The present invention relates to a method and an apparatus for tubularly drawing a tubular raw material of thermoplastic resin. Gas for forming a bubble to heatingly draw the tubular raw material is injected into the raw material from a direction opposite to a direction for transferring the raw material...http://www.google.es/patents/US4869863?utm_source=gb-gplus-sharePatente US4869863 - Method of and apparatus for tubularly drawing thermoplastic resin
Method of and apparatus for tubularly drawing thermoplastic resin
