A micro medical infusion device

Abstract

This invention discloses a miniature medical infusion device, relating to the field of medical device technology. The device includes a base, a top cover, a drug reservoir, a piston, a screw, a double-action ratchet drive mechanism, a counting sensor mechanism, a rotation sensor mechanism, a liquid level sensor mechanism, and a controller. The double-action ratchet drive mechanism uses a shape memory alloy wire as a power source. The shape memory alloy wire contracts and expands within one energizing cycle, driving the piston in linear motion via the double-action ratchet and screw, thus achieving continuous drug infusion. The device integrates sensing functions; the counting sensor mechanism, rotation sensor mechanism, and liquid level sensor mechanism utilize the infusion motion of the device itself to record and detect the number of drives, ratchet rotation angle, and piston position, eliminating the need for additional sensors. This device is small in size, provides stable and efficient infusion, has a long service life, and is free from electromagnetic interference, making it particularly suitable for portable medical infusion devices, achieving continuous, accurate, and reliable delivery of therapeutic fluids.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, specifically to a miniature infusion device based on shape memory alloy wire driven for the continuous delivery of therapeutic fluids to a patient. Background Technology

[0002] Portable infusion devices, such as those used for subcutaneous insulin infusion in diabetic patients, have become important medical devices. These devices typically include a reservoir, electromechanical pumping unit, control system, and infusion tubing, enabling continuous and precise infusion at variable flow rates, thereby improving treatment outcomes and reducing side effects.

[0003] Existing portable infusion devices mostly employ complex electromechanical systems (such as micromotors, gear trains, sensors, and electronic control units) to achieve fluid delivery and metering. While functionally complete, these devices suffer from significant drawbacks: complex structure, high manufacturing costs, large size and weight, relatively poor mechanical stability, and susceptibility to damage. Furthermore, the complexity of the system necessitates greater maintenance and specialized nursing knowledge. These factors collectively limit the widespread application of such devices, preventing many patients from benefiting from portable continuous subcutaneous infusion therapy.

[0004] Currently, there are also portable infusion devices that use shape memory alloy wires for driving, but the transmission mechanism can only feed once for each extension and retraction of the shape memory alloy wire, resulting in low infusion efficiency and short service life of the shape memory alloy wire.

[0005] The double-acting ratchet mechanism, because both strokes of its reciprocating oscillation are used for driving and there is no idle stroke, has twice the output speed of the single-acting ratchet mechanism at the same input oscillation frequency, resulting in high working efficiency. Compared to the impactful "drive-stop-drive-stop" motion of the single-acting ratchet mechanism, the double-acting ratchet mechanism has a shorter output motion interval and almost no pause time, making the overall motion smoother and reducing the inertial impact caused by intermittent starts and stops, resulting in smoother motion. Summary of the Invention

[0006] The present invention aims to solve the above-mentioned problems existing in the prior art and provide a miniature medical infusion device to overcome the defects of existing infusion devices such as high cost, complex structure, large size and weight, poor stability, low infusion efficiency and short life of shape memory alloy wire.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A miniature medical infusion device includes a base, a top cover, a drug reservoir, a piston, a screw, a double-action ratchet drive mechanism, a counting sensor mechanism, a rotation sensor mechanism, a liquid level sensor mechanism, and a controller.

[0009] The medicine storage tank is mounted on the base and is used to contain therapeutic liquid; the piston is disposed inside the medicine storage tank and can slide along its inner wall, and the piston is equipped with a sealing ring; one end of the screw is connected to the piston, and the other end is connected to the double-action ratchet drive mechanism; the double-action ratchet drive mechanism is used to drive the screw to make linear motion, thereby pushing the piston to discharge the liquid.

[0010] Further, the double-action ratchet drive mechanism includes: a ratchet, a rocker arm, a first pawl, a second pawl, a shape memory alloy wire, a return spring, a pulley assembly, and a power supply contact; the ratchet is rotatably mounted on the base, and the ratchet is threadedly connected to the screw. After the ratchet rotates, it drives the screw to move linearly along its axis through threaded transmission; the rocker arm is oscillatingly mounted on the base via a pivot; the first and second pawls are mounted at both ends of the rocker arm and engage with the ratchet to drive the ratchet to rotate in one direction; the shape memory alloy wire is wound around the pulley assembly, with one end connected to the rocker arm and the other end connected to the power supply contact; one end of the spring is fixed to a spring mounting column on the base, and the other end acts on the rocker arm, providing a return force opposite to the tension of the shape memory alloy wire; the power supply contact is used to provide current to the shape memory alloy wire.

[0011] Furthermore, the counting sensing mechanism includes a counter contact disposed on the base, and the rocker arm can contact or separate from the counter contact during the swinging process to form the on / off state of the counting circuit.

[0012] Furthermore, the rotary sensing mechanism includes a square hub disposed on the ratchet, a second electrode mounting base on the base, a second electrode contact, and a second electrode plate; the second electrode plate is mounted on the base via the second electrode mounting base, and the square hub rotates synchronously with the ratchet, which can periodically deform or reset the second electrode plate, thereby changing the contact state between the second electrode plate and the second electrode contact. By monitoring the number of times the circuit is switched on and off, the rotation angle of the ratchet can be determined.

[0013] Furthermore, the liquid level sensing mechanism includes a screw, a first electrode mounting base disposed on the base, a first electrode contact, and a first electrode plate; the first electrode plate is mounted on the base via the first electrode mounting base, and the end of the screw can act on the first electrode plate, pressing it to separate it from the first electrode contact, or releasing it to make it contact the first electrode contact. The position of the piston can be determined based on the on / off state of the liquid level sensing mechanism circuit.

[0014] Furthermore, the shape memory alloy wire is a nickel-titanium alloy wire.

[0015] Furthermore, the square hub is fixedly mounted on the ratchet.

[0016] Furthermore, the end of the screw has a conical chamfer for interacting with the first electrode plate of the liquid level sensing mechanism.

[0017] Furthermore, the rocker arm, the rotating shaft, and the counter contacts are all made of conductive material and connected to the circuit. The contact between the rocker arm and the counter contacts forms a circuit path to achieve counting.

[0018] Furthermore, the length of the first pawl is 4-6 mm, the length of the second pawl is 6-8 mm, the mounting hole spacing of the rocker arm is 7-9 mm, the number of teeth z of the ratchet is 20-40, and the module m is 0.5-1. The original length L0 of the spring is in the range of 6-10 mm, and the spring constant k is 32-190 N / m; the diameter d of the shape memory alloy wire is 0.044-0.06 mm, and the length l is 60-100 mm.

[0019] The present invention has the following beneficial effects:

[0020] 1. The dual-action ratchet drive mechanism in the miniature medical infusion device proposed in this invention employs a design that combines a dual-action ratchet mechanism with a compression spring, resulting in a device characterized by stable infusion, high efficiency, and long service life. Utilizing only a single shape memory alloy wire, each power cycle (on and off) causes the rocker arm to oscillate once, driving the ratchet to rotate twice in the same direction. This leads to higher output efficiency, a more stable overall infusion effect, and reduces the number of times the shape memory alloy wire is energized, thus extending the device's lifespan.

[0021] 2. This invention proposes a miniature medical infusion device that ingeniously utilizes the infusion motion of the device itself to achieve counting (number of drives) and position (piston position, ratchet rotation angle) detection, eliminating the need for additional complex sensors and further simplifying the system and circuitry. Specifically, for the counting sensing mechanism, a rocker arm is directly used as the moving contact of the circuit, forming an on / off circuit with the counter contact fixed on the base; for the rotation sensing mechanism, a square hub is directly fixed to the drive ratchet, and its rotation periodically presses / releases the second electrode plate, forming a circuit on / off state; for the liquid level sensing mechanism, the end geometry (conical chamfer) of the actuator screw is directly utilized, changing the pressure state on the first electrode plate when it reaches the end point, thereby triggering the circuit. By monitoring the number of on / off changes and the on / off state of the circuit, counting and position detection can be achieved.

[0022] 3. The miniature medical infusion device proposed in this invention employs a multi-pulley arrangement, enabling the shape memory alloy wire to achieve long-stroke winding within a limited space. This ensures sufficient contraction stroke while preventing the mechanism from expanding outwards, achieving efficient utilization of three-dimensional space and featuring small size and good stability. The drive, sensing, and transmission functions are integrated into a single design between the base and top cover, facilitating miniaturization and improving patient comfort and convenience. The simple mechanical structure, without complex electromechanical systems, reduces potential failure points and improves long-term stability and reliability.

[0023] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0024] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0025] Figure 1 This is an overall appearance drawing of the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of the present invention after the top cover is removed;

[0027] Figure 3 This is a schematic diagram of the structure of the present invention after removing the top cover and the medicine storage tank;

[0028] Figure 4 This is a top view of the present invention after removing the top cover and the medicine storage tank;

[0029] Figure 5 This is a schematic diagram of the double-action ratchet drive mechanism of the present invention after removing the top cover, medicine tank and base, which includes a counting sensor mechanism;

[0030] Figure 6 This is a schematic diagram of the liquid level sensing mechanism of the present invention;

[0031] Figure 7 , Figure 8 This is a left view of the principle of the liquid level sensing mechanism of the present invention (showing the untriggered and triggered states respectively).

[0032] Figure 9 , Figure 10 This is a schematic diagram of the principle of the rotary sensing mechanism of the present invention (showing the circuit open and closed states respectively).

[0033] Figure 11 This is a schematic diagram of the structure of the base of the present invention;

[0034] Figure 12This is a schematic diagram of the top cover of the present invention;

[0035] In the diagram, 1 is the base, 2 is the top cover, 3 is the sealing ring, 4 is the piston, 5 is the screw, 6 is the power supply contact, 7 is the shape memory alloy wire, 8 is the pulley block, 9 is the ratchet, 10 is the liquid level sensing mechanism, 11 is the rotary sensing mechanism, 12 is the spring mounting post, 13 is the spring plate, 14 is the spring, 15 is the rotating shaft, 16 is the counter contact, 17 is the rocker arm, 18 is the first pawl, 19 is the second pawl, 20 is the medicine storage tank, 21 is the spring mounting post, 801 is the pulley, 802 is the optical axis, 1001 is the first electrode mounting base, 1002 is the first electrode plate, 1003 is the first electrode contact, 1101 is the second electrode mounting base, 1102 is the second electrode plate, 1103 is the second electrode contact, and 1104 is the square hub. Detailed Implementation

[0036] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. This description is for illustrative purposes only and is not intended to limit the scope of protection of the present invention.

[0037] Reference Figures 1 to 12 The present invention provides a miniature medical infusion device, the main structure of which includes a base 1, a top cover 2, a medicine storage tank 20, a piston 4, a screw 5, a double-action ratchet drive mechanism, a counting sensor mechanism, a rotation sensor mechanism 11, and a liquid level sensor mechanism 10.

[0038] The device structure provided by this invention is shown in the figure. A medicine storage tank 20 is mounted on a base 1. A piston 4 is installed inside the medicine storage tank 20 and can slide within it. A sealing ring 3 is installed on the piston 4. A ratchet 9 is mounted on the base 1 and can rotate around its axis. The ratchet 9 and the screw 5 are connected by a thread. A rocker arm 17 is mounted on the base 1 via a rotating shaft 15 and can swing around the shaft 15. A counter contact 16 is mounted on the base 1 and can contact the rocker arm 17. A first pawl 18 and a second pawl 19 are respectively mounted on both sides of the rocker arm 17 and contact the ratchet 9. A spring plate 13 is mounted on the base 1 via a spring mounting post 12 and contacts the pawl 18. A spring 14 is mounted on the base 1 via a spring mounting post 21 and contacts the rocker arm 17. The pulley assembly 8 includes five sets of pulleys 801 and an optical shaft 802. The pulleys 801 are mounted on the base 1 and the end cap 2 via the optical shaft 802 and can rotate around the optical shaft 802. A shape memory alloy wire 7 is wound around a pulley 801, with one end connected to a rocker arm 17 and the other end connected to a power supply contact 6. The liquid level sensing mechanism 10 includes a first electrode plate 1002, a first electrode mounting base 1001, and a first electrode contact 1003. The rotation sensing mechanism 11 includes a second electrode plate 1102, a second electrode mounting base 1101, a second electrode contact 1103, and a square hub 1104. One end of the first electrode plate 1002 and the second electrode plate 1102 are respectively mounted on the base 1 via the first electrode mounting base 1001 and the second electrode mounting base 1101, and the other end contacts the first electrode contact 1003 and the second electrode contact 1104 respectively. The square hub 1104 is mounted on a ratchet 9 and rotates synchronously with the ratchet 9.

[0039] The double-action ratchet drive mechanism of this invention drives the double-action ratchet mechanism through a shape memory alloy wire 7 and a spring 14, and then the ratchet 9 drives the screw 5 and piston 4 to complete the liquid delivery. The shape memory alloy wire 7 is made of nickel-titanium alloy, which has a memory effect and is also conductive. When energized and heated, the shape memory effect of the metal is triggered, and the shape memory alloy wire 7 changes from an extended state to a contracted state. Subsequently, the power supply is lost, and the shape memory alloy wire 7 changes from a contracted state to an extended state after the temperature drops. The rocker arm 17, the rotating shaft 15, and the counter contact 16 are all conductive. When the shape memory alloy wire 7 is energized, the temperature rises, the shape memory alloy wire 7 contracts, pulls the rocker arm 17, the rocker arm 17 separates from the counter contact 16, the circuit is broken, the spring 14 is compressed, the rocker arm 17 drives the first pawl 18 to engage with the ratchet 9, driving the ratchet 9 to rotate one tooth pitch, while the second pawl 19 slides on the ratchet 9 one tooth pitch. When the shape memory alloy wire 7 is de-energized, its temperature drops, and it stretches, causing the rocker arm 17 to lose tension. At this point, the compressed spring 14 pushes the rocker arm 17 back to its original position, bringing it into contact with the counter contact 16, reconnecting the circuit and counting once. The rocker arm 17 then drives the second pawl 19 to engage with the ratchet wheel 9, causing the ratchet wheel to rotate one tooth pitch again. Simultaneously, the first pawl 18 slides one tooth pitch on the ratchet wheel 9. Due to the unidirectional nature of the double-action ratchet mechanism, the ratchet wheel 9 will not reverse direction during this process. One cycle of the shape memory alloy wire 7 being energized and de-energized enables the rocker arm 17 to complete one reciprocating swing, and through the first pawl 18 and the second pawl 19, drives the ratchet wheel 9 to rotate twice in one direction, reconnecting the counter circuit once and thus recording the number of rotations of the ratchet wheel 9.

[0040] When ratchet 9 rotates, it drives the square hub 1104 fixed to it to rotate synchronously. For example... Figure 9 As shown, when the edge of the square hub 1104 rotates to press against the second electrode plate 1102, the second electrode plate 1102 undergoes elastic deformation, separating from the second electrode contact 1103, and the circuit of the rotation sensing mechanism 11 is disconnected. Figure 10 As shown, when the plane of the square hub 1104 aligns with the second electrode plate 1102, the pressure is released, the second electrode plate 1102 elastically recovers and contacts the second electrode contact 1103, thus activating the circuit of the rotation sensing mechanism 11. The square hub 1104 rotates 90°, switching its state once, causing a change in the circuit's on / off state. By monitoring the number of circuit on / off changes, the number of 90° intervals traversed by the ratchet 9 can be determined, thereby enabling the measurement of the rotation angle.

[0041] The ratchet 9 and the screw 5 are connected by a thread. When the ratchet 9 rotates, it drives the screw 5 to move linearly along its axis through the threaded connection, thereby pushing the piston 4 on it to move inside the medicine storage tank 20, squeezing out the liquid inside the medicine storage tank 20, and completing the medicine delivery. By controlling the on / off cycle, the liquid delivery rate can be precisely controlled.

[0042] The end of screw 5 is chamfered into a conical shape. For example... Figure 6 , 7 As shown, when the liquid level in the piston does not reach the set value, the cylindrical surface of the screw 5 presses against the first electrode plate 1002, causing it to deform slightly. The first electrode plate 1002 then disconnects from the first electrode contact 1003, and the circuit of the liquid level sensing mechanism 10 is not connected. Figure 6 , 8 As shown, when the liquid level in the piston reaches the set value, the conical chamfered surface at the end of the screw contacts the first electrode plate 1002. The first electrode plate 1002 slowly returns to its original shape and contacts the first electrode contact 1003, thus activating the circuit of the liquid level sensing mechanism 10. Whether the liquid level in the piston has reached the set value can be determined by whether the circuit is activated. This signal can be used to indicate that the liquid in the medicine tank 19 is about to run out and needs to be replenished, realizing a simple liquid level endpoint detection function.

[0043] The controller controls the on / off state of the power supply contact 6. Current is output to the shape memory alloy wire 7 according to the required infusion rate. Simultaneously, the controller monitors the on / off signals of the counter contact 16 to record the number of drives, monitors the signal of the rotary sensing mechanism 11 to confirm whether mechanical movement has occurred, and monitors the signal of the liquid level sensing mechanism 10 to determine the liquid level status. These feedback signals can be used to implement closed-loop control, alarms (such as blockage, empty tank, mechanical failure), and other functions.

[0044] The present invention proposes a miniature medical infusion device whose movement process must meet certain mechanical and motion laws, and the specific calculation process will be given below.

[0045] The ratchet has z teeth and m module. The infusion rate is v mL / h. The pressure P1 required by the infusion device is equal to the tubing resistance, venous pressure, and hydrostatic pressure of the fluid column. The thrust required for the piston movement is F1.

[0046]

[0047] In the formula, P1 is the pressure that the infusion device needs to provide, and S1 is the cross-sectional area of ​​the piston.

[0048] The torque required for the lead screw to move is T.

[0049]

[0050] In the formula, F1 is the thrust generated by the lead screw, p is the lead of the lead screw, and η is the efficiency of the lead screw.

[0051] The required driving force F2 for the pawl

[0052]

[0053] In the formula, m is the module of the ratchet, and z is the number of teeth of the ratchet.

[0054] Spring constant k,

[0055]

[0056] In the formula, F3 is the spring pressure, L0 is the original length of the spring, and L is the length of the spring when compressed. Since the spring needs to drive the pawl, the spring pressure F3 must be greater than or equal to the driving force F2 required by the pawl.

[0057] The cross-sectional area S2 of the shape memory alloy wire

[0058]

[0059] In the formula, F4 is the residual tension of the shape memory alloy wire, and σ is the recovery stress of the shape memory alloy. Since the shape memory alloy wire needs to drive the ratchet and overcome the spring force, the residual tension of the shape memory alloy wire must be greater than or equal to the resultant force of the ratchet's required driving force F2 and the spring pressure F3.

[0060] The diameter d of the shape memory alloy wire,

[0061]

[0062] In the formula, S2 is the cross-sectional area of ​​the shape memory alloy wire.

[0063] Based on the above calculations, and considering the commonly used infusion rate v of 100~200 mL / h, and according to the device size requirements, the length of the first pawl of the double-acting ratchet is designed to be 4~6 mm, the length of the second pawl to be 6~8 mm, the pawl mounting hole spacing of the rocker arm to be 7~9 mm, the number of teeth z of the ratchet to be 20~40, and the module m to be 0.5~1. After verification using the above calculation formulas, the original length L0 of the spring is determined to be 6~10 mm, the spring constant k to be 32~190 N / m, the diameter d of the shape memory alloy wire to be 0.044~0.06 mm, and the length l to be 60~100 mm.

[0064] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0065] Example 1

[0066] A miniature medical infusion device includes a base, a top cover, a drug reservoir, a piston, a screw, a double-action ratchet drive mechanism, a counting sensor mechanism, a rotation sensor mechanism, a liquid level sensor mechanism, and a controller. The drug reservoir is mounted on the base, and the piston is disposed inside the drug reservoir and is slidable. One end of the screw is connected to the piston, and the other end is threadedly connected to the output part of the double-action ratchet drive mechanism. The double-action ratchet drive mechanism pushes the screw and piston to move axially along the drug reservoir to realize the infusion of the drug solution.

[0067] The double-action ratchet drive mechanism includes: a ratchet, a rocker arm, a first pawl, a second pawl, a shape memory alloy wire, a return spring, a pulley assembly, and a power supply contact. The ratchet is rotatably mounted on the base and is threadedly connected to the screw. The rocker arm is pivotally mounted on the base. The first and second pawls are mounted on the rocker arm and engage with the ratchet. The shape memory alloy wire is wound around the pulley assembly, with one end connected to the rocker arm and the other end connected to the power supply contact. One end of the return spring is fixed to a spring mounting post on the base, and the other end acts on the rocker arm, providing a return force opposite to the tension of the shape memory alloy wire. The power supply contact is used to supply current to the shape memory alloy wire.

[0068] The counting sensing mechanism includes a counter contact disposed on the base, and the rocker arm can contact or separate from the counter contact during the swinging process;

[0069] The rotary sensing mechanism includes a square hub disposed on the ratchet, a second electrode mounting base and a second electrode contact on the base, the second electrode plate being mounted on the base via the second electrode mounting base, and the square hub being able to act on the second electrode plate to make the second electrode plate contact or separate from the second electrode contact;

[0070] The liquid level sensing mechanism includes the screw, a first electrode mounting base disposed on the base, and a first electrode contact. The first electrode plate is mounted on the base through the first electrode mounting base. The end of the screw can act on the first electrode plate, causing the first electrode plate to contact or separate from the first electrode contact.

[0071] The selection and calculation of specific parameters are explained below.

[0072] Choose a ratchet with 20 teeth (z = 20) and a module (m = 1). The length of the first pawl is 4mm, the length of the second pawl is 6mm, and the pawl mounting hole spacing of the rocker arm is 7mm.

[0073] Normal saline was infused into a peripheral vein at a flow rate of 100 mL / h via a 24G indwelling needle. The calculated pressure required by the infusion device is P1 = 50 mmHg = 6.7 kPa.

[0074] The piston diameter is 20mm, and the thrust required for piston movement is... N.

[0075] Choose a standard trapezoidal leadscrew with a lead p = 2 mm and an efficiency η = 0.35. The driving torque of the leadscrew... =1.9 N·mm, meaning that a torque of 1.9 N·mm is required to drive the ratchet. The driving force required for the pawl. =0.19N.

[0076] Given a spring force F3 = 0.19 N, and a spring length L = 4 mm when compressed, choose a spring with an initial length L0 = 6~10 mm. Then, the spring constant... =32~95N / m.

[0077] Take the residual tensile force of the shape memory alloy wire N, the recovery stress σ of the shape memory alloy is 500 MPa, then the cross-sectional area = 0.00152mm²; diameter = 0.044mm.

[0078] The length l of the shape memory alloy wire can be changed by modifying the number of pulleys and the winding method of the shape memory alloy wire, and can be selected as 60mm.

[0079] Example 2

[0080] A miniature medical infusion device includes a base, a top cover, a drug reservoir, a piston, a screw, a double-action ratchet drive mechanism, a counting sensor mechanism, a rotation sensor mechanism, a liquid level sensor mechanism, and a controller. The drug reservoir is mounted on the base, and the piston is disposed inside the drug reservoir and is slidable. One end of the screw is connected to the piston, and the other end is threadedly connected to the output part of the double-action ratchet drive mechanism. The double-action ratchet drive mechanism pushes the screw and piston to move axially along the drug reservoir to realize the infusion of the drug solution.

[0081] The double-action ratchet drive mechanism includes: a ratchet, a rocker arm, a first pawl, a second pawl, a shape memory alloy wire, a return spring, a pulley assembly, and a power supply contact. The ratchet is rotatably mounted on the base and is threadedly connected to the screw. The rocker arm is pivotally mounted on the base. The first and second pawls are mounted on the rocker arm and engage with the ratchet. The shape memory alloy wire is wound around the pulley assembly, with one end connected to the rocker arm and the other end connected to the power supply contact. One end of the return spring is fixed to a spring mounting post on the base, and the other end acts on the rocker arm, providing a return force opposite to the tension of the shape memory alloy wire. The power supply contact is used to supply current to the shape memory alloy wire.

[0082] The counting sensing mechanism includes a counter contact disposed on the base, and the rocker arm can contact or separate from the counter contact during the swinging process;

[0083] The rotary sensing mechanism includes a square hub disposed on the ratchet, a second electrode mounting base and a second electrode contact on the base, the second electrode plate being mounted on the base via the second electrode mounting base, and the square hub being able to act on the second electrode plate to make the second electrode plate contact or separate from the second electrode contact;

[0084] The liquid level sensing mechanism includes the screw, a first electrode mounting base disposed on the base, and a first electrode contact. The first electrode plate is mounted on the base through the first electrode mounting base. The end of the screw can act on the first electrode plate, causing the first electrode plate to contact or separate from the first electrode contact.

[0085] The selection and calculation of specific parameters are explained below.

[0086] Select a ratchet with 40 teeth (z = 40) and a module (m = 0.5). The length of the first pawl is 6mm, the length of the second pawl is 8mm, and the pawl mounting hole spacing of the rocker arm is 9mm.

[0087] Normal saline was infused into a peripheral vein at a flow rate of 200 mL / h via a 24G indwelling needle. The calculated pressure required by the infusion device is P1 = 100 mmHg = 13.4 kPa.

[0088] The piston diameter is 20mm, and the thrust required for piston movement is... N.

[0089] Choose a standard trapezoidal leadscrew with a lead p = 2 mm and an efficiency η = 0.35. The driving torque of the leadscrew... =3.8 N·mm, meaning that a torque of 3.8 N·mm is required to drive the ratchet. The driving force required for the pawl. =0.38N.

[0090] Let the spring pressure F3 = 0.38N. The compressed length of the spring is L = 4mm. Choose a spring with an initial length L0 = 6~10mm. Then the spring constant... =63~190N / m.

[0091] Take the residual tensile force of the shape memory alloy wire N, the recovery stress σ of the shape memory alloy is 500 MPa, then the cross-sectional area = 0.003mm²; diameter = 0.06mm.

[0092] The length l of the shape memory alloy wire can be changed by modifying the number of pulleys and the winding method of the shape memory alloy wire, and can be selected as 100mm.

Claims

1. A miniature medical infusion device, characterized in that, The device includes a base, a top cover, a medicine storage tank, a piston, a screw, a double-action ratchet drive mechanism, a counting sensor mechanism, a rotation sensor mechanism, a liquid level sensor mechanism, and a controller. The medicine storage tank is mounted on the base, and the piston is located inside the medicine storage tank and can slide. One end of the screw is connected to the piston, and the other end is threadedly connected to the output part of the double-action ratchet drive mechanism. The double-action ratchet drive mechanism pushes the screw and the piston to move axially along the medicine storage tank to realize the infusion of medicine liquid. The double-action ratchet drive mechanism includes: a ratchet, a rocker arm, a first pawl, a second pawl, a shape memory alloy wire, a spring, a pulley assembly, and a power supply contact. The ratchet is rotatably mounted on the base and is threadedly connected to the screw. The rocker arm is pivotally mounted on the base. The first and second pawls are mounted on the rocker arm and engage with the ratchet. The shape memory alloy wire is wound around the pulley assembly, with one end connected to the rocker arm and the other end connected to the power supply contact. One end of the spring is fixed to a spring mounting post on the base, and the other end acts on the rocker arm, providing a restoring force opposite to the tension of the shape memory alloy wire. The power supply contact is used to supply current to the shape memory alloy wire. The counting sensing mechanism includes a counter contact disposed on the base, and the rocker arm can contact or separate from the counter contact during the swinging process; The rotary sensing mechanism includes a square hub disposed on the ratchet, a second electrode mounting base and a second electrode contact on the base, the second electrode plate being mounted on the base via the second electrode mounting base, and the square hub being able to act on the second electrode plate to make the second electrode plate contact or separate from the second electrode contact; The liquid level sensing mechanism includes the screw, a first electrode mounting base disposed on the base, and a first electrode contact. The first electrode plate is mounted on the base through the first electrode mounting base. The end of the screw can act on the first electrode plate, causing the first electrode plate to contact or separate from the first electrode contact.

2. The infusion device according to claim 1, characterized in that, In the dual-action ratchet drive mechanism, during one power-on / off cycle, the shape memory alloy wire contracts when energized, pulling the rocker arm, causing the first pawl to engage with the ratchet, driving the ratchet to rotate one tooth pitch, and the ratchet pushes the screw and piston to move one step; when the shape memory alloy wire expands when energized, the spring pushes the rocker arm to reset, causing the second pawl to engage with the ratchet, driving the ratchet to rotate another tooth pitch, and the ratchet pushes the screw and piston to move another step.

3. The infusion device according to claim 1, characterized in that, The counting sensing mechanism, the rocker arm, the rotating shaft on which the rocker arm is mounted, and the counter contact are all made of conductive material and connected to the circuit. The contact between the rocker arm and the counter contact forms a circuit path.

4. The infusion device according to claim 1, characterized in that, The rotary sensing mechanism is used to detect the rotation angle of the ratchet; the square hub is fixedly mounted on the ratchet, and the rotary sensing mechanism includes a second electrode plate, a second electrode mounting base, and a second electrode contact. The square hub rotates synchronously with the ratchet and can periodically change the contact state between the second electrode plate and the second electrode contact.

5. The infusion device according to claim 1, characterized in that, The liquid level sensing mechanism includes the first electrode plate, the first electrode mounting base, and the first electrode contact. The end of the screw has a conical chamfer, which can press the first electrode plate to separate it from the first electrode contact, or release the first electrode plate to make it contact the first electrode contact.

6. The infusion device according to claim 1, characterized in that, The pulley assembly includes pulleys and an optical shaft. The pulleys are mounted on the base and the top cover via the optical shaft and are rotatable, providing a winding mounting position for the shape memory alloy wire of sufficient length so that the shape memory alloy wire remains taut even when stretched.

7. The infusion device according to claim 1, characterized in that, The double-action ratchet drive mechanism is also provided with a spring plate, which is mounted on the base by a spring mounting post and contacts the pawl. The spring plate is used to provide a biasing force to the pawl toward the ratchet to prevent the pawl from falling off the ratchet.

8. The infusion device according to claim 1, characterized in that, The spring provides the driving force required by the pawl, and the shape memory alloy wire provides the resultant force of the driving force required by the pawl and the restoring force of the spring.

9. The infusion device according to claim 1, characterized in that, The controller is electrically connected to the power supply contact, the counting sensor, the rotation sensor, and the liquid level sensor of the double-action ratchet drive mechanism, respectively. The controller outputs current to the shape memory wire, accumulates the number of infusions based on the signal from the counting sensor, verifies whether the ratchet rotation is normal based on the signal from the rotation sensor, and determines whether the medicine is used up based on the signal from the liquid level sensor.

10. The infusion device according to claim 1, characterized in that, The length of the first pawl is 4-6 mm, the length of the second pawl is 6-8 mm, the pawl mounting hole spacing of the rocker arm is 7-9 mm, the number of teeth z of the ratchet is 20-40, and the module m is 0.5-1. The original length L0 of the spring is in the range of 6-10 mm, and the spring constant k is 32-190 N / m; the diameter d of the shape memory alloy wire is 0.044-0.06 mm, and the length l is 60-100 mm.

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