An injection device comprising:
- a housing comprising an inspection window,
- at least two springs, one of the at least two springs being a driving helical spring,
- a spring block connected to the housing and secured against rotation relative to the housing,
- a coupling tube extending above the spring block and above the housing
- a plunger at least partially surrounded by the coupling tube,
- wherein the driving helical spring is connected to the spring block,
- wherein the coupling tube is at least partially surrounded by the driving helical spring,
- wherein the coupling tube comprises a first internal diameter and a second internal diameter,
- wherein the plunger comprises a proximal end and a distal end,
- wherein at least a portion of the proximal end of the plunger is narrower than the first internal diameter of the coupling tube and wider than the second internal diameter of the coupling tube,
- wherein the coupling tube comprises at least a first protrusion and a second protrusion,
- wherein at least a portion of the first protrusion of the coupling tube is above the driving helical spring and above the spring block,
- wherein at least a portion of the second protrusion of the coupling tube is below the inspection window of the housing,
- wherein the spring block comprises an outer wall, an internal wall and a protrusion,
- wherein at least a portion of the protrusion of the spring block is curved,
- wherein the curved portion of the protrusion of the spring block at least partially extends beyond an outer diameter of the outer wall of the spring block,
- wherein the spring block comprises a first hole and a second hole,
- wherein the first hole of the spring block is separated from the second hole of the spring block by the internal wall of the spring block,
- wherein the coupling tube extends through the first hole of the spring block and is arranged non-coaxially with the second hole of the spring block,
- wherein the coupling tube is at least partially surrounded by a substantially cylindrical wall of a rotatable dose knob,
- wherein the substantially cylindrical wall of the rotatable dose knob at least partially covers the housing, the curved protrusion of the spring block, the outer wall of the spring block, the driving helical spring, and the internal wall of the spring block, and
- wherein the rotatable dose knob, the spring block, the coupling tube extending through the first hole, the plunger, and the driving helical spring are arranged coaxially.