Patent ID: 7662343

Claim:
A pipetting system comprising: a disposable pipette tip having a barrel with a lower opening through which liquid is aspirated into the barrel and dispensed from the barrel, a collar having an upper opening for receiving a pipette tip mounting shaft, the inside surface of the collar including a substantially circumferential locking element extending inward from the inside surface of the collar, and the lower end of the collar having 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 mounting shaft including a lower sealing section; and 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 spaced circumferentially around the locking section of the mounting shaft and located above the stop on the mounting shaft for engaging the locking element on the inside surface of the collar, and recessed relief portions in the upper locking section of the mounting shaft spanning circumferentially 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 locked on the mounting shaft over the stop and the lobes; and wherein a circumferential portion of the lower sealing section of the mounting shaft engages the upper end of the tip barrel to seal the tip barrel against the mounting shaft when the tip collar is locked onto the mounting shaft over the stop and lobes.