AU2001278417A1 — A liquid medication delivery device and a method of delivering an intended dose

USPTO Abstract

A liquid medication delivery device for, and a method of, delivering medication from a cartridge having a moveable piston at one end is disclosed. The piston has a first wall face that contacts the liquid in the cartridge and a second wall for engaging a piston rod that drives the piston. The first and second walls are moveable but the second wall tends to move more quickly then the first during administration of a dose of medication from the cartridge. To compensate for this difference in movement between the first and second wall faces, the rod first moves a distance corresponding to the amount that the first wall face must move to deliver the desired dose and then it continues to move past this position by an amount known as an overshoot distance. It is then retracted by a distance equal to the overshoot distance.