Hybrid pipette

A hybrid pipette comprising:

• a pipette casing;
• a slide shaft vertically movable in response to an operation of a pushbutton;
• a plunger disposed below said slide shaft, said plunger being vertically movable together with said slide shaft as one unit;
• an electric motor provided in coaxial relation to said slide shaft, said electric motor having an internally threaded hole;
• a tubular threaded member with an external thread on an outer periphery thereof, said tubular threaded member being coaxially and movably fitted on said slide shaft and being thread-engaged with the internally threaded hole in said electric motor to allow said slide shaft to move vertically;
• and
• at least one spring interposed between a predetermined position on said slide shaft and said tubular threaded member to urge said slide shaft and said plunger upwardly so that a predetermined portion of said slide shaft or said plunger abuts against a predetermined portion of said tubular threaded member or said pipette casing;
• wherein, in a manual operation mode, said slide shaft and said plunger move vertically in response to the operation of said pushbutton to perform suction and discharge of a liquid;
• and
• wherein, in a motor-driven operation mode, said tubular threaded member is driven by said electric motor so as to move vertically, thereby said plunger is moved vertically to perform suction and discharge of a liquid, and the length of said spring is maintained constant with no extension or compression thereof in the motor-driven operation mode.