Patent ID: 6352673
Filing Date: 2002-03-05
Classification: B01L

Abstract:
A fully manually controllable return springless manual air displacement pipette, comprising:a hand holdable housing; a plunger unit mounted for axial movement within the housing between upper and lower stops and a home position, the home position being a predetermined starting position for the plunger unit for a repeatable aspiration of a selected quantity of liquid into a tip extending from a pipette tip mounting shaft at a lower end of the pipette housing when the tip is immersed in the liquid and the lower stop defining an end position for the plunger unit at which substantially all liquid is dispensed by the pipette from the tip; an upper end portion of the plunger unit extending vertically from the housing for thumb or finger contact by a pipette user to move the plunger unit axially and precisely within the housing between the upper and lower stops; a piston extending from a lower end portion of the plunger unit through a fluid tight friction seal encircling the piston and into a cylinder within the pipette tip mounting shaft; and a spring mounted within the housing for exerting an upward force on the plunger unit which is insufficient to move the plunger unit upward from the home position to the upper stop upon a release of the plunger unit by the pipette user, whereby the pipette is return springless and the plunger unit is precisely manually moveable by the pipette user against the seal friction from the home position upward to the upper stop to aspirate the selected volume of liquid into the tip and is precisely manually moveable by the user against the seal friction downwardly from the upper stop to the lower stop to dispense the selected volume of liquid from the tip and is precisely manually moveable against the seal friction to the home position to return the plunger unit to its starting position for another aspiration of liquid into a tip secured to the mounting shaft.