| 摘要 |
<p>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.</p> |
