| abstract |
A drive mechanism for use in a drug delivery device comprising an epicyclic gearbox. This drive mechanism includes a housing having a helical thread; a piston rod having a non-circular cross section and an external helical thread; a dose dial sleeve, which is threadedly engaged with the housing and being rotatable with respect to the housing; and a drive sleeve, located between the housing and the piston rod, which is threadedly engaged with the piston rod. |