A device for moving a piston inside a cartridge having a cartridge body and the piston displaceable along a longitudinal axis of the cartridge body is presented. The device comprises a first portion having first coupler for coupling the cartridge body to the first portion such that in both directions of the longitudinal axis, a connection exists between the cartridge body and the first portion and a second portion having second coupler for coupling the piston to the second portion such that in both directions of the longitudinal axis, a connection exists between the piston and the second portion. The first and second portions move relative to each other to effect at least a forward displacement of the piston coupled to the second portion inside the cartridge body coupled to the first portion along the longitudinal axis. The second coupler establishes and releases the connection with the piston.
