spacers (62) are configured such that the second gap (5) is less than 0.5 mm.

5. The swing frame assembly according to any one of claims 2 to 4, characterized in that: The front support arm (21) includes two first connecting plates (212) which are parallel and spaced apart in the longitudinal direction, the front swing arm (32) is connected between the two first connecting plates (212) via a first pin shaft (7), and the first gasket (61) is arranged on the first pin shaft (7) and is located between the two first connecting plates (212) and the front swing arm (32), thereby defining the first gap (4).

6. The swing frame assembly according to claim 5, characterized in that: The plurality of first gaskets (61) are arranged between the front swing arm (32) and the first connecting plate (212) on the front side and / or between the front swing arm (32) and the first connecting plate (212) on the rear side.

7. The swing frame assembly according to claim 5, characterized in that: The rear support arm (22) includes two second connecting plates (222) which are parallel and spaced apart in the longitudinal direction, the rear swing arm (34) is connected between the two second connecting plates (222) via a second pin shaft (8), and the second gasket (62) is arranged on the second pin shaft (8) and is located between the two second connecting plates (222) and the rear swing arm (34), thereby defining the second gap (5).

8. The swing frame assembly according to claim 7, characterized in that: The plurality of second gaskets (62) are arranged between the rear swing arm (34) and the second connecting plate (222) on the front side and / or between the rear swing arm (34) and the second connecting plate (222) on the rear side.

9. The swing frame assembly according to claim 7, characterized in that: The swing frame body (3) further comprises two swing connection plates (35) which are parallel and opposite to each other in the transverse direction, wherein the two swing connection plates (35) are respectively connected to the two ends of the front swing arm (32) and the rear swing arm (34), and each is provided with a connection hole (351) for connecting to the rear axle.

10. An engineering machine, characterized in that: The invention comprises a rear frame (1) and a swing frame assembly according to any one of claims 1 to 9, wherein the rear frame (1) comprises a left side plate (11) and a right side plate (12), and the front support arm (21) and the rear support arm (22) are respectively arranged between the left side plate (11) and the right side plate (12).

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