Abstract:
A peristaltic pump is provided that simplifies the loading of tubing and automatically self-centers the tubing relative to the pump wheel, wherein the pump includes an elongated arm having slotted pinch forks for engaging the tubing. The pinch forks are arranged substantially tangential to the pump wheel to reduce tubing kinking. The pump further includes a spring-loaded clamp that moves the elongated arm between engaged and disengaged positions, the clamp optionally including a sensor element used to detect when the pump is ready for operation.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a peristaltic pump that provides simplified loading and improved kink-resistance.  
       BACKGROUND OF THE INVENTION  
       [0002]     Peristaltic pumps are widely used in the medical industry for pumping fluids and are preferred for their positive displacement and flow metering characteristics. In addition, because the fluid to be pumped is contained within replaceable tubing, the pump mechanism does not become contaminated with the fluid. Typically, in such pumps a flexible tube is engaged with one or more rollers that periodically compress the tubing in a lengthwise fashion, thereby propelling the fluid disposed within the tubing.  
         [0003]     In a typical peristaltic pump, the flexible tubing is disposed between a spring-biased semi-circular clamp and the periphery of a pump wheel, with further end clamps disposed on the pump housing at either end of the semi-circular clamp to retain the tubing centered on the pump wheel. The pump wheel carries a plurality of rollers spaced along the circumference of the pump wheel, wherein the rollers engage and ride along the tubing for the length of the semi-circular clamp. During rotation of the pump wheel, liquid is urged through the tubing in the direction of the wheel rotation. Backflow is prevented by ensuring that at least two rollers are engaged with the tubing at all times.  
         [0004]     One drawback associated with conventional peristaltic pumps involves difficulty in loading tubing, in that it may require considerable manipulation to arrange the tubing in the end clamps to ensure that the tubing is properly centered in the pump mechanism. Another drawback associated with conventional peristaltic pumps is that the tubing, when inadvertently placed in tension, has a tendency to kink against the end clamps during operation. A still further drawback is associated with maintaining the tubing centered on the pump wheel rollers.  
         [0005]     In view of these drawbacks of previously known devices, it would be desirable to provide a peristaltic pump having simplified loading.  
         [0006]     It also would be desirable to provide a peristaltic pump that is configured to reduce kinking of the tubing.  
         [0007]     It still further would be desirable to provide a peristaltic pump that self-centers the tubing within the pump mechanism.  
       SUMMARY OF THE INVENTION  
       [0008]     In view of the foregoing, it is an object of the present invention to provide a peristaltic pump having simplified loading.  
         [0009]     It is another object of this invention to provide a peristaltic pump that is configured to reduce kinking of the tubing.  
         [0010]     It also is an object of the present invention to provide a peristaltic pump that self-centers the tubing within the pump mechanism.  
         [0011]     These and other objects of the present invention are accomplished by providing a peristaltic pump having a compression arm that self-centers the tubing during loading, without the use of additional clamps located on the pump housing. The compression arm is biased against the pump wheel with a single, easy to manipulate clamp that incorporates a spring biasing mechanism. The simplified construction of the peristaltic pump of the present invention thereby reduces loading time with respect to clamp manipulation, provides self-centering of the tubing and enhanced resistance to kinking.  
         [0012]     According to one aspect of the invention, the compression arm includes an elongated curvilinear body having slotted pinch forks at either end that engage and confine the tubing to prevent slippage of the tubing relative to the pump wheel. The slotted pinch forks thereby serve to fix the tubing in position relative to the pump wheel and provide self-centering of the tubing. The pinch forks are oriented on the compression arm so as to minimize abrupt directional changes of the tubing, thereby reducing the risk of kinking. In addition, the pinch fork located after the pump wheel is sufficiently loose that it does not inhibit laminar flow, which might otherwise cause variability in the flow rates.  
         [0013]     The compression arm is arranged to pivot relative to the pump wheel to permit easy loading of the tubing, and includes a notch that mates with a projection of the clamp when the compression arm is locked into an engaged position with the pump wheel. To load the tube, the clamp is disengaged and the compression arm is rotated away from the pump wheel. The tubing then is inserted into the slots of the pinch forks, and the compression arm rotated against the pump wheel. The clamp is then engaged, thereby locking the compression arm and tubing against the rollers of the pump wheel.  
         [0014]     In accordance with a further aspect of the invention, a sensor is disposed in the clamp to determine whether the compression arm is in the engaged position or disengaged position. When the sensor detects that the compression arm is engaged against the pump wheel, it sends a signal that may be employed to activate the pump. The sensor also may be employed to determine whether tubing has been loaded onto the compression arm. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments, in which:  
         [0016]      FIG. 1  is an exploded view of the pump of the present invention;  
         [0017]      FIG. 2  is a perspective view of the pump with the compression arm disposed in the disengaged configuration;  
         [0018]      FIG. 3  is a perspective view of the pump with the compression arm disposed in the engaged configuration;  
         [0019]      FIG. 4  is an exploded view of the clamp employed in the pump of the present invention; and  
         [0020]      FIG. 5  is an exploded view of the pump wheel of the pump of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     Referring to  FIG. 1 , peristaltic pump  10  of the present invention includes pump wall  11  that defines interior and exterior surfaces of the pump. Mounting plate  12 , which supports motor  13  and sensor  14 , are mounted to the interior surface of the pump wall  11  so that shaft  15  of motor  13  extends through the pump wall to the exterior surface. Compression arm  16 , clamp  17  and pump wheel  18  are mounted to the exterior of pump wall  11 . The exterior of pump wall  11  further includes guard  19  that protects incidental contact with the exterior of pump wheel  18 .  
         [0022]     Motor  13  may be an electric motor and is the drive mechanism for pump  10 . In a preferred embodiment, motor  13  may be microprocessor controlled using system software comprising machine-readable or interpretable instructions for controlling the rotation of pump wheel. More preferably, motor  13  may be activated in accordance with signals generated by sensor  14  that indicate the status of compression arm  16 .  
         [0023]     Mounting plate  12  and motor  13  preferably are attached to pump wall  11  using suitable fasteners such as screws. Pins  20  and  21  extend from mounting plate  12  and pass through corresponding apertures in pump wall  11  to pivotally accept clamp  17  and compression arm  16 , respectively. The apertures through pump wall  11  preferably include gaskets  22  to substantially prevent ingress of fluids to the interior of the pump.  
         [0024]     Compression arm  16  is pivotally mounted on pin  21 , and includes pinch forks  23  and  24  disposed at either end. Pinch forks  23  and  24  comprise slots  25  and  26 , respectively, which are dimensioned to accept flexible plastic tubing of a predetermined diameter, e.g., having a 0.150 inch outside diameter. When inserted into slots  25  and  26 , the pinch forks engage the tubing and prevent relative longitudinal movement, but do not disturb laminar flow of fluid through the tubing. Compression arm  16  further comprises bearing surface  27  that is configured to surround an arc of pump wheel  18  and engage the tubing against the pump wheel.  
         [0025]     In accordance with the principles of the present invention, slots  25  and  26  of pinch forks  23  and  24  are arranged to automatically center the tubing on bearing surface  27  when the tubing is loaded into the compression arm. In addition, because the slots of the pinch forks are arranged substantially tangential to the pump wheel, the tubing is subjected to fewer abrupt directional changes than in conventional peristaltic pump designs, and thus the tubing in less likely to kink if inadvertently placed in tension.  
         [0026]     Clamp  17  is pivotally mounted on pin  20  and includes an internal spring-biasing feature that permits the clamp to lock into engagement with compression arm  16 . Clamp  17  further includes a projection that mates with a notch in the compression arm to lock the compression arm against pump wheel  18 . As described in greater detail below, pump wheel  18  includes a plurality of rollers that engage the tubing.  
         [0027]     Referring now to  FIGS. 2 and 3 , further details of the structure and operation of pump  10  of the present invention are described.  FIG. 2  depicts pump  10  with compression arm  16  and clamp  17  in an open, disengaged position suitable for loading tubing  100 , whereas  FIG. 3  depicts the pump in a closed, engaged position suitable for pump operation.  
         [0028]     In particular, in  FIG. 2 , clamp  17  is shown with projection  28  disengaged from notch  29  of compression arm, so that the clamp is pivoted on pin  20  against stop  30 . Stop  30  extends from the exterior surface of pump wall  11  and may be integrally formed with pump wall  11  or attached as a separate component thereto. Clamp  17  includes extension  31  that supports the compression arm in the open position when the clamp is pivoted against stop  30 . Tubing  100  is shown disposed in slots  25  and  26  of pinch forks  23  and  24 , respectively, with a mid-length portion of the tubing disposed against bearing surface  27 . When tubing  100  is so engaged with slots  25  and  26 , the slots confine and prevent slippage of the tubing and also center the tubing on bearing surface  27 , thereby facilitating loading of the tubing.  
         [0029]     In  FIG. 3 , compression arm  16  is depicted locked into engagement with pump wheel  18  by clamp  17 . More specifically, once tubing  100  is loaded onto the compression arm, clamp  17  is rotated in a counter clockwise direction about pivot  20 . This in turn causes compression arm  16  to ride along extension  31  of clamp  17 , causing the compression arm to pivot about pin  21  in a counter clockwise direction until the tubing and bearing surface  27  of the compression arm are disposed adjacent to pump wheel  18 . In this position, projection  28  of clamp  17  engages notch  29  of the compression arm and locks the latter into position relative to the pump wheel. Because clamp  17  includes an internal spring-biasing feature, tubing  100  is disposed against the rollers of pump wheel  18  with a force within a predetermined range suitable for the tubing diameter.  
         [0030]     To subsequently disengage the compression arm, clamp  17  is rotated in a clockwise direction about pivot  20 , thereby permitting compression arm  16  to pivot away from pump wheel  18 .  
         [0031]     In accordance with another aspect of the present invention, sensor  14  (see  FIG. 1 ) monitors whether tubing is loaded onto compression arm  16  and whether the compression arm is engaged with the pump wheel. For example, sensor  14  may comprise a position switch that is actuated when compression arm  16  is disposed a predetermined distance away from pump wheel  18 . The distance at which the switch is actuated may take into account the thickness of the tubing and the degree of deflection of the spring-biasing feature of clamp  17  to determine that tubing is loaded and the compression arm is engaged. In addition, the signal generated by sensor  14  may be used not only to determine that the pump is properly loaded and ready for operation, but also may be used to activate motor  13 .  
         [0032]     Referring now to  FIG. 4 , clamp  17  is described in further detail. Clamp  17  comprises handle  40 , base  41  having aperture  42  that receives pin  20 , spring  43  and sensor element  44  disposed in recess  45 . As discussed hereinabove, clamp  17  applies a spring-biased compressive load to compression arm  16  and tubing  100  that forces those components against pump wheel  18 . According to a preferred embodiment of the invention, sensor element  44  comprises a magnet that triggers sensor  14  when compression arm  16  is engaged or disengaged.  
         [0033]     Handle  40  includes a recess formed in its lower surface to accept the upper end of spring  43 , and extension  47  having elongated aperture  48 . Base  41  includes a recess formed in its upper surface to accept the lower end of spring  43 . Pin  20  extends through elongated aperture  48  to couple handle  40  to base  41 , so that spring  43  biases the pin  20  to the lower extremity of elongated aperture  48 . In this manner, handle  40  can be compressed against base  41  (and against the bias of spring  43 ) to permit projection  28  to move into and out of the engagement with notch  29  in compression arm  16 . Handle  40  further includes extension  31  that supports compression arm  16  when disengaged, and provides a ramp that guides notch  29  onto projection  28  during engagement of the compression arm to the pump wheel.  
         [0034]     Referring now to  FIG. 5 , pump wheel  18  comprises base  50 , cap  51 , plurality of rollers  52 , pins  53  and spring washers  54 . Each roller  52  includes lumen  55  dimensioned to receive pin  53 , so that the roller rotates freely on pin  53 . Base  50  includes recesses  56  configured to receive the first ends of pins  53  and spring washers  54 . Cap  52  includes similar recesses (not shown) configured to receive the other ends of pins  53 . Spring washers  54  minimize vibration and noise of the pump wheel during operation by applying axial load to rollers  52  against cap  51 . Although in the illustrated embodiment four rollers  52  are depicted, as would be understood by one of ordinary skill in the art, any number of rollers may be employed.  
         [0035]     As described hereinabove, pump wheel  18  is mounted on shaft  15  of motor  13 . When activated, rotation of shaft  15  induces rotation of pump wheel  18 . As depicted in  FIG. 3 , when compression arm  16  and tubing  100  are engaged with pump wheel  18 , rotation of pump wheel  18  causes rollers  52  to travel along tubing  100  in the vicinity of bearing surface  27  to thereby propel fluid disposed within the tubing. Because at least one roller  52  always remains in contact with tubing  100 , the pump  10  retains the positive displacement and flow metering characteristics favored in peristaltic pumps, while improving ease of set up and operation.  
         [0036]     When compression arm  16  is in engaged against pump wheel  18 , tubing  100  is engaged against rollers  52 . Slots  25  and  26  of compression arm  16  are sized to securely engage the tubing during pump operation without allowing the tubing to creep longitudinally. As will of course be understood, however, slots  25  and  26  also are sufficiently wide to avoid constricting the flow of fluid through tubing  100 . Advantageously, incorporation of pinch forks  23  and  24  into compression arm  16  permits simplified and expedited tube loading. In addition, because pinch forks  23  and  24  are aligned substantially tangential to pump wheel  18 , there is reduced risk of tubing kinking compared to tube clamps used in conventional peristaltic pumps.  
         [0037]     A method of loading pump  10  of the present invention is now described. Initially, clamp  17  is disengaged from compression arm  16  and the compression arm is rotated away from the pump wheel  18 . Tubing  100  is inserted along compression arm  16  and then is urged at either end into the slots of pinch forks  23  and  24 . Once the tubing has been loaded, clamp  17  is rotated in a counter clockwise direction about pivot  20 , thereby causing compression arm  16  to rotate in a counter clockwise direction about pivot  21 . When compression arm  16  is rotated into the engaged position against the rollers of pump wheel  18 , tubing  100  becomes compressed between bearing surface  27  of compression arm  16  and rollers  52 . When so engaged, projection  28  of clamp  17  mates with notch  29  of compression arm  16 , and sensor element  44  signals sensor  14  that the pump is ready for operation.  
         [0038]     To disengage the pump, clamp  17  is rotated in a clockwise direction about pivot  20  until it contacts stop  30 . This motion causes projection  28  to disengage from notch  29 , and permits compression arm to be rotated away from the pump wheel  18 .  
         [0039]     While preferred illustrative embodiments of the invention are described above, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the invention. The appended claims are intended to cover all such changes and modifications that fall within the true spirit and scope of the invention.