A safety hypodermic syringe is so designed that the needle assembly can be moved with the plunger assembly and received inside the barrel after the service of the syringe, and the plunger can be disconnected from the stopper and removed from the barrel for recycling. The barrel has an inside annular...http://www.google.es/patents/US6402721?utm_source=gb-gplus-sharePatente US6402721 - Safety hypodermic syringe with detachable plunger
