Injection pen

Abstract

The utility model belongs to medical technology field especially, and it is related to injection pen, the injection pen includes: push rod rotary drum and first rotary drum gear, the injection pen still includes stop structure, the stop structure includes: tooth part, it is along the circumferential distribution on the proximal end surface of push rod rotary drum, recess part is arranged on the distal end surface of first rotary drum gear, and the recess part is matched with tooth part, the height of tooth part is greater than the depth of recess part, wherein, when push rod rotary drum rotates to tooth part and is clamped into corresponding recess part, the proximal end surface of push rod rotary drum is opposite to the distal end surface of first rotary drum gear and stops, part of tooth part is stretched to the recess part outside to form redundancy gap, when tooth part and recess part fail, can pass through surface and surface contact and carry out safe redundancy, improve injection pen use accuracy.

Description

Technical Field

[0001] This utility model belongs to the field of medical technology, specifically relating to syringes, and more particularly to injection pens. Background Technology

[0002] As a portable drug delivery device, the injection pen is widely used in treatment areas requiring long-term, precise drug administration, such as diabetes and autoimmune diseases. Its core function lies in achieving precise control and reliable injection of drug dosage. The stability and reliability of the dosage setting and the execution mechanism directly determine the safety of the injection process and the user experience.

[0003] To ensure the accuracy and safety of the injection process, injection pens typically have a stop mechanism to precisely define the starting position (zero position) and ending position (maximum dose position) of the plunger cylinder during the dosage stroke. The long-term stability of both the zero and maximum dose positions is crucial. The accuracy of the zero position determines the baseline for dose setting, while the reliability of the maximum dose position directly relates to the effectiveness of preventing over-injection.

[0004] However, existing stop structures generally suffer from insufficient wear resistance. After prolonged and repeated use, the contact points of the stop structure are prone to wear. For zero-dose stops, this wear can cause the dosage setting reference point to drift, resulting in an inconsistent starting position for each injection; for maximum-dose stops, wear can cause changes in their limiting position. Both of these situations can lead to serious safety hazards, such as discrepancies between the actual injected dose and the set dose.

[0005] It should be noted that the information disclosed in this background section is only for understanding the background technology of the present application concept, and therefore, the above description is not considered to constitute prior art information. Utility Model Content

[0006] This disclosure provides at least one injection pen to solve the technical problem that the stop position is unreliable after repeated operation of the injection pen.

[0007] This disclosure provides an injection pen, which includes a push rod cylinder and a first cylinder gear. The injection pen also includes a stop structure. The stop structure includes: teeth distributed circumferentially on the proximal end face of the push rod cylinder; and a recess disposed on the distal end face of the first cylinder gear, wherein the recess engages with the teeth. The height of the teeth is greater than the depth of the recess. When the push rod cylinder rotates to the point where the teeth engage with the corresponding recess, the proximal end face of the push rod cylinder is stopped relative to the distal end face of the first cylinder gear, and a portion of the teeth extends outside the recess to form a redundant gap.

[0008] In one alternative embodiment, the toothed portion includes: a snap-fit ​​surface, the snap-fit ​​surface being a right-angled surface; the recess includes: a right-angled segment extending perpendicularly to the distal end surface; the snap-fit ​​surface is adapted to abut against the side of the right-angled segment.

[0009] In one alternative embodiment, the tooth further includes a guide surface, which is a ramp surface; the recess further includes an arc-shaped ramp section adapted to connect the right-angle section and the distal end face of the first rotary gear; the guide surface is adapted to slide along the arc-shaped ramp section.

[0010] In one optional embodiment, the number of teeth is three, and they are evenly spaced along the circumference of the push rod cylinder; the number of recesses is also three, and they are evenly spaced along the circumference of the first cylinder gear.

[0011] In one optional embodiment, the injection pen further includes: a rotary cylinder support with an internal thread on its inner wall, the axial end of which is formed as an abutment portion; the push rod rotary cylinder is connected to the internal thread of the rotary cylinder support through an external thread on its outer wall; the rotary cylinder support cooperates with the push rod rotary cylinder to limit the axial displacement of the push rod rotary cylinder.

[0012] In one optional embodiment, the inside of the rotary support of the injection pen is provided with a positioning groove, and the first rotary gear is provided with a positioning block that matches the positioning groove in the circumferential direction.

[0013] In one optional embodiment, the positioning block includes a first positioning mounting block and a second positioning mounting block, wherein the circumferential width of the first positioning mounting block is greater than the circumferential width of the second positioning mounting block; the positioning groove includes a wide groove adapted to the first positioning mounting block and a narrow groove adapted to the second positioning mounting block.

[0014] In one alternative embodiment, at least one clamping plane is provided on the circumferential outer wall of the first rotary gear.

[0015] In one optional embodiment, the injection pen further includes: a pen body; a rotating cylinder support disposed within the pen body, the inner wall of the rotating cylinder support having an internal thread, the axial end of which forms an abutment portion; the push rod rotating cylinder being connected to the internal thread of the rotating cylinder support via an external thread disposed on its outer wall; a first rotating cylinder gear; and an elastic locking portion disposed on the cylinder wall of the push rod rotating cylinder near its proximal end face; the elastic locking portion having a stop bevel, and at least three sides of the elastic locking portion having circumferentially hollowed out; The abutting part is a guide slope, which is adapted to abut against the stop slope.

[0016] In one alternative embodiment, the arc and direction of the extension trajectory of the elastic snap-fit ​​portion are consistent with the arc and direction of the external thread formed on the outer wall of the push rod cylinder.

[0017] The beneficial effects of this invention are as follows: This invention provides an injection pen that, by setting the teeth to abut against the recesses, achieves multi-point surface contact, effectively preventing wobbling and swaying of the plunger cylinder at the zero position, ensuring the accuracy of repeatable positioning when the dosage setting is zero, thereby guaranteeing the accuracy of drug delivery. Simultaneously, the redundant gap formed by the teeth engaging with the recesses allows the plunger cylinder to move axially a short distance of this redundant gap when the teeth are excessively compressed or broken due to accidental impact or wear, until the proximal end face of the plunger cylinder abuts against the distal end face of the first rotary gear. Therefore, in the event of failure of the teeth and recesses, surface-to-surface contact provides a safety redundancy.

[0018] Other features and advantages of this invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objectives and other advantages of this invention are realized and obtained through the structures particularly pointed out in the description and the accompanying drawings.

[0019] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 A perspective view of the injection pen provided for an embodiment of this disclosure; Figure 2 Cross-sectional view of the preferred embodiment of the stop structure provided in this disclosure; Figure 3 A perspective view of the drum support, push rod drum, and first drum gear in their separated states, provided in an embodiment of this disclosure. Figure 4 A partial cross-sectional view of the push rod cylinder and the first cylinder gear provided in an embodiment of this disclosure; Figure 5 A perspective view of the first rotary gear provided in an embodiment of this disclosure.

[0022] In the picture: 1. Pen body; 2. Rotary drum support; 21. Internal thread; 211. Abutment part; 22. Positioning groove; 221. Wide groove; 222. Narrow groove; 3. Push rod cylinder; 31. Proximal end face; 32. Tooth; 321. Engaging surface; 322. Guide surface; 33. Parallelogram hole; 34. Flexible engaging part; 341. Stop bevel; 35. External thread; 4. First rotary gear; 41. Distal end face; 42. Recess; 421. Right-angle section; 422. Circular arc ramp section; 43. Positioning block; 431. First positioning mounting block; 432. Second positioning mounting block; 44. Clamping plane; 5. Redundant gaps. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0024] In this document, when it is mentioned that a first component is located on a second component, this can mean that the first component can be directly formed on the second component, or that a third component can be inserted between the first and second components. Furthermore, in the accompanying drawings, the thickness of components may be exaggerated or reduced for the purpose of effectively describing the technical content.

[0025] In this document, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. As used herein, expressions such as “at least one of…” modify the entire list of elements when following a list of elements, rather than individual elements in the list. For example, the expression “at least one of a, b, and c” should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0026] The terminology used herein is for the purpose of describing specific exemplary configurations only and is not intended to be limiting. As used herein, the singular articles “a,” “an,” and “the” may also be intended to include plural forms unless otherwise clearly stated herein. The terms “comprising,” “including,” and “having” are inclusive and thus specify the presence of features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein should not be construed as requiring them to be performed in the specific order discussed or shown, unless specifically identified as such. Additional or alternative steps may be employed.

[0027] As used herein, the phrases “in one embodiment,” “according to one embodiment,” “in some embodiments,” etc., generally refer to the fact that a particular feature, structure, or characteristic following the phrase can be included in at least one embodiment of this disclosure. Therefore, a particular feature, structure, or characteristic can be included in more than one embodiment of this disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms “example,” “exemplary,” etc., are used to “serve as an example, instance, or illustration.” Any implementation, aspect, or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or superior to other implementations, aspects, or designs. Rather, the use of the terms “example,” “exemplary,” etc., is intended to present concepts in a specific manner.

[0028] Research has revealed a drawback in existing technologies: In related technologies, injection pens typically have a stop structure to limit the starting position (i.e., zero position) and / or ending position (i.e., maximum dose position) of the plunger cylinder during the dosage stroke. Among these, the limiting of the starting position (zero position) is particularly critical, as it not only determines the reference point for dose setting but also affects the reset of the mechanism after injection and the accuracy of the next dose setting.

[0029] However, in the existing technology, most injection pens use a stop structure at the distal end of the plunger (i.e., the end away from the patient's skin). The axial movement is terminated by the limiting protrusion or recess at this point cooperating with the housing or other fixed parts. Since the protrusion will interfere with the surrounding parts, after repeated operation for a long time, the protrusion will wear down and lose its stop effect, which poses a safety risk of zero-point drift of the stop dose, affecting reliability and service life.

[0030] The shortcomings of the above solutions are the result of the utility model inventor's practice and careful research. Therefore, the discovery process of the above problems and the solutions proposed in this disclosure should be considered as contributions made by the utility model inventor to this disclosure.

[0031] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0032] The following detailed description, with reference to the accompanying drawings, describes some embodiments of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0033] like Figures 1 to 5As shown, some embodiments provide an injection pen, the core improvement of which lies in the stop structure of the internal transmission mechanism, especially the limit of the push rod cylinder 3 at the zero position; the injection pen mainly includes a pen body 1, a cylinder support 2, a push rod cylinder 3 and a first cylinder gear 4; specifically, the injection pen includes: a push rod cylinder 3 and a first cylinder gear 4.

[0034] The pen body 1 serves as the outer shell of the injection pen, providing a grip for the user and protecting the internal precision components; its interior has a cavity for housing various functional components.

[0035] The rotating cylinder support 2 is fixedly installed in the internal cavity of the pen body 1; the main function of the rotating cylinder support 2 is to provide precise axial guidance and radial support for the push rod rotating cylinder 3, so as to ensure that the push rod rotating cylinder 3 can move stably along the predetermined path during the setting of dosage and injection; an abutment part 211 is provided on the inner wall of the rotating cylinder support 2.

[0036] The push rod cylinder 3 is rotatably housed within the cylinder support 2; the user sets the injection dose by rotating the push rod cylinder 3; the push rod cylinder 3 typically has a threaded structure (not shown in the figure) that meshes with the piston rod; when the push rod cylinder 3 is pressed down during injection, it drives the piston rod to move forward and push out the liquid medicine; the proximal end face 31 of the push rod cylinder 3 (i.e. the end face close to the patient's skin) is the key area where it interacts with the first cylinder gear 4.

[0037] Specifically, the rotating drum support 2 has an internal thread 21 on its inner wall, and the axial end of the internal thread 21 is formed as an abutment part 211; the push rod rotating drum 3 is connected to the internal thread 21 of the rotating drum support 2 through an external thread 35 on its outer wall; the rotating drum support 2 and the push rod rotating drum 3 cooperate to limit the axial displacement of the push rod rotating drum 3.

[0038] The first rotary gear 4 is arranged adjacent to the push rod rotary cylinder 3 and is usually linked with the dose indication mechanism (such as a digital sleeve); its distal end face 41 (i.e. the end face away from the patient's skin) is opposite to the proximal end face 31 of the push rod rotary cylinder 3, and a recess 42 that cooperates with the push rod rotary cylinder 3 is provided on it.

[0039] The first stop structure includes multiple teeth 32 distributed circumferentially on the near-end face 31 of the push rod cylinder 3. The teeth 32 and the recess 42 cooperate to form the first stop structure based on multi-point limiting of tooth groove meshing.

[0040] The first stop structure is the first line of defense to ensure the accuracy of the zero point of the dose. Its core lies in the cooperation between the push rod cylinder 3 and the first cylinder gear 4. Feature 1: teeth 32, which can also be multiple, are distributed circumferentially on the near end face 31 of the push rod cylinder 3. For example, there can be three teeth 32, which are evenly spaced along the circumference of the push rod cylinder 3. There are also three recesses 42, which are evenly spaced along the circumference of the first cylinder gear 4.

[0041] Specifically, in this embodiment, the number of teeth 32 is preferably three, and they are evenly distributed along the circumference of the push rod cylinder 3; this three-point layout has a significant stability advantage compared with the two-point layout commonly used in the prior art.

[0042] From a mechanical point of view, three points can define a plane, which can effectively prevent the push rod cylinder 3 from tilting or deflecting when it is stopped. When the three teeth 32 are in contact with the structure on the first cylinder gear 4 at the same time, the force is uniform and symmetrical, avoiding local stress concentration, thereby greatly improving the stability and reliability of the stopping process. In addition, moving the stopping structure from the outer peripheral surface of the push rod cylinder 3 (as mentioned above in the disadvantages of the prior art) to its end face, so that it is contained in the internal space of the cylinder support 2, effectively avoids unnecessary friction or interference with adjacent parts such as the inner wall of the pen body 1 and the dosage indicator component, reducing the assembly difficulty and the risk of wear under long-term use.

[0043] A recess 42 is provided on the distal end face 41 of the first rotary gear 4, and the recess 42 mates with the tooth 32; Feature 2: Several recesses 42 are provided on the distal end face 41 of the first rotary gear 4, and each recess 42 mates with the tooth 32 one by one; The number, position and shape of the recesses 42 precisely correspond to the tooth 32; This one-to-one mating relationship ensures that when the push rod rotary cylinder 3 rotates to the zero position, each tooth 32 can accurately embed into the corresponding recess 42, achieving precise positioning; The setting of the recesses 42 upgrades the limiting contact from "point-to-surface" or "line-to-surface" contact to "surface-to-surface" or "body-to-groove" inclusive contact, with a larger contact area and more uniform force distribution; This design not only improves the mechanical stability of the stop, but also provides a clear "click" feel during user operation, enhancing the user experience; This mating relationship constitutes the first layer of protection for the stop.

[0044] The height of the tooth 32 is greater than the depth of the recess 42; wherein, when the push rod cylinder 3 rotates to the point where the tooth 32 is respectively engaged in the corresponding recess 42, the near end face 31 of the push rod cylinder 3 is positioned relative to the far end face 41 of the first cylinder gear 4, and part of the tooth 32 extends out of the recess 42 to form a redundant gap 5.

[0045] Feature 3: The height of the teeth 32 is greater than the depth of the recesses 42. When all the teeth 32 are fully engaged in the bottom of the corresponding recesses 42, the near end face 31 of the push rod cylinder 3 and the far end face 41 of the first cylinder gear 4 are not tightly fitted, but a small axial gap is retained, namely the redundant gap 5.

[0046] First, the gap provides the necessary tolerance space for the assembly of the injection pen; the push rod cylinder 3 is usually assembled by axial insertion. If its bottom is rigidly and zero-clearancely abutting the top of the first cylinder gear 4, the pre-compression of the internal transmission components (such as the drive screw, spring, etc.) is easily out of control during the assembly process, which directly affects the accurate calibration of the dose zero point; second, considering that the components of the injection pen are mostly made of plastic, they will undergo slight thermal expansion and contraction or creep deformation under temperature changes or long-term stress. The redundant gap 5 provides a buffer space for this deformation, avoiding the internal stress caused by a completely rigid connection, thereby preventing the components from deforming or cracking.

[0047] The surface of the toothed part 32 facing the axis of the push rod rotary cylinder 3 is the engagement surface 321, which is a right-angled surface; the recess 42 includes: a right-angled segment 421, which is provided perpendicular to the distal end surface 41 of the first rotary cylinder gear 4; the engagement surface 321 is adapted to abut against the side of the right-angled segment 421.

[0048] Feature 4: The tooth 32 includes a locking surface 321, which is a right-angled surface; the recess 42 includes a right-angled segment 421, the extension direction of which is perpendicular to the distal end face 41; the locking surface 321 is adapted to abut against the side of the right-angled segment 421; this feature defines the main force-bearing surface when the stop occurs; the locking surface 321 is designed as a right-angled surface (i.e., a vertical surface parallel to the axis of the push rod cylinder 3), and the right-angled segment 421 of the recess 42 that mates with it is also a vertical surface; when the push rod cylinder When the 3-axis tends to continue moving towards the proximal end (i.e., the zero position direction), the snap-fit ​​surface 321 will form a large-area, highly stable vertical contact with the side of the right-angle section 421. This "straight-face contact with straight-face" structure can effectively resist axial impact force and prevent the push rod cylinder 3 from accidentally moving axially at the zero position, ensuring the absolute accuracy of the dose zero position. Compared with the limiting method of inclined surface or point contact in the prior art, this vertical surface cooperation has higher rigidity and stability and less wear.

[0049] Feature 5: The tooth 32 further includes a guide surface 322, which is a ramp surface; the recess 42 further includes an arc-shaped ramp section 422, which is suitable for connecting the right-angle section 421 and the distal end face 41 of the first rotary gear 4; the guide surface 322 is suitable for sliding along the arc-shaped ramp section 422; this feature defines the guiding mechanism for how the tooth 32 smoothly slides into the recess 42 during the reset process of the push rod rotary cylinder 3; the guide surface 322 is designed as a ramp surface, and the entrance of the recess 42 is provided with a matching arc-shaped ramp section 422; when the user rotates the push rod rotary cylinder 3 to return it to its original position... At zero position, the guide surface 322 slides smoothly along the arc-shaped ramp section 422. The design of the arc-shaped ramp makes the contact process a gradual and smooth transition, rather than a sudden impact. This brings two major benefits: first, it significantly reduces noise and impact during operation, providing a better user feel; second, it reduces impact wear of components at the moment of engagement, which is crucial for injection pens that need to be used thousands of times, as it directly relates to the long-term reliability and service life of the product. The aforementioned precise surface fit ensures smooth operation.

[0050] It should be further explained that the inside of the rotating drum support 2 is provided with a positioning groove 22, and the first rotating drum gear 4 is provided with a positioning block 43 that is adapted to the positioning groove 22 in the circumferential direction; the positioning block 43 includes a first positioning mounting block 431 and a second positioning mounting block 432, the circumferential width of the first positioning mounting block 431 is greater than the circumferential width of the second positioning mounting block 432; the positioning groove 22 includes a wide groove 221 adapted to the first positioning mounting block 431 and a narrow groove 222 adapted to the second positioning mounting block 432; at least one clamping plane 44 is provided on the outer circumferential wall of the first rotating drum gear.

[0051] The operator uses tweezers to hold the first rotary gear 4 through the clamping plane 44, aligning its positioning block 43 with the positioning groove 22 of the rotary support 2. Since the circumferential width of the first positioning mounting block 431 is greater than that of the second positioning mounting block 432, and the positioning groove 22 is divided into a wide groove 221 and a narrow groove 222, the first rotary gear 4 can only be smoothly installed into the rotary support 2 when the first positioning mounting block 431 corresponds to the wide groove 221 and the second positioning mounting block 432 corresponds to the narrow groove 222. This avoids misalignment of the teeth 32 and the recess 42 due to incorrect installation direction. Therefore, after assembly, the position of the recess 42 is stable, and the teeth 32 can always accurately engage with the recess 42, achieving reliable positioning.

[0052] The first rotary cylinder gear 4 is circumferentially fixed by the cooperation of the positioning block 43 and the positioning groove 22. The concave part 42 of its far end face 41 is precisely engaged with the tooth part 32 of the near end face 31 of the push rod rotary cylinder 3. When the push rod rotary cylinder 3 rotates, the stop structure of the tooth part 32 and the concave part 42 (with redundant clearance 5) restricts its excessive displacement, ensuring that the dose zero point does not drift.

[0053] In summary, the cooperation between the positioning groove 22 and the positioning block 43 avoids directional errors during the assembly stage through a foolproof design, ensures the function of the stop structure through a stable positioning relationship during the working stage, and enhances the ease of assembly by holding the clamping plane 44. Overall, it achieves the effect of "efficient assembly, accurate positioning, and reliable stop".

[0054] Some embodiments provide an injection pen, which includes: a stop structure as described above; and further includes: a pen body 1; a rotary support 2 disposed inside the pen body 1, the inner wall of the rotary support 2 having an internal thread 21, the axial end of which is formed as an abutment portion 211; a push rod rotary cylinder 3, which is connected to the internal thread 21 of the rotary support 2 by an external thread 35 disposed on its outer wall; a first rotary gear 4; an elastic locking portion 34 disposed on the cylinder wall of the push rod rotary cylinder 3 near its proximal end face 31; the elastic locking portion 34 has a stop inclined surface 341, and at least three sides of the elastic locking portion (34) are circumferentially hollowed out; the multiple hollows form a structure of an approximately parallelogram hole 33. The abutment portion 211 is a guide inclined surface, which is adapted to abut against the stop inclined surface 341; the extension trajectory arc and direction of the elastic locking portion 34 are consistent with the arc and direction of the external thread 35 formed on the outer wall of the push rod rotary cylinder 3.

[0055] The shape of the elastic snap-fit ​​part 34 is an optimization point of this embodiment; the arc and direction of its extension trajectory are consistent with the arc and direction of the external thread 35 formed on the outer wall of the push rod cylinder 3; this design makes the stop structure of the maximum single dose naturally integrated with the thread texture, which is not only more aesthetically pleasing in structure, but more importantly, it can reduce stress concentration when the push rod cylinder 3 rotates, making the force transmission smoother and the assembly process smoother.

[0056] The elastic locking part 34 has a stop slope 341; the abutting part 211 has a guide slope, which is adapted to abut against the stop slope 341; this is the core mating method of the maximum dose stop structure; the abutting surface of the elastic locking part 34 is designed as the stop slope 341, while the corresponding surface of the abutting part 211 on the rotating cylinder bracket 2 is designed as the guide slope; when the maximum dose stop is effective, it is a surface contact where the two slopes are in contact.

[0057] The advantages of inclined surface fitting are: First, it has a large contact area, uniform force distribution, and stability far superior to point contact, effectively limiting the axial movement of the push rod cylinder 3; Second, the inclined surface fit has a self-guiding effect, and even with slight deviations, it can achieve good fit through the sliding guidance of the inclined surface; Third, because it is a complete fit, the pressure per unit area is small, resulting in an extremely low wear rate, which significantly improves the service life and reliability of reusable pens.

[0058] The workflow of the injection pen provided in this embodiment is as follows: Dosage setting and injection: The user rotates the push rod cylinder 3 to set the dosage. At this time, the push rod cylinder 3 rotates and moves axially relative to the cylinder support 2 and the first cylinder gear 4. The main and secondary stop structures are not effective. Reset to zero: After injection, the user rotates the push rod cylinder 3 in the reverse direction to reset it; when it approaches zero, the guide surface 322 of the tooth 32 on the near end face 31 of the push rod cylinder 3 will slide along the arc slope section 422 of the concave portion 42 on the far end face 41 of the first cylinder gear 4, producing a slight change in feel and finally accompanied by a clear "click" sound, indicating that the engaging surface 321 of the tooth 32 and the right angle section 421 of the concave portion 42 are fully engaged, and the first double stop (main stop) is activated; at this time, the axial movement of the push rod cylinder 3 is precisely limited, and the dose indication is zeroed; since the height of the tooth 32 is greater than the depth of the concave portion 42, the redundant gap 5 exists, even if the tooth 32 is worn and the first double stop fails, the bottom surface of the push rod cylinder 3 can contact the top surface of the first cylinder gear 4, and the second stop structure is activated; In summary, this embodiment achieves a three-point stable limiting structure by setting circumferentially evenly distributed teeth 32 and recesses 42, significantly improving the rigidity and accuracy of the stop and avoiding interference with external components; by setting redundant gaps 5, necessary assembly tolerance and thermal deformation compensation space are obtained, internal stress is reduced, and long-term stability of zero-point calibration is ensured; by setting the cooperation between the right-angle locking surface 321 and the right-angle segment 421, the ability to resist axial impact is improved, ensuring that the zero position is unshakable; by setting the cooperation between the ramp guide surface 322 and the arc ramp segment 422, impact noise and wear during the reset process are reduced, improving user experience and product durability; by setting the abutment part 211 based on the inclined surface and the elastic locking part 34, a maximum dose stop structure is formed.

[0059] In the description of the embodiments of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0060] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this utility model 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 of this utility model. Furthermore, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence unless expressly indicated herein. Therefore, without departing from the teachings of the exemplary embodiments, the first element, component, region, layer, or segment discussed above may be referred to as the second element, component, region, layer, or segment.

[0061] Based on the above-described preferred embodiments of this utility model, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the technical concept of this utility model. The technical scope of this utility model is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. An injection pen, the injection pen comprising: The push rod rotary cylinder (3) and the first rotary cylinder gear (4) are characterized in that the injection pen further includes a stop structure; The stop structure includes: The teeth (32) are distributed circumferentially on the near end face (31) of the push rod cylinder (3); A recess (42) is provided on the distal end face (41) of the first rotary gear (4), and the recess (42) engages with the tooth (32); The height of the tooth (32) is greater than the depth of the recess (42); When the push rod cylinder (3) rotates to the point where the tooth (32) is engaged in the corresponding recess (42), the near end face (31) of the push rod cylinder (3) is positioned relative to the far end face (41) of the first cylinder gear (4), and part of the tooth (32) extends out of the recess (42) to form a redundant gap (5).

2. The injection pen as described in claim 1, characterized in that, The teeth (32) include: The snap-fit ​​surface (321) is a right-angled surface; The recess (42) includes: A right-angled segment (421) extends perpendicularly to the distal end face (41). The snap-fit ​​surface (321) is adapted to abut against the side of the right-angle segment (421).

3. The injection pen as described in claim 2, characterized in that, The teeth (32) also include: The guide surface (322) is a sloping surface; The recess (42) further includes: An arc ramp section (422) is adapted to connect the right-angle section (421) to the far end face (41) of the first rotary gear (4). The guide surface (322) is adapted to slide along the circular arc slope section (422).

4. The injection pen as described in claim 1, characterized in that, The number of teeth (32) is three, and they are evenly spaced along the circumference of the push rod cylinder (3); The number of the recesses (42) is also three, and they are evenly spaced along the circumference of the first rotary gear (4).

5. The injection pen as described in claim 1, characterized in that, Also includes: The rotating drum support (2) has an internal thread (21) on its inner wall, and the axial end of the internal thread (21) is formed as an abutment part (211). The push rod rotary cylinder (3) is connected to the internal thread (21) of the rotary cylinder bracket (2) by an external thread (35) provided on the outer wall; The rotating drum support (2) cooperates with the push rod rotating drum (3) to limit the axial displacement of the push rod rotating drum (3).

6. The injection pen according to any one of claims 1 to 5, characterized in that, The rotary support (2) of the injection pen has a positioning groove (22) inside. The first rotary gear (4) is provided with a positioning block (43) in the circumferential direction that is adapted to the positioning groove (22).

7. The injection pen as described in claim 6, characterized in that, The positioning block (43) includes a first positioning mounting block (431) and a second positioning mounting block (432), wherein the circumferential width of the first positioning mounting block (431) is greater than the circumferential width of the second positioning mounting block (432); The positioning groove (22) includes a wide groove (221) adapted to the first positioning mounting block (431) and a narrow groove (222) adapted to the second positioning mounting block (432).

8. The injection pen as described in claim 1, characterized in that, At least one clamping plane (44) is provided on the circumferential outer wall of the first rotary gear (4).

9. The injection pen as described in claim 1, characterized in that, Also includes: Pen body (1); Rotary cylinder support (2) is set inside the pen body (1). The inner wall of the rotary cylinder support (2) is provided with an internal thread (21), and the axial end of the internal thread (21) is formed as an abutment part (211). The push rod rotary cylinder (3) is connected to the internal thread (21) of the rotary cylinder bracket (2) through the external thread (35) provided on the outer wall; The push rod rotary cylinder (3) has an elastic snap-fit ​​part (34) on its cylinder wall near its near end face (31). The elastic snap-fit ​​part (34) has a stop slope (341), and at least three sides of the elastic snap-fit ​​part (34) are circumferentially hollowed out; The abutting part (211) is a guide slope, which is adapted to abut against the stop slope (341).

10. The injection pen as described in claim 9, characterized in that, The arc and direction of the extension trajectory of the elastic snap-fit ​​part (34) are consistent with the arc and direction of the external thread (35) formed on the outer wall of the push rod cylinder (3).

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