AUTOMATIC PEN-TYPE INJECTOR

摘要

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 to be ejected through the needle. There is, therefore, a two-step movement of the plunger, firstly together with the syringe through the medium of the O-ring, and secondly within the syringe container to force the plug forward, when a ledge (12) on the syringe container (3) is arrested by a stop (14), whereupon the frictional force between the plunger and the O-ring is relieved so that the plunger slides forward through the O-ring.