The container bottom base is provided with a double concave arch

Abstract

A plastic container (1) having a main axis (X) and comprising a body (5) and a bottom base (6) extending from the lower end of the body (5), the bottom base (6) comprising: a peripheral seat (7) defining a resting surface (8); a concave arch (10) extending from the periphery of a central section (11) of the bottom base (6) to the peripheral seat (7) and having a rounded outline with a concave surface facing outwards from the container (1); and a series of main reinforcing grooves (13) extending radially from the central section (11) at least to the peripheral seat (7). The concave arch (10) comprises two tangentially continuous annular concentric regions, namely a central region (15) and a peripheral region (16), which are continuous with one another and exhibit two different radii of curvature, the peripheral region (16) having a radius of curvature smaller than that of the central region (15). [Selected figure] Figure 3

Description

[Technical Field]

[0001] The present invention relates to improvements made to containers, in particular bottles or jars, which can be obtained by blowing, blow moulding or stretch blow moulding of preforms made of thermoplastic materials such as PET (polyethylene terephthalate), PE (polyethylene), PEF (polyethylene furanoate) or other suitable thermoplastic materials. [Background technology]

[0002] The production of containers by blow molding usually consists of inserting a preform, preheated above the glass transition temperature of the material, into a mold in which the container is engraved, and injecting a fluid (particularly a gas such as air, but also an incompressible fluid such as water) into the preform under pressure. Blowing can be completed by pre-stretching the preform with a sliding rod.

[0003] The double molecular orientation (bidirectional) that the material undergoes during blow molding (axial and radial, respectively parallel and perpendicular to the general axis of the container) gives the container a particular structural rigidity.

[0004] Such containers have a body extending between a neck at the top and a base at the bottom, the base being adapted to withstand hydrostatic pressure resulting from a column of liquid rising above the base and neck without significant deformation.

[0005] Containers intended to contain stationary liquids (e.g., bottles intended to contain drinking water) are most often provided with a spherical crown having an outwardly concave surface and a rounded bottom base of a generally low height. Such bases are often provided with substantially radially extending ribs distributed around the central concave surface, said ribs sometimes having various shapes and optionally extending below the wall of the body to reinforce the base (the surrounding section used to rest the base on a support).

[0006] In addition to withstanding the hydrostatic pressure resulting from the liquid column rising above them, such bases should also provide sufficient resistance to any additional stresses, however small, that may result from excessive internal pressure due to, for example, storage conditions.

[0007] In fact, when containers are stored in high heat, typically outdoors on pallets in direct sunlight, the temperature of the contents can reach or even exceed 50°C, causing the contents to expand and creating a pressure that exceeds a threshold, causing the base to invert, making the container unstable and increasing the risk of the entire pallet collapsing.

[0008] Similarly, if the container is stored in a refrigerator at temperatures that cause the contents to freeze, the freezing-induced expansion can cause the bottom base to invert, thus making the container unstable.

[0009] In addition to the above problems, manufacturers of thermoplastic containers such as PET are constantly seeking to make their containers lighter, which is reflected above all in the lighter weight of the container base, so that the bottom base of the container, which was a satisfactory shape a few years ago, is no longer suitable due to the considerable reduction in the amount of material used, or even the absence of such material.

[0010] Solutions have been envisaged which propose increasing the mechanical strength of the bottom base, but although this is effective, it requires both an increase in material which is incompatible with the aforementioned demand for lighter weight and high blowing pressures, which reduce the blowing capacity of the container (i.e. the ability of the container to be formed by blowing).

[0011] For several years, manufacturers have been working to find the best compromise between light weight, rigidity and resistance of the container. One option is to work on optimizing the structure and geometry of the container base.

[0012] A first object of the invention is therefore to propose a container in which the optimized structure and geometry of the base gives the container a good compromise between blowability, lightness and rigidity.

[0013] A second objective is to propose a container with a base that offers good resistance to inversion, dents (irreversible local deformation) and palletization, and that remains stable even under high pressure conditions and / or large internal volumes. Summary of the Invention

[0014] In this regard, the present invention provides a container as claimed in claim 1, said container being made of plastic and comprising a body and a bottom base, the bottom base having a concave arch presenting two tangentially successive annular concentric regions, one of said regions having a smaller radius of curvature than the other region.

[0015] In fact, the bottom base of the container of the invention comprises a peripheral seat defining a resting surface, a concave arch extending from the periphery of a central section of the bottom base to the peripheral seat and having a rounded outline with a concave surface facing the outside of the container, and a series of main reinforcing grooves extending radially from the central section at least to the peripheral seat. According to the invention, the concave arch comprises two tangentially continuous annular concentric regions, namely a central region and a peripheral region, said tangentially continuous annular concentric regions being mutually continuous and exhibiting two different radii of curvature, the peripheral region having a smaller radius of curvature than the central region.

[0016] The proposed bottom base makes it possible to propose a bottle with higher performance than the bottles currently on the market and tested, including better dent resistance, resistance to internal pressure and pallet stability.

[0017] A variety of additional structural features may be provided in the base of the claimed container. These additional features may be provided singly or in combination.

[0018] For example, the central region of the concave arch has a height defined as the height from the imaginary intersection of the central region of the concave arch and the major axis of the container to the resting surface.

[0019] More specifically, the height of the central region of the concave arch may be in the range of 3 mm to 10 mm.

[0020] According to a further feature, the central region of the concave arch has a radius of curvature about the major axis of the container.

[0021] In addition to the above characteristics, the radius of the peripheral region of the concave arch falls within the range of 3 mm to 8 mm. The center of the circle representing the radius does not have to be located at the center of the bearing surface.

[0022] This peripheral area of ​​concave arch increases the rigidity of the bottom base against low internal pressures caused by heat during storage or transport.

[0023] In a particular manner, the peripheral seat of the bottom base of the container of the invention has a width ranging from 0.7 mm to 5 mm. These values ​​of the width of the peripheral seat are smaller than the usual values ​​occurring in the same kind of bottom base. This feature contributes to the resistance of the bottom base to inversion due to internal pressure.

[0024] According to one possible option, the main reinforcing groove of the bottom base has a curvature that is continuous in the tangential direction and concentric with the central and peripheral regions of the concave arch.

[0025] This type of configuration allows for better performance than the currently tested bottom base for a 5mm deflection top load test. Performance is improved by 10-15%.

[0026] This also improves dent and pressure resistance, for example to pressures up to 1 bar.

[0027] As an additional feature, the main reinforcing groove has a depth that falls within the range of 1.5 mm to 3.5 mm.

[0028] The proposed depth of the main reinforcement groove allows to push the boundary of the groove fracture when pressure is applied. The result is a better result compared to the tested bottom base, with a score of +25%.

[0029] According to an additional structural feature, the main reinforcing groove has an opening angle that falls within the range of 40° to 80°.

[0030] According to a further possible feature, the bottom base of the claimed container comprises intermediate reinforcing grooves respectively arranged between two main reinforcing grooves.

[0031] The use of an intermediate reinforcing groove allows for a reduction in the surface with flat structures in the base, thereby strengthening the bottom base of the container and making it more resistant to pressure and dents.

[0032] In one possible arrangement, the intermediate reinforcing groove extends from the central region of the concave arch to at least the peripheral seat.

[0033] The fact that the bottom base has a fully structured surface contributes to avoiding inversion of the bottom base and to withstanding pressure.

[0034] As a further option, the main reinforcing groove and / or the intermediate reinforcing groove extend locally across the peripheral seat and also rise across the bottom base of the container towards the body of the container.

[0035] This feature makes it possible to have good resistance to lateral dents.

[0036] More specifically, the main reinforcing groove and / or the intermediate reinforcing groove rises toward the body of the container to a height within the range of 9 to 15 mm relative to the placement surface.

[0037] As a further characteristic of the claimed container, it can be mentioned that the central section has a hemispherical shape with a radius of 8 to 15 mm centered on the container axis and has a height relative to the support surface that falls within the range of 6 to 16 mm.

[0038] The central section with the proposed radius dimension is able to break up the amorphous material located at the bottom end of the preform during the blow molding process, thus contributing to a better distribution of the plastic material during the bidirectional movements (stretching and blowing), which directly affects the score obtained during the drop test carried out on the container.

[0039] Various additional features of the presented features may be provided alone or in combination with the features set forth in the proposed claims.

[0040] The invention will now be further described with reference to the following examples, which it will be understood are in no way intended to limit the invention as claimed.

[0041] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0042] [Figure 1] FIG. 1 is an overall view of a plastic container. [Figure 2] 2 is a bottom view of the container of FIG. 1 showing the bottom base according to the present invention. [Figure 3] FIG. 3 is a perspective view illustrating the bottom of the container of FIG. 2. [Figure 4] FIG. 4 is a front view of the bottom base of the container of FIGS. 2 and 3. [Figure 5] 5 is a cross-sectional view of the bottom base taken along line AA of FIG. 4. [Figure 6] FIG. 4 is a simplified cross-sectional view of the concave arch of the bottom base of FIGS. 2 and 3. [Figure 7] FIG. 4 is a detailed cross-sectional view of the main reinforcing groove of the bottom base of FIGS. 2 and 3. DETAILED DESCRIPTION OF THE INVENTION

[0043] As used herein, the words "comprises," "comprising," and similar words should not be construed in an exclusive or exhaustive sense. In other words, they are intended to mean "including, but not limited to."

[0044] Any reference herein to a prior art document should not be taken as an admission that such prior art is well known or forms part of the general knowledge in the art.

[0045] FIG. 1 shows a general view of a container 1, in this example a bottle, made by stretch blow molding of a preform made of thermoplastic material, for example PET (polyethylene terephthalate) or PEF (polyethylene furanoate).

[0046] The container 1 comprises, at its upper end, a neck 2 provided with a mouth 3. In the extension of the neck 2, the container 1 comprises, at its upper part, a shoulder 4 extending in the opposite direction to the neck 2, said shoulder 4 being extended by a side wall or body 5 of substantially cylindrical shape which is circumferentially around the main axis X of the container 1.

[0047] The container 1 further comprises a bottom 6 extending from the lower end of the body 5 opposite the neck 2. The bottom 6 comprises a peripheral seat 7 in the form of an annular ridge extending substantially axially in the extension of the body 5. The seat 7 terminates in a resting surface 8 (also called a seating surface) perpendicular to the axis X of the container 1, said seating surface 8 defining the lower end of the container 1 and enabling it to stand upright on a flat surface.

[0048] The peripheral seat 7 has a width ranging from 0.7 mm to 5 mm. This width of the peripheral seat 7 is smaller than the usual width of the seat of the bottom base. This particular width of the peripheral seat 7 contributes to increasing the resistance of the bottom base 6 to inversion due to pressure. This characteristic can be seen particularly in FIG. 6.

[0049] In FIG. 1, D represents the diameter of the container 1 resting on the seat 8, the term "diameter" covering not only the case where the container 1 (and therefore the bottom 6) has a circular contour (as shown), but also the case where the container 1 has a polygonal contour (e.g. a square), in which case the term "diameter" refers to the diameter of a circle inscribed in said polygon.

[0050] 2 to 7 are collectively described below.

[0051] 2 and 3, which show a bottom view and a perspective view of the bottom base of the container of FIG. 1 in which the features of the present invention are integrated, illustrate the bottom base 6 comprising, from the periphery 7 to the center, the already described peripheral seat 7, the concave arch 10, the central section 11, also called the push-up section, and, located in the center, an amorphous pellet 12 obtained as a result of deformation of the preform.

[0052] The central section 11 has a hemispherical shape with a radius of 8 to 15 mm, and has a height relative to the placement surface 8 that falls within the range of 6 to 16 mm.

[0053] As already indicated, the central section 11 has the function of contributing to a better distribution of the plastic material (especially the amorphous plastic material) in the bottom base during the bidirectional process.

[0054] At the center of the central section 11 is located an amorphous pellet 12, also called the injection point, which corresponds to the section into which the material of the preform used to make the container is injected and which can be used as a centering function during the formation of the container 1 by blowing.

[0055] The concave arch 10 has a rounded general shape that, in an unstressed state, i.e. when no contents are present in the container 1, is in the form of a substantially spherical dome with a concave surface facing outwards from the container 1. The arch 10 extends from the seat 7 to a central section 11 of the base 6, forming a protrusion that projects towards the interior of the container 1.

[0056] According to the invention and as can be seen from the figures, and more particularly from Figures 2, 4 and 6, the arch 10 comprises two annular concentric zones that are tangentially successive, said two concentric zones being: an annular central region 15 surrounding the central section 11 of the bottom base 6; an annular peripheral region 16 surrounding and contiguous with said central region 15; is.

[0057] The two concentric regions 15 and 16 are annular and tangentially continuous, and have two different radii of curvature.

[0058] As shown in FIG. 6, which represents a simplified cross-section of the concave arch 10 (without the reinforcing grooves 13 and 14), two concentric regions 15 and 16 can be visualized, with the peripheral region 16 having a radius of curvature that is smaller than the radius of curvature of the central region 15.

[0059] The central region 15 of the concave arch 10 has a radius of curvature centered on the major axis of the container.

[0060] The central region 15 of the concave arch has a height defined as the height from the imaginary intersection of the central region 15 of the concave arch and the main axis X of the container to the placement surface, which may be within the range of 3 mm to 10 mm.

[0061] The radius of curvature of the peripheral region 16 of the concave arch falls within the range of 3 mm to 8 mm. The center of the circle representing the radius does not have to be located at the center of the bearing surface 8.

[0062] The presence of the peripheral region 16, instead of the commonly used step, allows for better blowing capabilities due to a better "fingerprint" - that is, the thermoplastic resin flows better and comes into contact with the mold more easily during blowing of the container.

[0063] The peripheral region 16 of the concave arch is therefore responsible for stiffening the bottom base against additional pressure caused by heat during storage or transport.

[0064] Under high internal pressure conditions, the contents of the container exert pressure on the crushable bottom base 6. The concave arch 10 with both a central region 15 and a peripheral region 16 improves resistance by providing stiffening of the concave arch 10 in its intermediate region.

[0065] If the pressure becomes too high, the deformation of the bottom base 6 at the location of the concave arch 10 is limited to the peripheral region 16, which deforms towards the resting surface 8 and reunites with the surface of the peripheral seat 7, while the functionality of the central region 15 of the concave arch 10 is maintained.

[0066] As can be seen in the figures, and particularly in Figures 2 and 3, the bottom base 6 comprises a series of main reinforcing grooves 13. Said main reinforcing grooves 13 are recessed towards the interior of the container 1 and extend radially from the central section 11 to at least the peripheral seat 7. According to a preferred embodiment, as shown in the figures, the main reinforcing grooves 13 extend beyond the seat 7 and rise laterally across the lower part of the body 5 of the container 1.

[0067] In other words, the main grooves 13 extend radially over the entire arch 10, over the peripheral seat 7 and over part of the body 5. The seat surface 8 will therefore be understood to be discontinuous, as it is interrupted at each main groove 13. In this example, there are five main grooves 13, but this number may be more, in particular six or seven, for containers with different volumes.

[0068] As can be seen in FIG. 7, the main reinforcing groove 13 has a curvature that is continuous in the tangential direction and concentric with the central region 15 and the peripheral region 16 of the concave arch 10 .

[0069] In this case, continuity of the mechanical resistance of the main reinforcing groove is ensured.

[0070] In the presently proposed embodiment of the invention, the main reinforcing grooves 13 have a depth lying in the range of 1.5 mm to 3.5 mm and an opening angle lying in the range of 40° to 80°.

[0071] The proposed angle range of the opening angle ensures good blowing ability of the main reinforcing groove during the blowing process.

[0072] According to a preferred embodiment, the base 6 is further provided with a series of intermediate reinforcing grooves 14 located between the main grooves 13 and extending locally across the concave arch 10 so as to also contribute to stiffening the bottom base 6. As shown in Figures 2 and 3, the intermediate reinforcing grooves 14, like the main reinforcing grooves 13, extend outward from a central region 15 of the concave arch 10, beyond the peripheral seat 7, and rise laterally across the lower part of the body 5.

[0073] In an alternative embodiment not shown, the intermediate reinforcing groove 14 may extend from the central region 15 to the peripheral seat 7 , but not across the peripheral seat 7 .

[0074] In the presently proposed embodiment of the invention, the intermediate reinforcing grooves 14 are respectively arranged between two main reinforcing grooves 13 .

[0075] Both the main reinforcing groove 13 and the intermediate reinforcing groove 14 rise towards the body 5 of the container at a height relative to the resting surface 8 that is in the range of 9 to 15 mm.

[0076] Figure 5, a cross-sectional view of the base according to the invention (as shown in Figures 2 and 3) along line AA in Figure 4, illustrates the injection point 12, the central section 11 and the concave arch 10 with two tangentially consecutive annular concentric regions, namely the central region 15 and the peripheral region 16.

[0077] The cross-sectional view also illustrates one of the main reinforcing grooves 13 and one of the intermediate reinforcing grooves 14. The location, geometric arrangement and shape differences of the main reinforcing groove 13 and the intermediate reinforcing groove 14 are clearly shown.

[0078] The container 1 provided with the proposed bottom base 6 offers a good compromise between mechanical performance (i.e., the ability to withstand deformation alone, the ability to withstand deformation when palletized, the ability to withstand deformation when deformation occurs, and the ability of the container 1 to undergo deformation in a controlled manner) and blowability (i.e., the ability of the container 1 to be formed by blowing).

[0079] As already mentioned, the resistance of containers and bottles to deformation (inversion and / or dents) and breakage is essential to ensure product stability and to prevent loss during transport, but also to ensure that consumer satisfaction is not adversely affected during bottle handling and consumption. In this context, the bottom base of the containers and bottles plays an important role, particularly related to the stability and resistance of the bottle.

[0080] Comparative testing of pallet stability and dent resistance The objective of this study was to quantify the effect of bottle base weight and type on the overall performance (e.g., resistance) of a 12 g PET cylindrical bottle with a volume of 50 cl and a 25.5 g PET cylindrical bottle with a volume of 1.5 l.

[0081] The tests were performed on conventional bottles, i.e., bottles that are not considered lightweight bottles; however, due to the linearity of performance as a function of the weight of the plastic used to form the bottle, the results obtained in these comparative tests can be extrapolated to lightweight bottom bases.

[0082] The overall performance of the base was evaluated, with particular attention paid to the stability of the pallet and its resistance to dents during transport.

[0083] Four types of bottom bases were compared: Helium, V3, a competitor's base S, and the base proposed by the present invention (V4).

[0084] Helium, V3 and Base S are the bottom bases currently available on the market.

[0085] A complete palette was formed of bottles, all manufactured with a predetermined base.

[0086] For each bottle on the pallet, a visual inspection was evaluated for the following characteristics: - Lateral deformations and dents, - Central deformations and dents, - Bottles tilted at an angle, -Bottles that no longer stand upright,

[0087] The table below shows the percentage of bottles in a full pallet that have the standard value for both volumes tested. [Table 1]

[0088] As can be seen in the table above, the proposed bottom base (V4) performs better than the other tested bases for bottles with two different volumes (50cl and 1.5l) in terms of all tested characteristics. The first proposed optimization should be fully acknowledged.

[0089] Although the present invention has been described by way of example, it should be understood that variations and modifications can be made without departing from the scope of the invention as defined in the claims. Furthermore, where known equivalents exist to specific features, such equivalents are incorporated as if specifically referred to herein. [Explanation of symbols]

[0090] X Container axis 1 container 2 neck 3 Mouth 4 Shoulder 5 Main unit 6 Bottom Base 7 Surrounding seat 8 Placement surface 9 10 Concave Arch 11 Central section (push-up section) 12 Amorphous pellets 13 Main reinforcement groove 14 Intermediate reinforcement groove 15 Central area of ​​concave arch 16 Perimeter of a concave arch D Base diameter

Claims

1. A plastic container (1) having a main axis (X) and comprising a body (5) and a bottom base (6) extending from a lower end of the body (5), The bottom base (6) a peripheral seat (7) defining a resting surface (8); a concave arch (10) extending from the periphery of the central section (11) of the bottom base (6) to the peripheral seat (7) and having a rounded outline with a concave surface facing outwards from the container (1); a series of main reinforcing grooves (13) extending radially from said central section (11) to at least said peripheral seat (7); The container is characterized in that the concave arch (10) consists of two tangentially continuous annular concentric regions, namely a central region (15) and a peripheral region (16), which are mutually continuous concave regions, project inward towards the interior of the container and exhibit two different radii of curvature, the peripheral region (16) having a radius of curvature smaller than that of the central region (15).

2. 2. The container according to claim 1, characterized in that the central region (15) of the concave arch (10) has a height defined as the distance from the imaginary intersection of the central region (15) of the concave arch (10) and the main axis (X) of the container to the placement surface (8).

3. Container according to claim 2, characterized in that the height of the central region (15) of the concave arch (10) lies in the range of 3 mm to 10 mm.

4. Container according to any one of claims 1 to 3, characterized in that the central region (15) of the concave arch (10) has a radius of curvature centred on the main axis (X) of the container (1).

5. Container according to any one of claims 1 to 3, characterized in that the radius of curvature of the peripheral region (16) of the concave arch (10) lies in the range 3 mm to 8 mm.

6. Container according to any one of claims 1 to 5, characterized in that the peripheral seat (7) has a width lying in the range of 0.7 mm to 5 mm.

7. 7. A container according to any one of claims 1 to 6, characterized in that the main reinforcing groove (13) has a curvature that is continuous in the tangential direction and concentric with the central region (15) and the peripheral region (16) of the concave arch (10).

8. Container according to any one of the preceding claims, characterized in that the main reinforcing groove (13) has a depth lying in the range of 1.5 mm to 3.5 mm.

9. Container according to any one of the preceding claims, characterized in that the main reinforcing groove (13) has an opening angle lying in the range of 40° to 80°.

10. Container according to any one of claims 1 to 9, characterized in that it further comprises intermediate reinforcing grooves (14) respectively arranged between two main reinforcing grooves (13).

11. Container according to claim 10, characterized in that the intermediate reinforcing groove (14) extends from the central region (15) of the concave arch (10) at least to the peripheral seat (7).

12. A container as described in claim 10 or 11, characterized in that the main reinforcing groove and / or the intermediate reinforcing groove extend locally across the peripheral seat and also rise across the bottom base of the container towards the main body of the container.

13. Container according to claim 10 or 12, characterized in that the main reinforcing grooves (13) and / or the intermediate reinforcing grooves (14) rise towards the body (5) of the container to a height in the range of 9 to 15 mm relative to the placement surface (8).

14. Container according to any one of claims 1 to 13, characterized in that the central section (11) has a hemispherical shape with a radius of 8 to 15 mm and a height relative to the placement surface (8) that lies in the range of 6 to 16 mm.

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