Drive mechanism for a drug delivery device

A drug delivery device for dispensing of a dose of a medicinal product, comprising a housing and a cartridge comprising the medicinal product, the cartridge further comprising a piston slidably arranged in an axial direction, wherein the device further comprises a drive mechanism according to any one of the preceding claims.

A method of eliminating clearance between a piston and a piston rod in a drive mechanism of a drug delivery device, wherein the drive mechanism comprises a holder for a product-containing cartridge having a piston slidably arranged therein in an axial direction, wherein the piston rod is to be operably engaged with the cartridge's piston for dispensing of a dose of the medicinal product, further comprising an adjusting member attached to a proximal end of the piston or being pre-assembled to a distal portion of the piston rod, wherein the adjusting member comprises a receptacle to receive a distal portion of the piston rod, the method of eliminating said clearance during or after assembly of the drive mechanism comprises the steps of:

• axially moving of the piston rod relative to the adjusting member and/or axially moving the adjusting member relative to the piston for eliminating axial clearance between the piston and the piston rod,
• locking the piston rod's distal portion in place at an arbitrary position inside the adjusting member's receptacle by an interlock means adapted to interact with the adjusting member.