Protective cover for prefilled syringe

Abstract

The present invention belongs to the technical field of medical instruments, and particularly relates to a protective-type prefilled syringe. The prefilled syringe of the present invention comprises: a barrel for encapsulating a liquid; a needle hub unit mounted at a distal end of the barrel; a needle, which is mounted on the needle hub unit and is in communication with the barrel to allow the liquid to flow therethrough; and a needle cap, which is at least partially sleeved on the needle hub unit, in order to completely sleeve the needle. In addition, a protective cover for the prefilled syringe comprises a protective cover unit at least partially sleeved on the barrel and at least partially sleeved on the needle hub unit, wherein the protective cover unit comprises a protective cover body and a stop hook arranged at a proximal end of the protective cover body and used for pushing up a proximal end face of the needle hub unit; and at most two stop hooks are provided on the protective cover body. By means of the design of reducing the number of stop hooks and enlarging the area of the stop hook in the protective cover, even if a force perpendicular to an axial direction is accidentally applied during the process of axial pushing, the protective cover cannot be easily separated from the barrel.

Description

A protective cover for prefilled syringes Technical Field

[0001] The present invention belongs to the technical field of medical devices, and in particular relates to a protective prefilled syringe. Background Art

[0002] Prefilled syringes are injection devices used in the medical field that integrate the functions of a syringe and a medication container. These syringes are pre-filled with medication during the manufacturing process and sealed to protect the drug's purity and effectiveness. This pre-filled design makes use more convenient and quicker for medical staff, reducing the time and steps required for medication preparation. Furthermore, because prefilled syringes are single-use, they avoid the risk of cross-infection and enhance patient safety. Furthermore, strict sealing measures are implemented during the manufacturing process to effectively protect the drug's purity and stability, extending its shelf life.

[0003] The main components of a prefilled syringe include the syringe body, medication container, piston, needle, and protective cap. The syringe body is typically made of transparent material, allowing medical personnel to clearly observe the dosage and status of the medication solution. The medication container is typically made of glass or plastic, with a capacity tailored to the needs, allowing for different dosages of medication. The piston pushes the medication into the needle for injection. The needle then delivers the medication into the patient. The protective cap protects the needle before and after use.

[0004] However, existing prefilled syringes are often discarded after use, leaving the needle exposed and dangerous. To address this issue, operators often replace the removed protective cap. However, this approach has many drawbacks. First, the protective cap is custom-made for the needle, with a small opening, making it difficult to reinsert after removal. Second, the reinstallation process can easily result in the needle pricking the operator's hand.

[0005] To solve the above problems, a protective prefilled syringe with a protective cover has been proposed on the market. The inventor has previously applied for an invention patent in the related field, specifically CN114642793A, a prefilled syringe with a front shield. The protective cover can adjust the axial position by pushing and pulling, which is used to expose the needle to complete the injection, and to cover the needle and discard it after the injection to avoid needle sticks to others.

[0006] However, during actual use of the aforementioned syringe, it was discovered, referring to the specification of the application, that during step S1 of using the prefilled syringe, the operator is theoretically required to push the protective shield completely axially. However, in actual operation, the operator cannot perfectly push the protective shield axially and always applies a certain amount of force perpendicular to the axial direction to the protective shield, especially when operating with one hand. If the operator accidentally applies a force perpendicular to the axial direction to the protective shield while pushing the protective shield unit in the proximal axial direction (this direction is marked as β in Figure 1), the protective shield may directly detach from the syringe barrel. This is because when the force perpendicular to the axial direction is applied to the protective shield, the space between the two adjacent stop hooks responsible for clamping the syringe barrel expands outward, resulting in an excessive gap between the two stop hooks, causing the syringe barrel to directly pass through the two stop hooks, causing the protective shield to detach from the syringe barrel.

[0007] Therefore, there is a need for a protective cover for a prefilled syringe, which will not separate from the syringe barrel even if a force perpendicular to the axial direction is accidentally applied to the protective cover. Technical Solutions

[0008] The present invention aims to provide a protective cover for a prefilled syringe, which will not easily separate from the syringe even if a force perpendicular to the axial direction is accidentally applied to the protective cover during the process of axial pushing.

[0009] The present invention solves the above-mentioned problem by adopting a technical solution: a protective cover for a prefilled syringe, wherein the prefilled syringe comprises:

[0010] Syringes, used to package liquids;

[0011] A needle seat unit is mounted at the distal end of the syringe;

[0012] a needle, mounted on the needle hub unit and connected to the syringe to allow the liquid to flow;

[0013] a needle sheath, at least partially sheathed on the needle hub unit to completely sheath the needle;

[0014] In addition, the protective cover for the prefilled syringe includes a protective cover unit that is at least partially sleeved on the syringe and at least partially sleeved on the needle seat unit; the protective cover unit includes a protective cover body, a stop hook arranged at the proximal end of the protective cover body and used to lift the proximal end surface of the needle seat unit; a maximum of two stop hooks are arranged on the protective cover body.

[0015] In the present application, compared to CN114642793A, the protective shield limits the number of stop hooks to a maximum of two. This increases the circumferential length of the stop hooks. Even if the stop hooks deform perpendicularly to the axial direction when a force perpendicular to the axial direction is accidentally applied, they will not completely disengage from the needle hub unit. The advantage of this design is that by increasing the circumferential length of the stop hooks, the stop hooks can still provide sufficient support to prevent the stop hooks from dislocating from the needle hub unit even when a force perpendicular to the axial direction is accidentally applied. This ensures that the main body of the protective shield remains in a position on the syringe. It also ensures that the main body of the protective shield remains engaged with the needle hub unit during use, providing additional safety protection against accidental needlestick injuries.

[0016] In addition, the protective cover body is usually made of durable medical materials with sufficient strength and stability. It can completely cover the needle part of the syringe, thereby effectively preventing accidental contact and injury from the needle.

[0017] Additionally, syringes can be pre-filled with medication and sealed. They are commonly used to inject liquid medications such as vaccines and insulin. The main advantages of pre-filled syringes are convenience, hygiene, and accuracy. They provide precise dosing control and reduce the risk of cross-infection.

[0018] A further preferred technical solution is that: the protective cover unit further comprises a cantilever slot provided on the stop hook, and a cantilever provided on the inner side surface of the distal end of the cantilever slot and used to lift the distal end surface of the needle seat unit.

[0019] A further preferred technical solution is that: the angle of the stop hook is not less than 130°.

[0020] The syringe is generally a hollow cylinder with curved sides. Referring to Figure 7 , observing the stop hook from the axial direction reveals an arc that aligns with the syringe. This arc should be no less than 130°, as the larger the arc, the less likely the stop hook is to misalign with the needle hub. However, if the arc is less than 130°, there is a risk of the stop hook misaligning with the needle hub. Therefore, in this application, the angle and shape of the stop hook are crucial to the function of the protective shield. The arc of the stop hook should be sufficiently large to provide a better engagement effect and prevent the protective shield from detaching from the syringe.

[0021] A further preferred technical solution is that: two stop hooks are provided on the protective cover body, the distance between the two stop hooks is γ', the width of the protective cover body is γ, wherein γ':γ=(0.1-0.15):1.

[0022] Among them, by setting two stop hooks, the stability of the protective cover body can be increased. They can support each other to prevent the protective cover from unstable movement or tilting during use. And the two stop hooks can produce the same deformation, so that when the stop hooks are deformed, the protective cover body still has an axis that coincides with the syringe. The size of the spacing γ' between the two stop hooks affects the deformation ability and anti-detachment ability of the two stop hooks. If γ' is too large, there will be a risk of detachment from the needle seat unit during the deformation of the two stop hooks. If γ' is too small, it will be difficult for the two stop hooks to deform so that the proximal part of the protective cover body comes to the syringe to leak out the needle. Therefore, the ratio of γ':γ should be within a reasonable range.

[0023] A further preferred technical solution is that the stop hook includes a hook elastic member, a locking member arranged at the proximal end of the hook elastic member, and a hook surface arranged at the distal end of the locking member.

[0024] A further preferred technical solution is that: the stop hook further includes an inclined surface provided at the proximal end of the engaging member.

[0025] A further preferred technical solution is that the cantilever includes a cantilever elastic member and a raised surface arranged at the proximal end of the cantilever elastic member.

[0026] A further preferred technical solution is that: the cantilever further includes a protrusion arranged on the inner side of the cantilever elastic member and used to lift the needle sleeve.

[0027] A further preferred technical solution is that the protective cover unit further includes a force-guiding protrusion arranged on the protective cover body.

[0028] A further preferred technical solution is that the protective cover unit further includes a limiting ring provided at the distal end of the protective cover body and used to lift up the needle seat unit.

[0029] A further preferred technical solution is that the needle seat unit includes a needle seat and a ridge member provided on the needle seat.

[0030] A further preferred technical solution is that the convex ridge member includes a distal stop surface, a proximal stop surface, and a side stop surface for connecting the distal stop surface and the proximal stop surface.

[0031] A further preferred technical solution is that the maximum inner diameter of the limiting ring is smaller than the minimum outer diameter of the distal stop surface. Beneficial effects

[0032] In summary, the present invention has the following advantages:

[0033] 1. The design of the protective cover can help resist the force perpendicular to the axial direction, and improve the overall resistance through reasonable structure and shape;

[0034] 2. The design of the protective cover prevents the stop hook and the needle hub from misaligning. When a force perpendicular to the axial direction is applied, the structure and shape of the protective cover ensure that the stop hook and the needle hub remain correctly engaged, preventing misalignment between them.

[0035] 3. The widened cantilever design can greatly reduce the possibility of breakage during use, thereby improving the overall quality of the syringe.

[0036] 4. The combined design of the cantilever and the stop hook can minimize the number of petals at the proximal end of the protective cover, thereby further improving the effectiveness of the protective cover in resisting forces perpendicular to the axial direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic structural diagram of a prefilled syringe and a protective cover.

[0038] FIG2 is a schematic diagram of an explosion of the prefilled syringe and the protective cover in FIG1 .

[0039] FIG3 is a schematic diagram of the prefilled syringe and protective cover in FIG1 taken along line AA′.

[0040] FIG4 is a schematic structural diagram of the protective cover.

[0041] FIG5 is a schematic structural diagram of the protective cover rotated 180° based on the viewing angle of FIG4 .

[0042] FIG6 is a schematic diagram of the structure of the protective cover from an axial vertical perspective.

[0043] FIG7 is a schematic diagram of the structure of the protective cover when viewed from an axial perspective.

[0044] FIG8 is a schematic diagram of a cross section of the protective cover along line BB′ in FIG6 .

[0045] FIG9 is a schematic diagram of the connection between the protective cover unit and the needle seat unit.

[0046] In the accompanying drawings, the components represented by each reference numeral are as follows: syringe 1, needle seat unit 2, protective cover unit 4, needle sleeve 5, needle seat 202, ridge member 201, protective cover body 401, stop hook 402, cantilever groove 403, cantilever 404, force guiding protrusion 405, limiting ring 406, hook elastic member 402a, engaging member 402b, hook surface 402c, inclined surface 402d, cantilever elastic member 404a, top surface 404b, protrusion 404c. Modes for Carrying Out the Invention

[0047] 1. Distal end: refers to the syringe and the various components installed on the syringe in a normal manner, which is the end facing the needle.

[0048] 2. Proximal end: refers to the syringe and the various components installed on the syringe in a normal manner, which is away from the needle.

[0049] 3. Axis: refers to the line connecting the centroids of all cross sections of a component with a symmetrical cross section.

[0050] 4. Open: refers to the ability to expose the needle or needle sheath during operation.

[0051] 5. Closed: refers to the ability to cover the needle or needle cover during operation.

[0052] 6. Socketing: refers to the act of installing component one on the outer surface of component two when the inner diameter of component one is larger than the outer diameter of component two.

[0053] 7. Setting: refers to any method used to combine two parts together, such as bonding, snapping, welding, screwing, placement, etc.

[0054] 8. Lifting: refers to component one exerting force on component two, causing component two to move in a direction opposite to the position of component one.

[0055] 9. Minimum / Maximum Diameter: For components with a distinct axis, a cross-section perpendicular to the axis is taken. If the cross-section is approximately circular or polygonal, the narrowest portion of the cross-section is the minimum diameter of the component, and the widest portion of the cross-section is the maximum diameter. The minimum diameter of a given cross-section should not be greater than its maximum diameter.

[0056] The present invention will be further described in detail below with reference to the accompanying drawings.

[0057] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law. Example

[0058] In this embodiment, the prefilled syringe includes: a syringe 1, a needle seat unit 2, a protective cover unit 4, a needle sleeve 5,

[0059] The protective cover comprises: a protective cover unit 4, wherein:

[0060] The protective cover unit 4 includes a protective cover body 401, a stop hook 402, a cantilever groove 403, a cantilever 404, a force-guiding protrusion 405, and a limiting ring 406; wherein two stop hooks 402 are arranged on the protective cover body 401, the distance between the two stop hooks 402 is γ', and the width of the protective cover body 401 is γ, wherein γ':γ=0.15:1; the angle α of the stop hook 402 is 130°.

[0061] The needle hub unit 2 includes a ridge member 201 and a needle hub 202 .

[0062] The ridge member 201 includes a distal stop surface 201a and a proximal stop surface 201b.

[0063] The stop hook 402 includes a hook elastic member 402a, a locking member 402b, a hook surface 402c, and an inclined surface 402d.

[0064] The cantilever 404 includes a cantilever elastic member 404a, a raised surface 404b, and a protrusion 404c.

[0065] Referring to Figure 1, a schematic diagram of the prefilled syringe and its protective cover is shown. The prefilled syringe comprises a syringe 1 for encapsulating liquid, and a protective cover unit 4 at least partially attached to the syringe 1. The figure shows the protective prefilled syringe in its unused state, with the protective cover unit 4 attached to the syringe 1 and completely covering the needle guard 5. The protective cover unit 4 is coaxial with the syringe 1 and can slide proximally along the syringe 1.

[0066] Refer to Figure 2, which shows an exploded view of the prefilled syringe and protective cover shown in Figure 1. The needle hub unit 2 is mounted on the distal end of the syringe barrel 1; the needle is mounted on the needle hub unit 2 and communicates with the syringe barrel 1 to allow fluid flow; and the needle guard 5 is used to receive the needle. While the needle is not shown to facilitate illustration of other components, the specific location of the needle in the needle hub unit 2 can be imagined from a typical syringe. The syringe barrel 1, needle hub unit 2, protective cover unit 4, and needle guard 5 all share a common axis.

[0067] Referring to Figure 3, a schematic diagram of the prefilled syringe and protective cover shown in Figure 1, taken along line AA', is shown. It can be seen that the syringe 1 has a cylindrical hollow structure for encapsulating liquid. The syringe 1 is also equipped with an injection piston, as used in conventional syringes. By pushing the injection piston, the liquid medicine is pushed into the needle hub unit 2. The needle hub unit 2 has a channel at its axis that connects to the cylindrical cavity within the syringe 1. This channel also connects to the hollow structure within the needle, allowing liquid entering the needle hub unit 2 to pass through the needle to complete the injection process. The protective cover unit 4 is at least partially mounted on the syringe 1 and at least partially mounted on the needle hub unit 2. Furthermore, a needle cap 5 is at least partially mounted on the needle hub unit 2 to completely mount the needle.

[0068] Referring to Figure 4, a schematic diagram of the shield structure is shown. The shield unit 4 includes a shield body 401 and a stop hook 402 disposed at the proximal end of the shield body 401 for supporting the proximal end surface of the needle hub unit 2. Two stop hooks 402 are provided on the shield body 401. The hooks of the stop hooks 402 extend radially inward to engage the needle hub unit 2.

[0069] In particular, in the embodiment, the cantilever 404 is arranged in the cantilever groove 403 opened in the middle of the stop hook 402. This combination of the cantilever 404 and the stop hook 402 makes the stop hook 402 consist of only two petals, and does not have the cantilever 404 occupying space on the ring where the stop hook 402 cross section is located. That is, this design makes it possible for only two narrow gaps to exist between the stop hooks 402 and the stop hooks, while, for example, in the design of CN114642793A, the cantilever 404 does not have Designed side by side with or completely alongside the stop hook 402, the proximal end of the protective cover body 401 forms a four-petal structure, so that the stop hook 402 and the cantilever 404 will also form a narrow gap. Once this narrow gap exceeds two, it is easy for the other three gaps to provide retreat space for the cantilever 404 or the stop hook 402, and the other gap becomes very large, so that when the protective cover body 401 is subjected to a force perpendicular to the axial direction, the stop hook 402 will be separated from the needle seat unit 2.

[0070] In addition, it can be seen that the protective cover unit 4 further includes force-guiding protrusions 405 provided on the protective cover body 401. The force-guiding protrusions 405 are provided on opposite sides of the protective cover body 401. When the operator pinches the force-guiding protrusions 405 on opposite sides and pushes the protective cover body 401 toward the proximal end, the force applied perpendicular to the axial direction to the protective cover body 401 can be minimized.

[0071] In addition, it can be seen that the structure of the limiting ring 406 gradually shrinks from the proximal end to the distal end, that is, when the protective cover body 401 is pulled a certain distance toward the proximal end, the limiting ring 406 can clamp the needle seat unit 2 to stop the protective cover body 401 from moving.

[0072] In addition, the stop hook 402 cooperates with the cantilever 404 to keep the protective cover unit 4 in a form of at least partially sleeved on the syringe 1 and at least partially sleeved on the needle seat unit 2.

[0073] In summary, in this embodiment, the method for using the protective prefilled syringe is as follows:

[0074] S01. Pull the protective cover 401 toward the proximal end until it can no longer be pulled;

[0075] S02. Remove the needle sheath 5 and complete the injection;

[0076] S03. Pull the protective cover 401 toward the distal end, so that the cantilever 404 falls and engages with the stop hook 402 to be clamped on the ridge member 201, thereby completely covering the needle.

[0077] Referring to Figure 9, a schematic diagram illustrating the connection between the shield unit and the needle hub unit is shown. The needle hub unit 2 includes a needle hub 202 and a ridge member 201 disposed on the needle hub 202. The ridge member 201 includes a distal stop surface 201a, a proximal stop surface 201b, and a side stop surface 201c for connecting the distal stop surface 201a and the proximal stop surface 201b. The stop hook 402 includes a hook elastic member 402a, a locking member 402b disposed proximal to the hook elastic member 402a, a hook surface 402c disposed distal to the locking member 402b, and an inclined surface 402d disposed proximal to the locking member 402b. The cantilever 404 includes a cantilever elastic member 404a, a lifting surface 404b provided at the proximal end of the cantilever elastic member 404a, and a protrusion 404c provided on the inner side of the cantilever elastic member 404a and used to lift the needle sleeve 5. When the needle guard 5 is sleeved on the needle hub 202, the needle guard 5 can radially push up the protrusion 404c, so that the lifting surface 404b and the distal stop surface 201a are not at the same height. In other words, the distal stop surface 201a cannot restrict the lifting surface 404b. At this time, the protective cover body 401 can be pulled proximally to expose the needle guard 5. After step S02, the needle guard 5 no longer radially pushes up the protrusion 404c. At this time, step S03 is performed. The cantilevered elastic member 404a retracts radially inward due to its elasticity, so that the lifting surface 404b and the distal stop surface 201a are at the same height. At this time, the hook surface 402c of the stop hook 402 engages the ridge member 201 in front and back, thereby fixing the protective cover body 401. In addition, the inclined surface 402d facilitates the stop hook 402 to pass over the inclined groove at the distal end of the syringe 1 and reach the side of the syringe 1. Example

[0078] In this embodiment, the prefilled syringe is identical to that in the first embodiment, and the protective cover is substantially identical to that in the first embodiment, except that:

[0079] Wherein, γ':γ=0.1:1; the angle α of the stop hook 402 is 150°. Example

[0080] In this embodiment, the prefilled syringe is identical to that in the first embodiment, and the protective cover is substantially identical to that in the first embodiment, except that:

[0081] Wherein, γ':γ=0.12:1; the angle α of the stop hook 402 is 140°.

[0082] Comparative Example 1

[0083] In this comparative example, the prefilled syringe is identical to that in the first embodiment, and the protective cover includes the structure described in CN114642793A.

[0084] The prefilled syringes of Examples 1, 2, 3 and Comparative Example 1 were subjected to vertical axial force tests, and the results were as follows:

[0085]

[0086] The test method is to fix the syringe and apply a force perpendicular to the axial direction to the protective cover body 401. The Newton value shown in the table is the magnitude of the applied force. The results show that in Examples 1, 2, and 3, no detachment occurred when the applied force was less than 15N. However, in Comparative Example 1, detachment occurred when the applied force was 10N, indicating that the structure proposed in this application has the function of resisting forces perpendicular to the axial direction. In addition, by comparing Examples 1, 2, and 3, it was found that when γ':γ=0.1:1 and the angle α of the stop hook 402 is 150°, the protective cover has the best function of resisting forces perpendicular to the axial direction.

[0087] In addition, the same or similar reference numerals are used in the drawings and description to refer to the same or similar parts or steps whenever possible. The drawings are presented in simplified form and are not drawn to exact scale. For convenience and clarity only, directional terms such as top, bottom, left, right, upward, above, above, below, below, rear, and front may be used in the drawings. These and similar directional terms should not be construed as limiting the scope of this disclosure in any way.

Claims

1. A protective cover for a prefilled syringe, wherein the prefilled syringe comprises: A syringe (1), used for packaging liquid; A needle seat unit (2) mounted at the distal end of the syringe (1); A needle, mounted on the needle seat unit (2) and connected to the syringe (1) to allow the liquid to flow; A needle sleeve (5) at least partially sleeved on the needle hub unit (2) to completely sleeve the needle; The invention is characterized in that the protective cover for a prefilled syringe comprises a protective cover unit (4) which is at least partially sleeved on the syringe (1) and at least partially sleeved on the needle seat unit (2); the protective cover unit (4) comprises a protective cover body (401), and a stop hook (402) which is arranged at the proximal end of the protective cover body (401) and is used to lift the proximal end surface of the needle seat unit (2); at most two stop hooks (402) are arranged on the protective cover body (401).

2. A protective cover for a prefilled syringe according to claim 1, characterized in that: The protective cover unit (4) further comprises a cantilever groove (403) arranged on the stop hook (402), and a cantilever (404) arranged on the inner side surface of the distal end of the cantilever groove (403) and used to lift the distal end surface of the needle seat unit (2).

3. A protective cover for a prefilled syringe according to claim 1, characterized in that: The angle α of the stop hook (402) is not less than 130°.

4. A protective cover for a prefilled syringe according to claim 1, characterized in that: Two stop hooks (402) are arranged on the protective cover body (401), the distance between the two stop hooks (402) is γ', and the width of the protective cover body (401) is γ, wherein γ':γ=(0.1-0.15):

1.

5. A protective cover for a prefilled syringe according to claim 1, characterized in that: The stop hook (402) comprises a hook elastic member (402a), a snap-fit ​​member (402b) arranged at the proximal end of the hook elastic member (402a), and a hook surface (402c) arranged at the distal end of the snap-fit ​​member (402b).

6. A protective cover for a prefilled syringe according to claim 5, characterized in that: The stop hook (402) further comprises an inclined surface (402d) arranged at the proximal end of the engaging member (402b).

7. A protective cover for a prefilled syringe according to claim 2, characterized in that: The cantilever (404) comprises a cantilever elastic member (404a) and a raised surface (404b) arranged at the proximal end of the cantilever elastic member (404a).

8. A protective cover for a prefilled syringe according to claim 7, characterized in that: The cantilever (404) further comprises a protrusion (404c) which is arranged on the inner side of the cantilever elastic member (404a) and is used to lift up the needle sleeve (5).

9. A protective cover for a prefilled syringe according to claim 1, characterized in that: The protective cover unit (4) further comprises a force-guiding protrusion (405) arranged on the protective cover body (401).

10. A protective cover for a prefilled syringe according to claim 1, characterized in that: The protective cover unit (4) further comprises a limiting ring (406) which is arranged at the distal end of the protective cover body (401) and is used to lift up the needle seat unit (2).

11. A protective cover for a prefilled syringe according to claim 10, characterized in that: The needle seat unit (2) comprises a needle seat (202) and a convex ridge piece (201) arranged on the needle seat (202).

12. A protective cover for a prefilled syringe according to claim 11, characterized in that: The convex ridge member (201) comprises a distal stop surface (201a), a proximal stop surface (201b), and a side stop surface (201c) used for connecting the distal stop surface (201a) and the proximal stop surface (201b).

13. A protective cover for a prefilled syringe according to claim 10, characterized in that: The maximum inner diameter of the limiting ring (406) is smaller than the minimum outer diameter of the distal end stop surface (201a).

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