Patent ID: 8882723

Claim:
A drive mechanism for a drug delivery device, comprising: a housing, a unit which is attachable to the housing and removable from the housing, a drive member arranged inside the housing, the drive member being rotatable with respect to the housing, a rotation member arranged inside the housing, the rotation member being rotatable with respect to the housing, where the rotation member and the drive member abut each other and are unidirectionally rotationally engaged to each other when the unit is attached to the housing, a stop member rotationally locked with respect to the housing or forming part of the housing, where the stop member and the drive member abut each other and are unidirectionally rotationally engaged to each other when the unit is attached to the housing, a separating member disposed between the rotation member and the stop member, the separating member causing a separation and disengagement of the unidirectional rotational engagements between the rotation member and the drive member and between the stop member and drive member when the unit is removed, and a coupling feature of the separating member, the coupling feature being provided to engage the unit and to rotate the separating member when the unit is being attached to the housing or is being removed.