A planetary reducer multi-directional automatic spring pin assembly punch riveting anti-extrusion device
Patent Information
- Application Number
- CN202610907175.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-23
- Publication Date
- 2026-08-21
AI Technical Summary
[0003]传统的行星减速器组装方式多为人工或半自动操作,存在诸多不足:首先,行星轴与行星架的销孔对中精度要求高,人工校正效率低、误差大;其次,弹簧销的压装需要精确控制压入深度和压力,手工操作难以保证一致性;再者,冲铆工序需要精准控制形变量,人工冲铆质量不稳定
[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: through the coordinated work of the loading robot, the feeding robot, the intermediate transfer device and the finished product unloading robot, the planetary reducer is fully automated from pre-assembled product to finished product unloading, without the need for manual intervention, which greatly improves production efficiency.
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Figure CN122606301A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of planetary reducer spring pin assembly and processing equipment, specifically a multi-directional automated spring pin assembly and riveting anti-loosening equipment for planetary reducers. Background Technology
[0002] Planetary reducers are precision transmission devices widely used in the automotive industry. Their core components include planet carriers, planet shafts, planet gears, and staggered gears. During assembly, spring pins are pressed into the side pin holes of the planet carrier and planet shafts to achieve axial positioning and prevent the planet shafts of the reducer from dislodging under high-speed vehicle operation. Radial dislodgement of the spring pins is prevented by riveting the edges of the pin holes, thus achieving foolproof protection.
[0003] Traditional planetary reducer assembly methods are mostly manual or semi-automatic, which has many shortcomings: First, the alignment accuracy of the pin holes between the planetary shaft and the planetary carrier is high, and manual correction is inefficient and prone to large errors; Second, the pressing of the spring pins requires precise control of the pressing depth and pressure, and manual operation makes it difficult to ensure consistency; Third, the riveting process requires precise control of deformation, and manual riveting results in unstable quality.
[0004] Furthermore, the lack of automated connections between processes necessitates manual intervention in material handling, resulting in overall low efficiency. The absence of online inspection methods also allows defective products to easily flow into the next process. Therefore, a multi-directional automated spring pin assembly and riveting anti-detachment device for planetary reducers is needed. Summary of the Invention
[0005] The purpose of this invention is to provide a multi-directional automated spring pin assembly and riveting anti-loosening device for planetary reducers, thereby solving the above-mentioned problems.
[0006] To achieve the above objectives, the present invention provides the following technical solution: a multi-directional automated spring pin assembly and riveting anti-detachment device for planetary reducers, comprising a frame, on which a feeding robot and a transfer device are fixedly connected. Along the feeding direction of the feeding robot, a loading robot, a barcode scanner, a planetary shaft angle correction mechanism, a spring pin loading and pressing mechanism, a first NG unloading mechanism, a spring pin riveting mechanism, a second NG unloading mechanism, and a finished product unloading robot are sequentially arranged on the frame. Alignment rotation components are fixedly connected to the planetary shaft angle correction mechanism, the spring pin loading and pressing mechanism, and the spring pin riveting mechanism on the frame. The planetary shaft angle correction mechanism includes a correction bracket, a pin hole correction cylinder, a pin hole correction guide rod, a linear module, a shaft correction servo motor, a floating bit, a shaft correction laser displacement sensor, and a correction clamping cylinder. The correction bracket is fixedly connected to the frame, and the pin hole correction cylinder... The linear module, the rotating shaft correction laser displacement sensor, and the correction clamping cylinder are all fixedly connected to the frame and to the correction bracket. The rotating shaft correction servo motor is fixedly connected to the moving platform of the linear module. The floating bit is fixedly connected to the rotating shaft of the rotating shaft correction servo motor. The pin hole correction guide rod is fixedly connected to the piston rod of the pin hole correction cylinder. The spring pin feeding and pressing mechanism includes a pressing bracket, an implantation robot, an implantation servo press, an implantation clamping cylinder, a pressing top rod, a first pressure sensor, a vibrating feeder, and a first spring pin sensing laser displacement sensor. The pressing bracket and the vibrating feeder are both fixedly connected to the frame. The pressing top rod is fixedly connected to the sensing end of the first pressure sensor. The first pressure sensor is fixedly connected to the moving end of the implantation servo press. The implantation robot, the implantation clamping cylinder, and the first spring pin sensing laser displacement sensor are all fixedly connected to the pressing bracket.
[0007] Furthermore, there are multiple intermediate transfer devices, and these multiple intermediate transfer devices are linearly arranged on the rack.
[0008] Furthermore, the first NG unloading mechanism includes a conveyor line and an NG unloading robot, both of which are fixedly connected to the frame. The second NG unloading mechanism has the same structure as the first NG unloading mechanism.
[0009] Furthermore, the spring pin riveting mechanism includes a riveting bracket, a riveting servo press, a riveting clamping cylinder, a riveting head, a second pressure sensor, and a second spring pin sensing laser displacement sensor. The riveting bracket is fixedly connected to the frame. The riveting servo press, the riveting clamping cylinder, and the second spring pin sensing laser displacement sensor are all fixedly connected to the riveting bracket. The second pressure sensor is fixedly connected to the moving end of the riveting servo press, and the riveting head is fixedly connected to the sensing end of the second pressure sensor.
[0010] Furthermore, the end of the pin hole correction guide rod is provided with a tapered surface, and the end of the floating bit is provided with a protrusion.
[0011] Furthermore, the alignment and rotation assembly includes a rotary servo motor, a positioning fixture, and an angle positioning laser displacement sensor. The rotary servo motor and the angle positioning laser displacement sensor are both fixedly connected to the frame. The positioning fixture is fixedly connected to the rotating shaft of the rotary servo motor. The positioning fixture is provided with a sensing groove. The angle positioning laser displacement sensor is used to determine the angle of the positioning fixture in conjunction with the sensing groove.
[0012] Furthermore, both the positioning fixture and the intermediate transfer device are equipped with positioning grooves and anti-fooling rods.
[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: through the coordinated work of the loading robot, the feeding robot, the intermediate transfer device and the finished product unloading robot, the planetary reducer is fully automated from pre-assembled product to finished product unloading, without the need for manual intervention, which greatly improves production efficiency.
[0014] The planetary shaft angle correction mechanism uses a floating bit to cooperate with the planetary shaft groove to achieve initial alignment, and then uses a pin hole correction guide rod inserted into the side hole of the planetary carrier and the planetary shaft to achieve precise centering. The double correction ensures the coaxiality of the pin hole, providing a precise positioning basis for the subsequent spring pin press-fit.
[0015] The spring pin feeding and pressing mechanism achieves automatic feeding, automatic pressing, and online quality inspection of spring pins by incorporating a robotic arm for automatic material handling, an incorporating a servo press for precise control of the pressing depth, a first pressure sensor for real-time monitoring of the pressing force, and a first spring pin-sensing laser displacement sensor for detecting whether any pins are missing. This ensures stable and reliable pressing quality.
[0016] The spring pin riveting mechanism precisely controls the riveting stroke and force through a riveting servo press, and the second pressure sensor monitors the riveting force in real time to ensure that the pin hole deformation is appropriate. This effectively prevents the spring pin from coming out and avoids product scrap due to excessive riveting.
[0017] The system is equipped with a first NG unloading mechanism and a second NG unloading mechanism to automatically remove defective products after the pressing and riveting processes, respectively. This effectively prevents defective products from flowing into the next process or ultimately flowing out, thus ensuring product quality. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the isometric structure of the present invention.
[0019] Figure 2 This is a schematic diagram of the feeding robot of the present invention.
[0020] Figure 3 This is a schematic diagram of the alignment and rotation assembly of the present invention.
[0021] Figure 4 This is a schematic diagram of the planetary axis angle correction mechanism of the present invention.
[0022] Figure 5 This is a schematic diagram of the spring pin feeding and pressing mechanism of the present invention.
[0023] Figure 6 This is a schematic diagram of the first NG unloading mechanism of the present invention.
[0024] Figure 7 This is a schematic diagram of the spring pin riveting mechanism of the present invention.
[0025] Figure 8 This is a schematic diagram of a planetary reducer.
[0026] In the diagram: 1. Feeding robot; 2. Alignment rotary assembly; 201. Rotary servo motor; 202. Positioning fixture; 2021. Sensing slot; 203. Angle positioning laser displacement sensor; 3. Loading robot; 4. Planetary axis angle correction mechanism; 401. Correction bracket; 402. Pin hole correction cylinder; 403. Pin hole correction guide rod; 404. Linear module; 405. Rotary axis correction servo motor; 406. Floating bit; 407. Rotary axis correction laser displacement sensor; 408. Correction clamping cylinder; 5. Spring pin loading and pressing mechanism; 501. Pressing bracket; 502. Implantation robot; 503. Implantation servo motor 504. Pressing machine; 505. Insertion and clamping cylinder; 506. Pressing top rod; 507. First pressure sensor; 508. Vibrating feeder; 509. First spring pin induction laser displacement sensor; 600. First NG unloading mechanism; 601. Conveying line; 602. NG unloading robot; 701. Spring pin punching and riveting mechanism; 702. Punching and riveting servo press; 703. Punching and riveting clamping cylinder; 704. Punching and riveting head; 705. Second pressure sensor; 706. Second spring pin induction laser displacement sensor; 8. Second NG unloading mechanism; 9. Finished product unloading robot; 10. Intermediate transfer device; 11. Barcode scanner. Detailed Implementation
[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] Example:
[0029] Please see Figure 1-7The diagram illustrates a multi-directional automated spring pin assembly and riveting anti-detachment device for planetary reducers, comprising a frame on which a feeding robot 1 and a transfer device 10 are fixedly connected. Multiple transfer devices 10 are linearly arranged on the frame to carry products between workstations. Along the feeding direction of the feeding robot 1, the frame is sequentially equipped with a loading robot 3, a barcode scanner 11, a planetary shaft angle correction mechanism 4, a spring pin loading and pressing mechanism 5, a first NG unloading mechanism 6, a spring pin riveting mechanism 7, a second NG unloading mechanism 8, and a finished product unloading robot 9.
[0030] Alignment rotating components 2 are fixedly connected to the planetary shaft angle correction mechanism 4, the spring pin feeding and pressing mechanism 5, and the spring pin punching and riveting mechanism 7 on the frame. For example... Figure 4 As shown, the alignment and rotation assembly 2 includes a rotary servo motor 201, a positioning fixture 202, and an angle positioning laser displacement sensor 203. Both the rotary servo motor 201 and the angle positioning laser displacement sensor 203 are fixedly connected to the frame, and the positioning fixture 202 is fixedly connected to the rotating shaft of the rotary servo motor 201. The positioning fixture 202 is provided with a sensing groove 2021, which corresponds to the angle positioning laser displacement sensor 203. The positioning fixture 202 is provided with a positioning groove and a foolproof rod for positioning the product and preventing reverse rotation. The intermediate transfer fixture 10 is also provided with a positioning groove and a foolproof rod to ensure consistent product placement posture at each workstation.
[0031] The planetary axis angle correction mechanism 4 includes a correction bracket 401, a pin hole correction cylinder 402, a pin hole correction guide rod 403, a linear module 404, a shaft correction servo motor 405, a floating bit 406, a shaft correction laser displacement sensor 407, and a correction clamping cylinder 408. The correction bracket 401 and the pin hole correction cylinder 402 are fixedly connected to the frame. The linear module 404, the shaft correction laser displacement sensor 407, and the correction clamping cylinder 408 are all fixedly connected to the correction bracket 401. The shaft correction servo motor 405 is fixedly connected to the moving platform of the linear module 404, and the floating bit 406 is fixedly connected to the shaft of the shaft correction servo motor 405. The end of the floating bit 406 has a protrusion for engaging in a groove at the end of the planetary axis. The pin hole correction guide rod 403 is fixedly connected to the piston rod of the pin hole correction cylinder 402, and the end of the pin hole correction guide rod 403 has a tapered surface for easy insertion into the pin hole.
[0032] The spring pin feeding and pressing mechanism 5 includes a pressing bracket 501, an implantation robot 502, an implantation servo press 503, an implantation clamping cylinder 504, a pressing push rod 505, a first pressure sensor 506, a vibrating feeder 507, and a first spring pin sensing laser displacement sensor 508. The pressing bracket 501 and the vibrating feeder 507 are both fixedly connected to the frame. The pressing push rod 505 is fixedly connected to the sensing end of the first pressure sensor 506, and the first pressure sensor 506 is fixedly connected to the moving end of the implantation servo press 503. The implantation robot 502, the implantation clamping cylinder 504, and the first spring pin sensing laser displacement sensor 508 are all fixedly connected to the pressing bracket 501.
[0033] The spring pin riveting mechanism 7 includes a riveting bracket 701, a riveting servo press 702, a riveting clamping cylinder 703, a riveting head 704, a second pressure sensor 705, and a second spring pin sensing laser displacement sensor 706. The riveting bracket 701 is fixedly connected to the machine frame. The riveting servo press 702, the riveting clamping cylinder 703, and the second spring pin sensing laser displacement sensor 706 are all fixedly connected to the riveting bracket 701. The second pressure sensor 705 is fixedly connected to the moving end of the riveting servo press 702, and the riveting head 704 is fixedly connected to the sensing end of the second pressure sensor 705.
[0034] The first NG unloading mechanism 6 includes a conveyor line 601 and an NG unloading robot 602, both of which are fixedly connected to the frame. The second NG unloading mechanism 8 has the same structure as the first NG unloading mechanism 6, and also includes a conveyor line 601 and an NG unloading robot 602.
[0035] The workflow of this invention is as follows:
[0036] (a) Material loading and barcode scanning
[0037] First, the pre-assembled product (including planetary carrier, planetary shaft, and planetary gears) is placed on the intermediate transfer device 10 at the loading station. The loading robot 3 transports the product to the intermediate transfer device 10 at the barcode scanning station, and the barcode scanner 11 scans the QR code on the planetary carrier, records the product information, and binds it to subsequent testing data.
[0038] (ii) Correction of pin angle
[0039] After the QR code is scanned, the feeding robot 1 transports the correctly scanned product to the positioning fixture 202 of the alignment rotation assembly 2 at the shaft pin angle correction station. The product is driven by the rotary servo motor 201 to rotate the positioning fixture 202 to the first hole position to be corrected. The positioning fixture 202 is equipped with a sensing groove 2021, which, together with the angle positioning laser displacement sensor 203, determines whether the initial angle of the positioning fixture 202 is correct.
[0040] The calibration process consists of two stages:
[0041] The first stage is the axis angle correction: The axis correction laser displacement sensor 407 senses the groove on the planetary carrier. The piston rod of the correction clamping cylinder 408 extends and clamps the planetary carrier. The axis correction servo motor 405 drives the floating bit 406 to rotate, and the linear module 404 drives the floating bit 406 to descend. As the floating bit 406 rotates and descends, the protrusion at its end engages with the groove on the planetary carrier, completing the alignment. After the axis correction servo motor 405 stops and resets, the initial alignment is complete.
[0042] The second stage involves pin hole alignment and correction: Further alignment and correction are performed on the planetary shaft side holes and planet carrier side holes (where the spring pin is pressed in). The piston rod of the pin hole correction cylinder 402 extends, allowing the pin hole correction guide rod 403 to insert into the side holes of the planet carrier and planetary shaft, completing the alignment before retracting. After completing the alignment at this angle, the piston rod of the correction clamping cylinder 408 retracts, and the rotary servo motor 201 drives the positioning fixture 202 to rotate 90° for the next pin hole alignment. This process is repeated until all pin holes are positioned to ensure successful pressing of the spring pin in the next step.
[0043] (iii) Spring pin press-fit
[0044] After the planetary shaft hole and the planetary carrier hole are aligned, the feeding robot 1 transfers the product to the positioning fixture 202 of the alignment rotary assembly 2 at the spring pin press-fit station.
[0045] The spring pins are fed by a vibratory feeder 507. An implanted robotic arm 502 grasps a spring pin at the discharge end of the vibratory feeder 507 and moves it to the assembly station. Simultaneously, the product is rotated by a rotary servo motor 201 to the first assembly hole (which aligns with the spring pin at the assembly station). The piston rod of the implanted clamping cylinder 504 extends and clamps the product, preventing positional shift during assembly.
[0046] The implantation robot 502 initially inserts the end of the spring pin into the planetary carrier hole and holds it stationary. Then, the piston rod of the implantation servo press 503 extends, causing the pressing push rod 505 to press the spring pin into the pin holes of the planetary carrier and planetary shaft. At this point, the grippers of the implantation robot 502 open and return to their original position. The implantation servo press 503 continues its operation, pressing the spring pin to its final position before returning to its original position. Thus, one spring pin is assembled.
[0047] There are 4 installation positions on the product. The remaining 3 spring pins are assembled in sequence using the above process to complete the assembly of 4 sets of spring pins.
[0048] During the assembly process, if the pressure detected by the first pressure sensor 506 exceeds the acceptable range, or if the first spring pin sensing laser displacement sensor 508 detects a missing spring pin, the product is deemed to be defective.
[0049] (iv) First NG unloading
[0050] After the spring pin is installed, if the product is determined to be defective, the defective product will be picked up by the defective unloading robot 602 of the first defective unloading mechanism 6 and transferred to the conveyor line 601 for output. Qualified products will then enter the next process.
[0051] (v) Stamping and riveting
[0052] After the qualified spring pins are assembled, the feeding robot 1 moves the product to the positioning fixture 202 of the alignment rotary assembly 2 at the riveting station for riveting. The purpose of riveting is to use the deformation of the planetary carrier pin hole caused by riveting to prevent the spring pin from coming out radially.
[0053] The product is driven by a rotary servo motor 201 to rotate the positioning fixture 202 to the first riveting position. The piston rod of the riveting clamping cylinder 703 extends to clamp the product and prevent it from tilting during riveting. The riveting servo press 702 drives the riveting head 704 to rivet the pin hole of the planetary carrier of the product, using the deformation of the pin hole edge to stop the spring pin and prevent it from coming out. The above actions are repeated for the remaining three riveting positions until all riveting is completed.
[0054] If the pressure monitored by the second pressure sensor 705 exceeds the acceptable range during the riveting process, or if the second spring pin sensing laser displacement sensor 706 detects a missing spring pin, the product is deemed NG (Not Good).
[0055] (vi) Second NG unloading and finished product unloading
[0056] After the riveting process is completed, if the product is determined to be defective, the defective product will be picked up by the NG unloading robot of the second NG unloading mechanism 8 and transferred to the conveyor line for output. Finally, the qualified finished products after riveting are picked up by the finished product unloading robot 9 and unloaded.
[0057] In summary, this invention achieves fully automated operation of planetary reducers from shaft pin angle correction, spring pin pressing, riveting to finished product unloading. The processes are closely linked and online detection is comprehensive, improving the efficiency and quality of planetary reducer assembly.
[0058] In this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," "fixed," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0059] The above embodiments are used to further illustrate the present invention, but do not limit the present invention to these specific embodiments. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be understood as falling within the protection scope of the present invention.
Claims
1. A multi-directional automated spring pin assembly and riveting anti-loosening device for planetary reducers, characterized in that: The machine includes a frame on which a feeding robot (1) and a transfer device (10) are fixedly connected. Along the feeding direction of the feeding robot (1), the frame is sequentially equipped with a loading robot (3), a barcode scanner (11), a planetary shaft angle correction mechanism (4), a spring pin loading and pressing mechanism (5), a first NG unloading mechanism (6), a spring pin riveting mechanism (7), a second NG unloading mechanism (8), and a finished product unloading robot (9). Alignment rotation components (2) are fixedly connected to the planetary shaft angle correction mechanism (4), the spring pin loading and pressing mechanism (5), and the spring pin riveting mechanism (7) on the frame. The planetary shaft angle correction mechanism (4) includes a correction bracket (401), a pin hole correction cylinder (402), a pin hole correction guide rod (403), and a linear... The system includes a module (404), a shaft correction servo motor (405), a floating bit (406), a shaft correction laser displacement sensor (407), and a correction clamping cylinder (408). The correction bracket (401) is fixedly connected to the frame. The pin hole correction cylinder (402) is fixedly connected to the frame. The linear module (404), the shaft correction laser displacement sensor (407), and the correction clamping cylinder (408) are all fixedly connected to the correction bracket (401). The shaft correction servo motor (405) is fixedly connected to the moving platform of the linear module (404). The floating bit (406) is fixedly connected to the shaft of the shaft correction servo motor (405). The pin hole correction guide rod (403) is fixedly connected to the piston rod of the pin hole correction cylinder (402).
2. The multi-directional automated spring pin assembly and riveting anti-loosening device for planetary reducers according to claim 1, characterized in that: There are multiple intermediate transfer devices (10), and the multiple intermediate transfer devices (10) are linearly arranged on the rack.
3. The multi-directional automated spring pin assembly and riveting anti-loosening device for planetary reducers according to claim 1, characterized in that: The first NG unloading mechanism (6) includes a conveyor line (601) and an NG unloading robot (602). Both the conveyor line (601) and the NG unloading robot (602) are fixedly connected to the frame. The second NG unloading mechanism (8) has the same structure as the first NG unloading mechanism (6).
4. The multi-directional automated spring pin assembly and riveting anti-loosening device for planetary reducers according to claim 1, characterized in that: The spring pin riveting mechanism (7) includes a riveting bracket (701), a riveting servo press (702), a riveting clamping cylinder (703), a riveting head (704), a second pressure sensor (705), and a second spring pin sensing laser displacement sensor (706). The riveting bracket (701) is fixedly connected to the frame. The riveting servo press (702), the riveting clamping cylinder (703), and the second spring pin sensing laser displacement sensor (706) are all fixedly connected to the riveting bracket (701). The second pressure sensor (705) is fixedly connected to the moving end of the riveting servo press (702). The riveting head (704) is fixedly connected to the sensing end of the second pressure sensor (705).
5. The multi-directional automated spring pin assembly and riveting anti-loosening device for planetary reducers according to claim 1, characterized in that: The end of the pin hole correction guide rod (403) is provided with a tapered surface, and the end of the floating bit (406) is provided with a protrusion.
6. The multi-directional automated spring pin assembly and riveting anti-loosening device for planetary reducers according to claim 1, characterized in that: The alignment and rotation assembly (2) includes a rotary servo motor (201), a positioning fixture (202), and an angle positioning laser displacement sensor (203). The rotary servo motor (201) and the angle positioning laser displacement sensor (203) are both fixedly connected to the frame. The positioning fixture (202) is fixedly connected to the rotating shaft of the rotary servo motor (201). The positioning fixture (202) is provided with a sensing groove (2021). The angle positioning laser displacement sensor (203) is used to cooperate with the sensing groove (2021) to determine the angle of the positioning fixture (202).
7. The multi-directional automated spring pin assembly and riveting anti-loosening device for planetary reducers according to claim 6, characterized in that: The positioning fixture (202) and the intermediate transfer fixture (10) are both equipped with positioning grooves and anti-fooling rods.
8. The multi-directional automated spring pin assembly and riveting anti-loosening device for planetary reducers according to claim 1, characterized in that: The spring pin feeding and pressing mechanism (5) includes a pressing bracket (501), an implantation robot (502), an implantation servo press (503), an implantation clamping cylinder (504), a pressing top rod (505), a first pressure sensor (506), a vibrating feeder (507), and a first spring pin sensing laser displacement sensor (508). The pressing bracket (501) and the vibrating feeder (507) are both fixedly connected to the frame. The pressing top rod (505) is fixedly connected to the sensing end of the first pressure sensor (506). The first pressure sensor (506) is fixedly connected to the moving end of the implantation servo press (503). The implantation robot (502), the implantation clamping cylinder (504), and the first spring pin sensing laser displacement sensor (508) are all fixedly connected to the pressing bracket (501).