Patent ID: 6338622
Filing Date: 2002-01-15
Classification: B29C

Abstract:
A pipe molding die comprising:a throttle part including: a core; a shell part, fitted to said core, for forming a flow path through which a molten resin as a pipe raw material flows between said core and said shell part; a resin reservoir provided in at least one of said core and said shell part as a portion of said flow path, said resin reservoir having a recessed shape in cross-section which is formed in a curved-surface configuration and a ring-like shape circumscribing a central axis of said pipe molding die with this central axis centered, said flow path being substantially perpendicular to said resin reservoir; a first constricting portion immediately preceding said resin reservoir which constricts said flow path, said first constricting portion circumscribing said central axis of said pipe molding die, said first constricting portion having a continuous annular shape of a constant first diameter around an entire circumference of said first constricting portion; a first straight portion preceding said first constricting portion and circumscribing said central axis of said pipe molding die, said first straight portion having a second diameter; a first tapering portion immediately preceding said first constricting portion and interconnecting said first straight portion to said first constricting portion, said first tapering portion having a diameter which varies between said first diameter and said second diameter; a second constricting portion immediately following said resin reservoir which constricts said flow path, said second constricting portion circumscribing said central axis of said pipe molding die, said second constricting portion having a continuous annular shape of a constant third diameter around an entire circumference of said second constricting portion; a second straight portion following said second constricting portion and circumscribing said central axis of said pipe molding die, said second straight portion having a fourth diameter; and a second tapering portion immediately following said second constricting portion and interconnecting said second constricting portion to said second straight portion, said second tapering portion having a diameter which varies between said third diameter and said fourth diameter, wherein said molten resin flows sequentially past said first straight portion, said first tapering portion, said first constricting portion, said resin reservoir, said second constricting portion, said second tapering portion, and said second straight portion in a direction substantially parallel to said central axis of said pipe molding die.