Needleless injector and liquid suction method and liquid injection method thereof

Abstract

The invention discloses a needleless injector and a liquid suction method and a liquid injection method thereof, and relates to the technical field of medical instruments, the needleless injector comprises a main tube body, a first cavity and a second cavity are arranged in the main tube body; the piston is movably arranged in the second cavity; the first end of the first valve element extends into the first cavity, and a first guide cavity in butt joint with the communicating hole is formed in the first end of the first valve element; the first guide cavity communicates with the first gap through the first connecting hole; a first rubber ring sleeves the outer side of the first connecting hole; the front cover is connected with the second end of the first valve element, and an injection head is arranged on the side, away from the first valve element, of the front cover; the extension pipe is connected with the main pipe body; the first end of the second valve element extends into the injection cavity, and a second gap is formed between the first end of the second valve element and the inner wall of the injection cavity; the second valve element is provided with a third guide cavity, and the third guide cavity communicates with the second gap through a third connecting hole. The outer side of the second connecting hole is sleeved with a second rubber ring. The structure of the injector can be simplified, and the injection precision and the response speed are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to a needle-free syringe and a liquid aspirating method and a liquid injecting method thereof. Background Art

[0002] Needle-free syringes do not require needles. They are medical devices that apply high pressure to liquid medicine so that it can be injected into the patient's skin, subcutaneous tissue or muscle through a microhole at the end, thus saving the patient from the pain of needle pricks.

[0003] Currently, needle-free syringes commonly use spring-loaded steel ball valves or metal diaphragm valves to control the flow of medication. These mechanical valves have significant drawbacks: Unreliable dynamic sealing: During high-pressure injection, the steel ball can easily lose its seal due to inertial displacement, leading to backflow of medication that can exceed 5% of the total dose, causing dosage errors; Response hysteresis: The spring-loaded valve's mechanical action delays by approximately 10 milliseconds, hindering instantaneous injection of medication and affecting injection depth consistency; Structural complexity: To meet bidirectional sealing requirements, separate suction and injection valves are required, increasing the number of parts by over 30% and imposing stringent assembly precision requirements. Summary of the Invention

[0004] In order to solve the defects of the prior art, the present invention provides a needle-free syringe and its aspiration method and injection method, which can simplify the syringe structure and improve the injection accuracy and response speed.

[0005] In order to solve the above technical problems, the present invention provides a needle-free syringe in the first aspect, comprising: a main body, a first cavity and a second cavity are provided in the interior of the main body; the first cavity and the second cavity are connected through a connecting hole; a piston is movably arranged in the second cavity; the piston is connected to the booster device of the syringe; a first valve core, a first end of which extends into the first cavity, and the first end of the first valve core is provided with a first guide cavity docking with the connecting hole; a first gap is formed between the middle of the first cavity and the first valve core, and the first guide cavity is connected to the first gap through the first connecting hole; a first rubber ring is provided on the outside of the first connecting hole; wherein the first rubber ring opens or contracts under the action of external pressure to control the opening and closing of the first connecting hole; a front cover is connected to the second end of the first valve core, An injection head is provided on the side of the front cover away from the first valve core; a second guide cavity is provided at the second end of the first valve core, one end of the second guide cavity is connected to the injection head, and the second guide cavity is connected to the first gap through a second connecting hole; an extension tube is connected to the main body; an injection cavity is provided in the extension tube, and the injection cavity is connected to the second cavity; a second valve core, whose first end extends into the injection cavity, forms a second gap between the first end of the second valve core and the inner wall of the injection cavity; a liquid inlet cavity is provided at the second end of the second valve core, and the liquid inlet cavity is connected to the third guide cavity, and the third guide cavity is connected to the second gap through the third connecting hole; a second rubber ring is provided on the outside of the third connecting hole, wherein the second rubber ring opens or contracts under the action of external pressure to control the opening and closing of the third connecting hole.

[0006] As an improvement to the above scheme, there are at least three first connecting holes, and multiple first connecting holes are arranged in a ring around the outer wall of the first valve core; multiple first connecting holes are connected by a first V-shaped groove on the side away from the first guide cavity, and the first rubber ring is arranged in the first V-shaped groove.

[0007] As an improvement to the above scheme, there are at least three second communicating holes, and multiple second communicating holes are arranged in a ring around the outer wall of the second valve core; multiple second communicating holes are connected through a second V-shaped groove on the side away from the third guide cavity, and the second rubber ring is arranged in the second V-shaped groove.

[0008] As an improvement to the above solution, a first sealing ring is provided on the tube wall of the first valve core, and the first sealing ring abuts against the opening of the first cavity; a second sealing ring is provided on the tube wall of the second valve core, and the second sealing ring abuts against the opening of the liquid inlet cavity.

[0009] As an improvement of the above solution, the needle-free syringe further includes an upper cover, which is sleeved on the outer side of the second valve core and the extension tube, and is used to fix the second valve core to the extension tube.

[0010] As an improvement to the above-mentioned solution, a first sealing groove and a second sealing groove are circumferentially provided on the outer wall of the first valve core, the first sealing groove is located between the first gap and the connecting hole, and the second sealing groove is located between the first gap and the first sealing ring; a first sealing ring is provided in both the first sealing groove and the second sealing groove, and the outer wall of the first sealing ring abuts against the inner wall of the first cavity.

[0011] As an improvement to the above solution, at least one third sealing groove is provided on the outer wall of the second valve core extending into the injection cavity, a second sealing ring is provided in the third sealing groove, and the second sealing ring abuts against the inner wall of the injection cavity.

[0012] As an improvement to the above solution, a fourth sealing groove is circumferentially provided on the outer wall of the piston; a third sealing ring is sleeved in the fourth sealing groove, and the outer wall of the third sealing ring abuts against the inner wall of the second cavity.

[0013] In a second aspect, the present invention provides a method for aspirating liquid using a needle-free syringe, comprising the following steps:

[0014] Connect the external medicine bottle to the liquid inlet chamber;

[0015] The piston is driven to move away from the first cavity, thereby generating negative pressure in the second cavity;

[0016] The first rubber ring seals the first connecting hole under the action of negative pressure;

[0017] The second rubber ring is deformed and opened outward under the action of negative pressure, and the liquid medicine enters the second cavity through the liquid inlet cavity, the third guide cavity, the third connecting hole and the second gap in sequence.

[0018] In a third aspect, the present invention provides a method for injecting liquid using a needle-free syringe, comprising the following steps:

[0019] driving the piston to move toward the first cavity;

[0020] The second rubber ring contracts inwards under the strong action of the liquid, sealing the third connecting hole to block backflow;

[0021] The liquid medicine enters the first guide cavity through the connecting hole, pushes away the first rubber ring, flows into the first gap through the first connecting hole, then enters the second guide cavity through the second connecting hole, enters the injection head through the second guide cavity, and is finally ejected from the injection head.

[0022] The beneficial effects of implementing the present invention are:

[0023] A needle-free syringe in the present invention forms an adaptive seal by arranging a first rubber ring on the first valve core and a second rubber ring on the second valve core. Under negative pressure or high pressure, the rubber ring is triggered to deform in a directional manner, dynamically fits the sealing surface, and completely avoids the risk of sticking of traditional mechanical valves; at the same time, it reduces the number of independent parts of the valve, reduces the assembly complexity, and simplifies the structure of the syringe; the deformation response time of the rubber ring is significantly improved compared with the spring valve, eliminating injection delay and improving injection accuracy and response speed.

[0024] The present invention provides a method for aspirating and injecting liquid for a needle-free syringe, which drives the adaptive deformation of the first rubber ring and the second rubber ring through the fluid pressure difference to achieve precise flow control; when aspirating liquid, the first rubber ring seals the first connecting hole under the action of negative pressure; when injecting liquid, the second rubber ring contracts inward under the strong action of the drug liquid, sealing the third connecting hole to block backflow; it can effectively prevent the backflow of the drug liquid; at the same time, this method does not require external control components, and the single injection process is short in time. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic structural diagram of a needle-free syringe in an embodiment of the present application;

[0026] Figure 2 This is an exploded view of the structure of a needle-free syringe in an embodiment of the present application;

[0027] Figure 3 This is a cross-sectional view of the structure of a needle-free syringe in an embodiment of the present application;

[0028] Figure 4 This is a cross-sectional view of the structure of the main body and extension tube of a needle-free syringe in an embodiment of the present application;

[0029] Figure 5 This is a schematic diagram of liquid aspiration using a needle-free syringe in an embodiment of the present application;

[0030] Figure 6 This is a schematic diagram of liquid injection of a needle-free syringe in an embodiment of the present application.

[0031] The reference numerals are as follows: 100, main body; 110, first cavity; 111, first gap; 120, second cavity; 130, communicating hole; 200, piston; 210, fourth sealing groove; 211, third sealing ring; 300, first valve core; 310, first guide cavity; 311, first connecting hole; 320, first rubber ring; 330, second guide cavity; 331, second connecting hole; 340, first V-shaped groove; 350, first sealing ring; 360, first sealing groove; 370, second Sealing groove; 380, first sealing ring; 390, fifth sealing groove; 391, fourth sealing ring; 400, front cover; 410, injection head; 420, sleeve; 500, extension tube; 510, injection cavity; 511, second gap; 600, second valve core; 610, liquid inlet cavity; 620, third guide cavity; 621, third connecting hole; 630, second rubber ring; 640, second V-shaped groove; 650, second sealing ring; 660, third sealing groove; 661, second sealing ring; 700, upper cover. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be described in further detail below with reference to the accompanying drawings.

[0033] See also Figures 1 to 4 , Figure 1 This is a schematic structural diagram of a needle-free syringe in an embodiment of the present application; Figure 2 This is an exploded view of the structure of a needle-free syringe in an embodiment of the present application; Figure 3 This is a cross-sectional view of the structure of a needle-free syringe in an embodiment of the present application; Figure 41 is a cross-sectional view of the structure of the main body and extension tube of a needle-free syringe in an embodiment of the present application; as shown in the figure, the needle-free syringe comprises: a main body 100, in which a first cavity 110 and a second cavity 120 are provided; the first cavity 110 and the second cavity 120 are connected via a connecting hole 130; a piston 200 is movably arranged in the second cavity 120; the piston 200 is connected to the booster device of the syringe; a first valve core 300, a first end of which extends into the first cavity 110, and a second end of the first valve core 300 is connected to the booster device of the syringe; A first guide cavity 310 is provided at one end to connect with the communicating hole 130; a first gap 111 is formed between the middle of the first cavity 110 and the first valve core 300, and the first guide cavity 310 is connected to the first gap 111 through the first connecting hole 311; a first rubber ring 320 is sleeved on the outside of the first connecting hole 311; wherein, the first rubber ring 320 opens or contracts under the action of external pressure to control the opening and closing of the first connecting hole 311; the front cover 400 is connected to the second end of the first valve core 300, and the front cover 400 is connected to the second end of the first valve core 300. An injection head 410 is provided on the side of the cover 400 away from the first valve core 300; a second guide cavity 330 is provided at the second end of the first valve core 300, one end of the second guide cavity 330 is connected to the injection head 410, and the second guide cavity 330 is connected to the first gap 111 through a second connecting hole 331; an extension tube 500 is connected to the main body 100; an injection cavity 510 is provided in the extension tube 500, and the injection cavity 510 is connected to the second cavity 120; a second valve core 600, a first end of which extends into The injection cavity 510 forms a second gap 511 between the first end of the second valve core 600 and the inner wall of the injection cavity 510. The second end of the second valve core 600 is provided with a liquid inlet cavity 610, which communicates with a third guide cavity 620. The third guide cavity 620 communicates with the second gap 511 via a third connecting hole 621. A second rubber ring 630 is sleeved on the outer side of the third connecting hole 621. The second rubber ring 630 expands or contracts under external pressure to control the opening and closing of the third connecting hole 621. The first rubber ring 320 on the first valve core 300 and the second rubber ring 630 on the second valve core 600 form an adaptive seal. Under negative or high pressure, the rubber rings are triggered to deform in a directional manner, dynamically conforming to the sealing surface, completely avoiding the risk of sticking associated with traditional mechanical valves. This also reduces the number of independent valve parts, reduces assembly complexity, and simplifies the structure of the syringe. The rubber ring deformation response time is significantly improved compared to a spring valve, eliminating injection delays and improving injection accuracy and response speed.

[0034] Preferably, the radial width of the first gap 111 is 0.1 mm to 0.5 mm, and the radial width of the second gap 511 is 0.1 mm to 0.5 mm. The precise width design of the first and second gaps 111 and 511 reduces the residual amount of liquid medicine to less than 5 μL, a 70% reduction compared to conventional structures, and achieves a biopharmaceutical utilization rate exceeding 99%. The straight-through path through the first guide cavity 310, the first gap 111, and the second guide cavity 330 reduces turbulent energy loss by 90%, ensuring a stable injection of liquid medicine at a speed of 200 ± 5 m / s.

[0035] See also Figure 3 Furthermore, in this embodiment, at least three first communicating holes 130 are provided, and the plurality of first communicating holes 130 are annularly arranged around the outer wall of the first valve core 300. The plurality of first communicating holes 130 are connected by a first V-shaped groove 340 on the side away from the first guide cavity 310, and the first rubber ring 320 is sleeved within the first V-shaped groove 340. The cooperation between the first V-shaped groove 340 and the first rubber ring 320 effectively improves the airtightness of the first rubber ring 320. Furthermore, the first V-shaped groove 340 can guide the first rubber ring 320 to deform in a directional manner under negative or high pressure, thereby preventing the first rubber ring 320 from deviating.

[0036] See also Figure 3 Furthermore, in this embodiment, at least three second communication holes 130 are provided, and the plurality of second communication holes 130 are annularly arranged around the outer wall of the second valve core 600. The plurality of second communication holes 130 are connected by a second V-groove 640 on the side away from the third guide cavity 620, and the second rubber ring 630 is sleeved within the second V-groove 640. The second V-groove 640 cooperates with the second rubber ring 630 to effectively improve the airtightness of the second rubber ring 630. Furthermore, the second V-groove 640 can guide the second rubber ring 630 to deform in a directional manner under negative or high pressure, thereby preventing the second rubber ring 630 from deviating.

[0037] Preferably, the opening angle of the first V-shaped groove 340 is 60° to 120°, and the opening angle of the second V-shaped groove 640 is 60° to 120°.

[0038] See also Figure 3 Furthermore, in this embodiment, a first sealing ring 350 is provided on the wall of the first valve core 300, abutting the opening of the first cavity 110. A second sealing ring 650 is provided on the wall of the second valve core 600, abutting the opening of the liquid inlet cavity 610. The first sealing ring 350 blocks and seals the first cavity 110, while the second sealing ring 650 seals the liquid inlet cavity 610.

[0039] See also Figure 3 Furthermore, in this embodiment, the front cover 400 also includes a sleeve 420, which is sleeved on the inner side of the first sealing ring 350 and the main body 100, and the inner wall of the sleeve 420 is snap-fitted or threadedly connected to the outer wall of the main body 100, and the inner cavity of the sleeve 420 is connected to the injection head 410.

[0040] See also Figure 3 Furthermore, in this embodiment, the needle-free syringe further includes an upper cover 700, which is sleeved over the second valve core 600 and the outer side of the extension tube 500. The upper cover 700 is used to fix the second valve core 600 to the extension tube 500. Specifically, the upper cover 700 is snap-fitted to the outer side of the extension tube 500 and is threadedly connected to the second end of the second valve core 600.

[0041] See also Figure 2 and Figure 3 Furthermore, in this embodiment, a first sealing groove 360 ​​and a second sealing groove 370 are circumferentially defined on the outer wall of the first valve core 300. The first sealing groove 360 ​​is located between the first gap 111 and the connecting hole, and the second sealing groove 370 is located between the first gap 111 and the first sealing ring 350. A first sealing ring 380 is disposed within each of the first and second sealing grooves 360 and 370, with the outer wall of the first sealing ring 380 abutting against the inner wall of the first cavity 110. The provision of the first sealing groove 360, the second sealing groove 370, and the first sealing ring 380 improves the airtightness within the first cavity 110, ensuring that the liquid medicine within the first cavity 110 is propelled along a designated path.

[0042] See also Figure 2 and Figure 3 Furthermore, in this embodiment, a third sealing groove 660 is provided on the outer wall of the second valve core 600 on the side extending into the injection chamber 510. A second sealing ring 661 is disposed within the third sealing groove 660, and the second sealing ring 661 abuts against the inner wall of the injection chamber 510. The provision of the third sealing groove 660 and the second sealing ring 661 improves the airtightness within the injection chamber 510, ensuring that the liquid medicine is propelled along a designated path.

[0043] See also Figure 2 and Figure 3 Furthermore, in this embodiment, a fourth sealing groove 210 is circumferentially formed on the outer wall of the piston 200. A third sealing ring 211 is sleeved within the fourth sealing groove 210, with the outer wall of the third sealing ring 211 abutting against the inner wall of the second cavity 120. The fourth sealing groove 210 and the third sealing ring 211 improve the airtightness within the second cavity 120.

[0044] See also Figure 2 and Figure 3 Furthermore, in this embodiment, a fifth sealing groove 390 is circumferentially provided at the second end of the first valve core 300, and a fourth sealing ring 391 is provided in the fifth sealing groove 390. The outer wall of the fourth sealing ring 391 abuts against the inner wall of the sleeve 420 to improve the airtightness inside the front cover 400.

[0045] See also Figure 4 Preferably, the included angle between the extension tube 500 and the main body 100 is 30° to 90°, preferably 45°; the axial center lines of the first valve core 300 and the second valve core 600 are arranged non-parallel.

[0046] Preferably, the first rubber ring 320 and the second rubber ring 630 are made of medical silicone or fluororubber.

[0047] Preferably, the piston 200 is connected to a striker of a booster device.

[0048] See also Figure 5 , Figure 5 This is a schematic diagram of liquid aspiration of a needle-free syringe in an embodiment of the present application.

[0049] In a second aspect, this embodiment provides a method for aspirating liquid using a needle-free syringe, comprising the following steps:

[0050] Connecting the external medicine bottle to the liquid inlet chamber 610;

[0051] The piston 200 is driven by the booster device to move away from the first cavity 110, so that negative pressure is generated in the second cavity 120;

[0052] The first rubber ring 320 seals the first connecting hole 311 under the action of negative pressure;

[0053] The second rubber ring 630 is deformed and opened outward under the action of negative pressure, and the liquid medicine enters the second cavity 120 through the liquid inlet cavity 610, the third guide cavity 620, the third connecting hole 621 and the second gap 511 in sequence, completing the liquid absorption.

[0054] See also Figure 6 , Figure 6 This is a schematic diagram of liquid injection using a needle-free syringe in an embodiment of the present application;

[0055] In a third aspect, the present embodiment provides a method for injecting liquid using a needle-free syringe, comprising the following steps:

[0056] The piston 200 is driven by the booster device to move toward the first cavity 110;

[0057] The second rubber ring 630 contracts inwards under the pressure of the liquid, sealing the third connecting hole 621 to block backflow;

[0058] The liquid medicine enters the first guide cavity 310 through the connecting hole 130, pushes away the first rubber ring 320, flows into the first gap 111 through the first connecting hole 311, then enters the second guide cavity 330 through the second connecting hole 331, enters the injection head 410 through the second guiding cavity 330, and is finally ejected from the injection head 410.

[0059] From the above, it can be seen that a needle-free syringe in the present invention forms an adaptive seal by setting a first rubber ring on the first valve core and a second rubber ring on the second valve core, which triggers the directional deformation of the rubber ring under negative pressure or high pressure, dynamically fits the sealing surface, and completely avoids the risk of sticking of traditional mechanical valves; at the same time, it reduces the number of independent parts of the valve, reduces the assembly complexity, and simplifies the structure of the syringe; the deformation response time of the rubber ring is significantly improved compared with the spring valve, eliminating injection delays, and improving injection accuracy and response speed.

[0060] From the above, it can be seen that the liquid aspiration method and liquid injection method of a needle-free syringe in the present invention drives the adaptive deformation of the first rubber ring and the second rubber ring through the fluid pressure difference to achieve precise flow control; when aspirating liquid, the first rubber ring seals the first connecting hole under the action of negative pressure; when injecting liquid, the second rubber ring contracts inward under the high pressure of the drug liquid, sealing the third connecting hole to block backflow; it can effectively prevent the backflow of the drug liquid; at the same time, this method does not require external control components, and the single injection process is short in time.

[0061] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A needle-free syringe, characterized in that: include: A main body, wherein a first cavity and a second cavity are provided inside the main body; the first cavity and the second cavity are connected via a communication hole; A piston is movably disposed in the second cavity; the piston is connected to the booster device of the syringe; a first valve core, a first end of which extends into the first cavity, and a first guide cavity connected to the communicating hole is provided at the first end of the first valve core; A first gap is formed between the middle of the first cavity and the first valve core, and the first guide cavity is connected to the first gap through a first connecting hole; a first rubber ring is sleeved on the outer side of the first connecting hole; The first rubber ring expands or contracts under external pressure to control the opening and closing of the first connecting hole; the front cover is connected to the second end of the first valve core, and an injection head is provided on the side of the front cover away from the first valve core; the second end of the first valve core is provided with a second guide cavity, one end of the second guide cavity is connected to the injection head, and the second guide cavity is connected to the first gap through the second connecting hole; An extension tube connected to the main body; an injection cavity is provided in the extension tube, and the injection cavity is communicated with the second cavity; The first end of the second valve core extends into the injection cavity, and a second gap is formed between the first end of the second valve core and the inner wall of the injection cavity; the second end of the second valve core is provided with a liquid inlet cavity, the liquid inlet cavity is connected to the third guide cavity, and the third guide cavity is connected to the second gap through the third connecting hole; the outer side of the second connecting hole is provided with a third rubber ring The second rubber ring expands or contracts under external pressure to control the opening and closing of the third connecting hole.

2. The needle-free syringe according to claim 1, characterized in that: There are at least three first communicating holes, and the multiple first communicating holes are arranged in a ring around the outer wall of the first valve core; the multiple first communicating holes are connected by a first V-shaped groove on the side away from the first guide cavity, and the first rubber ring is set in the first V-shaped groove.

3. The needle-free syringe according to claim 1, characterized in that: There are at least three second communicating holes, and the multiple second communicating holes are arranged in a ring around the outer wall of the second valve core; the multiple second communicating holes are connected by a second V-shaped groove on the side away from the third guide cavity, and the second rubber ring is set in the second V-shaped groove.

4. The needle-free syringe according to claim 1, characterized in that: A first sealing ring is provided on the tube wall of the first valve core, and the first sealing ring abuts against the opening of the first cavity; A second sealing ring is provided on the tube wall of the second valve core, and the second sealing ring abuts against the opening of the liquid inlet cavity.

5. The needle-free syringe according to claim 1, characterized in that: The needle-free syringe further includes an upper cover, which is sleeved on the second valve core and the outer side of the extension tube, and is used to fix the second valve core to the extension tube.

6. The needle-free injector according to claim 4, characterized in that: A first sealing groove and a second sealing groove are circumferentially provided on the outer wall of the first valve core, the first sealing groove is located between the first gap and the connecting hole, and the second sealing groove is located between the first gap and the first sealing ring; a first sealing ring is provided in both the first sealing groove and the second sealing groove, and the outer wall of the first sealing ring abuts against the inner wall of the first cavity.

7. The needle-free injector according to claim 1, characterized in that: At least one third sealing groove is provided on the outer wall of the second valve core extending into the injection cavity. A second sealing ring is provided in the third sealing groove. The second sealing ring abuts against the inner wall of the injection cavity.

8. The needle-free injector according to claim 1, characterized in that: A fourth sealing groove is circumferentially provided on the outer wall of the piston; a third sealing ring is sleeved in the fourth sealing groove, and the outer wall of the third sealing ring abuts against the inner wall of the second cavity.

9. A method for aspirating liquid using a needle-free syringe according to any one of claims 1 to 8, characterized in that: The following steps are involved: Connect the external medicine bottle to the liquid inlet chamber; The piston is driven to move away from the first cavity, thereby generating negative pressure in the second cavity; The first rubber ring seals the first connecting hole under the action of negative pressure; The second rubber ring is deformed and opened outward under the action of negative pressure, and the liquid medicine enters the second cavity through the liquid inlet cavity, the third guide cavity, the third connecting hole and the second gap in sequence.

10. A method for injecting liquid using a needle-free syringe according to any one of claims 1 to 8, characterized in that: The following steps are involved: driving the piston to move toward the first cavity; The second rubber ring contracts inwards under the strong action of the liquid, sealing the third connecting hole to block backflow; The liquid medicine enters the first guide cavity through the connecting hole, pushes away the first rubber ring, flows into the first gap through the first connecting hole, then enters the second guide cavity through the second connecting hole, enters the injection head through the second guide cavity, and is finally ejected from the injection head.

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