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 
       [0001]    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 
       [0002]    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. 
         [0003]    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. 
         [0004]    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. 
         [0005]    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. 
         [0006]    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 
       [0007]    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. 
         [0008]    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. 
         [0009]    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. 
         [0010]    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. 
         [0011]    In highly preferred embodiments the default position of the piston is in the closed position. 
         [0012]    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. 
         [0013]    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. 
         [0014]    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. 
         [0015]    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. 
         [0016]    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. 
         [0017]    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 
         [0018]      FIG. 1  is a front view of a preferred embodiment of an electromagnetic pump; 
           [0019]      FIG. 2  is a perspective view of the pump housing of  FIG. 1  in the open position; 
           [0020]      FIG. 3  is an exploded view of the cassette of  FIG. 1 ; 
           [0021]      FIG. 4  is a perspective view of the cylinder of  FIG. 3 ; 
           [0022]      FIG. 5  is a perspective view of the bottom of the cassette cap of  FIG. 1 ; 
           [0023]      FIG. 6  is a side view of the barrier of  FIG. 3 ; 
           [0024]      FIG. 7  is a perspective view of the piston of  FIG. 3 ; 
           [0025]      FIG. 8  is a perspective view of the valve assembly of  FIG. 3 ; 
           [0026]      FIG. 9  is a perspective view of the main body of the valve assembly of  FIG. 3 ; 
           [0027]      FIG. 10  is a cutaway view of the cassette of  FIG. 1  in the open position; and 
           [0028]      FIG. 11  is a cutaway view of the cassette of  FIG. 1  in the closed position. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0029]    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. 
         [0030]    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. 
         [0031]    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. 
         [0032]    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. 
         [0033]    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 . 
         [0034]    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. 
         [0035]    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&amp;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 . 
         [0036]    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 . 
         [0037]    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. 
         [0038]    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&#39; 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. 
         [0039]    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.