Abstract: A hand-held pipette with a liquid dispensing knob at one end operably connected therewithin to a piston and piston cylinder assembly at the opposite end that is detachable from the pipette body for cleaning or replacement. An internal pawl and rack mechanism causes the piston to advance a small amount each time the knob is pressed, thereby repetitively dispensing small volumes of liquid therefrom. A second knob cooperatively engages an internal mechanism for both urging the piston to an overshoot position within the piston chamber and to disengage the piston from the internal mechanism in the pipette housing.

Abstract: A micropipettor having an adjustable stop threadedly engaged with an internal reciprocal plunger assembly for defining the stroke length of the plunger and thus of a fluid displacing piston that is attached to the plunger assembly. The adjustable stop is manipulated by operable connection with a volume adjustment knob provided on the outside of the micropipettor body. The plunger carries a coarse volume indicating scale and the volume adjustment knob is provided with a fine volume setting scale. Accidental changes in volume adjustments are avoided by two types of automatic locks: a frictional engagement of the internal volume adjustment mechanism unless the plunger is deliberately placed in a certain position by the operator, and a detent lock of the volume adjustment knob unless the operator deliberately depresses it.

Abstract: A micropipettor having an adjustable stop threadedly engaged with an internal reciprocal plunger assembly for defining the stroke length of the plunger and thus of a fluid displacing piston that is attached to the plunger assembly. The adjustable stop is manipulated by operable connection with a volume adjustment knob provided on the outside of the micropipettor body. The plunger carries a coarse volume indicating scale and the volume adjustment knob is provided with a fine volume setting scale. Accidental changes in volume adjustments are avoided by two types of automatic locks: a frictional engagement of the internal volume adjustment mechanism unless the plunger is deliberately placed in a certain position by the operator, and a detent lock of the volume adjustment knob unless the operator deliberately depresses it.

Abstract: A hand-held liquid dispenser of the type using a piston and piston cylinder for precise dispensing of desired volumes of liquid, including an improvement that automatically eliminates any air from the piston cylinder when an operator normally fills the piston cylinder with the desired liquid. A second piston of larger diameter than the first is disposed to draw fluid through the piston chamber at a much faster rate during a first short segment of an intake stroke than would the first piston, thereby to exhaust all dead air from the cylinder and fill it entirely with liquid.

Abstract: A hand-held micropipettor having a construction to impede transfer of heat from a handle to a portion enclosing a piston chamber, and means for drawing room air along the piston to effect its cooling when the micropipettor is operated. A compressible piston seal is held in place with a retainer urged in an axial direction by a resilient element with an uniform force independent of the position of the piston.

Abstract: A hand-held micropipettor having an improved tip ejector that is operable by the same thumb stroke of the user that operates a liquid transfer plunger therein. In one embodiment, the tip ejector has its own separate knob adjacent the liquid transfer plunger. In another embodiment, operation of the plunger itself causes a pipette tip to be ejected at the end of the liquid transfer plunger stroke.

Abstract: A device for accurately dispensing a volume of fluid that is predetermined by limiting the outward travel distance of a plunger within a fluid chamber. The plunger limit stop is attached to a scale post having raised indicia lines and is adjustable therealong by a detent engagement wherein the limit stop is selectively positioned to engage one of a plurality of notches formed on the scale post between its volume indicia raised lines.