A pipetting device is formed of a supporting frame, a slider mounted on the supporting frame for vertical movement, a plunger type stem having a lower end fittable within the upper end of an approximately inverted cone shaped nozzle tip, the stem being mounted for vertical movement on the slider, and...http://www.google.com/patents/US4785677?utm_source=gb-gplus-sharePatent US4785677 - Pipetting device having an automatic mechanism for replacing nozzle tips
