Flattened container having an arched bottom with a variable-width base

A container (1) made of plastic material, provided with an oblate body (2) and with a bottom (3) in the extension of the body (2) at a lower end thereof, the bottom (3) including: a peripheral base (7) defining an annular standing plane (8) whose contour exhibits, along a long axis, a large dimension A, and, along a short axis perpendicular to the long axis, a small dimension A′ that is strictly smaller than the large dimension, a concave arch (13) that extends from the base (7) to a central area (14); wherein the base has:

The invention relates to the field of containers obtained by blow molding or stretch-blow molding from a parison (for example, a preform or an intermediate container) of plastic material such as PET (polyethylene terephthalate).

The invention relates more particularly to flat containers, i.e., to containers exhibiting in cross-section a flattened shape, typically oval or rectangular. This type of container is particularly suited to certain applications (in particular cosmetics) in which the contents have a high viscosity, a pressure on the body of the container facilitating the flow of the contents.

This type of container, however, is not limited to cosmetic applications, and, for ergonomic reasons, it is also used in the packaging of beverages, the flattened section offering in effect a better grip, as is explained in the international application WO 2007/127789 (The Coca Cola Company) or its U.S. equivalent US 2010/0000963.

This advantage in terms of ergonomics, however, comes with a mechanical drawback, namely a certain instability, due to the flattening of the container, which increases the risk of falling over into an axial plane parallel to the small width of the container.

The stability of the container is inversely proportional to its ease of gripping. It is a compromise between these two constraints that is the object of the solution disclosed in the above-mentioned document WO 2007/127789, which proposes, on the one hand, to maintain the W/D ratio (where W is the large width of the container, and D its small width) of between 1.2 and 1.8, and, on the other hand, to provide the bottom of the container with rounded chamfers (sic) whose diameter is smaller in the small width of the container than in its large width.

In actuality, this solution provides only a partial answer to the problem of instability that affects flat containers. In practice, it is found that the natural instability (due to the flat shape) of such a container is often compounded by an instability due to defects in shape on the bottom because of its poor blowability (by “blowability” is meant its ability to take the shape of the mold) due to design defects (essentially of dimensioning).

The problems of blowability are especially difficult to solve on a flat container that inherently is more elongated in the direction of the large width than in the direction of the small width.

A first simple solution could consist in increasing the blow-molding pressure, but the manufacturers encounter necessities of controlling the power consumption of the machines, constraining the blow-molding pressure to a downward trend.

A second simple solution could consist in increasing the blow-molding time (and therefore the cycle time) to facilitate a better taking of an impression of the bottom, but this solution also encounters procedural constraints, whose purpose is to reduce the cycle time to increase the rates of production.

It is therefore understood that it is necessary to improve the shape of the containers to increase their stability while enhancing the blowability.

The purpose of the invention is to propose a flat container that is able to fulfill one or more (and preferably all) of the following objectives:good stability;good compromise between ergonomics and stability;good blowability;absence of (or almost no) defects of surface evenness on the bottom.

For this purpose, a container is proposed that is made of plastic material, provided with a flattened body and with a bottom in the lengthening of the body at its lower end, the bottom comprising:a peripheral base defining an annular standing plane whose contour exhibits, along a long axis, a large dimension A, and, along a short axis that is perpendicular to the long axis, a small dimension A′ that is strictly smaller than the large dimension, this base having:along the long axis, a width C such that:

0.03≤CA≤0.1along the short axis, a width C′ such that:

0.05≤C′A′≤0.15a concave arch that extends from the base to a central area.

Thus dimensioned, this container exhibits both a good rigidity in the area of its base (benefiting the stability of the container), in particular in the plane of the short axis, while offering a good blowability of the base.

Various characteristics can be foreseen, alone or in combination:the base has, between the standing plane and the arch, an inner annular ledge that is approximately perpendicular to the standing plane, this ledge extending, along the long axis, over a height D such that:

0.002≤DA≤0.1the height D of the ledge is such that:

0.01≤DA≤0.05the height D of the ledge is such that:

DA≅0.025the ledge extends, along the short axis, over a height D′ such that:

0.002≤D′A′≤0.1the height D′ of the ledge is such that:

0.01≤D′A′≤0.1the height D′ of the ledge is such that:

D′A′≅0.06the width C of the base along the long axis is such that:

CA≅0.05the width C′ of the base along the short axis is such that:

FIG. 1shows a container1formed by stretch-blow molding, inside a mold having the impression of the container1, of a preform of plastic material such as PET (polyethylene terephthalate).

Container1comprises a body2that extends along a main axis X and is lengthened, on a lower side, by a bottom3, and, on an upper side, opposite the bottom3, by a shoulder4itself lengthened by a neck5defining a rim.

At the junction between the body2, at its lower end, and the bottom3, the container1has an outer connecting fillet6having a small-radius (less than or equal to 2 mm) arc shape.

The bottom3comprises a peripheral base7that defines a continuous standing plane8, approximately perpendicular to the main axis X of the container1, and by which the bottom can set flat on a flat surface (in particular the upper surface of a table or of a conveyor belt, within a handling machine on a container production line).

The standing plane8is delimited transversely toward the outside (i.e., opposite the axis X of the container) by an outer perimeter9that is defined on the inside by the fillet6.

The container1has, in cross-section (i.e., perpendicular to its axis X), a flattened shape, in this case approximately oval. This shape extends to the bottom3, in particular in the area of the standing plane8, whose contour is approximately the same as the body2in cross-section and which, like an ellipse, has:along a long axis (in the cutting plane III-III inFIG. 2, or else in the plane of the sheet inFIG. 3), a large transverse extension A (called large dimension), measured perpendicular to the axis X in the area of the perimeter9, andalong a short axis, perpendicular to the long axis (i.e., in the cutting plane IV-IV inFIG. 2, or else in the plane of the sheet inFIG. 4), a transverse extension A′, also measured perpendicular to the axis X in the area of the perimeter, this small transverse extension (called small dimension) being strictly smaller than the large dimension A:

The base7comprises an inner annular ledge10that extends axially toward the interior of the container1in the lengthening of the standing plane8, approximately perpendicular in relation to it. According to a first embodiment illustrated inFIGS. 3 and 4, the base7comprises an inner fillet11having a small-radius (less than or equal to about 2 mm) arc shape, which connects the standing plane8to the ledge10.

According to a second embodiment illustrated inFIGS. 5 and 6, the base7comprises, instead of a fillet for connecting the standing plane8to the ledge10, a step11′ forming a setback at the junction between the standing plane8and the ledge10. This step11′ can be used as a recessed reserve making it possible to offset toward the interior of the container1a possible burr resulting from the flow of material from a seam of the mold in which the container is formed, this seam being defined between a wall of the mold (at the impression of the body and of the standing plane) and a mold bottom (at the impression of the arch).

The standing plane8is delimited transversely toward the interior (i.e., in the direction of the axis X of the container) by an inner perimeter12, defined on the outside by the inner fillet11(in the case of the first embodiment) or, respectively, by an inner edge of the step11′, at its junction with the ledge10(in the case of the second embodiment).

The bottom 3 further comprises a concave arch13, with concavity turned toward the exterior of the container1. This arch13extends from the base7, in the lengthening of the ledge10, to a central area14of the bottom that defines a piece that extends axially projecting toward the interior of the container1.

Noted:C is a width of the standing plane8(merged with a width of the base7), measured radially along the long axis between the inner perimeter12and the outer perimeter9, respectively between an inner edge of the step11′, at its junction with the ledge10, and the outer perimeter9;C′ is the width of the standing plane8measured radially along the short axis;D is a height of the ledge10(merged with an inner height of the base7), measured along the long axis (i.e., in the cutting plane III inFIG. 3, or in the plane of the sheet inFIG. 3orFIG. 5) between the standing plane8and the junction of the ledge10with the arch13;D′ is the height of the ledge10measured along the short axis (i.e., in the cutting plane IV inFIG. 3, or in the plane of the sheet inFIG. 4orFIG. 6).

The bottom 3 is designed to maximize the stability of the base7while facilitating its blowability.

For this purpose, the base7is dimensioned such that its width C can be varied as a function of its transverse extension. More specifically, the width C of the base7is dimensioned in the following manner:firstly, the width C of the base7along the long axis is such that:

CA≅0.05secondly, the width C′ of the base7along the short axis is such that:

Furthermore, the width C of the base7along the long axis is preferably strictly greater than its width C′ along the short axis:
C>C′

The ledge10is also dimensioned as a function of the transverse dimension of the base7:firstly, the height D of the base measured along the long axis is such that:

0.01≤DA≤0.05
and, according to a particular embodiment:

DA≅0.025secondly, the height D of the base measured along the long axis is such that:

0.01≤D’A’≤0.1
and, according to a particular embodiment:

This dimensioning makes it possible to maintain a good stability of the container1in particular in the plane of the short axis (i.e., the small dimension), while maintaining a good blowability of the container in the plane of the long axis, where the stretching is more difficult but where the stability of the container1is, of course, better.

The larger width of the standing plane8along the long axis contributes to a good blowability of the base7in this direction, minimizing the risk of the appearance of distortions (or defects of surface evenness) on the standing plane8.

In addition, the narrowness of the standing base7along the short axis imparts an almost linear character to it, which reduces the risks of hyperstatism of the base7and consequently increases the stability of the container1.

The dimensioning of the ledge10contributes in particular:to a better blowability of the bottom 3 in the plane of the long axis, by minimizing the amount of material that an axial stretching requires;to a better rigidity of the arch13, thanks to the variation of height of its outer perimeter (at its junction with the ledge10);to a greater rigidity of the base7along the short axis, benefiting its stability in this direction.

To form such a container1, it is preferable to resort to the boxing technique, in which the container1is blow molded in a mold provided with a lateral wall defining a cavity having the impression of the body2and a mold bottom that is mounted to move in relation to the wall between a low position in which the bottom is separated from the cavity, and a high position in which the bottom closes the cavity by completing the impression of the container1. The mold bottom, initially in low position, rises during the blow molding, which leads to an over-stretching of the material in the area of the bottom3, which can facilitate its impression-taking in particular in the area of the base7.