US Patent 9233215 Auto-injector with injection damper

An auto-injector comprising an elongate housing arranged to contain a syringe and displacing medicament, wherein the syringe is slidably arranged with respect to the housing, spring capable of: pushing a needle from a covered position inside the housing into an advanced position, operating the syringe to supply a dose of medicament, and retracting the syringe with the needle into the covered position. Activating means is arranged to lock the spring in a pressurized state prior to manual operation and capable of, upon manual operation, releasing the spring for injection. The spring is a single drive spring arranged for advancing the needle and for injecting the dose of medicament via a plunger. A damper is arranged with the plunger by a spline so as to cause rotation of either the plunger or the damper at least during part of a translation of the plunger in proximal direction.