Drive Mechanism of a Drug Delivery Device The present invention relates to a drive mechanism of a drug delivery device for dispensing of a dose of a medicament, the mechanism comprising: an elongated housing (20) extending in an axial direction (1, 2), a piston rod (70) to operably engage with a piston (16) of a cartridge (14) to displace the piston (16) in axial distal direction (1), a drive sleeve (50) rotatably supported in the housing (20) at least in a dose incrementing direction (5) against the action of a spring element (58), a ratchet mechanism (150) to rotatably fix the drive sleeve (50) relative to the housing (20), the ratchet mechanism (150) comprises a first ratchet body (151) and a second ratchet body (152), wherein the first ratchet body (151) has a first and a second ratchet element (94, 95) to alternately engage with a toothed profile (51) of the second ratchet body (152),&mdash；wherein one of the first and second ratchet bodies (151； 152) is operably engaged with the housing (20) and wherein the other one of the first and second ratchet bodies (152, 151) is operably engaged with the drive sleeve (50).
