INRICHTING VOOR HET VERVAARDIGEN VAN GEORIENTEERDE, HOLLE VOORWERPEN UIT THERMOPLASTISCHE KUNSTSTOF EN VOORWERP VERVAARDIGD ONDER TOEPASSING VAN DEZE INRICHTING.

摘要

In the manufacture of oriented hollow articles made of thermoplastic material by the steps of extruding a continuous hot tubular parison of thermoplastic material; pre-blowing such parison in a pre-blowing mold to produce preforms having a cylindrical body with a diameter not more than 20% greater than that of the parison; thermally conditioning the resulting preforms at a temperature sufficient to cause orientation of the thermoplastic material when it is being stretched; and effecting a final blow-molding of the thermally conditioned preforms, the mechanical properties of the resulting articles in the vicinity of their base are improved by carrying out the pre-blowing step while holding each parison tightly between two half-molds defining a cavity which has the shape, at the location of the base of the preform, of a quarter sphere of diameter equal to that of the preform, and cutting off the resulting flash by means on an elongated blade having a semicircular cross section and a diameter corresponding to that of the base of the cavity, and mounted at the base of one of the half-molds, the blade traveling against the base of the cavity in a direction perpendicular to the closure plane of the mold.