CN111658898B

CN111658898B - Self-destroying safety syringe

Info

Publication number: CN111658898B
Application number: CN202010708214.XA
Authority: CN
Inventors: 徐立; 徐雪花
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-07-22
Filing date: 2020-07-22
Publication date: 2022-07-22
Anticipated expiration: 2040-07-22
Also published as: CN111658898A

Abstract

The invention provides a self-destruction safety syringe, and belongs to the technical field of medical instruments. The automatic assembling device solves the problem that automatic assembling is achieved, and meanwhile the sealing effect and the needle head seat limiting effect are not enough. The self-destruction safety syringe comprises a syringe, a needle head seat, a sealing element and an expansion element, wherein the needle head seat, the sealing element and the expansion element are all arranged in the front end of the syringe, the sealing element is made of soft materials and is connected to the needle head seat, the sealing element is cylindrical, the rear end of the sealing element extends out of the needle head seat, a blocking part capable of preventing the sealing element from moving forwards is arranged on the needle head seat, the expansion element is arranged at the inner side of the rear end of the sealing element, and the expansion element pushes and presses the rear end of the sealing element against the inner wall of the front end of the syringe in a peripheral expansion mode to enable the rear end of the sealing element to deform under pressure to form sealing. The self-destruction safety syringe has the advantages of strong sealing performance, high stability, less residual liquid medicine after injection and the like.

Description

Self-destroying safety syringe

Technical Field

The invention belongs to the technical field of medical instruments, relates to a syringe, and particularly relates to a self-destruction safety syringe.

Background

Safety syringes with self-destruct function are thus increasingly used on a large scale in order to avoid poor viral infection with unsanitary syringes and to prevent used syringes from being reused or exposed needles to prick others. In order to ensure that the liquid medicine does not leak during injection, a seal is required to be formed between the needle head seat and the needle cylinder; meanwhile, in order to ensure that the needle can be smoothly inserted into the skin of a human body for injection, the movement of the needle holder into the syringe is limited. For example, the applicant has proposed a connection structure of a needle base and a needle cylinder of a safety syringe with patent number 201310724627.7, the front end of the needle cylinder is provided with a connecting cylinder with a slightly smaller outer diameter than the needle cylinder, the needle base is cylindrical and the front end of the needle base is used for being connected with a needle, the connection structure comprises a connecting sheet with elasticity at the rear end of the needle base and a connecting section I at the inner side of the connecting cylinder, the outer side of the connecting sheet is provided with a connecting section II, the connecting cylinder is sleeved on the connecting cylinder, the connecting sheet is provided with an expansion piece, the expansion piece is abutted against the inner side of the connecting sheet and expands the outer side of the connecting sheet to be contacted with the inner side of the connecting cylinder, the connecting section I is clamped with the connecting section II under the expansion action of the expansion piece, thereby limiting the movement of the needle base into the needle cylinder, and a sealing ring is arranged at the outer side of the needle base to ensure the sealing performance between the needle base and the needle cylinder.

However, since the sealing ring is small and cannot be fully automatically assembled in consideration of static electricity, manual assembly is mainly used, so that the assembly efficiency is low and the labor cost is higher and higher. Meanwhile, the needle head seat is made of hard plastics to ensure the use strength, so that the needle head seat can only be limited by matching a non-circular connecting piece with the expansion piece, and the sealing ring can only be arranged at the front end of the needle head seat, so that the residual quantity of liquid medicine in the needle cylinder after injection is more.

For example, a safety syringe disclosed in patent application No. 201210475052.5 has a locking element disposed on the inner side of a needle base, and the locking element is used to press the inner side of the needle base so that the needle base is firmly connected to the syringe barrel through a positioning structure to limit the movement of the needle base into the syringe barrel; at the same time, a seal is formed by the cooperation between the seal and the cylinder. Although the safety syringe does not use a sealing ring to realize automatic assembly, the locking piece is made of soft materials for realizing sealing, and the time from the factory to the use of the safety syringe can be at least 1-2 years, so that the limiting effect of the sealing and the needle seat is easily deteriorated or even failed due to the aging of the locking piece before the safety syringe is used.

The needle seat is connected with the needle and bears the reaction force generated during injection, and if the needle seat is made of soft materials, the needle seat can be seriously bent and deformed during injection, so that the needle seat is not practical.

Disclosure of Invention

The invention aims to solve the problems in the prior art, provides a self-destruction safety syringe, and solves the problems of insufficient sealing effect and needle seat limiting effect when automatic assembly is realized.

The purpose of the invention can be realized by the following technical scheme:

a self-destruction safety syringe comprises a syringe barrel, a needle head seat, a sealing element and an expansion element, wherein the needle head seat, the sealing element and the expansion element are all arranged in the front end of the syringe barrel, the sealing element is made of soft materials and is connected to the needle head seat, the self-destruction safety syringe is characterized in that the sealing element is cylindrical, the rear end of the sealing element extends out of the needle head seat, a blocking part capable of preventing the sealing element from moving forwards is arranged on the needle head seat, the expansion element is arranged at the inner side of the rear end of the sealing element, and the rear end of the sealing element is pressed on the inner wall of the front end of the syringe barrel in a mode of expanding towards the periphery by the expansion element and is deformed under pressure to form sealing.

When the syringe is assembled, the sealing element is connected to the needle head seat, the sealing element is cylindrical, the rear end of the sealing element extends out of the needle head seat, then the expansion element is plugged into the rear end of the sealing element, the sealing element is made of soft materials and has elasticity, so that the expansion element is propped against the inner wall of the rear end of the sealing element, the rear end of the sealing element can be expanded to the periphery to be propped against the inner wall of the front end of the syringe, and the rear end of the sealing element is extruded to deform under the action of the expansion element to form sealing with the inner wall of the front end of the syringe, so that liquid medicine cannot leak outwards; in addition, in the state, the sealing element is not easy to move backwards, and the front end of the sealing element is limited to move forwards by the blocking part on the needle head seat, so that the sealing element can be kept still in the normal injection state, and accordingly, the needle head seat can be limited to move backwards in the front end of the needle cylinder.

In the self-destruction safety syringe, the sealing element is set to be cylindrical by adopting a soft material, so that the sealing effect and the movement limiting effect of the needle head seat are realized simultaneously, and the use of a conventional sealing ring is cancelled, thereby realizing the automatic assembly of the self-destruction safety syringe; in addition, the sealing element is supported by the conventional expansion element, and the expansion element is not easy to age, so that the sealing element can be stably matched with the annular limiting part, and the sealing reliability and the reliability of limiting the backward movement of the needle head seat are improved.

In the self-destruction safety syringe, the inner wall of the front end of the syringe is provided with an annular limiting part, and the rear end of the sealing element is pressed against the annular limiting part and forms deformation matched with the shape of the annular limiting part.

The arrangement of the annular limiting part enables the sealing element to be clamped and matched with the needle cylinder after being deformed, and the reliability is further improved.

In the self-destruction safety syringe, the annular limiting part is a convex ring, and the rear end of the sealing element is covered outside the convex ring.

The annular limiting part is a convex ring, the expansion piece pushes the rear end of the sealing piece outwards to enable the sealing piece to be in contact with the convex ring, and the rear end of the sealing piece deforms to be matched with the convex ring to wrap the convex ring, so that stable sealing is formed between the sealing piece and the needle cylinder and the movement of the needle head seat to the needle cylinder is limited.

In the self-destruction safety syringe, the front side wall of the annular limiting part is inclined backwards, a plurality of inclined matching surfaces are distributed on the outer side of the sealing element close to the rear end part along the circumferential direction, and each matching surface abuts against the front side wall of the annular limiting part.

The front side wall of the annular limiting part is arranged in a backward inclining mode, the matching surface is arranged at the rear end of the sealing element, and when the rear end of the sealing element deforms, the sealing effect and the limiting effect can be further improved by means of the fact that the matching surface is attached to the front side wall of the annular limiting part. Meanwhile, when the expansion piece moves backwards and is separated from the sealing piece, if the rear end of the sealing piece is not completely reset, the guide effect can be formed by the front side wall of the annular limiting part and the matching surface, so that the rear end of the sealing piece automatically shrinks inwards to complete self-destruction.

In the above self-destruction safety syringe, the inner wall of the front end of the syringe is provided with a yielding section in front of the annular limiting part, and the yielding section has a taper.

Through setting up the section of stepping down that has the tapering, can step down for the outside expansion of sealing member rear end, ensure that sealing member rear end portion can furthest improves sealed and restriction effect through warping with the bulge loop cladding.

In the self-destruction safety syringe, as another technical scheme, the annular limiting part is an annular groove, and the rear end part of the sealing element is clamped in the annular groove.

The annular limiting part is an annular groove, and when the expansion piece is plugged into the inner side of the rear end of the sealing piece, the rear end part of the sealing piece can be expanded outwards and clamped into the annular groove, so that stable sealing and stable limitation of the needle head seat to the inside of the needle cylinder are formed.

In the above self-destruction safety syringe, the needle seat comprises a seat body and a positioning head fixedly connected to the rear end face of the seat body, the outer diameter of the seat body is larger than the outer diameter of the positioning head, the outer diameter of the seat body is larger than the inner diameter of the sealing element, the sealing element is sleeved on the positioning head, a seal is formed between the positioning head and the sealing element, and the blocking part is the rear end face of the seat body.

During the assembly, overlap the sealing member on the locating head, the sealing member inner wall can the roof pressure on the locating head outer peripheral face, and here also can form stable sealed for sealed effect is better, and ensures that the sealing member firmly connects on the locating head. The front end of the sealing element is abutted against the rear end face of the seat body, so that the sealing element cannot move forwards.

In the self-destruction safety syringe, the expansion piece comprises a connector inserted into the inner side of the positioning head and a squeezing ring fixedly connected to the outer side of the rear end of the connector, and the squeezing ring is positioned on the inner side of the rear end of the sealing piece and extrudes the rear end of the sealing piece outwards.

In the self-destruction type mounting syringe, the front side wall of the extrusion ring is inclined downwards, and the outer diameter of the extrusion ring is larger than the inner diameter of the sealing element.

The sealing member overlaps earlier on the locating head, then inserts the locating head inboard with the connector of extension piece, and the extrusion ring of extension piece can extrude in the rear end of sealing member under the guide effect of lateral wall in the front simultaneously to make the sealing member rear end can remain outward expansion joint all the time on cyclic annular spacing portion, improved sealed effect and movement limiting effect when realizing automatic equipment.

In the self-destruction safety syringe, the safety syringe further comprises a core bar which is slidably arranged in the needle cylinder, a plurality of buckling pieces are arranged on the inner side of the expansion piece along the circumferential direction, a buckling rod which can be inserted into the connector is arranged at the front end of the core bar, buckling parts which can be extruded between the buckling pieces are arranged on the buckling rod, a blocking part is arranged on the inner side of the rear end part of the positioning head, a clamping part which can be buckled on the blocking part is arranged on the outer side of the front end of the connector, and when the buckling parts extrude the buckling pieces, the core bar is pulled to drive the expansion piece to move backwards so as to enable the sealing piece to be loosened.

When the syringe is normally injected, the expanding piece is propped against the inner wall of the rear end of the sealing piece to expand the sealing piece towards four, and the sealing piece is propped against the annular limiting part to form stable sealing and limit the movement of the needle head seat towards the syringe. After the injection is finished, the buckling rod at the front end of the core rod is inserted into the connector of the expansion piece, and meanwhile, the buckling part on the buckling rod penetrates through the buckling pieces to form the excitation of the self-destruction function of the injector. Then, the core rod is pulled backwards, the expansion piece is buckled on each buckling piece through the buckling parts and moves backwards along with the core rod, so that the extrusion ring of the expansion piece is separated from the sealing piece, and the sealing piece is reset under the action of self elasticity after being loosened by the extrusion ring so as to remove the limitation that the needle head seat moves towards the inside of the needle cylinder; then when the expansion piece moves backwards to the clamping part to be buckled on the resisting part, the expansion piece and the needle head seat form linkage moving backwards, so that the needle head seat is finally pulled to the rear end of the needle cylinder to finish self-destruction.

Compared with the prior art, the self-destruction safety syringe has the following advantages:

1. the sealing element is adopted to simultaneously realize sealing and limit the backward movement of the needle head seat, the use of a sealing ring is cancelled, and the dual-purpose function of one object is realized, so that the automatic assembly of the injector can be realized;

2. the backward movement position of the needle head seat is limited, namely the sealing position, so that the residual quantity of the liquid medicine in the needle cylinder after the injection is finished is reduced;

3. the sealing element expansion piece is supported and is not easy to age, so that the sealing element can be stably matched with the annular limiting part, and the sealing reliability and the reliability of limiting the backward movement of the needle head seat are improved.

Drawings

Fig. 1 is a partial sectional view of the self-destruction safety syringe according to the first embodiment.

Fig. 2 is an enlarged view of the front end of the cylinder of fig. 1.

Figure 3 is a schematic view of the initial installation of the seal and needle hub into the forward end of the barrel according to one embodiment.

FIG. 4 is a cross-sectional view of a fastening portion passing through a fastening sheet to activate self-destruction according to an embodiment.

FIG. 5 is a schematic sectional view showing the core rod being pulled back after the self destruction is triggered according to the first embodiment.

FIG. 6 is a partial sectional view of the second embodiment of the self-destruction safety syringe.

In the figure, 1, a syringe; 1a, an annular limiting part; 1b, a yielding section; 2. a needle head seat; 2a, a seat body; 2a1, ribs; 2a2, blocking portion; 2b, a positioning head; 2b1, a stopper; 3. a seal member; 3a, a matching surface; 4. an expansion member; 4a, a connector; 4a1, a clip part; 4b, an extrusion ring; 4c, a buckling piece; 5. a core bar; 5a, a buckling rod; 5a1, a snap; 6. a rubber plug; 7. a needle.

Detailed Description

The following are specific embodiments of the present invention and are further described with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

Example one

As shown in figure 1, the self-destruction safety syringe comprises a syringe 1, a core rod 5, a needle seat 2, a sealing element 3 and an expansion element 4, wherein the core rod 5 is arranged in the syringe 1 in a sliding way, a rubber plug 6 is fixed at the position of the core rod 5 close to the front end part, and the needle seat 2, the sealing element 3 and the expansion element 4 are all arranged in the front end of the syringe 1. The needle seat 2 comprises a seat body 2a, the front end face of the seat body 2a is abutted against the inner side wall of the front end part of the needle cylinder 1, a plurality of convex strips 2a1 are distributed on the outer side of the seat body 2a along the circumferential direction, a plurality of anti-rotation strips are correspondingly distributed on the inner wall of the front end of the needle cylinder 1, each convex strip 2a1 is inserted into the space between two adjacent anti-rotation strips along the front-back direction, and the needle seat 2 can be prevented from rotating by means of the cooperation of the convex strips 2a1 and the anti-rotation strips. In order to ensure the use strength, the needle head seat 2 is still made of hard plastics, and the front end of the seat body 2a is fixedly provided with a needle head 7 extending out of the needle cylinder 1.

As shown in fig. 2 and fig. 3, the rear end of the seat body 2a is fixedly connected with a cylindrical positioning head 2b, the sealing element 3 is cylindrical and made of soft material, specifically PE, silica gel or EVA, etc., and the sealing element 3 is sleeved outside the positioning head 2b to form a seal. Specifically, the outer peripheral surface of the positioning head 2b and the inner peripheral surface of the seal 3 are both cylindrical surfaces, and the outer diameter of the positioning head 2b is larger than the inner diameter of the seal 3, so that when the seal 3 is sleeved outside the positioning head 2b, the inner peripheral surface of the seal 3 is pressed against the outer peripheral surface of the positioning head 2b under the action of self elasticity, and sealing is formed between the two surfaces. The outer diameter of the seat body 2a is larger than that of the positioning head 2b, and the front end face of the sealing element 3 is abutted against the rear end face of the seat body 2 a.

As shown in fig. 2 and fig. 3, the rear end of sealing element 3 extends out of positioning head 2b, needle holder 2 is provided with a blocking portion 2a2 capable of preventing sealing element 3 from moving forward, and blocking portion 2a2 is specifically the rear end face of holder body 2 a. The expansion piece 4 is made of hard plastic, the expansion piece 4 is arranged at the inner side of the rear end of the sealing element 3, and the expansion piece 4 presses the rear end of the sealing element 3 against the inner wall of the front end of the needle cylinder 1 in a peripheral expansion mode and enables the rear end of the sealing element to deform under pressure to form sealing. Specifically, the front inner wall of the syringe 1 is provided with an annular limiting part 1a, and the rear end of the sealing member 3 is pressed against the annular limiting part 1a and forms deformation matched with the shape thereof. The expansion piece 4 comprises a connector 4a inserted into the inner side of the positioning head 2b and a squeezing ring 4b fixedly connected to the outer side of the rear end of the connector 4a, and the squeezing ring 4b is positioned on the inner side of the rear end of the sealing element 3 and extrudes the rear end of the sealing element 3 outwards. The front end side wall of the pressing ring 4b is inclined downward, and the outer diameter of the pressing ring 4b is larger than the inner diameter of the seal 3. During assembly, the sealing element 3 is firstly sleeved on the positioning head 2b to form sealing, the rear end of the sealing element 3 extends out of the positioning head 2b, then the connector 4a of the expansion element 4 is inserted into the inner side of the positioning head 2b, and the extrusion ring 4b is extruded into the rear end part of the sealing element 3 under the guiding action of the front side wall, so that the rear end of the sealing element 3 is expanded outwards and is propped against the annular limiting part 1a to generate deformation to form sealing.

As shown in fig. 1 and 2, a plurality of fastening pieces 4c are provided on the inner side of the connector 4a along the circumferential direction, the front end of the core bar 5 has a fastening rod 5a capable of passing through the connector 4a, and the fastening rod 5a has a fastening portion 5a1 capable of being pushed out from between the fastening pieces 4 c. The inner side of the rear end of the positioning head 2b is provided with a resisting part 2b1, the outer side of the front end of the connecting head 4a is provided with a clamping part 4a1 which can be buckled on the resisting part 2b1, and when the buckling part 5a1 extrudes each buckling piece 4c, the core rod 5 is pulled, and the clamping part 4a1 buckles the resisting part 2b1, and then the expanding piece 4 is driven to move backwards to loosen the sealing element 3.

Further, as shown in fig. 2 and 3, the annular stopper 1a is a convex ring, and the rear end of the seal 3 is covered outside the convex ring. The front side wall of the annular limiting part 1a inclines backwards, a plurality of backwards-inclined matching surfaces 3a are distributed on the outer side of the sealing element 3 close to the rear end part along the circumferential direction, and each matching surface 3a is attached to the front side wall of the annular limiting part 1 a. The expanding piece 4 presses the rear end of the sealing member 3 outwards, so that the matching surface 3a is attached to the upper side wall of the annular limiting part 1a, and then the rear end part of the sealing member 3 deforms in the same shape as the annular limiting part 1a, so that the rear end of the sealing member 3 is equivalent to covering the annular limiting part 1a, and the sealing effect is better. The inner wall of the front end of the needle cylinder 1 is provided with a yielding section 1b in front of the annular limiting part 1a, and the yielding section 1b has a taper.

As shown in figure 1, under the injection state, the sealing element 3 is clamped on the annular limiting part 1a under the action of the expansion element 4, so that the movement of the needle head seat 2 to the syringe 1 is limited, and meanwhile, the sealing effect is formed.

As shown in fig. 4, after the injection is completed, the engaging rod 5a at the front end of the stem 5 is inserted into the connecting head 2b, and the engaging portion 5a1 is pushed through the engaging pieces 4c, so that the expansion member 4, the sealing member 3 and the inner wall of the cylinder 1 are still in the initial engagement state.

Then, as shown in fig. 5, the core rod 5 is pulled back to self-destroy the syringe, the buckling parts 5a1 are buckled on the buckling pieces 4c to make the expanding piece 4 move back together with the core rod 5, so that the extrusion ring 4b on the expanding piece 4 is pulled out from the back end of the sealing piece 3, the back end of the sealing piece 3 resets under the action of self-elasticity to separate from the ring-shaped limiting part 1a, thereby releasing the limitation of the needle head base 2 moving into the syringe 1. When the expansion piece 4 moves backwards to the clamping part 4a1 buckled on the resisting part 2b1 of the connector 2b, the expansion piece 4 and the needle seat 2 form linkage along the front and back direction, and the needle seat 2 moves backwards together to finally pull the needle 7 into the needle cylinder 1 for self-destruction.

Example two

The structure and principle of this embodiment are basically the same as those of the first embodiment, and the differences are as follows: in the present embodiment, the annular stopper portion 1a is an annular groove, and the end of the seal member 3 is fitted into the annular groove.

EXAMPLE III

The structure and principle of this embodiment are basically the same as those of the first embodiment, and the differences are as follows: in the present embodiment, as shown in fig. 6, the engagement piece 4c is provided inside the extrusion ring 4 b.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.

Claims

1. A self-destruction safety syringe comprises a syringe (1), a needle head seat (2), a sealing piece (3) and an expansion piece (4), wherein the needle head seat (2), the sealing piece (3) and the expansion piece (4) are all arranged in the front end of the syringe (1), the sealing piece (3) is made of soft materials and is connected to the needle head seat (2), the sealing piece (3) is cylindrical, the rear end of the sealing piece extends out of the needle head seat (2), a blocking part (2a2) capable of preventing the sealing piece (3) from moving forwards is arranged on the needle head seat (2), the expansion piece (4) is arranged at the inner side of the rear end of the sealing piece (3), and the expansion piece (4) pushes and presses the rear end of the sealing piece (3) against the inner wall of the front end of the syringe (1) in a mode of expanding towards the periphery and enables the rear end of the sealing piece to deform under pressure to form sealing.

2. The self-destruction safety syringe according to claim 1, wherein the front inner wall of the syringe (1) is provided with an annular limiting part (1a), and the rear end of the sealing member (3) is pressed against the annular limiting part (1a) and forms a deformation matching with the shape of the annular limiting part (1 a).

3. The self-destruction safety syringe according to claim 2, wherein the annular limiting part (1a) is a convex ring, and the rear end of the sealing element (3) is covered outside the convex ring.

4. The self-destruction safety syringe according to claim 3, wherein the front side wall of the annular limiting part (1a) is inclined backwards, a plurality of fitting surfaces (3a) inclined backwards are circumferentially distributed on the outer side of the sealing member (3) near the rear end part, and each fitting surface (3a) is attached to the front side wall of the annular limiting part (1 a).

5. A self-destruction safety syringe according to claim 4, wherein the front inner wall of the syringe (1) has a relief section (1b) in front of the annular limiting part (1a), and the relief section (1b) has a taper.

6. A self-destruction safety syringe according to claim 2, wherein the annular limiting part (1a) is an annular groove, and the rear end of the sealing member (3) is engaged in the annular groove.

7. The self-destruction safety syringe according to claim 1, wherein the needle holder (2) comprises a holder body (2a) and a positioning head (2b) fixedly connected to the rear end face of the holder body (2a), the outer diameter of the holder body (2a) is larger than the outer diameter of the positioning head (2b), the outer diameter of the positioning head (2b) is larger than the inner diameter of the sealing element (3), the sealing element (3) is sleeved on the positioning head (2b) and forms a seal therebetween, and the blocking portion (2a2) is the rear end face of the holder body (2 a).

8. A self-destruction safety syringe according to claim 7, wherein the expansion element (4) comprises a connector (4a) inserted inside the positioning head (2b) and a squeeze ring (4b) attached to the outside of the rear end of the connector (4a), the squeeze ring (4b) being located inside the rear end of the sealing element (3) and squeezing the rear end of the sealing element (3) outwards.

9. Self-destruction safety syringe according to claim 8, characterized in that the front side wall of the squeeze ring (4b) is inclined downwards, the outer diameter of the squeeze ring (4b) being greater than the inner diameter of the seal (3).

10. The self-destruction safety syringe according to claim 9, wherein the safety syringe further comprises a core rod (5) slidably disposed in the syringe (1), the inner side of the expansion member (4) is circumferentially provided with a plurality of buckling pieces (4c), the front end of the core rod (5) is provided with a buckling rod (5a) capable of being inserted into the connector (4a), the buckling rod (5a) is provided with buckling parts (5a1) capable of being squeezed between the buckling pieces (4c), the inner side of the rear end of the positioning head (2b) is provided with a resisting part (2b1), the outer side of the front end of the connector (4a) is provided with a clamping part (4a1) capable of being fastened on the resisting part (2b1), when the buckling parts (5a1) push through the buckling sheets (4c), the core bar (5) is pulled to drive the expansion piece (4) to move backwards to loosen the sealing piece (3) before the clamping part (4a1) is buckled on the resisting part (2b 1).