Patent ID: 7862544

Claim:
A drive device for a piston in a container containing an injectable product, said drive device comprising: a) a first shifting stage which may be shifted relative to a base part from a starting position and which, when shifted in an advancing direction, advances said piston in said container, displacing product from said container in doses; b) at least a second shifting stage which may be shifted in said advancing direction relative to said base part from a starting position and which, when shifted in said advancing direction, slaves said first shifting stage; c) wherein said first shifting stage may be shifted in said advancing direction relative to said second shifting stage, and said first shifting stage and said second shifting stage at least partially overlap, viewed in said advancing direction; d) and a drive for advancing said shifting stages; e) wherein said drive acts on one of said shifting stages via a first spindle drive; f) and wherein a second spindle drive is formed between said shifting stages; wherein: g) proceeding from said starting position of said shifting stages, said shifting stage which is first advanced by a pre-set shifting path length experiences a higher resistance, at least in sections, against possibly shifting even further than does the other of the shifting stages, such that said other shifting stage is likewise advanced, wherein said higher resistance is can be overcome by the drive device such that said shifting stage that is first advanced is advanced further in the advancing direction after overcoming the higher resistance.