A prefilled automatic injection pen

Abstract

The present invention relates to the technical field of injection pens, and discloses a pre-filled automatic injection pen comprising a pen body and a needle, a pen cap and a septum disposed on the outside of the pen body, and a clamping member disposed on the outside of the pen cap. The clamping member specifically comprises a fixed sleeve disposed on the outside of the pen cap, a clamping groove provided on the inside of the fixed sleeve, a sliding ring disposed above the fixed sleeve, and a clamping plate disposed at the bottom end of the sliding ring. The pre-filled automatic injection pen is provided with a clamping member. Before use, the clamping member is mounted on the needle, the septum is pressed against the skin surface, and the pen body is pushed. The fixed sleeve follows the movement of the pen body and slides outside the clamping plate, squeezing the two clamping plates inward, pinching the skin between the two clamping plates, and then the needle completes puncture. This makes it quick and convenient to use, can be operated with one hand, and is convenient for users to inject into the arm or buttocks. Injections into the abdomen or legs do not affect the normal use or portability of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of injection pens, in particular to a pre-filled automatic injection pen. Background Art

[0002] A prefilled autoinjector pen is a medical device that combines a prefilled syringe with an automatic injection mechanism, typically powered by a spring. During injection, by removing the safety pin at the rear or pressing the pen body, the spring releases its compressed kinetic energy, driving the plunger to push the piston inside the prefilled syringe forward, injecting the medication into the patient. Injection pens can be broadly divided into two types based on their usage scenario: disposable pens are often used for emergency and short-term medications, while reusable pens are often used for long-term treatment of chronic diseases.

[0003] Insulin injections are generally performed using a reusable injection pen, which consists of a pen body, an insulin cartridge and a needle. The needle has different models to choose from according to the user's body shape. Children and thin adults use 3-4 mm needles, ordinary adults use 4-5 mm needles, overweight adults use 5-6 mm needles, and obese adults use 6-8 mm needles. The right needle can enable insulin to be injected into the appropriate subcutaneous depth to control the body's absorption rate.

[0004] Patent publication number CN116617501A discloses a prefilled automatic injection pen, comprising a housing; a protective cap that can cause the internal protective rubber sleeve of the prefilled syringe to fall off when removed; the head of the needle shield is exposed outside the housing, and when it moves from an initial position to an extreme position, it can trigger a push rod to enter an actuated position, thereby releasing the safety locking buckle of the prefilled syringe; the prefilled syringe can be triggered to extend the needle shield for automatic needle insertion; the fixing seat initially defines the initial position of the prefilled syringe; the self-locking buckle can be locked with the fixing seat under the drive of the needle shield and lock the position of the needle shield after the needle is removed after the injection is completed; after the push rod is triggered by the needle shield, it drives the prefilled syringe to move under the drive of an excitation spring to complete automatic needle insertion, and further drives the rubber stopper inside the prefilled syringe to move for injection; the locking buckle initially defines the initial positions of the push rod and the sounder; the sounder can be activated by the push rod and knock on the fixing seat shell to produce a sound; the rear cover is fixed to the tail of the housing.

[0005] The existing technology has the following defects:

[0006] When injecting insulin, in order to ensure that the needle can enter the subcutaneous fat layer and avoid accidentally entering the muscle or epidermis, the skin is usually "pinched" first during the injection. Specifically, the skin of the injection area is pinched with the thumb and index finger to make it bulge outward. At the same time, in order to control the absorption efficiency and avoid fat hyperplasia, skin nodules, etc., the injection position is generally rotated in areas such as the abdomen, outer thigh, outer upper arm, and outer upper buttocks. However, it is difficult for the user to perform the skin pinching operation alone on the outer upper arm and outer upper buttocks, which makes the injection process risky. Summary of the Invention

[0007] In view of the problem that some areas of the prior art are inconvenient to pinch the skin, a pre-filled automatic injection pen is proposed.

[0008] The present application provides a pre-filled automatic injection pen, the purpose of which is to enable single-handed injection without manual pinching of the skin.

[0009] The technical solution of the present invention is: a prefilled automatic injection pen, comprising a pen body and a needle, a pen cap and a spacer ring disposed on the outside of the pen body, and a clamping member disposed on the outside of the pen cap, wherein the clamping member specifically comprises a fixed sleeve disposed on the outside of the pen cap, a clamping groove provided on the inside of the fixed sleeve, a sliding ring disposed above the fixed sleeve, and a clamping plate disposed at the lower end of the sliding ring;

[0010] The sliding sleeve is arranged on the outside of the pen cover, and the clamping plates are symmetrically provided with two pieces. The clamping plates are slidably installed in the clamping grooves. The outer wall of the clamping plate located below the fixed sleeve protrudes outward and is thickened. The clamping plate fits the outside of the pen cover. When in use, the spacer ring and the clamping piece are removed, the spacer ring is installed on the outside of the needle, and the fixed sleeve is installed on the outside of the spacer ring.

[0011] Furthermore, the clamping member further includes a guide groove provided on the inner side of the fixed sleeve, a guide plate provided on the inner side of the guide groove, a connecting ring provided between the two guide plates, an annular groove provided on the outer side of the fixed sleeve, a through hole provided between the annular groove and the guide groove, a positioning groove provided on a side of the guide plate close to the inner wall of the guide groove, a positioning bolt provided between the through hole and the positioning groove, a rotating ring provided on the inner side of the annular groove, and an adjusting groove provided on the inner wall of the rotating ring;

[0012] The guide plate slides in the guide groove, an elastic connector is provided between the connecting ring and the sliding ring, one end of the through hole is connected to the positioning groove, and the other end is connected to the adjustment groove, the part of the positioning bolt located in the positioning groove is set to be hemispherical, and the inner wall of the adjustment groove is provided with a pushing slope.

[0013] Furthermore, chamfers are provided on both sides of the bottom end of the clamping plate to narrow the bottom end of the clamping plate.

[0014] Furthermore, the clamping plate is configured to be arc-shaped, with the arc center located on the central axis of the pen cover, and the clamping plate is attached to the outer side of the pen cover.

[0015] Furthermore, the positioning grooves are divided into two groups, an upper group and an lower group, and the positioning grooves in the same group are symmetrically arranged.

[0016] Furthermore, the needle specifically includes a connecting sleeve arranged at the lower end of the pen body, an extension tube arranged at the lower end of the connecting sleeve, a needle column arranged at the lower end of the extension tube, and a protective sleeve arranged on the outer side of the extension tube;

[0017] The protective sleeve is wrapped around the outer side of the needle column, and the protective sleeve moves axially along the extension tube.

[0018] Furthermore, a damping pad is provided between the protective sleeve and the extension tube, so that the protective sleeve is slidably connected to the outside of the extension tube.

[0019] Furthermore, a thread is provided on the outer side of the extension tube, and a sliding member is provided on the inner side of the protective sleeve. The sliding member extends into the thread, so that the protective sleeve is threadedly connected to the extension tube.

[0020] Furthermore, a gasket is fixedly connected to the lower end of the protective cover.

[0021] Beneficial effects of the present invention:

[0022] 1. By setting a clamping piece, the clamping piece is installed on the needle head before use, the septum ring is pressed against the skin surface, the pen body is pushed, and the fixed sleeve follows the movement of the pen body and slides on the outside of the clamping plate, and the two clamping plates are squeezed inward, the skin between the two clamping plates is pinched, and then the needle completes the puncture. This is quick and convenient to use and can be operated with one hand, which is convenient for users to inject in the arm or buttocks. When injecting in the abdomen or leg, the clamping piece can be installed on the pen cover, or disassembled and stored separately, which does not affect the normal use or carrying of the device. At the same time, when the clamping piece is installed on the pen cover, the fixed sleeve is appropriately slid on the outside of the clamping plate, so that the clamping plate can hold the pen cover tightly, making its fixed state more stable.

[0023] 2. By setting a guide plate, when the connecting ring slides with the fixed sleeve, the elastic connecting part needs to be stretched first to separate the connecting ring from the sliding ring. In this way, a certain pressure will be generated on the skin before the clamping plate closes, and its bottom end will sink into the skin, which makes it easier to clamp the skin and clamp it more fully, which is more conducive to subsequent puncture and injection. When the clamping part needs to be fixed on the outside of the pen cover, the positioning bolt is unlocked using the adjustment slot to separate the guide plate and the fixed sleeve. When the fixed sleeve is slid, the connecting ring stops in place to avoid the elastic connecting part being stretched for a long time and fatigue damage.

[0024] 3. By setting a protective cover, the protective cover is wrapped around the outside of the needle column, which plays a double protection role together with the pen cover, to prevent the pen cover from accidentally falling off when the pen body is placed in the bag, and the needle column from accidentally injuring the user when the patient touches the pen body. At the same time, by moving the protective cover, the length of the needle column can be controlled, so that the puncture depth can be changed according to the patient's needs, ensuring the injection effect and injection safety.

[0025] 4. The threaded connection method makes it difficult for the protective sleeve to move when subjected to axial pressure. The connection between the protective sleeve and the extension tube is more stable, which is also more conducive to achieving precise adjustment, further ensuring the effectiveness and safety of injection. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A perspective view of the present invention;

[0027] Figure 2 This is a schematic diagram of the separation of the pen body and the pen cover of the present invention;

[0028] Figure 3 This is a schematic diagram of the pen body of the present invention;

[0029] Figure 4 This is a schematic diagram of the clamping member of the present invention;

[0030] Figure 5 This is a disassembly diagram of the clamping member of the present invention;

[0031] Figure 6 A top view of the clamping member of the present invention;

[0032] Figure 7 For the present invention Figure 6 Middle AA section view;

[0033] Figure 8 For the present invention Figure 6 Middle BB cross-section;

[0034] Figure 9 For the present invention Figure 7 Enlarged view of point C in the middle;

[0035] Figure 10 This is a schematic diagram of the needle in Example 3 of the present invention;

[0036] Figure 11 This is a schematic diagram of the needle in Example 4 of the present invention;

[0037] Figure 12 This is a disassembled diagram of the needle in Example 4 of the present invention.

[0038] In the picture:

[0039] 1. Pen body; 2. Needle; 21. Connecting sleeve; 22. Extension tube; 23. Needle column; 24. Protective sleeve; 25. Gasket; 3. Pen cap; 4. Spacer ring; 5. Clamping piece; 51. Fixed sleeve; 52. Clamping groove; 53. Sliding ring; 54. Clamping plate; 55. Guide groove; 56. Guide plate; 57. Connecting ring; 58. Annular groove; 59. Through hole; 510. Positioning groove; 511. Positioning bolt; 512. Rotating ring; 513. Adjustment groove. DETAILED DESCRIPTION

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0041] Example 1, reference Figures 1-9 , which is the first embodiment of the present invention, provides a prefilled automatic injection pen, including a pen body 1 and a needle 2, a pen cover 3 and a spacer ring 4 arranged on the outside of the pen body 1, and also includes a clamping member 5 arranged on the outside of the pen cover 3. The clamping member 5 specifically includes a fixed sleeve 51 arranged on the outside of the pen cover 3, a clamping groove 52 opened on the inside of the fixed sleeve 51, a sliding ring 53 arranged above the fixed sleeve 51, and a clamping plate 54 arranged at the lower end of the sliding ring 53.

[0042] Specifically, the pen body 1 is divided into two sections, which are threadedly connected. A cavity and an injection device are set inside the pen body 1, and a pre-filled insulin pen cartridge is filled in the cavity. An adjustment unit for controlling the amount of drug injection and an injection button for drug injection are set at the top of the pen body 1. The needle 2 is threadedly connected to the bottom end of the pen body 1. The pen cover 3 is clamped on the outside of the pen body 1. The spacer ring 4 can be clamped with the pen body 1 and can also be clamped with the needle 2. The fixed sleeve 51 can be clamped with the spacer ring 4 and can also be slidably sleeved on the outside of the pen cover 3. The sliding ring 53 is sleeved on the outside of the pen cover 3. The clamping plate 54 and the sliding ring 53 are integrally formed. The clamping plate 54 is provided with symmetrical The two pieces of the clamping plate 54 are slidably installed in the clamping slot 52. The outer wall of the clamping plate 54 located below the fixed sleeve 51 protrudes outward and is thickened. The clamping plate 54 fits the outside of the pen sleeve 3. When in use, the spacer ring 4 and the clamping piece 5 are removed, the spacer ring 4 is installed on the outside of the needle head 2, and the fixed sleeve 51 is installed on the outside of the spacer ring 4; the clamping plate 54 is set to an arc shape, and the center of the arc is located on the central axis of the pen sleeve 3. The clamping plate 54 fits the outside of the pen sleeve 3, so that the clamping plate 54 and the pen sleeve 3 fit more closely; chamfers are set on both sides of the bottom end of the clamping plate 54 to narrow the bottom end of the clamping plate 54, which is more convenient for clamping the human skin.

[0043] By providing a clamping piece 5, the clamping piece 5 is installed on the needle 2 before use, the spacer ring 4 is pressed against the skin surface, the pen body 1 is pushed, and the fixing sleeve 51 moves with the pen body 1 and slides on the outside of the clamping plate 54, squeezing the two clamping plates 54 inward, pinching the skin between the two clamping plates 54, and then the needle 2 completes the puncture. This is quick and convenient to use and can be operated with one hand, which is convenient for the user to inject in the arm or buttocks. When injecting in the abdomen or leg, the clamping piece 5 can be installed on the pen cover 3, or disassembled and stored separately, which does not affect the normal use or carrying of the device. At the same time, when the clamping piece 5 is installed on the pen cover 3, the fixing sleeve 51 is appropriately slid on the outside of the clamping plate 54, so that the clamping plate 54 can hold the pen cover 3 tightly, making its fixed state more stable.

[0044] The clamping member 5 further includes a guide groove 55 provided on the inner side of the fixed sleeve 51, a guide plate 56 provided on the inner side of the guide groove 55, a connecting ring 57 provided between the two guide plates 56, an annular groove 58 provided on the outer side of the fixed sleeve 51, a through hole 59 extending between the annular groove 58 and the guide groove 55, a positioning groove 510 provided on the side of the guide plate 56 close to the inner wall of the guide groove 55, a positioning bolt 511 provided between the through hole 59 and the positioning groove 510, a rotating ring 512 provided on the inner side of the annular groove 58, and an adjusting groove 513 provided on the inner wall of the rotating ring 512.

[0045] Specifically, the guide plate 56 slides in the guide groove 55, the connecting ring 57 and the guide plate 56 are formed as one piece, and an elastic connector is provided between the connecting ring 57 and the sliding ring 53. The elastic connector can be a spring or an elastic rope. The force required to stretch the elastic connector does not exceed 2N. One end of the through hole 59 is connected to the positioning groove 510, and the other end is connected to the adjustment groove 513. The positioning bolt 511 passes through the through hole 59 and enters the positioning groove 510. The part of the positioning bolt 511 located in the positioning groove 510 is set to be hemispherical. The rotating ring 512 is rotatably connected to the annular groove 58, and the inner wall of the adjustment groove 513 is provided with a pushing slope.

[0046] By setting the guide plate 56, when the connecting ring 57 slides following the fixed sleeve 51, the elastic connecting part needs to be stretched first before the connecting ring 57 is separated from the sliding ring 53. In this way, a certain pressure will be exerted on the skin before the clamping plate 54 is closed, and its bottom end will sink into the skin, which makes it more convenient to clamp the skin and clamp it more fully, which is more conducive to the subsequent puncture injection. When the clamping part 5 needs to be fixed on the outside of the pen cover 3, the positioning bolt 511 is unlocked by using the adjustment groove 513 to separate the guide plate 56 and the fixed sleeve 51. When the fixed sleeve 51 is slid, the connecting ring 57 stops in place to avoid the elastic connecting part being stretched for a long time and fatigue damage.

[0047] Specifically, the positioning grooves 510 are divided into two groups, upper and lower. The positioning grooves 510 in the same group are symmetrically arranged. When in use, the positioning bolt 511 penetrates into the lower positioning groove 510 to fix the guide plate 56 and the fixing sleeve 51. When not in use, the positioning bolt 511 penetrates into the upper positioning groove 510 to fix the guide plate 56 and the fixing sleeve 51, thereby ensuring the stability of the installation of the guide plate 56.

[0048] Example 2, reference Figure 1-Figure 3 、 Figure 10-12 , which is the second embodiment of the present invention. This embodiment differs from the first embodiment in that the needle 2 specifically includes a connecting sleeve 21 arranged at the lower end of the pen body 1, an extension tube 22 arranged at the lower end of the connecting sleeve 21, a needle column 23 arranged at the lower end of the extension tube 22, and a protective sleeve 24 arranged on the outer side of the extension tube 22.

[0049] The connecting sleeve 21 is threadedly connected to the pen body 1, and the connecting sleeve 21 and the extension tube 22 are formed as one piece. The needle column 23 is clamped at the lower end of the extension tube 22, and the protective sleeve 24 is wrapped around the outside of the needle column 23. The protective sleeve 24 moves axially along the extension tube 22. The lower end of the protective sleeve 24 is fixedly connected to a gasket 25. The gasket 25 is annular, and the needle column 23 can pass through the inside of the gasket 25. The gasket 25 is made of soft rubber to prevent the protective sleeve 24 from damaging the skin. A digital scale is provided on the outside of the extension tube 22, and the digital scale indicates the length of the needle column 23 located below the gasket 25. The length of the needle column 23 is not less than 8 mm.

[0050] An ultraviolet lamp is arranged in the pen cover 3. When the pen cover 3 is placed on the pen body 1, the ultraviolet lamp is lit for 30 seconds. The protective cover 24 and the gasket 25 are made of transparent materials.

[0051] By setting a protective cover 24, the protective cover 24 is wrapped around the outside of the needle column 23 and combined with the pen cover 3 to play a double protection role, so as to prevent the pen cover 3 from accidentally falling off when the pen body 1 is placed in a bag, and the needle column 23 from accidentally injuring the user when the patient touches the pen body 1. At the same time, by moving the protective cover 24, the length of the needle column 23 can be controlled, so that the puncture depth can be changed according to the patient's needs, thereby ensuring the injection effect and injection safety.

[0052] The remaining structures are the same as those of Example 1.

[0053] Example 3, reference Figure 10 , which is the third embodiment of the present invention. This embodiment is different from the second embodiment in that a damping pad is provided between the protective cover 24 and the extension tube 22, so that the protective cover 24 is slidably connected to the outside of the extension tube 22. This adjustment method is quick and convenient.

[0054] The remaining structures are the same as those of Example 2.

[0055] Example 4, reference Figure 11-12, which is the fourth embodiment of the present invention. This embodiment is different from the second embodiment in that: a thread is provided on the outer side of the extension tube 22, and a sliding member is provided on the inner side of the protective sleeve 24. The sliding member extends into the thread so that the protective sleeve 24 is threadedly connected to the extension tube 22. The sliding member can specifically be a plurality of elastic sheets tilted upward.

[0056] The threaded connection method makes it difficult for the protective sleeve 24 to move when subjected to axial pressure. The connection state between the protective sleeve 24 and the extension tube 22 is more stable and more conducive to achieving precise adjustment, further ensuring the effectiveness and safety of the injection.

[0057] The remaining structures are the same as those of Example 2.

[0058] Based on Examples 1-2, the working principle of the prefilled automatic injection pen of the present invention is as follows:

[0059] Remove the pen cap 3 from the pen body 1, split the pen body 1 into two, fill the pre-filled insulin cartridge into one section of the pen body 1, and then restore the pen body 1; turn the pen body 1 upside down to install the needle 2, then move the protective cover 24 according to the injection requirements, observe the digital scale on the outside of the extension tube 22, and make the needle column 23 exposed from under the gasket 25 to the corresponding length; remove the spacer ring 4 from the outside of the pen body 1, and then put it on the outside of the needle 2; rotate the rotating ring 512 to align the adjustment groove 513 with the through hole 59, then hold the clamping plate 54 with one hand and push the fixing sleeve 51 close to the sliding ring 53 with the other hand. The movement of the fixing sleeve 51 causes the positioning pin 511 to be pushed back and the positioning pin 511 enters the adjustment groove 513. The fixing sleeve 51 and the guide plate 56 are unlocked, and the fixing sleeve 51 moves away from the thickened part of the clamping plate 54. After the clamping plate 54 loses the pressing force, it expands outward and no longer holds the pen cover 3. After the fixing sleeve 51 cannot move, the through hole 59 docks with the upper positioning groove 510. At this time, the rotating ring 512 is rotated, and its inner pushing slope is used to send the positioning pin 511 into the upper positioning groove 510, and the fixing sleeve 51 and the guide plate 56 are locked again. Finally, the clamping piece 5 is removed from the pen cover 3 as a whole.

[0060] The fixing sleeve 51 is placed on the outside of the spacer ring 4, and the pen body 1 is brought close to the injection area so that the clamping plate 54 is pressed against the skin surface, and the arrangement direction of the two clamping plates 54 is kept the same as the direction of the skin texture. The pen body 1 is pressed forcefully, and the fixing sleeve 51 moves with the pen body 1, and the guide plate 56 and the connecting ring 57 move with the fixing sleeve 51. The connecting ring 57 drives the sliding ring 53 to move through the elastic connecting piece, and the sliding ring 53 pushes the clamping plate 54 to squeeze the skin, so that its bottom end sinks into the skin. Then the clamping plate 54 can no longer move, and the connecting ring 57 begins to stretch the elastic connecting piece and move. The fixing sleeve 51 slides on the outside of the clamping plate 54. When the fixing sleeve 51 slides to the thickened area of ​​the clamping plate 54, the two clamping plates 54 are squeezed toward the central axis of the pen body 1. The two clamping plates 54 move close to pinch the skin, and then the needle column 23 moves down to puncture the pinched skin to complete the injection.

[0061] After the injection is completed, the pen body 1 is released, each part is manually reset, and then the clamping member 5 is installed outside the pen cover 3.

[0062] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A pre-filled automatic injection pen, comprising a pen body (1) and a needle (2), a pen cover (3) and a spacer ring (4) arranged outside the pen body (1), characterized in that: A clamping member (5) is arranged on the outside of the pen cover (3), and the clamping member (5) specifically includes a fixed sleeve (51) arranged on the outside of the pen cover (3), a clamping groove (52) opened on the inside of the fixed sleeve (51), a sliding ring (53) arranged above the fixed sleeve (51), and a clamping plate (54) arranged at the lower end of the sliding ring (53); The sliding ring (53) is sleeved on the outside of the pen cover (3), and the clamping plate (54) is provided with two symmetrical pieces. The clamping plate (54) is slidably installed in the clamping groove (52). The outer wall of the clamping plate (54) located below the fixed sleeve (51) is protruded outward and thickened. The clamping plate (54) is attached to the outside of the pen cover (3). When in use, the spacer ring (4) and the clamping member (5) are removed, the spacer ring (4) is installed on the outside of the needle (2), and the fixed sleeve (51) is installed on the outside of the spacer ring (4); The clamping member (5) further includes a guide groove (55) provided on the inner side of the fixed sleeve (51), a guide plate (56) provided on the inner side of the guide groove (55), a connecting ring (57) provided between the two guide plates (56), an annular groove (58) provided on the outer side of the fixed sleeve (51), a through hole (59) provided between the annular groove (58) and the guide groove (55), a positioning groove (510) provided on the side of the guide plate (56) close to the inner wall of the guide groove (55), a positioning bolt (511) provided between the through hole (59) and the positioning groove (510), a rotating ring (512) provided on the inner side of the annular groove (58), and an adjusting groove (513) provided on the inner wall of the rotating ring (512); The guide plate (56) slides in the guide groove (55), an elastic connector is provided between the connecting ring (57) and the sliding ring (53), one end of the through hole (59) is connected to the positioning groove (510), and the other end is connected to the adjustment groove (513), the part of the positioning bolt (511) located in the positioning groove (510) is set to be hemispherical, and the inner wall of the adjustment groove (513) is provided with a pushing inclined surface; The needle (2) specifically comprises a connecting sleeve (21) arranged at the lower end of the pen body (1), an extension tube (22) arranged at the lower end of the connecting sleeve (21), a needle post (23) arranged at the lower end of the extension tube (22), and a protective sleeve (24) arranged outside the extension tube (22); The protective sleeve (24) is wrapped around the outside of the needle column (23), and the protective sleeve (24) moves axially along the extension tube (22); The outer side of the extension tube (22) is provided with a thread, and the inner side of the protective sleeve (24) is provided with a sliding member, which extends into the thread, so that the protective sleeve (24) and the extension tube (22) are threadedly connected.

2. The prefilled automatic injection pen according to claim 1, characterized in that: Chamfers are provided on both sides of the bottom end of the clamping plate (54) so ​​that the bottom end of the clamping plate (54) is narrowed.

3. The prefilled automatic injection pen according to claim 1, characterized in that: The clamping plate (54) is configured to be arc-shaped, with the center of the arc located on the central axis of the pen cover (3), and the clamping plate (54) is fitted onto the outside of the pen cover (3).

4. The prefilled automatic injection pen according to claim 1, characterized in that: The positioning grooves (510) are divided into two groups, an upper group and an lower group, and the positioning grooves (510) in the same group are symmetrically arranged.

5. The prefilled automatic injection pen according to claim 1, characterized in that: A damping pad is provided between the protective sleeve (24) and the extension tube (22), so that the protective sleeve (24) is slidably connected to the outside of the extension tube (22).

6. The prefilled automatic injection pen according to claim 1, characterized in that: A gasket (25) is fixedly connected to the lower end of the protective sleeve (24).

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