Patent Publication Number: US-7217105-B2

Title: Integrated pump and wash pump

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to an integrated pump and ceramic 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 ceramic valve 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 having a hollow, essentially conical interior surface into which is press fit a mating, essentially conical 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. Since organic solvents and diluents are sometimes used to form the liquid being pumped such as dimethylsulfoxide (DMSO) or tetrahydrofuran (THF), the valve rotor commonly swells which causes it to deteriorate. Also, the use of the conically shaped seal limits the pressure at which the liquid is pumped while retaining desired sealing since higher pressures increase the difficulty in rotating the valve rotor. Operating pressures are also limited due to the use of polymeric materials in the valve such as polytetrafluoroethylene (PTFE) which tend to cold flow at elevated pressures. 
   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 (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. 
   An additional problem encountered in presently available pumps is residue buildup at the pump seals which reduce useful pump life. While it may be possible to supply wash water to the pump seal to reduce residual build up, such an arrangement would require a separate motor to activate a pump for the wash water. 
   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 maimer 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 wherein internal seals can be cleaned periodically or continuously without the need for a motor in addition to the motor for the pump apparatus. 
   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) a ceramic valve wherein the sealing surfaces of a ceramic rotor and mating ceramic stator are flat and (c) a pump for a wash liquid for a seal of the displacement pump. Control apparatus, including a conventional microprocessor is provided to synchronize movement of the valve rotor and the piston position of the displacement pump so that liquid in the barrel is delivered to a point of use while the piston is traveling toward the ceramic valve and liquid is supplied to the barrel when the piston is traveling away from the ceramic valve. 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 flat ceramic sealing surfaces, in the ceramic valve, useful pressure at which the liquid is pumped can exceed useful pumping pressures with presently available syringe pumps. The pump for the wash liquid also is a displacement pump comprising a piston housed within a barrel but utilizing two check valves rather than a ceramic rotor and stator valve to control wash liquid flow from a reservoir to a seal for the displacement pump for the liquid barrel in element (a). 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of the displacement pump and ceramic valve of this invention. 
       FIG. 2  is a front view of the apparatus of  FIG. 1 . 
       FIG. 3  is a front view of a stator of the ceramic valve of this invention. 
       FIG. 4  is a side view of the stator of  FIG. 3 . 
       FIG. 5  is a front view of a rotor of the ceramic seal of this invention. 
       FIG. 6  is a partial cross-sectional view of the rotor of  FIG. 5 . 
       FIG. 7  is an exploded view of the rotor/stator coupling  18  shown in  FIG. 1 . 
       FIG. 8  is a cross-sectional view of the apparatus of this invention made of a multipiece housing. 
       FIG. 9  is an exploded view of this invention including a washing means. 
       FIG. 10  is a side view of a rotary solenoid that can be used in the present invention. 
       FIG. 11  is a cross-sectional view taken along line  11 — 11  of  FIG. 1 . 
       FIG. 12  is a cross-sectional view taken along line  12 — 12  of  FIG. 1 . 
       FIG. 13  is a cross-sectional view of a check valve useful in this invention. 
   

   DESCRIPTION OF SPECIFIC EMBODIMENTS 
   Referring to  FIGS. 1 and 2 , the pump apparatus  10  of this invention includes a housing  12  for a motor  14  which effects linear motion such as a stepper motor, a lead screw, a rotary solenoid or the like and a motor  16  which effects rotation. Motor  14  is connected to rotor/stator coupling  18  through arm  20  which can be rigid or a self aligning spring drive. The rotor/stator coupling  18  is biased into ceramic rotor  22  by spring  24 . Rotor  22  is sealed against ceramic stator  26  at stator flat polished surface  28  and rotor flat polished surface  30 . The ceramic rotor  20  and ceramic stator  26  can be formed of aluminum, zirconia, silica, tantalum oxide, or the like. Mating surfaces  28  and  30  are rendered flat such as by a conventional lapping process. Since mating surfaces  28  and  30  are flat, a significantly lower torque force at a given pressure is required to effect rotation of the rotor as compared to a conically shaped rotor and stator. 
   The stator  26  is positioned within 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. Housing  32  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 stator  26  and the piston  34  can be formed of a single element. The provision of this single element housing provides the advantage that the valve and displacement pump of this invention can be replaced simultaneously after the useful life of the pump and valve 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 convention 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 or the like and optional rulon guide  58 . The rulon guide aligns piston  34  into seal  56 . The piston  34  reciprocates within seal  56  and rulon guide  54 . The piston  34  is fixedly positioned in ferrule  60  which, in turn, is fixed within arm  62  by knob  50 . 
   As shown in  FIGS. 2 ,  3  and  4 , the stator  26  is in fluid communication with a fluid inlet  66  in head  26  and with fluid outlet  68  in head  26 . Fluid is introduced into housing  36  through fluid inlet  66  when piston  34  moves away from stator  26 . Fluid is passed through fluid outlet  68  when piston  34  moves toward stator  26 . The stator  26  includes fluid passageways  70 ,  72  and  74 . When rotor  22  ( FIG. 5 ) is rotated so that the fluid passageway  80  is in position  82 , fluid passes from fluid passageway  70  to fluid passageway  74  and then into housing  36 . When rotor  22  ( FIG. 5 ) is rotated so that fluid passageway is in position  84 , fluid passes from housing  36 , through fluid passageway  74  and through passageway  72  to a point of use (not shown). 
   Referring to  FIG. 7 , a rotor/stator coupling  18  which is a self-aligning spring drive is shown. The coupling  18  includes a spring housing  86 , a spring  88 . The spring  88  bears against pin  90  which is movable within slot  92 . Pin  90 , in turn, bears against pin  94  which fits into slot  96  of rotor  22 . Flange  98  fits into slot  100  of rotor  22 . Housing  96  is coupled to arm  20  ( FIG. 1 ) by keyway  102  which fits over a key (not shown) of arm  20  ( FIG. 1 ). When arm  20  is rotated, the rotation is transmitted to rotor  22  through flange  98  and slot  100 . It is important to have complete flat contact between surface  28  and  30  so that there is no leakage between position  82  and  84  ( FIG. 5 ). By the term “complete flat contact” as used herein is meant that flat surfaces  28  and  30  do not separate to effect partial contact between them. This complete flat contact is effected even when arm  20  on housing  86  are misaligned since pin  94  rotates within slot  96  and the misalignment is thereby corrected and not transmitted to surface  30  of rotor  22 . 
   Referring to  FIG. 8 , the pump apparatus  102  is shown wherein the housing is formed of a plurality of sections joined by threads. The housing  102  comprises a top section  104  for housing a stator  26 , a middle section  106  for housing a piston and a bottom section  108  through which the piston  34  extends. The housing  102  is provided with a threaded collar  110  which can be utilized to effect sealing between top section  104  and middle section  106 . 
   Referring to  FIG. 9 , an embodiment of this invention is shown having the capability of internal seals. Bottom housing section  108  is attached to middle housing section  106  by threads. Bottom section  108  is provided with seals  112  and  114  through which a piston (not shown) extends. Bottom section  108  is provided with inlet conduit  116  and outlet conduit  118  through which a wash liquid can be passed. The wash liquid is used to wash seals  112  and  114  as well as the interior of housing sections  106  and  108  thereby to prevent build-up at a deposit therein from liquid being pumped therein. Washing can be effected when a top surface of a piston (not shown) extends below conduits  106  and  108 . 
   Referring to  FIG. 10 , a rotary solenoid  120  is shown having electrical lead wires. Motors  14  and  16  are connected to a common control (not shown) so that the piston is correctly positioned to attain a desired fluid flow through stator  26  and rotor  22  as described above. Electrical leads  121  and  122  are connected to arm  123  positioned in housing  86  into which is positioned pin  94 . Pin  94  functions in the manner described above with reference to  FIG. 7  to effect rotation of rotor  22  relative to stator  26  to provide a fluid passageway  124 . 
     FIGS. 1 ,  11  and  12  show wherein two liquids including a wash liquid for the pump seals are simultaneously pumped. Each piston  34  and  11  is positioned within a seal  56  or  13  which can be formed, from (UHMWPE) or the like and optional rulon guide  58  or  15 . The rulon guides  58  and  15  align pistons  34  and  11  into seals  56  and  13 . The pistons  34  and  11  reciprocate within seals  56  and  11  and rulon guides  54  and  15 . The pistons  34  and  11  are fixedly positioned in ferrules  60  and  17  which, in turn, are fixed within arm  62  by knobs  50  and  52 . Both pistons  34  and  11  move together when arm  62  is moved by motor  16  ( FIG. 1 ). The volume ratio of the liquids delivered from barrels  19  and  21  with a single stroke of pistons  34  and  11  is controlled by the ratio of the sizes of the pistons  34  and  11 . 
   Referring to  FIGS. 11 and 12 , the housing can be formed of three pieces comprising piece  32 ,  25  and  27 . Housing piece  27  includes two valve seats  29  and  30  into which are positioned check valves  33  and  35 . Check valves  33  and  35  can have threads  37  and  39  to screw the valves  33  and  35  into valve seats  29  and  31  having internal threads (not shown). Housing  27  can be provided with threads  43  to secure housings  27  to housing  25 . Check valve  35  is connected to conduit  45  which in turn is connected to a reservoir for wash water (not shown). Check valve  33  is connected to conduit  47  which, in turn, is connected to seal  56  in order to deliver wash water to seal  56 . Conduit  49  is connected to seal  56  to remove wash water from seal  56 . The wash water substantially prevents build-up of contaminants within seal  56 . In use, when piston  11  moves toward check valves  33  and  35 , check valve  33  is open and check valve  35  is closed so that wash water is delivered through check valve  33  and conduit  47 . When piston  11  moves away from check valve  33 , check valve  33  is closed and check valve  35  is open so that fluid moves into barrel  21  through check valve  35  and conduit  45  from a fluid reservoir (not shown). 
   Referring to  FIG. 13 , the valve  33  includes a movable ball  126  which moves within valve seat  128  to block either conduit  130  or conduit  132  to effect fluid flow as described above.