Drug Delivery Device with a Drive Mechanism

A drug delivery device for selecting and dispensing a number of user variable doses of a medicament comprising:

• a housing having a longitudinal axis defined by a compartment for receiving a cartridge;
• a plunger suitable for acting on a bung of a cartridge retained in the housing;
• a spring arranged between the housing and the plunger;
• a retaining member coupled to the plunger;
• a release member operable in a first state and a second state, wherein, in the first state, the release member is configured to constrain the retaining member to the housing to inhibit movement of the plunger relative to the housing, and, in the second state, the release member is movable relative to the housing to allow the spring to move the plunger;
• and
• a dose setting member rotatable relative to the release member during dose setting and rotatable with the release member during dose dispensing.

A drive mechanism for a drug delivery device for selecting and dispensing a number of user variable doses of a medicament, the drive mechanism comprising:

• a plunger suitable for acting on a bung of a cartridge retained in a housing of the drug delivery device;
• a retaining member coupled to the plunger;
• a release member operable in a first state and a second state, wherein, in the first state, the release member is configured to constrain the retaining member to the housing to inhibit movement of the plunger, and, in the second state, the release member is movable relative to the housing to allow the plunger to move;
• and
• a dose setting member rotatable relative to the release member during dose setting and rotatable together with the release member during dose dispensing.