Highly accurate pumping device

Abstract

A highly accurate pumping device for aspirating and dispensing variable volumes of fluid is presented. The pumping device comprises a housing with a slotted optical sensor, a stepper motor with a fine pitch lead screw, a coupling linking the stepper motor shaft and the lead screw, an anti-backlash nut, an anti-rotation arm linking the plunger with the anti-backlash nut, an end of travel sensor feature integrated in the arm, and a top which incorporates a chamber and a lead screw bearing. A seal, located in the top, seals against the plunger and the chamber. The plunger is attached to the anti-rotation arm and eccentrically aligned to the lead screw. The pumping device further includes one or more ports through which fluid may be introduced into or out of the chamber. The pumping device may be easily changed to accommodate different full-scale volume requirements due to the self-aligning features.

1 . A highly accurate pumping device comprising: 
 a housing including an integral anti-rotation groove and mounting location for a slotted optical sensor;    a first top removably coupled to said housing;    a first chamber within a portion of said first top, said first chamber having a cone shape at one end;    a first plunger displaceable within a portion of said first chamber, which, in combination with said first chamber, is adapted for aspirating and dispensing;    ports within said first top, said ports allowing for the introduction of liquid into or out of said first chamber;    a coupler linking the lead screw and stepper motor shaft;    a stepper motor attached to said housing, which turns said lead screw for the purpose of moving said first plunger into or out of said first chamber;    
   
   
       2 . The pumping device of  claim 1  further comprising an anti-rotation arm removably coupled to an anti-backlash nut, the anti-rotation arm having an end of travel protrusion that interacts with a slotted optical sensor.  
   
   
       3 . The pumping device of  claim 1  wherein said first plunger is removably coupled to said anti-rotation arm.  
   
   
       4 . The pumping device of  claim 1  comprising a first seal disposed around said first plunger and against a surface of a recessed area of said first top.  
   
   
       5 . The pumping device of  claim 1  wherein one port is located proximally to said first seal and oriented with its axis perpendicular to the axis of said first chamber to allow incoming fluid to clear away residual air bubbles from said first seal.  
   
   
       6 . The pumping device of  claim 1  wherein one port is located distally from said first seal and axially aligned with said first chamber.  
   
   
       7 . The pumping device of  claim 1  comprising an end cap disposed to restrain said first seal in said first top.  
   
   
       8 . The pumping device of  claim 1  comprising a bearing disposed in a hole in said first top, said bearing axially aligned with said lead screw, through which one end of said lead screw protrudes.  
   
   
       9 . The pumping device of  claim 1  further comprising: 
 a second plunger having a different size than said first plunger;    a second top with a second chamber having a different size than said first chamber;    a second seal having a different size than said first seal, said second seal disposed in recessed area in said second top and restrained by an end cap; said second top, said second plunger and said second seal adapted to aspirate or dispense a second volume of liquid.