Abstract:
An infusion pump uses an improved shuttle mechanism to more reliably pump liquids in low volumes for medical and other purposes. The improved shuttle uses linear translation and wider, symmetric jaws to grasp infusate tubing and pump liquid infusate through the tubing. Adjustment of the linear motion allows a user to also adjust a pumping volume of the infusion pump. Other shuttles with wider jaws may also pump infusate using a rotary motion. In addition, more than one shuttle, such as two or three shuttles, may be used to approximate continuous pumping. A series of several smaller linear shuttles with sequential actuation may be used as a linear peristaltic pump for general peristaltic pump applications.

Description:
BACKGROUND 
     The field of the invention is infusion pumps and relates generally to systems, apparatuses, and methods for pumping or infusing volumes of medical fluids to a patient, typically via an intravenous route. 
     Infusion pumps are used to infuse drugs and liquids into patients, typically via intravenous lines. While some infusion pumps deal with relatively large volumes, there may be more interest in pumps with a capability of delivering only very small controlled volumes of liquid. The drugs used may be very important, such as analgesics, anesthetics including opiates, anti-inflammatory agents, insulin, anti-spasmodic drugs, antibiotics, chemotherapy agents, cardiovascular drugs, and the like. Many of these drugs are needed in very low doses on a continuous basis, so that the patient has a steady, reliable stream over a long period of time, such as 0.1 ml per hour. If pulses are used, the dosage rate may be measured in terms of nanoliters or microliters per pulse or bolus. Patients thus depend on infusion pumps for reliable, consistent delivery of very small volumes. 
     Some infusion pumps propel or pump the liquid of interest by admitting a quantity of liquid into a length of tubing and isolating that quantity, as by occluding a valve at an inlet of the tubing. A mechanism then opens a valve at an outlet of the tubing and another mechanism compresses or otherwise massages the length of tubing in question. Since the inlet is blocked by the closed valve, the liquid can only exit through the outlet, with an open valve. This method works. However, there are at least two drawbacks to this method. Present day infusion pumps, using this type of shuttle mechanism, may squeeze the length of tubing by pressing a moving shuttle against a stationary block. 
     In cross-section, the tube resides in a diamond-shaped groove or pumping chamber formed by the opposed shuttle and block. Typically, the profiles of the shuttle and the block, or stationary portion, are not very well suited for maintaining the tube in an ideal position throughout the entire compression cycle. Because of this, the profile of the shuttle and block do not always achieve full compression of the tube at any given point during the pumping cycle. For example, prior art infusion pumps operate by occluding tubing between a moving shuttle and a stationary block. The tubing is not completely occluded because prior art pumps do not entirely compress the tubing, leaving the ends of the tubing non-occluded. This situation has at least two disadvantages: an unpredictable amount of liquid remains in the tubing, negatively affecting pump accuracy, and full pumping capacity is not utilized. Over-squeezing the tubing to complete the occlusion can adversely affect tubing life, while under-squeezing lessens the pumping capacity and may adversely affect pumping volume control accuracy. 
     Typically, the inlet valve, shuttle, and outlet valves previously mentioned are operated via a single motor or actuator. The timing of the operation of each is accomplished by a mechanical linkage. Accordingly, each stroke of the shuttle mechanism pumps a fixed amount of fluid. Therefore, it is difficult or impossible to adjust the pumping capacity or other pumping characteristic of the pump. 
     SUMMARY 
     An improved infusion pump is provided in several embodiments. 
     One embodiment is an infusion pump. The infusion pump includes an inlet valve, an outlet valve, and a shuttle including a shuttle stationary portion and a shuttle moveable portion configured for squeezing a length of tubing between the shuttle stationary portion and the shuttle movable portion, wherein the shuttle moveable portion moves toward and away from the shuttle stationary portion to operate the infusion pump, wherein the shuttle stationary portion and the shuttle moveable portion each include a symmetrical groove for holding and squeezing the length of tubing, the groove symmetrical about a central axis of the groove. 
     Another embodiment is an infusion pump. The infusion pump includes a housing and contained within the housing, an inlet valve, an outlet valve, and a shuttle including a shuttle stationary portion and a shuttle moveable portion configured for squeezing a length of tubing between the shuttle stationary portion and the shuttle movable portion, wherein the shuttle moveable portion moves toward and away from the shuttle stationary portion to squeeze the tubing, wherein the shuttle stationary portion and the shuttle moveable portion each include a base with a symmetric channel for containing the tubing, each of the shuttle stationary portion and the shuttle movable portion including a plurality of transverse ridges and transverse recesses rising from the base and the channel, wherein a height of the ridges above the channel is less than an outer diameter of the tubing. 
     Another embodiment is a method of pumping an infusate. The method includes the steps of furnishing an infusion pump, the infusion pump including at least one shuttle having a shuttle stationary portion and a shuttle moving portion, wherein the shuttle stationary portion and the shuttle moveable portion each include a base with a symmetric channel and a plurality of ridges and recesses rising from the base and the channel, wherein the ridges on both sides of the channel are symmetrical. The method also includes controlling operation of the infusion pump by entering commands through at least one input to a controller of the pump, pumping infusate by periodically moving the shuttle moveable portion with respect to the shuttle stationary portion, whereby substantially all of an outer circumference of the tubing is in contact with the portions of the shuttle stationary portion and the shuttle moving portion, and sequentially opening and closing at least one valve of the infusion pump to admit the infusate and to allow the infusion pump to pump the infusate. 
     Another embodiment is a linear shuttle peristaltic pump. The linear shuttle peristaltic pump includes at least one stationary section, the at least one stationary section including a base, a symmetric channel, at least one ridge on a first side of the channel and at least one recess on a second side of the channel, wherein the channel is formed with symmetrical angles on each side of a center of the channel. The pump also includes a plurality of moveable sections, each moveable section including a base, a symmetric channel, a ridge on a first side of the channel and a recess on a second side of the channel, wherein the channel is formed with symmetrical angles on each side of a center of the channel, and wherein the at least one ridge and at least one recess in the at least one stationary section fit into the recesses and ridges of the moveable sections, and wherein when the at least one stationary section and the plurality of movable sections are assembled, the channels form an opening suitable for a length of tubing, whereby substantially all of an outer circumference of the tubing is in contact with portions of the at least one stationary section and portions of the moving sections when the moving sections operate to squeeze the length of tubing, and a plurality of linear actuators connected to the plurality of moveable sections, each of the plurality of linear actuators further including a sensor for reporting a position of the actuator. In another embodiment, the linear actuators are replaced with a single motor and a cam in contact with each of the plurality of moveable sections. 
     Another embodiment is a method of pumping a liquid. The method includes the steps of providing a linear shuttle peristaltic pump, the pump including a plurality of shuttle stationary sections and a plurality of shuttle moving sections, each of the sections having a symmetric groove with at least one transverse ridge and at least one transverse recess, wherein the ridges and the recesses of the stationary sections fit into matching recesses and ridges of the moving sections, and wherein substantially all of an outer circumference of tubing in the pump is in contact with surfaces of the stationary sections and the moving sections when the tubing is squeezed. The method also includes controlling operation of the linear shuttle peristaltic pump by entering commands through at least one input to a controller of the pump, pumping liquid by sequentially moving the shuttle moveable sections with respect to the shuttle stationary sections, and sequentially opening and closing at least one valve of the infusion pump to admit the infusate and to allow the infusion pump to pump the infusate. 
     Another embodiment is a geometry-controlled valve. The valve includes a stationary section, the stationary section including a base, a symmetric channel, at least one ridge on a first side of the channel and at least one recess on a second side of the channel, wherein the channel is formed with symmetrical angles on each side of a center of the channel, and a moveable section, the moveable section including a base, a symmetric channel, a ridge on a first side of the channel and a recess on a second side of the channel, wherein the channel is formed with symmetrical angles on each side of a center of the channel, and wherein the at least one ridge and at least one recess in the stationary section fit into the recesses and ridges of the moveable section, and wherein when the stationary section and the movable section are assembled, the channels form an opening suitable for a length of tubing, whereby substantially all of an outer circumference of the tubing is in contact with the portions of the stationary section and the moving section when the moving section operates to squeeze the length of tubing. 
     Additional features and advantages are described herein, and will be apparent from, the following Detailed Description and the Figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic view of an infusion pump controller with two infusion modules; 
         FIG. 2  is a partial cross-section of a prior-art infusion pump geometry; 
         FIG. 3  is a partial cross-section of a profile view of a new infusion pump shuttle geometry; 
         FIGS. 4A and 4B  are perspective views of an improved shuttle pump geometry; 
         FIGS. 5A and 5B  are partial cross-sectional views depicting filling and pumping phases of a shuttle pump with the improved geometry; 
         FIG. 6  is a perspective view of another shuttle design; 
         FIG. 7  is a perspective view of another shuttle geometry design; 
         FIG. 8  is a perspective view of yet another shuttle geometry design; 
         FIG. 9  is a perspective view of another application of the improved shuttle design; 
         FIG. 10  is a perspective view of an embodiment of a moving shuttle section; 
         FIG. 11  depicts another embodiment of a shuttle-type infusion pump; 
         FIG. 12  depicts yet another embodiment of a shuttle-type infusion pump; 
         FIGS. 13A and 13B  depict infusion pumping by the embodiment of  FIG. 6 ; and 
         FIG. 14  depicts an application wherein a single controller is used to control and monitor a plurality of infusion pumps for a patient. 
     
    
    
     DETAILED DESCRIPTION 
     One embodiment is depicted in  FIG. 1 . Infusion pump system  10  includes a housing  12  for the infusion pump microcontroller  28 , and also includes first infusion pump  14  and second infusion pump  16 , a video output  18  and an audio output or speaker  20 . The video output  18  is a screen, which may be a touch-screen, allowing for inputs to the microcontroller  28 . The infusion pump system  10  also includes inputs  26 , which may be conveniently located near screen  18 . The infusion pump system  10  includes additional inputs/outputs (I/O), including a landline  22  suitable for cable or other I/O, such as an intranet or cable for a home, a hospital or other care center. There is also an antenna  24  for wireless communication to and from a central monitoring station or other controller (not shown). The infusion pump system  10  includes a battery  25  and may also receive power from an external source via a power cord  27 . 
     The first infusion pump  14  receives liquid from a first container  34  and the second infusion pump  16  receives liquid from a second container  36 . The flow of liquid is then conveyed to the respective infusion pump via tubing  348 ,  366 . The tubing  348 ,  366  in this embodiment is continuous before and after the infusion pumps  14 ,  16  and extends to an access device connector  368  for each line. The access device connector  368  may be a vascular access device and may be used for administering a drug or other medicament to the patient. 
     The system controller is a microcontroller  28 , which includes a central processing unit (CPU), input/output capability (I/O), digital to analog converter (D/A), and random access memory (RAM) and read-only memory (ROM), and may include additional memory (MEM). A computer program for operating one or more infusion pumps  14 ,  16  is stored in MEM or ROM. Microcontroller  28  receives inputs from the drip counters  342 , to monitor the input to the infusion pumps. The microcontroller  28  also receives inputs from a number of sensors or devices associated with the infusion pumps  14 ,  16 , such as encoder data from rotary encoders on a motor driving the infusion pump, linear voltage displacement transducer (LVDT) data or other position or displacement data from linear actuators, voltage or current readings from temperature or pressure sensors in the infusion pumps  14 ,  16 , and the like. The data may be sent via wire harnesses  322 ,  324 ,  326 , or may be wireless, such as wireless signals conforming to the ZigBee/IEEE 805.15.4 wireless standard. The data may be received by the microcontroller  28  or the microcontroller  28  may include a separate interface for sensor circuits  32 , as shown. The infusion pumps  14 ,  16  in this embodiment have a separate section for driver circuits  30 , for driving or controlling linear actuators, rotary actuators, motors, and the like. 
     Infusion pump  14  is driven by a motor  148  driving an infusion pump moveable shuttle section  144  by a camming drive train  146 . The moveable shuttle section  144  squeezes tubing  348  against the shuttle stationary section  142  to pump the liquid from container  34 . Upper valve  140  opens to admit liquid into the tubing  348  and closes when the tubing  348  is full. Lower valve  141  then opens just before the controller  28  commands infusion pump  14  to actuate and cycle the moveable shuttle section  144 . With upper valve  140  closed and lower valve  141  open, the liquid is forced through the lower valve and downstream through connector  368 . An encoder or other feedback device on motor  148  informs controller  28  of the position of the motor  148 , and thus the position of the moveable shuttle section  144 , and also allows calculation of volume pumped by the infusion pump  14  by the computer program. 
     The second infusion pump  16  operates with linear actuators. A linear actuator is a device that develops force and motion, from an available energy source, in a linear manner, as opposed to a device that operates in a rotary manner, as one that receives torque directly from a rotary electric motor. Examples of linear actuators include electric linear solenoids, linear pneumatic actuators, and hydraulic cylinders. Other examples include ball screws and jack screws, and also cylinders actuated by a linear motor. Infusion pumps as described herein place a premium on space and on reliability. While many types of linear actuators may be used, lead screws and stepper motors from and Haydon Switch &amp; Instrument (HSI) of Waterbury, Conn., U.S.A. and from Portescap, West Chester, Pa., U.S.A., have been found useful for the present infusion pump application. 
     Infusion pump  16  includes a stationary portion  162  and two moveable shuttles  164 ,  166 , as well as three valves  160 ,  165 , and  170 , and five linear actuators  168 . The commands to the linear actuators  168  and their positions are reported via harness  326  to the driver circuit portion  30  and are also reported to the microcontroller  28 . Infusion pump  16  receives liquid from container  36  and drip chamber  346  and pumps via tubing  366 . In this embodiment, tubing  366  is a continuous piece of tubing  366  from the drip chamber  346  to connector  368 . Valve  165  closes and valve  160  opens to admit liquid into the tubing  366  downstream from valve  160 . When this portion of the tubing  366  is full, valve  160  closes, valve  165  opens, and shuttle  164  advances, pumping liquid downstream through valve  165 . Shuttle  166  is open to receive the liquid and valve  170  is closed. Then valve  165  closes, valve  170  is opened, and shuttle  166  closes, pumping the liquid downstream to connector  368  and to the patient. While shuttle  166  is closing, shuttle  164  retracts and valve  160  opens, admitting liquid upstream from valve  165 . The process is then repeated, with sequential advance and retraction of the shuttles and appropriate opening and closing of the valves. 
     The use of two shuttles smoothes the pumping process, so that part of the tubing is being pumped (emptied) while the remainder is being filled. When the first shuttle  164  pumps, the contents of the upper portion of the tubing  366  are discharged into the lower portion of the tubing  366  adjacent the second shuttle  166 . When the second shuttle  166  is pumping liquid to the patient, the tubing adjacent the first shuttle  164  is being re-filled. The tubing is quickly filled because the liquid has only to traverse the tubing immediately adjacent the first shuttle  164 . Using this technique, a smooth, virtually continuous flow is achieved. In this embodiment, intermediate valve  165  acts as both the outlet valve for upper shuttle  164  and as input valve for lower shuttle  166 . 
     Prior art infusion pumps, such as the one shown in cross-section in  FIG. 2 , do not uniformly squeeze the tubing  4 . Instead, an upper shuttle  6  and a lower stationary portion  7  may tend to compress the tubing so that a small amount of liquid may be left in the tubing, as seen in  FIG. 2 , thus contributing to inaccuracy in the operation of the infusion pump. In one embodiment of the infusion pump disclosed herein, shown in  FIG. 3 , the infusion pump has a central groove  8  that is symmetrical with respect to a center line L of the groove, with equal angles A on both sides  9  of the groove  8 . In one embodiment, the corner so formed has a gentle radius from about 0.020 inches to about 0.060 inches (about 0.50 mm to about 1.5 mm). A first embodiment of an improved shuttle pump made of a stationary block  40  and a moving shuttle  42  is depicted in  FIGS. 4A and 4B . 
     The block  40  and the shuttle  42  are each made of a base with a plurality of alternating ridges  46  and recesses  48 , with a central channel  44 . The ridges  46  of one portion fit into the recesses  48  of the other, allowing sliding movement of the moving shuttle  42  with respect to the stationary block  40 . The central channel  44  is configured for receiving a length of tubing, and should have a generous radius and be free from nicks and burrs. The ridges  46  rise perpendicularly from the base at the top and bottom edges of block  40  and shuttle  42 , but form an angle B to the central channel of about 45 degrees. In this embodiment, the angles B and the channel are symmetrical with respect to a horizontal plane H bisecting the central channel, i.e., angles B are equal. The sum of the two angles B is from about 60 degrees to about 120 degrees. The tubing will be held or contained in a symmetrical manner, helping to insure that the tubing is not distorted when pumping takes place. 
       FIGS. 5A and 5B  depict a cross-section of the joined stationary and moving portions. In  FIG. 5A , the stationary block  40  and moving shuttle  42  are aligned, exerting slight pressure on tubing  38 , which is contained within the area as shown between the block  40  and the shuttle  42 , with only sufficient pressure to deform normally round tubing  38  into the slightly compressed state shown.  FIG. 5A  depicts ridges  424  from shuttle  42 , which fit into recesses (not shown) of the block  40 . Tubing  38  rests in the open area and is symmetrical with respect to the horizontal plane H. Vertical plane V is perpendicular to the horizontal plane and is taken at the locus of the corner or central channel  44 . As seen in  FIG. 5A , about three-fourths of the diameter of tubing  38  is contained within the block  40 , while about one-fourth extends about the top (right) surface of shuttle  42 . 
     As seen in  FIG. 5B , the left and right portions, block  40  and shuttle  42 , match and overlap, and about three-fourths of the diameter of tubing  38  is also contained within the open area of shuttle  42 . The radius of the corner or central channel  44  in one embodiment is about 0.030 inches (about 0.75 mm). Base  402  of block  40  is the portion to the left of the vertical plane V. The base  404  of the shuttle  42  is similarly defined, but is to the right to of a vertical plane taken from the locus of its central channel. Block  40  has ridges  414  extending from its base  402 , while shuttle  42  has ridges  424  extending from its base  404 . In  FIG. 5B , shuttle  42  has moved downward to squeeze the tubing  38  and pump the liquid infusate within the tubing  38  to the patient. Tubing  38  is deformed within the space, but with this geometry, the entire outer circumference or periphery of the tubing  38 , adjacent to ridges  414 ,  424  is constrained between the matching ridges  414  of the block  40  and ridges  424  of the shuttle  42 . 
     Another embodiment of a block  410  and a shuttle  420  are shown in  FIG. 6 . The block  410  and shuttle  420  are configured to accommodate and squeeze tubing  38  between them. In this embodiment, fingers  406 ,  408  are added on both the block  410  and the shuttle  420  to help secure and squeeze the tubing  38 . In block  410 , rear fingers  406  and front fingers  408  are positioned adjacent the tubing  38  to fit into matching slots  48  in shuttle  420 . The fingers  406 ,  408  push against the tubing  38  and help to contain and squeeze the tubing  38  when the shuttle  420  contacts the tubing  38  by squeezing it against block  410 . In this depiction, shuttle  420  has rotated downward and away from contact with the tubing  38  and fingers  406 ,  408  in the block  410  are shown in contact with tubing  38 . Shuttle  420  also has rear fingers  406  (not shown), and front fingers  408  for performing the same function, containing and squeezing the tubing  38 , on the other side of the tubing. The fingers  406 ,  408  on shuttle  420  fit into matching slots or recesses  48  on block  410 . 
     The block  410  and shuttle  420  described above may also be made and used in smaller portions for occluding the tubing  38 . For example, instead of squeezing a longer portion of the tubing  38  for pumping, a much shorter version may be used as a valve.  FIGS. 7 and 8  depict an example. In  FIG. 7 , occluder  70  may be used as the stationary portion or block, or alternatively may be used as the moving portion or shuttle, of a valve to occlude tubing. Occluder  70  is similar to the stationary and moving portions described above. Occluder  70  includes a base portion  72 , a central channel  74 , a single ridge  76  and a single recess  78 . The occluder  70  shown is used with a matching occluder  70  atop occluder  70 , with the ridge  76  of one occluder  70  placed into the recess  78  of the other, and vice versa. By sliding or maneuvering one occluder  70  back and forth, a length of tubing may be opened and closed, thus allowing and ceasing flow of liquid in an infusion pump. This configuration has the same advantages as the shuttle pumps discussed above, in that the entire circumference or periphery of the tubing is occluded and is less likely to be subjected to excessive pressures, leading to premature failure. 
     Another embodiment of an occluder that is capable of acting as a valve is depicted in  FIG. 8 . In this embodiment, occluder  80  with base portion  82  includes two ridges  86  and two recesses  88 , a ridge  86  and a recess  88  on each side, the positions of the two reversed across the transverse central channel  84 . The embodiment is intended for use with two occluders  80 , one stationary and one moving, as with occluders  70 , block  40  and shuttle  42 . In addition, since both occluder embodiments  70 ,  80  may also be used to push liquid from the tubing, they may be used to pump the liquid. 
       FIG. 9  depicts an embodiment in which a plurality of occluder sections  70  are used for both the stationary and moving portions of a linear peristaltic pump  60 . In the figure, several stationary sections  70   a  are placed adjacent each other, their recesses  78  visible and accommodating ridges  76  from a matching number of identical moving portions  70   b  placed atop the stationary sections  70   a . The moving portions  70   b  are portrayed as staggered, as would be the sections of a linear peristaltic pump  60 . The moving sections  70   b  move in sequence, with a fixed small volume of liquid passing from one to another as each section  70   b  closes to pass the volume to the next and then opens to receive another small volume. The sections  70   b  are movable by linear actuators, e.g., solenoid actuators or other actuators (not shown). The volume pumped per unit time is variable if the displacement of the actuator is variable. For example, a three-position solenoid may be used to pump volumes in accordance with either of the two possible positions besides the closed position. Linear actuators that can be programmed to move a particular distance may also be used to control pumping volume. Of course, an inlet valve and an outlet valve may also be used with such a linear peristaltic pump  60 . It will be understood by those with skill in the art that the linear peristaltic pump  60  of  FIG. 9  could also operate with a single stationary portion (not shown), with appropriate ridges  76  and recesses  78 , and a plurality of moving portions  70   b  mounted to the stationary portion. This would make such a pump less expensive and easier to repair. 
     Other linear actuation embodiments are depicted in  FIGS. 10 and 11 . In  FIG. 10 , a infusion pump  120  includes an inlet valve  122 , an outlet valve  124 , a stationary or block section  125  and a shuttle or moving section  126 . The infusion pump  120  manipulates tubing  38  to pump infusion liquid. The valves  122 ,  124  are opened and closed by linear actuators  128 , which may be standard, 2-position electric solenoids. The shuttle  126  is moved linearly back and forth by linear actuator  130 . The block and shuttle  125 ,  126  may be similar to those depicted in  FIGS. 4A ,  4 B,  5 A and  5 B, or may be different. The timing of the valve  122 ,  124  openings and closings, and the actuation of linear actuators  128 ,  130 , i.e., the pumping, are determined by a controller (not shown), to which the linear actuators  128 ,  130  are connected, and, in this embodiment, by a computer program in the controller. An infusion pump  120  with a shuttle  126  whose motion is controlled by a linear actuator  130  is known as a linear shuttle infusion pump or, in context, a linear shuttle pump. 
       FIG. 11  depicts actuation for another infusion pump design with virtually continuous pumping motion. One problem with some designs is that periodically, no fluid is pumped in order to allow the tubing set to fill with more fluid. To eliminate this period of no flow, a second shuttle may be added so that the pump can continue to deliver liquid while the primary shuttle refills. Infusion pump  150  also manipulates tubing  38  to infuse liquid to a patient. In this embodiment, liquid is admitted through inlet valve  152  and is pumped first by primary shuttle  164 . Primary shuttle  164  pumps liquid to secondary shuttle  166 , which is only about half as long as primary shuttle  164 . In this embodiment, there is an intermediate valve  154  between the primary and secondary shuttles  164 ,  166 , but there is no outlet valve. 
     When the primary shuttle has finished pumping and is being replenished, inlet valve  152  is opened and intermediate valve  154  is closed. The secondary shuttle  166  continues the delivery of the fluid. Later, when the intermediate valve is open and the inlet valve is closed, the primary shuttle pumps fluid and fills the secondary shuttle  166 . Since the primary shuttle is twice as long and encounters twice the length of tubing, it pumps about twice as much volume as the secondary shuttle. Other embodiments may be used. 
     The linear movement of the shuttles and valves described in the above embodiments is easy to understand. However, there are also embodiments in which the tubing for an infusion pump is squeezed or actuated by rotary motion, using a shuttle  420  as depicted in  FIG. 6 . Thus, while linear-actuated embodiments depicted in  FIGS. 7 to 11  have advantages, other embodiments may achieve more uniform pumping using a single motor and one or more cam surfaces in engagement with the moveable shuttles or moveable sections. 
     Such an embodiment is further depicted in  FIGS. 12 ,  13 A and  13 B. Shuttle  420  includes a plurality of ridges  46  and recesses  48 , arrayed along a central transverse channel  460 . As mentioned above, shuttle  420  may also include fingers  422  for restoring the tubing  38  to an open configuration after an individual pumping sequence has been completed. Shuttle  420  includes a pivot  450  with a bore  452  for a pivot pin  454 . The shuttle  420  moves when a motor moves a cam  432  on camming surface  430 . The camming surface  430 , its movement amplified by lever arm  428 , causes shuttle  420  to pivot about pivot  450  and the pivot pin  454 , and forcing the ridges  46  against a length of tubing  38 , thus pumping liquid and infusing liquid into a patient. 
     Side views of closed and open positions of this embodiment are further shown in  FIGS. 13A-13B . In  FIG. 13A , stationary block  410  is fixed in place, as is tubing  38 . Shuttle  420  is squeezing tubing  38  in central space  460 . Motor rotates cam  432  clockwise against camming surface  430 , pressing down on camming surface  430 , and through lever arm  428 , urging moving shuttle  420  in a clockwise rotation, upwards against the tubing  38 . When the liquid in the tube  38  has been pumped, the moving shuttle  420  allows the tubing  38  to open and re-fill with the infusing liquid. In  FIG. 13B , cam  438  has rotated counter-clockwise, to allow clockwise pivoting about pivot  450  and pivot pin  454 . Tubing  38  can now refill until the next cycle occurs. 
       FIG. 14  depicts an application with an infusion pump system  100 . In this system  100 , infusion pump controller  112  controls a plurality of infusion pumps  114 , as described above. Each infusion pump  114  receives one liquid for infusing into a patient P, in this instance from containers  102 ,  104 , through drips  106 ,  108 , and W tubing  38  leading to the respective infusion pumps  114 . The tubing  38  optionally has a connector  110 , for addition of medicaments to the infusion liquid. The pumped liquid in this embodiment is output from each of the infusion pumps  114  through a check valve  116  and then though another length of IV tubing  38  to the patient P. The IV tubing  38  includes a clamp  118 . 
     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.