Snap ring assembling method of pneumatic unit

Abstract

The invention discloses a clamping ring assembling method of a pneumatic unit. The clamping ring assembling method sequentially comprises the steps that S1, an elastic clamping ring is preassembled on a connecting body on the bottom end face of a first tool in an expanded state; s2, a first tool is inserted from an assembly hole in the side face of the block, and a positioning hole axially formed in the connecting body is axially opposite to the upper end of the output shaft; the first tool is moved downwards until the positioning hole is connected to the upper end of the connecting shaft in a sleeving mode; s3, the second tool extends above the first tool, the front end of the second tool is in lap joint with the clamping ring, and the rear end of the second tool abuts against the first limiting face of the first tool; s4, a third tool is horizontally pushed in along the surface of the second tool, the upper end face of the third tool makes contact with the top face of the assembly hole, the lower end face of the third tool is provided with a first inclined face and acts on a second inclined face of the upper end face of the second tool, the front end of the second tool moves downwards, and the clamping ring is pushed to move downwards till the clamping ring is disengaged from the connecting body; after crossing the maximum outer diameter of the neck part, the elastic part contracts elastically and is clamped into the positioning groove; and S5, after the third tool and the second tool are removed, the first tool is lifted upwards and then axially withdrawn, and assembling is completed. The invention relates to the technical field of pneumatic units.

Description

Technical Field

[0001] This invention relates to the field of pneumatic unit technology, and more specifically to a method for assembling a retaining ring in a pneumatic unit. Background Technology

[0002] Existing pneumatic units for automotive air spring systems include a motor and a block, on which an eccentric wheel-piston linkage assembly and corresponding distribution lines are mounted. The eccentric wheel is connected to the motor drive and has an output shaft. The output shaft is fitted with a rolling bearing, and the inner ends of multiple pistons are respectively provided with positioning grooves for locking with the same retaining ring. The existing block has mounting holes on the surface facing away from the motor (hereinafter referred to as the "back side") for inserting the retaining ring. During installation, the retaining ring expands through a clamp-like structure and is inserted from the mounting hole on the back of the piston into the inner end, where it engages with the positioning groove on the inner end of the piston. During the assembly process, the retaining ring is easily damaged, reducing its service life.

[0003] The back of the block is usually fitted with a base assembly consisting of coils, circuit boards, etc. The internal chamber of this base assembly is usually at atmospheric pressure. If there is pressure leakage in the mounting holes, the base assembly may be subjected to high pressure and crack, which may lead to the risk of water immersion failure. Summary of the Invention

[0004] To address the shortcomings and defects of existing technologies, a snap ring assembly method with a reasonable assembly process is provided.

[0005] A method for assembling a retaining ring in a pneumatic unit. The pneumatic unit includes: The block has an eccentric wheel cavity and at least two piston cavities; An eccentric wheel is rotatably mounted inside an eccentric wheel cavity, and its output shaft is fitted with a rolling bearing. The piston is slidably disposed in the corresponding piston chamber, and its inner end surrounds the outer ring of the rolling bearing and is provided with a neck with a positioning groove. The motor's output end is connected to the eccentric wheel; A flexible retaining ring is used to engage with a positioning groove to lock the piston to the rolling bearing; The described snap ring assembly method includes, in sequence: S1 The elastic retaining ring is pre-installed in an expanded state on the connecting body at the bottom end face of the first tooling; S2 Insert the first tooling into the mounting hole on the side of the block. The axially opened positioning hole on the connecting body is axially opposite to the upper end of the output shaft. Move the first tooling downward until the positioning hole is fitted onto the upper end of the connecting shaft. S3 extends the second tooling above the first tooling, so that its front end overlaps the retaining ring and its rear end abuts against the first limiting surface of the first tooling; S4 The third tooling is pushed horizontally along the surface of the second tooling. The upper end face of the third tooling contacts the top surface of the assembly hole, and the lower end face has a first inclined surface, which acts on the second inclined surface of the upper end face of the second tooling, causing the front end of the second tooling to move down and push the retaining ring to move down until the retaining ring is disengaged from the connecting body, and after passing the maximum outer diameter of the neck, it elastically contracts and gets stuck in the positioning groove. S5 removes the third and second tooling, then lifts the first tooling and axially retracts it to complete the assembly.

[0006] With the above structure, the pneumatic unit of the present invention has the following advantages compared with the prior art: This application has an assembly hole on the end face of the block perpendicular to the output shaft axis, which extends to the eccentric wheel cavity. This can prevent pressure leakage from the assembly hole on the back of the block, which could cause the base assembly to crack under high pressure and fail due to water immersion, thus making the device more stable in operation.

[0007] To accommodate the assembly of retaining rings in the aforementioned pneumatic unit, the retaining ring assembly method of this application is as follows: the positioning hole of the first tooling is fitted onto the upper end of the output shaft to pre-position the output shaft, prevent shaft displacement, and ensure that the neck is aligned with the assembly hole, which facilitates the smooth progress of the retaining ring assembly step. Furthermore, after pre-positioning, the retaining ring on the connecting body is axially aligned with the neck and the connecting shaft, and the retaining ring is subjected to the downward pressure of the second tooling on the connecting body, moving downward until the retaining ring disengages from the connecting body, elastically contracts after passing the maximum outer diameter of the neck, and is locked into the positioning groove, which allows the retaining ring to be quickly and accurately installed into the positioning groove. Compared to the traditional method of installing the retaining ring with pliers, this method avoids damage to the retaining ring, extending its service life and making the device operate more stably.

[0008] As an improvement of the present invention, the first tooling body is a long strip structure extending from front to back. The connector is located on the bottom end face of the front end of the first tooling, has a downward extending structure, and at least part of its circumferential surface is a near-cylindrical structure. The positioning hole is provided along the axial direction of the connector. The retaining ring is clamped on the circumference of the connecting body.

[0009] As an improvement of the present invention, the retaining ring is provided with an inwardly bent arm. The bending arm enters the notch between the two necks, and the rotation of the retaining ring is restricted by the blocking action between the bending arm and the inner wall of the notch.

[0010] As an improvement of the present invention, the connecting body is provided with a groove, the groove receiving the bending arm.

[0011] As an improvement of the present invention, the first tooling is provided with a second limiting surface extending vertically. In step S1, the second limiting surface fits against the outer end face of the assembly hole to limit the insertion depth.

[0012] As an improvement of the present invention, the height of the first limiting surface is lower than the height of the upper end surface of the first tooling body; Furthermore, the first limiting surface extends from the main body of the first tooling to both sides. The second tooling has a U-shaped first arm, the front end of which passes over the first limiting surface and overlaps the upper end of the retaining ring. Furthermore, the first arm is supported at the tail end of the first limiting surface and serves as a fulcrum; In step S4, when the third tooling is advanced, the second tooling deflects downward around the fulcrum as the rotation center, causing the front drive retaining ring to move downward.

[0013] As an improvement of the present invention, the third tooling has a second arm with a U-shaped structure, and the first arm is arranged correspondingly to the second arm. The first inclined surface is located at the bottom of the front end of the second arm. Furthermore, the structure is designed with a gradually decreasing height from the front end to the rear end; The second inclined surface is located at the upper front end of the support arm, and its height gradually decreases from the front end to the rear end. As the third tooling continues to move forward, the first inclined plane acts on the second inclined plane, causing the front end of the second arm to move downward.

[0014] As an improvement of the present invention, the diameter of the connector is greater than or equal to the diameter of the positioning groove and the neck diameter at the upper end of the positioning groove. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention.

[0016] Figure 2 This is a schematic diagram of the block structure of the present invention.

[0017] Figure 3 This is a schematic diagram of the clasp assembly steps of the present invention.

[0018] Figure 4 This is the front view of the present invention.

[0019] Figure 5 This is the invention Figure 4 Schematic diagram of the cross-sectional structure along the AA direction.

[0020] Figure 6 This is a schematic diagram showing the position of the first tooling in step S2 of the present invention.

[0021] Figure 7 This is the invention Figure 6 Enlarged schematic diagram of the structure at point C.

[0022] Figure 8 This is a schematic diagram showing the positions of the first tooling and the second tooling in step S3 of the present invention.

[0023] Figure 9 This is a schematic diagram of the main view structure in step S3 of the present invention.

[0024] Figure 10 This is the invention Figure 9 Schematic diagram of the cross-sectional structure along the BB direction.

[0025] Figure 11 This is the invention Figure 10 Enlarged schematic diagram of the structure at point D.

[0026] Figure 12 This is a schematic diagram showing the positions of the first tooling, the second tooling, and the third tooling in step S4 of the present invention.

[0027] Figure 13 This is a schematic diagram showing the positions of the first tooling, the second tooling, and the third tooling in step S4 of the present invention.

[0028] Figure 14 This is a schematic diagram of the first tooling structure of the present invention.

[0029] Figure 15 This is a partial structural diagram of the first tooling of the present invention.

[0030] Figure 16 This is a schematic diagram of the second tooling structure of the present invention.

[0031] Figure 17 This is a schematic diagram of the structure of the second and third tooling of the present invention. Figure 18 This is an assembly diagram of the retaining ring of the present invention.

[0032] Figure 19 This is the invention Figure 18 Enlarged schematic diagram of the structure at point E in the middle.

[0033] Figure 20 This is a schematic diagram of the structure of the bracket pad assembly of the present invention.

[0034] The figure shows: 1. Block; 1.1. Eccentric wheel cavity; 1.2. Piston cavity; 1.3. Inlet hole; 1.4. Assembly hole; 2. Eccentric wheel; 2.1. Output shaft; 2.11. Rolling bearing; 3. Piston; 3.1. Neck; 3.11. Positioning groove; 3.12. Transition surface; 3.2. Notch; 3.3. Fork-shaped connecting part; 4. Motor; 5. Snap ring; 6. Bending arm; 7. Bracket pad assembly; 8. First tooling; 8.1. Connector; 8.11. Positioning hole; 8.12. Groove; 8.2. First limiting surface; 8.3. Second limiting surface; 9. Second tooling; 9.1. First support arm; 9.11. Second inclined surface; 10. Third tooling; 10.1. Second support arm; 10.11. First inclined surface. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0036] Please see Figure 1-20 As shown, A method for assembling a retaining ring in a pneumatic unit. The pneumatic unit includes: Block 1 has an eccentric wheel cavity 1.1 and at least two piston cavities 1.2; An eccentric wheel 2 is rotatably disposed within an eccentric wheel cavity 1.1, and its output shaft 2.1 is fitted with a rolling bearing 2.11; Piston 3 is slidably disposed in the corresponding piston chamber 1.2, and its inner end surrounds the outer ring of the rolling bearing 2.11 and is provided with a neck 3.1 with a positioning groove 3.11; Motor 4, the output end of which is connected to eccentric wheel 2; The elastic retaining ring 5 is used to engage with the positioning groove 3.11 to lock the piston 3 with the rolling bearing 2.11; The assembly method of the retaining ring 5 includes the following steps: S1 The elastic retaining ring 5 is pre-installed in an expanded state on the connecting body 8.1 at the bottom end face of the first tooling 8; S2 Insert the first tooling 8 into the assembly hole 1.4 on the side of block 1. The axially opened positioning hole 8.11 on the connecting body 8.1 is axially opposite to the upper end of the output shaft 2.1. Move the first tooling 8 downward until the positioning hole 8.11 is fitted onto the upper end of the connecting shaft. S3 extends the second tooling 9 above the first tooling 8, so that its front end overlaps the retaining ring 5 and its rear end abuts against the first limiting surface 8.2 of the first tooling 8; S4 pushes the third tooling horizontally along the surface of the second tooling 9. The upper end face of the third tooling contacts the top surface of the assembly hole 1.4, and the lower end face has a first inclined surface and a second support arm 10.11, which acts on the second inclined surface of the upper end face of the second tooling 9, causing the front end of the second tooling 9 to move down and push the retaining ring 5 to move down until the retaining ring 5 is disengaged from the connecting body 8.1, passes the maximum outer diameter of the neck 3.1, elastically contracts, and is locked into the positioning groove 3.11. S5 removes the third tooling and the second tooling 9, then lifts the first tooling 8 and axially withdraws it to complete the assembly.

[0037] This application provides an assembly hole 1.4 on the end face of block 1 perpendicular to the axis of the output shaft 2.1, which extends to the eccentric wheel cavity 1.1. This can prevent pressure leakage from the assembly hole 1.4 on the back of block 1, which could cause the base assembly to be subjected to high pressure and break, resulting in water immersion failure and making the device more stable in operation.

[0038] To accommodate the assembly of the retaining ring 5 in the pneumatic unit, the assembly method of the retaining ring 5 in this application is as follows: the positioning hole 8.11 of the first tooling 8 is fitted onto the upper end of the output shaft 2.1 to pre-position the output shaft 2.1, prevent the shaft from shifting, and ensure that the neck 3.1 is positively aligned with the assembly hole 1.4, which facilitates the smooth progress of the retaining ring 5 assembly step. Furthermore, after pre-positioning, the retaining ring 5 on the connecting body 8.1 is axially aligned with the neck 3.1 and the connecting shaft, and the retaining ring 5 is subjected to the downward pressure of the second tooling 9 on the connecting body 8.1, moving downward until the retaining ring 5 disengages from the connecting body 8.1, passes the maximum outer diameter of the neck 3.1, elastically contracts, and is locked into the positioning groove 3.11. This allows the retaining ring 5 to be quickly and accurately installed into the positioning groove 3.11. Compared with the traditional method of installing the retaining ring 5 with pliers, this method will not cause damage to the retaining ring 5, thus extending its service life and making the device operate more stably.

[0039] In some embodiments, the main body of the first tooling 8 is a long strip structure extending from front to back. The connector 8.1 is located on the bottom end face of the front end of the first tooling 8, and has a downward extending structure, with at least a portion of its circumferential surface being a near-cylindrical surface. The positioning hole 8.11 is provided along the axial direction of the connector 8.1. The retaining ring 5 is installed on the circumference of the connecting body 8.1.

[0040] After the above improvements, the cylindrical circumferential surface of the connector 8.1 is used to support the inner ring of the retaining ring 5, ensuring that it is stably in an elastic expansion state. The retaining ring 5 will not shrink on the connector 8.1 and does not need to expand again when it is installed into the positioning groove 3.11. The assembly process is reasonably designed, and the retaining ring 5 will not suffer from metal fatigue due to frequent expansion and contraction, thus extending its service life.

[0041] In some embodiments, the retaining ring 5 is provided with an inwardly bent arm 6. The bending arm 6 enters the notch 3.2 between the two necks 3.1. The bending arm 6 and the inner wall of the notch 3.2 block the rotation of the retaining ring 5, so that the retaining ring 5 is stably in the preset assembly position, thereby ensuring effective locking.

[0042] In some embodiments, the connector 8.1 is provided with a groove 8.12, which accommodates the bent arm 6. After the above improvement, the structure is more compact by accommodating the bent arm 6 with the groove 8.12, and during assembly, the lower opening of the groove 8.12 points to the notch 3.2, which makes it easier for the bent arm 6 to enter the notch 3.2.

[0043] In some embodiments, the first tooling 8 is provided with a second limiting surface 8.3 extending vertically. In step S1, the second limiting surface 8.3 fits against the outer end face of the assembly hole 1.4, which has the characteristics of reasonable design and avoids the first tooling 8 being inserted too deeply and damaging the parts.

[0044] In some embodiments, the height of the first limiting surface 8.2 is lower than the height of the upper end surface of the main body of the first tooling 8; Furthermore, the first limiting surface 8.2 extends from the main body of the first tooling 8 to both sides. The second tooling 9 has a U-shaped first arm. The front end of the first arm passes over the first limiting surface 8.2 and overlaps the upper end of the retaining ring 5. The U-shaped bottom of the first arm can contact the tail end of the main body to form a blocking fit, preventing the second tooling 9 from being inserted too deeply and damaging the parts. Furthermore, the first arm is supported at the tail end of the first limiting surface 8.2 and serves as a fulcrum; In step S5, when the third tooling is advanced, the second tooling 9 can easily deflect downwards around the fulcrum, causing the front drive retaining ring 5 to move downwards.

[0045] In some embodiments, the third tooling has a second arm with a U-shaped structure, and the first arm is arranged correspondingly to the second arm. When the third tooling is inserted, the U-shaped bottom of the second arm can also contact the tail end of the main body to form a blocking fit, preventing the third tooling from being inserted too deeply and damaging the parts. The first inclined plane and the second support arm, 10.11 are located at the bottom of the front end of the second support arm. Furthermore, the structure is designed with a gradually decreasing height from the front end to the rear end; The second inclined surface is located at the upper front end of the support arm, and the surface height gradually decreases from the front end to the rear end. During the continuous forward movement of the third tooling, the first inclined plane and the second arm, 10.11, act on the second inclined plane, causing the front end of the second arm to move down smoothly, so that the retaining ring 5 can be pressed into the positioning groove 3.11.

[0046] In some embodiments, the diameter of the connector 8.1 is greater than or equal to the diameter of the positioning groove 3.11 and the diameter of the neck 3.1 at the upper end of the positioning groove 3.11.

[0047] When the retaining ring 5 is set on the connector 8.1, it is forcibly expanded to the preset size to ensure that it can smoothly pass through the neck 3.1 and enter the positioning groove 3.11.

[0048] Preferably, after the retaining ring 5 is assembled, a plug can be set in the assembly hole 1.4 to seal the assembly hole 1.4 and prevent the medium from passing through; In some embodiments, bolt holes are provided on the side where the assembly hole 1.4 is located, and the bracket pad assembly 7 is fixed to the side where the assembly hole 1.4 is located by the cooperation of bolts and bolt holes. When the plug is subjected to high pressure impact, the component consisting of the bracket pad assembly 77 and bolts can act as a baffle to prevent the plug from splashing and causing damage.

[0049] The neck 3.1 is located on the upper surface of the inner end of the piston 3 and protrudes upward. An axial clearance is formed between the neck 3.1 and the upper end of the output shaft 2.1 and the top wall of the mounting hole 1.4.

[0050] The axial clearance is set to avoid the front ends of the retaining ring 5, the first tooling 8, the second tooling 9, and the third tooling, ensuring that the relevant parts can smoothly enter the preset position.

[0051] The neck 3.1 has a semi-circular structure. A semi-circular positioning groove 3.11 is opened on the circumference of the neck 3.1 along the arc path. The semi-circular neck 3.1 and the retaining ring 5 form a coaxial arc fit. During assembly, the retaining ring 5 can automatically align along the arc surface to ensure that all pistons 3 are in phase and reduce assembly errors. The output shaft 2.1 is located between the inner sides of the two necks 3.1 and at the center of the hole of the retaining ring 5. The output shaft 2.1 is located exactly between the inner sides of the two semi-circular necks 3.1 and at the center of the hole of the retaining ring 5, so that the radial pulling force of the retaining ring 5 on the pistons 3 on both sides is more uniform or less fluctuating, reducing vibration and noise.

[0052] The upper end face of the neck 3.1 forms an inclined transition surface 3.12, the height of which gradually decreases from the inner end to the outer end and points towards the positioning groove 3.11.

[0053] The inclined transition surface 3.12 reduces the friction area of ​​the retaining ring 5 passing over the maximum outer diameter surface above the positioning groove 3.11 of the neck 3 during the downward pressing process, thereby reducing the resistance during the retaining ring insertion process, making the assembly smoother and more efficient.

[0054] The vertical height of the neck 3.1 is lower than that of the output shaft 2.1, so as to form an axial gap between the upper end face of the neck 3.1 and the upper end face of the output shaft 2.1, which facilitates the effective fitting of the positioning hole 8.11 onto the upper end of the output shaft 2.1.

[0055] Please see Figure 7 As shown, the inner end of the piston 3 is provided with a fork-shaped connecting part 3.3, which surrounds the outer ring of the rolling bearing 2.11.

[0056] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for assembling a retaining ring in a pneumatic unit, characterized in that, The pneumatic unit includes: Block (1) has an eccentric wheel cavity (1.1) and at least two piston cavities (1.2). An eccentric wheel (2) is rotatably disposed in an eccentric wheel cavity (1.1), and its output shaft (2.1) is fitted with a rolling bearing (2.11). The piston (3) is slidably disposed in the corresponding piston chamber (1.2), and its inner end surrounds the outer ring of the rolling bearing (2.11) and is provided with a neck (3.1) with a positioning groove (3.11). The motor (4) is connected to the eccentric wheel (2) at its output end; A flexible retaining ring (5) is used to engage with a positioning groove (3.11) to lock the piston (3) with the rolling bearing (2.11); The assembly method of the retaining ring (5) includes the following steps: S1 The elastic retaining ring (5) is pre-installed in an expanded state on the connector (8.1) at the bottom end face of the first tooling (8); S2 Insert the first tooling (8) into the assembly hole (1.4) on the side of the block (1), and the positioning hole (8.11) on the connecting body (8.1) is axially opposite to the upper end of the output shaft (2.1); Move the first tooling (8) downwards until the positioning hole (8.11) is fitted onto the upper end of the connecting shaft; S3 extends the second tooling (9) above the first tooling (8), so that its front end overlaps the retaining ring (5) and its rear end abuts against the first limiting surface (8.2) of the first tooling (8). S4 pushes the third tooling horizontally along the surface of the second tooling (9). The upper end face of the third tooling contacts the top surface of the assembly hole (1.4). The lower end face has a first inclined surface (second support arm, 10.11) and acts on the second inclined surface of the upper end face of the second tooling (9), causing the front end of the second tooling (9) to move down and push the retaining ring (5) to move down until the retaining ring (5) is disengaged from the connecting body (8.1), and after passing the maximum outer diameter of the neck (3.1), it elastically contracts and is locked into the positioning groove (3.11). S5 Remove the third tooling and the second tooling (9), then lift the first tooling (8) and then axially withdraw to complete the assembly.

2. The method for assembling a retaining ring in a pneumatic unit according to claim 1, characterized in that: The main body of the first tooling (8) is a long strip structure extending from front to back. The connector (8.1) is located on the bottom end face of the front end of the first tooling (8), and has a downward extending structure, with at least a portion of its circumferential surface being a cylindrical structure. The positioning hole (8.11) is provided along the axial direction of the connector (8.1). The retaining ring (5) is clamped on the circumference of the connecting body (8.1).

3. The method for assembling a retaining ring in a pneumatic unit according to claim 2, characterized in that: The retaining ring (5) is provided with an inwardly bent arm (6). The bending arm (6) enters the notch (3.2) between the two necks (3.1), and the rotation of the retaining ring (5) is restricted by the blocking fit between the bending arm (6) and the inner wall of the notch (3.2).

4. The method for assembling a retaining ring in a pneumatic unit according to claim 3, characterized in that: The connector (8.1) is provided with a groove (8.12) that accommodates the bent arm (6).

5. The method for assembling a retaining ring in a pneumatic unit according to claim 1, characterized in that: The first tooling (8) is provided with a second limiting surface (8.3) extending vertically. In step S1, the second limiting surface (8.3) fits against the outer end face of the assembly hole (1.4) to limit the insertion depth.

6. The method for assembling a retaining ring in a pneumatic unit according to claim 1, characterized in that: The height of the first limiting surface (8.2) is lower than the height of the upper end surface of the main body of the first tooling (8); Furthermore, the first limiting surface (8.2) extends from the main body of the first tooling (8) to both sides. The second tooling (9) has a first arm with a U-shaped structure. The front end of the first arm passes over the first limiting surface (8.2) and overlaps the upper end of the retaining ring (5). Furthermore, the first arm is supported at the tail end of the first limiting surface (8.2) and serves as a fulcrum; In step S4, when the third tooling is advanced, the second tooling (9) deflects downward with the fulcrum as the rotation center, causing the front-end drive circlip (5) to move downward.

7. The method for assembling a retaining ring in a pneumatic unit according to claim 5, characterized in that: The third tooling has a second arm with a U-shaped structure, and the first arm is arranged correspondingly to the second arm. The first inclined surface (second arm, 10.11) is located at the bottom of the front end of the second arm. Furthermore, the structure is designed with a gradually decreasing height from the front end to the rear end; The second inclined surface is located at the upper front end of the support arm, and its height gradually decreases from the front end to the rear end. As the third tooling continues to move forward, the first inclined plane (second arm, 10.11) acts on the second inclined plane, causing the front end of the second arm to move downward.

8. The method for assembling a retaining ring in a pneumatic unit according to claim 2, characterized in that: The diameter of the connector (8.1) is greater than or equal to the diameter of the positioning groove (3.11) and the diameter of the neck (3.1) at the upper end of the positioning groove (3.11).

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