Mechanical controlling structure for a drug delivery device

A drug delivery device for dispensing a drug from a reservoir, the device comprising:

• a drive unit comprising an electronic control circuit and a coupling portion;
• and
• a reservoir unit comprising the reservoir and/or the drug, wherein the reservoir unit is attachable to the coupling portion,
• wherein the drive unit comprises a plurality of switching elements operatively coupled to the control circuit, and the reservoir unit comprises at least one actuation element adapted to selectively switch at least one switching element of the plurality of switching elements when the reservoir unit is attached to the drive unit,
• wherein the plurality of switching elements are mechanical switches and the at least one actuation element is a cam formed in an outer surface of a proximal portion of the reservoir unit, the cam comprising an inclined surface for gradual deflection of a corresponding switching element and an actuation surface adjacent to the inclined surface for maintaining the corresponding switching element in a switched state, and
• wherein a control signal is generated based on a selection of and a number of switched switching elements of the plurality of switching elements, and the control signal is sent to the control circuit and comprises an instruction for driving an automatic drive of the drive unit or for automatically setting a dose.