The invention relates to: A portable medication delivery device (1) comprising a medication
cartridge (11) having an outlet (111) and a movable
piston (112), and a housing (12) for holding said
cartridge, and a flexible
piston rod (13) being operable to engage and displace said
piston along an axis (113) of said
cartridge, and guiding means (14) for bending said
piston rod away from said axis, and actuating means (15), and driving means (16, 17) for transferring movement from said actuating means to said
piston rod, said driving means including a driving wheel (17) for displacing the
piston rod (13), said flexible piston rod comprising regularly spaced first members (330; 331; 332) adapted to mechanically cooperate with corresponding second members (171) on said driving wheel. The object of the present invention is to provide a medication
delivery system that combines compactness with an improved accuracy. The problem is solved in that said flexible piston rod (13) exhibits a linear or approximately linear path between said driving wheel (17) and said piston (112). This has the
advantage of yielding a compact, low-weight device with an improved
dose accuracy. The invention may e.g. be used in injection or infusion devices for a person's self-treatment of a
disease such as diabetes.