Pipettes
OwnerWilliam P. Keeganinventor
Life of this patent
Estimating the term…
Abstract
A mechanical pipette having a measuring piston that controls the volume of liquid drawn into the pipette reservoir and a substantially larger piston that assures that all of the liquid in the reservoir is expelled therefrom on a discharge stroke. On the discharge stroke, a valve is opened to admit air being compressed by the larger piston into the reservoir. Means are provided to adjust the displacement of the larger piston so as to control the pressure developed by the larger piston.
Claims11
A pipette comprising an overblow piston having a longitudinal aperture therein, plunger rod means extending through the aperture in said overblow piston in a non-airtight relationship, means for reciprocating said rod means with respect to said piston, washer means mounted on said rod means for engaging said piston to move it to a fixed position, sealing means mounted on said rod means for movement into engagement with said piston to form an airtight relationship between said rod means and said piston and for moving said piston away from its fixed position, and means for adjusting the spacing between said washer means and said sealing means whereby the distance moved by said piston from its fixed position is adjustable.
A pipette comprising, hollow housing means having a nozzle end and a remote end, means dividing the interior of said housing means into a first air chamber and a second air chamber, said dividing means having an air passageway connecting said first and said second air chambers, normally closed valve means for admitting air from said second air chamber into said first air chamber, a measuring piston movable in said first air chamber for aspirating a predetermined volume of liquid into a liquid reservoir, an overblow piston movable in said second air chamber for compressing air in said chamber, plunger means connected to said measuring piston and extending out of the remote end of said housing means, means biasing said plunger means to one limiting position, first means connected to said plunger means for engaging said overblow piston to move it to a first position wherein said second air chamber is vented to the outside of said housing means, second means for sealing said second air chamber and for engaging said overblow piston to move it in an air compressing direction to a second position, said second means being adjustably connected to said plunger means, and means external to said housing means for adjusting the position of said second means relative to said plunger means whereby the point at which said overblow piston is engaged by said second means can be varied and the stroke of said overblow piston thereby adjusted to control the degree of air compression in said second air chamber.
Dependencies are inferred from the claim text.