Abstract: The invention relates to an injection device wherein the drive element transferring rotation to the piston rod is divided into two elements which are able to move axially in relation to each other such that the drive mechanism can be released to allow the user to reset the piston rod and change the cartridge.

Abstract: The invention relates to a medical injection device having polymeric housing. The housing comprises a moulded outer housing element and a moulded ring-shaped unitary element. The ring-shaped unitary element carries a pointer and a thread segment in predetermined and correlated positions. The pointer points to indicia on a scale drum and the thread segments guides the scale drum. The outer housing element is moulded over the unitary element to form one single component.

Abstract: The invention relates to a drive mechanism for a medical injection device in which a piston rod (10) has a threaded outer surface and a not circular cross-section and engages a nut assembly (2, 102, 202) having either an internal thread (41, 141, 241) mating the outer thread (11) of the piston rod (10), or a shape mating the non-circular cross section of the piston rod (10). The nut assembly (2) comprises a first part (30, 130, 230) and a second part (40, 140, 240), which are connected by a hinge allowing the first part (30, 130, 230) and the second part (40, 140, 240) to tilt relatively to each other in a non-axial plane.