Method for forming containers by selective laser heating and free blow molding

Abstract

A method of manufacturing a container (14) from a blank (2) of thermoplastic material having a body (4) extending along a main axis (A), said manufacturing method comprising: a selective heating step, wherein the blank (2 ) of the body (4) is exposed to monochromatic or quasi-monochromatic infrared radiation, the radiant power being modulated along the main axis (A) of said body (4) so ​​that said body has a thermal annular region (4A, 4C, 4E , 4G, 4I) and cooler annular regions (4B, 4D, 4F, 4H) that have a temperature well above the glass transition temperature (Tg) of the material and the cooler annular regions a temperature close to said glass transition temperature (Tg); a forming step in which a pressurized fluid is injected into said preform (2) thus heated, said forming step being performed with free expansion.

Description

technical field [0001] The present invention relates to the manufacture of containers, in particular ampoules, vials, by forming from plastics material such as polyethylene terephthalate (PET) blanks (usually preforms, although intermediate containers may be involved). Background technique [0002] The manufacture of containers consists of two main steps: a heating step, during which the blank is exposed to electromagnetic radiation from an infrared emitting source; followed by a forming step, during which pressurized gas is injected into the thus heated blank , to give the blank the final container shape. [0003] The forming step usually takes place in a mold with a cavity for the container. Depending on the application, the container does not necessarily have a rotationally symmetric shape (the case of polygonal or flat shaped containers), posing a problem of material distribution during molding. One solution described in French patent FR2703944 (and its equivalent US p...

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Problems solved by technology

[0005] However, tests have revealed that, even with the application of the technique described in patent FR2703944, the non-uniform distribution of heating on the periphery of the preform effectively allows obtaining a uniform distribution of material in the formation of non-rotationally symmetrical containers, but at a lower temperature than the rest of the body The creation of an annular portion at a temperature still does not allow to obtain a thickening that can indeed increase the rigidity of the container

In fact, the temperature change in the preform is very gradual and limited in magnitude, so that, even with reflectors, it is not possible to obtain a thickness change as sharp as that shown on figure 12 of the aforementioned patent

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