A drive mechanism for an applicator for delivering multiple doses of medicament and a method of assembling said drive mechanism

A drive mechanism for an applicator for delivering multiple doses of medicament, the drive mechanism having a distal end facing the needle end of the applicator, the drive mechanism comprising:

• an axially moveable piston rod (2) having a non-circular cross-section and provided with an external thread (2b),
• a mounting member (4) provided with one member of a pair of blocking means, said pair comprising a toothed rim (4a, 3b) and at least one ratchet arm (3a, 4b);
• a drive sleeve (3) having an internal thread coupled with the external thread of the piston rod (2), the drive sleeve (3) being provided on the distal end with the other member of said pair of blocking means,
• wherein the blocking means of the mounting member (4a, 4b) and the blocking means of the drive sleeve (3a, 3b) cooperate radially during rotation of the drive sleeve (3), the rotation causing translation of the piston rod (2),
• characterized in that
• the drive mechanism further comprises a piston rod guide (5) provided with a central aperture (6), in which the piston rod (2) is axially movable and blocked in rotation,
• the piston rod guide (5) and the mounting member (4) being provided with coupling elements (5a, 5b, 4d) for preventing rotation of the piston rod guide (5) relative to the mounting member (4).