Patent Publication Number: US-2006008365-A1

Title: Integrated pump and check valve apparatus

Description:
BACKGROUND OF THE INVENTION  
      This invention relates to an integrated pump and check valve apparatus for pumping discrete liquid volumes to points of use of the liquid volumes. More particularly, this invention relates to an integrated displacement pump and check valve apparatus for pumping discrete liquid volumes to points of use.  
      At the present time, discrete liquid volumes are pumped with a syringe pump comprising a barrel, a face seal which moves within the barrel and a reciprocating plunger attached to the face seal. The syringe pump includes a valve construction formed of a polymeric composition which directs the pumped liquid volumes to a point of use. The valve construction includes a housing (stator) having a hollow, essentially interior surface into which is press fit a mating rotor. The rotor is provided with fluid passageways that control flow of liquid into the syringe pump and flow of liquid from the syringe pump while providing sealing between a pump inlet and a pump outlet. This configuration of syringe pump and rotor-stator valve requires two motors, one to drive the syringe and a second to drive the rotor.  
      While the available syringe pumps have been useful for their intended purpose, they also have disadvantages. In order to attain a tight fit between the barrel and the face seal, the manufacturing of both the barrel and face seal must be made at tight tolerances. In addition, when utilizing the most commonly used materials comprising a glass barrel and a polytetrafluoroethylene (PTFE) face seal, undesirable shedding of the PTFE occurs which contaminates the liquid being pumped. Furthermore, a tight fit between the barrel and face seal results in chattering of the face seal during its movement within the barrel. This leads to a loss of control of the liquid volume being pumped. In addition, the average useful life of presently available syringe pumps is only about 10 to about 100,000 cycles.  
      Accordingly, it would be desirable to provide a pump apparatus capable of delivering discrete liquid volumes to a point of use such as different areas of a sample tray in a manner which is repeatable for long time periods of 1,000,000 cycles or more. In addition, it would be desirable to provide such a pump apparatus which avoids shedding of polymeric particles during pumping. Furthermore, it would be desirable to provide such a pump which eliminates the need for a motor to activate a seal in order to direct fluid to a desired point of use.  
     SUMMARY OF THE INVENTION  
      The present invention provides a pumping apparatus comprising (a) a displacement pump having a liquid displacement element comprises a piston housed within a barrel, a high pressure seal and means for reciprocating the piston within the barrel and (b) check valves wherein the sealing is effected by activating a movable element under pressure of fluid being pumped without use of a motor. Liquid in the barrel is delivered to a point of use while the piston is traveling toward a check valve positioned between the piston and the point of use and liquid is supplied to the barrel when the piston is traveling away from the check valve positioned between the piston and the point of use. The moving piston is spaced apart from the inside surface of the barrel so that a frictional force between the piston and the barrel is prevented during pumping. By providing check valves between the piston and (a) the point of use and (b) a source reservoir for the liquid, motors for positioning the valves can be eliminated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a side view of the displacement pump and check valve apparatus of this invention.  
       FIG. 2  is a front view of the apparatus of  FIG. 1 .  
       FIG. 3  is a cross-sectional view of the apparatus of  FIG. 2  taken along line  3 - 3  of  FIG. 2 .  
       FIG. 4  is a cross-sectional view of a check valve useful in the present invention. 
    
    
     DESCRIPTION OF SPECIFIC EMBODIMENTS  
      Referring to  FIGS. 1, 2  and  3 , the pump apparatus  10  of this invention includes a housing  12  and a motor  16  which effects rotation. Housing  32  which can be formed of an opaque or transparent material which is resistant to the liquid being pumped such as acrylic, polyetherether ketone, or the like can be a single piece or a plurality of joined elements. The piston  34  can be formed of sapphire, glass or a ceramic or the like and is spaced apart from the interior wall  38  of housing  32 . When the piston  34  is so-positioned, a single stroke of the piston  34  during use of the pump will deliver a known volume of liquid depending upon the piston diameter and the stroke length. As shown in  FIG. 1 , the housing  32  for the check valve  45  and the piston  34  can be formed of a single element. The provision of this single element housing provides the advantage that the valve seats and displacement pump of this invention can be replaced simultaneously after the useful life of the pump is completed.  
      Motor  16  causes gear box  40  to reciprocate through pulley  41 , and gears  42 ,  44  and  46  and gear track  48 . Gear box  40  is positioned within track  47  which causes the piston  34  to move in a repeatable linear path stroke after stroke. As shown in  FIG. 1 , the stroke of the pump varies from position  50  and position  52  which typically can be between about 1.5 and 2.0 inches. It is to be understood that any conventional activating apparatus which causes piston  34  to reciprocate on a linear path can be utilized in the present invention.  
      The piston  34  is positioned within seal  56  which can be formed, for example of ultra high molecular weight polyethylene (VHMWPE) or the like and optional roulon guide  58 . The roulon guide aligns piston  34  into seal  56 . The piston  34  reciprocates within seal  56  and roulon guide  58 . The piston  34  is fixedly positioned in ferrule  60  which, in turn, is fixed within arm  62  by knob  64 .  
      As shown in  FIGS. 2 and 3 , the housing  32  can be formed of two pieces comprising piece  32   b  and  32   a . Housing piece  32   b  includes two valve seats  31  and  33  into which are positioned check valves  35  and  37 . Check valves  35  and  37  can have threads  39  and  41  to screw the valves  35  and  37  into valve seats  31  and  33  having internal threads (not shown). Housing  32   b  can be provided with threads  49  and  45  to secure housing  32   b  to housing  12 . Check valve  35  is connected to conduit  45 , which in turn is in fluid communication with a point of use for the fluid (not shown). Check valve  37  is connected with conduit  47  which, in turn, is connected to a reservoir for the fluid (not shown). In use, when piston  34  moves toward check valve  35 , check valve  35  is open and check valve  37  is closed so that fluid is delivered through check valve  35  and conduit  45  to a point of use of the fluid. When piston  34  moves away from check valve  35 , check valve  35  is closed and check valve  37  is open so that fluid moves into barrel  38  through check valve  37  and conduit  47  from a fluid reservoir.  
      Referring to  FIG. 4 , the valve  35 , like valve  37  includes a movable ball  70  which moves within valve seat  72  to block either conduit  74  or conduit  76  to effect fluid flow as described above.