EP2396246B1 - Container in which the base is provided with a double-seated flexible arch - 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.

Conventional stretching induces a bi-orientation of the material (axial and radial) which gives the final container a good structural rigidity. However, the bi-orientation induces in the material residual stresses which, during a hot filling (in particular with a liquid having a temperature greater than the glass transition temperature of the material), are released by causing a deformation of the container can make it unfit for sale.

It is known, to reduce the deformation of the container during hot filling, to complete the stretch blow molding by a heat treatment called heat setting (French translation of the English expression "heat set"), treatment by which the container is maintained. formed in contact with the heated mold wall at a temperature between 120 ° C and 250 ° C, for a predetermined time (usually a few seconds).

Heat-setting, however, only solves a part of the container deformation problems related to hot filling. Indeed, while cooling, the liquid and the air which overhangs it in the clogged container undergo a decrease in volume which tends to retract the container.

Several solutions have been envisaged to reduce the visible effects of such retraction. These solutions generally relate to the shape of the container.

Thus, it has been proposed to provide the body of the container with deformable panels which, during cooling of the liquid, bend under the effect of retraction. This solution is proven but it is not entirely satisfactory, because handling is made hazardous because of the flexible nature of the body.

It has therefore been proposed to postpone on the bottom the capacity of the container to deform (or to be deformed forcibly) to adapt to the retraction of the liquid accompanying its cooling. Thus, the document WO 2006/068511 proposes a container whose bottom can take two positions, namely an extended position in which the bottom extends projecting outside the container, and a retracted position in which the bottom extends inwardly of the container. The deployed position is adopted by the bottom before filling the container, while the retracted position is adopted after filling, to accompany the retraction of the liquid due to its cooling. The passage from the extended position to the retracted position may be forced by means of a tool by means of which the bottom is pressed towards the interior of the container (see Figures 12a to 12d). With this arrangement, it is possible to stiffen the body, to the benefit of the grip of the container.

However, the manufacture of this type of container causes handling difficulties. Indeed, the containers must be transferred, deployed funds from the blowing station to the filling station, then the filling station at the bottom turning station. It is conceivable to transport the containers by means of neck grippers to which the containers are suspended.

This handling, however, involves constraints due to the need to synchronize the transfer devices. In addition, it does not store the containers in buffer zones to compensate for jolts in the production line. This is why it is preferable to use transport on a conveyor equipped with a conveyor belt on which the containers rest by their bottom. However, because of the small diameter of the seat due to the conicity of the projecting bottom, the containers are unstable and the risk of tipping (and therefore conveyor clogging) is high.

In order to limit the risk of tipping containers during transport, some manufacturers use stabilizers with cups in which the bottoms of the projecting containers are received, cf. the document US 2007/0051073 (see in particular the Figure 5C ).

This solution is at first sight interesting, but it requires that the containers are properly positioned on their cups, except to further increase the risk of tipping. This handling, which requires great precision in the positioning of the containers in the stabilization devices, therefore implies constraints close to those induced by the use of the devices. clip transfer which, as we have already explained, appear objectionable in the present application.

The invention therefore aims to propose a solution for improving the safety of transport containers with projecting bottoms.

• une assise externe annulaire présentant une dimension transversale B prédéterminée telle que : $$0,95\le \frac{B}{C}\le 1$$
  
• une voûte déformable qui s'étend à l'intérieur de l'assise externe annulaire et qui, dans une position déployée, fait saillie vers l'extérieur du récipient et définit une assise interne annulaire présentant une dimension transversale A prédéterminée telle que : $$1,2\le \frac{B}{A}\le 1,4$$
  

For this purpose, the invention provides a plastic container, comprising a body and a bottom extending at a lower end of the container, the body having, at the junction with the bottom, an outer diameter C, container in which the background presents:

• an annular outer seat having a predetermined transverse dimension B such that: $$0,95\le \frac{B}{\mathrm{VS}}\le 1$$
  
• a deformable arch which extends inside the annular outer seat and which, in an extended position, projects outwards from the container and defines an annular inner seat having a predetermined transverse dimension A such that: $$1,2\le \frac{B}{\mathrm{AT}}\le 1,4$$
  

The container thus dimensioned has increased stability not only when it rests on its outer seat (after filling and inverting the vault accompanying the cooling of the liquid) but also when it rests on its internal seat (before filling), which is located , compared to known containers, deported to the periphery of the bottom.

est par exemple de 0,98.The report $\frac{B}{\mathrm{VS}}$

is for example 0.98.

est de 1,32.According to a first embodiment, the report $\frac{B}{\mathrm{AT}}$

is 1.32.

est de 1,23.According to another embodiment, the report $\frac{B}{\mathrm{AT}}$

is 1.23.

Moreover, the container preferably has, in the deployed position of the vault, an axial offset h between the outer seat and the inner seat such that: $$0,01\le \frac{h}{\mathrm{VS}}\le 0,1$$

est de 0,08.According to a first embodiment, the report $\frac{h}{\mathrm{VS}}$

is 0.08.

est de 0,014.According to a second embodiment, the report $\frac{h}{\mathrm{VS}}$

is 0.014.

In addition, the container preferably has, at a junction between the body and the bottom, a connection fillet having a radius r such that: $$\frac{r}{\mathrm{VS}}\le \frac{1}{100}$$

The tangent to the body, in the vicinity of its junction with the bottom, preferably forms with an axis of the container an angle less than 30 °.

In a particular embodiment, the body is, in the vicinity of its junction with the bottom, substantially cylindrical, the angle referred to above being then almost zero.

• la figure 1 est une vue d'élévation en coupe montrant un récipient selon un premier mode de réalisation ;
• la figure 2 est une vue de détail montrant le fond du récipient de la figure 1, dans une position déployée ;
• la figure 3 est une vue similaire à la figure 2, montrant le fond dans une position rétractée ;
• la figure 4 est une vue d'élévation en coupe montrant un récipient selon un deuxième mode de réalisation ;
• la figure 5 est une vue de détail montrant le fond du récipient de la figure 4, dans une position déployée ;
• la figure 6 est une vue similaire à la figure 5, montrant le fond dans une position rétractée.

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 sectional elevational view showing a container according to a first embodiment;
• the figure 2 is a detail view showing the bottom of the container of the figure 1 in an unfolded position;
• the figure 3 is a view similar to the figure 2 , showing the bottom in a retracted position;
• the figure 4 is a sectional elevational view showing a container according to a second embodiment;
• the figure 5 is a detail view showing the bottom of the container of the figure 4 in an unfolded position;
• the figure 6 is a view similar to the figure 5 , showing the bottom in a retracted position.

On the figure 1 and 3 two exemplary embodiments of a container 1 - in this case a wide-necked bottle - made by stretch-stretching from a thermoplastic preform such as PET (polyethylene terephthalate) have been shown. This container is preferably of the HR type, and is for this purpose manufactured by stretch blow molding within a mold whose wall is heated so as to increase the crystallinity level of the material by heat input.

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 extended by a side wall or body 5, which has a generally symmetrical 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 in the extension of the body 5.

As is clearly visible on the figures 2 and 5 , the body 5 is, in a lower portion of the container, substantially cylindrical and extends downwardly to a lower end 7 where it joins the bottom 6. The bottom 6 comprises, in the immediate vicinity of this junction 7 , an annular bead 8 forming, in a particular configuration described hereinafter, a circular outer seat 9 , through which the container 1 can lie flat on a flat surface such as a table (in current use) or the upper surface of a conveyor belt (to allow handling on the production line).

The bottom 6 further comprises a roof 10 which extends from the outer seat 9 towards the inside thereof, that is to say in the direction of the axis X of the vessel 1.

• Une position déployée, représentée sur les figures 2 et 5, dans laquelle la voûte 10 s'étend au moins en partie en saillie par rapport à l'assise 9 externe vers l'extérieur du récipient 1 (c'est-à-dire à l'opposé du col 2),
• Une position rétractée, représentée sur les figures 3 et 6, dans laquelle la voûte 10 s'étend en saillie par rapport à l'assise 9 externe vers l'intérieur du récipient 1 (c'est-à-dire en direction du col).

The vault 10 is deformable, and can adopt two positions, namely:

• An unfolded position, represented on figures 2 and 5 wherein the arch 10 extends at least partly projecting from the outer seat 9 towards the outside of the container 1 (i.e. opposite the neck 2),
• A retracted position, represented on the figures 3 and 6 wherein the arch 10 extends projecting from the outer seat 9 towards the interior of the container 1 (i.e. towards the neck).

The roof 10 comprises an annular membrane 11 , which extends from the bead 8 in the extension thereof in the direction of the axis X and projecting outwardly of the container 1. In the deployed position of the roof 10 , the membrane 11 is frustoconical of revolution about the axis X.

The arch 10 further comprises an annular medial portion 12 which has a cup-shaped concavity facing the outside of the container 1 and extends in the extension of the membrane 11 in the direction of the axis X and projecting towards the inside the container 1.

In this way, the membrane 11 and the median portion 12 together define, at their junction, an annular top portion 13 which, in the deployed position of the vault 10, constitutes the lowest zone of the container 1 (held vertically with its neck 2 open upwards) and thus forms an internal seat 14 , by which it can lie flat on a flat surface such as a table or the upper surface of a conveyor belt.

The vault 10 finally comprises, in the extension of the median portion 12 , a central pin 15 which extends around the axis X projecting towards the inside of the container 1.

• A le diamètre de l'assise 14 interne ;
• B le diamètre de l'assise 9 externe ;
• C le diamètre externe du fond 6, mesuré à la jonction 7 avec le corps 5 ;
• h l'extension axiale de la voûte 10, égale au décalage axial entre l'assise 14 interne et l'assise 9 externe, en position déployée de la voûte 10.

We notice :

• At the diameter of the inner seat 14 ;
• B the diameter of the outer seat 9 ;
• C the outer diameter of the bottom 6, measured at the junction 7 with the body 5;
• h the axial extension of the vault 10, equal to the axial offset between the inner seat 14 and the outer seat 9 , in the deployed position of the roof 10.

Although the term "diameter" commonly refers to the transverse dimension of an object having a symmetry of revolution about an axis (which is the case here), it is generalized in this context to containers that do not have symmetry of revolution, and whose cross-sectional profile would for example be square, oval, etc. In this case, the term "diameter" therefore refers more generally to the transverse dimension (width) measured in any plane of symmetry - or in any plane containing the X axis - of the container 1.

The inner seat 14 and the outer seat 9 are sized to provide a great stability of the container 1 laid flat both in the deployed position of the arch 10 (position in which the container 1 rests on the inner seat 14 ) that in its retracted position (in which the container 1 rests on the outer seat 9).

et $$1,2\le \frac{B}{A}\le 1,4$$

For this purpose, the diameters A, B and C are correlated according to the following relationships: $$0,95\le \frac{B}{\mathrm{VS}}\le 1$$

and $$1,2\le \frac{B}{\mathrm{AT}}\le 1,4$$

est de 0,98 environ.The relation (1) reveals that the outer seat 9 is deported as far as possible towards the periphery of the bottom 6, at its junction 7 with the body 5. At this junction 7 , which corresponds to the lower end of the body 5, the tangent to the body 5 forms with the axis X of the container 1 a small angle, less than 30 ° (in the exemplary embodiments shown, the body 5 has a cylindrical shape of revolution, so that this angle is substantially zero). The stability of the container 1 in the retracted position of the vault 1 is increased. It should be noted that, in the exemplary embodiments illustrated, the report $\frac{B}{\mathrm{VS}}$

is about 0.98.

), au bénéfice de la stabilité du récipient 1 en position déployée de la voûte 1, et d'autre part une maximisation de l'extension radiale de la membrane 11 (c'est-à-dire une maximisation du rapport $\frac{B}{A}$

) pour permettre un retournement non destructif de la voûte 10 vers sa position rétractée, à tout le moins sans que ce retournement ne provoque l'apparition de fissures ou d'amorces de rupture. Dans le premier exemple de réalisation, illustré sur les figures 1 à 3, le rapport $\frac{B}{A}$

est de 1,32 ; dans le second exemple de réalisation, illustré sur les figures 4 à 6, le rapport le rapport $\frac{B}{A}$

est de 1,23.The relationship (2) reveals that the ratio between the diameters B and A is close enough to 1, a gap between these two diameters being however unavoidable due to the presence of the flexible membrane 11 . The range recommended by the relation (2) ensures a good compromise between two objectives that are a priori contradictory, namely on the one hand a maximization of the diameter A (that is to say a minimization of the ratio $\frac{B}{\mathrm{AT}}$

), in favor of the stability of the container 1 in the deployed position of the vault 1, and secondly a maximization of the radial extension of the membrane 11 (that is to say a maximization of the ratio $\frac{B}{\mathrm{AT}}$

) to allow a non-destructive reversal of the vault 10 to its retracted position, at least without this reversal does not cause the appearance of cracks or failure primers. In the first embodiment, illustrated on the Figures 1 to 3 , The report $\frac{B}{\mathrm{AT}}$

is 1.32; in the second embodiment, illustrated on the Figures 4 to 6 , the report the report $\frac{B}{\mathrm{AT}}$

is 1.23.

The relations (1) and (2) can be combined to express a direct correlation between the diameters A and C: $$0,65\le \frac{\mathrm{AT}}{\mathrm{VS}}\le 0,85$$

est de 0,74 ; dans le second exemple de réalisation, illustré sur les figures 4 à 6, le rapport le rapport $\frac{A}{C}$

est de 0,80.This relation expresses differently the compromise mentioned above, the value of the diameter A of the inner seat 14 being as close as possible to that of the diameter C of the outer seat 9 to maximize the width of the seat 14 deployed position of the arch 10, while providing between the periphery of the bottom 6 (diameter C ) and the inner seat 14 (diameter C ) sufficient space to accommodate on the one hand the outer seat 9 (diameter B ) , maximum offset to the periphery of the bottom 6 (which expresses the relationship (1)), and secondly the flexible membrane 11 interposed between the two seats 9 and 14. In the first embodiment, illustrated on the Figures 1 to 3 , The report $\frac{\mathrm{AT}}{\mathrm{VS}}$

is 0.74; in the second embodiment, illustrated on the Figures 4 to 6 , the report the report $\frac{\mathrm{AT}}{\mathrm{VS}}$

is 0.80.

Furthermore, the value of the axial extension h of the arch 10 in the deployed position must be sufficiently high to allow an appropriate decrease in the volume of the container 1 during the overturning of the vault 10, corresponding to the cumulative volume decreases - due to the cooling - liquid and air present in the head space (defined between the liquid and the cap closing the container). However, two constraints tend, on the contrary, to minimize the axial extension of the arch 10 in the deployed position: on the one hand, the need, for stability purposes, not to excessively increase the overall height of the container 1; on the other hand, the need to facilitate the inversion of the vault 10. The following relation, which proposes to correlate the extension h to the diameter C of the bottom 6 while maintaining the ratio of these two dimensions in a predetermined range, offers a good compromise between these contradictory constraints: $$0,01\le \frac{h}{\mathrm{VS}}\le 0,1$$

est de 0,08. Cet exemple de réalisation, où le rapport $\frac{h}{C}$

est proche de la borne supérieure de la gamme préconisée, correspond à un cas où la dépression accompagnant dans le récipient le refroidissement du liquide peut se révéler insuffisante pour provoquer le retournement de la voûte 10. On peut alors forcer le retournement de la voûte 10 au moyen d'un outil par lequel on exercerait une force ascendante sur la voûte, par exemple au niveau du pion 15. Dans le second exemple de réalisation, illustré sur les figures 4 à 6, le rapport le rapport $\frac{h}{C}$

est de 0,014. Dans ce second exemple de réalisation, où le rapport $\frac{h}{C}$

est proche de la borne inférieure de la gamme préconisée, correspond au cas où la dépression accompagnant dans le récipient le refroidissement du liquide est suffisante pour provoquer le retournement de la voûte 10 sans qu'il soit nécessaire de forcer ce retournement au moyen d'un outil.In other words, the value of the axial extension h is between one hundredth and one tenth of the value of the diameter C of the bottom 6. In the first exemplary embodiment, illustrated in FIGS. Figures 1 to 3 , the report $\frac{h}{\mathrm{VS}}$

is 0.08. This exemplary embodiment, where the report $\frac{h}{\mathrm{VS}}$

is close to the upper limit of the recommended range, corresponds to a case where the depression accompanying in the container the cooling of the liquid may be insufficient to cause the inversion of the vault 10. It can then force the overturning of the vault 10 to using a tool by which one would exert an ascending force on the vault, for example at the level of the pawn 15. In the second example of embodiment, illustrated on the Figures 4 to 6 , the report the report $\frac{h}{\mathrm{VS}}$

is 0.014. In this second embodiment, where the report $\frac{h}{\mathrm{VS}}$

is close to the lower limit of the recommended range, corresponds to the case where the depression accompanying in the container the cooling of the liquid is sufficient to cause the overturning of the vault 10 without it being necessary to force this reversal by means of a tool.

Moreover, as can be seen in the figures, and more precisely on the Figures 2, 3 , 5 and 6 , the connection fillet between the body 5 of the container 1 and the bottom 6, which forms the outer part of the bead 8 defining the outer seat 9 , has a radius r of small curvature with respect to the diameter C, in comparison with a ordinary container.

More precisely, the dimensions r and C preferably check the following relation: $$\frac{r}{\mathrm{VS}}\le \frac{1}{100}$$

The rigidity of the outer seat 9 is increased. Thus, in practice, for a diameter C of the bottom of 100 mm (for example for a bottle with a capacity of 2 l), the radius r of the fillet is preferably less than 1 mm. For a diameter C of 60 mm (for example for a bottle with a capacity of 0.5 l), the radius r of the fillet is less than 0.6 mm, and for example 0.5 mm.

• une position basse, adoptée en début de soufflage, dans laquelle le fond de moule est écarté de l'ouverture vers le bas, et
• une position haute, adoptée en fin de soufflage, dans laquelle le fond de moule obture l'ouverture et repousse vers le haut la matière du fond 6 du récipient 1.

In order to manufacture a container 1 satisfying the dimensional constraint defined by relation (5), it will be preferable to use a stretch-blow molding technique in a mold comprising a side wall defining a lower opening and a mold bottom movable relative to the wall of the mold between:

• a low position, adopted at the beginning of blowing, in which the bottom of the mold is moved away from the opening towards the bottom, and
• a high position, adopted at the end of blowing, in which the mold bottom closes the opening and pushes up the material of the bottom 6 of the container 1.

This technique, called boxing, makes it possible to increase the drawing ratio of the container 1, to the advantage of its mechanical rigidity. By using a mold bottom whose diameter is substantially equal to the diameter of the side wall at the level of the lower opening, the radius r of the connection fillet between the body 5 and the bottom 6 of the container 1 can be reduced to a value respecting the recommendation of the relation (5).

Claims (10)

1. Container (1) made of plastic material, comprising a body (5) and a bottom (6) extending at a bottom end (7) of the container (1), the body (5) having, at the junction with the bottom (6), an outer diameter C, this container (1) being characterized in that the bottom (6) has:

   - an annular outer seat (9) having a predetermined transversal dimension B such that: $$0.95\le \frac{B}{C}\le 1$$

   

   - a deformable arch (10) which extends inside the annular outer seat (9) and which, in a deployed position, protrudes outwards from the container (1) and defines an annular inner seat (14) having a predetermined transversal dimension A such that: $$1.2\le \frac{B}{A}\le 1.4$$

   
2. Container (1) according to Claim 1, in which the B ratio $\frac{B}{C}$

   

   is 0.98.
3. Container (1) according to Claim 1 or 2, in which the ratio $\frac{B}{A}$

   

   is 1.32.
4. Container (1) according to Claim 1 or 2, in which the ratio $\frac{B}{A}$

   

   is 1.23.
5. Container (1) according to one of Claims 1 to 4, which has, in a deployed position of the arch (10), an axial offset h between the outer seat (9) and the inner seat (14) such that: $$0.01\le \frac{h}{C}\le 0.1$$

   
6. Container (1) according to Claim 5, in which the ratio $\frac{h}{C}$

   

   is 0.08.
7. Container (1) according to Claim 5, in which the ratio $\frac{h}{C}$

   

   is 0.014.
8. Container (1) according to one of Claims 1 to 7, which has, at a junction between the body (5) and the bottom (6) a connecting fillet having a radius r such that: $$\frac{r}{C}\le \frac{1}{100}$$

   
9. Container (1) according to one of Claims 1 to 8, in which the tangent to the body (5), in the vicinity of its junction with the bottom (6), forms, with a main axis of the container (1), an angle less than 30°.
10. Container (1) according to Claim 9, in which the body (5) is, in the vicinity of its junction with the bottom (6), substantially cylindrical.

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