Assembly for a medication delivery device and medication delivery device comprising such an assembly

An assembly for a medication delivery device comprising:

• a body,
• a piston rod adapted and arranged to be rotated with respect to the body in a dose setting state of the assembly for setting a dose of a medication and to be axially moved in a distal direction with respect to the body in a dose delivering state of the assembly for delivering the dose of the medication set, and
• a setting nut secured against rotational movement with respect to the body, axially movable with respect to the body, and helically coupled with the piston rod,
• wherein the setting nut is adapted and arranged to axially travel in the proximal direction with respect to the body for setting a dose of a medication when the piston rod is rotated with respect to the body in the dose setting state of the assembly due to being helically coupled with the piston rod,
• wherein the setting nut is adapted and arranged to axially travel in the distal direction with respect to the body for delivering the dose of the medication set when the piston rod is axially moved in the distal direction with respect to the body in the dose delivering state of the assembly, and
• further comprising fixing members on the piston rod and on the body, the fixing members engaging with each other to prevent rotational movement of the piston rod with respect to the body when the piston rod is axially moved in the distal direction with respect to the body in a dose delivering state of the assembly,
• wherein the fixing members on the body comprise one of fins and tracks, the other of the fins and tracks being on the piston rod, and wherein the fins are configured to engage in the tracks upon axial movement of the piston.