A device (700) for delivering a medicament to the body of a patient by injection into the skin or through the skin of a patient, comprising: a housing (705, 770) having a lower surface adapted to make contact with the skin of a patient, a needle opening in said lower surface and an upper surface, an injection needle (760) adapted for tissue penetration and for movement through the needle opening； a reservoir (710), disposed within said housing, said reservoir being in hydraulic communication with the injection needle； a pressurization system (735) to pressurize the reservoir； a protection member adapted to move away from the bottom surface, the protection member having a cover part arranged around the needle opening, and at least one post (794) protruding from the cover part； the protection member having a first position in which the amount of the protection member is initially disposed within the housing and the cover part is substantially coplanar with the lower surface of the housing, and a second position in which the sleeve of the member of protection is partially removed from the housing and the cover part at least partially covers the needle； and an elastic load element (793) disposed within the housing adapted to load the protection member towards the second position of the protection member； a mobile interposed element (790) having a first position, which prevents the movement of the protection member, and a second position, which allows the movement of the protection member, characterized in that when the device (700) is placed on the skin of the patient and activated, the interleaved element is moved from a first position to a second position whereby the loading element is allowed to load the protective member to the second position, therefore, when the device is removed from the skin, the protection member emerges from the housing and at least partially covers the needle, and in which the intercalated element is a movable mouse trap door (790).Un disposi
