A safety syringe

Abstract

The present invention relates to a safety syringe, comprising: a syringe barrel, on the inner wall surface of which a first groove is provided; a needle hub, on the outer wall surface of which at least two first clamping claws are provided, and the first clamping claws are clamped in the first groove; a plunger rod, which is hermetically and slidably arranged in the syringe barrel; at least two second clamping claws protruding radially are provided at the proximal end of the needle hub, a limiting member is provided at the distal end of the plunger rod, and the second clamping claws and the limiting member are in abutment through a slope surface; a third clamping claw protruding radially is provided on the needle hub; in the injection state, when the plunger rod slides towards the distal end, the second clamping claws are forced to slide along the slope surface and deformed radially of the syringe barrel under the action of the slope surface so as to cross over the limiting member and hook on the limiting member, and the third clamping claw abuts against the inner wall of the syringe barrel to prevent the needle hub from sliding relative to the syringe barrel; in the injection state or the retraction state, the first clamping claws are driven by the sliding of the plunger rod to disengage from the first clamping grooves. This can prevent the problem that the entire needle hub is pushed out due to excessive force applied to the needle hub.

Description

Technical Field

[0001] The present invention belongs to the technical field of medical devices, and particularly relates to a safety syringe. Background Art

[0002] Injection is an indispensable medical means in modern medicine, and a syringe is an essential medical device in medical treatment. If a syringe is not artificially damaged and is reused, it will cause cross-infection to patients or users, such as cross-infection caused by the transmission of some blood viruses.

[0003] Therefore, currently, generally, disposable self-destructive safety syringes are used in the market. However, many syringes require a great deal of force to complete injection when pushing forward, which may cause pain to the person being injected. At the same time, the structure of the syringe is complex, resulting in difficult manufacturing and being not suitable for mass production. Moreover, in the injection process of many safety syringes, if too much force is applied, the entire needle seat may fall off, resulting in problems such as syringe damage and reagent loss, which not only affect the use but also waste resources and increase costs. Summary of the Invention

[0004] Therefore, the present invention aims to solve the technical problem that the needle seat of a safety syringe is easily pushed out of the needle tube, and thus provides a safety syringe, including:

[0005] A syringe barrel, on the inner wall surface of which there is a first groove;

[0006] A needle seat, on the outer wall surface of which there are at least two first clamping claws, and the first clamping claws are clamped in the first groove;

[0007] A plunger rod, which is sealed and slidably arranged in the syringe barrel;

[0008] At the proximal end of the needle seat, there are at least two second clamping claws protruding radially, and at the distal end of the plunger rod, there is a limiting member. The second clamping claws and the limiting member are in abutment through a slope surface; on the needle seat, there is a third clamping claw protruding radially;

[0009] In the injection state, when the plunger rod slides towards the distal end, it forces the second clamping claws to slide along the slope surface and be deformed radially in the syringe barrel under the action of the slope surface to cross over the limiting member and hook on the limiting member, and the third clamping claw abuts against the inner wall of the syringe barrel to prevent the needle seat from sliding relative to the syringe barrel;

[0010] In the injection state or the retraction state, the first clamping claws are driven by the sliding of the plunger rod to disengage from the first clamping grooves.

[0011] Preferably, the limiting member is a limiting snap ring;

[0012] In the injection state, the second claw is radially contracted under the action of the slope surface in the syringe barrel and slides into the inner hole of the limit snap ring to cross the limit snap ring and hook on the limit snap ring.

[0013] Preferably, at least two first relief holes are provided on the side wall of the limit snap ring;

[0014] In the injection state, the second claws extend into the first relief holes one by one to hook on the side wall of the limit snap ring.

[0015] Preferably, the needle seat includes:

[0016] An annular body, the outer wall surface of which is sealingly arranged on the inner wall of the syringe barrel, and the inner hole of the annular body is for installing the needle tube;

[0017] At least two legs, two of which are evenly distributed on the same circumference, and the distal end of any one of the legs is fixed on the proximal cross section of the annular body;

[0018] The first claw, the second claw and the third claw are respectively and convexly fixed on the outer wall surface of the leg, the first claw is located between the second claw and the annular body, and the third claw is located between the first claw and the second claw;

[0019] In the injection state, the second claw slides along the slope surface to drive the leg to swing inwards in the radial direction of the syringe barrel, driving the first claw to disengage from the first groove.

[0020] Preferably, one end of the annular body is recessed downward with a fixing groove, and a fixing protrusion is provided on the inner wall of the syringe barrel, and the fixing protrusion is located in the fixing groove.

[0021] Preferably, the groove wall of the first groove at its proximal end is a first limiting slope inclined from the groove opening towards the groove bottom.

[0022] Preferably, the installation cavity of the syringe barrel includes a needle seat chamber and a transition chamber communicating with the needle seat chamber, and the inner diameter of the transition chamber is larger than the inner diameter of the needle seat chamber to form a first step structure between the needle seat chamber and the transition chamber;

[0023] The needle seat is arranged in the needle seat chamber, and the legs are arranged in the inner hole of the first step structure so that the second claws extend into the transition chamber.

[0024] Preferably, there are two legs, and they are evenly distributed on the same circumference;

[0025] In the injection state, the radial dimension of the two third claws is larger than the inner hole dimension of the first step structure.

[0026] Preferably, a rubber stopper is sleeved outside the core rod, and the core rod is slidably and sealingly arranged in the transition chamber through the rubber stopper.

[0027] Preferably, the proximal end of the rubber stopper is fixed on the core rod, and the distal end of the rubber stopper is tightly pressed against the end face of the proximal end of the first step structure under the extrusion force exerted when the core rod slides towards the distal end;

[0028] At least one annular sealing protrusion is arranged on the outer wall surface of the rubber stopper, and the sealing protrusion slidably and sealingly abuts against the inner wall surface of the transition chamber along with the core rod.

[0029] Preferably, the first step structure includes a first step and a second step distributed in a trapezoidal shape from the distal end towards the proximal end;

[0030] In the injection state, the third claw abuts against the step surface of the first step, the distal end face of the limit snap ring abuts against the proximal end face of the third claw, and the distal end face of the rubber stopper abuts against the step surface of the second step.

[0031] Preferably, the installation cavity further includes a limit chamber communicated with the proximal end of the transition chamber;

[0032] The inner diameter of the limit chamber is larger than the inner diameter of the transition chamber to form a second step structure between the transition chamber and the limit chamber;

[0033] The safety syringe further includes an elastic annular snap ring fixed on the outer wall surface of the core rod, and both the distal end face and the proximal end face of the elastic annular snap ring are provided with teeth; a limit protrusion is arranged on the inner wall surface of the limit chamber, and the outer diameter of the elastic annular snap ring in the free state is at least larger than the inner diameter of the proximal end of the transition chamber and larger than the inner diameter of the limit protrusion;

[0034] In the retraction state, the distal end of the elastic annular snap ring is restricted in the limit chamber by the proximal end of the second step structure, and the proximal end of the elastic annular snap ring abuts against the limit protrusion.

[0035] Preferably, it further includes a sleeve sleeved outside the core rod and located in the limit chamber;

[0036] An annular boss is arranged on the outer wall surface of the sleeve, and the outer peripheral wall of the annular boss fits against the inner wall surface of the limit chamber;

[0037] In the retraction state, the elastic annular snap ring is driven by the sliding of the core rod, and the teeth at the proximal end of the elastic annular snap ring abut against the annular boss to push the sleeve to slide towards the limit protrusion and abut against the limit protrusion.

[0038] Preferably, the second stepped structure includes a third step and a fourth step which are distributed in a stepped manner from the distal end towards the proximal end;

[0039] In the injection state, the distal end of the ferrule abuts against the step surface of the third step, and the annular boss abuts against the step surface of the fourth step; in the retraction state, the teeth at the distal end of the elastic annular snap ring can abut against the step surface of the third step.

[0040] Preferably, the transition chamber includes a straight tube section and a first reduced-diameter section fixed to the proximal end of the straight tube section, and the inner diameter of the first reduced-diameter section gradually decreases from its distal end towards the proximal end;

[0041] The outer diameter of the elastic annular snap ring in the free state is greater than the inner diameter of the first reduced-diameter section and less than or equal to the inner diameter of the straight tube section.

[0042] Preferably, an annular groove is provided on the outer wall surface of the core rod, and a breakable position is formed at the bottom of the annular groove.

[0043] The technical solution of the present invention has the following advantages:

[0044] 1. For the safety syringe provided by the present invention, when the core rod slides towards the distal end for injection, it forces the second claw to slide along the slope surface. The slope surface exerts a force on the second claw, which has a first component and a second component in the radial and axial directions of the syringe barrel respectively. Under the action of the first component, the second claw contracts or expands radially along the syringe barrel, and under the action of the second component, the second claw slides to cross the limiting member; afterwards, the force exerted by the slope surface on the second claw is withdrawn, and the second claw resets radially to hook on the limiting member to achieve the locking of the needle seat and the core rod. During this process, the sliding of the core rod indirectly exerts a force on the first claw, causing the first claw to slide out of the first groove; alternatively, after injection, when the core rod is retracted, since the second claw is locked on the limiting member, when the core rod slides towards the proximal end, it exerts a pulling force towards the proximal end on the needle seat, forcing the first claw to slide out of the first groove to achieve the separation of the needle seat and the syringe barrel; afterwards, the needle seat slides towards the proximal end as a whole with the core rod, shortening the retraction stroke of the core rod, requiring a small retraction pulling force, and at the same time eliminating the need for a locking ring, making the structure of the entire safety syringe simple and facilitating the production of the safety syringe.

[0045] 2. For the safety syringe provided by the present invention, when the core rod slides towards the distal end for injection, the third claw abuts against the inner wall of the syringe barrel, preventing the needle seat from sliding relative to the syringe barrel, thereby preventing the entire needle seat from being pushed out due to excessive force, and reducing problems such as syringe damage and resource waste caused by product quality production issues. In the retraction state, the third claw does not contact the inner wall of the syringe barrel, avoiding obstruction to the recycling of the syringe.

[0046] 3. For the safety syringe provided by the present invention, after the stepped locking teeth of the elastic annular snap ring enter the locked state during self-destruction, if a relatively large thrust is applied again, the locking teeth will generate tension towards the periphery from the upper locking position, making the locked state more secure. Unless the syringe structure is completely damaged, it is impossible for the needle seat to return to the transition chamber. At the same time, it can also prevent the needle seat from being completely detached from the syringe barrel under a relatively large pulling force. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0048] Figure 1 Schematic perspective view of the safety syringe provided in Embodiment 1 of the present invention;

[0049] Figure 2 is Figure 1 explosion schematic view of the safety syringe;

[0050] Figure 3 is Figure 1 schematic view of the structure of the needle seat;

[0051] Figure 4 is Figure 1 explosion schematic view of the partial core rod, rubber stopper and limit ring;

[0052] Figure 5 is Figure 1 schematic view of the structure of the ferrule;

[0053] Figure 6a is Figure 1 longitudinal sectional view of the syringe barrel;

[0054] Figure 6b is Figure 6a stereoscopic schematic view of the longitudinal section of the proximal end of the syringe barrel;

[0055] Figure 6c is Figure 6a schematic view of the longitudinal section of the proximal end of the syringe barrel;

[0056] Figure 6d is Figure 6a schematic view of the longitudinal section of the distal end of the syringe barrel;

[0057] Figure 7a is Figure 1Schematic diagram of the state of the distal end of the plunger rod and the needle hub of the safety syringe when not in use;

[0058] Figure 7b is Figure 1 Schematic diagram of the state of the proximal end of the plunger rod and the ferrule of the safety syringe when not in use;

[0059] Figure 8 is Figure 1 Schematic diagram of the state of the distal end of the plunger rod and the needle hub of the safety syringe after injection;

[0060] Figure 9 is Figure 1 Schematic diagram of the state of the proximal end of the plunger rod and the proximal end of the syringe barrel after the plunger rod is retracted after the safety syringe is completely injected. Detailed implementation manners

[0061] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0062] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0063] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0064] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0065] Embodiment 1

[0066] This embodiment provides a safety syringe, asFigure 1 and Figure 2 As shown, it includes a syringe barrel 1, a needle hub 3, a needle tube 4 and a plunger rod 2. Among them, the syringe barrel 1 has an installation cavity.

[0067] As Figure 2 and Figure 6d shown, a first groove 111 is provided on the inner wall surface of the installation cavity, and the distal end of the needle hub 3 is suitable for installing the needle tube 4. As Figure 3 shown, at least two first claws 34 are provided on the outer wall surface of the needle hub 3, and the first claws 34 are clamped in the first groove 111; the plunger rod 2 is arranged in the syringe barrel 1 in a sealed and slidable manner; at least two second claws 33 protruding radially are provided at the proximal end of the needle hub 3, a limiting member is provided at the distal end of the plunger rod 2, and the second claws 33 and the limiting member can be abutted against each other through a slope surface, and a third claw 35 protruding radially is also provided on the needle hub 3.

[0068] In this embodiment, the proximal end and the distal end are referenced with respect to the person operating the syringe. For example, the side close to the operating end of the plunger rod is the proximal end, and on the contrary, the side of the plunger rod close to the needle tube is the distal end.

[0069] When the plunger rod 2 slides towards the distal end for injection, it forces the second claws 33 to slide along the slope surface. The slope surface exerts a force on the second claws 33, which has a first component and a second component in the radial and axial directions of the syringe barrel 1 respectively. Under the action of the first component, the second claws 33 contract or expand radially along the syringe barrel 1, and under the action of the second component, the second claws 33 slide axially along the syringe barrel 1 to cross the limiting member; afterwards, the force exerted by the slope surface on the second claws 33 is withdrawn, and the second claws 33 radially reset under their own deformation ability to hook on the limiting member, realizing the locking of the needle hub 3 and the plunger rod 2.

[0070] During this process, the plunger rod 2 slides, thereby indirectly exerting a force on the first claws 34, causing the first claws 34 to slide out of the first groove 111 (the first way for the first claws to disengage from the first groove); alternatively, after injection, when the plunger rod 2 is retracted, since the second claws 33 are locked on the limiting member, when the plunger rod 2 slides towards the proximal end, a pulling force towards the proximal end is exerted on the needle hub 3, forcing the first claws 34 to slide out of the first groove 111 (the second way for the first claws to disengage from the first groove), and the needle hub 3 is separated from the syringe barrel 1.

[0071] The needle hub 3 slides integrally towards the proximal end along with the plunger rod 2, shortening the retraction stroke of the plunger rod 2, and the retraction pulling force is small. At the same time, without the setting of a locking ring, the structure of the entire safety syringe is simple.

[0072] As Figure 3 and Figure 4As shown, the second jaw 33 protrudes radially outwardly from the needle holder 3, and the limiting member is a limiting snap ring 21 fixed on the core rod 2. The end surface of the proximal end of the second jaw 33 is a first slope 331, and a second slope 211 is provided on the distal end of the limiting snap ring 21. The first slope 331 and the second slope 211 are in parallel abutment, and the inclination angles of the first slope 331 and the second slope 211 are the same. In Figure 3 and Figure 4 In and

[0073] , the first slope 331 and the second slope 211 are inclined from the outside to the inside and downward in the radial direction of the syringe barrel 1.

[0073] During the injection process, the core rod 2 drives the limiting snap ring 21 to slide towards the distal end. The second slope 211 of the limiting snap ring 21 slides along the first slope of the second jaw 33. The second jaw 33 is radially contracted under the action of the second slope 211 to slide into the inner hole of the limiting snap ring 21. When the first slope 331 of the second jaw 33 is separated from the second slope 211 of the core rod 2, the second jaw 33 is no longer affected by the acting force of the second slope 211 of the limiting snap ring 21, but radially resets, so that the second jaw 33 hooks on the proximal end surface of the limiting snap ring 21, realizing the locking fit between the needle holder 3 and the core rod 2.

[0074] As a deformation, for the above slopes, the second slope 211 can be provided only on the limiting snap ring 21, or the first slope 331 can be provided only on the second jaw 33. During the sliding process of the core rod 2, the second jaw 33 can also be radially contracted and deformed under the action of the slope, so that the second jaw 33 hooks on the limiting snap ring 21.

[0075] In the injection state, the third jaw 35 abuts against the inner wall of the syringe barrel 1 to prevent the needle holder 3 from sliding relative to the syringe barrel 1, thereby preventing the entire needle holder 3 from being pushed out due to excessive force, and reducing problems such as syringe damage and resource waste caused by product quality production problems. In the retraction state, the third jaw 35 does not contact the inner wall of the syringe barrel 1 to avoid hindering the recovery of the syringe.

[0076] Regarding the structure of the limiting snap ring 21, as Figure 4 shown, preferably, at least two first relief holes 212 are provided on the side wall of the limiting snap ring 21. For example, the above-mentioned second jaws 33 are two, and correspondingly, the first relief holes 212 are two. In the injection state, the second jaws 33 extend into the first relief holes 212 one by one to hook on the side wall of the limiting snap ring 21, ensuring the firmness of the locking between the second jaws 33 and the limiting snap ring 21 on the core rod 2.

[0077] As a variation, when there are multiple second claws 33, for example, there are three, four, five, six or more second claws 33, and the multiple second claws 33 are distributed on the same circumference, and correspondingly there are multiple first clearance holes 212, the second claws 33 extend into the first clearance holes 212 one by one to hook on the side wall of the limiting clamp 21.

[0078] For the structure of the needle seat 3, preferably, as shown in FIG. Figure 3 As shown, the needle seat 3 includes an annular body 31 and at least two legs 32. The outer wall of the annular body 31 is sealed in the installation cavity, and the inner hole of the annular body 31 is used for the needle tube 4 to be installed, wherein the two legs 32 are evenly distributed on the same circumference, and the distal end of any leg 32 is fixed to the proximal end surface of the annular body 31.

[0079] The first claw 34, the second claw 33 and the third claw 35 are protruded and fixed on the outer wall surface of the leg 32 in a one-to-one correspondence, the first claw 34 is located between the second claw 33 and the annular body 31, the third claw 35 is located between the first claw 34 and the second claw 33, and the first claw 34, the third claw 35 and the second claw 33 form a three-level claw on the leg 32. Optimally, the annular body 31, the leg 32, the first claw 34, the third claw 35 and the second claw 33 of the needle holder 3 are integrally formed and are all made of medical plastics, so that the safety syringe has a simple structure and is easy to process and manufacture, such as injection molding. Of course, other medical materials can also be used.

[0080] Preferably, there are multiple legs 32 on the needle seat 3, and preferably, multiple legs 32 are evenly distributed on the same circumference and fixed on the proximal end surface of the annular body 31; correspondingly, there are multiple first claws 34, third claws 35 and second claws 33, and the first claws 34, third claws 35 and second claws 33 are fixed on the outer wall surface of the legs 32 in a one-to-one correspondence. Through the arrangement of multiple legs 32 and second claws 33, when the second claws 33 are hooked and locked with the limiting clamp ring 21, multiple locking positions are formed to further ensure the firmness of the locking of the needle seat 3 and the core rod 2. When the syringe is in the injection state, multiple third claws 35 abut against the inner wall of the syringe 1 to form multiple blocking positions, further ensuring that the needle seat 3 and the syringe 1 slide.

[0081] like Figure 3 As shown, one end of the annular body 31 is recessed with a fixing groove 313, and the inner wall of the syringe 1 is provided with a fixing protrusion (not shown). When the annular body 31 is located in the syringe 1, the fixing protrusion is fixed in the fixing groove 313 to prevent the needle seat 3 from rotating in the injection state or the withdrawal state, resulting in the failure of the locking of the needle seat 3 and the core rod 2.

[0082] Since there is a certain distance between the two legs 32, when the second claw 33 slides, it is subjected to the force of the second slope surface 211 on the limit retaining ring 21, which can drive the two legs 32 to swing radially inward relative to the annular body 31 around their distal ends. The legs 32 drive the first claw 34 to move radially inward, forcing the first claw 34 to disengage from the first groove 111, so as to realize that in the injection state, the sliding of the core rod drives the first claw 34 to slide out of the first groove 111; thus, in the state where the core rod 2 is retracted, only a very small pulling force is required to make the second claw 33 slide along the second slope surface 211, and the separation of the first claw 34 from the first groove 111 is realized during the sliding process, facilitating the retraction of the needle seat 3 along with the core rod 2. That is, the legs 32 are swung radially inward by the radial force, forcing the first claw 34 to separate from the first groove 111.

[0083] Preferably, for example, in Figure 6d the groove wall on the proximal side of the proximal end of the first groove 111 can be a guiding arc surface inclined from the groove opening towards the groove bottom, that is, the first limiting slope 111b. The guiding arc surface is inclined downward and towards the axis of the syringe 1, which further facilitates the first claw 34 to slide out of the first groove 111 along the first limiting slope when the legs swing inward.

[0084] As a deformation, the above-mentioned needle seat 3 may not be provided with legs 32, and the first claw 34, the second claw 33 and the third claw 35 are directly provided on the annular body 31; during the injection process, the second slope surface 211 of the core rod 2 exerts a force on the second claw 33, but cannot drive the first claw 34 to disengage from the first groove 111; at this time, the groove wall at the proximal end of the first groove 111 is the above-mentioned first limiting slope 111b. During the retraction process, when a pulling force towards the proximal end is applied to the core rod 2, since the needle seat 3 is locked with the core rod 2, under this pulling force, the first claw 34 on the needle seat 3 will slide out of the first groove 111 along the guiding arc surface, that is, the first claw 34 is separated from the first groove 111 by the axial force, realizing the retraction action. During the injection process, the third claw 35 is always in contact with the inner wall of the syringe 1 to prevent sliding between the needle seat 3 and the syringe 1.

[0085] For the first groove 111, as Figure 6d shown, the groove wall at the distal end of the first groove 111 is also a third slope surface 111a inclined from the groove opening towards the groove bottom; correspondingly, a fourth slope surface that fits and abuts against the third slope surface 111a is provided on the outer wall surface of the first claw 34. That is, the outer peripheral surface at the distal end of the first claw 34 is a conical surface, and the conical surface of the first claw 34 fits and abuts against the third slope surface 111a of the first groove 111, increasing the sealing performance at the connection between the first claw 34 and the first groove 111.

[0086] Preferably, the inner wall shape of the first groove 111 matches the outer wall shape of the first claw 34, so that the first claw 34 is inserted into the first groove 111, and the two are completely fitted together, increasing the sealing performance at the connection.

[0087] For the installation cavity of the syringe 1, as Figure 6a shown, the installation cavity includes a needle seat chamber 11 and a transition chamber 12 that are sequentially arranged and connected from the distal end to the proximal end. The inner diameter of the transition chamber 12 is larger than that of the needle seat chamber 11 to form a first step structure 9 between the needle seat chamber 11 and the transition chamber 12. Among them, the needle seat 3 is installed in the needle seat chamber 11, and the above-mentioned first groove 111 is provided on the inner wall surface of the needle seat chamber 11.

[0088] Preferably, an annular step is provided on the inner wall surface of the needle seat chamber 11. Correspondingly, as Figure 3 and Figure 8 shown, a radially outwardly protruding outer edge is provided on the outer peripheral wall of the above-mentioned annular body 31, and a second annular groove 311 is provided on the outer edge. The outer edge abuts against the step surface of the annular step, and the sealing ring 312 is snap-fitted in the second annular groove 311, thereby realizing the sealed connection between the needle seat 3 and the needle seat chamber 11; at the same time, the annular step limits the needle seat 3 in the needle seat chamber 11. The proximal end of the needle tube 4 is inserted into the inner hole of the annular body 31, and its distal end extends out of the distal end of the syringe 1.

[0089] As Figure 2 and shown in FIG. 7, when there are two legs 32, the two legs 32 are evenly distributed on the same circumference, that is, the two legs 32 and the third claws 35 provided on the legs 32 are axially symmetrically arranged, and the radial dimension formed by the two third claws 35 is larger than the inner hole dimension of the first step structure 9, so that the third claws 35 abut against the first step structure 9.

[0090] As Figure 1 and Figure 2 shown, a protective sleeve 8 is also sleeved on the outer wall surface of the syringe 1 where the needle seat chamber 11 is located, playing a protective role for the needle tube 4. There are various fixing methods for the protective sleeve 8 and the syringe 1, which can be threaded fit or snap fit, or other existing fitting methods can be used.

[0091] For the plunger rod 2, as Figure 7a shown, a rubber stopper 5 is sleeved outside the plunger rod 2, and the plunger rod 2 is slidably and sealingly arranged in the transition chamber 12 through the rubber stopper 5. The leg is inserted into the inner hole of the first step structure 9, so that the second claw 33 extends into the transition chamber 12.

[0092] As Figure 7aAs shown, preferably, the proximal end of the rubber stopper 5 is fixed on the core rod 2. When the core rod 2 slides towards the distal end, the distal end of the rubber stopper 5 is tightly pressed against the end face of the proximal end of the first stepped structure 9 under the extrusion force. At least one annular sealing protrusion 51 is provided on the outer wall surface of the rubber stopper 5, and the sealing protrusion 51 is slidably and sealingly abutted against the inner wall surface of the transition chamber 12 along with the core rod 2.

[0093] Preferably, as Figure 4 and Figure 7a shown, a third annular groove 22 is provided on the outer wall surface of the core rod 2, and an annular mating protrusion 52 protruding radially inward is provided on the inner wall surface of the rubber stopper 5. The mating protrusion 52 is fitted in the third annular groove 22. Two sealing protrusions 51 are provided on the outer wall surface of the rubber stopper 5, and one sealing protrusion 51 is located on the outer wall surface of the distal end of the rubber stopper 5. The distal end of the rubber stopper 5 is sleeved on the outer wall surface of the limit snap ring 21 and does not extend beyond the distal end face of the limit snap ring 21.

[0094] As Figure 6d shown, the first stepped structure 9 includes a first step 91 and a second step 92 distributed in a trapezoidal shape from the distal end towards the proximal end. As Figure 8 shown, in the injection state, the third claw 35 abuts against the step surface of the first step 91, the distal end face of the limit snap ring 21 abuts against the proximal cross section of the third claw 35. Along the axial direction of the syringe barrel 1, the rubber stopper 5 is squeezed and deformed, and the distal end face of the rubber stopper 5 abuts against the step surface of the second step 92. The sealing protrusion 51 is sealed on the inner wall surface of the transition chamber 12, so as to achieve a sealed connection between the core rod 2 and the inner wall surface of the transition chamber 12 in the injection state. Among them, the third claw 35 abuts against the step surface of the first step 91, which can prevent the needle seat 3 from displacing during injection and avoid the overall detachment of the needle seat 3 from the syringe barrel 1 due to excessive force.

[0095] Further preferably, as Figure 8 shown, the outer diameter of the limit snap ring 21 is equal to the inner hole diameter of the first step 91, and the outer diameter of the limit snap ring 21 can be equal to the radial dimension of the two third claws 35. The distal wall surface of the limit snap ring 21 is attached to the proximal surface of the third claw 35, and the axial height of the limit snap ring 21 is equivalent to the axial height of the inner hole of the first step 91, further making the fitting between the two closer.

[0096] As Figure 6a shown, the installation cavity further includes a limit chamber 13 communicating with the proximal end of the transition chamber 12. The inner hole diameter of the limit chamber 13 is larger than the inner hole diameter of the transition chamber 12, so as to form a second stepped structure 10 between the transition chamber 12 and the limit chamber 13.

[0097] As Figure 4 and Figure 7aAs shown, the safety syringe also includes an elastic annular clamping ring 6 fixed on the outer wall surface of the core rod 2. For example, the outer peripheral wall of the core rod 2 is provided with a first truncated cone and a second truncated cone, and an annular clamping groove 24 is formed between the two truncated cones. The elastic annular clamping ring 6 is sleeved in the annular clamping groove 24, and the two ends of the elastic annular clamping ring 6 are respectively abutted on the first truncated cone and the second truncated cone. The distal end surface and the proximal section of the elastic annular clamping ring 6 are both provided with clamping teeth 62. Figure 6b and Figure 6c As shown, an annular limiting protrusion 131 is provided on the inner wall surface of the limiting chamber 13 .

[0098] For the elastic annular snap ring 6, if Figure 4 As shown, the elastic annular snap ring 6 is provided with a notch 61 on its outer peripheral wall, so that the elastic annular snap ring 6 has radial deformation space; the outer diameter of the elastic annular snap ring 6 in a free state is at least larger than the inner diameter of the proximal end of the transition chamber 12, and larger than the inner diameter of the limiting protrusion 131.

[0099] During the injection process, the elastic annular snap ring 6 slides toward the distal end along with the core rod 2. When the elastic annular snap ring 6 is squeezed by the inner wall surface of the proximal end of the transition chamber 12, the two ends of the notch 61 of the elastic annular snap ring 6 approach each other in the circumferential direction, and the radial contraction of the elastic annular snap ring 6 increases the deformation space relative to the existing pawl. The outer wall surface of the elastic annular snap ring 6 abuts against the inner wall surface of the transition chamber 12, reducing the friction between the elastic annular snap ring 6 and the inner wall surface of the transition chamber 12. Therefore, during the withdrawal process, when the core rod 2 drives the elastic annular snap ring 6 to slide toward the proximal end, the required pulling force is small.

[0100] When the elastic annular snap ring 6 slides into the limiting chamber 13, due to the absence of radial extrusion force, the two ends of the notch 61 of the elastic annular snap ring 6 are separated from each other in the circumferential direction, and the elastic annular snap ring 6 is restored to the initial state, so that the distal end of the elastic annular snap ring 6 is limited in the limiting chamber 13 by the proximal end face of the transition chamber 12 (i.e. the proximal end face of the second step structure 10), and its proximal end abuts on the limiting protrusion 131. When the core rod 2 slides toward the distal end again, the end face of the elastic annular snap ring 6 forms a surface abutment with the proximal end face of the transition chamber 12, which is not easy to damage the elastic annular snap ring 6 and makes it difficult for the core rod 2 to slide toward the distal direction for a second time, ensuring that the core rod 2 cannot be injected or withdrawn relative to the syringe 1 again, so that the safety performance of the safety syringe is high.

[0101] After the step-shaped latching teeth 62 of the elastic annular snap ring 6 complete the safety self-destruction and enter the locked state, if a large thrust is applied again, the latching teeth 62 will generate tension from the upper locked position to the outer periphery, making the locked state more secure. Unless the syringe structure is completely damaged, it is impossible for the needle seat 3 to return to the transition chamber 12. At the same time, it can also prevent the needle seat 3 from being completely separated from the syringe 1 due to a large pulling force.

[0102] Preferably, for example, as Figure 6b shown, the transition chamber 12 includes a straight tube section 122 and a first reduced diameter section 121 fixed to the proximal end of the straight tube section 122. The inner diameter of the first reduced diameter section 121 gradually decreases from its distal end towards the proximal end; the outer diameter of the elastic annular snap ring 6 in the free state is greater than the inner diameter of the first reduced diameter section and less than or equal to the inner diameter of the straight tube section 122. That is, the inner wall surface of the first reduced diameter section 121 forms a second limiting slope.

[0103] When the core rod 2 is retracted, the elastic annular snap ring 6 first slides in the straight tube section 122 of the transition chamber along with the core rod 2, and the elastic annular snap ring 6 does not undergo radial contraction; until the elastic annular snap ring 6 slides into the inner hole of the first reduced diameter section 121, the elastic annular snap ring 6 is radially contracted inward by the extrusion force of the inner hole wall of the first reduced diameter section, until the core rod 2 drives the elastic annular snap ring 6 into the limiting chamber 13, the elastic annular snap ring 6 is radially reset, the distal end of the elastic annular snap ring 6 is restricted in the limiting chamber 13 by the proximal end of the second step structure 10, and its proximal end abuts against the limiting protrusion 131. Since the inner diameter of the distal end of the second step structure 10 is equal to the inner diameter of the proximal end of the first reduced diameter section, thus, with the cooperation of the limiting protrusion 131 and the second step structure 10, the core rod 2 is restricted on the syringe barrel 1, and the core rod 2 cannot slide towards the proximal end and the distal end, avoiding the reuse of the safety syringe. During the entire retraction process, the elastic annular snap ring 6 only undergoes radial retraction under extrusion in the first reduced diameter section, further reducing the friction force between the outer peripheral wall of the elastic annular snap ring 6 and the transition chamber 12 and reducing the retraction pulling force.

[0104] Further preferably, as Figure 2 、 Figure 5 and Figure 7b shown, the safety syringe further includes a sleeve 7 sleeved outside the core rod 2 and located in the limiting chamber 13; an annular boss 71 is provided on the outer wall surface of the sleeve 7, the outer peripheral wall of the annular boss 71 fits on the inner wall surface of the limiting chamber 13, and the outer diameter of the elastic annular snap ring 6 in the free state is greater than the inner diameter of the sleeve 7 and less than the outer diameter of the annular boss 71.

[0105] During the retraction process of the core rod 2, after the elastic annular snap ring 6 gradually enters the limiting chamber 13 along with the core rod 2 and is reset, the elastic annular snap ring 6 is sleeved on the sleeve 7 and the proximal end of the elastic annular snap ring 6 abuts against the annular boss 71. As the core rod 2 continues to retract and slide, the elastic annular snap ring 6 drives the entire sleeve 7 to slide towards the limiting protrusion 131 by pushing the annular boss 71 until the annular boss 71 abuts against the limiting protrusion 131. Correspondingly, the distal end face of the elastic annular snap ring 6 is restricted in the limiting cavity by the proximal end of the second step structure 10 or directly abuts against the proximal end face of the second step structure, as Figure 9 shown, realizing the sliding limit of the core rod 2.

[0106] In this embodiment, by providing a ferrule 7, on the one hand, in cooperation with the elastic annular snap ring 6 and the limiting protrusion 131, the ferrule 7 plays a role in limiting the sliding of the core rod 2; on the other hand, the outer wall surface of the annular boss 71 on the ferrule 7 fits against the inner wall surface of the limiting chamber 13, forming a sliding seal connection therebetween.

[0107] Further preferably, as Figure 6b and Figure 6c shown, the above-mentioned second step structure 10 includes a third step 101 and a fourth step 102 that are distributed in a stepped manner from the distal end towards the proximal end; in the injection state, the distal end of the above-mentioned ferrule 7 abuts against the step surface of the third step 101, and the annular boss 71 abuts against the step surface of the fourth step 102, ensuring that in the injection state, the ferrule 7 and the annular boss 71 form a tightly abutted seal connection with the second step structure 10; in the retraction state, the distal end of the elastic annular snap ring 6 can abut against the step surface of the third step 101.

[0108] Preferably, in Figure 6c the limiting protrusion 131 is a third limiting slope that is inclined from the outside to the inside along the radial direction of the syringe barrel 1.

[0109] Regarding the structure of the ferrule 7, as Figure 5 and Figure 7b shown, the diameter of the inner hole of the ferrule 7 gradually decreases from the proximal end towards the distal end to form a second constriction, and the inner diameter at the distal end of the second constriction is equal to or slightly larger than the outer diameter of the core rod 2, facilitating the sliding of the core rod 2 in the inner hole of the ferrule 7. The outer wall surface at the proximal end of the ferrule 7 is a first conical surface 72 whose outer diameter gradually decreases from the proximal end towards the distal end, and the outer peripheral wall of the annular boss 71 is also a second conical surface 73 whose outer diameter gradually decreases from the proximal end towards the distal end; correspondingly, as Figure 6c shown, the axial wall surface of the above-mentioned third step 101 is a third conical surface 101a corresponding to the first conical surface 72, and the axial wall surface of the fourth step 102 is a fourth conical surface 102b corresponding to the second conical surface 73. In the injection state, the first conical surface 72 at the proximal end of the ferrule 7 and the second conical surface 73 of the annular boss 71 are respectively arranged in contact with the third conical surface of the third step 101 and the fourth conical surface of the fourth step 102.

[0110] More preferably, an annular V-shaped groove is provided on the outer wall surface of the core rod 2, and an easily breakable position 23 is formed at the bottom of the V-shaped groove, as Figure 4As shown, a handle portion is provided on the proximal end of the core rod 2, and the easily breakable position 23 is located between the elastic annular snap ring 6 and the handle portion. When the core rod 2 slides back, the elastic annular snap ring 6 is located in the limiting chamber 13, and the elastic annular snap ring 6 cooperates with the sleeve 7 to lock the core rod 2 in the limiting chamber 13. At this time, only by applying a force to the proximal end of the core rod 2, the core rod can be broken to completely destroy the safety syringe. The above-mentioned easily breakable position 23 makes the core rod 2 easier to break when stressed.

[0111] In addition, it should be noted that: the above-mentioned injection state refers to the entire injection process from the injection start position to the injection end position, including the injection start position and the injection end position; the above-mentioned retraction state refers to the entire retraction process from the retraction start position to the retraction end position after injection, including the retraction start position and the retraction end position.

[0112] The usage process of the safety syringe in this embodiment is as follows:

[0113] When the safety syringe is filled with liquid and injection is required, the core rod 2 is pushed to the top of the syringe barrel 1 (i.e., slide towards the distal end), and the second slope surface 211 of the limiting snap ring 21 abuts against the first slope surface 331 of the second claw 33.

[0114] As Figure 7a shown, at this time, when the core rod 2 is further pushed, since the distal end surface of the rubber stopper 5 abuts against the step surface of the second step 92, as the core rod 2 is continuously pushed, the rubber stopper 5 is squeezed and deformed, and the core rod 2 is relatively pushed into the inner hole of the first step 91 with respect to the rubber stopper 5. Due to the first slope surface of the second claw 33 and the characteristics of the elastic material, the second slope surface 211 of the limiting snap ring 21 continues to slide towards the top of the syringe barrel 1 along the first slope surface 331 of the second claw 33, causing the second claw 33 and the leg 32 to deform radially inward until the second claw 33 extends into the first relief hole 212 after passing over the second slope surface 211 and hooks on the side wall of the limiting snap ring 21, and the locking of the second claw 33 and the limiting snap ring 21 is achieved with only a small force. And the third claw 35 abuts against the first step 91, which can prevent excessive force from causing the needle seat 3 and the needle tube 1 to slide and avoid the needle seat 3 from detaching from the needle tube 1.

[0115] As Figure 8 shown, correspondingly, the sleeve is always in the Figure 7b shown state during this process; at the same time, since the second claw 33 and the leg 32 are stressed and contract towards the center, the first claw 34 is driven to slide off the first groove 111, that is, slide off the first limiting slope, and the needle seat 3 detaches from the needle seat chamber 11. At this time, the injection of the syringe is completed, and the distal end surface of the limiting snap ring 21 abuts against the proximal end surface of the third claw 35. Due to the presence of the O-ring, the residual amount of the liquid medicine inside the syringe reaches the minimum after the injection is completed.

[0116] After the injection is completed, as Figure 7b shown, pull back the plunger rod 2 (i.e., slide the plunger rod 2 towards the proximal end). Since the limit snap ring 21 of the plunger rod 2 is locked with the second claw 33, the plunger rod 2 will pull the needle seat 3 and the needle tube 4 back into the transition chamber 12 of the syringe barrel 1. When the plunger rod 2 is pulled back close to the bottom of the syringe barrel 1, due to the existence of the first constriction section (i.e., the second limiting slope), the outer diameter of the elastic ring-shaped snap ring 6 in the free state is larger than the inner diameter of the first constriction section. Therefore, the elastic ring-shaped snap ring 6 is squeezed and deformed by the pressure towards the center exerted by the second limiting slope, so that the elastic ring-shaped snap ring 6 crosses the second limiting slope. At this time, the proximal end of the elastic ring-shaped snap ring 6 abuts against the distal end of the annular boss 71 of the ferrule 7. As the plunger rod 2 continues to retract, the elastic ring-shaped snap ring 6 pushes the ferrule 7 to slide down along the inner cavity of the limiting chamber 13.

[0117] When the plunger rod 2 reaches the bottom, the elastic ring-shaped snap ring 6 pushes the ferrule 7 to the bottom of the syringe barrel 1, as Figure 9 shown. At this time, the lower part of the annular boss 71 on the ferrule 7 abuts and is fixed with the limiting protrusion 131 (i.e., the third limiting slope), and the upper end of the elastic ring-shaped snap ring 6 abuts or does not abut against the step surface of the third step 101 of the second step structure 10. The step surface of the third step 101 also blocks the distal end of the elastic ring-shaped snap ring 6 in the limiting chamber. Correspondingly, the needle tube is in the transition chamber of the syringe barrel. Since then, the entire plunger rod 2 and the needle seat 3 thereon are locked at the bottom in the syringe barrel 1 and cannot move any more. Finally, break off the plunger rod 2, and the syringe completes self-destruction. Moreover, the arrangement of the two end teeth 62 of the elastic ring-shaped snap ring 6 can prevent the needle seat 3 from disengaging from the limiting chamber 13 due to a large thrust or pressure.

[0118] The safety syringe of this embodiment enables the safety syringe to be completely self-destructed, has high safety performance, simple structure, low cost and simple manufacturing, and improves production efficiency. After the injection is completed, the needle seat 3 and the needle tube 4 of the safety syringe are completely fixed in the syringe barrel 1 of the syringe, which also avoids potential safety hazards caused by operation errors or the relatively thin syringe barrel 1. The plunger rod 2 has a small stroke during retraction, causing little pain to the patient; the structure is simple and can be applied to small-dose syringes such as 1 ml and 3 ml, especially vaccine syringes; due to the integrated structural characteristics of its needle seat 3 with the second claw 33, the first claw 34, and the third claw 35, the difficulty and cost of production and manufacturing are greatly reduced, the production efficiency is improved, the self-destruction operation of the syringe is simple, and the safety performance is strong, greatly reducing the risk of injury accidents of the safety syringe.

[0119] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A safety syringe, characterized in that, Comprising: A syringe barrel (1) having a first groove (111) provided on its inner wall surface; A needle hub (3) having at least two first claws (34) provided on its outer wall surface, and the first claws (34) are snap-fitted into the first groove (111); A plunger rod (2) hermetically and slidably disposed within the syringe barrel (1); At least two second claws (33) protruding radially are provided at the proximal end of the needle hub (3), a limiting member is provided at the distal end of the plunger rod (2), and the second claws (33) and the limiting member are in abutment through a slope surface; a third claw (35) protruding radially is provided on the needle hub (3); In the injection state, when the plunger rod (2) slides towards the distal end, it forces the second claws (33) to slide along the slope surface and deform radially of the syringe barrel under the action of the slope surface to cross over the limiting member and hook onto the limiting member, and the third claw (35) abuts against the inner wall of the syringe barrel (1) to prevent the needle hub (3) from sliding relative to the syringe barrel (1); In the injection state or the retraction state, the first claws (34) are driven by the sliding of the plunger rod (2) to disengage from the first groove (111); The installation cavity of the syringe barrel (1) includes a needle hub chamber (11) and a transition chamber (12) communicating with the needle hub chamber (11), and the inner diameter of the transition chamber (12) is larger than the inner diameter of the needle hub chamber (11) to form a first step structure (9) between the needle hub chamber (11) and the transition chamber (12); The installation cavity further includes a limiting chamber (13) communicating with the proximal end of the transition chamber (12); The inner diameter of the limiting chamber (13) is larger than the inner diameter of the transition chamber (12) to form a second step structure (10) between the transition chamber (12) and the limiting chamber (13); The safety syringe further includes an elastic annular snap ring (6) fixed on the outer wall surface of the plunger rod (2); a limiting protrusion (131) is provided on the inner wall surface of the limiting chamber (13), and the outer diameter of the elastic annular snap ring (6) in the free state is at least larger than the inner diameter of the proximal end of the transition chamber (12) and larger than the inner diameter of the limiting protrusion (131); In the retraction state, the distal end of the elastic annular snap ring (6) is restricted within the limiting chamber (13) by the proximal end of the second step structure, and the proximal end of the elastic annular snap ring (6) abuts against the limiting protrusion (131); An annular groove is provided on the outer wall surface of the plunger rod (2), and an easily breakable position (23) is formed at the bottom of the annular groove; 2. The safety syringe according to claim 1, wherein The limiting member is a limiting snap ring; In the injection state, the second claws (33) contract radially of the syringe barrel under the action of the slope surface to slide into the inner hole of the limiting snap ring (21) to cross over the limiting snap ring (21) and hook onto the limiting snap ring (21); 3. The safety syringe according to claim 2, wherein At least two first relief holes (212) are provided on the side wall of the limiting snap ring (21); In the injection state, the second claws (33) extend into the first relief holes (212) one by one to hook onto the side wall of the limiting snap ring (21); 4. The safety syringe according to claim 2 or 3, characterized in that, The needle hub (3) includes: An annular body (31), the outer wall surface of which is sealingly provided on the inner wall of the syringe barrel (1), and the inner hole of the annular body (31) is for installing a needle tube (4); At least two legs (32), two of the legs (32) being evenly distributed on the same circumference, and the distal end of any one of the legs (32) being fixed on the proximal cross-section of the annular body (31); The first claw (34), the second claw (33) and the third claw (35) are respectively and protrudingly fixed on the outer wall surface of the leg (32), the first claw (34) is located between the second claw (33) and the annular body (31), and the third claw (35) is located between the first claw (34) and the second claw (33); In the injection state, the second claw (33) slides along the slope surface to drive the leg (32) to swing inwards in the radial direction of the syringe barrel (1), and drive the first claw (34) to disengage from the first groove (111).

5. The safety syringe according to claim 4, characterized in that, One end of the annular body (31) is recessed downwards with a fixing groove (313), and a fixing protrusion is provided on the inner wall of the syringe barrel (1), and the fixing protrusion is located in the fixing groove (313).

6. The safety syringe according to any one of claims 1 to 3, characterized in that, The groove wall of the first groove (111) on its proximal end is a first limiting slope inclined from the groove opening towards the groove bottom.

7. The safety syringe according to claim 4, wherein, The needle seat (3) is arranged in the needle seat chamber (11), and the leg passes through the inner hole of the first step structure (9) so that the second claw (33) extends into the transition chamber (12).

8. The safety syringe according to claim 7, wherein There are two legs (32), and they are evenly distributed on the same circumference; In the injection state, the radial dimension of the two third claws (35) is greater than the inner hole dimension of the first step structure (9).

9. The safety syringe according to claim 7, wherein, A rubber stopper (5) is sleeved outside the core rod (2), and the core rod (2) is slidably and sealingly arranged in the transition chamber (12) through the rubber stopper (5).

10. The safety syringe according to claim 9, characterized in that, The proximal end of the rubber stopper (5) is fixed on the core rod (2), and the distal end of the rubber stopper (5) is tightly pressed against the proximal end face of the first step structure (9) under the extrusion force exerted when the core rod (2) slides towards the distal end. At least one annular sealing protrusion (51) is provided on the outer wall surface of the rubber stopper (5), and the sealing protrusion (51) slidably and sealingly abuts against the inner wall surface of the transition chamber (12) along with the core rod (2).

11. The safety syringe according to claim 10, characterized in that, The first step structure (9) includes a first step (91) and a second step (92) distributed in a trapezoidal shape from the distal end towards the proximal end; In the injection state, the third claw (35) abuts against the step surface of the first step (91), the distal end face of the limit snap ring (21) abuts against the proximal end face of the third claw (35), and the distal end face of the rubber stopper (5) abuts against the step surface of the second step (92).

12. The safety syringe according to any one of claims 7-11, characterized in that, The distal end face and the proximal end face of the elastic annular snap ring (6) are both provided with teeth (62).

13. The safety syringe according to claim 12, wherein It further includes a sleeve (7) sleeved outside the core rod (2) and located in the limit chamber (13); An annular boss (71) is provided on the outer wall surface of the ferrule (7), and the outer peripheral wall of the annular boss (71) is attached to the inner wall surface of the limiting chamber (13); In the retracted state, the elastic annular snap ring (6) is driven by the sliding of the core rod (2), and the teeth at the proximal end thereof abut against the annular boss (71) to push the ferrule (7) to slide towards the limiting projection (131) and abut against the limiting projection (131).

14. The safety syringe according to claim 13, wherein, The second stepped structure (10) includes a third step (101) and a fourth step (102) that are steppedly distributed from the distal end towards the proximal end; In the injection state, the distal end of the ferrule (7) abuts against the stepped surface of the third step (101), and the annular boss (71) abuts against the stepped surface of the fourth step (102); In the retracted state, the teeth at the distal end of the elastic annular snap ring (6) can abut against the stepped surface of the third step (101).

15. The safety syringe according to any one of claims 11, 13, and 14, characterized in that, The transition chamber (12) includes a straight tube section and a first reduced diameter section fixed to the proximal end of the straight tube section, and the inner diameter of the first reduced diameter section gradually decreases from its distal end towards the proximal end; The outer diameter of the elastic annular snap ring (6) in the free state is greater than the inner diameter of the first reduced diameter section and less than or equal to the inner diameter of the straight tube section.

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