MXPA98004744A - Preforma for the manufacture of containers of thermoplastic material with an inter division - Google Patents

Abstract

The present invention relates to a preform (9) of thermoplastic material having a body (11) provided with an internal division (10) of longitudinal extension at least partial and intended for manufacturing by molding, especially by blow or by stretching - blown, a container whose body has opposite areas that form two hollow spaces with convexity directed inward and subject by said internal division, characterized in that the body (11) of the preform (9) presents, in cross section, a shape contour not to circulate with two opposite zones (a, b) separated from each other by a minimum distance (d1) lower than the distances separating the other two zones from two opposite of said contour, because the inner division (10) extends between said two opposite zones (a, b) separated by a minimum distance (d1) and because said minimum distance (d1) is chosen such that, with respect to the perimeter of the body (11) of the preform, after the mo ldeo, the internal division (10) undergoes a transverse stretching regime that is substantially of the same value as the transverse or perimetric stretching regime suffered by the body (1).

Description

PREFORMA FOR THE MANUFACTURE OF CONTAINERS OF THERMOPLASTIC MATERIAL WITH AN INTERIOR DIVISION The present invention relates to improvements made to preforms of thermoplastic material having a body provided with an internal division of longitudinal extension at least partial and intended for the manufacture by molding, especially by blow or by blown stretch, of a container whose The body has opposite zones that form hollow depressions with convexity directed inwards and which are separated by said internal division. It is known to provide an interior partition to containers, especially bottles, of thermoplastic material such as PET polyethylene terephthalate, PEN polyethylene naphthalate, or others. Such a division can be total, that is, extended over the entire height of the container, to divide the interior volume of the container into two chambers that enclose two respective liquids that must not be mixed before being poured. As shown in Figure 1 of the accompanying drawing, the division 1 may also be partial, ie not extend beyond a part of the length of the body 2 of the container 3, to retain (hold) two opposite areas of the body of the container , for example to maintain two hollow apprehensions 4 in the body of a container filled with a liquid under pressure, depressions that, if not reinforced, risk deforming under the action of liquid pressure. It is known to manufacture such containers from preforms provided with an internal division, of total or partial longitudinal extension according to the type of final container to be obtained. Such a preform 5 with an internal division 6 of partial longitudinal extension, intended for the manufacture of the container of Figure 1, is shown in Figures 2 and 3 of the annexed drawing, in top view in cross-section according to line II-II of Figure 2. It has a general structure analogous to that of a preform without division with a neck 7 and a body of thick wall 8 that are formed in the classical manner. The inner division 6 has a thickness substantially lower than that of the thick wall of the body. When this known preform is subjected, after heating, to a stretch or stretch-blow process for obtaining a container, the internal separation undergoes a stretch in the same way as the body wall: the longitudinal stretch regime of the division is identical to the one suffered by the body (for example, to fix the ideas, typically from 2.22 to 3.5 for the polyethylene terephthalate grades used industrially today). On the other hand, when the body of the container to be obtained must have a localized transverse shrinkage - for example distance between the bottom of the apprehension spaces 4 of the container of Figure 1, the transverse stretch rate of the division is locally much lower than the transverse (or perimeter) stretch regime of the container body: to fix the ideas , the system of transversal or perimetric stretching of the body is in general at least of the order of 4, while the transverse stretching regime suffered by the division is here less than 4. It results in a disadvantageous difference of the characteristics of the material of the division and of the material of the body of the container: its material that has suffered an insufficient transverse elongation, to fully orient the molecular chains, the division is subjected to deformation when the container is subsequently subjected to severe conditions of use and is no longer able to effectively ensure its clamping function. The object of the invention is precisely to remedy this drawback and propose a technical solution that allows, during the blowing or stretching-blowing process, a transverse elongation regime substantially identical for the body of the preform and for the internal division, so that the constituent materials of one and the other have substantially similar physical and mechanical characteristics and behave in a homogeneous manner.

For these purposes and referring to Figures 4 and 5 of the accompanying drawing which illustrate respectively, in top view in cross section and on a scale substantially greater than that of Figure 3, two possible embodiments of a preform according to the invention that are given by way of non-limiting examples, a preform 9 as indicated in the preamble is essentially characterized, provided according to the invention, because its body 11 presents in cross-section, a non-circular contour with two opposite areas a and b separated from one another by a minimum distance dx and because said minimum distance dx is chosen so that, with respect to the perimeter of the body 11 of the preform, after molding, the internal division 10 undergoes a transverse stretch regime that is substantially of the same value as the regime of transverse (or perimetric) stretch suffered by the body. From the fact that, on the other hand, the correct development of the blow molding or stretch-blow molding process practically excludes the use of the preforms having a geometrically complex body, advantage will be taken of a preform 9 whose body 11 has a maximum transverse dimension d3, considered parallel to the inner division 10, which is substantially lower than its maximum transverse dimension d2, considered substantially perpendicular to the inner division 10, the The proportion of said transverse dimensions d3 and d2 is such that, after molding, the internal division 10 undergoes a transverse stretching regime that is substantially identical to the transverse stretching regime suffered by the body. Although other arrangements could be considered in principle, it is simpler, and sufficient for most practical applications, for the division 10 to extend centrally in a plane of symmetry of the body 11. It is desirable that the use of preforms according to the invention do not involve more than minimal adaptations of the manufacturing facilities of the containers for obtaining final containers of given shapes and characteristics (dimensions, thickness of walls, thermal resistance, etc.). However, the methods of use of the manufacturing process and the mentioned characteristics of the final containers depend on the characteristics of the initial preform, and in particular on the geometric dimensions of its body (perimeter, wall thickness, etc.). Thus a minimal modification of the manufacturing conditions and the manufacturing facilities to achieve a given container implies that the preform according to the invention retains the fundamental characteristics of the previous preforms for the exploitation of which the current manufacturing facilities are known. It is so in particular for the perimeter of the body. It is thus desirable in practice that, whatever the geometrical shape given to the body of the preform, the perimeter of the cross section of said body 11, at least in the part thereof equipped with an internal division, retains a value substantially analogous to the of the perimeter of the 8 cylindrical body of revolution of the traditional preform, while the internal division 10 is, in accordance with the above-discussed provisions of the invention, less large than the division 6 of the previous preforms. With this, the body 11 of the preform 9 arranged according to the invention can receive any shape that satisfies this basic condition. In particular, the body may be cylindrical, with especially an oval or elliptical cross-section as shown in Figure 4; the aforementioned two zones a and b are then the parts with the largest radius of curvature and the inner division 10 extends along the minor axis of the oval or of the ellipse, the previously mentioned distances dx and d2 are then identical. It is also possible to provide, as shown in Figure 5, a body with bilobal contour, the division 10 extends between the two lobes 12; the previously mentioned zones a and b are here the angled connecting parts of the two lobes. To facilitate the stretching process and reinforce the container, it is desirable that the division 10 be connected to the the wall of the preform by rounding the relatively large radius as shown in Figures 6 and 7 corresponding respectively to Figures 4 and 5. In the same manner as for the previous preforms, the interior partition may have a total longitudinal extension or partial with respect to the body of the preform. In the case of a partial division, it can optionally be provided that the particular shape given to the body 11 of the preform according to the invention does not extend longitudinally more than in correspondence with the division and that, for the rest of its longitudinal extension, the body is cylindrical of revolution as for a classical preform. Thanks to the arrangements adopted in accordance with the invention, an improved preform is made that is suitable for driving to a final container with internal division having the homogeneous characteristics and which is able to withstand, during its use, the thermal restrictions and / or mechanical parts without a noticeable deformation of the body assembly, and comprising areas of the body that were previously subject to deformation under the action of pressure filling fluid under pressure and that are now correctly retained by the correctly stretched and Conveniently satisfies its clamping function. As is evident and as is already apparent from the foregoing, the invention is not limited in any way to these modes of application and implementation that were considered more particularly; it covers, on the other hand, all the variants.

Claims (8)

1. Preform (9) of thermoplastic material having a body (11) provided with an internal division (10) of longitudinal extension at least partial and intended for manufacturing by molding, especially by blowing or by stretching, -spopping, of a container whose body has opposite areas that form two hollow spaces with convexity directed inward and subject by said internal division, characterized in that the body (11) of the preform (9) presents, in cross section, a contour of non-circular shape with two opposite zones (a, b) separated from each other by a minimum distance (d less than the distances separating the other zones two from two opposite of said contour, because the inner division (10) extends between said two opposite zones (a, b) separated by a minimum distance (dx) and because said minimum distance (dx) is chosen such that, with respect to the perimeter of the body (11) of the preform, after molding, the internal division (10) suffers a transverse stretching regime that is substantially of the same value as the transverse or perimetric stretching regime suffered by the body (11).

2. Preform according to claim 1, characterized in that the body (11) has a maximum transverse dimension (d3) considered parallel to the internal division that is substantially less than the maximum transverse dimension (d2) considered substantially perpendicular to the internal division, the proportion of said transverse dimensions (d3, d2) is then such that, after molding, the internal division (10) undergoes a transverse stretching regime that is substantially identical to the transverse stretching regime suffered by the body (11).

Preform according to claim 1 or 2, characterized in that the inner division (10) extends centrally in a plane of symmetry of the body (11).

4. Preform according to any of claims 1 to 3, characterized in that, at least in its part of correspondence with the internal division (10), the body (11) has a cylindrical contour.

Preform according to claims 3 and 4, characterized in that the cross section of the body (11) is approximately oval or elliptical, with the internal division (10) extending substantially along the minor axis of the oval or the ellipse.

6. Preform according to any of claims 1 to 3, characterized in that the body (11) has a contour of two lobes (12), the inner division (10) extends between the two lobes (12).

7. Preform according to any of claims 1 to 6, characterized in that the internal division extends over the entire length of the body (11).

8. Preform according to any of claims 1 to 6, characterized in that the internal division (10) extends only over a part of the length of the body (11) and because, in its part not provided with internal division, the body (11) is cylindrical of revolution.