CN114432542B

CN114432542B - Automatic injector

Info

Publication number: CN114432542B
Application number: CN202210104026.5A
Authority: CN
Inventors: 桑会庆; 吴亚金; 朱涛
Original assignee: Shanghai Umitai Medical Technology Co ltd
Current assignee: Shanghai Umitai Medical Technology Co ltd
Priority date: 2022-01-27
Filing date: 2022-01-27
Publication date: 2023-09-29
Anticipated expiration: 2042-01-27
Also published as: CN114432542A

Abstract

The application provides an automatic injector, which comprises a shell, an injector component, an pushing component and a pressing component, wherein the shell comprises a fixed cylinder body, an end cap and a connecting cylinder seat, the end cap is arranged at one end of the fixed cylinder body, and the connecting cylinder seat is arranged at the other end of the fixed cylinder body; the syringe assembly comprises a syringe barrel, a needle and a piston, wherein the syringe barrel contains medicine, the needle is connected to the front part of the syringe barrel, and the assembled end cap is positioned in front of the needle; the piston is arranged in the injector cylinder body and seals the injector cylinder body; the pushing assembly comprises a pushing rod, a pushing rod retainer and a pushing spring, the pushing rod retainer is arranged on the connecting cylinder seat, a bar-shaped groove along the length direction of the pushing rod is formed in the pushing rod, and the pushing spring is arranged in the bar-shaped groove; the push rod is provided with a front acting end and a rear connecting end, the front acting end stretches into the syringe cylinder and can be abutted against the piston, and the rear connecting end is connected to the push rod retainer and compresses the pushing spring; the pressing assembly includes a button. The application has the advantage of convenient operation.

Description

Automatic injector

Technical Field

The application belongs to the technical field of medical appliances, and particularly relates to an automatic injector.

Background

The needle heads of the existing pre-filled and sealed syringes (PFS) are exposed outside, so that fear is easily caused when a patient uses the syringe, and psychological stress is caused. Meanwhile, the needle is outside, so that no protection device is provided, and other unnecessary injuries are easily caused when the patient uses the needle. After the injection is finished, the needle is not well protected and is easy to cause injury.

The existing prefilled syringes (PFS) require a push rod to be operated to perform injection after the needle is inserted into the skin, are relatively complex, have relatively high requirements on operators, and most patients have fear for manually performing needle insertion and subcutaneous injection. When the manual injection is carried out on patients with serious illness, the shaking of hands can bring a large needle-inserting wound surface for the patients.

Therefore, improvements are needed.

Disclosure of Invention

The application aims to provide an automatic injector which is convenient to operate.

To achieve the above object, the present application provides an automatic injector comprising:

the shell comprises a fixed cylinder body, an end cap and a connecting cylinder seat, wherein the end cap is detachably arranged at one end of the fixed cylinder body, and the connecting cylinder seat is arranged at the other end of the fixed cylinder body;

a syringe assembly comprising a syringe barrel containing a medicament, a needle attached to the front of the syringe barrel, and a piston, wherein the assembled end cap is located in front of the needle; the piston is arranged in the injector cylinder body and seals the injector cylinder body;

the pushing assembly comprises a push rod, a push rod retainer and a pushing spring, the push rod retainer is arranged on the connecting cylinder seat, a strip-shaped groove along the length direction of the push rod is formed in the push rod, and the pushing spring is arranged in the strip-shaped groove; the push rod is provided with a front acting end and a rear connecting end, the front acting end stretches into the syringe cylinder and can be abutted against the piston, and the rear connecting end is connected to the push rod retainer and compresses the pushing spring;

the pressing assembly comprises a button which is arranged on the connecting cylinder seat;

the push rod moves forwards under the action of the pushing spring, the push rod is propped against the piston, the piston drives the syringe barrel to move forwards in the first stage to execute needle insertion operation, and then the piston is driven to move forwards in the second stage in the syringe barrel to execute injection operation.

In the technical scheme of the application, the rear connecting end in the initial state is connected with the push rod retainer, when the injector is used, the push rod is separated from the push rod retainer by pressing the button, and then the push rod moves forwards under the action of the pushing spring and is propped against the piston, on one hand, the piston can drive the whole syringe barrel to move forwards to execute the needle advancing operation firstly due to the existence of friction resistance, and on the other hand, when the syringe barrel reaches the set position (the needle advancing is completed at the moment), the push rod which continues to move forwards can drive the piston to continue to move forwards in the syringe barrel to execute the injection operation;

specifically, needle insertion operation and injection operation can be automatically realized by pressing a button, and the self-injection operation of a patient is convenient.

As another specific embodiment of the present application, the housing further comprises a mounting cylinder seat, the syringe cylinder is arranged on the fixed cylinder body through the mounting cylinder seat, the syringe cylinder can slide in the mounting cylinder seat, and a blocking part is arranged at the rear end of the syringe cylinder;

before the blocking part is propped against the mounting cylinder seat, the push rod drives the piston and the syringe cylinder to synchronously move forwards so as to execute the operation of advancing the needle;

after the blocking part is propped against the mounting cylinder seat, the push rod drives the piston to move forwards so as to execute injection operation.

In this scheme, carry out spacingly through the blocking part on the syringe barrel of installation barrel seat, can be according to the difference of model, the size of adjustment installation barrel seat to the needle needs of different advances of adaptation.

As another specific embodiment of the application, the rear connecting end comprises at least one elastic hook which is clamped on the push rod retainer to form limit connection.

As another specific embodiment of the application, the elastic hook is provided with a stop surface, the button is provided with a pushing surface, and the pushing surface acts on the stop surface to enable the elastic hook to move outwards by pressing the button, so that the elastic hook is separated from the push rod retainer.

As another specific embodiment of the application, the pressing component further comprises a knob, the knob is rotatably arranged on the connecting cylinder seat, the button is arranged on the knob, the connecting cylinder seat is provided with a convex rib, the button is provided with a clamping groove matched with the convex rib, and the relative position between the convex rib and the clamping groove is changed by rotating the knob to lock or unlock the button.

In this scheme, utilize the knob to lock or unblock to the button, under non-use state, be in the locking state with the button, no matter assemble or transportation at this moment, all have good security.

As another specific embodiment of the application, the application further comprises a sheath assembly, which comprises a telescopic sheath and a sheath connecting frame which are connected with each other, wherein the telescopic sheath is slidably arranged in the fixed cylinder, the telescopic sheath is positioned at the outer side of the syringe cylinder, the sheath connecting frame is provided with a limiting piece corresponding to the elastic hook, and the limiting piece is positioned at the outer side of the elastic hook and can limit the elastic hook to move outwards.

As another specific embodiment of the application, the sheath connecting frame is provided with a first boss, the knob is provided with a second boss corresponding to the first boss, the second boss is positioned behind the first boss to limit the backward movement of the sheath, and the relative position between the first boss and the second boss is changed by rotating the knob so as to release the limit of the second boss on the backward movement of the sheath.

In this scheme, utilize the knob to carry out spacingly to the sheath link, under non-use state, the sheath link can not backward movement, avoid the maloperation when using, promote the security.

As another specific embodiment of the application, the second boss is staggered with the first boss by rotating the knob, and meanwhile, the convex rib can be correspondingly matched with the clamping groove.

As another specific embodiment of the application, the sheath assembly further comprises a sheath spring for driving the telescopic sheath after injection to move forwards, wherein the sheath spring is arranged at the outer side of the sheath connecting frame;

a first limiting step is arranged on the sheath connecting frame, one end of the sheath spring is propped against the first limiting step, and the other end of the sheath spring is propped against the connecting cylinder seat;

after injection is completed, the injector cylinder moves forwards, and the sheath spring drives the sheath connecting frame to drive the telescopic sheath to move forwards until the telescopic sheath can completely cover the needle.

In this scheme, after the injection is accomplished, utilize the sheath spring to realize with flexible sheath forward automatic motion and stretch out to cover the syringe needle completely, ensure that the whole syringe needle of injection is invisible, avoid the fear of syringe needle.

As another specific embodiment of the application, the push rod retainer is provided with a limiting spring piece for limiting the backward retraction of the sheath connecting frame;

the sheath connecting frame is positioned at the outer side of the limiting elastic piece and can compress the limiting elastic piece;

a second limiting step is arranged on the sheath connecting frame;

the second limiting step and the sheath connecting frame synchronously move forwards to the front of the limiting elastic piece, the limiting elastic piece is ejected outwards at the moment, and the ejected limiting elastic piece can prop against the second limiting step to limit the backward movement of the sheath connecting frame.

In this scheme, utilize the elasticity deformability of spacing shell fragment to realize spacing to the sheath link after stretching out, the spacing shell fragment that pops out can offset with the spacing step of second, and the telescopic sheath covers the syringe needle completely and can't backward movement this moment, guarantees that the syringe needle can not touch after the injection is accomplished, avoids the secondary injury.

As another specific embodiment of the application, the pushing assembly further comprises a spring guide rod, the spring guide rod is arranged in the strip-shaped groove, and the pushing spring is sleeved on the spring guide rod.

The application has the following beneficial effects:

the automatic injector provided by the application can automatically insert the needle and start the injection operation by simply pressing the button on the skin, and has the advantages of convenience in operation and high comfort level;

the needle is invisible in the injection process, so that fear psychology of a patient is avoided;

the application is provided with a plurality of mechanisms with safety function, ensures the safety of assembly, transportation and use operation, and protects the needle after injection is completed by extending the telescopic sheath, so that the needle can not be touched, and secondary injury is avoided.

The present application will be described in further detail with reference to the accompanying drawings.

Drawings

FIG. 1 is a schematic view of the structure of an automatic injector of the present application;

FIG. 2 is a schematic cross-sectional view of an automatic injector of the present application;

FIG. 3 is an exploded schematic view of the automatic injector of the present application;

FIG. 4 is a schematic cross-sectional view in perspective of an auto-injector of the present application;

FIG. 5 is a second schematic cross-sectional view of an auto-injector according to the present application in a solid state;

FIG. 6 is a schematic view of an auto-injector of the present application in preparation for injection, with the telescoping sheath against the skin, with the button not pressed temporarily;

FIG. 7 is a schematic view of the automatic injector of the present application with the needle fully advanced and with the injection not being performed;

FIG. 8 is a schematic view of the automatic injector of the present application at the completion of an injection, with continued plunger feed to complete the injection operation;

FIG. 9 is a schematic view of the automatic injector of the present application after injection is completed, with the retractable sheath removed from the skin and the retractable sheath automatically ejected to protect the needle;

FIG. 10 is an enlarged schematic view at A in FIG. 2;

fig. 11 is an enlarged schematic view at B in fig. 6.

Detailed Description

In order that the above-recited objects, features and advantages of the present application will be more clearly understood, a more particular description of the application will be rendered by reference to the appended drawings and appended detailed description. It should be noted that, without conflict, the embodiments of the present application and features in the embodiments may be combined with each other.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, however, the present application may be practiced in other ways than those described herein, and the scope of the application is therefore not limited to the specific embodiments disclosed below.

Example 1

The present application provides an automatic injector, and in particular an automatic injection pen adapted for a pre-filled syringe, as shown in fig. 1-11, comprising a housing 100, a syringe assembly 200, a push assembly 300, a push assembly 400, and a sheath assembly 500.

The housing 100 includes a stationary cylinder 110, a mounting cylinder seat 120, an end cap 130, and a connecting cylinder seat 140;

the mounting cylinder base 120 is disposed in the fixed cylinder 110, the end cap 130 is a pen cap, which is detachably disposed at one end of the fixed cylinder 110, and the connecting cylinder base 140 is disposed at the other end of the fixed cylinder 110;

the syringe assembly 200 includes a syringe barrel 210 containing a drug therein, a needle 220 attached to the front of the syringe barrel 210, and a plunger 230, which is disposed within the syringe barrel 210 and seals the syringe barrel 210 by pushing the plunger 230 to move the drug within the syringe barrel 210, and a needle cap 240, which may be fitted over the needle 220 to form a guard, is disposed in front of the needle 220, and the assembled cap 130 is disposed in front of the needle 220;

the syringe barrel 210 is mounted on the fixed barrel 110 through the mounting barrel 120, and the syringe barrel 210 can slide within the mounting barrel 120 for a predetermined distance, which is actually defined herein according to the design requirements.

The propulsion assembly 300 includes a push rod 310, a push rod holder 320, a propulsion spring 330, and a spring guide 340;

the push rod retainer 320 is arranged on the connecting cylinder seat 140, the push rod 310 is provided with a strip-shaped groove 311 along the length direction, the pushing spring 330 is arranged in the strip-shaped groove 311, the spring guide rod 340 is arranged in the strip-shaped groove 311, and the pushing spring 330 is sleeved on the spring guide rod 340;

wherein the plunger 310 has a front acting end 310a and a rear connecting end 310b, the front acting end 310a extending into the syringe barrel 210 and being capable of abutting the piston 230, the rear connecting end 310b being connected to the plunger holder 320 and compressing the push spring 330;

the pressing assembly 400 includes a button 410 and a knob 420;

the knob 420 is rotatably arranged on the connecting cylinder seat 140, the button 410 is arranged on the knob 420, wherein the connecting cylinder seat 140 is provided with a convex rib 141, the button 410 is provided with a clamping groove 411 matched with the convex rib 141, the relative position between the convex rib 141 and the clamping groove 411 is changed by rotating the knob 420, and the button 410 is locked or unlocked, namely the button 410 can be pressed by rotating the knob 420 to a specified position, otherwise, the button 410 cannot be normally pressed, so that the safety protection effect is achieved.

By pressing the button 410 to disengage the rear connecting end 310b from the push rod holder 320, the push rod 310 moves forward under the action of the push spring 330, the push rod 310 abuts against the piston 230, and the syringe barrel 210 is driven to perform the first stage forward movement to perform the needle insertion operation, and then the piston 230 is driven to perform the second stage forward movement in the syringe barrel 210 to perform the injection operation.

Further, two elastic hooks 312 are disposed at the rear connecting end 310b, and the elastic hooks 312 are clamped on the push rod holder 320 to form a limiting connection, wherein the two elastic hooks 312 are distributed in opposite directions.

Specifically, a stop surface 313 is provided on the elastic hook 312, the stop surface 313 is in a slant or cambered surface structure, a push surface 412 is provided on the button 410, and by pressing the button 410, the push surface 412 acts on the stop surface 313 to move the elastic hook 312 outwards, so that the elastic hook 312 is separated from the push rod holder 320, and the constraint on the push rod 310 is released to move under the action of the push spring 330.

Correspondingly, the upper fixing connecting frame 350 and the lower fixing connecting frame 360 are arranged on the push rod 310, the upper fixing connecting frame 350 and the lower fixing connecting frame 360 are connected with the blocking part 211 to prevent the syringe barrel 210 from rotating, meanwhile, the upper fixing connecting frame 350 and the lower fixing connecting frame 360 can slide relative to the push rod 310, and the maximum displacement of the forward movement of the push rod can be indirectly limited through the design of the sizes of the upper fixing connecting frame 350 and the lower fixing connecting frame 360.

Wherein the upper and lower fixed connection frames 350 and 360 preferably abut against the push rod holder 320 in an initial state, thereby accurately positioning the syringe barrel 210 to prevent shaking.

Wherein, a blocking portion 211 is disposed at the rear end of the syringe barrel 210, before the blocking portion 211 abuts against the mounting barrel seat 120 (specifically, the blocking portion 211 drives the fixed connection frame 360 to abut against the mounting barrel seat 120), the push rod 310 drives the piston 230 to move forward synchronously with the syringe barrel 210 to perform the injection operation, and after the blocking portion 211 abuts against the mounting barrel seat 120 (specifically, the blocking portion 211 drives the fixed connection frame 360 to abut against the mounting barrel seat 120), the push rod 310 continues to move forward to perform the injection operation.

The sheath assembly 500 includes a telescopic sheath 510 and a sheath coupling frame 520 connected to each other, the telescopic sheath 510 being slidably disposed in the fixed cylinder 110, and the telescopic sheath 510 being disposed at an outer side of the syringe cylinder 210, a stopper 521 corresponding to the elastic hook 312 being disposed on the sheath coupling frame 520, the stopper 521 being disposed at an outer side of the elastic hook 312 and being capable of restricting the elastic hook 312 from moving outwards.

Wherein, be equipped with first boss 522 on the sheath link 520, be equipped with the second boss 421 that corresponds with first boss 522 on the knob 420, second boss 421 is located the rear of first boss 522 in order to restrict sheath link 520 backward movement, change the relative position between first boss 522 and the second boss 421 through rotating knob 420, in order to remove the restriction of second boss 421 to sheath link 520 backward movement, that is, in knob 420 in the initial condition, flexible sheath 510 is unable to retract backward, unable to carry out next step's operation, avoid the maloperation, play safety protection's effect.

Correspondingly, by rotating the knob 420, the second boss 421 and the first boss 522 are staggered, and the ribs 141 and the clamping slots 411 can correspondingly cooperate, that is, the push button 410 is pressed while the telescopic sheath 510 (the sheath connecting frame 520) can move backwards.

More specifically, the sheath assembly 500 further includes a sheath spring 530 for driving the telescopic sheath 510 after injection is completed to move forward, the sheath spring 530 is disposed at the outer side of the sheath connecting frame 520, a first limit step 523 is disposed on the sheath connecting frame 520, one end of the sheath spring 530 abuts against the first limit step 523, and the other end of the sheath spring 530 abuts against the connecting cylinder seat 140;

still further, the push rod holder 320 is provided with a limiting elastic piece 321 for limiting the backward retraction of the sheath connecting frame 520, and the sheath connecting frame 520 is positioned at the outer side of the limiting elastic piece 321 and compresses the limiting elastic piece 321.

In the initial state, the push rod 310 occupies the internal space of the push rod holder 320, and the limiting elastic piece 321 cannot elastically deform inwards, and at this time, the outer side of the limiting elastic piece 321 faces the sheath connecting frame 520 to form positioning, so that the sheath connecting frame 520 cannot move forwards.

The second limiting step 524 is arranged on the sheath connecting frame 520, the second limiting step 524 and the sheath connecting frame 520 synchronously move forward to the front of the limiting elastic piece 321, the push rod 310 can yield an inner space after moving forward, the sheath connecting frame 520 can inwards extrude the limiting elastic piece 321 to deform under the action of the sheath spring 530, the limiting elastic piece 321 returns under the action of elastic force, the limiting elastic piece 321 is ejected outwards, and the ejected limiting elastic piece 321 can prop against the second limiting step 524 to limit the backward movement of the sheath connecting frame 520, so that the needle 220 is protected after injection is finished, and secondary injury cannot be caused.

After the injection is completed, the syringe barrel 210 moves forward, and the sheath spring 530 drives the sheath connecting frame 520 to drive the telescopic sheath 510 to move forward, wherein the telescopic sheath 510 can completely cover the needle 220 to protect the needle 220.

The mounting cylinder 120 in this embodiment may be transparent or have a viewing notch, and accordingly, a window is formed at the position of the fixed cylinder 110 corresponding to the mounting cylinder 120 to more intuitively observe the injection process.

The specific operation process of this embodiment is shown in fig. 6-9, and is specifically as follows:

first, cap 130 and cap 240 on needle 220 are removed;

then, the knob 420 is turned, so that the second boss 421 and the first boss 522 are staggered while the clamping slot 411 is correspondingly matched with the rib 141, namely: the button 410 can be normally pressed, and when the telescopic sleeve is tightly attached to the skin, the telescopic sleeve moves backwards together with the sleeve fixing frame; at this time, the stopper 521 on the sheath connecting frame 520 no longer restricts the outward movement of the elastic hook 312;

then, the button 410 is pressed forward, under the action of the button 410, the elastic hook 312 moves outwards and is separated from the push rod holder 320 by the cooperation of the stop surface 313 and the pushing surface 412, under the action of the pushing spring 330, the push rod 310 moves forward, the push rod 310 abuts against the piston 230, the syringe barrel 210 is driven to move forward in the first stage to perform the needle advancing operation, until the stop part 211 drives the fixed connecting frame 360 to abut against the mounting barrel seat 120, and then the piston 230 is driven to move forward in the second stage in the syringe barrel 210 to perform the injection operation.

After the injection is completed, the sheath connecting frame 520 moves forward by the acting force of the sheath spring 530 to drive the telescopic sheath 510 to move forward until the limiting elastic sheet 321 on the push rod retainer 320 pops outwards, and the popped limiting elastic sheet 321 can prop against the second limiting step 524 to limit the backward movement of the sheath connecting frame 520, so that the needle 220 is protected after the injection is completed.

In this embodiment, when the push button 410 triggers the push spring 330 to release, the needle will advance, the syringe barrel 210 moves forward, the plunger 310 directly pushes against the piston 230, the piston 230 will drive the syringe barrel 210 to move forward, and after the front end is limited (i.e. the blocking part 211 drives the fixed connecting frame 360 to abut against the mounting barrel 120), the syringe barrel 210 stops moving forward, at this time, the needle 220 has been pricked into the skin, and the resistance of the needle 220 pricking into the skin is far smaller than the resistance of the piston 230 pushing, so the automatic needle-inserting function can be achieved, and the piston 230 injects the liquid medicine forward under the continuous forward action of the plunger 310.

The embodiment has multiple safety protection, the knob 420 can not act on the button 410 and the sheath connecting frame 520 under the condition that the knob 420 is not unlocked, so that the safety during transportation and taking of the injection device is ensured, the telescopic sheath 510 is provided with elasticity, the front end of the telescopic sheath 510 needs to be manually applied with external force when being tightly attached to an injection part, the injection device can be ensured to be pricked into the skin after being discharged, and meanwhile, the situation that the injection device is deviated or sliding misplacement can be prevented by continuously applying force is avoided.

The embodiment is used for self-injection of patients, can be matched with the existing pre-filled and sealed injector for use, has multiple protections, and avoids leakage of liquid medicine caused by misoperation; in addition, the automatic injection is performed in the embodiment, so that the self-injection operation of the patient is convenient, the needle 220 is not exposed in the whole process of the injection process, fear is avoided, and the needle 220 is protected after the injection is completed, so that secondary injury to the patient is avoided.

In the description of the present embodiment, "rear", "backward" and "upper", "upward" in the drawing indicate directions, and "front", "forward" in the drawing indicate directions, i.e. "lower", "lower" and "downward" in the drawing.

While the application has been described in terms of preferred embodiments, it is not intended to limit the scope of the application. It is intended that all modifications within the scope of the application, i.e., all equivalents thereof, be embraced by the application as they come within their scope without departing from the application.

Claims

1. An automatic injector, comprising:

a syringe assembly comprising a syringe barrel having a medicament contained therein, a needle attached to a front portion of the syringe barrel, and a piston, wherein the assembled end cap is located in front of the needle; the piston is arranged in the syringe cylinder body and seals the syringe cylinder body;

the pushing assembly comprises a pushing rod, a pushing rod retainer and a pushing spring, the pushing rod retainer is arranged on the connecting cylinder seat, a strip-shaped groove along the length direction of the pushing rod is formed in the pushing rod, and the pushing spring is arranged in the strip-shaped groove; the push rod is provided with a front acting end and a rear connecting end, the front acting end stretches into the syringe cylinder and can be abutted against the piston, and the rear connecting end is connected to the push rod retainer and compresses the pushing spring;

the pressing assembly comprises a button, and the button is arranged on the connecting cylinder seat;

the push rod is pushed to move forward under the action of the pushing spring, the push rod is propped against the piston, the piston drives the syringe barrel to move forward in a first stage to execute needle insertion operation, and then the piston is driven to move forward in a second stage in the syringe barrel to execute injection operation;

the shell further comprises an installation cylinder seat, the syringe cylinder is arranged on the fixed cylinder body through the installation cylinder seat, the syringe cylinder can slide in the installation cylinder seat, and a blocking part is arranged at the rear end of the syringe cylinder;

wherein before the blocking part abuts against the mounting cylinder seat, the push rod drives the piston and the syringe cylinder to synchronously move forwards so as to execute needle advancing operation;

after the blocking part abuts against the mounting cylinder seat, the push rod drives the piston to move forwards so as to execute injection operation.

2. The automatic injector of claim 1, wherein the rear connection end includes at least one resilient hook that snaps onto the pushrod holder to form a positive stop connection.

3. The automatic injector of claim 2, wherein a stop surface is provided on said flexible hook, and wherein a push surface is provided on said button, said push surface acting on said stop surface to move said flexible hook outwardly to disengage said flexible hook from said push rod holder by depressing said button.

4. The automatic injector of claim 3, wherein the pressing assembly further comprises a knob rotatably disposed on the connection hub, and a button disposed on the knob, wherein the connection hub is provided with a rib, the button is provided with a slot for engaging with the rib, and the button is locked or unlocked by rotating the knob to change the relative position between the rib and the slot.

5. The automatic injector of claim 4, further comprising a sheath assembly comprising a telescoping sheath and a sheath connector coupled to each other, the telescoping sheath slidably disposed within the stationary barrel and the telescoping sheath being positioned outside of the syringe barrel, the sheath connector having a stop corresponding to the resilient catch, the stop being positioned outside of the resilient catch and capable of limiting outward movement of the resilient catch.

6. The automatic injector of claim 5, wherein the sheath connector is provided with a first boss, the knob is provided with a second boss corresponding to the first boss, the second boss is positioned behind the first boss to limit the backward movement of the sheath connector, and the knob is rotated to change the relative position between the first boss and the second boss to release the limit of the backward movement of the sheath connector by the second boss.

7. The automatic injector of claim 5, wherein said sheath assembly further comprises a sheath spring for urging said telescoping sheath forward after injection is complete, said sheath spring being disposed outside of said sheath connector frame;

after injection is completed, the syringe barrel moves forwards, and the sheath spring drives the sheath connecting frame to drive the telescopic sheath to move forwards until the telescopic sheath can completely cover the needle.

8. The automatic injector of claim 7, wherein the push rod retainer is provided with a limit spring for limiting the backward retraction of the sheath connector;

a second limiting step is arranged on the sheath connecting frame;

the second limiting step and the sheath connecting frame synchronously move forwards to the front of the limiting elastic piece, the limiting elastic piece is ejected outwards at the moment, and the ejected limiting elastic piece can prop against the second limiting step to limit the sheath connecting frame to move backwards.

9. The automatic injector of claim 1, wherein the propulsion assembly further comprises a spring guide rod disposed within the slot, the propulsion spring being sleeved on the spring guide rod.