A large workpiece mounting auxiliary device for a gantry machine tool

Abstract

The application discloses a large workpiece mounting auxiliary device suitable for a gantry machine tool, which comprises lifting arms (1) symmetrically arranged on the two sides of the gantry machine tool, the arrangement positions of the lifting arms (1) correspond to positioning tools in a machine tool workbench, fixed pipes (2) are fixedly installed on the lifting output ends of the lifting arms (1), main body frames (3) are arranged on the fixed pipes (2), and horizontal adjusting assemblies (4) are arranged on the lower portions of the main body frames (3). The horizontal adjusting assembly is used for realizing multi-directional position fine adjustment of the workpiece, improving alignment and adaptation flexibility, and improving large workpiece mounting efficiency.

Description

Technical Field

[0001] This invention relates to the field of gantry milling, and particularly to an auxiliary device for mounting large workpieces adapted to gantry milling. Background Technology

[0002] The machining of heavy and large-sized workpieces such as large valve bodies requires the use of gantry milling machines, and the rapid clamping and positioning of the workpieces is a key process for production efficiency. Due to the large size and high weight of these workpieces, on-site installation usually uses gantry hoisting equipment in conjunction with a special positioning device to achieve alignment and fixation. The structural rationality of the positioning device directly determines the convenience of workpiece installation and the reliability of positioning.

[0003] There are already various workpiece positioning solutions for gantry milling machines in the existing technology. For example, Chinese utility model patent with announcement number CN217619182U discloses a positioning device for a CNC gantry milling machine with multiple workstations. The device includes a frame and a fixed block. A placement plate is slidably installed on the top of the frame, and a body is fixedly connected to the top of the frame. Two sliding rods are slidably installed on the inner wall of the fixed block. A rotating plate is rotatably connected to one end of each sliding rod. A first motor is fixedly installed on the top of each sliding rod. A slider is fixedly connected to the bottom of the fixed block. A slide rail is slidably installed on the surface of the slider. The workpiece is clamped and positioned by the extension and retraction of the sliding rods and the sliding cooperation of the slider.

[0004] However, in actual production applications, the above-mentioned positioning device has certain shortcomings: On the one hand, the positioning auxiliary component of the device is a fixed assembly structure. After the workpiece is positioned and clamped, the auxiliary component must be completely removed before subsequent processing can begin. The disassembly and assembly process is cumbersome and time-consuming, which not only reduces the overall installation and processing efficiency of large workpieces, but also easily causes the positioning reference to shift, resulting in accuracy loss. On the other hand, the device only has a single-direction sliding guide mechanism in the horizontal direction. The horizontal adjustment dimension is single and the adjustable range is limited. It cannot achieve multi-directional horizontal position fine adjustment, and the alignment and adaptation flexibility is poor. In actual operation, it is often still necessary to manually push the workpiece to complete the position fine adjustment, which is labor-intensive and the alignment accuracy is difficult to control stably. Summary of the Invention

[0005] The purpose of this invention is to provide an auxiliary device for installing large workpieces that is compatible with gantry milling machines. This invention achieves multi-directional fine-tuning of the workpiece's position through a horizontal adjustment component, improving alignment flexibility and increasing the efficiency of installing large workpieces.

[0006] The technical solution of this invention: A large workpiece installation auxiliary device adapted to a gantry milling machine includes lifting arms symmetrically arranged on both sides of the gantry milling machine. The arrangement of the lifting arms corresponds to the positioning fixture in the machine tool's worktable. A fixed pipe is fixedly installed at the lifting output end of the lifting arm. A main frame is mounted on the fixed pipe. A horizontal adjustment component is provided at the lower part of the main frame. An auxiliary clamping component is assembled at the moving end of the horizontal adjustment component. The horizontal adjustment component is used to drive the auxiliary clamping component to reciprocate and adjust along the horizontal X-axis and Y-axis directions, so that the end of the auxiliary clamping component reliably fits tightly against the side of the workpiece. Multiple hydraulic buffers are distributed on the machine tool's worktable and around the outer periphery of the positioning fixture. The hydraulic buffers are used to provide buffering and force relief during the process of the workpiece falling into position to the positioning fixture.

[0007] In the above-mentioned auxiliary device for installing large workpieces for gantry milling machines, the lifting arm includes a main body, with a moving wheel at the bottom of the main body and a positioning component on the bottom side of the main body; a drive motor is provided at the upper end of the main body, a lead screw is provided inside the main body, a lifting seat is fitted on the lead screw, the fixed tube is set on the lifting seat, and the extended end of the drive motor is connected to the upper end of the lead screw via a transmission gear set.

[0008] In the aforementioned auxiliary device for installing large workpieces adapted to gantry milling machines, the positioning component includes an inclined rib plate on the bottom side of the main body, and a side support is provided at the end of the inclined rib plate, with a positioning pin threadedly connected to the side support.

[0009] In the aforementioned auxiliary device for installing large workpieces for gantry milling machines, the fixed tube has multiple adjustment holes, and the main frame has connecting bolts that pass through the adjustment holes.

[0010] In the aforementioned auxiliary device for installing large workpieces adapted to gantry milling machines, the horizontal adjustment component includes an X-axis moving component connected to the main frame, a Y-axis moving component is provided on the moving end of the X-axis moving component, a fixed tube is provided at the bottom of the moving end of the Y-axis moving component, and the auxiliary clamping component is disposed inside the fixed tube.

[0011] In the aforementioned auxiliary device for installing large workpieces for gantry milling machines, the auxiliary clamping component includes a round rod disposed within a fixed pipe component. The end of the round rod has a square frame, and a support plate is disposed within the square frame. An adjusting cylinder is disposed on the support plate, and a push rod is disposed at the output end of the adjusting cylinder. A linkage frame is disposed at the end of the square frame, and rotatable clamping plates are disposed at both ends of the linkage frame. The clamping plates are in contact with the side of the workpiece, and the inner end of the clamping plates cooperates with the push rod through a toothed structure. The push rod controls the opening and closing angle between the clamping plates on both sides by lateral movement.

[0012] In the aforementioned auxiliary device for installing large workpieces for gantry milling machines, the inner end of the clamping plate has teeth, and the push rod is provided with multiple rings evenly arranged along the axial direction, with grooves between adjacent rings that fit with the teeth.

[0013] In the aforementioned auxiliary device for installing large workpieces adapted to gantry milling machines, the hydraulic buffer includes a base set on the machine tool worktable, a closed sleeve inside the base, a fixing block at the port of the closed sleeve, and the fixing block connected to the base; a hydraulic rod passes through the fixing block and the closed sleeve, the end of the hydraulic rod has a limiting block, the limiting block is set inside the closed sleeve, a spring is sleeved on the hydraulic rod, the upper end of the spring abuts against the upper end of the hydraulic rod, and the lower end of the spring abuts against the upper surface of the fixing block.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. This invention, through the dual-degree-of-freedom transmission structure of the horizontal adjustment component, can drive the auxiliary clamping component to independently feed and adjust in two orthogonal directions in the horizontal plane when a large workpiece is hoisted into the tooling. This breaks through the dimensional limitations of the traditional single-direction sliding mechanism, significantly widens the adjustable range of the horizontal position, and can accurately drive the workpiece to complete multi-directional position fine adjustment. There is no need to manually push heavy workpieces, which greatly reduces the intensity of operation. At the same time, the alignment accuracy is easier to stabilize and control, adapting to the alignment requirements of workpieces of different specifications and improving the flexibility of adaptation.

[0016] 2. This invention employs a lifting arm-driven overall auxiliary mechanism lifting and lowering scheme to avoid obstacles. After the workpiece is positioned and clamped, the lifting arm can drive the fixed pipe, main frame, horizontal adjustment components, and auxiliary clamping components to be lifted as a whole, moving them away from the side of the workpiece and clearing the processing space, without the need to dismantle the entire auxiliary positioning component. This significantly simplifies the workpiece installation process, shortens auxiliary operation time, and improves the overall installation and processing efficiency of large workpieces.

[0017] 3. The auxiliary clamping component adopts a cylinder-driven, tooth-linked opening and closing clamping design. By adjusting the lateral movement of the cylinder-driven push rod, and relying on the meshing transmission between the upper ring of the push rod and the teeth of the clamping plates, the opening and closing angles of the clamping plates on both sides are controlled synchronously, so that the clamping plates stably fit against the side of the workpiece. This structure provides uniform clamping force transmission and high locking reliability. It is not easy for the workpiece to slip or loosen during hoisting and positioning, which can effectively ensure the stability of the workpiece position and improve the positioning reliability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention;

[0019] Figure 2 This is a schematic diagram of a lifting arm;

[0020] Figure 3This is a schematic diagram of the moving wheels;

[0021] Figure 4 This is a schematic diagram of the horizontal adjustment component;

[0022] Figure 5 A schematic diagram of the auxiliary clamping component;

[0023] Figure 6 This is a schematic diagram of a hydraulic buffer component.

[0024] The labels in the attached diagram are as follows: 1-Lifting arm, 2-Fixed tube, 3-Main frame, 4-Horizontal adjustment component, 5-Auxiliary clamping component, 6-Hydraulic buffer component, 7-Main body, 8-Moving wheel, 9-Positioning component, 10-Drive motor, 11-Screw, 12-Lifting seat, 13-Slanted rib plate, 14-Side support, 15-Positioning pin, 16-Adjusting hole, 17-Connecting bolt, 18-X-axis moving component, 19-Y-axis moving component, 20-Fixed tube component, 21-Round rod, 22-Square frame, 23-Bracket plate, 24-Adjusting cylinder, 25-Push rod, 26-Linkage frame, 27-Clamping plate, 28-Gear, 29-Ring body, 30-Slot, 31-Base, 32-Enclosed sleeve, 33-Fixed block, 34-Hydraulic rod, 35-Limiting block, 36-Spring. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0026] Example: A large workpiece mounting auxiliary device adapted to a gantry milling machine includes lifting arms 1 symmetrically arranged on both sides of the gantry milling machine, as shown in the attached figure. Figure 1 and 2 As shown, the lifting arm 1 is positioned corresponding to the positioning fixture within the machine tool worktable. A fixed pipe 2 is fixedly installed at the lifting output end of the lifting arm 1. A main frame 3 is mounted on the fixed pipe 2. A horizontal adjustment component 4 is installed at the lower part of the main frame 3. An auxiliary clamping component 5 is mounted on the moving end of the horizontal adjustment component 4. The horizontal adjustment component 4 is used to drive the auxiliary clamping component 5 to reciprocate and adjust along the horizontal X-axis and Y-axis directions, so that the end of the auxiliary clamping component 5 reliably fits tightly against the side of the workpiece. Multiple hydraulic buffers 6 are distributed around the outer periphery of the positioning fixture on the machine tool worktable. The hydraulic buffers 6 are used to provide buffering and force relief during the process of the workpiece falling into position to the positioning fixture.

[0027] The lifting arm 1 includes a main body 7, and the bottom of the main body 7 is equipped with casters 8, as shown in the attached figure. Figure 3As shown, the bottom side of the main body 7 has a positioning component 9; a drive motor 10 is installed on the upper end of the main body 7, and a lead screw 11 is installed inside the main body 7. The upper and lower ends of the lead screw are installed inside the main body via bearings. A lifting seat 12 is fitted on the lead screw 11, and a fixing tube 2 is set on the lifting seat 12. The two sides of the lifting seat are in contact with the inner wall of the main body. The extended end of the drive motor 10 is connected to the upper end of the lead screw 11 via a transmission gear set. When the lifting arm is working, the drive motor outputs power, which drives the lead screw to rotate through the gear set. The lifting seat, which is fitted with the lead screw, moves up and down. The workpiece is hoisted from above the machine tool, and the hoisting mechanism slowly lowers the workpiece. During this process, the lifting seat slowly descends, and the moving speed is adapted to the descent speed of the hoisted workpiece. The positioning component 9 includes an inclined rib plate 13 on the bottom side of the main body 7. The end of the inclined rib plate 13 is provided with a side support 14, and a positioning pin 15 is threadedly connected to the side support 14. Pre-drilled holes on the ground allow the lifting arm to be flexibly moved to the target position on the side of the gantry milling machine via its bottom casters. Once the device is adjusted to the accurate position corresponding to the positioning fixture on the machine tool's worktable, the positioning pin on the side support is rotated, and the positioning pin is engaged in the hole via threaded feed, fixing the lifting arm in its current position. This prevents slippage and displacement of the device during workpiece clamping and alignment adjustment, ensuring the stability of the positioning reference of the entire auxiliary device. The fixed pipe 2 has multiple adjustment holes 16, and the main frame 3 has connecting bolts 17 that pass through the adjustment holes 16. The large valve bodies vary in size. To accommodate valve bodies of different sizes, the adjustment holes are spaced apart along the axial direction of the fixed pipe, forming multiple adjustable mounting positions. By changing the depth of the main frame inserted into the fixed pipe, the connecting bolts are inserted into the corresponding adjustment holes and locked, allowing adjustment of the extension length of the main frame towards the center of the worktable. This enables coarse adjustment of the initial working position of the auxiliary clamping device, adapting to large valve bodies of different diameters.

[0028] The horizontal adjustment assembly 4 includes an X-axis moving part 18 connected to the main frame 3, as shown in the attached figure. Figure 4 As shown, a Y-axis moving part 19 is provided on the moving end of the X-axis moving part 18. A fixed pipe part 20 is installed at the bottom of the moving end of the Y-axis moving part 19, and an auxiliary clamping part 5 is disposed inside the fixed pipe part 20. The X-axis moving part and the Y-axis moving part are mainly screw drive structures. The screw is driven to rotate by a motor, and a moving seat is fitted on the screw. The fixed pipe part is installed on the moving seat of the Y-axis moving part 19. Relying on the orthogonal arrangement of the X-axis moving part and the Y-axis moving part, the fixed pipe part and the auxiliary clamping part can be driven to reciprocate independently along the X and Y horizontal directions, respectively, breaking through the limitations of traditional single-direction adjustment. During the lifting and lowering of the workpiece, the auxiliary clamping part contacts the side of the workpiece and applies a horizontal pushing force to the workpiece, driving the heavy workpiece to complete the horizontal and vertical position fine adjustment.

[0029] The auxiliary clamping member 5 includes a round rod 21 disposed within the fixed tube member 20, as shown in the attached figure. Figure 5 As shown, the round rod 21 is connected to the fixed pipe fitting by bolts. The end of the round rod 21 has a square frame 22, inside which is a support plate 23. An adjusting cylinder 24 is mounted on the support plate 23, and a push rod 25 is installed at the output end of the adjusting cylinder 24. The end of the square frame 22 has a linkage frame 26, with rotatable clamping plates 27 at both ends. The clamping plates 27 are in contact with the side of the workpiece, and the inner end of the clamping plates 27 engages with the push rod 25 via a toothed structure. The push rod 25 controls the opening angle between the two clamping plates 27 by lateral movement. During the workpiece hoisting and lowering process, the clamping plates are in contact with the side of the large workpiece, and in conjunction with the feed thrust of the horizontal adjustment component, they form a lateral limit on the workpiece, constraining its horizontal movement and preventing swaying or slippage during the descent, thus assisting the workpiece in approaching the reference position of the positioning fixture. The adjusting cylinder drives the push rod to move laterally. The ring groove on the push rod engages with the inner teeth of the clamping plate, driving the clamping plates on both sides to rotate synchronously around the linkage frame, changing the opening angle between the clamping plates. The clamping opening range can be adjusted according to the workpiece's shape and size to adapt to the side contact of valve bodies with different diameters. The inner end of the clamping plate 27 has teeth 28, and the push rod 25 has multiple rings 29 evenly arranged along the axial direction. Adjacent rings 29 have grooves 30 that engage with the teeth 28. The linkage between the push rod and the clamping plate adopts a toothed groove structure. Relying on the mechanical linkage structure of the push rod ring groove engaging with the teeth of the clamping plate, the clamping plates on both sides open and close synchronously, with uniform force distribution, preventing one-sided tightening or one-sided disengagement, and ensuring high consistency in clamping posture.

[0030] The hydraulic buffer 6 includes a base 31 mounted on the machine tool worktable, as shown in the attached figure. Figure 6As shown, a sealing sleeve 32 is provided inside the base 31, and a fixing block 33 is provided at the port of the sealing sleeve 32. The fixing block 33 is connected to the base 31. A hydraulic rod 34 is inserted through the fixing block 33 and the sealing sleeve 32. A sealing mechanism is provided between the hydraulic rod and the fixing block to maintain a good seal of the sealing sleeve. The end of the hydraulic rod 34 has a limiting block 35, which is set inside the sealing sleeve 32. A spring 36 is sleeved on the hydraulic rod 34. The upper end of the spring 36 abuts against the upper end of the hydraulic rod 34, and the lower end of the spring 36 abuts against the upper surface of the fixing block 33. A positioning fixture is installed on the machine tool worktable. The hydraulic buffer is located on the side of the positioning fixture and contacts the bottom surface of the outer edge of the valve body. The top of the hydraulic rod is higher than the mounting surface of the positioning fixture. The hydraulic buffer adopts a composite structure combining hydraulic damping and spring elastic return. When the workpiece falls and contacts the upper end of the hydraulic rod, the hydraulic rod is pressed and retracts into the closed sleeve. The hydraulic medium inside the closed sleeve absorbs the impact energy brought by the weight of the workpiece, and the spring is simultaneously compressed and deformed. This can effectively dissipate the impact load when the heavy workpiece is hoisted and placed, which makes the valve body fall more stably on the positioning fixture. The bottom of the valve body rests on the mounting surface of the positioning fixture. A downward pressing clamp is set on the upper side of the outer edge of the valve body, which, together with the bottom hydraulic buffer, achieves stable positioning.

[0031] Working Principle: Before operation, the two symmetrically arranged lifting arms 1 are moved to preset positions on both sides of the gantry milling machine using the moving wheels 8 at the bottom of the lifting arm 1. This ensures that the entire device is precisely aligned with the workpiece positioning fixture inside the worktable. After the position is adjusted, the positioning pins 15 of the positioning component 9 on the bottom side of the lifting arm 1 are rotated. Through threaded feed, the positioning pins 15 are engaged in preset holes on the ground, locking the overall position of the lifting arm 1. During operation, the large workpiece is slowly lowered from above the gantry milling machine using external truss hoisting equipment. Throughout the continuous hoisting and lowering of the workpiece, the device is simultaneously activated and coordinated. The drive motor 10 of the lifting arm 1 starts, driving the lead screw 11 to rotate through the transmission gear set. The lifting seat 12 on the drive lead screw 11 slowly descends in sync with the workpiece lowering speed, causing the fixed tube 2, main frame 3, and lower structure to move together, ensuring that the auxiliary clamping component 5 always maintains a matching height with the side of the workpiece. At the same time, the horizontal adjustment component 4 is activated simultaneously, relying on the orthogonally arranged X-axis moving component 18 and Y-axis... The moving part 19 drives the auxiliary clamping part 5 to achieve independent micro-feeding of X and Y axes in the horizontal plane; during the dynamic fine adjustment process, the auxiliary clamping part 5 simultaneously completes adaptive clamping limit, and the adjusting cylinder 24 drives the push rod 25 to feed laterally. Relying on the meshing transmission between the groove 30 of the ring body 29 of the push rod 25 and the inner end tooth 28 of the clamping plate 27, the clamping plates 27 on both sides rotate symmetrically, and the opening and closing angle is precisely adjusted so that the clamping plates 27 always fit tightly against the outer walls of both sides of the workpiece, thus restraining the horizontal movement and sway of the workpiece. After the workpiece completes dynamic alignment and fine-tuning, it continues to fall until its bottom surface contacts multiple hydraulic buffers 6 arranged around the positioning fixture of the worktable. The hydraulic buffers 6 adopt a composite buffer structure of hydraulic damping and elastic reset of spring 36. The impact load generated by the workpiece's own weight presses down on the hydraulic rod 34, causing the hydraulic rod 34 to drive the end limit block 35 to retract into the closed sleeve 32, squeezing the hydraulic medium inside the closed sleeve 32 to absorb the impact energy. At the same time, the sleeved spring 36 is compressed and deformed synchronously, further dissipating the impact force of falling.

[0032] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. Furthermore, in these embodiments, "up," "down," "left," "right," "front," and "back" represent relative positions only, not absolute positions. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A large workpiece installation auxiliary device adapted to a gantry milling machine, comprising lifting arms (1) symmetrically arranged on both sides of the gantry milling machine, wherein the arrangement of the lifting arms (1) corresponds to the positioning fixtures in the machine tool table, characterized in that: The lifting arm (1) has a fixed pipe (2) fixedly installed at its lifting output end. A main frame (3) is mounted on the fixed pipe (2). A horizontal adjustment component (4) is provided at the lower part of the main frame (3). An auxiliary clamping component (5) is assembled at the moving end of the horizontal adjustment component (4). The horizontal adjustment component (4) is used to drive the auxiliary clamping component (5) to reciprocate along the horizontal X-axis and Y-axis directions to adjust the position so that the end of the auxiliary clamping component (5) is reliably close to the side of the workpiece. Multiple hydraulic buffers (6) are distributed on the machine tool worktable and around the outer periphery of the positioning fixture. The hydraulic buffers (6) are used to provide buffering and unloading force during the process of the workpiece falling into position to the positioning fixture.

2. The auxiliary device for installing large workpieces adapted to gantry milling machines according to claim 1, characterized in that: The lifting arm (1) includes a main body (7), with a moving wheel (8) at the bottom of the main body (7) and a positioning component (9) on the bottom side of the main body (7); a drive motor (10) is provided at the upper end of the main body (7), a lead screw (11) is provided inside the main body (7), a lifting seat (12) is fitted on the lead screw (11), the fixed tube (2) is set on the lifting seat (12), and the extended end of the drive motor (10) is connected to the upper end of the lead screw (11) via a transmission gear set.

3. The auxiliary device for installing large workpieces adapted to gantry milling machines according to claim 2, characterized in that: The positioning component (9) includes a sloping rib plate (13) on the bottom side of the main body (7), and a side support (14) is provided at the end of the sloping rib plate (13), and a positioning pin (15) is threadedly connected to the side support (14).

4. The auxiliary device for installing large workpieces adapted to gantry milling machines according to claim 1, characterized in that: The fixed tube (2) has multiple adjustment holes (16), and the main frame (3) has connecting bolts (17) that pass through the adjustment holes (16).

5. The auxiliary device for installing large workpieces adapted to gantry milling machines according to claim 1, characterized in that: The horizontal adjustment component (4) includes an X-axis moving part (18) connected to the main frame (3), a Y-axis moving part (19) is provided on the moving end of the X-axis moving part (18), a fixed tube part (20) is provided at the bottom of the moving end of the Y-axis moving part (19), and the auxiliary clamping part (5) is provided inside the fixed tube part (20).

6. The auxiliary device for installing large workpieces adapted to gantry milling machines according to claim 5, characterized in that: The auxiliary clamping component (5) includes a round rod (21) set inside the fixed pipe component (20). The end of the round rod (21) has a square frame (22). The square frame (22) has a support plate (23) inside. The support plate (23) has an adjusting cylinder (24). The output end of the adjusting cylinder (24) has a push rod (25). The end of the square frame (22) has a linkage frame (26). The two ends of the linkage frame (26) have rotatable clamping pieces (27). The clamping pieces (27) are in contact with the side of the workpiece. The inner end of the clamping pieces (27) is engaged with the push rod (25) through a toothed structure. The push rod (25) controls the opening and closing angle between the clamping pieces (27) on both sides by lateral movement.

7. The auxiliary device for installing large workpieces adapted to gantry milling machines according to claim 6, characterized in that: The inner end of the clamping piece (27) has teeth (28), and the push rod (25) is provided with a plurality of rings (29) evenly along the axial direction. There are grooves (30) between adjacent rings (29) that fit with the teeth (28).

8. The auxiliary device for installing large workpieces adapted to gantry milling machines according to claim 1, characterized in that: The hydraulic buffer (6) includes a base (31) set on the machine tool workbench, a closed sleeve (32) is provided inside the base (31), a fixing block (33) is provided at the port of the closed sleeve (32), and the fixing block (33) is connected to the base (31); a hydraulic rod (34) is passed through the fixing block (33) and the closed sleeve (32), and a limiting block (35) is provided at the end of the hydraulic rod (34), the limiting block (35) is set inside the closed sleeve (32), and a spring (36) is sleeved on the hydraulic rod (34), the upper end of the spring (36) abuts against the upper end of the hydraulic rod (34), and the lower end of the spring (36) abuts against the upper surface of the fixing block (33).

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