Abstract:
An infusion pump operable with a syringe having a syringe barrel and a syringe plunger includes a housing having a compartment to receive the syringe and defining a wall, and a syringe clamp moveable towards and away from the wall, the syringe clamp contacting the syringe barrel; a drive mechanism supported and structured and arranged to contact and end of the syringe plunger so as to be able to move the syringe plunger within the syringe barrel; a syringe barrel size sensor including a magnet operably coupled to the syringe clamp, and a sensing member supported by the housing and configured to generate an output indicative of a magnetic field associated with the magnet; and software installed on the pump and programmed to use the output to determine a size of the syringe barrel received by the compartment.

Description:
PRIORITY CLAIM 
       [0001]    This application claims priority to and the benefit as a divisional application of U.S. patent application Ser. No. 14/215,958, entitled “Infusion Pump Including Syringe Plunger Position Sensor”, filed Mar. 17, 2014, issued as U.S. Pat. No. 9,514,518, which is a continuation application of U.S. patent application Ser. No. 12/573,620, entitled “Infusion Pump With Battery Operation Capability”, filed Oct. 5, 2009, issued as U.S. Pat. No. 8,696,632, which is continuation application of U.S. patent application Ser. No. 11/319,350, entitled “Infusion Pump”, filed Dec. 28, 2005, issued as U.S. Pat. No. 7,608,060, which is a divisional application of U.S. patent application Ser. No. 10/172,807, entitled “Infusion Pump”, filed Jun. 14, 2002, issued as U.S. Pat. No. 7,018,361, the entire contents of each of which are incorporated herein by reference and relied upon. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to a pump and more particularly to an infusion pump for the delivery of a medication to a patient. 
         [0003]    Generally, medical patients sometimes require precise delivery of either continuous medication or medication at set periodic intervals. Medical pumps have been developed to provide controlled drug infusion wherein the drug can be administered at a precise rate that keeps the drug concentration within a therapeutic margin and out of an unnecessary or possibly toxic range. Basically, the medical pumps provide appropriate drug delivery to the patient at a controllable rate which does not require frequent attention. 
         [0004]    Medical pumps may facilitate administration of intravenous therapy to patients both in and outside of a clinical setting. Outside a clinical setting, doctors have found that in many instances patients can return to substantially normal lives, provided that they receive periodic or continuous intravenous administration of medication. Among the types of therapies requiring this kind of administration are antibiotic therapy, chemotherapy, pain control therapy, nutritional therapy, and several other types known by those skilled in the art. In many cases, patients receive multiple daily therapies. Certain medical conditions require infusions of drugs in solution over relatively short periods such as from 30 minutes to two hours. These conditions and others have combined to promote the development of increasingly lightweight, portable or ambulatory infusion pumps that can be worn by a patient and are capable of administering a continuous supply of medication at a desired rate, or provide several doses of medication at scheduled intervals. 
         [0005]    Configurations of infusion pumps include elastomeric pumps, which squeeze solution from flexible containers, such as balloons, into IV tubing for delivery to the patient. Alternatively, spring-loaded pumps pressurize the solution containers or reservoirs. Certain pump designs utilize cartridges containing flexible compartments that are squeezed by pressure rollers for discharging the solutions, such as in U.S. Pat. No. 4,741,736. Other references which disclose portable infusion pumps include U.S. Pat. No. 5,330,431 (showing an infusion pump in which standard pre-filled single dosage IV bags are squeezed by the use of a roller); U.S. Pat. No. 5,348,539 (showing an infusion pump in which prepackaged IV bags are squeezed by a bladder which is actuated by fluid pumped from a reservoir); U.S. Pat. No. 5,429,602 (showing a programmable portable infusion pump system for injecting one or more medicinal substances into an individual); and U.S. Pat. No. 5,554,123 (showing an infusion pump in which the amount of fluid required to pump a bladder sufficient to fully dispense solution from a bag is less than the volume of an IV bag.). Infusion pumps utilizing syringes are also known wherein a drive mechanism moves a plunger of the syringe to deliver fluid to a patient. Typically, these infusion pumps include a housing adapted to receive a syringe assembly, a drive mechanism adapted to move the syringe plunger, a pump control unit having a variety of operating controls, and a power source for powering the pump including the drive mechanism and controls. 
         [0006]    While the discussed prior art and other designs have recognized the need for an infusion pump which is smaller and more compact for mobile use by ambulatory patients or other patients, each has failed to address the need for a more suitable power source. Naturally, a portable pump must be supplied with an equally portable power source as a means for powering the pump motor. Batteries are a suitable choice of power for portable units. Some prior art pumps may use disposable batteries while other pumps may use rechargeable batteries. 
         [0007]    Disposable batteries have proven to have a longer life than the life of a rechargeable battery (with a single charge). Disposable batteries are also typically smaller than rechargeable battery units. However, there is an environmental disposal concern with such batteries, as they place a considerable burden on the environment. Disposable batteries are responsible for a major share of heavy metal pollution in domestic waste. Despite special collection efforts and consumer awareness campaigns, a high percentage of batteries sold still end up in domestic waste sites. Heavy metals eventually leak from the batteries into the ground soil, damaging the environment. 
         [0008]    Environmental concerns are greatly alleviated if rechargeable batteries are used in place of disposable batteries. However, where such batteries or battery packs are rechargeable, an AC outlet is usually necessary. A separate charger, as is well-known in the art, is also required for the recharging effort. Unfortunately, these facilities are not always readily available or accessible to the patient and, with respect to the usual adapters and extension cords, they add to the bulk and weight of the infusion pump system. Furthermore, in certain pumps utilizing rechargeable batteries, the pump itself must be used in the recharging effort as it typically houses the transformer used in the recharging process. 
         [0009]    Batteries and battery packs that are large and bulky significantly add to the weight of the portable infusion pump. Weight and size of the infusion pump is an important consideration because it may be carried about by nurses or other hospital personnel. The pump must also be sized to be attached to an I.V. pole. The I.V. pole, with attached pump, may be moved about in a hospital setting. In addition, where interrupted operation of the pump may have negative consequences, extra batteries or an extra battery pack may be added to the carrying necessities of the infusion pump. In some instances, the carrying of a second set of batteries or a back-up battery pack may double the weight of the power source. 
         [0010]    Thus, there is seen in the prior art advantages and disadvantages to both disposable and rechargeable battery powered pumps. It should be understood that under certain circumstances, a pump that uses disposable batteries may be preferable or the only option available (if no outlet is available). Under other circumstances, the benefits of lower cost and environmental concerns may dictate that rechargeable batteries are preferred. 
         [0011]    In addition to the above, customs and/or regulations of different sovereigns may dictate the use of one type of power source for a pump over another. For example, in the U.S., pumps powered by disposable batteries have long been preferred due to their convenience and ability to provide power for extended periods of time. On the other hand, in Europe, rechargeable battery powered pumps are preferred, due to environmental concerns with the disposal of battery waste. 
         [0012]    In light of the advantages and disadvantages that both disposable and rechargeable batteries provide, it may be desirable for some to alternate use of both battery types. However, it can be easily recognized that it would prove burdensome and a waste of space and resources to supply or have on hand two separate pumps, each utilizing a different battery type. 
         [0013]    It may also be desirable for manufacturers of pumps to satisfy the needs of users of rechargeable battery powered pumps as well as disposable battery powered pumps. However, it is costly for manufacturers of pumps to manage entirely separate lines of pump types or forego supplying one pump type over another. Thus, it is recognized that several advantages exist for a pump that can utilize both disposable and rechargeable batteries. There exists a need in the art for a pump that may utilize both disposable and rechargeable batteries. There also remains a need for a pump that utilizes rechargeable batteries that can be re-charged without the use of the pump. 
         [0014]    Additional problems have also been experienced with infusion pumps. For example, certain sensing systems that detect whether an occlusion is present in an infusion line have proven to be unreliable or too complex in construction. Certain syringe plunger position detectors and syringe barrel size detectors have also proven to be unreliable. In addition, drive mechanisms for syringe plungers have also proven to be unreliable as certain components become stripped or jammed adversely affecting the mechanism. 
         [0015]    The present invention is provided to solve these and other problems. 
       SUMMARY 
       [0016]    The present invention is generally directed to an infusion pump for delivering a flowable material, such as a fluid medication, to a patient through an infusion line. 
         [0017]    According to one aspect of the invention, the infusion pump is configured to be powered by either a disposable battery or a rechargeable battery. The infusion pump has a housing having a recess. A motor is positioned within the housing and is operably connected to an electrical contact disposed in the recess. The motor powers the pump. The recess is adapted to receive one of a disposable battery unit and a rechargeable battery unit. 
         [0018]    According to another aspect of the invention, the rechargeable battery may be in the form of a rechargeable battery unit. The rechargeable battery unit has a transformer positioned within the unit. A conductive element for providing power from an AC power outlet is coupled to the transformer. A switch is provided for receiving a first electronic signal indicative of whether the conductive element is providing power to the AC power source. A DC power source signal is provided by said AC power outlet and rectifying circuitry. A rechargeable battery source signal is provided from a receptacle within said rechargeable battery unit. The switch connects the DC power source signal to output terminals of the rechargeable battery unit only if the first electrical signal indicates that the conductive element is not providing power from the AC power source. 
         [0019]    According to another aspect of the invention, the infusion pump is adapted to receive a syringe having a syringe barrel moveably receiving a syringe plunger therein. The infusion pump has a housing defining a compartment adapted to receive the syringe. The compartment has a rear wall. The housing further has a curved lip generally adjacent to the rear wall. A clamp is connected to the housing and is positioned in the compartment in confronting relation to the rear wall. The syringe can be loaded into the compartment between the rear wall and the clamp wherein upon initial insertion, the curved lip is adapted to slidingly engage the syringe barrel allowing generally one-hand loading of the syringe into the compartment. Syringes of a variety of different sizes can be loaded into the pump in this fashion. The curved lip has a length generally in correspondence with a length of the syringe barrel adapted to be received in the compartment. The clamp is slidable by rollers positioned at one end of the clamp. 
         [0020]    According to another aspect of the invention, the infusion pump has a housing having a compartment adapted to receive a syringe having a barrel and a plunger. A drive mechanism is supported by the housing and is adapted to contact the plunger to move the plunger within the barrel. The drive mechanism further has a linearly moveable arm having a load cell mounted thereon. A load beam is pivotally connected to the arm. The load beam has one side contacting the load cell and another side adapted to contact the plunger. Upon movement of the arm to move the plunger, the load cell senses a reactive force from the load beam. The load cell converts the force into a usable signal wherein an occlusion is signaled if the usable signal is outside a predetermined acceptable range. 
         [0021]    According to another aspect of the invention, the infusion pump has a syringe plunger position sensor and a syringe barrel size sensor. Each sensor utilizes a magnet/linear sensor array assembly. 
         [0022]    According to a further aspect of the invention, the drive mechanism has a lead screw rotatably connected to a motor. A slide assembly has a threaded member wherein the threaded member is associated with the lead screw. The arm has one end connected to the slide assembly and one end adapted to be engaged with the syringe plunger. The threaded member is rotatably biased in engagement with the lead screw, wherein upon rotation of the lead screw by the motor, the slide assembly linearly moves the arm wherein the arm is adapted to move the syringe plunger within the syringe barrel. In one preferred embodiment, the threaded member is a rotary nut. 
         [0023]    According to another aspect of the invention, the infusion pump has improved communication capabilities. The pump has a user interface having a memory for storing infusion data. The pump has a data port wherein infusion data can be transferred via infrared communication from the pump to a personal digital assistant. 
         [0024]    Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0025]    To understand the present invention, it will now be described by way of example, with reference to the accompanying drawings in which: 
           [0026]      FIG. 1  is a front perspective view of one embodiment of an infusion pump which may be configured in accord with and embody the present invention; 
           [0027]      FIG. 2  is another front perspective view of the infusion pump of the present invention with an access door removed; 
           [0028]      FIG. 3 a    is a front elevation view of the infusion pump of the present invention; 
           [0029]      FIG. 3 b    is another front elevation view of the infusion pump of the present invention mounted in an alternative configuration; 
           [0030]      FIG. 4A  is a rear perspective view of the infusion pump of the present invention, showing a rechargeable battery unit associated therewith; 
           [0031]      FIG. 4B  is a rear perspective view of the infusion pump of the present invention, showing a disposable battery unit associated therewith; 
           [0032]      FIG. 5  is another rear perspective view of the infusion pump of the present invention with the battery unit removed; 
           [0033]      FIG. 6  is a rear elevation view of the infusion pump of the present invention; 
           [0034]      FIG. 7  is a side elevation view of the infusion pump of the present invention; 
           [0035]      FIG. 8  is an opposite side elevation view of the infusion pump of the present invention; 
           [0036]      FIG. 9  is a perspective view of the rechargeable battery unit shown in  FIG. 4A ; 
           [0037]      FIG. 10  is a side elevation view of the rechargeable battery unit shown in  FIG. 9 ; 
           [0038]      FIG. 11  is an end elevation view of the rechargeable battery unit shown in  FIG. 9 ; 
           [0039]      FIG. 12  is a electrical schematic view of the rechargeable battery unit; 
           [0040]      FIG. 13  is a perspective view of the disposable battery unit shown in  FIG. 4B ; 
           [0041]      FIG. 14  is a schematic view of a syringe drive mechanism and occlusion sensor for the infusion pump of the present invention; 
           [0042]      FIG. 15  is partial perspective view of the syringe drive mechanism and further showing a syringe plunger position indicator; 
           [0043]      FIG. 16  is a partial plan view of the syringe drive mechanism and further showing the syringe plunger position indicator; 
           [0044]      FIG. 17  is a partial plan view of the syringe plunger position indicator; 
           [0045]      FIG. 18  is a perspective underside view of the syringe drive mechanism and further showing a syringe barrel size indicator; 
           [0046]      FIG. 19  is an enlarged partial perspective view of a syringe barrel clamp of the infusion pump of the present invention; 
           [0047]      FIG. 20  is partial perspective view of a video display and pad associated with a user interface of the infusion pump of the present invention; 
           [0048]      FIG. 21  is a partial cross-sectional view of the video display mounted in a housing of the infusion pump; 
           [0049]      FIG. 22  is a partial perspective view of the syringe drive mechanism; 
           [0050]      FIG. 23  is a partial cross-sectional view of the syringe drive mechanism; 
           [0051]      FIG. 24  is a partial perspective view of a slide assembly of the syringe drive mechanism having a rotary nut in a disengaged position; 
           [0052]      FIG. 25  is a cross-sectional view of the slide assembly of  FIG. 24  in a disengaged position; 
           [0053]      FIG. 26  is a partial perspective view of the slide assembly wherein the rotary nut is in an engaged position; 
           [0054]      FIG. 27  is a cross-sectional view of the slide assembly of  FIG. 26  in an engaged position; 
           [0055]      FIG. 28  is a perspective view of the rotary nut; 
           [0056]      FIG. 29  is an elevation view of the rotary nut; 
           [0057]      FIG. 30  is an underside perspective view of the rotary nut; 
           [0058]      FIG. 31  is a schematic wiring diagram of a patient controlled analgesia button associated with the pump of the present invention, the button being in an at rest position; 
           [0059]      FIG. 32  is another schematic wiring diagram of the patient controlled analgesia button associated with the pump of the present invention, the button being in an actuated position; 
           [0060]      FIG. 33  is a table summarizing information revealed by the circuits associated with the button of  FIGS. 31 and 32   
       
    
    
     DETAILED DESCRIPTION 
       [0061]    While the present invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated. 
         [0062]    Referring to  FIG. 1 , therein is shown one embodiment of an infusion pump of the present invention generally referred to with the reference numeral  10 . The infusion pump  10  generally includes a housing  12  that supports a syringe assembly  14 , a user interface  16 , a power supply  18 , a drive mechanism  20  having an occlusion sensor  22  ( FIG. 14 ), and a syringe sensor system  24  ( FIGS. 15-18 ). 
         [0063]    While the present invention discloses a portable infusion pump, such as, for example, a syringe-based infusion pump, and their progeny, designed and manufactured by Baxter International, Inc. of Deerfield, Ill., it is understood that individual aspects of the invention that can be incorporated into other types of pumps or other electrical or medical devices. 
         [0064]    As shown in  FIGS. 1 and 2 , the housing  12  of the pump  10  has a generally contoured shape. The housing  12  includes a first member  26  and a second member  28  that are connected together to form a central cavity  30 . The central cavity  30  houses various components of the pump  10  including the user interface  16 . The first member  26  of the housing has an opening  32  that accommodates a display screen of the user interface  16 . As shown in  FIG. 5 , a rear portion of the housing  12  has a receptacle or recess  33  that is adapted to receive the power supply  18  to be described in greater detail below. At a bottom, front portion of the housing  12 , a container compartment or syringe compartment  34  is defined that accommodates the syringe assembly  14 , a portion of the drive mechanism  20  and other components. The first member  26  of the housing  12  has a hinged access door  36  that encloses the syringe assembly  14  in the compartment  34 . The access door  36  is preferably transparent in order for medical personnel to view the contents in the syringe assembly  14 . A lock  38  is provided with the door  36  to prevent unauthorized access to the syringe assembly  14 . The lock  38  is required because oftentimes drugs such as morphine are infused by the pump  10  and can be unfortunately subject to theft. An upper portion of the housing  12  is provided with a handle  40 . The housing  12  can be made from a variety of materials including various types of plastics and metals. As shown in  FIG. 4-8 , the housing  12  has a pole clamp  42  attached to the second member  28  of the housing  12 . The pole clamp  42  can have various designs and is adapted to mount the pump  10  on a pole assembly such as used in a hospital setting. In a preferred embodiment, the pole clamp  42  is adapted to be able to mount the pump  10  in various positions. For example, the pump  10  can be mounted in a generally horizontal position shown in  FIG. 3 a    or a generally vertical position shown in  FIG. 3   b.    
         [0065]      FIG. 2  discloses the syringe compartment  34  in greater detail. Generally, the syringe compartment  34  is dimensioned to receive and support the syringe assembly  14  as well as receive a portion of a pump actuator such as the drive mechanism  20 . Briefly, the syringe assembly  14  generally includes a syringe barrel  46  and a medical fluid member such as a syringe plunger  48 . The syringe barrel  46  contains medication and slidably receives the syringe plunger  48 . The syringe plunger  48  is driven by the drive mechanism to force medication from the syringe barrel  46  through a tube (not shown) and to a patient. The tube would have one end connected to an end of the syringe barrel  46  and another end adapted to be connected to a patient. 
         [0066]    The syringe compartment  34  has a rear wall  44  that is generally concave to receive the syringe barrel  46  of the syringe assembly  14 . The syringe barrel  46  of the syringe assembly  14  and rear wall  44  are generally in confronting relation. The housing  12  further has a curved lip  50  that in a preferred embodiment is integral with the rear wall  44 . The lip  50  aids in loading a syringe assembly  14  in the compartment  34  to be described in greater detail below. As shown in  FIGS. 2 and 19 , a syringe clamp  52  is movably mounted in the compartment  34 . The clamp  52  has a concave inner surface that faces the rear wall  44  and that fits over the syringe barrel  46 . As shown in  FIG. 18 , the clamp  52  is slidable along a rod assembly  54  to move the clamp  52  towards and away from the rear wall  44 . The clamp  52  can slide along the rod assembly  54  to accommodate different sized syringe barrels. As shown in  FIG. 19 , a base portion of the clamp  52  has a pair of rollers  56 , 58  that help reduce friction when the clamp  52  slides along the housing  12 . Due to tolerances, the clamp  52  may also pivot slightly. The clamp  52  is resiliently biased towards the rear wall  44 . The housing  12  and syringe compartment  34  are sized such that an entire syringe assembly, with plunger fully extended from the syringe barrel, is contained within the housing and can be enclosed by the access door  36 . No part of a syringe barrel or syringe plunger protrudes from the housing  12 . A portion of the drive mechanism  20  extends into the syringe compartment  34  to engage the plunger  48 . The access door  36  has an opening to accommodate the tube (not shown) that is attached to the syringe barrel  46  to deliver medication to the patient. 
         [0067]    As shown in  FIGS. 1-3 , the pump has a user interface  16 . Portions of the user interface  16  are described in greater detail in commonly-owned U.S. patent application Ser. No. 10/172,808 entitled “System And Method For Operating An Infusion Pump,” publication number 20040225252, now abandoned, filed concurrently herewith and incorporated by reference herein. The user interface  16  generally includes a display screen  60 , a first control panel  62  and a second control panel  64 , and associated electrical components and computer software contained within the housing  12  to operate the pump  10 . The display screen  60  displays all of the general operating parameters of the pump  10  and fits within the opening  32  in the housing  12 . The display screen  60  also acts as a touch screen for data to be inputted into the pump  10  by a user. As discussed, the pump  10  can be mounted in either a generally horizontal position ( FIG. 3 a   ) or a generally vertical position ( FIG. 3 b   ). The software associated with the user interface  16  has the ability to display information on the screen  60  in either a landscape orientation or a portrait orientation. When the pump is mounted in the horizontal configuration as shown in  FIG. 3 a   , information is displayed on the display screen  60  in a landscape configuration. Conversely, when the pump  10  is mounted in the vertical configuration as shown in  FIG. 3 b   , information is displayed on the display screen  60  in a portrait configuration. Thus, depending on how the pump  10  is mounted, the information can be read by users without the need to tilt one&#39;s head. This feature is described in greater detail in commonly-owned U.S. patent application Ser. No. 10/172,804 entitled “Dual-Orientation Display For Medical Devices,” filed concurrently herewith, and incorporated by reference herein. The first control panel  62  generally has a start button  66 , a stop button  68  and an alarm/alert button  70 . The second control panel  64  generally has a settings panel  72 , a history button  74  and a data port  76 . These controls will be described in greater detail below. 
         [0068]    The pump  10  and user interface  16  may utilize additional identification features regarding the medication delivered by the pump  10 . For example, and as shown in  FIG. 2 , the pump  10  may be equipped with an RFID (radio frequency identification) reader  86  that cooperates with an RFID tag  88  attached to the syringe barrel  46 . The RFID tag  86  has a transponder circuit and an antenna circuit. The RFID tag  86  can store significant information including, but not limited to, the type of medication, amount, concentration, as well as pumping parameters and instructions for the medication. The RFID reader  86  has energizer, demodulator and decoder circuits. The energizer circuit emits a low-frequency radio wave field that is used to power up the RFID tag  88 . This allows the tag  88  to send its stored information to the reader  86 . The information is demodulated and decoded where it then can be used by the computer associated with the user interface  16 . While several different configurations are possible, the RFID reader  86  can be mounted in pump housing adjacent the syringe compartment  34 . The RFID tag  88  is affixed generally to the syringe barrel  46 . When the syringe assembly  14  is properly inserted into the pump  10 , the RFID reader  86  automatically reads the information from the RFID tag  88 , which can be used to aid in properly operating the pump  10  for a particular patient. It is understood that other types of data reader/data carrier systems can also be used. 
         [0069]    As shown in  FIGS. 20 and 21 , the display screen  60  is equipped with a pad  78  about the outer periphery of the screen  60 . The pad  78  is a shock absorbent member made preferably of an elastomeric material. In one preferred embodiment, the pad  78  is made from polyurethane. The pad  78  has a face  80  that is positioned between the display screen  60  and an inner surface  82  of the first member  26  of the housing  12 . The pad  78  also has a sidewall  84  preferably integral with the face  80 . The pad  78  absorbs forces generated if the pump  10  is jostled, bumped or dropped, and minimizes the effect such occurrences have on the display screen  60 . The pad  78  also resists fluid infiltration into the housing  12 . 
         [0070]    The pump  10  of the present invention includes the power supply  18  that can take many different forms. In one preferred embodiment, the power supply  18  may be in the form of a rechargeable battery unit  90  or a disposable battery unit  92 . The rechargeable battery unit  90  is generally shown in  FIG. 4 a    and the disposable battery unit  92  is generally shown in  FIG. 4 b   . The pump  10  will operate with either unit  90 , 92  depending on the needs and desires of the user. As shown in  FIG. 5 , the pump  10  has an electrical contact  94  positioned in the recess  33  that is in electrical communication with the user interface components of the pump  10  as is known. The contact  94  will cooperate with a corresponding electrical contact on either of the rechargeable battery unit  90  or the disposable battery unit  92  as will be described. 
         [0071]      FIGS. 4 a    and  6 - 12  generally disclose the rechargeable battery unit  90 .  FIGS. 9-11  show the rechargeable battery unit  90  removed from the pump  10 . As shown in  FIGS. 4 a    and  11 , the rechargeable battery unit  90  generally includes a battery housing  96  having an electrical contact  98  to cooperate with the pump housing electrical contact  94 , a rechargeable battery  100 , associated electrical components  102 , and an AC power supply assembly  104 . 
         [0072]    As shown in  FIGS. 9-11 , the rechargeable battery unit housing  96  generally has a base member  106  and a cover member  108 . The base member  106  and cover member  108  are contoured wherein the housing  96  has a shallow first end  110  and a deeper second end  112 . The contour of the housing  96  is generally similar to the outer contour of the backside of the pump housing  12 .  FIG. 4 a   ,  6 - 8  show the unit  90  installed in the pump housing  12  illustrating the corresponding contours. As shown in  FIG. 11 , a bottom portion of the base member  106  supports the electrical contact  98 , and contacts the housing electrical contact  94  when the unit  90  is installed. As further shown, the battery unit housing  96  has a pair of posts  114  that laterally protrude from the housing  96 . The posts  114  cooperate with retainers in the pump housing  12  to retain the unit  90  within the housing  12 . A push button  116  is included on the housing cover  108  to retract the posts  114  when removing the unit  90  from the pump housing  12 . 
         [0073]    As further shown in  FIGS. 9 and 10 , the AC power supply assembly  104  has a power cord  118  and an associated terminal  120  that plugs into the housing  96 . The AC power supply assembly  104  has a plug that can be inserted into a standard electrical outlet to recharge the rechargeable battery  100  when necessary. AC power can also be supplied through the assembly  104  to power the pump  10 . 
         [0074]      FIG. 12  schematically shows the electrical components  102  that are associated with the rechargeable battery unit  90 . The electrical components  102  generally include a power supply  122  and a recharger assembly  124  that includes a recharger  126  and a diode mechanism in the form of a first diode  128  and a second diode  130 . The power supply  122 , in one preferred embodiment, is an off-line switching power supply. The power supply  122  generally includes a field-effect transistor (FET)  132 , connected to a transformer  134 , which in turn is connected to a power supply diode  136 . The power supply  122  has one connection to the AC power supply assembly  104 . The power supply  122  is also connected to the recharger  126 . The diodes  128 , 130  are generally connected to the recharger  126 , the power supply  122 , the rechargeable battery  100  and the terminal  98  so as to provide the desired power through the unit  90 . For example, when the plug of the AC power supply assembly  104  is not plugged into a wall outlet as shown in  FIG. 12 , the first and second diodes  128 , 130  are biased and configured such that power is being supplied by the rechargeable battery  100 . If the plug of the assembly  104  is plugged into a wall outlet, the power supply  122  provides 12 volts. When the 12 volts are sensed, the diodes  128 ,  130  are configured such that the rechargeable battery  100  is being recharged by the power supply  122  and the unit  90  is supplying power through the power supply  122  via the plugged in AC power supply assembly  104 . Accordingly, power can be switched from being supplied from the rechargeable battery  100  or from the wall outlet. It is further noted that because the rechargeable battery unit  90  houses the power supply  122 , the recharger  126  and the rechargeable battery  100  within the unit  90 , the battery  100  can be recharged without the use of the pump  10 . The battery  100  can be charged simply by plugging the cord of the power assembly  104 , connected to the unit  90 , into a wall outlet. The unit  90  need not be installed into the pump  10 . In prior art pumps, the pump itself is needed to recharge the battery. It is also understood that the rechargeable battery unit  90  can be defined without the AC power cord assembly  104  wherein the assembly  104  is considered a separate component removably attachable to the unit  90 . The battery units  90 , 92  may also be equipped with a microchip that is capable of transmitting data to the user interface  16  of the pump  10  such as the amount of charge left in the batteries being utilized. 
         [0075]      FIGS. 4 b    and  13  generally disclose the disposable battery unit  92 . The general structure of the disposable battery unit  92  is similar to the rechargeable battery unit  90 . The disposable battery unit has a housing  142  having an electrical contact  144  that will cooperate with the housing electrical contact  94  in the housing recess  33  (See  FIGS. 4 b    and  5 ). The housing  142  has a base member  146  and a cover member  148 . The base member  146  receives a plurality of disposable batteries  150 , and in a preferred embodiment, four D-cell batteries are utilized. It is understood, however, that other battery configurations are possible. The batteries are supported such that the batteries will supply electrical power through the contact  144  as is known. As shown in  FIG. 4 b   , the disposable battery unit  92  is received by the recess  33  of the pump  10  in the same fashion as the rechargeable battery unit  90  shown in  FIG. 4   a.    
         [0076]    Thus, depending on the desires of the user, the pump  10  may be powered by the rechargeable battery unit  90  or the disposable battery unit  92 . The pump  10  may be provided with multiple units  90 , 92  wherein the pump  10  can remain in use by replacing the unit  90 , 92  requiring either recharging, or new disposable batteries. 
         [0077]      FIGS. 14, 15 and 22-30  disclose the syringe drive mechanism  20 .  FIG. 14  represents a simplified schematic view. The syringe drive mechanism  20  is accommodated by the pump housing  12  and generally includes a motor  152 , a lead screw  154 , a connecting linkage  156  and a slide assembly  158 . Briefly, the connecting linkage  156  is connected to the slide assembly  158 , which is associated with the lead screw  154 . The slide assembly  158  which moves linearly in response to rotation of the lead screw  154  by the motor  152 . Linear movement of the connecting linkage  156  moves the syringe plunger  48 , having a plunger flange  48   a , a plunger arm  48   b  and plunger stopper  48   c , within the syringe barrel  46  to expel fluid from the syringe assembly  14 . 
         [0078]    As shown in  FIG. 14 , the motor  152  is operably connected to the lead screw  154  to rotate the lead screw  154  when the motor  152  is energized. The lead screw  154  has threads  160  that cooperate with a threaded member of the slide assembly  158  as will be described in greater detail below. 
         [0079]      FIGS. 14-18 and 22  generally show the connecting linkage  156 . The connecting linkage  156  generally includes a tube member  162  and a plunger engagement arm  164 . The tube member  162  is connected at one end to the slide assembly  158  and at another end to the plunger engagement arm  164 . As shown in  FIG. 22 , the tube member  162  houses a rod  166  that is connected to a lever  168  pivotally mounted on the engagement member  164 . As explained in greater detail below, the rod  166 , when actuated by the lever  168 , can disengage the slide assembly  158  from the lead screw  154 . This allows the slide assembly  158  to freely slide along the lead screw  154  to linearly position the plunger engagement arm  164  against the plunger  48  extending from the syringe barrel  46 . 
         [0080]    As further shown in  FIGS. 14, 15 and 22-23 , the slide assembly  158  generally includes a rail member  170  and a slide member  172 . The rail member  170  has a pair of legs  174  depending from a cover plate  176 . The slide member  172  slides beneath the cover plate  176  as can be appreciated from  FIG. 15 . The legs  174  have an inwardly protruding portion  175 . The rail member  170  is positioned within the housing  12  and adjacent the rear wall  44  of the syringe compartment  34 . 
         [0081]    As shown in  FIGS. 22-27 , the slide member  172  generally has a base  178  and a cover  180  that collectively support a threaded member  182  or rotary nut  182  therein. The base  178  has a countersunk bore  184  therethrough that is in communication with a channel  186 . The bore receives the rotary nut  182  and the channel  186  accommodates a portion of the rotary nut  182  and the lead screw  154 . The base  178  has a pair of cantilevered beams  188  that correspond in shape to the legs  174  of the rail member  170 . The beams  188  are slightly biased into frictional sliding engagement with the legs  174  and provide a smooth sliding movement of the slide member  172  along the rail member  170 . As shown in  FIG. 23 , the cover  180  fits over the rotary nut  182 . The cover  180  supports additional structure such as a pin  185  and lock arm  187  (See  FIG. 24 ). This structure will be described in greater detail below. 
         [0082]      FIGS. 28-30  further disclose the rotary nut  182 . The rotary nut  182  is a unitary member having a generally cylindrical base  190 . The base  190  has a lip  192  that engages the countersunk bore  184  in the slide member  172 . The base  190  has a first finger  194  and a second finger  196  depending therefrom. The fingers  194 , 196  are spaced to define an opening  197 . The opening  197  receives the lead screw  154 . Fingers  194  and  196  have first and second threaded portions  1989  respectively thereon that engage the threads  160  on the lead screw  154 . Fingers  194  and  196  have first and second threaded portions  198  respectively thereon that engage the threads  160  on the lead screw  154 . The threads  198  are positioned on generally opposed sides of the rotary nut  182 . The base  190  further has an over-rotation surface  200  and a rotation surface  202 . 
         [0083]    As further shown in  FIGS. 22-27 , the rotary nut  182  is received in the cylindrical bore  184  in the slide member  172 . The tube member  162  of the connecting linkage  156  is connected to the base  178  of the slide member  172 . The slide member  172  is positioned for sliding movement on the rail member  170 . The lead screw  154  is routed through the channel  186  in the slide member  172 .  FIGS. 26 and 27  show the rotary nut  182  in an engaged position with the lead screw  154 . In  FIG. 26 , the cover  180  of the slide member  172  is removed for clarity. The rotary nut  182  is rotationally biased into engagement with the lead screw  154  by a spring  204 . The threads  198  on each finger  192 , 194  of the rotary nut  182  engage generally opposed sides of the lead screw  154 . The over-rotation surface  200  engages the pin  185  (carried by the cover  180 ) to prevent over-rotation of the nut  182  into the lead screw  154 . This maximizes performance and minimizes wear of the threads  198  of the rotary nut  182 . With the threads  198 , 160  engaged, when the motor  152  rotates the lead screw  154 , the rotary nut  182  moves along the lead screw  154  which, in turn, linearly moves the slide member  172  and connecting linkage  156 . This pushes the plunger  48  into the syringe barrel  46  to displace medicament from the syringe assembly  14 . The lock arm  187  engages the base  190  of the rotary nut  182  to prevent the rotary nut  182  from disengaging under load such as from back pressure from the syringe assembly  14 . 
         [0084]    The rotary nut  182  can also be easily disengaged from the lead screw  154  which allows the slide member  172  to be positioned along the lead screw  154  such as when positioning the plunger engagement arm  164  against the syringe plunger  48 . As shown in  FIGS. 22, 24 and 25 , the lever  168  is rotated on the plunger engagement arm  164 . A camming action linearly moves the rod  166  within the tube member  162 . The rod  166  engages the rotation surface  202  to rotate the rotary nut  182 . The rotary nut  182  is rotated such that the threads  198  become disengaged from the threads  160  on the lead screw  154 . This allows the slide member  172  to slide freely along the rail member  170  to position the plunger engagement arm  164 . 
         [0085]    The rotary nut  182  provides several advantages over previous nut/lead screw arrangements using single or multiple half-nuts that engage the lead screw. Half-nuts require a high rate spring to bias the nut into engagement with the lead screw and prevent disengagement. This requires transverse side loading of the lead screw that causes wear and mechanism inefficiency. Because the rotary nut  182  is a unitary piece, misalignment problems between two half-nuts is also eliminated. The rotary nut  182  utilizes a positive stop and lock. Therefore, side loads, moments, over engagement and disengagement during pumping are eliminated and wear is minimized. 
         [0086]    The pump  10  is equipped with an occlusion sensor  22  to determine if an infusion line connected to the syringe barrel  46  is blocked. In one preferred embodiment of the invention, the occlusion sensor  22  is incorporated into the plunger engagement arm  164  of the drive mechanism  20 . As shown schematically in  FIG. 14 , the occlusion sensor  22  generally includes a load cell  210  and a load beam  212 . The load cell  210  is connected to a distal end of the plunger engagement arm  164 . The load beam  212  is connected to generally a mid-portion of the arm  164  through a pivotal connection  214 . The load beam  212  has a pusher block  216  that abuts against the end of the syringe plunger  48 . The load cell  210  is positioned adjacent to and in contact with a distal end  218  of the load beam  212 . Thus, one side of the load beam  212  contacts the load cell  210  and another side of the load beam  212  contacts the syringe plunger  48 . A flipper  220  can extend from the arm  164  and be abutted against the plunger  48  to assure the plunger  48  always remains in contact with the pusher block  216 . 
         [0087]    In operation, the drive mechanism  20  drives the arm  164  as described above. This in turn drives the load beam  212  wherein the pusher block  216  pushes against the plunger  48 . This forces and linearly moves the plunger  48  within the barrel  46 . The load cell  210  measures a reactive force from the force pushing against the load beam  212 . The circuitry associated with the load cell  210  converts the force to a usable signal. In a preferred embodiment, the usable signal is a voltage value. If too much force is required to move the plunger  48 , it signifies that the infusion line is blocked. In such a case, the voltage detected is greater than a predetermined value, and the sensor  22  signals an occlusion in the infusion line. Thus, if the usable signal is out of a predetermined range, an occlusion is sensed. A user can then remedy the situation. 
         [0088]      FIGS. 15-18  disclose various aspects of the syringe sensor system  24 . The system  24  generally includes a syringe plunger position sensor  230  and a syringe barrel size sensor  232 .  FIGS. 15-17  disclose the syringe plunger position sensor  230 . The sensor  230  is generally an eletromagnetic sensor that includes a magnet  234  and a plunger linear sensor array  236 . The magnet  234  is mounted generally on the arm  164  of the connecting linkage  156  of the drive mechanism  20 . The magnetic sensor in the form of a linear sensor array  236  has a plurality of sensors  238  in the form of magnets that are positioned directly adjacent to the linear path of the plunger movement. The magnet  234  has a magnetic field associated therewith. As shown in  FIG. 16-17 , the sensors  238  detect the orientation of the field lines in the magnetic field. The resulting signal is typically a sine wave. One sensor  238  has a specific length over which it can detect plunger movement. Then, the next sensor  238  will sense position. The sensors are initially calibrated wherein the pump software can determine the location of the plunger engagement arm  164  and, therefore, the plunger, based on the signal levels detected by each of the sensors  238 . The magnet  234  is positioned substantially at a distal end of the plunger  48 , or at the plunger head. The sensors  238  are directly adjacent the syringe plunger  48 . With such a configuration, a direct measurement of the plunger position is possible rather than relying on indirect measurements. The sensors  238  are also configured to compensate for temperature changes as the pump  10  may be utilized in different environments. 
         [0089]      FIG. 18  discloses the syringe barrel size sensor  232 . Similar to the plunger position  30  sensor  230 , the syringe barrel size sensor  232  is generally an electromagnetic sensor that includes a magnet  240  and a barrel linear sensor array  242 . The magnet  240  is mounted on the syringe barrel clamp assembly. The linear sensor array  242  is mounted generally adjacent thereto and has a sensor  244 . Because the movement of the syringe barrel clamp is less than the plunger movement, a single sensor  244  can be used. Similar to the syringe plunger position sensor, based on the signal levels sensed by the sensor  244 , the sensor  232  can determine what size syringe is loaded into the pump  10 . 
         [0090]    In operation, the pump  10  is mounted on a support structure such as a pole in either a horizontal or vertical configuration as shown in  FIGS. 3 a  and 3 b   . The access door  36  is opened and a syringe assembly  14  is loaded into the pump  10 . As shown in  FIGS. 1, 2 and 19 , the syringe assembly  14  can be conveniently loaded into the pump  10  with a single hand. Prior art pumps require both hands of a user to load the syringe. As shown in  FIG. 2 , the curved lip  50  allows the syringe  14  to slide easily into the syringe compartment  34 . As shown in  FIG. 19 , the rollers  56 , 58  associated with the syringe barrel clamp  52  allows the clamp  52  to slide upwards along the housing  12  in accepting the syringe  14  as in a snap-fit arrangement. When the syringe  14  is further inserted, the clamp  52  is biased back onto the syringe barrel  46 . The infusion line is attached to the syringe and connected intravenously to a patient. The access door  36  is locked. The operating parameters of the pump  10  are loaded into the pump software through the user interface  16 . The infusion therapy can then be started. 
         [0091]    The pump  10  can be equipped with several different features to enhance its operability. For example, the pump can accommodate patient-controlled analgesia (PCA). To that end and as shown in  FIG. 2 , the pump  10  can have a PCA button  299  wherein a user can further control the infusion therapy wherein the user can push the button to deliver additional doses of medication. The PCA button typically has a cord that can be plugged into the pump  10  as is generally known. The button  299  can be specially designed to be activated by a thumb of a patient. As further shown in  FIG. 2 , the button  299  can also be equipped with a fingerprint reader  301  to assure only the patient can activate the PCA button  299 . The fingerprint reader  301  is operably connected to the user interface  16 . The patient&#39;s fingerprint or thumbprint can be pre-loaded into the pump software of the user interface  16 . When the PCA button  299  is pushed, and the reader  301  reads the thumbprint, the software verifies the button  299  was pushed by the patient by comparing the print that was read with the stored thumbprint. The PCA button  299  can have peripheral structure to protect inadvertent actuation. The PCA button  299  can also be lighted so as so glow in the dark to aid patients in locating the button. 
         [0092]      FIGS. 31-33  disclose additional features associated with the PCA button  299 .  FIGS. 31 and 32  show wiring diagrams  300  and  301  for the PCA button. Wiring diagrams  300  and  301  include a first circuit  302 , a second circuit  304 , a third circuit  306 , a common ground  308 , and a 4-pole push button  310  carried by the PCA button  299 .  FIG. 31  shows a wiring diagram  300  having the push button  310  in an at rest position.  FIG. 32  shows wiring diagram  301  having the push button  310  in an actuated position. As shown in  FIGS. 31 and 32 , circuits  302 ,  304 , and  306  share a common ground  308 . Though a common ground  308  is the simplest way to wire circuits  302 ,  304 , and  306 , it is not required for the invention that the circuits  302 ,  304 , and  306  share a common ground  308 , as long as the circuits are able to provide signals to a microprocessor associated with the pump user interface  16 . Circuits  302 ,  304 , and  306  are designed to provide a status change in signal to the microprocessor. The status change may occur due to the installation of the PCA button  299  and associated wiring  312 . The status change may also occur due to a circuit being connected to ground through push button  310  versus when the circuits are open. Wiring  312  may be enclosed in a cable. 
         [0093]    Circuits  302 ,  304 , and  306  are maintained at an energized state when not connected to ground  308  through button  310 . Conversely, circuits  302 ,  304 , and  306  are at a ground state when connected to ground  308  through button  310 . For example, circuits  302 ,  304 , and  306  may maintain a small positive voltage when not connected to ground  308  through button  310 . The small positive voltage may be coordinated with desired input signals for the microprocessor while considering the safety requirements of the medical environment. 
         [0094]    As circuits  302 ,  304 , and  306  are maintained at an energized state, also known as a “HIGH” state, when not connected to ground, the circuits will all be in a HIGH state when button  310  is not installed. Installation may involve connecting the button  310  to the wiring  312 . Installation may also involve connecting the PCA button  299 , and therefore, pushbutton  310  and wiring  312  to infusion pump  10 . 
         [0095]    Wiring diagram  300  shows push button  310  in an at rest installed position. When button  310  is in the at rest installed position, first circuit  302  is connected to ground directly through wiring  312  and through contacts  310   b  and  310   a  and is therefore in the ground state, or “LOW” state. When button  310  is in the actuated position as shown in wiring diagram  301 , first circuit  302  is still connected to ground directly through wiring  312  and through contacts  310   c  and  310   d  and is therefore in the LOW state as long as button  310  is installed. 
         [0096]    When button  310  is in the at rest installed position, second circuit  304  is connected to ground  308  through contact  310   a  and is therefore in the LOW state. When button  310  is in the actuated position as shown in wiring diagram  301 , second circuit  304  is not connected to ground  308  and is therefore in the HIGH state. 
         [0097]    When button  310  is in the at rest installed position, third circuit  306  is not connected to ground  308  and is therefore in the HIGH state. When button  310  is in the actuated position as shown in wiring diagram  301 , third circuit  306  is connected to ground through contacts  310   c  and  310   d  and is therefore in the LOW state. 
         [0098]      FIG. 33  shows a table  400  summarizing information provided by the status signals of the three PCA circuits  302 ,  304 , and  306  of  FIGS. 31 and 32 . Table  400  shows that the PCA button is not installed if circuits  302 ,  304 , and  306  are all providing a HIGH status signal. If first circuit  302  and second circuit  304  are providing a LOW status signal, while circuit three is providing a HIGH status signal, the button  310  is installed and is in the rest position. If first circuit  302  and third circuit  306  are providing a LOW status signal, while second circuit  304  is providing a HIGH status signal, the button  310  is installed and is actuated. Various other combinations of status signals indicate that a fault exists. Potential faults include, but are not limited to, cable failures, switch malfunctions, and electronic circuit malfunctions. Thus, if one of the wires associated with the PCA button  299  becomes frayed and eventually breaks, a specific reading can be sensed by the user interface to indicate the PCA button  299  requires replacement. 
         [0099]    The pump  10  can also be designed with enhanced communication capabilities. For example, the pump  10  can communicate wirelessly with other devices such as a pharmacy computer or personal digital assistants (PDA) carried by hospital personnel. The pump  10  can also be monitored remotely such as from a nurse&#39;s station. The pump  10  can be equipped with various types of readers to receive patient information such as from swipe cards or bar-coded identification bracelets. The pump  10  may also utilize RFID readers and tags as discussed above. 
         [0100]    In one preferred embodiment of the invention, the pump  10  can communicate with a PDA  500  as shown in  FIG. 2 . The pump  10  has the infrared data port  76  that is operably coupled with the user interface  16  of the pump  10 . The user interface  16  has memory that stores information regarding pump history such as medications delivered, dosage, time, date etc. The information stored by the user interface  16  can be electronically transferred to the PDA  500  carried, for example, by medical personnel. For example, the history button  74  can be depressed on the pump control panel indicating a desire to download pump history. The pump  10  will prompt the user for a password on the video display  60 . The password may be necessary for certain regulatory requirements. The pump  10  will then prompt the user for a patient identification number so the proper pump history can be identified. The pump  10  then prompts the user to position the PDA  500  up to the data port  76 . Once positioned properly, the pump  10  downloads the proper pump history to the PDA  500 . The user can then view the data on the PDA  500 , print the pump history or sync the data to another computer as desired. The data can be formatted to be in paginated form. 
         [0101]    The pump  10  may also communicate directly to a printer. In one embodiment, a hand-held printer having an appropriate data port, can be held up to the data port  76  of the pump  10 . Via infrared communication, data can be transferred from the pump  10  and printed by the hand-held computer. 
         [0102]    As discussed, the pump  10  provides several advantages. The pump  10  can be powered by either a rechargeable battery unit or a disposable battery unit as is desired by the. user. Separate pumps are not required. Because the pump  10  can be powered by battery units, the pump  10  can be used in locations where there are limited electrical outlets. Furthermore, because the transformer for recharging the batteries is contained within the rechargeable battery unit rather than the pump, the rechargeable battery unit can be recharged simply by plugging the unit into a wall outlet. The pump is not required. Accordingly, the pump  10  can be equipped with a second unit and remain in use while the first unit is being recharged. Also, the transformer is better stored within the battery unit housing rather than being located at the end of the power cord. The syringe loaded is improved as a syringe assembly can be easily loaded with a single hand. The syringe sensors are improved and are more reliable. The sensors provide a direct measurement of, for example, plunger position rather than an indirect measurement. The magnet and sensors are positioned directly at the syringe plunger providing a direct measurement of plunger position. The sensor system has fewer parts in general and does not utilize additional moving parts that are subject to wear. This improves reliability. The rotary nut associated with the drive mechanism provides a more smooth and reliable mechanism. 
         [0103]    While the specific embodiments have been illustrated and described, numerous modifications can be made to the present invention, as described, by those of ordinary skill in the art without significantly departing from the spirit of the invention. The breadth of protection afforded this invention should be considered to be limited only by the scope of the accompanying claims. 
         [0104]    It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.