A device for perfusion administration of mastitis to a cow with pressure feedback

Abstract

The application discloses a dairy cow mastitis perfusion drug delivery device with pressure feedback, and belongs to the technical field of veterinary medical instruments. The device comprises a needle cylinder, a drug injection catheter, a one-way valve, a piston assembly, a push rod and a pressure feedback mechanism. The pressure feedback mechanism comprises a containing cavity arranged on the piston assembly, a pressure receiving part movably matched with the containing cavity, an elastic reset part, an expansion part arranged on the outer periphery of the piston assembly and a fluid channel connecting the containing cavity and the expansion part. When the perfusion resistance increases, the pressure receiving part is compressed by the reaction force of the drug liquid, the elastic reset part is forced to expand radially and press against the inner wall of the needle cylinder, and the fluid back pressure is converted into the tactile resistance feedback of the operator. The one-way valve is used for preventing backflow, and a sealing film can be selectively arranged to isolate the drug liquid area from the pressure feedback mechanism. The trigger threshold is adjusted through a sensitivity fine adjustment mechanism, abnormal pressure can be prompted in real time during the perfusion process, and mechanical damage to the mammary gland tissue of the dairy cow is avoided.

Description

Technical Field

[0001] This invention relates to the field of veterinary medical device technology, and more specifically, to an infusion drug delivery device for the treatment of mastitis in dairy cows. Background Technology

[0002] Mastitis in dairy cows is one of the most common diseases in dairy farming. Clinical treatment often involves intra-teeth infusion: the operator uses a syringe to directly infuse medication into the milk cisterns through the teat canal. The standard procedure uses a standard syringe consisting of a syringe barrel, piston, and plunger; the operator manually pushes the plunger to inject the medication into the milk cisterns through the teat canal.

[0003] However, when using the aforementioned conventional syringe for infusion, the operator can only roughly judge the injection resistance by feel, making it difficult to accurately obtain information about the pressure inside the breast cisterns. When the nipple duct is partially blocked, the breast cisterns are nearly full, or the breast tissue is significantly swollen due to inflammation, the reverse water pressure inside the breast cisterns may rise abnormally. If the operator continues to inject with the usual force at this time, the medication cannot be effectively absorbed and will continue to accumulate in the breast tissue, easily causing mechanical tearing of the breast tissue or aggravating inflammatory damage, affecting the treatment effect or even causing irreversible damage. Therefore, existing conventional infusion devices have the shortcoming of not being able to provide the operator with real-time and accurate feedback on breast cisternives pressure. Summary of the Invention

[0004] The purpose of this invention is to overcome the aforementioned shortcomings of the prior art and provide a pressure feedback infusion drug delivery device for dairy cow mastitis. This device can automatically convert fluid pressure into a change in mechanical resistance that the operator can perceive when abnormal back pressure occurs at the end of the infusion catheter, providing tactile feedback to alert the operator to stop forced drug delivery, thereby protecting the cow's mammary gland tissue.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A pressure feedback infusion drug delivery device for bovine mastitis, comprising: A syringe with a drug injection catheter connected to its front end; A one-way valve is provided between the fluid passage of the syringe and the injection catheter, and is configured to restrict the liquid to flow only from the syringe to the injection catheter in one direction. The piston assembly is slidably fitted inside the syringe. A push rod, the front end of which is connected to the piston assembly, is used to drive the piston assembly to perform axial reciprocating motion within the syringe; and The pressure feedback mechanism is configured to apply radial frictional resistance to the inner wall of the syringe when the fluid back pressure at the front end of the syringe increases.

[0006] The pressure feedback mechanism includes: a accommodating cavity disposed on the piston assembly, a pressure receiving member movably fitted to the side of the accommodating cavity facing the liquid outlet end, an expansion member disposed on the outer periphery of the piston assembly, a fluid channel connecting the accommodating cavity and the expansion member, and an elastic reset member disposed between the pressure receiving member and the accommodating cavity.

[0007] When the infusion resistance increases, the pressure-bearing component moves backward under the reaction force of the drug solution and compresses the elastic reset component, forcing the fluid in the accommodating cavity to enter the expansion component through the fluid channel, thereby driving the expansion component to expand outward and press against the inner wall of the syringe.

[0008] Furthermore, the piston assembly includes a piston; the receiving cavity is a pressure feedback cavity opened at the front end of the piston body; the pressure-receiving component is a piston cover movably fitted inside the pressure feedback cavity; the elastic reset component is a spring disposed between the piston cover and the bottom of the pressure feedback cavity; the expansion component is a resistance airbag ring-fitted on the rear extension of the piston, wherein the outer diameter of the resistance airbag is smaller than the inner diameter of the syringe under normal conditions, and a radial gap is left between the two; the fluid channel is a gas guiding channel opened inside the piston body.

[0009] Furthermore, it also includes a sensitivity fine-tuning mechanism, which includes a fine-tuning top plate movably disposed outside the push rod, the front end face of the fine-tuning top plate abutting the rear side of the resistance airbag; the fine-tuning top plate is configured to axially squeeze the resistance airbag under external force to change the initial state of the resistance airbag before lateral expansion, thereby changing the threshold that needs to be overcome to trigger feedback under the same front back pressure.

[0010] Furthermore, an adjusting sleeve is coaxially sleeved on the outer side of the push rod, and the inner end of the adjusting sleeve is movably sleeved on the fine-tuning top plate; by rotating or pushing and pulling the adjusting sleeve, it is displaced along the axial direction of the push rod, thereby driving the fine-tuning top plate to move back and forth.

[0011] Furthermore, a rear cover is installed at the rear end of the syringe, and a through hole is provided in the center of the rear cover. The push rod and the adjusting sleeve extend through the through hole to the outside of the syringe. Multiple guide holes are arranged in a circumferential array on the side of the piston facing the fine-tuning top plate, and multiple guide posts are correspondingly arranged on the side of the fine-tuning top plate facing the piston. The guide posts are slidably fitted into the corresponding guide holes to restrict the circumferential rotation of the fine-tuning top plate.

[0012] The fine-tuning top plate can also be threaded onto the push rod. A drive stop is provided on the end face of the fine-tuning top plate facing the rear cover, and a corresponding fixed stop is provided on the rear cover. When the push rod is pulled outward, the drive stop and the fixed stop are misaligned and abut against each other. When the push rod is rotated, the drive stop and the fixed stop are abutted and limited, and the fine-tuning top plate and the push rod rotate relative to each other. The position of the fine-tuning top plate on the push rod is changed by the thread, thereby compressing the resistance airbag.

[0013] Furthermore, the piston is covered with a sealing membrane on the side facing the liquid outlet; the outer edge of the sealing membrane is sealed to the piston, and the piston cover and the opening of the pressure feedback chamber are isolated inside the sealing membrane; when the fluid back pressure increases, the external fluid compresses the sealing membrane to undergo elastic deformation, and then drives the piston cover to overcome the spring force and retract into the pressure feedback chamber through the sealing membrane, thereby achieving physical isolation between the liquid area and the pressure feedback mechanism.

[0014] Furthermore, a sealing ring is embedded on the outer peripheral surface of the piston assembly, and the piston assembly maintains a sliding sealing fit with the inner wall of the syringe through the sealing ring.

[0015] Furthermore, the sealed space enclosed by the accommodating cavity, the fluid channel, and the expansion member is pre-filled with an incompressible working medium; the working medium is preferably medical-grade silicone oil or a physiologically compatible liquid, so that the minute displacement of the piston cover is instantly converted into the expansion deformation of the resistance airbag, reducing feedback delay.

[0016] Compared with existing technologies, this invention has the following beneficial effects: First, tactile pressure warning: When blockage, overfilling, or poor absorption occurs inside the breast cavity, leading to an abnormal increase in reverse pressure, the reaction force of the medication on the piston tip is transmitted to the piston cap through the sealing membrane. The piston cap overcomes the spring and compresses the pressure feedback chamber, pushing the medium inside into the resistance airbag through the air guide channel. This causes the resistance airbag to expand radially and compress the inner wall of the syringe. The operator can immediately sense a significant increase in injection resistance at the plunger, receiving intuitive feedback on the abnormal pressure, thereby promptly reducing the infusion rate or stopping the injection to avoid mechanical damage to breast tissue.

[0017] Second, physical isolation between the drug solution area and the mechanical feedback area: by completely wrapping the piston cover and the opening of the pressure feedback chamber with a sealing film, the drug solution can be prevented from seeping into the interior of the mechanism along the moving gap between the piston cover and the pressure feedback chamber, thereby ensuring the sensitivity and service life of the mechanism, and preventing drug waste and internal contamination of the device, which meets the stringent requirements of veterinary clinical practice for sterility and cross-contamination prevention of instruments.

[0018] Third, the feedback sensitivity is adjustable: by rotating the adjusting sleeve (or axially pushing and pulling to lock), the fine-tuning top plate can be moved back and forth, allowing the resistance bladder to be pre-compressed before infusion, changing its initial volume and initial radial position before lateral expansion. Therefore, under the same front-end back pressure conditions, only a small amount of medium needs to enter the resistance bladder to rapidly expand radially and grip the inner wall of the syringe, significantly reducing the threshold required to trigger feedback. This adjustable capability provides customized application options for different breeds of dairy cows, different disease stages, and different viscosities of medications.

[0019] Fourth, one-way backflow prevention: A one-way valve is installed between the syringe outlet and the injection tubing. This effectively prevents the injected medication or inflammatory secretions from flowing back into the syringe when the device is withdrawn or the injection is stopped, thus avoiding cross-infection and waste of medication. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of a pressure feedback infusion drug delivery device for mastitis in dairy cows according to the present invention. Figure 2 This is a schematic diagram of the internal cross-sectional structure of the present invention; Figure 3 for Figure 2 Enlarged structural diagram of section A in the middle; Figure 4 A schematic diagram of another implementation of the sensitivity fine-tuning mechanism; Figure 5 A partial cross-sectional view of another embodiment of the sensitivity fine-tuning mechanism; Figure 6 This is a schematic diagram of the emulsion tank injection operation of the present invention.

[0021] Explanation of reference numerals in the attached diagram: 1—syringe; 2—injection tubing; 3—one-way valve; 4—piston; 5—pressure feedback chamber; 6—piston cap; 7—spring; 8—resistance airbag; 9—air guide channel; 10—fine-tuning top plate; 11—push rod; 12—adjusting sleeve; 13—rear cover; 15—sealing ring; 16—drive stop; 17—fixed stop; 18—threaded section. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Example 1: As Figure 1-3As shown, this embodiment of the invention provides a pressure feedback infusion drug delivery device for dairy cow mastitis, which mainly consists of three parts: an injection component, a pressure feedback mechanism, and a sensitivity fine-tuning mechanism.

[0024] Injection assembly: includes a syringe 1, an injection catheter 2, a one-way valve 3, a piston 4, a push rod 11, and a rear cover 13. The syringe 1 is preferably made of a transparent medical polymer material (e.g., polycarbonate PC or polypropylene PP), with graduations on its outer wall for the operator to observe the remaining medication level in real time. The front end of the syringe 1 is the dispensing end, to which the injection catheter 2 is connected and installed. The front end of the injection catheter 2 is designed with a rounded and flexible blunt tip structure to allow for non-invasive passage through the cow's teat sphincter into the milk trough, avoiding damage to the inner wall of the teat. A one-way valve 3 is integrated between the dispensing end of the syringe 1 and the fluid channel of the injection catheter 2. The one-way valve 3 is preferably a duckbill valve or an umbrella-shaped silicone valve, whose conduction direction allows medication to flow unidirectionally from the syringe 1 to the injection catheter 2, thereby preventing backflow of liquid or medication from the milk trough when the device is withdrawn or injection is stopped, thus avoiding cross-infection.

[0025] Piston 4 is slidably fitted inside syringe 1. A sealing ring 15 (e.g., a medical-grade nitrile rubber or silicone O-ring) is nested on the outer circumference of piston 4. Piston 4 maintains sliding and sealing contact with the inner wall of syringe 1 through the sealing ring 15 to ensure that no medication leaks along the outer circumference of the piston during injection. A rear cover 13 is installed at the rear opening of syringe 1 for sealing. Push rod 11 passes through the central perforation of the rear cover 13, and the front end of push rod 11 is fixedly connected to piston 4. The operator can drive piston 4 to reciprocate axially inside syringe 1 by pushing push rod 11 from the outside.

[0026] Pressure Feedback Mechanism: The core innovation of this invention lies in the pressure feedback mechanism integrated onto the piston 4. A pressure feedback chamber 5 (i.e., a receiving cavity) is formed inwardly at the front end of the piston 4 body, with the opening of this chamber facing the liquid outlet. A piston cover 6 (i.e., a pressure-receiving component) is movably fitted within the pressure feedback chamber 5, and a spring 7 (i.e., an elastic reset component) abuts against the rear side of the piston cover 6 and the bottom of the pressure feedback chamber 5. Under normal conditions, the spring 7 lifts the piston cover 6, causing a portion of it to protrude beyond the opening of the pressure feedback chamber 5.

[0027] The piston 4 has a resistance airbag 8 (i.e., an expansion element) surrounding its extended section at the rear. The resistance airbag 8 is preferably made of highly elastic medical rubber or polyurethane elastomer. Under normal conditions, the outer diameter of the resistance airbag 8 is slightly smaller than the inner diameter of the syringe 1, with an appropriate radial gap between them to prevent frictional resistance. The piston 4 has an internal air channel 9 (i.e., a fluid channel). One end of the air channel 9 connects to the bottom of the pressure feedback chamber 5, and the other end connects to the inner cavity of the resistance airbag 8.

[0028] To physically isolate the medication area from the pressure feedback mechanism's movement gap, an elastic sealing film is placed over the medication-facing side of piston 4. The sealing film is preferably a medical-grade ultra-thin silicone film, whose outer edge is completely sealed to the piston 4 body via ultrasonic welding or a pressure ring method, thus completely enclosing the piston cap 6 and the opening of the pressure feedback chamber 5 inside the sealing film. During medication injection, reverse hydraulic pressure is transmitted to the piston cap 6 by causing the sealing film to elastically deform, preventing medication from seeping into the mechanism through the gap between the piston cap 6 and the pressure feedback chamber 5.

[0029] The working process of the pressure feedback mechanism is as follows: Under normal infusion conditions (unobstructed flow in the milk pool and normal absorption), the operator pushes the push rod 11, and the piston 4 moves forward as a whole to complete the injection. At this time, the reaction force of the liquid at the front end on the piston 4 is less than the preload of the spring 7. The piston cover 6 remains in place under the support of the spring 7, the resistance airbag 8 does not inflate, and the operator feels a smooth and easy injection.

[0030] When an abnormal feedback state occurs (severe adhesion and blockage inside the teat duct, or a sudden increase in internal pressure due to the milk trough being full of medication), continued injection by the operator will cause a sharp increase in the reaction force of the liquid at the tip of the syringe 1 against the piston 4. When this reverse water pressure exceeds the elastic force of the spring 7, the sealing membrane deforms under pressure and pushes the piston cap 6 backward into the pressure feedback chamber 5. The backward movement of the piston cap 6 compresses the volume of the pressure feedback chamber 5, forcing the pre-filled gas or incompressible liquid inside into the resistance bladder 8 through the air passage 9. The resistance bladder 8 thus expands radially, its outer wall pressing tightly against the inner wall of the syringe 1, generating significant frictional resistance. At this time, the operator will immediately feel a significant increase in the pushing force on the push rod 11 (i.e., a sharp increase in the resistance to piston movement), thus directly obtaining physical feedback on the medication infusion pressure, reminding the operator to reduce the infusion rate or stop injection, thereby protecting the cow's mammary gland tissue from irreversible water pressure tearing damage.

[0031] Example 2: Since dairy cows of different breeds and with different disease stages have different tolerance to pressure in their udders, and the viscosity of medications from different manufacturers varies, this example further incorporates a sensitivity fine-tuning mechanism on the rear side of the resistance airbag 8.

[0032] A fine-tuning top plate 10 is provided on the rear side of the resistance airbag 8, with its surface abutting against the rear side of the resistance airbag 8. An adjusting sleeve 12 is coaxially sleeved on the outside of the push rod 11, extending through the rear cover 13 of the syringe 1 to the outside of the syringe. The inner end of the adjusting sleeve 12 is movably connected to the fine-tuning top plate 10, allowing relative rotation but limiting their relative axial position. The adjusting sleeve 12 and the push rod 11 can be threaded or axially push-pull and locked snap-fit.

[0033] During operation, the operator rotates or pushes / pulls the adjusting sleeve 12, causing it to move axially along the push rod 11, which in turn moves the fine-tuning top plate 10 back and forth. When the fine-tuning top plate 10 moves forward, it exerts axial pressure on the resistance airbag 8, reducing its initial internal volume and generating a slight radial pre-expansion. In this pre-adjusted state, when encountering the same reverse resistance pressure, only a very small amount of medium needs to enter the resistance airbag 8 through the air guide channel 9 to rapidly expand it radially and tighten it against the inner wall of the syringe 1, achieving the function of "rapidly providing resistance and reducing the preset feedback pressure threshold." This allows for flexible adjustment of the tactile warning sensitivity based on the specific disease course of the dairy cow and the viscosity of the medication. To accurately adjust and change the pressure feedback tactile warning sensitivity, corresponding markers can be set. When adjusting the fine-tuning top plate 10, the tactile warning sensitivity can be controllably adjusted by aligning it with the corresponding marker. Figure 3 As shown, the corresponding pressure feedback value is marked according to the distance (such as d1, d2) of the movement of the fine-tuning top plate 10, forming three gears A, B, and C.

[0034] To prevent the fine-tuning top plate 10 from rotating along with the adjusting sleeve 12 and thus wearing out the airbag, the piston 4 has multiple guide holes arranged in a circumferential array on its side facing the fine-tuning top plate 10. Correspondingly, guide posts are provided on the side of the fine-tuning top plate 10 facing the piston 4, and these guide posts are slidably fitted into the guide holes. This structure ensures that when the adjusting sleeve 12 is rotated, the fine-tuning top plate 10 only undergoes pure axial translation and does not rotate circumferentially.

[0035] To reduce the transmission delay of pressure feedback, this embodiment preferably uses medical-grade silicone oil or a physiologically compatible liquid as the working medium within the sealed space enclosed by the pressure feedback chamber 5, the air guide channel 9, and the resistance airbag 8. Since liquids are incompressible, the minute displacement of the piston cover 6 can be instantly converted into the expansion deformation of the resistance airbag 8, achieving zero-delay feedback compared to air. Of course, this invention also supports using air as the working medium, which can be selected according to sensitivity requirements.

[0036] Example 3: The present invention also provides another embodiment of the sensitivity fine-tuning mechanism, specifically as follows: Figure 4 and Figure 5 As shown.

[0037] The difference between this embodiment and embodiment two is that the adjusting sleeve 12 is omitted, and a threaded section 18 is provided at the root of the push rod 11 (the part near the piston). Instead, the fine-tuning top plate 10 and the push rod 11 are directly threaded together, and the switching between the injection state and the fine-tuning state is achieved by the misalignment of the drive stop 16 and the fixed stop 17.

[0038] Specifically, a rear cover 13 is installed at the rear end of the syringe 1, and a through hole is provided in the center of the rear cover 13 for the push rod 11 to pass through. The fine-tuning top plate 10 is threaded onto the outer periphery of the push rod 11, and its front end face abuts against the rear side of the resistance airbag 8. A drive stop 16 is provided on the end face of the fine-tuning top plate 10 facing the rear cover 13, and a fixed stop 17 is correspondingly provided on the side of the rear cover 13 facing the fine-tuning top plate 10. The drive stop 16 and the fixed stop 17 are staggered from each other in the circumferential direction of the push rod 11.

[0039] Under normal injection conditions, the drive stop 16 and the fixed stop 17 are in a circumferentially misaligned position and do not contact each other. The fine-tuning top plate 10 moves axially back and forth along with the push rod 11, which will not interfere with the normal injection of the piston 4.

[0040] When fine-tuning the feedback sensitivity is required, the operator first pulls the push rod 11 outward a certain distance towards the rear end of the syringe 1, causing the drive stop 16 on the fine-tuning top plate 10 to axially pass over and abut against the fixed stop 17 on the rear cover 13, forming a misaligned and abutting limiting relationship. Then, the operator rotates the push rod 11. Because the drive stop 16 is abutted and limited by the fixed stop 17, the fine-tuning top plate 10 cannot rotate circumferentially with the push rod 11, thus generating relative rotation between the push rod 11 and the fine-tuning top plate 10. This relative rotation is converted into axial displacement of the fine-tuning top plate 10 along the push rod 11 via the threaded joint between them, causing the fine-tuning top plate 10 to move forward or backward towards the resistance airbag 8, thereby applying axial compression or releasing compression to the resistance airbag 8, changing the initial volume and initial radial position of the resistance airbag 8, and achieving fine-tuning of the feedback sensitivity.

[0041] This embodiment eliminates the adjusting sleeve 12, resulting in a more compact structure with fewer parts. The mechanical contact between the drive stop 16 and the fixed stop 17 enables reliable switching between the injection and fine-tuning states, preventing accidental rotation of the fine-tuning top plate 10 during injection. This makes operation intuitive and highly reliable. Simultaneously, the threaded pair between the fine-tuning top plate 10 and the push rod 11 provides continuous axial displacement, facilitating stepless fine adjustment of the pre-pressure of the resistance airbag 8 to meet the varying feedback threshold requirements of different breeds, disease stages, and drug viscosities.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pressure feedback infusion drug delivery device for dairy cow mastitis, comprising a syringe (1), an injection catheter (2), and a piston assembly; the front end of the syringe (1) is connected to the injection catheter (2), and the piston assembly is slidably fitted inside the syringe (1); a push rod (11) is provided on the piston assembly, and the push rod (11) is used to drive the piston assembly to perform axial reciprocating motion inside the syringe (1); Its features are, It also includes a pressure feedback mechanism, which includes: a accommodating cavity disposed on the piston assembly, a pressure receiving member movably fitted to the accommodating cavity on the side facing the liquid outlet end, an expansion member disposed on the outer periphery of the piston assembly, a fluid channel connecting the accommodating cavity and the expansion member, and an elastic reset member disposed between the pressure receiving member and the accommodating cavity; When the infusion resistance increases, the pressure-bearing component moves backward under the reaction force of the liquid and compresses the elastic reset component, forcing the fluid in the accommodating cavity to enter the expansion component through the fluid channel, thereby driving the expansion component to expand outward and press against the inner wall of the syringe (1), increasing the movement resistance of the piston assembly in the syringe (1), and thus feeding back to the operator that the internal pressure has increased.

2. The pressure feedback infusion drug delivery device for dairy cow mastitis according to claim 1, characterized in that, The piston assembly includes a piston (4); the receiving cavity is a pressure feedback cavity (5) opened at the front end of the piston (4) body; the pressure receiving component is a piston cover (6) movably fitted inside the pressure feedback cavity (5); the elastic reset component is a spring (7) disposed between the piston cover (6) and the bottom of the pressure feedback cavity (5); the expansion component is a resistance airbag (8) ringed on the rear extension of the piston (4), and under normal conditions, the outer diameter of the resistance airbag (8) is smaller than the inner diameter of the syringe (1), with a radial gap between them; the fluid channel is a gas guiding channel (9) opened inside the piston (4) body.

3. The pressure feedback infusion drug delivery device for dairy cow mastitis according to claim 2, characterized in that, It also includes a sensitivity fine-tuning mechanism, which includes a fine-tuning top plate (10) movably disposed outside the push rod (11), the front end face of the fine-tuning top plate (10) abutting the rear side of the resistance airbag (8); the fine-tuning top plate (10) is configured to axially squeeze the resistance airbag (8) under external force to change the initial state of the resistance airbag (8) before lateral expansion.

4. The pressure feedback infusion drug delivery device for dairy cow mastitis according to claim 3, characterized in that, An adjusting sleeve (12) is coaxially sleeved on the outer side of the push rod (11). The inner end of the adjusting sleeve (12) is movably sleeved on the fine-tuning top plate (10). The adjusting sleeve (12) drives the fine-tuning top plate (10) to move back and forth by axial displacement relative to the push rod (11). The adjusting sleeve (12) and the push rod (11) are threaded together, or the adjusting sleeve (12) and the push rod (11) are axially pushable and lockable by a snap-fit ​​connection.

5. The pressure feedback infusion drug delivery device for dairy cow mastitis according to claim 4, characterized in that, The syringe (1) is fitted with a rear cover (13) at its rear end. The rear cover (13) has a perforation at its center. The push rod (11) and the adjusting sleeve (12) extend through the perforation to the outside of the syringe (1). The piston (4) has multiple guide holes arranged in a circular array on the side facing the fine-tuning top plate (10). The fine-tuning top plate (10) has multiple guide posts arranged on the side facing the piston (4). The guide posts slide and fit into the corresponding guide holes to restrict the fine-tuning top plate (10) from rotating circumferentially.

6. The pressure feedback infusion drug delivery device for dairy cow mastitis according to claim 3, characterized in that, The syringe (1) has a rear cover (13) installed at its rear end. The fine-adjustment top plate (10) is threaded onto the push rod (11). A drive stop (16) is provided on the end face of the fine-adjustment top plate (10) facing the rear cover (13). A corresponding fixed stop (17) is provided on the rear cover (13). The push rod (11) is pulled outward to make the drive stop (16) and the fixed stop (17) misaligned and abut against each other. The push rod (11) is rotated, and the drive stop (16) and the fixed stop (17) abut against each other to limit the movement. The fine-adjustment top plate (10) and the push rod (11) rotate relative to each other. The fine-adjustment top plate (10) changes its position on the push rod (11) through the thread, thereby squeezing the resistance airbag (8).

7. The pressure feedback infusion drug delivery device for dairy cow mastitis according to claim 1, characterized in that, A sealing ring (15) is embedded on the outer peripheral surface of the piston assembly, and the piston assembly maintains a sliding sealing fit with the inner wall of the syringe (1) through the sealing ring (15).

8. A pressure feedback infusion drug delivery device for dairy cow mastitis according to claim 2, characterized in that, The sealed space enclosed by the accommodating cavity, the fluid channel, and the expansion member is pre-filled with an incompressible working medium; the working medium is medical-grade silicone oil or a physiologically compatible liquid.

9. A pressure feedback infusion drug delivery device for dairy cow mastitis according to claim 1, characterized in that, A one-way valve (3) is provided between the fluid passage of the syringe (1) and the injection catheter (2). The one-way valve (3) restricts the liquid to flow only from the syringe (1) to the injection catheter (2).

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