CONTAINER HAVING A PETALOID BASE WITH RIB FEET

Disclosed is a plastics container obtained by blow moulding or stretch blow moulding from a blank, this container including a body, a neck which extends at an upper end of the body and a petaloid base which extends at a lower end of the body, this petaloid base being provided with protruding feet that are separated by recessed valleys that extend radially from a central region of the base, each foot having an external wall which extends in continuation of the body and two side walls that each border a valley and are each connected to the external wall by a fillet, each foot being provided with at least one rib, a lateral portion of which overlaps the fillet.

The invention relates to the production of containers, particularly bottles, by blow molding or stretch blow molding from blanks (preforms or unfinished intermediate containers) from a thermoplastic material such as PET (polyethylene terephthalate).

A container generally comprises a body, which imparts to the container its volume, an open neck, which extends protruding from an upper end of the body and through which the container is filled (generally by means of a liquid or a paste), and a bottom, which closes the body opposite the neck and forms a base by which the container must be able to rest in a stable manner on a plane surface such as a table.

Generally, it is sought to impart to the bottom a good mechanical rigidity because, besides the fact that the bottom must form a stable seat for the container (not only during transporting operations following its filling but also during its storage and its everyday use by consumers), it must also withstand the hydrostatic pressure exerted by the contents, with possible thermal stresses caused by an elevated temperature of the contents when the contents are introduced hot into the container, or else with a possible pressure from gas dissolved in the liquid (classic case of carbonated beverages).

If it were possible for the container to stay upright, the ideal shape of the bottom would be a sphere, because it would distribute uniformly the stresses that are applied to it. There was a time when containers made of PET were produced with a spherical bottom on which an added cup-shaped base was fitted, made from a more flexible material (particularly from polypropylene, to make possible its snap-fitting onto the bottom). However, this design made recycling difficult, the two materials having to take different tracks, forcing operators responsible for the selective sorting to separate the base from the container themselves.

The development of the petaloid bottom made it possible to get around these problems: such a bottom comprises alternating protruding feet intended to ensure the vertical stand-up of the container placed on a horizontal plane surface, and convex valleys (generally in the shape of sphere portions) that absorb a portion of the forces (thermal, mechanical) exerted by the contents.

It is in containers having petaloid bottoms that carbonated beverages are ordinarily contained. The capacities of these containers can vary: for example, 0.2 L, 0.5 L, 1 L, 1.5 L, 2 L, or more.

Environmental standards (ever more restrictive) and the unpredictable nature of the price of raw materials are forcing manufacturers to reduce the amount of material used, which results in a decrease in weight (and therefore in thickness) of the containers.

On the lightweight petaloid bottoms, unwanted deformations are observed. In particular, on the feet, the appearance of wrinkles is noted. Apart from their unsightly nature, the wrinkles can form incipient breaks, especially when the containers are palletized: added to the stresses due to the internal pressure are actually stresses of compression due to the weight of the superposed containers.

Even the recent improvements made to the petaloid bottoms (see in particular the European patent application EP 2 560 887 in the name of the applicant) do not make it possible to get around these wrinkles.

An object is consequently to propose a petaloid bottom that, although lightweight, is, however, less subject to the uncontrolled deformations than the known petaloid bottoms.

For this purpose, a container made of plastic material obtained by blow molding or stretch blow molding from a blank is proposed, this container comprising a body, a neck that extends at an upper end of the body, and a petaloid bottom that extends at a lower end of the body, this petaloid bottom being provided with protruding feet, separated by hollow valleys that extend radially from a central area of the bottom, each foot having an outer wall that extends in continuation of the body and two sides each bordering a valley and that each adjoin the outer wall by a fillet, each foot being provided with at least one rib, a lateral portion of which straddles said fillet.

By deploying under pressure the contents of the container, this (or these) rib(s) absorb(s) a portion of the deformations induced within the foot that are thus channeled, which prevents the formation of unwanted wrinkles.

Various additional characteristics can be provided, alone or in combination:at least one rib has an inner end portion that extends at least partway over one side, in continuation of the lateral portion;at least one rib has an outer portion that extends at least partway over the outer wall of the foot, in continuation of the lateral portion;the rib stops, toward the exterior, on the outer wall of the foot;the container comprises at least one rib having two lateral portions that adjoin by the outer portion;the outer portion is arched;the (or each) lateral portion is arched in the direction opposite to the outer portion;the rib follows the contour of an intersection of the foot with a cylinder of revolution around a radial axis;the lateral portion is straight;the rib follows the contour of an intersection of the foot with a plane;the feet having ends that, for the container, define a placement plane, the above-mentioned intersection plane is parallel (or, as a variant, inclined in relation) to the placement plane;the container comprises at least two superposed ribs;the container comprises three superposed ribs;the ribs are equidistant;examined ascending in the direction of the neck from an end of the foot, the ribs are of increasing lengths;the ribs follow the contour of an intersection of the foot with coaxial cylinders of revolution, with a radial axis and with different radii;at least one rib stops, toward the interior, on the adjoining fillet between the outer wall and the side;the (or each) rib has a width of between 0.4 mm and 1.5 mm.

InFIG. 1, a container1is shown that is obtained by blow molding or stretch blow molding from a blank (a term designating a raw injection preform or an intermediate container intended to undergo one or more finishing operations) made of plastic material, for example of PET (polyethylene terephthalate).

The container1comprises a body2, which extends along an axis X that can constitute an axis of revolution of the body2, a neck3that extends at an upper end of the body2, and a petaloid bottom4that extends at a lower end of the body2, opposite the neck3.

The bottom4is provided with protruding feet5, separated two by two by hollow valleys6that extend radially from a central area7of the bottom4.

Each foot5extends in axial projection up to an end8. The ends8of the feet5are coplanar and together define a placement plane9by which the container1can rest in a stable manner on a horizontal plane surface (typically a table).

Each foot5has an outer wall10, which extends in continuation of the body2, and two sides11each bordering a valley6and which each adjoin the outer wall10by a fillet12.

According to an embodiment illustrated in the figures, and particularly inFIGS. 3 and 4, each fillet12will continue to grow from an upper end13of the valley6in the direction of the end8of the foot. In the same direction, the radius of the fillet12can be constant, or keep increasing.

As is also seen inFIGS. 3 and 4, each side11has a crescent shape (but this shape is not limiting). It will be noted that the boundaries between the different areas of the foot5are not sharp edges but are soft (otherwise, these boundaries would accumulate the stresses and would form, under load, an equal number of incipient breaks). For reasons of clarity, however, these boundaries have been visualized in the drawings (in the form of double dot-dash lines).

Each foot5has a plane symmetry relative to a radial plane R (containing the axis X of the container1) passing through its end8. Each foot5thus comprises a single outer wall10, symmetrical relative to this plane R, two fillets12that are the mirror image of one another relative to this plane R, and two sides11that are also the mirror image of one another relative to this plane R.

As is seen in the figures, each foot5is provided with at least one rib14. Seen in cross-section, this rib14protrudes (i.e., it forms a relief) toward the interior of the container1(FIG. 6). As a variant, this rib14protrudes toward the exterior of the container.

Regardless of its form (several of them are described below), the rib14comprises a lateral portion15that straddles the fillet12, i.e., this lateral portion15extends over at least one part of the width of the fillet12.

The number of ribs14present on each foot5can be a function of the volumetric capacity of the container1. Thus, in a large-capacity (1.5 L, 2 L or even 3 L) container1, each foot5can be provided with three ribs14(or three pairs of ribs14that are symmetrical relative to the radial plane of symmetry R of the foot) that are superposed (see the first bottom4illustrated inFIGS. 1 to 5, which comprises, for each foot5, an upper rib14.1, an intermediate rib14.2, and a lower rib14.3). In a medium-capacity (0.5 L or 1 L) container1, each foot5can be provided with two (or two pairs of) superposed ribs14(see the second bottom4illustrated inFIGS. 7, 8 and 9, which comprises, for each foot5, a pair of symmetrical upper ribs14.4and a pair of symmetrical lower ribs14.5). In a low-capacity (less than 0.5 L, for example 0.2 L) container1, each foot5can be provided with a single rib14(or with a single pair of ribs14that are symmetrical relative to the plane R of symmetry of the foot5).

At least one of the ribs14can have one or more of the following characteristics:the lateral portion15extends over the entire width of the fillet12, thus joining the outer wall10to one of the sides11of the foot5; this is the case with the upper rib14.1of the first bottom4(FIGS. 3 and 4) and with the ribs14.4,14.5of the second bottom4(FIGS. 7, 8, 9);the rib14extends over the side11, beyond the fillet12; the rib14then has an inner end portion16, which extends at least partway over the side11, in continuation of the lateral portion15; this is the case with the upper rib14.1of the first bottom4(FIGS. 3 and 4) and with the two ribs14.4,14.5of the second bottom4(FIGS. 7, 8, 9);the lateral portion15extends over one part only of the fillet12, extending from the outer wall10and stopping in the vicinity of the boundary between the fillet12and the side11: this is the case with the intermediate rib14.2of the first bottom4(FIGS. 3 and 4);the lateral portion15extends over one part only of the fillet12, starting from the outer wall10and stopping approximately halfway between the outer wall10and the side11: this is the case with the lower rib14.3of the first bottom4(FIGS. 3 and 4);the rib14has an outer portion17that extends at least partway over the outer wall10of the foot5, in continuation of the lateral portion15: this is the case with the upper rib14.1of the first bottom4(FIGS. 3 and 4) and with the two ribs14.4,14.5of the second bottom4(FIGS. 7, 8, 9);the rib14stops, toward the exterior, on the outer wall10of the foot5: the rib14then has an outer end portion18, which extends partway over the outer wall10: this is the case with the ribs14.4,14.5of the second bottom4ofFIGS. 7, 8, 9; the foot5illustrated in these figures comprises two superposed pairs of ribs14that are symmetrical relative to the plane R of symmetry of the foot5. The ribs14.4,14.5of each pair are separated from one another, their outer end portions18stopping at a distance from one another of several millimeters;the outer portion17extends over the entire width of the outer wall10: the rib14then comprises two lateral portions15that adjoin by the outer portion17: this is the case with the ribs14.1,14.2,14.3of the first bottom4ofFIGS. 3 and 4;the outer portion17is arched: this is the case with the ribs14.1,14.2,14.3of the first bottom4ofFIGS. 3 and 4, the outer portions17of which extend along an arch with its concavity turned toward the placement plane9;the (or each) lateral portion15is further arched in the opposite direction of the outer portion17: this is the case with the ribs14.1,14.2,14.3of the first bottom of FIGS.3and4, whose lateral portions15extend along an arch with its concavity turned toward the neck3;the rib14follows the contour of an intersection of the foot5with a cylinder C of revolution around a radial axis: this is the case with the ribs of the first bottom4ofFIGS. 3, 4 and 5; in this first bottom4, and as is clearly visible inFIG. 5, the ribs14.1,14.2,14.3follow the contour of an intersection of the foot5with the respective cylinders C1, C2, C3of revolution, with the same radial axis A and with different radii;in a variant, the rib14follows the contour of an intersection of the foot5with a plane P that is inclined relative to the placement plane9: this is the case with the ribs14.4,14.5of the second bottom4ofFIGS. 7, 8, 9; in a variant, the plane P could be parallel to the placement plane; in both cases, the (or each) lateral portion15appears straight instead of being arched;the rib14has a width L of between 0.4 mm and 1.5 mm.

It is conceivable to combine certain of the above-mentioned characteristics. At least one (or each) rib14could thus have an arched outer portion17and one (or each) straight lateral portion15.

Taking into account the rather intricate relief of the foot5, the general shape of each rib14depends on the angle along which the bottom4is observed.

Thus, when the first bottom4ofFIGS. 1 to 5is observed from below (FIG. 3), each rib14.1,14.2,14.3has an open U shape. When a foot5of this same bottom4is observed radially from the outside (see the foot5located in the center ofFIG. 4), each rib14.1,14.2,14.3has a circular shape. When a foot5of this first bottom4is observed from the side (see the feet5located on the sides ofFIG. 4), each rib14.1,14.2,14.3has a Gaussian shape.

When a foot5of the second bottom4ofFIGS. 7 to 9is observed from below (FIG. 9), each rib14.4,14.5also has an open U shape. When a foot of this same bottom is observed from the side (FIG. 8), each rib14.4,14.5extends along a straight line.

When each foot5comprises several superposed ribs14, the ribs14can, when examined ascending in the direction of the neck from the end8of the foot5, be of different lengths (for example, increasing, see the first bottom4illustrated inFIGS. 2, 3 and 4) or of the same length (see the second bottom4illustrated inFIGS. 7, 8 and 9).

When each foot5comprises a number of ribs14that is greater than or equal to three, they can be equidistant, as in the first bottom4illustrated inFIGS. 1 to 5.

The container1is designed to be filled with contents under pressure, typically a carbonated beverage, which produces in the container1a pressure that can reach 6 bars.

Its petaloid shape makes it possible for the bottom4to maintain its shape overall without collapsing, the valleys6ensuring, as a result of their spherical shape, a relatively homogeneous distribution of the stresses that they undergo because of the pressure of the contents. The feet5, for their part, are subject to significant variations of stresses because of their intricate shape. It has been found that the stresses accumulate in the fillets12, between the outer wall10and the sides11. Each rib14contributes, by being deployed toward the exterior of the container1(as illustrated in dashed lines inFIG. 6), to channeling the deformations caused by these stresses. In other words, the deformations are localized on the rib(s)14. Consequently, the uncontrolled (unwanted) deformations of the feet5are minimized, indeed eliminated, even when the container1is lightweight. The appearance of the container1is preserved, as well as its behavior under increased load (particularly when palletizing), with an equal or lower weight.