Abstract:
A multi-channel peristaltic pump in which each channel can be operated independently of the others. A peristaltic pump includes a plurality of motors, each of which drives a rotor shaft which is independently rotatable around an axis and which rotates a roller head having a plurality of rollers. The rotor shafts are disposed in a concentric manner. The peristaltic pump further can include a control system allowing an operator to selectively determine the speed and direction of rotation of each of the roller heads of the pump.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    Not Applicable 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
       [0003]    Not Applicable 
       INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
       [0004]    Not Applicable 
       FIELD OF THE INVENTION 
       [0005]    The present invention relates to pumps, such as those for analytical instruments, and more particularly to peristaltic pumps and methods of using the same, including in connection with analytical instruments and systems, and further including multi-channel peristaltic pumps. 
       BACKGROUND OF THE INVENTION 
       [0006]    Peristaltic pumps have been used in the past to provide a positive displacement of fluids to achieve pumping of the fluids. In conventional peristaltic pumps, a fluid within a flexible tube fitted within a casing is typically used. In such pumps, one or more rollers or shoes are rotated within the casing and compress the tube; as the roller or shoe compresses the tube in one location, the compression forces the movement of the fluid within the tube. Once the roller passes the location, the absence of fluid within the tube in that location induces the flow of fluid to that location in the tube. In conventional applications, the fluid to be pumped with a peristaltic pump is often sterile or of such a nature that it is desirable to avoid having the fluid contact any of the pump. Peristaltic pumps are useful for a wide variety of applications, including dialysis machines, metering pumps, dosing pumps, heart bypass pump machines, drug dispensing systems, infusion pumps, aquariums, analytical instruments, food and pharmaceutical manufacturing operations, and so forth. 
         [0007]    In some applications, it is desirable to have a peristaltic pump which has multiple heads, each having multiple rollers. In such pumps, it is therefore possible to simultaneously pump fluids located within multiple tubes. Such peristaltic pumps are sometimes said to have multiple channels. In addition, cartridges have been used in some conventional peristaltic pumps to make it easier to connect and disconnect tubing from the pump. For example, U.S. Pat. No. 7,214,038, issued on May 8, 2007, to Saxer et al., which is hereby incorporated by reference herein, discloses a removable cartridge which can be connected or disconnected from a peristaltic pump by a user with relative ease. Such a peristaltic pump and cartridges for same are commercially available from Ismatec, S.A., of Glattbrugg, Switzerland. In such conventional peristaltic pumps, it is conventional to have a single rotor which drives a shaft having one or more heads, with each head having a plurality of rollers. However, such multiple heads cannot be rotated independently of one another, such as a different speeds or the like. 
         [0008]    Attempts to provide individual control over the pumping action in multiple channel peristaltic pumps have been made in the past. For example, in U.S. Pat. No. 5,098,261, issued on Mar. 24, 1992, to Bertoncini, which is hereby incorporated by reference herein, a peristaltic pump is disclosed that includes elastic tubes that are stretched to varying degrees and, as a result of the Poisson effect from such stretching, reduces the flow path cross-section area in the tubes to varying degrees, in an attempt to allow variable flow speeds in the tubing located in different channels in the pump. 
         [0009]    Still another approach to provide independent control of the channels in a multiple channel peristaltic pump is provided in U.S. published patent application No. 2009/0035165, published Feb. 9, 2009, and listing Chang as an inventor, which is hereby incorporated by reference herein. In Chang, one or more roller segments are selectively locked or decoupled from a drive shaft and can be operated with a desired speed and direction. The pump shown in Chang includes two motors: one for selecting the channel or channels to be driven by a lead screw and the second for rotating the roller heads. 
         [0010]    Yet another example of a multi-channel peristaltic pump is described in U.S. published patent application No. 2001/0004143, which was published on Jan. 6, 2011, and names Beiriger et al as inventors, and which is incorporated by reference herein. In Beiriger et al., a multi-channel peristaltic pump is described with individually controlled rollers, which are free to rotate on a single shaft, and each of which is coupled to a worm gear. This approach describes control of the individual channels through the use of independent motors. However, this approach requires a fairly large device in order to accommodate the motors required and the gear mechanisms to translate the motor&#39;s rotation to the rollers. In this approach, the rollers need to be spaced further apart than may be desired. 
         [0011]    Another example of a multi-channel peristaltic pump used in a blood processing system is described in U.S. Pat. No. 6,695,803, issued on Feb. 24, 2004 to Robinson et al., which is incorporated by reference herein. In Robinson et al., a blood processing system including a peristaltic pump is described with three rollers which are coupled to three different motors and which share a single support shaft which is also used to rotate one of the rollers, with the two other rollers having hollow shafts through which the support shaft extends, with each of these two rollers able to rotate independently of the roller attached to the support shaft. 
         [0012]    However, none of the conventional pumps provide as much flexibility and ease of operation as may be desirable, such as by providing a multi-channel peristaltic pump such that an operator can selectively control the speed and direction of fluid flow in each of the channels independent of the other channels. Moreover, none of the conventional pumps provide such flexibility and do so with a compact size. 
       SUMMARY OF THE INVENTION 
       [0013]    In one embodiment, a multi-channel peristaltic pump is provided which comprises a plurality of channels, with each channel having a roller head with a plurality of rollers, and with each of the heads operable to rotate independently of one another, including at different speeds and in different directions, thus allowing the operator to independently control the speed, amount and direction of fluid flow independently in each of the channels in the multi-channel pump. The pump includes a plurality of concentric, nested drive shafts, with each of the drive shafts adapted to drive a corresponding roller head. Each of the drive shafts can be coupled to a motor, such as by a pulley or timing belt, with the motor being independently actuated and controlled by a user. A control system with a processor and memory and user input can be used to easily allow the operator to selectively operate the roller heads independently of one another. In another embodiment, a method is provided for controlling the speed and direction of the rollers on a plurality of roller heads in a multi-channel peristaltic pump, including the steps of selecting the speed, direction, or other parameters for the operation of the roller heads. 
         [0014]    It is an object to provide a multi-channel peristaltic pump in which the user can independently control the operation of each channel, and to do so without requiring a larger amount of space for multiple motors for the channels. 
         [0015]    It is yet another object to provide a multi-channel peristaltic pump in which the rollers of the heads are located sufficiently close so that removable cartridges can be used in connection with some or all of said heads. 
         [0016]    It is yet another object to minimize the space required for a multi-channel peristaltic pump with a plurality of independently operable channels, and further, to do so in a manner that nonetheless presents a greater surface area of the rollers of one or more channels for pumping action. 
         [0017]    These and other advantages will be apparent from the following detailed description and drawings of the illustrative embodiments of the present invention provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  provides an exploded isometric view of one embodiment of a multi-channel peristaltic pump. 
           [0019]      FIG. 2  provides an exploded side view of one embodiment of a multi-channel peristaltic pump. 
           [0020]      FIG. 3  provides an exploded cross-sectional view of one embodiment of a multi-channel peristaltic pump. 
           [0021]      FIG. 4  provides a close-up sectional view of an embodiment of a multi-channel peristaltic pump. 
           [0022]      FIG. 5  provides a view of yet another embodiment of a multi-channel peristaltic pump. 
           [0023]      FIG. 6  provides a view of still another embodiment of a multi-channel peristaltic pump. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    In  FIG. 1 , a multi-channel peristaltic pump  1  is shown. In  FIG. 1 , the pump  1  includes a housing, which has a face  5 . The pump  1  also has four roller heads  2 ,  4 ,  6 , and  8 , which are shown extending from face  5 . In addition, the pump  1  includes supports  7   a  and  7   b  which are located on opposite sides of the roller heads  2 ,  4 ,  6 , and  8 . In addition, a support  3  is provided to which supports  7   a  and  7   b  are connected. As will be discussed in more detail below, each of roller heads  2 ,  4 ,  6 , and  8  is rotatable around an axis. 
         [0025]    Referring now to  FIG. 2 , the pump  1  is shown in an alternative view. It will be understood that the same numbers will be used for the same components shown in the various figures of the pump  1  and its components herein. In  FIG. 2 , an exploded view of the pump  1  is provided. As shown in  FIG. 2 , the pump  1  has four motors  13 ,  15 ,  17 , and  19 , and coupled to each is a belt, such as by attaching each to a belt  18   a ,  18   b , and  18   c , and  18   d , respectively. When activated, each of motors  13 ,  15 ,  17 , and  19  will drive movement of the belts  18   a ,  18   b ,  18   c , and  18   d , respectively. As described in more detail below, the movement of the belts  18   a ,  18   b ,  18   c , and  18   d  will result in the movement of roller heads  2 ,  4 ,  6 , and  8 . The motors  13 ,  15 ,  17 , and  19  may be conventional motors, such as those commercially available from Lin Engineering of Morgan Hill, Calif. 
         [0026]    Referring now to  FIG. 1 , each of the roller heads  2 ,  4 ,  6 , and  8  has a plurality of rollers attached thereto. The rollers of each of the roller heads  2 ,  4 ,  6 , and  8  can vary in number, size and materials from the rollers of the other roller heads  2 ,  4 ,  6 , and  8 . As shown in  FIG. 1 , each of the roller heads  2 ,  4 ,  6 , and  8  has a plate  2   b ,  4   b ,  6   b , and  8   b , respectively. As also shown in  FIG. 1 , each of the plates  2   b ,  4   b ,  6   b , and  8   b  has one or more rollers attached thereto. In the embodiment shown in  FIG. 1 , the roller head  8  also has a second plate  8   a , which is located between the rollers on roller head  8  and the support  3 . As shown in  FIG. 1 , each of the plates  2   b ,  4   b ,  6   b , and  8   a  and  8   b  are generally circular in shape in this embodiment. 
         [0027]    In this embodiment of pump  1 , the rollers of the roller heads  2 ,  4 ,  6 , and  8  are made of polyethylene terephthalate (PET-P), and the roller flanges or rotors of the heads  2 ,  4 ,  6 , and  8  are made of aluminum. The shafts or rotors  22 ,  24 ,  26 , and  28  can be made of metals such as steel or stainless steel. It will be appreciated that the rollers, roller heads  2 ,  4 ,  6 , and  8 , and the rotors or shafts  22 ,  24 ,  26 , and  28  can be made of a variety of materials as may be desired, including without limitation the following: for rollers: any type of low coefficient of friction material, for the flanges or rotors of the roller heads and shafts: structurally stable materials for supporting the rollers and to have enough strength for torsion and bending stresses on the hollow shafts, such as: aluminum and steel alloys. It will be appreciated that, although not shown in  FIG. 1 , the rollers attached to the roller heads press against tubing (also not shown in  FIG. 1 ) which contains a fluid to be pumped, with the tubing held in place either against a casing (also not shown in  FIG. 1 ) on the other side of the tubing from the rollers, or with the tubing held against the rollers by a cartridge (also not shown in  FIG. 1 ) which can be removably attached to the pump  1 , with the tubing located within the body of the cartridge. 
         [0028]    In addition, each of the roller heads  2 ,  4 ,  6 , and  8  has a corresponding shaft (shafts  22 ,  24 ,  26 , and  28 , respectively) extending in one direction from the plates  2   b ,  4   b ,  6   b , and  8   b  of the roller heads  2 ,  4 ,  6 , and  8 . It will be seen that each of the shafts  22 ,  24 ,  26 , and  28  are circular around an axis, and that the corresponding roller heads  2 ,  4 ,  6 , and  8  are also circular around the same axis as their corresponding shafts  22 ,  24 ,  26 , and  28 . As shown in  FIG. 1 , the shafts  22 ,  24 ,  26 , and  28  have different diameters, for reasons explained below. In  FIG. 1 , it can be seen that in this particular embodiment, shaft  28  has the smallest diameter, shaft  26  has the next smallest diameter, shaft  24  has a diameter greater than that of shaft  26 , but less than that of shaft  22 , and shaft  22  has the largest diameter. As further detailed below, each of the shafts  22 ,  24 , and  26  has an internal hollow portion which is sized to receive and hold therein at least one of the other shafts  24 ,  26 , and  28 . In this embodiment, shaft  28  fits within the interior opening of shaft  26 , which in turn fits within the interior opening of shaft  24 , which in turn fits within the interior opening of shaft  22 . Those skilled in the art will appreciate that the shafts  22 ,  24 ,  26 , and  28  can have various diameters and that, depending on the outside diameters of the shafts  22 ,  24 ,  26 , and  28 , the interior openings of the other shafts may vary accordingly to receive and fit together. When assembled together, each of the shafts  22 ,  24 ,  26 , and  28  are located concentric with respect to each other and each of the shafts  22 ,  24 ,  26 , and  28 , as well as the corresponding roller heads  2 ,  4 ,  6 , and  8 , are rotatable around the same axis. 
         [0029]    Still referring to  FIG. 1 , it can be seen that the shafts  22 ,  24 ,  26 , and  28  are to be connected to pulleys  17   d ,  17   c ,  17   b  and  17   a , respectively. Each of the pulleys  17   d ,  17   c ,  17   b , and  17   a  is rotatable around the same axis as the shafts  22 ,  24 ,  26 , and  28  (and the roller heads  2 ,  4 ,  6 , and  8 ). In addition, each of the pulleys  17   d ,  17   c ,  17   b , and  17   a  has a belt  18   d ,  18   c ,  18   b , and  18   a , respectively, attached to it. The belts  18   a ,  18   b ,  18   c , and  18   d , in turn, are attached to motors  13 ,  15 ,  17 , and  19 , respectively. In operation, when any one or more of the motors  13 ,  15 ,  17 , and  19  is actuated, the motors  13 ,  15 ,  17 , and  19  can then move the belts  18   a ,  18   b ,  18   c , and  18   d , thereby rotating pulleys  17   a ,  17   b ,  17   c , and  17   d , respectively, and when pulleys  7   a ,  17   b ,  17   c , and  17   d  are rotated, the shafts  28 ,  26 ,  24 , and  22 , respectively, are rotated. As noted, when shafts  22 ,  24 ,  26 , and  28  are rotated, the corresponding roller heads  2 ,  4 ,  6 , and  8  are rotated. 
         [0030]    In the embodiment shown in  FIG. 1 , each of the shafts  22 ,  24 ,  26 , and  28  have the roller heads  2 ,  4 ,  6 , and  8 , respectively, attached at one end and are coupled to a belt  18   d , a 8   c ,  18   b , and  18   a , respectively, at their other ends. The belts  18   a ,  18   b ,  18   c , and  18   d  can be timing belts to provide for synchronous power transmission. Those skilled in the art will appreciate that, although the embodiment shown in  FIG. 1  provides for a separate motor and belt for each of shafts  22 ,  24 ,  26 , and  28 , a single motor could be used to rotate two or more of the shafts  22 ,  24 ,  26 , and  28 . For example, a single motor could be coupled to both shafts  22  and  24 , with separate motors and belts used to rotate each of shafts  26  and  28 . In addition, those skilled in the art will appreciate that instead of the belts and pulleys described herein, gears or other mechanisms may be used to rotate the shafts. 
         [0031]    In the embodiment shown in  FIG. 1 , each of the shafts  22 ,  24 ,  26 , and  28  are able to rotate independently with respect to each other. This allows a user to actuate any one or more of motors  13 ,  15 ,  17 , and  19  at the same time, at different times, at the same or different speeds, and in the same or different directions. Thus, in the embodiment shown in  FIG. 1 , each of the roller heads  2 ,  4 ,  6 , and  8  may, depending on the selection of a user (which may include a computer preprogrammed to operate in accordance with computer software), rotate alone, rotate at a different speed from one or more of the other roller heads  2 ,  4 ,  6 , and  8 , and may rotate in a direction opposite from that of one or more of the other roller heads  2 ,  4 ,  6 , and  8 . It will be appreciated that this aspect allows an operator of the pump  1  a great deal of flexibility in use of the pump  1 . Moreover, it will be appreciated that the rollers of the roller heads  2 ,  4 ,  6 , and  8  can be varied in size, number, and material, so that the pump  1  provides an operator of the pump  1  with an even greater amount of flexibility and choice in terms of operations and applications. 
         [0032]    It will also be appreciated that, although the embodiment shown in  FIG. 1  includes eight (8) rollers on each of roller heads  2 ,  4 ,  6 , and  8 , a the number and size of the rollers on the roller heads  2 ,  4 ,  6 , and  8  may be varied. For example, roller head  2  can have eight (8) rollers, roller head  4  can have six (6) rollers, roller head  6  can have six (6) rollers, and roller head  8  can have eight (8) rollers. Those skilled in the art will appreciate that varying the number and/or size of the rollers located on the roller heads  2 ,  4 ,  6 , and  8  will provide the user with greater flexibility for a variety of applications. 
         [0033]    Still referring to  FIG. 1 , it can be seen that the face plate  5  includes an opening  5   b . In the embodiment shown in  FIG. 1 , the opening  5   b  is substantially circular in shape and has a diameter that will allow at least a portion of shaft  22  to extend therethrough. Also shown in  FIG. 1  is a bearing  40 . In the embodiment shown in  FIG. 1 , the bearing  40  is of a size and shape selected to fit in the opening  5   b  of the face plate  5 . The bearing  40  can be of the same type of bearing as discussed below in connection with  FIGS. 3 and 4 . It will be understood that the bearing  40  has an interior opening through which shaft  22  (and the other shafts  24 ,  26 , and  28  disposed within shaft  22 ) extends. The bearing  40  facilitates the rotation of shaft  22  within the opening  5   b.    
         [0034]    In addition, face plate  5  is adapted to be attached to a support  30 . In the embodiment shown in  FIG. 1 , the support plate  30  provides both a bottom support and also a rear face for the pump  1 . Those skilled in the art will appreciate that the motors  13 ,  15 ,  17 , and  19  can all be attached to the bottom of the support  30 , such as by any conventional attachment mechanisms, including screws, glue, adhesives and the like. 
         [0035]    Referring now to  FIG. 2 , an exploded side view of the same embodiment of pump  1  is shown. As shown in  FIGS. 1 and 2 , the shafts  22 ,  24 ,  26 , and  28  are of different diameters, and the size of each of the shafts  22 ,  24 ,  26 , and  28  is selected to allow them to fit together in a concentric fashion. Shaft  28  can fit through and opening in roller head  6  and extend through the interior opening of shaft  26 . Shaft  26 , in turn, can fit through an opening in roller head  4  and extend through the interior opening of shaft  24 . Shaft  24 , in turn, fits through an opening in roller head  2  and extends through the interior opening of shaft  22 . As noted above, this allows for the shafts  22 ,  24 ,  26 , and  28  to be located concentric with respect to one another. In addition, this allows for the corresponding roller heads  2 ,  4 ,  6 , and  8  to be located adjacent to at least one of the other roller heads  2 ,  4 ,  6 , and  8 , thus allowing the pump  1  to be of a more compact size than would otherwise be the case. 
         [0036]    Now referring to  FIG. 3 , still another view of the pump  1  is provided. In  FIG. 3 , an exploded cross-sectional view of the pump  1  is provided. As before, the same numerals are used to indicate the same features and elements of pump  1  in  FIG. 3 . In the exploded, cross-sectional view of  FIG. 3 , the interior openings of the shafts  22 ,  24 , and  26  can be seen more clearly. (In this particular embodiment, shaft  28  is solid and does not have an interior opening as do shafts  22 ,  24 , and  26 .) In addition, the openings in the roller heads  2 ,  4 , and  6  can be seen more clearly. (In this particular embodiment, roller head  8  does not have an opening.) 
         [0037]    Still referring to  FIG. 3 , it can be seen that the interior openings of each of shafts  22 ,  24 , and  26  are circular in shape. As also shown in  FIG. 3 , located within shaft  22  are bearings  22   a  and  22   b , located within shaft  24  are bearings  24   a  and  24   b , and located within shaft  26  are bearings  26   a  and  26   b . Each of the bearings  22   a ,  22   b ,  24   a ,  24   b ,  26   a , and  26   b  are shown located at the respective ends of the interior openings of the shafts  22 ,  24 , and  26 , respectively. The bearings  22   a  and  22   b  facilitate and allow the easy rotation of shaft  24  when located within the interior opening of shaft  22 . Similarly, the bearings  24   a  and  24   b  facilitate and allow the easy rotation of shaft  26  when located within the interior opening of shaft  24 . In addition, the bearings  26   a  and  26   b  facilitate and allow the easy rotation of shaft  28  when located within the interior opening of shaft  26 . Thus, the bearings  22   a ,  22   b ,  24   a ,  24   b ,  26   a , and  26   b  help support the shafts  24 ,  26 , and  28 , respectively, while still allowing and facilitating the rotation of shafts  22 ,  24 ,  26 , and  28  independently of the other of shafts  22 ,  24 ,  26 , and  28 . 
         [0038]    It will be appreciated that in this embodiment, bearings  22   a  and  22   b  will be of a size selected to fit within the interior opening of shaft  22  and have an open internal diameter adapted to fit shaft  24 . Similarly, bearings  24   a  and  24   b  will be of a size selected to fit within the interior opening of shaft  24  and have an open internal diameter adapted to fit shaft  26 . Likewise, bearings  26   a  and  26   b  will be of a size selected to fit within the interior opening of shaft  26  and have an open internal diameter adapted to fit shaft  28 . The bearings  22   a ,  22   b ,  24   a ,  24   b ,  26   a , and  26   b  can be made of various materials, including without limitation the following: stainless steel and any other steel alloy combination. In addition, plastic or ceramics materials may be utilized too. The bearings  22   a ,  22   b ,  24   a ,  24   b ,  26   a , and  26   b  can be conventional, such as those obtained from Misumi USA Inc. of Schaumburg, Ill. Bearings  22   a ,  22   b ,  24   a ,  24   b ,  26   a , and  26   b  may be ball bearings or needle bearings of a size selected to fit snugly within the hollow interior portions of the shafts  22 ,  24 , and  26 , respectively. Alternatively, sleeve bearings or bushings could be used for bearings  22   a ,  22   b ,  24   a ,  24   b ,  26   a , and  26   b.    
         [0039]    Referring now to  FIG. 4 , a sectional view of the pump  1  as assembled is provided. It will be understood that for ease of reference, not all of the components of pump  1  as shown in  FIGS. 1-3  and described above are numbered and labeled in  FIG. 4 . In  FIG. 4 , the shafts  22 ,  24 ,  26 , and  28  are shown in a nested, concentric configuration, with shaft  28  located as the innermost, shaft  26  disposed about the outside of a portion of the length of shaft  28 , shaft  24  disposed about the outside of a portion of the length of shaft  26  and shaft  28 , and shaft  22  disposed outside of a portion of the length of shafts  24 ,  26 , and  28 . Although not shown in  FIG. 4 , it will be understood that each of the shafts  22 ,  24 ,  26 , and  28  may be coupled to a motor, pulley and belt so that each of the shafts  22 ,  24 ,  26 , and  28  may be rotated. In addition, roller heads  2 ,  4 ,  6 , and  8  are shown in  FIG. 4 , as is the plate  8   a  of roller head  8 . 
         [0040]    In  FIG. 4 , bearing  40  is shown located within the opening  5   b  of the face plate  5  of the pump  1 . Bearing  40  is also located within an opening in the support plate  32 . Bearing  40  thus allows and facilitates the rotation of shaft  22  without friction or interference from face plate  5  or support plate  32 . In addition, bearings  22   a ,  22   b ,  24   a ,  24   b ,  26   a , and  26   b  are shown in  FIG. 4 . As shown in  FIG. 4 , bearings  22   a  and  22   b  are located within an inner diameter portion of the shaft  22 , with bearing  22   a  located at or near a first end of the shaft  22  and bearing  22   b  located at or near the second end of shaft  22 . Similarly, bearings  24   a  and  24   b  are disposed within the interior hollow portion of shaft  24 , with bearing  24   a  located at or near a first end of the shaft  24  and bearing  24   b  located at or near a second end of the shaft  24 . In addition, bearings  26   a  and  26   b  are shown located within the interior hollow opening of shaft  26 , with bearing  26   a  located at or near a first end of the shaft  26  and bearing  26   b  located at or near a second end of the shaft  26 . As noted above, the bearings  22   a ,  22   b ,  24   a ,  24   b ,  26   a , and  26   b , as well as bearing  40 , allow the smooth rotation of the shafts  22 ,  24 ,  26 , and  28  when the shafts are actuated and rotate. It will be appreciated that more or less bearings can be used than the number of bearings shown and described herein. In addition, the bearings  22   a ,  22   b ,  24   a ,  24   b ,  26   a ,  26   b , and  40  can be of various types, such as those noted above, and need not be the same. Moreover, it should be noted that the locations of the bearings  22   a ,  22   b ,  24   a ,  24   b ,  26   a , and  26   b  can be varied as may be desired. 
         [0041]    In operation, a pump  1  in accordance with one or more embodiments herein can be provided with any desired number of roller heads, which may be 2 or more. In embodiments in which six, eight or more roller heads is desired, it may be desirable to locate the motors within the pump in such a way as to minimize the overall space needed for the pump  1 . An embodiment intended to achieve this objective is shown in  FIG. 5 . In  FIG. 5 , and pump  500  is shown. Pump  500  includes six roller heads  510 ,  511 ,  512 ,  513 ,  514 , and  515 . Although not shown in  FIG. 5 , each of the roller heads  510 ,  511 , and  512  has a shaft located concentric with the shafts of the other of the roller heads  510 ,  511 , and  512 . In addition, and although not shown, each of the roller heads  513 ,  514 , and  515  has a shaft located concentric with the shafts of the other of the roller heads  513 ,  514 , and  515 . In addition, each of the shafts of the roller heads  510 ,  511 ,  512 ,  513 ,  514 , and  515  is connected to a corresponding pulley (not shown for roller heads  510 ,  511 , and  512 ) which, in turn, is connected to a motor (also not shown in  FIG. 5  for roller heads  510 ,  511 , and  512 ). Because the shaft for roller head  512  can fit within the shaft for roller head  511 , which in turn can fit within the shaft for roller head  510 , each of the roller heads  510 ,  511 , and  512  can be connected to a separate motor (not shown) so that each of the roller heads  510 ,  511 , and  512  can be rotated at a speed and in a direction independently of each of the other of roller heads  510 ,  511 , and  512 . In addition, the shaft for roller head  513  can fit within the shaft for roller head  514 , which in turn can fit within the shaft for roller head  515 , so that each of the roller heads  513 ,  514 , and  515  can be connected to a separate motor (not shown), thus allowing each of the roller heads  513 ,  514 , and  515  to be rotated at a speed and in a direction independently of each of the other of roller heads  513 ,  514 , and  515 . Thus, the pump  500  can provide six roller heads  510 - 515  that can be rotated independently of one another, thus allowing an operator to choose to operate any one or more at a speed and in a direction that is the same as or different from that of any one or more of the other roller heads  510 - 515 . Moreover, as shown in  FIG. 5 , the three motors coupled to roller heads  510 ,  511 , and  512  can be located at one end or one side of the pump  500 , with the three motors coupled to roller heads  513 ,  514 , and  515 , respectively, located at the other end or side of the pump  500 . By placing the motors towards the respective ends of the pump  500 , the six roller heads  510 - 515  can be located much closer together, which allows for easier use and operation, as well as providing a more compact design for the pump  500 . 
         [0042]    The pump  1  can be provided with a processor and memory having programs or software stored therein for use in controlling the operation of the roller heads. It will be appreciated that the pump  1  can also have a display and one or more user input devices (such as a touch pad) by which the user can select various modes of operation for each of the roller heads. For example, the user may choose to use the input device so that the pump  1  will rotate a first roller head in a first direction and at a first speed, rotate a second roller head in the same direction but at a different speed, and also rotate a third roller head in a second direction and at a third speed. In this way, the pump  1  provides greater flexibility and ease of use for a greater variety of applications, yet maintains a compact size because multiple roller heads can be located closer together than in conventional peristaltic pumps that do not allow for such different modes of operation. For example, the pump  1  can be provided with a first roller head having six rollers of a first size, a second roller head with eight rollers of a second size, and also a third roller head with ten rollers of still a third size. Those skilled in the art will appreciate that the selection of the number and sizes of the rollers on the roller head can be made to provide greater control over the volumes and flow rate of the fluid to be pumped by the pump  1 . Control over such variables, together with control over the speed and direction of movement of each of the roller heads, provides the operator with a substantial amount of flexibility and control. 
         [0043]    Referring now to  FIG. 6 , an alternative embodiment of a peristaltic pump  600  is provided. In  FIG. 6 , a pump  600  is shown. The pump  600 , like the pump  500  shown in  FIG. 5 , includes six roller heads (not shown) coupled to six separate motors (not shown), with three of the motors located at or near a first end  602  of the pump  600 , and the other three motors located at or near the second end  604  of the pump  600 . As shown in  FIG. 6 , six removable cartridges  620 ,  622 ,  624 ,  626 ,  628  and  630  are attached to the pump  600 . These cartridges may be of a conventional type, such as those disclosed in U.S. Pat. No. 7,214,038, and such as those commercially available from Ismatec, S.A., of Glattbrugg, Switzerland. As also shown in  FIG. 6 , casing is provided for pump  600  to cover the motors and other components, including the processor, memory, and other components needed for controlling the operation of the pump  600 . In addition, pump  600  includes a display  610 , which provides for the display of information and also allows a user to input data and control or program the operation of the pump  600 , such as by programming the speed and direction of the six roller heads to which cartridges  620 ,  622 ,  624 ,  626 ,  628 , and  630  are removably attached. 
         [0044]    It will be appreciated that the foregoing description and the Figures are illustrative embodiments only and do not define the scope of the invention, which is defined by the scope of the claims. Those skilled in the art will appreciate that a variety of modifications and changes may be made to the embodiments described in detail herein without departing from the scope and spirit of the invention, which is defined only by the claims. For example, a different number of roller heads, motors, and the like may be used, and a variety of different materials may be used as well. In addition, the motors may be coupled to the shafts of the roller heads in different ways, and the motors may be of different types than those described herein. Similarly, removable cartridges need not be used, but may be desirable for ease of use and convenience.