Method and device for the production of an optimized neck contour on preforms

A method for producing preforms with an improved neck geometry beneath a threaded region or a transporting ring for a simplified subsequent blow-molding process, wherein the produced preform made of at least one thermoplastic material has a significantly thinner wall thickness in a neck region beneath the thread than in the thread itself, and the preform is provided in order to be formed into blow-molded containers, the method comprising:

• providing at least two channels having an increased wall thickness so that when the preform is blow molded the holding pressure is maintained, despite thin-walled regions, by the at least two channels with an increased wall thickness, or integrating at least two slides in the mold to produce the relatively thin wall thicknesses following an operation of filling the cavities and a certain process time period, or opening a mold once an outer skin of the preform has solidified following initial cooling for a shortest period of time possible;
• receiving the preforms from the open mold by a removal arm and cooling sleeves of the removal arm;
• cooling the preform stem, but not the neck region beneath the thread, by contact cooling with the cooling sleeves;
• and carrying out an embossing operation in which a plastically redeformable region is deformed mechanically by embossing elements, in accordance with repeatability necessary for further processing, by the plastic material being embossed by cooling, pressing and pushing operations, wherein a contour of the embossing elements is configured, in combination with a supporting pin, so that said contours are replicated in a reproducible manner on an open preform to the greatest extent following the deforming operation.

An apparatus for production of a preform with a geometry beneath a neck that is optimized for a blow-molding process, wherein the preform has a considerably thinner wall thickness in a region beneath a thread than in the thread itself, the apparatus comprising:

• a mold with at least one mold cavity for definitive shaping of the preforms;
• an injection-molding apparatus that plasticizes raw plastic material to introduce the plastic material into the cavities with the closed mold under pressure, the mold having channels or slides that ensure that a required holding pressure is maintained in the neck despite the reduced wall thickness, or the mold is responsible for the preform geometries in a first shaping step;
• a removal arm, which is equipped with at least one cooled cooling sleeve, equal in number to the number of cavities, for removing the preforms, the cooling-sleeve having an inner geometry that provides the preform stem, but not the region of the preform neck, with contact cooling;
• and an embossing apparatus that has embossing elements mounted in a radially floating manner and use a cone to deflect an axial force perpendicularly to an axis and to intensify said force to an extent for an embossing operation that deforms the neck beneath the threaded part by pulling, pressing and pushing operations, said neck being defined by a cavity between the embossing elements and a supporting pin so as to describe the contour and wall thickness of the neck in a repeatable manner.