CN114432542B - an automatic injector - Google Patents

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

an automatic injector

Technical field

The invention belongs to the technical field of medical devices, and specifically relates to an automatic injector.

Background technique

The needles of existing prefilled syringes (PFS) are exposed, which can easily cause fear and psychological stress for patients when using them. At the same time, since the needle is outside without any protective device, it is easy for the patient to cause other unnecessary injuries when using it. After the injection, the needle is not well protected and can easily cause injury.

With existing prefilled syringes (PFS), you need to operate the push rod after the needle is inserted into the skin to inject, which is relatively complicated and requires a high level of operators. Moreover, most patients are afraid of manually inserting needles and subcutaneous injections. psychology. For some patients with serious conditions, when manual injection is performed, shaking of the hand will cause greater injection trauma.

Therefore, improvements are needed.

Contents of the invention

The object of the present invention is to provide an automatic injector that is easy to operate.

In order to achieve the above object, the present invention provides an automatic injector, including:

The shell includes a fixed cylinder, an end cap and a connecting cylinder seat. The end cap is detachably provided at one end of the fixed cylinder, and the connecting cylinder seat is provided at the other end of the fixed cylinder;

A syringe assembly includes a syringe barrel, a needle and a piston. There is medicine in the syringe barrel. The needle is connected to the front of the syringe barrel, and the installed end cap is located in front of the needle; the piston is arranged in the syringe barrel and closed. syringe barrel;

Propulsion assembly, which includes a push rod, a push rod holder and a push spring. The push rod holder is arranged on the connecting cylinder seat. The push rod is provided with a strip groove along its length direction, and the push spring is set in the strip groove; The push rod has a front action end and a rear connection end. The front action end extends into the syringe barrel and can contact the piston. The rear connection end is connected to the push rod holder and compresses the push spring;

A pressing component includes a button, which is arranged on the connecting cylinder base;

By pressing the button, the rear connecting end is separated from the push rod holder, and the push rod moves forward under the action of the push spring. The push rod offsets the piston, and the piston first drives the syringe barrel to move forward in the first stage to execute The needle is inserted, and then the piston is driven to perform the second stage of forward movement in the syringe barrel to perform the injection operation.

In the above technical solution of the present invention, the rear connection end in the initial state is connected to the push rod holder. During use, the rear connection end is separated from the push rod holder by pressing the button. At this time, under the action of the pushing spring The lower push rod moves forward and offsets the piston. On the one hand, due to the existence of friction resistance, the piston will first drive the entire syringe barrel to move forward to perform the needle insertion operation. On the other hand, when the syringe barrel reaches the set position (At this point, the needle insertion is completed), the push rod that continues to move forward will drive the piston to continue moving forward in the syringe barrel to perform the injection operation;

Specifically, the needle insertion and injection operations can be automatically realized by pressing the button, making it convenient for patients to self-inject.

As another specific embodiment of the present invention, the housing further includes a mounting cylinder seat. The syringe barrel is set on the fixed cylinder through the mounting cylinder seat. The syringe barrel can slide in the mounting cylinder seat. At the rear end of the syringe barrel Provided with blocking portion;

Before the blocking part and the installation cylinder seat are offset, the push rod drives the piston and the syringe barrel to move forward synchronously to perform the needle insertion operation;

After the blocking part and the installation cylinder seat are offset, the push rod drives the piston to move forward to perform the injection operation.

In this solution, the blocking portion on the syringe barrel is limited by installing a barrel seat. The size of the installation barrel seat can be adjusted according to different models to adapt to different needle insertion needs.

As another specific embodiment of the present invention, the rear connection end includes at least one elastic hook, and the elastic hook is clamped on the push rod holder to form a limiting connection.

As another specific embodiment of the present invention, a stop surface is provided on the elastic hook, and a push surface is provided on the button. By pressing the button, the push surface acts on the stop surface to cause the elastic hook to move outward, causing the elastic hook to move outward. Disengage from the push rod retainer.

As another specific embodiment of the present invention, the pressing component further includes a knob. The knob is rotatably mounted on the connecting barrel base, and the button is mounted on the knob. The connecting barrel base is provided with a convex rib, and the button is provided with a convex rib corresponding to the convex rib. Matching the card slot, by turning the knob to change the relative position between the ribs and the card slot, the button can be locked or unlocked.

In this solution, the knob is used to lock or unlock the button. When not in use, the button is locked. At this time, it has good safety whether during assembly or transportation.

As another specific embodiment of the present invention, it also includes a sheath assembly, which includes a telescopic sheath and a sheath connecting frame connected to each other, the telescopic sheath is slidably disposed in the fixed barrel, and the telescopic sheath is located on the syringe barrel. On the outside of the body, the sheath connecting frame is provided with a limiting piece corresponding to the elastic hook. The limiting piece is located on the outside of the elastic hook and can limit the outward movement of the elastic hook.

As another specific embodiment of the present invention, the sheath connecting frame is provided with a first boss, and the knob is provided with a second boss corresponding to the first boss, and the second boss is located behind the first boss. To limit the backward movement of the sheath, the relative position between the first boss and the second boss is changed by turning the knob to release the second boss from restricting the backward movement of the sheath.

In this solution, a knob is used to limit the position of the sheath connecting frame. When not in use, the sheath connecting frame cannot move backwards to avoid misoperation during use and improve safety.

As another specific embodiment of the present invention, by rotating the knob, the second boss and the first boss are staggered, and at the same time, the ribs can be matched with the slots.

As another specific embodiment of the present invention, the sheath assembly also includes a sheath spring for driving the telescopic sheath to move forward after the injection is completed, and the sheath spring is arranged on the outside of the sheath connection frame;

A first limiting step is provided on the sheath connecting frame, one end of the sheath spring offsets the first limiting step, and the other end of the sheath spring offsets the connecting cylinder seat;

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

In this solution, after the injection is completed, the sheath spring is used to automatically move the telescopic sheath forward and extend it to completely cover the needle, ensuring that the needle is invisible during the entire injection process and avoiding needle fear.

As another specific embodiment of the present invention, the push rod cage is provided with a limiting elastic piece for limiting the backward retraction of the sheath connector;

The sheath connecting frame is located outside the limiting spring piece and can compress the limiting spring piece;

A second limiting step is provided on the sheath connecting frame;

The second limiting step and the sheath connecting frame move forward synchronously to the front of the limiting spring piece. At this time, the limiting spring piece pops out to the outside. The popped out limiting spring piece can offset the second limiting step to limit the direction of the sheath connecting frame. Post-movement.

In this solution, the elastic deformation ability of the limiting spring is used to limit the extended sheath connector. The pop-up limiting spring can offset the second limiting step. At this time, the telescopic sheath completely covers the needle and It cannot move backwards. Make sure the needle cannot be touched after the injection is completed to avoid secondary injury.

As another specific embodiment of the present invention, the propulsion assembly also includes a spring guide rod, the spring guide rod is arranged in the strip groove, and the propulsion spring is sleeved on the spring guide rod.

The invention has the following beneficial effects:

The automatic injector provided by the present invention can automatically insert the needle and start the injection operation by simply pressing the button on the skin, and has the advantages of convenient operation and high comfort;

In the present invention, the needle is invisible during the injection process, thus preventing patients from fearing the injection;

The invention is equipped with multiple safety mechanisms at the same time to ensure the safety of assembly, transportation, and use operations. After the injection is completed, the telescopic sheath extends to protect the needle, making the needle untouchable and avoiding secondary damage. .

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Description of the drawings

Figure 1 is a schematic structural diagram of the automatic injector of the present invention;

Figure 2 is a schematic cross-sectional view of the automatic injector of the present invention;

Figure 3 is an exploded schematic view of the automatic injector of the present invention;

Figure 4 is a schematic cross-sectional view of the automatic injector of the present invention in a three-dimensional state;

Figure 5 is a second schematic cross-sectional view of the automatic injector of the present invention in a three-dimensional state;

Figure 6 is a schematic diagram of the automatic injector of the present invention during preparation before injection. At this time, the telescopic sheath is close to the skin and the button is not pressed yet;

Figure 7 is a schematic diagram of the automatic injector of the present invention when the needle insertion is completed. At this time, the needle has completed the needle insertion operation and the injection operation has not yet been performed;

Figure 8 is a schematic diagram of the automatic injector of the present invention when the injection is completed. At this time, the piston continues to feed to complete the injection operation;

Figure 9 is a schematic diagram of the automatic injector of the present invention after the injection is completed. At this time, the telescopic sheath is removed from the skin, and the telescopic sheath automatically pops up to protect the needle;

Figure 10 is an enlarged schematic diagram of position A in Figure 2;

FIG. 11 is an enlarged schematic view of position B in FIG. 6 .

Detailed ways

In order to more clearly understand the above objects, features and advantages of the present invention, the present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, as long as there is no conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

Many specific details are set forth in the following description to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described here. Therefore, the protection scope of the present invention is not limited to the specific details disclosed below. Limitations of Examples.

Example 1

The present invention provides an automatic injector, specifically an automatic injection pen adapted to a prefilled syringe, as shown in Figures 1-11, including a housing 100, a syringe assembly 200, a pushing assembly 300, a pressing assembly 400 and a Sheath assembly 500.

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

The installation cylinder base 120 is provided in the fixed cylinder 110, the end cap 130 is the pen cap, which is detachably provided at one end of the fixed cylinder 110, and the connecting cylinder seat 140 is provided at the other end of the fixed cylinder 110;

The syringe assembly 200 includes a syringe barrel 210, a needle 220 and a piston 230. There is medicine in the syringe barrel 210. The needle 220 is connected to the front of the syringe barrel 210. A needle cap 240 can be assembled on the needle 220 to form protection. The installed end cap 130 is located in front of the needle 220, and the piston 230 is arranged in the syringe barrel 210 and seals the syringe barrel 210. The medicine in the syringe barrel 210 is injected by pushing the piston 230 to move in the syringe barrel 210;

The specific syringe barrel 210 is installed on the fixed barrel 110 through the mounting barrel seat 120. The syringe barrel 210 can slide within the mounting barrel seat 120 for a set distance, which is actually determined according to design needs.

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

The push rod holder 320 is disposed on the connecting barrel seat 140. The push rod 310 is provided with a strip groove 311 along its length direction. The push rod 330 is disposed in the strip groove 311. The spring guide rod 340 is disposed in the strip groove 311. inside, and the push spring 330 is set on the spring guide rod 340;

The push rod 310 has a front working end 310a and a rear connecting end 310b. The front working end 310a extends into the syringe barrel 210 and can abut the piston 230. The rear connecting end 310b is connected to the push rod holder 320 and compresses the pushing spring 330. ;

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

The knob 420 is rotatably mounted on the connecting tube seat 140, and the button 410 is mounted on the knob 420. The connecting tube seat 140 is provided with a convex rib 141, and the button 410 is provided with a slot 411 matching the convex rib 141. By rotating the knob 420 changes the relative position between the rib 141 and the slot 411 to lock or unlock the button 410, that is, the button 410 can be pressed by turning the knob 420 to the specified position, otherwise the button 410 cannot be pressed normally, so as to provide safety protection. Effect.

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

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

Specifically, the elastic hook 312 is provided with a stop surface 313, and the specific stop surface 313 is a sloped or arc-shaped structure. The button 410 is provided with a pushing surface 412. By pressing the button 410, the pushing surface 412 acts on the stop. The blocking surface 313 causes the elastic hook 312 to move outward, causing the elastic hook 312 to disengage from the push rod holder 320 to release the constraint on the push rod 310 and allow it to move under the action of the pushing spring 330 .

Correspondingly, the push rod 310 is provided with an upper fixed connector 350 and a lower fixed connector 360, which are connected to the blocking portion 211 through the upper fixed connector 350 and the lower fixed connector 360 to prevent the syringe barrel 210 from rotating. The fixed connection frame 350 and the lower fixed connection frame 360 can slide relative to the push rod 310. By designing the dimensions of the upper fixed connection frame 350 and the lower fixed connection frame 360, the maximum forward movement of the push rod can be indirectly limited.

In the initial state, the upper fixed connection frame 350 and the lower fixed connection frame 360 preferably offset the push rod holder 320, thereby accurately positioning the syringe barrel 210 to prevent shaking.

There is a blocking part 211 at the rear end of the syringe barrel 210. Before the blocking part 211 comes into contact with the mounting cylinder seat 120 (specifically, the blocking part 211 drives the lower fixed connection frame 360 to come into contact with the mounting cylinder seat 120), the push rod 310 drives The piston 230 and the syringe barrel 210 move forward synchronously to perform the needle insertion operation. After the blocking part 211 offsets the installation cylinder seat 120 (specifically, the blocking part 211 drives the lower fixed connection frame 360 to offset the installation cylinder seat 120), the push rod 310 continues to drive the piston 230 forward to perform the injection operation.

The sheath assembly 500 includes a telescopic sheath 510 and a sheath connecting frame 520 that are connected to each other. The telescopic sheath 510 is slidably disposed in the fixed barrel 110 and is located outside the syringe barrel 210. The sheath is connected to The frame 520 is provided with a limiting piece 521 corresponding to the elastic hook 312. The limiting piece 521 is located outside the elastic hook 312 and can limit the outward movement of the elastic hook 312.

Among them, the sheath connecting frame 520 is provided with a first boss 522, and the knob 420 is provided with a second boss 421 corresponding to the first boss 522. The second boss 421 is located behind the first boss 522 to limit The sheath connecting frame 520 moves backward, and the relative position between the first boss 522 and the second boss 421 is changed by rotating the knob 420, so as to release the restriction of the second boss 421 on the backward movement of the sheath connecting frame 520. That is to say, when the knob 420 is in the initial state, the telescopic sheath 510 cannot be retracted backward and cannot perform the next operation, thereby avoiding misoperation and achieving a safety protection effect.

Correspondingly, by rotating the knob 420, the second boss 421 and the first boss 522 are staggered, and at the same time, the ribs 141 can be matched with the slots 411, that is, the telescopic sheath 510 (sheath connection) is realized. The button 410 is pressed while the frame 520) can move backward.

More specifically, the sheath assembly 500 also includes a sheath spring 530 for driving the telescopic sheath 510 to move forward after the injection is completed. The sheath spring 530 is disposed on the outside of the sheath connecting frame 520. On the sheath connecting frame 520 There is a first limiting step 523, one end of the sheath spring 530 is against the first limiting step 523, and the other end of the sheath spring 530 is against the connecting cylinder seat 140;

Further, the push rod retainer 320 is provided with a limiting elastic piece 321 for limiting the backward retraction of the sheath connecting frame 520. The sheath connecting frame 520 is located outside the limiting elastic piece 321 and compresses the limiting elastic piece 321.

Among them, in the initial state, the push rod 310 itself occupies the internal space of the push rod cage 320 and prevents the limiting elastic piece 321 from elastically deforming inward. At this time, the outside of the limiting elastic piece 321 is positioned facing the sheath connecting frame 520. The sheath connecting frame 520 cannot move forward.

A second limiting step 524 is provided on the sheath connecting frame 520. The second limiting step 524 and the sheath connecting frame 520 move forward synchronously to the front of the limiting elastic piece 321. After the push rod 310 moves forward, it will Make way for the internal space. At this time, the sheath connecting frame 520 can press the limiting elastic piece 321 inward under the action of the sheath spring 530 to cause it to deform. Then the limiting elastic piece 321 returns to its position under the action of its elastic force. The time-limiting elastic piece 321 pops out to the outside, and the pop-up limiting elastic piece 321 can offset the second limiting step 524 to limit the backward movement of the sheath connecting frame 520, thereby protecting the needle 220 after the injection is completed, and preventing secondary damage. harm.

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

The mounting barrel seat 120 in this embodiment may be transparent or have a notch for observation. Correspondingly, a viewing window is formed on the fixed barrel 110 corresponding to the mounting barrel seat 120 to observe the injection process more intuitively.

The specific operation process of this embodiment is shown in Figure 6-9, as follows:

First, remove the end cap 130 and the needle cap 240 on the needle 220;

Then, rotate the knob 420 so that the slot 411 can match the convex rib 141 and at the same time the second boss 421 and the first boss 522 are staggered. That is, the button 410 can be pressed normally. When the telescopic sleeve is pressed against the skin, , the telescopic sleeve and the sleeve holder move backward together; at this time, the limiter 521 on the sheath connecting frame 520 no longer restricts the outward movement of the elastic hook 312;

Then, press the button 410 forward. Under the action of the button 410, the elastic hook 312 moves outward and detaches from the push rod holder 320 by using the cooperation of the stop surface 313 and the pushing surface 412. Under the action of the pushing spring 330 Down, the push rod 310 moves forward, and the push rod 310 offsets the piston 230, first driving the syringe barrel 210 to move forward in the first stage to perform the needle insertion operation, until the blocking part 211 drives the lower fixed connection frame 360 and the installation barrel seat 120 offsets each other, and then drives the piston 230 to perform a second stage of forward movement in the syringe barrel 210 to perform the injection operation.

After the injection is completed, using the force of the sheath spring 530, the sheath connecting frame 520 moves forward, driving the telescopic sheath 510 to move forward until the limiting spring piece 321 on the push rod retainer 320 pops out to the outside, and the pop-up limiter The elastic piece 321 can resist the second limiting step 524 to limit the backward movement of the sheath connecting frame 520, thereby protecting the needle 220 after the injection is completed.

This embodiment has an automatic needle insertion function. When the button 410 triggers the release of the push spring 330, the needle insertion action will be performed first. The entire syringe barrel 210 moves forward. During this process, the push rod 310 directly resists the piston 230. The piston 230 due to frictional resistance The existence of the syringe barrel 210 will first drive the entire syringe barrel 210 to move forward. After reaching the front end limit (that is, the blocking part 211 drives the lower fixed connection frame 360 to offset the installation barrel seat 120) the syringe barrel 210 stops moving forward. At this time, the needle 220 has already When the needle 220 is inserted into the subcutaneous tissue, the resistance of the needle 220 when inserted into the subcutaneous tissue is much smaller than the resistance of the piston 230, so the needle 230 can automatically insert the needle. Under the further forward action of the push rod 310, the piston 230 moves forward to inject the medical solution.

This embodiment has multiple safety protections. When the knob 420 is not unlocked, the button 410 and the sheath connector 520 cannot operate, ensuring the safety when transporting and taking the injection device. The telescopic sheath 510 is elastic. When the front end of the telescopic sheath 510 is close to the injection site, artificial external force is required to ensure that the injection device can be inserted into the skin after the needle is taken out. At the same time, continuous force can prevent the injection device from shifting or sliding out of position.

This embodiment is used for self-injection by the patient, and can be used with existing prefilled syringes. It also has multiple protections to avoid leakage of medicinal liquid caused by misoperation; in addition, this embodiment performs automatic injection, and the patient's self-injection is convenient to operate. , the needle 220 is not exposed throughout the injection process to avoid fear, and the needle 220 is protected after the injection is completed, and will not cause secondary harm to the patient.

In the description of this embodiment, the "back", "rear" and "backward" indicating the orientation are "up", "above" and "upward" in the drawings, and the "front" and "front" indicating the orientation are , "forward" means "down", "below" and "downward" in the drawings.

Although the preferred embodiments of the present invention are disclosed above, they are not intended to limit the scope of implementation of the present invention. Any person of ordinary skill in the art can make some improvements without departing from the scope of the present invention. That is, any equivalent improvements made in accordance with the present invention should be covered by the scope of the present invention.

Claims (9)

1. 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 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;

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 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;

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 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.