EP2049405B1 - Bottom of hollow ware obtained by the blow moulding or stretch-blow moulding of a thermoplastic hollow ware preform having such a bottom - Google Patents

Abstract

Bottom of hollow ware obtained by the blow molding or stretch-blow molding of a thermoplastic preform, this bottom having a transverse bearing surface and, on either side of this transverse bearing surface, a transverse external edge (7) and a concave internal wall with a transverse central portion (11) containing a disc (12) of material having a low crystallinity, this bottom including reinforcing ribs (1) having an outer edge (13) coming close to the transverse external edge (7) but without reaching this transverse external edge (7), these reinforcing ribs (1) hang an inner edge (14) coming close to the transverse central portion (11), but without reaching this transverse central portion (11), the transverse bearing surface being formed from segments (6a, 6b, 6c, 6d, 6e) interrupted by the reinforcing ribs (1), this hollow ware bottom (4) further including notches (2), the distal end portion (24) of which comes close to but does not reach the external edge (7) of the bottom, the proximal end portion (25) of the notches (2) being tangential with the transverse bearing surface but not opening into this transverse bearing surface.

Description

The invention relates to the bottom of hollow body and hollow body according to the preamble of claim 1.

The invention relates more particularly to hollow bodies obtained by blowing or stretching then blowing a preform injected with thermoplastic material (injection blow molding).

In recent years, the manufacture of plastic containers from pre-injected preforms has grown considerably, especially thanks to the use of polyethylene terephthalate (PET).

Meanwhile, other materials have been envisaged and / or used with more or less success such as, by way of non-limiting examples, polyethylene naphthalate (PEN), polypropylene (PP), polyacrylonitrile (PAN) or mixtures or overlays of various materials.

It is known that blowing or stretching causes a structural hardening of the PET. Blowing or stretching also causes crystallization induced by deformation, leaving the material translucent. For conventional deformation rates, the higher the crystallinity, the higher the deformation rate and the higher the deformation rate.

However, there is conventionally, in the center of the bottom of the hollow body, a very low crystallinity zone called "pellet" resulting from a portion of the preform that is only very slightly stretched during blowing or stretch blow molding. The longitudinal axis of the preform corresponds to that of the final container. As a result, during blow molding or stretch blow molding, the stretching of PET is almost zero in the center of the bottom of the container, and increases as one approaches the side wall of the container. .

Conventional bi-oriented PET containers exhibit, when they are heated to a temperature above the glass transition temperature, a large shrinkage, by stress release.

To alleviate this problem, it has long been known to carry out a heat treatment called "heat setting" treatment, in which, just after blowing of the preform and while the container is still in contact with the walls of the mold blowing, a temperature of between 120 and 250 ° C is applied to the material for a few seconds. Then the container is cooled while being kept under pressure.

Whatever their manufacturing process, thermoplastic containers must have good resistance of their bottom.

The bi-oriented PET has good mechanical and thermal resistance. But, as has been said above, the bottom of the containers is much less stretched than the body of the containers, so that the bottom has mechanical and thermal resistance lower than those of the body.

The same problem exists for the collar. The heat treatment of the necks makes it possible to increase their crystallinity. But the heat treatment of the necks (in amorphous PET) leads to isothermal crystallization forming spherulites, the thermo-hardened PET obtained is thus no longer translucent at all. If it is acceptable that the necks of bottles, relatively thick, are not translucent, a bottom of translucent bottle would harm the presentation of the packaged product.

The bottom of the container must withstand shocks, for example when the full container falls.

The container bottom must withstand the internal pressure, especially when the container contains a carbonated beverage. An internal overpressure may result from an increase in the storage temperature of the full bottles and / or the withdrawal of the plastic material from these bottles, this withdrawal generally occurring within two or three weeks of their manufacture and filling.

The bottles are transported under load palletized and stacked. So that, except for placement of inserts, the bottom of the bottles of the upper layers rest on the caps of the lower bottles and are subject to stresses of depression and punching.

The container bottom must withstand internal depressions that may occur, especially after the container has been hot filled, and then closed before its contents are cooled.

Any deformation of the bottom of the container affects the aesthetics of the product and the stability of the container stored upright.

The container bottom must resist creep.

The container as a whole, and in particular its bottom, must withstand the relatively severe thermal conditions encountered during hot filling or pasteurization.

When hot filling with a liquid at a temperature of at most 94 ° C, the bottom must have a relative aptitude for deformation. It is the same during the subsequent cooling, the bottom having to withstand the vacuum (vacuum compensation).

Pasteurization is carried out for certain flat liquids (non-carbonated fruit juices) or gaseous liquors (beer). During pasteurization, the liquid contained in the closed container may be carried for example at a temperature of between 60 and 80 ° C for about 20 minutes to 2 hours, the temperature being a function of the CO2 content. When the liquid to be pasteurized contains dissolved gas under pressure (carbonated beverage, beer), the material of the bottom of the container must not only support the increase in volume of the hot liquid, but also the increase of the pressure of the hot gas. During cooling, the pasteurized liquid reduces volume, the bottom of the container must also withstand this constraint.

It has been found that some containers have a bottom subject to sag during hot filling. This sinking of the bottom, outwardly, especially in the connection zone between the side wall of the container and the bottom, does not occur regularly around the container. So that the container becomes unstable. This collapse can come from a release of the stresses induced during the final blow of the hot shrunk blank.

Any deformation of the bottom of the container affects the aesthetics of the product and the stability of the container stored upright.

The bottom of the containers must sometimes withstand cleaning agents in the case of reusable containers.

In order to overcome all or part of the problems that may arise, it has been proposed to make the containers with petaloid bottoms. The bottom wall is then generally convex outward and has feet, typically four to six feet formed by excrescences regularly distributed on the bottom, and separated in pairs by a portion of the convex bottom wall. These petaloid bottoms are widely used for containers containing carbonated beverages. The radial recesses separating the feet absorb the forces due to the pressurization during filling and maintain the bearing surfaces of the feet in a plane substantially perpendicular to the axis of the container. This solution is not always satisfactory. Under the effect of internal pressure, the petaloid bottoms may burst. The petaloid bottoms can not always withstand the overpressure due to the increase in volume of the contents of the bottle, during a pasteurization.

Funds such as the one described in document FR 2 822 804 of the plaintiff. It describes a bottle bottom comprising in its central part a multi-branch cross-shaped footprint, this bottom being more petaloid type, each foot being provided with a stress absorption notch, separated radially from the end of the bottle. the corresponding branch of the cross-print. The introduction of these stress absorption notches allows, when constraints are experienced by a foot, the location at the notch of the deformation that can result. The installation of these notches leads to two more support zones on either side of each notch, these notches being partly placed in the seating area of the bottle.

It turns out that if the funds of the prior art solve only some of the problems posed, none is able, after a fall and a subsequent deformation, to recover its original shape, whether it is filled or not. The aim of the invention is to provide a new bottle bottom structure whose set of individual characteristics makes it possible to obtain a resistance superior to that of most funds currently known, and allows it to recover its shape after deformation.

At identical wall thickness, a bottom according to the invention will be more resistant than most previously known bottoms bottoms. In particular, it will have better resistance to vacuum.

A desired strength, a bottom according to the invention can be achieved with a lesser amount of material than most funds previously known.

The invention also aims to provide a bottle having a good resistance to hot filling and good resistance to pasteurization, while considering a possible significant lightening of the entire container, compared to known structures. Overall lightening of the container, from 5% to 20% is thus envisaged.

• un bord externe transversal ;
• une paroi interne concave avec une partie centrale transversale contenant une pastille de matériau à faible cristallinité, cette pastille correspondant au point d'injection de la préforme ;

ce fond comprenant des nervures de renfort ayant un bord extérieur venant à proximité du bord externe transversal mais sans atteindre ce bord externe transversal, ces nervures de renfort ayant un bord intérieur venant à proximité de la partie centrale transversale, mais sans atteindre cette partie centrale transversale,
la surface d'appui transversal étant formée de segments interrompus par les nervures de renfort,
ce fond de corps creux comprenant en outre des encoches dont la partie extrême distale vient au voisinage mais n'atteint pas le bord externe du fond, la partie extrême proximale des encoches venant en tangence de la surface d'appui transversal mais ne débouchant pas dans cette surface d'appui transversal.According to the first aspect, the invention relates to a bottom of a hollow body obtained by blow-molding or stretch blow molding of a preform made of thermoplastic material, this bottom comprising a transverse bearing surface and on either side of this surface. transversal support:

• a transverse outer edge;
• a concave inner wall with a transverse central portion containing a pellet of low crystallinity material, this pellet corresponding to the injection point of the preform;

this bottom comprising reinforcing ribs having an outer edge coming close to the transverse outer edge but without reaching this transverse outer edge, these reinforcing ribs having an inner edge coming close to the transverse central portion, but without reaching this transverse central portion; ,
the transverse bearing surface being formed of segments interrupted by the reinforcing ribs,
this hollow body bottom further comprising notches whose distal end portion comes in the vicinity but does not reach the outer edge of the bottom, the proximal end portion of the notches coming in tangency of the transverse bearing surface but not leading into this transverse support surface.

• la paroi interne concave est pourvue de gorges de renfort dont la partie extrême distale vient à proximité d'un segment de la surface d'appui transversal, mais sans atteindre ce segment, la partie extrême proximale de ces gorges de renfort venant à proximité de la partie centrale transversale mais sans atteindre cette partie centrale transversale ;
• les gorges de renfort comprennent une paroi de fond et deux ailes latérales et présentent un plan de symétrie ;
• les encoches comprennent une paroi de fond et deux ailes latérales et présentent un plan de symétrie ;
• la paroi de fond d'une gorge de renfort est sensiblement placée dans l'alignement de la paroi de fond d'une encoche et la partie extrême proximale de chaque gorge de renfort s'étend entre deux nervures de renfort ;
• la largeur des encoches est comprise entre 2 et 20 millimètres environ ;
• la profondeur de ces encoches est comprise entre 1 et 5 millimètres environ ;
• la pastille de matériau à faible cristallinité est en saillie en face externe dans la partie centrale transversale ;

In various embodiments, the background has the following characters, if any combined:

• the concave inner wall is provided with reinforcing grooves whose distal end portion comes close to a segment of the transverse bearing surface, but without reaching this segment, the proximal end portion of these reinforcing grooves coming in proximity to the transverse central part but without reaching this transverse central part;
• the reinforcement grooves comprise a bottom wall and two lateral wings and have a plane of symmetry;
• the notches comprise a bottom wall and two lateral wings and have a plane of symmetry;
• the bottom wall of a reinforcing groove is substantially placed in alignment with the bottom wall of a notch and the proximal end portion of each reinforcing groove extends between two reinforcing ribs;
• the width of the notches is between 2 and 20 millimeters approximately;
• the depth of these notches is between 1 and 5 millimeters approximately;
• the pellet of low crystallinity material is projecting on the outer face in the transverse central portion;

In an advantageous embodiment, with the exception of the reinforcing ribs and reinforcement grooves and grooves, the bottom is in the form of a body of revolution about an axis substantially perpendicular to its transverse bearing surface.

• au voisinage du bord externe, sensiblement tangent à une direction perpendiculaire à la surface d'appui transversale,
• au voisinage de la surface d'appui transversale, sensiblement tangent à cette surface d'appui transversale.

In a particular embodiment, the hollow body bottom has, in vertical radial section, between the outer edge and the transverse bearing surface, a profile which is:

• in the vicinity of the outer edge, substantially tangent to a direction perpendicular to the transverse bearing surface,
• in the vicinity of the transverse bearing surface, substantially tangential to the transverse bearing surface.

Advantageously, the bottom has, in vertical radial section, between the outer edge and the transverse support surface, a substantially parabolic profile.

The invention relates, according to a second aspect, to hollow bodies of thermoplastic material, in particular polyester such as PET, obtained by blow molding or stretch blow molding of a preform, these hollow bodies comprising a side wall and a bottom connected to this side wall. said bottom being as presented above.

• la figure 1 est une vue de dessous d'un fond de corps creux tel que par exemple une bouteille, selon un mode de réalisation de l'invention ;
• la figure 2 est une vue latérale du fond représenté en figure 1 ;
• la figure 3 est une vue en perspective du fond représenté en figures 1 et 2.

Other objects and advantages of the invention will emerge during the following description of embodiments, given by way of non-limiting examples, this description being made in the light of the appended drawings, in which:

• the figure 1 is a bottom view of a hollow body bottom such as for example a bottle, according to one embodiment of the invention;
• the figure 2 is a side view of the bottom represented in figure 1 ;
• the figure 3 is a perspective view of the bottom represented in Figures 1 and 2 .

With the exception of five radial ribs 1, five notches 2 and five grooves 3 reinforcement, the bottom 4 is in the form of a body of revolution about an axis 5 substantially perpendicular to its bearing surface transverse 6.

For this reason and for simplification, the bottom 4 will first be described in isolation from the radial ribs 1, notches 2 and reinforcement grooves 3, which will be the subject of a detailed description.

The bottom 4 will be described starting from its outer edge 7 and going radially towards the axis 5 of revolution.

The outer edge 7 is transverse and substantially corresponds to the junction between the bottom 4 and the side wall of the container (not shown). This outer edge 7 is placed at a height h7 relative to the transverse bearing surface 6 of the bottom 4 (and the bottle comprising the bottom 4, when the bottle is stored upright).

Between the outer edge 7 and the transverse bearing surface 6, the bottom 4 has in vertical radial section a substantially parabolic profile 8. At near the outer edge 7, this profile 8 is substantially tangent to a direction 9 perpendicular to the transverse bearing surface 6. In the vicinity of the transverse bearing surface 6, this profile 8 is substantially tangential to the transverse bearing surface. 6. The profile 8 thus provides a solution of continuity, without breaking of curvature, between the side wall of the container (not shown) and the transverse bearing surface 6.

The bottom 4 has a transverse bearing surface 6 of annular and segmented shape, as it will appear later. Starting from this transverse support surface 6 and going towards the axis 5 of revolution, the bottom 4 has, in vertical radial section, a substantially parabolic profile 10 and then a transverse central portion 11.

The transverse central portion 11 is placed at a height h11 with respect to the transverse support surface 6, this height h11 may be greater or smaller than that h7 of the outer edge 7.

An axial pellet 12 protrudes into the transverse central portion 11, this pellet 12 axial projecting downwards, that is to say the outside of the container provided with the bottom 4.

The radial reinforcing ribs 1 will now be described.

These radial ribs 1 have an outer edge 13 coming close to the outer edge 7 of the bottom 4, but without reaching this outer edge 7. A distance of a few millimeters thus separates the outer edge 13 (of the ribs 1) and the outer edge 7 ( from the bottom 4).

These radial ribs 1 have an inner edge 14 coming close to the transverse central portion 11, but without reaching this transverse central portion 11.

Each radial rib 1 comprises a bottom wall 15 and a flange 16, 17 on either side of the bottom wall 15. The bottom wall 15 is of decreasing width from the outer edge 13 to the inner edge 14 of the rib 1. As shown in the figures, the bottom wall 15 of a rib has a substantially constant curvature over any the radial length of this rib.

Each radial rib 1 has a plane of symmetry 18 which is vertical and radial.

The radial ribs 1 are leaned against a central chimney 19 in the center of which protrudes, downwards, the pellet 12, this central chimney being limited upwards by the transverse central portion 11.

The notches 2 will now be described.

These notches 2 extend radially. They comprise a bottom wall 20 and two lateral wings 21, 22. Each notch 2 has a vertical plane of symmetry 23 radial. The distal end portion 24 of these notches 2 comes in the vicinity but does not reach the outer edge 7 of the bottom 4. These notches 2 and have an output close to the vertical but at a distance from the joint plane. The distal end portion 24 of the notches is placed at a height h24 relative to the transverse bearing surface 6. In the embodiment shown, this height h24 is substantially half the height h7. The distance between the edge 7 and the distal end portion 24 of the notches is thus much greater than the distance between the edge 7 and the outer edge 13 of the ribs 1 of reinforcement.

The proximal end 25 of the notches 2 comes in tangency of the seat but does not open into this seat. The width of the notches is typically between 2 and 20 millimeters. The depth of these notches 2 varies according to the capacity of the bottle, and is typically 1.5 millimeters for a bottle of 0.5 liters (3 to 4 millimeters for a bottle of 1.5 liters). The depth of the notches 2 is less than the depth of the radial ribs 1, as it appears in particular in figure 3 .

The notches 2 participate in the overall resistance of the bottom 4 and in particular provide mechanical reinforcement of the portion of the bottom located beyond the seat and which is delimited by two neighboring ribs 1.

Reinforcing grooves 3 will now be described.

These reinforcement grooves 3 extend radially. They comprise a bottom wall 26 and two lateral wings 27, 28. Each reinforcement groove 3 has a radial vertical plane of symmetry 29. The distal end portion 30 of these reinforcement grooves 3 comes in the vicinity but does not reach the transverse bearing surface 6. The proximal end portion 31 of the reinforcement grooves 3 is leaned against the chimney 19 without reaching the central portion transverse 11.

In the embodiment shown, the bottom wall 26 of each reinforcing groove 3 extends radially in alignment with the bottom wall 20 of a notch 2. In other words, the plane of symmetry 23 of each notch 2 is substantially coincident with a plane of symmetry 29 of a groove 3 reinforcement.

• d'une partie extrême proximale 25 d'une encoche 2, cette partie extrême proximale 25 n'empiétant pas sur le secteur annulaire d'assise ;
• d'une partie extrême distale 30 d'une gorge 3 de renfort, cette partie extrême distale 30 n'empiétant pas non plus sur le secteur annulaire d'assise ;
• d'une aile 16, 17 d'une nervure 1 radiale, ces nervures 1 radiales séparant l'assise transversale en ses différents secteurs annulaires.

The transverse bearing surface 6 is thus formed of five annular sectors 6a, 6b, 6c, 6d, 6e, each of these annular sectors 6a, 6b, 6c, 6d, 6e being close to:

• a proximal end portion 25 of a notch 2, this proximal end portion 25 not encroaching on the annular seating sector;
• a distal end portion 30 of a reinforcement groove 3, this distal end portion 30 not encroaching either on the annular seating sector;
• a wing 16, 17 of a radial rib 1, these radial ribs 1 separating the transverse base in its various annular sectors.

The set of individual characteristics of the bottom of the bottle makes it possible to obtain a resistance greater than that of most currently known funds. At identical wall thickness, a bottom according to the invention will be more resistant than most previously known bottoms bottoms. A desired strength, a bottom according to the invention can be made with a material thickness less than most funds previously known.

A bottle comprising a bottom according to the invention has a good resistance to hot filling and good resistance to pasteurization. The central chimney 19 is particularly well reinforced with respect to creep or sag by the presence of reinforcement ribs 1 and reinforcing grooves 3.

A bottle comprising a bottom according to the invention also has good impact resistance on the lower part of the side wall. The presence of the notches 2 reduces the risk of plastic deformation of the bottle in the connection area between the side wall of a container and its seat.

The shape of the bottom of the bottle allows a reduction of the weight of material and this without weakening the seat or reducing too much the surface compared to conventional bottoms, while maintaining good resistance to hot filling (vacuum effects during cooling) and shocks. As an indication, a conventional 32g hot-fill bottle can be made with 26g of PET only, using a bottom according to the invention.

This background, which absorbs shocks very well, easily covers its shape after accidental deformation.

In the embodiment shown, the ribs 1 of reinforcement are five in number and substantially identical and equidistant. In other embodiments, the reinforcing ribs are more or less numerous, in particular to take into account the diameter of the bottom. The reinforcing ribs may be of different sizes, a first series may have a bottom wall narrower than the bottom wall of a second series of ribs.

In the embodiment shown, the notches, ribs and grooves are five in number and substantially identical and equidistant. The number of notches, ribs and grooves can be greater than five, in particular for large hollow bodies. By this arrangement, the ribs and notches cooperate best with the reinforcement of the bottom of the hollow body.

Claims (13)

1. Hollow-body bottom obtained by the blowing or blow-drawing of a thermoplastic preform, this bottom comprising a transverse bearing surface and, on either side of this transverse bearing surface:

   - a transverse outer edge (7);

   - a concave inner wall with a transverse central part (11) containing a slug (12) of material having low crystallinity, this slug corresponding to the injection point of the preform;

   this bottom comprising reinforcing ribs (1) having an external edge (13) coming into the vicinity of the transverse outer edge (7), but without reaching this transverse outer edge (7), these reinforcing ribs (1) having an internal edge (14) coming to the vicinity of the transverse central part (11), but without reaching this transverse central part (11), the transverse bearing surface being formed from segments (6a, 6b, 6c, 6d, 6e) interrupted by the reinforcing ribs (1), characterized in that this hollow-body bottom (4) comprises, furthermore, notches (2), the distal end part (24) of which comes into the vicinity of, but does not reach the outer edge (7) of the bottom, the proximal end part (25) of the notches (2) coming into tangency with the transverse bearing surface, but not issuing into this transverse bearing surface.
2. Hollow-body bottom according to Claim 1, characterized in that the concave inner wall is provided with reinforcing grooves (3), the distal end part (30) of which comes into proximity with a segment (6a, 6b, 6c, 6d, 6e) of the transverse bearing surface (6), but without reaching this segment (6a, 6b, 6c, 6d, 6e), the proximal end part (31) of these reinforcing grooves (3) coming into proximity with the transverse central part (11), but without reaching this transverse central part (11).
3. Hollow-body bottom according to Claim 2, characterized in that the reinforcing grooves (3) comprise a bottom wall (26) and two lateral wings (27, 28) and have a plane of symmetry (29).
4. Hollow-body bottom according to Claim 3, characterized in that the notches (2) comprise a bottom wall (20) and two lateral wings (21, 22) and have a plane of symmetry (23).
5. Hollow-body bottom according to Claim 4, characterized in that the bottom wall (26) of a reinforcing groove (3) is placed substantially in alignment with the bottom wall (20) of a notch (2), the proximal end part (31) of each reinforcing groove (3) extending between two reinforcing ribs (1).
6. Hollow-body bottom according to any one of the preceding claims, characterized in that the width of the notches (2) is between 2 and 20 millimetres.
7. Hollow-body bottom according to any one of the preceding claims, characterized in that the depth of the notches (2) is between 1 and 5 millimetres.
8. Hollow-body bottom according to any one of the preceding claims, characterized in that the slug (12) of material having low crystallinity projects on its outer face in the transverse central part (11).
9. Hollow-body bottom according to any one of the preceding claims, characterized in that the outer edge (7) is placed at a first height (h7) in relation to the transverse bearing surface, the transverse central part (11) being placed at a second height (h11) in relation to the transverse bearing surface.
10. Hollow-body bottom according to any one of the preceding claims, characterized in that, with the exception of the reinforcing ribs (1) and of the notches (2) and reinforcing grooves (3), the bottom (4) takes the form of a body of revolution about an axis (5) substantially perpendicular to its transverse bearing surface.
11. Hollow-body bottom according to Claim 10, characterized in that it has in vertical radial section, between the outer edge (7) and the transverse bearing surface, a profile which is:

    - in the vicinity of the outer edge (7), tangent to a direction perpendicular to the transverse bearing surface,

    - in the vicinity of the transverse bearing surface, tangent to this transverse bearing surface.
12. Hollow-body bottom according to Claim 11, characterized in that it has in vertical radial section, between the outer edge (7) and the transverse bearing surface, a parabolic profile.
13. Hollow-body bottom made from thermoplastic, in particular polyester, such as PET, obtained by the blowing or blow-drawing of a preform, this hollow body comprising a lateral wall and a bottom connected to this lateral wall, the said bottom being as presented in any one of the preceding claims.

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