Patent ID: 8397593

Claim:
A volume adjustable pipette, comprising: a housing; a plunger mounted for axial movement in the housing to and from a stop during aspiration of a fluid into and dispensing of the fluid from a tip extending from the housing; an axially moveable volume setting member in the housing defining the stop for the plunger and a volume setting for the pipette; volume adjusting means for axially moving the volume setting member in response to a turning of a volume adjusting member; a lock mechanism for selectively locking the position of the volume setting member; fine and coarse volume setting means respectively responsive to relatively large and small turnings of the volume adjusting member for sequentially moving the volume setting member relatively small and large axial distances, respectfully; and a viscous interface for limiting the strength and incidence of impacts between the plunger and the volume setting member when the plunger is axially moved, wherein the viscous interface is located between either the housing or an axially fixable component and either the plunger or a component coupled to the plunger; wherein the viscous interface is configured for damping plunger movement in response to an impact or a release of the plunger; and wherein the viscous interface is sufficiently viscous to prevent undesired movement of the volume setting member in response to the impact or release, without substantially adversely affecting the operation of the pipette.