US20100040490A1

US20100040490A1 - Volumetric Infusion Pump and Method

Info

Publication number: US20100040490A1
Application number: US12/190,132
Authority: US
Inventors: Anis Rahman
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-08-12
Filing date: 2008-08-12
Publication date: 2010-02-18

Abstract

In a first embodiment, an electromagnetic pump has a housing including first and second spaced apart electromagnets. A controller for controlling the magnets and a power source for powering the electromagnets within the housing. A removable cassette is in engagement with the housing between the first and second electromagnets and includes a cavity. The pump also has inlet and outlet ports in communication with the cavity and a magnetic piston disposed within the cavity. In preferred embodiments the electromagnets are capable of operating at different strengths and different polarities.

Description

FIELD OF THE INVENTION

The invention relates generally to the field of medial devices and more particularly to a portable self-contained medical pump capable of delivering precise doses.

BACKGROUND

The field of medical pumps has seen many improvements over the years, with numerous designs for specific types of uses. Examples includes pumps for the delivery of insulin, artificial heart pumps and many non-specific pump designs. Some of these designs incorporate electromagnets to produce the pump effect or utilize a removable medicine camber.
For example, U.S. Pat. No. 4,786,240 to Koroly et al. discloses a two chamber pump that utilizes an electromagnet within the chamber. Permanent magnets are placed at either ends of a chamber and an electromagnet is embedded within a flexible septum in the chamber. The polarity of the electromagnet is flipped thus alternately moving the electromagnet between the two permanent magnets, thus pumping fluid into and out of either side of the two pumping chambers created by the septum.
Another prior pump design is disclosed in U.S. Pat. No. 4,915,017 to Perlov. In this design diaphragms of various flexibility are utilized to create multi-chamber pumps. In some versions of the disclosed pump magnetic coils are utilized, along with a magnet in the diaphragm to count the number of time the pump has cycled and thus track the total flow of fluid through the pump.
In a third design, an electromagnetic pump is disclosed in U.S. Pat. No. 5,607,292 to Rao. In this design a single electromagnet is used in conjunction with elastromeric spring seals to pump fluid in and out of a chamber.
A final prior art pump design is disclosed in U.S. Pat. No. 7,377,907 to Shekalim. In this design a complex labyrinth is utilized to regulate flow from the pump and includes a removable cartridge to house the labyrinth and a fluid reservoir for the fluid to be delivered by the pump.

SUMMARY

In a first embodiment, an electromagnetic pump has a housing including first and second spaced apart electromagnets. A controller for controlling the magnets and a power source for powering the electromagnets within the housing. A removable cassette is in engagement with the housing between the first and second electromagnets and includes a cavity. The pump also has inlet and outlet ports in communication with the cavity and a magnetic piston disposed within the cavity. In preferred embodiments the electromagnets are capable of operating at different strengths and different polarities.
In some other embodiments, the piston is movable between a first open position and a second closed position. Also, the inlet and outlet ports may be part of the removable cassette. The inlet and outlet ports can take any form known in the art but it is preferred that the ports are one-way flapper valves.
In another embodiment the magnetic piston includes a piston body and a Neodymium magnet. Furthermore, the cavity may be on a first side of the piston and the piston includes an extension defining a passage on a second side of the piston. In such an embodiment the cassette would further include a sterile vent in communication with the passage. In further embodiments the cassette further includes a flexible barrier disposed within the cavity.
In yet other embodiments the electromagnetic pump further includes a first sensing device capable of detecting when the piston is in the closed position. It is preferred that the pump also include a second sensing device capable of detecting when the piston is in the open position. It is highly preferred that the first and second sensing devices are LED sensors and the cassette is capable of reflecting light from the LED sensors back to the LED sensors.
In highly preferred embodiments the default position of the piston is in the closed position.
In other embodiments a method of dispensing a liquid is disclosed. The method includes the step of providing an electromagnetic pump. The pump includes a housing including first and second spaced apart electromagnets, a controller for controlling the magnets within the housing, a power source for powering the electromagnets within the housing, a cassette in engagement with the housing between the first and second electromagnets and including a cavity, inlet and outlet ports in communication with the cavity and a magnetic piston disposed within the cavity. Next a liquid to be dispensed is supplied to the inlet port and the first electromagnet is powered to draw the piston into an open position thereby drawing the liquid through the inlet port and into the cavity. The first electromagnet is depowered and the second electromagnet is powered to draw the piston into a closed position thereby pushing the liquid out of the cavity and through the outlet port. In the current invention the concept of depowering the magnet includes, but is not limited to, two different operations. The first operation of depowering is removing the charge from the electromagnet in question thus allowing the pull from the opposite electromagnet to work on piston independently. Alternatively, the operation described as depowering is to reverse the polarity of the electromagnet thus pushing the piston if the electromagnet had been pulling it.
In another embodiment of the method, the method further includes the step of providing free-flow protection against liquid flowing back through the inlet port. It is preferred that the free-flow protection is provided via a one-way flapper valve. In addition, or separately free-flow protection can also be provided by the controller controlling the piston to default to the closed position.
In still further embodiments, the method also includes the step of sensing the position of the piston within the cavity. It is preferred that this step is accomplished by the housing including a sensor for reading the location of the piston. It is highly preferred that the sensor is an LED.
In other embodiments, the method further includes the step of calculating the volume of liquid delivered via movement of the piston. Preferably, after the step of powering the second electromagnet to draw the piston into a second position thereby pushing the liquid out of the cavity and through the outlet port, the second electromagnet is depowered, thereby allowing a cycle of powering the first electromagnet, depowering the first electromagnet, and powering the second electromagnet is capable of being repeated plurality of times. In such an embodiment the method further includes the step of calculating the total volume of liquid delivered via the plurality of cycles. It is highly preferred that the steps of calculating are performed by the controller.
In other preferred embodiments the cassette is removable. In such an embodiment, it is highly preferred that the method further include the step of sensing for the presence of the removable cassette in the pump.
Also, wherein the movement of the piston between the open and closed positions is at a velocity, it is preferred that the method further include the step of varying the velocity of the piston to control a rate of deliver. The method further includes varying the dwell time between depowering the first electromagnet and powering the second electromagnet to control the rate of delivery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a preferred embodiment of an electromagnetic pump;

FIG. 2 is a perspective view of the pump housing of FIG. 1 in the open position;

FIG. 3 is an exploded view of the cassette of FIG. 1;

FIG. 4 is a perspective view of the cylinder of FIG. 3;

FIG. 5 is a perspective view of the bottom of the cassette cap of FIG. 1;

FIG. 6 is a side view of the barrier of FIG. 3;

FIG. 7 is a perspective view of the piston of FIG. 3;

FIG. 8 is a perspective view of the valve assembly of FIG. 3;

FIG. 9 is a perspective view of the main body of the valve assembly of FIG. 3;

FIG. 10 is a cutaway view of the cassette of FIG. 1 in the open position; and

FIG. 11 is a cutaway view of the cassette of FIG. 1 in the closed position.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to FIGS. 1 and 2, a preferred embodiment of an electromagnetic pump 10 is shown. The pump 10 includes a housing 12 and a removable cassette 14. The housing 12 includes an upper portion 16 and a lower portion 18 and has a top 20, a bottom 22, and a front 24. At the top 20 of the housing 12 two magnet sections 26 are formed with a cassette space 28 formed between. The housing 12 is preferably made of plastic to keep weight at a minimum since this preferred embodiment is designed to be worn by the user. The cassette space 28 is bounded by the magnet sections 26 on the sides and a cassette receiving surface 30 on the bottom. The cassette 14 fits into the cassette space 28 and is held in place via a detent mechanism. However, any means of holding the cassette 14 in place could be utilized.
The front 24 of the housing 12 includes an LCD display 32 for display of information related to dosage to the user. The housing 12 shown varies between open and closed positions by the upper housing 16 and lower housing 18 being pivotally joined at the magnet sections 26. However, in other embodiments the upper and lower housings 16, 18 could be joined at the side or any other known manner. In yet other embodiments the housings could be separate but lock together to from a housing.
Referring now to FIG. 2, internally, the housing 12 includes a controller 34 mounted to the upper housing 16 and connected to the LCD display 32. The housing 12 further includes two variable power electromagnets 36 housed in the magnet sections 26 of the lower housing 18 which are controlled by the controller 34. For example a dipole custom electromagnet made by BOMAG company may be utilized. These electromagnets 36 thus have the ability to project stronger or weaker electromagnet fields based on power supplied to them. Two LED emitters/sensors 38 a and 38 b are also disposed within the housing 12 and controlled by the controller 36. The LED emitters/sensors 38 a and 38 b are positioned to be in alignment with the upper and lower positions of the piston of the cassette 14 respectively, which will be discussed in greater detail below. The LED emitters/sensors 38 are capable of emitting a light and detecting if the light is being reflected back or not. Because the LEDs 38 emit light into the cassette 14 the cassette receiving surface 30 of the housing 12 maybe clear to allow passage of the light or may incorporate holes for positioning of the LEDs 38. However in other embodiments infrared emitters could be utilized thus eliminating the need for transparency. LEDs 38, controller 34, electromagnets 36 and LCD display 32 all draw power from rechargeable battery pack 39 held within the lower housing 18. However other power supply setups could be utilized, for example, in some embodiments, the controller 34 could include a button cell lithium battery to power the LCD without draining the main battery. In yet other embodiments the device could be AC powered and/or DC powered primarily but AC powered during the recharging process.
Referring now to FIGS. 3-9 the cassette 14 of the pump 10 is shown in detail. The cassette 14 includes a cylinder 40, a top cap 42 and a bottom cap 44. The cylinder 40 is preferably of a clear plastic and has open top and bottom portions and defines an interior cavity 46. The cylinder 40 may also include an upper reflector 41 and a lower reflector 43. These reflectors are aligned opposite the LEDs 38 a and 38 b. The bottom cap 44 encloses the bottom of the cylinder 40 and is a sterile vent, made of a material such as expanded polytetrafluoroethylene (ePTFE) supported by an outer plastic ring.
Referring specifically to FIGS. 3, 5, 10 and 11 the top cap 42 is shown. The top cap 42 encloses the top of the cylinder 40 and is preferably made of plastic. The top cap 42 is circular and includes a top portion 48 and a lower portion 50. The top potion 48 includes an inlet connection 52 and an outlet connection 54. These connections 52, 54 define passages to corresponding inlet port 56 and outlet port 58 on the lower portion 50 of the top cap 42. The lower portion 50 also defines a valve recess 59. The top cap 42 also includes a cutout 60 along a ridge 62 around the lower portion 50. The cutout 60 allows light from the LED to pass into the cavity 46.
Referring again to FIGS. 3-9 the cassette 14 further includes a valve assembly 62, a barrier 64, a magnet 66, and a piston 68. The valve assembly includes a main body 70 which is sized to fit within the valve recess 59 of the top cap 42 and acts as a seal to separate the inlet port 56 and outlet port 58 from the cavity 46. The main body 70 defines two port openings 72 and two valve openings 74. A port opening 72 is aligned with each of the inlet port 56 and outlet port 58 when the valve assembly 62 is in place in the top cap 42. A one-way valve 76 covers each port opening 72. The valve 76 over the inlet port 56 opens into the cavity 46 and the valve 76 over the outlet port 58 opens into the top cap 42. Each valve 76 includes a base 80 connected to via a living hinge 82 to a flap 84. The valve 76 is attached to the main body 70 by a t-shaped extension 86 through the valve opening 74. The valves 76 are preferably made of a molded silicone material.
The barrier 64, magnet 66 and piston 68 are positioned within the cavity 46. Referring now to FIGS. 6, 10 and 11, the barrier 64 defines the inner cavity 88 or fluid area of the pump 10 which is in communication with the inlet port 56 and outlet port 58 via the valve assembly 62. The barrier 64 is preferably of a molded silicone material and includes an upper seal 90 and a cylinder portion 92 and a connecting ridge 94. The upper seal 90 includes an L-shaped extension 91 from the top of the barrier 64 that wraps around the top of the cylinder 40 and is held in place via any known methods. For example, if the cylinder 40 is made of plastic the barrier 64 may be held in place via ultrasonic welding. Alternatively, if the cylinder 40 is made of glass the barrier 64 may be adhesively attached to the top cap 42 and cylinder 40. The connecting ridge 94 is in contact with the magnet 66. The magnet 66 is circular and is a strong permanent magnet such as a D81-N50 Neodymium magnet from K&J Magnetics. Finally, the piston 68 includes an upper surface 96 which includes a circular seal 98 around a recess 100. The magnet 66 fits within the recess 100 and the connecting ridge 94 is in sealing contact with the seal 98. The piston 68 also defines an open interior opposite upper surface 96.
Referring now to FIGS. 10 and 11, the magnet 66 is primarily in one of two positions: an open position (FIG. 10) where the piston 68 is in contact with the bottom cap 44 and a closed position (FIG. 11) where the piston 68 (along with the magnet 66) compresses the barrier 64 toward the top of the cassette 14. This closed position is the default position for the magnet 66 whereby the inner cavity 88 is compressed closed and fluid cannot flow (even in the event of a valve failure) from the inlet port 56 to the outlet port 58.
In operation, a cassette 14 is inserted into the pump 10. The LEDs 38 then detect the presence of the cassette 14 because of the reflection of light from the reflectors 41, 43 back to the LEDs 38. The inlet connection 52 is connected to a source of fluid/medicine to be delivered and the outlet connection 54 is connected to the patient for delivery. The controller 34 sends a first control signal to the electromagnets 36 which in turn are powered to move the magnet 66 from the default closed position to the open position. When the magnet 66 is moved fluid is drawn from the inlet port 56 through the valve 76 and into the inner cavity 88. The magnets 36 are powered until the LED 38 b recognizes that the magnet has moved as far to the bottom of the cavity 46 as it can by the reflection from the reflector 43 being cut off. When the magnet 66 has moved as far as possible (into the open position), the inner cavity 88 then contains a known amount of fluid since the volume of the inner cavity 88 is known.
The controller then sends a second control signal to the electromagnets 36, which powers the electromagnets 36 to reverse the polarity thus pushing the magnet 66 toward the closed position. As the magnet 66 moves toward the closed position fluid is pushed out of the inner cavity 88 and through the outlet port 58 and its corresponding valve 76. Once the magnet reaches the closed position and activates (i.e. cut off the reflection from the reflector 41) the corresponding LED 38 a the controller 34 can calculate the amount of time it took to move the magnet 66 from the open position to the closed position. This amount of time can then be compared to an expected amount of time for such movement. The amount of time could vary based upon the viscosity of the fluid being delivered. If the time is longer than expected, the controller 34 can utilize more power in the next cycle (a cycle being from closed position to open position to closed position) to speed up delivery to reach a desired or preset delivery rate. This allows a high level of delivery accuracy. This pumps' delivery accuracy is also increased in that the pump can track the number of cycles and calculate the total delivery of fluid along with tracking the rate, this information can then be utilized to increase or decrease the pump rate accordingly.
While the principles of the invention have been shown and described in connection with specific embodiments, it is to be understood that such embodiments are by way of example and are not limiting.

Claims

1. A electromagnetic pump comprising:

a housing including first and second spaced apart electromagnets;

a controller for controlling the magnets within the housing;

a power source for powering the electromagnets within the housing;

a cassette in engagement with the housing between the first and second electromagnets and including a cavity;

an inlet port in communication with the cavity;

an outlet port in communication with the cavity; and

a magnetic piston disposed within the cavity.

2. The electromagnetic pump of claim 1 wherein the cassette is removable.

3. The electromagnetic pump of claim 1 wherein the piston is movable between a first open position and a second closed position.

4. The electromagnetic pump of claim 3 wherein the inlet port is part of the removable cassette.

5. The electromagnetic pump of claim 4 wherein the outlet port is part of the removable cassette.

6. The electromagnetic pump of claim 5 wherein the magnetic piston includes a piston body and a Neodymium magnet.

7. The electromagnetic pump of claim 5 wherein the cavity is on a first side of the piston and the piston includes an extension defining a passage on a second side of the piston, the cassette further including a sterile vent in communication with the passage.

8. The electromagnetic pump of claim 5 wherein the cassette further includes a flexible barrier disposed within the cavity.

9. The electromagnetic pump of claim 5 wherein the inlet port includes a one-way flapper valve.

10. The electromagnetic pump of claim 9 wherein the outlet port includes a one-way flapper valve.

11. The electromagnetic pump of claim 1 wherein the electromagnets are capable of operating at different strengths and different polarities.

12. The electromagnetic pump of claim 3 further comprising a first sensing device capable of detecting when the piston is in the closed position.

13. The electromagnetic pump of claim 12 further comprising a second sensing device capable of detecting when the piston is in the open position.

14. The electromagnetic pump of claim 13 wherein the first and second sensing devices are LED sensors and the cassette is capable of reflecting light from the LED sensors back to the LED sensors.

15. The electromagnetic pump of claim 3 wherein the default position of the piston is in the closed position.

16. A method of dispensing a liquid, the method comprising the steps of:

providing an electromagnetic pump including;

a housing including first and second spaced apart electromagnets,

a controller for controlling the magnets within the housing,

a power source for powering the electromagnets within the housing,

a cassette in engagement with the housing between the first and second electromagnets and including a cavity,

an inlet port in communication with the cavity,

an outlet port in communication with the cavity,

a magnetic piston disposed within the cavity;

supplying a liquid to be dispensed to the inlet port;

powering the electromagnets to draw the piston into an open position thereby drawing the liquid through the inlet port and into the cavity; and

powering the electromagnets to draw the piston into a closed position thereby pushing the liquid out of the cavity and through the outlet port.

17. The method of claim 16 further including the step of providing free-flow protection against liquid flowing back through the inlet port.

18. The method of claim 17 wherein the free-flow protection is provided by the controller controlling the piston to default to the closed position.

19. The method of claim 16 further including the step of sensing the position of the piston within the cavity.

20. The method of claim 19 where the housing includes a sensor for reading the location of the piston.

21. The method of claim 20 wherein the sensor is an LED.

22. The method of claim 18 further including the step of calculating the volume of liquid delivered via movement of the piston.

23. The method of claim 22 wherein after the step of powering the second electromagnet to draw the piston into a second position thereby pushing the liquid out of the cavity and through the outlet port, the second electromagnet is depowered, thereby allowing a cycle of powering the first electromagnet, depowering the first electromagnet, and powering the second electromagnet is capable of being repeated plurality of times, the method further including the step of:

calculating the total volume of liquid delivered via the plurality of cycles.

24. The method of claim 23 wherein the steps of calculating are performed by the controller.

25. The method of claim 16 wherein the cassette is removeable.

26. The method of claim 25 further including the step of sensing for the presence of the removable cassette in the pump.

27. The method of claim 23 wherein the movement of the piston between the open and closed positions is at a velocity, the method further comprising the step of varying the velocity of the piston to control a rate of delivery.

28. The method of claim 27 wherein the velocity is varied by comparing a required delivery rate to an actual delivery rate where the actual delivery rate is determined by sensing the position of the piston within the cavity.