Patent ID: 8758304
Filing Date: 2014-06-24
Classification: A61M

Abstract:
1. Auto-injector for administering a dose of a liquid medicament, comprising: an elongate housing arranged to contain a syringe with a hollow needle and a bung for sealing the syringe and displacing the medicament, the elongate housing having a distal end and a proximal end with an orifice intended to be applied against an injection site, wherein the syringe is slidably arranged with respect to the housing, spring means capable of, upon activation, pushing the needle from a covered position inside the housing into an advanced position through the orifice and past the proximal end as well as operating the syringe to supply the dose of medicament, activating means arranged to lock the spring means in a pressurized state prior to manual operation and capable of, upon manual operation, releasing the spring means for injection, wherein the spring means is a torsion spring grounded at one end in the housing and at the other end in a lead nut rotatable about a longitudinal axis but axially constrainable, wherein the lead nut, upon rotation, is arranged for translatively moving a piston rod by means of a lead screw thread, the piston rod being prevented from rotating relative to the housing and arranged to be coupled to the bung in order to push it towards the proximal end, wherein the lead nut is engaged to the housing in an initial position prior to manual operation of the activating means in a manner to prevent rotation and disengaged from the housing by the activating means upon manual operation, characterized in that the activating means is a trigger button, arranged at a distal end of the housing and operable by being pressed in proximal direction, wherein at least prior to manual operation the trigger button, the piston rod and the lead nut are coupled for joint translation in proximal direction, wherein the lead nut is engaged to the housing by at least one spline feature in the initial position and wherein the lead nut is arranged to disengage from the housing on translation in proximal direction from the initial position.