Accessory device for drug delivery device

An assembly comprising a drug delivery device and an add-on device adapted to be releasably mounted on the drug delivery device, the drug delivery device comprising:

• a device housing defining a general axis,
• a drug reservoir or structure for receiving a drug reservoir,
• drug expelling structure comprising a rotatable device dose setting member allowing a user to set a dose amount of drug to be expelled, and
• a device release member actuatable between a proximal position and a distal position, the proximal position allowing a dose amount to be set, the distal position allowing the drug expelling structure to expel a set dose,
• the add-on device comprising:
• first coupling structure adapted to releasably engage the device housing,
• second coupling structure adapted to releasably engage the device dose setting member,
• an add-on dose setting member which, with the add-on device mounted on the drug delivery device, is arranged to be (i) rotationally free but axially locked relative to the device housing, and (ii) rotationally locked relative to the device dose setting member,
• an add-on release member axially moveable between a proximal position and a distal position relative to the add-on dose setting member, the add-on release member being adapted to engage and actuate the device release member when moved distally,
• wherein the add-on dose setting member comprises the first coupling structure, and
• wherein the device housing comprises a circumferential groove in the vicinity of the device dose setting member, the first coupling structure being adapted to engage the groove rotationally free.

An assembly comprising a drug delivery device and an add-on device adapted to be releasably mounted on the drug delivery device, the drug delivery device comprising:—a device housing defining a general axis,—a drug reservoir or structure for receiving a drug reservoir,—drug expelling structure comprising a rotatable device dose setting member allowing a user to set a dose amount of drug to be expelled, and—a device release member actuatable between a proximal position and a distal position, the proximal position allowing a dose amount to be set, the distal position allowing the drug expelling structure to expel a set dose, the add-on device comprising:—first coupling structure adapted to releasably engage the device housing,—second coupling structure adapted to releasably engage the device dose setting member,—an add-on dose setting member which, with the add-on device mounted on the drug delivery device, is arranged to be (i) rotationally free but axially locked relative to the device housing, and (ii) rotationally locked relative to the device dose setting member,—an add-on release member axially moveable between a proximal position and a distal position relative to the add-on dose setting member, the add-on release member being adapted to engage and actuate the device release member when moved distally, and—a coupling member, the coupling member comprising the first coupling structure,—wherein the first coupling structure is adapted to mount the coupling member non-moveable on the device housing, the add-on dose setting member being coupled rotationally free to the coupling member.