Piston rod, injection head and needleless injector

Abstract

Provided is a piston rod which can be used for a needleless syringe and which comprises a syringe body and an injection head, the injection head comprising: a drug tube and a piston rod, the piston rod being movable in an axial direction inside the drug tube to suck an object to be injected in a storage container into the drug tube during a drug suction process, and the piston rod being movable in an axial direction inside the drug tube during an injection process. The piston rod comprises a rod part and a piston part, the near-side end part of the piston part is matched with the far-side part of the rod part to form a first sealing structure, and the first sealing structure is a one-way sealing structure and is kept in an open state in the medicine suction process; the sealing element is sealed to allow the to-be-injected substance to be sucked into the drug tube from the storage container, and is kept in a sealed state during injection to prevent the to-be-injected substance from flowing back into the storage container from the drug tube. The invention further provides an injection head and a needleless injector comprising the piston rod. According to the piston rod disclosed by the invention, the flow mode of the to-be-injected material in the medicine suction and injection process can be accurately controlled.

Description

Technical Field

[0001] The present invention relates to a medical device for injecting an injectable substance, in particular to a needle-free injector for injecting liquid medicines. More specifically, the present invention relates to a piston rod, an injection head and a needle-free injector. Background Art

[0002] In medical scenarios, when using a needle-free syringe, it is usually necessary to first install the injection head on the syringe body, and then extract the injection from a separately placed medicine storage bottle through the distal end of the medicine tube of the injection head for containing the injection. After the extraction is completed, the distal end of the medicine tube must be separated from the medicine storage bottle before injection. The operation process of this traditional syringe is relatively complicated and requires high skills from the operator. It is usually operated by professional medical staff and is not suitable as a home syringe for ordinary people to operate at home.

[0003] In view of this problem, the existing solution is to improve the structure of the syringe and improve the traditional external medicine storage bottle to an internal medicine storage bottle so that it can be accommodated in the syringe body. During operation, the drug suction process is first performed. Through the movement of the piston rod in the medicine tube, the injection is sucked from the medicine storage bottle in the syringe body into the receiving chamber through the proximal end of the medicine tube, and then the piston rod is operated to move in the medicine tube to push the injection to be ejected from the distal end of the medicine tube, thereby completing the injection.

[0004] However, the piston rods of the prior art usually have many defects, for example, it is difficult for the injection to enter the containing cavity of the medicine tube during the drug suction process, or it is easy for the injection to flow back from the medicine tube to the built-in medicine storage bottle during the injection process, etc. At present, there is no piston rod that can accurately control the drug suction and injection process to ensure that the drug suction and injection processes can be performed correctly and accurately.

[0005] Therefore, it is necessary to provide a piston rod, an injection head and a needle-free syringe having the piston rod, so as to at least partially solve the above-mentioned problems in the prior art. Summary of the invention

[0006] In order to overcome the above-mentioned shortcomings of the prior art and facilitate accurate control of the flow of the substance to be injected during the drug aspiration process and the injection process, the present invention provides a piston rod for a syringe to ensure that the drug aspiration and injection processes can be carried out appropriately and accurately.

[0007] In order to at least achieve the above-mentioned purpose, according to one aspect of the present invention, there is provided a piston rod for a needle-free syringe, the syringe comprising a syringe body and an injection head, the injection head being removably mounted to the syringe body for use with the syringe body, wherein the injection head comprises: a medicine tube for containing an injection substance sucked from a storage container storing the injection substance; and the piston rod, the piston rod being able to move in an axial direction relative to the medicine tube inside the medicine tube so as to suck the injection substance in the storage container into the medicine tube during the drug suction process, and to remove the injection substance in the medicine tube during the injection process. The substance to be injected is pushed out of the syringe through the injection micropore at the distal end of the medicine tube, and the piston rod comprises: a rod portion; and a piston portion, wherein the piston portion is located distal to the rod portion in the axial direction and is connected to the rod portion, wherein the proximal end of the piston portion and the distal portion of the rod portion cooperate with each other to form a first sealing structure, and the first sealing structure is constructed as a one-way sealing structure, which can remain in an open state during the drug suction process to allow the substance to be injected to be sucked into the medicine tube from the storage container, and can remain in a sealed state during the injection process to prevent the substance to be injected from flowing back from the medicine tube into the storage container.

[0008] In some preferred embodiments, the first sealing structure forms a one-way seal in the axial direction between the piston portion and the rod portion.

[0009] In some preferred embodiments, the rod portion extends in an axial direction and includes: a first annular portion located at the farthest side of the rod portion, the distal end of the first annular portion including a coupling portion, the coupling portion being used to engage with the proximal portion of the piston portion to prevent the piston portion from moving distally and disengaging from the rod portion; a second annular portion connected to the first annular portion and extending proximally from the first annular portion, the connection between the second annular portion and the first annular portion having a connecting wall perpendicular to the axial direction, a recessed portion extending proximally from the distal surface of the connecting wall is formed in the connecting wall, the recessed portion being configured to cooperate with the proximal end of the piston portion to form the first sealing structure; and an elongated main body portion connected to the second annular portion and extending proximally from the second annular portion.

[0010] In some preferred embodiments, the piston portion extends in an axial direction and is capable of moving between a proximal sealing position and a distal opening position relative to the rod portion under pressure, wherein the piston portion comprises: a head portion located at the farthest end of the piston portion, the outer diameter of the head portion matching the inner diameter of the lumen of the medicine tube to guide the axial movement of the piston rod in the medicine tube through the head portion; a middle portion connected to the head portion and extending proximally from the head portion; a first flange connected to the middle portion and extending proximally from the middle portion, the outer diameter of the first flange being larger than the outer diameter of the middle portion and being capable of engaging with the engaging portion of the rod portion to prevent the piston portion from moving distally and disengaging from the rod portion, and wherein the first flange is capable of moving in an axial direction within the first annular portion of the rod portion; and a boss portion connected to the first flange and extending proximally from the first flange, the boss portion being configured to cooperate with the recessed portion of the rod portion to form the first sealing structure.

[0011] In some preferred embodiments, the boss portion of the piston portion is configured to have an outer truncated cone shape extending proximally and having an outer conical surface, and wherein the recessed portion of the rod portion is configured to have an inner truncated cone shape extending proximally and having an inner conical surface matching the shape of the outer conical surface, wherein during the drug inhalation process, the piston portion is located at the distal open position relative to the rod portion to form a gap between the outer conical surface of the boss portion and the inner conical surface of the recessed portion, so that the first sealing structure is in the open state, and wherein during the injection process, the piston portion is located at the proximal sealing position relative to the rod portion, so that the outer conical surface of the boss portion contacts and fits tightly with the inner conical surface of the recessed portion, so that the first sealing structure is in the sealed state.

[0012] In some preferred embodiments, during the drug inhalation process, the proximal movement of the piston rod relative to the drug tube forms a negative pressure in the accommodating cavity of the distal portion of the drug tube, and the negative pressure and / or the impact pressure from the injection keep the piston portion in the open position.

[0013] In some preferred embodiments, during the injection process, the distal injection pressure acting on the proximal end of the piston rod maintains the piston portion in the sealing position.

[0014] In some preferred embodiments, the rod portion further comprises one or more openings formed in the circumferential side wall of the first annular component, wherein, in the open state of the first sealing structure, the substance to be injected can flow from the storage container into the accommodating cavity of the medicine tube through the one or more openings.

[0015] In some preferred embodiments, the engagement portion is configured as a plurality of claws distributed circumferentially, and each claw extends toward the radial inside of the first annular portion.

[0016] In some preferred embodiments, the engagement portion is configured as a second flange extending radially inwardly of the first annular portion.

[0017] In some preferred embodiments, the first flange and the second flange are flanges extending continuously in the circumferential direction or flanges distributed discontinuously in the circumferential direction, respectively.

[0018] In some preferred embodiments, the piston rod further comprises a second sealing structure, wherein the second sealing structure forms a seal in a circumferential direction between the rod portion and the medicine tube.

[0019] In some preferred embodiments, the outer diameter of the second annular portion of the rod portion is smaller than the outer diameters of the first annular portion and the main body portion, thereby forming an annular groove between the first annular portion and the main body portion, wherein the second sealing structure includes a sealing ring that can be accommodated in the annular groove to form a seal in the circumferential direction between the circumferential side wall of the second annular portion of the rod portion and the inner wall surface of the medicine tube.

[0020] In some preferred embodiments, the main body of the rod is provided with an elongated channel extending in an axial direction, and the elongated channel is used to accommodate a drug aspiration needle, wherein the drug aspiration needle extends from the storage container to the inner space of the second annular portion of the rod, and during the drug aspiration process, the injection can pass through the inner cavity of the drug aspiration needle and be sucked into the accommodating cavity of the drug tube via the inner space of the second annular portion and one or more orifices of the first annular portion.

[0021] In some preferred embodiments, the head of the piston portion includes a conical portion located distally and a cylindrical portion extending proximally from the conical portion, wherein the conical portion is used to push the substance to be injected in the medicine tube during the injection process so that the substance to be injected is ejected from the injection micropore at the distal end of the medicine tube; and wherein the cylindrical portion is used to guide the axial movement of the piston portion in the medicine tube.

[0022] In some preferred embodiments, the cylindrical portion includes a convex ring extending from the circumferential side wall of the cylindrical portion, and the outer periphery of the convex ring is provided with at least one notch. During the drug inhalation process, the injection can enter the accommodating cavity of the distal portion of the drug tube through the at least one notch.

[0023] In some preferred embodiments, the cylindrical portion includes at least two convex rings arranged in parallel in the axial direction, and the circumferential position of at least one notch of each convex ring at least partially overlaps with the circumferential position of at least one notch of the other convex rings.

[0024] In some preferred embodiments, each protruding ring has at least two notches arranged along the circumferential direction.

[0025] According to another aspect of the present invention, there is provided an injection head for a needle-free syringe, which can be removably mounted to a syringe body for use with the syringe body, and is characterized in that the injection head comprises: a medicine tube for containing an injectable substance drawn from a storage container storing the injectable substance; and a piston rod according to any one of the above schemes.

[0026] According to another aspect of the present invention, a needle-free syringe is provided, comprising a syringe body and an injection head, wherein the injection head can be removably mounted to the syringe body for use with the syringe body, and is characterized in that the injection head comprises: a medicine tube for containing an injection substance drawn from a storage container storing the injection substance; and a piston rod according to any one of the above schemes.

[0027] The technical solution of the present invention controls the flow mode of the material to be injected during the drug suction process and the injection process by setting a mutually matching one-way sealing structure at the proximal end of the piston part of the piston rod and the distal part of the rod part, ensuring that the material to be injected can be easily sucked into the medicine tube during the drug suction process and no backflow occurs during the injection process. Compared with the prior art, the piston rod for the syringe of the present invention, and the injection head and syringe having such a piston rod can achieve precise control of the flow direction and flow path of the material to be injected during the drug suction and injection processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to better understand the above and other purposes, features, advantages and functions of the present invention, reference may be made to the preferred embodiments shown in the accompanying drawings. The same reference numerals in the accompanying drawings refer to the same components. It should be understood by those skilled in the art that the accompanying drawings are intended to schematically illustrate the preferred embodiments of the present invention and have no limiting effect on the scope of the present invention, and the components in the drawings are not drawn to scale.

[0029] Figure 1 A perspective view of a syringe according to a preferred embodiment of the present invention is shown.

[0030] Figure 2 Shows Figure 1 Exploded view of the syringe shown.

[0031] Figure 3 Shows Figure 1 An exploded view of the injection head of the syringe is shown, along with some of the components within the outer housing of the syringe body.

[0032] Figure 4 A perspective view of a drug tube according to a preferred embodiment of the present invention is shown.

[0033] Figure 5 A perspective view of a piston rod according to a preferred embodiment of the present invention is shown.

[0034] Figure 6 A perspective view showing a distal portion of a rod portion of a piston rod according to a preferred embodiment of the present invention is shown.

[0035] Figure 7 A perspective view from another angle showing the distal portion of the rod portion of the piston rod according to a preferred embodiment of the present invention.

[0036] Figure 8 A perspective view showing a distal portion of a rod portion of a piston rod according to another preferred embodiment of the present invention is shown.

[0037] Fig. 9 A perspective view showing a piston portion of a piston rod according to a preferred embodiment of the present invention is shown.

[0038] Fig.10 A perspective view of a piston portion of a piston rod according to another preferred embodiment of the present invention is shown.

[0039] Fig.11A The figure shows the initial state of the piston portion and the rod portion of the piston rod according to the present invention after the injection head is mounted on the syringe body and before the drug inhalation process.

[0040] Fig. 11B The figure shows the matching state between the piston portion and the rod portion of the piston rod according to the present invention at the beginning stage of the drug inhalation process.

[0041] Fig. 11C The figure shows the matching state between the piston part and the rod part of the piston rod according to the present invention during the process of continuing to inhale medicine.

[0042] Fig.11D The figure shows the matching state of the piston part and the rod part of the piston rod according to the present invention during the exhaust process after the drug inhalation process is completed.

[0043] Fig.11E The figure shows the matching state between the piston part and the rod part of the piston rod according to the present invention during the injection process.

[0044] Fig. 12A A front view of a distal portion of a piston rod according to the invention is shown in an initial state.

[0045] Fig. 12B A front view of a distal portion of a piston rod according to the invention is shown during exhaustion. DETAILED DESCRIPTION

[0046] Hereinafter, the piston rod for a syringe according to the present invention, and the injection head and syringe having the piston rod will be described in detail with reference to the accompanying drawings. The following are only preferred embodiments according to the present invention, and those skilled in the art can think of other ways to implement the present invention based on the preferred embodiments, and the other ways also fall within the scope of the present invention.

[0047] The present invention provides a piston rod for a syringe, the syringe comprising a syringe body and an injection head, the injection head can be removably mounted on the syringe body for use with the syringe body, wherein the injection head comprises: a medicine tube, the medicine tube is used to accommodate the injection material sucked from a storage container storing the injection material to be injected; and a piston rod, the piston rod can move in the medicine tube in an axial direction relative to the medicine tube inside the medicine tube, so as to suck the injection material in the storage container into the medicine tube during the drug suction process, and to push the injection material in the medicine tube out of the syringe through the injection micropore at the distal end of the medicine tube during the injection process, the piston rod comprises: a rod portion; and a piston portion, the piston portion is located at the distal side of the rod portion in the axial direction and is connected to the rod portion, wherein the proximal end of the piston portion cooperates with the distal part of the rod portion to form a first sealing structure, the first sealing structure is constructed as a one-way sealing structure, can remain in an open state during the drug suction process to allow the injection material to be sucked from the storage container into the medicine tube, and can remain in a sealed state during the injection process to prevent the injection material from flowing back from the medicine tube into the storage container.

[0048] In order to better describe the piston rod according to the present invention and for ease of understanding, the overall structure of the syringe is first introduced below. The needle-free syringe according to the preferred embodiment of the present invention is described below.

[0049] First of all, it should be explained that the directional terms and positional terms mentioned in the present invention should be understood as relative directions and relative positions. The directional terms and positional terms mentioned in the present invention can be understood with reference to the accompanying drawings. For example, the "axial direction", "axial direction", etc. mentioned in the present invention can be understood as a direction parallel or approximately parallel to the longitudinal center axis of the syringe, that is, along the X direction in the accompanying drawings or parallel to the X direction in the accompanying drawings; the "radial direction", "radial direction", "circumferential direction", "circumferential direction", etc. mentioned in the present invention are all directions defined about the X axis, for example, the radial outer direction represents the direction away from the longitudinal center axis of the syringe, the radial inner direction represents the direction toward the longitudinal center axis of the syringe, and the circumferential direction represents the direction around the longitudinal center axis of the syringe; the "rotational direction" mentioned in the present invention can be understood as the direction of rotation around the X axis, which is roughly equivalent to the "circumferential direction". The “near”, “proximal”, “proximal end”, “proximal direction”, “rear”, “rear side”, “rear end”, “rear direction” etc. mentioned in the present invention are the direction along the axis X or parallel to the axis X, close to the operator's hand (considering that the operator holds the syringe to inhale and inject the medicine); the “distal”, “distal end”, “distal direction”, “front”, “front side”, “front end”, “front direction” etc. mentioned in the present invention are the direction along the axis X or parallel to the axis X, away from the operator's hand, and are also the direction in which the injection is ejected during the injection process.

[0050] Overall structure

[0051] Figure 1 shows an overall stereoscopic view of a syringe according to some preferred embodiments of the present invention, Figure 2 Shows Figure 1 Schematic diagram of the exploded view of the syringe. The syringe in this embodiment is a needle-free syringe. Unlike traditional syringes, needle-free syringes do not inject through a needle, but an injection micropore is set at the farthest end of the injection head. During injection, the substance to be injected is quickly ejected through the micropore to be injected into the patient's body. It should be pointed out that this article uses medicines, liquid medicines and other injectables as examples to describe the concept of the present invention, but this is only an example and is not restrictive. The substance to be injected can be various other types, such as physiological saline, glucose, solid particles, etc. As long as it is an injectable substance that can be injected into the human body by the needle-free syringe of the present invention, it falls within the protection scope of the present invention. The present invention does not limit the form and type of the substance to be injected.

[0052] refer to Figures 1 to 4 According to the preferred embodiment, the syringe 1 comprises the following components: an injection head 2, a syringe body 3, and a storage container 4. Each component can be packaged separately before use and assembled together when used.

[0053] The injection head 2 comprises: a medicine tube 21, which is used to contain the injectable substance to be injected drawn from the storage container 4; a cap 23, which can be removably matched with the distal portion of the medicine tube 21, so as to keep the medicine tube covered and sealed during the drug inhalation process described below (the cap 23 is provided with a Figure 3 The gasket 231 shown can close the injection micropore of the distal end of the medicine tube when the cap covers the medicine tube, and is removed during the injection process to expose the injection micropore; and the piston rod 22, which can move relative to the medicine tube 21 in the axial direction X inside the medicine tube 21, so as to suck the injection material in the storage container 4 into the medicine tube during the drug inhalation process, and push the injection material in the medicine tube 21 through the injection micropore of the medicine tube during the injection process, so that the injection material is ejected through the micropore to complete the injection. The storage container 4 can be, for example, a cartridge bottle according to national standards. The storage container 4 according to this preferred embodiment is a built-in storage container 4, especially a rear-mounted storage container 4 located near the injection head in the assembled state, which can be removably installed in the syringe 1, specifically installed in the internal space of the syringe body 3, so as to be used in conjunction with the syringe body 3 and the injection head 2. Of course, the present invention is not intended to limit the form of the storage container, which can also be a non-built-in type (that is, the storage container is a component separated from the syringe body, which is not installed inside the syringe body), and those skilled in the art can choose according to actual needs.

[0054] The syringe body 3 includes an outer shell 32, a rear shell 31, a first inner push rod 33, and a second inner push rod 34. The outer shell 31 accommodates various components in the syringe body, and is provided with an outer thread at the proximal end of the outer shell for cooperating with the inner thread at the distal end of the rear shell 31, so that the operator can rotate the rear shell 31 or the outer shell 32 to make the two move relative to each other in the axial direction. Figure 2 The outer housing 32 contains a first inner push rod 33 and a second inner push rod 34 located near the first inner push rod, wherein the first inner push rod 33 is used to accommodate the storage container 4, so as to carry the storage container during the entire operation process to drive the storage container to move. The two inner push rods 33 and 34 are fixed to each other (for example, by threaded engagement), and the second inner push rod 34 can be locked or unlocked with the rear housing 31 by engagement between a locking component (not shown) located near the second inner push rod 34 and a locking mechanism 35 (the locking mechanism 35 is fixedly disposed on the rear housing 31).

[0055] The injection head 2 may be removably mounted to the syringe body 3. Specifically, refer to Figure 2 and Figure 3The medicine tube 21 of the injection head 2 can be fixedly mounted to the external shell 32, for example, by the cooperation between the external thread 212 of the proximal part of the medicine tube 21 and the internal thread (not shown) of the external shell 32 near the distal opening (this will be described in detail below).

[0056] During the entire operation process after fixed installation, the medicine tube 21 remains fixed to the outer shell 32, and the movement of the medicine tube 21 is driven by the outer shell 32, and there is no relative movement between the two. The piston rod 22 of the injection head 2 can be fixedly installed to the first internal push rod 33 or to other components that are fixedly connected to the first internal push rod 33 by means of, for example, snap fastening, so that during the entire operation process such as the drug suction process and the injection process, the piston rod is relatively fixed to the first internal push rod and is driven by the first internal push rod to perform axial movement.

[0057] The operation process after installation of the syringe according to the present invention mainly includes the following processes: a pressurization and energy storage process, a medicine inhalation process, an exhaust process, and an injection process.

[0058] First, during the pressurization and energy storage process, initially, the actuation spring 39 located between the outer housing 32 and the rear housing 31 on the proximal side of the syringe is in a naturally stretched state without force, so that the outer housing 32 is located at a distal position relative to the rear housing 31. When the pressurization and energy storage begins, the operator rotates the outer housing 32 to make it move proximally relative to the rear housing 31 (realized by the threaded fit between the two). During this process, the distal portion of the outer housing 32 can exert force on the distal portion (e.g., the distal flange) of the first internal push rod 33, thereby simultaneously driving the first internal push rod 33 and the second internal push rod 34 to move in the proximal direction. When the outer housing 32 is screwed tight relative to the rear housing 31, the locking component (not shown) located on the proximal side of the second internal push rod 34 and the locking mechanism 35 are locked with each other, thereby locking the first and second internal push rods 33 and 34 to the rear housing 31. During this process, the actuation spring 39 is compressed and energy is stored to prepare for the final injection process.

[0059] The process of pressurizing and storing energy is followed by the process of inhaling medicine. During the process of inhaling medicine, the operator rotates the outer shell 32 to make it move distally relative to the rear shell 31 (still achieved by the threaded fit between the two), and at this time, the first and second internal push rods 33 and 34 are locked by the locking mechanism 35 and remain fixed relative to the rear shell 31, that is, during this process, the outer shell 32 moves distally relative to the first and second internal push rods 33 and 34. Since the medicine tube 21 is fixed relative to the outer shell 32, and the storage container 4 and the piston rod 22 are fixed relative to the first internal push rod 33, the medicine tube 21 moves distally relative to the storage container 4 and the piston rod 22. Furthermore, since the injection micropore at the distal end of the drug tube 21 is sealed by the cap 23 (for example, the cap 23 is provided with a sealing gasket 231 for sealing the injection micropore when the cap is covered on the drug tube 21), when the drug tube 21 moves distally relative to the piston rod 22, the distal portion of the lumen 213 of the drug tube 21 (that is, the chamber between the distal end of the piston rod and the distal end of the drug tube) forms a receiving chamber 215 (such as Fig. 11C As shown), the pressure in the accommodating chamber is relatively small, so the liquid in the storage container 4 can be sucked into the accommodating chamber through the needle 24 accommodated in the injection channel in the piston rod 22, thereby completing the drug absorption.

[0060] The drug inhalation process is followed by an exhaust process, which is an injection preparation step, the purpose of which is to exhaust the gas that may be mixed in the medicine tube 21 before injection. In this step, the cap 23 is first removed to expose the injection micropore at the distal end of the medicine tube 21. Then, the outer shell 32 is rotated to move slightly backward relative to the rear shell 31. During this process, since the locking mechanism 35 is still in a locked state, the first internal push rod 33 and the piston rod 22 remain fixed relative to the rear shell 31. In this way, the medicine tube 21 (fixed relative to the outer shell 32) actually moves slightly proximally relative to the piston rod 22 (fixed relative to the first internal push rod 33), and the piston rod 22 slightly compresses the accommodating chamber 215 in the medicine tube 21, and the gas in the accommodating chamber can be discharged from the injection micropore under the action of pressure.

[0061] Finally, the injection process is performed. In this process, the outer housing 32 and the medicine tube 21 are fixed relative to the rear housing 31, and the operator operates the locking mechanism 35 (for example, by pressing the button 351 at the proximal end of the syringe) to release the locking state between the locking member (not shown) located proximal to the first and second internal push rods, allowing the second internal push rod 34, the first internal push rod 33, the storage container 4 and the piston rod 22 to move rapidly distally relative to the rear housing 31 under the rebound action of the actuating spring 39, so that the injection is completed by the piston rod 22 quickly squeezing the injection material in the accommodating cavity of the medicine tube 21.

[0062] Piston rod

[0063] Next, refer to Figures 5 to 10 , a piston rod according to the present invention is described in detail.

[0064] As described above, the piston rod 22 of the injection head 2 is capable of moving in the lumen 213 of the medicine tube 21 in the axial direction X relative to the medicine tube 21, so as to draw the substance to be injected in the storage container 4 into the medicine tube 21 during the drug suction process, and to push the substance to be injected in the medicine tube out of the syringe 1 through the injection micropore at the distal end of the medicine tube 21 during the injection process.

[0065] refer to Figure 5 The piston rod 22 includes: a rod portion 221; and a piston portion 222, which is located at the distal end of the rod portion in the axial direction X and is connected to the rod portion 221. The proximal end of the piston portion 222 cooperates with the distal portion of the rod portion 221 to form a first sealing structure, and the first sealing structure is configured as a one-way sealing structure. The one-way sealing structure can remain in an open state during the drug inhalation process to allow the injection to be inhaled from the storage container 4 into the medicine tube 21, and can remain in a sealed state during the injection process to prevent the injection from flowing back from the medicine tube 21 into the storage container 4. Preferably, the first sealing structure forms a one-way seal in the axial direction X between the piston portion 222 and the rod portion 221, and the specific structure of the one-way seal will be described in detail below.

[0066] refer to Figure 6 and Figure 7 , which shows a rod portion of a piston rod according to a preferred embodiment of the present invention (for the sake of clarity, only the distal portion of the rod portion is shown in the figure). In this embodiment, the rod portion 221 extends along the axial direction X and includes a first annular portion 2211 located at the farthest side of the rod portion 221, and the distal end of the first annular portion includes an engagement portion, which is used to engage with the proximal portion of the piston portion 222 to prevent the piston portion 222 from moving distally away from the rod portion 221. The rod portion 221 also includes a second annular portion 2212 connected to the first annular portion 2211 and extending continuously from the first annular portion toward the proximal side, and the connection between the second annular portion and the first annular portion has a connecting wall 2215 extending perpendicular to the axial direction X, and a recessed portion 2216 extending from the distal surface of the connecting wall toward the proximal side is formed in the connecting wall, and the recessed portion is configured to cooperate with the proximal end of the piston portion 222 to form a first sealing structure. The stem portion 221 further includes an elongated body portion 2213 connected to the second annular portion 2212 and extending proximally therefrom.

[0067] refer to Fig. 9, which shows a piston portion of a piston rod according to a preferred embodiment of the present invention. The piston portion 222 extends in the axial direction X, and can move between a proximal sealing position and a distal open position relative to the rod portion 221 under pressure. Specifically, the piston portion 222 includes a head 2221 located at the farthest side of the piston portion, and the outer diameter of the head matches the inner diameter of the lumen 213 of the medicine tube 21, so that the axial movement of the piston rod 22 in the medicine tube 21 can be guided by the head 2221. The piston portion 222 also includes a middle portion 2222 connected to the head 2221 and extending proximally from the head, and a first flange 2223 connected to the middle portion 2222 and extending proximally from the middle portion, the outer diameter of the first flange 2223 is greater than the outer diameter of the middle portion, and can engage with the engaging portion of the rod portion 221 to prevent the piston portion from moving distally away from the rod portion. The first flange can move in the first annular portion 2211 of the rod portion 221 along the axial direction X to allow the piston portion to switch between the above-mentioned proximal sealing position and the distal open position relative to the rod portion 221. The piston portion 222 also includes a boss portion 2224 connected to the first flange 2223 and extending from the first flange toward the proximal side, and the boss portion is configured to cooperate with the recessed portion 2216 of the rod portion 221 to form a first sealing structure.

[0068] Continue to refer Figure 7 and Fig. 9 , the boss portion 2224 of the piston portion is configured to be an outer truncated cone shape extending toward the proximal side, and has an outer conical surface 22241. Corresponding to the boss portion 2224, the recessed portion 2216 of the rod portion 221 is configured to be an inner truncated cone shape extending toward the proximal side, and has an inner conical surface 22161 matching the shape of the outer conical surface 22241 of the boss portion. During the drug inhalation process, the piston portion 222 is located at the distal open position relative to the rod portion 221. At this time, a gap is formed between the outer conical surface 22241 of the boss portion 2224 and the inner conical surface 22161 of the recessed portion 2216 for the injection to flow into the accommodating cavity 215 of the drug tube, so that the first sealing structure is in an open state. During the injection process, the piston portion 222 is located at a proximal sealing position relative to the rod portion 221, so that the outer conical surface 22241 of the boss portion 2224 and the inner conical surface 22161 of the recessed portion 2216 are in contact with and tightly fit with each other, and there is no longer a gap for the injection to flow through, so that the first sealing structure is in a sealed state.

[0069] The shapes of the boss portion 2224 of the piston portion and the recessed portion 2216 of the rod portion are not limited to the above-mentioned conical shape, and can also be various shapes that can be matched to form a seal between each other that can be thought of by those skilled in the art. For example, the boss portion 2224 and the recessed portion 2216 have mutually matching outer cylindrical and inner cylindrical shapes, and the two respectively have outer cylindrical surfaces and inner cylindrical surfaces that can match each other. Or, for example, the boss portion 2224 and the recessed portion 2216 have mutually matching spherical shapes and concave spherical shapes, and the two respectively have outer spherical surfaces and inner spherical surfaces that can match each other. It should be noted that the present invention does not limit the type of sealing between the above-mentioned boss portion and the recessed portion, that is, a line seal or a surface seal can be formed between the two, and the boss portion and the recessed portion can have shapes that are different from each other but can match each other to at least form a line seal (that is, the boss portion and the recessed portion do not have to have a completely fitted joint surface, and the two can only achieve a sealing effect through a joint line). For example, the boss portion 2224 and the recessed portion 2216 may have an outer cylindrical shape and an inner conical shape that match each other, and the outer cylinder of the boss portion 2224 can be engaged with the inner cone of the recessed portion 2216 to form a sealing line between the two, thereby achieving sealing. Those skilled in the art can design the shapes of the boss portion and the recessed portion according to actual needs, as long as a line seal or a surface seal can be formed therebetween.

[0070] More specifically, during the drug inhalation process, the proximal movement of the piston rod 22 relative to the medicine tube 21 forms a negative pressure in the accommodating chamber 215 of the distal portion of the medicine tube 21. In addition, when the injection flows into the accommodating chamber 215 of the medicine tube, an impact pressure is generated on the piston portion 222 in the proximal portion. The negative pressure and / or the impact pressure from the injection maintain the piston portion in an open position. During the injection process, the injection pressure in the distal direction acting on the proximal end of the piston rod 22 pushes the rod portion 221 toward the piston portion 222, so as to maintain the inner conical surface 22161 of the rod portion and the outer conical surface 22241 of the piston portion in a state of mutual sealing (i.e., the piston portion is maintained in a sealed position relative to the rod portion 222).

[0071] Further, refer to Figure 7 The rod portion 221 also includes one or more openings 2217 opened on the circumferential side wall of the first annular component 2211, wherein, in the open state of the first sealing structure, the injection can flow from the storage container into the accommodating cavity 215 of the medicine tube through the one or more openings 2217.

[0072] Optionally, in Figure 6 and Figure 7 In the illustrated embodiment, the engaging portion of the rod portion 221 is configured as a plurality of claws 2214 distributed circumferentially, each claw extending radially inward from the inner wall surface of the first annular portion 2211 at a position close to the distal end. Figure 8 In the illustrated embodiment, the engaging portion of the rod portion 221 is configured as a second flange 2214' extending radially inwardly toward the inner wall surface of the first annular portion 2211 at a position close to the distal end. The second flange 2214' may be Figure 8 The flange shown is intermittently distributed along the circumferential direction (intermittent distribution facilitates engagement with the first flange of the piston part), or it can be a flange that extends continuously along the circumferential direction (continuous extension helps to ensure firmness and reliability of engagement with the first flange of the piston part). Similarly, the first flange 2223 of the piston part can be optionally Fig. 9 The flange shown extending continuously in the circumferential direction may also be a plurality of flanges distributed discontinuously in the circumferential direction (for example, Fig.10 The two flanges shown in the figure). Those skilled in the art can select the implementation mode and quantity of the engagement structure between the piston portion and the rod portion as needed, as long as the piston portion can move between the proximal sealing position and the distal opening position relative to the rod portion and will not move to the distal engagement portion of the rod portion. The present invention is not limited to this.

[0073] Furthermore, in order to ensure the seal between the rod portion 221 and the medicine tube 21, the piston rod 22 further includes a second sealing structure, which forms a seal in the circumferential direction between the rod portion 221 and the medicine tube 21. Specifically, the outer diameter of the second annular portion 2212 of the rod portion 221 is smaller than the outer diameters of the first annular portion 2211 and the main body portion, thereby forming an annular groove (such as Figure 6 As shown), wherein the second sealing structure includes a sealing ring 2218 (as shown Figure 7 As shown), the sealing ring can be accommodated in the annular groove to form a seal in the circumferential direction between the circumferential side wall of the second annular portion 2212 of the rod and the inner wall surface of the medicine tube 21.

[0074] Further, refer to Figure 7 The main body 2213 of the rod 221 is provided with an elongated channel extending in the axial direction X, and the elongated channel is used to accommodate the drug aspirating needle 24. The drug aspirating needle extends from the storage container 4 to the internal space defined by the second annular portion 2212 of the rod 221. During the drug aspirating process, the injection can be sucked into the accommodating cavity 215 of the drug tube 21 through the inner cavity of the drug aspirating needle 24, the internal space of the second annular portion and one or more orifices 2217 of the first annular portion.

[0075] Further, refer to Fig. 9The head 2221 of the piston part 222 includes a conical part 22211 located at the distal side and a cylindrical part 22212 extending from the conical part toward the proximal side. The conical part 22211 is used to push the injection material in the medicine tube 21 during the injection process, so that the injection material is ejected from the injection micropore at the distal end of the medicine tube. The outer diameter of the cylindrical part 22212 matches the inner diameter of the lumen of the medicine tube, and is used to guide the axial movement of the piston part 222 in the medicine tube 21.

[0076] In order to promote the axial relative movement of the cylindrical part 22212 in the lumen of the medicine tube and avoid excessive friction caused by directly using the cylindrical outer surface, a convex ring 22213 is provided at the radially outer extension of the circumferential side wall of the cylindrical part. The convex ring can transform the contact between the head 2221 of the piston part 222 and the inner wall surface of the lumen 213 from surface contact to line contact, thereby reducing friction. More preferably, at least two of the above-mentioned convex rings 22213 can be arranged in parallel along the axial direction X. This is because when a single convex ring is arranged, a single line contact is difficult to strictly limit the movement of the convex ring in the lumen in the axial direction, and the convex ring is easy to drive the entire head and the piston part to rotate in the lumen. When more than two convex rings are arranged, multiple line contacts can solve this problem, thereby limiting the movement of the piston part in the lumen in the axial direction, ensuring that it does not rotate or basically does not rotate.

[0077] Furthermore, in order to establish a flow path for the injection, each convex ring is provided with at least one notch 22214, and during the drug inhalation process, the injection can enter the accommodating cavity 215 of the distal portion of the drug tube through the notch 22214. It should be understood that the circumferential position of at least one notch 22214 of each convex ring at least partially overlaps with the circumferential position of at least one notch of other convex rings. Fig. 9 As shown, the positions of the notches of the two convex rings in the circumferential direction are completely aligned (of course, those skilled in the art can also set the positions of the notches on the two convex rings to be partially aligned). More preferably, each convex ring 22213 is arranged with at least two notches 22214 separately along the circumferential direction.

[0078] Next, combine FIG. 11A to FIG. 11E as well as FIG. 12A to FIG. 12B , describe in detail the state of the piston rod 22 during the operation of drug inhalation, injection, etc.

[0079] first, Fig.11AThe injection head 2 is shown in an initial state, which refers to the initial state after the injection head 2 is installed on the syringe body 3 (omitted in this figure for the sake of clarity) and before the operator starts to operate the drug inhalation process. At this time, the piston portion 222 of the piston rod 22 is located at a sealing position on the proximal side relative to the rod portion 221, that is, the outer conical surface 22241 of the boss portion 2224 of the piston portion 222 is in a tightly fitting sealing state with the inner conical surface 22161 of the recessed portion 2216 of the rod portion 221.

[0080] Fig. 11B The beginning stage of the drug inhalation process is shown. As described in the previous part, during the drug inhalation process in which the operator rotates the outer shell 32 to make it move distally relative to the rear shell 31, the outer shell 32 moves distally relative to the first and second internal push rods 33 and 34. Since the medicine tube 21 is fixed relative to the outer shell 32, and the storage container 4 and the piston rod 22 are fixed relative to the first internal push rod 33, during the drug inhalation process, the medicine tube 21 moves distally relative to the piston rod 22 and the storage container 4. Since the injection micropore at the distal end of the medicine tube 21 is closed by the sealing gasket 231 in the cap portion 23, when the medicine tube 21 moves distally relative to the piston rod 22, the pressure in the part of the lumen 213 of the medicine tube 21 located on the distal side of the piston portion is relatively small. The outer conical surface 22241 of the boss portion 2224 of the piston portion 222 is separated from the inner conical surface 22161 of the recessed portion 2216 of the rod portion 221 under negative pressure, forming a gap between the two (refer to Fig. 12A , which shows Fig. 11B The distal part of the piston rod at the beginning of the drug inhalation process shown in the figure clearly shows the state of a gap formed between the outer conical surface 22241 and the inner conical surface 22161) for the injection to flow through. Thus, in the initial stage of the drug inhalation process, the first sealing structure is opened by negative pressure.

[0081] Later reference Fig. 11C , the operator continues to rotate the outer housing 32 relative to the rear housing 31, so that the medicine tube 21 continues to move distally relative to the piston rod 22, and the first sealing structure is always kept open under the effect of negative pressure and / or the impact pressure of the injection material flowing toward the distal side, so as to allow the injection material to continuously flow into the accommodating cavity 215 of the medicine tube located at the distal side of the piston part through the gap between the outer conical surface 22241 of the boss part 2224 of the piston part 222 and the inner conical surface 22161 of the recessed part 2216 of the rod part 221 until the drug inhalation process is completed. In the above-mentioned drug inhalation stage, the cap part 23 always seals the injection micropore of the medicine tube.

[0082] Fig.11DThe figure shows the exhaust stage immediately after the completion of the drug inhalation process, which is before the injection process. In this exhaust stage, the operator removes the cap 23 to open the injection micropore at the distal end of the medicine tube, and then slightly rotates the outer shell 32 to make it move slightly proximally relative to the rear shell 31. In this way, the medicine tube 21 moves slightly proximally relative to the piston rod 22 accordingly, and under the pushing pressure of the piston rod 22, the air is squeezed out of the injection micropore of the medicine tube 21 to complete the exhaust. In this stage, when the operator starts to rotate the outer shell 32, the rod portion 221 of the piston rod 22 first moves slightly distally relative to the piston portion 222, so that the outer conical surface 22241 is in close contact with the inner conical surface 22161, and the gap between the two disappears, and the first sealing structure switches from the open state to the sealed state (reference Fig. 12B , which shows Fig.11D 2. The distal portion of the piston rod in the exhaust stage is shown in FIG. 1 , which clearly shows the close fit and gap-free state between the outer conical surface 22241 and the inner conical surface 22161). When the operator continues to rotate the outer housing 32 to exhaust, the rod portion 221 keeps pushing the piston portion 222 distally, and the first sealing structure keeps the sealing state.

[0083] refer to Fig.11E After the exhaust stage, the operator performs the injection operation, such as pressing the button 351 at the proximal end of the syringe to complete the injection process. During the injection process, the rod portion 221 keeps pushing the piston portion 222 distally, so that the outer conical surface 22241 and the inner conical surface 22161 are kept in close contact, so that the first sealing structure maintains a sealed state.

[0084] During the entire exhaust process and injection process, the injection micropores of the medicine tube remain open, and the first sealing structure remains sealed, so as to allow the injectable material in the accommodating cavity 215 of the medicine tube to be smoothly pushed by the piston rod 22 to be ejected from the injection micropores, and will not flow back into the storage container 4 through the first sealing structure between the piston part and the rod part under the action of pressure.

[0085] The present invention also provides an injection head which can be removably installed to the syringe body in a needle-free syringe for use together with the syringe body. The injection head comprises: a medicine tube for containing the injectable substance to be injected drawn from a storage container storing the injectable substance; and the aforementioned piston rod.

[0086] The present invention also provides a needle-free syringe, comprising a syringe body and an injection head, wherein the injection head can be removably mounted to the syringe body for use with the syringe body, wherein the injection head comprises: a medicine tube for accommodating an injectable substance drawn from a storage container storing the injectable substance; and the aforementioned piston rod.

[0087] It should be noted that the above-mentioned embodiments of the present invention can be combined and / or deformed in various ways, and the results of the combination and / or deformation should also be considered as embodiments of the present invention. The above description of various embodiments of the present invention is provided to a person of ordinary skill in the relevant field for the purpose of description. It is not intended to exclude or limit the present invention to a single disclosed embodiment. As above, a person of ordinary skill in the field of the above teachings will understand the various substitutions and variations of the present invention. Therefore, although some alternative embodiments are specifically described, a person of ordinary skill in the art will understand or relatively easily develop other embodiments. The present invention is intended to include all substitutions, modifications and variations of the present invention described herein, as well as other embodiments that fall within the spirit and scope of the present invention described above.

Claims

1. A piston rod (22), which can be used in a needle-free syringe, wherein the syringe comprises a syringe body (3) and an injection head (2), wherein the injection head (2) can be removably mounted to the syringe body (3) to be used in conjunction with the syringe body, wherein: The injection head (2) comprises: a medicine tube (21) for containing an injection substance drawn from a storage container (4) storing the injection substance; and The piston rod (22) is capable of moving in the axial direction relative to the medicine tube (21) inside the medicine tube so as to draw the substance to be injected in the storage container (4) into the medicine tube (21) during the drug inhalation process, and to push the substance to be injected in the medicine tube out of the needle-free injector (1) through the injection micro-hole at the distal end of the medicine tube (21) during the injection process. Characterized in that the piston rod (22) comprises: a rod portion (221); and a piston portion (222), the piston portion being located at a distal side of the rod portion in the axial direction (X) and being coupled to the rod portion, The proximal end of the piston portion (222) cooperates with the distal portion of the rod portion (221) to form a first sealing structure, and the first sealing structure is constructed as a one-way sealing structure, which can remain in an open state during the drug suction process to allow the injection to be sucked from the storage container (4) into the medicine tube (21), and can remain in a sealed state during the injection process to prevent the injection from flowing back from the medicine tube (21) into the storage container (4).

2. The piston rod (22) according to claim 1, characterized in that: The first sealing structure forms a one-way seal in the axial direction (X) between the piston portion (222) and the rod portion (221).

3. The piston rod (22) according to claim 2, characterized in that: The rod portion (221) extends along an axial direction (X) and comprises: a first annular portion (2211) located at the farthest side of the rod portion (221), wherein the distal end of the first annular portion comprises an engagement portion, and the engagement portion is used to engage with the proximal portion of the piston portion (222) to prevent the piston portion (222) from moving distally and disengaging from the rod portion (221); a second annular portion (2212) connected to the first annular portion (2211) and extending proximally from the first annular portion, wherein a connection between the second annular portion and the first annular portion comprises a connecting wall (2215) perpendicular to the axial direction (X), wherein a recessed portion (2216) extending proximally from a distal surface of the connecting wall is formed in the connecting wall, and the recessed portion is configured to cooperate with a proximal end of the piston portion (222) to form the first sealing structure; and An elongated body portion (2213) is connected to the second annular portion (2212) and extends proximally therefrom.

4. The piston rod (22) according to claim 3, characterized in that: The piston portion (222) extends in an axial direction (X) and is capable of moving between a proximal sealing position and a distal opening position relative to the rod portion (221) under pressure. Wherein, the piston part (222) comprises: a head portion (2221) located at the farthest side of the piston portion, the outer diameter of the head portion being matched with the inner diameter of the lumen (213) of the medicine tube (21), so as to guide the axial movement of the piston rod (22) in the medicine tube (21) through the head portion (2221); a middle portion (2222) connected to the head (2221) and extending proximally from the head; a first flange (2223) connected to the middle portion (2222) and extending proximally from the middle portion, the first flange (2223) having an outer diameter greater than an outer diameter of the middle portion and capable of engaging with an engagement portion of the rod portion to prevent the piston portion from moving distally away from the rod portion, and wherein the first flange is capable of moving in an axial direction within a first annular portion (2211) of the rod portion (221); and A boss portion (2224) is connected to the first flange (2223) and extends proximally from the first flange, wherein the boss portion is configured to cooperate with the recessed portion (2216) of the rod portion to form the first sealing structure.

5. The piston rod (22) according to claim 4, characterized in that The boss portion (2224) of the piston portion is configured to be in the shape of an outer truncated cone extending toward the proximal side and has an outer conical surface (22241), and The recessed portion (2216) of the rod portion is configured to be in the shape of an inner truncated cone extending toward the proximal side, and has an inner conical surface (22161) matching the shape of the outer conical surface. Wherein, during the drug inhalation process, the piston portion (222) is located at the distal open position relative to the rod portion (221) to form a gap between the outer conical surface (22241) of the boss portion (2224) and the inner conical surface (22161) of the recessed portion (2216), so that the first sealing structure is in the open state, and Wherein, during the injection process, the piston portion (222) is located at the proximal sealing position relative to the rod portion (221), so that the outer conical surface (22241) of the boss portion (2224) contacts and fits tightly with the inner conical surface (22161) of the recessed portion (2216), so that the first sealing structure is in the sealing state.

6. The piston rod (22) according to claim 5, characterized in that During the drug inhalation process, the proximal movement of the piston rod (22) relative to the drug tube (21) forms a negative pressure in the accommodating chamber (215) of the distal part of the drug tube (21), and the negative pressure and / or the impact pressure from the injection keep the piston part in the open position.

7. The piston rod (22) according to claim 5, characterized in that During the injection process, the distal injection pressure acting on the proximal end of the piston rod holds the piston portion in the sealing position.

8. The piston rod (22) according to claim 5, characterized in that The rod portion further comprises one or more openings (2217) formed on the circumferential side wall of the first annular component (2211). Wherein, in the open state of the first sealing structure, the substance to be injected can flow from the storage container into the containing cavity (215) of the medicine tube through the one or more openings (2217).

9. The piston rod (22) according to claim 4, characterized in that The engaging portion is configured as a plurality of circumferentially distributed claws (2214), each claw extending toward the radial inside of the first annular portion.

10. The piston rod (22) according to claim 4, characterized in that The engaging portion is configured as a second flange (2214') extending radially inwardly of the first annular portion (2211).

11. The piston rod (22) according to claim 10, characterized in that The first flange (2223) and the second flange (2214') are flanges extending continuously in the circumferential direction or flanges distributed discontinuously in the circumferential direction, respectively.

12. The piston rod (22) according to claim 3, characterized in that The piston rod further comprises a second sealing structure, wherein the second sealing structure forms a seal in a circumferential direction between the rod portion (221) and the medicine tube (21).

13. The piston rod (22) according to claim 12, characterized in that The outer diameter of the second annular portion (2212) of the rod portion (221) is smaller than the outer diameters of the first annular portion (2211) and the main body portion, thereby forming an annular groove between the first annular portion and the main body portion. Wherein, the second sealing structure includes a sealing ring (2218), which can be accommodated in the annular groove to form a seal in the circumferential direction between the circumferential side wall of the second annular portion (2212) of the rod and the inner wall surface of the medicine tube (21).

14. The piston rod (22) according to claim 8, characterized in that The main body of the rod (221) is provided with an elongated channel extending along the axial direction (X), wherein the elongated channel is used to accommodate the drug aspiration needle (24). The drug aspiration needle extends from the storage container (4) to the internal space of the second annular portion (2212) of the rod (221). During the drug aspiration process, the injection can be sucked into the accommodating cavity (215) of the drug tube (21) through the inner cavity of the drug aspiration needle (24) and the internal space of the second annular portion and one or more orifices (2217) of the first annular portion.

15. The piston rod (22) according to claim 4, characterized in that The head portion (2221) of the piston portion (222) includes a conical portion (22211) located at the distal side and a cylindrical portion (22212) extending from the conical portion toward the proximal side. The conical portion (22211) is used to push the substance to be injected in the medicine tube (21) during the injection process, so that the substance to be injected is ejected from the injection microhole at the distal end of the medicine tube; and Wherein, the cylindrical portion (22212) is used to guide the axial movement of the piston portion (222) in the medicine tube (21).

16. The piston rod (22) according to claim 15, characterized in that The cylindrical portion (22212) includes a convex ring (22213) extending from the circumferential side wall of the cylindrical portion, and the outer peripheral portion (22213) of the convex ring is provided with at least one notch (22214). During the drug inhalation process, the injection can enter the accommodating cavity (215) of the distal portion of the drug tube through the at least one notch (22214).

17. The piston rod according to claim 16, characterized in that The cylindrical portion comprises at least two convex rings (22213) arranged in parallel in the axial direction, and the circumferential position of at least one notch (22214) of each convex ring at least partially overlaps with the circumferential position of at least one notch of the other convex ring.

18. The piston rod (22) according to claim 17, characterized in that Each convex ring (22213) is provided with at least two notches (22214) along the circumferential direction.

19. An injection head (2) capable of being removably mounted on a syringe body (3) of a needle-free syringe for use with the syringe body, characterized in that: The injection head (2) comprises: a medicine tube (21) for containing an injection substance drawn from a storage container (4) storing the injection substance; and A piston rod (22) according to any one of claims 1 to 18.

20. A needle-free syringe (1), comprising a syringe body (3) and an injection head (2), wherein the injection head (2) can be removably mounted to the syringe body (3) to be used in conjunction with the syringe body, characterized in that: The injection head comprises: a medicine tube (21) for containing an injection drawn from a storage container storing the injection; and A piston rod (22) according to any one of claims 1 to 18.

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