| 摘要 |
The present invention relates to a drive mechanism which is suitable for an injection device (1; 101; 201; 301), especially a pen type drug delivery device. The mechanism comprises a housing (4; 104; 204; 304), a piston rod (9; 109; 209; 309) which is at least axially movable relative to the housing (4; 104; 204; 304) and a drive member (8; 108; 208; 308) which is coupled to the housing (4; 104; 204; 304) via a first clutch (18; 118; 218; 318) such that a relative rotation of the drive member (8; 108; 208; 308) about an axis of rotation with respect to the housing (4; 104; 204; 304) is prevented during dose setting and is allowed during dose dispensing. The drive member (8; 108; 208; 308) engages the piston rod (9; 109; 209; 309) such that a rotation of the drive member (8; 108; 208; 308) causes an axial movement of the piston rod (9; 109; 209; 309). (Re-)engagement of the first clutch (18; 118; 218; 318) causes rotation of the drive member (8; 108; 208; 308) with respect to the housing (4; 104; 204; 304) in a direction moving the piston rod (9; 109; 209; 309) in the proximal direction. |
