A mechanical arm for processing and welding automobile parts

Abstract

The application discloses a mechanical arm for automobile part machining and welding, which comprises a base, a large arm rotatably assembled at the upper end surface of the base, a small arm rotatably assembled at the other end of the large arm, a wrist joint arm rotatably connected at the end of the small arm, a connecting flange rotatably connected at the other end of the wrist joint arm, a welding gun unit installed at the lower end surface of the connecting flange, and an edge pressing unit assembled on the welding gun unit. The mechanical arm can continuously complete the "pressing-bending-welding" action in one clamping and positioning, greatly reduces the time for workpiece transfer and repeated positioning, significantly improves the production rhythm and overall machining efficiency, and can apply accurate and reliable clamping force to the adjacent area of the welding point, effectively inhibiting the micro-motion, warping and deformation of the thin plate part during welding.

Description

Technical Field

[0001] This invention belongs to the field of welding equipment technology, specifically a robotic arm for welding automotive parts. Background Technology

[0002] In the automotive manufacturing industry, the connection of thin sheet metal components (such as body panels, chassis structural components, and interior brackets) relies heavily on welding processes. Among these, resistance spot welding has become one of the most important connection methods due to its high efficiency, low cost, and ease of automation. However, traditional technologies result in thin sheet metal automotive components having poor rigidity, making them susceptible to fretting and warping during welding due to electrode pressure and thermal expansion. This leads to weld point misalignment, uneven weld nugget size, and even incomplete welds. Furthermore, traditional fixtures can only fix the components from the outside and cannot provide dynamic and precise constraints at the weld point. Multiple processes, such as positioning, pre-bending (if necessary), welding, and inspection, often need to be completed at different stations by different equipment. This requires frequent workpiece transfer and repeated positioning, resulting in low production efficiency and lengthy production lines.

[0003] Therefore, it is necessary to provide a robotic arm for machining and welding automotive parts to solve the problems mentioned in the background art. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides the following technical solution: a robotic arm for welding and processing automotive parts, comprising:

[0005] Base;

[0006] The upper arm, one end of which is rotatably mounted on the upper surface of the base;

[0007] The forearm is rotatably assembled at the other end of the upper arm;

[0008] A wrist joint arm, one end of which is rotatably connected to the end of the forearm, and the other end of which is rotatably connected to a connecting flange;

[0009] The welding torch unit is installed on the lower end face of the connecting flange;

[0010] The edge pressing unit is assembled on the welding gun unit.

[0011] Furthermore, as a preferred embodiment, the upper end of the welding torch unit is fixed with a torch changing disc, and the torch changing disc is detachably installed and fixed to the connecting flange.

[0012] Furthermore, preferably, the welding torch unit includes:

[0013] The side clamps are two parallel side clamps with an installation space between them;

[0014] There are two connecting plates arranged in parallel, both of which are located within the installation space. The lower ends of each side clamp are rotatably connected to the connecting plate.

[0015] The upper welding arm is vertically slidably disposed between the connecting plates;

[0016] A fixed arm, one end of which is fixed between two connecting plates by bolts;

[0017] The lower welding arm is fixed to the other end of the fixed arm; the lower welding arm is configured as an L-shaped structure, and the welding end of the lower welding arm is on the same vertical line as the welding end of the upper welding arm;

[0018] A propulsion cylinder is vertically fixed to the connecting plate, and the telescopic end of the propulsion cylinder is fixed to the upper welding arm;

[0019] The electrode head is fixed to the ends of the upper and lower welding arms.

[0020] Furthermore, preferably, the pressing unit includes:

[0021] The upper pressing device is slidably sleeved outside the upper welding arm;

[0022] A lifting cylinder is vertically arranged between the connecting plates, and the telescopic end of the lifting cylinder is connected to the upper pressing device;

[0023] The positioning plates are two parallel plates, each located outside the two connecting plates. The positioning plates have multiple positioning holes, and positioning screws for connecting to the lifting cylinder are installed in the positioning holes.

[0024] The lower pressing device is fixed on the lower welding arm.

[0025] Furthermore, as a preferred embodiment, each of the side clamps is rotatably connected to a hydraulic cylinder, one end of which is connected to the connecting plate.

[0026] Furthermore, preferably, the lower pressing device includes:

[0027] The side wing plates are two symmetrically arranged, and the two side wing plates are respectively fixed symmetrically on both sides of the lower welding arm;

[0028] The mounting plate is horizontally fixed between the two side wing plates and located above the lower welding arm;

[0029] A bearing seat is fixed on the side of the mounting plate away from the fixed arm, and a threaded sleeve is rotatably connected inside the bearing seat;

[0030] A shaft tube is vertically and slidably connected to the middle part of the shaft seat. The shaft tube is sleeved outside the lower welding arm and threadedly and slidably connected inside the threaded sleeve.

[0031] A steel sleeve is coaxially fixed above the shaft tube.

[0032] Furthermore, as a preferred embodiment, a rotating shaft is horizontally rotatably connected inside the mounting plate, and bevel gears are fixed at both ends of the rotating shaft. A first bevel gear is coaxially fixed outside the threaded sleeve, and the first bevel gear meshes with one of the bevel gears.

[0033] Furthermore, a drive shaft is rotatably connected inside the mounting plate, and a second bevel gear is fixed outside the drive shaft. The second bevel gear meshes with another bevel gear.

[0034] Furthermore, preferably, the upper pressing device includes:

[0035] An outer tube sleeve is slidably fitted outside the upper welding arm, and a bracket is fixed outside the outer tube sleeve. The lifting cylinder is connected to the bracket.

[0036] The lower pressure tube is coaxially fixed below the outer sleeve, and the lower end of the lower pressure tube is engaged with the steel sleeve.

[0037] The molding parts are multiple in number arranged circumferentially, and each molding part is connected to the lower end of the pressure tube.

[0038] Furthermore, as a preferred embodiment, the lower end of the pressure tube is slidably inserted into and connected to the steel sleeve, and the inner wall of the steel sleeve is provided with an arc-shaped groove.

[0039] Furthermore, as a preferred embodiment, a fixed shaft is slidably connected inside the outer tube sleeve, and a top tube is slidably connected inside the lower pressing tube. The upper end of the top tube is connected to the fixed shaft. A guide cavity is opened inside the outer tube sleeve, and the upper end of the fixed shaft is sealed and slidably disposed inside the guide cavity. An inner spring is sleeved on the fixed shaft.

[0040] The bracket has a hydraulic channel, one end of which is connected to the guide cavity.

[0041] Compared with the prior art, the beneficial effects of the present invention are:

[0042] The welding torch unit used in this invention is equipped with a clamping unit. The clamping unit can clamp and position the thin automotive sheet parts to be welded by cooperating with the lower and upper clamping devices. On the one hand, when the hydraulic cylinder extends and retracts, the clamping unit can bend the thin automotive sheet parts at a small angle. The clamping positioning and bending functions are directly integrated into the welding torch unit, so that the robotic arm can continuously complete the "clamping-bending-welding" action in one clamping and positioning, which greatly reduces the time for workpiece transfer and repeated positioning, and significantly improves the production cycle and overall processing efficiency. Moreover, it can apply precise and reliable clamping force to the area near the welding point, which effectively suppresses the micro-movement, warping and deformation of the thin sheet parts during welding. Especially for lap or folded welds, the tight clamping ensures the uniformity of the joint gap and improves the subsequent welding quality.

[0043] On the other hand, the lower and upper pressure devices work together to apply pressure to the surface of the thin-plate components, creating a pit at the welding position. This allows the upper and lower thin-plate components to achieve localized tight bonding and material pre-aggregation in the central area of ​​the weld joint. During welding, the current path is more concentrated, and heat is more easily accumulated in the central area at the bottom of the pit, which is conducive to forming a larger and deeper weld nugget. This directly improves the tensile and shear strength of the weld joint. Furthermore, the shaping component on the outer sleeve can further pressurize and shape the sidewalls at the bottom of the pit, which significantly increases the welding strength of the upper and lower thin-plate components. This results in a longer lifespan and higher reliability of the weld joint when subjected to long-term vehicle vibration loads. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0045] Figure 2 This is a schematic diagram of the welding torch unit in this invention;

[0046] Figure 3 This is a schematic diagram of the upper welding arm and the lower welding arm in this invention;

[0047] Figure 4 This is a cross-sectional view of the welding torch unit in this invention;

[0048] Figure 5 This is a schematic diagram of the lower pressing device in this invention;

[0049] Figure 6 This is a schematic diagram of the upper pressing device in this invention;

[0050] Figure 7 This is a schematic diagram of the structure of the outer sleeve and the steel sleeve in this invention.

[0051] In the diagram: 1. Base; 11. Upper arm; 12. Lower arm; 13. Wrist joint arm; 14. Connecting flange; 15. Torch changing disc; 2. Welding torch unit; 21. Side clamping plate; 22. Connecting plate; 23. Upper welding arm; 24. Fixed arm; 25. Lower welding arm; 26. Propulsion cylinder; 27. Electrode head; 3. Edge pressing unit; 31. Lifting cylinder; 32. Positioning plate; 33. Hydraulic cylinder; 4. Upper edge pressing device; 41. Outer sleeve; 42. Bracket; 43. Lower pressing tube; 44. Molded part; 45. Arc groove; 46. Fixed shaft; 47. Top tube; 48. Hydraulic channel; 5. Lower edge pressing device; 51. Side wing plate; 52. Mounting plate; 53. Shaft seat; 54. Threaded sleeve; 55. Shaft tube; 56. Steel sleeve; 57. Rotating shaft; 58. Bevel gear; 59. Drive shaft. Detailed Implementation

[0052] Please see Figures 1-5 In this embodiment of the invention, a robotic arm for welding automotive parts includes:

[0053] Base 1;

[0054] The upper arm 11 is rotatably mounted at one end on the upper surface of the base 1;

[0055] Forearm 12 is rotatably assembled at the other end of upper arm 11;

[0056] A wrist joint arm 13, one end of which is rotatably connected to the end of the forearm 12, and the other end of the wrist joint arm 13 is rotatably connected to a connecting flange 14;

[0057] The welding torch unit 2, mounted on the lower end face of the connecting flange 14, features a multi-degree-of-freedom design that ensures it can reach the welding position on the complex three-dimensional curved surface of the vehicle body in various postures. The upper arm 11 and the lower arm 12 provide a large positional coverage range, while the wrist joint arm 13 and the connecting flange 14 provide precise end-effector posture adjustment capabilities.

[0058] The edge-pressing unit 3 is mounted on the welding gun unit 2. The edge-pressing unit 3 can perform edge-pressing operations on the thin automotive sheet parts before the welding gun unit 2 starts welding. This can apply precise and reliable clamping force to the area near the welding point, effectively suppressing micro-movement, warping and deformation of the thin sheet parts during subsequent welding. On the other hand, it can also perform other auxiliary operations such as bending and shaping on the thin automotive sheet parts, improving the efficiency of the welding operation.

[0059] In this embodiment, a gun changing disc 15 is fixed to the upper end of the welding gun unit 2, and the gun changing disc 15 is detachably installed and fixed to the connecting flange 14, thereby facilitating the disassembly and replacement of the welding gun unit 2, improving equipment utilization, and allowing for flexible switching.

[0060] In a preferred embodiment, the welding torch unit 2 includes:

[0061] The side clamps 21 are two parallel ones, with an installation space between the two side clamps 21;

[0062] There are two connecting plates 22 arranged in parallel, and both connecting plates 22 are located in the installation space. The lower ends of each side clamping plate 21 are rotatably connected to the connecting plate 22.

[0063] The upper welding arm 23 is vertically slidably disposed between the connecting plates 22;

[0064] The fixed arm 24 is fixed at one end between the two connecting plates 22 by bolts;

[0065] The lower welding arm 25 is fixed to the other end of the fixed arm 24; the lower welding arm 25 is configured as an L-shaped structure, and the welding end of the lower welding arm 25 is on the same vertical line as the welding end of the upper welding arm 23.

[0066] The propulsion cylinder 26 is vertically fixed on the connecting plate 22, and the telescopic end of the propulsion cylinder 26 is fixed to the upper welding arm 23;

[0067] Electrode head 27 is fixed at the ends of the upper welding arm 23 and the lower welding arm 25. That is, during welding, when the upper arm 11 and the lower arm 12 of the robotic arm control the welding gun unit 2 to reach the designated welding position, the upper welding arm 23 of the welding gun unit 2 is above the upper automotive sheet metal part, and the lower welding arm 25 is below the lower automotive sheet metal part. The electrode head 27 at the end of the lower welding arm 25 is in contact with the lower automotive sheet metal part. Then, the upper welding arm 23 is pushed vertically by the propulsion cylinder 26 and moves towards the upper automotive sheet metal part. When the electrode head 27 at the end of the upper welding arm 23 contacts the upper automotive sheet metal part, the resistance heat generated by the current passing through the automotive sheet metal part can be used to melt the contact surface between the upper and lower automotive sheet metal parts to achieve welding.

[0068] In this embodiment, the pressing unit 3 includes:

[0069] The upper pressing device 4 is slidably sleeved outside the upper welding arm 23;

[0070] A lifting cylinder 31 is vertically arranged between the connecting plates 22. The telescopic end of the lifting cylinder 31 is connected to the upper pressing device 4 so that the upper pressing device 4 can be controlled to slide and contact the surface of the upper automotive sheet metal parts through the lifting cylinder 31.

[0071] The positioning plates 32 are two parallel plates, each located outside the two connecting plates 22. The positioning plates 32 have multiple positioning holes, and positioning screws for connecting to the lifting cylinder 31 are installed in the positioning holes to realize the installation and fixation of the lifting cylinder 31 and the connecting plate 22.

[0072] The lower pressing device 5 is fixed on the lower welding arm 25.

[0073] In this embodiment, each of the side clamping plates 21 is rotatably connected to a hydraulic cylinder 33. One end of the hydraulic cylinder 33 is connected to the connecting plate 22. When the upper pressing device 4 and the lower pressing device 5 cooperate to clamp and position the automotive sheet metal parts, the bending operation of the automotive sheet metal parts can be realized by the extension and retraction of the hydraulic cylinder 33. This allows for continuous completion of the "pressing-bending-welding" action, significantly reducing the time for workpiece transfer and repeated positioning, and significantly improving the production cycle and overall processing efficiency. On the other hand, for lap or folded weld seams, the tight pressing ensures the uniformity of the joint gap, improving the subsequent welding quality. It should be noted that during welding, the upper pressing device 4 and the lower pressing device 5 are detached from and do not contact the automotive sheet metal parts.

[0074] In this embodiment, the lower pressing device 5 includes:

[0075] The two side wing plates 51 are symmetrically arranged and are respectively fixed symmetrically on both sides of the lower welding arm 25.

[0076] Mounting plate 52 is horizontally fixed between the two side wing plates 51 and located above the lower welding arm 25;

[0077] A bearing seat 53 is fixed on the mounting plate 52 on the side away from the fixed arm 24, and a threaded sleeve 54 is rotatably connected inside the bearing seat 53;

[0078] The shaft tube 55 is vertically slidably connected to the middle part of the shaft seat 53. The shaft tube 55 is sleeved outside the lower welding arm 25 and is threadedly slidably connected inside the threaded sleeve 54.

[0079] The steel sleeve 56 is coaxially fixed above the shaft tube 55. The threaded sleeve 54 can control the axial sliding of the steel sleeve 56 during forward and reverse rotation, so that it can be sleeved or disengaged from the end of the lower welding arm 25. This arrangement can protect the electrode head 27 of the lower welding arm 25 by sleeve of the steel sleeve 56 when the welding unit 2 is not in use, effectively preventing the electrode head 27 from being accidentally bumped or scratched, and avoiding damage or deformation to its precision working surface (end face). It can also make full contact between the end of the steel sleeve 56 and the automotive sheet metal parts, and cooperate with the pressing device 4 to apply pressure and clamp the automotive sheet metal parts.

[0080] In a preferred embodiment, a rotating shaft 57 is horizontally rotatably connected inside the mounting plate 52, and bevel gears 58 are fixed at both ends of the rotating shaft 57. A first bevel gear is coaxially fixed outside the threaded sleeve 54, and the first bevel gear meshes with one of the bevel gears 58.

[0081] Furthermore, a drive shaft 59 is rotatably connected inside the mounting plate 52, and a second bevel gear is fixed outside the drive shaft 59. The second bevel gear meshes with another bevel gear 58. Thus, when the drive shaft 59 rotates, it can drive the bevel gear 58 to rotate using the second bevel gear, and the bevel gear 58 synchronously drives the threaded sleeve 54 to rotate, thereby realizing the axial sliding adjustment of the steel sleeve 56.

[0082] In this embodiment, the upper pressing device 4 includes:

[0083] The outer sleeve 41 is slidably sleeved on the outside of the upper welding arm 23. A bracket 42 is fixed on the outside of the outer sleeve 41. The lifting cylinder 31 is connected to the bracket 42.

[0084] The lower pressure tube 43 is coaxially fixed below the outer tube sleeve 41, and the lower end of the lower pressure tube 43 is engaged with the steel sleeve 56.

[0085] The molding parts 44 are multiple in number arranged circumferentially, and each molding part 44 is connected to the lower end of the pressure tube 43.

[0086] In this embodiment, the lower end of the pressure tube 43 is slidably inserted into and connected to the steel sleeve 56. The inner wall of the steel sleeve 56 is provided with an arc-shaped groove 45. During normal clamping and positioning, the lifting cylinder 31 can control the bracket 42 to drive the outer sleeve 41 to move downward synchronously. The end of the pressure tube 43 on the outer sleeve 41 can contact the surface of the automotive sheet metal component. At this time, the molding part 44 is retracted into the pressure tube 43. In this way, the pressure tube 43 can cooperate with the steel sleeve 56 to achieve surface deformation of the automotive sheet metal during gradual pressure application, forming a pit at the welding position. This allows the upper and lower sheet metal components to achieve local tight fit and material pre-aggregation in the central area of ​​the weld point. During electric welding, the current path is more concentrated, and heat is more easily accumulated in the central area at the bottom of the pit, which is conducive to forming a larger and deeper weld nugget. This directly improves the tensile strength and shear strength of the weld point, ensuring that the gap between the automotive sheet metal is almost zero.

[0087] In addition, the pits can also form a natural barrier, further blocking particles that splash out horizontally from the core area of ​​the weld nugget, thus preventing welding spatter from affecting the aesthetics of the automotive sheet metal surface.

[0088] In this embodiment, a fixed shaft 46 is slidably connected inside the outer sleeve 41, and a top tube 47 is slidably connected inside the lower pressing tube 43. The upper end of the top tube 47 is connected to the fixed shaft 46. A guide cavity is provided inside the outer sleeve 41. The upper end of the fixed shaft 46 is sealed and slidably disposed in the guide cavity. An inner spring is sleeved on the fixed shaft 46. The inner spring can use its elastic force to push the fixed shaft 46 upward.

[0089] The bracket 42 has a hydraulic channel 48, one end of which is connected to the guide cavity. When high-pressure oil enters the guide cavity through the hydraulic channel 48, it can hydraulically push the fixed shaft 46 downward. At this time, the top tube 47 gradually approaches the plastic part 44 as the fixed shaft 46 slides downward. When the lower end of the top tube 47 is completely flush with the lower end of the outer sleeve 41, it can push the inclined surface of the plastic part 44, causing the plastic part 44 to deflect. Each plastic part 44 is pushed out radially from the outer sleeve 41, thereby using the plastic part 44 to pressurize and shape the bottom side wall of the recess in the automotive thin plate parts. This can significantly increase the welding strength of the upper and lower thin plate parts, giving the weld joint a longer life and higher reliability when subjected to long-term vibration loads from the vehicle.

[0090] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A robotic arm for welding and processing automotive parts, characterized in that, It includes: Base (1); The upper arm (11) is rotatably mounted at one end on the upper surface of the base (1); The forearm (12) is rotatably assembled at the other end of the upper arm (11); A wrist joint arm (13) has one end rotatably connected to the end of the forearm (12), and the other end of the wrist joint arm (13) is rotatably connected to a connecting flange (14). The welding torch unit (2) is installed on the lower end face of the connecting flange (14); The edge pressing unit (3) is assembled on the welding gun unit (2); The welding torch unit (2) includes an upper welding arm (23) and a lower welding arm (25). The pressing unit (3) includes: The upper pressing device (4) is slidably sleeved outside the upper welding arm (23); The lower pressing device (5) is fixed on the lower welding arm (25); The lower pressing device (5) includes: A bearing seat (53) has a threaded sleeve (54) rotatably connected inside it. The shaft tube (55) is vertically slidably connected to the middle part of the shaft seat (53), the shaft tube (55) is sleeved outside the lower welding arm (25), and the shaft tube (55) is threadedly slidably connected inside the threaded sleeve (54); A steel sleeve (56) is coaxially fixed above the shaft tube (55); The upper pressing device (4) includes: The outer sleeve (41) is slidably mounted outside the upper welding arm (23); The pressure tube (43) is coaxially fixed below the outer sleeve (41). The lower end of the pressure tube (43) is connected to the steel sleeve (56). The lower end of the pressure tube (43) can be slidably inserted into the steel sleeve (56). The inner wall of the steel sleeve (56) is provided with an arc groove (45). The molding parts (44) are multiple in a circle, and each molding part (44) is connected to the lower end of the pressure tube (43).

2. The robotic arm for welding and processing automotive parts according to claim 1, characterized in that: The upper end of the welding torch unit (2) is fixed with a torch changing disc (15), and the torch changing disc (15) is detachably installed and fixed to the connecting flange (14).

3. The robotic arm for welding and processing automotive parts according to claim 1, characterized in that, The welding torch unit (2) also includes: The side clamps (21) are two parallel ones, with an installation space between the two side clamps (21); There are two connecting plates (22) arranged in parallel. Both connecting plates (22) are located in the installation space. The lower ends of each side clamp (21) are rotatably connected to the connecting plate (22). The upper welding arm (23) is vertically slidably arranged between the connecting plates (22). The fixed arm (24) is fixed at one end between two connecting plates (22) by bolts. The lower welding arm (25) is fixed at the other end of the fixed arm (24). The lower welding arm (25) is configured as an L-shaped structure, and the welding end of the lower welding arm (25) is on the same vertical line as the welding end of the upper welding arm (23). The propulsion cylinder (26) is vertically fixed on the connecting plate (22), and the telescopic end of the propulsion cylinder (26) is fixed to the upper welding arm (23); The electrode head (27) is fixed to the ends of the upper welding arm (23) and the lower welding arm (25).

4. The robotic arm for welding and processing automotive parts according to claim 3, characterized in that, The pressing unit (3) also includes: A lifting cylinder (31) is vertically arranged between the connecting plates (22), and the telescopic end of the lifting cylinder (31) is connected to the upper pressing device (4); The positioning plates (32) are two parallel plates, and the two positioning plates (32) are located outside the two connecting plates (22). The positioning plates (32) have multiple positioning holes, and positioning screws for connecting with the lifting cylinder (31) are installed in the positioning holes.

5. The robotic arm for welding automotive parts according to claim 3, characterized in that: Each of the side clamps (21) is rotatably connected to a hydraulic cylinder (33), one end of which is connected to the connecting plate (22).

6. The robotic arm for welding and processing automotive parts according to claim 1, characterized in that, The lower pressing device (5) also includes: The two side wing plates (51) are symmetrically arranged and are respectively fixed symmetrically on both sides of the lower welding arm (25); Mounting plate (52) is horizontally fixed between two side wing plates (51) and above the lower welding arm (25), and the bearing seat (53) is fixed on the mounting plate (52) on the side away from the fixing arm (24).

7. The robotic arm for welding automotive parts according to claim 6, characterized in that: The mounting plate (52) is horizontally rotatably connected to a rotating shaft (57), and both ends of the rotating shaft (57) are fixed with bevel gears (58). The threaded sleeve (54) is coaxially fixed with a first bevel gear, which meshes with one of the bevel gears (58). Furthermore, a drive shaft (59) is rotatably connected inside the mounting plate (52), and a second bevel gear is fixed outside the drive shaft (59). The second bevel gear meshes with another bevel gear (58).

8. The robotic arm for welding automotive parts according to claim 4, characterized in that, The outer sleeve (41) is fixed with a bracket (42), and the lifting cylinder (31) is connected to the bracket (42).

9. A robotic arm for welding automotive parts according to claim 8, characterized in that: A fixed shaft (46) is slidably connected inside the outer sleeve (41), and a top tube (47) is slidably connected inside the lower pressing tube (43). The upper end of the top tube (47) is connected to the fixed shaft (46). A guide cavity is opened inside the outer sleeve (41). The upper end of the fixed shaft (46) is sealed and slidably disposed in the guide cavity, and an inner spring is sleeved on the fixed shaft (46). The bracket (42) has a hydraulic channel (48) inside, and one end of the hydraulic channel (48) is connected to the guide cavity.

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