Patent ID: 6793868
Filing Date: 2004-09-21
Classification: B29C,B29D,Y10S,Y10T

Abstract:
In an injection molding method for producing a molding comprising the steps of:providing a mold assembly having a pair of molds including a mold surface forming a cavity having a preselected volume, at least one transfer surface for transferring a mirror surface formed by said mold surfaces to said molding, at least one non-transfer surface, and a gate for filling said cavity with a molten material by injection; injecting said molten material into said cavity via said gate and then cooling said molten material; providing at least one vent hole having a preselected opening area and at least one bore communicated to said vent hole in said at least one non-transfer surface for applying a preselected air pressure to said molding material; and continuously applying the air pressure via said vent hole even after a pressure of said molding material in said cavity has dropped to zero thereby causing said molten material to sink away from said vent hole; and providing a at least one step in said at least one non-transfer surface between said vent hole and said at least one transfer surface to prevent sinking of the molten material from proceeding from said at least one non-transfer surface to said at least one transfer surface.