Plunger used for injection molding apparatus

摘要

A plunger (1) used for an injection molding apparatus having a construction such that a molding material to be injected is supplied into a chamber (3) and the thus supplied molding material is pushed out from a nozzle (5) is disclosed. In the plunger, there is a buffer portion (10) for relieving friction between the inner surface of the chamber and the outer surface of the plunger, which is arranged on an outer surface of a tip portion of the plunger. Alternatively a planar tip surface of the plunger is arranged perpendicularly to a direction of a center axis of the plunger. The features of the buffer portion and the planar tip surface may be combined.