EP2580132B1 - Container including a ribbed, arched bottom - Google Patents

Description

The invention relates to the manufacture of containers, such as bottles or pots, obtained by blow molding or stretch blow molding from thermoplastic preforms.

The manufacture, by blowing, of a container generally consists in introducing into a mold to the imprint of the container a blank (term designating either a preform or an intermediate container obtained by pre-blowing a preform) previously heated to a temperature greater than the glass transition temperature of the material, and to inject into the blank a gas (such as air) under pressure (equal to or greater than 15 bar). The blowing can be completed by preliminary stretching of the blank by means of a sliding rod.

The double molecular orientation that the material undergoes during blowing (axial and radial, respectively parallel and perpendicular to the general axis of the container) gives the container a certain structural rigidity.

But the decrease - dictated by the market - of the amount of material used for the manufacture of containers requires manufacturers to use manufacturing tips or form to stiffen their containers, the bi-orientation being insufficient. As a result, with equal weight, two containers do not necessarily have the same mechanical performance (strength, rigidity).

A well-known method of increasing the stiffness of a container is heat-setting, which involves heating the mold wall to thermally increase the crystallinity level. This process, illustrated by the French patent FR 2 649 035 (Sidel ) and its American counterpart US5,145,632 , is used in particular for HR (heat resistant) applications, in which the container is hot filled.

But, because of its cost and the reduction of rate it imposes, this type of process can not be generalized to ordinary applications of the type flat water.

Another technical solution for increasing the structural rigidity of a container is to stretch the bottom of the container, by means of a special mold equipped with a mold bottom movable in translation which pushes the material (see in particular the European patent EP 1 069 983 ).

Overdrawing induces an increase in the rate of deformation of the material and therefore a mechanical increase in its crystallinity.

But this technique, called "boxing", requires that more material is allocated to the bottom, otherwise the structural rigidity induced by the over-stretching of the material will be burdened by its thinning. In addition to the induced overweight, it is necessary to raise the blowing pressure to conform the bottom.

In addition, bottom boxing is generally coupled with heat-setting, since it makes it possible to form deformable membranes that absorb the variations in volume of the container accompanying the retraction of the liquid initially filled with heat.

It is also known to provide the bottom with ribs, cf. eg. the document US 2009/0194546 which discloses a plastic container according to the preamble of claim 1.

To date, lightweight containers for ordinary applications, for which the heat-fixing or boxing technologies are not conceivable for the reasons mentioned above, do not have satisfactory mechanical performance. In particular, it has been found that, even if the rigidity of a lighter container seems sufficient during filling, its palletization is problematic, because the weight of the superposed containers exerts on the lower containers efforts such that the funds have tendency to roll, and the pallet to sag.

An object of the invention is to improve, at equal or lower weight, the mechanical performance of a container.

• une assise annulaire s'étendant sensiblement dans le prolongement du corps et définissant un plan de pose ;
• une voûte concave qui s'étend à partir d'une zone voisine de l'assise vers une zone centrale, cette voûte comprenant une série de raidisseurs qui s'étendent radialement depuis une zone centrale du fond jusqu'à une joue annulaire interne sensiblement perpendiculaire au plan de pose.

For this purpose, the invention provides a plastic container, provided with a body and a bottom extending at a lower end of the body, the bottom comprising:

• an annular seat extending substantially in the extension of the body and defining a laying plane;
• a concave arch that extends from an area adjacent to the seat to a central area, this vault comprising a series of stiffeners which extend radially from a central zone of the bottom to a substantially perpendicular inner annular cheek to the laying plan.

Such a container has increased stability and rigidity, thanks in particular to the combination of the wide seat (in the extension of the body) and the stiffened arch.

The axial dimension of the cheek and the radial dimension of the laying plane are preferably equivalent, to the benefit of the stability of the container.

In addition, the bottom may comprise an annular reinforcing lip at the junction between the seat and the roof, which joins two by two of the outer radial ends of the stiffeners. This annular lip has for example, in section, a V profile, projecting inwardly. At its junction with the stiffeners, the annular lip preferably has local expansion at its junction with the outer end of each stiffener.

According to one embodiment, each stiffener tapers from the central zone of the bottom to the seat, and the stiffeners together form a star pattern.

The vault comprises, for example, panels recessed between the stiffeners, and each stiffener comprises on its lateral edges double-radius connection fillets with the panels.

• la figure 1 est une vue de dessous en perspective d'un récipient en matière plastique ;
• la figure 2 est une en perspective, à échelle agrandie, montrant le fond du récipient de la figure 1 selon un premier mode de réalisation ;
• la figure 3 est une vue d'un détail du fond du récipient de la figure 2, selon l'encart III ;
• la figure 4 est une vue en plan de dessous du récipient ;
• la figure 5 est une section du fond du récipient, faite suivant la ligne de coupe brisée V-V de la figure 4 ;
• la figure 6 est une vue en coupe du fond du récipient, faite suivant la ligne de coupe VI-VI de la figure 4 ;
• la figure 7 est un détail de la section du fond, selon l'encart VII de la figure 5 ;
• la figure 8 est une vue en perspective, analogue à la figure 2, illustrant un deuxième mode de réalisation du fond du récipient ;
• les figures 9 et 10 sont des vues de détail en coupe, respectivement suivant les plan de coupe IX-IX et X-X de la figure 8 ;
• la figure 11 est une vue en perspective, analogue à la figure 2, illustrant un troisième mode de réalisation du fond du récipient ;
• les figures 12 et 13 sont des vues de détail en coupe, respectivement suivant les plan de coupe XII-XII et XIII-XIII de la figure 11 ;
• la figure 14 est une vue en perspective, analogue à la figure 2, illustrant un quatrième mode de réalisation du fond du récipient ;
• les figures 15 et 16 sont des vues de détail en coupe, respectivement suivant les plan de coupe XV-XV et XVI-XVI de la figure 14 ;
• la figure 17 est une vue en perspective, analogue à la figure 2, illustrant un cinquième mode de réalisation du fond du récipient ;
• les figures 18 et 19 sont des vues de détail en coupe, respectivement suivant les plan de coupe XVIII-XVIII et XIX-XIX de la figure 17 ;
• la figure 20 est une vue en perspective, analogue à la figure 2, illustrant un sixième mode de réalisation du fond du récipient ;
• la figure 21 est une vue d'élévation de côté du fond de la figure 20 ;
• la figure 22 est une vue en perspective, analogue à la figure 2, illustrant un septième mode de réalisation du fond du récipient ;
• les figures 23 et 24 sont des vues de détail en coupe, respectivement suivant les plan de coupe XXIII-XXIII et XXIV-XXIV de la figure 22.

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 bottom view of a plastic container;
• the figure 2 is a perspective, on an enlarged scale, showing the bottom of the container of the figure 1 according to a first embodiment;
• the figure 3 is a view of a detail of the bottom of the container of the figure 2 , according to box III;
• the figure 4 is a plan view from below of the container;
• the figure 5 is a section of the bottom of the container, made following the broken section line VV of the figure 4 ;
• the figure 6 is a sectional view of the bottom of the container, made along line VI-VI of section figure 4 ;
• the figure 7 is a detail of the bottom section, according to box VII of the figure 5 ;
• the figure 8 is a perspective view, similar to the figure 2 illustrating a second embodiment of the bottom of the container;
• the Figures 9 and 10 are detail views in section, respectively along the IX-IX and XX sectional plane of the figure 8 ;
• the figure 11 is a perspective view, similar to the figure 2 illustrating a third embodiment of the bottom of the container;
• the Figures 12 and 13 are detailed views in section, respectively along the section plane XII-XII and XIII-XIII of the figure 11 ;
• the figure 14 is a perspective view, similar to the figure 2 illustrating a fourth embodiment of the bottom of the container;
• the Figures 15 and 16 are detail views in section, respectively according to the sectional plan XV-XV and XVI-XVI of the figure 14 ;
• the figure 17 is a perspective view, similar to the figure 2 illustrating a fifth embodiment of the bottom of the container;
• the Figures 18 and 19 are detail views in section, respectively according to the sectional plan XVIII-XVIII and XIX-XIX of the figure 17 ;
• the figure 20 is a perspective view, similar to the figure 2 illustrating a sixth embodiment of the bottom of the container;
• the figure 21 is a side elevation view of the bottom of the figure 20 ;
• the figure 22 is a perspective view, similar to the figure 2 illustrating a seventh embodiment of the bottom of the container;
• the Figures 23 and 24 are detail views in section, respectively according to the sectional plan XXIII-XXIII and XXIV-XXIV of the figure 22 .

On the figure 1 is represented a container 1 in this case a bottle, made by stretching blow from a thermoplastic preform such as PET (polyethylene terephthalate).

This container 1 comprises, at an upper end, a threaded neck 2 , provided with a rim 3 . In the extension of the neck 2 , the container 1 comprises in its upper part a shoulder 4 flaring in the opposite direction to the neck 2 , this shoulder 4 being extended by a side wall or body 5 , generally cylindrical in shape of revolution around a main axis X of the container 1 .

The container 1 further comprises a bottom 6 which extends at a lower end of the container 1.

As can be seen in the drawings, and more particularly on the figures 5 , 6 and 7 , the bottom 6 comprises a seat 7 in the form of a thin annular bead which extends substantially axially in the extension of the body 5. The seat 7 ends with a face (continuous and annular, as in the examples of the Figures 2 to 19 and 22 to 24 , or formed of several coplanar facets, as in the example of Figures 20 and 21 ) which forms the lower end of the container 1 and defines a laying plane 8 perpendicular to the axis of the container 1 , by which it can rest stably on a plane surface S.

The laying plane 8 is connected outwards to an external lateral face 9 of the seat 7 (which extends in the extension of the body) by a fillet 10 with a small radius of curvature, that is to say of the order of a millimeter.

Towards the interior of the container 1, the seat 7 comprises an annular cheek 11 of a diameter D, which extends axially towards the interior of the container 1 in the extension of the laying plane 8 , substantially at right angles to to it, on a height H equivalent to the width L of the laying plane 8 , measured radially. Specifically, we will ensure that the ratio between the width. L of the laying plane 8 and the height H of the flange 11 is between 0.6 and 1.5: $$0,6\le \frac{\mathrm{The}}{H}\le 1,5$$

The laying plane 8 is connected inwardly to the cheek 11 by a fillet 12 which may be of small radius of curvature - less than or equal to about 1 mm, as in the examples of the Figures 2 to 16 and 20 to 24 - or medium radius - between 1 mm and 5 mm, as in the example of Figures 17 to 19 .

The bottom 6 further comprises a concave arch 13 (concavity facing the outside of the container 1 in the absence of stress, that is to say in the absence of content in the container 1 ), which is extends in the extension of the cheek 11 to a central zone 14 of the bottom 6 , circumscribed in a circle with a diameter d.

The vault 13 is shallow, and its curvature slightly pronounced. The maximum angle A1 of its tangent with a plane perpendicular to the axis of the container 1 (measured in this case on an outer edge of the vault 13 ) is weak, less than or equal to about 20 °.

In the central zone 14 , the bottom 6 comprises, in the extension of the vault 13, a central pin 15 which extends axially projecting towards the inside of the container 1.

The roof 13 is also provided with a series of stiffeners 16 in the form of projecting branches which extend radially from the central zone 14 of the bottom 6 to the cheek 11, and which together form a star pattern.

By an inner radial end 17 , the stiffeners 16 are connected to the central zone 14 of the bottom 6 . By an outer radial end 18 , the stiffeners 16 are connected to the cheek 11 . In all the illustrated embodiments, the stiffeners 16 are 8 in number, but this number is provided by way of example and could be different. More precisely, this number can be between 4 and 12; for purposes of mechanical strength, it is preferably between 6 and 10. Similarly, the height, width and shape of the stiffeners 16 may vary depending on the application. By way of example, as will be seen below, the stiffeners may be Y-shaped arcuate pointing towards the center or the periphery of the bottom, or straight, or in the form of X.

In order to give the bottom sufficient rigidity, care is taken to minimize the ratio d / D between the diameter d of the central zone 14 and the diameter D of the cheek 11 . The ratio d / D is preferably less than 1/2, otherwise the central zone 14 is not sufficiently rigid and may present a risk of overturning under the effect of the hydrostatic pressure of the contents of the container 1.

In the interstices between the stiffeners 16, the vault 13 defines panels 19 recessed whose profile is complementary to that of the stiffeners 16.

Each stiffener 16 has a lower face 20, concave, which extends in the extension of the surface of the central area 14 and two lateral edges 21 which form the leaves 22, 23 for connecting the bottom face 20 with the panels 19 recessed. As is clearly visible on the figures 3 , 8 , 11 , 14 , 17 , 20 and 22 , the edges 21 are double radius, and comprise a first fillet 22 profile convex, which is flush with the lower face 20, followed by a second discharge 23 to concave profile, which is flush with the panel 19.

As also appears from the drawings, the arch 13 is not connected to the flange 11 directly, but through an intermediate face 25 joining a generally frustoconical shape of revolution around the axis X of the container 1.

The container 1 can be manufactured by stretch blow molding from a plastic preform such as PET. For the formation of the bottom 6, it is advantageous to resort to a boxing operation.

Various particular embodiments, which have all the characteristics described above, but which differ in particular according to the shape of the stiffeners 16, the shape of the central zone 14 and the geometry of the seat, particularly in cheek level 11 .

A first embodiment is illustrated on the Figures 2 to 7 .

In this first embodiment, stiffeners 16 have a Y-shaped and are tapered from their inner end 17 to their outer end 18. As it clearly appears on the figure 3 , the opposite lateral edges 21 of the same stiffener 16 are not contiguous to the outer end 18 thereof, but leave a band 24 of the lower face 20 of the stiffener 16 as far as the cheek 11.

As is clearly visible on the figure 2 , the inner ends 17 of the stiffeners 16 are spaced apart from the central pin 15 , so that the central zone 14 forms between the pin 15 and the inner ends 17 , in the extension of the faces 20, a ring of material which encircles the pin 15.

In this first embodiment, as can easily be deduced from Figures 4 and 5 , the central zone 14 has a relatively large diameter D , the ratio d / D between the diameter d of the central zone 14 and the diameter D of the cheek 11 being close to 0.5. It is therefore necessary to give the bottom 6 additional rigidity.

• une facette 26 tronconique s'étendant dans le prolongement de la joue 11 et dont l'ouverture angulaire A2, mesurée par rapport à un plan perpendiculaire à l'axe X du récipient 1 (ou, en d'autres termes, avec le plan 8 de pose), est d'une valeur (d'environ 45°, comme cela est illustré sur la figure 7) supérieure ou égale à celle de l'angle A1 que forme avec ce même plan la tangente à la voûte 13 sur son bord périphérique externe ;
• un congé 27 de raccordement avec la voûte 13, à grand rayon de courbure (supérieur ou égal à 5 mm environ) ;
• une lèvre 28 annulaire de renfort qui, ceinturant le fond 6, joint les extrémités 18 externes des raidisseurs 16 deux à deux. La lèvre 28 présente en section un profil en V (figure 7), qui fait saillie en pointant sensiblement en direction de l'axe X.

In this case, this increased rigidity is assigned to the periphery of the bottom 6, by the particular geometry of the face 25, which comprises:

• a frustoconical facet 26 extending in the extension of the cheek 11 and whose angular aperture A2, measured with respect to a plane perpendicular to the axis X of the container 1 (or, in others terms, with the laying plane 8 ), is of a value (of approximately 45 °, as illustrated on the figure 7 ) greater than or equal to that of the angle A1 which forms with this same plane the tangent to the vault 13 on its outer peripheral edge;
• a fillet 27 connecting with the vault 13, with a large radius of curvature (greater than or equal to about 5 mm);
• an annular reinforcing lip 28 which, surrounding the bottom 6 , joins the outer ends 18 of the stiffeners 16 in pairs. The lip 28 has in section a V-shaped profile ( figure 7 ), which protrudes by pointing substantially in the direction of the X axis .

As is clearly visible on the figure 3 , the lip 28 has a local enlargement 29 at its junction with the outer end 18 of each stiffener 16.

The lip 28 has two flanks 30, 31, namely an outer flank 30 , on the side of the facet 26, and an inner flank 31 , on the side of the fillet 27 connecting with the vault 13. As can be seen in FIG. figure 7 , the outer flank 30 has in section a straight profile, and forms with a plane perpendicular to the axis (in other words with the laying plane 8 ) an angle A3 low, less than or equal to 20 ° . In the illustrated example, this angle A3 is about 10 °.

The inner sidewall 31 also has a straight profile, and forms, with the outer flank 30 an open angle (greater than 90 °) as the bisector of this angle forms with the facet a right or substantially right angle.

The annular lip 28 of reinforcement also contributes to the stiffening of the seat 7. On the one hand, it reduces the risk of crushing of the seat 7 in the gap between two stiffeners 16 , under the effect of stresses tending to cause a rolling of the bottom 6 . On the other hand, at its junction with the outer ends of the stiffeners 16 , it contributes to the rigidity of the connection between the stiffeners 16 and the seat 7 , in particular reducing the risk of torsion of the stiffeners 16 .

Finally, the fillet 12 has a small radius of curvature - less than or equal to about 1 mm.

A second embodiment is illustrated on the Figures 8, 9 and 10 .

In this second embodiment, the stiffeners 16 have a V-shaped profile, and tapering from their inner end 17 to their outer end 18 .

The central zone 14 is almost reduced to the pin 15, only a thin ring of material separating the inner ends 17 of the stiffeners 16 of the pin 15. The ratio d / D between the diameter d of the central zone 14 and the diameter D of the cheek 11 is relatively low, less than 1/3, and the rigidity of the bottom 6 is therefore relatively large. This is why the face 25 is devoid of annular reinforcing lip.

As we can actually see on the figure 10 , The face 25 of junction is smooth, and is limited to a truncated cone, the angular aperture A2, measured relative to a plane perpendicular to the axis X of the container 1 (or, in other words, with the laying plane 8 ), is of a value of approximately 45 °.

Moreover, as is visible on the figure 8 , in order to improve the blowing of the bottom 6, connecting fillets 32 are provided at the outer ends 18 of the stiffeners, at their junction with the face 25 and their junction with the cheek 11 .

The fillet 12 has a small radius of curvature - less than or equal to about 1 mm.

A third embodiment is illustrated on the Figures 11, 12 and 13 .

In this third embodiment, the stiffeners 16 have a straight profile in I, and have a substantially constant width over approximately their entire length.

The central zone 14 is reduced to the peg 15, which on its periphery delimits the internal ends 17 of the stiffeners 16. As can be seen in FIG. figure 11 , the pin 15 has a star-shaped profile, the inner ends 17 of the stiffeners 16 being thinned while being bevelled.

Measured at the inner end 17 of the stiffeners 16, the diameter d of the central zone 14 (coincides with the diameter of the pin 15 ) is such that the ratio d / D is about 1/4, and the rigidity of the bottom 6 is quite high. This is why the face 25 is devoid of annular reinforcing lip.

As we can actually see on the figure 13 , The face 25 of junction is smooth, and is limited to a truncated cone, the angular aperture A2, measured relative to a plane perpendicular to the axis X of the container 1 (or, in other words, with the laying plane 8 ), is of a value of approximately 45 °.

Moreover, as is visible on the figure 11 , in order to improve the blowing of the bottom 6, connecting fillets 32 are provided at the outer ends 18 of the stiffeners, at their junction with the face 25 and their junction with the cheek 11.

The fillet 12 has a small radius of curvature - less than or equal to about 1 mm.

A fourth embodiment is illustrated on the Figures 14, 15 and 16 .

In this fourth embodiment, the stiffeners 16 have an inverted Y profile, and have, for about half of their length, an I-shaped straight internal portion 33 of substantially constant width, which is extended by an outer portion 34 V inverted, which is widening from the inner portion 33 to the outer end 18 .

The central zone 14 is reduced to the peg 15, which on its periphery delimits the internal ends 17 of the stiffeners 16. As can be seen in FIG. figure 14 , the pin 15 has a star-shaped profile, the inner ends 17 of the stiffeners 16 being thinned while being bevelled.

Measured at the inner end 17 of the stiffeners 16, the diameter d of the central zone 14 (coincides with the diameter of the pin 15 ) is such that the ratio d / D is about 1/4, and the rigidity of the bottom 6 is quite high. This is why the face 25 is devoid of annular reinforcing lip.

As we can actually see on the figure 16 , The face 25 of junction is smooth, and is limited to a truncated cone, the angular aperture A2, measured relative to a plane perpendicular to the axis X of the container 1 (or, in other words, with the laying plane 8 ), is of a value of approximately 45 °.

Moreover, as is visible on the figure 14 , in order to improve the blowing of the bottom 6, 32 connection fillets are provided at the outer ends 18 of the stiffeners, at their junction with the face 25 and their junction with the cheek 11.

The fillet 12 has a small radius of curvature - less than or equal to about 1 mm.

A fifth embodiment is illustrated on the Figures 17, 18 and 19 .

In this fifth embodiment, the stiffeners 16 have an inverted Y profile, and have, for about half of their length, a straight internal portion 33 of I, of substantially constant width, which is extended by an outer portion 34 V inverted, which is widening from the inner portion 33 to the outer end 18 .

The central zone 14 is reduced to the peg 15, which on its periphery delimits the internal ends 17 of the stiffeners 16. As can be seen in FIG. figure 17 , the pin 15 has a star-shaped profile, the inner ends 17 of the stiffeners 16 being thinned while being bevelled.

Measured at the inner end 17 of the stiffeners 16, the diameter d of the central zone 14 (coincides with the diameter of the pin 15 ) is such that the ratio d / D is about 1/4, and the rigidity of the bottom 6 is quite high. This is why the face 25 is devoid of annular reinforcing lip.

As we can actually see on the figure 19 , The face 25 of junction is smooth, and is limited to a truncated cone, the angular aperture A2, measured relative to a plane perpendicular to the axis X of the container 1 (or, in other words, with the laying plane 8 ), is of a value of approximately 45 °.

Moreover, as is visible on the figure 17 , in order to improve the blowing of the bottom 6 , connecting fillets 32 are provided at the outer ends 18 of the stiffeners, at their junction with the face 25 and their junction with the cheek 11 .

The fillet 12 has an average radius of curvature of between 1 mm and 5 mm. In the illustrated example, the fillet 12 has a radius of curvature of approximately 2 mm and extends to the junction face 25. with the vault 13 ( figure 19 ), we see that it is an inner portion of the fillet 12 which forms the cheek 11 to which the stiffeners 16 are connected by their outer end 18 ( figure 18 ). This particularity of realization is made possible by the high rigidity of the bottom 6 conferred by the small diameter of the central zone 14 .

A sixth embodiment is illustrated on the Figures 20 and 21 .

In this sixth embodiment, the stiffeners 16 have an inverted Y profile, and have, for about half of their length, an I-shaped straight internal portion 33 of substantially constant width, which is extended by an outer portion 34 V inverted, which is widening from the inner portion 33 to the outer end 18 .

The central zone 14 is reduced to the peg 15 , which on its periphery delimits the internal ends 17 of the stiffeners 16. As can be seen in FIG. figure 20 , the pin 15 has a star-shaped profile, the inner ends 17 of the stiffeners 16 being thinned while being bevelled.

Measured at the inner end 17 of the stiffeners 16, the diameter d of the central zone 14 (coincides with the diameter of the pin 15 ) is such that the ratio d / D is about 1/4, and the rigidity of the bottom 6 is quite high. This is why the face 25 is devoid of annular reinforcement lip and is limited to a truncated cone whose angular aperture A2 , measured with respect to a plane perpendicular to the axis X of the container 1 (or, in other words, other words, with the plane 8 setting), is a value of about 45 °.

Moreover, as is visible on the figure 20 , in order to improve the blowing of the bottom 6, connecting fillets 32 are provided at the outer ends 18 of the stiffeners, at their junction with the face 25, and at their junction with the cheek 11.

The fillet 12 has a small radius of curvature - less than or equal to about 1 mm.

Moreover, as we see well on the figure 20 and even better on the figure 21 , The seat 7 is hollowed by arcuate notches 35 located angularly in each area between the outer ends 18 of two adjacent stiffeners 16. Thus, the laying plane 8 is discontinuous and is segmented into a peripheral series of coplanar facets 36 located in the extension of each stiffener 16 , andseparated in pairs by a notch 35 . When the container 1 is resting on a flat surface, only the facets 36 are in contact with this surface, the notches 35 being spaced apart. This configuration has the advantage of improving the blowing and better control the forming of the container 1, because in the seat 7 the material tends, when taking the footprint of the bottom 6, to widen naturally between the stiffeners 16 , due to the local solidification of the material at the moment when it reaches the footprints of the stiffeners 16, which occurs before the formation of the seat 7.

A seventh embodiment is illustrated on the Figures 22, 23 and 24 .

In this seventh embodiment, the stiffeners 16 have an inverted Y profile, and have, for about half of their length, a straight internal portion 33 of I, of substantially constant width, which is extended by an outer portion 34 V inverted, which is widening from the inner portion 33 to the outer end 18 .

The central zone 14 is reduced to the peg 15 , which on its periphery delimits the internal ends 17 of the stiffeners 16. As can be seen in FIG. figure 22 , the pin 15 has a star-shaped profile, the inner ends 17 of the stiffeners 16 being thinned while being bevelled.

Measured at the inner end 17 of the stiffeners 16 , the diameter d of the central zone 14 (coincides with the diameter of the pin 15 ) is such that the ratio d / D is about 1/4, and the rigidity of the bottom 6 is quite high. This is why the face 25 is devoid of annular reinforcement lip and is limited to a truncated cone whose angular aperture A2 , measured with respect to a plane perpendicular to the axis X of the container 1 (or, in other words, other words, with the plane 8 setting), is a value of about 45 °.

Moreover, as is visible on the figure 22 , in order to improve the blowing of the bottom 6 , connecting fillets 32 are provided at the outer ends 18 of the stiffeners, at their junction with the face 25 and their junction with the cheek 11 .

The fillet 12 has a small radius of curvature - less than or equal to about 1 mm.

Moreover, as we see well on the figure 22 , and as it also appears on Figures 23 and 24 which is superimposed, the seat 7 is reinforced by means of a peripheral series of curves 37 each formed radially inwards projecting on the cheek 11 , between the outer ends 18 of two adjacent stiffeners 16 . We see on the figure 22 that the curves 37 , which are convex in the direction of the axis X of the container 1 , locally reverse the curvature of the cheek 11 . As illustrated on the Figures 23 and 24 , the curves 37 locally widen the seat, whose width L is therefore variable between a minimum value L _min (at the level of the stiffeners, figure 23 ) and a maximum value L _max (in a median radial plane of the curves 37 , coincides with the sectional plane XXIV-XXIV).

This configuration has the advantage of reinforcing the rigidity of the bottom 6 , while improving the blowing ability and by better controlling the forming of the container 1 , because in the seat 7 the material tends, during the impression taking of the bottom 6 , to be stretched naturally between the stiffeners 16 , due to the local freezing of the material at the moment when it reaches the fingerprints of the stiffeners 16 , which occurs before the formation of the seat 7 .

Whatever the embodiment chosen, especially among those just described, the bottom structure 6 has equal weight with mechanical performance higher than that of the known funds. The wide seat 7 , whose diameter of the laying plane 8 is substantially equal to that of the body 5 in the vicinity of the bottom 6 , combined with the small radius of the outer leave 10 , provides the container 1 a better stability than a conventional seat of which the diameter of the laying plane is substantially smaller than the diameter of the body, and whose high radius fillet favors the rolling of the bottom.

This stability is further increased by the vault 13 stiffened. An unstiffened arch, the presence of which would be induced by the sole boxing of the bottom to make the wide seat, do not sufficiently limit the risk of collapse of the container 1 under the effect of a load such as that to which are subject palletized containers.

The stiffeners 16 in the form of branches do not only contribute to stiffening the vault 13 to reduce the risk of deformation thereof, the extreme deformation being the inversion of the vault. The stiffeners 16 act in the manner of struts, providing a radial recovery of the axial forces exerted on the roof 13 by the hydrostatic pressure of the contents of the container 1 . The stiffeners 16 bearing against the cheek 11 at their ends, the radial recovery of the forces is reflected in a permanent centrifugal radial stress exerted by the stiffeners 16 on the seat 7 via the cheek 11 , which helps to stiffen the seat 7 , particularly preventing ovalization.

Regarding the dimensional recommendations, tests have shown that the rigidity of the bottom 6 is optimal when the cheek 11. and the laying plane 8 have dimensions, respectively axial and radial, similar, as mentioned above.

In fact, the rigidity is the best when these dimensions are equal, but the performance granted by a ratio L / H of between 0.6 and 1.5 are good.

Claims (9)

1. Container (1) made of plastic, provided with a body (5) and a bottom (6) extending at a lower end of the body (5), the bottom (6) comprising:

   - an annular base (7) extending essentially in the extension of the body (5) and defining a resting plane (8);

   - a concave dome (13) which extends from a region adjacent to the base (7) to a central region (14) ;

   this container being characterized in that the dome (13) comprises a set of stiffeners (16) which extend radially from the central region (14) to an annular inner cheek (11) substantially perpendicular to the resting plane (8).
2. Container (1) according to Claim 1, characterized in that the bottom (6) has a frustoconical junction face (25) between the dome (13) and the cheek (11).
3. Container (1) according to Claim 1 or Claim 2, characterized in that the axial dimension (H) of the cheek (11) and the radial dimension (L) of the resting plane (8) are equivalent.
4. Container (1) according to one of the preceding claims, characterized in that the stiffeners (16) together form a star pattern.
5. Container (1) according to one of the preceding claims, characterized in that the bottom (6) comprises an annular reinforcing lip (28) at the junction between the base (7) and the dome (13), joining outer radial ends (18) of the stiffeners (16) in pairs.
6. Container (1) according to one of the preceding claims, characterized in that the dome (13) comprises recessed panels (19) between the stiffeners (16), and in that each stiffener (16) comprises, on its lateral edges, double-radius fillets (22, 23) for connecting to the panels (19).
7. Container according to one of Claims 1 to 6, characterized in that the resting plane (8) is continuous.
8. Container according to one of Claims 1 to 6, characterized in that the resting plane (8) is discontinuous and comprises a peripheral row of coplanar facets (36) which are separated by notches (35).
9. Container according to one of Claims 1 to 6, characterized in that the base (7) comprises a peripheral row of inward-projecting lobes (37).

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