PHARMACEUTICAL SYRINGE PISTON ROD

摘要

A pharmaceutical syringe piston rod and method for forming the distal end of the rod. The piston has a cavity with an internal thread having a first thread profile ( 18 ) when no external forces are applied to the piston and a second thread profile ( 40 ) different than the first thread profile when the piston is in the barrel of the syringe and the interior surface of the barrel applies a radially inwardly directed reactive force to the piston. The piston rod has a distal end with an external having an external thread profile substantially the same as the second thread profile of the piston. The external thread is formed from a casting of the cavity. The interior surface of the barrel applies substantially no additional radially inwardly directed reactive force to the exterior surface of the piston when the external thread engages the internal thread.