Pipette Tip Mounting Shaft

A pipette system comprising:

• disposable pipette tip having
• barrel with a lower opening through which liquid is aspirated into in the barrel and dispensed from the barrel,
• a collar having an upper opening for receiving a pipette tip mounting shaft, wherein the lower end of the collar has a larger inside diameter than the inside diameter at the upper end of the barrel, and a circumferential shelf that connects the lower end of the collar to the upper end of the barrel;
• and
• a pipette tip mounting shaft including
• an upper locking section, the locking section of the mounting shaft including a stop that engages the shelf of a pipette tip when the mounting shaft is fully inserted into the collar of the pipette tip, two or more outwardly extending lobes circumferentially spaced around the upper locking section of the mounting shaft and located above the stop on the mounting shaft for engaging the inside surface of the collar, and recessed relief portions spanning between the lobes and recessed relative to the lobes such that the collar distorts outwardly at the lobes and inwardly at the relief portions when the pipette tip is mounted on the mounting shaft over the stop and the lobes;
• wherein
• each lobe includes a peak portion that is located at a maximum outward distance from a longitudinal axis of the mounting shaft, an inclining ramp portion that slopes outward as the inclining ramp extends upward along the mounting shaft towards the peak portion in order to facilitate distortion of the pipette tip collar as the mounting shaft is inserted into the pipette tip, and a declining ramp portion that slopes inward as the declining ramp extends upward along the mounting shaft away from the peak.