Earphone assembly pressure maintaining module
By designing a pressure-holding module for earphone assembly, and utilizing magnetic clamps and mechanical transmission units to automate the assembly of the earphone stem end cap, the problem of difficult and inefficient alignment of the earphone stem and earphone stem end cap was solved, thereby improving production efficiency and assembly accuracy.
Patent Information
- Application Number
- CN202520128834.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-20
- Publication Date
- 2026-02-03
- Estimated Expiration
- 2035-01-20
AI Technical Summary
The alignment of the earphone stem and the earphone stem end cap is difficult, and manual installation is inefficient, resulting in low production efficiency.
Design an earphone assembly pressure-holding module, including a module base, a rotary pressing mechanism and a rotary pressure-holding mechanism. Utilize magnetic clamps and a mechanical transmission unit to achieve automated assembly of the earphone stem end cap. Through rotary pressing and pressure-holding actions, the earphone stem end cap is precisely installed to the tail end of the earphone stem.
It reduces the difficulty of manual alignment, improves the production efficiency and assembly accuracy of headphone assembly, simplifies the operation process, and improves the level of automation and product qualification rate.
Smart Images

Figure CN223863238U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of headphone assembly technology, and in particular to a headphone assembly pressure-holding module. Background Technology
[0002] One step in assembling the headphones is to apply glue to the end of the earpiece before inserting the end cap.
[0003] See Figure 1 When the earphones arrive, they are fixed in the earphone fixture 100, with the tail end of the earphone stem 200 protruding upwards to accommodate the earphone stem end cap 300. Currently, the earphone stem end cap 300 is assembled by a dispensing robot applying sealant to the tail end of the earphone stem 200, followed by manual insertion of the end cap into the tail end. This method has the following problems:
[0004] The earphone stem 200 and the earphone stem end cap 300 are small in size, making their alignment difficult, and manually installing the end cap is inefficient.
[0005] Therefore, this utility model is dedicated to developing a headphone assembly pressure-holding module for inserting the ear stem end cap into the tail end of the headphone ear stem, thereby reducing alignment difficulty and improving production efficiency.
[0006] The information disclosed in this background section is included only to enhance the understanding of the context of this disclosure, and therefore may contain information that does not constitute prior art known to those skilled in the art. Utility Model Content
[0007] One objective of this invention is to provide a headphone assembly pressure-holding module that can insert the ear stem end cap into the tail end of the headphone ear stem, thereby reducing alignment difficulty and improving production efficiency.
[0008] To achieve the above objectives, this utility model provides an earphone assembly pressure-holding module, comprising:
[0009] The module base has a fixture acupoint at its front end for the earphone fixture to enter; wherein the earphone fixture is used to install and fix the earphone stem, and the tail end of the earphone stem protrudes upward from the top surface of the earphone fixture;
[0010] A rotary pressing mechanism includes a magnetic clamp for holding the ear rod end cap, a clamping power unit for closing the magnetic clamp, and a pressing transmission unit for driving the magnetic clamp to rotate; wherein the magnetic clamp has a loading state in which it is driven by the pressing transmission unit to rotate inward so as to place the ear rod end cap into the magnetic clamp; and a pressing state in which it is driven by the pressing transmission unit to rotate outward so as to flip the ear rod end cap up and down and press it downward onto the tail end of the earphone ear rod;
[0011] A rotating pressure-holding mechanism, comprising a pressure-holding head and a pressure-holding transmission unit for driving the pressure-holding head to flip down and press against the end cap of the earphone stem that is already fastened to the earphone stem.
[0012] Optionally, the press-fit transmission unit includes a transmission joint rotatably connected to the module base, and an L-shaped connector connecting the transmission joint to the magnetic clamp.
[0013] Optionally, the L-shaped connector is provided with a fixing magnet, and the magnetic clamp includes:
[0014] A fixing plate is fixed to the L-shaped connector, and an opening and fixing magnet is provided at the end of the fixing plate away from the ear rod end cap.
[0015] A rotating clamping plate, the middle part of which is hinged to the fixed clamping plate, and the rotating clamping plate is provided with an opening movable magnet for magnetically connecting with the opening fixed magnet to maintain the opening state, and a closing movable magnet for magnetically connecting with the fixed closing magnet to maintain the closing state.
[0016] Optionally, the rotating clamp has an outwardly protruding operating part at the end away from the ear rod end cap.
[0017] Optionally, the clamping power unit includes a clamping plate pusher and a pusher linear drive mechanism for driving the clamping plate pusher to move up and down.
[0018] in:
[0019] The linear drive mechanism of the pusher wheel drives the clamping plate pusher wheel upward, so that after the clamping plate pusher wheel pushes the operating part upward, the rotating clamping plate rotates to the clamping state;
[0020] The linear drive mechanism drives the clamping plate pusher downwards, so that after the clamping plate pusher pushes the operating part downwards, the rotating clamping plate rotates to the open clamping state.
[0021] Optionally, the pressure-holding transmission unit includes:
[0022] A pressure-holding rotary seat, which is hinged to the module base;
[0023] A pressure-holding slider is slidably connected to the pressure-holding rotary seat; wherein the pressure-holding head is mounted on the pressure-holding slider.
[0024] A pressure-holding spring is located on the side of the pressure-holding slider away from the end cap of the lug, and is used to drive the pressure-holding head downward to elastically press the end cap of the lug.
[0025] Optionally, a rotating buckle is provided on the side of the pressure-holding rotating seat.
[0026] Optionally, the module base is provided with a buckle limiting plate that engages with the rotating buckle;
[0027] When the pressure-holding transmission unit drives the pressure-holding head to press down on the ear rod end cap, the rotating buckle engages with the buckle limiting plate.
[0028] The beneficial effects of this utility model are as follows: It provides an earphone assembly pressure-holding module. When it is necessary to install the ear stem end cap to the tail end of the earphone ear stem, the steps are as follows:
[0029] S10: The press-fit transmission unit drives the magnetic clamp to rotate inward to the loading state, avoiding the fixture acupoint; then, the earphone fixture with the earphone stem fixed is placed on the fixture acupoint of the module base, ensuring that the tail end of the earphone stem protrudes upward;
[0030] S20: The dispensing robot applies adhesive to the end of the earphone stem;
[0031] S30: Operate the rotary pressing mechanism. The specific steps are as follows:
[0032] S301: The worker can manually or through a loading robot open the magnetic clamp and then place the ear rod end cap into the magnetic clamp;
[0033] S302: The clamping power unit closes the magnetic clamp, so that the magnetic clamp holds the end cap of the ear rod;
[0034] S303: The press-fit transmission unit drives the magnetic clamp to rotate outward to the pressing state, and the ear rod end cap is pressed down into the ear rod that has been glued;
[0035] S304: The worker manually or through the loading robot opens the magnetic clamp to release the end cap of the ear rod; the pressing transmission unit drives the magnetic clamp to rotate inward to the loading state;
[0036] S40: Operate the rotating pressure holding mechanism. The pressure holding transmission unit drives the pressure holding head to flip down to press the end cap of the lug downwards and perform pressure holding.
[0037] Through the above steps, the headphone assembly pressure-holding module achieves efficient and precise assembly of the earpiece end cap, reducing the difficulty of manual alignment and improving production efficiency. Attached Figure Description
[0038] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0039] Figure 1 An assembly diagram of the earphone stem and earphone stem end cap provided for the background art;
[0040] Figure 2 This is a schematic diagram of the headphone assembly pressure-holding module in the loading state provided in the embodiment;
[0041] Figure 3 This is a schematic diagram of the structure of the headphone assembly pressure-holding module provided in the embodiment when the ear rod end cap is pressed into the headphone ear rod;
[0042] Figure 4 A schematic diagram of the structure of the earphone assembly pressure-holding module provided in the embodiment when it holds pressure on the ear rod end cap;
[0043] Figure 5 This is a schematic diagram of the magnetic clamp provided in the embodiment.
[0044] In the picture:
[0045] 100. Earphone fixture; 200. Earphone stem; 300. Earphone stem end cap;
[0046] 1. Module base; 101. Acupuncture points;
[0047] 2. Rotary pressing mechanism;
[0048] 201. Magnetic clamp; 2011. Fixed clamping plate; 2012. Rotating clamping plate; 2012a. Operating part; 2013. Opening clamping fixed magnet; 2014. Opening clamping movable magnet; 2015. Closing clamping movable magnet;
[0049] 202. Clamping power unit; 2021. Clamping plate pusher;
[0050] 203. Press-fit transmission unit; 2031. Transmission joint; 2032. L-shaped connector; 2033. Fixing clamping magnet;
[0051] 3. Rotary pressure holding mechanism; 301. Pressure holding head; 302. Pressure holding rotary seat; 3021. Snap-on limit plate; 303. Pressure holding slider; 304. Pressure holding spring; 305. Rotary snap-on. Detailed Implementation
[0052] In this utility model, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this utility model. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this utility model, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.
[0053] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit the invention.
[0054] In the description of this utility model, the term "and / or" is used to describe the logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and A and B exist simultaneously. Additionally, the character " / " generally indicates that the preceding and following objects have an "or" logical relationship.
[0055] In this invention, terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any actual quantity, hierarchy, or order between these entities or operations.
[0056] Without further limitations, the use of terms such as “comprising,” “including,” “having,” or other similar expressions in this invention is intended to cover non-exclusive inclusion, which does not exclude the presence of additional elements in a process, method, or product that includes the stated elements, such that a process, method, or product that includes a series of elements may include not only those defined elements but also other elements not expressly listed, or elements inherent to such a process, method, or product.
[0057] Similar to the understanding in the Examination Guidelines, in this utility model, expressions such as "greater than," "less than," and "exceeding" are understood to exclude the stated number; expressions such as "above," "below," and "within" are understood to include the stated number. Furthermore, in the description of the embodiments of this utility model, "multiple" means two or more (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups" and "multiple times," unless otherwise explicitly specified.
[0058] In the description of the embodiments of this utility model, the space-related expressions used, such as "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "vertical," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," indicate the orientation or positional relationship based on the orientation or positional relationship shown in the specific embodiments or drawings. They are only for the convenience of describing the specific embodiments of this utility model or for the reader's understanding, and do not indicate or imply that the device or component referred to must have a specific position, a specific orientation, or be constructed or operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this utility model.
[0059] Unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," and "setting," as used in the description of the embodiments of this utility model, should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two components or the interaction between two components. For those skilled in the art to which this utility model pertains, the specific meaning of the above terms in the embodiments of this utility model can be understood according to the specific circumstances.
[0060] This utility model provides a headphone assembly pressure-holding module for... Figure 1 The ear stem end cap 300 shown is assembled into the earphone ear stem 200, see [reference]. Figures 2-4 The headphone assembly pressure holding module includes a module base 1, a rotary pressing mechanism 2, and a rotary pressure holding mechanism 3.
[0061] The front end of the module base 1 is provided with a fixture acupoint 101 for the earphone fixture 100 to enter; wherein, the earphone fixture 100 is used to install and fix the earphone stem 200, and the tail end of the earphone stem 200 protrudes upward from the top surface of the earphone fixture 100.
[0062] The rotary pressing mechanism 2 includes a magnetic clamp 201 for holding the ear rod end cap 300, a clamping power unit 202 for closing the magnetic clamp 201, and a pressing transmission unit 203 for driving the magnetic clamp 201 to rotate; wherein, the magnetic clamp 201 has a loading state in which it is driven by the pressing transmission unit 203 to rotate inward so as to put the ear rod end cap 300 into the magnetic clamp 201; and a pressing state in which it is driven by the pressing transmission unit 203 to rotate outward so as to flip the ear rod end cap 300 up and down and press it downward onto the tail end of the earphone ear rod 200.
[0063] The rotating pressure-holding mechanism 3 includes a pressure-holding head 301 and a pressure-holding transmission unit for driving the pressure-holding head 301 to flip down and press against the ear rod end cap 300 that is already clamped to the ear rod 200.
[0064] The headphone assembly pressure-holding module provided in this embodiment has the following steps when the ear stem end cap 300 needs to be installed onto the tail end of the headphone ear stem 200:
[0065] S10: The press-fit transmission unit 203 drives the magnetic clamp 201 to rotate inward to the loading state, avoiding the fixture acupoint 101; then, the earphone fixture 100 with the earphone stem 200 fixed is placed on the fixture acupoint 101 of the module base 1, ensuring that the tail end of the earphone stem 200 protrudes upward.
[0066] S20: The dispensing robot performs dispensing of adhesive at the tail end of the earphone stem 200;
[0067] S30: Operate the rotary pressing mechanism 2. The specific steps are as follows:
[0068] S301: The worker manually or through the loading robot opens the magnetic clamp 201, and then puts the ear rod end cap 300 into the magnetic clamp 201;
[0069] S302: The clamping power unit 202 closes the magnetic clamp 201, so that the magnetic clamp 201 holds the ear rod end cap 300.
[0070] S303: The press-fit transmission unit 203 drives the magnetic clamp 201 to rotate outward to the pressing state, and the ear stem end cap 300 is pressed down into the earphone ear stem 200 that has been glued.
[0071] S304: The worker manually or through the loading robot opens the magnetic clamp 201 to release the ear rod end cap 300; the pressing transmission unit 203 drives the magnetic clamp 201 to rotate inward to the loading state;
[0072] S40: Operate the rotating pressure holding mechanism 3. The pressure holding transmission unit drives the pressure holding head 301 to flip down to press the end cap 300 of the lug downwards and perform pressure holding.
[0073] Through the above steps, the headphone assembly pressure-holding module achieves efficient and precise assembly of the ear rod end cap 300, reducing the difficulty of manual alignment and improving production efficiency.
[0074] See Figure 5 The press-fit transmission unit 203 includes a transmission joint 2031 rotatably connected to the module base 1, and an L-shaped connector 2032 connecting the transmission joint 2031 to the magnetic clamp 201. By connecting the drive end of the press-fit rotary drive mechanism to the transmission joint 2031, the magnetic clamp 201 can be driven to rotate around the axis of the transmission joint 2031, thereby switching between the loading state and the pressing state.
[0075] The L-shaped connector 2032 is provided with a fixed clamping magnet 2033, and the magnetic clamp 201 includes a fixed clamping plate 2011 and a rotating clamping plate 2012. The fixed clamping plate 2011 is fixed to the L-shaped connector 2032, and an opening clamping fixed magnet 2013 is provided at one end of the fixed clamping plate 2011 away from the ear rod end cap 300. The middle part of the rotating clamping plate 2012 is hinged to the fixed clamping plate 2011, and the rotating clamping plate 2012 is provided with an opening movable magnet 2014 for magnetically connecting with the opening clamping fixed magnet 2013 to maintain the open clamping state, and a closing movable magnet 2015 for magnetically connecting with the fixed clamping magnet 2033 to maintain the closed clamping state.
[0076] The rotating clamp 2012 has an outwardly protruding operating part 2012a at one end away from the ear rod end cap 300. The clamping power unit 202 includes a clamp pusher 2021 and a pusher linear drive mechanism for driving the clamp pusher 2021 to move up and down.
[0077] in:
[0078] The linear drive mechanism drives the clamping plate pusher 2021 upward, so that after the clamping plate pusher 2021 pushes the operating part 2012a upward, the rotating clamping plate 2012 rotates to the clamping state.
[0079] The linear drive mechanism drives the clamping plate pusher 2021 downward, so that after the clamping plate pusher 2021 pushes the operating part 2012a downward, the rotating clamping plate 2012 rotates to the open clamping state.
[0080] When it is necessary to open the magnetic clamp 201, push the operating part 2012a downward to make the rotating clamp 2012 rotate to the open clamping state;
[0081] At this time, the opening and closing movable magnet 2014 interacts with the opening and closing fixed magnet 2013 on the fixed clamping plate 2011, and the magnetic clamp 201 remains open, in preparation for the insertion of the ear rod end cap 300.
[0082] When it is necessary to close the magnetic clamp 201, the linear drive mechanism of the push wheel drives the clamping plate push wheel 2021 upward, and the clamping plate push wheel 2021 pushes the operating part 2012a from bottom to top, thereby causing the rotating clamping plate 2012 to rotate to the clamping state.
[0083] At this time, the movable clamping magnet 2015 on the rotating clamping plate 2012 interacts with the fixed clamping magnet 2033 on the fixed clamping plate 2011, and the magnetic clamp 201 remains closed, holding the ear rod end cap 300.
[0084] The pressure-holding transmission unit includes a pressure-holding rotating seat 302, a pressure-holding slider 303, and a pressure-holding spring 304. The pressure-holding rotating seat 302 is hinged to the module base 1; the pressure-holding slider 303 is slidably connected to the pressure-holding rotating seat 302; wherein, the pressure-holding head 301 is mounted on the pressure-holding slider 303; the pressure-holding spring 304 is located on the side of the pressure-holding slider 303 away from the ear rod end cap 300, and is used to drive the pressure-holding head 301 to elastically press the ear rod end cap 300 downward.
[0085] The design of the pressure-holding spring 304 enables the pressure-holding head 301 to elastically press the lug end cap 300, ensuring the consistency and stability of the assembly.
[0086] Optionally, a rotating buckle 305 is provided on the side of the pressure-holding rotating seat 302. The module base 1 is provided with a buckle limiting plate 3021 that engages with the rotating buckle 305; when the pressure-holding transmission unit drives the pressure-holding head 301 to press down on the ear rod end cap 300, the rotating buckle 305 engages with the buckle limiting plate 3021.
[0087] The snap-fit design of the buckle limit plate 3021 and the rotating buckle 305 ensures that the position of the pressure holding head 301 will not change unexpectedly during the pressure holding process, thus improving the safety of operation. When the pressure holding is completed and the earphone fixture 100 needs to be removed, the worker can manually or through a robotic arm to open the rotating buckle 305.
[0088] The headphone assembly pressure-holding module provided in this embodiment has the following beneficial effects:
[0089] ① Increased automation: The combined use of the rotary pressing mechanism 2 and the rotary pressure holding mechanism 3 enables automated assembly of the ear rod end cap 300, greatly reducing manual operation and improving production efficiency and automation level.
[0090] ② Improved assembly precision: The assembly process of the ear rod end cap 300 is completed through precise mechanical movements, which reduces human error and improves the assembly precision and pass rate of the product.
[0091] ③ Ease of operation: The magnetic opening and closing clamp design simplifies the operation process, making it easier for workers to operate and reducing skill requirements.
[0092] ④ Compact structure: By using L-shaped connector 2032 and compact design, the space occupied by the module is reduced, making it suitable for space constraints on the production line.
[0093] It should be noted that the linear drive mechanism mentioned in this utility model can be a cylinder, hydraulic cylinder, electric cylinder, or motor lead screw linear module, etc., and the rotary drive mechanism mentioned can be a brushed motor, brushless motor, or rotary cylinder, etc. This utility model does not limit the specific structural form of the linear drive mechanism and the rotary drive mechanism.
[0094] Finally, it should be noted that although the above embodiments have been described in the text and drawings of this application, this should not limit the scope of patent protection of this application. Any technical solutions that are based on the essential concept of this application and utilize the content described in the text and drawings of this application, resulting in equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this application.
Claims
1. A headphone assembly pressure-holding module, characterized in that, include: The module base (1) has a fixture acupoint (101) at its front end for the earphone fixture (100) to enter; wherein the earphone fixture (100) is used to install and fix the earphone stem (200), and the tail end of the earphone stem (200) protrudes upward from the top surface of the earphone fixture (100). A rotary pressing mechanism (2) includes a magnetic clamp (201) for holding the ear rod end cap (300), a clamping power unit (202) for closing the magnetic clamp (201), and a pressing transmission unit (203) for driving the magnetic clamp (201) to rotate; wherein the magnetic clamp (201) has a loading state driven by the pressing transmission unit (203) to rotate inward so as to place the ear rod end cap (300) into the magnetic clamp (201); and a pressing state driven by the pressing transmission unit (203) to rotate outward to flip the ear rod end cap (300) up and down and press it downward onto the tail end of the earphone ear rod (200); The rotating pressure holding mechanism (3) includes a pressure holding head (301) and a pressure holding transmission unit for driving the pressure holding head (301) to flip down and press against the ear rod end cap (300) that is already attached to the ear rod (200).
2. The headphone assembly pressure-holding module according to claim 1, characterized in that, The press-fit transmission unit (203) includes a transmission joint (2031) rotatably connected to the module base (1) and an L-shaped connector (2032) connecting the transmission joint (2031) to the magnetic clamp (201).
3. The headphone assembly pressure-holding module according to claim 2, characterized in that, The L-shaped connector (2032) is provided with a fixing clamping magnet (2033), and the magnetic clamp (201) includes: A fixing plate (2011) is fixed to the L-shaped connector (2032), and an opening and fixing magnet (2013) is provided at one end of the fixing plate (2011) away from the ear rod end cap (300). A rotating clamping plate (2012) is hinged to the fixed clamping plate (2011) at its middle part. The rotating clamping plate (2012) is provided with an opening clamping movable magnet (2014) for magnetically connecting with the opening clamping fixed magnet (2013) to maintain the opening clamping state, and a closing clamping movable magnet (2015) for magnetically connecting with the fixed closing clamping magnet (2033) to maintain the closing clamping state.
4. The headphone assembly pressure-holding module according to claim 3, characterized in that, The rotating clamp (2012) has an outwardly protruding operating part (2012a) at the end away from the ear rod end cap (300).
5. The headphone assembly pressure-holding module according to claim 4, characterized in that, The clamping power unit (202) includes a clamping plate pusher (2021) and a pusher linear drive mechanism for driving the clamping plate pusher (2021) to move up and down; in: The linear drive mechanism of the pusher wheel drives the clamping plate pusher wheel (2021) upward, so that after the clamping plate pusher wheel (2021) pushes the operating part (2012a) upward, the rotating clamping plate (2012) rotates to the clamping state; The linear drive mechanism drives the clamping plate pusher (2021) downward, so that after the clamping plate pusher (2021) pushes the operating part (2012a) downward, the rotating clamping plate (2012) rotates to the open clamping state.
6. The headphone assembly pressure-holding module according to claim 1, characterized in that, The pressure-holding transmission unit includes: Pressure holding rotary seat (302), the pressure holding rotary seat (302) is hinged to the module base (1); A pressure-holding slider (303) is slidably connected to the pressure-holding rotating seat (302); wherein the pressure-holding head (301) is mounted on the pressure-holding slider (303); A pressure-holding spring (304) is located on the side of the pressure-holding slider (303) away from the ear rod end cap (300), and is used to drive the pressure-holding head (301) to elastically press the ear rod end cap (300) downward.
7. The headphone assembly pressure-holding module according to claim 6, characterized in that, The pressure-holding rotary seat (302) is provided with a rotary buckle (305) on its side.
8. The headphone assembly pressure-holding module according to claim 7, characterized in that, The module base (1) is provided with a buckle limiting plate (3021) that engages with the rotating buckle (305). When the pressure holding transmission unit drives the pressure holding head (301) to press down on the ear rod end cap (300), the rotating buckle (305) engages with the buckle limiting plate (3021).