Patent ID: 8486007

Claim:
An injection device configured for dispensing a substance from a dual or multi-chamber cartridge, said cartridge having a bung moveable in a first reconstitution phase of movement and a second, dosing phase of movement, said device comprising: a body portion ( 12 ); a plunger ( 24 ) mounted in said body portion for longitudinal movement with respect thereto in a forward dispensing direction to co-operate in use with said bung ( 18 ″ 18 ′); a plunger drive element ( 34 ) disposed adjacent said plunger for driving said plunger; and a drive mechanism releasable to apply drive to said plunger drive element; said plunger having a drive portion ( 24 ″) adapted to drivingly engage a complementary drive portion ( 33 a ) on said drive element and adapted to impart dosing movement to said plunger ( 24 ); said drive portion extending only partly along said plunger to leave a forward non-drive portion; whereby, during a reconstitution phase, said plunger may be moved longitudinally forward from a position with the non-drive portion adjacent said drive element but not in driving engagement therewith, to bring its drive portion into driving engagement with the drive portion on said drive element.