Spritzgiessdüse mit teilweise ungeheiztem Heizelement und Verfahren

摘要

An injection molding nozzle and method of making it having an electrical heating element (68) extending in a pair of alternating coils (70) in a spiral channel (80) around a central melt passage (44). The heating element (68) has a U-shaped bend (72) near the forward end (50) of the nozzle and two ends (74) at an external terminal (76) near the rear end (94). A central wire (82) in the heating element has a fine coiled heating portion (88) extending between two larger diameter conductive portions (90,92) which extend to the terminal. One of the conductive portions (90,92) of the central wire (82) is a predetermined length longer than the other and extends in one of the alternating coils (70) of the heating element along a rear portion (48) of the nozzle adjacent the terminal (76). The heating portion (88) of the wire extends in both of the alternating coils (70) of the heating element along a forward portion (50) of the nozzle so the heating element provides substantially less heat along the rear portion (48) than along the forward portion (50) of the nozzle.