Liquid-pushing stable injection pen and its working method

Abstract

The present invention belongs to the technical field of instruments for injecting a medium into or onto a human body, and specifically relates to a liquid-pushing stable injection pen and a working method thereof. The liquid-pushing stable injection pen comprises: a housing; a driving mechanism, which is arranged in the housing and comprises: a screw and a push block, wherein the push block is rotatably arranged on the engaging end of the screw through an engaging cavity thereon; a holding mechanism, which is arranged on the engaging end of the screw, and the holding mechanism extends outward and abuts against the inner wall of the engaging cavity to maintain the stability of the push block; wherein, when injecting medicine, the screw rotates and moves downward to abut against the push block, and then pushes the push block to move synchronously, and at the same time, the holding mechanism is forced to retract and release the limit. The liquid-pushing stable injection pen and the working method thereof are provided with a holding mechanism on the engaging end of the screw, so that when the screw stops injecting medicine, the holding mechanism extends outward and abuts against the inner wall of the engaging cavity, thereby tightening the push block on the engaging end of the screw, that is, maintaining the stability of the push block and preventing the push block from shaking.

Description

Technical Field

[0001] The present invention belongs to the technical field of devices for injecting a medium into or onto a human body, and specifically relates to a syringe, and more particularly to a liquid-pushing stable injection pen and a working method thereof. Background Art

[0002] An injection pen is a commonly used medical device that can be filled with the required injection cartridge, then installed with an injection needle, and finally the drug solution can be injected by pressing or twisting.

[0003] In the related art, a driving mechanism is provided in the injection pen, which drives the injection of medicine into the cartridge by pressing the driving mechanism. The driving mechanism comprises at least a screw and a push block, which drives the push block to squeeze the cartridge to achieve injection by rotating and moving the screw downward. However, the inventors have found that after the injection is completed, there is a certain probability of jamming when the next injection is performed.

[0004] Therefore, reducing the probability of the above-mentioned jamming phenomenon is a technical problem that those skilled in the art urgently need to solve.

[0005] It should be noted that the above information disclosed in this background technology section is only used to understand the background technology of the present application concept, and therefore, the above description is not considered to constitute information of the prior art. Summary of the Invention

[0006] The embodiments of the present disclosure at least provide a liquid-pushing stable injection pen and a working method thereof.

[0007] In the first aspect, an embodiment of the present disclosure provides a liquid-pushing stable injection pen, comprising: a shell; a driving mechanism, arranged in the shell and comprising: a screw and a push block, the push block being rotatably arranged on the engaging end of the screw through the engaging cavity thereon; a retaining mechanism, arranged on the engaging end of the screw, the retaining mechanism extending outward and abutting against the inner wall of the engaging cavity to maintain the stability of the push block; wherein, when injecting medicine, the screw rotates and moves downward to abut against the push block, pushing the push block to move synchronously, and at the same time the retaining mechanism is forced to retract and release the limit.

[0008] In an optional embodiment, the retaining mechanism includes: an elastic lifting assembly and a pair of elastic retaining assemblies; the elastic lifting assembly is axially inserted on the end face of the engaging end, and the elastic retaining assembly is radially inserted on the side wall of the engaging end and connected to the elastic lifting assembly; the elastic lifting assembly extends out of the end face of the engaging end and rests on the bottom surface of the engaging cavity, and at the same time, the elastic lifting assembly pushes the elastic retaining assembly to extend outward and rest on the side wall of the engaging cavity; when injecting medicine, the screw rotates and moves downward to compress the elastic lifting assembly to retract, and at the same time, the elastic retaining assembly retracts to release the limit.

[0009] In an optional embodiment, a first mounting hole is provided on the end face of the locking end; the elastic lifting assembly is arranged in the first mounting hole and includes: a first elastic member and a cylinder, the first elastic member pushes the cylinder to extend out of the end face of the locking end; when injecting medicine, the screw rod rotates downward to compress and retract the cylinder.

[0010] In an optional embodiment, a pair of second mounting holes are opened on the side wall of the engaging end, and the second mounting holes are connected to the first mounting hole; the elastic retaining assembly is arranged in the corresponding second mounting holes, and includes: a second elastic member and a retaining plate, and the second elastic member is sleeved on the retaining plate to push the retaining plate to move inward and resist against the cylinder.

[0011] In an optional embodiment, the side wall of the cylinder is provided with a pair of first inclined surfaces; the retaining plate is provided with a second inclined surface on the side facing the cylinder, and the second inclined surface is against the corresponding first inclined surface; the first elastic member pushes the end face of the cylinder to extend out of the engaging end, and at the same time, the cylinder pushes the corresponding retaining plate to extend outward and against the side wall of the engaging cavity through the corresponding first inclined surface; when injecting medicine, the screw rotates and moves downward to retract the cylinder, and at the same time, the second elastic member drives the corresponding retaining plate to retract.

[0012] In an optional embodiment, an avoidance groove is provided at the inner end of the second mounting hole, and an annular boss is provided on the side wall of the retaining plate; the two ends of the second elastic member respectively abut against the annular boss and the avoidance groove to push the retaining plate against the cylinder.

[0013] In an optional embodiment, a spherical protrusion is provided on the lower end surface of the cylinder; when injecting medicine, the cylinder retracts and causes the spherical protrusion to protrude from the end surface of the screw rod.

[0014] In an optional embodiment, a pair of prisms are provided on the side wall of the cylinder, and the outer end faces of the prisms are provided with the first inclined surface; wherein the prisms are located in the avoidance groove.

[0015] On the second aspect, the embodiment of the present disclosure also provides a working method of the liquid-pushing stable injection pen as described above, including: rotating the push block to be set on the engaging end of the screw through the engaging cavity; extending the retaining mechanism outward and resting against the inner wall of the engaging cavity to maintain the stability of the push block; when injecting medicine, the screw is rotated downward to force the retaining mechanism to retract and release the limit.

[0016] In an optional embodiment, the elastic lifting component of the retaining mechanism extends out of the end face of the engaging end and abuts against the bottom surface of the engaging cavity, and at the same time, the elastic lifting component pushes the elastic retaining component of the retaining mechanism to extend outward and abut against the side wall of the engaging cavity; when injecting medicine, the elastic lifting component is compressed and retracted by rotating the screw rod downward, and the elastic retaining component retracts to release the limit.

[0017] The beneficial effect of the present invention is that the liquid-pushing stable injection pen and its working method are provided with a retaining mechanism on the engaging end of the screw rod, so that when the screw rod stops injecting medicine, the retaining mechanism extends outward and rests against the inner wall of the engaging cavity, thereby tightening the push block on the engaging end of the screw rod, thereby maintaining the stability of the push block and preventing the push block from shaking with the injection pen; at the same time, when the screw rod rotates and moves downward during injection, the downward movement of the screw rod will push the push block, thereby causing the retaining mechanism to be forced to retract and release the limit, thereby facilitating the rotation of the screw rod and not hindering the rotation of the screw rod.

[0018] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description and the drawings.

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are specifically cited herein and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 A schematic structural diagram of a liquid-pushing stable injection pen provided in an embodiment of the present disclosure;

[0022] Figure 2 A schematic structural diagram of a driving mechanism provided in an embodiment of the present disclosure;

[0023] Figure 3 A schematic cross-sectional view of a liquid-pushing stable injection pen provided by an embodiment of the present disclosure when not injecting;

[0024] Figure 4 A schematic diagram of the cross-sectional structure of a liquid-pushing stable injection pen during injection provided by an embodiment of the present disclosure;

[0025] Figure 5 A schematic structural diagram of an elastic lifting assembly provided in an embodiment of the present disclosure.

[0026] In the picture:

[0027] Shell 1;

[0028] Driving mechanism 2, screw rod 21, engaging end 211, first mounting hole 212, second mounting hole 213, avoidance groove 214, push block 22, engaging cavity 221;

[0029] Holding mechanism 3, elastic lifting component 31, first elastic member 311, cylinder 312, first inclined surface 313, spherical protrusion 314, prism 315, elastic holding component 32, second elastic member 321, holding piece 322, second inclined surface 323, annular boss 324. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0031] In the related art, after the injection stops, the screw 21 no longer presses against the push block 22, causing the push block 22 to shake when the injection pen shakes, or even tilt. Then, during the next injection, the screw 21 will drive the tilted push block 22 to squeeze the cartridge, causing uneven force on the cartridge and unstable injection.

[0032] It should be noted that similar reference numerals and letters represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. In addition, in the drawings, the thickness of components may be exaggerated or reduced in order to effectively describe the technical content.

[0033] The following embodiments of the present invention are described in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features therein may be combined with each other.

[0034] like Figure 1 As shown, at least one embodiment provides a liquid-pushing stable injection pen, comprising: a housing 1 and a drive mechanism 2, wherein the drive mechanism 2 is disposed in the housing 1 and is used to squeeze a cartridge to achieve drug injection.

[0035] like Figure 2 As shown, in some embodiments, the driving mechanism 2 includes: a screw rod 21 and a push block 22. The push block 22 is rotatably arranged at the end of the screw rod 21, and the push block 22 is abutted against the cartridge. The screw rod 21 rotates and moves downward to abut against the push block 22, thereby driving the push block 22 to move synchronously, so that the push block 22 squeezes the cartridge to achieve drug injection.

[0036] like Figure 3As shown, in some embodiments, a locking cavity 221 is provided on the push block 22 , and the push block 22 is rotatably disposed on the locking end 211 of the screw rod 21 through the locking cavity 221 .

[0037] In the related art, after the injection stops, the screw 21 no longer presses against the push block 22, causing the push block 22 to shake when the injection pen shakes, or even tilt. Then, during the next injection, the screw 21 will drive the tilted push block 22 to squeeze the cartridge, causing uneven force on the cartridge and unstable injection.

[0038] In order to solve the above problems, Figure 3 、 Figure 4 As shown, in some embodiments, a holding mechanism 3 is provided on the engaging end 211 of the screw rod 21; after the injection of the medicine is stopped, the holding mechanism 3 extends outward and abuts against the inner wall of the engaging cavity 221, so that the push block 22 is tightened on the engaging end 211 of the screw rod 21, that is, the stability of the push block 22 is maintained, and the push block 22 is prevented from shaking with the injection pen; and, when the screw rod 21 rotates and moves downward during the injection, the downward movement of the screw rod 21 will first compress the holding mechanism 3 and then abut against the push block 22. Even if the holding mechanism 3 is forced to retract and the limit is released, the rotation of the screw rod 21 is facilitated, and the obstruction to the rotation of the screw rod 21 is reduced.

[0039] like Figure 3 As shown, in some embodiments, the retaining mechanism 3 includes: an elastic lifting component 31 and a pair of elastic retaining components 32; the elastic lifting component 31 is axially inserted on the end face of the locking end 211, and the elastic retaining component 32 is radially inserted on the side wall of the locking end 211 and connected to the elastic lifting component 31.

[0040] In this embodiment, the elastic lifting component 31 extends out of the end face of the locking end 211 and abuts against the bottom surface of the locking cavity 221. Its first function is: when no medicine is injected, the locking end 211 is extended to push the two elastic retaining components 32 to extend outward and abut against the side wall of the locking cavity 221, so that the push block 22 is tightened and remains stable without shaking; the second function of the elastic lifting component 31 is: when the medicine is injected, it is forced to retract, and the two elastic retaining components 32 also retract, thereby solving the problem of limiting the push block 22 and avoiding obstruction to the rotating screw rod 21.

[0041] like Figure 4 As shown, in some embodiments, a first mounting hole 212 is opened on the end surface of the locking end 211; the elastic lifting assembly 31 is arranged in the first mounting hole 212, and includes: a first elastic member 311 and a cylinder 312, the first elastic member 311 pushes the cylinder 312 to extend out of the end surface of the locking end 211.

[0042] In this embodiment, a first mounting hole 212 is provided on the end face of the locking end 211 along the axis of the screw rod 21. The first elastic member 311 can be, but is not limited to, a spring. When no medicine is injected, the first elastic member 311 pushes the cylinder 312 out of the end face of the locking end 211. When medicine is injected, the cylinder 312 is squeezed by the first elastic member 311 and retracts into the locking end 211.

[0043] like Figure 5 As shown, in some embodiments, a pair of second mounting holes 213 are opened on the side wall of the locking end 211, and the second mounting holes 213 are connected to the first mounting hole 212; the elastic retaining assembly 32 is arranged in the corresponding second mounting hole 213, and includes: a second elastic member 321 and a retaining plate 322, the second elastic member 321 is sleeved on the retaining plate 322 to push the retaining plate 322 to move inward and resist against the cylinder 312.

[0044] In this embodiment, when no medicine is injected, the first elastic member 311 pushes the cylinder 312 to extend out of the end face of the locking end 211. The outward movement of the cylinder 312 will squeeze the retaining plate 322, causing the retaining plate 322 to compress the second elastic member 321 so that it extends outward and abuts against the inner wall of the locking cavity 221, thereby preventing the push block 22 from shaking.

[0045] like Figure 3 As shown, in some embodiments, a pair of first inclined surfaces 313 are provided on the sidewall of the cylinder 312 ; a second inclined surface 323 is provided on the side of the retaining plate 322 facing the cylinder 312 , and the second inclined surface 323 abuts against the corresponding first inclined surface 313 .

[0046] In this embodiment, the cylinder 312 and the retaining piece 322 are linked by the first inclined surface 313 and the second inclined surface 323; specifically, when no medicine is injected, the first elastic member 311 pushes the cylinder 312 to extend out of the end face of the engaging end 211, and the cylinder 312 squeezes the second inclined surface 323 by the descent of the first inclined surface 313, thereby causing the retaining piece 322 to move outward; when medicine is injected, the cylinder 312 squeezes the first elastic member 311 to retract, and the cylinder 312 rises by the first inclined surface 313, leaving space for the retaining piece 322 to retract, thereby contacting the retaining piece 322 to limit the push block 22.

[0047] like Figure 3 As shown, in some embodiments, an avoidance groove 214 is provided at the inner end of the second mounting hole 213, and an annular boss 324 is provided on the side wall of the retaining plate 322; the two ends of the second elastic member 321 respectively abut against the annular boss 324 and the avoidance groove 214 to push the retaining plate 322 against the cylinder 312.

[0048] like Figure 4As shown, in some embodiments, a spherical protrusion 314 is provided on the lower end surface of the cylinder 312 ; when injecting medicine, the cylinder 312 retracts and causes the spherical protrusion 314 to protrude from the end surface of the screw rod 21 .

[0049] In this embodiment, the cylinder 312 is not completely retracted into the first mounting hole 212 in order to reduce the contact surface between the screw rod 21 and the push block 22 , thereby reducing friction.

[0050] like Figure 3 As shown, in some embodiments, a pair of prisms 315 are provided on the sidewall of the cylinder 312 , and a first inclined surface 313 is formed on the outer end surface of the prisms 315 ; wherein the prisms 315 are located in the avoidance groove 214 .

[0051] At least one embodiment provides a method for operating a liquid-pushing stable injection pen, comprising: rotating the push block 22 to be set on the engaging end 211 of the screw rod 21 through the engaging cavity 221; extending the retaining mechanism 3 outward and resting against the inner wall of the engaging cavity 221 to maintain the stability of the push block 22; and when injecting medicine, the screw rod 21 is rotated downward to force the retaining mechanism 3 to retract and release the limit.

[0052] In some embodiments, the elastic lifting component 31 of the retaining mechanism 3 extends out of the end face of the locking end 211 and rests on the bottom surface of the locking cavity 221, and at the same time, the elastic lifting component 31 pushes the elastic retaining component 32 of the retaining mechanism 3 to extend outward and rest on the side wall of the locking cavity 221; when injecting medicine, the elastic lifting component 31 is compressed and retracted by rotating the screw rod 21 downward, and at the same time, the elastic retaining component 32 retracts to release the limit.

[0053] Regarding the specific structure and implementation process of the liquid-pushing stable injection pen, please refer to the relevant discussion in the above embodiments and will not be repeated here.

[0054] To sum up, the present liquid-pushing stable injection pen and its working method are provided with a retaining mechanism 3 on the engaging end 211 of the screw rod 21, so that when the screw rod 21 stops injecting medicine, the retaining mechanism 3 extends outward and abuts against the inner wall of the engaging cavity 221, thereby tightening the push block 22 on the engaging end 211 of the screw rod 21, that is, maintaining the stability of the push block 22 and preventing the push block 22 from shaking with the injection pen; at the same time, when the screw rod 21 rotates and moves downward during injection, the downward movement of the screw rod 21 will push the push block 22, and then the retaining mechanism 3 is forced to retract and release the limit, that is, it facilitates the rotation of the screw rod 21 and does not hinder the rotation of the screw rod 21.

[0055] Herein, when it is mentioned that a first component is located on a second component, this may mean that the first component may be directly formed on the second component or a third component may be interposed between the first component and the second component.

[0056] As used herein, when an element or layer is referred to as being "located on," "engaged to," "connected to," "attached to," or "coupled to" another element or layer, it may be directly located on, engaged, connected, attached to, or coupled to the other element or layer, or there may be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly engaged to," "directly connected to," "directly attached to," or "directly coupled to" another element or layer, there may be no intervening elements or layers. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0057] Herein, example 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..." when following a list of elements modify the entire list of elements, rather than modifying 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.

[0058] The terms used herein are only used to describe specific exemplary configurations and are 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 indicated herein. The terms "comprise", "include" and "have" are inclusive and therefore specify the presence of features, steps, operations, elements and / or components, but do not exclude 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 interpreted as necessarily requiring them to be performed in the particular order discussed or shown, unless specifically identified as an execution order. Additional or alternative steps may be adopted.

[0059] As used herein, the phrases "in one embodiment," "according to one embodiment," "in some embodiments," and the like generally refer to the fact that the particular feature, structure, or characteristic following the phrase may be included in at least one embodiment of the present disclosure. Thus, a particular feature, structure, or characteristic may be included in more than one embodiment of the present disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms "example," "exemplary," and the like 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 advantageous over other implementations, aspects, or designs. Instead, the use of the terms "example," "exemplary," and the like is intended to present concepts in a concrete manner.

[0060] In the description of the embodiments of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0061] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, terms such as "first", "second" and other numerical terms do not imply an order or sequence when used herein unless expressly indicated above. Therefore, without departing from the teachings of the example embodiments, the first element, component, region, layer or section discussed above may be referred to as a second element, component, region, layer or section.

[0062] Spatially relative terms, such as "inside," "outside," "below," "beneath," "down," "above," "on," etc., may be used herein to describe the relationship of one element or feature to another element or feature as illustrated in the figures. In addition to the orientations depicted in the figures, spatially relative terms may be intended to encompass different orientations of the device in use or operation. For example, if the device in the figures is flipped, an element described as being "below" or "below" other elements or features will be oriented to be "above" the other elements or features. Thus, the example term "below" may encompass both above and below orientations. The device may be oriented otherwise (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein are interpreted accordingly.

[0063] In the above discussion, unless otherwise indicated, the terms "about," "approximately," "substantially," etc., when used to describe a numerical value, mean a variation of + / - 10% of the value.

[0064] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A liquid-pushing stable injection pen, characterized in that: include: housing (1); A driving mechanism (2) is disposed in the housing (1) and comprises: a screw rod (21) and a push block (22), wherein the push block (22) is rotatably disposed on the engaging end (211) of the screw rod (21) through an engaging cavity (221) thereon; A retaining mechanism (3) is provided on the engaging end (211) of the screw rod (21), wherein the retaining mechanism (3) extends outward and abuts against the inner wall of the engaging cavity (221) to maintain the stability of the push block (22); When injecting medicine, the screw rod (21) rotates and moves downward to contact the push block (22), pushing the push block (22) to move synchronously, and at the same time, the holding mechanism (3) is forced to retract and release the limit; The holding mechanism (3) comprises: an elastic lifting component (31) and a pair of elastic holding components (32); The elastic lifting component (31) is inserted axially on the end surface of the engaging end (211), and the elastic retaining component (32) is inserted radially on the side wall of the engaging end (211) and connected to the elastic lifting component (31); The elastic lifting component (31) extends out of the end surface of the engaging end (211) and abuts against the bottom surface of the engaging cavity (221), and at the same time, the elastic lifting component (31) pushes the elastic retaining component (32) to extend outward and abut against the side wall of the engaging cavity (221); During drug injection, the screw rod (21) rotates and moves downward to compress the elastic lifting component (31) and retract it, while the elastic retaining component (32) retracts to release the limit.

2. The liquid-pushing stable injection pen according to claim 1, characterized in that: A first mounting hole (212) is formed on the end surface of the engaging end (211); The elastic lifting assembly (31) is arranged in the first mounting hole (212) and comprises: a first elastic member (311) and a cylinder (312), wherein the first elastic member (311) pushes the cylinder (312) to extend out of the end surface of the engaging end (211); When injecting medicine, the screw rod (21) rotates and moves downward to compress and retract the cylinder (312).

3. The liquid-pushing stable injection pen according to claim 2, characterized in that: A pair of second mounting holes (213) are formed on the side wall of the engaging end (211), and the second mounting holes (213) are in communication with the first mounting holes (212); The elastic retaining assembly (32) is arranged in the corresponding second mounting hole (213) and comprises: a second elastic member (321) and a retaining plate (322); the second elastic member (321) is sleeved on the retaining plate (322) to push the retaining plate (322) to move inward and abut against the cylinder (312).

4. The liquid-pushing stable injection pen according to claim 3, characterized in that: The side wall of the cylinder (312) is provided with a pair of first inclined surfaces (313); A second inclined surface (323) is provided on the side of the retaining plate (322) facing the cylinder (312), and the second inclined surface (323) abuts against the corresponding first inclined surface (313); The first elastic member (311) pushes the cylinder (312) to extend out of the end surface of the engaging end (211), and at the same time, the cylinder (312) pushes the corresponding retaining sheet (322) through the corresponding first inclined surface (313) to extend outward and press against the side wall of the engaging cavity (221); When injecting medicine, the screw rod (21) rotates and moves downward to retract the cylinder (312), and at the same time, the second elastic member (321) drives the corresponding retaining plate (322) to retract.

5. The liquid-pushing stable injection pen according to claim 4, characterized in that: An avoidance groove (214) is provided at the inner end of the second mounting hole (213), and an annular boss (324) is provided on the side wall of the retaining plate (322); The two ends of the second elastic member (321) respectively abut against the annular boss (324) and the avoidance groove (214) to push the retaining plate (322) to abut against the cylinder (312).

6. The liquid-pushing stable injection pen according to claim 5, characterized in that: The lower end surface of the cylinder (312) is provided with a spherical protrusion (314); When injecting medicine, the cylinder (312) retracts and causes the spherical protrusion (314) to protrude from the end surface of the screw rod (21).

7. The liquid-pushing stable injection pen according to claim 6, characterized in that: A pair of prisms (315) are provided on the sidewall of the cylinder (312), and the outer end surfaces of the prisms (315) are provided with the first inclined surface (313); wherein The prism (315) is located in the avoidance groove (214).

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