Patent ID: 7421913

Claim:
Pipette having an axially relocatable control button ( 1 ), a pressure sensor, which is integrated into the control button ( 1 ), a lifting rod ( 3 ), coupled with the control button ( 1 ) and having a stopping bead ( 21 ), a hollow driving spindle ( 11 ), accommodating the lifting rod ( 3 ) and being axially relocatable, a twisting lock ( 13 ), preventing the driving spindle ( 11 ) from being twisted, a turnable driving nut ( 10 ) having screw thread engagement with the driving spindle ( 11 ), an axial support of the driving nut ( 10 ), an electric driving motor ( 2 ) with a motor shaft ( 6 ), a gear ( 8 , 9 ) between the motor shaft ( 6 ) and the driving nut ( 2 ), an electric power supply, an electric control system, connected to the pressure sensor, the electric driving motor ( 2 ) and the electric power supply, which provides an electric voltage to the electric driving motor ( 2 ) upon a push on the control button ( 1 ) which is indicated by the pressure sensor, so that the motor relocates the driving spindle ( 11 ) via the gear ( 8 , 9 ) in the direction of a relocation of the control button ( 1 ) by the push, the driving spindle ( 11 ) taking the lifting rod ( 3 ) along with it on its stopping bead ( 21 ), a plunger ( 22 ), coaxially displaceable with respect to the lifting rod ( 3 ), a cylinder ( 23 ), connected to an opening ( 38 ) which leads outward and in which the plunger ( 22 ) is sealingly guided, and a plunger spring ( 26 ), loading the plunger ( 22 ) in the direction of an end of the lifting rod.