Patent ID: 8808250

Claim:
Auto-injector for administering a dose of a liquid medicament (M), comprising: an elongate outer casing arranged to contain a syringe with a hollow needle and a stopper for sealing the syringe and displacing the medicament (M), the outer casing having a distal end (D) and a proximal end (P) with an orifice intended to be applied against an injection site, wherein the syringe is slidably arranged with respect to the outer casing, a spring capable of, upon activation: pushing the needle from a covered position inside the outer casing into an advanced position through the orifice and past the proximal end (P), operating the syringe to supply the dose of medicament (M), and retracting the syringe with the needle into the covered position after delivering the medicament (M), an activation mechanism arranged to lock the spring in a pressurized state prior to manual operation and capable of, upon manual operation, releasing the spring for injection, a first gear member rotatable relative to the outer casing, a second gear member non-rotatable relative to first member and the outer casing and threadedly engaged with the first gear member, characterized in that the spring is a torsion spring grounded at one end in the outer casing and at the other end in a first gear member rotatable about a longitudinal axis, wherein the first gear member, upon rotation, is arranged for translatively moving a second gear member toward the proximal end (P), the second gear member prevented from rotating and coupled to the stopper in order to push it towards the proximal end (P), wherein the first gear member is engaged with the activation mechanism prior to manual operation in a manner to prevent rotation and disengaged from the activation mechanism upon manual operation.