Wall-mounted loudspeaker box support

Abstract

The utility model provides a wall-mounted sound box support, and relates to the technical field of sound box connection, the wall-mounted sound box support comprises a fixed support and a supporting rod, one end of the supporting rod is rotatably connected to the fixed support along the horizontal direction, and the other end of the supporting rod is connected with an insertion tube with an adjustable angle in the vertical direction. The side wall of the inserting pipe is connected with at least one supporting block capable of stretching and retracting in the radial direction of the inserting pipe, an actuating piece capable of moving up and down to drive the supporting block to stretch and retract in the radial direction is arranged in the inserting pipe, and the lower end of the inserting pipe is connected with a driving assembly used for driving the actuating piece to move up and down. The wall-mounted sound box support disclosed by the utility model effectively improves the stability of a sound box insertion structure, avoids potential safety hazards, and improves the sound effect of a sound box.

Description

Technical Field

[0001] The utility model relates to the technical field of speaker connection, in particular to a wall-mounted speaker bracket. Background Art

[0002] A speaker is a device that converts electrical signals into sound signals, and authenticity is a key criterion for evaluating speaker performance. Active speakers are audio systems equipped with a power amplifier (or PA). This integrated amplifier and speaker system can be directly paired with common audio sources (such as portable players, CD players, DVD players, and VCRs) to create a complete audio system. When speakers need to be used in a higher location, they are typically mounted directly on a speaker stand or wall-mounted on a wall or building surface.

[0003] In the prior art, patent CN216017081U discloses a speaker wall mount comprising a mounting base and a support rod. A support column is connected to the outer end of the support rod, and the support column is plugged into a pre-set insertion hole on the bottom of the speaker. In this speaker connection structure, since there is no other locking mechanism between the upper end of the support column and the speaker base, the speaker is easily shaken between the speaker and the speaker stand due to the high height of the speaker after being installed on the speaker stand, posing a safety hazard. Alternatively, the speaker may generate noise due to collision caused by resonance, making it difficult to achieve optimal sound quality. Summary of the Invention

[0004] In order to overcome at least one of the above defects in the prior art, the present invention provides a wall-mounted speaker bracket to solve the problems in the prior art of unstable assembly between the speaker and the fixed pipe, resulting in safety hazards and poor sound quality.

[0005] The utility model provides a wall-mounted speaker bracket: it comprises a fixed bracket and a support rod, one end of the support rod is connected to the fixed bracket in a vertically adjustable angle, the other end of the support rod is connected to a support assembly for inserting and fixing the speaker, the support assembly comprises an insertion tube vertically connected to the support rod, at least one support block capable of radially extending and contracting is connected to the side wall of the insertion tube, an actuator capable of moving up and down to drive the support block to radially extend and contract is arranged in the insertion tube, and the lower end of the insertion tube is connected to a drive assembly for driving the actuator to move up and down.

[0006] Compared with the prior art, the wall-mounted speaker bracket of the present invention has the following advantages:

[0007] In the speaker stand structure of the present invention, a fixed bracket is connected to the outer wall of a building or a bracket, a support rod is rotatably connected to the fixed bracket in the horizontal direction, and a plug-in tube for plugging the speaker is connected to the support rod. The angle between the plug-in tube and the support rod can be adjusted in the vertical direction to achieve the vertical tilt angle adjustment of the speaker, so as to better meet the sound effect direction requirements of different occasions; and in the above structure, the speaker can also be adjusted in the horizontal direction by horizontally rotating the support rod; in addition, in this structure, the plug-in tube cooperates with the plug-in hole at the bottom of the speaker, After the insertion is completed, the actuator is driven upward by operating the driving assembly. Under the action of the actuator, the support block can be expanded radially outward until it is tightened and limited on the inner wall of the insertion hole at the bottom of the speaker, thereby realizing the insertion and locking effect with the speaker base, thereby ensuring a stable connection between the speaker and the connecting body, and no noise is generated due to wind shaking, etc., and the sound effect of the speaker is not affected; when disassembling, it is also only necessary to operate the driving assembly to drive the actuator to move down and reset, so that the support block no longer contacts the inner wall of the insertion hole, and the insertion tube can be easily pulled out of the socket, which is very convenient.

[0008] As an improvement, the end of the support rod away from the fixed bracket is connected to a fixing seat, which is provided with a mounting slot with an upper opening. An adapter is connected to the outer wall of the cartridge tube. The adapter is vertically adjustable within the mounting slot, and a clearance notch is provided at the bottom of the mounting slot for the operating portion of the lower end of the drive assembly to pass through. In this structure, the cartridge tube achieves angle adjustment through the rotational connection between the adapter and the fixing seat, which not only facilitates angle adjustment but also ensures the strength of the connection structure.

[0009] In a further improvement, the upper end of the adapter is provided with a plurality of adjustment holes extending through its two side walls and distributed in a circular arc direction. The lower end of the adapter is provided with positioning holes extending through its two side walls. Adjustment bolts and positioning bolts are provided on the two side walls of the mounting slot, distributed vertically. The positioning bolts are inserted into the positioning holes. The adjustment bolts are used to insert into any of the adjustment holes to adjust the angle of the insertion tube. In the above-mentioned improved structure, the adjustment holes are provided on the adapter located inside the mounting slot, which is hidden from the outside and has a high aesthetic appearance. Moreover, when adjusting the angle, only the upper adjustment bolts need to be operated, and the lower positioning bolts do not need to be removed. This can play a certain role in fixing the speaker during the angle adjustment process and prevent it from accidentally falling.

[0010] In a further improvement, at least one radially deformable support member is disposed within the insertion tube. A through-hole is formed in the sidewall of the insertion tube, and a support block is disposed on the outer wall of the support member, capable of extending through the through-hole. When the drive assembly drives the actuator upward, the actuator is configured to cause the support member to deform radially outward until the support block extends out of the through-hole. In this improved structure, the upward movement of the actuator causes the support member to deform radially outward, allowing the outer end of the support block to pass through the through-hole and abut against the inner wall of the insertion hole pre-set at the bottom of the speaker. When the speaker needs to be disassembled, the actuator is simply driven downward in the opposite direction, which is very convenient.

[0011] In a further improvement, the actuator is a cylindrical top post with a tapered portion at its upper end, the diameter of which gradually decreases from top to bottom. The inner side of the support member is a conical surface that matches the tapered portion. In this improved structure, the arrangement of the tapered portion and the tapered surface allows the support member to be radially deflected when the top post moves upward, thereby allowing the support block to pass through the through hole and tighten against the inner wall of the speaker base socket.

[0012] In a further improvement, a blind cap is connected to the top of the insertion tube, and a limiting tube is provided at the lower end of the blind cap to engage with the insertion tube. A limiting slot is defined on the outer circumferential wall of the limiting tube, and the upper end of the support member fits within the limiting slot. A clearance is provided between the lower outer wall of the support member and the inner wall of the insertion tube to allow for radial deformation of the support member. In this improved structure, the blind cap is used to pre-position the support member. During installation, the blind cap only needs to be inserted into the top of the insertion tube to position the support block at the lower end of the support member relative to the through hole, which is very convenient.

[0013] In a further improvement, three support members are distributed along the circumference of the insertion tube, and three limiting slots are circumferentially arranged on the outer wall of the limiting tube. The limiting slots are T-shaped slots, and the upper end of the support member is provided with a T-shaped block that matches the T-shaped slot. In this improved structure, the three circumferential support members can better ensure a locking fit with the speaker base socket, and the T-shaped slot structure facilitates quick installation of the support member and the cover.

[0014] Furthermore, the drive assembly includes an adjustment screw and a drive nut. The drive nut is connected to the bottom of the insertion tube's inner cavity, and the adjustment screw fits within the drive nut. The upper end of the adjustment screw is connected to the actuator, and the lower end of the adjustment screw extends through the avoidance notch. In this structure, when the adjustment screw is rotated, the spiral mating surface acts to move the actuator up and down, thereby driving the support block to move radially, ultimately achieving locking and loosening with the insertion hole at the bottom of the speaker. This structure is simple and easy to operate.

[0015] Preferably, the adjustment screw is a long bolt, with a mounting hole defined at the lower end of the actuator. The bolt head of the long bolt fits within the mounting hole, and a bottom cap is connected to the bottom of the actuator to limit the bolt head. A knob is attached to the end of the long bolt. This structure directly uses a conventional long bolt as the adjustment screw, saving costs and facilitating installation with the actuator. Furthermore, the knob attached to the lower end of the long bolt facilitates rotation of the adjustment screw, improving the convenience of speaker installation and removal.

[0016] Preferably, the two side plates at the upper end of the mounting groove and the upper end of the adapter are arc-shaped portions of equal radius, and the arc formed by the centers of the plurality of adjustment holes is concentrically arranged with the arc-shaped portion. In this structure, the arc-shaped portion is arranged to better ensure the aesthetic appearance.

[0017] Other improved features and advantages of the present invention will be described in the following detailed description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be achieved and obtained by the structures specifically pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a three-dimensional structural diagram of the wall-mounted speaker bracket of the present utility model;

[0019] Figure 2 This is a partial exploded structural diagram of the wall-mounted speaker bracket of the present utility model;

[0020] Figure 3 This is a partial cross-sectional view of the wall-mounted speaker bracket of the present invention;

[0021] Figure 4 This is a partial exploded structural diagram of the wall-mounted speaker bracket of the present invention.

[0022] Description of reference numerals:

[0023] 1. Fixed bracket; 2. Support rod; 3. Insert tube; 4. Support block; 5. Actuator; 6. Fixed seat; 7. Mounting slot; 8. Adapter seat; 9. Avoidance gap; 10. Adjustment through hole; 11. Positioning through hole; 12. Adjustment bolt; 13. Positioning bolt; 14. Support member; 15. Mounting through hole; 16. Cone; 17. Blind cover; 18. Limiting tube; 19. Limiting slot; 20. T-shaped block; 21. Adjusting screw; 22. Drive nut; 23. Mounting hole; 24. Bottom cover; 25. Knob; 26. Welding window; 27. Fixed plate. DETAILED DESCRIPTION

[0024] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of the present application and are not intended to limit the scope of protection of the embodiments of the present application. Those skilled in the art may adjust them as needed to suit specific application scenarios.

[0025] In the description of the embodiments of this application, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of this application based on the specific circumstances.

[0026] In the embodiments of the present application, unless otherwise clearly specified and limited, the first feature at the "upper end" or "lower end" of the second feature may be in direct contact with the first and second features, or the first and second features may be in indirect contact through an intermediate medium.

[0027] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] See also Figures 1 to 4 As shown, an embodiment of the present application discloses a wall-mounted speaker bracket, which is mainly used for wall-mounting speakers to meet height requirements.

[0029] Specifically, the speaker comprises a fixed bracket 1 and a support rod 2. One end of the support rod 2 is rotatably connected to the fixed bracket 1 in the horizontal direction. The other end of the support rod 2 is connected to a plug-in tube 3 whose angle can be adjusted vertically. The side wall of the plug-in tube 3 is connected to at least one support block 4 that can expand and contract radially. An actuator 5 that can move up and down to drive the support block 4 to expand and contract radially is provided in the plug-in tube 3. The lower end of the plug-in tube 3 is connected to a driving assembly for driving the actuator 5 to move up and down. When installing the speaker, the fixed bracket 1 is first fixed to a corresponding height position, and then the speaker is mounted on the plug-in tube 3. The driving assembly drives the actuator 5 up and down to drive the support block 4 to move radially outward to abut against the inner wall of the plug-in hole preset at the bottom of the speaker to achieve fixed limit. Finally, the angle between the support rod 2 and the fixed bracket can be adjusted according to the angle requirement of the speaker. The speaker has a simple structure and is easy to install. In addition, the connection between the speaker and the support assembly is stable and not easy to shake.

[0030] In addition, in the above structure, the support rod 2 and the fixed bracket 1 are horizontally rotatably connected, which means that two fixed plates 27 spaced apart vertically are connected to the outer wall of the fixed bracket 1, and one end of the support rod 2 is connected between the two fixed plates 27 through a rotating shaft.

[0031] In this embodiment, see the attached Figure 2A fixing seat 6 is connected to the end of the support rod 2 away from the fixed bracket 1. The fixing seat 6 is provided with a mounting groove 7 with an upper opening. An adapter seat 8 is connected to the outer wall of the insertion tube 3. The adapter seat 8 is connected in the mounting groove 7 at an adjustable angle in the vertical direction, and a relief notch 9 is provided at the bottom of the mounting groove 7 for the operating part of the lower end of the drive assembly to pass through. Specifically, in this structure, the support rod 2 is a hollow rectangular tube structure. The mounting seat includes a first rectangular tube with an upper opening and a second rectangular tube with a lower opening. One end of the first rectangular tube is clamped from bottom to top on the lower part of the end of the support rod 2 away from the fixed bracket 1. The second rectangular tube is clamped from top to bottom on the upper part of the end of the support rod 2 away from the fixed bracket 1 and is located between the two side plates of the first rectangular tube. The first rectangular tube, the second rectangular ring and the support rod 2 are connected and fixed by two locking pin shafts. This connection method not only facilitates the processing of the connecting parts, but also improves the structural strength of the connection. In addition, a mounting groove 7 with an upper opening is formed at the other end of the first rectangular tube, and an adapter seat 8 is installed in the mounting groove 7 at the other end of the first rectangular tube. The tilt angle of the speaker can be adjusted by adjusting the angle of the adapter seat 8 in the mounting groove 7.

[0032] More specifically, in the above structure, the upper end of the adapter 8 is provided with a plurality of adjustment holes 10 extending through its two side walls and arranged in an arc shape. The lower end of the adapter 8 is provided with positioning holes 11 extending through its two side walls. Adjustment bolts 12 and positioning bolts 13 are provided on the two side walls of the mounting groove 7, arranged vertically. The positioning bolts 13 are inserted into the positioning holes 11. The adjustment bolts 12 are adapted to engage with any of the adjustment holes 10 to adjust the angle of the inserted tube 3. To enhance the aesthetics of the angle adjustment process of the adapter 8, the upper side plates of the mounting groove 7 and the upper end of the adapter 8 are each formed as arcs of equal radius. The arc formed by the centers of the multiple adjustment holes 10 is concentric with the arcs. In this structure, when the adapter 8 is rotated, the positioning bolts 13 serve as the rotation axis, i.e., the adapter 8 rotates about the positioning bolts 13, ensuring rotational stability. Furthermore, in this structure, both the adjustment bolts 12 and the positioning bolts 13 are locking bolts, making connection convenient and the structure strong. Furthermore, in this embodiment, angle markings are engraved on the outer wall of the fixing base 6 at positions corresponding to the plurality of adjustment holes 10. This structure is primarily used for angle adjustment between 0° and 30°, which generally meets the current range of use and facilitates the rotation of the adapter 8 within the mounting slot 7 to a desired angular position. Of course, in other embodiments, for use in special circumstances, the rotation adjustment range of the adapter 8 can be wider, not just limited to 0° to 30°.

[0033] In this embodiment, see the attached Figure 3 and 4At least one radially deformable support member 14 is disposed within the insertion tube 3. A mounting hole 15 is defined in the sidewall of the insertion tube 3, and a support block 4 is disposed on the outer wall of the support member 14, which extends through the mounting hole 15. When the drive assembly drives the actuator 5 upward, the actuator 5 is configured to cause the support member 14 to deform radially outward until the support block 4 extends through the mounting hole 15 and abuts against the inner wall of the speaker insertion hole. Specifically, when the drive assembly drives the actuator 5 upward, the actuator 5 is configured to cause the support member 14 to deform radially outward until the support block 4 extends through the mounting hole 15, thereby achieving a tight lock with the inner wall of the speaker base insertion hole and ensuring the stability of the connection structure. In this structure, the support member 14 is preferably made of plastic, and the support block 4 and the support member 14 are integrally injection molded. Of course, to further ensure the locking force between the support block 4 and the speaker base insertion hole, a rubber anti-slip pad may also be bonded to the outer wall of the support block 4.

[0034] Specifically, in this embodiment, see the attached Figure 3 The actuator 5 is a cylindrical top post, and its upper end is provided with a tapered portion 16, whose diameter gradually decreases from top to bottom. Accordingly, the inner side of the support member 14 is a tapered surface that matches the tapered portion 16. Preferably, the top post is a hollow tube to minimize weight while ensuring ejection strength. In other embodiments, a corresponding guiding slope can be provided on the outer surface of the top end of the top post, and the inner wall of the support member 14 can also be a sloped surface.

[0035] For further information, see the attached Figure 4 A blind cap 17 is connected to the top of the insertion tube 3. The lower end of the blind cap 17 is provided with a limiting tube 18 that is inserted and matched with the insertion tube 3. A limiting slot 19 is provided on the side wall of the limiting tube 18. The upper end of the support member 14 is fitted into the limiting slot 19. A clearance is left between the lower outer wall of the support member 14 and the inner wall of the insertion tube 3 to allow for radial deformation of the support member 14. In this embodiment, preferably, there are three support members 14 distributed along the circumference of the insertion tube 3, and the limiting slots 19 are three circumferentially provided on the side wall of the limiting tube 18. The limiting slots 19 are T-slots. The upper ends of the three support members 14 are each provided with a T-shaped block 20 for matching with the three T-slots. During installation, the T-shaped block 20 on the upper end of the support member 14 is simply pressed horizontally from the outside to the inside into the corresponding T-slot.

[0036] In addition, see the attached Figure 3In this embodiment, the drive assembly includes an adjusting screw 21 and a driving nut 22. The driving nut 22 is connected to the bottom of the inner cavity of the insertion tube 3. The adjusting screw 21 fits in the driving nut 22. The upper end of the adjusting screw 21 is connected to the actuator 5, and the lower end of the adjusting screw 21 passes through the avoidance gap 9 at the bottom of the mounting groove 7. Preferably, the adjusting screw 21 is a long bolt. The lower end of the actuator 5 is provided with a mounting hole 23. The bolt head of the long bolt is fitted in the mounting hole 23, and the bottom of the actuator 5 is connected with a bottom cover 24 for limiting the bolt head. The bottom cover 24 is welded and fixed to the lower end of the top column, and a connecting hole is provided in the middle of the bottom cover 24. The screw portion of the long bolt extends downward from the connecting hole and the threaded hole of the driving nut 22 in sequence, and the screw end of the long bolt is equipped with a knob 25, which is convenient for the operator to manually rotate the adjusting screw 21 to achieve quick disassembly and assembly of the speaker. In the above structure, the drive nut 22 is fixed to the inner wall of the lower end of the inserting tube 3 by welding. In order to increase the welding firmness, a plurality of welding windows 26 are opened on the outer peripheral wall of the lower end of the inserting tube 3.

[0037] In the description of the embodiments of the present application, it should be noted that in the description of the present application, terms such as "upper" and "lower" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present application.

[0038] In the description of this application, the description with reference to the terms "this embodiment", "some embodiments", etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are mutually inconsistent.

[0039] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A wall-mounted speaker bracket, comprising a fixing bracket (1) and a support rod (2), characterized in that: One end of the support rod (2) is rotatably connected to the fixed bracket (1) in the horizontal direction, and the other end of the support rod (2) is connected to a plug-in tube (3) whose angle can be adjusted in the vertical direction. The side wall of the plug-in tube (3) is connected to at least one support block (4) that can be extended and contracted in its radial direction. An actuator (5) that can move up and down to drive the support block (4) to radially extend and contract is provided in the plug-in tube (3), and a driving component for driving the actuator (5) to move up and down is connected to the lower end of the plug-in tube (3).

2. The wall-mounted speaker bracket according to claim 1, characterized in that: The support rod (2) is connected to a fixing seat (6) at one end away from the fixing bracket (1), and a mounting groove (7) with an upper opening is provided on the fixing seat (6). An adapter seat (8) is connected to the outer wall of the insertion tube (3), and the adapter seat (8) is connected in the mounting groove (7) at an adjustable angle in the vertical direction, and an avoidance notch (9) is provided at the bottom of the mounting groove (7) for the operating part of the lower end of the driving component to pass through.

3. The wall-mounted speaker bracket according to claim 2, characterized in that: The upper end of the adapter seat (8) is provided with a plurality of adjustment holes (10) penetrating the two side walls thereof and distributed in an arc shape, the lower end of the adapter seat (8) is provided with a positioning hole (11) penetrating the two side walls, and the two side walls of the mounting groove (7) are provided with adjustment bolts (12) and positioning bolts (13) distributed up and down, the positioning bolts (13) are inserted into the positioning hole (11), and the adjustment bolt (12) is used to be inserted into any one of the adjustment holes (10) to achieve angle adjustment of the insertion tube (3).

4. The wall-mounted speaker bracket according to any one of claims 1 to 3, characterized in that: At least one support member (14) capable of deforming in its radial direction is provided in the insertion tube (3), a mounting through hole (15) is provided on the side wall of the insertion tube (3), and a support block (4) capable of extending out of the mounting through hole (15) is provided on the outer wall of the support member (14); when the driving assembly drives the actuator (5) to move upward, the actuator (5) is used to drive the support member (14) to deform radially outward until the support block (4) extends out of the mounting through hole (15).

5. The wall-mounted speaker bracket according to claim 4, characterized in that: The actuating member (5) is a cylindrical top column, and the upper end of the top column is provided with a cone (16) whose diameter gradually decreases from top to bottom, and the inner side surface of the supporting member (14) is a cone surface matching the cone (16).

6. The wall-mounted speaker bracket according to claim 4, characterized in that: The top of the insertion tube (3) is connected with a blind cover (17), and the lower end of the blind cover (17) is provided with a limit tube (18) that is inserted and matched with the insertion tube (3). A limit slot (19) is provided on the outer peripheral wall of the limit tube (18), and the upper end of the support member (14) is fitted in the limit slot (19). A movable gap for radial deformation of the support member (14) is reserved between the lower end outer wall of the support member (14) and the inner wall of the insertion tube (3).

7. The wall-mounted speaker bracket according to claim 6, characterized in that: The support members (14) are three and distributed along the circumference of the insertion tube (3); the limiting slots (19) are three and are circumferentially arranged on the outer peripheral wall of the limiting tube (18); and the limiting slots (19) are T-shaped slots, and the upper end of the support member (14) is provided with a T-shaped block (20) that matches the T-shaped slot.

8. The wall-mounted speaker bracket according to claim 2, characterized in that: The driving assembly includes an adjusting screw (21) and a driving nut (22), wherein the driving nut (22) is connected to the bottom of the inner cavity of the insertion tube (3), the adjusting screw (21) is fitted in the driving nut (22), and the upper end of the adjusting screw (21) is connected to the actuator (5), and the lower end of the adjusting screw (21) passes through the avoidance gap (9).

9. The wall-mounted speaker bracket according to claim 8, characterized in that: The adjusting screw (21) is a long bolt, and a mounting hole (23) is provided at the lower end of the actuating member (5). The bolt head of the long bolt is fitted into the mounting hole (23), and a bottom cover (24) for limiting the bolt head is connected to the bottom of the actuating member (5); a knob (25) is fitted at the end of the screw of the long bolt.

10. The wall-mounted speaker bracket according to claim 3, characterized in that: The two side plates at the upper end of the installation groove (7) and the upper end of the adapter seat (8) are both arc-shaped portions with equal radius, and the arc formed by the centers of the plurality of adjustment through holes (10) is concentrically arranged with the arc-shaped portion.

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