Double walled containers, esp. vacuum flasks - where inner wall is formed by high speed spinning of hot, preformed gob

摘要

The outer wall of the vessel or flask is first made with the required shape tapering towards a neck. A preformed gob is also made, and is placed on neck while hot, so that part of the gob projects into the outer wall. Spinning is then used so the hot gob forms the inner wall of the flask; and the cavity between the walls is evacuated. The gob is pref. provided with a shoulded which rests on neck; and the gob is pref. made in a press or by blow-moulding. Neck is pref. heated before applying the hot gob, which pref. includes multi-start screw threads on its external dia. An efficient seal is obtd. in the neck of the flask between the outer and inner walls.