Medication injector apparatus with drive assembly that facilitates reset

An injection clicker assembly of a medication injector apparatus, the apparatus including a drive screw advanceable in a distal direction to shift a movable plunger of a cartridge so as to force medication from an outlet of the cartridge, a drive sleeve of a dose injecting mechanism rotatable in a first direction within a housing of the apparatus, the drive sleeve including a distal facing surface and defining a longitudinal bore in which the drive screw extends, and a clutch connected to the drive screw, the clutch rotated by engagement with the drive sleeve distal facing surface to thereby rotate and advance the drive screw through a nut within the housing, the injection clicker assembly comprising:

• a collar arranged coaxially on the drive sleeve at a location proximal of the distal facing surface of the drive sleeve, said collar connected to the drive sleeve to be axially movable relative thereto and rotatably fixed thereto when the drive sleeve rotates in the first direction, said collar including a plurality of teeth extending in an axial direction and adapted to engage mating teeth of a stop surface one of integrally formed with and non-rotatably connected to a housing of the apparatus;
• a biasing element adapted to force said collar axially into meshing engagement with said stop surface;
• and
• said collar and said stop surface being complementarily configured such that during rotation of the drive sleeve in the first direction, and due to a returning force applied to said collar by said biasing element, said collar oscillates axially on said drive sleeve as said collar teeth slide over said stop surface teeth to provide an audible clicking sound that indicates injecting use of the apparatus.