Automatic injection device with actively triggered syringe withdrawal

1. An injection device, comprising:

a housing, including a container carrier having a medicament container and a needle attached to the medicament container;

a needle shield slidably arranged inside the housing with a contact part configured for application against an injection site;

an activation mechanism interactively connected to the needle shield and configured, upon manual activation, for initiating a penetration sequence, wherein the activation mechanism comprises first flexible arms having inwardly extending ledges on a penetration sleeve, recesses on a lock-out sleeve, a circumferential groove on an activation housing, and an activation button having inwardly extending parts facing the first flexible arms;

a penetration mechanism interactively connected to the activation mechanism and configured for performing an automatic penetration of the needle, wherein the penetration mechanism comprises tongues arranged on the activation housing and snap-fitted to the container carrier, outwardly extending protrusions arranged on second flexible arms on the activation housing, a retraction release ring abutting the outwardly extending protrusions, and a penetration spring arranged between the retraction release ring and an inner rear wall of the penetration sleeve;

an injection mechanism interactively connected to the penetration mechanism and configured for triggering and performing an automatic injection of the medicament, wherein the injection mechanism comprises flexible tongues arranged on the activation housing, each tongue having inwardly directed ledges, a plunger rod having a circumferential groove where the inwardly directed ledges are positioned when the device is unarmed, and an injection spring arranged between a front wall of the plunger rod and a rear wall of the activation housing;

a withdrawal mechanism interactively connected to the injection mechanism and configured for triggering and performing an automatic withdrawal of the needle, wherein the withdrawal mechanism comprises a penetration retraction spring arranged between the retraction release ring and protrusions arranged on the activation housing and the second flexible arms on the activation housing; and

an active triggering withdrawal mechanism interactively connected to the withdrawal mechanism and configured for allowing the withdrawal mechanism to be triggered when the injection device starts to be removed from the injection site, wherein the active triggering withdrawal mechanism comprises grooves arranged on a lock plate surrounding the activation housing, and corresponding ledges arranged on the protrusions of the second flexible arms, such that when the penetration spring urges the activation housing and the container carrier forward, the ledges engage the grooves for preventing the second flexible arms from being moved inward;

wherein when the injection device is removed or lifted from the injection site, a front surface of the lock-out sleeve causes the lock plate to move forward so that the ledges come out of contact with the grooves, enabling the flexible arms to collapse inward, allowing the retraction release ring to pass the protrusions of the second flexible arms, such that the container carrier is drawn into the housing by the force of the retraction spring acting on the protrusions.

2. The injection device of claim 1 , wherein the needle shield is initially held inside the housing when the device is unarmed.

3. The injection device of claim 2 , wherein the needle shield is arranged to be manually pulled such that protrusions of the needle shield enter a recess on an inner surface of the housing for arming the injection device and is connected to the lock-out sleeve by snap-in members.

4. The injection device of claim 3 , wherein the ledges contact a wall of the circumferential groove, and the recesses are arranged adjacent the first flexible arms blocking movement of the activation button when the device is unarmed.

5. The injection device of claim 4 , wherein the lock-out sleeve and the needle shield are arranged to be resiliently moved due to interaction between the tongues of the lock sleeve and inclined surfaces of the penetration sleeve, when the injection device is lifted or removed from the injection site.