Abstract:
A peristaltic pump includes a rotating member operably coupled to a drive. The rotating member includes a plurality of rollers arranged in a circular configuration. A guide member defines a channel configured to direct a peristaltic tube around the rotating member so that the peristaltic tube interfaces with the plurality of rollers. The peristaltic tube is pressed against the plurality of rollers by a retaining shoe. The retaining shoe contains surface irregularities configured to restrict movement of the peristaltic tube. A keeper braces the restraining shoe against the peristaltic tube. The rotating rollers compressing the peristaltic tube against the retaining shoe as the rotating member rotates results in a peristaltic action that produces a nearly pulse free linear flow.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of 35 U.S.C. §119(e) of U.S. Provisional Application Ser. No. 61/364,474, filed Jul. 15, 2010, and titled “LINEAR FLOW PERISTALTIC PUMP,” which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     A peristaltic pump (roller pump) is a type of positive displacement pump used for pumping fluids contained within a flexible tube. A peristaltic pump can use a turning cam to place part of a tube under compression, closing or occluding a section of the tube, and forcing the fluid to be pumped to move through the tube. The tube reopens to its natural state after the passing of the cam. This pumping process may be referred to as peristalsis. Peristaltic pumps may be used in laboratory instrumentation, including sample preparation devices, analytic devices, and so forth. For example, peristaltic pumps may be used to move fluids in a clean or sterile environment without the disturbances resulting from shear forces. Further, it is often desirable to use peristaltic pumps to pump clean, sterile, or aggressive fluids because cross contamination with exposed pump components does not occur. 
     SUMMARY 
     A peristaltic pump is disclosed. In one or more implementations, the peristaltic pump includes a rotating member operably coupled to a drive. The drive may be disposed at least partially within a pump housing. The rotating member includes a plurality of rollers coupled to the rotating member in a circular configuration, where the plurality of rollers is configured to orbit about the axis of the rotating member. A guide member coupled to the pump housing defines a channel configured to direct a peristaltic tube around the rotating member so that the peristaltic tube interfaces with the plurality of rollers. The peristaltic tube is pressed against the plurality of rollers by a retaining shoe. The retaining shoe contains surface irregularities configured to restrict movement of the peristaltic tube. The peristaltic pump also includes a keeper for bracing the retaining shoe against the peristaltic tube. The rotating rollers compressing the peristaltic tube against the retaining shoe as the rotating member rotates results in a peristaltic action that produces a nearly pulse free linear flow. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
    
    
     
       DRAWINGS 
       The Detailed Description is described with reference to the accompanying figures. The use of the same reference numbers in different instances in the description and the figures may indicate similar or identical items. 
         FIG. 1  is an isometric view illustrating a peristaltic pump, shown in an opened position ready to receive a peristaltic tube in accordance with an example implementation of the present disclosure. 
         FIG. 2  is an isometric view of the peristaltic pump illustrated in  FIG. 1 , where the peristaltic pump is shown with peristaltic tubes in a pumping position. 
         FIG. 3  is a partial isometric view of the peristaltic pump illustrated in  FIG. 1 , further illustrating retaining shoes in an opened position. 
         FIG. 4  is a partial cross-sectional top plan view of the peristaltic pump illustrated in  FIG. 1 , where the peristaltic pump is shown in a pumping position. 
         FIG. 5  is a partial cross-sectional side elevation view of the linear flow peristaltic pump illustrated in  FIG. 1 , where the peristaltic pump is shown in a pumping position. 
         FIG. 6  is an isometric view illustrating another peristaltic pump in accordance with an example implementation of the present disclosure. 
         FIG. 7  is a graph illustrating the effect of drive speed on flow rate for a peristaltic pump implemented in accordance with an example implementation of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
     Linear flow is highly desirable in a variety of circumstances. Pulse free or nearly pulse free pumping is also highly desirable. For example, it may be desirable to pump slurries (e.g., suspensions of one or more solids in a liquid), viscous, shear-sensitive, and/or aggressive fluids without subjecting such materials to excessive turbulent mixing, pulsations, and/or shear forces. Accordingly, the present disclosure is directed to a peristaltic pump that can provide both linear flow and nearly pulse free operation. One or more peristaltic tubes are guided through a guide member, around a rotating member with rollers, and back through the guide member. Retaining shoes, braced by a keeper, compress the peristaltic tubes against the rollers. The retaining shoes may include surface irregularities to restrict movement of a peristaltic tube. The rotating member rotates, rolling the rollers along the peristaltic tube. The compression of the peristaltic tube by the rollers results in a peristaltic action that pumps the fluid through the peristaltic tube. The shoe may be configured to compress the peristaltic tube in such a way that only one roller pinches the peristaltic tube at a time. Further, multiple rollers may pinch the peristaltic tube at a time. Implementations of the present disclosure may provide nearly pulse free pumping even at low flow rates. Further, flow rate may be linearly related to the speed of the rotating member, resulting in linear flow. 
     In the following discussion, example implementations of peristaltic pumps are first described. 
     Example Implementations 
       FIGS. 1 through 6  illustrate peristaltic pumps in accordance with example implementations of the present disclosure. As shown, a peristaltic pump may be implemented as a linear flow peristaltic pump  100 . The linear flow peristaltic pump  100  may include a guide member  102  for guiding a peristaltic tube  200  around a rotating member  104 . The rotating member  104  may be coupled with a number of rollers  106  for contacting the peristaltic tube  200 , where the rollers are arranged in a circular configuration generally centered on the axis of rotation of the rotating member  104 . Linear flow peristaltic pump  100  may further include a retaining shoe  108  for bracing (pressing) the peristaltic tube  200  against the rollers  106 , and a keeper  110  for locking (bracing) the retaining shoe  108  against the peristaltic tube  200 . The rollers  106  compressing the peristaltic tube  200  against the retaining shoe  108  provide for a peristaltic pumping action when the rotating member  104  is rotated, causing the rollers  106  to revolve/orbit about the axis of rotation of the rotating member  104 . The linear flow peristaltic pump  100  may further include a pump housing  114  for supporting the guide member  102 , rotating member  104 , retaining shoe  108 , and/or the keeper  110 . In implementations, the keeper  110  may be adjustable (e.g., movable with respect to the pump housing  114 ). In other implementations, the keeper  110  may be stationary (e.g., fixed with respect to the pump housing  114 ). In implementations, the keeper  110  can be integrally formed with the pump housing  114 . 
     Guide member  102  may define a single channel or multiple channels  103 . Channels  103  may be configured to guide a tube (e.g., peristaltic tube  200 ) around the rotating member  104 . Guide member  102  may include two guides  105  for a single channel  103  or multiple guides  105  for multiple channels  103 . In implementations, guide member  102  can define four channels  103  with two guides  105  for each channel. Further, the guides  105  for each channel  103  can be located on opposing sides of the guide member  102 . Thus, it should be noted that channels  103  are not necessarily continuous around the rotating member  104 . Peristaltic tube  200  is placed in a semi-elliptical shape as it is guided through the guide member  102  on one side, around the rotating member  104  and guided back through the guide member  102  on the opposite side. Multiple guide members  102  may also be used. Guide member  102  may comprise a concave shape configured to allow the guide member  102  to extend on either side of the rotating member  104  partially around the rotating member  104  (e.g., as illustrated in  FIG. 4 ). Guide member  102  may be formed from a variety of materials including metal, plastic, wood, nylon, ceramic, and so forth. However these materials are provided by way of example only, and are not meant to be restrictive of the present disclosure. In embodiments, guide member  102  may be an integral part of pump housing  114  or may be coupled to pump housing  114 . 
     Rotating member  104  may be substantially cylindrical in nature, having a substantially circular base plate  502  coupled to a substantially circular top plate  504 . The base plate  502  and top plate  504  may have the same diameter or different diameters. Base plate  502  and top plate  504  may be configured for supporting rollers  106  in a circular configuration generally centered on the axis of rotation of the rotating member  104 . The rollers  106  may be oriented longitudinally perpendicular to the base plate  502  and top plate  504 , wherein the length of the rollers  106  may determine the distance between the base plate  502  and top plate  504 . Rotating member  104  may be coupled to the pump housing  114  using a bearing, or another rotational support structure. The bearing may provide an axis of rotation for the rotating member  104 . Rotating member  104  may further include a receiving end for receiving rotational power from a drive (power source), such as a motor  500 , a drive shaft, gearing, and so forth. Rotating member  104  may be operably coupled to the drive. In some implementations (e.g., as illustrated in  FIG. 5 ), rotating member  104  is directly connected to motor  500 . In other implementations, rotating member  104  can be coupled to motor  500  via gears or other mechanisms for transferring power from the motor  500  to the rotating member  104 . For example, gears may be used to change rotational speed and/or torque characteristics of the power delivered from the motor  500 . In implementations, motor  500  can be at least partially contained within the pump housing  114 . 
     In operation, the rollers  106  may compress the peristaltic tube  200  as the rotating member  104  rotates, providing a peristaltic action. Each roller  106  may have a substantially cylindrical shape with a longitudinal axis extending between the base plate  502  and top plate  504  of the rotating member  104 . The longitudinal axis of each roller  106  may be substantially parallel to the axis of rotation of the rotating member  104 . Rollers  106  may be in a circular configuration around the rotating member  104 . Thus, as the rotating member  104  is rotated, the rollers  106  orbit about the axis of rotation of the rotating member  104 . 
     It should be noted that the diameter of a roller  106  with respect to the peristaltic tubing  200  may alter pumping performance. For example, a roller  106  having a smaller diameter may compress a smaller area of peristaltic tube  200  as compared with a roller  106  having a larger diameter. In some implementations, a reduced area of compression may lead to reduced stretching of peristaltic tube  200 , leading to improved tube performance and/or a longer usable life for a tube. Further, it should be noted that smaller diameter rollers  106  may allow for an increased number of rollers  106  on rotating member  104  as compared with rollers  106  having a larger diameter. Smaller diameter rollers  106  may alter the increments of fluid pumped. For example, different combinations of roller diameters and numbers of rollers may allow for varying pulsation of fluid pumping. In one specific implementation, twelve (12) rollers  106  may be included with the linear flow peristaltic pump  100 . However, in other implementations, more than twelve rollers or fewer than twelve rollers can be included with the linear flow peristaltic pump  100 . 
     Retaining shoe  108  may press the peristaltic tube  200  against the rollers  106 . Shoe  108  may include a curvature correlating with the circular configuration of the rollers  106 . Further, shoe  108  may include a lower planar surface  301  and a corresponding upper planar surface  303 , an inner concave surface  305  correlating with the circular configuration of the rollers  106 , and an outer surface  307 , which may be convex, planar, concave, or of some other geometry. Shoe  108  may be plastic, metal, wood, nylon and so forth. However these materials are provided by way of example only, and are not meant to be restrictive of the present disclosure. 
     Shoe  108  may rotate about an axis of rotation  308 . Rotation about axis  308  may allow the shoe  108  to compress the peristaltic tube  200  when shoe  108  is in a closed position, and release compression when shoe  108  is in an open position. Peristaltic tube  200  may be accessible when shoe  108  is in an open position. In implementations, axis  308  may be on a single end of the shoe  108  resulting in a pivoting end near the axis  308  and a swinging end opposite the pivoting end. 
     Referring now to  FIG. 3 , the lower planar surface  301  may extend beyond the inner concave surface  305  resulting in a lower ridge  302 . The upper planar surface  303  may also extend beyond the inner concave surface  305  resulting in an upper ridge  304 . Lower ridge  302  and/or upper ridge  304  may restrict or prevent the peristaltic tube  200  from moving beyond lower ridge  302  and/or upper ridge  304 .  FIG. 3  depicts an implementation with four shoes  108  coupled together. Generally, one shoe  108  can be used per channel  103 ; thus, in a four channel implementation, four shoes  108 A through  108 D can be used, with one shoe  108  per channel  103 . In an implementation with more than one shoe  108  (e.g., as illustrated in  FIG. 3 ), a rod  306  inserted in the swinging end of a number of shoes  108  may be used to keep the shoes  108  together. Rod  306  may be formed of carbon fiber or another material for keeping the shoes  108  together. Each shoe  108  may contain a through hole or a partial hole in the swinging end of the shoe  108 , for the purpose of receiving rod  306 . In  FIG. 3 , shoes  108 A and  108 D include partial holes and shoes  108 B and  108 C include through holes. The diameter of a through hole or a partial hole may be larger than the diameter of the rod  306 , allowing for individual adjustment of each shoe  108 , one relative to another. Further, rod  306  may be generally linear, or may include a shape that varies for biasing one or more of the shoes  108  relative to the other shoes, such as the rod  306  seen in  FIG. 3 , which biases shoe  108 C relative to shoes  108 A,  108 B and  108 D. For example, rod  306  may include various segments that are not coaxial with respect to a long dimension of the rod. In  FIG. 3 , for instance, a longitudinal axis of a segment of rod  306  that extends through shoe  108 C is not coaxial with longitudinal axes of rod segments that extend through shoes  108 A,  108 B, and  108 D. 
     Referring again to  FIG. 3 , the inner concave surface  305  may contain surface irregularities, such as striations  300 . Surface irregularities can include one or more ridges, grooves, marks, and/or disturbances on the inner concave surface  305  that can be raised and/or recessed. In implementations, surface irregularities may occur naturally in a material (e.g. as part of a materials naturally occurring structure) or can be the result of manufacture or process (e.g. machined, molded, and so forth). For example, striations  300  may restrict movement of the peristaltic tube  200  (e.g., restricting lengthwise stretching of the peristaltic tube  200 , restricting movement of the peristaltic tube  200  in a longitudinal direction along the lengthwise curvature of the peristaltic tube  200 , and/or restricting movement of the peristaltic tube  200  in a lateral direction perpendicular to the lengthwise curvature of the peristaltic tube  200 ). Further, striations  300  may allow for incremental peristaltic tube  200  segments to be stretched one at a time allowing for low pulse pumping and/or extended tube life. 
     Keeper  110  may brace the retaining shoe  108  against the peristaltic tube  200 . Keeper  110  may rotate about an axis  402 . Referring to  FIG. 4 , shoe  108  may include a receiver  400  to receive the keeper  110 . The keeper  110  may function to lock the retaining shoe  108  in place. For example, keeper  110  may rotate about axis  402  and interface with receiver  400  to lock shoe  108  in place. Receiver  400  may be a slot, groove, or another feature for receiving the keeper  110 . Keeper  110  may include an adjustment mechanism  112  for adjusting the compression between the shoe  108  and the rollers  106 . In implementations, the adjustment mechanism  112  may be a set screw. It should be noted that adjustment of the shoe  108  by adjustment mechanism  112  may have a limited effect on flow rate through a peristaltic tube  200 , which may be desirable, such as during extended use of the pump  100  during which different users may operate the pump  100  and use the keeper  110 . 
     Peristaltic tubing  200  may be compressed between the rollers  106  and the shoe  108  to allow fluid to be pumped by a peristaltic action as the rotating member  104  rotates. Referring now to  FIG. 5 , the compression of the peristaltic tube  200  between the shoes  108  and rollers  106  is shown. Generally, the compression of rollers against a peristaltic tube may function to wear out the peristaltic tube, resulting in limited tube life and memory effects in the peristaltic tube. In implementations of the present disclosure, roller  106  wear on peristaltic tube  200  may be reduced, resulting in improved tube lifetime and reduced memory effects of tube compression. 
     Referring specifically to  FIG. 6 , another specific implementation is shown. A configuration of two linear flow peristaltic pumps  100  is shown. Pumps  100  may be distinct and separate, or may be integrated together in a variety of configurations. Integration may include utilizing a single pump housing  114  as in  FIG. 6 . Because flow rate is linear, a configuration of more than one linear flow peristaltic pump  100  may be used to mix multiple flow rates. Because the flow rates are linear, desired concentrations or dilutions may be achieved accurately and continuously without a residence chamber. For example, one rotating member  104  of a first peristaltic pump may have a different diameter and/or may be operated at a different speed than another rotating member  104  of another peristaltic pump. Thus, the two pumps may pump at different flow rates. When outputs of the peristaltic pumps are combined, the varying flow rates may provide a resulting mixture that contains a higher concentration of fluid from one pump than from another. By varying the flow rate, this concentration can be changed accordingly. However, two pumps are mentioned by way of example only, and are not meant to be restrictive of the present disclosure. Thus, the outputs of more than two pumps can be combined, such as combining the output of three or more pumps to control mixtures of three or more fluids. 
     Referring to  FIG. 7 , the effect of drive speed on flow rate is shown for several example implementations. In  FIG. 7 , flow rate is plotted with respect to drive motor speed through three different peristaltic tubes implemented with peristaltic pumps in accordance with the present disclosure. As shown in  FIG. 7 , the relationship between flow rate and drive motor speed is at least substantially linear for the three tubes. This can be seen, for example, by R 2  measurements corresponding to linear regression analysis of the drive speed vs. flow rate data included in the legend of the graph in  FIG. 7 . It is noted that the linear relationship may hold for very low flow rates (e.g., as represented by data at or between zero (0) and one thousand (1,000) steps per minute (steps/min) on the graph in  FIG. 7 ). 
     With reference to other example implementations of the present disclosure, a table containing flow rate calibration for peristaltic pump tubing having various diameters is included below. 
     
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 Inside 
                 Calibration Slope 
               
               
                   
                 Diameter 
                 (mL/min per RPM) 
               
               
                   
                   
               
             
             
               
                   
                 0.13 mm 
                 0.00060 
               
               
                   
                 0.19 mm 
                 0.00129 
               
               
                   
                 0.27 mm 
                 0.00266 
               
               
                   
                 0.38 mm 
                 0.00468 
               
               
                   
                 0.44 mm 
                 0.00763 
               
               
                   
                 0.51 mm 
                 0.00948 
               
               
                   
                 0.57 mm 
                 0.01144 
               
               
                   
                 0.64 mm 
                 0.01395 
               
               
                   
                 0.76 mm 
                 0.01871 
               
               
                   
                 0.89 mm 
                 0.02423 
               
               
                   
                 0.95 mm 
                 0.02809 
               
               
                   
                 1.02 mm 
                 0.03052 
               
               
                   
                 1.09 mm 
                 0.03320 
               
               
                   
                 1.14 mm 
                 0.03538 
               
               
                   
                 1.22 mm 
                 0.04608 
               
               
                   
                 1.30 mm 
                 0.04714 
               
               
                   
                 1.42 mm 
                 0.05034 
               
               
                   
                 1.52 mm 
                 0.05125 
               
               
                   
                 1.65 mm 
                 0.05500 
               
               
                   
                 1.75 mm 
                 0.05776 
               
               
                   
                 1.85 mm 
                 0.06116 
               
               
                   
                 2.06 mm 
                 0.06356 
               
               
                   
                 2.20 mm 
                 0.06480 
               
               
                   
                 2.54 mm 
                 0.06680 
               
               
                   
                 2.79 mm 
                 0.06860 
               
               
                   
                 3.17 mm 
                 0.06964 
               
               
                   
                   
               
             
          
         
       
     
     CONCLUSION 
     Although the subject matter has been described in language specific to structural features and/or process operations, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.