Multilayer thermoplast vessel - made by blowing inner skin into outer shell

摘要

A method of making a multilayer thermoplastic container or tube consists of inflating a rough inside an already formed outer vessel. The rough is introduced in the thermoplastic state and is kept warm and soft, the blowing being effected by a nozzle which penetrates into and supports the rough and has a valve at its end. Blowing is continued until the rough has expanded to form an inner skin against the outer vessel. Specif., axial spacer ribs in one layer at the neck form escape ducts for the blowing gas. The method ensures the same multilayer structure throughout, without special welded neck fittings.