Drive assembly for a drug delivery device and drug delivery device

1. A drive assembly for a drug delivery device, comprising:

a housing with a proximal end and a distal end, and a longitudinal axis (A) extending between the proximal end and the distal end,

a rotation sleeve being rotatable relative to the housing,

a drive member is axially moveable relative to the housing, and

a piston rod being axially moveable relative to the housing,

wherein the piston rod is in mechanical cooperation with the rotation sleeve to be moveable in the distal direction relative to the housing when the rotation sleeve rotates in a first direction (D 1 ) and to be stationary in axial direction relative to the housing when the rotation sleeve rotates in a second direction (D 2 ) opposite to the first direction (D 1 ),

wherein the rotation sleeve is in mechanical cooperation with the drive member to be rotatable relative to the housing when the drive member is displaced in axial direction relative to the rotation sleeve.

2. The drive assembly according to claim 1 , wherein the rotation sleeve rotates in the first direction (D 1 ) relative to the housing when the drive member is displaced in the distal direction, and rotates in the second direction (D 2 ) when the drive member is displaced in the proximal direction.

3. The drive assembly according to claim 1 , wherein the drive member and the rotation sleeve are in engagement by a thread.

4. The drive assembly according to claim 1 , wherein the rotation sleeve comprises a radial protrusion being arranged in axial direction between two sections of the housing, the two sections preventing an axial movement of the rotation sleeve.

5. The drive assembly according to claim 1 , wherein the piston rod has an outer surface provided with at least one guide track arranged on the outer surface, and the rotation sleeve comprises a guide piece being disposed and being movable in the guide track.

6. The drive assembly according to claim 5 , wherein the guide track forms a zigzag-like line on the outer surface of the piston rod, the zigzag-like line essentially extending in axial direction.

7. The drive assembly according to claim 5 , wherein the guide track comprises first sections and second sections, the first sections being perpendicular relative to the longitudinal axis (A) and the second sections being oblique relative to the longitudinal axis (A).

8. The drive assembly according to claim 7 , wherein the first sections are designed to prevent an axial movement of the piston rod and have an extension perpendicular relative to the longitudinal axis (A) which limits the rotational movement of the rotation sleeve.

9. The drive assembly according to claim 7 , wherein the second sections are designed to convert rotational movement of the rotation sleeve in the first direction into axial movement of the piston rod.

10. The drive assembly according to one of the claims 7 to 9 , wherein the guide track comprises at least one priming section being arranged between one of the first sections and one of the second sections.

11. The drive assembly according to claim 5 , wherein the guide track comprises at least one end section being designed to limit the axial movement of the piston rod.

12. The drive assembly according to claim 1 , wherein the piston rod is splined to the housing.

13. A drug delivery device comprising the drive assembly according to claim 1 , wherein the drug delivery device further comprises a medication containing cartridge and the piston rod interacts with a bung being arranged in the medication containing cartridge to dispense the medication.