Swing device for boom and excavator

Abstract

The present application relates to a rotary structure, in order to solve the problem that the rotary mechanism bears huge bending moment when the rotary working device of the existing excavator works, the present application constructs a swing arm rotary device and an excavator, wherein the swing arm rotary device comprises a rotary platform, a rotary mechanism fixed on the front part of the rotary platform, a swing arm support fixed on the rotary rotating part of the rotary mechanism, a limiting part arranged on the rear part of the swing arm support, and a limiting bearing part fixed on the rotary platform at the position behind the swing arm support; the limiting part has an upper limiting surface, the limiting bearing part has a lower bearing surface, the upper limiting surface and the lower bearing surface are a pair of rotary fitting surfaces, when the swing arm support rotates to face the front of the rotary platform, the lower bearing surface is located on the upper side of the upper limiting surface and the lower bearing surface is fitted with the upper limiting surface. The limiting part and the limiting bearing part of the present application offset the moment generated by the working device on the swing arm support, and reduce the bending moment on the rotary mechanism.

Description

Technical Field

[0001] This invention relates to a slewing structure, and more specifically, to a boom slewing device and an excavator. Background Technology

[0002] An excavator consists of a lower body and an upper body mounted on the lower body for slewing. The upper body includes a slewing platform, a working device mounted at the front of the slewing platform, and other components and systems mounted on the slewing platform. Most excavators have a boom support welded onto the slewing platform for connecting the boom and boom cylinder of the working device. Some excavators, for operational needs or other purposes, have the working device mounted via a slewing mechanism; that is, the lower part of the slewing mechanism is connected to the slewing platform, and the upper part of the slewing mechanism is connected to the boom support. When the slewing mechanism rotates, it drives the working device to rotate.

[0003] When the excavator's working device is in operation, the force on its attachments is transmitted to the slewing platform through the stick, stick cylinder, boom, and boom cylinder. Due to the leverage effect of components such as the stick and boom, a huge bending moment is generated in the slewing mechanism. To ensure that the slewing mechanism can withstand the maximum bending moment that may occur during excavator operation, the strength requirements of the slewing mechanism are high, resulting in high manufacturing costs. In addition, the slewing mechanism is relatively large, making it inconvenient to arrange on some machines with limited space. Summary of the Invention

[0004] The technical problem to be solved by the present invention is the problem of the huge bending moment that the slewing mechanism of the existing excavator slewing device bears during operation. The present invention provides a boom slewing device and an excavator to reduce the bending moment borne by the slewing mechanism during operation.

[0005] The technical solution of this invention to achieve its objective is as follows: a boom slewing device is constructed, including a slewing platform, a slewing mechanism with a slewing fixing part fixed to the front of the slewing platform, and a boom support fixed to the slewing rotating part of the slewing mechanism. A limiting part is provided at the rear of the boom support, and a limiting bearing part is fixed at a position on the slewing platform located behind the boom support. The limiting part has an upper limiting surface, and the limiting bearing part has a lower bearing surface. The upper limiting surface and the lower bearing surface are a pair of slewing contact surfaces. When the boom support rotates to face directly in front of the slewing platform, the lower bearing surface is located above the upper limiting surface and the lower bearing surface is in contact with the upper limiting surface.

[0006] When an excavator is operating, the boom support typically faces the front of the slewing platform. At this time, the excavator's working device is located at the front of the slewing platform, and the attachment end of the working device is suspended in the air. Due to the weight of the working device itself and the weight of the material carried by the attachment (such as material in the excavator bucket or material being lifted by a hoist), a forward tilting moment is generated on the boom support. This causes the rear of the boom support to tend to tilt upwards. In this invention, a limiting part is provided on the boom support, and a limiting bearing part is provided on the slewing platform. When the excavator is operating and the rear of the boom support tilts upwards, the limiting bearing part presses down on the upper limiting surface of the limiting part through its lower bearing surface, applying a downward force to prevent it from tilting upwards. This generates a moment on the boom support opposite to the forward tilting moment, thereby reducing the bending moment generated by the working device on the slewing mechanism.

[0007] In the boom slewing device of the present invention, the limiting part may further have a lower limiting surface, and the limiting bearing part may further have an upper bearing surface. The lower limiting surface and the upper bearing surface are a pair of rotating contact surfaces. When the boom support rotates to face directly in front of the slewing platform, the upper bearing surface is located below the lower limiting surface, and the lower limiting surface and the upper bearing surface are in vertical contact. When the attachment end of the working device touches the ground, a forward tilting moment is generated on the boom support. At this time, the rear of the boom support tends to press downward. At this time, the limiting bearing part supports the lower limiting surface on the limiting part through its upper bearing surface, applying an upward force to prevent it from pressing downward, generating a moment on the boom support opposite to the direction of the backward tilting moment, thereby reducing the bending moment generated by the working device on the slewing mechanism.

[0008] In the boom slewing device of the present invention, the upper limit surface and the lower limit surface are arranged opposite each other on the limiting part, and the lower bearing surface and the upper bearing surface are arranged opposite each other on the limiting bearing part, with the limiting bearing part located between the upper limit surface and the lower limit surface. Alternatively, the upper limit surface and the lower limit surface are arranged opposite each other on the limiting part, and the lower bearing surface and the upper bearing surface are arranged opposite each other on the limiting bearing part; the limiting part is located between the lower bearing surface and the upper bearing surface.

[0009] In the boom slewing device of the present invention, both the limiting part and the limiting bearing part include wear-resistant plates that are detachably fixedly installed, and each limiting surface and each bearing surface are arranged on the corresponding wear-resistant plate.

[0010] In the boom slewing device of the present invention, the boom support includes a support plate and a hinge seat welded to the support plate, and the limiting part is arranged on the upper side of the support plate and located behind the hinge seat.

[0011] In the boom slewing device of the present invention, a lower positioning pin sleeve is provided on the slewing platform, and an upper positioning pin sleeve is provided on the support plate that can be coaxially aligned with the lower positioning pin sleeve. A positioning pin is installed in the upper positioning pin sleeve that can pass downward through the hole on the support plate and be inserted into the lower positioning pin sleeve.

[0012] In the boom slewing device of the present invention, a lower limit block is provided on the slewing platform, and an upper limit block is provided on the lower side of the support plate, which can abut against the lower limit block for limiting. When the lower positioning pin sleeve and the upper positioning pin sleeve are coaxially aligned, the lower limit block abuts against the upper limit block.

[0013] The technical solution of the present invention to achieve its purpose is as follows: an excavator is constructed having the aforementioned boom slewing device, wherein the lower ends of the boom and the boom cylinder are connected to the boom support.

[0014] In the excavator of this invention, the slewing mechanism is configured to rotate at least 180 degrees. When the boom support faces directly behind the slewing platform, the lower locating pin sleeve on the slewing platform and the upper locating pin sleeve on the boom support are coaxially aligned, and locating pins are inserted into the coaxially aligned lower and upper locating pin sleeves. In this excavator, after lowering the canopy height, the slewing mechanism rotates the boom support to face directly behind the slewing platform, thereby positioning the boom and stick directly above the slewing platform, reducing the excavator's length and facilitating its transport as a whole machine.

[0015] Compared with the prior art, the boom slewing device of the present invention, by setting mutually abutting limiting parts and limiting bearing parts on the boom support and the slewing platform, offsets part of the torque generated by the working device on the boom support and reduces the bending moment on the slewing mechanism. Attached Figure Description

[0016] Figure 1 This is a structural schematic diagram of the excavator of the present invention.

[0017] Figure 2 This is a schematic diagram of the working device of the excavator of the present invention after rotating 180 degrees.

[0018] Figure 3 This is a schematic diagram of the boom slewing device of the present invention.

[0019] Figure 4 This is a schematic diagram of the boom support structure in the boom slewing device of the present invention.

[0020] Figure 5 This is a schematic diagram of the structure of the bottom of the boom support in the boom slewing device of the present invention.

[0021] Figure 6 This is a side view of the boom support in the boom slewing device of the present invention.

[0022] Figure 7 yes Figure 6 A magnified view of the middle limiting part.

[0023] Figure 8 This is a schematic diagram of the front part of the slewing platform in the boom slewing device of the present invention.

[0024] Figure 9 This is a side view of the boom slewing device of the present invention.

[0025] Figure 10 yes Figure 9 A schematic diagram of the structure at point A in the middle.

[0026] Figure 11 This is a schematic diagram of the state of the boom slewing device of the present invention after it has slew 180 degrees.

[0027] Figure 12 This is a schematic diagram of the slewing mechanism in the boom slewing device of the present invention.

[0028] Figure 13 This is a cross-sectional view of the slewing mechanism in the boom slewing device of the present invention.

[0029] Component names and serial numbers in the diagram:

[0030] Working device 100, boom 11, stick 12, attachments 13, boom cylinder 14, stick cylinder 15, bucket cylinder 16.

[0031] The lower part of the vehicle body is 200.

[0032] Upper body 300, slewing platform 30, cab roof 32.

[0033] 400 boom slewing device.

[0034] Boom support 40, support plate 401, boom hinge seat 402, boom cylinder hinge seat 403, limiting part 404, upper limit surface 405, lower limit surface 406, lower limit wear plate 407, upper limit wear plate 408, gasket 409, upper positioning pin sleeve 410, positioning pin 411, upper limit block 412, boom support annular mounting surface 413.

[0035] Rotary mechanism 50, rotary fixed part 51, rotary rotating part 52, drive motor 53, worm gear 54, worm 55.

[0036] The rotary mechanism includes an annular mounting surface 301, a limiting bearing part 302, a lower bearing surface 303, an upper bearing surface 304, an upper bearing wear-resistant plate 305, a lower bearing wear-resistant plate 306, a lower positioning pin sleeve 307, and a lower limiting block 308. Detailed Implementation

[0037] The specific implementation plan is described below with reference to the attached diagram.

[0038] Example 1.

[0039] like Figure 3 As shown, the boom slewing device 400 includes a slewing platform 30, a slewing mechanism 50, and a boom support 40. The boom support 40 is mounted on the front of the slewing platform 30 via the slewing mechanism 50.

[0040] like Figure 4 Figure 5 As shown, the boom support 40 includes a support plate 401 and a hinge seat welded to the support plate 401. The support plate 401 is arranged parallel to the slewing platform 30. The hinge seat includes a boom hinge seat 402 for hinged boom 11 and a boom cylinder hinge seat 403 for hinged boom cylinder 14. The boom cylinder hinge seat 403 is arranged in front of the boom hinge seat 402.

[0041] like Figure 1 As shown, the boom support 40 is used to connect the working device 100, which includes a boom 11, a stick 12, attachments 13, a boom cylinder 14, a stick cylinder 15, and a bucket cylinder 16. The attachment 13 can be a bucket or a breaker hammer, etc. The attachment 13, stick 12, boom 11, and boom hinge seat 402 are connected sequentially. The boom cylinder 14 is connected at both ends to the boom 11 and the boom cylinder hinge seat 403. The extension and retraction of the boom cylinder 14 pushes the boom 11 up and down. The stick cylinder 15 is connected at both ends to the boom 11 and the stick 12, respectively. The extension and retraction of the stick cylinder 15 pushes the stick 12 to swing relative to the boom 11. One end of the bucket cylinder 16 is connected to the stick 12, and the other end is connected to the attachment 13 via a linkage mechanism. The extension and retraction of the bucket cylinder 16 pushes the attachment 13 to swing relative to the stick.

[0042] like Figure 6 Figure 7 As shown, a limiting part 404 is provided at the rear of the boom support 40. The limiting part 404 is arranged on the upper side of the support plate 401 and the rear side of the boom hinge seat 402. The limiting part 404 has an upper limiting surface 405 and a lower limiting surface 406, which are arranged vertically opposite to each other on the limiting part 404. The upper limiting surface 405 is located on the lower side, and the lower limiting surface 406 is located on the upper side. There is a certain distance between the two, so that the limiting part 404 presents a groove shape with the opening facing the rear of the boom support.

[0043] like Figure 8As shown, a limiting support part 302 is provided at the front of the slewing platform 30, and the limiting support part 302 is located behind the slewing mechanism 50. The limiting support part 302 has a lower support surface 303 and an upper support surface 304. The lower support surface 303 is located on the lower side of the limiting support part 302, and the upper support surface 304 is located on the upper side of the limiting support part 302. The upper support surface 304 and the lower support surface 303 are arranged opposite each other on the limiting support part 302, thereby forming a protruding block-shaped structure on the limiting support part 302 that protrudes towards the boom support 40.

[0044] like Figure 9 Figure 10 As shown, when the boom support 40 rotates under the drive of the slewing mechanism 50 until its front orientation is consistent with the front orientation of the slewing platform 30, that is, when the rear of the boom support 40 faces the rear of the slewing platform 30, the lower bearing surface 303 and the upper limit surface 405 are in contact with each other, and the lower limit surface 406 and the upper bearing surface 304 are in contact with each other.

[0045] The upper limit surface 405 and the lower bearing surface 303 are a pair of rotating mating surfaces. That is, when the lower bearing surface 303 and the upper limit surface 405 are in contact and the boom support 40 rotates, the upper limit surface 405 can slide tightly against the lower bearing surface 303. The lower limit surface 406 and the upper bearing surface 304 are another pair of rotating mating surfaces. Optionally, the mating surfaces in a pair of rotating mating surfaces are planes.

[0046] Optionally, a wear-resistant plate is installed on the limiting part 404, and the upper limiting surface 405 and the lower limiting surface 406 are disposed on the corresponding wear-resistant plates. For example... Figure 7 As shown, a lower wear-resistant plate 407 and an upper wear-resistant plate 408 are installed on the limiting part 404. The upper wear-resistant plate 408 and the lower wear-resistant plate 407 are arranged opposite each other in the vertical direction and are fixed by bolts. The gap between the upper wear-resistant plate 408 and the lower wear-resistant plate 407 is used to accommodate the limiting support part 302. The upper limiting surface 405 is arranged on the top surface of the lower wear-resistant plate 407, and the lower limiting surface 406 is arranged on the bottom surface of the upper wear-resistant plate 408. Optionally, a shim 409 of appropriate thickness can be arranged on the bottom surface of the lower wear-resistant plate 407 and the top surface of the upper wear-resistant plate 408 to adjust and control the distance between the upper limiting surface 405 and the lower limiting surface 406, so that this distance matches the distance between the lower bearing surface 303 and the upper bearing surface 304 on the limiting support part 302.

[0047] A wear-resistant plate is installed on the limiting bearing part 302, and the lower bearing surface 303 and the upper bearing surface 304 are set on the corresponding wear-resistant plates. For example... Figure 8As shown, an upper wear-resistant plate 305 and a lower wear-resistant plate 306 are installed on the limiting bearing part 302. The upper wear-resistant plate 305 and the lower wear-resistant plate 306 are arranged opposite each other in the vertical direction and are fixed by bolts. The upper wear-resistant plate 305 is arranged on the upper side, and the lower wear-resistant plate 306 is arranged on the lower side. The upper bearing surface 304 is arranged on the top surface of the upper wear-resistant plate 305, and the lower bearing surface 303 is arranged on the bottom surface of the lower wear-resistant plate 306. Optionally, shims 409 of appropriate thickness can be arranged on the bottom surface of the upper wear-resistant plate 305 and the top surface of the lower wear-resistant plate 306 to adjust and control the distance between the upper bearing surface 304 and the lower bearing surface 303, so that this distance is the same as the distance between the lower limiting surface 406 and the upper limiting surface 405 on the limiting part 404.

[0048] Wear-resistant plates are provided to reduce wear on parts when the limiting part 404 and the limiting bearing part 302 are in contact and slide relative to each other. The wear-resistant plates are also replaceable, thus extending the overall structure's service life. By setting shims 409, the distance and vertical position between the lower bearing surface 303 and the upper bearing surface 304, and the distance and vertical position between the upper limiting surface 405 and the lower limiting surface 406 are adjusted. This ensures that when the boom support 40 rotates, the limiting bearing part 302 can smoothly enter between the lower limiting surface 406 and the upper limiting surface 405 of the limiting part 404, and that the lower bearing surface 303 and the upper bearing surface 304 are in close contact with the upper limiting surface 405 and the lower limiting surface 406.

[0049] like Figure 12 Figure 13 As shown, the slewing mechanism 50 includes a slewing fixed part 51, a slewing rotating part 52 slewingly mounted on the slewing fixed part 51, and a slewing drive device mounted on the slewing fixed part 51. The top of the slewing rotating part 52 is bolted to the boom support annular mounting surface 413 at the bottom of the support plate 401. The bottom of the slewing fixed part 51 is bolted to the slewing mechanism annular mounting surface 301 on the slewing platform 30. The slewing drive device includes a drive motor 53 and a worm gear 55 driven by the drive motor 53. The slewing rotating part 52 has a worm wheel 54 that cooperates with the worm gear 55. The drive motor 53 drives the slewing rotating part 52 through the worm wheel 54 and the worm gear 55 to reduce speed, thereby realizing the slewing rotation of the boom support 40 relative to the slewing platform 30.

[0050] Alternatively, the slewing mechanism 50 can also take other forms, such as a slewing bearing structure connecting the upper body 300 and the lower body 200 of the excavator, driven by a slewing hydraulic motor and a reducer.

[0051] like Figure 1As shown, a working device 100 is installed on the boom support 40 for connecting with the boom 11 and the boom cylinder 14. The force on the working device 100 is applied to the boom support 40 through the boom 11 and the boom cylinder 14. The boom support 40 generates a corresponding force on the slewing mechanism 50, which in turn generates a bending moment in the corresponding direction on the slewing mechanism 50.

[0052] like Figure 1 Figure 2 As shown, the excavator's working device 100 interacts with the work object via attachments 13. When the excavator operates using the working device 100, the working device 100 is usually located in front of the slewing platform 30. In most cases, the forward orientation of the boom support 40 (towards the attachment end) is consistent with the direct front direction of the slewing platform 30. In some cases, the working device 100 needs to be deflected for operation, that is, the forward orientation of the boom support 40 is directed towards the oblique front of the slewing platform 30. When the boom support 40 is facing directly in front of or diagonally in front of the slewing platform 30, the force exerted by the working device 100 on the boom support can be divided into two types. One is the forward tilting force. At this time, the attachment 13 is suspended in the air or the attachment 13 is digging material in the material. The force on the working device 100 at this time is the resultant force of the working device 100's own weight, the weight of the material being dug, and the digging resistance (if any), which forms the forward tilting force. This forward tilting force generates a forward tilting moment on the boom support 40, causing the rear of the boom support 40 to tilt upward. The forward tilting moment will generate a forward bending moment on the slewing mechanism 50.

[0053] Another force exerted by the working device 100 on the boom support 40 is a tilting force. After the attachment 13 of the working device 100 touches the ground, the boom cylinder 14 continues to retract, causing the boom 11 to move downward relative to the slewing platform 30. At this time, the force exerted by the ground on the attachment 13 is transmitted to the boom support 40 through the working device 100, and the boom support 40 exhibits a tilting force. Under the action of the tilting force, the boom support 40 has a tendency to flip backward (the rear part of the boom support 40 moves downward).

[0054] When a forward tilting force is applied to the boom support 40 during excavator operation, such as Figure 10As shown, the lower bearing surface 303 on the limiting bearing part 302 abuts against the upper limiting surface 405 on the limiting part 404, preventing the limiting part 404 from flipping upwards. The force balancing device 100 of the limiting bearing part 302 on the limiting part 404 generates a forward tilting force on the boom support 40, thereby reducing the forward bending moment generated by the boom support 40 on the slewing mechanism 50. Similarly, when a backward tilting force occurs on the boom support 40 during excavator operation, the upper bearing surface 304 on the limiting bearing part 302 abuts against the lower limiting surface 406 on the limiting part 404, preventing the limiting part 404 from flipping downwards. The force balancing device 100 of the limiting bearing part 302 on the limiting part 404 generates a backward tilting force on the boom support 40, thereby reducing the backward bending moment generated by the boom support 40 on the slewing mechanism 50. The force balancing working device 100 generated by the interaction between the limiting part 404 and the limiting bearing part 302 reduces the bending moment generated on the slewing mechanism 50 by the resultant force on the boom support 40 on the boom support 40.

[0055] In the boom slewing device, optionally, only the lower bearing surface 303 is provided on the limiting bearing part 302, and only the upper limiting surface 405 is provided on the limiting part 404. The limiting part 404 and the limiting bearing part 302 only interact to reduce the forward bending moment on the slewing mechanism 50 when a forward tilting force occurs on the boom support 40, and do not intervene when a backward tilting force occurs on the boom support 40. Due to the structural and operational characteristics of excavators, the maximum forward tilting force generated on the boom support 40 is greater than the maximum backward tilting force generated on the boom support 40, and the occurrence of forward tilting force on the boom support 40 is more frequent than the occurrence of backward tilting force, resulting in a greater adverse impact on the slewing mechanism.

[0056] In the boom slewing device, the upper limit surface 405 and the lower limit surface 406 on the limiting part 404 can optionally be arranged opposite each other, so that the limiting part 404 presents a protrusion shape protruding behind the boom support 40. Correspondingly, on the limiting bearing part 302, the upper bearing surface 304 and the lower bearing surface 303 are arranged opposite each other with an upper and lower interval, and the limiting bearing part 302 presents a groove structure with the slot facing the boom support 40.

[0057] In the boom slewing device, it is possible to select, such as Figure 3 Figure 4 Figure 8As shown, a lower positioning pin sleeve 307 is provided on the rotary platform 30, and an upper positioning pin sleeve 410 is provided on the support plate 401 that can be coaxially aligned with the lower positioning pin sleeve 307. A positioning pin 411 is installed in the upper positioning pin sleeve 410 that can pass downward through the hole on the support plate 401 and be inserted into the lower positioning pin sleeve 307. When the slewing mechanism 50 drives the boom support 40 to rotate to a certain azimuth angle, such as when the front of the boom support 40 is aligned with the front end of the slewing platform 30, or when the front of the boom support 40 is aligned with the rear end of the slewing platform 30, or when the boom support 40 is deflected relative to the slewing platform 30 to a predetermined angle, the lower positioning pin sleeve 307 is coaxially aligned with the upper positioning pin sleeve 410. The positioning pin 411 in the upper positioning pin sleeve 410 passes through the hole on the support plate 401 and is inserted into the lower positioning pin sleeve 307, so that the boom support 40 and the slewing platform 30 are directly pinned together and cannot rotate. This prevents the torque generated on the boom support 40 during the operation of the working device 100 from being transmitted to the slewing mechanism 50, thereby protecting the slewing mechanism 50 during excavator operation.

[0058] In the boom slewing device, selectively, when the positioning angle of the boom support 40 relative to the slewing platform 30 is one or two positions, such as when the front orientation of the boom support 40 is consistent with the front end orientation of the slewing platform 30 and the front orientation of the boom support 40 is consistent with the rear end orientation of the slewing platform 30, a lower limit block 308 can be provided on the slewing platform 30. Figure 8 As shown, an upper limit block 412 is provided on the lower side of the support plate 401, which can abut against the lower limit block 308 for limiting. Figure 5 As shown, when the lower positioning pin sleeve 307 and the upper positioning pin sleeve 410 are coaxially aligned, the lower limit block 308 and the upper limit block 412 abut against each other, as shown. Figure 3 As shown. The contact between the upper limit block 412 and the lower limit block 308 facilitates adjustment to make the lower positioning pin sleeve 307 coaxially aligned with the upper positioning pin sleeve 410.

[0059] This embodiment also provides an excavator having the aforementioned boom slewing device 400, wherein the lower ends of the boom 11 and boom cylinder 14 in the working device 100 are connected to the boom support 40. This excavator can be a wheeled excavator, and its structure is as follows: Figure 1 Figure 2 As shown. It can also be a tracked excavator.

[0060] In the excavator, optionally, the slewing mechanism 50 is configured to rotate at least 180 degrees, such as... Figure 11 As shown, the boom support 40 can rotate to face directly behind the slewing platform 30. In excavators, as... Figure 2As shown, the cab roof 32 can be configured as a telescopic lifting type. Lowering the height of the cab roof 32 can reduce the overall height of the machine. By rotating the slewing mechanism 50, the boom support 40 is oriented towards the rear of the slewing platform 30, placing the boom 11 directly above the slewing platform 30. The stick 12 is then vertically suspended behind the excavator, reducing the overall length of the excavator. Figure 2 As shown, this allows for a more compact transport configuration, facilitating the transport of the excavator as a whole machine, such as by using a container for transport.

Claims

1. A boom slewing device, comprising a slewing platform, a slewing mechanism with a slewing fixing part fixed to the front of the slewing platform, and a boom support fixed to the slewing rotating part of the slewing mechanism, characterized in that, The boom support is provided with a limiting part at the rear, and a limiting bearing part is fixed at the position of the slewing platform behind the boom support; the limiting part has an upper limiting surface, and the limiting bearing part has a lower bearing surface. The upper limiting surface and the lower bearing surface are a pair of rotating contact surfaces. When the boom support rotates to face the front of the slewing platform, the lower bearing surface is located above the upper limiting surface and the lower bearing surface is in contact with the upper limiting surface.

2. The boom slewing device according to claim 1, characterized in that... The limiting part has a lower limiting surface, and the limiting bearing part has an upper bearing surface. The lower limiting surface and the upper bearing surface are a pair of rotating contact surfaces. When the boom support rotates to face the front of the slewing platform, the upper bearing surface is located below the lower limiting surface and the lower limiting surface and the upper bearing surface are in contact.

3. The boom slewing device according to claim 2, characterized in that, The upper limit surface and the lower limit surface are arranged opposite each other on the limiting part, and the lower bearing surface and the upper bearing surface are arranged opposite each other on the limiting bearing part.

4. The boom slewing device according to claim 2, characterized in that, The upper limit surface and the lower limit surface are arranged opposite to each other on the limiting part, and the lower bearing surface and the upper bearing surface are arranged opposite each other on the limiting bearing part.

5. The boom slewing device according to any one of claims 1 to 4, characterized in that, Both the limiting part and the limiting bearing part include wear-resistant plates that can be detachably and fixedly installed, and each limiting surface and each bearing surface are arranged on the corresponding wear-resistant plate.

6. The boom slewing device according to any one of claims 1 to 4, characterized in that, The boom support includes a support plate and a hinge seat welded to the support plate. The limiting part is arranged on the upper side of the support plate and located behind the hinge seat.

7. The boom slewing device according to claim 6, characterized in that, The rotating platform is provided with a lower positioning pin sleeve, and the support plate is provided with an upper positioning pin sleeve that can be coaxially aligned with the lower positioning pin sleeve. The upper positioning pin sleeve is equipped with a positioning pin that can pass downward through the hole in the support plate and be inserted into the lower positioning pin sleeve.

8. The boom slewing device according to claim 7, characterized in that, The rotary platform is provided with a lower limit block, and the lower side of the support plate is provided with an upper limit block that can abut against the lower limit block for limiting. When the lower positioning pin sleeve and the upper positioning pin sleeve are coaxially aligned, the lower limit block abuts against the upper limit block.

9. An excavator, characterized in that, The boom slewing device has any one of claims 1 to 8, wherein the lower ends of the boom and the boom cylinder are connected to the boom support.

10. The excavator according to claim 9, characterized in that, The slewing mechanism is configured to rotate at least 180 degrees, and when the boom support is slewing directly behind the slewing platform, the lower positioning pin sleeve on the slewing platform is coaxially aligned with the upper positioning pin sleeve on the boom support, and positioning pins are inserted into the coaxially aligned lower and upper positioning pin sleeves.

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