Abstract:
An infusion pump unit includes a housing sized to allow the pump unit to be carried as a portable unit. The housing contains a controllable pumping system for pumping fluid. The pump actuator is lighter, smaller, quieter and less power consuming.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation of U.S. patent application Ser. No. 11/041,189 filed on Jan. 21, 2005 by Morten Mernoe, which is a continuation of International Application No. PCT/DK2003/000507 filed Jul. 21, 2003, which claims priority to Denmark Patent Application No. PA200201133 filed on Apr. 24, 2002. The disclosures of these previous applications are incorporated herein by reference. 
     
    
     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not Applicable  
       BACKGROUND OF THE INVENTION  
       [0003]     The present invention generally relates to the technical field of infusing a liquid to a patient or person by means of an infusion pump, e.g. at a hospital. The present invention also relates to infusion of liquid to an animal. More precisely, the present invention relates to an infusion pump system and an infusion pump unit of a universal applicable structure for infusing a liquid into a patient or person.  
         [0004]     At hospitals or nurse houses, it is often necessary to supply medication or body liquids to a person by means of an infusion pump in which instance the medication or the body liquids are infused into the body of the patient or person in question through a catheter which is connected to the blood transportation system of the patient or person, e.g. a vein or a venule. The usual technique of supplying medication by means of an infusion system to a patient or person involves the supply of physiologic liquid to the patient which physiologic volume is supplied at a specific rate and which serves as a diluting liquid as the medication is supplied to the physiologic liquid also at a specific rate such as one or two drops of medication per time period varying from a second or a few seconds to several minutes or even hours. The medication of a patient or person may in some applications involve the supply of the medication directly to the patient or person by means of the infusion pump.  
         [0005]     U.S. Pat. No. 6,270,478 discloses an infusion pump system allowing the patient or person using the infusion pump system to shift from a position sitting or lying in a bed and move around without necessitating the substitution or shift of the stationary infusion pump to a portable infusion pump as the infusion pump system constitutes a universally applicable or combined portable and stationary infusion pump system.  
         [0006]     An advantage of this known system relates to the fact that the infusion pump system may be used in different pumping modes as the infusion pump system includes several programmes for different operational modes and further preferably includes input means for input of different operational programmes. U.S. Pat. No. 6,270,478 is hereby incorporated herein by reference.  
         [0007]     The pump actuator of the infusion pump units of this known system comprises a magnetic core and a solenoid coil. This actuator is rather bulky, noisy and heavy and requires a relatively large input of electrical energy.  
       SUMMARY  
       [0008]     It is an object of the present invention to provide an infusion pump system, an infusion pump unit for said system and an infusion pump in general were the pump actuator is lighter, smaller, quieter and less power consuming.  
         [0009]     According to one aspect of the invention this object is achieved by providing a shape memory alloy actuator as the pump actuator, and said shape memory actuator comprises: 
        a body arranged displaceable between a first and a second position, 
            releasable holding means adapted for holding said body in said first position, 
                at least one first and at least one second wire made of a shape memory alloy such as nitinol, said first wire being at one end connected to said body such that shortening of the length of said first wire exerts a force on said body for moving said body from said second to said first position, and     a biasing means, such as a tension spring, a compression spring, a straight or arcuate flat spring or a piston and cylinder mechanism, arranged and adapted for biasing said body for moving said body from said first to said second position,    
                said second wire having one end connected to said holding means such that shortening of the length of said second wire releases said holding means for allowing said biasing means to move said body from said first position to said second position.    
               
 
         [0015]     According to another aspect this object is obtained by providing a shape memory alloy actuator as the pump actuator, and said shape memory actuator comprises: 
        a body arranged displaceable between a first and a second position,     at least one first wire made of a shape memory alloy such as nitinol, said first wire being at one end connected to said body such that shortening of the length of said first wire exerts a force on said body for moving said body from said second to said first position,     a biasing means, such as a tension spring, a compression spring, a straight or arcuate flat spring or a piston and cylinder mechanism, and     a rotatably arranged intermediate member such as a lever or a disc connected to said body and to said biasing means,     said biasing means being adapted for exerting a rotation force on said intermediate member for rotating said intermediate member around an axis of rotation in a first direction of rotation from a first angular position to a second angular position, said intermediate member being connected to said body such that rotation of said intermediate member in said first direction of rotation displaces said body from said first position to said second position, and     said biasing means and said intermediate member being arranged and adapted such that the lever or moment arm of said rotation force with respect to said axis of rotation is larger when said intermediate member is in said second angular position than when said intermediate member is in said first angular position such that said lever or moment arm of said rotation force increases when said intermediate member rotates in said first direction of rotation.        
 
         [0022]     According to a yet further aspect of the invention this object is achieved by providing a shape memory alloy actuator as the pump actuator, and said shape memory actuator comprises: 
        a body arranged displaceable between a first and a second position, 
            at least one first wire made of a shape memory alloy such as nitinol, said first wire being at one end connected to said body such that shortening of the length of said first wire exerts a force on said body for moving said body from said second to said first position,     a biasing means, such as a tension spring, a compression spring, a straight or arcuate flat spring or a piston and cylinder mechanism, and     a rotatably arranged intermediate member such as a lever or an arm connected to said body at a force transmission point on said body and connected to or integral with said biasing means, 
 
 said biasing means being adapted for exerting a rotation force on said intermediate member for rotating said intermediate member around an axis of rotation in a first direction of rotation from a first angular position to a second angular position, said intermediate member being connected to said body such that rotation of said intermediate member in said first direction of rotation displaces said body in from said first position to said second position, and 
 
 said intermediate member and said body being arranged and adapted such that said rotation force is transmitted to said body as a displacement force applied at said force transmission point for moving said body from said first to said second position, and such that the lever or moment arm of said displacement force with respect to said axis of rotation is larger when said intermediate member is in said first angular position than when said intermediate member is in said second angular position such that said lever or moment arm of said displacement force with respect to said axis of rotation 
   
               
 
         [0027]     Hereby a quiet, light, mechanically efficient and compact infusion pump is obtained.  
         [0028]     In a yet further aspect the present invention relates to a fluid pump, preferably for use in an infusion pump system, an infusion pump unit or as an infusion pump, said fluid pump comprising: 
        a flexible tube connected to a fluid inlet at one end and connected to a fluid exit at the opposite end,     at least three flattening bodies for flattening said tube against an abutment element and arranged along the length of said tube, said bodies being arranged displaceable between a first position, wherein said body is pressed against said abutment element with said tube flattened between said body and said abutment element, and a second position spaced so far from said abutment element that said tube at least partly has regained an open configuration,     at least one first wire for each flattening body and made of a shape memory alloy, said first wire being at one end connected to said body such that shortening of the length of said first wire exerts a force on said body for moving said body from said first to said second position, and     a biasing means, such as a tension spring, a compression spring, a straight or arcuate flat spring or a piston and cylinder mechanism, for each of said flattening bodies and connected to said flattening body such that a biasing force is exerted on said flattening body in a direction from said second position to said first position.        
 
         [0033]     Hereby an exceptionally light, simple and quiet infusion pump is obtained where the elements that are to be replaced for each infusion are relatively inexpensive and easy to replace.  
         [0034]     In a yet further aspect the present invention relates to an infusion pump for infusing a fluid or a paste in a patient, preferably a portable infusion pump and preferably for use in infusing insulin or a pain killer fluid in a patient, said infusion pump comprising: 
        a housing, 
            a cartridge, ampoule or syringe containing said fluid or paste and removably arranged in said housing and having an outlet aperture and a piston element slidably arranged inside said syringe such that said piston is displaceable towards said outlet aperture,     a spindle connected to said piston element and arranged such that rotation of said spindle in a first rotational direction displaces said piston towards said outlet aperture     a shape memory alloy actuator incorporated in a shape memory alloy motor comprising:     said shape memory alloy actuator having: 
                a body arranged displaceable between a first and a second position,     at least one first wire made of a shape memory alloy such as nitinol, said first wire being at one end connected to said body such that shortening of the length of said first wire exerts a first displacement force on said body for moving said body from said second to said first position,     a biasing means, such as a tension spring, a compression spring, a straight or arcuate flat spring or a piston and cylinder mechanism arranged and adapted for exerting a second displacement force on said body for moving said body from said first to said second position,    
                and     a gear having a first and second rotation direction, 
 
 said body having a portion adapted to fit between two adjacent teeth of said gear, and said body and said gear being adapted and arranged such that in said first position said portion is located between a pair of teeth of said gear and in said second position said portion is located between the adjacent pair of teeth of said gear reckoned in said second rotation direction of said gear such that said second displacement force will cause said body to rotate said gear in said first direction, and 
 
 said gear being connected to said spindle, preferably via at least one further gear such that rotation of said gear in said first direction causes said spindle to rotate in said first rotational direction. 
   
               
 
         [0045]     In a yet further aspect the present invention relates to an infusion pump for infusing a fluid or a paste in a patient, preferably a portable infusion pump and preferably for use in infusing insulin or a pain killer fluid in a patient, said infusion pump comprising: 
        a housing, 
            a cartridge, ampoule or syringe containing said fluid or paste and removably arranged in said housing and having an outlet aperture and a piston element slidably arranged inside said syringe such that said piston is displaceable towards said outlet aperture,     said shape memory alloy actuator, having 
                a body arranged displaceable between a first and a second position,     at least one first wire made of a shape memory alloy such as nitinol, said first wire being at one end connected to said body such that shortening of the length of said first wire exerts a first displacement force on said body for moving said body from said second to said first position,     a biasing means, such as a tension spring, a compression spring, a straight or arcuate flat spring or a piston and cylinder mechanism arranged and adapted for exerting a second displacement force on said body for moving said body from said first to said second position,    
                and     a rack having a first and second displacement direction and abutting said piston such that displacement of said rack in said second displacement direction displaces said piston towards said outlet aperture, 
 
 said body having a portion adapted to fit between two adjacent teeth of said rack, and said body and said rack being adapted and arranged such that in said first position said portion is located between a pair of teeth of said rack and in said second position said portion is located between the adjacent pair of teeth of said gear reckoned in said second displacement direction of said rack such that said second displacement force will cause said body to displace said rack in said first direction. 
   
               
 
         [0054]     In a final aspect the present invention relates to an infusion pump system, comprising: 
        at least one infusion pump unit, comprising:     a housing of a size allowing said infusion pump unit to be carried by a user as a portable infusion pump unit, said housing defining an exterior surface,     a fluid inlet provided accessibly at said exterior surface for establishing fluid communication from an external infusion bag to said fluid inlet,     a fluid outlet provided accessibly at said exterior surface for establishing fluid communication to an infusion site,     a controllable pumping system included within said housing and having an inlet and an outlet, said inlet being connected to said fluid inlet and said outlet being connected to said fluid outlet for allowing transfer of fluid from said fluid inlet to said fluid outlet through activating said controllable pumping system,     an electronic control means received within said housing for controlling the operation of said controllable pumping system, said electronic control means including at least two preset pumping programs for allowing said controllable pumping system to be controlled in at least two alternative infusion pumping operations, and     a power supply unit housed within said housing for supplying power to said controllable pumping system and to said electronic control means and connectable through exterior terminals provided at said exterior surface of said housing to external electric energy supply means,        
 
         [0062]     a stationary receptor system including: 
        at least one receptor means for receiving and fixating one of said infusion pump unit therein so as to maintain said infusion pump unit in a stationary mode and exposing said fluid inlet and fluid outlet of said infusion pump unit for allowing access thereto and having first terminals connectable to said exterior terminals for supplying said electric energy to said power supply unit of said at least one infusion pump unit and further having second terminals connectable to third terminals of a second receptor means for supplying power to said second receptor means,     a mains supply unit for receiving electric energy from the mains supply and having second terminals connectable to said third terminals for supplying said electric energy to said receptor means and thereby to said power supply unit of said at least one infusion pump unit, said mains supply unit constituting said external electric supply means, and     fastening means for fastening said receptor means adjacent one another and for fastening said mains supply unit adjacent one of said receptor means.        
 
         [0066]     In the currently preferred embodiment, said system further comprises a carrier frame for carrying one infusion pump unit and provided with receiving means for receiving said infusion pump unit and preferably with releasable holding means for holding a container of infusion fluid communicating with said fluid inlet of said infusion pump unit, said receptor means and said carrier frame having cooperating connection means for allowing said frame to be connected to said receptor means such that said external terminals are connected to said first terminals.  
         [0067]     Hereby a flexible system is obtained where an optional number of receptor means may be arranged adjacent one another and where great flexibility is achieved as to the transport of an infusion pump unit with the corresponding patient. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0068]     In the following the invention will be explained more in detail in connection with various embodiments thereof shown, solely by way of example, in the accompanying drawings in which  
         [0069]      FIG. 1  is a perspective and schematic view of a first embodiment of a portable infusion pump unit according to the present invention,  
         [0070]      FIG. 2  is an elevational and partly sectional view of the first embodiment of the portable infusion pump unit illustrated in  FIG. 1 ,  
         [0071]      FIG. 3  is a schematic view of the interior of the first embodiment of the portable infusion pump unit illustrated in  FIGS. 1 and 2 , disclosing the flow path thereof,  
         [0072]      FIG. 4  is a schematic view illustrating a possible application of the first embodiment of the portable infusion pump unit illustrated in  FIGS. 1, 2  and  3 ,  
         [0073]      FIG. 5  is a perspective and schematic view illustrating the application of the first embodiment of the portable infusion pump unit illustrated in  FIGS. 1-4  in a stationary charger and fixation system for providing a stationary infusion pump system,  
         [0074]      FIGS. 6 and 7  are schematic illustrations of a first embodiment of a pump actuator according to the invention in two different positions, namely with the activating pin fully retracted in  FIG. 6 , and with the activating pin fully extended in  FIG. 7 ,  
         [0075]      FIGS. 8 and 9  are schematic illustrations of a second and third embodiment, respectively, of a pump actuator according to the invention,  
         [0076]      FIGS. 10-12  are schematic illustrations of three stages in the operation of a fourth embodiment of an actuator according to the invention,  
         [0077]      FIG. 13  is a graph showing two curves of Contraction versus Force for shape memory alloy wires for different biasing systems for the actuators according to the invention, and  
         [0078]      FIG. 14  is a graph showing the relationship between various forces in Newton and the distance of displacement of a piston pump plunger in mm by the actuator shown in  FIGS. 10-12 .  
         [0079]      FIGS. 15 and 16  are schematic illustrations similar to  FIG. 2  of a second embodiment of an infusion pump unit according to the invention illustrating the use of the shape memory alloy actuators of  FIGS. 6-7  and  FIGS. 10-12 , respectively, as the pump actuators  
         [0080]      FIG. 17  is a sequence of schematic illustrations showing various stages in the pumping cycle of a fluid pumping system according to the invention utilising SMA actuators,  
         [0081]      FIG. 18  schematically illustrates two stages in the operation of an SMA actuator incorporated in the pumping system in  FIG. 17 ,  
         [0082]      FIG. 19  is a schematic illustration of a first embodiment of a shape memory alloy actuator motor for use in an infusion pump according to the invention,  
         [0083]      FIG. 20  is a schematic illustration of a second embodiment of a shape memory alloy actuator motor for use in an infusion pump according to the invention,  
         [0084]      FIG. 21  is a schematic, partly sectional view of an infusion device according to the invention particularly well suited for dispensing insulin to a diabetes patient,  
         [0085]      FIG. 22  is a schematic view of the actuator and dispensing syringe of the device in  FIG. 21 ,  
         [0086]      FIG. 23  is a schematic view of a second embodiment of an actuator and a dispensing syringe for incorporation in the device in  FIG. 21   
         [0087]      FIG. 24  is a schematic view of a rack-type SMA actuator for incorporation in the device in  FIG. 21 ,  
         [0088]      FIG. 25  is a perspective and schematic view illustrating an alternative application of the first embodiment of the portable infusion pump unit illustrated in  FIGS. 1-4  in a stationary charger and fixation system for providing a stationary infusion pump system, and  
         [0089]      FIG. 26  is a perspective and schematic view of the components of the system in  FIG. 25 . 
     
    
     DETAILED DESCRIPTION  
       [0090]     In the drawings, a first embodiment of a portable infusion pump unit or apparatus is disclosed designated the reference numeral  10  in its entirety. The apparatus  10  comprises a housing composed of two shell-like housing parts  12  and  14  constituting a front and rear housing part, respectively. The front an rear housing parts  12  and  14 , respectively, are easily disassembled allowing the user to obtain access to the interior of the apparatus for substituting an interior fluid passage component to be described in greater detail below with reference to  FIG. 3  constituting a disposable pre-sterilized component which is easily demounted after use and readily replaced prior to use. From the rear side of the housing part  14 , a clip  16  allowing the apparatus  10  to be fixed to a strap or a belt extends. It is to be realised that terms such as upper, lower, front, rear, etc., unless otherwise stated, in the present context define positions or orientations determined by the intentional application of the apparatus  10  as the apparatus is positioned in an upright and substantially vertical position, e.g. received in the belt of a user by means of the clip  16  or otherwise positioned exteriorly or non-implantatedly relative to the user.  
         [0091]     In the front housing part  12 , a display  20  is provided, comprising two sets of two digits designated the reference numerals  22  and  24 , respectively, for displaying digits representing the time lapsed or the time remaining for infusion operation expressed in minutes and hours, respectively, or seconds and minutes, respectively, or alternatively for displaying digits representing the supply of infusion liquid as expressed in volume per time unit, e.g. ml per hour. The display  20  further includes a display area  26  for informing the user and/or a person operating the infusion pump apparatus  10  or nursing the user regarding the operational mode of the apparatus, such as standby or running information. Furthermore, the display  20  includes a number of individual displays positioned above one another and above the standby/running display  26 , one of which is designated the reference numeral  28 . These individual displays  28  are adapted to display information such as the operational mode, e.g. the information that the apparatus is in a program mode, information regarding whatever information is presented on the two-digit displays  22 ,  24 , such as the time remaining for infusion operation, the total time of the infusion operation, whether or not the apparatus is running or is to be started, or any other relevant information to be presented to the user or operator. The display  20  further includes three individual alarm displays  30 ,  32  and  34  for informing the user of the presence of air in the infusion pump circuitry, pressure fault or failure or low battery, respectively. A further display  36  informs the user or operator of the program sequence presently used or programmed, which program sequence is represented by a digit displaced by a 1-digit display  38 . A 3-digit display  40  of the display  20  represents information to the user or operator regarding the infusion supply measured in ml per hour or similar relevant measure or ratio.  
         [0092]     Below the display  20 , a keyboard  42  is provided including a set of keys, one of which is designated the reference numeral  44  for allowing the user/operator to control the portable infusion pump unit  10  to perform a specific operation or to program the apparatus by shifting between specific program sequences by increasing a specific digit displayed in a 1-, 2- or 3-digit display, such as the displays  22 ,  24 ,  38  and  40 , by increasing or reducing the digit in question and by shifting a cursor route relative to the various individual displays of the display  20  for allowing the user/operator to modify the operational mode or shift between various preset programs of the apparatus.  
         [0093]     At the one side wall of the housing, composed by the housing parts  12  and  14  of the unit or apparatus  10 , two terminals  46  and  48  are provided for allowing the apparatus  10  to be connected to an electronic charger for supplying electric power to an internal rechargeable battery pack or cell of the apparatus. The terminals  46  and  48  may alternatively or additionally serve as input/output terminals for establishing communication between the apparatus  10  and an external apparatus or equipment such as an external data logging apparatus or surveillance apparatus or further alternatively for communicating with an external processing unit such as a personal computer or data logging apparatus. Still further, the apparatus  10  may be provided with a conventional input/output terminal such as a conventional RS 232 terminal for establishing communication between the apparatus  10  and an external computer such as the above-mentioned personal computer for processing data produced by the apparatus concerning the operational mode of the apparatus and also supplementary data produced by the apparatus or auxiliary equipment, e.g. data representing the temperature of the infusion liquid supplied by the apparatus  10  or data supplied by additional external measuring or surveillance equipment. In the top wall of the housing of the apparatus  10  two recesses are provided for receiving two tube connectors  50  and  52  constituting a fluid inlet and a fluid outlet, respectively, of the above-mentioned fluid passage component to be described in further detail below with reference to  FIG. 3 . As is evident from  FIG. 2 , a further fluid outlet  54  is provided in the bottom wall of the housing of the apparatus  10  opposite to the fluid outlet  52 .  
         [0094]     In  FIG. 2 , the interior structure of the portable infusion pump unit or apparatus  10  is disclosed, illustrating the fluid inlet  50  and the fluid outlets  52  and  54 . In  FIG. 2 , the reference numerals  56  and  58  designate two printed circuit boards including the electronic circuitry of the apparatus and including the display, the rechargeable power pack or cell circuitry and the CPU-circuitry of the apparatus controlling the overall operation of the apparatus including the infusion operation. Alternatively, the electronic circuitry of the apparatus may be included in a single printed circuit board or, alternatively, three or more printed circuit boards. The internal re-chargeable battery pack or cell is designated the reference numeral  60 .  
         [0095]     In  FIG. 2 , the internal flow system of the portable infusion pump apparatus  10  is disclosed, constituting a disposable and replaceable fluid passage component as mentioned above and including an inlet tube  62  connected to the fluid inlet  50 . Two capacitive detectors  64  and  66  are mounted on the inlet tube  62  and communicate with the electronic circuitry of the apparatus housed on the printed circuit board  56  and  58  for detecting presence of air bubbles, if any, in the infusion liquid input to the fluid inlet  50 . At its output end, the inlet tube  62  communicates with a first check valve  68  which constitutes an inlet to a pump housing component  70 , in which an internal fluid passage is provided, as will be described in greater details below with reference to  FIG. 3 , which fluid passage terminates in an output or second check valve  72  from which two branched-off outlet tubes  74  and  76  communicate with the fluid outlets  54  and  52 , respectively. For transferring the infusion liquid or any other liquid input to the portable infusion pump unit  10  through the fluid inlet  50  to an application site through one of the fluid outlets  52  and  54 , a piston type pump actuator  78  is provided. The internal flow system of the portable infusion pump comprising the fluid inlet  50 , the inlet tube  52 , the capacitive detectors  64  and  66  belonging to the inlet tube  62 , the first check valve  68 , the pump housing component  70 , the output check valve  72 , the outlet tubes  74  and  76 , and the outlets  52  and  54  constitute an integral disposable and replaceable fluid passage component to be described in greater detail below with reference to  FIG. 3 .  
         [0096]     In  FIG. 3 , the interior of the check valves and also the pump housing component  70  is disclosed in greater detail. The first check valve  58  basically comprises a central circular cylindrical housing component  80  from which a frusto-conical top part  81  extends upwardly communicating with the inlet tube  62  and arresting an inlet filter element  82  at the transition between the frusto-conical top part  81  and the cylindrical housing component  80 . The cylindrical housing component  80  comprises a central annular oral component  84  which is sealed off in the initial or non-active position by a downwardly deflectable sealing membrane  86 . Provided the pressure below the sealing membrane  86  is lower than the pressure above the membrane  86 , the membrane  86  is forced downwardly allowing liquid to pass through the central aperture of the central annular component  84  and further through apertures  87  provided offset relatively to the centre of the sealing membrane  86 .  
         [0097]     The first check valve  68  communicates with an inlet passage  88  of the pumping house component  70  terminating in an inner chamber defined within an upwardly protruding annular top housing component  90  in which a reciprocating plunger  94  of the piston pump actuator  78  is movable in the direction to and from an abutting pin  96  which separates the inlet passage  88  from an outlet passage  98 . The interspace between the reciprocating plunger of the piston pump  78  and the inner surface of the annular top housing component  90  is sealed by means of a highly flexible sealing gasket  92 .  
         [0098]     The outlet passage  98  communicates with the above described second check valve  72  which is basically of a configuration similar to and functioning as a check valve similar to the above described first check valve  58 , however differing from the above described first check valve in that the second check valve  72  does not include any filter element similar to the filter element  82 . The second check valve  72  includes a downwardly protruding annular housing part  100 , which is cast integral with the pumping house component  70 , fulfilling, however, the same purpose as the above described annular housing part  80  of the first check valve. From the annular housing part  100 , a downwardly protruding frusto-conical housing part  101  similar to the above described frusto-conical housing part  81  extends communicating with the outlet tube  74  and similarly the outlet tube  76  described above with reference to  FIG. 2 . Within the annular housing part  100 , a sealing membrane  102  similar to the above described sealing member  86  is received, which includes apertures  103  similar to the apertures  87  described above. The sealing membrane  102  communicates with a conical bore  99  communicating with the outlet passage  98  for sealing off communication from the outlet passage  98 , through the conical bore  99  to the outlet tube  74  provided the sealing membrane  102  rests against an abutting lower surface defining the lower boundary of the conical bore  99 .  
         [0099]     The pumping operation of the portable infusion pump unit  10  is established as follows. Initially, the first check valve  68  and the second check valve  72  are in their initial and sealing positions. It is also assumed that liquid is present within the inlet tube  62  within the inlet passage  88  and the outlet passage  98  and also within the outlet tube  74 . The piston pump actuator  78  is activated through the supply of an electric signal such as an alternating electric signal or a pulsed signal causing the reciprocating plunger  94  to move upwardly or downwardly. The piston pump actuator  78  will be described in greater detail below with reference to  FIGS. 6-12 . The plunger  94  is pressed downwardly in relation to the orientation of the piston pump actuator  78  shown in  FIG. 3 .  
         [0100]     Assuming that the first movement of the reciprocating plunger  94  is in movement upwardly, a relative vacuum is created within the inlet passage  88  and the outlet passage  98  by the increase of the volume defined below the sealing gasket  92 . Through the creation of the relative vacuum within the inlet passage  88 , the first check valve  68  is operated as the downwardly deflectable sealing membrane  86  is caused to move downwardly allowing liquid to flow into the inlet channel  88  through the central aperture of the central annular component  84  as described above. At the same time, the relative vacuum within the outlet passage  98  creates a relative vacuum above the sealing membrane  102  which is biased so as to prevent free flow through the second check valve  72  urging or forcing the sealing membrane into sealing off and abutting engagement with a wall part circumferentially encircling and defining the conical bore  99 , and consequently preventing liquid from being transferred from the outlet passage  98  to the outlet tube  74 . In summary, during the raising of the reciprocating plunger  94 , the first check valve  68  is activated and caused to open whereas the second check valve  72  is blocked.  
         [0101]     As the reciprocating plunger is moved downwardly, a relative increased pressure is created within the inlet passage  88  and the outlet passage  98  and the operations of the first and second check valves are shifted as the relative increased pressure within the inlet passage  88  causes the first check valve  68  to block and seal off whereas the increased pressure within the outlet passage  98  causes the second check valve  72  to open allowing the fluid present within the outlet passage  98  to be forced out through the conical passage  99 , through the apertures  103  of the sealing membrane  102  and further into the outlet tube  74 . The rate of transfer and consequence the flow of liquid from the outlet tube  74  is controlled by the rate of operation of the piston pump actuator  78  as an increased frequency of reciprocating the reciprocating plunger  94  increases the velocity of flow of fluid or liquid from the inlet tube  62  to the outlet tube  74 .  
         [0102]     Above the second check valve  72 , a bypass valve is provided, comprising a sealing membrane  104  which is acted upon by a central stem element  106  of a turnable knob  108  so as to force the sealing membrane  104  into sealing off and abutting engagement with a conical bore  105  provided above and in registration with the above described conical bore  99 . Provided the conical bore  105  is sealed off by means of the sealing membrane  104 , the bypass valve is not in operation. Provided the sealing membrane  104  is raised from its sealing off and abutting engagement with the conical bore  105  as the knob  108  is rotated for causing elevation of the actuator stem  106 , communication from the outlet passage  98  is established through a bypass passage  110 , bypassing the communication from the outlet passage  98  through the conical passage  99  for allowing fluid to flow from the outlet passage  98  through the bypass passage  110  and further through the apertures  103  of the sealing membrane  102  which is consequently not functioning as the bypass valve is in operation.  
         [0103]     The piston pump actuator  78 , which may constitute a replaceable component of the portable infusion pump unit or apparatus  10 , may provide a specific stroke and, consequently, a specific flow volume per stroke. Therefore, the actuator  78  is preferably provided with a switch cooperating with a switch of the electronic circuitry of the apparatus for informing the microprocessor of the electronic circuitry of the apparatus of the type of piston pump actuator included within the apparatus at present. The technique of providing information to the microprocessor concerning the type of piston pump included within the apparatus at present may be established by means of numerous techniques well-known in the art per se such as by means of code switches, optic capacitive or inductive readers, or simply by means of a feedback circuit monitoring the work rate of the piston pump actuator.  
         [0104]     In  FIG. 3 , an inlet tube  112  is shown establishing communication from the inlet tube  62  through the fluid inlet  50  not shown in  FIG. 3 , however, shown in  FIG. 2  from an infusion bag  114  which may constitute an infusion bag including an infusion liquid simply constituting physiological liquid or additionally or alternatively a drug suspended in any appropriate liquid, or alternatively blood plasma. The outlet from the outlet tube  74  of the portable infusion pump unit  10  shown in  FIG. 4  is connected to an outlet tube  116  through the fluid outlet  54 , not shown in  FIG. 3 , however, shown in  FIG. 2 , which external outlet tube  116  communicates with a cannular assembly  118  of a basically conventional structure.  
         [0105]     The inlet tube  112  and the outlet tube  116  may constitute separate inlet and outlet tubes to be connected to the infusion pump unit  10  through the inlet and outlet  50  and  52  or, alternatively,  54 , respectively. Alternatively, and preferably, the inlet tube  112  and the outlet tube  116  constitute integral components of the disposable and replaceable fluid passage component illustrated in  FIG. 3 , which fluid passage component is cooperating with and activated by means of the piston pump actuator  78 . Further alternatively, the infusion bag  114  may be configurated and housed within a container component which is configurated so as to allow the infusion bag  114  to be received and supported on top of the infusion pump unit or apparatus  10  as the above-mentioned receiver is simply connected to and supported by the housing of the portable infusion unit or apparatus  10 .  
         [0106]     The infusion of liquid from the infusion bag  104  is further illustrated in  FIG. 4 , in which the portable infusion pump  10  is received and fixed relative to an individual  120  by means of a belt or strap  122  on which the infusion bag  114  is further fixated. In  FIG. 4 , the external inlet tube  112 , the external outlet tube  116  and the cannular assembly  118  are also illustrated.  
         [0107]     In  FIG. 5 , the above described first embodiment of the portable infusion pump unit or apparatus  10  is shown in duplicate received within a stationary receptor  140  in which a plurality of receptor compartments  142  are defined. Each of the receptor compartments  142  is provided with a set of charger terminals for establishing electrical conductive communication with the charger terminal  46  and  48  of the apparatus or unit  10  received within the receptor compartment  140  in question for charging the internal rechargeable battery pack or cell of the apparatus or unit through the supply of electric energy from a mains power supply unit of the receptor assembly  140  which mains supply power supply unit receives electric power through a coiled mains supply wire  148  terminating in a mains plug  150  which is received in a mains AC outlet socket  152 .  
         [0108]     The receptor assembly  140  further includes a set of indicator lamps  144  and  146 . Provided none of the indicator lamps  144  and  146  corresponding to a specific receptor compartment  142  are turned off, the indication informs the user or operator that no charging is taking place in the receptor compartment in question. Provided a portable infusion pump unit is received within a specific receptor compartment  142 , one of the lamps  144  and  146  corresponding to the receptor compartment is turned off, one of which informs the user or operator that the potable infusion pump unit in question is to be recharged, or alternatively the other lamp is turned on informing the user or operator that the portable infusion pump unit in question is fully charged and ready for use. Alternative information display modes, such as flashing of lamps for informing malfunction in the rechargeable battery pack or cell of the portable infusion pump is of course also readily deduceable.  
         [0109]     In connection with infusion pumps, particularly portable medicinal infusion pumps, it is important that the pumping action be carried out by a very compact actuator functioning as quietly as possible, with as low energy consumption as possible and with as small a waste heat production as possible.  
         [0110]     The pump actuator  78  in  FIGS. 2 and 3  is, according to the invention, a shape memory alloy actuator which embodies all the above desirable characteristics. Several shape memory alloy actuators for use as a pump actuator in medicinal infusion pumps will be described in following, it being understood that these actuators are particularly useful as the pump actuator  78  in  FIGS. 2 and 3 .  
         [0111]     Referring now to  FIGS. 6 and 7 , a pivotable body in the form of a circular disc  1 ′ is arranged for pivoting around a central pivot  2 ′ fixedly attached to a not shown frame of the actuator, and the disc  1 ′ is provided with a peripheral extension  3 ′ and a yoke-like peripheral extension  5 ′. A tension coil spring  6 ′ is at one end thereof pivotably attached to a fastening pin  7 ′ fixedly attached to said frame and is at the other end thereof pivotably attached to a fastening pin  8 ′ fixedly attached to the peripheral extension  3 ′.  
         [0112]     Two wires or filaments  9 ′ and  10 ′ of a shape memory alloy such as nickel titanium alloy or nitinol, for instance supplied by the company DYNALLOY, INC, of Costa Mesa, Calif., USA, under the trade name FLEXINOL, are attached at one end thereof to electrically conductive terminals  11 ′ and  12 ′, respectively, fixedly attached to said frame.  
         [0113]     The other end of each of the wires  9 ′ and  10  is attached to an electrically conductive terminal  13 ′ fixedly attached to the periphery of the disc  1 ′. The wires  9 ′ and  10 ′ extend along the periphery of the disc  1 ′ such that the wires  9 ′ and  10 ′ when tensioned extend along and are supported by said periphery. In the drawings the wires  9 ′ and  10 ′ are shown spaced from said periphery for the sake of clarity.  
         [0114]     A sliding body  14 ′ having two arms  15 ′ and  16 ′ is arranged for sliding movement between two stop pins  17 ′ and  18 ′ attached to the frame. A pin  19 ′ attached to the sliding body  14 ′ is received in the fork  5   a ′ of the yoke-like extension  5 ′ such that the pin  19 ′ may slide and rotate freely in the fork when the disc  1 ′ pivots from the position shown in  FIG. 6  to the position shown in  FIG. 7  thereby slidingly displacing the body  14 ′ from abutment against stop pin  18 ′ to abutment against stop pin  17 ′ with the arm  15 ′, constituting the activating pin of the actuator, fully extended.  
         [0115]     A proximity sensor  20 ′ is attached to the frame and connected to not shown electrical conductors for transmitting a signal from the sensor to a not shown receiver. The terminals  11 ′ and  12 ′ are likewise each connected to an electrical conductor, not shown, connected to a not shown power source for supplying electrical power to the wires  9 ′ and  10 ′ for resistance heating thereof, the terminal  13 ′ being likewise connected to the not shown power source through a not shown electrical conductor for closing the resistance heating circuit.  
         [0116]     In use, the wires  9 ′ and  10 ′ are intermittently heated to the transformation or transition temperature (from martensitic to austenitic state) of the shape memory alloy which temperature for nitinol is approximately 90° C. Thereby the length of the wire is shortened. When the wire cools to below 90° C. the length thereof reverts to normal, i.e. the wire lengthens. The speed at which the shortening takes place, i.e. the contraction time, is directly related to the current input. i.e. the voltage applied over the terminals  11 ′ or  12 ′ and  13 ′.  
         [0117]     In the position depicted in  FIG. 6 , the intermediate disc  1 ′ is in its outermost counter clock-wise position with the arm  15 ′ fully retracted and with the wire  9 ′ cooled to below 90° C. and the wire  10 ′ heated to above 90° C. by applying an electrical voltage between the terminal  12 ′ and  13 ′ whereby an electrical current will flow through the wire  10 ′. The disc  1 ′ has therefore been rotated counter clock-wise to the position shown by the contraction force exerted by the wire  10 ′.  
         [0118]     In the next step, the wire  10 ′ is cooled to below 90° C. and thereby lengthens to the shape indicated by the dotted line  10   a ′ in  FIG. 6 . The actuator is now ready to perform an activating extension of the arm  15 ′ towards the left, the end of the arm  15 ′ being intended to come into contact with a not shown plunger  94  and depress or activate same during the movement of the arm  15 ′ to the extended leftwards position thereof as depicted in  FIG. 7 .  
         [0119]     Thereafter or simultaneously, the wire  9 ′ is heated to above 90° C. whereby it contracts and exerts a clock-wise force on the disc  1 ′ pivoting it clock-wise around the pivot  2 ′ past the balance position of the disc  1 ′ and spring  6 ′ in which the attachment pins  7 ′ and  8 ′ of the spring  6 ′ are aligned with the pivot  2 ′.  
         [0120]     When the disc  1 ′ has rotated clock-wise past said balance point, the tension force exerted by the spring  7 ′ will continue the clock-wise rotation of the disc  1 ′ to the position shown in  FIG. 7  with the arm  15 ′ fully extended and the wire  9 ′ slack though still above 90° C. This is the actual activating movement of the actuator where the force applied to the sliding body  14 ′ by the extension  5 ′ increases because of the increasing lever of force or moment arm of the tension force exerted by the spring  6 ′ on the intermediate disc  1 ′ with respect to the pivot  2 ′ or axis of rotation of the disc  1 ′.  
         [0121]     For applications where the force necessary to perform the function of the actuator, such as depressing the pump plunger  94  in  FIG. 3 , increases during the activating stroke, said increase of the spring force moment arm as the disc  1 ′ rotates is a very advantageous feature as will be explained more in detail in connection with  FIGS. 13 and 14  in the following.  
         [0122]     An increase of the activating force of the actuator during the activating stroke is also achieved or enhanced by decreasing the distance of the pin  19 ′ from the pivot  2 ′ or axis of rotation of the disc  1 ′ during the activating stroke whereby the moment arm or lever of force of the displacement force exerted on the pin  19 ′ by the yoke-like extension  5 ′ with respect to the pivot  2 ′ is decreased and thereby the displacement force is increased during the activating stroke. This shortening of said distance can be seen from the situation in  FIG. 6  at the beginning of the activation stroke to the situation in  FIG. 7  at the end of the activation stroke.  
         [0123]     Finally, the wire  10 ′ is heated above 90° C. so that it contracts and pivots the disc  1 ′ back to the position shown in  FIG. 6  whereby the activating cycle is ready to be repeated.  
         [0124]     The length of the wire  10 ′ is larger than the length of the wire  9 ′ because the contraction or shortening of the wire  10 ′ must be large enough to pivot the disc  1 ′ from the position shown in  FIG. 7  past the balance point mentioned above while the shortening of the wire  9 ′ only has to be enough the pivot the disc  1 ′ from the position shown in  FIG. 6  past said balance point.  
         [0125]     Nitinol wires will typically contract about 3%-6% when heated past the transition temperature. The uncontracted length of the wire  10 ′ should be enough to ensure that the uncontracted wire is fully extended in the position shown in  FIG. 7  and that the contracted wire  10 ′ is fully extended when the disc  1 ′ is at least slightly past said balance point in the counter-clockwise direction, i.e. the uncontracted length of wire  10 ′ should be about 22-25 times the distance of travel of terminal  13 ′ between the  FIG. 7  position thereof and the balance point position thereof.  
         [0126]     The necessary contraction force to be exerted by wires  9 ′ and  10 ′ are rather different because the contraction force of wire  9 ′ only has to counteract the torque or moment of the spring force of spring  6 ′ with the relatively small torque arm in  FIG. 6  while the contraction force of wire  10 ′ has to counteract the considerably larger torque of said spring force in  FIG. 7 . The contraction force of a nitinol wire is larger the larger the diameter or cross sectional area of the wire. The cross sectional area of wire  10 ′ is thus considerably larger than the cross sectional area of wire  9 ′ or there may be a number of wires  10 ′ with the same cross sectional area.  
         [0127]     The latter possibility is chosen if it is necessary that the cooling-off time for the wires  10 ′ is as short of possible so that the interval between the activating cycles may be as short as possible. Several small diameter wires with a certain total cross sectional area will cool more rapidly than a single larger diameter wire with the same cross sectional area.  
         [0128]     The signal emitted by the proximity sensor  20 ′ each time the extension  3 ′ is in the position shown in  FIG. 7  may be utilised for many different purposes such as for instance a mere monitoring of the correct function of the actuator or for controlling the timing of the heating of the wires  9 ′ and  10 ′ and thereby the timing of the activating stroke of the sliding body  14 ′. Naturally, the location of the proximity sensor or of any other type of sensor for sensing the position of the disc  1 ′ may be varied according to the purpose thereof, and several such sensors may be provided in different locations for instance for achieving a more complex control of the timing of the activating effect of the actuator.  
         [0129]     Referring now to  FIG. 8 , this embodiment differs from the embodiment of  FIGS. 6-7  in that a double activating effect may be achieved for each cycle of heating and cooling the shape memory wires  21 ′ and  22 ′ that in this case are of equal length and cross sectional area. The rotation of the disc  1 ′ counter-clockwise and clockwise is limited by stop pins  23 ′ and  24 ′, respectively.  
         [0130]     The activating member may be a sliding body similar to body  14 ′ in  FIG. 6-7  where both the arm  15 ′ and the arm  16 ′ perform an activating function, or the activating function may be a pull/push activation by for instance arm  15 ′.  
         [0131]     The disc  1 ′ may alternatively be provided with a central torsion shaft projecting at right angles to the plane of the disc  1 ′ as a prolongation of the pivot  2 ′ such that the torsion shaft functions as the activating member by for instance rotating a lever to and fro. Many different types of activating members connected to the disc  1 ′ will be obvious to those skilled in the art.  
         [0132]     In the position shown in  FIG. 8 , the disc  1 ′ has just performed an activating rotation counter-clockwise under the influence of the counter-clockwise torque of the force of the spring  6 ′ and is ready for the initiation of a rotation clockwise by heating the wire  21 ′ so that the disc  1 ′ is rotated against the counter-clockwise torque of the spring force until the balance point is passed. Then the activating rotation clock-wise is performed by the clock-wise torque of the spring force. Also in this embodiment the moment arm of the activating force of the spring  6 ′ increases during the activating stroke in both directions.  
         [0133]     Referring now to  FIG. 9 , the terminal  13 ′ of the embodiments of  FIGS. 6-8  has been substituted by a combined terminal and abutment member  28 ′ for abutting the stop pins  24 ′ and  25 ′. Furthermore, another type of biasing means is utilized, namely a piston and cylinder mechanism comprising a pressurized cylinder  24 ′ pivotably attached to pin  7 ′, a piston  26 ′ and a piston rod  27 ′ pivotably attached to the disc  1 ′ by means of a pin  27 ′.  
         [0134]     The piston and cylinder mechanism  24 ′- 25 ′ functions like a compression spring and could in fact be substituted by a compression spring. In  FIG. 9  the disc  1 ′ is in the balance point position where the pin  7 ′, the pin  27 ′ and the pivot  2 ′ are aligned such that the pressure exerted on the disc  1 ′ by the piston rod  25 ′ does not produce any torque on the disc  1 ′. In the situation shown in  FIG. 9 , the wire  22 ′ is contracting and rotating the disc counter clock-wise past the balance point. As soon as the balance point has been passed, the torque from the piston rod  25 ′ will cause the activating counter clock-wise rotation of the disc  1 ′ until the member  28 ′ abuts the stop pin  23 ′ whereupon a clockwise rotation may be initiated in a manner very similar to that described above in relation to  FIG. 8 .  
         [0135]     The tension spring  6 ′ in  FIGS. 6-7  could also be substituted by a piston and cylinder mechanism or a compression spring in an arrangement similar to  FIG. 9 .  
         [0136]     Referring now to  FIGS. 10-12  an activating body  30 ′ is arranged linearly displaceable in the directions of arrows R 1  and R 2  under the influence of a shape memory alloy wire  31 ′ and a two-armed lever  32 ′.  
         [0137]     One end of the wire  31 ′ is attached to the body  30 ′ at  33 ′ and the other end is attached to a fixed portion  37   a ′ of a not shown frame of the actuator, the wire  31 ′ extending around a pulley  34 ′ pivotably arranged on a slide  35 ′ displaceable in the directions of the arrows R 1  and R 2 . A compression spring  36 ′ is arranged between the body  30 ′ and the slide  35 ′ and extends through a passage through a fixed portion  37 ′ of said frame.  
         [0138]     The two-armed lever  32 ′ is arranged pivotable around a pivot  38 ′, one arm  39 ′ of the lever abutting a pin  40 ′ on the body  30 ′ and the other arm  41 ′ of the lever being attached at  42 ′ to one end of a tension spring  43 ′, the other end being attached to a fixed portion  44 ′ of said frame such that displacement of the body  30 ′ in the direction of arrow R 1  tensions the spring  43 ′ via rotation of the intermediate lever  32 ′.  
         [0139]     A pawl or hook element  45 ′ is arranged pivotable around a pivot  46 ′ such that a hook or projection  47 ′ of the hook element  45 ′ may be received in a matching recess  48 ′ in the body  30 ′. A shape memory alloy wire  49 ′ is at one end attached to the hook element  45 ′ and at the other end attached to a fixed portion  50 ′ of said frame. A compression spring  51 ′ is arranged between the fixed portion  50 ′ and the hook element  45 ′ 
         [0140]     In use, the body  30 ′ is moved to and fro in the direction of the arrows R 1  and R 2  to activate the plunger  94  during the activating stroke of the body in the direction R 1 .  
         [0141]     In  FIG. 10  the wire  31 ′ is cooled to below the transformation temperature of the alloy (for instance by sandwiching the wire between two aluminum rails coated with PTFE) and is at its maximum length and is maintained taut by the biasing action of the compression spring  36 ′. The hook  47 ′ is received in the recess  48 ′ and holds the body  30 ′ against the biasing force of the spring  43 ′ transmitted to the pin  40 ′ by means of the lever  32 ′. The wire  49 ′ is also in its cool state and at its maximum length.  
         [0142]     When the activating stroke is to be initiated, the wire  49 ′ is heated to the transformation temperature and shortens or contracts, thereby pivoting the hook element  45 ′ against the biasing force of the spring  51 ′ such that the hook  47 ′ is pulled out of the recess  48 ′ to the release position shown in  FIG. 11 . The body  30 ′ is thus released for displacement in direction R 1  under the influence of the lever  32 ′ pivoted by the spring  43 ′.  
         [0143]     During the activating stroke of body  30 ′ in direction R 1  the lever or moment arm of the force exerted by the spring  43 ′ relative to the pivot  38 ′ or the axis of rotation of the lever  32 ′ increases such that the displacement force exerted on the pin  40 ′ by the arm  39 ′ increases as the body  30 ′ is displaced in the direction R 1 .  
         [0144]     Likewise, during the activating stroke by the body  30 ′ in direction R 1 , the lever or moment arm of the displacement force exerted by the arm  39 ′ on the pin  40 ′ relative to the pivot  38 ′ decreases whereby said displacement force increases as the body  30 ′ is displaced in the direction R 1 .  
         [0145]     When the slide  35 ′ abuts the fixed frame portion  37 ′, the activating stroke in direction R 1  will be stopped as shown in  FIG. 11 . In practice the activating stroke preferably is stopped by the resistance to the activating stroke of the body  30 ′ by the plunger  94  being activated such that the stroke is stopped before the slide  35 ′ abuts the fixed frame portion  37 ′.  
         [0146]     So as to cock the actuator again, the wire  49 ′ is cooled to allow the spring  51 ′ to pivot the hook element  45 ′ towards the holding position thereof while the wire  31 ′ is heated until it shortens and thereby causes the slide  35 ′ to abut the fixed frame portion  37 ′ and the pulley  34 ′ to rotate clock-wise while the body  30 ′ is displaced in the direction R 2  against the force of the spring  43 ′ that thereby is lengthened while the lever  32 ′ pivots counter clock-wise. When the body  30 ′ has reached the position shown in  FIG. 12 , the hook  47 ′ is pressed into the recess  48 ′ and the wire  31 ′ may then be cooled so that the situation in  FIG. 10  is re-established ready to initiate a new activation cycle of the actuator.  
         [0147]     During the tensioning of the spring  43 ′, the force exerted by the wire  31 ′ necessary for this tensioning is largest at the beginning of the displacement of the body  30 ′ in the direction R 2  because of the large moment arm of the force of the spring  43 ′ and the small moment arm of the rotation force of the pin  40 ′ on the arm  39 ′, and the force exerted by the wire  31 ′ decreases as the body  30 ′ is displaced in the direction R 2 . This is an advantageous development of the force in the wire  31 ′ during the cocking of the actuator as will be explained more in detail in the following in connection with  FIGS. 13 and 14 .  
         [0148]     By adapting the actuator according to the invention such that the activating stroke is performed by a force exerted by a biasing means, a further advantage is obtained in that any blocking of the activating stroke of the activating body, for instance because the pump plunger  94  is blocked, will only entail that the activation stroke is stopped with no damage to the SMA wire. If the activating stroke were carried out under the influence of a shortening of a shape memory alloy wire, said wire would probably be damaged or snapped if the activating stroke were blocked.  
         [0149]     The extra length of the wire  31 ′ obtained by means of the pulley  34 ′ is advantageous for giving a longer activating stroke with a compact construction of the actuator.  
         [0150]     The heating of the wires  31 ′ and  49 ′ is carried out in a manner similar to the heating of the wires  9 ′ and  10 ′ in  FIGS. 6-7  by means of not shown electrically conductive connections of the ends thereof to the battery pack  60  of the infusion pump unit according to the invention.  
         [0151]     Referring now to  FIG. 13 , the curve or line  80 ′ indicates the relationship between the force exerted by an SMA wire on a body in one direction while the body id biased by a tension spring in the opposite direction as a function of the contraction or shortening thereof. The force increases proportionally with the contraction because of the proportional increase of the spring force of the spring when it is stretched by contraction of the wire.  
         [0152]     The line or curve  81  is symbolic of the curves corresponding to the relationship between contraction and force exerted for the embodiments of  FIGS. 6-9  where the force in the wires  10 ′,  22 ′,  24 ′ and  31 ′, respectively is largest at the beginning of the contraction or shortening, and the contraction length of the wire is much larger because of the variation in the length of the moment arm or arms during the activating stroke as described above.  
         [0153]     In this manner, a high coefficient of mechanical efficiency is obtained because the longer contraction distance for a given input of energy to heat the SMA wires gives an increased input of energy into the activating system.  
         [0154]     The actual curves  81  will not be linear but will reflect the varying rate of change of the moment arm or moment arms during the activating stroke.  
         [0155]     Referring now to  FIG. 14  and  FIGS. 10-12 , an actuator as shown in  FIGS. 10-12  is applied to depress the plunger  94  of the infusion pump in  FIG. 3  thereof with the body  30 ′.  
         [0156]     The plunger  94  and body  30 ′ travel from 0.2 mm to 3.4 mm during the activating stroke of the body  30 ′. The force required to displace the plunger increases substantially proportionally from approx. 0.5 N to approx. 2N where the force increases steeply because the plunger has reached the end of its path.  
         [0157]     The force exerted by the spring  43 ′ on the body  30 ′ and thus the plunger  94  develops as an increasing parable-like curve corresponding to the curve for the tension or force in the SMA wire  31 ′ necessary to retract the body  30 ′ against the leveraged force of the spring  43 ′.  
         [0158]     It is clear that the curves show that the actuator according to the invention can produce an increasing force as the displacement increases which is very advantageous in applications such as pumping with piston pumps where the force required increases with the distance traveled by the plunger.  
         [0159]     Referring now to  FIGS. 15 and 16 , the infusion pump unit  10  is very similar to the infusion pump unit  10  of  FIG. 2 , the sole difference being the location of the print cards  56  and  58 . The actuators of  FIGS. 6-7  and  10 - 12  are utilized as the pump actuator  78  in  FIG. 15  and  FIG. 16 , respectively. The SMA wires are supplied with electrical current for heating by the battery pack  60   
         [0160]     The SMA actuators of  FIGS. 6-7  and  10 - 12  are particularly well-suited for depressing the pump membrane  92  (see  FIG. 3 ) as the force needed for this operation increases as the membrane is depressed and the fluid is pressed out into the conduit  98 . Furthermore, the operation of the SMA actuators is very quiet and the energy consumption is low while the space requirements are limited and the weight low.  
         [0161]     As an example the SMA wire  31 ′ of the SMA pump actuator of  FIG. 16  is supplied with 4 amperes during 4 milliseconds for each pump depression cycle, and the maximum number of depression cycles for the infusion pump is normally of the order of magnitude of 10,000 cycles/hour.  
         [0162]     Referring now to  FIGS. 17 and 18 , a fluid pumping system  60 ′ comprises a flexible tube  61 ′ extending through or between at least three clamping devices  62 ′- 64 ′ arranged adjacent one another. As illustrated in  FIG. 18  the clamping devices each comprise a pivotable jaw  65 ′ that is arranged to pivot towards a fixed jaw  66 ′ to flatten the tube  61 ′ extending between the jaws  65 ′ and  66 ′ and to pivot away from the fixed jaw  66 ′ to allow the tube  61  to return to its natural open shape.  
         [0163]     Each of the pivotable jaws  65 ′ is attached to one end of a biasing means such as a tension spring  67 ′ the other end of which is attached to a fixed portion  68 ′ of a not shown frame. Each of the pivotable jaws  65 ′ is furthermore attached to one end of a shape memory alloy wire  69 ′ the other end of which is attached to a fixed portion  70 ′ of said frame. The jaws  65 ′ are held in the closed position against jaw  66 ′ by the springs  67 ′ with the tube  61 ′ flattened while shortening or contraction of the SMA wires  69 ′ opens the clamping devices by pivoting the jaws  65 ′ away from the fixed jaw  66 ′.  
         [0164]     The pumping action is achieved by the sequence indicated from left to right in  FIG. 17 , all three clamping devices  62 ′- 64 ′ being clamped shut in the first stage from the left with all three wires  69 ′ cooled to below the transition temperature and therefore slack.  
         [0165]     In the second stage from the left devices  63 ′ and  64 ′ are opened by heating the corresponding wires  69 ′ to above the transition temperature whereby fluid enters the thus opened portion of the tube  61 ′ as indicated by arrow R 5 .  
         [0166]     In the third stage from the left device  64 ′ is clamped shut by cooling the corresponding wire  69 ′ such that the corresponding spring  67 ′ can pull the corresponding jaw  65 ′ against the tube  61 ′ flattening it. Hereby a portion of fluid is trapped a space  71 ′ in the tube  61 ′.  
         [0167]     In the fourth stage from the left, the device  61 ′ opens while the device  62 ′ closes whereby the portion of fluid trapped in the space  71 ′ is forced to flow in the direction of arrow R 6  whereafter device  61 ′ is closed and the first stage from the left has been re-established to begin a new pumping cycle.  
         [0168]     If more than three clamping devices are utilized, the pumping effect will be enhanced.  
         [0169]     This “finger” pump may substitute the pumping system in  FIGS. 3, 15  and  16  as well as the check valves  68  and  72 , and the pumping system (tube  61 ′) may still be replaced without replacing the pump actuator by threading the tube  61 ′ from between the jaws  65 ′ and  66 ′. Thereby an extremely cheap replaceable pump is provided.  
         [0170]     The pivoting of each of the jaws  65 ′ of the clamping devices  62 ′- 64 ′ towards the fixed jaw  66 ′ may be achieved by means of a body  15 ′ of the actuator in  FIG. 6  or a body  30 ′ of the actuator in  FIG. 5 .  
         [0171]     The tube  61 ′ may alternatively be flattened directly by said bodies  15 ′ or  30 ′ without the use of a clamping device. Hereby, a particularly simple pumping system is achieved where the replacement of the tube  61 ′ is particularly simple.  
         [0172]     Referring now to  FIG. 19 , a toothed wheel or gear  55 ″ is rotatably arranged on a power output shaft  56 ″ journalled in a not shown frame of the actuator motor. A body  57 ″ having an edge portion  58 ″ fitting between two neighbouring teeth  59 ″ of the gear  55 ″ is arranged in said frame displaceable between the position shown in full lines and the position shown in dotted lines.  
         [0173]     A shape memory alloy wire  60 ″ is at one end attached to the body  57 ″ and at the other end to a fixed portion  61 ″ of said frame. A coiled flat or wire spring  62 ″ integral with or connected to an arm  63 ″ is attached to said frame such that said arm  63 ″ may pivot around one end thereof opposite the free end thereof. The arm  63 ″ abuts a pin  64 ″ on the body  57 ″.  
         [0174]     A pawl  65 ″ is pivotably arranged on a pivot  66 ″ and is biased by a tension spring  67 ″ so as to constantly abut the rim of the gear  55 ″.  
         [0175]     In use, the gear  55 ″ is turned clock-wise by the body  57 ″ being displaced from the full line position to the dotted line position thereof by the force of the spring  62 ″ acting through the intermediate arm  63 ″ on the pin  64 ″, whereby the gear advances the width of one tooth  59 ″ and the pawl  65 ″ moves from locking engagement between one pair of teeth  59 ″ to a locking position between the next pair of teeth in the counter clock-wise direction.  
         [0176]     When the gear is locked against rotating counter clock-wise by the pawl  65 ″, the SMA wire  60 ″ is heated and shortens whereby the body is displaced from the dotted line position to the full line position against the force of the intermediate arm  63 ″ on the pin  64 ″ thereby cocking the spring  62 ″.  
         [0177]     The lever or moment arm of the displacement force exerted by the intermediate arm in the clock-wise direction with respect to the pivoting point of the arm decreases as the body is displaced in the activating direction from the full line position to the dotted line position whereby the displacement force exerted by the intermediate arm  63 ″ on the pin  64 ″ increases.  
         [0178]     Referring now to  FIG. 20 , a SMA actuator motor similar to the motor of  FIG. 19  is shown, the spring  62 ″ and intermediate arm  63 ″ being substituted by a tension spring  68 ″ fastened to the body  57 ″ and to a fixed portion  69 ″ of a not shown frame.  
         [0179]     The operation of the motor of  FIG. 20  is very similar to the one in  FIG. 19  except that the displacement force exerted on the body  57 ″ by the spring  68 ″ is exerted directly and declines substantially proportionally with the distance of displacement.  
         [0180]     Referring now to  FIG. 21 , an infusion pump  70 ″ particularly well suited for infusing insulin to a diabetes patient comprises a housing  71 ″ containing a display  72 ″, on/off buttons  73 ″, print cards  74 ″ and a not shown battery pack. These elements will not be described further as they are well known to those skilled in the art and may vary greatly within the scope of the invention as defined by the appended patent claims.  
         [0181]     A dispensing cartridge, ampoule or syringe  75 ″ is replaceably arranged in the housing  71 ″ and has an outlet nozzle  76 ″ for communication with a not shown conduit means connected to the patient for delivering the fluid, preferably insulin, in the syringe  75 ″ to said patient in a controlled manner either continuously or according to a predetermined sequence.  
         [0182]     A piston  77 ″ is slidably arranged in the syringe  75 ″. A threaded rod or spindle  78 ″ abuts the piston  77 ″ for displacing it towards the outlet nozzle  76 ″ and meshes with a gear  79 ″ meshing with a pinion  80 ″ rotated by a shape memory alloy motor for displacing the spindle  78 ″ towards the outlet nozzle  76 ″.  
         [0183]     Referring now to  FIG. 22 , the SMA motor of  FIG. 20  is shown arranged and adapted for rotating the pinion  80 ″ such that rotation of the gear  55 ″ is geared down to a much slower rotation of the spindle  78 ″ so as to dispense the liquid or paste in the syringe  75 ″ in very small amounts.  
         [0184]     The SMA motor of  FIG. 19  may very advantageously replace the motor of  FIG. 19  in the configuration of  FIG. 22  because of the reverse characteristic of the spring  62 ″ compared to the characteristic of spring  68 ″ as discussed in connection with  FIGS. 13 and 14 .  
         [0185]     Referring now to  FIG. 23 , a different embodiment of the piston operation is illustrated, a double headed piston  81 ″ being displaced by an arm  82 ″ mounted on a carrier block  83 ″ rotatably mounted on a spindle  84 ″ such that rotation of the spindle  83 ″ displaces the block  83 ″, arm  82 ″ and piston  81 ″ towards the nozzle  76 ″ for expelling liquid or paste in the syringe  75 ″.  
         [0186]     The spindle meshes with a gear  85 ″ meshing with a pinion  86 ″ attached to the shaft  56 ″ of the SMA motor of  FIG. 19 , the spring  67 ″ not being shown for the sake of clarity.  
         [0187]     Referring now to  FIG. 24 , a rack  70 ′″ is arranged displaceable in a not shown frame in the direction R 4  and a body  71 ′″ is arranged displaceable in the directions R 3  and R 4  as well as transversely thereto. A SMA wire  72 ′″ is attached to the body  71 ′″ and to a fixed portion  73 ′″ of said frame. A coil spring  74 ′″ attached to said frame and integral with or connected to an intermediate arm  75 ′″ exerts a displacement force on a pin  76 ′″ of the body  71 ′″ through the intermediate arm  75 ′″ in a manner very similar to spring  62 ″ in  FIG. 19 .  
         [0188]     The rack  70 ′″ advances the distance of the width of one tooth  78 ′″ thereof in the direction R 4  for every cycle of heating and cooling of the SMA wire  72 ′″ in the same way as gear  55 ″ in  FIG. 19  is rotated by wire  60 ″, spring  62 ″, intermediate arm  63 ″ and body  57 ″ in  FIG. 19 .  
         [0189]     The rack  70 ″ may be used to push the piston  77 ″ in  FIG. 22  or piston  81 ″ in  FIG. 23  by means of front end  77 ′″, to empty said cylinder of liquid or paste through an aperture in said cylinder.  
         [0190]     Referring now to  FIGS. 25 and 26 , an optional number of infusion pump units  10  with corresponding inlet tube  112  and infusion bag  114  may be aggregated in a system of individual docking stations  100 ′ arranged on a not shown standard hospital rack allowing horizontally adjustable location of the docking stations  100 ′ that such two or more stations may be aligned abutting one another as shown in  FIG. 25 .  
         [0191]     A power distribution and computer connection box  101 ′ having connections  102 ′ to a power source and a computer is also adapted for abutting a docking station  100 ′ in aligned configuration therewith.  
         [0192]     The distribution box  101 ′ has a number of female contact plugs  103 ′ for mating with corresponding, not shown, male contact plugs in a lateral wall of a docking station  100 ′. A diode  101   a ′ indicates whether the distribution box is functioning or not. Each docking station has a number of female contact plugs  104 ′ in the opposite lateral wall identical to contact plugs  103 ′ for mating with said not shown male contact plugs of an adjacent docking station  100 ′.  
         [0193]     The female and male contact plugs distribute electrical energy to the individual docking station and to the individual infusion pumps  10  docked in the docking stations  100 ′ via female contact plugs  105 ′ mating with not shown corresponding male contact plugs in the bottom of each infusion pump  10 .  
         [0194]     Each infusion pump  10  is carried by a carrying frame  106 ′ between arms  107 ′ thereof and supported on a bottom platform  108 ′ thereof. A hook  109 ′ is provided on the carrying frame  106 ′ for hooking into an aperture  110 ′ of the infusion bag  114 . The frame  106  furthermore has a top aperture  111 ′ for receiving a hook on a bed or wheel chair when the pump  10  and bag  114  are to be removed from the docking station  100 ′ for following a patient away from the fixed docking station array.  
         [0195]     Each docking station  100 ′ is provided with three diodes  112 ′ for indicating status of the docking station and the pump as regards power supply, pumping status and fluid supply or other parameters desired monitored. Each docking station furthermore has two opposed grooves for slidingly receiving the lateral edges of a frame  106 ′ 
         [0196]     The system of  FIG. 25  affords great flexibility as to number of infusion pumps per patient and as regards mode of transport together with the patient either on the frame  106 ′ or removed therefrom.