Patent ID: 7273472

Claim:
A drive device for a piston in a container containing an injectable product, said drive device comprising: 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; 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; and a drive for advancing said shifting stages; 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; said drive acts on one of said shifting stages via a first spindle drive; a second spindle drive is formed between said shifting stages; 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 said other shifting stage, such that said other shifting stage is likewise advanced; a resistance area is formed on a surface area of said first shifting stage; a resistance counter area is formed on a surface area with respect to which said first shifting stage may be shifted in said advancing direction; said higher resistance is generated by a pressure exerted onto said resistance counter area by said resistance area; and a flexible resistance element is arranged between said resistance area and said resistance counter area.