Pipette tip and mounting shaft with staggered offset locking feature

A pipette system comprising a tip mounting shaft and a disposable pipette tip, wherein the tip mounting shaft comprises:

• an upper locking section having a stop, four outwardly extending lobes located above the stop and spaced circumferentially around the locking section of the mounting shaft, and recessed relief portions spanning circumferentially between the lobes and recessed relative to the lobes, each respective lobe having a peak being spaced longitudinally above the stop on the mounting shaft, and said tip mounting shaft also including a sealing area located below the stop, wherein the four outwardly extending lobes comprise a first pair of lobes and a second pair of lobes, wherein each lobe has an inclining ramp, a peak, and a declining ramp, and the distance between the peak of the lobes in the first pair of lobes to the stop is different from the distance between the peak of the lobes in the second pair of lobes to the stop;
• and
• the disposable pipette tip comprises:
• a barrel having a lower opening through which liquid is aspirated into the barrel and dispensed from the barrel, wherein the diameter of the lower opening is less than the diameter of the barrel at an upper end of the barrel;
• a collar having a continuous inner surface with a circular circumference in its relaxed state, an upper opening for receiving the tip mounting shaft, and a lower end with an inside diameter that is larger than an inside diameter of the upper end of the barrel;
• a circumferential tip shoulder connecting the lower end of the collar to the upper end of the barrel;
• a locking ring extending inward from the continuous inner surface of the collar to engage the locking lobes, said locking ring extending around the entire circumference of the collar or substantially around the entire circumference of the collar and located at a rim of the upper opening of the collar and above the circumferential shoulder;
• means for sealing against sealing area on the mounting shaft below the stop on the mounting shaft;
• wherein the collar of the disposable pipette tip is sufficiently flexible to distort outwardly at the lobes on the mounting shaft and inwardly at the recessed relief portions on the mounting shaft between the lobes when the pipette tip is being mounted on to the tip mounting shaft, and further when the tip mounting shaft is inserted into the collar of the disposable pipette tip to mount the disposable pipette tip to the tip mounting shaft, the locking ring in the collar of the disposable pipette tip engages the first pair of lobes and clears the peaks of the first pair of lobes on the tip mounting shaft before engaging the second pair of lobes and clearing the peaks of the second pair of lobes.