track (62), such that the rotatable ring (60) move helically in relation to the housing assembly (10, 20) upon rotation of the rotatable ring (60) relatively to the housing assembly (10, 20).
10. An injection device for injecting a liquid drug according to any claims 1 to 6, wherein the needle shield assembly (140, 140A, 140B) or the housing assembly (10, 20) is provided with a protrusion (111) and the other of the needle shield assembly (140, 140A, 140B) or the housing assembly (110, 120) is provided with a helical track (148) such that the needle shield assembly (140, 140A, 140B) move helically in relation to the housing assembly (10, 20; 110, 120) upon rotation of the needle shield assembly (140, 140A, 140B relatively to the housing assembly (10, 20).
11. An injection device for injecting a liquid drug according to claim 10, wherein the needle shield assembly (140, 140A, 140B) is provided with a window (139) and the housing assem-bly (110, 120) is provided with an opening (113) and which window (139) is brought into alignment with the opening (113) when the needle shield assembly (140, 140A, MOB) is ro-tated relatively to the housing assembly (110, 120).
12. An injection device for injecting a liquid drug according to any of the previous claims, wherein the needle shield assembly (40, 40A, 40B, 60; 140, 140A, 140B) carries a cleaning unit (50; 150) comprising the cleaning chamber (51; 151).
13. An injection device for injecting a liquid drug according to any of the previous claims,
wherein the cleaning agent contained in the cleaning chamber (50; 150) is the same liquid
drug as contained in the cartridge and wherein the liquid drug comprises a preservative.
14. An injection device for injecting a liquid drug according to any of the previous claims, wherein the needle shield assembly (40, 40A, 40B, 60;140, 140A, 140B) distally is provided with a distal surface (42;142) having an opening (41;141) surrounded by a recess (45;145).
15. An injection device for injecting a liquid drug according to claim 14, wherein the distal tip (33; 133) of the needle cannula (30; 130) in the second position is positioned in the recess (45; 145).