Abstract: The invention relates to a manual control part of a suction device with a valve, which manual control part can be adjoined downstream by a suction line and upstream by a pipette or pipette tip. The manual control part consists of a cylindrical, elastically deformable jacket, which defines a receiving space for a valve body, and of a valve body, which is received in the jacket and which defines, within the receiving space, a first space located in the upstream direction and a second space located in the downstream direction. In the valve body a flow connection between the first space and the second space is provided by at least one radially outwardly directed valve seat with a valve opening. The valve seat bears on the inner wall of the jacket, wherein the jacket can be compressed laterally of the valve seat in order to open the valve. In this way, the inner wall is moved away from the at least one valve seat.

Abstract: The periodic axial movement of the rotary piston (6) is performed by a cam mechanism which has a cam surface (8) rotating around the piston axis and a cam follower (9) that is in functional connection with the cam holder. The relative position of the cam holder determines the piston stroke in the course of one revolution. In this arrangement, the drive shaft (5) can extend coaxially with the piston (6). In a particularly advantageous manner, the follower is pressed against the cam holder under spring pre-tension.