主权项 |
1. A volume adjustable, manual pipette comprising:
an upper pipette body adapted to be held in the hand of a user, and having an axial bore: a plunger shaft assembly mounted in the axial bore of the upper pipette body for reciprocating vertical motion, the plunger shaft assembly comprising: a plunger shaft having a button that extends upward from the upper pipette body and a plunger positioning boss; and a piston holder connected to and extending downward from the button and moving in unison with the button, the plunger shaft and the plunger positioning boss; a pipetting piston operatively coupled to a lower end of piston holder so that the pipetting piston moves in unison with the plunger button and piston holder, and a volume adjustment mechanism having repositionable restraint steps that stop retraction of the plunger positioning boss to set a full stroke length of the plunger shaft and pipetting piston, said volume adjustment mechanism including a series of three rotatable step cylinders that surround the plunger shaft assembly and are manually rotated to set the position of the repositionable restraint steps; wherein each step cylinder has steps with a fixed height and the height of the steps on each step cylinder is different from the height of the steps on the other step cylinders. |