BLOWING HEAD FOR PLASTICS FOIL

摘要

An apparatus for forming a thin-wall and flattenable synthetic-resin tube has inner and outer nozzle parts generally centered on a common axis and defining an annular passage centered on the axis. At least one of the parts is formed with an annular and substantially closed chamber juxtaposed with the passage and extending axially therealong. A hot plastic mass is fed under pressure to one end of the passage so that it passes axially along the passage to emerge from the other end thereof as a tube. A body of liquid partially fills the chamber, this liquid being vaporizable generally at the temperature of the hot mass in the passage. Thus the liquid is vaporized at hot spots of the passage and the vapor thus produced condenses in cool spots of the passage. The space in the chamber above the liquid body is normally largely evacuated. The liquid may be water.