Patent ID: 6533021
Filing Date: 2003-03-18
Classification: B22D

Abstract:
A mold for a metal hot-runner injection molding machine, comprising:a movable mold plate having a cavity; a fixed mold plate having a nozzle made of ceramic for injecting molten metal into said cavity and having a tip and a passage; a metallic outer tube covering a periphery of the nozzle to have a gap therebetween such that the molten metal flows into the gap through the passage; an induction heating coil wound around the metallic outer tube as heating means for heating metal existing in said nozzle situated at a position away from the tip; a gate cut portion where gate cutting is performed, said gate cut portion being situated in the nozzle between the heating means and the tip such that temperature of the metal in the nozzle upon mold opening can be kept stably to allow the metal in a metal solidified state close to a metal melting temperature; temperature measurement means arranged adjacent to the gate cut portion for measuring the temperature of the metal in said gate cut portion; heating control means connected to the heating means for providing a control of heating of said nozzle by said heating means on a basis of a result of measurement by said temperature measurement means, said heating control means controlling the heating means to allow the metal in the nozzle adjacent to the heating means always in a molten state at a time of an operation; and heat insulation means arranged on said nozzle so as to cover at least an area where said gate cut portion is formed, said heat insulation means adjusting a temperature distribution of the metal in the nozzle from a portion where the heating means is formed to the tip of the nozzle.