Metering head, metering device comprising a metering head, and method for metering by means of a metering head

A metering head for a metering machine or another metering device, comprising:

• a carrier, on which a plurality of parallel attachments for picking up pipette tips are arranged adjacent to each other, wherein each of the plurality of parallel attachments comprises:
• a tube which has an at least partially peripheral supporting protrusion that projects at a tube bottom end from a tube outer perimeter,
• a first sleeve which surrounds the tube and can be axially shifted on the tube,
• an elastomer first O-ring which surrounds the tube and is arranged adjacent to a first sleeve bottom end of the first sleeve;
• a second sleeve which surrounds the tube above the first sleeve, said second sleeve being constructed and arranged to be axially shifted on the tube, and
• an elastomer second O-ring which surrounds the tube, the second O-ring being arranged adjacent to a second bottom end of the second sleeve, and the second O-ring adjoins the first sleeve at the second bottom end of the second sleeve, and
• wherein the first sleeve and the second sleeve can be shifted between a release position at a first distance from the at least partially peripheral supporting protrusion and a clamping position at a second distance from the at least partially peripheral supporting protrusion, the second distance being smaller than the first distance in the clamping position, the second end of the second sleeve being pressed into the second O-ring, and a tapering of the first sleeve being pressed into the first O-ring, and the first O-ring and the second O-ring are expanded in order to securely clamp the pipette tips shoved onto each of the plurality of parallel attachments, and
• a shifter assembly that is coupled to the first sleeve and the second sleeve of each of the plurality of parallel attachments, the shifter assembly being designed to shift the first sleeve and the second sleeve between the release position and the clamping position.