Patent ID: 7771398

Claim:
A delivery device that comprises: a fluid cartridge holder comprising a cartridge containing fluid, a housing, a piston drive mechanism situated within the housing and comprising a hollow piston rod and a drive-shaft, which hollow piston rod has an internal thread on at least a portion of its inner surface and a non-circular outer section, and which drive-shaft has an external thread which mates with the internal thread of the hollow piston rod forming a thread connection and being axially restrained in the proximal direction relative to the housing, a piston drive mechanism for rotating the drive-shaft such that upon activation of the driving mechanism the piston rod is forced to move axially in the distal direction causing ejection of the fluid from the cartridge, the delivery device further characterized in that the internal threads on the hollow piston rod and the external threads on the drive shaft are not exposed when the cartridge holder is removed.