EP2580133B1 - Container including an arched bottom having a square seat - 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. 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 technical solution to promote the structural rigidity of a container consists in over-stretching 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", does not guarantee that the rigidity of the bottom will be satisfactory; that's why we usually combine it with form tips. However, not all forms are permissible due to the blowing constraints of the material (so-called "blowing" means the ability of the container to be formed by blowing, or in other words the ability of the material to conform properly to the mold cavity).

Another technique is to strengthen the bottom by means of impressions, cf. eg. the document WO 2006/100374 (SIDEL).

The document US 2009/0159556 A1 discloses a container according to the preamble of claim 1.

We therefore seek a good compromise in the choice of the parameters that we want to maximize (including rigidity and blowing) and those that we want on the contrary to minimize (including weight and blowing pressure).

To date, lightweight containers for ordinary applications (including still water) have insufficient 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 and, preferably, at equal or lower blowing pressure, the mechanical performance of a container, while maximizing its blowing.

• Une assise annulaire s'étendant sensiblement dans le prolongement du corps et définissant un plan de pose et une joue annulaire interne sensiblement perpendiculaire au plan de pose ;
• Une voûte concave qui s'étend à partir d'une zone voisine de l'assise vers une zone centrale ;

caractérisé en ce que la dimension axiale H de la joue et la dimension radiale L du plan de pose sont telles que : $$0,6\le \frac{L}{H}\le 1,5$$

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 and an inner annular cheek substantially perpendicular to the laying plane;
• A concave arch that extends from an area near the seat to a central area;

characterized in that the axial dimension H of the cheek and the radial dimension L of the laying plane are such that: $$0,6\le \frac{\mathrm{The}}{H}\le 1,5$$

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 square seat.

According to a particular embodiment, the axial dimension H of the cheek and the radial dimension L of the laying plane are such that: $$0,8\le \frac{\mathrm{The}}{H}\le 1,2$$

The axial dimension of the cheek and the radial dimension of the laying plane are preferably substantially equal.

• une série de raidisseurs qui s'étendent radialement depuis la zone centrale jusqu'à l'assise ;
• une face de jonction (qui est par exemple tronconique et présente une ouverture angulaire prédéterminée) entre la voûte et la joue ;
• une série périphérique de galbes, faisant saillie depuis la face de jonction vers l'intérieur entre les raidisseurs et qui peuvent modifier localement (en l'augmentant ou au contraire en la diminuant) l'ouverture angulaire de la face de jonction.

According to one embodiment, the container further comprises:

• a series of stiffeners extending radially from the central zone to the seat;
• a junction face (which is for example frustoconical and has a predetermined angular aperture) between the arch and the cheek;
• a peripheral series of curves, projecting from the junction face inwardly between the stiffeners and which can modify locally (by increasing or decreasing it) the angular aperture of the junction face.

According to a particular embodiment, each curve has an arcuate inner edge, which projects over the arch, and lateral edges which may be non-parallel.

• la figure 1 est une vue en perspective par-dessous 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 exemple de réalisation ;
• la figure 3 est une section du fond du récipient de la figure 2 ;
• la figure 4 est un détail de la section du fond, selon l'encart IV de la figure 3 ;
• la figure 5 est une vue en perspective, analogue à la figure 2, illustrant un deuxième mode de réalisation du fond du récipient ;
• les figures 6 et 7 sont des vues de détail en coupe, respectivement suivant les plan de coupe VI-VI et VII-VII de la figure 5 ;
• la figure 8 est une vue en perspective, analogue à la figure 5, illustrant une variante 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 5, illustrant une autre variante 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.

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 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 section of the bottom of the container of the figure 2 ;
• the figure 4 is a detail of the bottom section, according to inset IV of the figure 3 ;
• the figure 5 is a perspective view, similar to the figure 2 illustrating a second embodiment of the bottom of the container;
• the Figures 6 and 7 are detail views in section, respectively along the section plane VI-VI and VII-VII of the figure 5 ;
• the figure 8 is a perspective view, similar to the figure 5 illustrating an alternative 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 5 , illustrating another alternative 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 .

On the figure 1 is shown a container 1 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 direction opposite to the neck 2 , this shoulder 4 being extended by a side wall or body 5 , of generally cylindrical 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, the base 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 continuous annular face 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 the latter can rest stably on a surface S plane ( figure 3 ).

The laying plane 8 extends radially over a width L and is connected outwards to an external lateral face 9 of the seat 7 (which extends in the extension of the body) by an outer fillet 10 with a small radius 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 that extends axially inwardly of the container 1 in the extension of the laying plane 8 , substantially at right angles to it.

The laying plane 8 is connected inwardly to the cheek 11 by an inner fillet 12 preferably with a small radius of curvature - less than or equal to about 1 mm.

The bottom 6 further comprises a concave arch 13 (with concavity turned towards 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 extends in the extension of the cheek 11 to a central zone 14 of the bottom 6 .

As is visible on the figure 3 , the vault 13 is shallow, and its curvature little pronounced. The maximum angle A1 of its tangent with a plane perpendicular to the X axis of the container 1 (measured in this case on an outer edge of the vault 13 ) is small - less than or equal to about 21 °.

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 .

As it appears in the drawings, the vault 13 is not connected to the cheek 11 directly, but via a junction face 16 of generally frustoconical shape of revolution about the axis X of the container 1 , whose the angle A2 with a plane perpendicular to the axis X of the container 1 is between 31 ° and 70 °.

The cheek 11 extends axially over a height H whose ratio to the width L of the laying plane 8 is between 0.6 and 1.5: $$0,6\le \frac{\mathrm{The}}{H}\le 1,5$$

Preferably, the L / H ratio is closer to 1, being between 0.8 and 1.2: $$0,8\le \frac{\mathrm{The}}{H}\le 1,2$$

One can even ensure that the ratio L / H is substantially equal to 1: $$\frac{\mathrm{The}}{H}\cong 1$$

Thus, the seat 7 has in section a substantially square profile, as is visible on the figures 4 , 6 , 9 and 12 .

The result for the container 1 , on the one hand, a good rigidity and good stability both during filling and during its palletization and, secondly, a good blowing.

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 substantially equal, but the performance granted by a ratio L over H between 0.6 and 1.5 are good.

Furthermore, the wide seat 7 , the 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 conventional seat whose diameter of the laying plane is substantially less than the diameter of the body, and whose leave high radius promotes the rolling of the bottom.

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 features described above, but which differ according to the geometry of the vault and / or the seat, are now described in more detail.

In a first embodiment, illustrated on the figures 2 , 3 and 4 it can be seen that the roof 13 is smooth and is in the form of a spherical cap.

The w / o ratio is about 0.68: $$\frac{\mathrm{The}}{H}\cong 0,68$$

The junction face 16 is smooth, and is limited to a truncated cone whose angle A2 is relatively pronounced, its value being about 65 °, thus giving the vicinity of the seat 7 a good structural rigidity.

The relative simplicity of shape of the bottom 6 gives it a good puffability, which allows to blow the container 1 at a moderate pressure, less than or equal to 25 bars.

In a second embodiment, illustrated on the Figures 5 to 13 , the vault 13 is provided with a series of stiffeners 17 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.

In this embodiment, the stiffeners 17 are connected to the central zone 14 of the bottom 6 by an inner radial end 18 and are connected to the flange 11 by an outer radial end 19 . In the examples illustrated, the stiffeners 17 are 8, but this number is provided as an 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, the width and the shape of the stiffeners 17 may vary according to the applications. The stiffeners 17 may be straight or arcuate in the shape of a Y pointing either towards the center or towards the periphery of the bottom, or in the form of X. In the examples illustrated, the stiffeners 17 have an inverted Y profile, and have, on the half of their length about a 20 right in the inner portion of substantially constant width, which is extended by an external portion 21 inverted V, which widens since the inner portion 20 towards the outer end 19 .

In the interstices between the stiffeners 17 , the vault 13 defines panels 22 recessed whose profile is complementary to that of the stiffeners 17 .

Each stiffener 17 has a concave lower face 23 which extends in the extension of the surface of the central zone 14 and two lateral edges 24 which form fillets 25 , 26 for connecting the lower face 23 with the recessed panels 22 . As is clearly visible on the figures 5 , 8 , and 11 , the edges 24 are double radius, and comprise a first fillet 25 convex profile, which is flush with the lower face 23 , followed by a second fillet 26 concave profile, which is flush with the panel 22 .

The central zone 14 of the bottom 6 is reduced to the pin 15 , which on its periphery delimits the internal ends 18 of the stiffeners 17 . As can be seen in FIG. 14, the peg 15 has a star-shaped profile, the internal ends 18 of the stiffeners 17 being thinned while being bevelled.

As is visible on the figures 5 , 8 and 11 , to improve the blowing of the bottom 6 , leaves 27 are provided at the outer ends 19 of the stiffeners, to ensure their connection with the face 16 of junction, on the one hand, and with the cheek 11 , on the other hand.

The ratio L / H is substantially equal to 1: $$\frac{\mathrm{The}}{H}\cong 1$$

In addition, the bottom 6 is reinforced by means of a peripheral series of curves 28 each formed radially inwards projecting, on the face 16 of junction between the cheek 11 and the roof 13 , between the outer ends 19 of two adjacent stiffeners 17 . The curves 28 are convex in the direction of the axis X of the container 1 and locally reverse the curvature of the face 16 . The curves 28 also have the effect of locally modifying the angular aperture A2 of the face 16 .

• un bord 29 intérieur arqué qui s'étend en saillie par rapport à la face 16 en direction de l'axe X, et déborde sur la voûte 13 (plus précisément sur le panneau 22) ;
• un bord 30 exterieur qui s'étend à la limite entre la joue 11 et la face 16 (dans les exemples de réalisation des figures 5 et 8) ou déborde sur la joue (dans l'exemple de réalisation de la figure 11) ; le bord 30 extérieur peut être droit (figure 5) ou arqué vers l'extérieur du récipient 1 (figures 8 et 11) ;
• deux bords 31 latéraux non parallèles qui s'étendent dans une direction sensiblement radiale au-travers de la face 16 et vont en s'écartant l'un de l'autre, soit de l'extérieur vers l'intérieur du récipient 1 (dans les exemples de réalisation des figures 5 et 8), soit à l'inverse de l'intérieur vers l'extérieur (dans l'exemple de réalisation de la figure 11).

As is visible on the figures 5 , 8 and 11 each curve 28 has a substantially trapezoidal contour, and comprises:

• an arcuate inner edge 29 which protrudes from the face 16 in the direction of the X axis, and projects over the vault 13 (more precisely on the panel 22 );
• an outer edge 30 which extends at the boundary between the cheek 11 and the face 16 (in the embodiments of FIGS. figures 5 and 8 ) or overflows on the cheek (in the embodiment of the figure 11 ); the outer edge 30 may be straight ( figure 5 ) or arched outward of container 1 ( figures 8 and 11 );
• two non-parallel lateral edges 31 which extend in a substantially radial direction across the face 16 and move away from each other, either from the outside to the inside of the container 1 (in the examples of realization of the figures 5 and 8 ), or conversely from the inside to the outside (in the embodiment of the figure 11 ).

In the exemplary embodiment of Figures 5, 6 and 7 the two lateral edges 31 deviate from each other towards the inside of the container 1 , and form an angle close to 90 °.

As can be seen by comparing the sections of Figures 6 and 7 the curve 28 has the effect of decreasing the angular aperture A2 of the face 16 : approximately 45 ° outside the curve 28 (FIG. figure 6 ), the angle A2 is about 35 ° in a median radial plane to the curve 28 (corresponding to the section plane VII-VII).

In a variant, illustrated on the Figures 8, 9 and 10 the lateral edges 31 deviate from each other towards the inside of the container 1 and form a closed angle, less than 45 ° (in this case about 31 °). As is visible on the figure 8 , The outer edge 30, arcuate outwardly of the container 1, beyond (at least) partially on the cheek 11.

As this is also visible by comparison of the sections of the Figures 9 and 10 , the curve 28 has the effect of decreasing rather weakly the angular aperture A2 of the face 16: approximately 45 ° outside the curve 28 ( figure 9 ), the angle A2 is about 40 ° in a median radial plane to the curve 28 (corresponding to the cutting plane XX).

In another variant, illustrated on the Figures 11, 12 and 13 the lateral edges 31 are spaced apart from each other towards the outside of the container 1 , and form an angle close to 60 °.

We see on the figure 11 that the outer edge 31 of the curve 28 extends almost entirely on the cheek 11 . Moreover, as is visible on Figures 11 and 13 , the curve 28 has, along its outer edge 31 , a recess 32 , so that the curve 28 has the effect of substantially increasing the angular aperture A2 of the face 16: about 45 ° to the outside the curve ( figure 12 ), the angle A2 is about 55 ° in a median plane with the curve 28 (corresponding to the plane of section XIII-XIII).

In this second embodiment, the presence of the stiffeners 17 increases the rigidity of the vault 13 , and reduces the risk of subsidence of the bottom 6 under the effect of a load such as that to which the palletized containers are subjected.

In addition, the stiffeners 17 , by their shape, act in the manner of struts, ensuring 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 17 bearing against the cheek 11 at their ends, the radial recovery of the forces results in a permanent centrifugal radial stress exerted by the stiffeners 17 on the seat 7 via the cheek 11 , which contributes to stiffen the seat 7 , notably by preventing its ovalisation.

Curves 28 have two main functions. A first function of the curves 28 is to increase the rigidity of the bottom at the junction between the arch 13 and the seat 7 between the stiffeners 17 ; a second function is to compensate for the degradation of the bottom blowing 6 due to the presence of the stiffeners 17 .

Indeed, during the molding of the bottom 6 , the material reaches first impressions corresponding to the side edges 24 of the stiffeners 17 , where it tends to freeze locally before reaching the seat 7 . As a result, during the impression taking of the bottom, a tension of the material between the stiffeners 17 , at the junction face 16 and the seat 7 . The presence of the curves 28 facilitates, thanks to the inversion local of the curvature of the junction face 16 and the offset generated by the recess 32 , the impression of the material between the stiffeners 17 , both at the face 16 and the seat 7 .

In this way, the blowing pressure can be maintained at a value of less than 28 bars, and in practice between 20 bars and 28 bars.

Claims (10)

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

   - an annular seat (7) extending substantially in line with the body (5) and terminated by a continuous and annular face that forms the lower end of the container (1), defines a resting plane (8) perpendicular to the axis of the container (1), by which the latter can rest stably on a flat surface, and an inner annular cheek (11) that is essentially perpendicular to the resting plane;

   - a concave vault (13) which extends from a zone adjacent to the seat (7) to a central zone (14);

   characterized in that the axial dimension H of the cheek and the radial dimension L of the resting plane are such that: $$\mathrm{0.6}\le \mathrm{L}/\mathrm{H}\le \mathrm{1.5}$$

   

   the resting plane (8) connecting to an outer lateral face (9) of the seat (7) by an outer round (10) having a small radius of curvature, in the millimetre range, the resting plane (8) connecting to the annular cheek (11) by an inner round (12) having a small radius of curvature, less than or equal to approximately 1 mm.
2. Container (1) according to Claim 1, characterized in that the axial dimension H of the cheek and the radial dimension L of the resting plane are such that: $$\mathrm{0.8}\le \mathrm{L}/\mathrm{H}\le \mathrm{1.2}$$

   
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 essentially equal.
4. Container according to one of the preceding claims, characterized in that it comprises:

   - a row of stiffeners (17) which extend radially from the central region (14) to the seat (7);

   - a junction face (16) between the vault (13) and the cheek (11) ;

   - a peripheral row of curves (28) projecting inward from the junction face (16), between the stiffeners (17).
5. Container according to Claim 4, characterized in that the junction face (16) is frustoconical and has a predetermined angular opening (A2).
6. Container according to Claim 5, characterized in that each curve (28) locally modifies the angular opening (A2) of the junction face (16).
7. Container according to Claim 6, characterized in that each curve (28) locally reduces the angular opening (A2) of the junction face (16).
8. Container according to Claim 6, characterized in that each curve (28) locally increases the angular opening (A2) of the junction face (16).
9. Container according to one of Claims 4 to 8, characterized in that each curve (28) has an arcuate inner edge (29) which projects toward the vault (13).
10. Container according to one of Claims 4 to 9, characterized in that each curve (28) has non-parallel lateral edges (31).

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