Needleless injector

Abstract

The needleless injector comprises an injection push rod, a spring pull rod, a power spring and a pushing device, the injection push rod moves forwards to compress an injection cavity and moves backwards to expand the injection cavity, and the front end of the spring pull rod is connected with the rear end of the injection push rod. The power spring abuts against the spring pull rod to prevent the injection push rod from moving backwards, and the pushing end of the pushing device is used for driving the spring pull rod to move backwards and enabling the power spring to be in an elastic compression state. In the liquid pumping process, liquid pumping is mainly achieved through driving of the pushing device, and the action of the pushing device is generally stable and slow. When injection is carried out, operation is achieved through the spring force of the power spring, the injection process is generally fast and stable, and at the moment, the spring force can just achieve the effect. The pushing device and the power spring are arranged to be matched with each other, so that the liquid pumping process and the injection process can meet respective characteristics, and the injection effect is better in the whole automatic injection process.

Description

Technical Field

[0001] The utility model relates to the technical field of drug liquid injection, and more specifically to a needle-free syringe. Background Art

[0002] Needle-free injection is a new injection technology that achieves the purpose of drug injection without needle puncture. It has the advantages of reducing the pain and fear of drug injection, reducing the risk of bacterial infection, avoiding accidents such as needle scratches and breakage, rapid drug absorption, no subcutaneous nodules after long-term use, and high injection efficiency.

[0003] At present, some needle-free syringes generally use a driving motor as a propulsion device to complete injection and extraction. The inventors have found that because the injection and extraction, the injection push rod movement mode is different, the current propulsion device is difficult to take into account both.

[0004] In summary, how to effectively solve the problem of poor injection effect of current syringes is an urgent problem that technicians in this field need to solve. Utility Model Content

[0005] In view of this, the purpose of the present utility model is to provide a needle-free syringe, which can effectively solve the problem of poor injection effect of current syringes.

[0006] In order to achieve the above object, the utility model provides the following technical solutions:

[0007] A needle-free syringe comprises an injection push rod, a spring pull rod, a power spring and a pushing device. The injection push rod moves forward to compress an injection cavity and moves backward to expand the injection cavity. The front end of the spring pull rod is connected to the rear end of the injection push rod. The power spring abuts against the spring pull rod to prevent the injection push rod from moving backward. The pushing end of the pushing device is used to drive the spring pull rod to move backward and put the power spring in an elastically compressed state.

[0008] In the above-mentioned needle-free syringe, the process of extracting liquid is mainly achieved by driving the pushing device, and the movement of the pushing device is generally relatively smooth and slow. As for injection, the operation is realized by the spring force of the power spring. The injection process is generally fast and stable, and the spring force can just achieve the above-mentioned effect. In the above-mentioned needle-free syringe, the pushing device and the power spring are arranged to cooperate with each other so that the extraction and injection processes can meet their respective characteristics, thereby ensuring a better injection effect during the entire automatic injection process. In summary, the needle-free syringe can effectively solve the problem of poor injection effect of current syringes.

[0009] In some technical schemes, the pushing device includes a driving motor and a cam structure installed on the main shaft of the driving motor, and the rear end of the spring pull rod has a cam shaft seat abutting against the wheel surface of the cam structure; the cam structure has a spiral wheel surface and an axial extension structure connecting the two ends of the spiral wheel surface.

[0010] In some technical solutions, the pushing device includes a motor base, the driving motor is installed on the motor base, and the cam structure is rotatably installed on the motor base; a magnet is provided on the cam structure; and a Hall sensor is also included which is relatively fixed to the motor base to stop the driving motor from rotating when the magnet is detected to be approaching.

[0011] In some technical schemes, the radial outer side of the connecting tube portion at the front end of the cam structure is matched with the motor seat through a bearing, and the connecting tube portion is inserted forward into the motor seat; the rear end of the connecting tube portion abuts against the motor seat through a gasket, and the front end abuts against the motor seat through a locking nut sleeved on the outside and threadedly connected for axial fixation; the wheel surface portion of the cam structure is arranged at the rear end of the connecting tube portion; the main shaft of the driving motor is inserted into the inner hole of the connecting tube portion and fixed by a radially extending pin.

[0012] In some technical schemes, it also includes a spring housing, which has a spring cavity for accommodating the spring pull rod, the rear end of the spring pull rod is slidingly matched with the cavity wall of the spring cavity, the front end of the spring pull rod is sleeved and fixed with a guide ring, the outer periphery of the guide ring is slidingly matched with the cavity wall of the spring cavity, the power spring is sleeved on the spring pull rod, the front end of the power spring is fixedly connected to the guide ring, and the rear end of the power spring is fixedly mounted on the inner protrusion inside the spring cavity.

[0013] In some technical schemes, an injection shell is also included, and the injection push rod includes an injection rod portion and a driving rod portion which are arranged in sequence along the injection direction, the injection rod portion is slidably matched with the medicine cavity of the injection shell along the front-to-back direction, and the driving rod portion extends into the medicine cavity; the injection rod portion and the driving rod portion are connected by a flexible structure to transmit force in the front-to-back direction, and have a relative range of motion of a predetermined size in a direction perpendicular to the front-to-back direction.

[0014] In some technical solutions, the flexible structure includes a latching protrusion and a latching groove that limits the forward and backward movement of the latching protrusion, and a gap is formed between the neck of the latching protrusion and the avoidance opening of the groove wall on one side of the latching groove so that relative movement in a vertical direction in the forward and backward direction is possible; one of the latching protrusion and the latching groove is arranged on the injection rod part, and the other is arranged on the driving rod part.

[0015] In some technical solutions, the front end of the medicine cavity has a medicine outlet, and the medicine outlet is provided with a nozzle; the outside of the nozzle has a protruding trigger stopper; the trigger stopper is connected to the injection shell through an elastic member; and a proximity switch is provided on the injection shell to respond when the trigger stopper moves relative to the injection shell to extend the nozzle.

[0016] In some technical solutions, the injection housing is provided with a Luer connector connected to the medicine cavity through a medicine inlet one-way valve.

[0017] In some technical solutions, the Luer connector is connected to the liquid storage device through a hose. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic diagram of the structure of a needle-free syringe provided by an embodiment of the utility model;

[0020] Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure of the needle-free syringe at AA;

[0021] Figure 3 for Figure 1 A schematic diagram of the cross-sectional structure of the needle-free syringe at BB;

[0022] Figure 4 This is a schematic structural diagram of a camshaft seat provided in an embodiment of the utility model.

[0023] The following are marked in the accompanying drawings:

[0024] 1. Cam structure; 2. Magnet; 3. Ejector bearing; 4. Motor seat; 5. Shock-absorbing pad; 6. Motor connecting piece; 7. Motor fixing cover; 8. Driving motor; 9. Spring housing; 10. Proximity switch; 11. Injection housing; 12. Drug inlet check valve; 13. Hall sensor;

[0025] 14. Camshaft seat; 15. Spring pull rod; 16. Shock absorbing nut; 17. Inner protrusion; 18. Spring cavity; 19. Power spring; 20. Guide ring; 21. Push rod seat; 22. Drive rod; 23. Injection rod; 24. Plastic guide sleeve; 25. O-ring; 26. Circular retaining ring; 27. Medicine cavity; 28. Nozzle check valve; 29. ​​Trigger stopper; 30. Nozzle; 31. Elastic part;

[0026] 32. Washer; 33. Deep groove ball bearing; 34. Spindle; 35. Lock nut;

[0027] 36. Roller. DETAILED DESCRIPTION

[0028] The embodiment of the utility model discloses a needle-free syringe, which can effectively solve the problem of poor injection effect of current syringes.

[0029] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0030] See also Figure 1-Figure 3 , Figure 1 A schematic diagram of the structure of a needle-free syringe provided by an embodiment of the utility model; Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure of the needle-free syringe at AA; Figure 3 for Figure 1 A schematic diagram of the cross-sectional structure of the needle-free syringe at BB; Figure 4 This is a schematic structural diagram of a camshaft seat provided in an embodiment of the utility model.

[0031] In some embodiments, a needle-free syringe is provided. Specifically, the needle-free syringe mainly includes an injection push rod, a spring pull rod 15, a power spring 19 and a pushing device, and of course also includes some other decoupling components. For example, on the injection part, not only the above-mentioned injection push rod is provided, but also an injection shell 11 forming a medicine cavity 27 is provided, and at the power spring 19 part, not only the power spring 19 and the spring pull rod 15 are provided, but also a spring shell 9 is provided to form a spring cavity 18.

[0032] The injection push rod moves forward to compress the injection cavity and moves backward to expand the injection cavity. A medicine cavity 27 is generally provided in the injection shell 11, and the injection push rod and the cavity wall of the medicine cavity 27 are slidably matched. The front end of the medicine cavity 27 forms a medicine outlet to connect the nozzle 30 or other injection components. The portion of the medicine cavity 27 between the front end of the injection push rod and the medicine outlet constitutes the injection cavity. When the injection push rod slides toward the medicine outlet, the injection cavity becomes shorter, that is, the volume becomes smaller. This process is generally an injection process; and when the injection push rod moves away from the medicine outlet, the side length of the injection cavity, that is, the volume becomes larger. This process is generally a liquid extraction process. It should be noted that the forward direction generally refers to the injection direction, and the opposite direction is the backward direction.

[0033] The front end of the spring pull rod 15 is connected to the rear end of the injection push rod, which can be integrally formed or fixedly connected, and can be specifically set as needed. If multiple spring pull rods 15 are provided, the front ends of the spring pull rods 15 are generally connected through the push rod seat 21, and the rear end of the injection push rod is connected to the middle of the push rod seat 21, and specifically can be connected by screws.

[0034] The power spring 19 abuts against the spring pull rod 15 to prevent the injection push rod from moving backwards, wherein the power spring 19 can be sleeved on the spring pull rod 15, or can abut against the rear end of the spring pull rod 15. The power spring 19 is generally a compression spring, and of course, under some needs, a tension spring can also be used to form elastic deformation to store energy during the backward movement of the injection push rod.

[0035] The pushing end of the pushing device is used to drive the spring pull rod 15 to move backward and make the power spring 19 elastically compressed to store energy. When the pushing end of the pushing device is loosened, or the spring pull rod 15 is released, the spring pull rod 15 moves forward under the action of the power spring 19 to drive the injection push rod to complete the injection. The pushing device, such as a pneumatic telescopic cylinder or a hydraulic telescopic cylinder, can release pressure instantly through the pressurized chamber, and then the spring pull rod 15 moves forward under the elastic force of the power spring 19 to complete the injection.

[0036] In the above-mentioned needle-free syringe, the process of extracting liquid is mainly achieved by driving the pushing device, and the movement of the pushing device is generally relatively stable and slow. As for injection, this operation is achieved by the spring force of the power spring 19. The injection process is generally fast and stable, and the spring force at this time can just achieve the above-mentioned effect. In the above-mentioned needle-free syringe, the pushing device and the power spring 19 are arranged to cooperate with each other so that the extraction and injection processes can meet their respective characteristics, thereby ensuring a better injection effect during the entire automatic injection process. In summary, the needle-free syringe can effectively solve the problem of poor injection effect of current syringes.

[0037] In some embodiments, it is preferred that the pushing device includes a driving motor 8, and the driving motor 8 and the spring pull rod 15 can be driven by a gear rack.

[0038] For better operation, the preferred pushing device here also includes a cam structure 1 installed on the main shaft 34 of the driving motor 8, and the rear end of the corresponding spring pull rod 15 has a camshaft seat 14 that abuts on the wheel surface of the cam structure 1. The cam structure 1 has a spiral wheel surface and an axial extension structure connecting the two ends of the spiral wheel surface, so that when the spiral wheel surface abuts against the roller 36 on the camshaft seat 14, the spring pull rod 15 is pushed to move backward smoothly, and the liquid is pumped at the end of the spiral wheel surface. Then the driving motor 8 drives the cam structure 1 to continue to rotate, so that the roller 36 of the camshaft seat 14 moves to the axial extension structure and is no longer supported by the front and rear directions. At this time, under the action of the power spring 19, the roller 36 moves forward along the axial extension structure. At the same time, in this process, driven by the spring pull rod 15, the injection push rod moves forward, and when the roller 36 moves to the initial end of the above-mentioned spiral wheel surface, the injection is completed. Then the cam structure 1 continues to rotate, at which time the spiral wheel surface continues to abut against the roller 36, and then the electric roller 36 continues to move backward to complete the injection.

[0039] In some embodiments, the camshaft seat 14 can be fixed to the rear end of the spring pull rod 15 by screws. When there are multiple spring pull rods 15, the rear ends of each spring pull rod 15 are connected to the cam bearing seat by screws. For example, the spring pull rod 15 can be a circular tube, and the inner wall of the tube openings at both ends is provided with threads. At the rear end, the screw passes through the camshaft seat 14, is inserted into the rear end tube opening, and is threadedly connected; and at the front end, the screw passes through the push seat, is inserted into the front end tube opening, and is threadedly connected. The push seat and the injection push rod are connected by a pin. Specifically, a socket is provided on the push seat, and the rear end of the injection push rod is inserted into the socket, and then connected by a pin on the wall of the socket, so that a movable connection is formed between the push seat and the injection push rod to reduce or avoid the transmission of lateral force in the vertical front-back direction.

[0040] In some embodiments, in order to facilitate installation, the pushing device generally also includes a motor base 4, the body of the above-mentioned drive motor 8 is installed on the motor base 4, the cam structure 1 is rotatably installed on the motor base 4 to be supported by the motor base 4, and the main shaft 34 of the drive motor 8 provides rotational torque.

[0041] In some embodiments, the body of the driving motor 8 and the motor base 4 are preferably connected by screws, and a shock-absorbing pad 5, a motor connecting plate 6 and a motor fixing cover 7 are sequentially arranged between the motor base 4 and the above-mentioned screws.

[0042] In some embodiments, after the liquid extraction is completed, it is generally necessary to stop the liquid extraction, so a sensor can be provided to detect whether the liquid extraction is completed. The specific sensor can be used to detect whether the cam structure 1 rotates to a preset position. The sensor can be an infrared sensor, a touch switch, etc.

[0043] For the convenience of detection, it is preferred that a magnet 2 is provided on the cam structure 1. Correspondingly, a Hall sensor 13 fixed relatively to the motor base 4 is also included to stop the driving motor 8 from rotating when the magnet 2 is detected to be close. Because the pumping is completed, the driving motor 8 stops rotating to stop pumping. Of course, at this time, the roller 36 should not have rotated to the axial extension structure.

[0044] Taking into account the reaction time and other issues, a flat transition wheel surface can be provided between the axial extension structure and the spiral wheel surface. The flat transition wheel surface is perpendicular to the axis. At this time, the force transmitted to the roller 36 by the power spring 19 is just perpendicular to the flat transition wheel surface.

[0045] In some embodiments, the cam structure 1 can be directly installed on the main shaft 34 of the drive motor 8. However, in order to facilitate the installation of the above-mentioned cam structure 1, it is preferred that the radial outer side of the connecting tube portion at the front end of the cam structure 1 is matched with the motor seat 4 through a bearing, so that the cam structure 1 can better bear the load of the motor seat 4.

[0046] The above-mentioned connecting pipe part is inserted forward into the motor seat 4, and the rear end of the connecting pipe part abuts against the motor seat 4 through the gasket 32, and the front end abuts against the motor seat 4 through the locking nut 35 which is sleeved on the outside and threadedly connected, so as to be axially fixed. The axis between the connecting pipe part and the motor seat 4 is fixed by the locking nut 35, and because the drive motor 8 is fixedly installed on the drive motor 8 seat 4, the connecting pipe part and the drive motor 8 maintain a stable position in the axial direction, further avoiding the transmission of power in the axial direction between each other. The bearing between the connecting pipe part and the motor seat 4 is preferably a deep groove ball bearing 33. Further, the axial force is transmitted between the gasket 32 ​​and the corresponding shoulder of the connecting pipe part through the ejector bearing 3.

[0047] The wheel surface of the cam structure 1 is arranged at the rear end of the connecting pipe. The main shaft 34 of the driving motor 8 is inserted into the inner hole of the connecting pipe and fixed by radially extending pins to achieve torque transmission. During assembly, the gasket 32 ​​is first sleeved on the connecting pipe, and the connecting pipe is inserted forward into the bearing of the motor seat 4. Then, the locking nut 35 is sleeved on the front end of the connecting pipe, and the locking nut 35 is tightened by rotation. Before or after this, the main shaft 34 is inserted into the connecting pipe and then fixed by pins.

[0048] In some embodiments, a spring housing 9 is generally included, wherein the spring housing 9 has a spring cavity 18 for accommodating a spring pull rod 15, and a power spring 19 is generally sleeved on the spring pull rod 15. In order to facilitate the compression deformation of the spring pull rod 15 and the elastic recovery elongation. It is preferred that the rear end of the spring pull rod 15 slides with the cavity wall of the spring cavity 18, and the front end of the spring pull rod 15 is sleeved and fixed with a guide ring 20. The outer periphery of the guide ring 20 slides with the cavity wall of the spring cavity 18, and the front end of the power spring 19 is fixedly connected to the guide ring 20 to be guided by the guide ring 20. The rear end of the power spring 19 is fixedly mounted on the inner protrusion 17 inside the spring cavity to form an axial support. It should be noted that the guide ring 20 can be installed between the push seat and the front end of the power spring 19. Specifically, the inner protrusion 17 can be a limiter threadedly connected to the cavity wall of the rear end of the spring cavity. In order to achieve better shock absorption, the inner protrusion 17 can be sleeved on the spring pull rod 15, and a shock absorbing nut 16 is provided between the inner protrusion 17 and the spring pull rod 15. The outer edge of the guide ring 20 is tightly fitted with the inner wall of the spring cavity 18, and plays a guiding and positioning role during the compression or release of the power spring 19, thereby avoiding the unstable injection pressure of the needle-free syringe caused by the deviation of the power spring 19.

[0049] In some embodiments, an injection housing 11 is also included. In the medicine cavity 27 of the injection housing 11, the injection push rod is generally an integrally molded rod, but the integrally molded rod has relatively high guiding accuracy requirements. Based on this, it is preferred that the injection push rod includes an injection rod portion 23 and a driving rod portion 22 arranged in sequence along the injection direction, wherein the injection rod portion 23 slides with the medicine cavity 27 of the injection housing 11 in the front-to-back direction, and the driving rod portion 22 extends into the medicine cavity 27; the injection rod portion 23 and the driving rod portion 22 are connected by a flexible structure to transmit force in the front-to-back direction, and have a relative range of motion of a predetermined size in a direction perpendicular to the front-to-back direction. The injection rod portion 23 is generally provided with a plastic guide sleeve 24, a circular retaining ring 26 and an O-ring 25.

[0050] The predetermined relative range of motion is generally set to correspond to the axis deviation range between the injection rod 23 and the drive rod 22 to fully meet the deviation requirements, so that the vertical force in the front-to-back direction is not transmitted between the drive rod 22 and the injection rod 23, thereby reducing the impact of the axis error.

[0051] The driving rod 22 is connected to the push seat, and the push seat drives the driving rod 22 to move in the front-to-back direction. Through the flexible structure, the front-to-back direction can transmit the force to the injection rod 23, thereby driving the injection rod 23 to complete the injection. In the above injection structure, because of the flexible structure connection, it is only necessary to make the injection rod 23 and the medicine cavity 27 reach high-precision coaxiality, and there is no need to make the driving rod 22 and the medicine cavity 27 reach high-precision coaxiality, which reduces the coaxiality requirements and can meet the injection drive.

[0052] In some embodiments, the flexible structure can achieve the above flexibility requirements through a mechanical structure, or can be achieved through a material body formed by a flexible material, such as a colloid, a cloth structure, a rope structure, etc. The mechanical structure is a chain structure, a buckle structure, etc.

[0053] In some embodiments, the flexible structure may include a protrusion and a slot for limiting the forward and backward movement of the protrusion, and a gap may be formed between the neck of the protrusion and the avoidance opening of the slot wall on one side of the slot, so that the protrusion can move relative to the front and rear direction in a vertical direction; one of the protrusion and the slot is provided on the injection rod 23, and the other is provided on the driving rod 22. The slot is provided on the injection rod 23, and may be integrally formed, welded, screwed, etc.; the driving rod 22 is provided with a corresponding protrusion, such as integrally formed, welded, screwed, etc.

[0054] The front end of the driving rod 22 can have a slot extending in the first direction in the slot depth direction, and the front side slot wall of the slot has a avoidance opening extending in the first direction in the middle of the second direction, wherein the second direction, the first direction and the front-to-back direction are all arranged perpendicular to each other.

[0055] The protrusion of the card protrusion is installed into the card slot along the first direction, and has a certain movable gap in the first direction and the second direction to form a flexible movable range, and can move relatively in any vertical direction of the front and rear directions.

[0056] The neck of the clamping protrusion is located in the avoidance opening and has a movable gap in the first direction, and in the second direction, both sides of the neck and the avoidance opening have movable gaps, so that any vertical direction in the front-back direction can move relative to each other.

[0057] In some embodiments, the front end of the medicine cavity 27 can be provided with a medicine outlet, and the medicine outlet is provided with a nozzle 30. The outside of the nozzle 30 has a protruding trigger stopper 29, which is a cylindrical structure with a hollow wall. The trigger stopper 29 is connected to the injection housing 11 through an elastic member 31, so that it can be pressed and moved backward, so that the nozzle 30 can be extended to perform injection. The injection housing 11 is provided with a proximity switch 10 to respond when the trigger stopper 29 moves relative to the injection housing 11 to extend the nozzle 30. When the proximity switch 10 responds, the drive motor 8 can respond accordingly, so that the cam structure 1 continues to rotate by a preset angle, so that the roller 36 rotates to the axial extension structure, and then stops rotating. At this time, because the front side of the roller 36 no longer has a wheel surface support, under the action of the power spring 19, the camshaft seat 14, the spring pull rod 15, and the injection push rod move forward as a whole to compress the injection cavity and complete the injection. Generally speaking, a nozzle check valve 28 is provided between the nozzle 30 and the medicine outlet. And preferably, the surface where the sealing ring on the nozzle one-way valve 28 contacts the liquid outlet of the cylinder body is not perpendicular to the axis of the cylinder body.

[0058] In some embodiments, in order to facilitate and quickly introduce the drug solution into the injection cavity, it is preferred that the injection housing 11 is provided with a Luer connector connected to the drug cavity 27 through the drug inlet check valve 12. Further, the Luer connector can be connected to the liquid storage device through a hose. The drug inlet check valve 12 and the Luer connector are generally connected by a hose, but can also be connected by a non-hose connection. The liquid storage device can provide drug solution or cleaning solution for the needle-free syringe.

[0059] In some embodiments, the injection housing 11 is generally a plastic housing, and the spring housing 9 is also generally a plastic housing.

[0060] In some embodiments, the injection housing 11 and the spring housing 9 are fixedly connected or integrally formed, and the solid connection is such as screw connection, welding, etc.

[0061] In some embodiments, a complete machine housing is also included for installing the main body of the above-mentioned syringe. A main control panel and a display screen are also provided at the complete machine housing. A power supply can be provided at the handle of the complete machine housing. The power supply is a quick-plug battery or an external mobile battery.

[0062] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0063] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A needle-free syringe, characterized in that: It includes an injection push rod, a spring pull rod, a power spring and a pushing device. The injection push rod moves forward to compress the injection cavity and moves backward to expand the injection cavity. The front end of the spring pull rod is connected to the rear end of the injection push rod. The power spring abuts against the spring pull rod to prevent the injection push rod from moving backward. The pushing end of the pushing device is used to drive the spring pull rod to move backward and put the power spring in an elastic compression state.

2. The needle-free injector according to claim 1, characterized in that: The pushing device includes a driving motor and a cam structure installed on the main shaft of the driving motor. The rear end of the spring pull rod has a camshaft seat abutting against the wheel surface of the cam structure; the cam structure has a spiral wheel surface and an axial extension structure connecting the two ends of the spiral wheel surface.

3. The needle-free injector according to claim 2, characterized in that: The pushing device includes a motor base, the driving motor is installed on the motor base, and the cam structure is rotatably installed on the motor base; a magnet is provided on the cam structure; and a Hall sensor is also included which is relatively fixed to the motor base to stop the driving motor from rotating when the magnet is detected to be approaching.

4. The needle-free injector according to claim 3, characterized in that: The radial outer side of the connecting tube portion at the front end of the cam structure is matched with the motor seat through a bearing, and the connecting tube portion is inserted forward into the motor seat; the rear end of the connecting tube portion abuts against the motor seat through a gasket, and the front end abuts against the motor seat through a locking nut sleeved on the outside and threadedly connected for axial fixation; the wheel surface portion of the cam structure is arranged at the rear end of the connecting tube portion; the main shaft of the driving motor is inserted into the inner hole of the connecting tube portion and fixed therein by a radially extending pin.

5. The needle-free injector according to any one of claims 1 to 4, characterized in that: It also includes a spring housing, which has a spring cavity for accommodating the spring pull rod, the rear end of the spring pull rod is slidably matched with the cavity wall of the spring cavity, the front end of the spring pull rod is sleeved and fixed with a guide ring, the outer periphery of the guide ring is slidably matched with the cavity wall of the spring cavity, the power spring is sleeved on the spring pull rod, the front end of the power spring is fixedly connected to the guide ring, and the rear end of the power spring is fixedly mounted on the inner protrusion inside the spring cavity.

6. The needle-free injector according to any one of claims 1 to 4, characterized in that: It also includes an injection shell, the injection push rod includes an injection rod portion and a driving rod portion which are sequentially arranged along the injection direction, the injection rod portion slidingly cooperates with the medicine cavity of the injection shell along the front-to-back direction, and the driving rod portion extends into the medicine cavity; the injection rod portion and the driving rod portion are connected by a flexible structure to transmit force in the front-to-back direction, and have a relative range of motion of a predetermined size in a direction perpendicular to the front-to-back direction.

7. The needle-free injector according to claim 6, characterized in that: The flexible structure includes a clamping protrusion and a clamping groove that limits the forward and backward movement of the clamping protrusion. A gap is formed between the neck of the clamping protrusion and the avoidance opening of the groove wall on one side of the clamping groove so that relative movement in the vertical direction of the forward and backward direction is possible; one of the clamping protrusion and the clamping groove is arranged on the injection rod part, and the other is arranged on the driving rod part.

8. The needle-free injector according to claim 7, characterized in that: The front end of the medicine cavity has a medicine outlet, and the medicine outlet is provided with a nozzle; the outside of the nozzle has a protruding trigger stopper; the trigger stopper is connected to the injection shell through an elastic member; a proximity switch is provided on the injection shell to respond when the trigger stopper moves relative to the injection shell to extend the nozzle.

9. The needle-free injector according to claim 7, characterized in that: The injection housing is provided with a Luer connector which is connected to the medicine cavity through a medicine inlet one-way valve.

10. The needle-free injector according to claim 9, characterized in that: The Luer connector is connected to the liquid storage device through a hose.

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