Pipette

Abstract

A pipette comprising a handle portion, whose upper end is provided with a press knob with shaft and inside which a piston rod is fitted. To the bottom end of the piston rod is connected a piston or, by the intermediate of a common actuating means of the pistons, several pistons and, for each piston, a cylinder part, which is fastened to the frame construction of the handle portion. The piston rod and the press knob shaft, which are parallel to each other, are placed at a distance from each other, and their surfaces facing each other are shaped as jointly operative with a cogwheel or friction wheel fitted between them and journalled on the handle portion by means of a shaft. Then, when the press knob is depressed, by the intermediate of the press knob shaft, of the cogwheel or friction wheel, and of the piston rod, the piston or the pistons in each cylinder portion can be shifted from the lower position into the upper position so as to suck liquid into the tip vessel connected to each cylinder portion. A freewheel is stationarily fitted inside the cogwheel or friction wheel, or a freewheel is fitted inside an operating means mounted on the shaft of the cogwheel or friction wheel, such as, for example, a dosage lever. The freewheel is coupled to its shaft in one direction so that, when the shaft is turned back and forth by means of the operating means, such as the dosage lever mounted on the shaft, repeated depressions of the operating means, such as the dosage lever, produce shifting of the piston rod stepwise downwards while the pivoting angle of the operating means, such as the dosage lever, determines the magnitude of the dose to be removed at a time from the tip vessel or tip vessels.