Process for forming a container by selective laser heating and free blowing

Abstract

The invention relates to a process for manufacturing a container (14) from a thermoplastic preform (2) carrying a body (4) that extends along a main axis (A), which process comprises: - a selective heating step in which the body (4) of the preform (2) is exposed to monochromatic or pseudomonochromatic infrared radiation, the power of which is modulated along the main axis (A) of the body (4) so that the latter has an alternation of hot annular regions (4A, 4C, 4E, 4G, 4I), the temperature of which is very much greater than the glass transition temperature (Tg) of the thermoplastic, and comparatively cooler annular regions (4B, 4D, 4F, 4H), the temperature of which is close to the glass transition temperature (Tg); and - a forming step in which a pressurized fluid is injected into the preform (2) thus heated, this step resulting in 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 FR2 703 944 (and its equivalent US...

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Problems solved by technology

[0005] However, tests have revealed that, even with the application of the technique described in patent FR2 703 944, 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 that of the main body The creation of an annular part of the temperature of the rest 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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