Patent ID: 7879007

Claim:
An injection device comprising: a) a housing; b) a product container accommodated by the housing, in which a plunger is accommodated so that it can be moved in a distal direction to dispense product; c) a plunger rod acting on the plunger in the distal direction; and d) a spring acting on the plunger rod in the distal direction, wherein the spring comprises at least two adjacent spring portions which have a different buckling resistance for an identical length when the plunger rod is in a distal position, and wherein the spring is a coil spring with coils extending adjacent to one another in a spiral about a spring axis, which coil spring is used as a compression spring for an injection device and wherein the at least two spring portions comprise a first axial spring portion with a first buckling resistance in a relaxed state and a second axial spring portion with a second, higher buckling resistance in the relaxed state; and e) wherein the coils in the second spring portion lie next to one another and in contact with one another in a block when the plunger rod is in the distal position such that the second, higher buckling resistance is obtained across the second spring portion.