Edward W Carroll

US Patent:

44359896, Mar 13, 1984

Filed:

Dec 4, 1981

Appl. No.:

6/327393

Inventors:

Richard C. Meyer - La Habra CA
Edward L. Carroll - Garden Grove CA

Assignee:

Beckman Instruments, Inc. - Fullerton CA

International Classification:

G01F 1300
B01L 302

US Classification:

7386414

Abstract:

Plunger operated pipet operable to execute different lengths of plunger movement during successive fluid pickup and fluid discharge operations or strokes. A stop member is movable between first and second locations in the pipet body to halt plunger movement at two different positions. A drive spring for driving the stop member from one location to the other is energized by a manually operable arming element and is retained in one location against action of the drive spring during a first plunger stroke. A release mechanism responsive to plunger movement during the first stroke disables the retaining means allowing the drive spring to move the stop member to the second location at which position the plunger is halted during the succeeding discharge stroke. The arming element is actuated by and in response to positioning of a replaceable tip on the pipet body. The arming element exerts a force on the tip sufficient to expel the tip from the body unless the tip is properly seated on the body thus ensuring that the pipet is armed if the tip is properly seated.