CN111658895A

CN111658895A - Retractable safety syringe

Info

Publication number: CN111658895A
Application number: CN202010545875.5A
Authority: CN
Inventors: 徐立; 徐雪花
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-06-16
Filing date: 2020-06-16
Publication date: 2020-09-15

Abstract

The invention provides a retractable safety syringe, and belongs to the technical field of medical instruments. The problems of poor controllability and high operation requirement on operators in the prior art are solved. The retraction type safety syringe comprises a syringe, a needle head seat, a push rod in the syringe and a rubber plug on the push rod, wherein an annular groove is formed in the inner side of the rubber plug, a check sheet is arranged on the push rod, a self-destruction structure is arranged between the front part of the push rod and the needle head seat, a plurality of action parts capable of abutting against the rear end face of the rubber plug are arranged on the outer side of the check sheet, the vertical distance from the outermost side of each action part to the central axis of the push rod is smaller than the inner radius of the annular groove, and when the front end of the rubber plug abuts against the inner wall of the front end of the syringe or the rear end of the needle head seat, the push rod is pushed to. The retractable safety syringe has the advantages of low operation requirement, high controllability, convenience in use and the like.

Description

Retractable safety syringe

Technical Field

The invention belongs to the technical field of medical instruments, and relates to an injector, in particular to a retractable safety injector.

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. At present, safety syringes with self-destruction function are basically of retraction type, and generally include a syringe, a needle seat with a needle head, a push rod arranged in the syringe, and a rubber plug sleeved on the push rod, when injection is completed (i.e. the rubber plug is hit to the zero line position of the syringe), the front end of the push rod is inserted into the needle seat, at this time, the push rod is continuously pushed to make the front end of the rubber plug extruded and the push rod can continuously move forward, so that the push rod and the needle seat can be connected together under the action of a self-destruction structure to activate the self-destruction function of the syringe, then the needle head and the needle seat are pulled into the syringe through the push rod, and then the push rod is broken to make the needle head and the needle seat limited in the syringe to complete self-destruction, specifically refer to a safety self-destruction syringe disclosed in patent application No. 201010202077.9.

At present, most of safety syringes in the market are designed to have a self-destruction function triggered when a rubber plug hits a zero line, namely, medical staff push a push rod to complete the injection of liquid medicine, and the front end of the push rod is directly connected with a needle head seat through a self-destruction structure. However, this method has a drawback that the medical staff needs to discharge air before drawing the liquid medicine into the syringe, and the hospital staff is used to directly drive the rubber plug to the zero line of the syringe (because the optimal air discharge effect can be obtained) in this step, but due to the above arrangement, the syringe is often damaged by itself before being used, and the syringe cannot be used, so that the controllability is poor, and the operation requirement on the operator is high.

In order to solve the above problems, one of the ways that can be easily conceived by those skilled in the art is a disposable syringe and a plunger for a disposable syringe as disclosed in patent application No. 201210188526.8, which is to prevent a rubber plug from being pushed back to a stop, so that the rubber plug is not self-destructed when it is hit to a zero line of a syringe, and at the same time, the plunger is deformed backward when the plunger is further pushed after completion of injection, so that the plunger can be further moved forward to activate self-destruction;

another way is a safety trigger device in a safety syringe as disclosed in patent application No. 201410025398.4, which is to set a plurality of trigger protrusions, support the rubber plug by the trigger protrusions during injection to prevent the rubber plug from backing up, and deform the rubber plug by the action of the trigger protrusions after injection is finished, so that the push rod can move forward to trigger self-destruction;

or as disclosed in patent application No. 201320292188.2, the core bar structure of the self-destruction syringe is provided with a plurality of easily deformable support bars on the core bar, the total support force of each support bar is greater than the liquid medicine reaction force applied by the core bar during injection to ensure the support of the rubber plug, and the core bar is continuously pushed after the injection is finished to completely deform or break each support bar, so that the push rod can continuously move forward to trigger the self-destruction.

Disclosure of Invention

The invention aims to solve the problems in the prior art, provides a retractable safety syringe, and solves the problems of poor controllability and high operation requirement on operators.

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

the retractable safety syringe comprises a syringe, a needle head seat clamped in the front end of the syringe, a push rod arranged in the syringe in a sliding manner, and a rubber plug sleeved on the push rod, wherein an annular groove is formed in the inner side of the rubber plug, a backstop sheet is arranged on the push rod, and a self-destruction structure is arranged between the front part of the push rod and the needle head seat.

Before injection, the push rod is pushed forwards to the position where the front end of the rubber plug abuts against the inner wall of the front end of the syringe, namely the zero line of the syringe is reached, so that air in the syringe is exhausted, but the self-destruction structure of the injector is not excited. Then, the medical staff sucks the liquid medicine into the syringe, and pushes the push rod forwards again until the front end of the rubber plug abuts against the inner wall of the syringe to complete the injection of the liquid medicine. At the moment, the medical staff continues to push the push rod, the front end of the rubber plug is limited by the inner wall of the front end of the needle cylinder or the rear end of the needle head seat to move, and each action part on the backstop sheet can extrude the rear end of the rubber plug. Because the perpendicular distance from the outermost side of each action part to the central axis of the push rod is smaller than the inner radius of the annular groove, the position acted by each action part just corresponds to the annular groove, so that the contact part of the rear end of the rubber plug and each action part can be extruded to deform in the annular groove through each action part, and the push rod can have a certain moving distance before the safety syringe is excited to be self-destructed.

The rear end of the rubber plug is extruded by the action part to deform towards the annular groove before the self-destruction is triggered, namely, a state is added between two states of exhausting operation of medical personnel and triggering the safety syringe, so that the medical personnel are not easy to directly trigger the self-destruction when the push rod is driven to the bottom, the operation requirement on the medical personnel is greatly reduced, the controllability of the syringe in use is improved, the operation trouble of a user is avoided, and the user can use the syringe according to a habitual operation method. Compared with the first mode in the prior art, the retraction type safety syringe adopts a mode that the pushing part deforms to enable the push rod to continuously move forwards, and the retraction type safety syringe adopts a mode that the rear end of the rubber plug deforms, and belongs to different working principles; and in the conventional thinking of the personnel in the field, the deformation of the front end of the whole rubber plug is realized, but the deformation of the rear end of the extrusion rubber plug into the annular groove is not realized in the scheme.

In the above retractable safety syringe, the action portion is in a shape of a sharp corner or a rounded corner.

The shape of the sharp angle or the round angle leads the force acted on the rear end surface of the rubber plug to be more concentrated, especially the end part can stably extrude the rear end of the rubber plug to deform towards the annular groove, and the operation requirement on medical staff is reduced.

In the above retractable safety syringe, the plunger is injection molded, the anti-retraction piece is a regular polygon piece with an even number of sides, and the action part is each corner of the regular polygon piece with the even number of sides.

The push rods are all formed by injection molding, and the mold opening is carried out in the simplest mode of half-opening. Therefore, the anti-return sheet is set to be a regular polygon sheet with even number of sides, so that the push rod in the retraction type safety syringe can still open the die in a split mode, and the convenience of molding is ensured; meanwhile, each angle on the regular polygon piece with the even number of edges can be directly used as an action part, so that the operation controllability is improved, and the operation requirement on medical staff is reduced.

In the second or third method of the prior art, no matter the excitation bosses or the elastic supporting bars are directly formed by the split-die method in actual production, the excitation bosses or the elastic supporting bars are additionally connected to the push rod after the push rod is formed, so that the production difficulty is low, and the reliability in use is poor.

In the above retractable safety syringe, as another technical scheme, the push rod is injection molded, the anti-retraction sheet is a diamond sheet with one diagonal length larger than the other diagonal length, and the action part is an angle connected with a longer diagonal in the diamond sheet.

By adopting the arrangement of the diamond-shaped sheet structure, the push rod can be simultaneously used for opening the mold in a split mode and enabling the rear end of the rubber plug to deform into the annular groove.

In the above retractable safety syringe, as another technical solution, the push rod is injection molded, the anti-retraction plate is an elliptical plate, and the action portions are two ends of the major axis of the elliptical plate.

In foretell retraction type safety syringe, the push rod on be equipped with the separation blade that is located the annular groove and can follow its removal, separation blade rear end face and the distance between the terminal surface before the stopping piece be H1, the annular groove is close to the distance between one side cell wall of stopping piece and the plug rear end face and is H2, H1 is greater than H2 and makes formation can supply the clearance of stepping down of plug lower extreme to the annular groove internal deformation between separation blade and the annular groove is close to one side cell wall of stopping piece.

The abdicating gap provides a space for the rubber plug to deform into the annular groove when the rear end of the rubber plug is just extruded, and the blocking piece is prevented from blocking the deformation of the rubber plug into the annular groove.

In foretell retraction formula safety syringe, the push rod include the body of rod, the terminal surface has the platform that forms clearance fit with the cylinder before the body of rod, the preceding terminal surface center of platform links firmly the cross connecting block of transversal personally submitting, the separation blade links firmly in the preceding terminal surface of connecting block, the backstop piece is the slice and links firmly on the connecting block, the preceding terminal surface center of separation blade has linked firmly the lock pole, self-destruction structure locates between lock pole and the syringe needle seat.

In the above retraction type safety syringe, the distance between the rear end face of the anti-retraction plate and the front end face of the platform is H3, and the distance H2 between the groove wall of one side of the annular groove close to the anti-retraction plate and the rear end face of the rubber plug is greater than H3.

The distance H2 between the groove wall of one side of the annular groove close to the anti-return piece and the rear end face of the rubber plug is greater than the distance H3 between the anti-return piece and the platform, so that the phenomenon that the annular groove is excessively deformed inwards to enable the anti-return piece to be directly poked into the annular groove can be avoided, and the operation controllability and the use reliability of the retractable safety syringe are ensured.

In the above retractable safety syringe, the self-destruction structure comprises a buckling part arranged on the inner side of the needle head seat and a buckling ring arranged on the outer side of the buckling rod, the buckling part is sheet-shaped and inclines forwards, the outer peripheral surface of the buckling ring has taper, and the buckling ring is positioned on the inner side of the buckling part when the front end of the rubber plug is abutted against the inner wall of the front end of the syringe or the rear end of the needle head seat.

When the injection is finished, the front end of the rubber plug is abutted against the inner wall of the front end of the syringe or the rear end of the needle head seat, and the buckling ring is positioned on the inner side of the buckling part at the moment, which means that the buckling ring does not pass through the buckling part, namely, the self-destruction is not triggered.

In the above retractable safety syringe, the distance between the front end face of the blocking piece and the wall of the annular groove on the side away from the anti-retraction piece is H4, when the front end of the rubber plug abuts against the inner wall of the front end of the syringe or the rear end of the needle seat, the distance between the rearmost position of the buckling ring and the foremost position of the buckling part is H5, and H4 is at least 1.2 times of H5.

The distance H4 between the baffle plate and the side wall of the annular groove departing from the retaining plate is at least 1.2 times the distance H5 between the rearmost position of the buckling ring and the foremost position of the buckling part at the end of injection, so that the push rod can have a small distance of moving forwards before the self-destruction is triggered to improve the operation controllability.

Compared with the prior art, the retraction type safety syringe has the following advantages:

1. the rear end of the rubber plug is extruded by the action part to deform into the annular groove before the self-destruction is triggered, namely, a state is added between two states of exhausting operation of medical personnel and triggering the safety syringe, so that the medical personnel are not easy to directly trigger the self-destruction when the push rod is driven to the bottom, the operation requirement on the medical personnel is greatly reduced, the controllability of the syringe in use is improved, the operation trouble of a user is avoided, and the user can use the syringe according to a habitual operation method;

2. the push rod keeps the production mode of the split die, so that the structure is simpler, the manufacture is more convenient, and the cost is low.

Drawings

FIG. 1 is a schematic view of the present retractable safety syringe at the end of an air purge or injection according to one embodiment.

Fig. 2 is a partial enlarged view of the push rod and the rubber plug in fig. 1.

FIG. 3 is a transverse cross-sectional view of the connection block near the backstop tab in one embodiment.

Fig. 4 is a schematic view of the retractable safety syringe at positions H1, H2, H3, H4 and H5.

FIG. 5 is a schematic view of the retractable safety syringe in accordance with one embodiment of the present invention when self-destruction is triggered.

Fig. 6 is a partial enlarged view of the push rod and the rubber plug in fig. 5.

FIG. 7 is a schematic view of the engagement between the withdrawing stop piece and the rear end face of the rubber plug according to an embodiment.

FIG. 8 is a transverse sectional view of the joint block near the check ring in the second embodiment.

FIG. 9 is a schematic view of the second embodiment of the engagement between the withdrawing stop piece and the rear end face of the rubber plug.

In the figure, 1, a syringe; 1a, a matching part; 1b, a stop block; 1c, zero bit line; 2. a needle head seat; 2a, a buckling part; 3. a push rod; 3a, a baffle plate; 3b, a backstop sheet; 3b1, acting part; 3c, a rod body; 3c1, platform; 3c2, break position; 3d, connecting blocks; 3e, buckling the rod; 3e1, snap ring; 4. a rubber plug; 4a, an annular groove; 4b, through holes; 5. a abdication gap; 6. a needle head;

h1, the distance between the rear end face of the stop piece and the front end face of the backstop piece;

h2, the distance between the groove wall of one side of the annular groove close to the backstop sheet and the rear end face of the rubber plug;

h3, the distance between the rear end face of the anti-return sheet and the front end face of the platform;

h4, the distance between the front end face of the blocking piece and the groove wall of one side of the annular groove departing from the anti-return piece;

h5, distance between the back end face of the buckling ring and the front end face of the buckling part at the end of injection.

Detailed Description

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

Example one

As shown in fig. 1, the retractable safety syringe comprises a syringe 1, a needle base 2, a push rod 3, a rubber plug 4 and a needle 6. The front end of the needle cylinder 1 has a convex matching part 1a, the needle seat 2 is clamped in the matching part 1a (the specific matching relationship between the two can refer to a connection structure of the needle seat and the needle cylinder of the safety syringe disclosed in patent application No. 201310724627.7, which is not described herein), and the needle 6 is fixed at the front end of the needle seat 2. The push rod 3 is arranged in the syringe 1 in a sliding way, the rubber plug 4 is in a block shape and is sleeved on the push rod 3, and a self-destruction structure is arranged between the front part of the push rod 3 and the needle head seat 2.

As shown in fig. 1 and 2, the plunger 3 specifically includes a rod 3c, a platform 3c1 is provided on the front end surface of the rod 3c for forming a clearance fit with the syringe 1, and a breaking point 3c2 is provided on the rod 3c near the platform 3c 1. The connecting block 3d with a cross-shaped cross section is fixedly connected to the center of the front end face of the platform 3c1, the baffle 3a is fixedly connected to the front end face of the connecting block 3d, the buckling rod 3e is fixedly connected to the center of the front end face of the baffle 3a, when the injection is finished, the front end of the buckling rod 3e is inserted into the needle head seat 2, and the self-destruction structure is arranged between the buckling rod 3e and the needle head seat 2. A stop block 1b is arranged in the rear end of the syringe 1, and the rear end surface of the platform 3c1 can be propped against the stop block 1b when the push rod 3 is pulled backwards. Furthermore, the self-destruction structure comprises a buckling part 2a arranged on the inner side of the needle seat 2 and a buckling ring 3e1 arranged on the outer side of the buckling rod 3e, wherein the buckling part 2a is sheet-shaped and inclines forwards, and the peripheral surface of the buckling ring 3e1 has taper.

As shown in fig. 1, 2, 3 and 8, the rubber plug 4 is sleeved on the buckling rod 3e, the inner side of the rubber plug 4 is provided with an annular groove 4a, the baffle plate 3a is located in the annular groove 4a, the groove width of the annular groove 4a in the front-back direction is larger than the thickness of the baffle plate 3a, so that the baffle plate 3a can move forward along the annular groove 4a when the push rod 3 moves forward to realize self-destruction, and the radius of the baffle plate 3a is smaller than the inner diameter of the annular groove 4a, wherein the baffle plate 3a is a circular plate. The center of the rear end face of the rubber plug 4 is provided with a through hole 4b, the through hole 4b is communicated with the annular groove 4a, and the connecting block 3d penetrates through the through hole 4 b. The connecting block 3d is also fixedly connected with a check piece 3b, and the check piece 3b is positioned between the blocking piece 3a and the platform 3c 1. The outside of the stopping sheet 3b is provided with a plurality of action parts 3b1 which are propped against the rear end face of the rubber plug 4, the vertical distance from the outermost side of each action part 3b to the central axis of the push rod 3 is less than the inner radius of the annular groove 4a, the action part 3b1 is in a sharp angle shape or a circular angle shape, when the front end of the rubber plug 4 is propped against the inner wall of the front end of the needle cylinder 1, the push rod 3 is pushed to extrude the rear end of the rubber plug 4 into the annular groove 4a before the buckling part 2a extrudes the buckling ring 3e1 (namely before self-destruction is triggered). Further, the push rod 3 is formed by injection molding, the anti-return piece 3b is a regular polygon piece with even number of sides, the acting part 3b1 is each corner of the regular polygon piece with even number of sides, the anti-return piece 3b is a square piece in the embodiment, and the side length of the anti-return piece 3b is more than 1.2 times larger than the maximum size of the connecting block 3d, so as to ensure that the anti-return piece 3b has certain elasticity.

As shown in fig. 4, in the present embodiment, the distance between the blocking plate 3a and the anti-retreat plate 3b is H1, the distance between the groove wall of the annular groove 4a on the side close to the anti-retreat plate 3b and the rear end surface of the rubber plug 4 is H2, and H1 is greater than H2. The distance H1 between separation blade 3a and the backstop piece 3b is greater than the shape slot and is close to the distance H2 between one side cell wall of backstop piece 3b and the plug 4 rear end face, so when the plug 4 rear end face leans on with each effect portion 3b1 on the backstop piece 3b counterbalance, can make separation blade 3a rear end face be higher than the annular slot 4a and be close to one side cell wall of backstop piece 3b to form and to supply the clearance 5 of stepping down of the deformation in the annular slot 4a of plug 4 rear end. The distance between the anti-return piece 3b and the platform 3c1 is H3, and H3 is greater than the distance H2 between the groove wall of the annular groove 4a close to the anti-return piece 3b and the rear end face of the rubber plug 4. In addition, the distance between the blocking piece 3a and the groove wall of the side of the annular groove 4a departing from the anti-return piece 3b is H4, when the front end of the rubber plug 4 abuts against the inner wall of the front end of the syringe 1 or the rear end of the needle seat 2, the distance between the rearmost position of the buckling ring 3e1 and the foremost position of the buckling part 2a is H5, and H4 is at least 1.2 times of H5.

Before injection, the push rod 3 is pushed forwards to the position where the front end of the rubber plug 4 abuts against the inner wall of the front end of the syringe 1 to reach the zero line 1c on the syringe 1, at the moment, air in the syringe 1 is exhausted, meanwhile, the push rod 3 and the rubber plug 4 do not move relatively, the needle head seat 2 and the push rod 3 are not connected together under the action of a self-destruction structure, so that the self-destruction function of the injector is not excited, and the state of the injector after air exhaust is shown in fig. 1. Then, the needle 6 is inserted into the vial, and then the plunger 3 is pulled backward to draw the liquid medicine into the cylinder 1. Then, the push rod 3 is pushed forward again to perform the injection of the liquid medicine. In the process of air discharge or liquid medicine injection, the rubber plug 4 is supported by the anti-return sheet 3b, but because the front end of the rubber plug 4 is not blocked by the inner wall of the syringe 1, the action part 3b1 does not generate enough extrusion force on the rubber plug 4 to deform the rubber plug 4 into the annular groove 4a under the state, and therefore, the push rod 3 and the rubber plug 4 do not move relatively.

After the injection is finished, the front end of the rubber plug 4 abuts against the inner wall of the front end of the needle cylinder 1 again, and then the push rod 3 is continuously pushed forwards. At this time, since the forward moving path of the rubber plug 4 is blocked by the inner wall of the front end of the syringe 1, and the pushing force applied to the pushing rod 3 acts on the rear end surface of the rubber plug 4 by virtue of the acting portions 3b1 on the anti-return piece 3b, a yielding gap 5 is formed between the blocking piece 3a and one side wall of the annular groove 4a close to the anti-return piece 3b, so that the blocking piece 3a does not support the rear end of the rubber plug 4, and thus each acting portion 3b1 can extrude the rear end of the rubber plug 4, so that the portion of the rear end of the rubber plug 4 close to the through hole 4b can deform into the annular groove 4a, which is equivalent to the extending deformation of the outer side portion of the rear end of the rubber plug 4 toward the anti-return piece 3b and the platform 3c1, as shown in fig. 5 and 6, in this state, the pushing rod 3 can move forward for a certain distance, but the engaging ring 3e1 does not extrude from. After the rear end of the rubber plug 4 is deformed into the annular groove 4a, the pushing force is continuously applied to further move the pushing rod 3 forward, so that the buckling ring 3e1 on the buckling rod 3e is pushed through the center of the buckling part 2a to trigger self-destruction. Finally, the push rod 3 is pulled back only, the rear end face of the buckling ring 3e1 is buckled on the buckling part 2a, so that the push rod 3 is connected with the needle seat 2 to form linkage, therefore, the push rod 3 together with the needle seat 2 and the needle 6 is retracted into the needle cylinder 1, and then the push rod 3 is broken at the self-breaking position 3c2 to complete the final self-destruction. In the process that the action part 3b1 presses the rear end of the rubber plug 4 to deform into the annular groove 4a, the action part 3b1 slightly deforms backwards, but the pushing rod 3 can move forwards after the injection is finished, so that the rear end of the rubber plug 4 deforms, but not the anti-return piece 3b deforms.

The rear end of the rubber plug 4 is extruded by the action part 3b1 to deform towards the annular groove 4a before the self-destruction is triggered, which is equivalent to that a state is added between the two states of exhausting operation of medical personnel and triggering the safety syringe, so that the medical personnel is not easy to directly trigger the self-destruction when the push rod 3 is driven to the bottom, the operation requirement on the medical personnel is greatly reduced, the controllability of the syringe in use is improved, the trouble of a user in operation is avoided, and the user can use the syringe according to the habitual operation method.

Example two

The structure and principle of this embodiment are basically the same as those of the first embodiment, except that: as shown in fig. 8 and 9, in the present embodiment, the check flap 3b is a diamond-shaped flap in which one diagonal length is longer than the other diagonal length, and the acting portion 3b1 is the corner of the diamond-shaped flap to which the longer diagonal is connected.

EXAMPLE III

The structure and principle of this embodiment are basically the same as those of the first embodiment, except that: in the present embodiment, the retaining pieces 3b are elliptical pieces, and the action portions 3b1 are at both end positions where the major axes of the elliptical pieces are located.

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. Retraction type safety syringe, including cylinder (1), needle seat (2) of joint in cylinder (1) front end, slide and set up push rod (3) in cylinder (1) and cup joint plug (4) on push rod (3), plug (4) inboard be equipped with annular slot (4a), be equipped with on push rod (3) and stop piece (3b), be equipped with self-destruction structure between push rod (3) front portion and needle seat (2), its characterized in that, stop piece (3b) outside have a plurality of can with plug (4) rear end face support against effect portion (3b1), the outside of each effect portion (3b1) to push rod (3) the central axis vertical distance be less than the inner radius of annular slot (4a), when plug (4) front end and cylinder (1) front end inner wall or needle seat (2) rear end support against mutually, promote push rod (3) can make each effect portion (3b1) with annular slot (4) rear end to support against annular slot (4) rear end before self-destruction structure works 4a) And (4) internal extrusion deformation.

2. A retractable safety syringe as claimed in claim 1, wherein the action portion (3b1) is in the form of a sharp corner or a rounded corner.

3. A retractable safety syringe as claimed in claim 2, wherein the plunger (3) is formed by injection molding, the retaining piece (3b) is a regular polygon piece having an even number of sides, and the acting portion (3b1) is each corner of the regular polygon piece having an even number of sides.

4. A retractable safety syringe as claimed in claim 2, wherein the plunger (3) is injection moulded, the retaining tab (3b) is a diamond shaped tab having one diagonal of greater length than the other, and the active portion (3b1) is the corner of the diamond shaped tab to which the longer diagonal is connected.

5. A retractable safety syringe as claimed in claim 2, wherein the plunger (3) is injection moulded, the retaining tab (3b) is an elliptical tab and the active portion (3b1) is at the end of the major axis of the elliptical tab.

6. A retractable safety syringe as claimed in claim 1, 2, 3, 4 or 5, wherein the plunger (3) is provided with a stopper (3a) which is located in the annular groove (4a) and can move along the annular groove, the distance between the rear end face of the stopper (3a) and the front end face of the anti-retraction plate (3b) is H1, the distance between the groove wall of the annular groove (4a) at the side close to the anti-retraction plate (3b) and the rear end face of the rubber plug (4) is H2, and H1 is greater than H2, so that a abdicating gap (5) for the lower end of the rubber plug (4) to deform into the annular groove (4a) is formed between the stopper (3a) and the groove wall of the annular groove (4a) at the side close to the anti-retraction plate (3 b).

7. A retractable safety syringe as claimed in claim 6, wherein the plunger (3) comprises a rod body (3c), the front end face of the rod body (3c) is provided with a platform (3c1) which is in clearance fit with the syringe (1), the center of the front end face of the platform (3c1) is fixedly connected with a connecting block (3d) with a cross-shaped cross section, the blocking piece (3a) is fixedly connected with the front end face of the connecting block (3d), the backstop piece (3b) is in a sheet shape and is fixedly connected with the connecting block (3d), the center of the front end face of the blocking piece (3a) is fixedly connected with a buckling rod (3e), and the self-destruction structure is arranged between the buckling rod (3e) and the needle seat (2).

8. A retractable safety syringe as claimed in claim 7, wherein the distance between the rear end face of the retaining tab (3b) and the front end face of the platform (3c1) is H3, and the distance H2 between the groove wall of the annular groove (4a) on the side close to the retaining tab (3b) and the rear end face of the rubber plug (4) is greater than H3.

9. A retractable safety syringe as claimed in claim 7, wherein the self-destruction structure comprises a buckling portion (2a) disposed inside the needle holder (2) and a buckling ring (3e1) disposed outside the buckling rod (3e), the buckling portion (2a) is sheet-shaped and inclined forward, the outer peripheral surface of the buckling ring (3e1) has a taper, when the front end of the rubber plug (4) abuts against the inner wall of the front end of the syringe (1) or the rear end of the needle holder (2), the buckling ring (3e1) is located inside the buckling portion (2 a).

10. A retractable safety syringe as claimed in claim 9, wherein the distance between the front end face of the catch (3a) and the wall of the annular groove (4a) on the side away from the retaining tab (3b) is H4, the distance between the rearmost position of the engaging ring (3e1) and the foremost position of the engaging portion (2a) is H5 when the front end of the rubber plug (4) abuts against the inner wall of the front end of the syringe (1) or the rear end of the needle holder (2), and H4 is at least 1.2 times as large as H5.