An automatic injection pen

Abstract

This application discloses an automatic injection pen, comprising: a housing; an injection assembly installed within one end of the housing, the injection assembly including a safety cap, a push rod retainer, a push rod installed within the push rod retainer, a trigger retainer sleeved outside the push rod retainer, a blocking member fixedly installed within the housing, and an injection spring abutting between the blocking member and the push rod; a trigger assembly installed within the other end of the housing, the trigger assembly including a needle tip protective sleeve, a pen cartridge holder fixedly installed within the housing, and a trigger spring abutting between the pen cartridge holder and the needle tip protective sleeve; and a syringe installed between the injection assembly and the trigger assembly, the syringe being disposed within the pen cartridge holder, one end of the push rod being disposed inside one end of the syringe, the trigger retainer being fixedly connected to the needle tip protective sleeve, and the blocking member being fixedly connected to the push rod retainer. This automatic injection pen can achieve prevention of accidental triggering before use, reliable linkage during injection, and safe locking of the needle after injection.

Description

Technical Field

[0001] This application relates to the field of medical device technology, specifically to an automatic injection pen. Background Technology

[0002] In the field of medical device technology, automated injection pens have become an important tool widely used in drug therapy because they can significantly reduce the difficulty of injection operations and reduce the pain experienced by patients during the injection process. They have been welcomed by many medical professionals and patients.

[0003] When not in use, existing automatic injection pens are prone to accidental release of the injection spring due to external pressure or accidental activation, resulting in drug waste or accidental injury. During injection, the triggering mechanism lacks a clear travel lock, which can easily cause jamming or premature reset, affecting injection reliability. After injection, the needle protector often fails to lock automatically and securely in the protective position, posing a risk of needlestick injury due to accidental needle exposure.

[0004] Therefore, there is an urgent need for an automatic injection pen that can prevent accidental triggering before use, reliably link during injection, and safely lock the needle after injection. Summary of the Invention

[0005] In view of the safety hazards of existing automatic injection pens, such as accidental triggering due to misoperation before use, poor reliability during injection, and needle exposure after injection that can cause needlestick injuries, this application provides an automatic injection pen that systematically solves the safety problems throughout the entire life cycle of the automatic injection pen through multiple mechanical interlocks and sequential triggering mechanisms.

[0006] Specifically, the following technical solutions are included: This application provides an automatic injection pen, comprising: shell; An injection assembly is installed at one end inside the housing. The injection assembly includes a safety cap, a push rod retainer, a push rod installed inside the push rod retainer, a trigger retainer sleeved outside the push rod retainer, a blocking member fixedly installed inside the housing, and an injection spring abutting between the blocking member and the push rod. A trigger assembly is installed at the other end inside the housing. The trigger assembly includes a needle tip protective sleeve, a pen refill holder fixedly installed inside the housing, and a trigger spring abutting between the pen refill holder and the needle tip protective sleeve. A syringe is installed between the injection assembly and the trigger assembly. The syringe is disposed inside the pen cartridge holder. One end of the plunger is disposed inside one end of the syringe. The trigger retainer is fixedly connected to the needle tip protective sleeve. The blocking member is fixedly connected to the plunger retainer. Before the injection begins, the safety cap is inserted into the blocking member to restrict the movement of the trigger retainer, thus keeping the injection assembly in a non-triggerable state. When the safety cap is pulled out of the blocking member, the trigger retainer moves through the needle tip protective sleeve, thereby triggering the injection assembly to squeeze the syringe to complete the injection operation.

[0007] In one embodiment of this application, the safety cap is provided with a second arm, and a first protrusion is provided on the outer side of the end of the second arm; the blocking member is provided with a first spring arm, and a protrusion is provided on the outer side of the first spring arm; When the safety cap is inserted into the blocking member, the second arm is located between the first spring arm and the push rod fixing member, and the first protrusion supports the first spring arm outward so that the protrusion on the outer side of the first spring arm abuts against the top of the trigger retainer. When the safety cap is pulled out of the blocking member, the second arm retracts from between the first spring arm and the push rod fixing member, the first spring arm retracts inward, and the protrusion on the outer side of the first spring arm separates from the trigger retainer, so that the trigger retainer can be moved.

[0008] In one embodiment of this application, the push rod fixing member has a fourth protrusion on its side, the second arm end has a first groove on its inner side, the safety cap is inserted into the blocking member, and the fourth protrusion cooperates with the first groove.

[0009] In one embodiment of this application, the top of the trigger retainer is provided with a second protrusion, the inner side of the second protrusion is provided with a chamfer, and the protrusion on the outer side of the first spring arm is inclined upward and cooperates with the chamfer on the inner side of the second protrusion.

[0010] In one embodiment of this application, the trigger retainer has a second slot on its side and a raised step on its inner wall; the push rod fixing member has a spring arm hook and a third spring arm on its side, and both the inner and outer sides of the spring arm hook have protrusions, with the inner protrusion being inclined; the push rod has a third slot, a fourth slot below the third slot, and a hole on one side of the third and fourth slots; the push rod fixing member is sleeved on the upper part of the push rod, and the outer side of the third spring arm has a downwardly inclined protrusion, and the inner wall of the trigger retainer also has a third upwardly inclined protrusion, with the outer protrusion of the third spring arm cooperating with the third protrusion of the trigger retainer; Before the injection begins, the protrusion on the outer side of the spring arm hook engages with the protrusion step, and the protrusion on the inner side of the spring arm hook engages with the fourth slot, so that the spring arm hook is fixed in the fourth slot; and the third spring arm is supported by the outer wall of the push rod, so that the third protrusion abuts against the outer protrusion of the third spring arm to limit the movement of the trigger retainer. During the injection process, the safety cap is pulled out and the trigger retainer is moved upward by the needle tip protective sleeve, so that the second slot moves to the outer protrusion of the spring arm hook. The outer protrusion of the spring arm hook cooperates with the second slot to make the spring arm hook expand outward. The inner protrusion of the spring arm hook disengages from the fourth slot under the elastic force of the injection spring. The injection spring drives the push rod to squeeze the syringe to complete the injection. After injection, the hole of the push rod moves to the third spring arm of the push rod fixing member. The third spring arm engages with the hole to allow it to retract inward. The needle tip protective sleeve and the trigger retainer move downward under the elastic force of the trigger spring. The third protrusion slides past the outer protrusion of the third spring arm and is locked below the outer protrusion of the third spring arm, preventing the trigger retainer from moving upward. The protrusion step moves to the outer protrusion of the spring arm hook. The protrusion on the outer side of the spring arm hook engages with the protrusion step to allow the spring arm hook to retract inward. The protrusion on the inner side of the spring arm hook engages with the third slot to fix the spring arm hook in the third slot.

[0011] In one embodiment of this application, the top of the outer shell is provided with a fifth slot and an arc-shaped groove located on one side of the fifth slot; The blocking member has a first buckle on its side, and the fifth slot cooperates with the first buckle, so that the first buckle can be locked in the fifth slot; The safety cap is also provided with a first arm, which is shorter than the second arm. The arc-shaped groove cooperates with the first arm, and the first arm can extend into the arc-shaped groove.

[0012] In one embodiment of this application, the pen refill holder is provided with a third buckle, and the side of the outer shell is provided with a sixth slot. The third buckle cooperates with the sixth slot, and the third buckle can be locked in the sixth slot. The bottom of the pen refill holder is provided with an axial protrusion, and the trigger spring is sleeved on the outside of the plurality of axial protrusions and abuts against the axial protrusions.

[0013] In one embodiment of this application, the needle tip protective sleeve is provided with a third arm, the third arm is provided with a seventh slot and an eighth slot located below the seventh slot; The trigger retainer is provided with a second spring arm on its side, and the seventh slot cooperates with the second spring arm, so that the second spring arm can be locked in the seventh slot; The pen refill holder has a fourth spring arm on its side, and the eighth slot cooperates with the fourth spring arm, so that the fourth spring arm can be locked in the eighth slot.

[0014] In one embodiment of this application, the blocking member is sleeved on the upper part of the push rod fixing member, the blocking member has a first slot on its side, the push rod fixing member has a second buckle on its side, and the second buckle cooperates with the first slot, and the second buckle can be locked in the first slot.

[0015] In one embodiment of this application, a cap is also included, the cap being mounted on the bottom of the housing, the bottom of the housing being provided with a rotating protrusion and a plug block located below the rotating protrusion; The cap is fixedly connected to the inside of the cap, and the inner wall of the cap column is provided with several inwardly extending barbs. The barbs cooperate with the syringe and are used to hook the needle tip sheath provided at the end of the syringe. The inner wall of the cap is provided with a fifth protrusion, which is rotatably engaged with the rotating protrusion. The plug block engages with the fifth protrusion so that the cap can be fixed to the bottom of the outer shell.

[0016] The beneficial effects of this application are: This application utilizes a multi-interlocking mechanism comprised of a safety cap, a blocking element, and a trigger retainer to significantly enhance the safety of the automatic injection pen before use. Specifically, in the initial state, the safety cap is inserted into the blocking element. The first protrusion on the outer side of its second arm supports the first spring arm of the blocking element outward, preventing it from retracting inward and thus holding the top of the trigger retainer in place. Simultaneously, the third spring arm of the push rod fixing element is supported by the outer wall of the push rod, causing the oblique third protrusion of the trigger retainer to overlap the outer protrusion of the third spring arm, restricting the downward movement of the trigger retainer. Therefore, both ends of the trigger retainer are reliably locked, preventing injection even from being triggered by accidental impact or compression. This structurally eliminates the risk of accidental triggering and ensures absolute safety before use.

[0017] During injection triggering, this application achieves controllable and reliable execution of the injection sequence through precise engagement of the locking slot and the spring arm. Specifically, when the safety cap is removed and the needle tip protective sleeve is pushed upward, the needle tip protective sleeve moves the trigger retainer upward, causing the second locking slot of the trigger retainer to move to the outer protrusion of the spring arm hook on the push rod fixing member, providing space for the spring arm hook to expand outward. The inner protrusion of the spring arm hook then unlocks, and driven by the stored energy of the injection spring, the push rod moves smoothly downward to squeeze the syringe, completing the injection. This linkage mechanism ensures that the injection action is initiated only under a clear trigger operation, and that the injection process is smooth and stable, avoiding jamming or mid-injection failure, thus improving the reliability and safety of the injection.

[0018] After injection, this application achieves immediate and permanent safety coverage of the syringe needle. When the plunger moves downward to its endpoint, the plunger hole moves to the third spring arm of the plunger retainer. The third spring arm retracts inward, and the trigger retainer automatically moves downward under the elastic force of the trigger spring. Its third protrusion slides past the outer protrusion of the third spring arm and is locked below it, preventing the trigger retainer from moving upward again. At this time, the needle tip protective sleeve linked to the trigger retainer completely covers the syringe needle and forms a one-way lock, effectively preventing needlestick injuries caused by accidental contact or improper operation after injection, providing reliable safety protection for patients and users. Attached Figure Description

[0019] Figure 1 This is an exploded view of the automatic injection pen of this application.

[0020] Figure 2 This is a front view of the automatic injection pen in its initial state according to this application.

[0021] Figure 3 This is a cross-sectional view of the automatic injection pen of this application in its initial state.

[0022] Figure 4 for Figure 3 A magnified view of A in the middle.

[0023] Figure 5 This is a front view of the automatic injection pen in the injection state of this application.

[0024] Figure 6 This is a cross-sectional view of the automatic injection pen in the injection state of this application.

[0025] Figure 7 This is a perspective view of the safety cap of this application.

[0026] Figure 8 This is a perspective view of the blocking component of this application.

[0027] Figure 9 This is a perspective view of the trigger retainer in this application.

[0028] Figure 10 This is a cross-sectional view of the trigger retainer in this application.

[0029] Figure 11 This is a perspective view of the push rod fixing component of this application.

[0030] Figure 12 This is a perspective view of the push rod in this application.

[0031] Figure 13 This is a perspective view of the casing of this application.

[0032] Figure 14 This is a perspective view of the pen refill holder of this application.

[0033] Figure 15 This is a perspective view of the needle tip protective sleeve of this application.

[0034] Figure 16 This is a perspective view of the cap of this application.

[0035] In the diagram: 1. Safety cap; 101. First arm; 102. Second arm; 103. First groove; 104. First protrusion; 105. Center post; 2. Blocking element; 201. First buckle; 202. First spring arm; 203. First slot; 3. Trigger retainer; 301. Second protrusion; 302. Second slot; 303. Second spring arm; 304. Protrusion step; 305. Third protrusion; 4. Injection spring; 5. Push rod fixing element; 501. Second buckle; 502. Fourth protrusion; 503. Spring arm hook; 504. Third spring arm; 6. Push rod; 601. Third slot 602, Hole; 603, Fourth Slot; 7, Outer Shell; 701, Fifth Slot; 702, Arc-shaped Slot; 703, Sixth Slot; 704, Rotating Protrusion; 705, Insert Block; 8, Syringe; 9, Pen Refill Holder; 901, Third Buckle; 902, Fourth Spring Arm; 903, Axial Protrusion; 10, Trigger Spring; 11, Needle Tip Protective Sheath; 1101, Seventh Slot; 1102, Eighth Slot; 1103, Third Arm; 12, Cap; 1201, Barb; 1202, Fifth Protrusion; 1203, Cap Post; 1300, Injection Assembly; 1400, Trigger Assembly. Detailed Implementation

[0036] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0037] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions.

[0038] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0039] like Figures 1 to 16 As shown, this application provides an automatic injection pen, including a housing 7, an injection assembly 1300 installed at one end inside the housing 7, a trigger assembly 1400 installed at the other end inside the housing 7, a syringe 8 installed between the injection assembly 1300 and the trigger assembly 1400, and a cap 12 installed at the bottom of the housing 7. The trigger assembly 1400 triggers the injection assembly 1300, and the injection assembly 1300 squeezes the syringe 8 to complete the injection operation. The syringe 8 is used for storing and injecting medication.

[0040] In some embodiments, the injection assembly 1300 includes a push rod retainer 5, a push rod 6 installed within the push rod retainer 5, a trigger retainer 3 sleeved outside the push rod retainer 5, a blocking member 2 fixedly installed within the housing 7, a safety cap 1 inserted into the blocking member 2, and an injection spring 4 abutting between the blocking member 2 and the push rod 6; the trigger assembly 1400 includes a needle tip protective sleeve 11, a pen refill holder 9 fixedly installed within the housing 7, and a trigger spring 10 abutting between the pen refill holder 9 and the needle tip protective sleeve 11; the syringe 8 is disposed within the pen refill holder 9, one end of the push rod 6 is disposed inside one end of the syringe 8, the trigger retainer 3 is fixedly connected to the needle tip protective sleeve 11, and the blocking member 2 is fixedly connected to the push rod retainer 5. The safety cap 1 is designed to be pluggable. In the initial state, the safety cap 1 is inserted into the blocking member 2 and cannot trigger automatic injection. When the safety cap 1 is pulled out from the blocking member 2, the injection component 1300 becomes a triggerable automatic injection form. The injection component 1300 is triggered by the needle tip protective sleeve 11 to squeeze the syringe 8 to complete the injection operation.

[0041] Optionally, the injection spring 4 is disposed inside the push rod 6, with one end of the injection spring 4 abutting against the bottom of the push rod 6 and the other end abutting against the top of the blocking member 2. The trigger spring 10 is disposed inside the needle tip protective sleeve 11, with one end of the trigger spring 10 abutting against the bottom of the needle tip protective sleeve 11 and the other end abutting against the bottom of the pen refill holder 9.

[0042] In some embodiments, one end of the safety cap 1 is provided with a first arm 101, a second arm 102 and a central post 105. The first arm 101 is shorter than the second arm 102. The two first arms 101 and the two second arms 102 are symmetrically arranged on both sides of one end of the safety cap 1. The first arms 101 and the second arms 102 are staggered. The central post 105 is located at the center of one end of the safety cap 1. The inner side of the end of the second arm 102 is provided with a first groove 103, and the outer side of the end of the second arm 102 is provided with a first protrusion 104.

[0043] In some embodiments, the blocking member 2 is a hollow cylindrical structure with one end open. The side of the blocking member 2 is provided with a first buckle 201, a first spring arm 202, and a first slot 203. The outer side of the first spring arm 202 is provided with a protrusion. The two first buckles 201 and the two first spring arms 202 are symmetrically arranged on both sides of the blocking member 2. The first spring arm 202 is located below the first buckle 201, and the first slot 203 is located on one side of the first buckle 201 and the first spring arm 202. The central post 105 is inserted into the blocking member 2 to play a guiding and stabilizing role, and the injection spring 4 is sleeved on the outside of the central post 105.

[0044] In some embodiments, the trigger retainer 3 is a hollow cylindrical structure and is movable. The top of the trigger retainer 3 is provided with second protrusions 301 on both sides. The side of the trigger retainer 3 is provided with a second slot 302 and a second spring arm 303 located below the second slot 302. The inner wall of the trigger retainer 3 is provided with a protruding step 304 and a third protrusion 305 located on the lower side of the protruding step 304. The third protrusion 305 is inclined upward. The inner side of the second protrusion 301 is provided with a chamfer. The protrusion on the outer side of the first spring arm 202 is inclined upward and cooperates with the chamfer on the inner side of the second protrusion 301.

[0045] In some embodiments, the push rod fixing member 5 is a hollow cylindrical structure. The push rod fixing member 5 has a second buckle 501, a fourth protrusion 502, a spring arm hook 503 located below the second buckle 501, and a third spring arm 504 located below the fourth protrusion 502. The inner and outer sides of the spring arm hook 503 are provided with protrusions, wherein the inner protrusion is set with an inclined surface to facilitate the engagement with the slot of the push rod 6 to achieve unlocking and locking. The blocking member 2 is sleeved on the upper part of the push rod fixing member 5, and the second buckle 501 engages with the first slot 203, so that the second buckle 501 can be locked in the first slot 203.

[0046] In its initial state, the safety cap 1 is inserted into the blocking member 2, and the second arm 102 is located between the first spring arm 202 and the push rod fixing member 5 of the blocking member 2. This structure ensures that the space for the first spring arm 202 to retract inward is occupied by the second arm 102, thereby limiting the inward displacement of the first spring arm 202. The fourth protrusion 502 cooperates with the first groove 103 to form a locking structure, increasing the damping feel when the safety cap 1 is pulled out and preventing the safety cap 1 from accidentally falling off due to slight vibration or collision. The first protrusion 104 pushes the first spring arm 202 outward, so that the protrusion on the outer side of the first spring arm 202 abuts against the top of the trigger retainer 3, thereby limiting the upward movement of the trigger retainer 3. Thus, the trigger retainer 3 is reliably locked, and even if it is subjected to accidental collision or squeezing, the injection action cannot be triggered, thus structurally eliminating the risk of accidental triggering and ensuring absolute safety before use.

[0047] When injection is required, the user pulls out the safety cap 1. The first protrusion 104 releases its outward support to the first spring arm 202, allowing the first spring arm 202 to retract inward. Simultaneously, the second arm 102 disengages from between the first spring arm 202 and the push rod fixing member 5, enabling the first spring arm 202 to retract inward. This releases the locking of the trigger retainer 3, causing the protrusion on the outer side of the first spring arm 202 to separate from the trigger retainer 3, allowing the trigger retainer 3 to move upward and trigger the injection action. Furthermore, because the inner side of the second protrusion 301 of the trigger retainer 3 is chamfered, and the protrusion on the outer side of the first spring arm 202 is tilted upward and cooperates with the chamfer on the inner side of the second protrusion 301, the trigger retainer 3 can move upward more smoothly.

[0048] Therefore, the automatic injection pen provided in this application forms multiple interlocks with the safety cap 1, the first spring arm 202 of the blocking member 2, and the fourth protrusion 502 of the push rod fixing member 5, which reliably locks the trigger retainer 3 in the initial state, thus eliminating the risk of accidental triggering from a structural perspective and significantly improving the safety of the automatic injection pen before use.

[0049] In some embodiments, the push rod 6 is a stepped hollow cylindrical structure. The push rod 6 has a third slot 601, a fourth slot 603 located below the third slot 601, and a hole 602 located on one side of the third slot 601 and the fourth slot 603. The third slot 601 corresponds to the locking position after the injection is completed, and the fourth slot 603 corresponds to the locking position before the injection begins. The push rod fixing component 5 is sleeved on the upper part of the push rod 6. Before the injection begins, the protrusion on the inner side of the spring arm hook 503 engages with the fourth slot 603, so that the spring arm hook 503 of the push rod fixing component 5 is fixed in the fourth slot 603 of the push rod 6. During the injection, the protrusion on the inner side of the spring arm hook 503 moves from the fourth slot 603 to the third slot 601, and the third spring arm 504 engages with the hole 602. After the injection is completed, the protrusion on the inner side of the spring arm hook 503 engages with the third slot 601, so that the spring arm hook 503 of the push rod fixing component 5 is fixed in the third slot 601 of the push rod 6. The position of the hole 602 is designed such that when the push rod 6 moves to the injection endpoint, the hole 602 moves exactly to the third spring arm 504 of the push rod fixing component 5, providing space for the third spring arm 504 to retract inward.

[0050] In this embodiment, in the initial state: before injection begins, the push rod retainer 5 is fitted onto the upper part of the push rod 6, and the protrusion on the inner side of the spring arm hook 503 engages with the fourth slot 603 of the push rod 6, fixing the spring arm hook 503 of the push rod retainer 5 in the fourth slot 603 of the push rod 6. At this time, the push rod 6 is locked in the initial position and cannot move downwards. At the same time, the protrusion on the outer side of the spring arm hook 503 engages with the protruding step 304 of the trigger retainer 3, preventing the spring arm hook 503 from expanding outwards. This structure ensures that the inner protrusion of the spring arm hook 503 remains engaged with the fourth slot 603, preventing accidental unlocking due to vibration or external force. In addition, the third protrusion 305 on the inner wall of the trigger retainer 3 abuts against the outer protrusion of the third spring arm 504 of the push rod retainer 5, providing auxiliary support for the trigger retainer 3 and further enhancing the stability of the initial state. At this time, the injection spring 4 is in a compressed and stored state between the push rod 6 and the blocking member 2, but because the spring arm hook 503 is locked in the fourth slot 603 of the push rod 6, the push rod 6 cannot move downward and the injection action cannot be performed.

[0051] Injection Triggering Process: When the user pushes the needle tip protective sleeve 11 upwards, the needle tip protective sleeve 11, being fixedly connected to the second spring arm 303 of the trigger retainer 3, causes the trigger retainer 3 to move upwards. During the upward movement of the trigger retainer 3, its second slot 302 moves to the outer protrusion of the spring arm hook 503 of the push rod fixing member 5. At this time, the outer protrusion of the spring arm hook 503 engages with the second slot 302 of the trigger retainer 3, providing space for the spring arm hook 503 to expand outwards. After the spring arm hook 503 expands outwards, its inner protrusion also expands outwards. Since the inner protrusion of the spring arm hook 503 is sloped, under the elastic force of the injection spring 4, the inner protrusion of the spring arm hook 503 slides out of the fourth slot 603 of the push rod 6, unlocking the injection action. After unlocking, the push rod 6 moves smoothly downwards under the drive of the injection spring 4, squeezing the syringe 8 to complete the injection operation.

[0052] Injection completion locking: When the push rod 6 moves downward to its endpoint, the protrusion on the inner side of the spring arm hook 503 moves to the third slot 601 of the push rod 6. Simultaneously, the needle tip protective sleeve 11 drives the trigger retainer 3 to move downward. During this downward movement, the protruding step 304 of the trigger retainer 3 moves to the outer protrusion of the spring arm hook 503 of the push rod fixing member 5. At this point, the outer protrusion of the spring arm hook 503 engages with the protruding step 304 of the trigger retainer 3, preventing the spring arm hook 503 from expanding outward. Consequently, the inner protrusion of the spring arm hook 503 engages with the third slot 601 of the push rod 6, fixing the inner protrusion of the spring arm hook 503 of the push rod fixing member 5 in the third slot 601 of the push rod 6, thus locking the push rod 6 in the injection completion position. This endpoint locking structure ensures that the push rod 6 remains stable after injection and will not rebound due to residual spring force or external force, thus guaranteeing the integrity of the injection.

[0053] The automatic injection pen provided in this application achieves trigger control of the injection action through the cooperation of the outer protrusion of the spring arm hook 503 with the protruding step 304 and the second slot 302 of the trigger retainer 3; through the cooperation of the inner protrusion of the spring arm hook 503 with the fourth slot 603 and the third slot 601 of the push rod 6, the initial locking and end-point locking of the push rod 6 are achieved, ensuring that the push rod 6 is in a stable locked state before and after injection, avoiding accidental displacement caused by vibration or external force. The two locking positions of the fourth slot 603 and the third slot 601 correspond to the pre-injection and post-injection positions, respectively, forming a complete stroke control closed loop, ensuring the smooth and stable injection process and the reliability of the injection results.

[0054] Therefore, this automatic injection pen achieves sequential control of the injection stroke through the cooperation between the outer protrusion of the spring arm hook 503 and the trigger retainer 3, and achieves precise locking of the position of the push rod 6 through the cooperation between the inner protrusion of the spring arm hook 503 and the double slot structure on the push rod 6, thus realizing precise segmented control of the push rod 6's stroke. It integrates triggering, stroke control, and endpoint locking into one compact structure, ensuring reliable linkage and effectively avoiding jamming or mid-injection failure during the injection process, thereby improving the reliability of the automatic injection pen.

[0055] In some embodiments, the outer shell 7 is a hollow cylindrical structure. The top of the outer shell 7 is provided with a fifth slot 701 and an arc-shaped groove 702 located on one side of the fifth slot 701. The side of the outer shell 7 is provided with a sixth slot 703 located below the fifth slot 701. The bottom of the outer shell 7 is provided with a rotating protrusion 704 and an insertion block 705 located below the rotating protrusion 704. The fifth slot 701 cooperates with the first buckle 201 of the blocking member 2, and the first buckle 201 can be locked in the fifth slot 701. The arc-shaped groove 702 cooperates with the first arm 101 of the safety cap 1, and the first arm 101 can extend into the arc-shaped groove 702.

[0056] In some embodiments, the pen refill holder 9 is a hollow cylindrical structure. The top of the pen refill holder 9 is provided with a third buckle 901, the side of the pen refill holder 9 is provided with a fourth spring arm 902, and the bottom of the pen refill holder 9 is provided with an axial protrusion 903. The trigger spring 10 is sleeved on the multiple axial protrusions 903 and abuts against the axial protrusions 903. The third buckle 901 cooperates with the sixth slot 703 of the outer shell 7, and the third buckle 901 can be locked in the sixth slot 703.

[0057] In some embodiments, the needle tip protective sleeve 11 has a U-shaped structure and is provided with symmetrically arranged third arms 1103. The third arms 1103 are provided with a seventh slot 1101 and an eighth slot 1102 located below the seventh slot 1101. The seventh slot 1101 cooperates with the second spring arm 303 of the trigger retainer 3, and the second spring arm 303 can be locked in the seventh slot 1101. The eighth slot 1102 cooperates with the fourth spring arm 902 of the pen refill holder 9, and the fourth spring arm 902 can be locked in the eighth slot 1102, thereby realizing the sliding cooperation between the needle tip protective sleeve 11 and the pen refill holder 9, so that the needle tip protective sleeve 11 can move axially relative to the pen refill holder 9.

[0058] In some embodiments, the outer side of the third spring arm 504 is provided with a downwardly inclined protrusion, which engages with the third protrusion 305 of the trigger retainer 3. In this embodiment, the third protrusion 305 on the inner wall of the trigger retainer 3 is inclined upward, facilitating unidirectional sliding over the third spring arm 504. The third spring arm 504 has a certain elasticity, capable of retracting inward under external force and returning to its original position after the external force is released.

[0059] During the injection process, the needle tip protective sleeve 11 is pushed upward, and the trigger spring 10 is compressed and stored. When the unlocking condition is met, the trigger spring 10 releases its elasticity, driving the needle tip protective sleeve 11 to move downward.

[0060] Initial state: Before injection begins, the push rod 6 is in its initial position, and the third spring arm 504 of the push rod retainer 5 is supported by the outer wall of the push rod 6, maintaining an outwardly expanded state. The third protrusion 305 of the trigger retainer 3 abuts against the upper part of the outer protrusion of the third spring arm 504. At this time, the trigger spring 10 is in a compressed state, but due to the support of the outer protrusion of the third spring arm 504, the trigger retainer 3 cannot move downward.

[0061] Injection process: When the user triggers the injection action, the push rod 6 moves downward under the drive of the injection spring 4, squeezing the syringe 8 to complete the injection. The user needs to continuously press the needle tip protective sleeve 11 to trigger the injection action, so the trigger retainer 3 cannot move downward.

[0062] Locking after injection: When the push rod 6 moves downward to the end point (i.e., injection is complete), the hole 602 of the push rod 6 moves to the third spring arm 504 of the push rod fixing member 5. At this time, the third spring arm 504 loses the support of the outer wall of the push rod 6 and can retract inward under the action of external force, entering the hole 602. As the third spring arm 504 retracts inward, its obstruction to the third protrusion 305 of the trigger retainer 3 is released. Under the elastic force of the trigger spring 10, the needle tip protective sleeve 11 drives the trigger retainer 3 to move downward. The third protrusion 305 of the trigger retainer 3 slides over the outer protrusion of the third spring arm 504 of the push rod fixing member 5. Since the third protrusion 305 is inclined upward and the outer protrusion of the third spring arm 504 is inclined downward, the outer protrusion of the third spring arm 504 cooperates with the third protrusion 305, so that the third protrusion 305 can smoothly slide downward over the outer protrusion of the third spring arm 504. After the third protrusion 305 has completely slid past the outer protrusion of the third spring arm 504, the third spring arm 504 returns to its outwardly expanding state, and the outer protrusion of the third spring arm 504 is locked above the third protrusion 305. At this time, the third protrusion 305 is unidirectionally locked by the outer protrusion of the third spring arm 504 and cannot move upward. At this time, since the trigger retainer 3 is fixedly connected to the needle tip protective sleeve 11, the needle tip protective sleeve 11 also cannot move upward and always remains in the position covering the needle tip of the syringe 8, forming a permanent safety lock.

[0063] Therefore, the automatic injection pen provided in this application has a one-way locking mechanism formed by the cooperation between the third protrusion 305 and the outer protrusion of the third spring arm 504. When the trigger retainer 3 moves downward, the third protrusion 305, which is inclined upward, cooperates with the outer protrusion of the third spring arm 504, which is inclined downward, allowing the third protrusion 305 to slide smoothly downward over the outer protrusion of the third spring arm 504. When the trigger retainer 3 is subjected to an upward external force, the reverse inclined surface of the third protrusion 305 abuts against the bottom surface of the outer protrusion of the third spring arm 504, preventing it from moving upward. This achieves one-way locking, preventing the trigger retainer 3 from moving upward again, forming a reliable anti-retraction structure, and effectively preventing the needle tip protective sleeve 11 from retracting again due to external force. Thus, the automatic injection pen achieves automatic locking of the needle tip protective sleeve 11 through the cooperation of the hole 602 of the push rod 6 and the third spring arm 504 of the push rod fixing part 5; through the cooperation of the third protrusion 305 and the inclined surface of the outer protrusion of the third spring arm 504, a one-way locking mechanism is achieved, ensuring that the needle tip protective sleeve 11 cannot be retracted after the injection, thus achieving automatic locking of the needle tip protective sleeve 11 and ensuring that the needle is always safely covered after the injection. The structure is compact and the linkage is reliable, effectively preventing needle stick injuries caused by accidental contact or improper operation after injection, and providing reliable safety protection for patients and users.

[0064] In some embodiments, a cap post 1203 is fixedly connected inside the cap 12. The inner wall of the cap post 1203 is provided with a plurality of inwardly extending barbs 1201. The barbs 1201 cooperate with the syringe 8 and are used to hook the needle tip sheath provided at the end of the syringe 8. The inner wall of the cap 12 is provided with a fifth protrusion 1202. The fifth protrusion 1202 is rotatably engaged with the rotating protrusion 704 of the outer shell 7. The plug block 705 cooperates with the fifth protrusion 1202 so that the cap 12 can be fixed to the bottom of the outer shell 7.

[0065] In this embodiment, the cap 12 is fitted onto the bottom of the outer shell 7, causing the fifth protrusion 1202 to be misaligned with the rotating protrusion 704. Then, the cap 12 is rotated, causing the rotating protrusion 704 to screw into the space between the two fifth protrusions 1202 and engage with them. This achieves circumferential limiting between the outer shell 7 and the cap 12, preventing rotation after the outer shell 7 and the cap 12 are engaged. The insertion block 705 cooperates with the fifth protrusion 1202, allowing the bottom of the fifth protrusion 1202 to abut against the top of the insertion block 705, thereby achieving axial limiting between the outer shell 7 and the cap 12 and preventing axial displacement between the outer shell 7 and the cap 12. Thus, through the engagement between the plug block 705 and the fifth protrusion 1202, and the engagement between the rotating protrusion 704 and the fifth protrusion 1202, axial and circumferential limiting between the outer shell 7 and the cap 12 are achieved, preventing axial displacement and rotation between the outer shell 7 and the cap 12, thereby firmly fixing the cap 12 to the bottom of the outer shell 7.

[0066] The installation process for this automatic injection pen is as follows: 1. The fourth slot 603 of the push rod 6 is engaged with the inner protrusion of the spring arm hook 503 of the push rod fixing part 5; 2. The protruding step 304 inside the trigger retainer 3 engages with the outer protrusion of the spring arm hook 503 of the push rod fixing member 5, and the third protrusion 305 abuts against the third spring arm 504. 3. Place the injection spring 4 into the push rod 6. The first slot 203 of the blocking member 2 is fixed to the second buckle 501 protruding from the outside of the push rod fixing member 5. The injection spring 4 abuts between the push rod 6 and the blocking member 2. 4. Insert the safety cap 1 into the hole provided above the blocking member 2. The second arm 102 of the safety cap 1 cooperates with the first spring arm 202 of the blocking member 2. The above whole assembly forms the injection assembly 1300. 5. Place the syringe 8 into the pen refill holder 9. Assemble the pen refill holder 9 with the outer shell 7. The third buckle 901 protruding from the outside of the pen refill holder 9 is fixed with the sixth slot 703 of the outer shell 7. Fix the injection assembly 1300 to the outer shell 7. The fifth slot 701 of the outer shell 7 is fixed with the first buckle 201 of the blocking member 2. 6. Place the trigger spring 10 into the needle tip protective sleeve 11. The second spring arm 303 protruding from the outside of the trigger retainer 3 engages with the seventh slot 1101 of the needle tip protective sleeve 11. The fourth spring arm 902 protruding from the outside of the pen refill holder 9 engages with the eighth slot 1102 of the needle tip protective sleeve 11. 7. Align the fifth protrusion 1202 of the cap 12 with the rotating protrusion 704 of the outer shell 7, and align the plug block 705 of the outer shell 7 with the fifth protrusion 1202 to rotate the cap 12 to the bottom of the outer shell 7, thereby completing the installation of the entire automatic injection pen.

[0067] In use, the inner protrusion of the spring arm hook 503 of the push rod fixing member 5 of the automatic injection pen locks the fourth slot 603 of the push rod 6, and the outer protrusion of the spring arm hook 503 is locked by the protruding step 304 inside the trigger retainer 3. The injection spring 4 stores force between the blocking member 2 and the push rod 6. In the initial state, the inner side of the second arm 102 of the safety cap 1 rests against the outer wall of the push rod fixing member 5. The first protrusion 104 on the outer side of the second arm 102 supports the first spring arm 202 of the blocking member 2 outward, so that the first spring arm 202 has no space to retract inward, so that the first spring arm 202 abuts against the top of the trigger retainer 3, so that the trigger retainer 3 cannot move upward, and thus cannot be triggered. Among them, the first groove 103 on the inner side of the second arm 102 cooperates with the fourth protrusion 502 on the outer side of the push rod fixing member 5 to prevent the safety cap 1 from falling out easily and to increase the damping. Furthermore, in the initial state, the inner side of the third spring arm 504 of the push rod fixing member 5 is supported by the outer wall of the push rod 6, preventing the third spring arm 504 from retracting inward. This causes the third protrusion 305 of the trigger retainer 3, which is obliquely upward, to rest on the outer protrusion of the third spring arm 504, thus preventing the trigger retainer 3 from moving downward. Therefore, in the initial state, the upper and lower ends of the trigger retainer 3 are held in place by the blocking member 2 and the push rod fixing member 5, effectively preventing accidental triggering and increasing safety.

[0068] Upon triggering, the safety cap 1 is first pulled out of the blocking member 2. Without the support of the first protrusion 104 on the outer side of the second arm 102 of the safety cap 1, the first spring arm 202 of the blocking member 2 has room to retract inward, thus separating the first spring arm 202 from the trigger retainer 3, allowing the trigger retainer 3 to move upward. Furthermore, because the inner side of the second protrusion 301 of the trigger retainer 3 is chamfered, and the protrusion on the outer side of the first spring arm 202 is angled upward and cooperates with the chamfer on the inner side of the second protrusion 301, the trigger retainer 3 can move upward more smoothly.

[0069] Before the injection begins, the outer protrusion of the spring arm hook 503 engages with the protruding step 304 of the trigger retainer 3, causing the spring arm hook 503 to be blocked by the protruding step 304 and retract inward, thereby causing the inner protrusion of the spring arm hook 503 to engage with the fourth slot 603, so that the spring arm hook 503 of the push rod fixing member 5 is fixed in the fourth slot 603 of the push rod 6.

[0070] When the needle tip protective sleeve 11 is pushed upward, the seventh slot 1101 of the needle tip protective sleeve 11 is fixedly engaged with the second spring arm 303 of the trigger retainer 3. When the needle tip protective sleeve 11 is pushed upward, the needle tip protective sleeve 11 drives the trigger retainer 3 to move upward. The needle tip protective sleeve 11 drives the second slot 302 of the trigger retainer 3 to move to the outer protrusion of the spring arm hook 503 of the push rod fixing member 5. The outer protrusion of the spring arm hook 503 engages with the second slot 302 of the trigger retainer 3, so that the spring arm hook 503 has space to expand outward, and thus the inner protrusion of the spring arm hook 503 also expands outward. Since the inner protrusion of the spring arm hook 503 is set at an angle, and under the action of the injection spring 4, the inner protrusion of the spring arm hook 503 disengages from the fourth slot 603, triggering the injection action. The push rod 6 moves downward, squeezing the syringe 8 to complete the injection operation.

[0071] Furthermore, during the downward movement of the push rod 6, the hole 602 of the push rod 6 moves to the third spring arm 504 of the push rod fixing member 5. At this time, the third spring arm 504 can retract inward. Under the elastic force of the trigger spring 10, the needle tip protective sleeve 11 is pushed downward. The needle tip protective sleeve 11 drives the trigger retainer 3 to move downward. The third protrusion 305 of the trigger retainer 3 slides past the outer protrusion of the third spring arm 504 of the push rod fixing member 5 and moves below it. At this time, due to the inclined surface design between the third protrusion 305 and the outer protrusion of the third spring arm 504, the third protrusion 305 is stuck below the outer protrusion of the third spring arm 504, and the trigger retainer 3 cannot move upward. At this time, the needle inside the syringe 8 is completely protected by the needle tip protective sleeve 11 to avoid pricking the user and further increase the safety of the device. After the injection is completed, the inner protrusion of the spring arm hook 503 cooperates with the third slot 601 so that the spring arm hook 503 of the push rod fixing member 5 is fixed in the third slot 601 of the push rod 6.

[0072] Furthermore, the automatic injection pen places the trigger spring 10 between the needle tip protector 11 and the refill holder 9 for easy assembly. During installation, the third clip 901 on the outside of the refill holder 9 is fixed to the sixth slot 703 of the outer casing 7. Therefore, the trigger spring 10 provides a downward elastic force to the needle tip protector 11. Under normal circumstances, when the injection assembly 1300 is installed downwards and with the outer casing 7, the second spring arm 303 in the trigger retainer 3 cannot engage with the seventh slot 1101 of the needle tip protector 11. The cap 12 needs to push the needle tip protector 11 upwards a certain distance. If the cap 12 is pulled out axially, the downward elastic force of the trigger spring 10 will cause the cap 12 to pop out. Therefore, the automatic injection pen provided in this application has a cap The cap 12 is modified to be pulled out by rotation. The fifth protrusion 1202 of the cap 12 and the rotating protrusion 704 of the outer shell 7 are rotated together, so that the rotating protrusion 704 is engaged between the two fifth protrusions 1202, thereby achieving circumferential limiting between the outer shell 7 and the cap 12 and preventing rotation after the outer shell 7 and the cap 12 are engaged together. The insertion block 705 of the outer shell 7 is engaged with the fifth protrusion 1202, so that the bottom of the fifth protrusion 1202 can abut against the top of the insertion block 705, thereby achieving axial limiting between the outer shell 7 and the cap 12 and preventing axial displacement between the outer shell 7 and the cap 12.

[0073] Therefore, this application further improves the assembly safety and ease of use of the product by optimizing the arrangement of the trigger spring 10 and the rotational connection structure of the cap 12. The trigger spring 10 is located between the needle tip protective sleeve 11 and the pen refill holder 9. During the assembly stage, it is fixed by the third buckle 901 of the pen refill holder 9 and the sixth slot 703 of the outer shell 7, thus overcoming the preload force of the trigger spring 10. At the same time, the cap 12 is connected by a rotational engagement between the fifth protrusion 1202 and the rotating protrusion 704 of the outer shell 7. Compared with the traditional axially pulled-out cap 12, this effectively avoids the cap 12 from accidentally popping out due to the elasticity of the trigger spring 10, making the assembly process safer and easier, and further ensuring the overall safety of the product in the manufacturing and use stages.

[0074] Preferably, the auto-injection pen can be used to inject drugs including but not limited to adrenaline.

[0075] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. An automatic injection pen, characterized in that, include: Outer shell (7); An injection assembly (1300) is installed at one end inside the housing (7). The injection assembly (1300) includes a safety cap (1), a push rod fixing member (5), a push rod (6) installed inside the push rod fixing member (5), a trigger retainer (3) sleeved outside the push rod fixing member (5), a blocking member (2) fixedly installed inside the housing (7), and an injection spring (4) abutting between the blocking member (2) and the push rod (6). The trigger assembly (1400) is installed at the other end inside the housing (7). The trigger assembly (1400) includes a needle tip protective sleeve (11), a pen refill holder (9) fixedly installed inside the housing (7), and a trigger spring (10) abutting between the pen refill holder (9) and the needle tip protective sleeve (11). The syringe (8) is installed between the injection assembly (1300) and the trigger assembly (1400). The syringe (8) is located inside the pen cartridge holder (9). One end of the push rod (6) is located inside one end of the syringe (8). The trigger retainer (3) is fixedly connected to the needle tip protective sleeve (11). The blocking member (2) is fixedly connected to the push rod fixing member (5). Before the injection begins, the safety cap (1) is inserted into the blocking member (2) to restrict the movement of the trigger retainer (3) and put the injection assembly (1300) in an untriggerable state. When the safety cap (1) is pulled out from the blocking member (2), the trigger retainer (3) is moved by the needle tip protective sleeve (11) to trigger the injection assembly (1300) to squeeze the syringe (8) to complete the injection operation; The safety cap (1) is provided with a second arm (102), and a first protrusion (104) is provided on the outer side of the end of the second arm (102); the blocking member (2) is provided with a first spring arm (202), and a protrusion is provided on the outer side of the first spring arm (202); When the safety cap (1) is inserted into the blocking member (2), the second arm (102) is located between the first spring arm (202) and the push rod fixing member (5), and the first protrusion (104) supports the first spring arm (202) outward so that the protrusion on the outside of the first spring arm (202) abuts against the top of the trigger retainer (3); When the safety cap (1) is pulled out from the blocking member (2), the second arm (102) exits between the first spring arm (202) and the push rod fixing member (5), the first spring arm (202) retracts inward, and the protrusion on the outside of the first spring arm (202) separates from the trigger retainer (3) so that the trigger retainer (3) can be moved.

2. The automatic injection pen according to claim 1, characterized in that, The push rod fixing member (5) has a fourth protrusion (502) on its side, and the second arm (102) has a first groove (103) on its inner side. The safety cap (1) is inserted into the blocking member (2), and the fourth protrusion (502) cooperates with the first groove (103).

3. The automatic injection pen according to claim 1, characterized in that, The top of the trigger retainer (3) is provided with a second protrusion (301), and the inner side of the second protrusion (301) is provided with a chamfer. The protrusion on the outer side of the first spring arm (202) is inclined upward and cooperates with the chamfer on the inner side of the second protrusion (301).

4. The automatic injection pen according to any one of claims 1-3, characterized in that, The trigger retainer (3) has a second slot (302) on its side and a protruding step (304) on its inner wall; the push rod fixing member (5) has a spring arm hook (503) and a third spring arm (504) on its side, and the inner and outer sides of the spring arm hook (503) are provided with protrusions, with the inner protrusion being inclined; the push rod (6) has a third slot (601) on its side and a fourth lock located below the third slot (601). The groove (603) and the hole (602) located on one side of the third slot (601) and the fourth slot (603); the push rod fixing member (5) is sleeved on the upper part of the push rod (6), the outer side of the third spring arm (504) is provided with a downwardly inclined protrusion, and the inner wall of the trigger retainer (3) is also provided with a third protrusion (305) upwardly inclined, and the outer protrusion of the third spring arm (504) cooperates with the third protrusion (305) of the trigger retainer (3); Before the injection begins, the protrusion on the outer side of the spring arm hook (503) engages with the protrusion step (304), and the protrusion on the inner side of the spring arm hook (503) engages with the fourth slot (603) to fix the spring arm hook (503) in the fourth slot (603); and the third spring arm (504) is supported by the outer wall of the push rod (6), so that the third protrusion (305) abuts against the outer protrusion of the third spring arm (504) to restrict the movement of the trigger retainer (3); During the injection process, the safety cap (1) is pulled out and the trigger retainer (3) is moved upward by the needle tip protective sleeve (11), so that the second slot (302) moves to the outer protrusion of the spring arm hook (503). The outer protrusion of the spring arm hook (503) cooperates with the second slot (302) to make the spring arm hook (503) expand outward. The inner protrusion of the spring arm hook (503) disengages from the fourth slot (603) under the elastic force of the injection spring (4). The injection spring (4) drives the push rod (6) to squeeze the syringe (8) to complete the injection. After the injection is completed, the hole (602) of the push rod (6) moves to the third spring arm (504) of the push rod fixing member (5). The third spring arm (504) cooperates with the hole (602) so that the third spring arm (504) can retract inward. The needle tip protective sleeve (11) and the trigger retainer (3) move downward under the elastic force of the trigger spring (10). The third protrusion (305) slides over the outer protrusion of the third spring arm (504) and is locked in the third spring arm (504). 4) Below the outer protrusion, so that the trigger retainer (3) cannot move upward; and the protruding step (304) moves to the outer protrusion of the spring arm hook (503), the outer protrusion of the spring arm hook (503) cooperates with the protruding step (304) to make the spring arm hook (503) retract inward, and the inner protrusion of the spring arm hook (503) cooperates with the third slot (601) to fix the spring arm hook (503) in the third slot (601).

5. The automatic injection pen according to claim 1, characterized in that, The top of the outer shell (7) is provided with a fifth slot (701) and an arc-shaped groove (702) located on one side of the fifth slot (701). The blocking member (2) is provided with a first buckle (201) on its side, and the fifth slot (701) cooperates with the first buckle (201), and the first buckle (201) can be locked in the fifth slot (701); The safety cap (1) is also provided with a first arm (101), which is shorter than the second arm (102). The arc groove (702) cooperates with the first arm (101), and the first arm (101) can extend into the arc groove (702).

6. The automatic injection pen according to claim 1, characterized in that, The pen refill holder (9) is provided with a third buckle (901), and the outer shell (7) is provided with a sixth slot (703) on the side. The third buckle (901) cooperates with the sixth slot (703) and the third buckle (901) can be locked in the sixth slot (703). The bottom of the pen refill holder (9) is provided with an axial protrusion (903), and the trigger spring (10) is sleeved on the outside of the plurality of axial protrusions (903) and abuts against the axial protrusions (903).

7. The automatic injection pen according to claim 1, characterized in that, The needle tip protective sleeve (11) is provided with a third arm (1103), the third arm (1103) is provided with a seventh slot (1101) and an eighth slot (1102) located below the seventh slot (1101). The trigger retainer (3) has a second spring arm (303) on its side. The seventh slot (1101) cooperates with the second spring arm (303), and the second spring arm (303) can be locked in the seventh slot (1101). The pen refill holder (9) is provided with a fourth spring arm (902) on its side. The eighth slot (1102) cooperates with the fourth spring arm (902), and the fourth spring arm (902) can be locked in the eighth slot (1102).

8. The automatic injection pen according to claim 1, characterized in that, The blocking member (2) is sleeved on the upper part of the push rod fixing member (5). The blocking member (2) has a first slot (203) on its side and the push rod fixing member (5) has a second buckle (501) on its side. The second buckle (501) cooperates with the first slot (203) and can be locked in the first slot (203).

9. The automatic injection pen according to claim 1, characterized in that, It also includes a cap (12), which is installed on the bottom of the housing (7), and the bottom of the housing (7) is provided with a rotating protrusion (704) and a plug block (705) located below the rotating protrusion (704). The cap (12) is fixedly connected to the inside of the cap post (1203). The inner wall of the cap post (1203) is provided with several inwardly extending barbs (1201). The barbs (1201) cooperate with the syringe (8). The barbs (1201) are used to hook the needle tip sheath provided at the end of the syringe (8). The inner wall of the cap (12) is provided with a fifth protrusion (1202), which is rotatably engaged with the rotating protrusion (704). The plug block (705) engages with the fifth protrusion (1202) so that the cap (12) can be fixed to the bottom of the outer shell (7).

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