A 3D printing device for metal printing

Abstract

This invention discloses a 3D printing device for metal printing, belonging to the technical field of 3D printing devices. Specifically, it includes a printing stage structure and a laser cladding module disposed within a LENS system. The laser cladding module is positioned above the printing stage structure. The main body of the printing stage structure is a rotatable lifting stage. Removable snap-fit ​​mounting seats are installed at both the top and bottom of the lifting stage. A printing substrate is fixedly connected to the surface of the snap-fit ​​mounting seats. The laser cladding module performs metal workpiece forming and printing on the printing substrate. After printing is completed, the lifting stage automatically flips over to continue printing on a second printing substrate. This invention effectively recovers scattered metal powder during the printing process through a vibration mechanism and flipping action, combined with the protective design of a sealed working chamber. This powder recovery method reduces powder waste and lowers the potential hazards of open powder handling.

Description

Technical Field

[0001] This invention relates to the field of 3D printing apparatus technology, and more particularly to a 3D printing apparatus for metal printing. Background Technology

[0002] 3D printing, also known as additive manufacturing, is a technology that manufactures solid objects by layering materials based on a three-dimensional digital model. It breaks through the limitations of traditional subtractive manufacturing, enabling the efficient and precise production of parts with complex structures, and has been widely applied in various fields such as industry, medicine, construction, and education.

[0003] A search revealed a Chinese patent application with patent number 202011170316.7, which discloses a forming mechanism for a metal 3D printing device. During operation, the processing plate is placed on a rotating platform for quick and easy installation and fixation. Rubber rings prevent slippage, ensuring excellent stability, saving processing time, and improving efficiency. During processing, the rotating platform and the finished product can rotate, allowing for flexible and convenient adjustment. After processing, a first servo motor drives a lead screw to rotate, which in turn moves the lifting platform down along a slide bar via a ball bearing sleeve. When the lifting platform is flush with the empty shelf, a second electric telescopic rod resets, and a reset spring drives a T-shaped rod to reset. Then, the first electric telescopic rod moves the positioning box down along a limit rod to reset, allowing the processing plate to quickly disengage from its position.

[0004] The metal 3D printing device forming mechanism in the above patent has the following shortcomings: In actual use, due to the low utilization rate of metal powder, a small amount of metal powder will remain inside the printing chamber. Most of the residual powder will adhere to the metal workpiece. Therefore, storing the processed workpiece in the above manner will cause metal powder to be suspended inside the storage space, which poses a certain safety hazard. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a 3D printing device for metal printing.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A 3D printing device for metal printing includes a printing stage structure and a laser cladding module disposed inside a LENS system. The laser cladding module is disposed above the printing stage structure. The main body of the printing stage structure is configured as a rotatable lifting stage. The top and bottom ends of the lifting stage are equipped with detachable snap-fit ​​mounting seats. A printing substrate is fixedly connected to the surface of the snap-fit ​​mounting seats. The laser cladding module performs metal workpiece forming and printing on the printing substrate. After printing is completed, the lifting stage automatically flips over and continues printing on a second printing substrate. The front end of the lifting platform is provided with a rotating bearing seat, and guide rods two are slidably installed on both sides of the rotating bearing seat; the rear end of the lifting platform is provided with a limit seat, and two symmetrically arranged limit slides are installed on the back of the limit seat, and guide rods one are slidably installed inside the limit slides. The bottom ends of the rotating bearing seat and the limiting card seat are both fixedly installed with lifting plates. The lifting plates are connected to electric hydraulic cylinders. The two electric hydraulic cylinders are linked together, and sliding protective baffles are provided on both sides of the lifting platform.

[0007] As a preferred embodiment of the present invention: the bottom ends of the second guide rod and the first guide rod are connected to a bearing base plate, and protective side plates are fixedly installed on both sides of the bearing base plate. Two mounting brackets are symmetrically arranged at the top between the two protective side plates, and telescopic cylinders are fixedly installed inside the mounting brackets.

[0008] Based on the aforementioned scheme: both sides of the mounting bracket are fixedly connected with baffle support arms for supporting the protective baffle, the baffle support arms are fixedly connected to the protective side plate, and the telescopic end of the telescopic cylinder is fixed to the protective baffle.

[0009] As a preferred embodiment of the present invention: a limiting connecting seat is provided at the tail end of the lifting platform, and a plurality of limiting rods are fixedly connected to the front end of the limiting connecting seat. The limiting rods pass through the lifting platform and extend outward.

[0010] Based on the aforementioned scheme: the tail end of the limiting connecting seat is fixedly connected to a rotating connecting seat, the rotating connecting seat is rotatably connected to the limiting card seat, and the back of the rotating connecting seat is fixedly connected to a rotating connecting shaft.

[0011] Based on the aforementioned scheme: the rotating connecting shaft is connected to a servo motor via a gear pair, the bottom end of the servo motor is equipped with a motor mounting base, the motor mounting base is fixed to the limit card seat, and a protective mounting shell is also installed on the back of the limit card seat.

[0012] As a preferred embodiment of the present invention: the front end of the lifting platform is provided with a fixed connecting seat, the fixed connecting seat is fixedly connected to a plurality of limiting rods, and a rotating mounting column is fixedly connected to the front side of the fixed connecting seat.

[0013] Based on the aforementioned scheme: the rotating mounting column is rotatably connected to the fixed connecting seat, the fixed connecting seat has a mating mounting groove on its front side, a limiting rotating arm is provided on the upper part of the mating mounting groove, and the limiting rotating arm is fixedly connected to the rotating mounting column.

[0014] Based on the aforementioned scheme: a cylinder mounting seat is fixedly installed at the lower part of the mounting groove, a lifting cylinder is fixedly installed inside the cylinder mounting seat, and a limit slide is fixedly installed at the top of the telescopic end of the lifting cylinder.

[0015] Based on the aforementioned scheme: the limiting slide is configured as an inverted U-shape, with its two sides slidably connected to the groove wall of the mating mounting groove, and a protective cover plate is also installed inside the mating mounting groove.

[0016] The beneficial effects of this invention are as follows: 1. This 3D printing device for metal printing effectively recovers scattered metal powder during the printing process through vibration mechanism and flipping action, combined with the protective design of a sealed working chamber; this powder recovery method reduces powder waste and lowers the potential dangers of open powder handling.

[0017] 2. This 3D printing device for metal printing adopts a flip-up dual-station lifting platform design. After one printing substrate completes the printing of a metal workpiece, the lifting platform automatically flips over, and the other printing substrate then enters the printing station to continue working. This "print-flip-reprint" cycle mode completely solves the problem that traditional single-station equipment needs to stop and wait for the workpiece to cool, disassemble, and re-clamp, realizing continuous operation of metal 3D printing, significantly shortening the production cycle of a unit workpiece, and improving equipment utilization.

[0018] 3. In this 3D printing device for metal printing, the printing stage structure, as part of the motion control platform, is only responsible for the Z-axis motion, while the XYZ three-axis motion of the laser cladding module is controlled by the CNC worktable or the robotic arm. This clearly defined motion control method ensures the motion accuracy of the laser cladding module, while reducing the motion complexity of the stage and minimizing the impact of motion errors on printing quality. Attached Figure Description

[0019] Figure 1 This is a three-dimensional structural diagram of the printing platform structure of the present invention; Figure 2 This is a partial structural diagram of the printing platform structure of the present invention; Figure 3 For the present invention Figure 2 Schematic diagram of partial cross-section structure Figure 1 ; Figure 4 For the present invention Figure 3 A magnified schematic diagram of the partial structure at point A in the middle; Figure 5 For the present invention Figure 2 Schematic diagram of partial cross-section structure Figure 2 ; Figure 6For the present invention Figure 5 A magnified schematic diagram of the structure at point A in the middle.

[0020] In the diagram: 1. Laser cladding module; 2. Support base plate; 3. Protective side plate; 4. Mounting bracket; 5. Telescopic cylinder; 6. Protective baffle; 7. Lifting platform; 8. Snap-fit ​​mounting seat; 9. Printing substrate; 10. Limiting connecting seat; 11. Rotating connecting seat; 12. Limiting clamp; 13. Limiting slide; 14. Protective mounting shell; 15. Guide column one; 16. Fixed connecting seat; 17. Rotating support seat; 18. Protective cover plate; 19. Guide column two; 20. Lifting enclosure; 21. Electric hydraulic cylinder; 22. Baffle support arm; 23. Limiting insertion rod; 24. Rotating mounting column; 25. Limiting rotating arm; 26. Limiting slide; 27. Cylinder mounting seat; 28. Lifting cylinder; 29. ​​Rotating connecting shaft; 30. Servo motor; 31. Motor mounting seat. Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0022] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0023] A 3D printing apparatus for metal printing, such as Figures 1 to 6 As shown, the system includes a printing stage structure and a laser cladding module 1 located inside the LENS system. The laser cladding module 1 is located above the printing stage structure. The LENS system is a laser melting and air-jet metal powder forming system. Its structure mainly consists of a laser, a powder feeding system, a cladding head (nozzle), a motion control platform, a protective gas system, a control system, and a sealed working chamber. All components work together to achieve precise melting and layer-by-layer deposition of metal powder.

[0024] The laser cladding module 1, also known as the cladding head, is directly connected to the laser and the powder feeding system. The printing stage structure described in this application is part of the motion control platform. The CNC worktable (XYZ three-axis) or robot arm (multi-degree-of-freedom) that controls the movement of the laser cladding module 1 is another part of the motion control platform. This part of the motion control platform only controls the movement of the laser cladding module 1 to print metal workpieces. The Z-axis movement range is small, or there is no Z-axis movement. The printing stage structure only performs Z-axis movement during the workpiece printing process.

[0025] The LENS system is a publicly available technology, and those skilled in the art can learn about the system from various sources. This application mainly optimizes the printing stage structure, so other components of the LENS system are not described in detail.

[0026] The main body of the printing stage structure is a flip-up lifting stage 7. The top and bottom of the lifting stage 7 are equipped with detachable snap-fit ​​mounting bases 8. The surface of the snap-fit ​​mounting base 8 is fixedly connected to the printing substrate 9. The laser cladding module 1 performs metal workpiece forming and printing on the printing substrate 9. After printing is completed, the lifting stage 7 automatically flips over and continues printing on the second printing substrate 9 to realize continuous processing of metal 3D printing. At the same time, the printed workpiece is cooled, and some metal powder is vibrated off by the vibration generated during the printing process.

[0027] The front end of the lifting platform 7 is provided with a fixed connecting seat 16. A rotating mounting column 24 is welded to the middle of the front end of the fixed connecting seat 16. A rotating bearing seat 17 is rotatably mounted on the rotating mounting column 24 through a bearing. A mating mounting groove is opened on the front side of the rotating bearing seat 17. The front end of the rotating mounting column 24 is located inside the mating mounting groove.

[0028] A limiting rotating arm 25 is fixedly installed at the front end of the rotating mounting column 24. The two ends of the limiting rotating arm 25 are set as smooth arc surfaces. The axis of the smooth arc surface coincides with the axis of the rotating mounting column 24, and the top of the groove wall on both sides of the mounting groove is adapted to the smooth arc surface. The top surface of the limiting rotating arm 25 is flush with the top surface of the fixed connecting seat 16.

[0029] A cylinder mounting base 27 is fixedly installed at the lower part of the mounting slot. A lifting cylinder 28 is fixedly installed inside the cylinder mounting base 27. A limit slide 26 is fixedly installed at the top of the telescopic end of the lifting cylinder 28. The lifting cylinder 28 is selected as a model with a fixed stroke. When it is fully extended, it can drive the limit slide 26 to abut against the lower surface of the limit rotating arm 25, thereby preventing the limit rotating arm 25 from rotating.

[0030] The limiting slide 26 is set as an inverted U-shape, with its two sides slidably connected to the groove wall of the mating installation groove, and a protective cover plate 18 is also installed inside the mating installation groove, which completely covers the mating installation groove; and guide rods 19 are slidably installed inside the grooves on both sides of the mating installation groove through linear bearings.

[0031] The tail end of the lifting platform 7 is provided with a limit connecting seat 10. Multiple limit plugs 23 are fixedly connected to the front end of the limit connecting seat 10. The limit plugs 23 pass through the lifting platform 7 and extend outward. Their extended ends are fixed to the fixed connecting seat 16 by nuts, so that the fixed connecting seat 16 and the limit connecting seat 10 cooperate to clamp the lifting platform 7.

[0032] The tail end of the limiting connecting seat 10 is fixedly connected to a rotating connecting seat 11, the outer wall of the rotating connecting seat 11 is rotatably connected to the limiting card seat 12, and the back of the rotating connecting seat 11 is fixedly connected to a rotating connecting shaft 29.

[0033] The rotating connecting seat 11 is integrally cast from two coaxial frustums and is coaxial with the rotating connecting shaft 29; the diameter of the frustum closer to the lifting platform 7 is larger than the diameter of the other frustum, and a bearing is installed on the outer wall of the smaller diameter frustum, with the outer ring of the bearing fixed to the limiting seat 12.

[0034] A motor mounting base 31 is fixedly installed on the lower part of the back of the limit card holder 12. A servo motor 30 is fixedly installed inside the motor mounting base 31. The servo motor 30 is connected to the rotating connecting shaft 29 through a gear pair.

[0035] The servo motor 30 controls the rotation of the rotating connecting seat 11, which in turn drives the lifting platform 7 to rotate via the limit connecting seat 10. The rotation angle range of the lifting platform 7 is [0°, 180°]. Figure 2 As shown, the rotation angle of the lifting platform 7 is 0 degrees at this time.

[0036] Two symmetrically arranged limit slides 13 are installed on the back of the limit card seat 12. A guide rod 15 is slidably installed inside the limit slide 13 through a linear bearing. A protective mounting shell 14 is fixedly installed between the two limit slides 13. The protective mounting shell 14 is fixedly connected to the limit card seat 12 and covers the servo motor 30 and other structures to prevent metal powder from affecting them.

[0037] The bottom ends of guide pole 219 and guide pole 15 are connected to a bearing base plate 2. The bottom ends of rotating bearing seat 17 and limit card seat 12 are both fixedly installed with lifting plate 20. The lifting plate 20 is connected to an electric hydraulic cylinder 21. The two electric hydraulic cylinders 21 are linked and lift synchronously with the same lifting distance, and the selected model can be controlled.

[0038] The lifting enclosure 20 includes an integrally formed horizontal plate and a vertical plate. The horizontal plate is directly connected to the telescopic end of the electric hydraulic cylinder 21, and the vertical plate is set on the side of the horizontal plate near the lifting platform 7 to protect the printed workpiece located below the lifting platform 7.

[0039] Both sides of the lifting platform 7 are equipped with sliding protective baffles 6. Each protective baffle 6 includes an integrally formed horizontal baffle and a vertical baffle. The vertical baffle rests against both sides of the lifting platform 7. Figure 2 As shown, when the lifting platform 7 is at its highest point, the top surface of the snap-fit ​​mounting base 8 and the upper surface of the horizontal baffle are in the same plane.

[0040] Protective side plates 3 are fixedly installed on both sides of the supporting base plate 2. Two mounting brackets 4 are symmetrically arranged on the top between the two protective side plates 3. The mounting brackets 4 are away from the lifting platform 7 and are welded to the protective side plates 3. A telescopic cylinder 5 is fixedly installed inside the mounting bracket 4. The telescopic end of the telescopic cylinder 5 is fixed to the vertical baffle of the protective baffle 6.

[0041] Both sides of the mounting bracket 4 are fixedly connected with baffle support arms 22 for supporting the protective baffle 6. The baffle support arms 22 are fixedly connected to the protective side plate 3, and the top of both sides of the vertical baffle are provided with support arm slots for accommodating the baffle support arms 22. The baffle support arms 22 will not obstruct the rotation of the lifting platform 7.

[0042] The printing stage structure is located inside the sealed working chamber of the LENS system, and the support base plate 2 is fixedly installed on the bottom wall of the sealed working chamber.

[0043] The servo motor 30, lifting cylinder 28, electric hydraulic cylinder 21 and telescopic cylinder 5 of the printing stage structure are all controlled by an independent controller. This controller is connected to the LENS system, and the LENS system sends instructions to the controller, which controls the printing stage structure to execute the commands.

[0044] The linkage method of the two electric hydraulic cylinders 21 is existing technology. At the same time, the two electric hydraulic cylinders 21 are also equipped with displacement detection sensors to ensure that the extension and retraction distances of the two electric hydraulic cylinders 21 are the same, thus ensuring the smooth lifting and lowering of the lifting platform 7.

[0045] The two telescopic cylinders 5 are linked in the same way as existing technology, controlling the two protective baffles 6 to move closer to or further away from the lifting platform 7 simultaneously; and the telescopic cylinders 5 and the lifting cylinders 28 use the same air source as power, and the airflow is split through the diversion valve to achieve independent control (existing technology).

[0046] The servo motor 30 and the lifting cylinder 28 are started sequentially. Before starting the servo motor 30, the lifting cylinder 28 is first driven to lower the limiting slide 26, releasing the limitation of the limiting slide 26 on the limiting rotating arm 25. After the servo motor 30 drives the lifting platform 7 to rotate, the lifting cylinder 28 is started again, causing the limiting slide 26 to rise, which again limits the limiting rotating arm 25, keeping the upper surface of the lifting platform 7 in a horizontal state, so that the laser cladding module 1 can print metal workpieces on the printing substrate 9.

[0047] An angle sensor is also provided on the rotating connecting seat 11 to monitor the rotation angle of the rotating connecting seat 11 so that the controller can start and stop the servo motor 30 and avoid excessive rotation of the lifting platform 7. Due to the setting of the limiting slide 26, the normal operation of the lifting platform 7 will not be affected if the rotation angle of the lifting platform 7 is slightly smaller or slightly larger. When the limiting slide 26 restricts the limiting rotating arm 25, it will automatically adjust the level of the upper surface of the lifting platform 7.

[0048] Working principle: Reference Figures 1 to 6 Assemble the printing stage structure as shown in the figure and install it into the LENS system. First, the controller retracts the two telescopic cylinders 5, moving the protective baffle 6 away from the lifting platform 7. Then, the controller retracts the electric hydraulic cylinder 21, lowering the lifting platform 7 until it is below the vertical baffle of the protective baffle 6. The locking mounting seats 8 are then installed on the upper and lower surfaces of the lifting platform 7. Finally, the lifting platform 7 is restored to its original position. Figure 2 The state shown is as follows; then the laser cladding module 1 is controlled to print metal workpieces on the printing substrate 9; during the printing process, the controller controls the electric hydraulic cylinder 21 to retract at the same length, cooperating with the laser cladding module 1 to print the workpiece layer by layer; after the upper printing substrate 9 has completed the workpiece printing, the two telescopic cylinders 5 are controlled to retract again, so that the protective baffle 6 is away from the lifting platform 7; then the lifting cylinder 28 is controlled to retract, driving the limiting slide 26 to descend, releasing the limitation of the limiting slide 26 on the limiting rotating arm 25, then the servo motor 30 is started, controlling the lifting platform 7 to rotate the printed workpiece ninety degrees, then the lifting cylinder 28 is started again, causing the limiting slide 26 to rise, again limiting the limiting rotating arm 25; then the electric hydraulic cylinder 21 is controlled to extend, driving the lifting platform 7 to rise, so that the printing substrate 9 is in the state shown. Figure 2 The state shown is then restored, and the telescopic cylinder 5 is extended, returning to its original state. Figure 2 The state shown.

[0049] There are two ways to disassemble the printed workpiece. One is to disassemble them one by one after both printing substrates 9 have finished printing, replace the two snap-fit ​​mounting bases 8 simultaneously, and then print again. This method can quickly perform 3D printing of metal workpieces and shorten machine downtime. The other method is to first disassemble the snap-fit ​​mounting base 8 after both printing substrates 9 have finished printing, replace it with a new snap-fit ​​mounting base 8, and then print again on the new printing substrate 9. This method can thoroughly clean the metal powder from each printed workpiece and reduce safety hazards.

[0050] The above description is only 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 3D printing apparatus for metal printing, comprising a printing stage structure and a laser cladding module (1) disposed within a LENS system, the laser cladding module (1) being disposed above the printing stage structure, characterized in that: The main body of the printing platform structure is a flip-up lifting platform (7). The top and bottom ends of the lifting platform (7) are equipped with detachable snap-fit ​​mounting bases (8). The surface of the snap-fit ​​mounting base (8) is fixedly connected to the printing substrate (9). The laser cladding module (1) performs metal workpiece forming printing on the printing substrate (9). After printing is completed, the lifting platform (7) automatically flips and continues printing on the second printing substrate (9). The lifting platform (7) is provided with a rotating bearing seat (17) at the front end, and guide rods (19) are slidably installed on both sides of the rotating bearing seat (17); the lifting platform (7) is provided with a limit seat (12) at the rear end, and two symmetrically arranged limit slides (13) are installed on the back of the limit seat (12), and guide rods (15) are slidably installed inside the limit slides (13). The bottom ends of the rotating bearing seat (17) and the limiting card seat (12) are both fixedly installed with lifting plates (20). The lifting plates (20) are connected to electric hydraulic cylinders (21). The two electric hydraulic cylinders (21) are linked together, and the two sides of the lifting platform (7) are provided with sliding protective baffles (6).

2. The 3D printing apparatus for metal printing according to claim 1, characterized in that: The bottom ends of the guide pole 2 (19) and guide pole 1 (15) are connected to a bearing base plate (2). Protective side plates (3) are fixedly installed on both sides of the bearing base plate (2). Two mounting brackets (4) are symmetrically arranged on the top between the two protective side plates (3). Telescopic cylinders (5) are fixedly installed inside the mounting brackets (4).

3. A 3D printing apparatus for metal printing according to claim 2, characterized in that: Both sides of the mounting bracket (4) are fixedly connected to baffle support arms (22) for supporting the protective baffle (6). The baffle support arms (22) are fixedly connected to the protective side plate (3), and the telescopic end of the telescopic cylinder (5) is fixed to the protective baffle (6).

4. A 3D printing apparatus for metal printing according to claim 1, characterized in that: The tail end of the lifting platform (7) is provided with a limiting connecting seat (10), and the front end of the limiting connecting seat (10) is fixedly connected with a plurality of limiting rods (23). The limiting rods (23) pass through the lifting platform (7) and extend outward.

5. A 3D printing apparatus for metal printing according to claim 4, characterized in that: The tail end of the limiting connecting seat (10) is fixedly connected to a rotating connecting seat (11), the rotating connecting seat (11) is rotatably connected to the limiting card seat (12), and the back side of the rotating connecting seat (11) is fixedly connected to a rotating connecting shaft (29).

6. A 3D printing apparatus for metal printing according to claim 5, characterized in that: The rotating connecting shaft (29) is connected to a servo motor (30) via a gear pair. A motor mounting base (31) is installed at the bottom of the servo motor (30). The motor mounting base (31) is fixed to the limiting card seat (12), and a protective mounting shell (14) is installed on the back of the limiting card seat (12).

7. A 3D printing apparatus for metal printing according to claim 1, characterized in that: The front end of the lifting platform (7) is provided with a fixed connecting seat (16), which is fixedly connected to a plurality of limiting rods (23), and a rotating mounting column (24) is fixedly connected to the front of the fixed connecting seat (16).

8. A 3D printing apparatus for metal printing according to claim 7, characterized in that: The rotating mounting column (24) is rotatably connected to the fixed connecting seat (16). The fixed connecting seat (16) has a mating mounting groove on its front side. A limiting rotating arm (25) is provided on the upper part of the mating mounting groove. The limiting rotating arm (25) is fixedly connected to the rotating mounting column (24).

9. A 3D printing apparatus for metal printing according to claim 8, characterized in that: A cylinder mounting seat (27) is fixedly installed at the lower part of the mounting groove. A lifting cylinder (28) is fixedly installed inside the cylinder mounting seat (27). A limit slide (26) is fixedly installed at the top of the telescopic end of the lifting cylinder (28).

10. A 3D printing apparatus for metal printing according to claim 9, characterized in that: The limiting slide (26) is configured as an inverted U-shape, with its two sides slidably connected to the groove wall of the mating mounting groove, and a protective cover plate (18) is also installed inside the mating mounting groove.

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