State changing appliance for a drug delivery device

A system comprising a drug delivery device of the type capable of displaying a set dose of drug to be expelled therefrom, and a state changing appliance structured for detachable attachment to the drug delivery device,

• wherein the drug delivery device comprises:
• a first exterior portion, and
• a second exterior portion, the first exterior portion and the second exterior portion being capable of undergoing relative angular displacement from a first relative position defining a first state of the drug delivery device to a second relative position defining a second state of the drug delivery device, and
• wherein the state changing appliance comprises:
• a first coupling structure configured for rotational fixation with respect to the first exterior portion, wherein the first coupling structure is configured to engage with the first exterior portion in a first rotational interlocking connection, and wherein one of the first coupling structure and the first exterior portion comprises a plurality of circumferentially spaced apart first interface structures and the other of the first coupling structure and the first exterior portion comprises a first dedicated geometry adapted for engagement or abutment with one or more of the plurality of circumferentially spaced apart first interface structures,
• a second coupling structure configured for rotational fixation with respect to the second exterior portion, the first coupling structure and the second coupling structure being capable of undergoing relative angular displacement, and the second coupling structure is configured to engage with the second exterior portion in a second rotational interlocking connection at a plurality of relative angular orientations of the state changing appliance and the drug delivery device, and wherein one of the second coupling structure and the second exterior portion comprises a plurality of circumferentially spaced apart second interface structures and the other of the second coupling structure and the second exterior portion comprises a second dedicated geometry adapted for engagement or abutment with one or more of the plurality of circumferentially spaced apart second interface structures, and
• a limiter mechanism adapted to define a maximum for the relative angular displacement between the first coupling structure and the second coupling structure.