Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Differential temperature conditioning
Patent
1995-10-13
1997-10-28
Timm, Catherine
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Differential temperature conditioning
425526, B29C 4968
Patent
active
056815212
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns improvements introduced in the heat treatment of the body of a preform or of an intermediate-stage container made of a thermoplastic material, this treatment being carried out during the process of manufacture of a container, such as a flask or bottle, in particular by blowing or stretching-blowing, during which heat treatment the preform, while being made to rotate on itself, travels through a heating furnace.
There exist manufacturing processes involving a single blowing operation. Starting with an injection-produced preform, these processes consist in heating this preform and then injecting it and, potentially stretching it, so as to produce the final container.
There also exist processes which entail several distinct blowing and/or stretching/blowing operations. Beginning with an injected preform, these operations consist in effecting a first blowing operation to produce an intermediate container, which is, in turn, reheated and blown once again to produce the final container. A process of this kind and the various steps involved therein is described in Patents Nos. EP-A-0 442 836 and U.S. Pat. No. 5, 229, 042, held by the Applicant. To introduce some precision into the discussion, FIG. 1, attached, illustrates the diagrammatic shapes obtained during a process comprising two successive blowing and/or stretching-blowing operations and carried out under the conditions indicated in the aforementioned documents: i.e., the initial preform 1 (which is molded or injected) is transformed by a first blowing and/or stretching-blowing operation into a longitudinally- or transversely-oversized container 1.sub.1, which then undergoes heat treatment which, by virtue of the release of stresses, produces an intermediate, contracted container 1.sub.2. After heating, the latter is then, in turn, subjected to a second blowing or stretching-blowing operation, at the end of which the final container 1.sub.3 is obtained.
As illustrated in the attached drawings, with respect to a container preform 1, whether molded or injected, comprising a substantially cylindrical thick-walled body generated by rotation and, at one end, a hemispherical thick-walled bottom 3 and, at the other, a neck 4 incorporating its final shape and dimensions, the aforementioned preliminary heating operation consists in heating the body alone of the preform (excluding the neck) to a temperature greater than the vitreous transition temperature Tg of the thermoplastic material making up the preform.
In practice, heating is carried out by causing the preforms to travel in an oven 5 comprising at least one lateral heating wall (incorporating, for example, heating tubes 6 attached to the oven wall), while at the same time causing the preforms to rotate on themselves (arrow 7) so as to make the temperature within the material uniform. Protective means, i.e., shields 8 in the form of parallel tracks, ensure heat protection of the neck 4. A reflecting panel 9 may preferably be positioned opposite the tubes 6 to reflect back toward the bodies 2 of the preforms the fraction of the thermal radiation passing between two successive bodies.
When containers are produced having bodies that are approximately cylindrical and generated by rotation, the subsequent blowing or stretching-blowing process, which is performed in a mold on a heated preform or on the intermediate container, causes substantially uniform stretching of the heated, softened thermoplastic material in all radial directions (determined in relation to the preform axis). In this case, a container body possessing an even, uniform structure and a lateral wall having substantially constant thickness is produced.
However, problems arise when attempts are made to deviate from this conventional process.
First, difficulties are encountered when the final container is not approximately cylindrical and generated by rotation: for example, containers having a polygonal transverse section, whether triangular, quadrilateral, or pentagonal in particular, in wh
REFERENCES:
patent: 3775524 (1973-11-01), Seefluth
patent: 3950459 (1976-04-01), Seefluth
patent: 4147487 (1979-04-01), Dickson et al.
patent: 4151249 (1979-04-01), Lee
patent: 4657502 (1987-04-01), Rydmann
patent: 4928835 (1990-05-01), Collette et al.
patent: 5229042 (1993-07-01), Denis et al.
patent: 5256341 (1993-10-01), Denis et al.
Emmer Gerard
La Barre Paul
Sidel
Timm Catherine
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