Self-ligating bracket convenient to assemble

Abstract

The self-ligating bracket convenient to assemble comprises a bracket body and a lock cover, one side of the bracket body is used for being bonded with a tooth surface, an arch wire groove is formed in the other side of the bracket body, and the lock cover is installed on the bracket body in a sliding mode; the two ends of the shaft wire are clamped to the side, close to the bottom of the sliding groove, of the lock cover, and a first sliding groove is formed in the position, between the two ends of the shaft wire, of the lock cover; the limiting block is installed at the groove bottom of the sliding groove and corresponds to the first sliding groove in position, the limiting block is installed in the first sliding groove in a sliding mode, and a first guide face is arranged on the side, close to the lock cover, of the limiting block. Or the two ends of the shaft wire are clamped to the groove bottom of the sliding groove, and a second sliding groove is formed in the position, between the two ends of the shaft wire, of the groove bottom of the sliding groove; the limiting block is installed on the lock cover and corresponds to the position of the second sliding groove, the limiting block is installed in the second sliding groove in a sliding mode, and a second guide face is arranged on the side, close to the groove bottom of the sliding groove, of the limiting block. The method has the effect of improving the overall assembly efficiency.

Description

Technical Field

[0001] The present invention relates to the field of dental medicine, and in particular to a self-locking bracket with convenient assembly. Background Art

[0002] Currently, in the field of orthodontics, the bracket, as an important part of the fixed orthodontic appliance, its design directly affects the effect of tooth correction, the comfort of the patient and the convenience of treatment. The new self-locking bracket realizes the direct locking of the arch wire through the built-in self-locking mechanism, without additional ligation steps, thus greatly simplifying the installation process and improving the work efficiency.

[0003] Existing self-locking brackets include a bracket body, an axle wire and a lock cover. The bracket body is provided with an arch wire groove for the arch wire to be inserted. The lock cover is slidably installed on the bracket body to stabilize the arch wire in the arch wire groove. The bracket is provided with an axle hole, and both ends of the axle hole extend out of the bracket body. The axle wire is inserted into the axle hole and deformed to lock the lock cover at the corresponding position on the bracket body. After the axle wire is inserted into the axle hole, the two ends of the axle wire are welded to the axle hole by a welding torch.

[0004] In view of the above related technologies, since the axle wire needs to be welded to the axle hole, the overall assembly efficiency is low. Summary of the Invention

[0005] In order to improve the overall assembly efficiency, the present application provides a self-locking bracket with convenient assembly.

[0006] A self-locking bracket with convenient assembly provided by the present application adopts the following technical solutions:

[0007] A self-locking bracket with convenient assembly includes a bracket body and a lock cover. One side of the bracket body is used for bonding to the tooth surface, and the other side is provided with an arch wire groove. The side of the bracket body where the arch wire groove is opened is provided with a sliding groove communicating with the arch wire groove. The lock cover is slidably installed on the bracket body through the sliding groove, and further includes an axle wire and a limiting block. The axle wire extends perpendicular to the sliding direction of the lock cover.

[0008] Both ends of the axle wire are clamped on the side of the bottom of the lock cover close to the sliding groove. The lock cover is provided with a first sliding groove at the position between the two ends of the axle wire, and the first sliding groove extends out of the lock cover in the sliding direction of the lock cover. The limiting block is installed at the bottom of the sliding groove and corresponds to the position of the first sliding groove. The limiting block is slidably installed in the first sliding groove. One side of the limiting block close to the lock cover is provided with a first guiding surface. The axle wire is located on the side of the limiting block close to the arch wire groove.

[0009] Or:

[0010] The two ends of the axis wire are clamped in the bottom of the sliding groove, and the bottom of the sliding groove is provided with a second sliding groove between the two ends of the axis wire, and the second sliding groove extends out of the sliding groove in the sliding direction of the lock cover; the limit block is installed on the lock cover and corresponds to the position of the second sliding groove, and the limit block is slidably installed in the second sliding groove, and a second guide surface is provided on the side of the limit block close to the bottom of the sliding groove; the axis wire is located on the side of the limit block away from the archwire slot.

[0011] By adopting the above technical solution, when in use, the axis wire is installed at the bottom of the lock cover or the sliding groove by a snap-fitting manner; then the lock cover is inserted into the sliding groove from top to bottom, so that the limit block enters the first sliding groove or the second sliding groove. When the limit block abuts against the axis wire, the lock cover continues to be pressed, and the axis wire is deformed at the position corresponding to the first sliding groove or the second sliding groove until the axis wire passes over the limit block, the axis wire is restored, and the lock cover completely blocks the arch wire slot; when it is necessary to slide the lock cover to open the arch wire slot, the axis wire needs to be re-deformed by the limit block and then pass through the limit The positioning block is formed by a positioning block, so the locking cover can be positioned; the above structure still uses the traditional axis wire to position the locking cover, but there is no need to open an axis hole, no need to perform welding operations, and no need to design other customized spring pieces. The assembly is simple and stable, and it is not easy to fall out; and the axis wire is in a natural state when the locking cover is locked. During the correction process, the number of unlocking times is very small, and the bracket is in the locked state for a long time. Therefore, compared with some situations where the locking cover is in a compressed state after the positioning is completed, it is not easy to deform and fail, and the locking cover can be opened smoothly when it needs to be opened.

[0012] Preferably, when the limit block is installed at the bottom of the sliding groove, a locking protrusion is installed at the bottom of the sliding groove on the side of the limit block away from the arch wire groove; when the limit block is installed on the lock cover, a locking protrusion is installed on the side of the lock cover close to the arch wire slot; there is a spacing between the locking protrusion and the limit block and an unlocking groove is formed, and the side of the limit block away from the unlocking groove is a locking groove; the side of the locking protrusion away from the limit block is provided with an inclined surface for guiding the axis wire into the unlocking groove.

[0013] By adopting the above technical solution, when the lock cover is slid into the sliding groove and slides to the corresponding position of the axis wire, the inclined surface on the locking protrusion can be used to deform the two ends of the axis wire and enter the unlocking groove. If the lock cover is pressed continuously, the axis wire can be deformed again and enter the locking groove through the action of the limit block, thereby completing the installation of the lock cover. When the arch wire slot needs to be opened subsequently, the lock cover is moved to make the axis wire deform and enter the unlocking groove. The locking protrusion can keep the lock cover in the sliding groove, and it will not leave the sliding groove due to excessive force and enter the patient's mouth.

[0014] Preferably, when the axis wire is installed on the lock cover, first clamping grooves are opened on both sides of the first slide groove, and the two ends of the axis wire are respectively clamped in the two first clamping grooves; the depth of the first slide groove is greater than the depth of the first clamping groove.

[0015] By adopting the above technical solution, the installation of the shaft wire is simple. Through the limiting effect between the first clamping groove and the bottom of the sliding groove, the shaft wire can be stabilized in the first clamping groove during the sliding process of the locking cover. Therefore, after the shaft hole and welding installation are eliminated, the installation stability of the shaft wire can still be guaranteed.

[0016] Preferably, when the axis wire is installed at the bottom of the sliding groove, a limiting seat is installed at the bottom of the sliding groove, the second sliding groove is opened on the limiting seat, the limiting seat is located on both sides of the second sliding groove and has second clamping grooves, and the two ends of the axis wire are respectively clamped in the two second clamping grooves; the depth of the second sliding groove is greater than the depth of the second clamping groove; the lock cover is provided with a limiting groove with an opening at the bottom, the limiting seat is slidably installed in the limiting groove, and the limiting block is installed at the bottom of the limiting groove.

[0017] By adopting the above technical solution, the installation of the shaft wire is simple. Through the limiting effect between the second clamping groove and the bottom of the limiting groove, the shaft wire can be stabilized in the second clamping groove during the sliding process of the locking cover. Therefore, after the shaft hole and welding installation are eliminated, the installation stability of the shaft wire can still be guaranteed.

[0018] Preferably, the first guide surface and the second guide surface are both arc-shaped.

[0019] By adopting the above technical solution, the first guide surface and the second guide surface are set to be arc-shaped so that the deformation of the axial wire guide is smoother.

[0020] Preferably, the bracket body is provided with limiting sliding grooves on both sides of the bottom of the sliding groove, and limiting sliding blocks are provided on both sides of the lock cover, and the limiting sliding blocks are slidingly installed on the bracket body through the limiting sliding grooves.

[0021] By adopting the above technical solution, when the lock cover is moved to slide in the sliding groove, the limiting slider slides in the limiting sliding groove, so that the lock cover can slide stably and smoothly in the sliding groove.

[0022] Preferably, a buckle groove is provided on the bracket body near the notch of the archwire slot and directly opposite to the locking cover.

[0023] By adopting the above technical solution, when the lock cover needs to be opened, a tool such as a probe can be inserted into the buckle groove, and the lock cover can be opened by prying it lightly, providing operating space and facilitating use.

[0024] Preferably, a force block is provided on one side of the locking cover away from the bottom of the sliding groove and close to one end of the archwire groove.

[0025] By adopting the above technical solution, when using a probe or other tool to open the lock cover, the torque at the contact point between the probe and the lock cover is increased, and the lock cover can be opened upward with less force, thereby improving the convenience of opening the lock cover.

[0026] In summary, the present application includes at least one of the following beneficial technical effects:

[0027] 1. The traditional axis wire is still used to position the lock cover, but there is no need to open an axis hole, perform welding operations, or design other customized springs. The assembly is simple and stable, and it is not easy to fall out. In addition, the axis wire is in a natural state when the lock cover is locked. During the correction process, the number of unlockings is very small, and the bracket is in the locked state for a long time. Therefore, compared with some situations where the lock cover is in a compressed state after the positioning is completed, it is not easy to deform and fail, and the lock cover can be opened smoothly when it needs to be opened;

[0028] 2. When the archwire slot needs to be opened, the lock cover is moved so that the axis wire is deformed and enters the unlocking slot. The locking protrusion can keep the lock cover in the sliding slot and will not be separated from the sliding slot and enter the patient's mouth due to excessive force;

[0029] 3. Directly press the two ends of the shaft wire into the first clamping groove or the second clamping groove, which is easy to install. Through the limiting effect between the first clamping groove and the bottom of the sliding groove or the limiting effect between the second clamping groove and the bottom of the limiting groove, the shaft wire can be stabilized in the first clamping groove or the second clamping groove during the sliding process of the lock cover. Therefore, after the shaft hole and welding installation are cancelled, the shaft wire can still ensure its installation stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the overall structure of Example 1 of the present application.

[0031] Figure 2 It is a cross-sectional view of the overall structure of Example 1 of the present application.

[0032] Figure 3 It is a schematic diagram of the lock cover structure of Example 1 of the present application.

[0033] Figure 4 It is a schematic diagram of the bracket body structure of Example 1 of the present application.

[0034] Figure 5 It is a schematic diagram of the overall structure of Example 2 of the present application.

[0035] Figure 6 It is a cross-sectional view of the overall structure of Example 2 of the present application.

[0036] Figure 7 It is a schematic diagram of the bracket body structure of Embodiment 2 of the present application.

[0037] Figure 8 It is a schematic diagram of the lock cover structure of Embodiment 2 of the present application.

[0038] Explanation of reference numerals:

[0039] 1. Bracket body; 11. Bottom plate; 12. Arch wire groove; 13. Sliding groove; 14. Limit sliding groove; 15. Buckle groove; 16. Limit seat; 17. Second sliding groove; 18. Second clamping groove; 2. Lock cover; 21. Limit slider; 22. First sliding groove; 23. First clamping groove; 24. Force application block; 25. Limit groove; 3. Axial wire; 4. Limit block; 41. First guiding surface; 42. Second guiding surface; 5. Anti-lock convex block; 51. Inclined surface; 6. Unlocking groove; 7. Locking groove. Detailed implementation manners

[0040] The following is a further detailed description of the present application in conjunction with the attached Figure 1-8 drawings.

[0041] Embodiment 1 of the present application discloses a self-locking bracket with convenient assembly.

[0042] Embodiment 1

[0043] Referring to Figure 1 and Figure 2 , the self-locking bracket includes a bracket body 1 and a lock cover 2. A bottom plate 11 is fixedly installed on one side of the bracket body 1, and an arch wire groove 12 is provided on the other side. The cross-sectional area of the bottom plate 11 is larger than that of the bracket body 1. The bottom plate 11 is in an arc shape adapted to the tooth surface. The side of the bottom plate 11 away from the bracket body 1 is used for bonding to the tooth surface. A reticulation is provided on the side of the bottom plate 11 away from the bracket body 1, so that the bottom plate 11 is more firmly adhered to the tooth surface; a sliding groove 13 is provided on the side of the bracket body 1 where the arch wire groove 12 is opened. The sliding groove 13 extends upward in a direction perpendicular to the depth of the arch wire groove 12. One end of the sliding groove 13 communicates with the arch wire groove 12, and the other end extends out of the top of the bracket body 1. The lock cover 2 is slidably installed on the bracket body 1 through the sliding groove 13. One end of the lock cover 2 abuts against the notch of the arch wire groove 12 and the side away from the sliding groove 13, and the other end extends to the top of the sliding groove 13. Thus, after the arch wire is inserted into the arch wire groove 12, the sliding lock cover 2 can limit the arch wire in the arch wire groove 12.

[0044] Referring to Figure 1 , Figure 3 and Figure 4, on both sides of the bottom of the sliding groove 13 of the bracket body 1, limiting sliding grooves 14 are provided, and the limiting sliding grooves 14 extend in the extending direction of the sliding groove 13; on both sides of the locking cover 2, limiting sliding blocks 21 are integrally formed, and the limiting sliding blocks 21 extend in the extending direction of the limiting sliding groove 14. The limiting sliding blocks 21 are slidably installed on the bracket body 1 through the limiting sliding grooves 14, so that the locking cover 2 can stably slide in the sliding groove 13 in the extending direction of the sliding groove 13.

[0045] Refer to Figure 2 and Figure 3 , the self-locking bracket further includes an arch wire 3, a limiting block 4 and a locking prevention projection 5. In the middle position on one side of the locking cover 2 close to the bottom of the sliding groove 13, a first sliding groove 22 is provided, and the first sliding groove 22 extends in the sliding direction of the locking cover 2. Both ends of the first sliding groove 22 extend out of the locking cover 2; on both sides of the locking cover 2 where the first sliding groove 22 is located, first clamping grooves 23 are provided, and the first clamping grooves 23 extend in a direction perpendicular to the sliding direction of the locking cover 2; the depth of the first sliding groove 22 is greater than the depth of the first clamping groove 23; both ends of the arch wire 3 are respectively clamped in the two first clamping grooves 23, so that the installation of the arch wire 3 can be completed.

[0046] Refer to Figure 2 and Figure 4 , the limiting block 4 is integrally formed on the bottom of the sliding groove 13 and at a position corresponding to the first sliding groove 22. On the side of the limiting block 4 close to the locking cover 2, a first guiding surface 41 is provided. The first guiding surface 41 can be arc-shaped, triangular, etc. In this embodiment, the first guiding surface 41 is arc-shaped; the locking prevention projection 5 is integrally formed and installed on the bottom of the sliding groove 13 and on the side of the limiting block 4 away from the arch wire groove 12. The locking prevention projection 5 and the limiting block 4 are on the same straight line. Both the locking prevention projection 5 and the limiting block 4 are slidably installed in the first sliding groove 22; there is a distance between the locking prevention projection 5 and the limiting block 4 and an unlocking groove 6 is formed. The side of the limiting block 4 away from the unlocking groove 6 is a locking groove 7; on the side of the locking prevention projection 5 away from the limiting block 4, an inclined surface 51 for guiding the arch wire 3 into the unlocking groove 6 is provided.

[0047] When the locking cover 2 slides into the sliding groove 13, the locking prevention projection 5 and the limiting block 4 synchronously slide into the first sliding groove 22. Through the inclined surface 51 on the locking prevention projection 5 and the first guiding surface 41 of the limiting block 4, the arch wire 3 is deformed and smoothly enters the locking groove 7; when the locking cover 2 needs to be opened, the locking cover 2 is toggled, so that the arch wire 3 is deformed and enters the unlocking groove 6, and the arch wire can be smoothly taken out from the arch wire groove 12.

[0048] Refer to Figure 1, a buckle groove 15 is formed at the notch position of the bracket body 1 close to the mouth of the arch wire groove 12 and facing the locking cover 2. A force application block 24 is integrally formed at the bottom side of the locking cover 2 away from the sliding groove 13 and close to the buckle groove 15. Thus, when the locking cover 2 needs to be opened, tools such as a probe can be inserted into the buckle groove 15, and with a slight force, the locking cover 2 can be opened.

[0049] The implementation principle of Embodiment 1 is as follows: During use, both ends of the shaft wire 3 are clamped in the first clamping groove 23; then the locking cover 2 is inserted into the sliding groove 13 from top to bottom, so that the anti-lock convex block 5 and the limiting block 4 slide into the first sliding groove 22 synchronously. When the limiting block 4 abuts against the shaft wire 3, continue to press the locking cover 2. The shaft wire 3 deforms at the position corresponding to the first sliding groove 22 until the shaft wire 3 crosses the limiting block 4 and enters the locking groove 7. The shaft wire 3 resumes its shape, and the locking cover 2 completely blocks the arch wire groove 12; when it is necessary to slide the locking cover 2 to open the arch wire groove 12, the locking cover 2 is pried at the buckle groove 15, so that the shaft wire 3 deforms again through the action of the limiting block 4 and crosses the limiting block 4 to enter the unlocking groove 6. Therefore, the positioning of the locking cover 2 can be achieved, facilitating the removal of the arch wire.

[0050] Embodiment 2

[0051] Refer to Figure 5 , Figure 6 and Figure 7 , the difference between this embodiment and Embodiment 1 is that a limiting seat 16 is integrally formed at the bottom of the sliding groove 13. The locking cover 2 is provided with a limiting groove 25. One end of the limiting groove 25 close to the arch wire groove 12 is open and communicates with the arch wire groove 12. The limiting seat 16 is slidably installed in the limiting groove 25; the limiting seat 16 is provided with a second sliding groove 17, and the second sliding groove 17 extends out of the limiting seat 16 in the sliding direction of the locking cover 2; the limiting seat 16 is provided with second clamping grooves 18 on both sides of the second sliding groove 17. The second clamping grooves 18 extend in a direction perpendicular to the second sliding groove 17. The depth of the second sliding groove 17 is greater than the depth of the second clamping groove 18. Both ends of the shaft wire 3 are respectively clamped in the two second clamping grooves 18, thus completing the installation of the shaft wire 3.

[0052] Refer to Figure 6 and Figure 8 , both the limiting block 4 and the anti-lock convex block 5 are integrally formed at the bottom of the limiting groove 25 and corresponding to the position of the second sliding groove 17. A second guiding surface 42 is provided on the bottom side of the limiting block 4 close to the second sliding groove 17. The second guiding surface 42 can be arc-shaped, triangular, etc. In this embodiment, the second guiding surface 42 is arc-shaped; the anti-lock convex block 5 is provided on the side of the limiting block 4 close to the arch wire groove 12. Both the anti-lock convex block 5 and the limiting block 4 are slidably installed in the second sliding groove 17.

[0053] The implementation principle of Embodiment 2 is as follows: When in use, both ends of the shaft wire 3 are clamped in the second clamping groove 18; then the locking cover 2 is inserted into the sliding groove 13 from top to bottom, so that the anti-locking protrusion 5 and the limiting block 4 slide into the second sliding groove 17 synchronously. When the limiting block 4 abuts against the shaft wire 3, continue to press the locking cover 2, and the shaft wire 3 deforms at the position corresponding to the first sliding groove 22 until the shaft wire 3 crosses the limiting block 4 and enters the locking groove 7. The shaft wire 3 resumes its shape, and the locking cover 2 completely blocks the arch wire groove 12; when it is necessary to slide the locking cover 2 to open the arch wire groove 12, the locking cover 2 is pried at the buckle groove 15, so that the shaft wire 3 deforms again through the action of the limiting block 4 and crosses the limiting block 4 to enter the unlocking groove 6. Therefore, the positioning of the locking cover 2 can be achieved, which is convenient for taking out the arch wire.

[0054] The above are all the preferred embodiments of this application, and the protection scope of this application is not limited thereby. Therefore, all equivalent changes made according to the structure, shape, and principle of this application shall be covered within the protection scope of this application.

Claims

1. A self-locking bracket with convenient assembly, comprising a bracket body (1) and a lock cover (2). One side of the bracket body (1) is used for bonding to the tooth surface, and the other side is provided with an arch wire groove (12). A sliding groove (13) communicating with the arch wire groove (12) is opened on the side of the bracket body (1) where the arch wire groove (12) is opened. The lock cover (2) is slidably installed on the bracket body (1) through the sliding groove (13), and is characterized in that, It further includes an axoneme (3) and a limiting block (4), and the axoneme (3) extends in a direction perpendicular to the sliding direction of the lock cover (2); Both ends of the axoneme (3) are clamped on the side of the bottom of the lock cover (2) close to the sliding groove (13). A first sliding groove (22) is formed at a position between both ends of the axoneme (3) on the lock cover (2), and the first sliding groove (22) extends out of the lock cover (2) in the sliding direction of the lock cover (2); the limiting block (4) is installed at the bottom of the sliding groove (13) and corresponds to the position of the first sliding groove (22), the limiting block (4) is slidably installed in the first sliding groove (22), and a first guiding surface (41) is arranged on the side of the limiting block (4) close to the lock cover (2); the axoneme (3) is located on the side of the limiting block (4) close to the arch wire groove (12); Or: Both ends of the axoneme (3) are clamped on the bottom of the sliding groove (13). A second sliding groove (17) is formed at a position between both ends of the axoneme (3) on the bottom of the sliding groove (13), and the second sliding groove (17) extends out of the sliding groove (13) in the sliding direction of the lock cover (2); the limiting block (4) is installed on the lock cover (2) and corresponds to the position of the second sliding groove (17), the limiting block (4) is slidably installed in the second sliding groove (17), and a second guiding surface (42) is arranged on the side of the limiting block (4) close to the bottom of the sliding groove (13); the axoneme (3) is located on the side of the limiting block (4) away from the arch wire groove (12).

2. The self-locking bracket with convenient assembly according to claim 1, wherein When the limiting block (4) is installed at the bottom of the sliding groove (13), a locking stop projection (5) is installed on the side of the bottom of the sliding groove (13) away from the arch wire groove (12) with respect to the limiting block (4); when the limiting block (4) is installed on the lock cover (2), a locking stop projection (5) is installed on the side of the lock cover (2) close to the arch wire groove (12); there is a gap between the locking stop projection (5) and the limiting block (4) to form an unlocking groove (6), and the side of the limiting block (4) away from the unlocking groove (6) is a locking groove (7); an inclined surface (51) for guiding the axoneme (3) into the unlocking groove (6) is arranged on the side of the locking stop projection (5) away from the limiting block (4).

3. The self-locking bracket with convenient assembly according to claim 1, wherein, When the axoneme (3) is installed on the lock cover (2), first clamping grooves (23) are formed on both sides of the first sliding groove (22), and both ends of the axoneme (3) are respectively clamped in the two first clamping grooves (23); the depth of the first sliding groove (22) is greater than the depth of the first clamping groove (23).

4. The self-locking bracket with convenient assembly according to claim 1, wherein When the axle wire (3) is installed at the bottom of the sliding groove (13), a limiting seat (16) is installed at the bottom of the sliding groove (13). The second sliding groove (17) is opened in the limiting seat (16). Second clamping grooves (18) are opened on both sides of the limiting seat (16) where the second sliding groove (17) is located. Both ends of the axle wire (3) are respectively clamped in the two second clamping grooves (18); the depth of the second sliding groove (17) is greater than the depth of the second clamping groove (18); a limiting groove (25) with an opening at the bottom is opened on the lock cover (2), the limiting seat (16) is slidably installed in the limiting groove (25), and a limiting block (4) is installed at the bottom of the limiting groove (25).

5. The self-locking bracket with convenient assembly according to claim 1, characterized in that Both the first guiding surface (41) and the second guiding surface (42) are arc-shaped.

6. The self-locking bracket with convenient assembly according to claim 1, wherein Limiting sliding grooves (14) are respectively opened at both side positions of the bottom of the sliding groove (13) of the bracket body (1). Limiting sliding blocks (21) are arranged on both sides of the lock cover (2), and the limiting sliding blocks (21) are slidably installed on the bracket body (1) through the limiting sliding grooves (14).

7. The self-locking bracket with convenient assembly according to claim 1, wherein, A buckling groove (15) is opened at the position of the bracket body (1) close to the notch of the arch wire groove (12) and facing the lock cover (2).

8. The self-locking bracket with convenient assembly according to claim 7, wherein, A force application block (24) is arranged at one end of the lock cover (2) far from the bottom of the sliding groove (13) and close to the arch wire groove (12).

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