A method of making a retracting needle assembly for use with a syringe barrel having a cylindrical collar and a plunger having a release element with a sharp distal end includes an outer hub having a passageway therethrough and an inner hub having a proximal end, a distal end and a conduit therethrough....http://www.google.es/patents/US6517516?utm_source=gb-gplus-sharePatente US6517516 - Method of making a retracting needle syringe
