Abstract: A method is disclosed for forming a plastic container by a blow molding operation. In the method, a tubular thermoplastic parison is blown to a preform within a first mold by a blow pipe inserted into one axial open end of the parison. Prior to removing the preform from the first mold, a secondary opening is formed in the wall of the preform, either by a spike-shaped piercing surface over which the parison is expanded or by a vent port through which blow air is exhausted to rupture an opening in the preform wall. The preform is then transferred to a second mold, which pinches shut the initial blowing opening of the preform. A second blow pin is inserted into the secondary opening to supply blow air under pressure to expand the preform to a container.

Abstract: 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 th

Abstract: In a blow molding machine a tubular parison is extruded around a blow pin, a two-part mold is closed and the parison is expanded by air pressure against the internal wall of the mold. Each mold half at its top neck carries a sealing member comprising a first insert, which is a shear insert, in the form of an approximately flat one-half ring to sever the parison against the blow pin; a second insert, which is a seal insert, in the form of a flat approximately one-half ring, to seal the parison against the blow pin; and a base member, in the form of an approximately one-half ring, having an inverted shelf to locate and support the shear and seal inserts.