The present disclosure relates to a medicament injection device (1) comprising a housing (3) arranged to receive a medicament container (11a), a needle cover (9) movable relative to the housing (3), from a retracted position, in which it engages the housing (3) and enables medicament delivery, to an extended position, a plunger rod (7), and a plunger driver (5) movable relative to the housing (3) from all initial position to a final position, and arranged to actuate the plunger rod (7), wherein the plunger rod (7) has a first guide arrangement and the housing (3) has a second guide arrangement, the first guide arrangement (7d) and the second guide arrangement being arranged to cooperate to guide movement of the plunger rod (7) relative to the housing (3), wherein the first guide arrangement and the second guide arrangement in a first stage provide a linear motion path for the plunger rod (7), enabling the plunger rod (7) to initially move in the axial direction and in a second stage provide a rotation motion path for the plunger rod (7), enabling the plunger rod (7) to rotate relative to the housing (3) to release the plunger rod (7) from the plunger driver (5), whereby the plunger driver (5) attains a released state enabling movement of the plunger driver (5) to its final position, wherein in the released state the plunger driver (5) is arranged to release the needle cover (9) from the housing (3) and to actuate the needle cover (9) to its extended position.La présente invention concerne un dispositif d'injection de médicament (1) comprenant un boîtier (3) conçu pour recevoir un récipient de médicament (11a), un couvercle d'aiguille (9) mobile par rapport au boîtier (3) d'une position rétractée, dans laquelle il vient en prise avec le boîtier (3) et permet l'administration de médicament, à une position étendue, une tige de piston (7), et un élément d'entraînement de piston (5) mobile par rapport au boîtier (3) d'une position initiale à une position finale, et conçu
