Abstract:
A mini lead screw pump monitors the rotation of a lead screw by using a magnetoresistive sensor and an MCU, and uses feedback to control the rotation direction and speed of the lead screw through a motor controller so as to control the speed of infusion to a patient. Furthermore, this mini lead screw pump can control the infusion speed of insulin according to the patient&#39;s blood sugar concentration monitored by CGM. This mini lead screw pump has several advantages, comprising high sensitivity, high reliability, low power consumption, low cost, and ease of use.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a medical device, and in particular, to a mini lead screw pump for driving an insulin pump. 
       BACKGROUND ART 
       [0002]    As the number of diabetic patients increases globally, the demand for insulin pumps is also increasing. An insulin pump needs to inject insulin at a low dosage at a constant rate or a large dosage according to the requirements of a diabetic patient to correct high blood sugar after a meal is eaten. The insulin pump can inject insulin according to a basic dosage distribution diagram of the diabetic patient, and therefore, the blood sugar concentration in the blood of the patient can be kept at the same level, and organs of the patient bear less pressure. Accordingly, the insulin pump must be capable of injecting insulin at a small dosage (about 0.1-1.0 cm 3 /day) continuously, and be capable of adjusting the speed of injection (that is, the basic dosage speed and the large dosage speed) in a wide range, to meet different requirements of patients. As a result, many insulin pumps available in the market are mini lead screw pumps; the mini lead screw pump drives a sleeve to move within a reservoir, to input the insulin inside the reservoir into the body of the patient. A motor for rotating the lead screw may be a stepper motor that can control the rotation speed precisely. On one hand, using the stepper motor increases the price of the insulin pump, the price of this type of insulin pump may be up to 5000 dollars, which greatly limits the use by patients. On the other hand, the precision of the stepper motor controlling the infusion speed depends on the number of phases and the number of beats, and the more the number of phases and the number of beats are, the higher the precision is. Low-frequency vibration easily occurs when the stepper motor rotates at a low speed. Step loss or locked rotor easily occurs at an over-high start-up frequency or overly high load, and overshoot may occur if the rotation speed is too high when the motor stops. In order to reduce the price of the insulin pump, the present invention uses a magnetoresistive angle sensor and a DC motor together to replace the stepper motor, thereby reducing the cost of the insulin pump, and improving the performance of the insulin pump. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention relates to a mini lead screw for driving an insulin pump, which uses feedback to control the infusion speed by using a magnetoresistive angle sensor and a continuous glucose monitor (CGM) in combination with a micro control unit (MCU), and replaces the manner of controlling the infusion speed by using a stepper motor. The present invention can use other motors to replace the stepper motor, and may also be used with the stepper motor, thereby improving the precision and reliability of the infusion speed of insulin or other liquid. 
         [0004]    A mini lead screw pump, mounted within a pump box, the mini lead screw pump comprising a motor, the motor driving the lead screw and a driving head connected to the lead screw, the lead screw rotating in a nut having a thread in a direction opposite to that of a thread of the lead screw, thereby driving the driving head to push a sleeve to move within a reservoir, where the mini lead screw pump further comprises 
         [0005]    at least one permanent magnet rotating co-axially with the lead screw; 
         [0006]    a magnetoresistive angle sensor capable of sensing a magnetic field generated by the at least one permanent magnet, the magnetoresistive angle sensor being located within a unidirectional and saturated area of the magnetic field generated by the at least one permanent magnet; and 
         [0007]    an MCU receiving a signal of the magnetoresistive angle sensor and using feedback to control the rotation direction and speed of the lead screw according to the signal of the magnetoresistive angle sensor. 
         [0008]    Preferably, the magnetoresistive angle sensor is a biaxial magnetic angle sensor, two orthogonal uniaxial magnetic angle sensors, or a uniaxial or biaxial linear magnetic sensor. 
         [0009]    Preferably, the magnetoresistive angle sensor is an AMR, a GMR or a TMR sensor. 
         [0010]    Preferably, the central axis of the permanent magnet and the central axis of the lead screw pass through the center of the magnetoresistive angle sensor. 
         [0011]    Preferably, the at least one permanent magnet is a one-piece permanent magnet or a split-type permanent magnet, and is disc-shaped, ring-shaped or square-shaped. 
         [0012]    Preferably, the at least one permanent magnet is two permanent magnets, each of the permanent magnets has multiple different magnetic poles, and the two permanent magnets are located at two ends of the lead screw respectively or disposed at the same end of the lead screw as a string. 
         [0013]    Preferably, the MCU controls the rotation direction and speed of the motor through a motor controller. 
         [0014]    Preferably, the MCU comprises a magnetoresistive sensor information management unit, the magnetoresistive sensor information management unit comprises a motor angle counting unit for monitoring the angle of the motor, a lead screw position unit for calculating a linear movement position of the lead screw and/or a sleeve position unit for calculating a position of the sleeve in the reservoir, a solution volume unit for calculating the volume of a solution in the reservoir, and a flow velocity unit for converting the rotation speed of the lead screw into the infusion speed of the reservoir. 
         [0015]    Preferably, the MCU has a wired and/or wireless data communication interconnecting function. 
         [0016]    Preferably, the MCU receives a signal sent by a CGM connected thereto, and calculates an actually required infusion speed according to a CGM look-up table preset in the MCU. 
         [0017]    Preferably, the mini lead screw pump comprises a comparison unit for comparing the infusion speed of the mini lead screw pump and the actually required infusion speed, and the MCU adjusts the rotation speed of the lead screw according to comparison data feedback of the comparison unit. 
         [0018]    Preferably, the motor is a DC motor or a stepper motor. 
         [0019]    Preferably, a transmission device connecting the motor and the lead screw is included. 
         [0020]    Preferably, a slideway or a guide rod is included, the slideway or guide rod is parallel to the lead screw, and the driving head slides within the slideway or slides along the guide rod. 
         [0021]    Preferably, an anti-backlash device located on the lead screw is included. 
         [0022]    A method for manufacturing a mini lead screw pump described above, the mini lead screw pump comprising a lead screw and a driving head connected to the lead screw, and the lead screw rotating clockwise or counterclockwise, thereby driving the driving head to push a sleeve to move within a reservoir, wherein the method comprises: 
         [0023]    mounting at least one permanent magnet on the lead screw such that it is rotatable co-axially with the lead screw, and mounting a magnetoresistive angle sensor at a position within a unidirectional and saturated area of a magnetic field generated by the at least one permanent magnet; and 
         [0024]    mounting an MCU for using feedback to control the rotation direction and speed of the lead screw according to a signal of the magnetoresistive angle sensor. 
         [0025]    Preferably, the magnetoresistive angle sensor is an AMR, a GMR or a TMR sensor. 
         [0026]    According to the present invention, a common DC motor is used instead of an expensive stepper motor, thus reducing the cost of an insulin pump. Moreover, the application of the low-power consumption magnetoresistive angle sensor may also reduce the power consumption of the insulin pump and reduce the frequency of charging, which is an important improvement for an insulin pump generally powered by batteries, thereby facilitating the use. In conclusion, the insulin pump of the present invention has several advantages, including high sensitivity, high reliability, low power consumption, low cost, and ease of use. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a schematic top view of an insulin pump; 
           [0028]      FIG. 2  is a schematic diagram of a permanent magnet and the magnetization direction thereof; 
           [0029]      FIG. 3  is a control principle diagram of an MCU; 
           [0030]      FIG. 4  is a principle diagram of a magnetoresistive sensor information management unit; and 
           [0031]      FIG. 5  is a conversion curve. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    The above description is merely a summary of the technical solution of the present invention. In order to describe the technical measures of the present invention more clearly and implement the present invention according to the content of the specification, the present invention will be described in detail below with reference to embodiments and accompanying drawings. Specific implementations of the present invention are provided in detail by the following embodiments. 
         [0033]      FIG. 1  is a schematic top view of a mini lead screw pump or an insulin pump  2 . The pump comprises a motor  52 , a lead screw  22  and a driving head  18  driven by the motor  52 , and is mounted within a pump box  15 . The pump box  15  has a box cover  35 . A reservoir  4  has a sleeve  8  capable of moving therein. A locking connector  3  (Luer lock) connects the reservoir  4  and a connector  5  of an infusion tube, and the connector  5  of the infusion tube is connected to a hose for infusing insulin to the body of a patient. 
         [0034]    One end of the lead screw  22  connected to the motor  52  is rotatably fixed to a front base  16 A, and the other end is rotatably fixed to a rear base  16 B. In order to drive the driving head  18 , the lead screw  22  is connected to the driving head  18  through a linkage rod  61  so as to convert the rotation thereof to the translation of the driving head  18 , and can rotate in a nut  7  having an internal thread matched with an external thread of the lead screw  22 . The nut  7  is fixed to the pump box  15 . Through a mechanical transmission device capable of changing the rotation speed, including one or more reduction gears  13  and gears  31 , the motor  52  drives the lead screw  22  to rotate in the nut  7  clockwise or counterclockwise. Therefore, the lead screw  22  drives the driving head  18  to move back and forth linearly along a direction parallel to the slideway  17 . The slideway  17  is a groove allowing the driving head  18  to slide therein, and is parallel to the lead screw  22 . To reduce cost, a pulley and a transmission belt may be used to replace the gear  31  and the reduction gear  13  between the motor  52 , the reduction gear  13  and the gear  31 . An anti-backlash device  19  is mounted on the lead screw  22  to prevent backlash. 
         [0035]    The slideway  17  may not be used, but a guide rod is used for stabilization and guiding, and the guide rod is parallel to the lead screw  22 . The number of guide rods for stabilization may be one or more. 
         [0036]    The motor  52  may be a DC motor, an AC motor, a stepper motor, a servo motor, or the like. 
         [0037]    The mini lead screw pump further comprises a magnetoresistive angle sensor  28  and at least one permanent magnet  30  rotating co-axially with the lead screw  22 , wherein the magnetoresistive angle sensor  28  is stationary and can sense a magnetic field generated by the permanent magnet  30 . 
         [0038]    The driving head  18  has a pair of reservoir clips  14  capable of fixing reservoirs  4  with different diameters to the same injector central axis or different injector central axes, to hold the sleeve  8 ; therefore, when the lead screw  22  rotates in the nut  7 , the driving head  18  moves linearly along the direction of the slideway  17 , thereby pushing the sleeve  8  to move in the reservoir  4 . The pump box  15  is provided with a pair of syringe clips  12 , which can fix reservoirs  4  with different diameters to the same injector central axis or different injector central axes. 
         [0039]      FIG. 2A  is a schematic sectional diagram of a positional relation between the magnetoresistive angle sensor  28  and the permanent magnet  30  and  FIG. 2B  to  FIG. 2D  are schematic diagrams of the magnetization direction of the permanent magnet  30 . The lead screw  22  has a long axis  100  in the direction of Z-axis direction, which is perpendicular to XY plane, passes through the center of the permanent magnet  30 , and is coaxial with the permanent magnet  30 . The central axis of the permanent magnet  30  and the central axis of the lead screw  22  pass through the center of the magnetoresistive angle sensor  28 . The magnetoresistive angle sensor  28  is a biaxial magnetic angle sensor or two orthogonal uniaxial rotary sensors, and may also be a linear sensor or a biaxial linear sensor. The magnetoresistive angle sensor  28  is an AMR, a GMR, or a TMR sensor.  FIG. 2B ,  FIG. 2C  and  FIG. 2D  show a part of permanent magnets applicable to the present invention. The permanent magnet  30  is disc-shaped, ring-shaped or square-shaped, and is a one-piece permanent magnet or a split-type permanent magnet. The permanent magnet  30  may also comprise two magnets, and each permanent magnet has a different number of multiple magnetic poles. The surface area of the magnetoresistive angle sensor  28  on the XY plane is less than the coverage area of the permanent magnet  30  on the XY plane. The permanent magnet  30  is magnetized along the diameter or the diagonal direction, and the magnetization direction thereof is perpendicular to the Z-axis direction or the long-axis direction of the lead screw  22 . The disc-shaped or ring-shaped permanent magnet is magnetized along the diameter direction, and the square-shaped permanent magnet is magnetized along the diagonal direction. The permanent magnet  30  may be located at one end of the lead screw  22  away from the motor  52 , and may also be located at the same end with the motor  52 . If the permanent magnet  30  comprises two magnets, the two permanent magnets are respectively located at two ends of the lead screw  22  or disposed at the same end of the lead screw  22  as a string. The permanent magnet  30  may be located near or away from the magnetoresistive angle sensor  28 . If the two permanent magnets are disposed at the same end of the lead screw  22  as a string, the magnetoresistive angle sensor  28  may be located near or away from the lead screw. The magnetoresistive angle sensor  28  is located within a unidirectional and saturated area of the magnetic field of the permanent magnet  30 . 
         [0040]      FIG. 3  is a control principle diagram of an MCU  50 . The insulin pump  2  comprises the MCU  50 , which receives a signal from the magnetoresistive angle sensor  28 , and controls the rotation direction and speed of the motor  52  through a motor controller/motor control unit  48  connected thereto. Moreover, the MCU  50  is further connected with an operation keyboard  56 , a display  60  and a battery  64 . The display  60  and the keyboard  56  are located on the box cover  35 . 
         [0041]    The motor controller  48  is further used to monitor an output signal of the magnetoresistive angle sensor  28 , and if the preset sleeve position and infusion speed are found, the motor controller  48  may activate an alarm  54  connected thereto. 
         [0042]    The MCU  50  displays information that should be known by a user of the insulin pump  2  on the display  60 . The user can also communicate with the insulin pump  2  by using the keyboard  56  connected to the MCU  50 . The MCU  50  is connected to a force sensor  51 , the force sensor  51  may detect a force applied to the reservoir  4 , and when the force exceeds a preset value, the force sensor  51  may activate the alarm  54  through the motor controller  48 . A typical design of the force sensor  51  is a bridge structure, which uses analog-digital conversion (ADCs) and a differential programmable gain to amplify input or uses ADCs and external differential equipment for signal adjustment for the amplification. 
         [0043]    The battery  64  provides power required by an electrical device and the motor  52 . The power display depends on a simple battery voltage or a temperature sensor  27 . The reading of the voltage or temperature is digitized on an ADC  23 . The MCU  50  may receive the digitized data, process the data, and determine the remaining power by using a pre-stored look-up table. The power is displayed on the display  60 . When the power is too low, the alarm  54  may send an alarm. 
         [0044]    A power management unit  66  connected to the battery  64  converts the battery to a low-power consumption state when the power supply is turned off or when the insulin pump  2  is not in use. 
         [0045]    In a multi-voltage system, the simplest method of generating a power-up reset signal is monitoring a logic power source. During power up, the logic voltage rises above its threshold value, and a multi-voltage monitoring reset watchdog  59  connected to the power management unit  66  starts a reset stage, to ensure starting the MCU  50  sequentially. The multi-voltage monitoring reset watchdog  59  continues detecting any possible short-time power supply problem or power outage as long as the voltage of the power source of the host is within a specified specification. The existing multi-voltage monitoring reset watchdog  59  available in the market can monitor two, three or even four power supply voltages. 
         [0046]    When the user inputs information, a visual or acoustic signal should be provided. The display  60  provides the dosage and infusion speed of insulin, remaining power, time and date, prompt and system alarm (that is, blocking or low remaining insulin). The display  60  may also provide information about self-test during power up. A sound player  33  must have a self-test function, and this self-test function can receive sound by indirectly monitoring the impedance of a micro speaker or placing a loudspeaker beside the micro speaker, to determine whether the sound is at an appropriate level. An automatic amplifier  35  connected to the sound player  33  is used to adjust the volume. The display  60  may be a touch screen. If the display  60  is a touch screen, it is preferably disposed at an inner side of the box cover  35 . 
         [0047]    The insulin pump  2  requires that a visual and acoustical alarm is provided when an error is found, a specified time is reached or any event to be alarmed occurs. The alarm  54  may send an alarm when the following event occurs: low power, battery failure, low insulin, no insulin in an insulin bottle, excessive insulin amount, pump pause, pump failure (there may be many different situations), blocking and the like. A single LED may also be used to display an operating state of the insulin pump  2 , where red indicates an abnormal state, and green indicates a normal state. 
         [0048]    An electrostatic protection  37  is implemented by using an electronic device with built-in protection or using an electrostatic discharge (ESD) line protection. 
         [0049]    A data port  39  allows data transfer and downloading upgrade software, and also allows inputting a historical file to application software such that a doctor helps the treatment. 
         [0050]    The MCU  50  may further be provided with a wired and/or wireless data communication interconnection module. A clock pulse source  53  and a radio frequency link  55  receive, from the CGM  45 , data about glucose concentration in the body of the patient. If the CGM  45  is used, a Bluetooth ISM-band may be used to receive the signal. The CGM  45  provides the glucose concentration in the body of the patient. The MCU  50  has a CGM look-up table preset therein, for looking up the glucose concentration in the body of the patient and the input speed of insulin. The MCU  50  receives a signal sent by the CGM  45  connected thereto, and calculates an actually required infusion speed according to the CGM look-up table preset in the MCU  50 . The MCU  50  has a comparison unit  47 . The MCU  50  converts the rotation speed of the lead screw  22  to the insulin infusion speed, the comparison unit  47  compares the insulin infusion speed with the actually required infusion speed specified in the CGM look-up table according to the glucose concentration in the body of the patient, and the MCU  50  adjusts the rotation speed of the lead screw  22  according to the comparison result. 
         [0051]    A multiplexer (mux)  25  is used to select the signal input to the ADC  23 . 
         [0052]    A real-time clock (RTC)  68  is used to record changes of a program in real time, and is also used to tell time and record time. 
         [0053]    No matter how the device is mounted in the system, the power supply fluctuates, the temperature changes and the time elapses, the VREF  21  provides a fixed voltage. 
         [0054]    A current limiter  33  connected to the MCU  50  limits an upper limit of the current used, to prevent short circuit or similar problems. A level converter  29  connected to the MCU  50  provides a conversion interface for elements using different voltages. A memory card  46  is a data storage device of an electronic flash memory for the current limiter  33  and the level converter  29  to use. 
         [0055]    When a stepper motor is used, in addition to that the motor  52  itself has a function of adjusting the rotation speed of the motor, the MCU  50  may further use feedback to adjust and control the speed of the motor  52  through the motor controller  48  according to the signal of the magnetoresistive angle sensor  28 , such that the infusion speed is more precise. 
         [0056]      FIG. 4  shows the principle of a magnetoresistive angle sensor information management unit  49  in the MCU  50 . The magnetoresistive angle sensor information management unit  49  comprises a motor rotation circle counting unit  66 , a lead screw position unit  70 , a sleeve position unit  74 , a solution volume unit  68  and a flow velocity unit  72 , and is preset with a conversion table of an infusion volume of the reservoir  4  to the position of the sleeve  8  within the reservoir  4 , a conversion table of the position of the sleeve  8  of the reservoir  4  in the reservoir  4  to the position of the lead screw  22 , and an algorithm of the rotation circles of the lead screw  22  to the position of the lead screw  22 . 
         [0057]    When the insulin pump  2  is used, it is necessary to calibrate the insulin pump. The MCU  50  can be used to calibrate the insulin pump  2 , and can calculate the volume and speed of infusion. The lead screw  22  rotates, and the sleeve  8  moves accordingly. The motor rotation circles counting unit  66  records the rotation circles and time of the lead screw  22  according to the signal of the magnetoresistive angle sensor  28 . According to the rotation circles of the lead screw  22  and the algorithm, preset in the MCU  50 , of the rotation circles of the lead screw  22  to the position of the lead screw  22 , 
         [0000]      Distance of linear movement of the lead screw=(angle)*(longitudinal screw pitch) 
         [0058]    the lead screw position unit  70  can calculate the position of the lead screw  22  or a linear distance of its movement in the Z-axis direction. Meanwhile, according to the conversion table of the position of the lead screw  22  to the position of the sleeve  8  in the reservoir  4 , the sleeve position unit  74  may know the position of the sleeve  8  in the reservoir  4 . Further, the solution volume unit  68  may know the volume of infusion or remaining liquid volume according to the conversion table of the diameter of the reservoir  4  to the position of the sleeve  8  thereof within the reservoir  4 . The flow velocity unit  72  may calculate the speed of infusion according to the volume and time of infusion. If the conversion table of the rotation circles of the lead screw  22  to the infusion volume of the reservoir  4  is preset, the flow velocity unit  72  may record the rotation circles and time of the lead screw  22  according to the conversion table and the motor rotation circles counting unit  66 , thereby calculating the speed of infusion more quickly. When the infusion speed deviates from a preset value too high or too low, the MCU  50  may instruct the motor controller  48  to adjust the rotation direction and speed of the motor  52 . According to the position of the sleeve  8  in the reservoir  4  provided by the sleeve position unit  74  or according to the data of infusion volume provided by the solution volume unit  68 , the MCU  50  may instruct the motor controller  48  to adjust the rotation direction and speed of the motor  52 . 
         [0059]    The calibration process of the insulin pump  2  is as follows: an empty reservoir  4  is placed on an injector pump  2 , the magnetoresistive angle sensor information management unit  49  records the position of the sleeve  8  in the reservoir  4  detected by the magnetoresistive sensor  28 , then, a liquid with a known volume is added to the reservoir  4 , the volume value is input to the MCU  50 , and the magnetoresistive angle sensor information management unit  49  can obtain a relation of the liquid volume with the position of the sleeve  8  in the reservoir  4  and a relation with the position of the lead screw  22 , thereby calculating calibration parameters. 
         [0060]      FIG. 5  is a conversion curve of the magnetoresistive angle sensor  28 . When the permanent magnet  30  rotates with the lead screw  22  along a rotation direction  101 , curves of X-axis and Y-axis magnetic field components changing along with the angle that are detected by the magnetoresistive angle sensor  28  are shown by the curves  41  and  42  in  FIG. 4  respectively. The magnetoresistive angle sensor  28  converts the magnetic field amplitude generated by the permanent magnet  30  to an analog voltage signal, and the obtained analog voltage signal can be output directly or output after being converted to a digital signal by using an analog-to-digital conversion circuit (ADC). The angle of the permanent magnet  30 , that is, the angle of the lead screw  22 , may be known according to the output signal. 
         [0061]    A method for manufacturing the above mini lead screw pump/insulin pump  2  is briefly described as follows: at least one permanent magnet  30  is mounted on a lead screw  22  such that it can rotate co-axially with the lead screw  22 , and a magnetoresistive angle sensor  28  is mounted at a position within a unidirectional and saturated area in a magnetic field generated by the at least one permanent magnet  30 ; then, an MCU  50  for using feedback to control the rotation direction and speed of the lead screw  22  rotated by the motor  52  according to the signal of the magnetoresistive angle sensor  28  is mounted. 
         [0062]    The above descriptions are merely preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes, and the implementations in the present invention may also have different combinations and changes. Any modification, equivalent replacement, improvement or the like made without departing from the spirit and principle of the present invention shall all fall within the protection scope of the present invention.