A metering head for a metering machine or another metering device, comprising:
- a carrier (2), on which a plurality of parallel attachments (42) for picking up pipette tips (43) are arranged adjacent to each other,
- a stop plate (75) that has a plurality of first holes (76) through which attachments (42) extend, wherein each attachment (42) has the following features:
- a tube (18) which has a supporting protrusion (30) at the bottom end that protrudes outward and extends peripherally at least partially,
- at least one sleeve (32, 38) with a peripheral tapering (33, 39) at the bottom end which surrounds the tube (18) and can be axially shifted on the tube (18),
- at least one elastomer O-ring (31, 37) which surrounds the tube (18) and is arranged adjacent to the tapering (33, 39), and
- the sleeves (32, 38) can be shifted between a release position at a first distance from the supporting projections (30) and a clamping position at a second distance from the supporting projections (30) that is smaller than the first distance;
- in the clamping position, the sleeves (38) with the taperings (39) are pressed into the adjacent O-rings (37), and the O-rings (31, 37) are expanded in order to securely clamp the pipette tips (43) shoved onto the attachments (42),
- a first shifting apparatus (74) that is coupled to the sleeves (32, 38) of all the attachments (42), and is designed to shift the sleeves (32, 38) between the release position and clamping position,
- a second shifting apparatus (77) that is connected to the stop plate (75) and is designed to shift the stop plate (75) between a stop position at a first distance from the supporting projections (30) and an ejection position at a second distance from the supporting projections (30) that is smaller than the first distance in order to shove pipette tips (43) on the attachments (42) in the stop position until contacting the stop plate (75), and to eject them from the attachments (42) by shifting the stop plate (75) from the stop position to the ejection position,
- wherein the second shifting apparatus (77) comprises rocker arms (80) that are pivotably mounted on the carrier (2), transmission shafts (78) that are coupled to the sleeves (32, 38) and each contact one end of a rocker arm (80), and ejection shafts (81) which are securely connected to the stop plate (75) and each lie against another end of a rocker arm (80) so that when the sleeves (32, 38) are shifted into the release position, the transmission shafts (78) pivot the rocker arms (80), and they press the stop plate (75) via the ejection shafts (81) out of the stop position into the ejection position.