Pipette

摘要

A pipette for transferring liquid samples includes a body having a handle and a base. A piston assembly is axially movable in the body. A movable lower stop is placed in the path of the piston assembly to stop the piston to limit the length of an intake stroke and is withdrawn from the path to permit axial overtravel during a discharge stroke. The lower stop is positively controlled by a manually operated mechanism including a stop control push button at the top of the handle in front of a piston push button. A mechanism for ejecting a tip from the base includes a lever at the top of the handle providing a mechanical advantage when pressed at either end. In an alternate embodiment, a dual spring overtravel arrangement is used, with the piston return spring telescoped within the overtravel spring.