Dose delivery mechanism

A dose delivery mechanism for a medicament delivery device comprising:

• a housing;
• a piston rod;
• and
• an adjusting element,
• the housing configured to connect to a medicament container sealed by a plunger,
• the dose delivery mechanism having a preassembled state and an assembled state,
• in the assembled state, the dose delivery mechanism configured to move the piston rod axially in a proximal direction with respect to the housing during dose delivery such that the piston rod exerts an axial force in the proximal direction on the plunger of the medicament container to expel a medicament from the medicament container,
• in the preassembled state, the adjusting element configured to perform a rotation with respect to the housing, the rotation causing axial movement of the piston rod to adjust an axial position of the piston rod with respect to the housing prior to transfer of the dose delivery mechanism from the preassembled state into the assembled state,
• an outer rim of the adjusting element accessible such that during assembly of the device in the preassembled state the rotation of the adjusting element and the axial movement of the piston rod is capable of being affected,
• the adjusting element configured to perform the rotation at least while being in a preassembled position with respect to the housing,
• the preassembled position being a most distal position of the adjusting element with respect to the housing in the preassembled state,
• the dose delivery mechanism configured to transfer the rotation of the adjusting element into the axial movement of the piston rod via a single threaded connection in the preassembled state, and
• the threaded connection comprises a first threaded element threadedly engaged with a second threaded element.