Patent ID: 8876782

Claim:
An injection device comprising, an exterior housing having a first part and a second part permanently connected to each other forming a disposable pen-type injector where the first part contains a non-removable multi-dose cartridge of medicament and the second part contains a dose setting and delivery mechanism that is configured for manual dose selection and for a stored energy drive during dose delivery, where the dose setting and delivery mechanism comprises, a) a dose dial grip; b) a clutch that couples the dose dial grip to a drive sleeve so that they are rotationally fixed during dose setting and that uncouples the dose dial grip and drive sleeve during dose delivery; c) a non-circular cross section piston rod threadedly engaged with an interior housing fixed to the second part of the exterior housing, where the piston rod is fixed axially and rotationally during dose setting and rotates and moves axially during dose delivery; d) a stored energy drive mechanism configured for use in dose delivery to drive the drive sleeve causing the piston rod to rotate; e) a dose dial sleeve coupled to the drive sleeve and not rotatable relative to the piston rod during dose delivery; and f) a unidirectional coupling located between the housing and the piston rod, the unidirectional coupling configured to prevent movement of the piston rod in a distal direction and to allow the piston rod to move in a proximal direction.