The invention refers to an auto-injector (1) for administering a dose of a liquid medicament (M), comprising: - an elongate housing (2) arranged to contain a syringe (7) with a hollow needle (19) and a stopper (10) for sealing the syringe (7) and displacing the medicament (M), the elongate housing (2) having a distal end (D) and a proximal end (P) with an orifice intended to be applied against an injection site, wherein the syringe (7) is slidably arranged with respect to the housing (2), - spring means (14) capable of, upon activation, pushing the needle (9) from a covered position inside the housing (2) into an advanced position through the orifice and past the proximal end (P), operating the syringe (7) to supply the dose of medicament (M), and covering the needle (19) on removal of the auto-injector (1) from the injection site, - activating means (4, 20, 24) arranged to lock the spring means (14) in a pressurized state prior to manual operation and capable of, upon manual operation, releasing the spring means (14) for injection, characterized in that the spring means (14) is a torsion spring (14), wherein a first gear arrangement (13, 13.1, 9) and a second gear arrangement (15, 11.1, 11) are arranged for respectively converting torque from a first end (14.1) and a second end (14.2) of the torsion spring (14) into a translative force, wherein the first end (14.1) is arranged to be groundable in the housing (2) while the second end (14.2) is configured to act on a plunger (11) through the second gear arrangement (15, 11.1, 11) for advancing the needle (19) and supplying the dose, wherein the activating means (4, 20, 24) is arranged to block or release the second gear arrangement (15, 11.1, 11) and wherein the first end (14.1) is releasable from the ground in the housing (2) for causing a translation through the first gear arrangement (13, 13.1, 9) resulting in the needle (19) getting covered.L'invention concerne un injecteur automatique (1) qui permet d'a
