A syringe (1) is moved bodily forward by a plunger (7) (after release of a spring 8) by acting through an O-ring pressing onto an enlarged head (16) of a syringe container (3), in order to expose the needle (5) of the syringe before the plunger acts on a plug (4) within the syringe to cause the liquid...http://www.google.com/patents/US20060167413?utm_source=gb-gplus-sharePatent US20060167413 - Automatic pen-type injector
