Patent ID: 7175813

Claim:
A volume adjustable pipette ( 10 ; 10 ′; 10 ″) comprising a housing ( 12 ), a plunger ( 20 ) mounted for axial movement in the housing to and from a stop ( 32 s ; 32 s ′; 32 s ′) during aspiration of a fluid into and dispensing of the fluid from a tip extending from the housing, an axially moveable volume setting member ( 32 ; 32 ′; 32 ″) in the housing defining the stop ( 32 s ; 32 s ′; 32 s ′) for the plunger and a volume setting for the pipette, a turnable volume adjusting member ( 33 ; 33 ′; 33 ′) and volume adjusting means ( 22 ; 22 ′; 22 ″) for axially moving the volume setting member ( 32 ; 32 ′; 32 ″) in response to a turning of the volume adjusting member ( 33 ; 33 ′; 33 ′), characterized by: coarse volume setting means ( 34 ; 34 ′; 34 ″) in the volume adjusting means ( 22 ; 22 ′; 22 ″) responsive to a turning of the volume adjusting member ( 33 ; 33 ′; 33 ′) for axially moving the volume setting member ( 32 ; 32 ′; 32 ″) relatively large axial distances in response to relatively small turnings of the volume adjusting member ( 33 ; 33 ′; 33 ′); fine volume setting means ( 35 ; 35 ′; 35 ″) in the volume adjusting means ( 22 ; 22 ′; 22 ″) responsive to a turning of the volume adjusting member ( 33 ; 33 ′;′ 33 ′) for axially moving the volume setting member ( 32 ; 32 ′; 32 ″) relatively small axial distances in response to relatively large turnings of the volume adjusting member ( 33 ; 33 ′; 33 ′); one of the coarse and fine volume setting means ( 34 , 34 ′; 35 , 35 ′; 35 ″) defining a one of the volume setting means and the other of the coarse and fine volume setting means defining an other of the volume setting means, the one of the volume setting means being characterized by a force threshold ( 58 ; 87 ; 96 ) for axial movement of the volume setting member ( 32 ; 32 ′; 32 ″) by the one of the volume setting means that is exceeded by a predetermined movement of the other of the volume setting means in response to a turning of the volume adjusting member ( 33 ; 33 ′; 33 ′); and means ( 60 , 61 ; 60 ′, 61 , 61 ′; 60 ″, 61 ″) for overcoming the force threshold ( 58 ; 87 ; 96 ) in response to a turning of the volume adjusting member ( 33 ; 33 ′; 33 ′).