Drug injection device with resettable mechanism allowing piston rod retraction upon drug cartridge change

摘要

A drug delivery device for selecting and dispensing a number of user variable doses of a medicament. The device comprises a housing, a dose setting element rotatable relative to the housing during dose setting and dose dispensing, a drive member coupled to the dose setting member via a clutch, and a piston rod coupled to the housing and to the drive member Further, the device further comprises a cartridge holder removably attached to the housing and a reset element, which is permanently rotationally constrained to the housing and rotationally constrained to the drive member during dose setting, and at least one spring acting on the reset element, such that, if the cartridge holder is detached from the housing, the reset element is axially moved relative to the housing into a position in which the drive member is allowed to rotate relative to the housing.