Medicament injection apparatus, comprising: main body is arranged to receive drug cartridge Needle stand, the needle stand carries needle, wherein the needle stand can be axially moveable relative to the main body With rotatable cap, far-end of the cap in described device, wherein the cap is removably connected to the needle stand, releasable arrangement between the main body and the cap, the releasable arrangement includes induction element and trough of belt connecting rod, wherein the trough of belt linkage arrangement makes the induction element at least partly follow predefined paths in the axial direction at during the moving in rotation of the cap, thus as the cap is rotated up predetermined point, the proximal end for making the needle stand be axially toward described device is mobile, wherein the main body includes drug cartridge retainer, the drug cartridge retainer includes the induction element suspended from the drug cartridge retainer, for being engaged with the cap.
