EP2697125B1 - Double-valley petaloid container bottom - 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 (for example a liquid), a body, which gives the container its volume, and a bottom, which closes the body opposite the neck and forms, are introduced or extracted. a base for holding and maintaining the container, when it rests 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 valleys 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 forces (thermal, mechanical) undergone by the bottom (weight of the contents and / or superimposed containers, if any).

The documents US 5454481 , FR2772720 , US 5988416 and US 2010/072165 present bottles with petaloid bottoms for carbonated beverages. The document US 4249667 discloses a plastic container, provided with a petaloid-shaped bottom according to the preamble of claim 1. It is known that the mechanical performance (i.e., in practice, its rigidity) of a petaloid bottom increases with the height of the bottom, because of the increase of the average height of the feet, that is to say the height of the protrusion that form each foot compared to the valleys which border it. But the bottom flowability, that is to say the ease with which the material can flow from the valleys to the feet, decreases concomitantly.

A compromise is therefore sought between mechanical performance and blowing.

To date, the known solutions (see in particular the French patent application FR 2,897,292 or its American counterpart US 2009/020682 ) do not provide the best compromise.

It therefore seems desirable to improve the known funds in this direction.

For this purpose, there is provided a plastic container comprising a body and a petaloid bottom as defined in claim 1. The recess creates a discontinuity in the junction zone on the valleys. Thus, it allows, on the one hand, to increase the rigidity of the bottom. The position of the recess improves the blowing at constant bottom height. On the other hand, the recess reduces the height of the feet, that is to say the measured dimension axially from the seat, defining a laying plane, to the periphery.

• le rapport entre le diamètre du cercle de pose et le diamètre de la périphérie est supérieur à ½ ;
• chaque décrochement définit deux points d'inflexion successifs, les décrochements définissant ensemble un premier cercle d'inflexion et un deuxième cercle d'inflexion, le diamètre du premier cercle d'inflexion étant inférieur au diamètre du deuxième cercle d'inflexion ;
• le rapport entre le diamètre du cercle de pose et le diamètre du deuxième cercle d'inflexion est compris entre 1,3 et 0,7 ;
• la tangente au premier point d'inflexion forme un angle avec une direction verticale inférieur à l'angle formé par la tangente au deuxième point d'inflexion avec la direction verticale ;
• le fond est muni de rainures radiales s'étendant le long des vallées ;
• la valeur du décalage E et la valeur du premier rayon C de courbure sont telles que leur rapport E/C est compris entre 1/100 et 1/25 ;
• le rapport E/C est de 1/50 environ ;
• la section centrale et la section périphérique présentent des centres de courbure non confondus ;
• la section centrale et la section périphérique présentent des rayons de courbure différents.

This container may also include the following features, taken separately or in combination:

• the ratio between the diameter of the laying circle and the diameter of the periphery is greater than ½;
• each recess defines two successive points of inflection, the recesses defining together a first inflection circle and a second inflection circle, the diameter of the first inflection circle being smaller than the diameter of the second inflection circle;
• the ratio between the diameter of the laying circle and the diameter of the second inflection circle is between 1.3 and 0.7;
• the tangent to the first inflection point forms an angle with a vertical direction less than the angle formed by the tangent to the second point of inflection with the vertical direction;
• the bottom is provided with radial grooves extending along the valleys;
• the value of the offset E and the value of the first radius C of curvature are such that their E / C ratio is between 1/100 and 1/25;
• the E / C ratio is about 1/50;
• the central section and the peripheral section have uncombined centers of curvature;
• the central section and the peripheral section have different radii of curvature.

• 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 coupe partielle d'un détail du fond de la figure 3, selon le plan de coupe V-V ;
• la figure 6 est une vue en coupe du fond de la figure 3, selon le plan de coupe VI-VI ;
• la figure 7 est une vue en coupe du fond de la figure 3 selon le plan de coupe VII-VII ;
• la figure 8 est une vue de détail de la figure 7 ;
• la figure 9 est une vue en perspective d'un fond selon un autre mode de réalisation ;
• la figure 10 est une vue en coupe radiale du fond de la figure 9.

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 partial section of a detail from the bottom of the figure 3 , according to the VV cutting plane;
• the figure 6 is a sectional view of the bottom of the figure 3 according to section plane VI-VI;
• the figure 7 is a sectional view of the bottom of the figure 3 according to section plane VII-VII;
• the figure 8 is a detail view of the figure 7 ;
• the figure 9 is a perspective view of a bottom according to another embodiment;
• the figure 10 is a radial sectional view of the bottom of the figure 9 .

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 defining a vertical direction, and comprises a body 2 forming the side wall of the container 1 and a bottom 3, which extends the body 2 and closes the latter at a lower end thereof forming the bottom wall of the container 1.

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 protuberances protruding outwardly from 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, towards a periphery 7 of the bottom 3 where it is connected to the body 2. A diameter of the periphery, denoted by A, is defined as being the minimum diameter of the circle in which the periphery 7 is inscribed . According to the embodiment preferred embodiment illustrated in the figures, the periphery 7 is circular, it being understood that the periphery 7 may be of any shape.

As is clearly visible on the 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 5 are included in a laying plane and together form a seat, through which the container 1 can rest on a flat surface (for example a table).

We define a pose circle 10 (materialized on the figure 3 by a circle in phantom) by the circle circumscribed at the vertices 8. In practice, the vertices 8 may have a certain thickness in the laying plane, so that the laying circle 10 may have a certain radial width (although weak in view of the diameter of the circle 10 ) and thus be in the form of a ring. Note B the diameter of the circle 10 pose.

Each foot 5 has an end face 11 which extends gently from 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 7 ). More specifically, as illustrated on the figure 7 , the end face 11 is slightly curved, concave towards the outside of the container 1, the concavity being accentuated near the central zone 6 of the bottom 3.

As is clearly visible on the figures 2 and 3 , the feet 5 are separated in pairs by portions of the bottom wall 4 called valleys 12, which extend radially in a star from the central zone 6 to the periphery 7.

The valleys 12 are concave outwards in cross section (that is to say in a plane perpendicular to the radial direction, cf. Figures 4 to 6 ). The radius of curvature of the valleys 12, measured in cross section, may be variable. More specifically, it is preferably low near the central zone 6 , and relatively greater near the periphery 7.

We see on Figures 3 to 6 that each valley 12 widens from the central zone 6 towards the periphery 7 that it joins. This widening is preferably continuous, that is to say that the edges of the valleys 12 form between them, at any point, a non-zero angle. In the example shown, the valleys 12 have a contour in plan tulip-shaped (or bell) but this form is not restrictive, and the edges of the valleys 12 may be straight (the valleys 12 then having a contour V). As can be seen in particular on the figure 2 , each valley 12 is devoid of branching (in particular on the periphery side 7 ) , and thus forms a unitary hollow reserve.

We see on figures 2 and 3 that the feet 5 are equal in number to the valleys 12. In the example illustrated in the drawings, the bottom 3 comprises five feet 5 and five valleys 12, 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 13 each bordering a valley 12 laterally. As can be seen in FIG. figure 4 the flanks 13 are not vertical (because the bottom 3 would then be difficult or impossible to blow), but inclined by approaching from the valley 12 to the end face 11 of a foot 5. As shown in FIG. figure 3 , the flanks 13 are connected to the end face 11 by a fillet 14.

Each foot 5 is further delimited radially by an external face 15 which extends in the extension of the body 2 to the vicinity of the apex 8, to which the external face 15 is connected by a fillet 16. At the periphery of the bottom 3, the outer face 15 is connected to the body 2 by a fillet.

The outer face 15 is not cylindrical, but substantially conical of revolution around the main axis X. More specifically, the outer face 15 is inclined toward the central area 6 of the bottom 3 of the container 1 when approaching the laying plane. Furthermore, in radial section, the outer side 15 is not straight but convex.

The vertices 8 of the feet 5 are thus shifted towards the central zone 6 of the base 3, that is to say that they are not at right of the periphery 7. More precisely, the vertices 8 of the feet 5 are positioned so that the laying circle 10 is located radially recessed relative to the periphery 7, that is to say with respect to the circle in which is inscribed the periphery 7. In addition, the ratio between the diameter B of the laying circle 10 and the diameter A of the periphery 7 is less than 4/5.

Preferably, the ratio between the diameter B of the laying circle 10 and the diameter A of the periphery 7 is between 2/5 and 4/5, and more preferably, the ratio between the diameters B and A is greater than 1. / 2, for example (as in the example shown) equal to 7/10.

• une section 17 centrale qui s'étend depuis la zone 6 centrale du fond 3 jusqu'à une zone 18 de jonction située à l'aplomb du cercle 10 de pose, et qui présente, dans un plan radial, un premier rayon C de courbure,
• une section 19 périphérique, qui s'étend depuis la zone 18 de jonction jusqu'à la périphérie 7, et présente, dans ledit plan radial, un deuxième rayon D de courbure, cette section 19 périphérique étant décalée vers l'extérieur du récipient 1 par rapport à la section 17 centrale, la zone 18 de jonction formant un décrochement 20.

Moreover, as illustrated on the figure 2 , and right on the figure 7 , the valleys 12 present:

• a central section 17 which extends from the central area 6 of the base 3 to a region 18 of junction located plumb with the circle 10 of installation, and which has, in a radial plane, a first radius of curvature C ,
• a peripheral section 19 , which extends from the junction zone 18 to the periphery 7, and has, in said radial plane, a second radius D of curvature, this peripheral section 19 being shifted towards the outside of the container 1 relative to the central section 17 , the junction zone 18 forming a recess 20.

The curvature C and D rays are not necessarily constant but may vary with the distance to the main axis X; in addition, the centers of curvature of sections 17 and 19 are not necessarily confused or located on the main axis X of the container.

E is the value of the offset between the central section 17 and the peripheral section 19 . This offset E is defined as follows.

We consider a foot 5 and a valley 12 that is brought into section in the same radial plane (that of the figure 7 ) by rotation about the main axis X of the container 1. Note O _p the center of curvature of the foot 5 at the top 8 and O _c the center of curvature of the central section 17 . We draw a reference axis R , joining the centers O _p and O _c . Note P ₁ the point of intersection of the reference axis R and the central section 17 , and P ₂ the point of intersection of the reference axis R and the peripheral section 19 . If necessary, the central section 17 and the peripheral section 19 can be extended by extrapolation, to determine the points of intersection P ₁ and P ₂ . The offset E is then considered equal to the distance between the points of intersection P ₁ and P ₂ .

The value of the offset E may be between 0.5 mm and 6 mm, depending on the capacity of the container 1. For example, for a container 1 with a capacity of 1.5 L, the offset E is between 0.8 mm and 2 mm.

In addition, it defines a relationship between the difference E and the first radius of curvature C of the central section 17, denoted W / C ratio. The ratio E / C is then advantageously between 1/100 and 1/25 and is for example equal to 1/50, as on the Figures 1 to 8 .

• une première section (la section 17 centrale), convexe vers l'extérieur du récipient 1,
• une deuxième section (la zone 18 de jonction), concave vers l'extérieur du récipient 1, et
• une troisième section (la section 19 périphérique), de nouveau convexe vers l'extérieur du récipient 1.

The recess 20 thus creates a discontinuity in the zone 18 of junction on the valleys 12. More exactly, the recess 20 defines two successive points 21, 22 of inflection: a first point 21 of inflection to the change of concavity between the section 17 and the junction area 18 and a second point 22 of inflection between the junction area 18 and the peripheral section 19 . Thus, each valley 12 presents successively, in a radial plane:

• a first section (the central section 17 ) convex towards the outside of the container 1,
• a second section (the junction zone 18 ), concave towards the outside of the container 1, and
• a third section (the peripheral section 19 ), again convex towards the outside of the container 1.

The first inflection 21 is softer than the second point of inflection 22, the angle α between the tangent to the first point of inflection 21 and the vertical direction is smaller than the angle β formed between the tangent to second inflection point 22 and the vertical direction. For example, the angle α between the tangent to the first point of inflection 21 and the vertical direction is between 40 ° and 65 °, and is for example equal to 55 °, while the angle β between the tangent to the second point of inflection 22 and the vertical direction is between 70 ° and 85 °, and is for example equal to 80 °.

Area 18 junction is located plumb with the circle 10 of pose, that is to say the circle 10 and the laying zone 18 junction, when viewed projected by rotation about the main axis X in the same radial plane (that of figure 7 ), are substantially aligned in the vertical direction (parallel to the main X axis). It is possible to define, as for the laying circle 10 , a first inflection circle 23 , passing through the first points 21 of inflection of the valleys 12 of the bottom 3 and a second inflection circle 24 passing through the second points. 22 inflexion valleys bottom 3 (shown in phantom on the figure 3 ). It goes without saying that, given the position of the first inflection points 21 and the second inflection points 22 , the diameter F of the first inflection circle 23 is smaller than the diameter G of the second inflection circle 24 .

Thus, preferably, in projection on the laying plane, the second inflection circle 24 is between the central zone 6 of the bottom 3 and the laying circle 10 . Alternatively, the laying circle 10 may be for example between the two circles 23, 24 inflection. The ratio between the diameter B of the circle 10 of pose and the diameter G of the second circle 24 of inflection is preferably between 1.3 and 0.7, and is for example equal to about 1.1.

The step 20 makes it possible, on the one hand, to increase the rigidity of the bottom 3. Its position, on the other hand, makes it possible to improve the blowing, at the level of the constant bottom 3 .

Indeed, on the one hand, the stresses generated for example by a pressure internal to the container 1 tend to accentuate the convexity of the valleys 12. The recess 20, offering a sudden variation of curvature in the valleys 12, and more exactly by introducing a concavity change between the peripheral section 19 and the central section 17 , reduces the deformability of the valleys 12.

On the other hand, the recess 20 reduces the height of the feet 5, that is to say the dimension measured axially from the laying plane to the plane of the periphery 7. In other words, the feet 5 are connected at the periphery 7 of the bottom 3 at a height lower than petaloid funds of the state of the art, for equivalent performance.

Indeed, the outwardly displaced position of the container 1 of the peripheral section 19 relative to the central section 17 (that is to say the presence of the recess 20 ), combined with the position of the junction zone 18 in line with the laying circle 10 , the peripheral section 19 joins the periphery 7 at a lower height than if the central section 17 was extended to the periphery 7.

In order to illustrate the phenomenon, we have extended figure 7 the central section 17 in a continuous way (in dotted line, on the right). Thus, it is clear that if such an extension was made in reality it would require to shift the periphery 7 to the top of the container 1. This would result in an increase in the height of the feet 5.

However, it appears that the blowing of the bottom 3, and more precisely the feet 5, decreases as the height thereof increases. From an experimental point of view, the material of the container being formed first reaches the cavities of the mold corresponding to the valleys 12. In contact with these cavities, the material cools, which instantly reduces its creep capacity, and increases the pressure required to force the material to reach the cavities of the mold corresponding to the apices 8.

The offset towards the outside of the container 1 of the peripheral section 19 brings the valleys 12 closer to the vertices 8, which reduces the necessary time and / or the necessary blowing pressure, to reach the top 8 of the feet 5. has been determined that, when the recess 20 is substantially in line with the circle 10 of installation, the diameter B has a relationship with the diameter a of the periphery 7 of less than 4/5, the bottom of the mechanical performances remain 3 satisfactory despite the decrease in the height of the feet 5 (and thus the height of the bottom 3 ) .

To further improve the mechanical performance of the bottom 3, the presence of the recess 20 between the central section 17 and the peripheral section 19 can be combined with additional features to stiffen the bottom 3.

Thus, according to a first variant embodiment, visible on the figure 9 , The bottom 3 can it be provided with radial grooves 25 extending recessed inwardly of the container 1, at the bottom and along the valleys 12 along a center line of a valley 12, from a vicinity of the central zone 6 to the vicinity of the periphery 7. The grooves 25 serve to further increase the rigidity of the bottom 3. Under the effect of the mechanical stresses exerted on the container 1 (in particular under the effect the pressure prevailing in the container filled with a carbonated liquid), the grooves 25 tend to flow, expanding and flattening, which causes an enlargement of the valleys 12 and, consequently, a verticalization of the feet 5 which opposes the overall subsidence of the bottom 3.

According to a second variant embodiment, the peripheral section 19 can be connected to the periphery 7 by means of an external section 26 ( Figures 9 and 10 ), concave in the absence of constraints, which increases the mechanical performance of the bottom 3. Indeed, under the effect of a pressure inside the container 1, for example when filling the container 1, the central section 17 and section 19 both convex, of each valley 12, tend to inflate, while a reversal of the concave external section 26 , which then adopts a convex profile. The peripheral section 19 and the outer section 26 then form in fine a single continuous convex profile. 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. , thus limiting the collapse of the central zone 6 .

Finally, according to a third embodiment variant, not shown in the figures, the feet 5 of the bottom 3 can be stiffened thanks to the formation of a projecting protruding stop, as described in the document FR 2,897,292 , in the name of the plaintiff.

The combination of the central section 17 , the recess 20, the peripheral section 19 with additional means to stiffen the bottom 3, such as the grooves 25, the outer section 26 or the projecting edge on the feet 5, then ensures the good bottom blowing 3, while ensuring the good resistance of the bottom 3 to the mechanical stresses experienced by the container 1.

Claims (10)

1. Container (1) made of plastic material comprising a body (2) and a petaloid bottom (3) extending the body (2) from a periphery (7), the bottom (3) comprising a bottom wall (4) of outwardly convex general shape, from which there project feet (5) defining crests (8) which together form a base inscribed inside a seating circle (10) of diameter (B) for which a ratio with a diameter (A) of the periphery (7) is less than 4/5, the feet (5) being separated one from the next by portions of the bottom wall (4) which form recessed valleys (12) extending radially from a central zone (6) of the bottom as far as the periphery (7), each valley (12) comprising two adjacent sections, namely:

   - a central section (17) which extends from the central zone (6) of the bottom (3) as far as a junction zone (18) situated in vertical alignment with the seating circle (10), and has, in a radial plane, a first radius (C) of curvature,

   - a peripheral section (19), which extends from the junction zone (18) as far as the periphery (7), and has, in the said radial plane, a second radius (D) of curvature, characterized in that this peripheral section (19) is offset towards the outside of the container (1) by an offset value (E) with respect to the central section (17), the junction zone (18) forming a discontinuity (20) which defines two successive points (21, 22) of inflection,

   - the value of the offset (E) between the central section (17) and the peripheral section (19) being equal to the distance between two points of intersection P₁ and P₂, P₁ being the point of intersection of a reference axis (R) with the central section (17), and P₂ the point of intersection of the reference axis (R) with the peripheral section (19), the reference axis (R) joining two centres O_p and O_c, O_p being the centre of curvature of a foot (5) at the crest (8) and O_c the centre of curvature of the central section (17), the central section (17) and the peripheral section (19) being able to be extended by extrapolation in order to determine the points of intersection P₁ and P₂.
2. Container (1) according to Claim 1, in which the ratio between the diameter (B) of the seating circle (10) and the diameter (A) of the periphery (7) is greater than 1/2.
3. Container (1) according to Claim 1 or Claim 2, in which the discontinuities (20) together define a first circle (23) of inflection passing through the first points (21) of inflection and a second circle (24) of inflection passing through the second points (22) of inflection, the diameter (F) of the first circle (23) of inflection being less than the diameter (G) of the second circle (24) of inflection.
4. Container (1) according to Claim 3, in which the ratio between the diameter (B) of the seating circle (10) and the diameter (G) of the second circle (24) of inflection is comprised between 1.3 and 0.7.
5. Container (1) according to one of Claims 3 and 4, in which the tangent to the first point (21) of inflection forms with a vertical direction an angle (α) that is smaller than the angle (β) formed with the vertical direction by the tangent to the second point (22) of inflection.
6. Container (1) according to one of the preceding claims, in which the bottom (3) is provided with radial grooves (25) extending along the valleys (12) .
7. Container (1) according to one of the preceding claims, in which the value of the offset (E) and the value of the first radius (C) of curvature are such that their ratio E/C is comprised between 1/100 and 1/25.
8. Container (1) according to Claim 7, in which the ratio E/C is around 1/50.
9. Container (1) according to one of the preceding claims, in which the central section (17) and the peripheral section (19) have non-coincident centres of curvature.
10. Container (1) according to one of the preceding claims, in which the central section (17) and the peripheral section (19) have different radii of curvature.

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