Closed tendon extractor

Abstract

The application relates to a closed tendon extractor, which comprises a handle part, an operating mechanism and a tendon extraction assembly. The handle part comprises a handle, a mounting groove, a shaft hole and a blind hole arranged in the handle and communicated with one end of the mounting groove away from the shaft hole. The operating mechanism comprises a push button arranged in the mounting groove and an elastic piece connected with the bottom of the blind hole. The elastic piece is arranged in a spaced mode with the push button in a natural state. The tendon extraction assembly comprises a core rod connected with one end of the push button and penetrating through the shaft hole, and an outer tube. The end of the core rod is connected with a cutting sleeve, and the end of the outer tube is provided with a cutting inner tube. The cutting inner tube is provided with a cutting gap. The push button is pushed in a direction close to the blind hole. The cutting sleeve is moved in a direction close to the cutting gap under the auxiliary action of the elastic piece, so that the cutting sleeve and the cutting gap jointly provide a shearing force to cut the tendon located at the cutting gap. The application has the effects of convenient operation and stable and reliable tendon cutting.

Description

Technical Field

[0001] This application relates to the technical field of medical devices, and in particular to a closed tendon harvesting device. Background Technology

[0002] Tendon harvesters are specialized tools used in medical or biological research to extract animal tendons, and are widely used in biomedical experiments, food processing, and sports medicine. As these industries increasingly demand higher precision and efficiency in their experiments, the design and functional optimization of tendon harvesters, as key equipment, are particularly important. Closed-incision tendon harvesters, especially those used in medical settings, remove ruptured or diseased tendons (such as the Achilles tendon and patellar tendon) through small incisions or punctures, minimizing tissue damage. Closed-incision tendon harvesters achieve precise cutting and extraction of the target tendon through specific mechanical structures.

[0003] In the existing technology, when cutting tendons, the operator manually pushes the push button closer to the cutting part. The pushing force required for cutting depends entirely on the operator's hand force. The cutting force control is unstable, which can cause the push button to loosen and cause unnecessary cutting to the tendon.

[0004] Existing closed tendon harvesting devices are prone to component detachment during cutting due to improper operation, affecting overall usability and safety. Therefore, designing a convenient and stable closed tendon harvesting device has become a technical problem to be solved. Utility Model Content

[0005] To address the aforementioned technical problems, this application provides a closed tendon harvesting device.

[0006] The closed tendon harvesting device provided in this application adopts the following technical solution: A closed tendon harvesting device, comprising: The handle portion includes a handle, a mounting groove formed on the handle, a shaft hole communicating with the mounting groove, and a blind hole formed in the handle. The blind hole is connected to the end of the mounting groove away from the shaft hole, and the blind hole is coaxial with the shaft hole. An operating mechanism, comprising a push button and an elastic element disposed in the mounting slot, the elastic element being connected to the bottom of a blind hole, and the elastic element being spaced apart from the push button in its natural state; and The tendon retrieval assembly includes a core rod connected to one end of the push button and passing through the shaft hole, and an outer tube connected to the handle. The outer tube sleeves the core rod and is coaxially arranged. A cutting sleeve is connected to the end of the core rod. An inner cutting tube located inside the cutting sleeve is provided at the end of the outer tube. The inner cutting tube has a cutting notch. Pushing the push button towards the blind hole allows the push button to move the cutting sleeve towards the cutting notch with the assistance of the elastic element, so that the cutting sleeve and the cutting notch together provide shearing force to cut the tendon located at the cutting notch.

[0007] By adopting the above technical solution, the core rod and cutting sleeve can be moved by pushing the push button. The shearing force provided by the cutting sleeve and the cutting notch is used to cut the tendon located at the cutting notch, thus realizing the tendon retrieval function. A blind hole associated with the mounting groove and shaft hole is opened in the handle, and an elastic element is placed in the blind hole and connected to the push button. This allows for automatic reset after the push button is operated, facilitating the reuse of the tendon retrieval device and improving operational efficiency. Furthermore, the structural design of the blind hole and shaft hole being coaxial ensures the stability and smooth operation of each component of the operating mechanism, which helps to improve the overall performance of the tendon retrieval device.

[0008] Preferably, the bottom of the push button is fixedly connected to a guide tube, the guide tube can slide in the blind hole, and the elastic element is located inside the guide tube.

[0009] By adopting the above technical solution, the guide tube can guide and limit the elastic element and the push button, preventing the spring from deforming.

[0010] Preferably, the outer tube surface is provided with a guide groove, the inner wall of the cutting sleeve is provided with a guide block, the guide block cooperates with the guide groove to restrict the cutting sleeve from moving along the axial direction of the outer tube, the cross-sectional shape of the guide groove is rectangular, and the cross-sectional shape of the guide block matches the guide groove.

[0011] By adopting the above technical solution, the guide groove on the surface of the outer tube and the guide block on the inner wall of the cutting sleeve cooperate to restrict the movement of the cutting sleeve along the axial direction of the outer tube, ensuring the accuracy of the movement direction of the cutting sleeve. The guide groove and guide block with matching rectangular cross-sectional shapes can enhance the stability of their cooperation, making the cutting operation more precise and reliable.

[0012] Preferably, the cutting sleeve has an annular cutting edge at one end near the cutting notch, the cutting notch has an arc-shaped structure, and the inclination direction of the annular cutting edge is consistent with the opening direction of the cutting notch.

[0013] By adopting the above technical solution, the annular cutting edge of the cutting sleeve near the cutting notch matches the arc-shaped cutting notch, and the inclination direction of the annular cutting edge is consistent with the opening direction of the cutting notch. This structure allows the cutting sleeve and the cutting notch to provide more efficient and precise shearing force together, and better cut the tendon located at the cutting notch.

[0014] Preferably, the cutting sleeve and the core rod are detachably connected by a fixing pin.

[0015] By adopting the above technical solution, the cutting sleeve and the core rod are detachably connected by a fixing pin, which facilitates the replacement, repair or cleaning of the cutting sleeve and improves the flexibility and ease of maintenance of the tendon harvester.

[0016] Preferably, it also includes a self-locking mechanism, which is disposed in the blind hole and connected to the push button. The self-locking mechanism is used to automatically lock the push button when it abuts against the end of the mounting groove near the blind hole.

[0017] By adopting the above technical solution, the handle provides the mounting base, the push button of the operating mechanism can control the action of the tendon retrieval component, the cutting sleeve and the cutting inner tube of the tendon retrieval component work together to cut the tendon, the elastic element can help the push button reset, and the self-locking mechanism can realize automatic locking when the push button abuts against the end of the mounting groove near the blind hole, preventing the push button from moving accidentally and affecting the stability and safety of the tendon retrieval operation.

[0018] Preferably, the self-locking mechanism includes a protrusion disposed on the inner wall of the blind hole, a release component, and a locking component. A circular through hole is formed on the surface of the handle portion, and the circular through hole is connected to the blind hole. The protrusion is located on the circular through hole near the circular edge of the push button. The release component is installed on the outer wall of the handle and located on the circular edge of the circular through hole. The locking component is fixedly connected to the push button and can cooperate with the protrusion to lock the push button.

[0019] By adopting the above technical solution, the self-locking mechanism is set in the blind hole and connected to the push button. The protrusion, release component and locking component on the inner wall of the blind hole cooperate with each other. The locking component is fixedly connected to the push button and can cooperate with the protrusion to lock the push button, preventing the push button from moving at will and ensuring the stability and accuracy of the cutting operation.

[0020] Preferably, the snap-fit ​​assembly includes a connecting rod and an elastic buckle. The connecting rod extends into the blind hole and is fixedly connected to the push button. The elastic buckle is fixedly connected to the end of the connecting rod away from the push button. The elastic element is sleeved on the connecting rod.

[0021] By adopting the above technical solution, the self-locking mechanism is used to automatically lock the push button. The connecting rod of the snap-fit ​​component is fixed on the push button, the elastic buckle is fixed on the end of the connecting rod, and the elastic element is sleeved on the connecting rod. This enables the push button to be locked when it abuts against the end of the mounting groove near the blind hole, and ensures that the push button can be normally reset under the action of the elastic element, which facilitates the smooth operation of tendon removal and reuse.

[0022] Preferably, the release assembly includes a reset member and a pressing member, the pressing member being fixedly connected to the reset member, the pressing member being located within the circular through hole, and the length of the pressing member being greater than the sum of the lengths of the circular through hole and the protrusion.

[0023] By adopting the above technical solution, the reset component and the squeezing component of the release component are fixedly connected. The squeezing component is located in the circular through hole and its length is greater than the sum of the length of the circular through hole and the protrusion. This setting allows the reset component to deform when the push button needs to be unlocked by pressing the squeezing component, which can overcome the obstruction of the protrusion on the locking component, thereby facilitating the release of the locked state of the push button and realizing flexible control of the push button position during tendon cutting operation.

[0024] Preferably, a limiting plate is provided on the inner wall of the blind hole, and the connecting rod includes an abutting part near the push button and a locking part near the protrusion. The limiting plate is located between the protrusion and the abutting part. The outer diameter of the abutting part is larger than the outer diameter of the locking part. The limiting plate has a circular hole, the size of which corresponds to the size of the locking part, and the size of the blind hole corresponds to the size of the abutting part. The elastic element is sleeved on the abutting part and its two ends abut against the limiting plate and the push button, respectively.

[0025] By adopting the above technical solution, the limiting plate plays a positioning and guiding role for the connecting rod, ensuring that the connecting rod moves along the prescribed path. The different outer diameters of the abutting part and the snap-fit ​​part are designed to match the size of the limiting plate and the blind hole, further precisely constraining the movement of the connecting rod. The elastic element is sleeved on the abutting part and its two ends abut against the limiting plate and the push button respectively, ensuring that the push button can be reliably reset after being pushed, thereby ensuring the stability and reliability of the entire tendon retrieval device operation.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. The self-locking assembly enables a detachable connection between the handle and the operating mechanism, ensuring the reliability of the connection structure, effectively preventing parts from loosening during operation, and improving the stability and safety of the tendon retrieval process; 2. The transmission connection design between the tendon extraction component and the operating mechanism can precisely control the cutting action, ensuring the integrity of tendon extraction and operational efficiency. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a closed tendon harvesting device provided in Embodiment 1 of this application; Figure 2 yes Figure 1 Schematic diagram of cross section along direction aa; Figure 3 yes Figure 1 Schematic diagram of the middle handle section; Figure 4 yes Figure 1 Schematic diagram of the structure of the cutting sleeve; Figure 5 This application provides a schematic diagram of the structure of a closed tendon harvesting device according to Embodiment 2. Figure 6 yes Figure 5 A magnified view of part A in the diagram.

[0028] Explanation of reference numerals in the attached drawings: 1. Handle; 11. Handle; 12. Mounting groove; 13. Shaft hole; 14. Blind hole; 15. Circular through hole; 2. Operating mechanism; 21. Push button; 22. Elastic element; 23. Guide tube; 3. Tendon retrieval assembly; 31. Core rod; 32. Outer tube; 321. Guide groove; 33. Cutting sleeve; 331. Guide block; 332. Annular cutting edge; 34. Cutting inner tube; 341. Cutting notch; 35. Fixing pin; 4. Self-locking mechanism; 41. Protrusion; 42. Release assembly; 421. Reset element; 422. Pressing element; 43. Snap-fit ​​assembly; 431. Connecting rod; 4311. Abutment part; 4312. Snap-fit ​​part; 432. Elastic buckle; 44. Limiting plate; 441. Circular hole. Detailed Implementation

[0029] The following is in conjunction with the appendix Figure 1-6 This application will be described in further detail.

[0030] Example 1 refer to Figure 1 This application discloses a closed-mouth tendon harvester. The closed-mouth tendon harvester provided in this application includes a handle 1, an operating mechanism 2, and a tendon harvesting assembly 3. The operating mechanism 2 is disposed in the mounting groove 12 of the handle 1. The core rod 31 of the tendon harvesting assembly 3 is connected to the push button 21 of the operating mechanism 2 and passes through the shaft hole 13 of the handle 1. An outer tube 32 is fitted over the core rod 31 and connected to the handle 11. This structure allows the push button 21 to move the cutting sleeve 33, which, together with the cutting notch 341 of the inner cutting tube 34, forms a shearing force to cut the tendon, achieving precise harvesting of tendon tissue. This is because the movement of the push button 21 can precisely control the position of the cutting sleeve 33, thereby accurately cooperating with the cutting notch 341 to cut the tendon.

[0031] refer to Figure 1 , Figure 2and Figure 3 Specifically, the handle part 1 includes a handle 11, a mounting groove 12 formed on the handle 11, a shaft hole 13 communicating with the mounting groove 12, and a blind hole 14 formed inside the handle 11. The handle 11 generally adopts an ergonomic design to facilitate operation by the doctor, for example, it can be a cylindrical shape with a comfortable grip, and its material can be plastic or metal, etc., which have a certain strength and durability. The mounting groove 12 is used to install the push button 21 of the operating mechanism 2, and its shape should be adapted to the push button 21, usually it can be a rectangular groove. The shaft hole 13 provides a passage for the core rod 31 to pass through, ensuring that the core rod 31 can move smoothly. The blind hole 14 is connected to the end of the mounting groove 12 away from the shaft hole 13 and the blind hole 14 is coaxial with the shaft hole 13.

[0032] refer to Figure 1 and Figure 2 The operating mechanism 2 includes a push button 21, an elastic element 22, and a guide tube 23 disposed in the mounting groove 12. The push button 21 is generally a block structure, convenient for the doctor to push with their fingers. Its surface can be designed with a non-slip texture to prevent slippage during operation. The push button 21 can slide in a specific direction within the mounting groove 12, which must be consistent with the movement direction of the core rod 31 to accurately transmit power. The elastic element 22 can be a spring, located within a blind hole 14 in the handle 11 and connected to the push button 21. The guide tube 23 is fixedly connected to the end of the push button 21 near the elastic element 22. The guide tube 23 can slide within the blind hole 14, and the elastic element 22 is located within the guide tube 23. When the push button 21 is pulled towards the blind hole 14, the elastic element 22 is compressed. When the push button 21 is released, the elastic element 22 returns the push button 21 to its initial position for easy operation next time.

[0033] refer to Figures 1-3 The tendon-removing assembly 3 includes a core rod 31 connected to one end of the push button 21 and passing through a shaft hole 13, and an outer tube 32 connected to the handle 11. The outer tube 32 is fitted over the core rod 31 and is coaxially arranged. The core rod 31 serves to transmit power to the push button 21. It is generally a slender rod-shaped structure, and the material can be stainless steel to ensure sufficient strength. The outer tube 32 is fitted over the core rod 31, providing some protection and guidance for the core rod 31. The outer tube 32 can also be made of stainless steel. A cutting sleeve 33 is connected to the end of the core rod 31, and an inner cutting tube 34 located inside the cutting sleeve 33 is provided at the end of the outer tube 32. The inner cutting tube 34 has a cutting notch 341.

[0034] The connection between the cutting sleeve 33 and the core rod 31 can be achieved in various ways, such as using a fixing pin 35 for a detachable connection. Using a fixing pin 35 facilitates operation when the cutting sleeve 33 is damaged or needs to be replaced with a different specification cutting sleeve 33. The cutting notch 341 of the inner cutting tube 34 is used to accommodate the tendon. When the push button 21 is pushed to move the cutting sleeve 33 axially towards the cutting notch 341, the cutting sleeve 33 and the cutting notch 341 together provide shearing force to cut the tendon located at the cutting notch 341. An annular cutting edge 332 is provided at one end of the cutting sleeve 33 near the cutting notch 341. The cutting notch 341 has an arc-shaped structure, and the inclination direction of the cutting edge 332 is consistent with the opening direction of the cutting notch 341. This design makes cutting smoother and improves cutting efficiency and accuracy.

[0035] refer to Figure 4 Furthermore, a guide groove 321 is provided on the surface of the outer tube 32, and a guide block 331 is provided on the inner wall of the cutting sleeve 33. The guide block 331 cooperates with the guide groove 321 to restrict the axial movement of the cutting sleeve 33 along the outer tube 32. The cross-sectional shape of the guide groove 321 is rectangular, and the cross-sectional shape of the guide block 331 matches that of the guide groove 321. This guiding structure ensures that the cutting sleeve 33 will not deviate during movement, making the cutting more accurate.

[0036] The implementation principle of the closed tendon harvester in this application embodiment is as follows: When a tendon harvesting operation is required, the operator pulls the push button 21 toward the blind hole 14. The push button 21 compresses the elastic element 22 to expose the cutting notch 341. The tendon to be cut is passed through the cutting notch 341. When it has passed the required tendon length, the operator pushes the push button 21 in conjunction with the elastic element 22 to make the annular blade 332 cover the cutting notch 341. The resulting shearing force cuts the tendon.

[0037] Example 2 refer to Figure 5 Compared to Embodiment 1, this embodiment differs in that it also includes a self-locking mechanism 4. The self-locking mechanism 4 is disposed within the blind hole 14 and connected to the push button 21. It automatically locks the push button 21 when it abuts against the end of the mounting groove 12 near the blind hole 14. The self-locking mechanism 4 includes a protrusion 41 disposed on the inner wall of the blind hole 14, a release component 42, and a locking component 43. A circular through hole 15 is formed on the surface of the handle 11, which is connected to the blind hole 14. The protrusion 41 is located on the circular edge of the through hole 15 near the push button 21. The release component 42 is installed on the outer wall of the handle 11 and located on the circular edge of the through hole 15. The locking component 43 is fixedly connected to the push button 21 and can cooperate with the protrusion 41 to lock the push button 21.

[0038] refer to Figure 5 and Figure 6Specifically, the snap-fit ​​assembly 43 includes a connecting rod 431 and an elastic buckle 432. The connecting rod 431 extends into the blind hole 14 and is fixedly connected to the push button 21. The elastic buckle 432 is fixedly connected to the end of the connecting rod 431 away from the push button 21. The elastic element 22 is sleeved on the connecting rod 431. The release assembly 42 includes a reset element 421 and a pressing element 422. The pressing element 422 is fixedly connected to the reset element 421. The reset element 421 can be made of rubber. The pressing element 422 is a columnar structure that fits into the circular through hole 15. The length of the pressing element 422 is greater than the sum of the lengths of the circular through hole 15 and the protrusion 41.

[0039] refer to Figure 5 and Figure 6 The connecting rod 431 includes an abutting portion 4311 near the push button 21 and a locking portion 4312 near the protrusion 41. A limiting plate 44 is provided on the inner wall of the blind hole 14, located between the protrusion 41 and the abutting portion 4311. The outer diameter of the abutting portion 4311 is larger than the outer diameter of the locking portion 4312. The limiting plate 44 has a circular hole 441, the size of which corresponds to the size of the locking portion 4312. The size of the blind hole 14 corresponds to the size of the abutting portion 4311. The elastic member 22 is sleeved on the abutting portion 4311 and its two ends abut against the limiting plate 44 and the push button 21, respectively. When the push button 21 is pushed to the designated position, the elastic buckle 432 of the locking assembly 43 engages with the protrusion 41 to lock it in place. The elastic buckle 432 is made of elastic metal or plastic, such as shape memory alloy, to prevent the push button 21 from moving accidentally. When unlocking is required, pressing the squeezing member 422 of the release assembly 42 causes the reset member 421 to deform, causing the squeezing member 422 to press the elastic latch 432, thereby separating the elastic latch 432 from the protrusion 41. The push button 21 returns to its initial position under the action of the elastic member 22. The abutment part 4311 and the latching part 4312 can be made of different material combinations. For example, the abutment part 4311 can be made of high-strength alloy steel, and the latching part 4312 can be made of lightweight aluminum alloy to optimize weight distribution and structural strength.

[0040] The implementation principle of the closed tendon harvester in this application embodiment is as follows: When the push button 21 compresses the elastic element 22 to perform the tendon harvesting operation, the operator needs to control the push button 21 by hand to prevent the push button 21 from loosening. The self-locking mechanism 4 can automatically lock when the push button 21 reaches the designated position by engaging the elastic buckle 432 with the protrusion 41 to prevent misoperation and ensure the safety of the operation. Pressing the reset element 421 can separate the elastic buckle 432 from the protrusion 41, thereby completing the tendon cutting operation.

[0041] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A closed-mouth tendon harvesting device, characterized in that, include: The handle part (1) includes a handle (11), a mounting groove (12) formed on the handle (11), a shaft hole (13) communicating with the mounting groove (12), and a blind hole (14) formed in the handle (11). The blind hole (14) is connected to one end of the mounting groove (12) away from the shaft hole (13), and the blind hole (14) is coaxial with the shaft hole (13). Operating mechanism (2), the operating mechanism (2) includes a push button (21) disposed in the mounting groove (12) and an elastic element (22), the elastic element (22) being connected to the bottom of the blind hole (14), and the elastic element (22) being spaced apart from the push button (21) in its natural state; and A tendon harvesting assembly (3) includes a core rod (31) connected to one end of the push button (21) and passing through the shaft hole (13), and an outer tube (32) connected to the handle (11). The outer tube (32) is sleeved on the core rod (31) and coaxially arranged. A cutting sleeve (33) is connected to the end of the core rod (31), and an inner cutting tube (34) located inside the cutting sleeve (33) is provided at the end of the outer tube (32). The inner cutting tube (34) has a cutting notch (341). Pushing the push button (21) towards the blind hole (14) allows the push button (21) to move the cutting sleeve (33) towards the cutting notch (341) with the assistance of the elastic member (22), so that the cutting sleeve (33) and the cutting notch (341) together provide shearing force to cut the tendon located at the cutting notch (341).

2. The closed tendon harvesting device according to claim 1, characterized in that: The bottom of the push button (21) is fixedly connected to a guide tube (23), which can slide in the blind hole (14), and the elastic element (22) is located inside the guide tube (23).

3. The closed tendon harvesting device according to claim 2, characterized in that: The outer tube (32) is provided with a guide groove (321) on its surface, and the inner wall of the cutting sleeve (33) is provided with a guide block (331). The guide block (331) cooperates with the guide groove (321) to restrict the cutting sleeve (33) from moving axially along the outer tube (32). The cross-sectional shape of the guide groove (321) is rectangular, and the cross-sectional shape of the guide block (331) matches that of the guide groove (321).

4. The closed tendon harvesting device according to claim 2, characterized in that: The cutting sleeve (33) is provided with an annular cutting edge (332) at one end near the cutting notch (341). The cutting notch (341) has an arc-shaped structure, and the inclination direction of the cutting edge (332) is consistent with the opening direction of the cutting notch (341).

5. A closed tendon harvesting device according to claim 2, characterized in that: The cutting sleeve (33) and the core rod (31) are detachably connected by a fixing pin (35).

6. A closed tendon harvesting device according to claim 2, characterized in that: It also includes a self-locking mechanism (4), which is disposed in the blind hole (14) and connected to the push button (21). The self-locking mechanism (4) is used to achieve automatic locking when the push button (21) abuts against the end of the mounting groove (12) near the blind hole (14).

7. A closed tendon harvesting device according to claim 6, characterized in that: The self-locking mechanism (4) includes a protrusion (41) disposed on the inner wall of the blind hole (14), a release component (42) and a locking component (43). A circular through hole (15) is provided on the surface of the handle (1). The circular through hole (15) is connected to the blind hole (14). The protrusion (41) is located near the circular edge of the push button (21) in the circular through hole (15). The release component (42) is installed on the outer wall of the handle (11) and is located on the circular edge of the circular through hole (15). The locking component (43) is fixedly connected to the push button (21) and can cooperate with the protrusion (41) to lock the push button (21).

8. A closed tendon harvesting device according to claim 7, characterized in that: The snap-fit ​​assembly (43) includes a connecting rod (431) and an elastic buckle (432). The connecting rod (431) extends into the blind hole (14) and is fixedly connected to the push button (21). The elastic buckle (432) is fixedly connected to the end of the connecting rod (431) away from the push button (21). The elastic element (22) is sleeved on the connecting rod (431).

9. A closed tendon harvesting device according to claim 7, characterized in that: The release assembly (42) includes a reset member (421) and a pressing member (422). The pressing member (422) is fixedly connected to the reset member (421). The pressing member (422) is located inside the circular through hole (15). The length of the pressing member (422) is greater than the sum of the lengths of the circular through hole (15) and the protrusion (41).

10. A closed tendon harvesting device according to claim 8, characterized in that: The inner wall of the blind hole (14) is provided with a limiting plate (44). The connecting rod (431) includes an abutting part (4311) near the push button (21) and a snap-fit ​​part (4312) near the protrusion (41). The inner wall of the blind hole (14) is provided with a limiting plate (44). The limiting plate (44) is located between the protrusion (41) and the abutting part (4311). The outer diameter of the abutting part (4311) is larger than the outer diameter of the snap-fit ​​part (4312). The limiting plate (44) has a circular hole (441). The size of the circular hole (441) corresponds to the size of the snap-fit ​​part (4312). The size of the blind hole (14) corresponds to the size of the abutting part (4311). The elastic element (22) is sleeved on the abutting part (4311) and its two ends abut against the limiting plate (44) and the push button (21) respectively.

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