EP2643225B1 - Combined petaloid base of a container - Google Patents

Description

The invention relates to the manufacture of containers, in particular bottles, obtained by blow molding or stretch blow molding from preforms or intermediate containers of thermoplastic material.

A container generally comprises an open neck, through which the contents (usually a liquid), a body, which gives the container its volume, and a bottom, which closes the body opposite the neck and forms a base for maintain and hold the container when it is resting on a surface.

The containers for carbonated beverages, in which the pressure of the gas dissolved in the liquid induces significant mechanical stresses, are mainly provided with petaloid-shaped bottoms: the bottom comprises projecting feet, in the form of petals, separated by portions of convex wall, called hollows or valleys, which extend radially from a central zone of the bottom. The feet are intended to maintain the container placed on a surface; the valleys are intended to absorb the efforts (thermal, mechanical) exerted by the contents. Such containers are described in European patents EP 0 350 782 and EP 0 703 152 .

The performance of a petaloid bottom is measured by its mechanical strength - that is to say its ability to deform in a limited or controlled manner - not only during filling, but also during storage of the container. The storage can be prolonged, and carried out under conditions of temperature and hygrometry severe which one meets exceptionally in the temperate countries but usually in the countries with continental climate, tropical or desert.

A frequent deformation that one wishes to avoid is the collapse of the central zone of the bottom, because it results in a modification of the configuration of the feet and, ultimately, a lack of stability of the container. This problem is known, cf. for example the French patent application FR 2,897,292 (or its American counterpart US 2009/020682 ), and also FR 2,772,720 which describes a container according to the preamble of claim 1, but the solutions proposed in the past do not offer a compromise that satisfies the constraints of mechanical performance, ideally high, weight, ideally low, and blowing, ideally easy.

It therefore appears desirable to provide a container whose petaloid bottom offers such a compromise.

For this purpose, there is provided a plastic container comprising a body and a petaloid bottom extending the body, the bottom comprising a bottom wall of generally convex outward shape, which project feet formed by excrescences, the feet being separated in pairs by portions of the bottom wall forming recessed valleys which extend radially from a central zone of the bottom to a periphery of the bottom, a vessel in which each valley widens from the central zone to the periphery, and has a concave portion located near the periphery.

According to the invention, the bottom comprises a radial extension groove dug at the bottom of each valley.

Such a container has the advantage of having increased resistance to deformation. In particular, there is a good maintenance of the central zone of the bottom under the hydrostatic pressure, possibly combined with the pressure of the dissolved gas in the case of a carbonated beverage. These performances are observed not only during filling but also during prolonged storage under severe conditions of hygrometry and pressure.

Each valley preferably has an angular aperture of between 22 ° and 30 °, for example about 25 °.

The concave portion preferably has a radius of curvature of between 0.20 · A and 0.70 · A (where A is the overall diameter of the bottom), and for example about 0.40 · A.

Furthermore, each foot is preferably provided with an outer face which, in radial section, has a convex profile whose radius of curvature is greater than the overall diameter of the bottom, and for example equal to three times the overall diameter of the bottom. .

• la figure 1 est une vue en perspective de dessous d'un récipient à fond pétaloïde ;
• la figure 2 est vue à échelle agrandie du fond du récipient de la figure 1 ;
• la figure 3 est une vue en plan de dessous du fond de la figure 2 ;
• la figure 4 est une coupe partielle d'un détail du fond de la figure 3, selon le plan de coupe IV-IV ;
• la figure 5 est une vue en coupe du fond de la figure 3, selon le plan de coupe V-V.

Other objects and advantages of the invention will become apparent in the light of the description given hereinafter with reference to the appended drawings in which:

• the figure 1 is a perspective view from below of a container with petaloid bottom;
• the figure 2 is seen on an enlarged scale from the bottom of the container of the figure 1 ;
• the figure 3 is a plan view from below the bottom of the figure 2 ;
• the figure 4 is a partial section of a detail from the bottom of the figure 3 according to section plane IV-IV;
• the figure 5 is a sectional view of the bottom of the figure 3 , according to the VV cutting plane.

On the figure 1 is shown, in perspective from below, a container 1 - in this case a bottle - obtained by blowing or stretching blow from a preform of thermoplastic material, for example polyethylene terephthalate (PET), previously heated.

The container 1 extends along a main axis X and comprises a lateral wall 2 called body, and a bottom 3 which extends and closes the body 2 at a lower end thereof.

The bottom 3 is petaloid, and comprises a bottom wall 4 generally shaped convex outwardly of the container 1 (that is to say down when the container is laid flat).

The bottom 3 also comprises a series of feet 5 formed by outwardly protruding protrusions of the container 1, and which extend from a central zone 6 of the bottom 3 in the form of a pellet, where the material has remained substantially amorphous , toward a periphery 7 of the base 3 when the latter is connected to the body 2. Note in the overall diameter of the bottom 3, measured at its periphery 7 ( figure 5 ).

As you can see, this is clearly visible figures 2 and 3 the feet 5 become tapered from the inside to the outside of the container 1 (i.e. down), and widening from the central zone 6 to the periphery 7.

The most protruding parts or vertices 8 of the feet 4 are coplanar and together form a seat 9 through which the container can rest on a flat surface (for example a table). As is visible on the figures 2 and 3 , the seat 9 (materialized on the figure 3 by a dashed circle), is located radially recessed relative to the periphery 7. Note B the diameter of the seat 9, and C the total height of the bottom 3, measured axially from the seating plane 9 until at the periphery 7 of the bottom 3, where the latter is connected to the body 2.

• une section 11 interne de forme sphérique à concavité tournée vers l'extérieur, centrée sur l'axe X du récipient 1 et dont on note L le rayon de courbure et S le diamètre ;
• une section 12 externe plane, prolongeant radialement la section 11 interne et moins inclinée que celle-ci, et formant avec le plan d'assise 9 (également dénommé plan de pose) un angle noté T.

Each foot 5 has an end face 10 which extends gently down the central zone 6 of the bottom 3 towards the apex 8, so that the foot 5 has a substantially triangular profile in radial section ( figure 5 ). More specifically, as illustrated on the figure 5 The end face 10 has a double slope, and comprises:

• an inner section 11 of spherical shape concavity turned outwardly, centered on the axis X of the container 1 and whose L radius of curvature and S the diameter;
• a flat outer section 12 , radially extending the inner section 11 and less inclined than the latter, and forming with the plane 9 (also called laying plane) an angle noted T.

We denote E the axial extension 10 of the end face (also referred to as boom or bottom of the guard), measured between the seat 9 and the central plane 6 area.

We see on the figure 3 10 that the end face widens from the central zone 6 towards the periphery 7. We denote by H the mean angular aperture of the end face 10, measured in the base plane 9 between two virtual lines joining the axis X at the intersection of the edges 10 of the end face and the circle (diameter B in broken lines in figure 3 ) joining the vertices 8 of the feet 5.

As is clearly visible on the figures 2 and 3 , the feet 5 are separated in pairs by portions 13 of the bottom wall 4 called valleys, which extend radially in a star from the central zone 6 to the periphery 7.

The valleys 13 are concave outwards in cross section (that is to say in a plane perpendicular to the radial direction, cf. figure 4 ). U is the radius of curvature of the valleys 13, measured in cross section. This radius U can be variable. More specifically, it is preferably low near the central zone 6 , and relatively greater near the periphery 7 (see the numerical values in the table below).

• au voisinage de la zone 6 centrale, une section 14 interne convexe vers l'extérieur en section radiale, dont on note K le rayon de courbure, et
• au voisinage de la périphérie 7, une section 15 externe concave vers l'extérieur en section radiale, dont on note N le rayon de courbure et qui se raccorde à la périphérie 7 par un congé 16 convexe dont on note J le rayon. On note O l'extension radiale de cette portion 15 concave, mesurée perpendiculairement à l'axe X (figure 5).

Moreover, as illustrated on the figure 2 , and right on the figure 5 , the valleys 13 present:

• in the vicinity of the central zone 6, a convex internal section 14 outward in the radial section, which we denote by K the radius of curvature, and
• in the vicinity of the periphery 7, a concave outer section 15 outward in the radial section, it is noted that N is the radius of curvature and which is connected to the periphery 7 by a convex 16 which leave J we denote the radius. We denote O the radial extent of this concave portion 15, measured perpendicularly to the axis X ( figure 5 ).

We see on figures 2 and 3 the feet 5 are equal in number to the valleys 13. In the example illustrated in the drawings, the bottom 3 comprises five feet 5 and five valleys 13, regularly alternated and distributed in a star. This number is a good compromise; it could however be less (but greater than or equal to three), or greater (but preferably less than or equal to seven).

Each foot 5 has two substantially planar flanks 17 each bordering a valley 13 laterally . As can be seen in FIG. figure 4 the flanks 17 are not vertical (because the bottom 3 would be difficult or impossible to blow), but inclined opening from the valley 13 to the outside. F is the average angular aperture between the flanks 17, which designates the average transverse angular aperture of the valley 13. As illustrated in FIG. figure 3 The flanks 17 are connected to the end face 10 by a fillet 18 which is note I radius.

Each foot 5 is also radially delimited by an external face 19 which extends in the extension of the body 3 to the vicinity of the top 8, in which the outer face 19 is connected by a fillet 20 which is a D radius measured in a radial plane ( figure 5 ). The outer face 19 is not cylindrical but substantially conical of revolution about the X axis . Moreover, in radial section this face is not straight but convex with a large radius of curvature, noted R (left on the figure 5 ). At the periphery of the bottom 3, the face 19 is connected to the body 3 by a leave of which we note Q the radius, measured in a radial plane.

According to a preferred embodiment, illustrated in the drawings, the bottom 3 is furthermore provided with radial grooves 22 which extend recess towards the inside of the container 1, at the bottom and along the valleys 8. More specifically, each groove 22 extends along a median line of a valley 13, from a neighborhood of the central zone 6 to the vicinity of the periphery 7.

Each groove 22 has a plan ( figure 3 ) an oblong shape, whose edges are parallel over most of the length, and whose ends are both tapered. In radial section ( figure 4 ), each groove 22 has a flared U-shaped profile. We note V the depth of the grooves 22.

The grooves 22 have the function of stiffening the bottom 3. Under the effect of the mechanical stresses exerted on the container 1 (in particular under the effect of the pressure prevailing in the container filled with a carbonated liquid), the grooves 22 tend flowing by expanding and flattening, which causes an enlargement of the valleys 13 and, consequently, a verticalization of the feet 5 which opposes the overall subsidence of the bottom 3.

We see on the figure 3 that each valley 13 widens from the central zone 6 towards the periphery 7. This widening is preferably continuous, that is to say that the edges of the valleys 13 form between them an angle at any point not zero. In the example shown, the valleys 13 have a tulip-shaped (or bell-shaped) outline in plan, but this shape is not limiting, and the edges of the valleys 13 could be straight (the valleys 13 then having a contour in V). We denote by G the mean angular aperture of the valleys 13, measured in a plane perpendicular to the X axis between two virtual lines (in phantom lines on the figure 3 ) joining the X axis and the radial ends of the lateral edges of the valleys 13.

As can be seen in particular on the figure 2 each valley 13 is devoid of branching (especially on the periphery side 7), and thus forms a unitary hollow reserve.

We denote by M the average axial depth of each valley 13, that is to say the distance, measured parallel to the X axis , between the apex 8 of the feet 5 and the point of the valley 13 situated at the diameter B, at the vertical of vertex 8 (cf. figure 5 ).

A preferred range (i.e., a minimum value and a maximum value) and a preferred example of indicative value for each of the parameters E to N and Q to V are summarized in the table below. which can be variable and are for the most part (with the exception of the parameters F, G, H, T and V) calculated according to one of the parameters A, B and D, which correspond to fixed dimensions imposed by the type (including capacity) of the container produced. The height C of the bottom 3 is also a fixed parameter; it is the only independent parameter, that is to say that it does not depend on any other parameter and that none of the other parameters is calculated according to it. Parameter Min value Max value Indicative value (± 10%) E 0.08 · B 0.12 · B 0.10 · B F 35 ° 60 ° 46 ° BOY WUT 22 ° 30 ° 25 ° H 5 ° 15 ° 7 ° I 0.70 · D D 0.90 · D J 0.40 · D D 0.70 · D K · A 0.40 · A 0.60 · A 0.50 The 0.20 · B 0.50 · B 0.32 · B M 0.20 · B 0.35 · B 0.27 · B NOT · A 0.20 · A 0.70 · A 0.40 O 0.05 · B 0.15 · B 0.10 · B Q · A 0.20 · A 0.50 · A 0.35 R AT 4 · A 3 · A S 0.50 · B 0.80 · B 0.60 · B T 5 ° 12 ° 8 ° U 0.10 · B 0.50 · B V 0.50 mm 1.5 mm 1 mm

Tests have validated these choices by demonstrating the superiority of the mechanical performance of the bottom 3 compared to existing funds. In particular, the tests conducted by varying the parameters make it possible to formulate the hypothesis that, if all the parameters have an influence on the mechanical performance of the bottom 3, it is the combination of the angular aperture (angle G) valleys 13 and the existence of the concave section 15 external valleys (N range) that has a major influence.

More specifically, this combination makes it possible to minimize the axial movements of the central zone 6 . Indeed, under the internal pressure of the container 1, on the one hand a swelling of the convex section 14 of the valleys 13, on the other hand a reversal of the section Concave 15 which adopts a convex profile in the extension of the section 14, so that the sections 14 and 15 ultimately form a single continuous convex profile (shown by dashed lines on the right figure 5 ) having a radius P of curvature greater than the radius K of curvature of the section 14 at rest. It seems that this combined deformation exerts on the central zone 6 an axial force directed towards the interior of the container 1 which opposes the force resulting from the hydrostatic thrust to which is added the additional pressure due to the dissolved gas, limiting thus the collapse of the central zone 6 .

These effects are not observed on a bottom whose valleys have parallel edges, nor on a bottom whose valleys are entirely convex in radial section.

We have seen in the table that the value of N radius of curvature of the outer concave section 15 of the valleys 13 is linked to the value of the diameter A Overall the bottom 13. According to the tests, it seems important that the radius is less than N to the diameter A, and even less than about 2/3 · A (we have retained as upper bound 0.70 · A, and as preferred value 0.40 · A), without this radius N being too weak (the lower bound retained is 0.20 · A).

Among all the other parameters, the value of the radius R, combined with the parameters G and N, obviously contributes (but in a secondary manner with respect to them) to maintain the central zone 6 at a substantially constant height after filling. More precisely, it seems important that the value of the radius R be high: we have chosen it greater than the overall diameter A of the container, and equal to triple of A in the preferred example. During filling, there is a slight bending of the outer face 19 , which contributes to exert on the entire foot 5 a lever effect articulated around the vertex 8. This lever effect exerts on the central zone 6 an axial force directed towards the interior of the container 1, which opposes the force resulting from the hydrostatic thrust to which is added the additional pressure due to the dissolved gas, thus limiting the collapse of the central zone 6 .

Claims (7)

1. Container (1) made of plastic comprising a body (2) and a petaloid base (3) extending the body (2), the base (3) comprising a bottom wall (4) of outwardly convex overall shape, from which there project feet (5) formed by outgrowths separated each from the next by bottom-wall portions forming recessed valleys (13) extending radially from a central zone (6) of the base as far as a periphery (7) of the base, each valley (13) widening as it extends from the central zone (6) towards the periphery (7) and having a concave portion (15) located near the periphery (7), characterized in that the base (3) comprises a radially extending groove (22) hollowed into the bottom of each valley (13).
2. Container (1) according to Claim 1, characterized in that each valley (13) has an angular aperture (G) of between 22° and 30°.
3. Container (1) according to Claim 2, characterized in that each valley (13) has an angular aperture (G) of around 25°.
4. Container (1) according to one of Claims 1 to 3, characterized in that the concave portion (15) has a radius (N) of curvature of between 0.20·A and 0.70-A, where A is the overall diameter of the base.
5. Container (1) according to Claim 4, characterized in that the concave portion (15) has a radius (N) of curvature equal to 0.40·A.
6. Container (1) according to one of Claims 1 to 5, characterized in that each foot (5) is provided with an external face (19) which, in radial section, has a convex profile of which the radius (R) of curvature is greater than the overall diameter (A) of the base (3).
7. Container (1) according to Claim 6, characterized in that the radius (R) of curvature of the external face (19) is approximately equal to three times the overall diameter (A) of the base.

Images