Pen-type syringe

Abstract

The utility model discloses a pen type syringe, including shell, second ratchet wheel and screw rod, the proximal end of shell is provided with the sleeve joint part, be provided with second pawl on the sleeve joint part, the second ratchet wheel sets up in the inside of sleeve joint part, and the center is provided with non -circular hole, the screw rod movably sets up in the shell, and its partial sliding penetrates the non -circular hole of second ratchet wheel, wherein, pen type syringe is in the operating state, second pawl with second ratchet wheel contact and lock it dead, make the screw rod can only axial forwardly move, the second ratchet wheel with second pawl separates and is allowed to rotate under the dressing state, make the screw rod can rotate and move back, this pen type syringe cooperation through second ratchet wheel, pawl, can prevent the screw rod backward movement caused by vibration or repeated operation, has guaranteed the reliability of injection dose accuracy, supports repeated use and the dressing operation is simple and convenient, has effectively reduced the use cost, and has reduced the equipment waste.

Description

Technical Field

[0001] This utility model relates to the field of medical devices, and in particular to a pen-type syringe for manual drug delivery. Background Technology

[0002] Diabetic patients need to control their condition by injecting insulin. The practicality of insulin pens eliminates the need to draw insulin from insulin vials with a syringe. They use pre-filled pens to inject directly, improving the convenience of insulin injection and making it easier for diabetic patients to operate on their own.

[0003] Insulin manufacturers typically use cartridge vials for pen injectors to pre-fill the insulin, which patients then assemble into the pen for injection. The vials used in pen injectors are cartridge-type, such as... Figure 17 As shown, this is a cartridge bottle. The inner side of the borosilicate glass bottle A is cylindrical, and a rubber piston B is inserted to seal it. The bottle is filled with medication C. The injection pen pushes the rubber piston B to dispense a measured amount of medication C from the bottle opening a (in conjunction with a special needle accessory) and inject it into the patient's body.

[0004] Currently, many similar injection pens exist on the market. For example, Chinese patent CN 201631814 U discloses a disposable adjustable-dosage insulin injection pen. Research has found that because the positioning block is fixedly connected to the injection cannula, the screw cannot reverse or retract once it has completely squeezed out the insulin from the cannula. Therefore, the device is not reusable and is disposable. This is undoubtedly disadvantageous for patients, as it increases treatment costs and is inconvenient to carry and use.

[0005] Further research and development are still needed to develop a reusable insulin pen that is easy for patients to operate and use. Utility Model Content

[0006] The purpose of this invention is to provide a pen-type injector that, by optimizing the ratchet structure at the screw, enables the device to be reused, thereby reducing the cost of use for patients.

[0007] The purpose of this utility model is achieved through the following technical solution:

[0008] A pen-type syringe includes a housing, a second ratchet, and a screw. A sleeve is provided at the proximal end of the housing, and a second pawl is provided on the sleeve. The second ratchet is disposed inside the sleeve and has a non-circular hole at its center. The screw is movably disposed within the housing, and a portion of it slides through the non-circular hole of the second ratchet. In operation, the second pawl contacts and locks the second ratchet, preventing the screw from moving forward axially. In medication changing mode, the second ratchet separates from the second pawl and is allowed to rotate, allowing the screw to rotate backward.

[0009] In an alternative embodiment, a pen refill holder is also included, wherein, in the operating state, the distal end of the pen refill holder is connected to the sleeve and radially presses against the second pawl; while in the dressing change state, the distal end of the pen refill holder is separated from the sleeve.

[0010] In an alternative embodiment, the socket is provided with a clearance opening, the second pawl is located within the clearance opening, and a protruding mating surface is provided on the side of the pawl away from the second ratchet.

[0011] In an optional embodiment, the socket is provided with an L-shaped groove, and the inner side of the far end of the pen refill holder is provided with a locking block; wherein the locking block is rotatably engaged with the L-shaped groove.

[0012] In an alternative embodiment, the L-shaped groove includes an insertion section and a locking section, and a retaining rib is provided in the locking section, so that the locking block can be limited by the retaining rib after it is transferred from the insertion section to the locking section.

[0013] In an alternative embodiment, a guide post is also included, which is disposed within the housing and threadedly connected to the screw, and the guide post is restricted to rotating only in one direction.

[0014] In an alternative embodiment, a first ratchet is provided at the proximal end of the housing, and a first pawl is provided at the proximal end of the guide post;

[0015] The first ratchet engages with the first pawl, causing the guide post to rotate only in a clockwise direction.

[0016] In an alternative embodiment, the screw has at least one cross-section along the axial direction, and the cross-section of the screw matches the non-circular hole.

[0017] In an alternative embodiment, the pen refill holder contains a replaceable medicine bottle, the medicine bottle contains a piston, and the proximal end of the screw is detachably connected to the piston.

[0018] In an alternative embodiment, the proximal end of the pen refill holder is provided with a removable needle.

[0019] Compared with the prior art, the beneficial effects of this utility model include at least the following:

[0020] 1. The syringe, through the cooperation of the second ratchet and pawl, can prevent the screw from retracting due to vibration or repeated operation, thus ensuring the reliability of the injection dosage accuracy.

[0021] 2. It supports reuse and the dressing change operation is simple and convenient, which effectively reduces the cost of use and reduces equipment waste.

[0022] 3. The drive mechanism has fewer parts and a simpler overall structure, which reduces costs and the risk of drive instability.

[0023] 4. The transmission parts on each component are relatively dispersed, avoiding the increased assembly difficulty caused by the transmission parts being too concentrated in the same location, as well as the transmission stability problems caused by concentrated force. Attached Figure Description

[0024] Figure 1 This is a three-dimensional schematic diagram of the pen-type syringe of the present invention.

[0025] Figure 2 This is a 3D diagram of a pen-type syringe with the cap removed.

[0026] Figure 3 yes Figure 2 Axial sectional view.

[0027] Figure 4 This is a partial structural schematic diagram of the pen-type syringe of the present invention.

[0028] Figure 5 This is a schematic diagram of the assembly structure of the outer shell and the adjusting column.

[0029] Figure 6 This is a schematic diagram of the three-dimensional structure of the adjusting column.

[0030] Figure 7 This is a schematic diagram of the assembly structure of the adjusting column and the transmission column.

[0031] Figure 8 This is a three-dimensional structural diagram of the transmission column.

[0032] Figure 9 This is a schematic diagram of the assembly structure of the guide post with the outer shell and the transmission post.

[0033] Figure 10 This is a schematic diagram of the three-dimensional structure of the guide column.

[0034] Figure 11 This is a schematic diagram of the driving structure of the pen-type syringe of the present invention.

[0035] Figure 12 yes Figure 4 A cross-sectional view along the AA direction.

[0036] Figure 13 This is a schematic diagram of the assembly structure of the screw, the second ratchet, and the guide post.

[0037] Figure 14 yes Figure 4 A cross-sectional view along the BB direction.

[0038] Figure 15 This is a schematic diagram of the exploded structure of the screw and the second ratchet.

[0039] Figure 16 This is a schematic diagram of the assembly structure of the pen refill holder and the outer casing.

[0040] Figure 17 This is a schematic diagram of the structure of a medicine bottle.

[0041] In the picture:

[0042] 1. Housing; 101. Viewing window; 102. Coarse thread groove; 103. First ratchet; 104. Socket; 105. Second pawl; 1051. Mating surface; 106. Clearance opening; 107. L-shaped groove; 1071. Insertion section; 1072. Locking section; 1073. Retaining rib;

[0043] 2. Adjusting column; 201. Dosage scale; 202. Coarse thread; 203. First tooth;

[0044] 3. Drive column; 301. Second tooth; 302. Raised rib;

[0045] 4. Guide post; 401. Groove; 402. Internal thread; 403. First pawl;

[0046] 5. Screw; 501. Cut surface;

[0047] 6. Knob;

[0048] 7. Support column; 701. Extension section;

[0049] 8. Buttons;

[0050] 9. Spring;

[0051] 10. Lens;

[0052] 11. Pen refill holder; 1101. Strip opening; 1102. Clip;

[0053] 12. Needle;

[0054] 13. Medicine bottle; 1301. Piston;

[0055] 14. Second ratchet; 1401. Non-circular hole;

[0056] 15. Pen cap. Detailed Implementation

[0057] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to make the present invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted.

[0058] The terms used to describe position and direction in this utility model are illustrated with the accompanying drawings, but may be changed as needed, and all such changes are included within the scope of protection of this utility model.

[0059] First, the relative positions of the components are explained: the proximal end in this application can be understood as the end closer to the injection site, and correspondingly, the distal end is the end farther from the injection site. Furthermore, the operating state refers to the use of a pen syringe, including the injection dose preset stage and the injection stage. The medication changing state refers to the stage where the pen cartridge holder 11 is separated from the outer casing 1.

[0060] See Figures 1 to 12 As shown, this application discloses a pen-type syringe that can be used to inject drugs into subcutaneous, intramuscular, or venous sites, including but not limited to insulin.

[0061] like Figure 2 and Figure 3 As shown, the pen-type syringe generally includes a housing 1, a drive mechanism partially built into the housing 1, a cartridge holder 11 connected to the proximal end of the housing 1, and a needle 12 connected to the proximal end of the cartridge holder 11. In this application, the cartridge holder 11 is compatible with a 3ml standard vial 13 (cassette), and after being assembled into the housing 1, it forms a compartment to hold the vial 13. In use, operating the drive mechanism allows the medication to be injected into the target site through the needle 12.

[0062] from Figure 1 and Figure 2 As can be seen, the outer shell 1 serves as the handheld part of the syringe, preferably having a cylindrical structure, and a viewing window 101 is provided on its side. An arrow is positioned at the center line of the viewing window 101 to align with the dosage scale 201, thereby precisely controlling the injection dosage. In one example, the viewing window 101 is positioned at the distal end of the outer shell 1 to prevent interference with the grip and thus avoid affecting dosage reading.

[0063] Figure 3The specific structure of the drive mechanism in the built-in pre-shell 1 is shown. This mechanism mainly includes components such as adjusting column 2, transmission column 3, guide column 4, and screw 5. Among them, adjusting column 2, transmission column 3, and guide column 4 are all circular tube structures.

[0064] Specifically, such as Figure 5 As shown, the adjusting post 2 is disposed on the inner side of the housing 1 and threadedly connected thereto. In one example, the inner side of the housing 1 is provided with an axially extending coarse thread groove 102, and the outer side of the proximal end of the adjusting post 2 is provided with a coarse thread 202 that mates with the coarse thread groove 102. In this application, the adjusting post 2 is defined such that counterclockwise rotation causes it to retract relative to the housing 1, while when pressed, the adjusting post 2 can spiral (clockwise) forward relative to the housing 1.

[0065] Continue reading Figure 6 As shown, the outer periphery of the adjusting column 2 is provided with a spirally arranged dose scale 201, which corresponds to the viewing window 101. The scale range can be 1-60 units (each unit corresponds to 0.01 ml), and the adjusting column 2 can be set to correspond to 1 unit dose for every 12° rotation. Additionally, a knob 6 is connected to the distal end of the adjusting column 2. The knob 6 can be rigidly connected to the adjusting column 2 using a snap-fit ​​or other means to facilitate control of the adjusting column 2 for preset injection dose.

[0066] See Figure 7 and Figure 8 As shown, the transmission column 3 is located inside the adjusting column 2, with its proximal end interlocked with the adjusting column 2 and its distal end connected to the button 8 via the support column 7. In this application, the transmission column 3 selectively engages with the adjusting column 2. Specifically, the two are separated during the injection dose preset stage, during which no transmission action occurs. Only when the injection stage begins can the transmission column 3 form a rigid connection with the adjusting column 2 and achieve synchronous rotation. In one example, a first tooth 203 is provided on the proximal inner side of the adjusting column 2, and a second tooth 301 is provided on the proximal end of the transmission column 3. The second tooth 301 can maintain elastic engagement with the first tooth 203 under the action of an elastic element (such as a spring 9). Note that the force applied by the elastic element is small, and without additional pressure, this force does not restrict the relative rotation between the first tooth 203 and the second tooth 301. When knob 6 is rotated counterclockwise, adjusting column 2 rotates accordingly, but transmission column 3 does not rotate. During this process, the first tooth 203 rotates relative to the second tooth 301 and contacts it, producing a "click-click-click" sound, indicating that the injection dosage preset adjustment is in progress. After pressing button 8, pressure causes the first tooth 203 to mesh with the second tooth 301, forming a rigid connection between adjusting column 2 and transmission column 3. This causes adjusting column 2 to spiral forward clockwise while simultaneously driving transmission column 3 to spiral forward synchronously.

[0067] Continue watching 9 and Figure 10As shown, the guide post 4 is disposed on the inner side of the transmission post 3 and slidably engaged with it to ensure synchronous rotation between the two. In one example, the inner side of the transmission post 3 is provided with a protruding rib 302, and the outer side of the guide post 4 is provided with a groove 401 extending axially; wherein, the protruding rib 302 and the groove 401 are slidably engaged to ensure that the axial movement is free from jamming.

[0068] Furthermore, the guide post 4 is restricted to rotating only in one direction, such as clockwise. In one example, a first ratchet 103 is provided at the proximal end of the housing 1 (see...). Figure 5 The guide post 4 is provided with a first pawl 403 at its proximal end (see...). Figure 10 In this embodiment, the first ratchet 103 engages with the first pawl 403, causing the guide post 4 to rotate only clockwise. Note that in this application, the connecting force between the first ratchet 103 and the first pawl 403 must be greater than the force applied to the adjusting post 2 by the elastic element, so that during the preset injection dosage stage, the adjusting post 2 cannot drive the transmission post 3 to rotate, and only a phenomenon similar to "tooth skipping" will occur, producing a tooth-like sound.

[0069] like Figure 11 As shown, the screw 5 is disposed inside the guide post 4 and threadedly connected to it. In one example, the inner side of the proximal end of the guide post 4 is provided with an internal thread 402 that mates with the screw 5. Furthermore, a guide ring 502 is provided at the distal end of the screw 5, which slides with the guide post 4 to ensure the stability of the screw 5's movement. When the guide post 4 rotates clockwise, the screw 5 can automatically move forward under its drive, thereby providing a pushing force to the piston 1301 of the target object, such as the medicine bottle 13. The advancing speed of the screw 5 can be approximately 0.5 mm / s ± 0.05 mm to achieve a better injection effect.

[0070] See Figures 2 to 11 As shown, the steps for using the pen-type syringe are as follows:

[0071] S1. Insert the medicine bottle 13 into the pen refill holder 11 and connect and fix the pen refill holder 11 to the outer shell 1.

[0072] S2. Rotate the knob 6 counterclockwise to preset the injection dose until the required dose scale 201 appears in the viewing window 101. During this period, the first ratchet 103 and the first pawl 403 cooperate to lock the guide post 4 circumferentially, so that the screw 5 remains stationary. However, the second tooth 301 of the transmission post 3 can contact the first tooth 203 of the adjustment post 2 and make a toothing sound as a reminder.

[0073] S3. Press button 8. Under pressure, the second tooth 301 of the transmission column 3 forms a rigid connection with the first tooth 203 of the adjustment column 2. At the same time, the adjustment column 2 rotates clockwise and moves forward under the cooperation of the coarse thread 202 and the coarse groove 102 until the injection dose is zero and then stops. During this period, the transmission column 3 rotates clockwise in sync with the adjustment column 2.

[0074] S4. With the cooperation of the rib 302 and the groove 401, the guide post 4 synchronously drives the transmission post 3 to rotate clockwise, and drives the screw 5 to move forward through the internal thread 402 at the near end.

[0075] S5, the screw 5 pushes the piston 1301 and squeezes out a specific dose of medicine from the bottle, and injects it into the target area of ​​the object through the needle 12.

[0076] The main focus of this application is the improved design of the syringe's drive mechanism. As described above, compared to traditional drive mechanisms, this mechanism has fewer parts and a simpler overall structure, reducing costs and the risk of drive instability. Furthermore, the transmission components (such as teeth, grooves, and threads) on each part are more dispersed, which is advantageous for assembly design. This avoids the increased assembly difficulty caused by excessive concentration of transmission components in the same location, as well as problems with transmission stability caused by concentrated forces, thereby improving drive stability.

[0077] See Figure 7 As shown, in some embodiments, the proximal end of the support column 7 abuts against the transmission column 3 to support the transmission column 3 and ensure its circumferential rotation. Preferably, at least one of the proximal end of the support column 7 and / or the distal end of the transmission column 3 may be provided with a smooth and wear-resistant coating or an arc-shaped structure (not shown) to reduce friction and improve the smoothness of rotation of the transmission column 3.

[0078] An extension 701 is provided at the distal end of the support column 7. This extension 701 extends to the outside of the adjusting column 2 and connects to the button 8. The slightly longer design allows the button 8 to form a certain pressing gap with the knob 6 in the axial direction after assembly, so as to avoid the knob 6 affecting the pressing operation. In addition, the extension 701 also cooperates with the knob 6 to form a spring groove. A spring 9 is provided in the spring groove to apply force to the transmission column 3, so that it can be disengaged from the adjusting column 2.

[0079] See Figure 5 , Figure 6 and Figure 11 As shown, in some embodiments, the first ratchet 103 and the first tooth 203 extend toward each other and respectively form a limiting block 108 and a mating block 204. When the injection dose is zeroed, the limiting block 108 can precisely abut against the mating block 204, thereby accurately limiting the zeroing position and effectively preventing the adjustment column 2 from retracting too far and affecting the accuracy of the subsequent injection dose preset.

[0080] See Figure 3 and Figure 11 As shown, in some embodiments, a lens 10 is provided at the viewing window 101. The lens 10 is preferably a convex lens, which can magnify the dose scale 201 while providing dust protection, making it easier to identify and observe. Typically, the magnification of the lens 10 is about 1.5 times to ensure that the dose scale 201 is clearly visible.

[0081] See Figure 2 As shown, in some embodiments, the pen refill holder 11 is provided with a slot 1101 on its side, which is arranged axially to allow for real-time observation of the remaining amount of medicine in the medicine bottle 13.

[0082] Furthermore, the proximal end of the pen refill holder 11 is detachably connected to the needle 12. This detachable needle 12 design adapts to different injection requirements and effectively prevents contamination problems that may occur when changing different medications. Figure 16 As shown in this application, the needle 12 can be fixed to the proximal end of the pen refill holder 11 by means of threads.

[0083] Similarly, the distal end of the pen refill holder 11 is detachably connected to the outer casing 1 to facilitate the replacement of the medicine bottle 13. As an example, the proximal end of the outer casing 1 is provided with a sleeve portion 104, on which an L-shaped groove 107 is provided; correspondingly, the inner side of the distal end of the pen refill holder 11 is provided with a locking block 1102, wherein the locking block 1102 can be quickly connected by rotating and engaging with the L-shaped groove 107. More specifically, the L-shaped groove 107 includes an insertion section 1071 and a locking section 1072, and a retaining rib 1073 is provided in the locking section 1072. After the locking block 1102 moves from the insertion section 1071 to the locking section 1072, it can be limited by the retaining rib 1073, thereby improving the fixing effect after connection. Furthermore, the rib 1073 also has a certain anti-accidental touch effect. Because of its existence, if the pen refill holder 11 needs to be separated from the sleeve part 104, the reverse rotation needs to overcome the resistance of the rib 1073, that is, a greater force is required to remove the locking block 1102 from the L-shaped groove 107, thereby preventing the pen refill holder 11 and the outer shell 1 from loosening, and improving reliability.

[0084] In further design, see Figures 1 to 16 As shown, the pen-type syringe of this application also includes a second ratchet 14 and a second pawl 105. The second ratchet 14 is disposed inside the sleeve portion 104, and has a non-circular hole 1401 at its center, as shown... Figure 15 The rectangular hole 1401 is shown, and the screw 5 slides through this non-circular hole 1401. A second pawl 105 is provided on the sleeve 104 and is capable of radial elastic deformation. Figure 16It can be understood that the interaction between the second ratchet 14 and the second pawl 105 is actually controlled by the pen cartridge holder 11. The second pawl 105 only contacts and engages with the second ratchet 14 while the pen cartridge holder 11 is mounted on the sleeve portion 104 to restrict the free rotation of the screw 5. Specifically, when the pen syringe is in operation, since the pen cartridge holder 11 is mounted on the sleeve portion 104 of the outer shell 1, the second pawl 105 will retract radially due to the pressure of its inner wall, causing it to contact and lock the second ratchet 14. Furthermore, because the non-circular hole 1401 of the second ratchet 14 restricts the screw 5 (the two can only move axially and cannot rotate circumferentially), this means that when the drug in the syringe is not consumed, the screw 5 can only move axially forward under the control of the drive mechanism, and will not retract due to vibration or repeated operation, thus affecting the accuracy of the injection dosage. Moreover, the presence of the second ratchet 14 further improves the stability of the screw 5's movement. In the medication changing state, since the pen refill holder 11 needs to be separated from the outer shell 1, after the pen refill holder 11 on the sleeve part 104 is removed, the second pawl 105 automatically expands radially outward and separates from the second ratchet 14. At this time, the second ratchet 14 is allowed to rotate freely. By reversing the second ratchet 14 or the screw 5, the screw 5 can be returned to the initial position, waiting to be used again after assembling the new medicine bottle 13.

[0085] See Figure 4 and Figure 14 As shown, in some embodiments, the sleeve portion 104 is provided with a clearance opening 106, and the second pawl 105 is located within the clearance opening 106 to ensure that the second pawl 105 can undergo elastic deformation in the radial direction. Furthermore, a protruding mating surface 1051 is provided on the side of the second pawl 105 away from the second ratchet 14. This mating surface 1051 is a convex surface with inclined guide surfaces on both sides to facilitate mating with the inner wall of the pen refill holder 11.

[0086] See Figure 13 As shown, in some embodiments, the proximal end of the screw 5 is detachably connected to the piston 1301 for convenient drug replacement. For example, the proximal end of the screw 5 is provided with a quick connector, and the corresponding distal end of the piston 1301 is provided with a quick interface. The quick connector and quick interface correspond to each other and can be quickly connected by plugging and unplugging.

[0087] See Figure 15 As shown, in some embodiments, the screw 5 has at least one cross-section 501 along its axial direction. For example, cross-sections 501 are provided on both sides of its axial direction, resulting in a rectangular cross-section of the screw 5. Correspondingly, the non-circular hole 1401 is a rectangular hole and matches the cross-section of the screw 5, which allows the screw 5 to move axially relative to the second ratchet 14, but not to rotate axially.

[0088] See Figures 5 to 10As shown, in some embodiments, the proximal end of the housing 1 is integrally formed with a first ratchet 103 and a sleeve portion 104, the proximal end of the adjusting post 2 is integrally formed with a first tooth portion 203, the proximal end of the transmission post 3 is integrally formed with a second tooth portion 301 and a protruding rib 302, and the proximal end of the guide post 4 is integrally formed with a first pawl 403. This integral forming allows each transmission component to be directly integrated onto its corresponding part, facilitating assembly while reducing the number of parts and lowering production costs.

[0089] In some embodiments, a soft rubber sleeve is provided on the side of the housing 1 away from the viewing window 101. The soft rubber sleeve has a wave-shaped structure that adapts to the knuckles, which increases friction and improves grip comfort.

[0090] In some embodiments, a pen cap 15 is provided on the pen refill holder 11, and the two are fitted together in an interference manner to protect the needle 12 and / or the medicine bottle 13.

[0091] Although embodiments of the present utility have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present utility. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present utility without departing from the principles and spirit of the present utility, and all such changes should fall within the protection scope of the claims of the present utility.

Claims

1. A pen-type injector, characterized in that, include: The outer shell (1) has a socket (104) at its proximal end, and a second pawl (105) is provided on the socket (104). The second ratchet (14) is located inside the sleeve (104) and has a non-circular hole (1401) at its center. The screw (5) is movably disposed within the housing (1), and a portion thereof slides through the non-circular hole (1401) of the second ratchet (14). In the pen syringe, when in operation, the second pawl (105) contacts and locks the second ratchet (14), causing the screw (5) to move forward axially only; when changing medication, the second ratchet (14) separates from the second pawl (105) and is allowed to rotate, causing the screw (5) to rotate backward.

2. The pen injector of claim 1, wherein, It also includes a pen refill holder (11), wherein, in the operating state, the distal end of the pen refill holder (11) is connected to the sleeve (104) and radially presses the second pawl (105); while in the dressing change state, the distal end of the pen refill holder (11) is separated from the sleeve (104).

3. The pen injector of claim 2, wherein, The socket (104) is provided with a relief opening (106), the second pawl (105) is located in the relief opening (106), and a protruding mating surface (1051) is provided on the side away from the second ratchet (14).

4. The pen injector of claim 2, wherein, The socket (104) is provided with an L-shaped groove (107), and the pen refill holder (11) is provided with a locking block (1102) on the inner side of its far end; wherein the locking block (1102) is rotatably connected to the L-shaped groove (107).

5. The pen injector of claim 1, wherein, The L-shaped groove (107) includes an insertion section (1071) and a locking section (1072), and a retaining rib (1073) is provided in the locking section (1072). After the locking block (1102) moves from the insertion section (1071) to the locking section (1072), it can be limited by the retaining rib (1073).

6. The pen injector of claim 1, wherein, It also includes a guide post (4), which is disposed inside the housing (1) and threadedly connected to the screw (5), and the guide post (4) is restricted to rotating only in one direction.

7. The pen injector of claim 6, wherein, The near end of the outer casing (1) is also provided with a first ratchet (103), and the near end of the guide post (4) is provided with a first pawl (403). The first ratchet (103) engages with the first pawl (403), causing the guide post (4) to rotate only in a clockwise direction.

8. The pen injector of claim 1, wherein, The screw (5) has at least one cross section (501) along the axial direction, and the cross section of the screw (5) matches the non-circular hole (1401).

9. The pen injector of claim 2, wherein, The pen refill holder (11) is provided with a replaceable medicine bottle (13), and the medicine bottle (13) is provided with a piston (1301). The proximal end of the screw (5) is detachably connected to the piston (1301).

10. The pen injector of claim 2, wherein, The pen refill holder (11) is provided with a detachable needle (12) at its proximal end.

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