CONTAINER PREFORM MADE OF PLASTIC

Abstract

The invention relates to a container preform made of plastics material having a body exhibiting symmetry of revolution about a central axis and a bottom closing the body from one of its ends. The bottom having an annular bead forming a standing plane of the preform, and the bottom has an external skin oriented toward the outside of the preform and an internal skin oriented toward the inside of the preform. At least one of the internal skin and the external skin has, radially from the central axis as far as the annular bead, a profile having a break in curvature.

Claims

1. A container preform (1) made of plastics material, comprising: a body (3) exhibiting symmetry of revolution about a central axis (X); and a bottom (4) closing the body (3) from one of its ends, the bottom (4) having an annular bead (8) forming a standing plane of the preform (1), the bottom (4) having an external skin (Pe) oriented toward the outside of the preform (1) and an internal skin (Pi) oriented toward the inside of the preform (1), the preform having a joint plane (12) at an intersection between the bottom (4) and the body (3), the joint plane (12) having a thickness (EP), wherein: at least one of the internal skin (Pi) and the external skin (Pe) has, radially from the central axis (X) as far as the annular bead (8), a profile having a break in curvature, and a first portion (9) of the profile has a diameter (d) less than or equal to 40% of a diameter (D) of the preform (1) at the joint plane (12).

2. The container preform (1) as claimed in claim 1, wherein the profile comprises, from the central axis (X) as far as the annular bead (8): the first portion (9) having a first radius of curvature; a second portion (10) extending the first portion (9) and having a second radius of curvature; a third portion (11) extending the second portion (10) and having a third radius of curvature, the break in curvature being formed by the second radius of curvature exhibited by the second portion (10).

3. The container preform (1) as claimed in claim 2, wherein the second radius is less than 9 mm.

4. The container preform (1) as claimed in claim 2, wherein the first portion (9) of the profile has a flat, concave or convex shape.

5. The container preform (1) as claimed in claim 1, wherein the profile has a maximum height (H), measured along the central axis (X), greater than or equal to 5% and less than or equal to 40% of the thickness (EP) of the joint plane (12).

6. The container preform (1) as claimed in claim 5, wherein the profile of the internal skin (Pi) has a maximum height (Hi) different from the maximum height (He) of the profile of the external skin (Pe).

7. The container preform (1) as claimed in claim 1, wherein the bottom (4) has a thickness (EF) greater than or equal to 60% and less than or equal to 100% of the thickness (EP) of the joint plane (12).

8. The container preform (1) as claimed in claim 7, wherein the thickness (EF) of the bottom (4) is greater than or equal to 70% and less than or equal to 90% of the thickness (EP) of the joint plane (12).

9. The container preform (1) as claimed in claim 1, wherein the first portion (9) of the profile has a diameter (d) greater than or equal to 3 mm.

10. The container preform (1) as claimed in claim 1, wherein the profile of the internal skin (Pi) is parallel to the profile of the external skin (Pe).

11. The container preform (1) as claimed in claim 3, wherein the first portion (9) of the profile has a flat, concave or convex shape.

12. The container preform (1) as claimed in claim 2, wherein the profile has a maximum height (H), measured along the central axis (X), greater than or equal to 5% and less than or equal to 40% of the thickness (EP) of the joint plane (12).

13. The container preform (1) as claimed in claim 3, wherein the profile has a maximum height (H), measured along the central axis (X), greater than or equal to 5% and less than or equal to 40% of the thickness (EP) of the joint plane (12).

14. The container preform (1) as claimed in claim 4, wherein the profile has a maximum height (H), measured along the central axis (X), greater than or equal to 5% and less than or equal to 40% of the thickness (EP) of the joint plane (12).

15. The container preform (1) as claimed in claim 2, wherein the bottom (4) has a thickness (EF) greater than or equal to 60% and less than or equal to 100% of the thickness (EP) of the joint plane (12).

16. The container preform (1) as claimed in claim 3, wherein the bottom (4) has a thickness (EF) greater than or equal to 60% and less than or equal to 100% of the thickness (EP) of the joint plane (12).

17. The container preform (1) as claimed in claim 4, wherein the bottom (4) has a thickness (EF) greater than or equal to 60% and less than or equal to 100% of the thickness (EP) of the joint plane (12).

18. The container preform (1) as claimed in claim 2, wherein the first portion (9) of the profile has a diameter (d) greater than or equal to 3 mm.

19. The container preform (1) as claimed in claim 3, wherein the first portion (9) of the profile has a diameter (d) greater than or equal to 3 mm.

20. The container preform (1) as claimed in claim 2, wherein the profile of the internal skin (Pi) is parallel to the profile of the external skin (Pe).

Description

[0068] Other features and advantages of the invention will become more clearly apparent on reading the following description of various preferred embodiments of the invention, which are given by way of illustrative and non-limiting example, and the appended drawings in which:

[0069] FIG. 1 is a perspective view of a preform according to the invention, having an inset of details on an enlarged scale;

[0070] FIG. 2 is a schematic view of a profile of an internal or external skin of a preform according to the invention;

[0071] FIG. 3 is a schematic representation in section of a preform according to the invention, according to a first embodiment;

[0072] FIG. 4 is a schematic representation in section of a preform according to the invention, according to a second embodiment;

[0073] FIG. 5 is a schematic representation in section of a preform, according to a third embodiment;

[0074] FIG. 6 is a schematic view in section of a preform in a mold during a stretch-blow-molding phase.

[0075] FIG. 1 illustrates a preform 1 made of plastics material according to the invention. This preform 1 is used for producing containers made of plastics material.

[0076] The preform 1 comprises: [0077] a neck 2; [0078] a body 3; [0079] a bottom 4.

[0080] More precisely, the body 3 has, at a first end, the neck 2 from which it is separated by a flange 5 and, at an opposite second end, the bottom 4 which closes the preform 1.

[0081] As illustrated in FIG. 1, the neck 2 comprises a screw thread 6 allowing a cap to be attached when the preform has been transformed into a container and the latter has been closed and filled, and a bead 7 forming retaining means for retaining a tamperproof ring secured to a cap (not shown).

[0082] The preform 1 is essentially a cylinder of revolution about a central axis X.

[0083] More particularly, the body 3 and the bottom 4 are advantageously cylinders of revolution about the central axis X.

[0084] The neck 2, for its part, partially exhibits symmetry of revolution about the central axis X, only the screw thread 6 is not symmetrical.

[0085] As illustrated in FIGS. 3, 4 and 5, when it is viewed in section, the preform 1 has an internal skin Pi and an external skin Pe.

[0086] By way of illustrative and non-limiting example, the preform is made of PET, the glass transition temperature of which is about 75 degrees.

[0087] Still with reference to FIGS. 3, 4 and 5, the bottom 4 has an annular bead 8 forming a standing plane of the preform 1.

[0088] More precisely, this annular bead 8 forms a continuous line describing a circle, or in exceptional cases an ovoid shape depending on the overall shape of the preform.

[0089] With reference to FIG. 2 which illustrates a skin P of the preform 1, independently of whether it concerns an internal skin Pi or an external skin Pe, the skin P has, radially, from the central axis X as far as the annular bead 8, a profile having a break in curvature.

[0090] What is denoted by a break in curvature is a break in the profile of the skin P.

[0091] In other words, the profile is not realized by one line having a single radius of curvature, but comprises several lines each having its own radius of curvature.

[0092] More precisely, and as is generally implemented in the prior art, the internal skin Pi or the external skin Pe defines a generally single curve. The presence of the break therefore divides this curve into at least two portions each having a different radius.

[0093] Still with reference to FIG. 2, the profile comprises, from the central axis X as far as the annular bead 8: [0094] a first portion 9 having a first radius of curvature; [0095] a second portion 10 extending the first portion 9 and having a second radius of curvature; [0096] a third portion 11 extending the second portion 10 and having a third radius of curvature.

[0097] The break in curvature is then formed by the second radius of curvature exhibited by the second portion 10.

[0098] According to a preferred embodiment, the second radius of curvature is less than or equal to 9 mm.

[0099] Such a value makes it possible to create the break in curvature in such a way as to implement a real and clear distinction between the first portion 9 and the third portion 11.

[0100] More precisely, the second portion 10, by way of its second radius, makes it possible to prevent a continuity of radius between the first portion 9 and the third portion 11.

[0101] More particularly, by extending, in a hypothetical manner, the first portion 9 and the third portion 11, it is possible to observe an intersection between the extensions thereof. This intersection is unique and not realized by a colinearity as would have been the case in the absence of the second portion 10 or by way of a second portion 10 having a radius of curvature equal to the first radius of curvature and/or to the third radius of curvature, and having a center of radius of curvature identical to the first radius of curvature and/or to the third radius of curvature.

[0102] The break in curvature may also be defined by a center of radius of curvature of the second portion 10 separate from the center of radius of curvature of the first portion 9 and/or of the third portion 11.

[0103] Thus, by way of this distinction between the centers of radii of curvature, it is impossible to have a continuous profile between the first radius of curvature and the third radius of curvature. More precisely, the profile is necessarily marked by a break in curvature by virtue of the distinction between the centers of radii of curvature.

[0104] The first portion 9 of the profile has a flat, concave or convex shape.

[0105] With reference to FIG. 5, the preform has a joint plane 12 at an intersection between the bottom 4 and the body 3, the joint plane 12 having a thickness EP.

[0106] With reference to FIG. 2, the profile has a maximum height H measured along the central axis, which height H is greater than or equal to 5% of the thickness EP of the joint plane 12 and less than or equal to 40% of said thickness EP of the joint plane 12.

[0107] According to the embodiments illustrated in FIGS. 3 to 5, the profile of the internal skin Pi has a maximum height Hi equal to the maximum height He of the profile of the external skin Pe (so as not to complicate the figures, the references He and Hi are visible only in FIG. 4).

[0108] In a variant, the profile of the internal skin Pi has a maximum height Hi different from the maximum height He of the profile of the external skin Pe.

[0109] Furthermore, the first portion 9 of the profile has a diameter d greater than or equal to 3 mm.

[0110] Preferably, and in any event, the diameter d of the first portion 9 of the profile is less than or equal to 40% of a diameter D of the preform 1 at the joint plane 12, as is illustrated in FIG. 5.

[0111] In other words, the radius measured between the central axis X and the second portion 10 is preferably greater than or equal to 1.5 mm and less than or equal to 20% of the diameter D.

[0112] As illustrated in FIGS. 3 and 5, the profile of the internal skin Pi is parallel to the profile of the external skin Pe.

[0113] In other words, the internal skin Pi and the external skin Pe have a homothety of degree 1.

[0114] By contrast, as is illustrated in FIG. 4, the internal skin Pi and the external skin Pe are at least partially parallel to one another, the bottom 4 of the preform 1 and more particularly the internal skin Pi and the external skin Pe then have a homothety of degree greater than degree 1.

[0115] According to a first embodiment illustrated in FIG. 3, the first portion 9 of the internal skin Pi and the first portion 9 of the external skin Pe both have a concave shape oriented toward the inside of the preform 1.

[0116] According to a second embodiment illustrated in FIG. 4, the first portion 9 of the internal skin Pi and the first portion 9 of the external skin Pe both have a convex shape oriented toward the inside of the preform 1.

[0117] According to a third embodiment illustrated in FIG. 5, the first portion 9 of the internal skin Pi and the first portion 9 of the external skin Pe are both flat.

[0118] It is of course possible for other embodiments to be used. By way of example, the internal skin Pi may have a convex shape over its first portion 9 and the first portion 9 of the external skin Pe may have a concave shape.

[0119] In contrast, the first portion 9 of the external skin Pe may have a convex shape and the first portion 9 of the internal skin Pi may have a concave shape.

[0120] According to another embodiment that is not illustrated, one of the first portion 9 of the external skin Pe and the first portion 9 of the internal skin Pi has a flat, concave or convex shape, and the other of the first portions 9 of the external skin Pe and of the internal skin Pi has a different shape.

[0121] With reference to FIG. 3, the bottom 4 has a thickness EF, measured along the central axis X between the internal skin Pi and the external skin Pe, greater than or equal to 60% of the thickness EP of the joint plane 12 and less than or equal to 100% of said thickness EP of the joint plane 12.

[0122] Preferably, the thickness EF of the bottom 4 is greater than or equal to 70% of the thickness EP of the joint plane 12 and less than 90% of the thickness EP of the joint plane 12.

[0123] As illustrated in FIG. 5, the bottom 4 of the preform thickens from the annular bead 8 as far as the joint plane 12.

[0124] The bottom 4 of the preform according to the invention makes it possible, notably by virtue of its break in curvature: [0125] to prevent the bottoms of containers from collapsing upon exiting a blow-molding mold; [0126] to optimize the centering of the preform 1 on the bottom of a mold M and/or the centering of a stretching rod T, T′ on the bottom of the preform, during a stretch-blow-molding phase, as illustrated in FIG. 6; [0127] to improve the performance of the containers formed with respect to internal or external mechanical stresses on the container; [0128] to increase the production rates of containers.

[0129] With reference to FIG. 6, two variants of stretching rods T, T′ are shown. A first variant (reference T) makes it possible to press the plastics material of the preform 1 against the mold M. A second variant (reference T′) makes it possible, in addition, to reinforce the centering of the preform 1 by surrounding the first portion 9, the second portion 10 and at least partially the third portion 11 of the bottom 4.

[0130] More particularly, the break in curvature forms a reinforcement making it possible to limit the collapse of the bottom of the container, and notably of the bottom of the arch of the container, said arch being formed by the first portion 9 of the preform 1. Specifically, the break in curvature forms a means for arresting the collapse of the bottom of the container and makes it possible to maintain an arch in the container. This limitation of the collapse is enhanced by the physical memory of PET.

[0131] Such a collapse occurs notably when the bottom of the container has not been cooled sufficiently upon exiting the mold, such a lack of cooling generally coinciding with too short a contact time between the plastics material and the mold during the manufacture of the container, and more precisely during the blow-molding or stretch-blow-molding step.

[0132] The offset formed by the first portion 9, the second portion 10 and the third portion 11 of the profile of the external skin Pe with the annular bead 8 of the preform 1 makes it possible to ensure that the preform 1 is centered on the bottom of the mold M during the stretch-blow-molding phases. To this end, the mold M may notably have a projection with the impression of the annular bead 8 of the preform 1 or of the profile of the external skin Pe of the preform 1 so as to allow the shapes of the preform 1 and the bottom of the mold M to cooperate.

[0133] Finally, the blow-molding rates may be increased by virtue of the preform 1 according to the invention since, even in the absence of prolonged contact between the material and the mold during the blow molding or stretch blow molding, the deformation of the bottom of the container upon exiting the mold is controlled and/or limited, thus allowing the container to be used in spite of a risk of deformation, since the avoidance of the collapse of the bottom allows the container to maintain its stability on a standing plane. In addition, the deformation of the bottom may be barely perceptible for the user depending on the value of the radii of curvature of each of the first portion 9, the second portion 10 and the third portion 11 of the preform 1.