A device for automatic injection of a product into an injection site, the injection device comprising: a container having an open proximal end and a substantially closed distal end and being intended to receive the product and provided at the distal end with an injection needle having a tip, wherein the injection needle provides an outlet port for the container; a housing (9, 11, 68, 72, 93), intended to receive, at least partially, the container, the container being movable relative to the housing (9, 11, 68, 72, 93) between an initial position, in which the injection needle is contained within the housing (9, 11, 68, 72, 93), an insertion position, distally spaced relative to the initial position and in which the injection needle is exposed over a predetermined length, and a final position in which the injection needle is contained within the housing (9, 11, 68, 72, 93); retaining means, arranged to maintain the container in the insertion position; deactivating means, arranged to automatically release the retaining means and cause the container to move to the final position; temporizing means, arranged to control the release of the retaining means by the deactivating means until substantially all of the product contained within the container has been caused to pass through the outlet port and the injection needle before the container moves to the final position; a needle shield covering the tip of the injection needle, and a deshielder coupled with the housing (9, 11, 68, 72, 93), the deshielder including: a cap engaged with the needle shield, wherein removal of the cap from the housing (9, 11, 68, 72, 93) causes removal of the needle shield from the needle characterized in that, the housing (9, 11, 68, 72, 93) comprises grooves for guiding the translation of the cap without rotation of the cap or the needle shield with respect to the needle, the device further comprises a ring engaged with the housing (9, 11, 68, 72, 93); and, breakable bridges connecting the cap and the ring, wherein, in an initial pre-use state, the cap is connected with the ring by the bridges with the needle shield covering the needle, and wherein, the cap is removable from the housing (9, 11, 68, 72, 93) by application of a distal pulling force thereby breaking of the bridges. a container having an open proximal end and a substantially closed distal end and being intended to receive the product and provided at the distal end with an injection needle having a tip, wherein the injection needle provides an outlet port for the container; a housing (9, 11, 68, 72, 93), intended to receive, at least partially, the container, the container being movable relative to the housing (9, 11, 68, 72, 93) between an initial position, in which the injection needle is contained within the housing (9, 11, 68, 72, 93), an insertion position, distally spaced relative to the initial position and in which the injection needle is exposed over a predetermined length, and a final position in which the injection needle is contained within the housing (9, 11, 68, 72, 93); retaining means, arranged to maintain the container in the insertion position; deactivating means, arranged to automatically release the retaining means and cause the container to move to the final position; temporizing means, arranged to control the release of the retaining means by the deactivating means until substantially all of the product contained within the container has been caused to pass through the outlet port and the injection needle before the container moves to the final position; a needle shield covering the tip of the injection needle, and a deshielder coupled with the housing (9, 11, 68, 72, 93), the deshielder including: a cap engaged with the needle shield, wherein removal of the cap from the housing (9, 11, 68, 72, 93) causes removal of the needle shield from the needle characterized in that, the housing (9, 11, 68, 72, 93) comprises grooves for guiding the translation of the cap without rotation of the cap or the needle shield with respect to the needle, the device further comprises a ring engaged with the housing (9, 11, 68, 72, 93); and, breakable bridges connecting the cap and the ring, wherein, in an initial pre-use state, the cap is connected with the ring by the bridges with the needle shield covering the needle, and wherein, the cap is removable from the housing (9, 11, 68, 72, 93) by application of a distal pulling force thereby breaking of the bridges.